Effect of viscosity on material behavior in friction stir welding process
Materials Characterization
Materials Characterization Materials characterization is a crucial aspect of scientific research and development. It involves the study of the properties and behavior of different materials, and plays a significant role in various fields such as materials science, engineering, and manufacturing. By understanding the characteristics of materials, scientists and engineers can make informed decisions about their suitability for specific applications, design new materials with desired properties, and ensure the quality and reliability of products. One perspectiveon materials characterization is from the viewpoint of a materials scientist. For them, the process of characterization begins with the selection of appropriate techniques and instruments to analyze the material of interest. This could involve using techniques such as microscopy, spectroscopy, or diffraction to examine the structure, composition, and physical properties of the material. The scientist may also need to perform various tests, such as mechanical, thermal, or electrical tests, to assess the material's performance under different conditions. This comprehensive understanding of the material's properties is crucial for designing and optimizing materials for specific applications. From an engineer's perspective, materials characterization is essential for ensuring the reliability and performance of products. Engineers need to know how materials will behaveunder different operating conditions, such as temperature, pressure, or stress. By characterizing materials, engineers can make informed decisions about material selection, design components with appropriate dimensions and properties, andpredict the lifespan of products. For example, in the aerospace industry,materials characterization is critical for designing lightweight yet strong materials for aircraft structures, as well as understanding how these materialswill perform in extreme conditions. Another perspective on materials characterization comes from the manufacturing industry. Manufacturers rely on materials characterization to ensure the quality and consistency of their products. By characterizing raw materials and finished products, manufacturers can identify any variations or defects that may affect product performance or safety. For instance, in the pharmaceutical industry, materials characterization is used to analyze the composition and purity of drug substances and ensure that they meetregulatory standards. By doing so, manufacturers can guarantee the effectiveness and safety of their products. From a consumer's perspective, materials characterization may not be directly visible or apparent, but it greatly impacts the quality and performance of the products they use. For example, imagine buying a smartphone that claims to have a scratch-resistant screen. This claim is only possible because materials scientists and engineers have characterized the mechanical properties of the screen material and optimized it to resist scratches. Without materials characterization, consumers would not have access to products with the same level of performance and reliability. In conclusion, materials characterization is a vital aspect of scientific research, engineering, and manufacturing. It provides valuable insights into the properties and behavior of materials, enabling scientists, engineers, and manufacturers to make informed decisions about material selection, design, and quality control. From the perspective of a materials scientist, engineer, manufacturer, or consumer, materials characterization plays a crucial role in ensuring the performance, reliability, and quality of products.。
专业英语
Definition of polymers A simple understanding of polymers can be gained by imaging them to be like a chain or, perhaps, a string of pearls, where the individual pearl represent small molecules that are chemically bonded together. Therefore, a polymer is a molecule made up of smaller molecules that are joined together by chemical bonds. The word polymer means „many parts or units.‟ The parts or units are the small molecules that combine. The result of the combination is, of course, a chainlike molecule (polymer). Usually the polymer chains are long, often consisting of hundreds of units, but polymers consisting of only a few units linked together are also known and can be commercially valuable.
Figure 1.1 Diagram illustrating the definition of plastics.
As Figure 1.1 shows, all materials can be classified as gases, simple liquids, or solids, with the understanding that most materials can be converted from one state to another through heating or cooling. If only materials that are structural solids at normal temperatures are examined, three major types of materials are encountered: metals, polymers, and ceramics. The polymer materials can be further divided into synthetic polymers and natural polymers. Most synthetic polymers are those that do not occur naturally and are represented by materials such as nylon, polyethylene, and polyester. Some synthetic polymers could be manufactured copies of naturally occurring materials (such as
低温、紫外胁迫对植物的影响的英语
低温、紫外胁迫对植物的影响的英语1. The effects of low temperature and UV stress on plants have been extensively studied.2. Researchers have investigated the impact of low temperature and UV stress on different plant species.3. This study aims to analyze the responses of plants to low temperature and UV stress.4. The effects of low temperature and UV stress can be detrimental to plant growth and development.5. Understanding the mechanisms underlying the response of plants to low temperature and UV stress is important for crop breeding.6. Low temperature and UV stress can induce significant changes in physiological and biochemical processes in plants.7. Recent studies have shown that low temperature and UV stress can alter the expression of genes involved in plant defense mechanisms.8. The effects of low temperature and UV stress on plants are mediated by various signaling pathways.9. Plant tolerance to low temperature and UV stress can be enhanced through genetic modification.10. The effects of low temperature and UV stress on plants can vary depending on the duration and intensity of exposure.11. Low temperature and UV stress can lead to the accumulation of reactive oxygen species in plants.12. The production of antioxidants is increased in response to low temperature and UV stress in plants.13. Certain plant species have developed specific mechanisms to cope with low temperature and UV stress.14. The effects of low temperature and UV stress on photosynthesis in plants have been extensively studied.15. Plant growth and development can be hindered by low temperature and UV stress.16. The effects of low temperature and UV stress on plant metabolism have been well-documented.17. Low temperature and UV stress can affect the nutritional composition of plants.18. Plants exposed to low temperature and UV stress may exhibit changes in leaf morphology.19. The effects of low temperature and UV stress on plant reproductive processes have been investigated.20. Stress-responsive genes are upregulated in plants subjected to low temperature and UV stress.21. Low temperature and UV stress can lead to alterations in plant hormone signaling pathways.22. Plant defense mechanisms are activated in response to low temperature and UV stress.23. The effects of low temperature and UV stress on plant water relations have been studied.24. Low temperature and UV stress can induce cell membrane damage in plants.25. The impact of low temperature and UV stress on plant yield and quality has been evaluated.26. Strategies for mitigating the effects of low temperature and UV stress on plants are being explored.。
纳米材料与蛋白相互作用
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Downloaded by RES CENTER OF ECO ENVIR SCIENCE RCEES on September 15, 2015 | Publication Date (Web): August 13, 2015 | doi: 10.1021/acsami.5b05895
Received: July 1, 2015 Accepted: August 7, 2015 Published: August 7, 2015
18880
DOI: 10.1021/acsami.5b05895 ACS Appl. Mater. Interfaces 2015, 7, 18880−18890
ACS Applied Materials & Interfaces α-Chymotrypsin (α-ChT) is an important digestive enzyme component in pancreatic juice, and it performs proteolysis in the duodenum. It is commonly used as an excellent enzyme model for studying the nanomaterial-induced enzymatic activity inhibition because of its well-defined structure and extensively characterized enzymatic properties. In this work, we focused on the structure and activity changes of α-ChT when they were absorbed onto multiwalled carbon nanotubes (MWCNTs) with gradient functionalization densities. A combination of techniques like fluorescence, circular dichroism (CD) spectroscopy, ζ-potential analysis, atomic force microscopy (AFM), and bicinchoninic acid (BCA) assay was used to detail the interaction between CNTs and α-ChT in the hope of revealing the role of the CNT functional group density. The findings regarding the protein structural and activity alterations provide fundamental understandings for the toxicological effects of CNTs.
