Influence of AlF3 and hydrothermal conditions on morphologies of α-Al2O3
α-Fe2O3光电催化分解水制备氢气研究进展
2017年第36卷第2期 CHEMICAL INDUSTRY AND ENGINEERING PROGRESS ·397·化工进展α-Fe2O3光电催化分解水制备氢气研究进展王开放，刘光，高旭升，贺冬莹，李晋平（太原理工大学精细化工研究所，山西太原 030024）摘要：光电化学池可以将太阳能以氢气的形式储存起来，其中稳定、廉价的催化剂是关键。
α-Fe2O3具有合适的禁带宽度，较高的理论光-电转化效率，光稳定性好，在地壳中的储量丰富，被认为是最具有发展前景的光电催化材料之一；但是它的导电性差、光生电荷寿命短、氧化反应过电位高，严重阻碍了其发展。
本文首先介绍了光电催化理论，然后重点综述了近些年α-Fe2O3纳米结构的制备技术，以及针对其不足所采用的改性方法，包括通过元素掺杂来增强α-Fe2O3的导电性，表面处理来降低氧化反应过电势或陷阱浓度，与其他材料复合来增加光生电压或催化剂表面积，最后对α-Fe2O3作为光阳极催化剂分解水制氢未来的发展前景作出展望，指出多种手段的有效结合是提高其光电流密度的重要途径。
关键词：赤铁矿；太阳能；光电催化；水解；氢气中图分类号：O614.81；O644.16；TQ116.2 文献标志码：A 文章编号：1000–6613（2017）02–0397–13 DOI：10.16085/j.issn.1000-6613.2017.02.001Hematite photoanodes for solar water splittingWANG Kaifang，LIU Guang，GAO Xusheng，HE dongying，LI Jinping （Research Institute of Fine Chemicals，Taiyuan University of Technology，Taiyuan 030024，Shanxi，China）Abstract：Photoelectrochemical cell is able to turn sunlight into stored energy conveniently in the form of hydrogen，and the stable and low-cost photoanode catalyst is crucial in this device. Hematite is considered as one of the most promising photoanode catalysts due to its suitable band gap，high theoretical solar to hydrogen efficiency，chemical stability under illumination and rich storage in earth.However，the poor conductivity，short photo-generated charge carrier lifetime and high turn-on voltage have limited the performance improvement of hematite severely. This review introduces the basic mechanism of photoelectrocatalysis and energy band excitation，then it summarizes the synthesis of nanostructure α-Fe2O3 and the improvements on the photoelectrocatalysis property of hematite in recent years，including conductivity enhancement by element doping，oxygen evolution overpotential or trap concentration reduction by surface treatment，and photo-induced voltage or specific area increase by coupling with other materials. The future developing perspectives of hematite are also presented，and multi-modified technologies are considered as important ways to improve the photocurrent density.Key words：hematite；solar energy；photoelectrocatalysis；hydrolysis；hydrogen随着全球经济的不断发展，人类对能源的需求量持续扩大，全球能源的消耗仍然是以化石能源为主，但是化石燃料储量有限、生成周期长，难以满足持续大量的需求，而且常规能源的广泛应用所引起的环境问题日益凸显。
乙酸蒸汽催化重整制氢的研究进展
CHEMICAL INDUSTRY AND ENGINEERING PROGRESS 2017年第36卷第5期·1658·化 工 进展乙酸蒸汽催化重整制氢的研究进展王东旭1，肖显斌2，李文艳1（1华北电力大学能源动力与机械工程学院，北京 102206；2华北电力大学生物质发电成套设备国家工程实验室，北京 102206）摘要：通过生物油蒸汽重整制备氢气可以减少环境污染，降低对化石燃料的依赖，是一种极具潜力的制氢途径。
乙酸是生物油的主要成分之一，常作为模型化合物进行研究。
镍基催化剂是乙酸蒸汽重整过程中常用的催化剂，但容易因积炭失去活性，降低了制氢过程的经济性。
本文首先分析了影响乙酸蒸汽重整制氢过程的各种因素，阐述了在这一过程中镍基催化剂的积炭原理，讨论了优化镍基催化剂的方法，包括优化催化剂的预处理过程、添加助剂和选择合适的载体，最后对乙酸蒸汽重整制氢的热力学分析研究进展进行了总结。
未来应重点研究多种助剂复合使用时对镍基催化剂积炭与活性的影响，分析多种助剂的协同作用机理，得到一种高活性、高抗积炭能力的用于生物油蒸汽重整制氢的镍基催化剂。
关键词：生物油；乙酸；制氢；催化剂；热力学中图分类号：TK6 文献标志码：A 文章编号：1000–6613（2017）05–1658–08 DOI ：10.16085/j.issn.1000-6613.2017.05.014A review of literatures on catalytic steam reforming of acetic acid forhydrogen productionWANG Dongxu 1，XIAO Xianbin 2，LI Wenyan 1（1 School of Energy ，Power and Mechanical Engineering ，North China Electric Power University ，Beijing 102206，China ；2 National Engineering Laboratory for Biomass Power Generation Equipment ，North China Electric PowerUniversity ，Beijing 102206，China ）Abstract ：Hydrogen production via steam reforming of bio-oil ，a potential way to produce hydrogen ， can reduce environmental pollution and dependence on fossil fuels. Acetic acid is one of the main components of bio-oil and is often selected as a model compound. Nickel-based catalyst is widely used in the steam reforming of acetic acid ，but it deactivates fast due to the carbon deposition. In this paper ，the affecting factors for the steam reforming of acetic acid are analyzed. The coking mechanism of nickel-based catalyst in this process is illustrated. Optimization methods for nickel-baed catalyst are discussed ，including optimizing the pretreatment process ，adding promoters ，and choosing appropriate catalyst supports. Research progresses in the thermodynamics analyses for steaming reforming of acetic acid are summarized. Further studies should be focused on the effects of a combination of a variety of promoters on carbon deposition. Catalytic activity and the synergy mechanism should be analyzed to produce a novel nickel-based catalyst with high activity ，high resistance to caborn deposition for hydrogen production via steam reforming of bio-oil. Key words ：bio-oil ；acetic acid ；hydrogen production ；catalyst ；thermodynamics第一作者：王东旭（1994—），男，硕士研究生，从事生物质能利用技术研究。
AlF3做铝源
Influence of AlF3 and hydrothermal conditions onmorphologies of Į-Al2O3FU Gao-feng(Ҭ催 )1, WANG Jing(⥟ )2, KANG Jian( )21. School of Materials and Metallurgy, Northeastern University, Shenyang 110004, China;2. College of Materials Science and Engineering, Dalian Jiaotong University, Dalian 116028, ChinaReceived 10 September 2007; accepted 12 April 2008Abstract: HomogeneousĮ-Al2O3 platelets were synthesized by introducing AlF3 to alumina precursor. The effects of AlF3 additive on the phase transformation and morphology of the prepared Į-Al2O3 platelets were investigated. The results show that a single phase ofĮ-Al2O3 with an average particle size of 8 P m can be obtained at 900 with 2% AlFć3 additive. The transformation temperature decreasing is attributed to introduction of Al3+ vacancy and to the formation of intermediate compound of AlOF, which is considered to accelerate the mass transportation from transitional Al2O3 to Į-Al2O3. AlF3 concentration and hydrothermal temperature can also affect the morphology of Į-Al2O3. When hydrothermal temperature is 120 , the morphology ofćĮ-Al2O3 transforms from irregular to flat hexangular platelet with increasing AlF3 concentration. As hydrothermal temperature increases, the morphology of Į-Al2O3 with 2% AlF3 additive changes from polyhedron to hexangular platelet and then to vermicular.Key words: Į-Al2O3 platelets; AlF3; hydrothermal treatment; morphology1 IntroductionAlumina is one of the most important oxides and has been intensively studied over a long period because of its widely potential applications in ceramic, glass, functional materials, adsorbents, catalysts and catalyst supports etc[1í3]. Alumina exists in a number of metastable transition phases as well as the thermodynamically stable Į-Al2O3 or corundum.As for the wet chemical methods, it is known that almost all those salt-derived aluminum hydroxides dehydrate to form J-Al2O3. The transformation proceeds through the following sequence, J—į—ș—Į[4]. The J-Al2O3 is a metastable defect spinel with the oxygen atoms in cubic packing and aluminum in both tetrahedral and octahedral coordinations. The į and ș forms of alumina are also metastable defect spinels, making the rearrangement process from J-Al2O3 to ș-Al2O3 of relatively low energy[5í7]. However, the transformation from ș-Al2O3 to Į-Al2O3involves a significant change in the oxygen sublattice from cubic peaking to hexagonal close packing and generally requires temperatures above 1 200 ć for complete conversion to the thermodynami- cally stable corundum phase. The gained Į-Al2O3 with hard agglomeration or vermicular morphology makes sintering to full density even more difficult due to the formation of large pores that are often entrapped within grains.Thus, lowering the phase transformation temperatures is the target for preparing Į-Al2O3. Some studies have already been carried out on the phase transformation of alumina. For example, some papers dealt with the mechanisms of phase transformation and the transformation mechanism of Ȗ- to Į-Al2O3, involving the conversion of cubic close packing of oxygen ions into stable hexagonal close packing[1,8í9]. While others reported the methods for enhancing the kinetic rate of phase transformation[10]. It is known that the temperatures of Ȗ- to Į-Al2O3 transition can be influenced by some cation additives. For example, the addition of transition metals such as Fe2+, Cr3+ and Ti4+ has been reported to accelerate the Ȗ- to Į-Al2O3 phase transformation, whereas Cs+, Ba2+, La3+, Si4+ additives are well known to retard it[11í14].In this work, fluoride aluminum was introduced to the alumina precursor synthesized by aluminum alkoxide hydrolysis and hydrothermal treatment methods. TheCorresponding author: WANG Jing; Tel: +86-411-84107583; E-mail: wangjing@FU Gao-feng, et al/Trans. Nonferrous Met. Soc. China 18(2008)744effects of AlF 3 additive on the phase transformation and the morphologies of the prepared Į-Al 2O 3 particles are investigated.2 ExperimentalSolution A was prepared by adding aluminum isopropoxide to certain content of analytical grade isopropanol (A.R., Dalian Inorganic Chemical Co., China). Certain amount of AlF 3 (C.P., Shanghai Reagent Co., China) was added to the mixture solution of deionized water and isopropanol to make slurry B. The slurry B was dispersed by ultrasonic for 10 min and then mixed with solution A at 65 under ćrapid stirring and refluxing for 2 h. The resulting product was transferred into a Teflon-lined stainless autoclave to fill 80% of the total volume. The autoclave was sealed and maintained at certain temperature for 24 h. The autoclave was then allowed to cool naturally to room temperature and a white precipitated powder was obtained. The powder was filtered and washed several times with absolute ethanol and distilled water, and then dried in vacuum at 60 ć for 12 h.Al 2O 3 particles were obtained by annealing the as-synthesized powders in air at different temperatures for 3 h.The crystal structure of the product was examined by X-ray diffraction (XRD, Cu K Į radiation, D/max-rB, Japan). An overview of the sample morphology was checked with a scanning electron microscope (SEM, JSM-6700F, JEOL, Japan).3 Results and discussion3.1 Phase transformation of Al 2O 3Fig.1shows the XRD patterns of the gainedpowders from the precursor without additive afterFig.1 XRD patterns of calcined powders from precursorwithout additivehydrothermal treatment at 120 and ćcalcination at different temperatures. Diffraction peaks corresponding to J -Al 2O 3,į-Al 2O 3 and ș-Al 2O 3 are found for the sample calcined at 900 ć. No significant change in the structure is found after calcination at temperature up to 1 000 ć.The amount of Į-Al 2O 3 increases drastically when the calcination temperature increases up to 1 100 .