2 effect of variables electroless nickel

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碳纤维表面化学镀镍的研究进展

采用化学镀镍能改善碳纤维表面的润湿性，提高复合材
料的力学性能。Ｒａｍｓ等［２０］采用化学镀技术在碳纤维表面镀
上一层镍，与铝粉混合加热到６５０～９５０℃成型。研究发现，
在碳纤维与基体的界面形成Ａｌ－Ｎｉ过渡金属，限制了纤维的
２碳纤维化学镀镍的研究进展
碳纤维根据其合成方式和直径不同可分为：有机前驱体碳纤维、气相生长碳纤维（ＶＧＣＦ）、碳纳米管（ＣＮＴｓ）。下面分别介绍上述碳纤维表面化学镀的最新研究成果及其应用前景。
２．１有机前驱体碳纤维
有机前驱体碳纤维是指以含碳量在９０％以上的高强度、高模量、耐高温的纤维作为功能材料，短切碳纤维具有碳纤维所具有的优异物理、化学性能，而且由于短纤维无规排列，性能呈各向同性，在金属中加入碳纤维制成的复合材料大大提高其耐磨性、抗冲击性和耐疲劳性。但碳纤维与基体界面较差的润湿性影响了复合材料的性能，在碳纤维表面化学镀镍恰恰解决了上述问题，改善了耐磨擦、耐腐蚀、力学强
度等性能，扩大了应用领域。通过化学镀沉积一层金属镍，能明显提高碳纤维的电性
能。Ｔｚｅｎｇ［１７，１８］采用化学镀技术在ＰＡＮ基碳纤维表面沉积的Ｎｉ－Ｐ层如图１所示（（ａ）、（ｃ）为原始碳纤维，（ｂ）、（ｄ）为镀镍的碳纤维）。研究了热处理对碳纤维复合镀层电性能的影响。结果表明，镀层是微晶相和无定相的混合体，随着热处理温度的升高，形成Ｎｉ和Ｎｉ３Ｐ两个稳定相，复合镀层的电阻下降，热处理温度超过３００℃以后，电阻反而增加，这与Ｎｉ３Ｐ相形成有关。同时对碳纤维进行石墨化处理发现：镀有Ｎｉ层的碳纤维更容易进行石墨化，镀Ｎｉ的碳纤维经１４００℃热处理的石墨化度比纯碳纤维经过２４００℃热处理的高，Ｎｉ层起催化的作用。

Electric Field Gradient Theory with Surface Effect for Nano-Dielectrics

2 Corresponding author. Tel & Fax: 86-29-82660977; E-mail: sshen@
2 Copyright © 2009 Tech Science Press
CMES, vol.1389, no.1,boratory for Strength and Vibration, School of Aerospace, Xi’an Jiaotong University, 28 West Xianning Road, Xi’an, Shaanxi 710049, P.R. China
Shuling Hu1, Shengping Shen1;2
Abstract: The electric ﬁeld gradient effect is very strong for nanoscale dielectrics. In addition, neither the surface effect nor electrostatic force can be ignored. In this paper, the electric Gibbs free energy variational principle for nanosized dielectrics is established with the strain/electric ﬁeld gradient effects, as well as the effects of surface and electrostatic force. As regards the surface effects both the surface stress and surface polarization are considered. From this variational principle, the governing equations and the generalized electromechanical Young-Laplace equations, which take into account the effects of strain/electric ﬁeld gradient, surface and electrostatic force, are derived. The generalized bulk and surface electrostatic stress are obtained from the variational principle naturally. The form are different from those derived from the ﬂexoelectric theory. Based on the present theory, the size-dependent electromechanical phenomenon in nano-dielectrics can be predicted.

NiSe2_NF 溶剂热硒化泡沫镍

In situ Grown Pyramid Structures of Nickel Diselenides Dependent on Oxidized Nickel Foam as Ef ﬁcient Electrocatalyst for Oxygen Evolution ReactionXiao Li a ,Guan-Qun Han a ,b ,Yan-Ru Liu a ,Bin Dong a ,b ,*,Xiao Shang a ,Wen-Hui Hu a ,Yong-Ming Chai a ,Yun-Qi Liu a ,Chen-Guang Liu a ,*a State Key Laboratory of Heavy Oil Processing,China University of Petroleum (East China),Qingdao 266580,PR China bCollege of Science,China University of Petroleum (East China),Qingdao 266580,PR ChinaA R T I C L E I N F OArticle history:Received 16December 2015Received in revised form 1April 2016Accepted 20April 2016Available online 21April 2016Keywords:nickel diselenides nickel foam in situ grownoxidation pretreatment oxygen evolution reactionA B S T R A C TIn situ grown pyramid structures of nickel diselenides (NiSe 2)have been synthesized using oxidized nickel foam (NF(Ox))assubstrate bya facile solvothermal selenization.XRD results show that NiSe phaseon NFand NiSe 2phase on NF (Ox)have been obtained after the identical selenization process,respectively.The nanorods morphology of NiSe on NF and pyramid structure of NiSe 2on NF (Ox)have been revealed by SEM images.The different structure and morphology of NiSe/NF compared with NiSe 2/NF (Ox)can be ascribed to the oxidation pretreatment of NF which af ﬁliates the formation of ultrathin b -Ni(OH)2nanosheets on NF.The electrochemical measurements for oxygen evolution reaction (OER)exhibit an enhanced electrocatalytic activity of NiSe 2/NF (Ox)with onset potential of 1.54V (vs.RHE)and small Tafel slope of 96mV dec À1.Moreover,NiSe 2/NF (Ox)possesses lower charge-transfer resistance (R ct )indicating a faster electron transfer rate than NiSe/NF.The excellent stability further con ﬁrms the improved elctrocatalytic performance of NiSe 2/NF (Ox).We speculate that the high Ni 2+proportion and octahedral structure of NiSe 2may be the keys for excellent electrocatalytic properties for OER.ã2016Elsevier Ltd.All rights reserved.1.IntroductionThe urgent demand for global environmental protection and the severe energy crisis have accelerated the development of the clean and renewable energy ﬁelds [1].Hydrogen is considered as the most promising energy carrier and the best alternative for traditional fossil fuels due to the advantages of high calori ﬁc value,abundant source and outstanding character of pollution-free [2–6].Electrochemical water splitting has been basically mature for producing hydrogen and oxygen promoted by electrolysis derived from variable and intermittent renewables,such as solar,wind and tidal power [7,8].Nevertheless,as a key half-reaction associated with water splitting,the anodic oxygen evolution reaction (OER)has slow reaction rate owing to multi-steps transfer of four electrons with high activation energy and large overpotentials [9,10],which has seriously constrained the conversion ef ﬁciency ofwater electrolysis.Therefore,electrode materials with highly electrocatalytic activity for OER have been pursued to reduce the overpotential and enhance conversion ef ﬁciency.Such enhance-ment of electrocatalytic activity is highly related to the electrode surface properties because of the heterogeneous nature of electrocatalysis.The electrode has a signi ﬁcant in ﬂuence on the electro-transfer,reaction rates with reactants,intermediates,and products,promoting the whole electrocataltic reaction and remaining unchanged upon its completion [11].At present,RuO 2,IrO 2and their hybrids as electrode materials demonstrate the most ef ﬁcient performances for OER [12,13].However,high cost and scarcity have limited their replication on a mass production scale [14,15].The alternative OER electrocatalysts from earth-abundant elements have been explored such as group VI oxides,hydroxides or chalcogenides including nickel hydroxide (b -Ni(OH)2)[16,17],cobalt oxide (Co 3O 4)[18,19],cobalt disul ﬁde (CoS 2)[20],cobalt diselenide (CoSe 2)[21],etc.However,these candidates have been proved to process inferior electrocatalytic performances in nature [22].It is worth noting that designing different nanostructure and crystal phase of electrocatalysts may increase the number of active sites to enhance the electrocatalytic activity.For instance,Jin ’s*Corresponding authors at:State Key Laboratory of Heavy Oil Processing,China University of Petroleum (East China),Qingdao 266580,PR China.Tel.:+8653286981376;fax:+8653286981787.E-mail addresses:dongbin@ (B.Dong),cgliu@ (C.-G.Liu)./10.1016/j.electacta.2016.04.1080013-4686/ã2016Elsevier Ltd.All rights reserved.Electrochimica Acta 205(2016)77–84Contents lists available at ScienceDirectElectrochimica Actaj o u r n a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /e l e c t a c tagroup has recently prepared novel porous b-Ni(OH)2nanosheets with excellent and stable elctrocatalytic activity for OER[23]using layered double hydroxide(LDH)nanoplates as precursors.Sun’s group reported NiSe nanowireﬁlm supported on three dimen-sional(3D)nickel foam(NF)with enhanced electrocatalytic activity and stability for OER[24].3D architectures of NF have been proved to offer more active sites and enhanced electro-catalytic activity and stability for OER[25].The above researches have suggested that novel nanostructuring may be the key to obtain the excellent OER electrocatalysts.Herein,we synthesized in situ grown pyramid structures of nickel diselenides(NiSe2)based on oxidized nickel foam(NF (Ox))for theﬁrst time,referred to as NiSe2/NF(Ox).The oxidation pretreatment of NF will provide not only3D skeleton structure but also ultrathin b-Ni(OH)2nanosheets on the surface of NF[24],which may decide the crystal phase and morphology of Ni x Se y during selenization.XRD and SEM results show the crystalline structure of synthesized Ni x Se y has surprisingly varied from hexagonal NiSe based on bare NF to cubic pyrite-type NiSe2based on NF(Ox)with the morphology changing from short nanorods to evenly distributed pyramids structure.The electrochemical measurements of NiSe2/NF(Ox) indicate prominent improvements of OER activity and electrical conductivity compared to NiSe/NF,and also revealing a long-term stability in basic media.The enhanced mechanisms of OER activity have been discussed.2.Experimental2.1.Materials and CharacterizationAll of the reagents were of analytical grade and used as obtained without further puriﬁcation.NF with thickness of1.0mm,surface density of350g mÀ2was purchased from Shenzhen Poxon Machinery Technology Co.,Ltd.The phase analysis of samples was conducted by X-ray diffraction(XRD,X’Pert PRO MPD,Cu KR).The valence states of elements were examined by X-ray photoelectron spectroscopy (XPS,VG ESCALABMK II,Al K a(1486.6eV)).And the morphology and structure of samples were characterized by scanning electron microscopy(SEM,Hitachi,S-4800)and transmission electron microscopy(TEM,FEI Tecnai G2).2.2.Preparation of NF(Ox)SamplesThe similar chemical oxidation method that has been reported [26]was used to prepare NF(Ox)as a precursor.Firstly,NF was cut into pieces of1Â2cm2and then ultrasonically washed before use with0.1M H2SO4,acetone,ethanol and water for20min, respectively.Secondly,the wet pieces of NF were sealed into a glass vials for24h.Afterwards,above pieces of NF were taken out and immersed in a mixed solution containing30mL,3M NaOH and 15mL,1M(NH4)2S2O8and sealed for6h at room temperature. Finally,NF(Ox)samples were rinsed with ethanol and deionized water for several times and dried at150 C for6h.Fig.1.(a)XRD patterns of NF(Ox),NiSe/NF and NiSe2/NF(Ox).Crystal structure of(b)hexagonal phase NiSe and(c)cubic phase NiSe2. 78X.Li et al./Electrochimica Acta205(2016)77–842.3.Preparation of NiSe 2/NF (Ox)and NiSe/NF SamplesA facile solvothermal selenization process has been conducted using Se powder and ethanol to prepare in situ grown nickel selenides on NF substrate [24].In a typical process,NiSe 2/NF (Ox)samples were prepared as following.0.118g Se powder was added into 2mL deionized water containing 0.13g NaHB 4.A clear NaHSe solution was obtained after moderate stirring.Meanwhile,N 2was purged into 60mL ethanol for 30min to eliminate the dissolved oxygen.The fresh prepared NaHSe solution was quickly added into above ethanol under N 2ﬂow.After that,the solution was transferredinto a 100mL Te ﬂon-lined stainless steel autoclave with three pieces of NF (Ox)samples as substrates.The hydrothermal reaction was maintained in an electric oven at 140 C for 12h.Following the autoclave cooled down at room temperature,the samples were rinsed with ethanol and deionized water for several times and dried at 60 C for 8h.For comparison,NiSe/NF samples were prepared by the same selenization method on the bare NF without chemical oxidation pretreatment.To investigate the growth of NiSe 2/NF (Ox)during selenization,NiSe 2/NF (Ox)-4h and NiSe 2/NF (Ox)-8h samples are also synthesized by controlling the selenization time for 4h and 8h,respectively.Fig.2.(a)XPS survey spectra for NiSe 2/NF (Ox)in the (c)Ni 2p,(e)Se 3d regions.(b)XPS survey spectra for NiSe/NF in the (d)Ni 2p,(f)Se 3d regions.X.Li et al./Electrochimica Acta 205(2016)77–84792.4.Electrochemical MeasurementsThe electrochemical measurements were performed on an electrochemical workstation(Gamry Reference600Instrument, USA)with a three-electrode system in a1M KOH aqueous solution (pH=$14)using a sample NF as the working electrode,Pt foil as the counter electrode and a saturated calomel electrode(SCE)as the reference electrode.O2was purged into the electrolyte for30min to saturate the electrolyte prior to each electrochemical measure-ment.The polarization curve was obtained by consecutive linear sweep voltammetry(LSV)from0to0.8V(vs.SCE)with a scan rate of20mV sÀ1until there is no evident variation.Electric impedance spectroscopy(EIS)was carried out from105Hz to0.1Hz at an overpotential of0.45V(vs.SCE).Stability is tested by cyclic voltammetry(CV)at a sweep rate of100mV sÀ1for500cycles.3.Result and discussionFig.1a shows XRD patterns of NF(Ox),NiSe/NF and NiSe2/NF (Ox).The obviously sharp diffraction peaks of the three samples at around43.94 and51.34 may arise from the metallic NF substrate (PDF No.03-065-0380).And the peaks at around21.83 belong to the amorphous glass slide.The main peaks of NiSe/NF including (101),(102),(110)and(202)planes can be exactly indexed to that of NiSe(PDF No.03-065-6014),and no impurity can be detected. Similarly,the main planes of NiSe2/NF(Ox)such as(200),(210), (211),(311),(023),(321)and(421)are also well-matched with that of NiSe2(PDF No.03-065-5016).Obviously,the oxidation pretreatment of NF brings the change of the crystal structure from hexagonal phase NiSe(in Fig.1b)into distinct cubic phase NiSe2with a pyrite-type octahedral structure(in Fig.1c).While the presence of b-Ni(OH)2on NF(Ox)is not conﬁrmed by the XRD analysis,which probably owes to the tiny amount not enough for detection,it can be further conﬁrmed by SEM.Fig.2shows XPS survey spectra for NiSe2/NF(Ox)and NiSe/NF. As shown in Fig.2a and2b,the characteristic peaks of Ni and Se can be clearly observed in both NiSe2/NF(Ox)and NiSe/NF.In addition,the peaks of C1s and O1s may derive from contamina-tion and surface oxidation[27].Considering that the solvother-mal reaction,drying step or chemical oxidation pretreatment inevitably causes the surface oxidation of NF substrate,the emergencies of O1s signals may represent the existences of nickel oxides[24].In Fig.2c and2d,the comparison of Ni2p peaks from NiSe2/NF(Ox)and NiSe/NF is clearly presented,respectively. For both of the two samples,the peaks at872.9and855.4eV correspond to Ni2+[28,29]which is regarded as one kind of unusual valence states Ni playing important roles in improving OER catalytic performance[30].However,Ni3+centered at 874.4and856.5eV[29]derived from surface oxidation may be inactive for OER owing to the high valence states and difﬁculties in further oxidation to active sites.Therefore,the higher proportion of Ni2+in NiSe2/NF(Ox)may predict a better OER performance.In fact,for the two samples,the ratio of Ni2+to Ni3+ can be elucidated by calculations of Ni2p peak area with a result of5.7:1in NiSe2/NF(Ox)and3.5:1in NiSe/NF,which implies the better electrocatalytic activity of NiSe2/NF(Ox)for OER. Meanwhile,the peaks at852.8and870.2eV belong to metallic Ni from NF substrate[28].Fig.2e and f show the Se3d region where the splitting peaks of3d3/2and3d5/2representsÀ2valence of Se,and the relative lower and broad peak near58.6eV indicates the surface oxidation state of Se species[31].Finally,XPS spectra for as-prepared NiSe2/NF(Ox)and NiSe/NF also reveal the about 1:2and1:1Ni:Se ratio corresponding with the crystal phase analysis in XRD.Fig.3presents SEM images of the bare NF and NF(Ox).In Fig.3a, the macroscopic3D skeleton of bare NF can be observed.And the smooth surface with no impurities forms the substrate of anode electrode material(in Fig.3b).The unique3D structure and high surface area of NF are advantages for ideal substrate.Fig.3c shows that b-Ni(OH)2ﬁlm homogeneously covers on the surface of3D NF after oxidation pretreatment.Under higher magniﬁcation(as shown in Fig.3d),b-Ni(OH)2ﬁlm is composed of manynanosheets Fig.3.Low(a)and high(b)magniﬁcation SEM images of the bare NF;low(c)and high(d)magniﬁcation SEM images of NF(Ox).80X.Li et al./Electrochimica Acta205(2016)77–84with a partly cross-linked structure grown on the surface of 3D NF [26].Fig.4shows SEM images of different morphologies of NiSe/NF and NiSe 2/NF (Ox).Fig.4a exhibits a network-like ﬁlm of NiSe grown on the 3D NF.Under higher magni ﬁcation,the network-like ﬁlm is composed of many nanorods and a few nanowires (as shown in Fig.4b and c).With further TEM analysis of NiSe scratched off NiSe/NF samples (see in Fig.S1),it can be clearly observed that the diameter of NiSe nanorods is about 70nm and the average length is around 1m m.The small amount of nanowires with the length ranging from 2to 4m m may be the intermediates during the growth process of nanorods.Fig.4d and e indicate that a homogeneous ﬁlm entirely covers on the skeleton of NF (Ox).There look like many pyramids on the surface of the ﬁlm under higher magni ﬁcation (as shown in Fig.4f).The morphology of distributed NiSe 2pyramids on NiSe 2/NF (Ox)is evidently different from the morphology of NiSe/NF nanorods.The pyramid structures of NiSe 2may belong to octahedron con ﬁguration of cubic system consistent with XRD results.Therefore,the oxidation pretreatment of NF is responsible for the different structure and morphologybetween NiSe 2pyramids and NiSe nanorods.To clearly observe the growth of NiSe 2pyramids,SEM images of NiSe 2/NF (Ox)-4h and NiSe 2/NF (Ox)-8h at different times during the growth of NiSe 2are further revealed in Fig.5.It can be seen that NiSe 2pyramids increases gradually and distributes densely with the prolonging of selenization process.Meanwhile,a large amount of irregularly little cubes,which can be assigned to the intermediates of standard NiSe 2pyramids,emerge on NiSe 2/NF (Ox)-8h (in Fig.5d),however,there still exists large area of exposed Ni (Ox)surface suggesting the incomplete of selenization process for 8h.For NiSe 2growing on NiSe 2/NF (Ox)after selenization for 12h (in Fig.4f),the thick layer of densely distributed NiSe 2pyramids and intermediates has already formed.Accordingly,that some parts of surface morphol-ogy do not look exactly standard pyramid structures may owe to the large amount of NiSe 2pyramids or their intermediates with different sizes strongly overlaying each other.The growth mechanisms of the different types of Ni x Se y grown on bare NF or NF (Ox)could be explained by the following putative chemical equations.2NaHSe +O 2!2Se #+2NaOH(1)Fig.4.Low (a)and high (b and c)magni ﬁcation SEM images of NiSe 2/NF (Ox);low (d)and high (e and f)magni ﬁcation SEM images of NiSe/NF.X.Li et al./Electrochimica Acta 205(2016)77–84816Ni(OH)2+13Se +Se 2À!6NiSe 2#+2SeO 3À+6H 2O(2)Ni ðOH Þ2!Ni2þþ2OH Àð3À1Þ3Se þ6OH À!2Se 2ÀþSeO 3Àþ3H 2Oð3À2ÞNi +2CH 3CH 2OH +Se 2À!NiSe #+2CH 3CH 2O À+H 2"(4)The prepared NaHSe solution tends to be easily oxidized into amorphous red Se even under N 2atmosphere (Equation (1)),which facilitates the growth of NiSe 2described as Equation (2).The detailed growth mechanisms are as follows:(1)The b -Ni(OH)2layer on NF (Ox)gradually decomposes into Ni 2+and OH À(Equation (3-1))with increasing temperature of solvothermal reaction,which creates a relative much stronger basic environ-ment and a large quantity of Ni 2+;(2)The disproportionation of Se with excess OH Àcan provide more Se 2À(Equation (3-2))which is the key to synthesize NiSe 2.Therefore,the high density of Se 2Àaggregating around Ni 2+af ﬁliates the formation of NiSe 2crystal nucleus whose octahedron skeleton are composed of 6Se atoms located at the corners with 1Ni atom in the central position (Fig.1c).For the growth process of NiSe/NF,there ’s no existing Ni 2+participating the reaction with Se 2Àowing to the absence of Ni (OH)2.Besides,the alkalinity of solution is not strong enough to promote more Se 2Àby the disproportionation of Se.Therefore,only NiSe,whose formation needs less Se 2À,emerges instead of NiSe 2(Equation (4)).Summing up the above growth mechanisms of NiSe 2and NiSe,the oxidation pretreatment of NF plays a dominant role in the transformation of crystal phases.The ir-corrected electrocatalytic performances for OER based on projected geometry area of NiSe 2/NF (Ox),NiSe/NF,NF (Ox)and bare NF electrodes are shown in Fig.6.Fig.6a presents their polarization curves on the reversible hydrogen electrode (RHE)scale in 1M KOH electrolyte.As is evident from the enhancement of current density and the earliest onset potential (1.54V vs.RHE)of OER,NiSe 2/NF (Ox)demonstrates much superior electro-catalytic activity than NiSe/NF,NF (Ox)and bare NF samples.However,the obvious oxidation peaks at around 1.4V (vs.RHE)are observed for NiSe 2/NF (Ox),NiSe/NF and NF (Ox),which can be assigned to the surface reactions from Ni 2+to active Ni 3+species (Equation (5),(6)and (7))[32–35].The obtained active Ni 3+species including NiSe 2(OH),NiSe(OH)and NiO(OH)have been speculated to be the real active sites for OER [30],[32],however,different types of transformations from Ni 2+to active sites may differ signi ﬁcantly in their ease of reactions leading to the different amount of active sites.Such distinction may be resulted from the disparities of unique crystal structures between NiSe 2and NiSe.As shown in Fig.1c,the central Ni atom is octahedrally bonded to adjacent 6Se atoms composing a pyrite-type crystal structure in NiSe 2,whereas 1Ni atom is attached to only 3Se atoms in NiSe (in Fig.1b).The much higher density of Se atoms in NiSe 2compared with NiSe means the stronger electronegativity atmosphere.Thus,the shell electrons of Ni 2+in NiSe 2can be more easily attracted by Se atoms to facilitate the oxidation reaction into more Ni 3+as active sites for OER.Accordingly,NiSe 2demonstrates enhanced activity for OER during anodic polariza-tion compared with NiSe.As for Ni (Ox),the inferior OER performance may owe much to the smaller amount of active sites generated by ultrathin b -Ni(OH)2nanosheets on Ni (Ox)as shown in SEM images of Fig.3d.NiSe 2+OH À!NiSe 2(OH)+e À(5)Fig.5.Low (a)and high (b)magni ﬁcation SEM images of NiSe 2/NF (Ox)–4h prepared by solvothermal reaction for 4h;low (c)and high (d)magni ﬁcation SEM images of NiSe 2/NF (Ox)–8h prepared by solvothermal reaction for 8h.82X.Li et al./Electrochimica Acta 205(2016)77–84NiSe +OH À!NiSe(OH)+e À(6)Ni(OH)2+OH À!NiO(OH)+H 2O +eÀ(7)Fig.6b shows the Tafel plots of NiSe 2/NF (Ox),NiSe/NF,NF (Ox)and bare NF.It can be observed that Tafel slope has been signi ﬁcantly reduced from 153mV dec À1of NiSe/NF to 96mV dec À1of NiSe 2/NF (Ox),which indicates a higher OER rate for NiSe 2/NF (Ox)and is in agreement with the polarization curves.As shown in Fig.6c,the electrochemical impedances spectra (EIS)of NiSe 2/NF (Ox),NiSe/NF and NF (Ox)under 0.45V (vs.SCE)are compared and the mesured EIS data have been ﬁtted and analyzed using Zview software.It can be seen that the simulated results are in good agreement with the experimental data.The insert equivalent circuit obtained from ﬁtting spectra is further attached with the related electrochemical parameters of equivalent circuit:solution resistance (R s ),charge-transfer resistance (R ct )and constant phaseelement (CPE).Estimates of these circuit parameters are presented in Table ing CPE to replace capacitance is due to the high degree of roughness and inhomogeneity of the electrode and it hardly exhibits pure capacitance in real electrochemical process [36,37].In comparison of the simulated R ct of samples,NiSe 2/NF (Ox)with smallest R ct value means a best overall catalytic activity according to that R ct is proportional to the number of active sites and the site activity on the electrode material [38].The analysis of EIS data reinforce the highest OER activity of NiSe 2/NF (Ox)as con ﬁrmed in LSV results.To ﬁnally investigate the stability of synthesized NiSe 2/NF (Ox),500cycles of CV tests are conducted with a satisfying result as shown in Fig.6d.The current density and onset potential of polarization curve remain almost unchanged after stability tests.The enlargement of oxidation peak may be attributed to the arrival to a steady state with a certain content of active Ni 3+on the electrode as CV measurements continues.The signi ﬁcantly enhanced activity for OER can be ascribed to the composition and unique crystal structure of NiSe 2/NF (Ox).On the one hand,the higher proportion of Ni 2+in NiSe 2/NF (Ox)compared with NiSe/NF as shown in XPS spectra of Ni 2p region (Fig.2c and d)would provide more active Ni 3+,representing the better activity as expected.On the other hand,the octahedral structure of NiSe 2accelerates the oxidation tendency of Ni 2+into Ni 3+which can enhance the amount of active sites improving the OER performance of NiSe 2/NF (Ox)as discussed above.In summary,the higher Ni 2+proportion and octahedralstructureFig.6.Electrocatalytic performances for OER of NiSe 2/NF (Ox),NiSe/NF,NF (Ox)and NF.(a)Polarization curves based on RHE in 1M KOH electrolyte;(b)Tafel plots extracted from (a);(c)EIS plots of NiSe 2/NF (Ox),NiSe/NF,NF (Ox)at 0.45V (vs.SCE)from 105Hz to 0.1Hz;(d)Polarization curves of NiSe 2/NF (Ox)before and after 500cycles used for stability tests.Table 1Simulated parameters of the elements in equivalent circuits for OER of NiSe 2/NF (Ox),NiSe/NF and NF (Ox)at 0.45V (vs.SCE)in O 2saturated 1.0M KOH.R s (V cm 2)R ct (V cm 2)CPE-T (F cm À2)CPE-P (F cm À2)NiSe 2/NF (Ox) 2.154 6.4840.3370.417NiSe/NF 2.24618.3260.2940.428NF (Ox)3.762146.0200.0230.481X.Li et al./Electrochimica Acta 205(2016)77–8483of NiSe2could synergistically increase the amount of active Ni3+ and lead to a signiﬁcantly enhanced OER performance.4.ConclusionThe oxidized NF was utilized to in situ prepare novel NiSe2 pyramid structures by a facile solvothermal selenization.The ultrathin b-Ni(OH)2nanosheets grown on NF after oxidation pretreatment may be responsible for the formation of NiSe2 pyramids rather than NiSe nanorods.The electrochemical meas-urements for OER activity demonstrate that NiSe2/NF(Ox)has the enhanced electrocatalytic activity including the smaller over-potential,Tafel slope and charge-transfer resistance in comparison with NiSe/NF,which may be due to the high content of Ni2+and inherently octahedral structure of NiSe2.Therefore,designing novel nanostructures based on oxidized NF may provide a choice for preparing OER eletrocatalysts with excellent performances.AcknowledgementsThis work isﬁnancially supported by the National Natural Science Foundation of China(U1162203and21106185)and the Fundamental Research Funds for the Central Universities (15CX05031A).Appendix A.Supplementary dataSupplementary data associated with this article can be found,in the online version,at /10.1016/j. electacta.2016.04.108.References[1]D.G.Vlachos,S.Caratzoulas,The roles of catalysis and reaction engineering inovercoming the energy and the environment 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铝表面前处理及化学沉积镍初期行为