分析化学专业英语词汇总结
专业英语词汇-----分析化学第一章绪论分析化学：analytical chemistry定性分析：qualitative analysis定量分析：quantitative analysis物理分析：physical analysis物理化学分析：physico-chemical analysis仪器分析法：instrumental analysis流动注射分析法：flow injection analysis；FIA顺序注射分析法：sequentical injection analysis;SIA化学计量学：chemometrics第二章误差的分析数据处理绝对误差：absolute error相对误差：relative error系统误差：systematic error可定误差：determinate error随机误差：accidental error不可定误差：indeterminate error准确度：accuracy精确度：precision偏差：debiation，d平均偏差：average debiation相对平均偏差：relative average debiation标准偏差（标准差）：standerd deviation;S相对平均偏差：relatibe standard deviation;RSD变异系数：coefficient of variation误差传递：propagation of error有效数字：significant figure置信水平：confidence level显著性水平：level of significance合并标准偏差（组合标准差）：pooled standard debiation 舍弃商：rejection quotient ;Q化学定量分析第三章滴定分析概论滴定分析法：titrametric analysis滴定：titration容量分析法:volumetric analysis化学计量点：stoichiometric point等当点：equivalent point电荷平衡：charge balance电荷平衡式：charge balance equation质量平衡：mass balance物料平衡：material balance质量平衡式：mass balance equation第四章酸碱滴定法酸碱滴定法：acid-base titrations 质子自递反应：auto protolysis reaction质子自递常数：autoprotolysis constant质子条件式:proton balance equation酸碱指示剂：acid-base indicator指示剂常数：indicator constant变色范围：colour change interval混合指示剂：mixed indicator双指示剂滴定法：double indicator titration第五章非水滴定法非水滴定法：nonaqueous titrations质子溶剂：protonic solvent酸性溶剂：acid solvent碱性溶剂：basic solvent两性溶剂:amphototeric solvent无质子溶剂：aprotic solvent均化效应：differentiatin g effect区分性溶剂：differentiating solvent离子化：ionization离解：dissociation结晶紫：crystal violet萘酚苯甲醇: α-naphthalphenol benzyl alcohol奎哪啶红：quinadinered百里酚蓝：thymol blue偶氮紫：azo violet溴酚蓝：bromophenol blue第六章配位滴定法配位滴定法：compleximetry乙二胺四乙酸：ethylenediamine tetraacetic acid,EDTA 螯合物：chelate compound金属指示剂：metal lochrome indcator第七章氧化还原滴定法氧化还原滴定法：oxidation-reduction titration碘量法：iodimetry溴量法：bromimetry ]溴量法：bromine method铈量法：cerimetry高锰酸钾法：potassium permanganate method条件电位：conditional potential溴酸钾法：potassium bromate method硫酸铈法：cerium sulphate method偏高碘酸：metaperiodic acid高碘酸盐：periodate亚硝酸钠法：sodium nitrite method重氮化反应：diazotization reaction重氮化滴定法：diazotization titration亚硝基化反应：nitrozation reaction亚硝基化滴定法：nitrozation titration外指示剂：external indicator外指示剂：outside indicator重铬酸钾法：potassium dichromate method 第八章沉淀滴定法沉淀滴定法：precipitation titration容量滴定法：volumetric precipitation method 银量法：argentometric method第九章重量分析法重量分析法：gravimetric analysis挥发法：volatilization method引湿水（湿存水）：water of hydroscopicity 包埋(藏)水：occluded water吸入水：water of imbibition结晶水：water of crystallization组成水：water of composition液-液萃取法：liquid-liquid extration溶剂萃取法：solvent extration反萃取：counter extraction分配系数：partition coefficient分配比：distribution ratio离子对（离子缔合物）：ion pair沉淀形式：precipitation forms称量形式：weighing forms仪器分析概述物理分析：physical analysis物理化学分析：physicochemical analysis仪器分析：instrumental analysis第十章电位法及永停滴定法电化学分析：electrochemical analysis电解法：electrolytic analysis method电重量法：electrogravimetry库仑法：coulo metry库仑滴定法：coulo metric titration电导法：conductometry电导分析法：conductometric analysis电导滴定法：conductometric titration电位法：potentiometry直接电位法：dirext potentiometry电位滴定法：potentiometric titration伏安法：voltammetry极谱法：polarography溶出法：stripping method电流滴定法：amperometric titration化学双电层：chemical double layer相界电位：phase boundary potential 金属电极电位：electrode potential化学电池：chemical cell液接界面：liquid junction boundary原电池：galvanic cell电解池：electrolytic cell负极：cathode正极：anode电池电动势：eletromotive force指示电极：indicator electrode参比电极：reference electroade标准氢电极：standard hydrogen electrode一级参比电极：primary reference electrode饱和甘汞电极：saturated calomel electrode银－氯化银电极：silver silver-chloride electrode液接界面：liquid junction boundary不对称电位：asymmetry potential表观PH值：apparent PH复合PH电极：combination PH electrode离子选择电极：ion selective electrode敏感器：sensor晶体电极:crystalline electrodes均相膜电极：homogeneous membrance electrodes非均相膜电极：heterogeneous membrance electrodes非晶体电极：non- crystalline electrodes刚性基质电极：rigid matrix electrode流流体载动电极：electrode with a mobile carrier气敏电极：gas sensing electrodes酶电极：enzyme electrodes金属氧化物半导体场效应晶体管：MOSFET离子选择场效应管：ISFET总离子强度调节缓冲剂：total ion strength adjustment buffer,TISAB永停滴定法：dead-stop titration双电流滴定法（双安培滴定法）：double amperometric titration 第十一章光谱分析法概论普朗克常数：Plank constant电磁波谱：electromagnetic spectrum光谱：spectrum光谱分析法：spectroscopic analysis原子发射光谱法：atomic emission spectroscopy质量谱：mass spectrum质谱法：mass spectroscopy,MS第十二章紫外－可见分光光度法紫外－可见分光光度法：ultraviolet and visible spectrophotometry;UV-vis肩峰：shoulder peak末端吸收：end absorbtion生色团：chromophore助色团：auxochrome红移：red shift长移：bathochromic shift短移：hypsochromic shift蓝（紫）移：blue shift增色效应（浓色效应）：hyperchromic effect减色效应（淡色效应）：hypochromic effect强带：strong band弱带：weak band吸收带：absorption band透光率：transmitance,T吸光度：absorbance谱带宽度：band width杂散光：stray light噪声：noise暗噪声：dark noise散粒噪声：signal shot noise闪耀光栅：blazed grating全息光栅：holographic grating光二极管阵列检测器：photodiode array detector 偏最小二乘法：partial least squares method ,PLS褶合光谱法：convolution spectrometry褶合变换：convolution transform,CT离散小波变换：wavelet transform,WT多尺度细化分析：multiscale analysis供电子取代基：electron donating group吸电子取代基：electron with-drawing group第十三章荧光分析法荧光：fluorescence荧光分析法：fluorometryX-射线荧光分析法：X-ray fluorometry原子荧光分析法：atomic fluorometry分子荧光分析法：molecular fluorometry振动弛豫：vibrational relaxation内转换：internal conversion外转换：external conversion体系间跨越：intersystem crossing激发光谱：excitation spectrum荧光光谱：fluorescence spectrum斯托克斯位移：Stokes shift荧光寿命：fluorescence life time荧光效率：fluorescence efficiency荧光量子产率：fluorescence quantum yield荧光熄灭法：fluorescence quenching method散射光：scattering light瑞利光：R a yleith scattering light拉曼光：Raman scattering lightAbbe refractometer 阿贝折射仪absorbance 吸收度absorbance ratio 吸收度比值absorption 吸收absorption curve 吸收曲线absorption spectrum 吸收光谱absorptivity 吸收系数accuracy 准确度acid-dye colorimetry 酸性染料比色法acidimetry 酸量法acid-insoluble ash 酸不溶性灰分acidity 酸度activity 活度第十四章色谱法additive 添加剂additivity 加和性adjusted retention time 调整保留时间adsorbent 吸附剂adsorption 吸附affinity chromatography 亲和色谱法aliquot （一）份alkalinity 碱度alumina 氧化铝ambient temperature 室温ammonium thiocyanate 硫氰酸铵analytical quality control（AQC）分析质量控制anhydrous substance 干燥品anionic surfactant titration 阴离子表面活性剂滴定法antibiotics-microbial test 抗生素微生物检定法antioxidant 抗氧剂appendix 附录application of sample 点样area normalization method 面积归一化法argentimetry 银量法arsenic 砷arsenic stain 砷斑ascending development 上行展开ash-free filter paper 无灰滤纸（定量滤纸）assay 含量测定assay tolerance 含量限度atmospheric pressure ionization(API) 大气压离子化attenuation 衰减back extraction 反萃取back titration 回滴法bacterial endotoxins test 细菌内毒素检查法band absorption 谱带吸收baseline correction 基线校正baseline drift 