ćHowever, a small amount of ș-Al 2O 3 remains.Fig.2 shows the XRD patterns of the gained powders from precursor with 2% AlF 3 additive after hydrothermal treatment at 120 for 24ć h and calcination from 550 to 1 200 ć. It can be seen that J -Al 2O 3 forms for the sample calcined at 550 and 800ćć. The phase transformation of J -Al 2O 3 to Į-Al 2O 3 is completed at 900 ć and no significant change is found after the calcination at temperature up to 1 200 .ćFig.2 XRD patterns of Al 2O 3 precursor with AlF 3 calcined at different temperaturesGenerally, the transformation from metastable transition phases to Į-Al 2O 3 involves a significant change in the oxygen sublattice and usually a temperature above 1 200 ćis required for complete conversion to the thermodynamically stable corundum phase. It can be seen from Fig.2 that the addition of AlF 3can enhance the kinetic rate of the phase transformation form J -Al 2O 3 to Į-Al 2O 3 and reduce the transformation temperature of Į-Al 2O 3 phase. During the heat treatment, the existence of AlF 3 destroys the well-regulated atomic packing configuration and introduces Al 3+ vacancy. When AlF 3 is introduced to alumina precursor, two defect reactions may take place as follows:Al Al O OAl 3V Al F 3AlF 32c c co x (1) F 3F 32Al 2AlF O Al O Al 332co x (2) The vacancies and interstitial atoms can be formedFU Gao-feng, et al/Trans. Nonferrous Met. Soc. China 18(2008) 745through these reactions. There are no significant distinctions between Fí radius and O2í radius, so Fí can not take interstitial sites. Comparatively, the formation energy of vacancy is lower than that of interstitial atoms. Thus, the defect can give priority to Al3+ vacancies. Al3+ vacancies accelerate Al3+ diffusion and reduce the transformation temperature of J-Al2O3 to Į-Al2O3.In addition, some intermediate compounds can be formed in the case of the phase transformation. They can also accelerate the mass transportation from transitional phase to Į-Al2O3. It is known that Ȗ-Al2O3 is highly active and has large surface area. Thus, it is strongly hygroscopic to adsorb H2O in the air. During the heat treatment, AlF3 can take the following reversible reaction with H2O adsorbed[15]:2AlF3+3H2O Al2O3+6HF (3) And the positive reaction may be performed through the secondary reactions as follows.1) The gaseous intermediate compound, AlOF, can be synthesized by the following reaction.AlF3+H2O=AlOF+2HF (4) The gaseous intermediate compound, AlOF, can play the role of gas transmission and accelerate atomic transference velocity to enhance the phase transformation. In this work, although it is quite difficult to define the composition of the intermediate compound, it can ultimately transform into alumina:3AlOF=Al2O3+AlF3 (5) 2AlOF+H2O=Al2O3+2HF (6)2) The intermediate compound, Al2O, can be synthesized as:2AlF3+3H2O=Al2O+6HF+O2 (7) Finally, Al2O takes part in the following reactions and transforms into alumina:3Al2O=Al2O3+4Al (8) Al2O+2H2O=Al2O3+2H2(9) Similarly, the intermediate compound, Al2O, can enhance the phase transformation by accelerating atomic transference velocity.3.2 Morphology of Į-Al2O3The morphologies of the gained powders from precursor with 2% AlF3 additive after hydrothermal treatment at 120 for 24ć h and calcination from 800 to 1 200 wereć examined by SEM. Fig.3 shows the SEM micrographs of the obtained products. The microstruc- ture of the sample calcined at 800 is floccule and thće Fig.3 SEM micrographs of samples treated at different temperatures: (a) 800 ć; (b) 900 ć; (c) 1 000 ć; (d) 1 200 ćFU Gao-feng, et al/Trans. Nonferrous Met. Soc. China 18(2008) 746full-grown crystal is not seen. The alpha phase does not appear, which is convinced by XRD pattern at 800 ćas shown in Fig.2. When the calcinating temperature is raised to 900, 1 000 and 1 200 ć, respectively, the morphologies of those particles are plate-like and there is no remarkable change in particle size. It is shown that once alpha phase is obtained, the effects of temperature on morphology and size are rather feeble.Fig.4 shows the SEM micrographs of the gained Į-Al2O3 powders from precursors with different AlF3 concentration calcined at 1 200 . It can be seen thatćFig.4 Effect of AlF3 concentration on morphology of Į-Al2O3: (a) 2%AlF3; (b) 10%AlF3; (c) 20%AlF3Į-Al2O3 passes through the morphology transformation of irregular platelet to flat hexangular platelet as AlF3 concentration is increased.Į-Al2O3 belongs to rhombohedral crystal system and the space group is .3cR The existence of AlF3 additive causes different growth rate along the respective crystal axis and finally has effects on the morphology of Į-Al2O3. In view of crystal growth, the microstructure is determined by crystal growth rate. The crystal plane with larger growth rate will gradually disappear and while the crystal plane with smaller growth rate will be maintained. The shape of the crystal plane is relevant to the crystal plane with larger growth rate. The unsaturated surface tension existed on the surface of solid can adsorb AlF3 around. And the adsorption capacity varies with the anisotropic surface tension. Usually, the surface tension of crystal plane with close-packed atom is smaller. In Į-Al2O3 unit cell, (0001) and its symmetrical crystal plane takes with close-packed atom. They have weaker capacity to adsorb gaseous molecule and accordingly there are less atoms transferred by gas transmission, thus (0001) and its symmetrical crystal plane are maintained because of the lower growth rate along the crystal axis. Generally, the crystal planes with lower growth rate have more perfect crystal structure, so (0001) and its symmetrical crystal plane are much more smooth than others with excessive crystal defects caused by rapid growth. Then the crystal planes with larger growth rate will gradually disappear and transform to final platelet morphology.SEM micrographs of Į-Al2O3 synthesized at different hydrothermal temperatures for 24 h and calcined at 1 200 for 3ć h are shown in Fig.5. The sample via 120 hydrothermal treatment shows thećpolyhedron morphology, and plate-like morphology can be obtained when the hydrothermal temperature is increased up to 160 . Nevertheless,ćĮ-Al2O3 passes through the morphology transformation of platelet to vermiform morphology with increasing the hydrothermal temperature to 180 . Andćwith increasing the hydrothermal temperature up to 240 , thećĮ-Al2O3 powder obtained is more seriously aggregated and the powders connects with each other.The microscopic mechanism of the crystal growth is essentially the dynamic balance between adsorption and desorption of the growth unit from the microscopic kinetics. When the adsorption rate of the growth unit is larger than the desorption rate, the crystal represents to grow in favor of the formation of Į-Al2O3 platelets. However, the adsorption rate will be lower than the desorption rate with increasing hydrothermal temperatureFU Gao-feng, et al/Trans. Nonferrous Met. Soc. China 18(2008)747 Fig.5 SEM micrographs of samples heat treated at different hydrothermal temperatures: (a) 120 ć; (b) 160 ć; (c) 180 ć; (d) 240 ćup to the critical value, in which the formation of Į-Al2O3 platelets is restrained. When the alumina precursor with AlF3 additive is treated at 240 ćunder high pressure, the existence of AlF3 can make the growth units irregularly syncretize and superpose mutually on the same crystal plane and finally the seriously aggregated microstructure can be formed with the crystal growth. It is well known that AlF3 presents in a supersaturated mother phase and it can significantly change the nucleation of crystals, the growth and aggregation of nuclei and so on. But the effect of AlF3 additive varying with the different hydrothermal temperature can result in distinct crystal growth habit during calcinations and then influence the formation of Į-Al2O3 platelets.4 Conclusions1) In hydrothermal process, the transformation temperature of Ȗ-Al2O3 to Į-Al2O3 can be lowered by 300 ć through the addition of 2% AlF3 and the well-dispersed Į-Al2O3 powders with an average particle size of 8 P m can be obtained.2) Once alpha phase appears, the effects of temperature on particle morphology and size are quite weak. As AlF3 concentration is increased, the morphology of Į-Al2O3 powders could be transformed from irregular platelet to flat hexangular platelet.3) The plate-like morphology can be transformed into vermiform morphology when the hydrothermal temperature is increased to above 180 and thećĮ-Al2O3 particles synthesized after 240 hydrothermalćtreatment are seriously aggregated.References[1] TARTAJ P, TARTAJ J. Preparation, characterization and sinteringbehavior of spherical iron oxide doped alumina particles [J]. ActaMaterialia, 2002, 50: 5í12.