铝及其合金密度小、比强度高，常被用于制造管道、汽车化油器等．但其硬度低、耐磨和耐腐蚀性
Ｒｅｃｅｉｖｅｄ：Ｏｃｔｏｂｅｒ８，２０１１：Ｒｅｖｉｓｅｄ：Ｎｏｖｅｍｂｅｒ１６，２０１１；ＰｕｂｌｉｓｈｅｄｏｎＷｅｂ：Ｄｅｃｅｍｂｅｒ１，２０１１．
（ＯＣＰ）ａｓａｆｕｎｃｔｉｏｎｏｆｔｉｍｅ（ＥｏｃＰ—ｆ）．Ｓｃａｎｎｉｎｇｅｌｅｃｔｒｏｎｍｉｃｒｏｓｃｏｐｙ（ＳＥＭ）ｗａｓｕｓｅｄｔｏｏｂｓｅｒｖｅｔｈｅｓｕｒｆａｃｅ
ｍｏｒｐｈｏｌｏｇｙｏｆｔｈｅｐｒｅｔｒｅａｔｅｄｓｐｅｃｉｍｅｎｓ．Ｄｕｒｉｎｇｔｈｅｉｎｉｔｉａｌｓｔａｇｅｓｏｆｔｈｅｅｌｅｃｔｒｏｌｅｓｓｎｉｃｋｅｌｄｅｐｏｓｉｔｉｏｎ，ａｌｌｐｒｅｔｒｅａｔｅｄａｎｄｕｎ．ｐｒｅｔｒｅａｔｅｄａｌｕｍｉｎｕｍｓｕｂｓｔｒａｔｅｓｅｘｐｅｒｉｅｎｃｅｄｒｅｍｏｖａＩｏｆｔｈｅｏｘｉｄｅｆ¨ｍ，ａｃｔｉｖａｔｉｏｎ，ｍｉｘｅｄｃｏｎｔｒｏｌａｎｄｅｌｅｃｔｒｏｌｅｓｓｎｉｃｋｅＩｄｅｐｏｓｉｔｉｏｎ．Ａｆｔｅｒｎｉｃｋｅｌｉｍｍｅｒｓｉｏｎａｎｄｅｌｅｃｔｒｏｌｅｓｓｎｉｃｋｅｌｐｒｅ－ｐｌａｔｉｎｇ．ｆｉｎｅｎｉｃｋｅＩｐａｒｔｉｃｌｅｓｗｅｒｅａＲａｃｈｅｄｔｏｔｈｅｓｕｒｆａｃｅｏｆｔｈｅａｌｕｍｉｎｕｍ．ＯｕｒｅｘｐｅｒｉｍｅｎｔａＩｒｅｓｕｌｔｓ．ｉｎｃｌｕｄｉｎｇＥｏｃＰ－ｔａｎｄＳＥＭ．ｉｎｄｉｃａｔｅｔｈａｔｅｌｅｃｔｒｏｌｅｓｓｎｉｃｋｅｌｐｌａｔｉｎｇｉｎａｗｅａｋａｃｉｄｉｃｂａｔｈｗａｓｓｕｃｃｅｓｓｆｕｌｌｙａｃｃｏｍｐｌｉｓｈｅｄｏｎｔｈｅａＩｕｍｉｎｕｍｐｒｅｔｒｅａｔｅｄｗｉｔｈａｄｏｕｂｌｅｔｒｅａｔｍｅｎｔｏｆｅｌｅｃｔｒｏｌｅｓｓｎｉｃｋｅＩｐｒｅ—ｐｌａｔｉｎｇｉｎａｎａｌｋａｌｉｎｅｎｉｃｋｅＩｓｏｌｕｔｉｏｎｃｏｎｔａｉｎｉｎｇａｃｏｍｐｌｅｘｉｎｇａｇｅｎｔａｎｄａｒｅｄｕｃｔａｎｔ．ＴｈｅｎｉｃｋｅＩｃｏａｔｉｎｇｏｂｔａｉｎｅｄａｄｈｅｒｅｄｔｏｔｈｅａｌｕｍｉｎｕｍｓｕｂｓｔｒａｔｅ，ｈａｄａｇｒａｎｕｌａｒａｐｐｅａｒａｎｃｅａｎｄａｎａｍｏｒｐｈｏｕｓｓｔｒｕｃｔｕｒｅ．

Atg8, a ubiquitin-like protein required for autophagosome formation

Atg8,a Ubiquitin-like Protein Required for Autophagosome Formation,Mediates Membrane Tethering and HemifusionHitoshi Nakatogawa,1,2Yoshinobu Ichimura,1,3and Yoshinori Ohsumi1,*1Department of Cell Biology,National Institute for Basic Biology,Okazaki444-8585,Japan2PRESTO,Japan Science and Technology Agency,Saitama332-0012,Japan3Present address:Department of Biochemistry,Juntendo University School of Medicine,Bunkyo-ku,Tokyo113-8421,Japan. *Correspondence:yohsumi@nibb.ac.jpDOI10.1016/j.cell.2007.05.021SUMMARYAutophagy involves de novo formation of double membrane-bound structures called autophagosomes,which engulf material to be degraded in lytic compartments.Atg8is a ubiq-uitin-like protein required for this process in Saccharomyces cerevisiae that can be conju-gated to the lipid phosphatidylethanolamine by a ubiquitin-like system.Here,we show using an in vitro system that Atg8mediates the teth-ering and hemifusion of membranes,which are evoked by the lipidation of the protein and reversibly modulated by the deconjugation enzyme Atg4.Mutational analyses suggest that membrane tethering and hemifusion ob-served in vitro represent an authentic function of Atg8in autophagosome formation in vivo.In addition,electron microscopic analyses indicate that these functions of Atg8are in-volved in the expansion of autophagosomal membranes.Our results provide further insights into the mechanisms underlying the unique membrane dynamics of autophagy and also in-dicate the functional versatility of ubiquitin-like proteins.INTRODUCTIONAutophagy is an evolutionally conserved protein degrada-tion pathway in eukaryotes that is essential for cell survival under nutrient-limiting conditions(Levine and Klionsky, 2004).In addition,recent studies have revealed a wide variety of physiological roles for autophagy(Mizushima, 2005)as well as its relevance to diseases(Cuervo,2004). During autophagy,cup-shaped,single membrane-bound structures called isolation membranes appear and expand,which results in the sequestration of a portion of the cytosol and often organelles.Eventually,spherical, double membrane-bound structures called autophago-somes are formed(Baba et al.,1994),and then delivered to and fused with lysosomes or vacuoles to allow their contents to be degraded.Studies in S.cerevisiae have identiﬁed18ATG genes required for autophagosome formation,most of which are also found in higher eukary-otes(Levine and Klionsky,2004).Recent studies have shown that Atg proteins constituteﬁve functional groups: (i)the Atg1protein kinase complex,(ii)the Atg14-contain-ing phosphatidylinositol-3kinase complex,(iii)the Atg12-Atg5protein conjugation system,(iv)the Atg8lipid con-jugation system,and(v)the Atg9membrane protein recycling system(Yorimitsu and Klionsky,2005).The mechanisms by which these units act collaboratively with lipid molecules to form the autophagosomes,how-ever,are still poorly understood.Atg8is one of two ubiquitin-like proteins required for autophagosome formation(Mizushima et al.,1998;Ichi-mura et al.,2000).Because it has been shown that Atg8 and its homologs(LC3in mammals)localize on the isola-tion membranes and the autophagosomes,these proteins have been used in various studies as reliable markers for the induction and progression of autophagy(Kirisako et al.,1999;Kabeya et al.,2000;Yoshimoto et al.,2004). In S.cerevisiae,Atg8is synthesized with an arginine resi-due at the C terminus,which is immediately removed by the cysteine protease Atg4(Kirisako et al.,2000).The resulting Atg8G116protein has a glycine residue at the new C terminus and can serve as substrate in a ubiqui-tin-like conjugation reaction catalyzed by Atg7and Atg3, which correspond to the E1and E2enzymes of the ubiq-uitination system,respectively(Ichimura et al.,2000). Remarkably,unlike other ubiquitin-like conjugation sys-tems,Atg8is conjugated to the lipid phosphatidylethanol-amine(PE),thereby Atg8is anchored to membranes (Ichimura et al.,2000;Kirisako et al.,2000).Immunoelec-tron microscopy revealed that Atg8,probably as a PE-conjugated form(Atg8-PE),is predominantly localized on the isolation membranes rather than on the complete autophagosomes(Kirisako et al.,1999),suggesting that Atg8-PE plays a pivotal role in the process of autophago-some formation.The precise function of Atg8-PE,how-ever,has remained unknown.The conjugation of Atg8to PE is reversible;Atg4also functions as a deconjugation enzyme,resulting in the Cell130,165–178,July13,2007ª2007Elsevier Inc.165release of Atg8from the membrane(Kirisako et al.,2000). This reaction is thought to be important for the regulation of the function of Atg8and/or the recycling of Atg8after it has fulﬁlled its role in autophagosome formation.We reconstituted the Atg8-PE conjugation reaction in vitro with puriﬁed components(Ichimura et al.,2004). Here,we show using this system that Atg8mediates the tethering and hemifusion of liposomes in response to the conjugation with PE.These phenomena observed in vitro are suggested to reﬂect a bonaﬁde in vivo function of Atg8 in the expansion of the isolation membrane.Based on mutational analyses and structural information,the mech-anisms of Atg8-mediated membrane tethering and hemi-fusion as well as its regulation are discussed.This study sheds light on the molecular basis of unconventional membrane dynamics during autophagy,which is gov-erned by the Atg proteins.RESULTSLipidation of Atg8Causes Clustering of LiposomesIn VitroAs reported previously(Ichimura et al.,2004),when puri-ﬁed Atg8G116(hereafter,referred to as Atg8),Atg7,and Atg3were incubated with liposomes containing PE in the presence of ATP,Atg8-PE was efﬁciently formed (Figure1A,lanes1–6).Intriguingly,the reaction mixture became turbid during the incubation(Figure1B),which under a light microscope,was found to be a result of grad-ually forming aggregates(Figure1C).Both the degree of turbidity and the size of the aggregates appeared to corre-late with the amount of Atg8-PE produced in the mixture. Size-distribution analyses using dynamic light scattering (DLS)clearly showed that the aggregates formed in an Atg8-PE dose-dependent manner(Figure1D).These aggregates disappeared when the samples were treated with the detergent CHAPS(Figure1E,+CHAPS).In addi-tion,if a small amount of PE modiﬁed with theﬂuorescent dye7-nitro-2,1,3-benzoxadiazol-4-yl(NBD)was included in the liposome preparation,the aggregates became uniformlyﬂuorescent(Figure1E,NBD-PE).These results suggest that the aggregates generated during the produc-tion of Atg8-PE were clusters of liposomes.When the proteins were denatured with urea,the clus-ters of liposomes dissociated,although Atg8remained conjugated to PE(Figure1E,+urea and Figure1F,lane 2),indicating that the liposomes aggregated due to some function of the Atg8protein rather than an artifact caused by Atg8-PE as the lipid with the extraordinarily large head group.When the aggregates were sedimented by centrifugation,Atg8-PE co-precipitated with the lipo-somes(Figure1G,lane2),whereas Atg7,Atg3,and unconjugated Atg8did not(Figure1G,lane3).The sedimented liposomes containing Atg8-PE remained clustered even if they were brieﬂy sonicated(Figure1H, ppt.).These results suggested that Atg8-PE molecules function to tether together membranes to which they are anchored.Atg8-PE Also Mediates Liposome FusionWe also examined if membrane fusion occurred between the liposomes connected by Atg8-PE.To this end,we took advantage of a well-characterized lipid mixing assay (Struck et al.,1981).This method is based on energy transfer from NBD to lissamine rhodamine B(Rho),each of which is conjugated to PE.Because the amino group of the ethanolamine moiety is modiﬁed with the dyes, these lipids cannot be conjugated with Atg8.If both of the conjugated dyes are present at appropriate concen-trations in the same liposome,theﬂuorescence of NBD is effectively quenched by Rho(Figure2A,compare col-umns1and4).If a‘‘NBD+Rho’’liposome is fused with a‘‘nonlabeled’’liposome,which results in an increase of the average distance between the two dyes on the membrane,the NBDﬂuorescence will be dequenched.A mixture of the nonlabeled and NBD+Rho liposomes were subjected to the conjugation reaction.The resulting liposome clusters were dissociated by proteinase K treat-ment,followed byﬂuorescence measurements.Remark-ably,a signiﬁcant ATP-dependent increase of theﬂuores-cence was observed(ATP is required for the production of Atg8-PE;Figure2B,column6).This increasedﬂuores-cence was not observed with samples of nonlabeled lipo-somes alone,NBD+Rho liposomes alone,or a mixture of nonlabeled liposomes and liposomes containing NBD-PE but not Rho-PE(Figure2B,columns1-3).These results suggest that membrane fusion occurred between the lipo-somes tethered together by Atg8-PE.The increasedﬂuo-rescence was only observed if the reaction mixture was treated with proteinase K(Figure2B,columns4and6). This appeared to be due to the presence of Atg7and/or Atg3rather than Atg8or some effect of the clustering, because the NBDﬂuorescence was not increased by the addition of Atg4(Figure2B,column5),which detached Atg8from the membranes and dissociated the clusters of liposomes(see below).Instead,decreasing the con-centrations of the conjugation enzymes allowed the dequenching of the NBDﬂuorescence to be detected without proteinase K digestion(Figure2B,column7). The fusion of the liposomes was examined with various amounts of Atg8(Figure2C).The level of fusion increased Atg8dose-dependently and reached maximum at2m M (Figure2C).In contrast,a larger amount of Atg8produced an inhibitory effect(data not shown).This suggested that formation of the large aggregates resulted from excessive tethering by Atg8-PE,which no longer lead to fusion. We also carried out time-course experiments to roughly estimate the fusion rate using the lower concentrations of the conjugation enzymes(Figure2D),which eliminated the need for the proteinase K treatment(Figure2B).It should be noted that the incubation time includes the times re-quired for the formation of Atg8-PE and the subsequent tethering and fusion reactions.Under these conditions, the band of Atg8-PE could be seen on an SDS-PAGE gel after a10min incubation,and the reaction was completed within30min(Figure S1in the Supplemental Data available with this article online).It appeared that166Cell130,165–178,July13,2007ª2007Elsevier Inc.Figure1.Membrane Tethering Function of Atg8-PE In Vitro(A–C)Puriﬁed Atg8(10m M),Atg7(1m M),and Atg3(1m M)were incubated with liposomes(350m M lipids)composed of55mol%DOPE,30mol% POPC,and15mol%blPI in the presence(lanes1–6)or absence(lanes7–12)of1mM ATP at30 C for the indicated time periods,followed by urea-SDS-PAGE and CBB-staining(A),measurement of the absorbance at600nm(B),or observation under a light microscope(Nomarski images)(C).(D)Conjugation reactions with the various amounts of Atg8were performed as described in(A).After incubation for60min,the size distribution of the aggregates was examined using DLS measurements.d.nm,apparent diameter(nm).(E and F)The conjugation reactions were carried out as described in(A).They were further incubated at30 C for30min in the presence of either 6M urea or1%CHAPS and were then subjected to microscopy(E)or urea-SDS-PAGE and CBB-staining(F).The reaction was also performed with liposomes containing1mol%NBD-labeled DOPE(thus containing54mol%unlabeled DOPE),followed byﬂuorescence microscopy.Aﬂuo-rescence image with aﬁlter for YFP(NBD-PE,FL)and a Nomarski image(NBD-PE,DIC)are shown.(G and H)Atg8(30m M),Atg7(2m M),and Atg3(2m M)were incubated with liposomes(350m M lipids)consisting of70mol%DOPE and30mol% POPC in the presence of1mM ATP at30 C for45min(total).The mixture was microcentrifuged at15,000rpm for10min to generate the pellet (ppt.)and the supernatant(sup.)fractions.The fractions were brieﬂy sonicated and were analyzed by urea-SDS-PAGE(G)or observed under a light microscope(H).In this experiment,blPI was omitted to prevent Atg7and Atg3from tightly binding to the liposome.We showed that Atg8could also cause hemifusion of liposomes with this lipid composition.Cell130,165–178,July13,2007ª2007Elsevier Inc.167the liposomes began to fuse shortly after the formation of Atg8-PE.The fusion reaction proceeded concurrently with the conjugation reaction and continued for 30min after the completion of the Atg8-PE production (Figure 2D,ﬁlled circles).Small liposomes <100nm in diameter tend to sponta-neously fuse (Chen et al.,2006),and the liposomes we used in the above experiments were 70nm in diameter (Figure 1D).However,we also showed that Atg8-PEcaused a signiﬁcant level of fusion between larger lipo-somes in spite of their stability against spontaneous fusion (Figure S1).Taken together,these results suggest that not only tethering but also fusion of the liposomes is mediated by Atg8-PE.The Atg8-Mediated Membrane Fusion Is Hemifusion Recent in vitro studies on membrane fusion mediated by SNARE proteins and a class of viral proteinsrevealedFigure 2.Membrane Hemifusion Occurs between Liposomes Tethered by Atg8-PE(A and B)Nonlabeled (55mol%DOPE,30mol%POPC,and 15mol%blPI),NBD-labeled (55mol%DOPE,29mol%POPC,15mol%blPI,and 1mol%NBD-DOPE),and NBD+Rho-labeled (55mol%DOPE,27.5mol%POPC,15mol%blPI,1mol%NBD-DOPE,and 1.5mol%Rho-DOPE)liposomes were mixed in the differ-ent combinations and ratios indicated.Their relative intensities of the NBD ﬂuorescence ob-served are shown (the value obtained with a 4:1mixture of the nonlabeled and NBD+Rho lipo-somes was deﬁned as 1)(A).These mixtures of liposomes were incubated with Atg8(4m M),Atg7(0.5or 1.0m M),and Atg3(0.5or 1.0m M)in the presence (ﬁlled columns)or absence (open columns)of 1mM ATP for 60min,and were then treated with 1unit/ml apyrase.The mixtures were further incubated for 30min with the buffer (columns 4and 7),1m M Atg4(columns 5and 8),or 0.2mg/ml proteinase K (columns 1-3,6and 9),followed by measure-ment of the NBD ﬂuorescence.The experi-ments were repeated three times and the average ﬂuorescence values divided by those obtained from the original liposome samples (F/F 0)are presented with error bars for the stan-dard deviations (B).(C)A 4:1mixture of the nonlabeled and NBD+Rho liposomes was incubated with various amounts of Atg8,1.0m M Atg7,and 1.0m M Atg3in the presence (open circles)or absence (ﬁlled circles)of ATP,and the samples were then treated with proteinase K,followed by measuring the NBD ﬂuorescence.(D)The conjugation reactions were performed with the mixed liposomes used for the lipid mixing assay,0.5m M Atg7,and 0.5m M Atg3in the presence or absence of Atg8(4m M)and ATP.After incubation for the indicated time periods,an aliquot of the samples was immediately subjected to the ﬂuorescence measurements.The values that were obtained by subtracting the signals observed in the absence of ATP from those observed in the presence of ATP are presented.(E)The lipid mixing assay was performed with 4m M Atg8,1m M Atg7,and 1m M Atg3in the presence or absence of ATP (white bars in columns 3and 2,respectively)as described in(C).For PEG-induced fusion reactions,the mixed liposomes were incubated at 37C for 30min in the presence or absence of 12.5%PEG 3350(white bars in columns 5and 4,respectively).These samples as well as the original liposomes (column 1)were then incubated with 20mM sodium dithionite on ice for 20min in the presence (black bars)or absence (gray bars)of 0.5%Triton X-100,followed by the NBD ﬂuorescence measurement.168Cell 130,165–178,July 13,2007ª2007Elsevier Inc.that fusion proceeds through an intermediate state called hemifusion,in which outer(contacting)leaﬂets of two apposed lipid bilayers merge,while inner(distal)leaﬂets remain intact(Chernomordik and Kozlov,2005).It was also reported that fusion can be arrested or delayed at the hemifusion state under some conditions.Therefore, we investigated whether the liposome fusion caused by Atg8in vitro was complete fusion(the merger of both inner and outer leaﬂets)or hemifusion(Figure2E).This can be examined using the membrane impermeable reductant sodium dithionite that selectively abolishes theﬂuores-cence of NBD conjugated to the lipid head group in the outer leaﬂet(Meers et al.,2000).Accordingly,when so-dium dithionite was added to the original liposomes,the background level of the NBDﬂuorescence was decreased by about50%,whereas it was hardly detected in the pres-ence of the detergent(Figure2E,column1).Strikingly,the NBDﬂuorescence increased by the Atg8-mediated fusion was totally eliminated by addition of sodium dithionite to the same level as those observed in the original lipo-somes and the reaction mixture incubated without ATP (Figure2F,columns1-3).Whereas,we conﬁrmed that in liposome fusion induced by polyethylene glycol(PEG), which causes complete fusion(Akiyama and Ito,2003), about half of the increasedﬂuorescence was retained af-ter sodium dithionite treatment(Figure2F,columns4and 5).Taken together,membrane fusion mediated by Atg8 in vitro was suggested to be hemifusion.To obtain direct evidence of hemifusion,we analyzed the morphology of liposomes by electron microscopy (Figures3A–3E),in which liposomal membranes were observed as double white lines that correspond to the outer and inner leaﬂets.When the clusters of liposomes formed by Atg8-PE were analyzed,tight junctions between the liposomes were observed(Figures3B and 3C,arrowheads).Consistent with the biochemical results suggesting that complete fusion does not occur,the size of the individual liposomes did not appear to signiﬁcantly increase(compare Figures3A and3B).Instead,hallmarks of hemifusion,trifurcated structures formed by one contin-uous outer leaﬂet and two separate inner leaﬂets,could be observed at the junction between the liposomes(Figures 3C–3E,arrows).These results strongly support our con-clusion that Atg8-PE causes hemifusion of liposomes. Atg8Forms a Multimer in Responseto the Conjugation with PEWe also performed immunoelectron microscopy of the liposomes clustered by Atg8-PE(Figures3F–3I).Intrigu-ingly,Atg8-PE tended to be enriched at the junction be-tween the liposomes(Figures3G–3J).While,if the mixture incubated without ATP was similarly analyzed,the signal was rarely observed on the liposome(Figure3F;the gold particles observed should represent unconjugated Atg8 adsorbed onto the grid).These results indicate that Atg8-PE is directly involved in the tethering and hemifu-sion of liposomes.We observed that‘‘naked’’liposomes do not associate with liposomes carrying Atg8-PE(data not shown), suggesting that tethering should be achieved due to interactions between Atg8-PE molecules on different membranes.We therefore examined the intermolecular interaction of Atg8-PE by crosslinking experiments(Fig-ure4).The reaction mixture containing Atg8-PE or unconjugated Atg8was incubated with the lysine-to-lysine reactive crosslinker DSS.We found that a crosslink adduct with a molecular weight of 24kDa on a SDS-PAGE gel speciﬁcally appeared in the sample containing Atg8-PE(Figure4A,lane5).Considering the molecular weights of the proteins included,this adduct should represent an Atg8-PE homodimer.Immunoblotting anal-yses with anti-Atg8revealed that two additional crosslink adducts of about37and100kDa were also speciﬁcally produced in the Atg8-PE-containing sample(Figure4B, lanes2–4and Figure S2).These products were immuno-stained neither with anti-Atg7nor anti-Atg3(data not shown),suggesting that they represent a trimer and a larger multimer of Atg8-PE,respectively,and thus that Atg8multimerizes in response to PE conjugation. We also showed that this multimerization correlates with the membrane tethering ability of Atg8(see below), indicating that interactions between Atg8-PE molecules on different membranes are responsible for the tethering of the membranes.The Membrane-Tethering and HemifusionFunctions of Atg8Are Modulatedby the Deconjugation Enzyme Atg4Our results suggest that the membrane-tethering and hemifusion functions of Atg8are evoked by the conjuga-tion with PE,whereas Atg4functions as a deconjugase that cleaves the linkage between Atg8and PE(Kirisako et al.,2000).We reconstituted this reaction in vitro.After producing Atg8-PE using the conjugation reaction,the re-action was terminated by adding apyrase to deplete the remaining ATP.When puriﬁed Atg4was then added, Atg8-PE was rapidly and almost completely deconjugated (Figure4C,lanes1-6).In contrast,when the Atg4was pretreated with the cysteine protease inhibitor N-ethylma-leimide(NEM),the deconjugation reaction did not occur (Figure4C,lanes7–12).These results clearly show that Atg4is sufﬁcient for the deconjugation of Atg8-PE.Upon deconjugation,the liposome aggregates immediately dissociated(Figure4D).In addition,we found that multi-merization of Atg8is also reversible;the crosslink adducts corresponding to the Atg8-PE dimer(Figure4A,lane6)as well as the trimer and the multimer(data not shown)were hardly formed when DSS was added after the deconjuga-tion reaction.We also showed that the presence of Atg4in the conjugation reaction retarded the accumulation of Atg8-PE and accordingly interfered with the tethering and hemifusion of the liposomes(data not shown).It was indicated that membrane tethering and hemifusion by Atg8can be regulated by the balance between the conjugation and deconjugation reactions.Cell130,165–178,July13,2007ª2007Elsevier Inc.169Identiﬁcation of Mutations that Impair the Postconjugational Function of Atg8In VivoIf the function of Atg8-PE we observed in vitro was involved in autophagosome formation in vivo,Atg8mutants deﬁ-cient for this function should result in defective autophagy.To examine this idea,we performed structure-based and systematic mutational analyses of Atg8(Figure 5).The structures of mammalian homologs revealed that Atg8family proteins consist of two domains:an N-terminal heli-cal domain (NHD)and a C-terminal ubiquitin-like domain (ULD)(Paz et al.,2000;Coyle et al.,2002;Sugawara et al.,2004;Figures 5E–5H).Among the highly conserved residues in the ULD,we selected those with side chains that were exposed on the domain surface (Figure 5A),and individually replaced them with alanine,except that serine was substituted for Ala75.Consequently,we didnot mutate residues suggested to be important for interac-tions with the conjugation enzymes,because these resi-dues are conserved only for their hydrophobic nature (Sugawara et al.,2004).The Atg8variants were expressed from centromeric plasmids in D atg8yeast cells,and their autophagic activities were biochemically assessed (see Supplemental Experimental Procedures ).In nutrient-rich media,the autophagic activity was low in all of the mutant cells as well as in the wild-type cells (data not shown).In contrast,in nitrogen starvation conditions,which strongly induced autophagy,a number of mutants were found to have defective autophagic phenotypes (Figure 5B).Ala-nine replacement of seven residues,Ile32,Lys48,Leu50,Arg65,Asp102,Phe104,and Tyr106,signiﬁcantly impaired the autophagic activity to 30%–60%of that of the wild-type (Figure 5B).Immunoblotting analyses showedthatFigure 3.Electron Microscopic Analyses of the Liposomes Tethered and Hemi-fused by Atg8-PEConjugation reactions were performed with 4m M Atg8,1m M Atg7,and 1m M Atg3in the presence (B–E and G–I)or absence (A and F)of ATP for 60min and subjected to phospho-tungstic acid-staining and electron micros-copy (A–E).The junctions between the lipo-somes and the structures suggested to represent hemifusion are indicated with arrow-heads and arrows,respectively.The same samples were also subjected to immunostain-ing using puriﬁed anti-Atg8-IN-13and anti-rab-bit IgG conjugated with 5nm gold particles,fol-lowed by phosphotungstic acid-staining and electron microscopic observation (F–I).To as-sess the enrichment of Atg8-PE at the junction of the liposomes (J),images of two contacting liposomes as shown in G and H were randomly picked up (n =41).The lengths of contacting (CR)and noncontacting regions (non-CR)of the liposomal membranes were measured (white bars),thereby the number of gold parti-cles on each region (gray bars)was divided,in which the length of the contacting region was doubled,to calculate the linear density (black bars).The average values are presented with error bars for the standard deviations.170Cell 130,165–178,July 13,2007ª2007Elsevier Inc.a substantial amount of each of the Atg8mutant proteins accumulated in the cells (Figure 5D),although there were some differences in their mobilities in SDS-PAGE analysis;for instance the PE-conjugated and unconjugated forms of the D102A mutant exhibited almost the same mobility.None of the mutations signiﬁcantly affected the formation of Atg8-PE (Figure 5D),suggesting that the mutations impaired a function of Atg8that was exerted after the conjugation with PE.Notably,these mutants accumulated different levels of unconjugated Atg8under the starvation conditions (Figure 5D,starvation),which allowed us to classify them into three groups.For the class I mutants K48A and L50A,the levels of the unconjugated forms were similar to that of the wild-type (Figure 5D,denoted in purple).On the other hand,compared to the wild-type,lower levels of the unconjugated forms were detected in the class II mutants I32A,D102A,F104A and Y106A (Figure 5D,denoted in red),whereas a larger amount of the unconju-gated class III mutant R65A accumulated (Figure 5D,denoted in orange).We then mapped the mutated resi-dues onto the three-dimensional structure of LC3(Suga-wara et al.,2004),which revealed that class of the mutant corresponded to the location of the mutation.All the class II residues were clustered in a speciﬁc region on the ULD (hereafter,referred to as the class II region),and the two neighboring class I residues were located close to the class II region (Figure 5E).In contrast,the class III residue was located away from the other mutated residues (Fig-ures 5G and 5H).The NHD of Atg8contains two helices:a 1and a 2(Figure 5A).We constructed two mutants,one with a dele-tion of a 1(D N8)and a second bearing deletions of both helices (D N24).It was shown that the NHD is involved in autophagy partially but signiﬁcantly;the D N8and D N24mutations decreased the autophagic activity by about 30and 40%,respectively (Figure 5C).We also showed that the deletions did not affect the stability of the proteins or the formation of the PE conjugates (Figure S3).Effects of the Atg8Mutations on the Membrane-Tethering FunctionWe next examined whether the mutations affected the liposome-clustering ability of Atg8in vitro (Figure 6).Figure 4.The Membrane-Tethering Function and Multimerization of Atg8Are Reversibly Regulated in Response to Conjugation with PE(A)Conjugation reactions were performed as described in Figure 3in the presence (lanes 2,3,5,and 6)or absence (lanes 1and 4)of ATP.They were mixed with 1unit/ml apyrase,and then incubated with (lanes 3and 6)or with-out (lanes 1,2,4,and 5)puriﬁed Atg4(0.5m M)at 30 C for 30min.These samples were further incubated with (lanes 4–6)or without (lanes 1–3)100m M DSS for 30min,and then analyzed by urea-SDS-PAGE and CBB-staining.(B)The reaction mixture including ATP was in-cubated with different concentrations of DSS as indicated,followed by urea-SDS-PAGE and immunoblotting with anti-Atg8-IN13.We also identiﬁed a crosslink product that reacted with anti-Atg3(Atg8xAtg3).(C and D)The conjugation reactions performed as described in Figure 1A were mixed with 1unit/ml apyrase.Atg4(0.5m M)pretreated with (lanes 7–12)or without (lanes 1–6)10mM NEM was then added,and the samples were incubated for the indicated time periods and subjected to urea-SDS-PAGE and CBB-stain-ing (C).The same samples were also observed under a light microscope (D).Cell 130,165–178,July 13,2007ª2007Elsevier Inc.171。