基线漂移batch, lot 批batch(lot) number 批号Benttendorff method 白田道夫（检砷）法between day (day to day, inter-day) precision 日间精密度between run (inter-run) precision 批间精密度biotransformation 生物转化bioavailability test 生物利用度试验bioequivalence test 生物等效试验biopharmaceutical analysis 体内药物分析，生物药物分析blank test 空白试验boiling range 沸程British Pharmacopeia (BP) 英国药典bromate titration 溴酸盐滴定法bromimetry 溴量法bromocresol green 溴甲酚绿bromocresol purple 溴甲酚紫bromophenol blue 溴酚蓝bromothymol blue 溴麝香草酚蓝bulk drug, pharmaceutical product 原料药buret 滴定管by-product 副产物calibration curve 校正曲线calomel electrode 甘汞电极calorimetry 量热分析capacity factor 容量因子capillary zone electrophoresis (CZE) 毛细管区带电泳capillary gas chromatography 毛细管气相色谱法carrier gas 载气cation-exchange resin 阳离子交换树脂ceri(o)metry 铈量法characteristics, description 性状check valve 单向阀chemical shift 化学位移chelate compound 鳌合物chemically bonded phase 化学键合相chemical equivalent 化学当量Chinese Pharmacopeia (ChP) 中国药典Chinese material medicine 中成药Chinese materia medica 中药学Chinese materia medica preparation 中药制剂Chinese Pharmaceutical Association (CPA) 中国药学会chiral 手性的chiral stationary phase (CSP) 手性固定相chiral separation 手性分离chirality 手性chiral carbon atom 手性碳原子chromatogram 色谱图chromatography 色谱法chromatographic column 色谱柱chromatographic condition 色谱条件chromatographic data processor 色谱数据处理机chromatographic work station 色谱工作站clarity 澄清度clathrate, inclusion compound 包合物clearance 清除率clinical pharmacy 临床药学coefficient of distribution 分配系数coefficient of variation 变异系数color change interval （指示剂）变色范围color reaction 显色反应colorimetric analysis 比色分析colorimetry 比色法column capacity 柱容量column dead volume 柱死体积column efficiency 柱效column interstitial volume 柱隙体积column outlet pressure 柱出口压column temperature 柱温column pressure 柱压column volume 柱体积column overload 柱超载column switching 柱切换committee of drug evaluation 药品审评委员会comparative test 比较试验completeness of solution 溶液的澄清度compound medicines 复方药computer-aided pharmaceutical analysis 计算机辅助药物分析concentration-time curve 浓度－时间曲线confidence interval 置信区间confidence level 置信水平confidence limit 置信限congealing point 凝点congo red 刚果红（指示剂）content uniformity 装量差异controlled trial 对照试验correlation coefficient 相关系数contrast test 对照试验counter ion 反离子（平衡离子）cresol red 甲酚红（指示剂）crucible 坩埚crude drug 生药crystal violet 结晶紫（指示剂）cuvette, cell 比色池cyanide 氰化物cyclodextrin 环糊精cylinder, graduate cylinder, measuring cylinder 量筒cylinder-plate assay 管碟测定法daughter ion （质谱）子离子dead space 死体积dead-stop titration 永停滴定法dead time 死时间decolorization 脱色decomposition point 分解点deflection 偏差deflection point 拐点degassing 脱气deionized water 去离子水deliquescence 潮解depressor substances test 降压物质检查法derivative spectrophotometry 导数分光光度法derivatization 衍生化descending development 下行展开desiccant 干燥剂detection 检查detector 检测器developer, developing reagent 展开剂developing chamber 展开室deviation 偏差dextrose 右旋糖，葡萄糖diastereoisomer 非对映异构体diazotization 重氮化2,6-dichlorindophenol titration 2,6-二氯靛酚滴定法differential scanning calorimetry (DSC) 差示扫描热量法differential spectrophotometry 差示分光光度法differential thermal analysis (DTA) 差示热分析differentiating solvent 区分性溶剂diffusion 扩散digestion 消化diphastic titration 双相滴定disintegration test 崩解试验dispersion 分散度dissolubility 溶解度dissolution test 溶出度检查distilling range 馏程distribution chromatography 分配色谱distribution coefficient 分配系数dose 剂量drug control institutions 药检机构drug quality control 药品质量控制drug release 药物释放度drug standard 药品标准drying to constant weight 干燥至恒重dual wavelength spectrophotometry 双波长分光光度法duplicate test 重复试验effective constituent 有效成分effective plate number 有效板数efficiency of column 柱效electron capture detector 电子捕获检测器electron impact ionization 电子轰击离子化electrophoresis 电泳electrospray interface 电喷雾接口electromigration injection 电迁移进样elimination 消除eluate 洗脱液elution 洗脱emission spectrochemical analysis 发射光谱分析enantiomer 对映体end absorption 末端吸收end point correction 终点校正endogenous substances 内源性物质enzyme immunoassay(EIA) 酶免疫分析enzyme drug 酶类药物enzyme induction 酶诱导enzyme inhibition 酶抑制eosin sodium 曙红钠（指示剂）epimer 差向异构体equilibrium constant 平衡常数equivalence point 等当点error in volumetric analysis 容量分析误差excitation spectrum 激发光谱exclusion chromatography 排阻色谱法expiration date 失效期external standard method 外标法extract 提取物extraction gravimetry 提取重量法extraction titration 提取容量法extrapolated method 外插法，外推法factor 系数，因数，因子feature 特征Fehling’s reaction 费林反应field disorption ionization 场解吸离子化field ionization 场致离子化filter 过滤，滤光片filtration 过滤fineness of the particles 颗粒细度flame ionization detector(FID) 火焰离子化检测器flame emission spectrum 火焰发射光谱flask 烧瓶flow cell 流通池flow injection analysis 流动注射分析flow rate 流速fluorescamine 荧胺fluorescence immunoassay(FIA) 荧光免疫分析fluorescence polarization immunoassay(FPIA) 荧光偏振免疫分析fluorescent agent 荧光剂fluorescence spectrophotometry 荧光分光光度法fluorescence detection 荧光检测器fluorimetyr 荧光分析法foreign odor 异臭foreign pigment 有色杂质formulary 处方集fraction 馏分freezing test 结冻试验funnel 漏斗fused peaks, overlapped peaks 重叠峰fused silica 熔融石英gas chromatography(GC) 气相色谱法gas-liquid chromatography(GLC) 气液色谱法gas purifier 气体净化器gel filtration chromatography 凝胶过滤色谱法gel permeation chromatography 凝胶渗透色谱法general identification test 一般鉴别试验general notices （药典）凡例general requirements （药典）通则good clinical practices(GCP) 药品临床管理规范good laboratory practices(GLP) 药品实验室管理规范good manufacturing practices(GMP) 药品生产质量管理规范good supply practices(GSP) 药品供应管理规范gradient elution 梯度洗脱grating 光栅gravimetric method 重量法Gutzeit test 古蔡（检砷）法half peak width 半峰宽[halide] disk method, wafer method, pellet method 压片法head-space concentrating injector 顶空浓缩进样器heavy metal 重金属heat conductivity 热导率height equivalent to a theoretical plate 理论塔板高度height of an effective plate 有效塔板高度high-performance liquid chromatography (HPLC) 高效液相色谱法high-performance thin-layer chromatography (HPTLC) 高效薄层色谱法hydrate 水合物hydrolysis 水解hydrophilicity 亲水性hydrophobicity 疏水性hydroscopic 吸湿的hydroxyl value 羟值hyperchromic effect 浓色效应hypochromic effect 淡色效应identification 鉴别ignition to constant weight 灼烧至恒重immobile phase 固定相immunoassay 免疫测定impurity 杂质inactivation 失活index 索引indicator 指示剂indicator electrode 指示电极inhibitor 抑制剂injecting septum 进样隔膜胶垫injection valve 进样阀instrumental analysis 仪器分析insulin assay 胰岛素生物检定法integrator 积分仪intercept 截距interface 接口interference filter 干涉滤光片intermediate 中间体internal standard substance 内标物质international unit(IU) 国际单位in vitro 体外in vivo 体内iodide 碘化物iodoform reaction 碘仿反应iodometry 碘量法ion-exchange cellulose 离子交换纤维素ion pair chromatography 离子对色谱ion suppression 离子抑制ionic strength 离子强度ion-pairing agent 离子对试剂ionization 电离，离子化ionization region 离子化区irreversible indicator 不可逆指示剂irreversible potential 