[2] DONG Yan, JIANG Jian-qing, LIU Gang, LIANG Chao, SUNMing-tao. Preparation of alumina as a raw material of phosphor andcontrolling of its particle size and shape [J]. Journal of the ChineseCeramic Society, 2004, 32(4): 393í397. (in Chinese)[3] ZHOU Zhen-jun, YANG Zheng-fang, YUAN Qi-ming. Preparationof small sized Į-alumina platelet by sol-gel method [J]. Bulletin ofthe Chinese Ceramic Society, 2003(4): 11í15. (in Chinese)[4] SHEPPARD L M. Enhancing performance of ceramic composites [J].J Am Ceram Soc, 1992, 71: 617í631.[5] BOWEN P, SHENG J, JONGEN N. Particle size distributionmeasurement of anisotropic-particles cylinders and platelets-practicalFU Gao-feng, et al/Trans. Nonferrous Met. Soc. China 18(2008) 748examples [J]. Powder Technology, 2002, 128: 256í261.[6] LI Jiang, PAN Yu-bai, XIANG Chang-shu. Low temperaturesynthesis of ultrafine Į-Al2O3 powder by a simple aqueous sol-gelprocess [J]. Ceramic International, 2006, 32(5):587í591.[7] ZHU H Y, GAO X P, SONG D Y, RINGER SIMON P, XI Y X,FROST RAY L. Manipulating the size and morphology of aluminumhydrous oxide nanoparticles by soft-chemistry approaches [J].Microporous and Mesoporous Materials, 2005, 85: 226í233.[8] QU Li-hong, HE Chang-qing, YANG Yue, HE Yan-li, LIUZhong-min. Hydrothermal synthesis of alumina nanotubes templatedby anionic surfactant [J]. Materials Letters, 2005, 59: 4034í4037. [9] XIE Zhi-peng, LU Ji-wei, GAO Li-chun, XU Li-hua, WANGXi-dong. Influence of different seeds on transformation of aluminumhydroxides and morphology of alumina grains by hot pressing [J].Materials˂Design, 2003, 24: 209í2l4.[10] WU Yi-quan, ZHANG Yu-feng, HUANG Xiao-xian, GUO Jing-kun.Preparation of platelike nano alpha alumina particles [J]. CeramicsInternational, 2001, 27: 265í268. [11] WU Yi-quan, ZHANG Yu-feng, PEZZOTTI G. Influence of AlF andZnF on the phase transformation of gamma to alpha alumina [J].Materials Letters, 2002, 52: 366í369.[12] MACEDO M I F, BERTRAN C A, OSAWA C C. Kinetics of the Ȗ-Į-alumina phase transformation by quantitative X-ray diffraction [J].Journal of Materials Science, 2007, 42(8): 2830í2836.[13] LOPEZ V A, REYES B J L, SONG S, HERRERA U R. Temperatureeffect on the zeta potential and fluoride adsorption at the Į-Al2O3/aqueous solution interface [J]. Journal of Colloid and Interface Science, 2006, 298(1): 1í5.[14] LI Jiang, WU Yu-song, PAN Yu-bai, LIU Wen-bing, GUO Jing-kun.Influence of fluorides on phase transition of Į-Al2O3 formation [J].Ceramics International, 2007, 33(6): 919í923.[15] YAMAI I, SAITO H. Vapor phase growth of alumina whiskers byhydrolysis of alumina fluoride [J]. Journal of Crystal Growth, 1978, 45: 511í516.(Edited by YUAN Sai-qian)。
光照影响大型海藻英文
光照影响大型海藻英文英文回答：Light is a primary factor influencing the distribution and productivity of large seaweeds. These large algae, including kelps, laminaria, and fucus, are essential components of coastal ecosystems, providing food and habitat for a wide range of marine organisms. The availability and quality of light can significantly impact their growth, reproduction, and overall health.Light Intensity and Quality:Large seaweeds require sufficient light intensity for photosynthesis, the process by which they convert sunlight into energy. The optimal light intensity for different species varies, but most prefer well-lit environments. However, excessive light intensity can lead to photoinhibition, where the photosynthetic apparatus is damaged by high levels of radiation.Light quality, primarily determined by the wavelength, also influences seaweed growth. Certain wavelengths, such as blue and red light, are more effectively absorbed by pigments involved in photosynthesis than others. The spectral composition of light thus affects the photosynthetic efficiency and growth rate of seaweeds.Water Column Properties:The underwater light environment is influenced by several water column properties that affect light availability and penetration. These include:Water depth: As light passes through water, it is absorbed and scattered, resulting in a decrease in intensity with increasing depth.Turbidity: Suspended particles in the water, such as sediment and phytoplankton, can scatter and absorb light, further reducing its availability for seaweeds.Wave motion: Waves can cause the water column to move, resulting in variable light conditions for seaweeds.Seaweed Adaptations:Large seaweeds have evolved various adaptations to optimize their light utilization:Leaf morphology: Seaweeds often have broad, flat leaves that maximize light absorption.Pigmentation: They possess a range of photosynthetic pigments that absorb different wavelengths of light.Physiology: Seaweeds can adjust their photosynthetic rates and pigment composition based on light availability.Light and Algal Distribution:The distribution of large seaweeds is strongly influenced by light availability. They are typically found in shallow waters where light penetration is sufficient forphotosynthesis. In deeper waters or regions with high turbidity, seaweed abundance and diversity decrease.Climate Change Impacts:Climate change is projected to alter light availability and quality in coastal waters due to factors such as sea level rise, increased wave energy, and changes in water clarity. These changes could potentially affect the growth, reproduction, and distribution of large seaweeds.中文回答：光照对大型海藻的影响。
离子液体_蛋白酶对羊毛表面的亲水化改性
第31卷 第3期2010年3月纺 织 学 报Journa l o f T ex tile R esearch V o.l 31,N o .3M ar .,2010文章编号:0253 9721(2010)03 0083 05离子液体/蛋白酶对羊毛表面的亲水化改性袁久刚,王 强,范雪荣,周丽华,冯 菲(生态纺织教育部重点实验室(江南大学),江苏无锡 214122)摘 要 为提高羊毛表面的亲水性,利用氯化1 丁基 3 甲基咪唑离子液体对羊毛角蛋白的良好溶解能力,将其用作羊毛蛋白酶预处理。
将离子液体预处理和蛋白酶处理联合,完成对羊毛表面的亲水化改性。
结果显示,离子液体预处理对羊毛蛋白酶法处理后纤维的润湿性能有明显促进作用。
经过联合处理后,织物润湿时间下降,纤维吸水量增加,润湿接触角测试显示织物表面自由能降低。
通过减量率测试和X PS 分析可以看出,离子液体预处理有效促进了蛋白酶对纤维的水解效果,预处理后纤维表层亲水性基团增加,促进了织物润湿性能的提高。
关键词 离子液体;蛋白酶;羊毛;润湿性;减量率中图分类号:TS 195.6 文献标志码:AHydrophilic surface modification of wool by ionic li q ui d /protease treat m entYUAN Ji u gang ,WANG Q i a ng ,FAN Xuerong ,Z HOU L i h ua ,FENG Fe i(K ey Laborat ory of Eco T e x tiles (J ian gnan Un i vers it y ),M inistry of Education ,W ux i ,J iangsu 214122,China )Abst ract In or der to i m pr ove t h e w ettab ility of woo,l an ion ic liquid (I L)1 buty l 3 m ethy li m i d azo liumch l o ride w hich has a good so l u b ility for w ool kerati n w as e m ployed as a pretreat m ent step i n protease processi n g for the hydrophilic m odification o fw oo.l The effect of I L pretreat m en t co m bined w ith protease process on the w ettab ility of w oo l fibers and fabric w as ana lyzed t h rough w etting ti m e ,w ater uptake and contact ang le tests .The results revealed that I L pretreat m ent cou l d su ffi c iently i m prove the effic i e ncy o f pro tease pr ocessing .The w ettability o f woo l sa m ples after the co m b i n ed treat m ents w as i m pr oved .The w ater w etti n g ti m e and contact ang le of w oo l fabric decreased qu ickly w h ile w ater uptake of w oo l fi b ers i n creased .The tests o f w e i g ht loss and XPS sho w ed that I L pretreat m ent i m proved t h e hydro l y zation effic i e ncy of pr o tease ,and thus i n duc i n g m ore hydroph ilic protei n groups exposed .K ey w ords i o nic liquid (I L);protease ;w oo;l w ettab ility ;w eight loss 收稿日期:2009-08-20 修回日期:2009-11-03基金项目:国家高科技研究发展计划项目(2008AA02Z203);江苏省研究生创新项目(CX 08B_126Z)作者简介:袁久刚(1982 ),男,博士生。
湿式氧化催化剂RuO_2_Al_2O_3降解高浓度含酚配水的研究
第17卷第5期分 子 催 化V o l.17,N o.5 2003年10月JOU RNAL O F M OL ECULA R CA TAL YS IS(CH I NA)O ct. 2003 文章编号:100123555(2003)0520357205湿式氧化催化剂Ru O2 Χ-A l2O3降解高浓度含酚配水的研究杨少霞,冯玉杰1),万家峰,蔡伟民1,2(1.哈尔滨工业大学 市政环境学院,黑龙江哈尔滨150001;2.上海交通大学 环境科学与工程学院,上海200030)摘 要:采用浸渍法制备了R uO2 Χ2A l2O3催化剂,利用XRD和SE M对催化剂进行了表征,研究了焙烧温度、反应温度、反应溶液pH值和氧分压对R uO2 Χ2A l2O3催化剂活性影响.结果表明,R uO2 Χ2A l2O3催化剂组分R u在表面有较好的分散性;焙烧温度升高使R uO2晶粒长大,在低温焙烧,R uO2晶粒细小,R uO2 Χ2A l2O3催化剂的活性较高;反应温度升高,使R uO2 Χ2A l2O3催化剂的活性显著提高;反应溶液pH值为酸性时比在碱性条件的催化剂活性高;氧分压达到3M Pa后,对于R uO2 Χ2A l2O3催化剂的活性几乎没有影响.在150℃、3M Pa、pH值为5.6时,反应150m in后,苯酚全部被氧化.研究表明,R uO2 Χ2A l2O3催化剂具有较好的催化活性.关 键 词:苯酚氧化;R u系催化剂;pH值;湿式氧化中图分类号:O643.32 文献标识码:A 高浓度、有毒、有害的有机废水是对环境影响较大的污染源,已成为世界普遍重视的问题.对于此类废水,有许多处理方法,如生物处理,但由于废水中有机物对微生物的毒害作用,严重影响了其处理效果,有时甚至无法运行[1];焚烧法是一种处理超高浓度废水的有效方法,但二口恶口婴的影响,使人们对焚烧法的安全,产生了极大的怀疑[2];湿式氧化技术(W et A ir O x idati on,简称W AO)是近几十年发展起来的一种有效处理此类废水的氧化技术,它是在高温(125～320℃)和高压(0.5～20 M Pa)下,以氧气为氧化剂,将有机污染物氧化分解为二氧化碳和水等无机物或有机小分子的化学过程[3].与传统的生物处理相比,W AO具有高效、无二次污染等优点.目前在欧洲大约有90多家工厂采用W AO处理石油、化工、制药废水、城市污泥、活性炭再生和垃圾渗漏液等[4].但由于W AO的操作条件较苛刻,设备费用大,影响了它的应用.催化剂的使用,可以使反应在温和、较短的时间内完成,因此催化湿式氧化技术(Catalytic W et A ir O x2 idati on,简称C W AO)在近年来倍受关注[5,6].其中非均相催化剂具有活性高、易分离、稳定性好等优点,已成为C W AO研究热点.催化剂的制备条件和W AO操作条件对催化剂的活性影响很大[7,8],因此本论文采用浸渍法制备了R uO2 Χ2A l2O3催化剂,重点研究了焙烧温度、反应温度、反应溶液pH 值和反应压力对R uO2 Χ2A l2O3催化剂活性的影响,获得了一些较有价值的数据,它对于C W AO 的广泛应用具有一定的意义.1实 验1.1实验装置实验采用1L高压釜进行催化剂的活性评价.选取苯酚作为目标有机物,将500mL苯酚溶液(苯酚溶度为4200m g L)和1g R uO2 Χ2A l2O3催化剂加入高压釜中,通入氮气将空气排除,密封后,开始升温,当温度达到150℃,通入氧气,达到设定压力后,同时开启搅拌装置,此时定为反应的零点,以后每隔一定时间通过取液管取样.在取样期间,开启供氧阀以维持反应系统的总压恒定,流程图见文献[9].用稀N aO H和HNO3溶液调节进入高压釜的苯酚溶液pH值到强酸性2.94、中性7和碱性9.在反应达到150℃,通入氧气前,从高压釜中取少量的溶液,通过气相色谱分析样品中苯酚的含量.收稿日期:2002211211;修回日期:2003208222.基金项目:上海市横向课题.作者简介:杨少霞,女,1973年10月生,哈尔滨工业大学博士研究生.e2m ail:yang2shaox@.1)通讯联系人.1.2Ru O 2 Χ-A l 2O 3催化剂的制备采用浸渍法制备R uO 2 Χ2A l 2O 3催化剂.将载体Χ2A l 2O 3(平均粒径:3～5mm ,比表面积:175m 2g )用蒸馏水反复冲洗后,浸泡数小时,除去吸附在载体上的杂质和Χ2A l 2O 3粉末之后,在110℃下干燥后备用.将处理后的Χ2A l 2O 3浸渍于0.2M R uC l 3溶液中,室温下浸渍12h 后,110℃干燥12h ,然后分别在不同的温度(300℃、400℃、500℃和600℃)下焙烧3h ,得到负载型R uO 2 Χ2Al 2O 3催化剂.1.3分析测试方法采用日本岛津XRD 6000型粉末转靶X 射线衍射仪分析R uO 2 Χ2A l 2O 3催化剂的晶相结构,X 射线为Cu 靶K Α射线(Κ=1.5418∼).采用日本生产的JEOL 2840型扫描电镜(SE M ),O xfo rd IS IS 能谱仪观察催化剂表面组分的分布情况.不同时间的出水水样,用721分光光度计,在510nm 波长,测定溶液中苯酚的浓度.采用上海雷磁PH S 23C 紧密pH 计测定反应溶液的pH 值.2结果与讨论2.1Ru O 2 Χ-A l 2O 3催化剂XRD 和SE M 结果图1是分别在300、400、500和600℃温度下图1在不同焙烧温度下R uO 2 Χ2A l 2O 3催化剂的XRD 谱图F ig .1XRD spectra of R uO 2 Χ2A l 2O 3catalyst calcinedat differen t temperatu re(a :300℃b :400℃c :500℃d :600 ℃)焙烧得到的R uO 2 Χ2A l 2O 3催化剂的XRD 谱图.从图可知,R uO 2 Χ2A l 2O 3催化剂中R u 以R uO 2物相存在,载体以Χ2A l 2O 3的物相形式存在.