Inhibition_of_Direct_Electrolytic_Ammonia_Oxidation_Due_to_a_Change_in_Local_pH1

Inhibition of Direct Electrolytic Ammonia Oxidation Due to a Change in Local pHHanspeter Zöllig,Eberhard Morgenroth,Kai M.Udert *Eawag,Swiss Federal Institute of Aquatic Science and Technology,Überlandstrasse 133,8600Dübendorf,SwitzerlandA R T I C L E I N F O Article history:Received 31January 2015Received in revised form 17February 2015Accepted 18February 2015Available online 9March 2015Keywords:Iridium dioxide low alkalinity water treatmentNernstian diffusion layer acid-base equilibriumA B S T R A C TElectrochemical ammonia oxidation has gained a lot of attention recently as an ef ﬁcient method for ammonia removal from wastewater,for the use in ammonia-based fuel cells and the production of high purity hydrogen.Thermally decomposed iridium oxide ﬁlms (TDIROF)have been shown to be catalytically active for direct ammonia oxidation in aqueous solutions if NH 3is present.However,the process was reported to be rapidly inhibited on TDIROF.Herein,we show that this fast inhibition of direct ammonia oxidation does not result from surface poisoning by adsorbed elemental nitrogen (N ads ).Instead,we propose that direct ammonia oxidation and oxygen evolution can lead to a drop of the local pH at the electrode resulting in a low availability of the actual reactant,NH 3.The hypothesis was tested with cyclic voltammetry (CV)experiments on stagnant and rotating disk electrodes (RDE).The CV experiments on the stagnant electrode revealed that the decrease of the ammonia oxidation peaks was considerably reduced by introducing an idle phase at open circuit potential between subsequent scans.Furthermore,the polarization of the TDIROF electrode into the hydrogen evolution region (HER)resulted in increased ammonia oxidation peaks in the following anodic scans which can be explained with an increased local pH after the consumption of protons in the HER.On the RDE,the ammonia oxidation peaks did not decrease in immediately consecutive scans.These ﬁndings would not be expected if surface poisoning was responsible for the fast inhibition but they are in good agreement with the proposed mechanism of pH induced limitation by the reactant,NH 3.The plausibility of the mechanism was also supported by our numerical simulations of the processes in the Nernstian diffusion layer.The knowledge about this inhibition mechanism of direct ammonia oxidation is especially important for the design of electrochemical cells for wastewater treatment.The mechanism is not only valid for TDIROF but also for other electrodes because it is independent of the electrode material.ã2015The Authors.Published by Elsevier Ltd.This is an open access article under the CC BY license(/licenses/by/4.0/).1.IntroductionDirect ammonia oxidation at catalytically active surfaces can be used for the electrolytic removal of ammonia from wastewater [1,2].Additionally,the process was suggested for the use in fuel cells where ammonia acts as a substitute for hydrogen [3]and for the production of high purity hydrogen in ammonia electrolyzers [4].In contrast to indirect oxidation with active chlorine species,which is mostly employed for wastewater treatment,direct ammonia oxidation does not produce chlorinated by-products such as chlorate,perchlorate or organic chlorinated substances.Furthermore,direct oxidation usually proceeds at lower anode potentials than chlorine formation.Consequently,a high current ef ﬁciency and a lower speci ﬁc energy demand can be achievedmaking direct ammonia oxidation attractive for wastewater treatment.Direct ammonia oxidation was shown to be technically feasible on isostatically pressed ﬁne grain graphite without concomitant chlorine formation [5].However,the ammonia removal rate was low in real stored urine (2.9Æ0.3gN Ám À2Ád À1)and mineralization of the graphite electrode occurred as a side reaction.Although the mineralization was slow,the graphite electrode has to be considered a consumable.Corrosion problems were also reported with Ni/Ni(OH)2anodes [6].In order to reduce maintenance and material consumption,it would be desirable to ﬁnd more stable electrode materials that are suitable for direct ammonia oxidation.The catalytic activity for direct ammonia oxidation was demonstrated for thermally decomposed iridium oxide ﬁlms (TDIROF,[7])or boron-doped diamond electrodes (BDD,[8]).Both electrodes are stable when they are used as anodes.TDIROF electrodes further have the advantage that they are easy to fabricate and that they have a comparatively low overpotential for*Corresponding author.Tel.:+41587655360;fax:+41587655802.E-mail address:kai.udert@eawag.ch (K.M.Udert)./10.1016/j.electacta.2015.02.1620013-4686/ã2015The Authors.Published by Elsevier Ltd.This is an open access article under the CC BY license (/licenses/by/4.0/).Electrochimica Acta 165(2015)348–355Contents lists available at ScienceDirectElectrochimica Actaj o u rn a l h o m e p a g e :w w w.e l s e v i e r.c o m /l o c a t e /e l e c t a c tadirect ammonia oxidation(Table1).The low overpotential eventually leads to a high selectivity towards direct ammonia oxidation and to low speciﬁc energy requirements.However,the costs for the precious metal iridium are a drawback of this electrode.Kapałka et al.[7]found that ammonia oxidation peaks of consecutive cyclic voltammograms decreased dramatically on TDIROF if the lower return potential was above the hydrogen evolution region(HER).The authors interpreted these results as an electrode deactivation through surface poisoning by adsorbed intermediate nitrogen species(NH2,ads,NH ads,N ads)formed during the direct ammonia oxidation process initially proposed by Gerischer and Mauerer[9]for platinum(Pt,Eqs.(1)–(5)).NH3ðaqÞÐNH3;ads(1) NH3;adsÐNH2;adsþHþþeÀ(2) NH2;adsÐNH adsþHþþeÀ(3) NH x;adsþNH y;adsÐN2þðxþyÞHþþðxþyÞeÀ(4) NH adsÐNH adsþHþþeÀ(5) where x,y=1or2.This interpretation is often used to explain the decreasing activity of electrodes during direct ammonia oxidation in aqueous media[10].It is mainly based on theﬁndings of de Vooys et al.[11] who identiﬁed N ads as an electrode poison on transition metal electrodes(such as Ru,Rh,Pd)and who generalized the mechanism of direct ammonia oxidation(Eqs.(1)–(5))to transition metal electrodes.However,deactivation of the electrode by surface poisoning might not be the only process leading to lower ammonia oxidation peaks in cyclic voltammetry(CV).In fact,it has been demonstrated for TDIROF[7]and other electrode materials[5,6,8]that direct ammonia oxidation is highly pH sensitive because the actual reactant is NH3while NH4+cannot be oxidized directly.Apparently, direct ammonia oxidation itself(Eqs.(2)–(4)),but also many other anodic processes such as oxygen evolution(Eq.(6)),release a large number of protons.2H2O!O2þ4Hþþ4eÀ(6) This can lead to a strong pH drop in the Nernstian diffusion layer if the electrolyte is not buffered.The consequence is a shift in the local ammonia speciation according to the acid-base equilibrium, resulting in a low availability of reactive NH3.The hypothesis of this study is that decreasing ammonia oxidation peaks on TDIROF in subsequent scans could be due to a drop of the local pH in the Nernstian diffusion layer caused by acidic anodic reactions.To test this hypothesis,we evaluated the ammonia oxidation peaks of CV experiments with varying lower return potentials in stagnant electrolytes.Furthermore,we employed a rotating disc electrode(RDE)to control the thickness of the Nerstian diffusion layer under well-deﬁned hydraulic conditions.These experiments were complemented with numeri-cal simulations of the ammonia concentration proﬁles in the Nernstian diffusion layer to show that the proposed mechanism is plausible.2.ExperimentalThe TDIROF electrodes were prepared by thermal decomposi-tion of a precursor solution(0.25molÁLÀ1H2IrCl6(99.9%,ABCR GmbH&Co,Karlsruhe,Germany)in i-propanol(99.8%,Merck KGaA,Darmstadt,Germany))on a titanium substrate(grade2, BIBUS METALS AG,Fehraltorf,Switzerland)as previously reported [7].The titanium was sand blasted,treated in1molÁLÀ1oxalic acid (99.5%,Fluka Chemie GmbH,Buchs,Switzerland)at95 C for one hour,rinsed with nanopure water and dried in an oven at105 C for 5minutes.Several layers were deposited to reach theﬁnal loading. Each IrO2layer was applied by pipetting the precursor solution onto one side of the substrate and distributing it evenly with a brush.The i-propanol was evaporated in an oven at105 C for 10minutes followed by a tempering of the electrodes at500 C for 10minutes.A pair of rectangular electrodes(5cmÁ4cm)was loaded with0.63Æ0.00mgÁcmÀ2and three RDEs(diameter 15mm)with0.81Æ0.14mgÁcmÀ2.As aﬁnal step,the TDIROF was annealed at500 C for1hour.The electrodes were character-ized using a scanning electron microscope(SEM,Nova NanoSEM 230,FEI,Hillsboro,USA).Elemental analysis was performed with an energy dispersive X-ray(EDX)system(INCA4.15,X MAX80, Oxford,UK)attached to the microscope.Results are provided in the supplementary information in section A.The CV experiments in stagnant electrolyte were performed in a one-compartment cell(50mL)with a three electrode setup.The rectangular TDIROF working electrode was pressed against a hole in the bottom of the cell exposing a geometric surface area of 0.5cm2to the electrolyte.The sealing between the electrode and the cell was made out of a silicon O-ring.The reference electrode (Hg/Hg2SO4/K2SO4(MSE),Ref601,Radiometer Analytical,Villeur-banne,France)was contained in a Luggin capillaryﬁlled with saturated K2SO4(99%,Fluka).The tip of the Luggin capillary was placed2mm above the working electrode.A Pt-wire(geometric surface area: 1.26cm2)was used as the counter electrode.A potentiostat(PGU10V-1A-IMP-S,Ingenieurbüro Peter Schrems, Münster,Germany)controlled the working electrode potential. The working electrode potential and the current density were recorded with the EcmWin software(EcmWin V2.4,Ingenieurbüro Peter Schrems).The temperature and pH were measured continuously(SenTix41connected to pH196,WTW,Weilheim, Germany)but no temperature control was installed.The same potentiostat and pH meter were used in the CV experiments on a RDE but another one-compartment cell(200mL) with three electrodes was used.The TDIROF-RDE was sealed in a Teﬂon cylinder exposing a geometric surface area of0.95cm2. The cylinder was plugged on the rotator(Jaissle Rotator,Jaissle Elektronik,Waiblingen,Germany)and inserted into the electrolyte from the top.The reference electrode(MSE,HgE11,Sensortechnik Meinsberg,Waldheim,Germany)was contained in a Luggin capillaryﬁlled with saturated K2SO4(99%,Fluka).The angled tip of the capillary was placed3mm from the RDE.A Pt-foil(geometric surface area:10.62cm2)was utilized as the counter electrode.Table1Comparison of onset potentials and peak potentials for direct ammonia oxidationon thermally decomposed iridium oxideﬁlms(TDIROF),isostatically pressedﬁnegrain graphite and boron-doped diamond(BDD)at pH=9.Electrode Material On-set potential Peak potential[V vs.SHE][V vs.SHE]TDIROF[7]0.9 1.1Graphite[5] 1.0 1.4Ni/Ni(OH)2[6] 1.1 1.3BDD[8] 1.6 2.2H.Zöllig et al./Electrochimica Acta165(2015)348–355349The electrolyte temperature was controlled at25Æ0.1 C with a thermostat(Colora Messtechnik GmbH,Lorch,Germany).All experiments were performed in0.5molÁLÀ1Na2SO4(99%,Merck)+ 0.125molÁLÀ1(NH4)2SO4(99.5%,Merck)dissolved in nanopure water.The pH value was adjusted by dosing NaOH(99%,Merck).3.CalculationsWe developed a dynamic numerical1D-model to simulate pH, NH3and NH4+concentrations in the Nernstian diffusion layer of the working electrode.The Nernstian diffusion layer was divided into segments of uniform thickness in which the concentrations were assumed to be homogeneous.The heterogeneous electrochemical reactions of direct ammonia oxidation and oxygen evolution were assumed to affect only the lowest of these segments which we will call the reaction zone.Oxygen evolution was taken into account according to Eq.(6)and direct ammonia oxidation was assumed to lead exclusively to molecular nitrogen for reasons of simplicity: NH3!0:5N2þ3Hþþ3eÀ(7) The surface speciﬁc reaction rate r X(mmolÁcmÀ2ÁsÀ1)of thecompound X was estimated based on the measured current density j(mAÁcmÀ2)according to Faraday’s law:r NH3¼Àj NH3FÁn NH3(8)r O2¼Àj O2FÁn O2(9)r Hþ¼n O2Ár O2Àn NH3Ár NH3(10) where F=96485CÁmolÀ1is the Faraday constant,n O2=4(À)and n NH3=3(À)are the number of electrons transferred according to Eqs.(6)and(7).The current density was allocated to the two electrochemical processes as follows:j NH3¼j NHÀj b if:0:3V<E w<0:68V and j NH3>0mAÁcmÀ2(11)j o2¼j NHÀj b if:0:68V<E w and j O2>0mAÁcmÀ2(12) The subscript NH denotes the current density measured duringCV in0.5molÁLÀ1Na2SO4+0.125molÁLÀ1(NH4)2SO4+NaOH and b denotes the background current density measured in 0.5molÁLÀ1Na2SO4+NaOH.The j b was subtracted to account for non-faradaic currents.E w(V)is the potential of the working electrode.The acid-base equilibrium of ammonia was modeled according to the mass action law in all segments individually and was assumed to be in equilibrium instantaneously.The conditional equilibrium constant(K c)was calculated from K¼10ÀpK a (pK a=9.25[12])with the activity coefﬁcients of NH3(g NH3¼1) and NH4+(g NH4¼0:42)accounting for the ionic strength I c=1.88 molÁLÀ1in the supporting electrolyte.The activity coefﬁcients were estimated in the chemical speciation software PHREEQC[13] using the Pitzer approach with a database extended by Pitzer parameters for ammonium[6].The pK c-value was found to be9.62.The concentration of X was denoted with c X in molÁLÀ1.K C¼KÁgNH4gNH3¼c NH3Ác Hþc NHþ4(13)The massﬂux J Xi,i+1(mmolÁcmÀ2ÁsÀ1)of species X from segment i to segment i+1was modeled with Fick’sﬁrst law of diffusion (Eq.(14)).The massﬂux by migration was neglected because of the high conductivity of the used electrolytes[14].J Xi;iþ1¼ÀD Xðc X;iÀc X;iþ1ÞD y(14)The values of the implemented diffusion coefﬁcients were D NH3=1.5Á10À5cm2ÁsÀ1,D NH4+=1.957Á10À5cm2ÁsÀ1, D H+=9.311Á10À5cm2ÁsÀ1[12]and D y(cm)was the thickness of one segment in perpendicular direction to the electrode surface.When an RDE was used,the thickness of the Nernstian diffusion layer d N(cm)was deﬁned by the hydraulic conditions and could be calculated with Eq.(15)[15]depending on the angular velocity v (sÀ1),the kinematic viscosity of water n=8.93Á10À3cm2ÁsÀ1and the diffusion coefﬁcient of ammonia.d N¼1:6ÁvÀ1=2Án1=6ÁD NH31=3(15)This numerical model was implemented in Berkeley Madonna (Berkeley Madonna Inc.Berkeley,USA,Version8.3.18).4.Results4.1.CV experiments in stagnant and agitated electrolytesThe cyclic voltammograms in Fig.1show a strong inhibition of direct ammonia oxidation on our TDIROF electrodes in immedi-ately consecutive scans conﬁrming theﬁndings of Kapałka et al.[7]. The ammonia oxidation peak in the forward scans(a1)as well as the ammonia oxidation peak in the backward scans(a2)decreased continuously from theﬁrst to theﬁfth scan.The peak a1decreasedFig.1.Five consecutive scans on a TDIROF electrode in0.5molÁL-1Na2SO4+0.125 molÁL-1(NH4)2SO4+NaOH at pH=9.25.Scan rate200mVÁs-1,upper return potential:0.8V vs.MSE,lower return potential:-1.1V vs.MSE,T=25.2 C,counter electrode:Pt-wire.The circles( )at0.3and-0.5V vs.MSE mark the points at which the concentration proﬁles in Fig.5and Fig.7were calculated.350H.Zöllig et al./Electrochimica Acta165(2015)348–355in ﬁve scans by 32%.It is important to note that the scans were performed without interruption;the lag phase was 19seconds between two consecutive ammonia oxidation peaks.Thus,the time for diffusion to equilibrate the reactant and pH gradients in the Nernstian diffusion layer was limited.In compliance with the interpretation of Kapa łka et al.[7],the peak a2appears because ammonia is not oxidized in the OER.It was hypothesized that NH 3oxidation requires the redox couple IrO (OH)2/IrO 2(OH)present at anode potentials of about 0.3to 0.7V vs.MSE.Above potentials of 0.7V vs.MSE,the iridium is completely oxidized to IrO 3which excludes the oxidation of ammonia in the OER.However,the oxidation to IrO 3is reversible and therefore ammonia oxidation restarts in the backward scan.The lower return potential was clearly above the HER in which protons would be consumed according to Eq.(16).2H þþ2e À!H 2(16)As the HER was not reached,the protons released during the anodic reactions of ammonia oxidation (Eq.(2)–(4))or oxygen evolution (Eq.(6))were not consumed by hydrogen evolution during the cathodic polarization of the electrode.This means that the reduction of the peaks a1and a2could very well result from a reactant limitation due to a drop in local pH.Fig.2A shows ﬁve immediately consecutive CV scans in which the TDIROF electrode was polarized moderately into the HER (lower return potential -1.5V vs.MSE).The ammonia oxidation peaks a1and a2were nearly identical,just the ﬁrst scan showed slightly smaller peaks.An even more pronounced difference between the ﬁrst and the consecutive scans can be seen in Fig.2B presenting the data of an experiment where the electrode was strongly polarized into the HER (lower return potential -1.7V vs.MSE).In this case,the ammonia oxidation peaks of the scans two to ﬁve (again all nearly identical)were clearly higher than in the ﬁrst scan.In contrast to the experiment where the HER was not reached (Fig.1),the polarization of the working electrode into the HER resulted in the consumption of protons according to Eq.(16).The longer the electrode was polarized into the HER,the higher were the ammonia oxidation peaks a1and a2in the following anodicpolarizations.This very likely resulted from a higher NH 3concentration in the reaction zone after strong hydrogen evolu-tion.Compared to the experiment with immediate consecutive scans (Fig.1),a considerably lower reduction of a1and a2was observed if an idle period of 4minutes was inserted between individual scans,even if the lower return potential was kept above the HER (Fig.3).The peak a1decreased by no more than 11%from the ﬁrst to the ninth scan which is clearly less than with immediately consecutive scans.This ﬁnding corroborates our hypothesis of an effect in the diffusion layer.Due to the diffusion of protons,ammonia andFig.2.A:Five consecutive scans on TDIROF in 0.5mol ÁL -1Na 2SO 4+0.125mol ÁL -1(NH 4)2SO 4+NaOH with a lower return potential of -1.5V vs.MSE.B:The same as in A but with a lower return potential of -1.7V vs.MSE.The red solid line marks the 5th scan.Scan rate 200mV Ás -1,upper return potential:0.8V vs.MSE,pH =9.25,T =25.3 C,counter electrode:Pt-wire.Fig.3.Three CV scans on TDIROF in 0.5mol ÁL -1Na 2SO 4+0.125mol ÁL -1(NH 4)2SO 4+NaOH at pH =9.25.An idle period of 4minutes was introduced between each scan during which the electrolyte was stirred.The points (4)at -0.4V and (5)at 0.3V vs.MSE at which the concentration pro ﬁles in Fig.6were calculated are indicated with the circles ( ).Scan rate 200mV Ás -1,upper return potential:0.8V vs.MSE,lower return potential:-0.9V vs.MSE,T =23.4 C,counter electrode:Pt-wire.H.Zöllig et al./Electrochimica Acta 165(2015)348–355351ammonium,similar NH3concentrations must have been reached in the reaction zone prior to each anodic polarization which resulted in comparable ammonia oxidation peaks.If the much lower decrease of a1and a2would have resulted from the reduction of poisonous N ads,a reduction peak would have been expected in the backward scans.However,this was neither the case with or without idle periods between the scans(Fig.1and Fig.3,respectively).Also the reduction of N ads during the idle phase was very unlikely because the OCP was almost constant between the scans(mean OCP value of all idle periods-0.413Æ0.003V vs. MSE)and certainly did not reach values below the lower return potential(supplementary information B).In Fig.4we presentﬁve immediately consecutive cyclic voltammograms recorded on an RDE at an angular velocity of 91rpm.In contrast to the scans in stagnant electrolyte without idle phase,the scans following theﬁrst scan on the RDE did not result in a strong decrease of the direct ammonia oxidation peaks a1or a2. In fact,the peak a1only decreased by5%from theﬁrst to the second scan.In the following scans,the decrease of peak a1was small(around0.6%in each scan)resulting in a total peak decrease from theﬁrst to theﬁfth scan of7%.Also in this experiment,the lower return potential(-0.9V vs. MSE)was chosen clearly above the HER and even0.2V higher than in the experiment in stagnant electrolyte(Fig.1).The time in which concentration gradients could even out was short(17s)and the protons released during direct ammonia oxidation(Eq.(1)–(4)) and oxygen evolution(Eq.(6))could not be consumed by hydrogen evolution.However,by making use of an RDE we were able to control the hydraulics at the working electrode and therewith to reduce d N.The consequences of this can be shown with our model calculations and are presented in the next section.4.2.Concentration proﬁles in the Nernstian diffusion layer during CVThe electrochemical measurements all supported our hypothesis but they did not show how the diffusion in the electrolyte proceeded and whether the proposed mechanism would be plausible on the observed special and temporal scale.To get more information about the concentration proﬁles in the diffusion layer we used the dynamic computer model.The initial conditions of the three state variables were chosen as c NH3¼0:07476and c NHþ4¼0:1752molNÁLÀ1and pH=9.25in all simulations.In Fig.5,simulated concentration proﬁles are given for the characteristic points of the voltammogram in Fig.1.The concentration proﬁles show that the time between ammoniaFig. 4.Five consecutive scans on a rotating TDIROF electrode in0.5molÁL-1 Na2SO4+0.125molÁL-1(NH4)2SO4+NaOH at pH=9.25.The circles( )at0.3and -0.5V vs.MSE mark the points at which the concentration proﬁles in Fig.7were calculated.Scan rate200mVÁs-1,upper return potential:0.8V vs.MSE,lower return potential:-0.9V vs.MSE,T=25.0 C,counter electrode:Pt-foil.Fig. 5.A:Calculated pH proﬁles in the vicinity of the electrode.B:NH3 concentration proﬁles in the vicinity of the electrode.The proﬁles correspond to point(4)just before the ammonia oxidation peaks a1appeared in the experiment presented in Fig.1(immediately consecutive scans,bulk pH=9.25).Fig. 6.A:Calculated pH proﬁles.B:NH3concentration proﬁles.The proﬁles correspond to the points(4)and(5)in theﬁrst idle phase indicated in Fig.3 (4minutes idle phase between scans,bulk pH=9.25).352H.Zöllig et al./Electrochimica Acta165(2015)348–355oxidation peaks in immediately subsequent scans was too short for the pH gradient to equalize(Fig.5A).Consequently,the regions in the vicinity of the electrode became more and more acidic with every scan.Due to the acid-base equilibrium,the change in pH resulted in a strong shift of ammonia ly,the NH3 concentration dropped considerably(Fig.5B).Thus,the concen-tration of the reactant(NH3)became lower during every anodic scan resulting in smaller direct ammonia oxidation peaks.Figs.6A and B display simulated concentration proﬁles at the points marked in Fig.3during the experiment where an idle phase of4minutes was inserted between the scans.The proﬁles at the beginning of theﬁrst idle phase were calculated at the same point in time since the start of the experiment as the proﬁles calculated before the second scan in the experiment without an idle phase. These concentration proﬁles form Fig.5and Fig.6are directly comparable.The proﬁles in Figs.6A and B were less pronounced because the anodic currents in the foregoing scan were smaller. After theﬁrst idle phase,just before the second anodic polarization started(point(5)in Fig.3),there still was a small shift of ammonia speciation in the reaction zone(Fig.6B).This explains the small reduction of the ammonia oxidation peaks in the following scan and in all additional cycles until the ninth scan.The idle time between the scans allowed concentrations to equalize almost completely before a new anodic polarization so that comparable ammonia oxidation peaks were measured.In stagnant electrolyte,the Nernstian diffusion layer has no limit and could theoretically expand deep into the bulk liquid. From the concentration proﬁles in Fig.5A it can be deduced that the maximal d N was close to 1.5mm during the experiment presented in Fig.1.On the RDE,d N was hydraulically controlled and much thinner.With Eq.(15)it was calculated to be d N=0.15mm for the applied rotational speed of91rpm.The consequences were the buildup of distinctly different concentration proﬁles of H+,NH4+ and NH3compared to the stagnant electrolyte leading to a considerably different diffusion behavior.A comparison of four concentration proﬁles between theﬁrst anodic polarization and the second anodic polarization in stagnant electrolyte(A,B,and C)and in agitated electrolyte(D,E,and F)is shown in Fig.7.In the stagnant electrolyte and on the RDE,a speciation shift due to a change in local pH appeared.However, when d N was hydraulically controlled on the RDE the concentra-tion gradients evened out much faster.The reason for this was the more pronounced concentration gradients due to a thinner and limited Nernstian diffusion layer.The result was faster diffusion allowing concentrations to draw level quickly.Consequently,the concentration of NH3in the reaction zone at point4prior to the second anodic polarization was much closer to the one found prior to theﬁrst scan(compare the proﬁles4at distance0from the electrode in Figs.7B and E).This is remarkable and demonstrates the importance of d N.It should be noted that the time until point 4was reached in the CV on the RDE was shorter,because the lower return potential was higher than in the experiments with stagnant electrolyte(Fig.1).5.Discussion5.1.Mechanisms inhibiting direct ammonia oxidationGerischer and Mauerer[9]distinguished between a fast and a slow passivation of direct ammonia oxidation on Pt.They found that the fast passivation was reversible by simply letting the working electrode rest at OCP.On the other hand,the slowFig.7.A,B,and C:Calculated concentration proﬁles during the second scan of the experiment in stagnant electrolyte presented in Fig.1.D,E,and F:Calculated concentration proﬁles during the second scan of the experiment on the RDE presented in Fig.4during which the Nernstian diffusion layer was hydraulically controlled at d N=0.15mm.The numbers in the plots correspond to the numbers in the Fig.1and Fig.4indicating the point in time at which the proﬁle was calculated.H.Zöllig et al./Electrochimica Acta165(2015)348–355353。