不可逆电位isoabsorptive point 等吸收点isocratic elution 等溶剂组成洗脱isoelectric point 等电点isoosmotic solution 等渗溶液isotherm 等温线Karl Fischer titration 卡尔·费歇尔滴定kinematic viscosity 运动黏度Kjeldahl method for nitrogen 凯氏定氮法Kober reagent 科伯试剂Kovats retention index 科瓦茨保留指数labelled amount 标示量leading peak 前延峰least square method 最小二乘法leveling effect 均化效应licensed pharmacist 执业药师limit control 限量控制limit of detection(LOD) 检测限limit of quantitation(LOQ) 定量限limit test （杂质）限度（或限量）试验limutus amebocyte lysate(LAL) 鲎试验linearity and range 线性及范围linearity scanning 线性扫描liquid chromatograph/mass spectrometer (LC/MS) 液质联用仪litmus paper 石蕊试纸loss on drying 干燥失重low pressure gradient pump 低压梯度泵luminescence 发光lyophilization 冷冻干燥main constituent 主成分make-up gas 尾吹气maltol reaction 麦牙酚试验Marquis test 马奎斯试验mass analyzer detector 质量分析检测器mass spectrometric analysis 质谱分析mass spectrum 质谱图mean deviation 平均偏差measuring flask, volumetric flask 量瓶measuring pipet(te) 刻度吸量管medicinal herb 草药melting point 熔点melting range 熔距metabolite 代谢物metastable ion 亚稳离子methyl orange 甲基橙methyl red 甲基红micellar chromatography 胶束色谱法micellar electrokinetic capillary chromatography(MECC, MEKC) 胶束电动毛细管色谱法micelle 胶束microanalysis 微量分析microcrystal 微晶microdialysis 微透析micropacked column 微型填充柱microsome 微粒体microsyringe 微量注射器migration time 迁移时间millipore filtration 微孔过滤minimum fill 最低装量mobile phase 流动相modifier 改性剂，调节剂molecular formula 分子式monitor 检测，监测monochromator 单色器monographs 正文mortar 研钵moving belt interface 传送带接口multidimensional detection 多维检测multiple linear regression 多元线性回归multivariate calibration 多元校正natural product 天然产物Nessler glasses(tube) 奈斯勒比色管Nessler’s r eagent 碱性碘化汞钾试液neutralization 中和nitrogen content 总氮量nonaqueous acid-base titration 非水酸碱滴定nonprescription drug, over the counter drugs (OTC drugs) 非处方药nonproprietary name, generic name 非专有名nonspecific impurity 一般杂质non-volatile matter 不挥发物normal phase 正相normalization 归一化法notice 凡例nujol mull method 石蜡糊法octadecylsilane chemically bonded silica 十八烷基硅烷键合硅胶octylsilane 辛（烷）基硅烷odorless 无臭official name 法定名official specifications 法定标准official test 法定试验on-column detector 柱上检测器on-column injection 柱头进样on-line degasser 在线脱气设备on the dried basis 按干燥品计opalescence 乳浊open tubular column 开管色谱柱optical activity 光学活性optical isomerism 旋光异构optical purity 光学纯度optimization function 优化函数organic volatile impurities 有机挥发性杂质orthogonal function spectrophotometry 正交函数分光光度法orthogonal test 正交试验orthophenanthroline 邻二氮菲outlier 可疑数据，逸出值overtones 倍频峰，泛频峰oxidation-reduction titration 氧化还原滴定oxygen flask combustion 氧瓶燃烧packed column 填充柱packing material 色谱柱填料palladium ion colorimetry 钯离子比色法parallel analysis 平行分析parent ion 母离子particulate matter 不溶性微粒partition coefficient 分配系数parts per million (ppm) 百万分之几pattern recognition 模式识别peak symmetry 峰不对称性peak valley 峰谷peak width at half height 半峰宽percent transmittance 透光百分率pH indicator absorbance ratio method? pH指示剂吸光度比值法pharmaceutical analysis 药物分析pharmacopeia 药典pharmacy 药学phenolphthalein 酚酞photodiode array detector(DAD) 光电二极管阵列检测器photometer 光度计pipeclay triangle 泥三角pipet(te) 吸移管，精密量取planar chromatography 平板色谱法plate storage rack 薄层板贮箱polarimeter 旋光计polarimetry 旋光测定法polarity 极性polyacrylamide gel 聚丙酰胺凝胶polydextran gel 葡聚糖凝胶polystyrene gel 聚苯乙烯凝胶polystyrene film 聚苯乙烯薄膜porous polymer beads 高分子多孔小球post-column derivatization 柱后衍生化potentiometer 电位计potentiometric titration 电位滴定法precipitation form 沉淀形式precision 精密度pre-column derivatization 柱前衍生化preparation 制剂prescription drug 处方药pretreatment 预处理primary standard 基准物质principal component analysis 主成分分析programmed temperature gas chromatography 程序升温气相色谱法prototype drug 原型药物provisions for new drug approval 新药审批办法purification 纯化purity 纯度pyrogen 热原pycnometric method 比重瓶法quality control(QC) 质量控制quality evaluation 质量评价quality standard 质量标准quantitative determination 定量测定quantitative analysis 定量分析quasi-molecular ion 准分子离子racemization 消旋化radioimmunoassay 放射免疫分析法random sampling 随机抽样rational use of drug 合理用药readily carbonizable substance 易炭化物reagent sprayer 试剂喷雾器recovery 回收率reference electrode 参比电极refractive index 折光指数related substance 有关物质relative density 相对密度relative intensity 相对强度repeatability 重复性replicate determination 平行测定reproducibility 重现性residual basic hydrolysis method 剩余碱水解法residual liquid junction potential 残余液接电位residual titration 剩余滴定residue on ignition 炽灼残渣resolution 分辨率，分离度response time 响应时间retention 保留reversed phase chromatography 反相色谱法reverse osmosis 反渗透rider peak 驼峰rinse 清洗，淋洗robustness 可靠性，稳定性routine analysis 常规分析round 修约（数字）ruggedness 耐用性safety 安全性Sakaguchi test 坂口试验salt bridge 盐桥salting out 盐析sample applicator 点样器sample application 点样sample on-line pretreatment 试样在线预处理sampling 取样saponification value 皂化值saturated calomel electrode(SCE) 饱和甘汞电极selectivity 选择性separatory funnel 分液漏斗shoulder peak 肩峰signal to noise ratio 信噪比significant difference 显著性差异significant figure 有效数字significant level 显著性水平significant testing 显著性检验silanophilic interaction 亲硅羟基作用silica gel 硅胶silver chloride electrode 氯化银电极similarity 相似性simultaneous equations method 解线性方程组法size exclusion chromatography(SEC) 空间排阻色谱法sodium dodecylsulfate, SDS 十二烷基硫酸钠sodium hexanesulfonate 己烷磺酸钠sodium taurocholate 牛璜胆酸钠sodium tetraphenylborate 四苯硼钠sodium thiosulphate 硫代硫酸钠solid-phase extraction 固相萃取solubility 溶解度solvent front 溶剂前沿solvophobic interaction 疏溶剂作用specific absorbance 吸收系数specification 规格specificity 专属性specific rotation 比旋度specific weight 比重spiked 加入标准的split injection 分流进样splitless injection 无分流进样spray reagent （平板色谱中的）显色剂spreader 铺板机stability 稳定性standard color solution 标准比色液standard deviation 标准差standardization 标定standard operating procedure(SOP) 标准操作规程standard substance 标准品stationary phase coating 固定相涂布starch indicator 淀粉指示剂statistical error 统计误差sterility test 无菌试验stirring bar 搅拌棒stock solution 储备液stoichiometric point 化学计量点storage 贮藏stray light 杂散光substituent 取代基substrate 底物sulfate 硫酸盐sulphated ash 硫酸盐灰分supercritical fluid chromatography(SFC) 超临界流体色谱法support 载体（担体）suspension 悬浊液swelling degree 膨胀度symmetry factor 对称因子syringe pump 注射泵systematic error 系统误差system model 系统模型system suitability 系统适用性tablet 片剂tailing factor 拖尾因子tailing peak 拖尾峰tailing-suppressing reagent 扫尾剂test of hypothesis 假设检验test solution(TS) 试液tetrazolium colorimetry 四氮唑比色法therapeutic drug monitoring(TDM) 治疗药物监测thermal analysis 热分析法thermal conductivity detector 热导检测器thermocouple detector 热电偶检测器thermogravimetric analysis(TGA) 热重分析法thermospray interface 热喷雾接口The United States Pharmacopoeia(USP) 美国药典The Pharmacopoeia of Japan(JP) 日本药局方thin layer chromatography(TLC) 薄层色谱法thiochrome reaction 硫色素反应three-dimensional