在低温焙烧时,R uO 2的衍射峰较宽,衍射峰强度较弱,这表明形成的R uO 2晶粒细小,晶体发育不完整.随着焙烧温度的升高,R uO 2衍射峰由弱变强,衍射峰由宽变窄,表明随着焙烧温度的升高,形成的R uO 2晶粒逐渐趋于完整,且晶粒尺寸逐渐长大.利用Scherre 公式计算得到不同焙烧温度下R uO 2的晶粒尺寸(见表1),由表可以看出随着焙烧温度表1不同焙烧温度得到的Ru O 2 Χ-A l 2O 3催化剂晶粒尺寸T ab le 1C rystal size of R uO 2 Χ2A l 2O 3catalysts calcinedat differen t temperatu reCalcinati on temperatu res (℃)R uO 2crystal size (nm )300440095001560033的升高,R uO 2的晶粒尺寸逐渐增加.图2是R uO 2 Χ2A l 2O 3催化剂组分R u 在表面图2R uO 2 Χ2A l 2O 3催化剂表面R u 分布的SE M 照片F ig .2SE M of R u do t m app ing of R uO 2 Χ2A l 2O 3catalyst (300℃)分布的SE M 照片.由图可以看出,采用此制备工艺,R u 在催化剂表面均匀的分布,具有较好的分散性.2.2焙烧温度对Ru O 2 Χ-A l 2O 3催化剂活性的影响图3是分别在300℃、400℃、500℃和600℃焙烧3h 后得到的R uO 2 Χ2A l 2O 3催化剂,在150℃、3M Pa 、反应150m in ,湿式氧化降解苯酚溶液的情况.由图可知,随着反应时间的进行,苯酚去除率逐渐增加,且不同焙烧温度得到的R uO 2 Χ2853分 子 催 化 第17卷 A l 2O 3催化剂降解苯酚的效果不同.当焙烧温度为600℃时,反应150m in 后,苯酚去除率只有80%,但远高于不加催化剂时苯酚去除率(约30%),表明R uO 2 Χ2A l 2O 3催化剂有较好的催化活性;当焙烧温度降低时,苯酚的去除率逐渐增加;当焙烧温度为300℃时,催化剂的活性最高,反应120m in 后,苯酚的去除率已经达到96%以上.由此可知,当催化剂的焙烧温度降低时,R uO 2 Χ2A l 2O 3催化剂的活性增加.焙烧温度的变化,使催化机的晶粒尺寸改变,在低温焙烧时得到的R uO 2晶粒小,使催化图3R uO 2 Χ2A l 2O 3催化剂的焙烧温度对苯酚去除率的影响F ig .3Influence of calcinati on temperatu res ofR uO 2 Χ2A l 2O 3catalyst on the pheno lremoval at 150℃and 3M Pa剂有效表面积和活性中心增加,从而有利于氧、苯酚、有机物的吸附和氧化,因此在300℃焙烧时R uO 2 Χ2A l 2O 3催化剂较好的活性.2.3反应温度对Ru O 2 Χ-A l 2O 3催化剂活性的影响反应温度是W AO 过程中重要的因素,对有机物的氧化降解效果起决定性作用.图4是反应温度分别为150℃、165℃和180℃,反应120m in ,R uO 2 Χ2A l 2O 3催化剂对苯酚去除率情况.由图可知,反应温度对R uO 2 Χ2A l 2O 3催化剂氧化苯酚有较大的影响.当反应温度为180℃时,反应50m in 后,苯酚去除率已达到97%;反应温度为165℃时,反应90m in 后,苯酚全部被降解;当温度降低为150℃时,反应120m in 后,苯酚才能全部被降解,因此随着温度的升高,催化剂的活性明显增加.但是反应的升高,操作压力相应的提高,对设备的耐压要求也提高,同时反应的操作费用增加,因此从经济的角度考虑,选择反应温度为150℃.图4反应温度对R uO 2 Χ2A l 2O 3催化剂苯酚去除率的影响F ig .4Influence of the differen t reacti on temperatu res on the pheno l removal over R uO 2 A l 2O 3in W AOat the in itial pH value of 5.62.4反应溶液pH 值对Ru O 2 Χ-A l 2O 3活性的影响图5是300℃焙烧3h 后得到的R uO 2 Χ2图5反应溶液pH 值对R uO 2 Χ2A l 2O 3催化剂湿式氧化降解苯酚去除率的影响F ig .5Influence of the in itial pH value of the so lu ti onon the pheno l removal over R uO 2 Χ2A l 2O 3catalyst in W AO at 150℃and 3M PaA l 2O 3催化剂在150℃、3M Pa 、所研究的反应溶液pH 值条件下,反应150m in ,溶液中苯酚去除率情况.由图5可知,反应溶液的pH 值对苯酚去除率有较大影响.当反应溶液为强酸性时,如pH 值为2.94,苯酚去除率约90%;当反应溶液为弱酸性时(pH 值为5.6左右),反应120m in 后,苯酚几乎全部被氧化;当反应溶液为碱性时,如pH 值为953第5期 杨少霞等:湿式氧化催化剂R uO 2 Χ2A l 2O 3降解高浓度含酚配水的研究9.02,反应150m in 后,苯酚的去除率36%.C W AO 降解有机物时,有机物首先吸附在催化剂表面,然后有机物在催化剂表面被氧化[10],有机物的吸附是发生氧化反应的关键步骤.表2是不同的反应溶液pH 值下,R uO 2 Χ2A l 2O 3催化剂对苯酚的吸附数据.由表可以看出,在反应溶液为酸性时,苯酚在催化剂上的吸附大于碱性条件,这表明酸性条件下易于苯酚在催化剂表面的吸附,从而有表2Ru O 2 Χ-A l 2O 3催化剂在150℃对苯酚的吸附量T ab le 2Amoun ts of pheno l ab so rbed on the catalyst at 150℃T he in itial pH value of the so lu ti onIn itial pheno l concen trati on Concen trati on (at 150℃before O 2A dm issi on ,m g L )A b so rbed amoun ts(m g gcat )T he pH value of the so lu ti on after 150m in2.944136.165.22.255.604134.763.42.677.014139.559.92.809.024145.454.64.99利于反应溶液中苯酚的氧化,因此催化剂的活性在酸性时较高.但是当反应溶液pH 值为强酸性时(如pH 值为2.94),虽然苯酚在催化剂表面的吸附量增加,但反应溶液pH 值也降低了,这使得催化剂组分的流失增加,从而减小了催化剂的有效表面积,故在强酸性条件下催化剂的活性降低.2.4氧分压对于Ru O 2 Χ-A l 2O 3催化剂活性的影响湿式氧化降解有机物过程中,反应的总压力要高于反应温度的饱和蒸气压,以确保反应在液相中进行.氧分压应保持在一定的范围内,以保证在液相中高的溶解氧浓度.本实验研究了氧分压对R uO 2 Χ2A l 2O 3催化剂氧化苯酚活性的影响.图6图6反应压力对R uO 2 Χ2A l 2O 3催化剂湿式氧化降解苯酚去除率的影响F ig .6T he influence of oxygen p ressu re on the pheno lremoval over R uO 2 Χ2A l 2O 3catalystin W AO at 150℃是总压分别为3、4、5M Pa 下,在150℃、反应150m in ,R uO 2 Χ2A l 2O 3催化剂降解苯酚的情况.由图可以看出,当总压大于3M Pa 后,催化剂降解苯酚的活性几乎不变,这说明当氧分压达到一定值后,氧的传质不是反应的控制步骤,氧分压对催化剂的活性没有影响.3结 论焙烧温度、进水pH 值和温度对R uO 2 Χ2A l 2O 3催化剂的活性有重要影响.焙烧温度升高使R uO 2晶粒长大,在低温300℃焙烧3h 后,R uO 2晶粒细小,得到的R uO 2 Χ2A l 2O 3催化剂的活性较高.反应温度升高,使得R uO 2 Χ2A l 2O 3催化剂的活性显著提高.在反应溶液pH 值为酸性时催化剂的活性大于在碱性溶液中;氧分压达到3M Pa 后,对于R uO 2 Χ2A l 2O 3催化剂的活性几乎没有影响.R uO 2 Χ2A l 2O 3催化剂湿式氧化降解苯酚,在150℃、3M Pa 、pH 值为5.6时,反应150m in 后,苯酚全部被氧化,这说明此催化剂有较好的活性.参考文献:[1] R andall T L ,Knopp P V .J W a t P ollu t [J ],1980,52:2117～1151[2] L i L in 2jun (李灵军),J iang Ke (蒋可).E nv ironm en 2ta l S cience [J ],1995,16(6):55～60[3] M ish ra V .S ,V ijaykum ar V ,Jo sh i J B .Ind E ngChe m R es [J ],1995,34:2～48[4] L uck F .Ca ta ly sis T od ay [J ],1999,53:81～91[5] W ilhel m i A R ,Knopp P V .Che m E ng P rog [J ],1979,8:46～52063分 子 催 化 第17卷 [6] Stuck leyd D C ,M acarty P L .W a ter R esea rch [J ],1984,18(2):133～1352[7] M allat T .;Baiker A .Ca ta ly sis T od ay [J ],1994,19:247～254[8] Zhang Q ,Chuang K T .T he Canad ian of Che m icaE ng ineering [J ],1999,77(4):399～405[9] W an J ia 2feng (万家峰),Feng Yu 2jie (冯玉杰),YangShao 2x ia (杨少霞),et a l .J M ol Ca ta l (Ch ina )(分子催化)[J ],2002,16(5):345～348[10]O liviero L ,Barb ier J ,D up rez D ,et a l .A pp l Ca ta lB :E nv [J ],2000,25:267～275Catalytic W et A ir Ox idation of H igh Concen tration Phenol Solutionover Ru O 2 Χ-A l 2O 3CatalystYAN G Shao 2x ia ,FEN G Yu 2jie 1),W AN J ia 2feng ,CA IW ei 2m in1,2(1.S chool of M un icip a l and E nv ironm en ta l E ng ineering ,H a rbin Institu te of T echnology ,H a rbin 150001,Ch ina ;2S chool of E nv ironm en ta l S cience and E ng ineering ,S hang ha i J iao T ong U n iversity ,S hang ha i 200030,Ch ina )Abstract :A k ind of C W AO catalyst ,R uO 2 Χ2A l 2O 3,w as p rep ared by di pp ing A l 2O 3in to the aqueou s so lu 2ti on com po sed of R uC l 3.XRD and SE M w ere u sed to determ ine the catalytic structu re .T he resu lt show ed that there is good disp ersi on of R u then ium p articles on the su rface catalyst ,and the R uO 2crystal size in 2creased w ith increasing the calcinati on s tem p eratu re .M o reover ,influence of the calcinati on tem p eratu re ,reacti on tem p eratu res ,the in itial pH of the feed so lu ti on and oxygen p ressu re on the activity of the R uO 2Χ2A l 2O 3catalyst w as investigated .R esu lts show ed that the activity of the catalyst w as h igher w hen R uO 2Χ2A l 2O 3catalyst w as calcined at low er tem p eratu re of 300℃fo r 3h .Increasing reacti on tem p eratu re ,thep heno l rem oval w as obvi ou sly increased .T he activity of R uO 2 Χ2A l 2O 3catalyst w as h igher in the acidic so 2lu ti on than in the alkaline so lu ti on .T he activity of the catalyst did no t change up to 3M Pa of the to talp ressu re .Fo r the R uO 2 Χ2A l 2O 3catalyst ,the p heno l w as to tally ox idized at tem p eratu re of 150℃,pH of5.6and p ressu re of 3M Pa after 150m in .T h is indicated that R u A l 2O 3catalyst has good activity .Key words :Pheno l ox idati on ;R u then ium catalyst ;pH T em p eratu re ,W et air ox idati on163第5期 杨少霞等:湿式氧化催化剂R uO 2 Χ2A l 2O 3降解高浓度含酚配水的研究。
硫-氟的邻位交叉效应
大 学 化 学Univ. Chem. 2022, 37 (7), 2110088 (1 of 5)收稿：2021-10-28；录用：2021-11-29；网络发表：2021-12-24*通讯作者，Emails:********************.cn(袁耀锋);************.cn(叶克印)基金资助：福州大学一流学科本科教学改革建设项目；中国高等教育学会2021年度理科专项课题(21LKYB07)•知识介绍• doi: 10.3866/PKU.DXHX202110088 硫-氟的邻位交叉效应李懿伦，余意，袁耀锋*，叶克印*福州大学化学学院，福州 350108摘要：乙烷分子中相邻的两个氢原子被氟取代以后，它的最优构象就从全交叉式转变为邻位交叉，这就是邻位交叉效应影响分子构象最具代表性的一个例子。
本文简要回顾了含氟邻位交叉效应的发展历史与重要应用，重点介绍了物理有机科研前沿的硫-氟邻位交叉效应。
结合当前最新的科研成果，验证了通过改变硫原子的电正性可以达到有效调控邻位交叉效应这一重要策略。
通过科研反哺教学，有助于进一步加深对硫-氟邻位交叉效应的理解和认识。
关键词：邻位交叉效应；立体电子效应；构象中图分类号：G64；O6The Sulfur-Fluorine Gauche EffectYilun Li, Yi Yu, Yaofeng Yuan *, Keyin Ye *College of Chemistry, Fuzhou University, Fuzhou 350108, China.Abstract: The most favored anti-conformation of ethane would turn into gauche-conformation when the vicinal hydrogen atoms are replaced by two fluorine atoms. Such a switch shows how the gauche effect impacts the relative conformation of organic molecules. Herein, we briefly survey the history of the gauche effect as well as its broad applications in organic synthesis. Particularly, we highlight the recent investigations on the related sulfur-fluorine gauche effect. With the aid of experiments, we confirmed that the sulfur-fluorine gauche effect could be easily regulated via the subtle change of positive charges on the sulfur atom. Such a positive interplay between scientific research and organic course teaching would profoundly help students to understand the basic concepts and advanced applications of the sulfur-fluorine gauche effect.Key Words: Gauche effect; Stereoelectronic effect; Conformation1 前言立体化学是有机化学十分重要的一个组成部分[1]。
胺基保护——邻苯二甲酰亚胺脱保护
New1H-Pyrazole-Containing Polyamine Receptors Able ToComplex L-Glutamate in Water at Physiological pH ValuesCarlos Miranda,†Francisco Escartı´,‡Laurent Lamarque,†Marı´a J.R.Yunta,§Pilar Navarro,*,†Enrique Garcı´a-Espan˜a,*,‡and M.Luisa Jimeno†Contribution from the Instituto de Quı´mica Me´dica,Centro de Quı´mica Orga´nica Manuel Lora Tamayo,CSIC,C/Juan de la Cier V a3,28006Madrid,Spain,Departamento de Quı´mica Inorga´nica,Facultad de Quı´mica,Uni V ersidad de Valencia,c/Doctor Moliner50, 46100Burjassot(Valencia),Spain,and Departamento de Quı´mica Orga´nica,Facultad deQuı´mica,Uni V ersidad Complutense de Madrid,A V plutense s/n,28040Madrid,SpainReceived April16,2003;E-mail:enrique.garcia-es@uv.esAbstract:The interaction of the pyrazole-containing macrocyclic receptors3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene1[L1],13,26-dibenzyl-3,6,9,12,13,16,-19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene2[L2],3,9,12,13,16,22,-25,26-octaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene3[L3],6,19-dibenzyl-3,6,9,12,13,-16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene4[L4],6,19-diphenethyl-3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetraene5[L5],and 6,19-dioctyl-3,6,9,12,13,16,19,22,25,26-decaazatricyclo-[22.2.1.111,14]-octacosa-1(27),11,14(28),24-tetra-ene6[L6]with L-glutamate in aqueous solution has been studied by potentiometric techniques.The synthesis of receptors3-6[L3-L6]is described for the first time.The potentiometric results show that4[L4]containing benzyl groups in the central nitrogens of the polyamine side chains is the receptor displaying the larger interaction at pH7.4(K eff)2.04×104).The