2023-2024学年江苏省南京市第五高级中学高三7月英语摸底测试卷

2023-2024学年江苏省南京市第五高级中学高三7月英语摸底测试卷1. Why does the woman call the man?A．To place an order. B．To report a delay. C．To arrange a deliverydate.2. What does the woman want the man to do?A．Collect her book. B．Lend her a book. C．Buy some juice.3. What is the woman looking for?A．Her handbag. B．Her passport. C．Her boarding pass.4. What will the weather probably be like this afternoon?A．Rainy. B．Foggy. C．Sunny.5. What are the speakers talking about?A．A tree. B．A survey C．A country听下面一段较长对话，回答以下小题。

6. How will the woman go to the meeting center?A．On foot. B．By car. C．By taxi.7. Where does the conversation probably take place?A．In a restaurant. B．In a hotel. C．At a train station.听下面一段较长对话，回答以下小题。

8. What did the woman dislike about the concert?A．The venue. B．The singer. C．The music.9. What did the speakers think of the support bands?A．Moving. B．Surprising. C．Disappointing.听下面一段较长对话，回答以下小题。

脯氨酸与植物的抗逆性

脯氨酸与植物的抗逆性王宝增（河北省廊坊师范学院生命科学学院065000）摘要本文主要介绍了脯氨酸在植物体中的合成与分解以及脯氨酸与植物抗逆性的关系。

关键词脯氨酸逆境胁迫相容性溶质抗逆性植物一生中会受到多种不利环境的影响，在诸多逆境因素中，由干旱、盐渍等因素引起的渗透胁迫（os-motic stress）是限制植物生长发育和作物产量的主要原因。

许多植物在逆境胁迫中都会积累一些相容性溶质（compatible solute），如脯氨酸、甜菜碱、糖醇等，这些物质溶解度高，没有毒性，在细胞中积累不会干扰细胞内正常的生化反应，并且可以抵抗渗透胁迫［1］。

在已知的相容性溶质中，脯氨酸在植物中的分布最为广泛［2］。

1脯氨酸在植物体中的积累脯氨酸作为蛋白质氨基酸中的一员，在植物初生代谢中的作用尤为重要。

人们在萎蔫的黑麦中首先发现了脯氨酸积累这一现象［3］。

之后，在逆境胁迫下的其他植物中也发现了脯氨酸的积累。

植物在遭受干旱、盐渍、强光与重金属污染和其他生物胁迫过程中都会有脯氨酸的大量积累，少则十几倍，多则几十倍甚至上百倍。

许多研究表明，脯氨酸主要分布在细胞质中，调节胞质和液泡之间渗透势的平衡［4］。

在水分胁迫中，它优先在细胞质中积累。

例如马铃薯细胞在正常水分条件下，细胞内的脯氨酸有34%积累在液泡中；但当其处于水分亏缺条件下时，液泡中脯氨酸含量下降，细胞质中脯氨酸含量上升［5］。

2脯氨酸的合成与分解在植物中，脯氨酸的合成主要来自谷氨酸，合成反应主要在叶绿体中完成。

谷氨酸在吡咯啉－5－羧酸合成酶（P5CS）催化下还原成谷氨酸半缩醛，后者自发转变成吡咯啉－5－羧酸（P5C），吡咯啉－5－羧酸还原酶（P5CR）进一步将吡咯啉－5－羧酸还原成脯氨酸。

在大多数植物中，吡咯啉－5－羧酸合成酶由2个基因编码，吡咯啉－5－羧酸还原酶由1个基因编码。

脯氨酸的分解代谢在线粒体中完成，分别由脯氨酸脱氢酶（PDH）和吡咯啉－5－羧酸脱氢酶（P5CDH）催化完成，脯氨酸脱氢酶催化脯氨酸转变成吡咯啉－5－羧酸，吡咯啉－5－羧酸脱氢酶催化吡咯啉－5－羧酸氧化成谷氨酸。

基质效应在生物样品质谱分析中的优化措施研究

基质效应在生物样品质谱分析中的优化措施研究吴文静【摘要】高效液相色谱-质谱联用法（LC - MS /MS ）由于其高灵敏度和高选择性现阶段被广泛应用于食品检测、环境评估等方面的样品定量分析.然而,由于实际样品特别是复杂样品分析中基质效应的存在,样品分析进程以及检测结果的特异性、灵敏度和准确度都会受到影响.本文立足于实际的生物样品质谱分析,阐述了基质效应的产生原因、检测及评定方法,其优化措施包括四个方面,即样品前处理的优化、色谱条件的优化、质谱条件的优化以及同位素内标的选择.【期刊名称】《信阳农林学院学报》【年(卷),期】2017(027)004【总页数】5页(P115-118)【关键词】高效液相色谱一质谱联用基质效应生物样品分析【作者】吴文静【作者单位】安徽公安职业学院公安科学技术系,安徽合肥230031;【正文语种】中文【中图分类】O657.63高效液相色谱－质谱联用法（液相质谱，HPLC－MS／MS）是一种高灵敏度和高选择性的样品定量分析方法，由于其高效样品的选择性和准确的测定能力而被广泛推广应用于食品相关检测、环境风险评估、农药残留分析、药物组分以及代谢研究中［1－2］。