chromatogram 三维色谱图thymol 百里酚（麝香草酚）（指示剂）thymolphthalein 百里酚酞（麝香草酚酞）（指示剂）thymolsulfonphthalein ( thymol blue) 百里酚蓝（麝香草酚蓝）（指示剂）titer, titre 滴定度time-resolved fluoroimmunoassay 时间分辨荧光免疫法titrant 滴定剂titration error 滴定误差titrimetric analysis 滴定分析法tolerance 容许限toluene distillation method 甲苯蒸馏法toluidine blue 甲苯胺蓝（指示剂）total ash 总灰分total quality control(TQC) 全面质量控制traditional drugs 传统药traditional Chinese medicine 中药transfer pipet 移液管turbidance 混浊turbidimetric assay 浊度测定法turbidimetry 比浊法turbidity 浊度ultracentrifugation 超速离心ultrasonic mixer 超生混合器ultraviolet irradiation 紫外线照射undue toxicity 异常毒性uniform design 均匀设计uniformity of dosage units 含量均匀度uniformity of volume 装量均匀性（装量差异）uniformity of weight 重量均匀性（片重差异）validity 可靠性variance 方差versus …对…，…与…的关系曲线viscosity 粘度volatile oil determination apparatus 挥发油测定器volatilization 挥发法volumetric analysis 容量分析volumetric solution(VS) 滴定液vortex mixer 涡旋混合器watch glass 表面皿wave length 波长wave number 波数weighing bottle 称量瓶weighing form 称量形式weights 砝码well-closed container 密闭容器xylene cyanol blue FF 二甲苯蓝FF（指示剂）xylenol orange 二甲酚橙（指示剂）zigzag scanning 锯齿扫描zone electrophoresis 区带电泳zwitterions 两性离子zymolysis 酶解作用簡體書目錄Chapter 1 Introduction 緒論1.1 The nature of analytical chemistry 分析化學的性質1.2 The role of analytical chemistry 分析化學的作用1.3 The classification of analytical chemistry分析化學的分類1.4 The total analytical process分析全過程Terms to understand重點內容概述Chapter 2 Errors and Data Treatment in Quantitative Analysis 定量分析中的誤差及數據處理2.1 Fundamental terms of errors誤差的基本術語2.2 Types of errors in experimental data實驗數據中的誤差類型2.2.1 Systematic errors 系統誤差2.2.2 Random errors偶然誤差2.3 Evaluation of analytical data分析數據的評價2.3.1 Tests of significance顯著性檢驗2.3.2 Rejecting data可疑值取捨2.4 Significant figures有效數字ProblemsTerms to understand重點內容概述Chapter 3 Titrimetric Analysis滴定分析法3.1 General principles基本原理3.1.1 Relevant terms of titrimetric analysis滴定分析相關術語3.1.2 The preparation of standard solution and the expression of concentration 標準溶液的配製與濃度表示方法3.1.3 The types of titrimetric reactions滴定反應類型3.2 Acid-base titration酸鹼滴定3.2.1 Acid-base equilibria 酸鹼平衡3.2.2 Titration curves滴定曲線3.2.3 Acid-base indicators酸鹼指示劑3.2.4 Applications of acid-base titration酸鹼滴定的應用3.3 Complexometric titration配位滴定3.3.1 Metal-chelate complexes金屬螯合物3.3.2 EDTA 乙二胺四乙酸3.3.3 EDTA titration curves EDTA滴定曲線3.3.4 Metal Ion indicators金屬離子指示劑3.3.5 Applications of EDTA titration techniques EDTA滴定方法的應用3.4 Oxidation-reduction titration氧化還原滴定3.4.1 Redox reactions氧化還原反應3.4.2 Rate of redox reactions氧化還原反應的速率3.4.3 Titration curves滴定曲線3.4.4 Redox indicators氧化還原指示劑3.4.5 Applications of redox titrations氧化還原滴定的應用3.5 Precipitation titration沉澱滴定3.5.1 Precipitation reactions沉澱滴定反應3.5.2 Titration curves滴定曲線3.5.3 End-point detection終點檢測ProblemsTerms to understand重點內容概述Chapter 4 Potentiometry 電位分析法4.1 Introduction簡介4.1.1 Classes and characteristics分類及性質4.1.2 Definition定義4.2 Types of potentiometric electrodes電極種類4.2.1 Reference electrodes 參比電極4.2.2 Indicator electrodes指示電極4.2.3 Electrode response and selectivity電極響應及選擇性4.3 Potentiometric methods and application電位法及應用4.3.1 Direct potentiometric measurement 直接電位法4.3.2 Potentiometric titrations電位滴定4.3.3 Applications of potentiometry 電位法應用ProblemsTerlns to understand重點內容概述Chapter 5 Chromatography色譜法5.1 An introduction to chromatographic methods色譜法概述5.2 Fundamental theory of gas chromatography氣相色譜基本原理5.2.1 Plate theory塔板理論5.2.2 Kinetic theory(rate theory) 速率理論5.2.3 The resolution Rs as a measure of peak separation 分離度5.3 Gas chromatography 氣相色譜5.3.1 Components of a gas chromatograph 氣相色譜儀的組成5.3.2 Stationary phases for gas-liquid chromatography 氣液色譜固定相5.3.3 Applications of gas-liquid chromatography 氣液色譜的應用5.3.4 Adsorption chromatography 吸附色譜5.4 High performance liquid chromatography 高效液相色譜5.4.1 Instrumentation 儀器組成5.4.2 High-performance partition chromatography 高效分配色譜5.5 Miscellaneous separation methods 其他分離方法5.5.1 High-performance ion-exchange chromatography 高效離子交換色譜5.5.2 Capillary electrophoresis 毛細管電泳5.5.3 Planar chromatography 平板色譜ProblemsTerms to understand重點內容概述Chapter 6 Atomic Absorption Spectrometry原子吸收光譜分析法6.1 Introduction 概述6.2 Principles 原理6.2.1 The process of AAS，resonance line and absorption line 原子吸收光譜法的過程，共振線及吸收線6.2.2 The number of ground atom and the temperature of flame 基態原子數與光焰溫度6.2.3 Quantitative analysis of AAS原子吸收光譜定量分析6.3 Instrumentation 儀器6.3.1 Primary radiation sources 光源6.3.2 Atomizer 原子儀器6.3.3 Optical dispersive systems 分光系統6.3.4 Detectors 檢測器6.3.5 Signal measurements 信號測量6.4 Quantitative measurements and interferences 定量測定及干擾6.4.1 Quantitative measurements 定量測定6.4.2 Interferences 干擾6.4.3 Sensitivity6.5 Applications of AAS原子吸收光譜法的應用ProblemsTerms to understand重點內容概述Chapter 7 Ultraviolet and Visible Spectrophotometry 紫外-可見分光光度法7.1 Introduction簡介7.2 Ultraviolet and visible absorption spectroscopy 紫外-可見吸收光譜7.2.1 Introduction for radiant energy 輻射能簡介7.2.2 Selective absorption of radiation and absorbance spectrum 物質對光的選擇性吸收和吸收光譜7.2.3 Absorbing species and electron transition 吸收物質與電子躍遷7.3 Law of absorption吸收定律7.3.1 Lambert-Beer's law朗伯-比爾定律7.3.2 Absorptivity吸光係數7.3.3 Apparent deviations from Beer's law對比爾定律的明顯偏離7.4 Instruments儀器7.5 General types of spectrophotometer分光光度計種類7.6 Application of UV-Vis absorption spectroscopy 紫外-可見吸收光譜的應用7.6.1 Application of absorption measurement to qualitative analysis 光吸收測定在定性分析上的應用7.6.2 Quantitative analysis by absorption measurements 光吸收測量定量分析法7.6.3 Derivative spectrophotometry 導數分光光度法ProblemsTerms to understand重點內容概述Chapter 8 Infrared Absorption Spectroscopy紅外吸收光譜8.1 Theory of infrared absorption紅外吸收基本原理8.1.1 Dipole changes during vibrations and rotations 振轉運動中的偶極距變化8.1.2 Mechanical model of stretching vibrations 伸縮振動機械模型8.1.3 Quantum treatment of vibrations 振動的量子力學處理、8.1.4 Types of molecular vibrations分子振動形式8.2 Infrared instrument components紅外儀器組成8.2.1 Wavelength selection波長選擇8.2.2 Sampling techniques 採樣技術8.2.3 Infrared spectrophotometers for qualitative analysis 定性分析用紅外分光光度計8.2.4 Other techniques其他技術8.3 The group frequencies of functional groups in organic compounds 有機化合物官能團的特徵頻率8.4 The factors affecting group frequencies 影響基團特徵吸收頻率的因素8.4.1 Adjacent groups 鄰近基團的影響。
合金粘度的影响英文文献
合金粘度的影响英文文献
以下是关于合金粘度的影响的英文文献：
1. Saito, H., et al. "Effects of alloying elements on the viscosity of liquid Fe-based alloys." Journal of Non-Crystalline Solids 357.1 (2011): 47-53.
2. Wang, J., et al. "Influence of alloying elements on the viscosity of liquid Al-Cu alloys." Transactions of Nonferrous Metals Society of China 22.7 (2012): 1567-1572.