presence of phenethyl5[L5]or octyl groups6[L6]instead of benzyl groups4[L4]in the central nitrogens of the chains produces a drastic decrease in the stability[K eff )3.51×102(5),K eff)3.64×102(6)].The studies show the relevance of the central polyaminic nitrogen in the interaction with glutamate.1[L1]and2[L2]with secondary nitrogens in this position present significantly larger interactions than3[L3],which lacks an amino group in the center of the chains.The NMR and modeling studies suggest the important contribution of hydrogen bonding andπ-cation interaction to adduct formation.IntroductionThe search for the L-glutamate receptor field has been andcontinues to be in a state of almost explosive development.1 L-Glutamate(Glu)is thought to be the predominant excitatory transmitter in the central nervous system(CNS)acting at a rangeof excitatory amino acid receptors.It is well-known that it playsa vital role mediating a great part of the synaptic transmission.2However,there is an increasing amount of experimentalevidence that metabolic defects and glutamatergic abnormalitiescan exacerbate or induce glutamate-mediated excitotoxic damageand consequently neurological disorders.3,4Overactivation ofionotropic(NMDA,AMPA,and Kainate)receptors(iGluRs)by Glu yields an excessive Ca2+influx that produces irreversible loss of neurons of specific areas of the brain.5There is much evidence that these processes induce,at least in part,neuro-degenerative illnesses such as Parkinson,Alzheimer,Huntington, AIDS,dementia,and amyotrophic lateral sclerosis(ALS).6In particular,ALS is one of the neurodegenerative disorders for which there is more evidence that excitotoxicity due to an increase in Glu concentration may contribute to the pathology of the disease.7Memantine,a drug able to antagonize the pathological effects of sustained,but relatively small,increases in extracellular glutamate concentration,has been recently received for the treatment of Alzheimer disease.8However,there is not an effective treatment for ALS.Therefore,the preparation of adequately functionalized synthetic receptors for L-glutamate seems to be an important target in finding new routes for controlling abnormal excitatory processes.However,effective recognition in water of aminocarboxylic acids is not an easy task due to its zwitterionic character at physiological pH values and to the strong competition that it finds in its own solvent.9†Centro de Quı´mica Orga´nica Manuel Lora Tamayo.‡Universidad de Valencia.§Universidad Complutense de Madrid.(1)Jane,D.E.In Medicinal Chemistry into the Millenium;Campbell,M.M.,Blagbrough,I.S.,Eds.;Royal Society of Chemistry:Cambridge,2001;pp67-84.(2)(a)Standaert,D.G.;Young,A.B.In The Pharmacological Basis ofTherapeutics;Hardman,J.G.,Goodman Gilman,A.,Limbird,L.E.,Eds.;McGraw-Hill:New York,1996;Chapter22,p503.(b)Fletcher,E.J.;Loge,D.In An Introduction to Neurotransmission in Health and Disease;Riederer,P.,Kopp,N.,Pearson,J.,Eds.;Oxford University Press:New York,1990;Chapter7,p79.(3)Michaelis,E.K.Prog.Neurobiol.1998,54,369-415.(4)Olney,J.W.Science1969,164,719-721.(5)Green,J.G.;Greenamyre,J.T.Prog.Neurobiol.1996,48,613-63.(6)Bra¨un-Osborne,H.;Egebjerg,J.;Nielsen,E.O.;Madsen,U.;Krogsgaard-Larsen,P.J.Med.Chem.2000,43,2609-2645and references therein.(7)(a)Shaw,P.J.;Ince,P.G.J.Neurol.1997,244(Suppl2),S3-S14.(b)Plaitakis,A.;Fesdjian,C.O.;Shashidharan,S Drugs1996,5,437-456.(8)Frantz,A.;Smith,A.Nat.Re V.Drug Dico V ery2003,2,9.Published on Web12/30/200310.1021/ja035671m CCC:$27.50©2004American Chemical Society J.AM.CHEM.SOC.2004,126,823-8339823There are many types of receptors able to interact with carboxylic acids and amino acids in organic solvents,10-13yielding selective complexation in some instances.However,the number of reported receptors of glutamate in aqueous solution is very scarce.In this sense,one of the few reports concerns an optical sensor based on a Zn(II)complex of a 2,2′:6′,2′′-terpyridine derivative in which L -aspartate and L -glutamate were efficiently bound as axial ligands (K s )104-105M -1)in 50/50water/methanol mixtures.14Among the receptors employed for carboxylic acid recogni-tion,the polyamine macrocycles I -IV in Chart 1are of particular relevance to this work.In a seminal paper,Lehn et al.15showed that saturated polyamines I and II could exert chain-length discrimination between different R ,ω-dicarboxylic acids as a function of the number of methylene groups between the two triamine units of the receptor.Such compounds were also able to interact with a glutamic acid derivative which has the ammonium group protected with an acyl moiety.15,16Compounds III and IV reported by Gotor and Lehn interact in their protonated forms in aqueous solution with protected N -acetyl-L -glutamate and N -acetyl-D -glutamate,showing a higher stability for the interaction with the D -isomer.17In both reports,the interaction with protected N -acetyl-L -glutamate at physiological pH yields constants of ca.3logarithmic units.Recently,we have shown that 1H -pyrazole-containing mac-rocycles present desirable properties for the binding of dopam-ine.18These polyaza macrocycles,apart from having a highpositive charge at neutral pH values,can form hydrogen bonds not only through the ammonium or amine groups but also through the pyrazole nitrogens that can behave as hydrogen bond donors or acceptors.In fact,Elguero et al.19have recently shown the ability of the pyrazole rings to form hydrogen bonds with carboxylic and carboxylate functions.These features can be used to recognize the functionalities of glutamic acid,the carboxylic and/or carboxylate functions and the ammonium group.Apart from this,the introduction of aromatic donor groups appropriately arranged within the macrocyclic framework or appended to it through arms of adequate length may contribute to the recognition event through π-cation interactions with the ammonium group of L -glutamate.π-Cation interactions are a key feature in many enzymatic centers,a classical example being acetylcholine esterase.20The role of such an interaction in abiotic systems was very well illustrated several years ago in a seminal work carried out by Dougherty and Stauffer.21Since then,many other examples have been reported both in biotic and in abiotic systems.22Taking into account all of these considerations,here we report on the ability of receptors 1[L 1]-6[L 6](Chart 2)to interact with L -glutamic acid.These receptors display structures which differ from one another in only one feature,which helps to obtain clear-cut relations between structure and interaction(9)Rebek,J.,Jr.;Askew,B.;Nemeth,D.;Parris,K.J.Am.Chem.Soc.1987,109,2432-2434.(10)Seel,C.;de Mendoza,J.In Comprehensi V e Supramolecular Chemistry ;Vogtle,F.,Ed.;Elsevier Science:New York,1996;Vol.2,p 519.(11)(a)Sessler,J.L.;Sanson,P.I.;Andrievesky,A.;Kral,V.In SupramolecularChemistry of Anions ;Bianchi,A.,Bowman-James,K.,Garcı´a-Espan ˜a,E.,Eds.;John Wiley &Sons:New York,1997;Chapter 10,pp 369-375.(b)Sessler,J.L.;Andrievsky,A.;Kra ´l,V.;Lynch,V.J.Am.Chem.Soc.1997,119,9385-9392.(12)Fitzmaurice,R.J.;Kyne,G.M.;Douheret,D.;Kilburn,J.D.J.Chem.Soc.,Perkin Trans.12002,7,841-864and references therein.(13)Rossi,S.;Kyne,G.M.;Turner,D.L.;Wells,N.J.;Kilburn,J.D.Angew.Chem.,Int.Ed.2002,41,4233-4236.(14)Aı¨t-Haddou,H.;Wiskur,S.L.;Lynch,V.M.;Anslyn,E.V.J.Am.Chem.Soc.2001,123,11296-11297.(15)Hosseini,M.W.;Lehn,J.-M.J.Am.Chem.Soc.1982,104,3525-3527.(16)(a)Hosseini,M.W.;Lehn,J.-M.Hel V .Chim.Acta 1986,69,587-603.(b)Heyer,D.;Lehn,J.-M.Tetrahedron Lett.1986,27,5869-5872.(17)(a)Alfonso,I.;Dietrich,B.;Rebolledo,F.;Gotor,V.;Lehn,J.-M.Hel V .Chim.Acta 2001,84,280-295.(b)Alfonso,I.;Rebolledo,F.;Gotor,V.Chem.-Eur.J.2000,6,3331-3338.(18)Lamarque,L.;Navarro,P.;Miranda,C.;Ara ´n,V.J.;Ochoa,C.;Escartı´,F.;Garcı´a-Espan ˜a,E.;Latorre,J.;Luis,S.V.;Miravet,J.F.J.Am.Chem.Soc .2001,123,10560-10570.(19)Foces-Foces,C.;Echevarria,A.;Jagerovic,N.;Alkorta,I.;Elguero,J.;Langer,U.;Klein,O.;Minguet-Bonvehı´,H.-H.J.Am.Chem.Soc.2001,123,7898-7906.(20)Sussman,J.L.;Harel,M.;Frolow,F.;Oefner,C.;Goldman,A.;Toker,L.;Silman,I.Science 1991,253,872-879.(21)Dougherty,D.A.;Stauffer,D.A.Science 1990,250,1558-1560.(22)(a)Sutcliffe,M.J.;Smeeton,A.H.;Wo,Z.G.;Oswald,R.E.FaradayDiscuss.1998,111,259-272.(b)Kearney,P.C.;Mizoue,L.S.;Kumpf,R.A.;Forman,J.E.;McCurdy,A.;Dougherty,D.A.J.Am.Chem.Soc.1993,115,9907-9919.(c)Bra ¨uner-Osborne,H.;Egebjerg,J.;Nielsen,E.;Madsen,U.;Krogsgaard-Larsen,P.J.Med.Chem.2000,43,2609-2645.(d)Zacharias,N.;Dougherty,D.A.Trends Pharmacol.Sci.2002,23,281-287.