近几年，随着液质技术的快速发展，与检测相关的基质效应问题也开始被广泛关注。

基质效应作为质谱检测中存在的必然问题，对样品检测、分析方法和结果的特异性、灵敏度和准确度都有显著影响［3］。

目前，国外的学者已经开展了大量的与基质效应相关的工作和研究，但国内相关的研究还未能构成完整的研究体系。

本文结合国内外相关文献，对液质检测过程中基质效应的产生原因、相关作用以及目前常规的检测方法和消除或降低基质干扰的途径等问题进行阐述。

1 基质效应产生机制及影响基质效应指的是在样品检测过程中，除待测组分以外的其它物质对待测组分的分析进程产生的干扰，并影响检测结果的灵敏度和准确性。

基质效应的产生主要是源于样品中的待测组分与基质成分在离子化过程中的竞争。

沙子吸附铅

Journal of Hazardous Materials B137(2006)384–395Removal of copper(II)and lead(II)from aqueoussolution by manganese oxide coated sand I.Characterization and kinetic studyRunping Han a ,∗,Weihua Zou a ,Zongpei Zhang a ,Jie Shi a ,Jiujun Yang baDepartment of Chemistry,Zhengzhou University,No.75of Daxue North Road,Zhengzhou 450052,PR ChinabCollege of Material Science and Engineering,Zhengzhou University,No.75of Daxue North Road,Zhengzhou 450052,PR ChinaReceived 8November 2005;received in revised form 25December 2005;accepted 13February 2006Available online 28February 2006AbstractThe preparation,characterization,and sorption properties for Cu(II)and Pb(II)of manganese oxide coated sand (MOCS)were investigated.A scanning electron microscope (SEM),X-ray diffraction spectrum (XRD)and BET analyses were used to observe the surface properties of the coated layer.An energy dispersive analysis of X-ray (EDAX)and X-ray photoelectron spectroscopy (XPS)were used for characterizing metal adsorption sites on the surface of MOCS.The quantity of manganese on MOCS was determined by means of acid digestion analysis.The adsorption experiments were carried out as a function of solution pH,adsorbent dose,ionic strength,contact time and temperature.Binding of Cu(II)and Pb(II)ions with MOCS was highly pH dependent with an increase in the extent of adsorption with the pH of the media inves-tigated.After the Cu(II)and Pb(II)adsorption by MOCS,the pH in solution was decreased.Cu(II)and Pb(II)uptake were found to increase with the temperature.Further,the removal efﬁciency of Cu(II)and Pb(II)increased with increasing adsorbent dose and decreased with ionic strength.The pseudo-ﬁrst-order kinetic model,pseudo-second-order kinetic model,intraparticle diffusion model and Elovich equation model were used to describe the kinetic data and the data constants were evaluated.The pseudo-second-order model was the best choice among all the kinetic models to describe the adsorption behavior of Cu(II)and Pb(II)onto MOCS,suggesting that the adsorption mechanism might be a chemisorption process.The activation energy of adsorption (E a )was determined as Cu(II)4.98kJ mol −1and Pb(II)2.10kJ mol −1,respectively.The low value of E a shows that Cu(II)and Pb(II)adsorption process by MOCS may involve a non-activated chemical adsorption and a physical sorption.©2006Elsevier B.V .All rights reserved.Keywords:Manganese oxide coated sand (MOCS);Cu(II);Pb(II);Adsorption kinetic1.IntroductionThe presence ofheavy metals in the aquatic environment is a major concern due to their extreme toxicity towards aquatic life,human beings,and the environment.Heavy metal ions from wastewaters are commonly removed by chemical precipitation,ion-exchange,reverse osmosis processes,and adsorption by activated carbon.Over the last few decades,adsorption has gained importance as an effective puriﬁcation and separation technique used in wastewater treatment,and the removal of heavy metals from metal-laden tap or wastewater∗Corresponding author.Tel.:+8637167763707;fax:+8637167763220.E-mail address:rphan67@ (R.Han).is considered an important application of adsorption processes using a suitable adsorbent [1,2].In recent years,many researchers have applied metal oxides to adsorption of heavy metals from metal-laden tap or wastewa-ter [3].Adsorption can remove metals over a wider pH range and lower concentrations than precipitation [4].Iron,aluminum,and manganese oxides are typically thought to be the most important scavengers of heavy metals in aqueous solution or wastewater due to their relatively high surface area,microporous structure,and possess OH functional groups capable of reacting with met-als,phosphate and other speciﬁcally sorbing ions [5].However,most metal oxides are available only as ﬁne powders or are gener-ated in aqueous suspension as hydroxide ﬂoc or gel.Under such conditions,solid/liquid separation is fairly difﬁcult.In addition,metal oxides along are not suitable as a ﬁlter medium because of0304-3894/$–see front matter ©2006Elsevier B.V .All rights reserved.doi:10.1016/j.jhazmat.2006.02.021R.Han et al./Journal of Hazardous Materials B137(2006)384–395385their low hydraulic conductivity.Recently,several researchers have developed techniques for coating metal oxides onto the surface of sand to overcome the problem of using metal oxides powers in water treatment.Many reports have shown the impor-tance of these surface coatings in controlling metal distribution in soils and sediments[3,6,7].In recent years,coated minerals have been studied because of their potential application as effective sorbents[3,8,9].Iron oxide coated meterials for heavy metal removal have been proved successful for the enhancement of treatment capacity and efﬁciency when compared with uncoatedﬁlter media,such as sil-ica sand[10–14],granular activated carbon[15]and polymeric media[16,17].For example,Edwards and Benjamin[7]found that coated media have similar properties to unattached coating materials in removing metals over a wide pH range,and that Fe oxide coated sand was more effective than uncoated sand.Bai-ley et al.[18]used iron oxide coated sand to remove hexavalent chromium from a synthetic waste stream.The inﬂuent contained 20mg l−1Cr(VI)and better than99%removal was achieved. Satpathi and Chaudhuri[19]and Viraraghavan et al.[20]have recently reported on the ability of this medium to adsorb metals from electroplating rinse waters and arsenic from drinking water sources,respectively.Green-Pedersen and Pind reported that a ferrihydrite-coated montmorillonite surface had a larger speciﬁc surface area and an increased sorption capacity for Ni(II)com-pared to the pure systems[21].Meng and Letterman[22]found that the adsorption properties of oxide mixtures are determined by the relative amount of the components.They also found that ion adsorption on aluminum oxide-coated silica was better mod-eled assuming uniform coverage of the oxide rather than using two distinct surfaces[23].Lo and Chen[8]determined the effect of Al oxide mineralogy,amount of oxide coating,and acid-and alkali-resistance on the removal of selenium from water.Bran-dao and Galembecket reported that the impregnation of cellulose acetates with manganese dioxide resulted in high removal efﬁ-cient of Cu(II),Pb(II),and Zn(II)from aqueous solutions[24]. Al-Degs and Khraisheh[25]also reported that diatomite and manganese oxide modiﬁed diatomite are effective adsorbents for removing Pb2+,Cu2+,and Cd2+ions.The sorption capac-ity of Mn-diatomite was considerably increased compared to the original material for removing the studied metals.Filtration quality of diatomite is signiﬁcantly increased after modiﬁcation with Mn-oxides.Merkle et al.[26–28]reported that manganese dioxide coated sand was effective for removal of arsenic from ground water in column experiments.Merkle et al.developed a manganese oxide coating method on anthracite to improve the removal of Mn2+from drinking water and hazardous waste efﬂuent.They generated aﬁlter media with an increased surface area after coating with manganese oxides and found manganese oxide coated media have the ability to adsorb and coprecipi-tate a variety of inorganic species.Stahl and James[29]found their manganese oxide coated sands generated a larger surface area and increased adsorption capability with increasing pH as compared to uncoated silica sand.Additional researchers have been investigated to evalu-ate coating characteristics.X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),Fourier transform infrared spectroscopy(FTIR),transmission electron microscopy(TEM), and scanning electron microscopy(SEM)have been used as well to identify components,distribution,and structure of surface oxide coating[7,9,30,31].An energy dispersive X-ray (EDAX)technique of analysis has been used to characterize metal adsorption sites on the sorbent surface.Typically,oxide was non-uniform over the surface as both the oxide and substratum had been observed[7].The research described here was designed to investigate characteristics of manganese oxide coated sand(MOCS)and test the properties of MOCS as an adsorbent for removing copper(II)and lead(II)from synthetic solutions in batch system.SEM/EDAX,XRD,XPS and BET analysis were employed to examine the properties of adsorption reactions for Cu(II)and Pb(II)ions on MOCS in water.The system variables studied include pH,MOCS dose,ionic strength,contact time and temperature.The kinetic parameters,such as E a,k1,k2, have been calculated to determine rate constants and adsorption mechanism.1.1.Kinetic parameters of adsorptionThe models of adsorption kinetics were correlated with the solution uptake rate,hence these models are important in water treatment process design.In order to analyze the adsorption kinetics of MOCS,four kinetic models including the pseudo-ﬁrst-order equation[32],the pseudo-second-order equation[33], Elovich equation[34],and intraparticle diffusion model[35] were applied to experimental data obtained from batch metal removal experiments.A pseudo-ﬁrst-order kinetic model of Lagergen is given as log(q e−q t)=log q e−K1t2.303(1)A pseudo-second-order kinetic model istq t=1(K2q2e)+tq e(2) andh=K2q2e(3) an intraparticle diffusion model isq t=K t t1/2+C(4) and an Elovich equation model is shown asq t=ln(αβ)β+ln tβ(5) where q e and q t are the amount of solute adsorbed per unit adsorbent at equilibrium and any time,respectively(mmol g−1), k1the pseudo-ﬁrst-order rate constant for the adsorption process (min−1),k2the rate constant of pseudo-second-order adsorption (g mmol−1min−1),K t the intraparticle diffusion rate constant (mmol g−1min−1),h the initial sorption rate of pseudo-second-order adsorption(mmol g−1min−1),C the intercept,αthe initial sorption rate of Elovich equation(mmol g−1min−1),and386R.Han et al./Journal of Hazardous Materials B137(2006)384–395the parameter βis related to the extent of surface coverage and activation energy for chemisorption (g mmol −1).A straight line of log(q e −q t )versus t ,t /q t versus t ,q t versus ln t ,or q t versus t 1/2suggests the applicability of this kinetic model and kinetic parameters can be determined from the slope and intercept of the plot.1.2.Determination of thermodynamic parametersThe activation energy for metal ions adsorption was calcu-lated by the Arrhenius equation [36]:k =k 0exp −E aRT (6)where k 0is the temperature independent factor ing mmol −1min −1,E a the activation energy of the reaction of adsorption in kJ mol −1,R the gas constant (8.314J mol −1K −1)and T is the adsorption absolute temperature (K).The linear form is:ln k =−E aRT+ln k 0(7)when ln k is plotted versus 1/T ,a straight line with slope –E a /R is obtained.2.Materials and methods 2.1.AdsorbentThe quartz sand was provided from Zhengzhou’s Company of tap water in China.The diameter of the sand was ranged in size from 0.99to 0.67mm.The sand was soaked in 0.1mol l −1hydrochloric acid solution for 24h,rinsed with distilled water and dried at 373K in the oven in preparation for surface coating.Manganese oxide coated sand was accomplished by utilizing a reductive procedure modiﬁed to precipitate colloids of man-ganese oxide on the media surface.A boiling solution containing potassium permanganate was poured over dried sand placed in a beaker,and hydrochloric acid (37.5%,W HCl /W H 2O )solution was added dropwise into the solution.After stirring for 1h,the media was ﬁltered,washed to pH 7.0using distilled water,dried at room temperature,and stored in polypropylene bottle for future use.2.2.Metal solutionsAll chemicals and reagents used for experiments and anal-yses were of analytical grade.Stock solutions of 2000mg l −1Pb(II)and Cu(II)were prepared from Cu(NO 3)2and Pb(NO 3)2in distilled,deionized water containing a few drops of concen-trated HNO 3to prevent the precipitation of Cu(II)and Pb(II)by hydrolysis.The initial pH of the working solution was adjusted by addition of HNO 3or NaOH solution.2.3.Mineral identiﬁcationThe mineralogy of the sample was characterized by X-ray diffraction (XRD)(Tokyo Shibaura Model ADG-01E).Pho-tomicrography of the exterior surface of uncoated sand and man-ganese oxide coated sand was obtained by SEM (JEOL6335F-SEM,Japan).The distribution of elemental concentrations for the solid sample can be analyzed using the mapping analysis of SEM/EDAX (JEOL SEM (JSM-6301)/OXFORD EDX,Japan).The existence of Cu(II)and Pb(II)ions on the surface of manganese oxide coated sand was also conﬁrmed by using EDAX.Samples for EDAX analysis were coated with thin carbon ﬁlm in order to avoid the inﬂuence of any charge effect during the SEM operation.The samples of MOCS and MOCS adsorbed with copper/lead ions were also analyzed by X-ray photoelectron spectroscopy (XPS)(ESCA3600Shimduz).2.4.Speciﬁc surface area and pore size distribution analysesAnalyses of physical characteristics of MOCS included spe-ciﬁc surface area,and pore size distributions.The speciﬁc sur-face area of MOCS and pore volumes were test using the nitrogen adsorption method with NOV A 1000High-Speed,Automated Surface Area and Pore Size Analyer (Quantachrome Corpora-tion,America)at 77K,and the BET adsorption model was used in the calculation.Calculation of pore size followed the method of BJH according to implemented software routines.2.5.Methods of adsorption studiesBatch adsorption studies were conducted by shaking the ﬂasks at 120rpm for a period of time using a water bath cum mechanical shaker.Following a systematic work on the sorp-tion uptake capacity of Cu(II)and Pb(II)in batch systems were studied in the present work.The experimental process was as following:put a certain quantity of MOCS into conical ﬂasks,then,added the solute of metals of copper or lead in single component system,vibrated sometime at a constant speed of 120rpm in a shaking water bath,when reached the sorption equilibrium after 180min,took out the conical ﬂasks,ﬁltrated to separate MOCS and the solution.No other solutions were provided for additional ionic strength expect for the effect of ionic strength.The concentration of the free metal ions in the ﬁltrate was analyzed using ﬂame atomic absorption spectrometer (AAS)(Aanalyst 300,Perkin Elmer).The uptake of the metal ions was calculated by the difference in their initial and ﬁnal concentrations.Effect of pH (1.4–6.5),quantity of MOCS,contact time,temperature (288–318K)was studied.The pH of the solutions at the beginning and end of experiments was measured.Each experiment was repeated three times and the results given were the average values.2.5.1.Effect of contact time and temperature on Cu(II)and Pb(II)adsorptionA 2.0g l −1sample of MOCS was added to each 20ml of Cu(II)or Pb(II)solutions with initial concentration of Cu(II)0.315mmol l −1and Pb(II)0.579mmol l −1,respectively.The temperature was controlled with a water bath at the temperature ranged from 294to 318K for the studies.Adsorbent of MOCS and metal solution were separated at pre-determined time inter-R.Han et al./Journal of Hazardous Materials B137(2006)384–395387 vals,ﬁltered and analyzed for residual Cu(II)and Pb(II)ionconcentrations.2.5.2.Effect of pH on the sorption of Cu(II)and Pb(II)byMOCSThe effect of pH on the adsorption capacity of MOCSwas investigated using solutions of0.157mmol l−1Cu(II)and0.393mmol l−1Pb(II)for a pH range of1.4–6.5at293K.A20g l−1of MOCS was added to20ml of Cu(II)and Pb(II)solu-tions.Experiments could not be performed at higher pH valuesdue to low solubility of metal ions.2.5.3.Effect of MOCS doseIt was tested by the addition of sodium nitrate and calciumnitrate to the solution of Cu(II)and Pb(II),respectively.The doseof adsorbents were varied from10to80g l−1keeping initial con-centration of copper0.157mmol l−1and lead0.393mmol l−1,respectively,and contact time was180min at the temperature of293K.2.5.4.Effect of ionic strength on Cu(II)and Pb(II)adsorptionThe concentration of NaNO3and Ca(NO3)2used rangedfrom0to0.2mol l−1.The dose of adsorbents were20g l−1,the initial concentration of copper0.157mmol l−1and lead0.393mmol l−1,respectively,and contact time was180min atthe temperature of293K.The data obtained in batch model studies was used to calculatethe equilibrium metal uptake capacity.It was calculated for eachsample of copper by using the following expression:q t=v(C0−C t)m(8)where q t is the amount of metal ions adsorbed on the MOCS at time t(mmol g−1),C0and C t the initial and liquid-phase concentrations of metal ions at time t(mmol l−1),v the volume of the aqueous phase(l)and m is the dry weight of the adsorbent(g).3.Results and discussion3.1.Mineralogy of manganese oxide coated sandThe samples of sand coated with manganese oxide were dark colored(brown–black)precipitates,indicating the presence of manganese in the form of insoluble oxides.The X-ray diffrac-tion spectrum(XRD)of the samples(data not shown)revealed that the manganese oxide were totally amorphous,as there was not any peak detected,indicative of a speciﬁc crystalline phase. SEM photographs in Fig.1were taken at10,000×magniﬁ-cations to observe the surface morphology of uncoated sand and manganese oxide coated sand,respectively.SEM images of acid-washed uncoated quartz sand in Fig.1(a)showed very ordered silica crystals at the surface.The virgin sand had a rela-tively uniform and smooth surface and small cracks,micropores or light roughness could be found on the sand -paring the images of virgin(Fig.1(a))and manganeseoxide Fig.1.SEM micrograph of sample:(a)sand;(b)manganese oxide coated sand. coated sand(Fig.1(b)),MOCS had a signiﬁcantly rougher sur-face than plain sand and the coated sand surfaces were apparently occupied by newborn manganese oxides,which were formed during the coating process.Fig.1(b)also showed manganese oxides,formed in clusters,apparently on occupied surfaces.At the micron scale,the synthetic coating was composed of small particles on top of a more consolidated coating.In most regions individual particles of manganese oxide(diameter=2–3␮m) appeared to be growing in clumps in surface depressions and coating cracks.The amount of manganese on the surface of the MOCS,measured through acid digestion analysis,was approx-imately5.46mg Mn/g-sand.3.2.SEM/EDAX analysisThe elements indicated as being associated with manganese oxide coated were detected by the energy dispersive X-ray spec-trometer system(EDAX)using a standardless qualitative EDAX analytical technique.The peak heights in the EDAX spectra are proportional to the metallic elements concentration.The quali-tative EDAX spectra for MOCS(Fig.2(a))indicated that Mn,O,388R.Han et al./Journal of Hazardous Materials B137(2006)384–395Fig.2.EDAX spectrum of MOCS under:(a)adsorbed without copper and lead ion;(b)adsorbed copper ions;(c)adsorbed lead ions.Si,and K are the main constituents.These had been known as the principal elements of MOCS.EDAX analysis yielded indirect evidence for the mechanism of manganese oxide on the surface of MOCS.The peak of Si occurred in EDAX showed that man-ganese oxides do not covered a full surface of the MOCS.If the solid sample of MOCS caused a change of elemental con-stitution through adsorption reaction,it could be inferred that manganese oxide has already brought about chemical interac-tion with adsorbate.The EDAX spectrum for copper and lead system was illustrated in Fig.2(b and c).It could be seen that copper and lead ion became one element of solid sample in this spectrum.The reason was that copper and lead ions were chemisorbed on the surface of MOCS.Dot mapping can provide an indication of the qualitative abundance of mapping elements.The elemental distribution mapping of EDAX for the sample of MOCS and MOCS adsorbed copper or lead ions is illustrated in Fig.3.The bright points represented the single of the element from the solid sam-ple.A laryer of manganese oxide coating is clearly shown in the dot map for Mn in Fig.3(a),and a high density of white dots indicates manganese is the most abundant element.Results indicated that manganese oxide was spread over the surface of MOCS,and was a constituent part of the solid sample.The ele-ment distribution mapping of EDAX for the sample ofMOCS Fig.3.EDAX results of MOCS(white images in mapping represent the cor-responding element):(a)adsorbed without copper and lead ion;(b)adsorbed copper ions;(c)adsorbed lead ions.R.Han et al./Journal of Hazardous Materials B137(2006)384–395389Fig.4.XPS wide scan of the manganese oxide coated sand. reacting with copper and lead ions is illustrated in Fig.3(b and c).Copper or lead ions were spread over the surfaces of MOCS. Results indicated that manganese oxide produces chemical bond with copper or lead ions.Thus,copper or lead element was a constituent part of the solid sample.3.3.Surface characterization using the X-ray photoelectron spectroscopy(XPS)XPS analyses were performed on samples of MOCS alone and reacting with copper or lead ions.The wide scan of MOCS is presented in Fig.4.It can be noticed that the major elements constituent are manganese,oxygen,and silicon.Detailed spectra of the peaks are shown in Fig.5.Manganese oxides are generally expressed with the chemical formula of MnO x,due to the multiple valence states exhibited by Mn.Therefore,it is reasonable to measure the average oxidation state for a manganese mineral[37].The observation of the Mn 2p3/2peak at641.9eV and the separation between this and the Mn2p1/2peak of11.4eV indicates the manganese exhibited oxidation between Mn3+and Mn4+as shown from the auger plot,but it can be seen to show Mn4+predominantly from the Mn2p3/2peaks[38].The large peak in Fig.5(b)is a sum of the two peaks at 529.3and533.1eV,which can be assigned to O1s;a low bind-ing energy at529.7eV,which is generally accepted as lattice oxygen in the form of O2−(metal oxygen bond).This peak is characteristic of the oxygen in manganese oxides.The second peak at533.4eV can be assigned to surface adsorbed oxygen in the form of OH−[38].As seen the XPS spectra of the sample of MOCS reacting with copper,Fig.6(a)shows the binding energies of the observed photoelectron peaks of Cu2p3/2,2p1/2.The binding energy of the Cu2p3/2peak at a value of933.9eV shows the presence of copper(+2).The XPS spectra obtained after Pb(II)adsorption on MOCS is presented in Fig.6(b).Fig.6(b)shows that doublets charac-teristic of lead appear,respectively,at138.3eV(assigned to Pb 4f7/2)and at143.8eV(assigned to Pb4f5/2)after loadingMOCSFig.5.XPS detailed spectra of MOCS:(a)Mn2p3/2;(b)O1s.with Pb(II)solution.The peak observed at138.3eV agrees with the138.0eV value reported for PbO[39].This shows aﬁxation of lead onto MOCS during the process.3.4.Speciﬁc surface area and pore size distribution analysesThe speciﬁc surface areas for sand and MOCS under un/adsorbed Pb(II)ions are summarized in Table1.Plain uncoated sand had a surface area of0.674m2g−1.A surface coating of manganese oxide increased the surface area of sand to0.712m2g−1,while average pore diameter decreased from 51.42to42.77˚A.This may be caused by the increase in both Table1Speciﬁc surface areas and average pore diameters for sand and various MOCSSurface area(m2g−1)Average pore diameter(˚A) Sand0.67451.42Unadsorbed a0.71242.77Adsorbed b0.55239.64Desorbed c0.70142.71a Without reacting with Pb(II)ions.b After reacting with Pb(II)ions.c After soaking with0.5mol l−1acid solution.390R.Han et al./Journal of Hazardous Materials B137(2006)384–395Fig.6.XPS detailed spectra of MOCS reacting with(a)copper;(b)lead. inner and surface porosity after adding the manganese oxides admixture.After reacting with Pb(II)ions,the pore size distribu-tion of MOCS had been changed,and parts of pores disappeared through the adsorption process.The results indicated the parts of pores were occupied with Pb(II)ions and average pore diameters decreased simultaneously,compared with unadsorbed MOCS, the surface area value of adsorbed MOCS is decreased,varying from of0.712to0.552m2g−1.Besides,pore size distribution of desorbed MOCS was similar to that of unadsorbed MOCS. The surface area of desorbed MOCS increased and average pore diameter also increased after regeneration with acid solution. The results indicated Pb(II)ions could be desorbed from the surface site of micropore and mesopores.3.5.Effect of contact time and temperature on Cu(II)andPb(II)adsorptionEffect of contact time and temperature on the adsorption of the copper(II)and lead(II)on MOCS was illustrated in Fig.7(a and b).The uptake equilibrium of Cu(II)and Pb(II) were achieved after180min and no remarkable changes were observed for higher reaction times(not shown in Fig.7).The shapes of the curves representing metal uptake versus time suggest that a two-step mechanism occurs.Theﬁrstportion Fig.7.Effect of contact time on Cu(II)and Pb(II)ions adsorption at pH4and various temperatures:(a)adsorption capacity vs.time;(b)adsorption percent vs.time(C0(Cu)=0.315mmol l−1,C0(Pb)=0.579mmol l−1).indicates that a rapid adsorption occurs during theﬁrst30min after which equilibrium is slowly achieved.Almost80%of total removal for both Cu(II)and Pb(II)occurred within60min.The equilibrium time required for maximum removal of Cu(II)and Pb(II)were90and120min at all the experimental temperatures, respectively.As a consequence,180min was chosen as the reac-tion time required to reaching pseudo-equilibrium in the present “equilibrium”adsorption experiments.Higher removal for cop-per and lead ions was also observed in the higher temperature range.This was due to the increasing tendency of adsorbate ions to adsorb from the interface to the solution with increasing temperature and it is suggested that the sorption of Cu(II)and Pb(II)by MOCS may involve not only physical but also chem-ical sorption.The metal uptake versus time curves at different temperatures are single,smooth and continuous leading to sat-uration,suggesting possible monolayer coverage of Cu(II)and Pb(II)on the surface of MOCS[40].3.6.Effect of pH on the sorption of Cu(II)and Pb(II)by MOCSIt is well known that the pH of the system is an important vari-able in the adsorption process.The charge of the adsorbate and the adsorbent often depends on the pH of the solution.The man-R.Han et al./Journal of Hazardous Materials B137(2006)384–395391 ganese oxide surface charge is also dependent on the solution pHdue to exchange of H+ions.The surface groups of manganeseoxide are amphoteric and can function as an acid or a base[41].The oxide surface can undergo protonation and deprotonationin response to changes in solution pH.As shown in Fig.8,the uptake of free ionic copper and leaddepends on pH,increasing with pH from1.4to5.1for Cu(II)and1.4to4.3for Pb(II).Above these pH levels,the adsorptioncurves increased very slightly or tended to level out.At low pH,Cu(II)and Pb(II)removal were inhibited possibly as result ofa competition between hydrogen and metal ions on the sorp-tion sites,with an apparent preponderance of hydrogen ions.Asthe pH increased,the negative charge density on MOCS sur-face increases due to deprotonation of the metal binding sitesand thus the adsorption of metal ions increased.The increase inadsorption with the decrease in H+ion concentration(high pH)indicates that ion exchange is one of major adsorption process.Above pH6.0,insoluble copper or lead hydroxide starts precip-itating from the solution,making true sorption studies impossi-ble.Therefore,at these pH values,both adsorption and precipita-tion are the effective mechanisms to remove the Cu(II)and Pb(II)in aqueous solution.At higher pH values,Cu(II)and Pb(II)inaqueous solution convert to different hydrolysis products.In order to understand the adsorption mechanism,the varia-tion of pH in a solution and the metal ions adsorbed on MOCSduring adsorption were measured,and the results are shown inFig.8.The pH of the solution at the end of experiments wasobserved to be decreased after adsorption by MOCS.Theseresults indicated that the mechanism by means of which Cu(II)and Pb(II)ion was adsorbed onto MOCS perhaps involved anexchange reaction of Cu2+or Pb2+with H+on the surface andsurface complex formation.According to the principle of ion-exchange,the more metalions that is adsorbed onto MOCS,the more hydrogen ions arereleased,thus the pH value was decreased.The complex reac-tions of Cu2+and Pb2+with manganese oxide may be writtenas follows(X=Cu,Pb and Y=Pb)[42]:MnOH+X2+ MnO−X2++H+(9)MnO−+X2+ MnO−X2+(10)Fig.8.Effect of pH on adsorption of Cu(II)and Pb(II)by MOCS.2(MnOH)+X2+ (MnO−)2X2++2H+(11)2(MnO−)+X2+ (MnO−)2X2+(12)MnOH+X2++H2O MnOXOH+2H+(13)MnOH+2Y2++H2O MnOY2OH2++2H+(14)Eqs.(9)–(14)showed the hydrogen ion concentration increasedwith an increasing amount of Cu(II)or Pb(II)ion adsorbed onthe MOCS surface.3.7.Effect of MOCS doseFig.9shows the adsorption of Cu(II)and Pb(II)as a functionof adsorbent dosage.It was observed that percent adsorptionof Cu(II)and Pb(II)increased from29to99%and19to99%with increasing adsorbent load from10to80g l−1,respectively.This was because of the availability of more and more bindingsites for complexation of Cu(II)ions.On the other hand,theplot of adsorption per unit of adsorbent versus adsorbent doserevealed that the unit adsorption capacity was high at low dosesand reduced at high dose.There are many factors,which can con-tribute to this adsorbent concentration effect.The most importantfactor is that adsorption sites remain unsaturated during theadsorption reaction.This is due to the fact that as the dosageof adsorbent is increased,there is less commensurate increasein adsorption resulting from the lower adsorptive capacity uti-lization of the adsorbent.It is readily understood that the numberof available adsorption sites increases by increasing the adsor-bent dose and it,therefore,results in the increase of the amountof adsorbed metal ions.The decrease in equilibrium uptake withincrease in the adsorbent dose is mainly because of unsaturationof adsorption sites through the adsorption process.The corre-sponding linear plots of the values of percentage removal(Γ)against dose(m s)were regressed to obtain expressions for thesevalues in terms of the m s parameters.This relationship is asfollows:for Cu(II):Γ=m s0.221+6.61×10−3m s(15)Fig.9.Effect of dosage of MOCS on Cu(II)and Pb(II)removal.。