3. Anwar, Hafeez, et al. "Effect of alloying elements on the viscosity of liquid Ni-based alloys." Journal of Applied Physics 106.11 (2009): 113519.
4. Zhang, H., et al. "The effect of alloying elements on the viscosity of liquid Sn-Bi alloys." Journal of Alloys and Compounds 787 (2019): 1110-111
5.
这些文献研究了不同合金元素对合金粘度的影响，提供了相关的实验结果和分析。
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Effect of Crystallographic Structure of MnO2 on Its Electrochemical Capacitance Properties
Effect of Crystallographic Structure of MnO2on Its Electrochemical Capacitance PropertiesS.Devaraj and N.Munichandraiah*Department of Inorganic and Physical Chemistry,Indian Institute of Science,Bangalore-560012,IndiaRecei V ed:No V ember14,2007;In Final Form:January7,2008MnO2is currently under extensive investigations for its capacitance properties.MnO2crystallizes into severalcrystallographic structures,namely,R, ,γ,δ,andλstructures.Because these structures differ in the wayMnO6octahedra are interlinked,they possess tunnels or interlayers with gaps of different magnitudes.Becausecapacitance properties are due to intercalation/deintercalation of protons or cations in MnO2,only somecrystallographic structures,which possess sufficient gaps to accommodate these ions,are expected to beuseful for capacitance studies.In order to examine the dependence of capacitance on crystal structure,thepresent study involves preparation of these various crystal phases of MnO2in nanodimensions and to evaluatetheir capacitance properties.Results of R-MnO2prepared by a microemulsion route(R-MnO2(m))are alsoused for comparison.Spherical particles of about50nm,nanorods of30-50nm in diameter,or interlockedfibers of10-20nm in diameters are formed,which depend on the crystal structure and the method ofpreparation.The specific capacitance(SC)measured for MnO2is found to depend strongly on thecrystallographic structure,and it decreases in the following order:R(m)>R=δ>γ>λ> .A SC valueof297F g-1is obtained for R-MnO2(m),whereas it is9F g-1for -MnO2.A wide(∼4.6Å)tunnel size andlarge surface area of R-MnO2(m)are ascribed as favorable factors for its high SC.A large interlayer separation(∼7Å)also facilitates insertion of cations inδ-MnO2resulting in a SC close to236F g-1.A narrow tunnelsize(1.89Å)does not allow intercalation of cations into -MnO2.As a result,it provides a very small SC.1.IntroductionIn recent years,electrochemical capacitors(ECs)have received a great attention in the filed of electrochemical energy storage and conversion because of their high power capability and long cycle-life.An EC is useful as an auxiliary energy device along with a primary power source such as a battery or a fuel cell for power enhancement in short pulse applications.1-4 Charge storage mechanisms in EC capacitor materials include separation of charges at the interface between the electrode and the electrolyte and/or fast faradaic reactions occurring at the electrode.Capacitance,which arises from separation of charges, is generally called electric double-layer capacitance(EDLC). Capacitance due to a faradaic process is known as pseudoca-pacitance.Because the magnitude of capacitance of these types of capacitors is several times greater than that of conventional capacitors,ECs are also known as supercapacitors or ultraca-pacitors.Various materials investigated for ECs include(i)carboneous materials,(ii)conducting polymers,and(iii)transition-metal oxides.3Among transition-metal oxides,amorphous hydrous ruthenium oxide(RuO2‚x H2O)has specific capacitance(SC) as high as760F g-1because of the solid-state pseudofaradaic reaction.5-8However,the high cost,low porosity,and toxic nature of RuO2limit commercialization of supercapacitors employing this material.Therefore,there is a need to investigate alternate transition-metal oxides,which are cheap,available in abundance,nontoxic,and environmentally friendly.Manganese dioxide has attracted much attention9-21because it has these favorable properties and it is widely used as a cathode material in batteries.22However,the SC values reported are lower than the values obtained for RuO2‚x H2O,and studies on various ways of increasing the SC are reported.14,15Hydrous MnO2exhibits pseudocapacitance behavior in several aqueous electrolytes of alkali salts such as Li2SO4,Na2-SO4,K2SO4,and so forth.Transition of Mn4+/Mn3+involving a single electron transfer is responsible for the pseudocapacitance behavior of MnO2.10,23,24MnO2exists in several crystallographic forms,which are known as R, ,γ,δ,andλforms.22,25The R, ,andγforms possess1D tunnels in their structures,theδis a2D layered compound,and theλis a3D spinel structure. The properties of MnO2largely depend on its crystallographic nature.Because of various crystallographic structures,MnO2 is useful as a molecular sieve,26a catalyst,27and an electrode material in batteries22as well as in supercapacitors.9-21Because these structures differ in the way MnO6octahedra are inter-linked,they possess tunnels or interlayers with gaps of different magnitudes.Because capacitance properties are due to intercala-tion/deintercalation of protons or cations in MnO2,only the crystallographic structures,which possess sufficient gaps to accommodate these ions,are anticipated to be useful for capacitance studies.It is expected that the amount of alkali cations or protons intercalated/extracted into/from MnO2lattice and hence its SC largely depends on either the size of the tunnel or the interlayer separation between sheets of MnO6octahedra. MnO2with three different crystallographic forms(R, ,and γ)was prepared by the hydrothermal-electrochemical method, and lithium insertion behavior was studied.28,29R-andγ-MnO2 were prepared by the electrolysis of aqueous MnSO4solution containing various alkali and alkaline earth salts at various pH and potential values.It was found that the crystallographic structure of MnO2depends on the radius of the alkali or alkaline earth metal-ion,the pH,and the potential.30Brousse et al.studied the dependence of capacitance on surface area for various*Corresponding author.Tel:+91-80-22933183.Fax:+91-80-23600683.E-mail:muni@ipc.iisc.ernet.in.4406J.Phys.Chem.C2008,112,4406-441710.1021/jp7108785CCC:$40.75©2008American Chemical SocietyPublished on Web02/26/2008amorphous and crystalline samples of MnO 2.31On the basis of cyclic voltammetric data,SC values were calculated.The SC values obtained for δ-MnO 2were in the range of 80-110F g -1,which was slightly smaller than the values found for amorphous samples.The SC values obtained for -MnO 2(5F g -1),γ-MnO 2(30F g -1),and λ-MnO 2(70F g -1)were smaller than the values obtained for δ-MnO 2.31The present trend of research in many fields is to employ nanosize materials,which are expected to possess better properties than the micrometer-size materials.Studies on the capacitance properties of various crystallographic forms of MnO 2are scarce in the literature.31The intention of the present study is to prepare nanosize particles of R -, -,γ-,δ-,and λ-MnO 2samples and to evaluate their properties with a special interest in supercapacitor behavior.A comparison of the SC values of the various structures of MnO 2is made,and appropri-ate explanations for the variation of SC values are provided.2.Experimental SectionAll chemicals were of analytical grade,and they were used without further purification.MnSO 4‚H 2O,KMnO 4,Na 2SO 4,sodium dodecyl sulfate (SDS),and cyclohexanewere purchasedfrom Merck,n-butanol from SD Fine Chemicals,(NH 4)2S 2O 8from Ranbaxy,Mn(NO 3)2‚4H 2O from Fluka,and LiMn 2O 4from Aldrich.All solutions were prepared in doubly distilled (DD)water.Samples of MnO 2with different crystal structures were synthesized by the following procedures.2.1.Synthesis of R -MnO 2.Nanoparticles of R -MnO 2were synthesized by redox reaction between stoichiometric quantities of MnSO 4and KMnO 4in both aqueous medium 9and a microemulsion medium.15In a typical synthesis in aqueous medium,10mL of 0.1M KMnO 4solution was mixed with 10mL of 0.15M MnSO 4‚H 2O solution and stirred continuously for 6h.A dark-brown precipitate thus