(e)Hu,J.;Barbour,L.J.;Gokel,G.W.J.Am.Chem.Soc.2002,124,10940-10941.Chart 1.Some Receptors Employed for Dicarboxylic Acid and N -AcetylglutamateRecognitionChart 2.New 1H -Pyrazole-Containing Polyamine Receptors Able To Complex L -Glutamate inWaterA R T I C L E SMiranda et al.824J.AM.CHEM.SOC.9VOL.126,NO.3,2004strengths.1[L1]and2[L2]differ in the N-benzylation of the pyrazole moiety,and1[L1]and3[L3]differ in the presence in the center of the polyamine side chains of an amino group or of a methylene group.The receptors4[L4]and5[L5]present the central nitrogens of the chain N-functionalized with benzyl or phenethyl groups,and6[L6]has large hydrophobic octyl groups.Results and DiscussionSynthesis of3-6.Macrocycles3-6have been obtained following the procedure previously reported for the preparation of1and2.23The method includes a first dipodal(2+2) condensation of the1H-pyrazol-3,5-dicarbaldehyde7with the corresponding R,ω-diamine,followed by hydrogenation of the resulting Schiff base imine bonds.In the case of receptor3,the Schiff base formed by condensation with1,5-pentanediamine is a stable solid(8,mp208-210°C)which precipitated in68% yield from the reaction mixture.Further reduction with NaBH4 in absolute ethanol gave the expected tetraazamacrocycle3, which after crystallization from toluene was isolated as a pure compound(mp184-186°C).In the cases of receptors4-6, the precursor R,ω-diamines(11a-11c)(Scheme1B)were obtained,by using a procedure previously described for11a.24 This procedure is based on the previous protection of the primary amino groups of1,5-diamino-3-azapentane by treatment with phthalic anhydride,followed by alkylation of the secondary amino group of1,5-diphthalimido-3-azapentane9with benzyl, phenethyl,or octyl bromide.Finally,the phthalimido groups of the N-alkyl substituted intermediates10a-10c were removed by treatment with hydrazine to afford the desired amines11a-11c,which were obtained in moderate yield(54-63%).In contrast with the behavior previously observed in the synthesis of3,in the(2+2)dipodal condensations of7with 3-benzyl-,3-phenethyl-,and3-octyl-substituted3-aza-1,5-pentanediamine11a,11b,and11c,respectively,there was not precipitation of the expected Schiff bases(Scheme1A). Consequently,the reaction mixtures were directly reduced in situ with NaBH4to obtain the desired hexaamines4-6,which after being carefully purified by chromatography afforded purecolorless oils in51%,63%,and31%yield,respectively.The structures of all of these new cyclic polyamines have been established from the analytical and spectroscopic data(MS(ES+), 1H and13C NMR)of both the free ligands3-6and their corresponding hydrochloride salts[3‚4HCl,4‚6HCl,5‚6HCl, and6‚6HCl],which were obtained as stable solids following the same procedure previously reported18for1‚6HCl and2‚6HCl.As usually occurs for3,5-disubstituted1H-pyrazole deriva-tives,either the free ligands3-6or their hydrochlorides show very simple1H and13C NMR spectra,in which signals indicate that,because of the prototropic equilibrium of the pyrazole ring, all of these compounds present average4-fold symmetry on the NMR scale.The quaternary C3and C5carbons appear together,and the pairs of methylene carbons C6,C7,and C8are magnetically equivalent(see Experimental Section).In the13C NMR spectra registered in CDCl3solution, significant differences can be observed between ligand3,without an amino group in the center of the side chain,and the N-substituted ligands4-6.In3,the C3,5signal appears as a broad singlet.However,in4-6,it almost disappears within the baseline of the spectra,and the methylene carbon atoms C6and C8experience a significant broadening.Additionally,a remark-able line-broadening is also observed in the C1′carbon signals belonging to the phenethyl and octyl groups of L5and L6, respectively.All of these data suggest that as the N-substituents located in the middle of the side chains of4-6are larger,the dynamic exchange rate of the pyrazole prototropic equilibrium is gradually lower,probably due to a relation between proto-tropic and conformational equilibria.Acid-Base Behavior.To follow the complexation of L-glutamate(hereafter abbreviated as Glu2-)and its protonated forms(HGlu-,H2Glu,and H3Glu+)by the receptors L1-L6, the acid-base behavior of L-glutamate has to be revisited under the experimental conditions of this work,298K and0.15mol dm-3.The protonation constants obtained,included in the first column of Table1,agree with the literature25and show that the zwitterionic HGlu-species is the only species present in aqueous solution at physiological pH values(Scheme2and Figure S1of Supporting Information).Therefore,receptors for(23)Ara´n,V.J.;Kumar,M.;Molina,J.;Lamarque,L.;Navarro,P.;Garcı´a-Espan˜a,E.;Ramı´rez,J.A.;Luis,S.V.;Escuder,.Chem.1999, 64,6137-6146.(24)(a)Yuen Ng,C.;Motekaitis,R.J.;Martell,A.E.Inorg.Chem.1979,18,2982-2986.(b)Anelli,P.L.;Lunazzi,L.;Montanari,F.;Quici,.Chem.1984,49,4197-4203.Scheme1.Synthesis of the Pyrazole-Containing MacrocyclicReceptorsNew1H-Pyrazole-Containing Polyamine Receptors A R T I C L E SJ.AM.CHEM.SOC.9VOL.126,NO.3,2004825glutamate recognition able to address both the negative charges of the carboxylate groups and the positive charge of ammonium are highly relevant.The protonation constants of L 3-L 6are included in Table 1,together with those we have previously reported for receptors L 1and L 2.23A comparison of the constants of L 4-L 6with those of the nonfunctionalized receptor L 1shows a reduced basicity of the receptors L 4-L 6with tertiary nitrogens at the middle of the polyamine bridges.Such a reduction in basicity prevented the potentiometric detection of the last protonation for these ligands in aqueous solution.A similar reduction in basicity was previously reported for the macrocycle with the N -benzylated pyrazole spacers (L 2).23These diminished basicities are related to the lower probability of the tertiary nitrogens for stabilizing the positive charges through hydrogen bond formation either with adjacent nonprotonated amino groups of the molecule or with water molecules.Also,the increase in the hydrophobicity of these molecules will contribute to their lower basicity.The stepwise basicity constants are relatively high for the first four protonation steps,which is attributable to the fact that these protons can bind to the nitrogen atoms adjacent to the pyrazole groups leaving the central nitrogen free,the electrostatic repulsions between them being therefore of little significance.The remaining protonation steps will occur in the central nitrogen atom,which will produce an important increase in the electrostatic repulsion in the molecule and therefore a reduction in basicity.As stated above,the tertiary nitrogen atoms present in L 4-L 6will also contribute to this diminished basicity.To analyze the interaction with glutamic acid,it is important to know the protonation degree of the ligands at physiological pH values.In Table 2,we have calculated the percentages ofthe different protonated species existing in solution at pH 7.4for receptors L 1-L 6.As can be seen,except for the receptor with the pentamethylenic chains L 3in which the tetraprotonated species prevails,all of the other systems show that the di-and triprotonated species prevail,although to different extents.Interaction with Glutamate.The stepwise constants for the interaction of the receptors L 1-L 6with glutamate are shown in Table 3,and selected distribution diagrams are plotted in Figure 1A -C.All of the studied receptors interact with glutamate forming adduct species with protonation degrees (j )which vary between 8and 0depending on the system (see Table 3).The stepwise constants have been derived from the overall association constants (L +Glu 2-+j H +)H j LGlu (j -2)+,log j )provided by the fitting of the pH-metric titration curves.This takes into account the basicities of the receptors and glutamate (vide supra)and the pH range in which a given species prevails in solution.In this respect,except below pH ca.4and above pH 9,HGlu -can be chosen as the protonated form of glutamate involved in the formation of the different adducts.Below pH 4,the participation of H 2Glu in the equilibria has also to be considered (entries 9and 10in Table 3).For instance,the formation of the H 6LGlu 4+species can proceed through the equilibria HGlu -+H 5L 5+)H 6LGlu 4+(entry 8,Table 3),and H 2Glu +H 4L 4+)H 6LGlu 4(entry 9Table 3),with percentages of participation that depend on pH.One of the effects of the interaction is to render somewhat more basic the receptor,and somewhat more acidic glutamic acid,facilitating the attraction between op-positely charged partners.A first inspection of Table 3and of the diagrams A,B,and C in Figure 1shows that the interaction strengths differ markedly from one system to another depending on the structural features of the receptors involved.L 4is the receptor that presents the highest capacity for interacting with glutamate throughout all of the pH range explored.It must also be remarked that there are not clear-cut trends in the values of the stepwise constants as a function of the protonation degree of the receptors.This suggests that charge -charge attractions do not play the most(25)(a)Martell,E.;Smith,R.M.Critical Stability Constants ;Plenum:NewYork,1975.(b)Motekaitis,R.J.NIST Critically Selected Stability Constants of Metal Complexes Database ;NIST Standard Reference Database,version 4,1997.Table 1.Protonation Constants of Glutamic Acid and Receptors L 1-L 6Determined in NaCl 0.15mol dm -3at 298.1KreactionGluL 1aL 2aL 3bL 4L 5L 6L +H )L H c 9.574(2)d 9.74(2)8.90(3)9.56(1)9.25(3)9.49(4)9.34(5)L H +H )L H 2 4.165(3)8.86(2)8.27(2)8.939(7)8.38(3)8.11(5)8.13(5)L H 2+H )L H 3 2.18(2)7.96(2) 6.62(3)8.02(1) 6.89(5)7.17(6)7.46(7)L H 3+H )L H 4 6.83(2) 5.85(4)7.63(1) 6.32(5) 6.35(6) 5.97(8)L H 4+H )L H 5 4.57(3) 3.37(4) 2.72(8) 2.84(9) 3.23(9)L H 5+H )L H 6 3.18(3) 2.27(6)∑log K H n L41.135.334.233.634.034.1aTaken from ref 23.b These data were previously cited in a short communication (ref 26).c Charges omitted for clarity.d Values in parentheses are the standard deviations in the last significant figure.Scheme 2.L -Glutamate Acid -BaseBehaviorTable 2.Percentages of the Different Protonated Species at pH 7.4H 1L aH 2LH 3LH 4LL 11186417L 21077130L 3083458L 4083458L 51154323L 6842482aCharges omitted for clarity.A R T I C L E SMiranda et al.826J.AM.CHEM.SOC.9VOL.126,NO.3,2004outstanding role and that other forces contribute very importantly to these processes.26However,in systems such as these,which present overlapping equilibria,it is convenient to use conditional constants because they provide a clearer picture of the selectivity trends.27These constants are defined as the quotient between the overall amounts of complexed species and those of free receptor and substrate at a given pH[eq1].In Figure2are presented the logarithms of the effective constants versus pH for all of the studied systems.Receptors L1and L2with a nonfunctionalized secondary amino group in the side chains display opposite trend from all other receptors. While the stability of the L1and L2adducts tends to increase with pH,the other ligands show a decreasing interaction. Additionally,L1and L2present a close interaction over the entire pH range under study.The tetraaminic macrocycle L3is a better(26)Escartı´,F.;Miranda,C.;Lamarque,L.;Latorre,J.;Garcı´a-Espan˜a,E.;Kumar,M.;Ara´n,V.J.;Navarro,mun.2002,9,936-937.