广东省江门市新会第一中学2023-2024学年高三热身考试英语试题

广东省江门市新会第一中学2023-2024学年高三热身考试英语试题一、阅读理解Upcoming Events in Essex County Environmental CenterLITTLE EXPLORERS Mondays -May 6, 20, June 3, 17For ages 2 and 3; 10am to 1lam; For ages 2 and 5; 3pm to 4pmJoin us for explorations of nature as we study plants and animals and observe the colors, shapes, and sounds in the Center’s forest habitat. Please come dressed and prepared for all weather conditions; all classes include an outdoor adventure. All children must be walking and accompanied by an adult. Maximum of two children per adult. All sessions are limited to 10 children. Fee: $15 per child per session. FOREST FRIENDS CLUBThursdays -May 9, June 6, 4pm to 5pmFor children ages 5 through 10We’ll explore the forest to investigate nature in our wooded wetland habitat. Together we hope to raise our children’s nature responsibilities and offer an opportunity to take part in hands-on conservation projects. Fee: $12 per child per session. SPRING WILD EDIBLE W ALK Friday, May 10, 6pm to 7:30pmFor familiesTake a walk in the forest to identify and discuss the variety of forest groceries available for harvest. You’ll meet Spice Bush, Mountain Mint and others. Learn some folklore (FIA) behind the plants and we’ll discuss proper identification, growing environment and methods of preparation while walking. Fee: $40 per family (up to two adults and two children) or $12 per child, $15 per adult.4-H YOUNG GARDENERS CLUBSaturdays -May 4, 18, 25, 10am to 11 amFor children in grades K-12Have you ever wondered how vegetables and flowers grow? How to find a rainbow in a garden? The 4-H Young Gardener’s Club can guide you to find the answers to these questions and more. Learning and fun happen all the time here. Meet in Garibaldi Hall. Advanced registrationrequired; please call 973 3531337.1．When can children join in hands-on projects?A．On May 6.B．On May 9.C．On May 10.D．On May 18. 2．How much should a couple with three kids pay at least for the Spring Wild Edible Walk?A．$40.B．$52.C．$55.D．$67.3．What do the four events have in common?A．They are targeted at families.B．They focus on theoretical courses.C．They offer experiences in nature.D．They present local folk cultures.18 years ago, a 14-year-old boy from Kasungu district in Malawi was forced to drop out of school for lack of fees. At the same time, a severe famine was destroying his village, claiming people’s lives and leaving desperation in its wake.This was a situation to break the strongest of minds but William Kamkwamba did not give up. Young as he was, he knew that education was where his future lay. He found hope in the library and feasted on the knowledge that he harvested from its books. It was there that he came across a science textbook entitled Using Energy. He learned that he could generate electricity using wind. The youngster realized that, if mastered, this power could help his village in exceptional ways.Armed with determination and an iron will, the teenager set out to build a windmill out of random materials from a scrapyard (垃圾场). Though his outside world was collapsing to dust, the youngster did not hesitate about his purpose. He defended himself from all doubt and criticism. He worked tirelessly until his dream of bringing electricity to his village became reality. Soon, he was caught in the center of media attention that took him to new places that he would never have stepped on without his invention.In his village, the dust has not settled yet and the winds of change continue to blow across the land. Windmills pump water to irrigate crops, sweeping away another period of hunger. William’s former primary school boasts new and stronger buildings, thanks to the help of well-wishers and the villagers’ united efforts.What seemed like a hopeless situation has been turned into an inspirational story that motivates each and every one of us, persuading us that no misfortune is set in stone. Williamrefused to be a school drop-out forever. He sought solutions for his problems and continued fighting even when the going got tough. He was able to rise above poverty to become a graduate from one of America’s best universities, Dartmouth College.4．What inspired William to bring electricity to his village?A．His realization of the impact of electricity.B．His awareness of the role of education.C．The science textbook entitled Using Energy.D．The severe famine destroying hisvillage.5．What can we learn from paragraph 3?A．All people didn’t support William’s dream at first.B．The public had little interest in William’s invention.C．The invention enabled William to make a big fortune.D．The windmill is energy-efficient and environmentally friendly.6．What does the underlined words “set in stone”in the last paragraph mean?A．Visible.B．Avoidable.C．Unchangeable.D．Unpredictable. 7．What message does the author want to convey in this story?A．Knowledge feasts mind and education promises wealth.B．Necessity inspires invention and hardship makes heroes.C．Criticism promotes success and doubt facilitates creation.D．Adversity motivates inspiration and support pushes solutions.Researchers at the Tokyo University of Science (TUS) have developed a groundbreaking sweat biosensor that opens up new possibilities for real-time health monitoring.Wearable sensors, typically worn directly on the skin, can monitor vital signs such as heart rate, blood pressure, and muscle activity. However, designing chemical sensors for detecting substance in bodily liquid, like sweat, has proven more complex due to issues of skin irritation (刺激) and accuracy when integrated into clothing.Addressing these challenges, the research team at TUS used a technique called “heat-transfer Printing” to fix a thin, flexible chloride ion (氯离子) sensor onto a clothing base and then integrated it into clothes such as T-shirts. Further, health signs such as chloride ion concentration in sweat can be measured by simply wearing them. By moving the sensor outside ofthe clothing piece, skin irritation is prevented. The wicking effect (芯吸效应) of fiber helps distributing sweat evenly between the sensor’s electrodes (电极), ensuring stable electrical contact and therefore improving the accuracy.Additionally, the team carefully selected skin-friendly materials and conducted various experiments using artificial sweat to prove the sensor’s accuracy in measuring chloride ion concentration. To assess its practicality, the team tested the sensor on a volunteer who engaged in a 30-minute exercise on a still bicycle. Measurements of bodily liquid were taken every five minutes and compared with the data collected by the sensor. The wearable sensor reliably measured the concentration of chloride ions in sweat. Moreover, the sensor has the capability to deliver data wirelessly, enabling real-time health monitoring.This breakthrough can boost the development of advanced healthcare devices that offer precise and convenient monitoring of important health indicators. With the power of these tiny electronics, researchers are pushing the boundaries of healthcare innovation to improve disease prevention and overall well-being.8．What is paragraph 2 mainly about?A．Varieties of sweat biosensors.B．Popularity of wearable equipment.C．Complexity in monitoring vital body signs.D．Difficulties in designing chemical sensors.9．What contributes to the even distribution of sweat between the sensor’s electrodes?A．The technique of heat-transfer printing.B．The chloride ion sensor.C．The wicking effect of fibre.D．Selected skin-friendly materials.10．What is the purpose of the test on the volunteer?A．To evaluate the sensor’s reliability.B．To improve the volunteer’s performance.C．To determine the sensor’s duration.D．To ensure the volunteer’s well-being.11．What is the author’s attitude toward the new technology?A．Critical.B．Expectant.C．Reserved.D．Doubtful.An ancient, interdependent relationship that contributes to food systems and ecosystem stability across the globe could be changing.Many flowering plants can self-pollinate (自花传粉), or transfer pollen between their own blossoms for seed generation and reproduction, but most of these plants have relied on pollinators such as butterflies and bees to reproduce. Now — during declines reported in many pollinator populations — a new study on the evolution of one flower species’ mating system has revealed a remarkable change that could worsen the challenges faced by the plants’ insect partners.The flowers reproductive evolution may be linked to environmental changes such as habitat destruction and rapid ongoing decreases in pollinator biodiversity, according to Samson Acoca-Pidolle, who led the study published December 19 in the journal New Phytologist.Comparing seeds of wild field pansies (三色堇) collected decades ago in France with the plants’ modern descendants. Acoca-Pidolle and his colleagues discovered that today’s flowers are smaller and produce less nectar (花蜜) as a result of increased self-pollination, which has direct impacts on pollinator behavior.The pansies of the past self-fertilized less and attracted far more pollinators than those of the present, according to the study.“It seems that it’s only traits (特性) that are involved in plant-pollinator interaction that are evolving, ” said Acoca-Pidolle. The changes could restrict the plants’ ability to adapt to future environmental changes and have implications for “all of floral biodiversity” — potentially decreasing flowering plants’ genetic, species and ecosystem variation.“This may increase the pollinator decline and cause a negative feedback cycle,” study coauthor Pierre-Olivier Cheptou told CNN.” If plants produce less nectar, there will be less food available to pollinators, which will in turn accelerate the rate at which the animals’ numbers decrease“, he explained.“The major message is that we are currently seeing the evolutionary breakdown of plant pollinators in the wild,” said Cheptou, an evolutionary ecologist at the French National Centre for Scientific Research and professor at the University of Montpellier.12．Which of the following may contribute to the flowers’ reproductive evolution?A．Changed behaviour of pollinators.B．Severe pollution to the habitats.C．Continuing decline in pollinator biodiversity.D．Increased plant-pollinator interaction. 13．Why were pansies in the past larger and produced more nectar?A．They self-pollinated less.B．They had a better mating system.C．They attracted less pollinators.D．They were fertilized by themselves. 14．What is the result of the changes in the flowers’ reproductive evolution?A．The flowering plants may have more variations.B．The evolution of wild plant pollinators is collapsing.C．The numbers of the animals will increase more rapidly.D．The plants will adapt to the environmental changes better.15．Which is the best title for the text?A．Pollinator Populations: Declining.B．Flowering Plants: Selfing.C．Interdependent Relationship: Maintaining.D．Floral Diversity: Increasing.Things To Remember On Y our First Solo Travel AdventureIf you’ve ever thought about just taking a trip yourself instead of waiting for someone to join you, you’re not alone. 16 However, do you count yourself among the many who have tried it? If you’re planning your own solo trip, here are four important things to keep in mind.17 Since you’re traveling solo, how you choose to explore it is entirely up to you. This is your chance to do whatever you want whenever you want because this time, you’re running the show.Don’t be afraid to talk to random people. Though there is someone who poses a threat, it’s important to remember that not everyone is out to get you. 18 That’s because you’re a novelty, a person from another country who is visiting theirs. Therefore, instead of putting on your headphones or instantly seeing them as weirdos, use this spontaneous chat as a chance to meet the locals or get recommendations for things to do during your trip.It’s okay to have bad days. 19 It happens and it’s completely okay to take some time to process whatever it is you’re feeling. Take yourself to a movie or spend the day dong something relaxing like writing in your journal or reading on the beach.It’s okay to start small. 20 Start by doing a staycation in another part of town, spending a few days in a new locale a bus or train ride away. Just do whatever you’re comfortablewith and see how it all feels for you.A．You are the boss of your own adventure.B．You need to make an unusual travel choice.C．It’s no secret that solo travel is on the rise.D．Sometimes things can go incredibly wrong.E．People like you simply don’t know how to start.F．Most of the time people are just curious and try to be friendly.G．Remember, your first solo trip doesn’t have to be to a whole other continent.二、完形填空One day, hundreds of people were stuck in traffic on the highway in below-freezing temperatures due to a snowstorm. With the conditions making it 21 for rescue workers to help, many were trapped overnight with no access to 22 .But one stuck driver found a 23 spot in the despair. As she was sitting in her car fearing the 24 , Casey Holihan and her husband, John Noe, 25 a bread truck just ahead of them in the jam. Willing to try just about anything, they called the customer service number listed on the back of the truck and left a 26 begging for the driver to open the back and 27 bread to the hungry passengers around them. It was a last-ditch effort, and the couple wasn’t very 28 about getting a response. But to their 29 they soon received a phone call from the company’s owner, Chuck Paterakis, with the news that he was 30 the truck’s driver to open up and pass out loaves of bread from his cargo. Overjoyed by the news, Holihan and Noe 31 the truck’s driver to bring much-needed things to the cars around them.The simple loaves of bread were surely a ray of 32 in an impossibly disturbing situation. Holihan herself calls it “one of the 33 moments” she’s ever witnessed. This company could have made a(n) 34 from the bread but instead chose to help the people around them. That is just so incredible that someone chose 35 over profit, especially in a situation where people were so desperate.21．A．stressful B．effortless C．practical D．difficult22．A．water B．necessities C．bread D．blankets 23．A．new B．familiar C．bright D．strange 24．A．least B．best C．most D．worst 25．A．spotted B．realized C．stared D．knew 26．A．number B．message C．note D．clue 27．A．lend B．sell C．distribute D．send 28．A．upset B．optimistic C．excited D．anxious 29．A．relief B．regret C．surprise D．credit 30．A．consulting B．guiding C．begging D．instructing 31．A．kept up with B．teamed up with C．met up with D．put up with 32．A．hope B．truth C．inspiration D．faith 33．A．happiest B．bravest C．kindest D．friendliest 34．A．profit B．difference C．living D．contribution 35．A．welfare B．fame C．award D．humanity三、语法填空阅读下面材料，在空白处填入适当的内容(一个单词)或括号内单词的正确形式。

BSENISO17638-2016焊缝的无损检验.磁粒子检验

EUROPEAN STANDARD NORME EUROPÉENNE EUROPÄISCHE NORM EN ISO 17638 November 2016ICS 25.160.40 Supersedes EN ISO 17638:2009English VersionNon-destructive testing of welds - Magnetic particletesting (ISO 17638:2016)Contrôle non destructif des assemblages soudés - Magnétoscopie (ISO 17638:2016) Zerstörungsfreie Prüfung von Schweißverbindungen - Magnetpulverprüfung (ISO 17638:2016)This European Standard was approved by CEN on 2 October 2016.CEN members are bound to comply with the CEN/CENELEC Internal Regulations which stipulate the conditions for giving this European Standard the status of a national standard without any alteration. Up-to-date lists and bibliographical references concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN member.This European Standard exists in three official versions (English, French, German). A version in any other language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC Management Centre has the same status as the official versions.CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and United Kingdom.EUROPEAN COMMITTEE FOR STANDARDIZATIONC O M I TÉE UR O PÉE N DE N O R M A L I SA T I O NE UR O PÄI SC HE S KO M I T E E FÜR N O R M UN GCEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels© 2016 CEN All rights of exploitation in any form and by any means reservedworldwide for CEN national Members.Ref. No. EN ISO 17638:2016 EBS EN ISO 17638:2016EN ISO 17638:2016 (E) 3European forewordThis document (EN ISO 17638:2016) has been prepared by Technical Committee ISO/TC 44 “Welding and allied processes” in collaboration with Technical Committee CEN/TC 121 “Welding and allied processes” the secretariat of which is held by DIN. This European Standard shall be given the status of a national standard, either by publication of an identical text or by endorsement, at the latest by May 2017, and conflicting national standards shall be withdrawn at the latest by May 2017. Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights. This document supersedes EN ISO 17638:2009. According to the CEN-CENELEC Internal Regulations, the national standards organizations of the following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and the United Kingdom. Endorsement noticeThe text of ISO 17638:2016 has been approved by CEN as EN ISO 17638:2016 without any modification.BS EN ISO 17638:2016ISO 17638:2016(E) Contents PageForeword (iv)1 Scope (1)2 Normative references (1)3 Terms and definitions (1)4 Safety precautions (1)5 General (1)5.1 Information required prior to testing (1)5.2 Additional pre-test information (2)5.3 Personnel qualification (2)5.4 Surface conditions and preparation (2)5.5 Magnetizing (2)5.5.1 Magnetizing equipment (2)5.5.2 Verification of magnetization (3)5.6 Application techniques (3)5.6.1 Field directions and testing area (3)5.6.2 Typical magnetic testing techniques (6)5.7 Detection media (9)5.7.1 General (9)5.7.2 Verification of detection media performance (9)5.8 Viewing conditions (10)5.9 Application of detection media (10)5.10 Overall performance test (10)5.11 False indications (10)5.12 Recording of indications (10)5.13 Demagnetization (11)5.14 Test report (11)Annex A (informative) Variables affecting the sensitivity of magnetic particle testing (13)Bibliography (15)© ISO 2016 – All rights reserved iiiBS EN ISO 17638:2016ISO 17638:2016(E)ForewordISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, governmental and non-governmental, in liaison with ISO, also take part in the work. ISO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization.The procedures used to develop this document and those intended for its further maintenance are described in the ISO/IEC Directives, Part 1. In particular the different approval criteria needed for the different types of ISO documents should be noted. This document was drafted in accordance with the editorial rules of the ISO/IEC Directives, Part 2 (see /directives). Attention is drawn to the possibility that some of the elements of this document may be the subject of patent rights. ISO shall not be held responsible for identifying any or all such patent rights. Details of any patent rights identified during the development of the document will be in the Introduction and/or on the ISO list of patent declarations received (see /patents).Any trade name used in this document is information given for the convenience of users and does not constitute an endorsement.For an explanation on the meaning of ISO specific terms and expressions related to conformity assessment, as well as information about ISO’s adherence to the World Trade Organization (WTO) principles in the Technical Barriers to Trade (TBT) see the following URL: /iso/foreword.html. The committee responsible for this document is ISO/TC 44, Welding and allied processes, Subcommittee 5, Testing and inspection of welds.This second edition cancels and replaces the first edition (ISO 17638:2003), which has been technically revised.Requests for official interpretations of any aspect of this document should be directed to the Secretariat of ISO/TC 44/SC 5 via your national standards body. A complete listing of these bodies can be found at .© ISO 2016 – All rights reservedBS EN ISO 17638:2016 INTERNATIONAL STANDARD ISO 17638:2016(E)Non-destructive testing of welds — Magnetic particle testing1 ScopeThis document specifies techniques for detection of surface imperfections in welds in ferromagnetic materials, including the heat affected zones, by means of magnetic particle testing. The techniques are suitable for most welding processes and joint configurations. Variations in the basic techniques that will provide a higher or lower test sensitivity are described in Annex A.This document does not specify acceptance levels of the indications. Further information on acceptance levels for indications may be found in ISO 23278 or in product or application standards.2 Normative referencesThe following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 3059, Non-destructive testing — Penetrant testing and magnetic particle testing — Viewing conditions ISO 9934-1:2015, Non-destructive testing — Magnetic particle testing — Part 1: General principles ISO 9934-2, Non-destructive testing — Magnetic particle testing — Part 2: Detection media ISO 9934-3, Non-destructive testing — Magnetic particle testing — Part 3: Equipment3 Terms and definitionsFor the purposes of this document, the terms and definitions given in ISO 12707 and ISO 17635 apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses:— IEC Electropedia: available at /— ISO Online browsing platform: available at /obp4 Safety precautionsSpecial consideration shall be given to toxic, inflammable and/or volatile materials, electrical safety and unfiltered UV radiation.Magnetic particle testing often creates high magnetic fields close to the object under test and the magnetising equipment. Items sensitive to these fields should be excluded from such areas.5 General5.1 Information required prior to testingPrior to testing, the following items shall be specified (where applicable):a)specific test procedure;b)certification requirements for NDT personnel;© ISO 2016 – All rights reserved 1BS EN ISO 17638:2016ISO 17638:2016(E)extent of coverage;state of manufacture;testing techniques to be used;overall performance test;any demagnetization;acceptance level;action necessary for unacceptable indications.5.2 Additional pre-test informationPrior to testing, the following additional information can also be required:type and designation of the parent and weld materials;welding process;location and extent of welds to be tested;joint preparation and dimensions;location and extent of any repairs;post-weld treatment (if any);surface conditions.Operators may ask for further information that could be helpful in determining the nature of any indications detected.5.3 Personnel qualificationMagnetic particle testing of welds and the evaluation of results for final acceptance shall be performed by qualified and capable personnel. It is recommended that personnel be qualified in accordance with ISO 9712 or an equivalent standard at an appropriate level in the relevant industry sector.5.4 Surface conditions and preparationAreas to be tested shall be dry unless appropriate products for wet surfaces are used. It may be necessary to improve the surface condition, e.g. by use of abrasive paper or local grinding to permit accurate interpretation of indications.Any cleaning or surface preparation shall not be detrimental to the material, the surface finish or the magnetic testing media. Detection media shall be used within the temperature range limitations set by the manufacturer.5.5 Magnetizing5.5.1 Magnetizing equipmentGeneral magnetization requirements shall be in accordance with ISO 9934-1:2015, Clause 8. Unless otherwise specified, for example, in an application standard, the following types of alternating current-magnetizing equipment shall be used: electromagnetic yokes;© ISO 2016 – All rights reservedBS EN ISO 17638:2016ISO 17638:2016(E)b)current flow equipment with prods;c)adjacent or threading conductors or coil techniques.DC electromagnets and permanent magnets may only be used by agreement at the time of enquiry and order.The magnetizing equipment shall conform to ISO 9934-3.Where prods are used, precautions shall be taken to minimize overheating, burning or arcing at the contact tips. Removal of arc burns shall be carried out where necessary. The affected area shall be tested by a suitable method to ensure the integrity of the surface.5.5.2 Verification of magnetizationFor the verification of magnetization, see ISO 9934-1:2015, 8.2.For structural steels in welds, a tangential field between 2 kA/m to 6 kA/m (r.m.s.) is recommended. The adequacy of the surface flux density shall be established by one or more of the following methods: a)by testing a representative component containing fine natural or artificial discontinuities in the least favourable locations;b)measurement of the tangential field strength as close as possible to the surface using a Hall effect probe; the appropriate tangential field strength can be difficult to measure close to abrupt changes in the shape of a component or where flux leaves the surface of a component;c)calculation of the approximate current value in order to achieve the recommended tangential field strength; the calculation can be based on the current values specified in Figure 5 and Figure 6;d)by the use of other methods based on established principles.Flux indicators (i.e. shim-type) placed in contact with the surface under test provide a guide to the magnitude and direction of the tangential field strength, but should not be used to verify that the tangential field strength is acceptable.NOTE Information on b) is given in ISO 9934-3.5.6 Application techniques5.6.1 Field directions and testing areaThe detectability of an imperfection depends on the angle of its major axis with respect to the direction of the magnetic field. This is explained for one direction of magnetization in Figure 1.© ISO 2016 – All rights reserved 3BS EN ISO 17638:2016ISO 17638:2016(E)Keymagnetic field direction αangle between the magnetic field and the direction of the imperfection optimum sensitivity αmin minimum angle for imperfection detection reducing sensitivity αi example of imperfection orientationinsufficient sensitivity Figure 1 — Directions of detectable imperfectionsTo ensure detection of imperfections in all orientations, the welds shall be magnetized in two directions approximately perpendicular to each other with a maximum deviation of 30°. This can be achieved using one or more magnetization methods.Testing in only one field direction is not recommended but may be carried out if specified, for example, in an application standard.When using yokes or prods, there will be an area of the component in the vicinity of each pole piece or tip that will be impossible to test due to excessive magnetic field strength. This is usually seen as furring of particles.Care shall be taken to ensure adequate overlap of the testing areas as shown in Figure 2 and Figure 3.© ISO 2016 – All rights reservedBS EN ISO 17638:2016ISO 17638:2016(E)Dimensions in millimetresKeyd separation between the poles (yoke/prod )Figure 2 — Examples of effective testing area (shaded) for magnetizing with yokes and prods © ISO 2016 – All rights reserved 5BS EN ISO 17638:2016ISO 17638:2016(E)Keyeffective area overlap Figure 3 — Overlap of effective areas5.6.2 Typical magnetic testing techniquesMagnetic particle testing techniques for common weld joint configurations are shown in Figure 4, Figure 5 and Figure 6. Values are given for guidance purposes only. Where possible, the same directions of magnetization and field overlaps should be used for other weld geometries to be tested. The width of the flux current (in case of flux current technique) or of the magnetic flow (in case of magnetic flow technique) path in the material, d , shall be greater than or equal to the width of the weld and the heat affected zone +50 mm and in all cases, the weld and the heat affected zone shall be included in the effective area. The direction of magnetization with respect to the orientation of the weld shall be specified.© ISO 2016 – All rights reservedBS EN ISO 17638:2016 ISO 17638:2016(E)Dimensions in millimetresd ≥ 75b ≤ d/2β ≈ 90ºd1 ≥ 75b1 ≤ d1/2b2 ≤ d2 – 50d2≥ 75d1 ≥ 75d2 ≥ 75b1 ≤ d1/2b2 ≤ d2 − 50d1 ≥ 75d2 > 75b1 ≤ d1/2b2 ≤ d2 − 50Key1longitudinal cracks2transverse cracksFigure 4 — Typical magnetizing techniques for yokes© ISO 2016 – All rights reserved 7BS EN ISO 17638:2016 ISO 17638:2016(E)Dimensions in millimetresd ≥ 75b ≤ d/2β ≈ 90ºd ≥ 75b ≤ d/2d ≥ 75b ≤ d/2d ≥ 75b ≤ d/2Figure 5 — Typical magnetizing techniques for prods, using a magnetizing current prod spacing© ISO 2016 – All rights reservedBS EN ISO 17638:2016ISO 17638:2016(E)Dimensions in millimetres20 ≤ a ≤ 50 N ·I ≥ 8D 20 ≤ a ≤ 50 N ·I ≥ 8D20 ≤ a ≤ 50 N ·I ≥ 8DKeyN number of turns I current (r.m.s)a distance between weld and coil or cableFigure 6 — Typical magnetizing techniques for flexible cables or coils (for longitudinal cracks)5.7 Detection media5.7.1 GeneralDetection media may be either in dry powder form or magnetic inks in accordance with ISO 9934-2.5.7.2Verification of detection media performanceThe detection media used shall fulfil the requirements of ISO 9934-2.© ISO 2016 – All rights reserved9BS EN ISO 17638:2016ISO 17638:2016(E)Indications obtained with the medium to be verified shall be compared against those obtained from a medium having a known and acceptable performance. For this purpose, the reference indications may be real imperfections,photograph(s), andreplica(s).5.8 Viewing conditionsThe viewing conditions shall be in accordance with ISO 3059.5.9 Application of detection mediaAfter the object has been prepared for testing, the detection medium shall be applied by spraying, flooding or dusting immediately prior to and during the magnetization. Following this, time shall be allowed for indications to form before removal of the magnetic field.When magnetic suspensions are used, the magnetic field shall be maintained within the object until the majority of the suspension carrier liquid has drained away from the test surface. This will prevent any indications being washed away.Depending on the material being tested, its surface condition and magnetic permeability, indications will normally remain on the surface even after removal of the magnetic field due to residual magnetism within the part (mainly at the location of the poles). However, the presence of residual magnetism shall not be presumed and post evaluation techniques after removal of the prime magnetic field source are only permitted when a component has been proven by an overall performance test to retain magnetic indications.5.10 Overall performance testWhen specified, an overall performance test of the system sensitivity for each procedure shall be carried out on site. The performance test shall be designed to ensure a proper functioning of the entire chain of parameters including the equipment, the magnetic field strength and direction, surface characteristics, detection media and illumination.The most reliable test is to use representative test pieces containing real imperfections of known type, location, size and size-distribution. Where these are not available, fabricated test pieces with artificial imperfections or flux shunting indicators of the cross or disc or shim-type may be used.The test pieces shall be demagnetized and free from indications resulting from previous tests.NOTE It can be necessary to perform an overall performance test of the system sensitivity for each specific procedure on site.5.11 False indicationsFalse indications which may mask relevant indications can arise for many reasons, such as changes in magnetic permeability, very important geometry variation in, for example, the heat affected zone. Where masking is suspected, the test surface shall be dressed or alternative test methods should be used.5.12 Recording of indicationsIndications can be recorded in one or more of the following ways by using: description in writing;sketches;10 © ISO 2016 – All rights reservedBS EN ISO 17638:2016ISO 17638:2016(E)c)photography;d)transparent adhesive tape;e)transparent varnish for “freezing” the indication on the surface tested;f)peelable contrast coating;g)video recording;h)magnetic particle dispersion in an epoxy curable resin;i)magnetic tapes;j)electronic scanning.5.13 DemagnetizationAfter testing welds with alternating current, residual magnetization will normally be low and there will generally be no need for demagnetization of the object under test.If demagnetization is required, it shall be carried out using a defined method and to a predefined level. For metal cutting processes, a typical residual field strength value of H < 0,4 kA/m is recommended.5.14 Test reportA test report shall be prepared.The report should contain at least the following:a)name of the company carrying out the test;b)the object tested;c)date of testing;d)parent and weld materials;e)any post weld heat treatment;f)type of joint;g)material thickness;h)welding process(es);i)temperature of the test object and the detection media (when using media in circulation) throughout testing duration;j)identity of the test procedure and description of the parameters used, including the following:— type of magnetization;— type of current;— detection media;— viewing conditions;k)details and results of the overall performance test, where applicable;l)acceptance levels;© ISO 2016 – All rights reserved 11BS EN ISO 17638:2016ISO 17638:2016(E)m)description and location of all recordable indications;test results with reference to acceptance levels;names, relevant qualification and signatures of personnel who carried out the test.12 © ISO 2016 – All rights reservedBS EN ISO 17638:2016ISO 17638:2016(E)Annex A(informative)Variables affecting the sensitivity of magnetic particle testingA.1 Surface conditions and preparationThe maximum test sensitivity that can be achieved by any magnetic testing method is dependent on many variables but can be seriously affected by the surface roughness of the object and any irregularities present. In some cases, it can be necessary to— dress undercut and surface irregularities by grinding, and— remove or reduce the weld reinforcement.Surfaces covered with a thin non-ferromagnetic coatings up to 50 µm thickness may be tested provided the colour is contrasting with the colour of the detection medium used. Above this thickness, the sensitivity of the method decreases and may be demonstrated to be sufficiently sensitive before proceeding with the test.A.2 Magnetizing equipment characteristicsThe use of alternating current gives the best sensitivity for detecting surface imperfections. Yokes produce an adequate magnetic field in simple butt-welds but where the flux is reduced by gaps or the path is excessive through the object, as in T-joints a reduction of sensitivity can occur.For complex joint configurations, i.e. branch connections with an inclined angle of less than 90°, testing using yokes might be inadequate. Prods or cable wrapping with current flow will, in these cases, prove more suitable.A.3 Magnetic field strength and permeabilityThe field strength required to produce an indication strong enough to be detected during magnetic particle testing is dependent mainly on the magnetic permeability of the object. Generally, magnetic permeability is high in softer magnetic materials, for example, low alloy steels and low in harder magnetic materials, i.e. martensitic steels. Because permeability is a function of the magnetizing current, low permeability materials usually require application of a higher magnetization value than do softer alloys to produce the same flux density. It is essential, therefore, to establish that flux density values are adequate before beginning the magnetic particle testing.A.4 Detection mediaMagnetic particle suspensions will usually give a higher sensitivity for detecting surface imperfections than dry powders.Fluorescent magnetic detection media usually give a higher test sensitivity than colour contrast media, because of the higher contrast between the darkened background and the fluorescent indication. The sensitivity of the fluorescent method will, nevertheless, decrease in proportion to any increase in the roughness of the surface to which magnetic particles adhere and can cause a disturbing background fluorescence.© ISO 2016 – All rights reserved 13BS EN ISO 17638:2016ISO 17638:2016(E)Where the background illumination cannot be adequately lowered or where background fluorescence is disturbing, coloured detection media in conjunction with the smoothing effect of a contrast aid will usually give better sensitivity.14 © ISO 2016 – All rights reservedBS EN ISO 17638:2016ISO 17638:2016(E)Bibliography[1] ISO 9712, Non-destructive testing — Qualification and certification of NDT personnel[2] ISO 12707, Non-destructive testing — Magnetic particle testing — Vocabulary[3] ISO 17635, Non-destructive testing of welds — General rules for metallic materials[4] ISO 23278, Non-destructive testing of welds — Magnetic particle testing — Acceptance levels © ISO 2016 – All rights reserved 15This page deliberately left blank。