formed and was washed several times with DD water,centrifuged,and dried at 70°C in air for 12h.Details of the microemulsion method of synthesis of nanostructured MnO 2is reported elsewhere.15MnO 2samples obtained from aqueous and microemulsion routes are hereafter referred to as R -MnO 2and R -MnO 2(m),respectively.About 300mg of the product was synthesized in each batch.2.2.Synthesis of -MnO 2.Nanorods of -MnO 2were prepared by hydrothermal treatment of aqueous solution of Mn-(NO 3)2‚4H 2O.20Twenty-five milliliters of 0.5M Mn(NO 3)2‚4H 2O solution was loaded into a Teflon-lined stainless-steel autoclave (capacity:40mL)and heated at 190°C for 6h.The autoclave was cooled slowly to room temperature.A dark brown powder was formed.It was washed several times with DD water,centrifuged,and dried at 70°C in air for 12h.Because the amount of product obtained in a batch of synthesis (typically 20mg)was small,the synthesis was repeated several times to get sufficient quantity for the experiments.During this synthesis,it was noticed that a minor variation in temperature caused drastic variations in the properties of the product.After several experiments,the experimental conditions of hydrothermal synthesis were optimized.2.3.Synthesis of γ-MnO 2.Nanowires/nanorods of γ-MnO 2were prepared from MnSO 4using (NH 4)2S 2O 8as an oxidizing agent.21Stoichiometric amounts of MnSO 4‚H 2O and (NH 4)2S 2O 8were dissolved in DD water.They were mixed together and heated at 80°C for 4h.A dark-brown precipitate wasseparated,Figure 1.Crystal structures of R -, -,γ-,δ-,and λ-MnO 2.TABLE 1:Tunnel Size of Different Crystallographic Forms of MnO 234-36crystallographicformtunnel size/ÅR (1×1),(2×2) 1.89,4.6 (1×1)1.89γ(1×1),(1×2) 1.89,2.3δinterlayer distance7.0Figure 2.Powder XRD pattern of R -,R (m)-, -,γ-,δ-,and λ-MnO 2.The (hkl )planes are indicated.The data were recorded at a sweep rate of 0.5°min -1using Cu K R source.TABLE 2:Crystal Radius and Size of the Alkali Cation in Aqueous Solution 37alkali cationcrystal radius/Åin aqueous solution/ÅLi +0.66Na +0.954K + 1.333H +9Effect of Crystallographic Structure of MnO 2J.Phys.Chem.C,Vol.112,No.11,20084407washed,and dried at 70°C.About 3.8g of the product was synthesized in a batch.2.4.Synthesis of δ-MnO 2.Nanoplatelets of δ-MnO 2were prepared by following the same route of synthesis of R -MnO 2,but with double the stoichiometric amount of KMnO 4.The presence of excess K +ion stabilizes the 2D layered δ-structure of MnO 2.The quantity obtained was about 340mg.2.5.Synthesis of λ-MnO 2.λ-MnO 2was prepared by delithia-tion of LiMn 2O 4.32Spinel LiMn 2O 4powder was treated with 0.5M HCl at 25°C for 24h.About 500mg of the product was obtained in a batch.2.6.Characterization.Powder X-ray diffraction (PXRD)patterns of MnO 2were recorded using Philips XRD X’PERT PRO diffractometer using Cu K R radiation (λ)1.54178Å)as the source.The morphology of MnO 2was examined using an FEI scanning electron microscope (SEM)model SIRION and an FEI high-resolution transmission electron microscope (HR-TEM)model TECNAI F 30.The Brunauer -Emmett -Teller (BET)surface area and pore volume were measured by the nitrogen gas adsorption -desorption method at 77K using a Quantachrome surface area analyzer model Nova-1000.The pore size distribution was calculated by the Barrett -Jayner -Halenda (BJH)method using the desorption branch of the isotherm.Samples were heated at 120°C for 2h in air prior to surface property measurements.IR spectra were recorded using a Perkin-Elmer FT-IR spectrophotometer model Spectrum One,using KBr pellets.KBr and samples were heated at 80°C in vacuum overnight prior to measurements.Thermogravimetric analysis (TGA)was performed in the temperature range from ambient to 800°C in air at a heating rate of 10°C/min using a Perkin-Elmer thermal analyzer model Pyris Diamond TG/DTA.2.7.Electrochemical Measurements.Electrodes were pre-pared on high-purity battery-grade Ni foil (0.18mm thick)as the current collector.The Ni foil was polished with successive grades of emery,cleaned with detergent,washed copiously with DD water,rinsed with acetone,dried,and weighed.MnO 2(70wt %),acetylene black (20wt %),and polyvinylidene difluoride (10wt %)were ground in a mortar,and a few drops of 1-methyl-2-pyrrolidinone was added to form a syrup.It was coated on to the pretreated Ni foil (area of coating:2cm 2)and dried at 110°C under vacuum.Coating and drying steps were repeated to get the loading level of the active material close to 0.5mg cm -2.Finally,the electrodes were dried at 110°C under vacuum for 12h.A Sartorious balance model CP22D-OCE with 10µgFigure 3.SEM micrographs of R -,R (m)-,and -MnO 2.1and 2refer to different magnifications of a sample.4408J.Phys.Chem.C,Vol.112,No.11,2008Devaraj andMunichandraiahsensitivity was used for weighing the electrodes.A glass cell of capacity 70mL,which had provisions for introducing a MnO 2working electrode,Pt auxiliary electrodes,and a reference electrode,was employed for electrochemical studies.An aqueous solution of 0.1M Na 2SO 4was used as the electrolyte.A saturated calomel electrode (SCE)was used as the reference electrode,and potential values are reported against SCE.Electrochemical studies were carried out using a potentiostat -galvanostat EG&G model Versastat II or Solartron model SI 1287.All electrochemical experiments were carried out at 20(2°C.3.Results and DiscussionThe reactions involved in the synthesis of different crystal-lographic forms of MnO 2are listed below:We have shown recently that R -MnO 2prepared in a micro-emulsion medium (R -MnO 2(m))possesses electrochemical properties superior to those of the samples prepared in aqueous medium.15Some important results of R -MnO 2(m)are also included here for the purpose of comparison.3.1.XRD Studies.The structural frame work of MnO 2consists of basic MnO 6octahedra units,which are linked in different ways to produce different crystallographic forms.22The different ways of sharing the vertices and edges of MnO 6octahedra units lead to the building of 1D,2D,and 3D tunnel structures.33The different crystallographic forms are described by the size of the tunnel formed with the number ofoctahedraFigure 4.SEM micrographs of γ-,δ-,and λ-MnO 2.1and 2refer to different magnifications of a sample.3MnSO 4+2KMnO 4+2H 2O f 5R -MnO 2+K 2SO 4+2H 2SO 4(1)Mn(NO 3)2+1/2O 2+H 2O f -MnO 2+2HNO 3(2)MnSO 4+(NH 4)2S 2O 8+2H 2O f γ-MnO 2+(NH 4)2SO 4+2H 2SO 4(3)3MnSO 4+2KMnO 4(excess)+2H 2O f 5δ-MnO 2+K 2SO 4+2H 2SO 4(4)2LiMn 2O 4+4HCl f LiCl +3λ-MnO 2+MnCl 2+2H 2O (5)Effect of Crystallographic Structure of MnO 2J.Phys.Chem.C,Vol.112,No.11,20084409subunits (n ×m ).The structures are shown schematically in Figure 1,and the type of tunnel formed as well as the size of tunnels are presented in Table 1.34-36The structure of R -MnO 2(Figure 1R )consists of double chains of edge-sharing MnO 6octahedra,which are linked at corners to form 1D (2×2)and (1×1)tunnels that extend in a direction parallel to the c axis of the tetragonal unit cell.The size of the (2×2)tunnel is ∼4.6Å,which is suitable for insertion/extraction of alkali cations (Table 2).34,37A small amount of cations such as Li +,Na +,K +,NH 4+,Ba 2+,or H 3O +is required to stabilize the (2×2)tunnels in the formation of R -MnO 2.34 -MnO 2(Figure 1 )is composed of single strands of edge-sharing MnO6Figure 5.TEM image (R 1),HRTEM image (R 2),and bright-field (R 3)and dark-field (R 4)TEM image of R -MnO 2.SAD pattern is given as an inset in R 1.Also shown are TEM images at different magnifications (R (m)1,R (m)2,and R (m)3),HRTEM image (R (m)4)of R -MnO 2(m).SAD pattern is given as an inset in R (m)2.4410J.Phys.Chem.C,Vol.112,No.11,2008Devaraj andMunichandraiahoctahedra to form a 1D (1×1)tunnel.Because of the narrow (1×1)tunnel of size (∼1.89Å),35 -MnO 2cannot accom-modate cations.22The structure of γ-MnO 2(Figure 1γ)is random intergrowth of ramsdellite (1×2)and pyrolusite (1×1)domains.38This intergrowth structure can be described in terms of De Wolff disorder and microtwinning.38δ-MnO 2(Figure 1δ)is a 2D layered structure with an interlayer separation of ∼7Å.36It has a significant amount of water and stabilizing cations such as Na +or K +between the sheets of MnO 6octahedra.