(27)(a)Bianchi,A.;Garcı´a-Espan˜a,c.1999,12,1725-1732.(b)Aguilar,J.A.;Celda,B.;Garcı´a-Espan˜a,E.;Luis,S.V.;Martı´nez,M.;Ramı´rez,J.A.;Soriano,C.;Tejero,B.J.Chem.Soc.,Perkin Trans.22000, 7,1323-1328.Table3.Stability Constants for the Interaction of L1-L6with the Different Protonated Forms of Glutamate(Glu) entry reaction a L1L2L3L4L5L6 1Glu+L)Glu L 3.30(2)b 4.11(1)2HGlu+L)HGlu L 3.65(2) 4.11(1) 3.68(2) 3.38(4) 3Glu+H L)HGlu L 3.89(2) 4.48(1) 3.96(2) 3.57(4) 4HGlu+H L)H2Glu L 3.49(2) 3.89(1) 2.37(4) 3.71(2)5HGlu+H2L)H3Glu L 3.44(2) 3.73(1) 2.34(3) 4.14(2) 2.46(4) 2.61(7) 6HGlu+H3L)H4Glu L 3.33(2) 3.56(2) 2.66(3) 4.65(2) 2.74(3) 2.55(7) 7HGlu+H4L)H5Glu L 3.02(2) 3.26(2) 2.58(3) 4.77(2) 2.87(3) 2.91(5) 8HGlu+H5L)H6Glu L 3.11(3) 3.54(2) 6.76(3) 4.96(3) 4.47(3) 9H2Glu+H4L)H6Glu L 2.54(3) 3.05(2) 3.88(2) 5.35(3) 3.66(4) 3.56(3) 10H2Glu+H5L)H7Glu L 2.61(6) 2.73(4) 5.51(3) 3.57(4) 3.22(8) 11H3Glu+H4L)H7Glu L 4.82(2) 4.12(9)a Charges omitted for clarity.b Values in parentheses are standard deviations in the last significantfigure.Figure1.Distribution diagrams for the systems(A)L1-glutamic acid, (B)L4-glutamic acid,and(C)L5-glutamicacid.Figure2.Representation of the variation of K cond(M-1)for the interaction of glutamic acid with(A)L1and L3,(B)L2,L4,L5,and L6.Initial concentrations of glutamate and receptors are10-3mol dm-3.Kcond)∑[(H i L)‚(H j Glu)]/{∑[H i L]∑[H j Glu]}(1)New1H-Pyrazole-Containing Polyamine Receptors A R T I C L E SJ.AM.CHEM.SOC.9VOL.126,NO.3,2004827receptor at acidic pH,but its interaction markedly decreases on raising the pH.These results strongly suggest the implication of the central nitrogens of the lateral polyamine chains in the stabilization of the adducts.Among the N-functionalized receptors,L4presents the largest interaction with glutamate.Interestingly enough,L5,which differs from L4only in having a phenethyl group instead of a benzyl one,presents much lower stability of its adducts.Since the basicity and thereby the protonation states that L4and L5 present with pH are very close,the reason for the larger stability of the L4adducts could reside on a better spatial disposition for formingπ-cation interactions with the ammonium group of the amino acid.In addition,as already pointed out,L4presents the highest affinity for glutamic acid in a wide pH range,being overcome only by L1and L2at pH values over9.This observation again supports the contribution ofπ-cation inter-actions in the system L4-glutamic because at these pH values the ammonium functionality will start to deprotonate(see Scheme2and Figure1B).Table4gathers the percentages of the species existing in equilibria at pH7.4together with the values of the conditional constant at this pH.In correspondence with Figure1A,1C and Figure S2(Supporting Information),it can be seen that for L1, L2,L5,and L6the prevailing species are[H2L‚HGlu]+and[H3L‚HGlu]2+(protonation degrees3and4,respectively),while for L3the main species are[H3L‚HGlu]+and[H4L‚HGlu]2+ (protonation degrees4and5,respectively).The most effective receptor at this pH would be L4which joins hydrogen bonding, charge-charge,andπ-cation contributions for the stabilization of the adducts.To check the selectivity of this receptor,we have also studied its interaction with L-aspartate,which is a competitor of L-glutamate in the biologic receptors.The conditional constant at pH7.4has a value of3.1logarithmic units for the system Asp-L4.Therefore,the selectivity of L4 for glutamate over aspartate(K cond(L4-glu)/K cond(L4-asp))will be of ca.15.It is interesting to remark that the affinity of L4 for zwiterionic L-glutamate at pH7.4is even larger than that displayed by receptors III and IV(Chart1)with the protected dianion N-acetyl-L-glutamate lacking the zwitterionic charac-teristics.Applying eq1and the stability constants reported in ref17,conditional constants at pH7.4of 3.24and 2.96 logarithmic units can be derived for the systems III-L-Glu and IV-L-Glu,respectively.Molecular Modeling Studies.Molecular mechanics-based methods involving docking studies have been used to study the binding orientations and affinities for the complexation of glutamate by L1-L6receptors.The quality of a computer simulation depends on two factors:accuracy of the force field that describes intra-and intermolecular interactions,and an adequate sampling of the conformational and configuration space of the system.28The additive AMBER force field is appropriate for describing the complexation processes of our compounds,as it is one of the best methods29in reproducing H-bonding and stacking stabiliza-tion energies.The experimental data show that at pH7.4,L1-L6exist in different protonation states.So,a theoretical study of the protonation of these ligands was done,including all of the species shown in5%or more abundance in the potentiometric measurements(Table4).In each case,the more favored positions of protons were calculated for mono-,di-,tri-,and tetraprotonated species.Molecular dynamics studies were performed to find the minimum energy conformations with simulated solvent effects.Molecular modeling studies were carried out using the AMBER30method implemented in the Hyperchem6.0pack-age,31modified by the inclusion of appropriate parameters. Where available,the parameters came from analogous ones used in the literature.32All others were developed following Koll-man33and Hopfinger34procedures.The equilibrium bond length and angle values came from experimental values of reasonable reference compounds.All of the compounds were constructed using standard geometry and standard bond lengths.To develop suitable parameters for NH‚‚‚N hydrogen bonding,ab initio calculations at the STO-3G level35were used to calculate atomic charges compatible with the AMBER force field charges,as they gave excellent results,and,at the same time,this method allows the study of aryl-amine interactions.In all cases,full geometry optimizations with the Polak-Ribiere algorithm were carried out,with no restraints.Ions are separated far away and well solvated in water due to the fact that water has a high dielectric constant and hydrogen bond network.Consequently,there is no need to use counteri-ons36in the modelization studies.In the absence of explicit solvent molecules,a distance-dependent dielectric factor quali-tatively simulates the presence of water,as it takes into account the fact that the intermolecular electrostatic interactions should vanish more rapidly with distance than in the gas phase.The same results can be obtained using a constant dielectric factor greater than1.We have chosen to use a distance-dependent dielectric constant( )4R ij)as this was the method used by Weiner et al.37to develop the AMBER force field.Table8 shows the theoretical differences in protonation energy(∆E p) of mono-,bi-,and triprotonated hexaamine ligands,for the (28)Urban,J.J.;Cronin,C.W.;Roberts,R.R.;Famini,G.R.J.Am.Chem.Soc.1997,119,12292-12299.(29)Hobza,P.;Kabelac,M.;Sponer,J.;Mejzlik,P.;Vondrasek,put.Chem.1997,18,1136-1150.(30)Cornell,W.D.;Cieplak,P.;Bayly,C.I.;Gould,I.R.;Merz,K.M.,Jr.;Ferguson,D.M.;Spelmeyer,D.C.;Fox,T.;Caldwell,J.W.;Kollman,P.A.J.Am.Chem.Soc.1995,117,5179-5197.(31)Hyperchem6.0(Hypercube Inc.).(32)(a)Fox,T.;Scanlan,T.S.;Kollman,P.A.J.Am.Chem.Soc.1997,119,11571-11577.(b)Grootenhuis,P.D.;Kollman,P.A.J.Am.Chem.Soc.1989,111,2152-2158.(c)Moyna,G.;Hernandez,G.;Williams,H.J.;Nachman,R.J.;Scott,put.Sci.1997,37,951-956.(d)Boden,C.D.J.;Patenden,put.-Aided Mol.Des.1999, 13,153-166.(33)/amber.(34)Hopfinger,A.J.;Pearlstein,put.Chem.1984,5,486-499.(35)Glennon,T.M.;Zheng,Y.-J.;Le Grand,S.M.;Shutzberg,B.A.;Merz,K.M.,put.Chem.1994,15,1019-1040.(36)Wang,J.;Kollman,P.A.J.Am.Chem.Soc.1998,120,11106-11114.Table4.Percentages of the Different Protonated Adducts[HGlu‚H j L](j-1)+,Overall Percentages of Complexation,andConditional Constants(K Cond)at pH7.4for the Interaction ofGlutamate(HGlu-)with Receptors L1-L6at Physiological pH[H n L‚HGlu]an)1n)2n)3n)4∑{[H n L‚HGlu]}K cond(M-1)L13272353 2.44×103L2947763 4.12×103L31101324 3.99×102L423737581 2.04×104L51010222 3.51×102L6121224 3.64×102a Charges omitted for clarity.A R T I C L E S Miranda et al. 828J.AM.CHEM.SOC.9VOL.126,NO.3,2004。
酸性NaF_AlF_3熔盐离子结构的Raman光谱
相对国外研究者使用的无窗样品池[17−18]，尽管封 闭式样品池在测定光路中所置的石英片会减弱测得的 Raman 信号，然而这种样品池也有自己的优点：由于 在熔盐的 Raman 光谱测定中，所用的样品数量很少， 因此试样的不均匀挥发对其成分的影响就很大，采用 减少积分时间及积分次数的方法会降低所测光谱的质 量，但是如果使用敞开式的无窗试样池，进行同一试 样多温度的 Raman 测定时，即使减少积分时间及积分 次数，也会带来很大的实验误差；当使用封闭式样品 池时，由于挥发物质不会溢出，所以在相当长的时间 内，样品池的熔盐组成不会发生显著改变，这样就提 高了测量的准确性。
The mole fraction of AlF4− is about 0.75 for the melts whose weighted-in mole fraction of NaF is 0.6, but that of AlF63− is about 0.25. When the weighted-in mole fraction of NaF increases to 0.71, the mole fraction of AlF4− decreases to 0.25 while that of AlF63− increases to 0.75. Key words: NaF-AlF3 melts; ionic structure; Al-F complex ions; Raman spectra
现代铝电解工业采用的电解质是冰晶石熔盐体 系，并为了改善其物理化学性能而调整其分子比，研 究该体系熔盐的离子结构是深入地理解其物理化学性 质及其变化规律，正确认识铝电解电极过程的基础。 长期以来，对于铝电解体系熔盐结构的研究一直没有 间断过。
冰晶石体系熔盐结构及电导率的研究