BECO PR深层过滤膜商品说明说明书

Technical Data Sheet Depth FiltrationBECO® PR RangeDepth Filter Sheets for the Pharmaceutical IndustryBECO PR depth filter sheets meet the highdemands of the pharmaceutical industry.Exceptionally pure raw materials and a specialproduction method produce BECO PR depth filtersheets with low endotoxin content. The specialcharacteristic of this range is high endotoxinretention during the filtration of manypharmaceutical products.The specific advantages of BECO PR depth filtersheets:-High endotoxin retention as well as a maximummicrobial retention rate.-The innovative production process guarantees anendotoxin content of less than < 0.125 EU/ml.-Maximum raw material purity for minimummigration of soluble ions.-The ideal combination of various filtrationmechanisms (surface, adsorption, depth filtration)and adsorptive properties ensures maximumreliability.-Comprehensive quality assurance for all raw andauxiliary materials and intensive in-process controlsensure consistent quality of the finished products.-Before delivery, the endotoxin content of< 0.125 EU/ml of all BECO PR depth filter sheets istested with the help of an LAL test. A certificate isavailable on request.- A Validation Guide is available upon request.Microbial Reduction and RemovalBECO PR Steril S 100, PR Steril S 80, PR Steril 40BECO depth filter sheets boast high microbial retentionrates achieved through the tight-pored structure and anelectrokinetic potential with an adsorptive effect.These depth filter sheets are particularly suitable aspre-filters for subsequent membrane filtration becauseof their high capacity to retain endotoxins and colloidalcomponents.Fine FiltrationBECO PR 12BECO depth filter sheets for achieving a high degree of clarification. These depth filter sheets reliably retain ultra-fine particles and provide bioburden reduction.In practice, these depth filter sheets serve as ideal pre-filters for protection of membrane filters, reverse osmosis systems, and to protect chromatography columns. Clarifying Filtration and Coarse FiltrationBECO PR 5, PR 1BECO depth filter sheets with large-volume cavity structure. These depth filter sheets have a high dirt-holding capacity for particles and are very suitable forclarifying filtration applications.Physical DataThis information is intended as a guideline for the selection of BECO depth filter sheets.The water flow is a laboratory value characterizing the different BECO depth filter sheet types.It is not the recommended flow rate.22PR Steril27295 0.1 0.15 (3.9) 58 > 7.3 (50) 0.7 (30) < 0.125 S100PR Steril27280 0.2 0.15 (3.9) 50 > 11.6 (80) 1.1 (46) < 0.125 S80PR Steril27240 0.4 0.15 (3.9) 49 > 7.3 (50) 1.5 (61) < 0.125 40PR 12 27212 0.8 0.15 (3.9) 50 > 18.9 (130) 4.3 (175) < 0.125PR 5 27205 2.0 0.15 (3.9) 50 > 8.7 (60) 8.1 (330) < 0.125PR 1 27200 4.0 0.17 (4.3) 48 > 6.5 (45) 58.4 (2381) < 0.125 * 100 kPa = 1 bar** Endotoxin content analysis after rinsing with 1.23 gal/ft² (50 l/m²) of WFI (Water for Injection)Chemical DataBECO depth filter sheets meet the requirements of LFGB*, Recommendation XXXVI/1 issued by BfR**, and the test criteria of FDA*** Directive CFR 21 § 177.2260.Chemical resistance of the BECO depth filter sheets to different solvents over a contact time of 3 hours at 68 °F (20 °C). The chemical compatibilities listed in the table below are a guide only.Aqueous solutions: Organic solvents:Sugar solution, 10% r nc Hydrochloric acid, 1% r nc Methanol r nc With 1% free chlorine r nc Hydrochloric acid, 3% r nc Ethanol r nc r nc Hydrochloric acid, 5% r nc Isopropanol r nc With 1% hydrogenperoxideWith 30% formaldehyde r nc Hydrochloric acid, 10% r nc Toluene r nc With 10% ethanol r nc Nitric acid, 1% r nc Xylene r nc With 40% ethanol r nc Nitric acid, 3% r nc Acetone r nc With 98% ethanol r nc Nitric acid, 5% r nc Methyl ethyl ketone r nc Caustic soda, 1% r nc Nitric acid, 10% r nc n-hexane r nc Caustic soda, 2% r nc Sulfuric acid, 1% r nc Dioxan r nc Caustic soda, 4% r 0 Sulfuric acid, 3% r nc Cyclohexane r nc Ammonia solution, 1% r nc Sulfuric acid, 5% r nc Tetrachloroethylene r nc Ammonia solution, 3% r nc Sulfuric acid, 10% r nc Ethylene glycol r nc Ammonia solution, 5% r nc Acetic acid, 1% r nc Dimethyl sulfide r ncr ncAcetic acid, 3% r nc N, N-DimethylformamideAcetic acid, 5% r ncAcetic acid, 10% r 0r = resistant nc = no change0 = slight opalescence* = German Food, Commodity, and Feed Act ** = Federal Institute of Risk Assessment *** = Food and Drug Administration; USAPyrogens/EndotoxinsPyrogens are biological or chemical substances whichcan induce a rise in body temperature. One commonexample are endotoxins. These are cell wall components known as lipopolysaccharides, that are embedded in the outer membrane of gram-negativebacteria.Quantitative evidence of endotoxins can be determinedusing the LAL test (L imulus A mebocyte L ysate). This method is an efficient and economical alternative to therabbit fever test. An independent institute examines thedepth filter sheets. The endotoxin content of the specimens examined is specified in EU/ml (E ndotoxin U nits).The measurement is carried out after rinsing with1.23 gal/ft² (50 l/m²) of WFI water.Endotoxin Retention RateTo measure endotoxin retention, a 40% glucose solution containing a defined amount of lipopolysaccharide (LPS)in pyrogen-free water is passed through a depth filter sheet. A defined sample of the filtrate is then measuredby means of the LAL test. Filtration flow rate: 12.3 gal/ft 2/h(500 l/m 2/h)Sampling after: 1.23 gal/ft² and 6.14 gal/ft²(50 l/m 2 and 250 l/m 2)Amount of endotoxin added: 2.2 mg LPS E. Coli 055:B5, this equals 4.4 µg LPS/ml or4.4 x 104 EU/mlThe endotoxin retention rate is indicated in the following graphic.Endotoxin Retention Rate of BECO PR Depth FilterSheets989799100Application Examples:Dialysis concentratexHuman albumin x Photoresist x I-globulin x xCoagulation factors x x Plasmaexpander solutionsx xEnzymeproduction x xHormones x x xAmino acids x x x Infusion solutions x x x Vaccine production x x x Serums from rabbits, sheep,horses, cattle, calves x x xComponentsBECO depth filter sheets are made from particularly pure natural materials, i.e., finely fibrillated cellulosefibers from deciduous and coniferous trees, cationic charge carriers, and high quality, particularly purediatomaceous earth.Instructions for Correct UseBECO depth filter sheets require careful handling when inserting them into the plate and frame filter. Avoid banging, bending, and rubbing the sheets. Do not use damaged depth filter sheets.InsertingEach BECO depth filter sheet has a rough side and a smooth side. The rough side of the depth filter sheet is the unfiltrate side; the smooth side is the filtrate side. Always ensure that the filtrate side is in contact with the clear filtrate plate when inserting the sheets.Sanitizing and Sterilizing (Optional)The wetted BECO depth filter sheets may be sterilized with hot water or saturated steam up to a maximum temperature of 273.2 °F (134 °C). The pressed filter package should be loosened slightly. Make sure to sterilize the entire filter system thoroughly. Do not apply final pressure until after the filter package has cooled down.Sterilizing with Hot WaterThe flow velocity should at least equal the filtration capacity. The water should be softened and free of impurities.Temperature: 185 °F (85 °C)Duration: 30 minutes after the temperature hasreached 185 °F (85 °C) at all valves. Pressure: At least 7.2 psi (50 kPa, 0.5 bar) at thefilter outlet.Sterilizing with SteamSteam quality: The steam must free of foreign particlesand impurities.Temperature: Max. 273.2 °F (134 °C)(saturated steam)Duration: Approx. 20 minutes after steam escapesfrom all filter valves.Rinsing: After sterilizing with 1.23 gal/ft² (50 l/m²)at 1.25 times the flow rate.Filter Preparation and FiltrationUnless already completed after sterilization, Eaton recommends pre-rinsing the closed filter with 1.23 gal/ft² (50 l/m²) of water at 1.25 times the flow rate prior to the first filtration. Depending on the application, this usually equals a rinsing time of 10 to 20 minutes. Test the entire filter for leakage at maximum operating pressure.High-proof alcohol solutions and chemical products that do not allow pre-rinsing with water should be circulated for 10 to 20 minutes. Dispose of the rinsing solution after rinsing.Differential PressureTerminate the filtration process when a differential pressure of 43.5 psi (300 kPa, 3 bar) is reached. For safety reasons, a differential pressure of 21.8 psi(150 kPa, 1.5 bar) should not be exceeded in applications for separating microorganisms.SafetyWhen used and handled correctly, there are no known unfavorable effects associated with this product. Further safety information can be found in the relevant Material Safety Data Sheet, which can be downloaded from our website. Waste DisposalDue to their composition BECO depth filter sheets are biodegradable. Comply with relevant current regulations, depending on the filtered product.StorageBECO depth filter sheets consist of strongly adsorptive materials. The product must be handled carefully during shipping and storage. Store the depth filter sheets in a dry, odor-free, and well-ventilated place. Do not expose the depth filter sheets to direct sunlight. BECO depth filter sheets are intended for immediate use and should be used within 36 months after production date.Available FormatsAll common square or round filter sizes are available for delivery. Special formats are available on request. Quality Assurance According to DIN EN ISO 9001 The Quality Management System of Eaton Technologies GmbH has been certified according to DIN EN ISO 9001.This certification verifies that a fully functioning comprehensive Quality Assurance System covering product development, contract controls, choice of suppliers, receiving inspections, production, final inspection, inventory management, and shipment has been implemented.Extensive quality assurance measures incorporate adherence to technical function criteria and chemical purity and quality recognized as safe under the German legislation governing the production of foods and beverages.All information is given to the best of our knowledge. However, the validity of the information cannot be guaranteed for every application, working practice and operating condition. Misuse of the product will result in all warrantees being voided.Subject to change in the interest of technical progress.North America44 Apple StreetTinton Falls, NJ 07724Toll Free: 800 656-3344(North America only)Tel: +1 732 212-4700Europe/Africa/Middle EastAuf der Heide 253947 Nettersheim, Germany Tel: +49 2486 809-0Friedensstraße 4168804 Altlußheim, Germany Tel: +49 6205 2094-0An den Nahewiesen 2455450 Langenlonsheim, Germany Tel: +49 6704 204-0 ChinaNo. 3, Lane 280,Linhong RoadChangning District, 200335Shanghai, P.R. ChinaTel: +86 21 5200-0099Singapore100G Pasir Panjang Road #07-08Singapore 118523Tel: +65 6825-1668BrazilRua Clark, 2061 - Macuco13279-400 - Valinhos, BrazilTel: +55 11 3616-8400For more information, pleaseemail us at ********************or visit /filtration© 2018 Eaton. All rights reserved. All trademarks andregistered trademarks are the property of their respectiveowners. All information and recommendations appearing inthis brochure concerning the use of products describedherein are based on tests believed to be reliable. However,it is the user’s responsibility to determine the suitability forhis own use of such products. Since the actual use byothers is beyond our control, no guarantee, expressed orimplied, is made by Eaton as to the effects of such use orthe results to be obtained. Eaton assumes no liabilityarising out of the use by others of such products. Nor is theinformation herein to be construed as absolutely complete,since additional information may be necessary or desirablewhen particular or exceptional conditions or circumstancesexist or because of applicable laws or governmentregulations.EN1 A 2.1.6.406-2018。

H12

ReviewA mini-review on ammonia decomposition catalysts for on-sitegeneration of hydrogen for fuel cell applicationsS.F.Yin a ,b ,c ,B.Q.Xu b ,*,X.P.Zhou c ,C.T.Au a ,*aDepartment of Chemistry,Center for Surface Analysis and Research,Hong Kong Baptist University,Kowloon Tong,Hong Kong,ChinabInnovative Catalysis Program,Key Lab of Organic Optoelectronics &Molecular Engineering,Department of Chemistry,Tsinghua University,Beijing 100084,ChinacCollege of Chemistry and Chemical Engineering,Hunan University,Hunan 410082,ChinaReceived 18May 2004;received in revised form 24August 2004;accepted 16September 2004Available online 28Ocotober 2004AbstractDue to the drive for better environmental protection and energy conversion efﬁciency,on-site generation of CO x -free hydrogen from ammonia decomposition for fuel cell applications has attracted much attention.The development of high performance solid catalysts is essential for the supply of such hydrogen from ammonia.In this mini-review,we provide a summary of the reaction kinetics of catalytic ammonia parisons are then made among the catalysts that have different active components,supports,and promoters.According to the works reported in the literature and our recent research results,Ru is the most active catalyst,carbon nanotubes (CNTs)are the most effective support,and KOH is the best promoter.An increase in Ru dispersion results in better catalytic performance.Both support basicity and conductivity are important criteria for a NH 3decomposition catalyst of high efﬁciency;and it seems possible to generate novel advanced support,such as oxide-CNTs nanocomposite materials,that bears such characteristics.Also,proper removal of the electron-withdrawing entities that originate from the precursors of active component,support or promoter can be effective in enhancing the catalytic activity of a Ru catalyst.#2004Elsevier B.V .All rights reserved.Keywords:Ammonia decomposition;Hydrogen generation;Ruthenium catalyst;Reaction kinetics;Catalyst support;Catalyst promoterContents 1.Reaction kinetics of ammonia decomposition .........................................................22.Ammonia decomposition catalyst..................................................................32.1.Active component........................................................................32.2.Support...............................................................................52.3.Promoter..............................................................................63.Effect of the electron-withdrawing groups............................................................74.Conclusions.................................................................................8Acknowledgements...............................................................................8References.....................................................................................8/locate/apcataH2is the cleanest fuel ever known and H2O is the only product of its combustion.Proton exchange membrane fuel cell(PEMFC)uses hydrogen as fuel source,and its energy conversion efﬁciency is40–60%[1].Also,the generation of energy(electricity)either through mobile or stationary PEMFC stacks is100%green,since it produces no pollutant or noise.Currently,the commercialization of fuel cell-based processes has been hampered due to problems related to:(i)delivery and storage of hydrogen,and(ii) catalyst and reactor stability for on-board or on-site generation of hydrogen in an integrated fuel cell system [2].Till now,there is no H2-storage material that can satisfy the practical requirements of fuel cell application,and the generation of a suitable one will take time and a lot of research efforts.Recently,on-site generation of hydrogen has become an interesting alternative[2–17].The hydrogen generated from carbonaceous substances(e.g.methanol, methane)inevitably includes CO x(x=1,2)that degrades cell electrodes even at extremely low concentrations[3–7]. The use of ammonia as a hydrogen provider appears to be abetter choice because there is no CO x generation,and the unconverted NH3can be reduced to less than200ppb level by means of a suitable absorber[2,8–17].In addition,at room temperature(R.T.)and around8atm,NH3is in its liquid form and storage is not a problem.Also,the hydrogen storage capacity(17.7wt.%)and energy density (3000Wh/kg)of ammonia is higher than those of methanol and other fuels.From an economical standpoint,it has been reported that,compared to methanol reforming,NH3 decomposition is a more economical process for hydrogen generation[18,19].It appears that the on-site technique for ammonia-based hydrogen generation could by-pass the problems related to the puriﬁcation and storage of hydrogen.As far as the research of NH3decomposition is concerned,it is as old as that of NH3synthesis.The works before the1990s on NH3decomposition were mainly conducted to gain insight into the reaction kinetics of NH3 synthesis[20–33].There are reported works on nitriding processes[34–37]and NH3abatement[38–40].In the kinetics studies of NH3synthesis,research on NH3 decomposition was mainly performed with diluted NH3. The studies on NH3abatement yielded a number of catalysts commonly operated at temperatures higher than873K. Recently,reports on H2generation from pure NH3have been published[2,8–10].However,catalytic activities were low even tely,a highly active and stable catalyst for H2generation from NH3was generated by adopting Ru as active component,multi-wall carbon nanotubes(CNTs)as support,and KOH as promoter[13–17].It was reported that the use of MgO–CNTs nanocomposites as support can improve the catalytic activity of Ru;at623K,the H2 formation rate is26.1mmol/(min g cat)or585ml/(min g cat) over a K–Ru/MgO–CNTs catalyst containing equal weights of MgO and CNTs[15],the most active for the decomposition reaction so far.However,there is still room for further improvement;NH3decomposition is endother-mic,and the equilibrium conversion of NH3at673K is 99.1%[Fig.1shows the equilibrium conversion of NH3at different temperatures under normal pressure(1atm)].In the ﬁrst part of this mini-review,a summary is presented on the kinetics and mechanism of ammonia decomposition.Then, the aspects of catalyst development will be explained.We describe factors that exert inﬂuences on the catalyst performance.The electron-withdrawing groups that show negative effects on the catalyst performance are also addressed.1.Reaction kinetics of ammonia decompositionThe catalysis of NH3synthesis has been extensively studied in every aspect during the last century[41–63].In the mid-1990s,carbon-based Ru catalysts were invented and commercialized by BP group and Kellogg group[64].The experience and knowledge gained about these synthesis catalysts have been applied in the later development of ammonia decomposition catalysts.It has been proposed that, over W and Mo,N–H bond cleavage and recombinative desorption of surface nitrogen atoms are slow irreversible steps in NH3decomposition;NH3is activated via a direct dissociative adsorption step,and the adsorbed N atoms are the most abundant reactive intermediate[65].This model seems applicable for NH3decomposition on Pt catalyst,as described by Lo¨fﬂer and Schmidt[21].Tsai and Weinberg [24]proposed that NH3dissociates from an adsorbed precursor state,subtly different from that proposed by Boudart and Dje´ga-Mariadassou[65].According to Tsai and coworkers,at very low pressures,the rate-limiting step of NH3decomposition on a Ru(0001)surface is temperature-dependent.Below approximately650K,the recombinative desorption of nitrogen atoms is rate limiting,whereas aboveS.F.Yin et al./Applied Catalysis A:General277(2004)1–92750K the cleavage of the N–H bond of adsorbed NH3is rate limiting.Concomitantly,the apparent activation energy was observed to decrease from180kJ/mol at the low tempera-tures to21kJ/mol at high parison of experimental activation energies with those calculated by Shustorovich and Bell[66]based on BOC Morse potential method suggested that the rate-determining step of ammonia decomposition is recombinative desorption of N2on Ru as well as Pt,Fe and Re.However,these kinetic models fail to address the inhibitive effect of H2observed on Ru single-crystal surfaces[67].Egawa et al.[67]used deuterated NH3 and obtained evidence to conﬁrm that the inhibition by H2 was a consequence of an equilibrium established among adsorbed N atoms,gas-phase NH3,and gas-phase H2,and that recombinative desorption of nitrogen adatoms was the rate-determining step.Vitvitskii et al.came to a similar idea based on experimental results acquired with diluted NH3[68].To gain additional information about the effect of H2on this reaction as well as to examine kinetic behavior and obtain turnover frequencies at higher reactant pressures, Bradford et al.[33]made a study on NH3decomposition over Ru/C catalyst.By varying the NH3partial pressure between10and90Torr while adjusting the Heﬂow to maintain a constantﬂow rate of the gas mixture,they found that at643and663K there is a nearﬁrst-order dependence on NH3,along with a dependence order on H2betweenÀ3/ 2andÀ2over small(1–2nm)Ru crystallites supported on carbon.Based on the apparent activation energy,they proposed a kinetic model in which both N–H bond cleavage and recombinative desorption of nitrogen adatoms are slow kinetic steps,and nitrogen atoms are the most abundant reaction intermediate;this kinetic model is similar to that proposed in Ref.[65].In this model,NH2–H bond cleavage is a reversible step(Eq.(1)),whereas the recombinative desorption step of nitrogen adatoms is irreversible(Eq.(2)).This model provides an excellent statisticalﬁt to experimental kinetic data obtained at the two temperatures under reaction conditions of much higher H2and NH3pressures.However,it is not clear whether the model is feasible when pure ammonia is applied as the raw material.2½NHÃ3þÃ@NHÃ2þHÃ (1) 2NÃ!N2þ2Ã(2)Chellappa et al.[2]investigated the decomposition kinetics of pure ammonia over Ni–Pt/Al2O3;the work was conducted to gain kinetic data for ammonia-based hydrogen generation for PEMFC applications.They found that the decomposition kinetics of pure ammonia is quite different from those reported previously with diluted ammonia(at low NH3concentrations)for the reaction.Under high NH3 pressure(50–780Torr)and at high temperature(793–963K),the expression that isﬁrst-order on NH3appears to be adequate for predicting NH3conversion under potential conditions of PEMFC processor.It is possible that hydrogen inhibition is inﬂuenced by both NH3pressure and temperature.The activation energy appears to be catalyst-speciﬁc,implying that N–H bond cleavage is not a rate-determining step.They also concluded that,at a temperature above793K and ammonia pressures above100Torr,there is no hydrogen inhibition and no apparent change in reaction order with respect to NH3.Our N2-TPD and TOF data disclosed that the lower the temperature for N2desorption,the larger was the TOF over the Ru catalysts[14],in support of the proposition that the recombinative desorption of nitrogen adatoms is the rate-determining step in NH3decomposition.Although direct data on the chemical nature of the key reaction intermediate on the catalyst are not available,it is reasonable to deduce that the recombinative desorption of nitrogen adatoms is the slowest step in NH3decomposition when pure NH3is used as the reactant.2.Ammonia decomposition catalyst2.1.Active componentMany metals,alloys,and compounds of noble metal characters have been tested for ammonia decomposition. There are works on Fe[9,14],Ni[8,9,12,14],Pt[9,14],Ru [8,9,13–17,26,33,69],Ir[8],Pd[14],Rh[14],Ni–Pt[2],Ni/ Ru[10],Pd/Pt/Ru/La[10],Fe–MO x(M=Ce,Al,Si,Sr,and Zr)[70].The works on alloys are Zr1Àx Ti x M1M2alloy(M1, M2=Cr,Mn,Fe,Co,Ni;x=0–1)with or without about20–50wt.%of Al[11].The compounds of noble metal characters are nitrides[71–73],and carbides of metals [73,74].Other materials have also been tested for the reaction but they showed low catalytic activities[75,76]. Before1990,Fe-based catalysts had attracted much attention[33].In the last decade or so,a lot of work has been focused on Ru catalysts[26,33].More recently, attention has been paid to the use of metal nitrides and carbides[71–74]as well as alloys as active components for the decomposition reaction[11].Papaolymerou and Bontozoglou[26]conducted a study of NH3decomposition over polycrystalline wires or foils of Pd,Ir,Pt,and Rh(Fig.2).At a partial pressure of NH3equal to1Torr,the NH3decomposition rate can be ranked in the order of Ir>Rh>Pt>Pd within a reaction temperature range of500–1200K.Although there is discrepancy above 1200K,such an order is referable because the catalysts for on-site generation of hydrogen work below1200K.In terms of TOF,NH3conversion or H2formation rate,Goodman and coworkers[8]found that the catalytic activity of NH3 decomposition decreased in the order Ru>Ir>Ni for equal nominal metal loading by weight(Table1)when pure NH3was employed as reactant.We conducted a systematic investigation on the effects of active metals(Ru,Rh,Pt,Pd, Ni,Fe)on the reaction with CNTs being the support,and found that,under the same reaction conditions,the NH3S.F.Yin et al./Applied Catalysis A:General277(2004)1–93conversion over Ru is much higher than those over the other metals (Fig.3).Similar to the conversion data,the TOFs of the CNTs-supported metal catalysts can be arranged in the order of Ru >Rh ﬃNi >Pt ﬃPd >Fe,also showing that Ru is the most active.With respect to Fe catalysts,some researchers suggested that the active component is in fact the unstable FeN x [36].Although some metal nitrides and carbides have properties qualitatively similar to those of noble metals,they show much lower catalytic activity for NH 3decomposition,and are easily affected by reaction atmosphere (e.g.a small amount of O 2or H 2O can deactivate the catalysts)[71–74].Obviously,Ru is the most active for NH 3decomposition.Ru has been also regarded as the most active metal in catalyzing the ammonia synthesis reaction;the commercia-lized Ru/carbon catalysts are much more active than the conventional Fe-based ones [48].The Ru/AC (AC:stands for activated carbon)has been regarded as the second-generation catalyst to replace the Fe ones for ammoniasynthesis.In addition,Ru is a very stable catalyst for NH 3decomposition as well as NH 3synthesis because no Ru nitrides are formed.It should be noted that nickel is a cheap metal and is only inferior to Ru,Ir,and Rh in activity.As far as the cost is concerned,Ni could be an attractive alternative.The differences in activity of these active components are usually explained on the basis of reaction kinetics;nitrogen desorption is generally regarded as the rate-determining step.Therefore,the catalytic activity of metals has been studied in relation to the apparent activation energy (E a )for desorption of nitrogen [8,26].The effect of the loading of active component was also studied [77].In the investigated range of 0–35wt.%,NH 3conversion increases with the initial increment of Ru loading,then a maximum appears at 15wt.%.Further increase of Ru loading reduces the NH 3conversion.This phenomenon is understandable if one realizes that,at high loading,the buried Ru sublayers are not accessible.Dissimilar to NH 3conversion,the TOF increases within the Ru loading range.It seems that the decomposition of NH 3is structure-sensitive.Similar results were observed in NH 3synthesis [41,63,78,79].S.F .Yin et al./Applied Catalysis A:General 277(2004)1–94Table 1NH 3conversion and H 2formation rates for SiO 2-supported metal catalysts a (Ref.[8])Temperature (K)10%Ni/SiO 2b 10%Ir/SiO 2b10%Ru/SiO 2b Conversion (%)Rate (H 2)(mmol/min g cat )Conversion (%)Rate (H 2)(mmol/min g cat )Conversion (%)Rate (H 2)(mmol/min g cat )673 1.40.4 3.9 1.214.3 4.5723 4.2 1.38.1 2.636.411.477310.5 3.318.2 5.764.020.082321.6 6.830.49.5––87336.411.456.017.69730.392370.021.1––9930.9973––9830.6––a Reaction conditions:catalyst load 0.1g,NH 3ﬂow 50ml/min [GHSV NH 3is ca.30,000ml/(h g cat )].bSurface metal atoms per gram catalyst,10%Ni/SiO 2:9.6Â1018;10%Ir/SiO 2:1.0Â1019;Ru/SiO 2:6.8Â1018.Fig.3.NH 3conversion and H 2formation over CNTs-supported metal catalysts [the molar loadings of the active metal in the catalysts are ca.4.75Â10À4mol/g cat ;reaction conditions:673K,GHSV NH 3=30,000ml/(h g cat )](Ref.[14]).In addition,the precursor of the active component can have an effect on the catalyst performance,because the precursor can bring in impurities(to be discussed in a later section).Also,the Ru precursor has an effect on Ru dispersion.The Ru dispersion in K–Ru/CNTs prepared from Ru(acac)3precursor is10%higher than those from Ru nitrosyl nitrate,and the NH3conversion on the former catalyst is ca.15%higher than that on the latter[77].This phenomenon was also found in ammonia synthesis.For example,compared to the cases when Ru(CO)12was used as a precursor,Ru dispersion was doubled,and the activity of the Ru–BaO/AC catalyst doubled too when Ru(acac)3was adopted as the precursor[47].2.2.SupportSupports have been employed to enhance the dispersion and surface area of the active components.A good support should at least possess the properties of(i)being stable under reaction conditions,and(ii)having a high speciﬁc surface area.However,a support often exerts other effects on the catalytic performance of an active catalyst.Such phenomena have been also observed in the ammonia decomposition catalyst system.The Al2O3-supported Ru or Ir catalysts showed activities for ammonia decomposition lower than those supported on SiO2,respectively;the TOF over Ni/ HZSM-5was much lower than that over Ni/HY and Ni/SiO2 (the data for the supported catalysts are shown in Fig.4)[8]. It was disclosed that the apparent activation energy(E a)of these supported Ni catalysts are in the range of80–90kJ/ mol,lower than those of Niﬁlm(180kJ/mol)and Ni wires (209kJ/mol).Similarly,there are large discrepancies in E abetween the supported Ru catalysts and Ruﬁlms.Unlike the cases of Ni and Ru metals,there is little difference in activation energy between the wires and supported catalysts of Ir,Pt,Rh,and Pd,respectively[8,26].Recently,we have demonstrated that the catalytic performance of Ru catalyst is support-dependent[13–16]. As shown in Table2,under similar reaction conditions,the order of NH3conversion can be ranked as Ru/CNTs>Ru/ MgO>Ru/TiO2ﬃRu/Al2O3ﬃRu/ZrO2>Ru/AC>Ru/ ZrO2–BD(the ZrO2–BD was prepared by reﬂux-digestion in a glass vessel of ZrO(OH)2in aqueous NH4OH solution at pH=11.5,followed by calcination at873K[80];this oxide was acidic due to the presence of Si4+ions extracted from the wall of the glass vessel during the preparation[14]). We deduced that the excellent catalytic performance of Ru/CNTs is related to the high dispersion of Ru and to the high purity of CNTs.Moreover,we considered that the conductivity of the support is very important for high catalytic efﬁciency.A conductive support is beneﬁcial for the transfer of electrons from promoter and/or support to Ru, a process that would facilitate the recombinative desorption of surface N atoms.The correlation of the TOF data with support acidity–basicity property(in Table2)showed that there is a declining trend in catalytic activity with the decrease in support basicity.In other words,a support of high acidity is unsuitable for NH3decomposition,whereas a support of strong basicity is highly beneﬁcial for high catalytic efﬁciency.The deduction was further conﬁrmed by the reaction data(also in Table2)obtained over Ru/K–CNTs and Ru/K–ZrO2–BD,where K–CNTs and K–ZrO2–BD were prepared by modiﬁcation of CNTs and ZrO2–BD with KOH,respectively[14].These modiﬁcations led to remarkable increases in catalytic activity of the supported Ru catalysts both in NH3conversion and TOF NH3.According to the deduction that the conductivity (graphitization degree of carbon materials)and basicity are crucial parameters of an effective support,we prepared nanocomposite MgO–CNTs materials and used them as support for Ru.Temperature-programmed hydrogenation results showed that the presence of MgO leads to an enhanced thermal stability of CNTs in hydrogen.We consider that the stabilization of CNTs in the nanocompo-sites is a consequence of MgO–CNTs interaction due to reactions between functional groups that exist on CNTs (e.g.,hydroxyl,carbonyl,and carboxyl groups)and MgO (e.g.,hydroxyl group).As shown in Fig.5,the Ru/MgO–CNTs catalyst with an equal weight of MgO and CNTs exhibits catalytic activity higher than those of Ru/MgO andS.F.Yin et al./Applied Catalysis A:General277(2004)1–95Ru/CNTs;similar result was observed over the correspond-ing KNO 3-modi ﬁed samples [15].The results reassure us that our deductions can serve as a reliable strategy for the design of support material.Another piece of evidence was provided in the work of Rama Rao and coworkers [81].They prepared Ru catalysts supported on carbon-covered alumina (CCA);since CCA offers the purity of carbon and reduces the acidity of alumina,better catalytic activity was achieved for ammonia synthesis.The works of Aika and coworkers disclosed the importance of support basicity for an ef ﬁcient ammonia synthesis catalyst [43,44].Our N 2-TPD results disclosed that the stronger the support basicity,the easier the N 2desorption is [14].Since carbon materials are effective supports for NH 3decomposition and synthesis,it is worth investigating their stability under thermal treatments.It has been pointed out that thermal treatments of active carbon at extremely high temperatures under inert gas atmospheres could change its textural property,usually a sharp decrease in total pore volume due to the loss of micropores [46,59].To some extent,the thermal treatments led to a higher degree ofgraphitization,and such structure modi ﬁcation of carbon was commonly regarded as the cause for the high activity of the supported catalyst.Kowalczyk et al.[59]found that,when active carbon was treated thermally at 2173K in inert gas,there was a remarkable increase in the degree of graphitization,and that the Ru catalyst deposited on the thermally modi ﬁed carbon was much more active than that deposited on the untreated carbon.In addition,Zhong and Aika [46]found that the removal of impurities in activated carbon had a signi ﬁcant effect on the catalytic behavior of the supported catalyst.They succeeded in eliminating electronegative impurities such as S,N,O,and Cl by treating commercial AC with hydrogen at 1073K (or 1188K)for 12h or longer.When AC that had been treated thermally with hydrogen was used as the support,the catalytic activity of Ru became remarkably higher;such ef ﬁciency is also independent of the carbon source.These results are further evidence in support of the contention that the purity and graphitization degree of the carbon materials are essential parameters for better catalyst performance in ammonia synthesis.Li and coworkers [63,82]came to a similar conclusion when graphitic nano ﬁlaments were used as support for Ru –Ba catalysts in NH 3synthesis.It is therefore con ﬁrmed that the support of Ru catalyst for NH 3decomposition should concomitantly possess the following properties:(i)basicity,(ii)conductivity,(iii)low concentration of electron-withdrawing groups,(iv)high thermal stability,and (v)high surface area (for good dispersion of Ru).Therefore,the development of composite support (MgO –CNTs as described previously)seems to be a viable way of generating better Ru catalyst.2.3.PromoterAlkali,alkaline earth,or rare earth metal ions are known to be ef ﬁcient promoters for supported Ru or Fe catalysts in NH 3synthesis [41–53];Ba and Cs ions were found to be effective promoters as well.Small metal particles tend to sinter during thermal treatment,and a promoter acts as an effective adjuvant for preventing Ru or Fe from sintering.S.F .Yin et al./Applied Catalysis A:General 277(2004)1–96Table 2Effect of support on catalytic performance of Ru catalysts for NH 3decomposition (Ref.[14]).Catalyst code Reaction data a Surface property of support b NH 3conversion (%)Hydrogen formation (mmol/min g cat )TOF H 2(s À1)NH 3desorption peak (K)CO 2desorption peak (K)Ru/CNTs 3.7 6.2 1.1––Ru/MgO 3.2 5.4 2.0–375,442,572Ru/TiO 2 2.6 4.3 1.5415408Ru/Al 2O 3 2.3 3.80.5369440Ru/ZrO 2 2.2 3.7 1.3453435Ru/AC1.62.7 1.2––Ru/ZrO 2–BD 0.8 1.30.4403,610–Ru/K –CNTs c7.312.2 2.0–381,839Ru/K –ZrO 2–BD c5.38.52.2–395,829a Reaction conditions:673K,GHSV NH 3=150,000ml/(h g cat ).b Measured by NH 3-TPD and CO 2-TPD techniques.cThe atomic ratios of K/Ru were 1in these twosamples.Fig.5.Effect of support on NH 3conversion over Ru and KNO 3-modi ﬁed Ru catalysts [atomic ratios of K/Ru are 2in the modi ﬁed catalysts,1:1in MgO –CNTs (1:1)represents mass (or weight)ratio of MgO to CNTs;reaction conditions:673K,GHSV NH 3=60,000ml/(h g cat )](Ref.[15]).Compared to NH3synthesis,information on the effect of promoters on NH3decomposition catalysts is limited and inconsistent.We employed rare earth,alkali,and alkaline earth metal nitrates to modify Ru/CNTs,and systematically investigated the effects of the promoter cations and the amount of potassium on the morphologic structure and catalysis of Ru/ CNTs[17].Although the modiﬁcation causes a reduction in both surface area and pore volume of the Ru/CNTs catalyst, little effect was observed on the size and morphology of the Ru particles.Interestingly,the modifying agents show an inhibitive effect on CNTs methanation,raising the onset temperature by ca.10–80K and reducing the methanation rate.Over the K-modiﬁed Ru catalysts,we observed that the onset temperatures for methanation were30–50K higher than that of‘‘pure’’CNTs support.Over the modiﬁed catalysts,we found that the order ofcatalytic activity can be arranged as K–Ru>Na–Ru>Li–Ru>Ce–Ru>Ba–Ru>La–Ru>Ca–Ru>Ru(Fig.6), signifying that within the same groups(K,Na,and Li;Ba and Ca),the higher the electronegativity of the promoter,the lower is the NH3conversion.However,in the study of the reverse NH3synthesis reaction,it has been found[50,63] that Ba2+ions are more effective than K+ions for promoting Ru.Of all the potassium salts adopted,KNO3,KOH,and K2CO3show similar promotional effects(Table3).With the understanding that thermal treatment can lead to KNO3and K2CO3decomposition and K2O generation,and K2O reacts readily with H2O to form KOH,we deduce that KOH and/or K2O is the active status of the promoter.By varying the anions of potassium salts,we have proven the above deduction.Unlike KOH,the active phase of Ba(OH)2is likely to be BaO(due to the thermodynamic equilibrium of BaO/Ba(OH)2).The activity of Ru–K/CNTs increases with an initial rise in KNO3amount,and reached a maximum at a K/Ru atomic ratio of around2.Further increase in K/Ru ratio would result in a reduction in the catalytic activity[17]. The results of N2-TPD investigation revealed that the promotional effects of a modiﬁer are a combined result of(i) enhancing the desorption of nitrogen adatoms,and(ii) decreasing the apparent activation energy of the decom-position reaction.Certainly,the promotional effect is also dependent on the adopted active component.On the basis of equal K amounts, the promotional effect of K on Ru is more pronounced than that on Fe[31–32].In another set of experiments,we observed that KOH modiﬁcation can also result in activity enhancement of a Ni/ZrO2catalyst for NH3decomposition, although the degree of enhancement is much lower than that observed over the Ru-based catalysts.The promotion is also sensitive to the type of support;KOH modiﬁcation exerts a greater effect on the activity of Ru/CNTs than that of Ru/ MgO(Fig.5).This is because electron transfer from promoter to Ru is more feasible in the case of a conductive support[13].3.Effect of the electron-withdrawing groupsFrom the previous description of the catalysts for ammonia decomposition,one can see that Ru is the most active component,CNTs is the most effective support,and KOH is the best promoter.However,the catalytic performance of the Ru–K/CNTs catalyst can also be affected by the presence of impurities and/or residual surface groups.It is known that there are various functional groups(e.g.–COOH,–OH)on carbon materials[46]that would cause negative effects on the electronic structure of metal catalysts for NH3decomposition and synthesis.Such groups,nevertheless,are responsible for the anchoring of the metal on the carbon materials and are beneﬁcial for Ru dispersion.For metal oxide supports,there are inevitably small amounts of impurities(such as SO42À,ClÀ,PO43À),which are strong inhibitors of Ru catalysts.The presence of SO42Àand PO43Àin Ru/CNTs leads to a large decrease in catalytic activity(Table3)and an increase in apparent activationS.F.Yin et al./Applied Catalysis A:General277(2004)1–97Table3NH3conversion and H2formation over Ru/CNTs catalysts modiﬁed by potassium with different anions at673and723K(Ref.[17])Sample code NH3conversion(%)H2formation rate (mmol/min g cat)673K723K673K723K Ru8.80 5.8921.714.5 Ru–KNO349.733.385.257.1 Ru–KOH47.231.683.255.7 Ru–K2CO346.731.382.455.2 Ru–KF22.114.843.128.9 Ru–KCl16.811.334.323.0 Ru–KBr8.51 5.7019.312.9 Ru–K2SO40.110.07 1.120.75 Ru–K3PO40.210.13 1.82 1.22 Atomic ratios of Ru/K are1in all the modiﬁed samples.Reaction condition: GHSV NH3=60,000ml/(h g cat).。

Contour Series Electronic Eye Barrier-Free Water C

Fig.1 – HRFER-EE-QFigure 1 2ModelHRFER-EE-QHRFSER-EE-QDescriptionContour Series - Extended ReachContour Series - Dual InstallationReview these instructions before beginning installation. Be sure that installation conforms to all plumbing, electrical and other applicable codes.When installation is complete, ensure these instructions are left in the plastic bag provided inside the installed unit for future reference.Service to be performed by authorized service personnel only.INSTALLERNOTE: It is common practice to ground electrical hardware such as telephones, computers and other devices to available water lines. This can, however, cause electrical feedback in the plumbing circuit, which results in an“electrolysis” effect occurring in the fountain. This may result in water which has a metallic taste to it or has aFig. 2 – HRFSER-EE-Q97880C (Rev. F - 08/16)Page 197880C (Rev. F - 08/16)Page 2Figure 3 – Water Supply ConnectionsInstallation PackageThe components for installation are packed in three separate boxes, regardless of the type of unit being installed. The boxes contain the following:Box No. 1: Wall Frame(s)Box No. 2: Remote Chiller, SJ8-QBox No. 3: Fountain(s), Arm(s) and PanelsAdditional materials, as noted in the Parts List, are also shipped in these boxes.Number Required26837C 26839C 26833C 27026C 5500060427623C 550006615500066510032274056011100834389011157724389011157734389011262754389015005C 22525C 28823C 27240C 31375C 000000032731376C 31384C 3841700140045C 45662C 45663C 50203C 50986C 51409C 51544C 55905C 56082C 56092C 56159C 61313C 70016C 1126275438901000001994100000216270817C 70989C1234567891011121314151617181920212223242526272829303132333435Parts ListUpper Panel (HRFER-EE)Upper Panel (HRFSER-EE)Lower Panel (HRFER-EE)Lower Panel (HRFSER-EE)Standard Reach Arm Extended Reach Arm (EE)Bottom Cover - Standard Reach Bottom Cover - Extended Reach (EE)Bubbler GasketScrew #10-24 x .62 HHMS Screw 5/16-18 x .75Hex Nut 5/16-18Screw #10-24 x .50 PHTC Regulator Retaining Nut Regulator Mounting Bracket Regulator Mounting Bracket Support BracketSolenoid Valve Assy. 115V Solenoid Valve Assy. 220/230V Power Cord 115V Sensor Assy.Screw #8-18 x .37 HHSM Hex Nut Push Button Push Button Sleeve Strain Relief Bushing Regulator Holder Spacer BubblerBubbler - EasyFlex (Option)Regulator NutPoly Tubing 1/4” (Cut To Length)Bubbler NippleRegulator - W/Red Spring NutScrew #10-24 x .50 PHTC Fitting - Tee 1/4” (3 Pack)Fitting - Union 1/4” (3 Pack)Fitting - Elbow 1/4”Ground Screw #8-36 x .37ItemPart No.DescriptionHRFER-EE-QSee Fig.1-1--1-124447-1-1111121--11211111122-11111, 2211, 2213, 2213, 2222222222195, 85, 85, 82220212021181818215, 820, 2120202120, 212119192615, 161920, 21212116151818-1-11111458812111111112411122221122221-11HRFSER-EE-Q1/4” O.D. TUBE WATER INLET TO COOLER3/8” O.D. TUBE CONNECT COLD WATER SUPPLYBUILDING WATERINLETNOTE: WATERFLOWDIRECTION SERVICE STOP (NOT FURNISHED)97880C (Rev. F - 08/16)Page 3Parts List Continued75507C 75672C LK46498525C 45784C 45796C 55996C 7200152775674C 56369C3637383940414243NS NSFitting - 1/4” NPTF Cap Screw #6-32 x .25Drain Assy. (Includes items 39 thru 43)Kit - Strainer & Ferrule Assy./Gasket Drain Trap Fitting - Elbow 1/4”Strainer (Supplied with Chiller)Rubber Washer Allen Wrench 7/64Edge Trim - 2FT.ItemPart No.DescriptionSee Fig.2-111111118202222222215, 1622-212222121-HRFER-EE-QHRFSER-EE-QNS means not shownPage 4BOLT FRAMES TOGETHERWITH 5/16" x 3/4" (19mm) BOLTS (4 REQ'D - PROVIDED)P/N 111577243890HOOK RODS (2)P/N 101567442730CHILLER SHELF P/N 27638CFigure 5 – Rough-In Assembly Dual-Station Mounting FramePage 597880C (Rev. F - 08/16)Page 6CHILLER SHELF P/N 27638CHOOK RODS (2)P/N 101567443730Figure 8 – Rough-In Assembly Single-Station Mounting FramePage 797880C (Rev. F - 08/16)Page 897880C (Rev. F - 08/16)Page 912. These products are designed to operate on 20-105 PSIsupply line pressure.warranty.Figure 15 – HRFER-EE-Q Tube RoutingFigure 14 – Stream HeightFigure 16 – HRFSER-EE-Q Tube Routing4227CHILLER OUTLET3327 - TO BUBBLERCHILLER INLET4227CHILLER OUTLET3227 - TO BUBBLER272727Page 10Stream Regulator: If orifice is clean, regulate flow as in Step 14 of the installation instructions. If replacement is necessary, see parts list for correct regulator part number.Figure 20 – Push Button/Regulator Assembly1119293713Figure 19 – View of Bubbler Assembly256282222 CAMDEN COURTOAK BROOK, IL 60523630.574.3500PRINTED IN U.S.A.FOR PARTS, CONTACT YOUR LOCAL DISTRIBUTOR OR VISIT OUR WEBSITE Page 1197880C (Rev. F - 08/16)。

差分脉冲溶出伏安法

实验条件：
Cd
Pb
富集：，120s 溶出：
清洗：， 120s
脉冲幅度 80mV 脉冲周期 200ms 脉冲宽度 5ms
Effect of the experimental variables
GNFs–NA溶液体积
GNFs–NA膜厚度的影响：溶液体积达到3 μL时灵敏度很高，3-7 μL 峰电流值降低。
富集时间
30 s 到 120 s峰电流线性增加，120 s之后线性不明显。
由于电极表面负载量饱和，电流增加的幅度变小。
Effect of the experimental variables
Bi(III)的浓度
从100到400 μg/L峰电流随Bi膜厚度的增加而增大，400 μg/L以后峰电流降低，并且峰变宽。
Effect of the experimental variables
Effect of the experimental variables 阳极溶出伏安法工作原理得到良好的线性工作曲线，这是定量应用的基础。得到良好的线性工作曲线，这是定量应用的基础。阳极溶出伏安法工作原理溶液体积达到3 μL时灵敏度很高，3-7 μL峰电流值降低。 Effect of the experimental variables GNFs–NA溶液体积得到良好的线性工作曲线，这是定量应用的基础。得到良好的线性工作曲线，这是定量应用的基础。它是在缓慢线性扫描的电压（5-10mV/s）上迭加一个振幅为50-100mV的周期性脉冲，并在刚好加脉冲之前和脉冲的后期分别测量电流，将这两次电流的差值由电子线路放大输出。
Differential Pulse Stripping Voltammetry