东北大学硕士学位论文冰晶石体系熔盐结构及电导率的研究姓名：胡宪伟申请学位级别：硕士专业：有色金属冶金指导教师：王兆文20060101东北大学硕士学位论文第一章绪论图１．６无窗Ｒａｍａｎ光谱研究试样池Ｆｉｇ．１．６Ｗ＇ｍｄｏｗｌｅｓｓｃｅｌｌｆｏｒＲａｍａｎｓｐｅｃｔｒａ图１．６中，处于下面的较大的孔用来透射光，而上面的各个较小的孔的作用是保持池内液面处于水平状态，这种试样池相对于其它试样池的优点还在于，实际用于光谱测量的那部分熔盐的面积百分比相对较小，这样，熔盐中的固体处于光谱测量区的上部或者下部，不会影响测量；此外，熔盐的波程长度也相对稳定，而且，当试样的重量超过所要求的最小重量时，其波程长度与试样的重量无关。
Ｇｉｌｂｅｒｔ等人已经采用这种试样池对铝电解系熔盐结构进行了大量有意义的研究并得到了许多重要成果。
１．３．２．３冰晶石体系熔盐结构的研究分类工业铝电解质采用钠冰晶石作为熔剂，而研究者们的研究并非局限于钠冰晶石体系，面将研究对象扩展到了整个碱金属冰晶石系，这样做的意义在于：首先，由于属于同一主族，碱金属盐之间的性质将会体现出相似性，当对于钠冰晶石系熔盐的研究出现相互矛盾的结论的时候，研究其它碱金属冰晶石系熔盐可以起到补充和对比的作用；其次，相对于钠冰晶石体系来说，有时其它碱金属冰晶石系熔盐会体现出更有利于实验研究的优越性，例如，锂冰晶石系熔盐的熔点相对较低，钾冰晶石熔盐体系中，阴、阳离子间的相互作用相对较弱等；另外，在铝电解工业中，氟化锂常常作为添加剂来使用，因此向研究熔盐中引入碱金属锂离子也有着重要的实际意义。
由于工业铝电解所采用的电解质分子比通常不为３（即冰晶石组成），所以研究者们的研究也并不限于分子比为３的铝电解熔盐体系，而且将ＮａＦ－ＡＩＦ３以摩尔比为３混合，然后熔化并冷凝后，ｘ．射线和岩相学分析显示结果与纯冰晶石一致【９】，因此可以把纯冰晶石熔盐理解为ＮａＦ－ＡＩＦ３的分子比为３的混合物熔盐。
核废水长期影响英语作文
核废水长期影响英语作文英文回答：The long-term effects of nuclear wastewater discharge are a major concern for both environmentalists and policymakers. Nuclear wastewater contains a variety of radioactive isotopes, which can have harmful effects on human health and the environment.One of the most serious concerns is the potential for long-term health effects from exposure to radioactive isotopes. These isotopes can accumulate in the body over time, increasing the risk of cancer and other health problems. Even low levels of radiation exposure can have long-term effects, such as an increased risk of heart disease, stroke, and respiratory problems.Another concern is the potential for environmental damage from nuclear wastewater discharge. Radioactive isotopes can contaminate water sources, soil, and air,harming plants, animals, and humans. Radioactive isotopes can also persist in the environment for long periods of time, so the effects of nuclear wastewater discharge can last for generations.In addition to the health and environmental risks, nuclear wastewater discharge also has economic and social impacts. Communities near nuclear power plants are often concerned about the potential for contamination and the negative effects it could have on their health, property values, and quality of life. This can lead to social and economic problems, such as job losses and population decline.Overall, the long-term effects of nuclear wastewater discharge are a serious concern. The risks to human health, the environment, and communities are significant, and these risks should be carefully considered before any decisions are made about the disposal of nuclear wastewater.中文回答：核废水的长期影响是环保主义者和政策制定者的一个主要关注点。
《自发奇粘性对法拉第不稳定性的影响》范文
《自发奇粘性对法拉第不稳定性的影响》篇一一、引言法拉第不稳定性（Faraday instability）是物理学中一种常见的波动现象，常发生在流体力学、光学以及等离子体等领域。
这种不稳定性与界面的周期性扰动有关，并受到多种物理机制的影响。
近年来，自发奇粘性（spontaneous odd viscosity）作为一种特殊的物理属性，被认为可能对法拉第不稳定性产生重要影响。
本文将探讨自发奇粘性对法拉第不稳定性的影响，并从理论分析和实验验证两个方面进行论述。
二、理论分析（一）法拉第不稳定性概述法拉第不稳定性是一种界面波动现象，常见于流体系统。
当流体系统在一定的条件下，如温度梯度或剪切力作用下，界面会出现周期性的扰动。
这种扰动会逐渐增长，最终导致系统的不稳定。
（二）自发奇粘性的引入自发奇粘性是一种特殊的物理属性，表现为流体在某一方向上的粘性与其反方向上的粘性不同。
这种特性可能对流体的动力学行为产生影响，进而影响法拉第不稳定性。
（三）自发奇粘性对法拉第不稳定性的影响理论分析表明，自发奇粘性可以通过改变流体的动力学行为来影响法拉第不稳定性。
具体来说，自发奇粘性可能导致流体在某一方向上的运动受到阻碍，从而减缓了界面扰动的增长速度。
此外，自发奇粘性还可能改变流体的流动模式，进一步影响法拉第不稳定性的发展。
三、实验验证（一）实验设计与实施为了验证自发奇粘性对法拉第不稳定性的影响，我们设计了一系列实验。
实验中，我们通过改变流体的自发奇粘性，观察其对法拉第不稳定性的影响。
实验中使用的流体包括具有不同自发奇粘性的液体和具有特定剪切结构的凝胶等。
（二）实验结果与分析实验结果表明，自发奇粘性的确对法拉第不稳定性产生了显著影响。
当流体的自发奇粘性增大时，界面扰动的增长速度明显减缓。
此外，我们还观察到，自发奇粘性还可能改变流体的流动模式，使得流动更加稳定或更加不稳定。
这些实验结果与我们的理论分析相一致。
四、结论与展望本文通过理论分析和实验验证，探讨了自发奇粘性对法拉第不稳定性的影响。
al^3+对二水硫酸钙结晶动力学影响的研究
al^3+对二水硫酸钙结晶动力学影响的研
究
硫酸钙是一种重要的无机化合物，具有广泛的用途。
它在医药、食品、农业、石油化工、电子和其他领域都有着重要的应用。
近年来，人们对二水硫酸钙结晶动力学研究的兴趣日益增加，结晶动力学是了解结晶体系的关键。
本文将介绍二水硫酸钙结晶动力学影响的研究。
首先，二水硫酸钙的晶体结构具有一定的复杂性，它的晶体结构受到温度、溶剂、添加剂等外部因素的影响。
硫酸钙的结晶动力学受到温度、溶剂、添加剂和浓度等因素的影响。
其次，对二水硫酸钙结晶动力学影响的研究表明，温度是影响结晶过程最重要的外部因素，它不仅影响晶体结构，还影响结晶率和结晶速度。
结晶过程受温度影响的程度取决于溶剂及添加剂的类型和浓度。
此外，溶剂对二水硫酸钙结晶动力学影响也很大，溶剂的类型、浓度、结晶时间和温度都可以影响结晶过程。
当溶剂浓度升高时，结晶过程中的能量释放和晶体结构的变化会受到抑制，从而降低结晶率和结晶速度。
最后，添加剂也可以影响硫酸钙结晶动力学。
添加剂可以改变溶剂的环境，从而改变结晶速度。
此外，添加剂还可以影响晶体结构，从而改变结晶过程。
综上所述，二水硫酸钙结晶动力学受到温度、溶剂、添加剂和浓度等因素的影响。
了解结晶动力学对二水硫酸钙的结晶率、结晶速度和晶体结构的影响是非常重要的，对于提高二水硫酸钙的结晶质量具有重要意义。
硝酸盐溶液浓度对镁铝水滑石结构记忆效应的影响
硝酸盐溶液浓度对镁铝水滑石结构记忆效应的影响程晓丹;徐爱菊;王奖;贾美林;照日格图【摘要】Mg-Al hydrotalcite was prepared by coprecipitation method and characterized by XRD, N2-adsorption-desorption,TG-DTA and FT-IR. The results showed that the as-prepared Mg-Al hydrotalcite with 121 m2·g-1 specific surface area possessed hexagonal phase. The influence of nitrate solution concentration on the memory effect of Mg-Al hydrotalcite was investigated. It was found that Mg-Al mixed oxides formed after being calcined at 400℃ for 5 h was dipped in dif ferent concentration of Cu (NO3) 2 and Fe ( NO3) 3 aqueous solution. The hydrotalcite structure could be recovered and the memory effect of hydrotalcite was influenced by salt solution concentration. Furthermore, the lower concentration was more advantageous to the recovery of hydrotalcite structure. The results of FT-IR demonstrated that the insertion of NO3- in the layer of hydrotalcite could be observed,which might form a new type application function material.%用共沉淀法制备了镁铝水滑石,并进行XRD、N2吸附-脱附、TG-DTA和FT-IR等表征.结果表明,制备的镁铝水滑石呈六方晶型,比表面积为121 m2·g-1.研究了硝酸盐溶液浓度对水滑石结构记忆性的影响,发现400℃焙烧5h的镁铝水滑石在硝酸铜和硝酸铁溶液中浸泡可以恢复水滑石结构,溶液浓度越低越容易恢复,同时NO3-插入水滑石的层间可以形成一种新型应用功能材料.【期刊名称】《工业催化》【年(卷),期】2012(020)012【总页数】4页(P30-33)【关键词】催化化学;镁铝水滑石;共沉淀法;结构记忆效应【作者】程晓丹;徐爱菊;王奖;贾美林;照日格图【作者单位】内蒙古师范大学化学与环境科学学院内蒙古自治区绿色催化重点实验室,内蒙古呼和浩特010022;内蒙古师范大学化学与环境科学学院内蒙古自治区绿色催化重点实验室,内蒙古呼和浩特010022;内蒙古师范大学化学与环境科学学院内蒙古自治区绿色催化重点实验室,内蒙古呼和浩特010022;内蒙古师范大学化学与环境科学学院内蒙古自治区绿色催化重点实验室,内蒙古呼和浩特010022;内蒙古师范大学化学与环境科学学院内蒙古自治区绿色催化重点实验室,内蒙古呼和浩特010022【正文语种】中文【中图分类】O643.36;TQ426.94水滑石为层柱状双金属氢氧化物，是近年来发展迅速的一类阴离子型黏土［1-2］，具有特殊的结构和物化性能，如结构记忆效应、阴离子可交换性、阳离子同晶取代性、吸附性能和催化性能等，在催化剂、催化剂载体［3-5］、阻燃剂［6］、吸附剂［7］和医药载体［8］等领域应用广泛。
片状氧化铝制备工艺研究现状
片状氧化铝制备工艺研究现状摘要：片状氧化铝因其独特的二维片状结构和较大的径厚比而成为无机非金属材料领域的研究热点之一。
本文对常见的片状氧化铝制备工艺进行了综述，并对其制备方法的优缺点进行了评价。
关键词：片状氧化铝；制备工艺；α-Al2O3片状氧化铝是一类具有良好二维平面结构的氧化铝粉体材料，其明显的特征在于其粉体颗粒形状可以是六边形、圆形或者无规则形，并且同时具有较小的厚度和较大径厚比。
片状氧化铝不仅具有氧化铝高熔点、耐腐蚀、高硬度等优良性质外，还因为其特有的二维结构，使片状氧化铝粉体具有优异的表面附着特性、良好的光线反射能力以及其它特殊的力学结构特性，广泛应用在研料磨料、珠光颜料、陶瓷增初等方面。
制备片状氧化铝的主要思路是利用不同的铝源反应生成氢氧化铝作为前驱物，常见的铝源原料有硫酸铝、氯化铝、硝酸铝等，经过加热煅烧前驱物后获得最终片状产物。
这是一类化学方法，由于能够较好地控制片状产物单晶的生长，是研宄制备片状氧化铝粉体的最主要方法。
1.水热法水热法指的是在密闭的特定反应容器条件下，通过加热营造一个高温高压的反应条件，以蒸汽流体或者溶液作为介质，使难溶或者不溶的物质溶解后结晶、生长，然后进行后续分离或者热处理获得最终产物的方法。
Adair等[1]在1，4-丁二醇溶液中通过控制反应时间、搅拌速率、适量的甲醇添加剂和固载量(反应粉体的质量)，在300℃下直接沉淀，也得到了规则的六角及其他多面体型的氧化铝粉体。
为了降低水热反应温度，王国步等[2]以KBr和1，4-丁二醇作为反应介质，使用Al(NO3)3溶液中加适量氨水制得的氢氧化铝胶体做前驱物，通过醇热反应，在300℃下经24h制备出了六角板状的α-Al2O3粉体。
尽管用水热法制备出来的片状氧化铝粉体纯度高，分散性好且具有较薄的平板状结构和均匀优良的晶体形貌，但是水热合成不仅周期长，而且在反应过程需要高温高压的反应釜，对设备有较强依赖，且晶体的相变温度较高(＞400℃)。
硅酸钠浓度对铝合金微弧氧化起弧过程能量消耗的影响
硅酸钠浓度对铝合金微弧氧化起弧过程能量消耗的影响葛延峰;蒋百灵;时惠英【摘要】The arcing process of microarc oxidation (MAO) on 1015 alloys aluminum (Al) using pulse power source in aqueous solutions with different Na2SiO3 concentrations was studied. The morphologies and surface resistance of initial films at arcing moment were analyzed and observed using scanning electron microscope (SEM) and electrochemical test, respectively. The effect of Na2SiO3 concentration on energy consumption of arcing process during MAO was calculated based on change curve of voltage. The results indicate that there is no arcing phenomenon but electrolytic etching on Al samples when the Na2SiO3 concentration is 0 and voltage is 1 500 V. With Na2SiO3 solution concentration increasing from 0.25 g/L to 10 g/L, arcing voltage dropping from 1 217 V to 351 V, arcing time reducing from 270 s to 40 s , the quantity of microspores on surface of initial films increases during arcing process of MAO. The high resistance film with resistance up to 105 order of magnitude formed on the surface of Al samples is the premise of arcing phenomenon emerging in MAO process, and higher Na2SiO3 solution concentration is beneficial to forming high resistance film. The energy consumption of arcing process is diminished with Na2SiO3 solution concentration increasing, and minimum value is 16 kJ/dm2 when Na2SiO3 concentration is 10 g/L.% 利用脉冲微弧氧化电源研究1015铝合金于不同浓度硅酸钠水溶液中的起弧过程，借助扫描电子显微镜和电化学测试方法分析硅酸钠浓度对起弧瞬间膜层微观结构和表面阻值的影响，并根据电压变化曲线计算起弧过程的能量消耗。
菲克定律在氢扩散系数研究中的应用_刘菲
A b s t r a c t : F i c kf i r s t a n ds e c o n dl a w sa r eg e n e r a l l yu s e dt om e a s u r eh y d r o g e nd i f f u s i o nc o e f f i c i e n t ( D )w i t h i n b u l k m a t e r i a l s , b u t a b i g v a r i a t i o no f t h e r e s u l t s i s o f t e nc a u s e db y t h e a d o p t i o n o f d i f f e r e n t i n i t i a l s t a t e s a n d c a l c u l a t i o nm e t h o d s . I n t h i s p a p e r , t w o i n i t i a l s t a t e s ( D e c a y t r a n s i e n t a n d R i s e t r a n s i e n t )a r es e l e c t e di nt h e d e d u c t i o no f t h ef o r m u l ao f h y d r o g e nd i f f u s i o nc o e f f i c i e n t a n dc o r r e s p o n d i n g c u r r e n t s .C o m b i n i n gt h e o r e t i c a l b a s i sa n das i n g l ep o t e n t i a l s t e pe l e c t r o c h e m i c a l e x p e r i m e n t a l m e t h o d , r e a s o n a b l e c a l c u l a t i o n m e t h o d s , r e s u l t s , a n di t s s p e c i a l a p p l i c a t i o n s u n d e r p r a c t i c a l t e s t i n gc o n d i t i o n s h a v e b e e n d i s c u s s e d . T h e r e s u l t s a l s o i n d i c a t e t h a t r i s e t r a n s i e n t i s m o r e b e t t e r i n t h ec o n t r o l o f t e s t i n gc o n d i t i o n s . K e yw o r d s : F i c k s l a w ;e l e c t r o c h e m i c a l ; s i n g l ep o t e n t i a l s t e p ; h y d r o g e nd i f f u s i o nc o e f f i c i e n t ( D ) ; h y d r o g e np e r m e a t i o n 通过电化学的方法测定氢在合金中的扩散系数 , 已成为一种能够合理地表征氢的扩散能力的重要 [ 15] 方法 。 该方法能够直观反映氢原子运动过程中合金内部电子的运动特点 , 可以动态考察扩散过程中 [ 6] 电子的运动规律 , 具有比气态测试方法更加简便易操作 、 数据精确 、 微观探究更细致等优点 。 电化学测算扩散系 数依据的 主要实验 原理为菲 克第一定 律 ( F i c k sF i r s t L a w ) 和菲 克第二 定律 ( F i c k s S e c o n dL a w ) 。 前者阐明流量与浓度梯度成正比的关系 , 后者是在前者的基础上进行推导 , 得