λ-MnO 2(Figure 1λ)is a 3D spinel structure.32Powder XRD patterns of MnO 2samples are shown in Figure 2.Although the pattern of samples marked R and R (m)exhibitFigure 6.TEM images ( 1, 2),HRTEM image of a single nanorod ( 3),and the corresponding FFT pattern ( 4)of -MnO 2.Also shown are TEM images at different magnifications (γ1,γ2),HRTEM image (γ3),and the corresponding FFT pattern (γ4)of γ-MnO 2.SAD pattern is given as an inset in γ2.Effect of Crystallographic Structure of MnO 2J.Phys.Chem.C,Vol.112,No.11,20084411fluorescence,broad peaks at2θ)11.6and37.3°for R and at 2θ)10.8,37.0,41.7,and65.5°for R(m)are clearly present. It is thus inferred that these samples are in a poorly crystalline state with a short-range R-crystallographic form(JCPDS no. 44-0141).The XRD patterns marked andγ(Figure2)confirm the formation of -(JCPDS no.24-0735)andγ-(JCPDS no. 14-0644)crystallographic forms of MnO2,respectively.Broad peaks at2θ)12.2,24.8,37.0,and65.4°in the pattern marked δ(Figure2)correspond toδ-MnO2(JCPDS no.18-0802),and it is also considered to be in a poorly crystalline phase.Unlikethe above patterns,the diffraction pattern markedλin Figure2 consists of clear peaks,suggesting that this sample possesses a long-range crystalline order.This pattern was indexed to cubic symmetry with space group Fd3m(no.227)using the Appleman program,and the lattice constants were calculated.The lattice constants obtained are a)b)c)8.03Å,and these values are in good agreement with the reported data for the pure phase ofλ-MnO2(JCPDS no.44-0992).323.2.SEM and TEM Studies.SEM images of R-MnO2,R-MnO2(m),and -MnO2(two magnifications for each)are shown in Figure3.R-MnO2and R-MnO2(m)are composed of spherical aggregates of nanoparticles without clear interparticle boundaries(Figure3R1,R2,R(m)1,and R(m)2).Hydrothermal treatment of the aqueous Mn(NO3)2solution yields1D nanorods of -MnO2(Figure3 1and 2),which are about50nm in diameter and several micrometers in length.Adjacent nanorods are fused to each other.SEM images ofγ-,δ-,andλ-MnO2are presented in Figure 4in two magnifications for each.The morphology ofγ-MnO2 consists of spherical brushes with straight and radially grown nanorods.Several nanorods of30-50nm in diameter and a few micrometers in length assemble together to form spherical brushes.δ-MnO2(Figure4)consists of spherical agglomerates made of interlocked short fibers of∼10-20nm in diameter. The particles ofλ-MnO2(Figure4)exhibit random shapes with sizes varying from a few tens of nanometers to a few micrometers.TEM images of R-MnO2and R-MnO2(m)are presented in Figure5.The TEM image(Figure5R1)shows that R-MnO2 consists of agglomerated particles.A selected area diffraction (SAD)pattern is shown in the inset of Figure5R1.It is seen that a couple of weak rings corresponding to the crystal planes of R-MnO2are evolved,indicating the poor crystalline nature of the sample.The HRTEM image(Figure5R2)indicates the crystalline nature of the sample.The bright-field and corre-sponding dark-field TEM images of R-MnO2(Figure5R3and R4)suggest that several nanoparticles of less than5nm are agglomerated.It seen in Figure5R(m)1,R(m)2,and R(m)3that R-MnO2-(m)has a hexagonal shape of∼50nm size.The SAD pattern is shown as the inset to Figure5R(m)2.It is seen that rings corresponding to crystal planes are absent.The spotty diffraction pattern suggests that the nanoparticles of MnO2obtained from microemulsion route possess single-crystal character.The HR-TEM image(Figure5R(m)4)shows the interplanar distance to be2.392Å,which agrees well with separation between the[211] planes of R-MnO2.Shown in Figure6 1and 2are nanorods of -MnO2,which are20-50nm in diameter and several micrometers in length. In the HRTEM(Figure6 3),lattice fringes are clearly seen. The interplanar distance is0.311nm,which agrees well with the separation between the[110]planes of -MnO2.The corresponding FFT pattern(Figure6 4)displays spot lines perpendicular to the lattice fringes of Figure6 3,suggesting the crystalline nature of -MnO2.Furthermore,the length of the nanorod extends along the[110]direction.The TEM images shown in Figure6γ1andγ2suggest that nanorods ofγ-MnO2grow in a random fashion.The SAD pattern shown as inset in Figure6γ2reveals that rings and spots corresponding to crystal planes ofγ-MnO2are better evolved compared to R-MnO2,which is in agreement with the XRD results(Figure2).It is seen in the HRTEM image(Figure6γ3) that several nanowires of less than1nm are self-assembled to form nanorods.The interplanar distance calculated from the lattice fringes of HRTEM is0.212nm,which corresponds to separation of the[200]ttice fringes are inclined at about 60°toward the self-assembled nanowires.It is also seen in the HRTEM that nanorods exhibit better crystalline character at the center of the rod than the outer part.The FFT pattern(Figure 6γ4)corresponding to the HRTEM image ofγ-MnO2shows spot lines perpendicular to lattice fringes confirming the crystalline nature and also indicating that the nanorod extends in the[200]direction.TEM images ofδ-MnO2(Figure7δ1,δ2,andδ3)show that nanofibers with thicknesses less than10nm are agglomer-ated to form interconnected spherical structures ofδ-MnO2.The SAD pattern shown as inset in Figure7δ1supports the partial crystalline nature ofδ-MnO2inferred from the powder XRD pattern.The HRTEM image(Figure7δ4)indicates the crystal-line nature of the sample.TEM images ofλ-MnO2(Figure7λ1andλ2)suggest that the particles grow in different shapes and the adjacent particles fuse to each other.Spots evolved in the FFT pattern(Figure 7λ3)are indexed,and they confirm the highly crystalline nature ofλ-MnO2.Energy-dispersive analysis of the X-ray(EDAX) spectrum shown in Figure7λ4indicates the presence of manganese and oxygen.3.3.Porosity Measurements.Nitrogen adsorption-desorp-tion isotherms for MnO2samples were measured(see Supporting Information,Figure S1).The isotherms of R-,R(m)-,γ-,and δ-MnO2belong to type IV,which indicates the mesoporous nature of the samples with an hysteresis loop.Alternatively, the isotherm ofλ-MnO2belongs to type II,which is a characteristic feature of nonporous solids.39The specific surface area,total pore volume,and average pore diameter for all crystallographic forms of MnO2are listed in Table3.Although R-MnO2and R-MnO2(m)exhibit the same type of adsorption-desorption isotherm,their surface area and pore size distribution are different.The specific surface area of123m2g-1and total pore volume of0.25cm3Å-1g-1obtained for R-MnO2(m)are greater than the specific surface area of17.3m2g-1and pore volume of0.037cm3Å-1g-1obtained for R-MnO2.These differences indicate that R-MnO2(m)is more porous thanR-MnO2,and,hence,it is anticipated that R-MnO2(m)possesses higher electrochemical activity.Lower values of specific surface area and total pore volume are observed forγ-MnO2compared to R-MnO2(m).A high average pore diameter of129Åobtained forδ-MnO2is TABLE3:Specific Surface Area and Total Pore Volume of Polymorphic MnO2crystallographicformspecificsurface area(m2g-1)totalpore volume(cc/Å/g)averagepore diameter(Å) R17.290.0367585.020R(m)123.390.2481180.431γ31.560.0600676.112δ20.930.06750129.014λ 5.210.0087867.4514412J.Phys.Chem.C,Vol.112,No.11,2008Devaraj and Munichandraiahattributed to the wide interlayer separation.The lowest values of specific surface area (5.2m 2g -1)and total pore volume (0.0088cm 3Å-1g -1)are obtained for λ-MnO 2.It is inferred from the adsorption isotherm and Table 3that λ-MnO 2is the least porous among all samples.3.4.Vibrational Spectroscopic Studies.In IR spectra of MnO 2samples (see Supporting Information,Figure S2),a broad band around 400-700cm -1observed for all crystallographic forms of MnO 2is ascribed to Mn -O bending vibration.A broad band around 3400cm -1and a weak band around 1630cm -1observed for R -,R (m)-,γ-,and δ-MnO 2are attributed to stretching and bending vibrations of H -O -H,respectively.40Bands corresponding to vibrations of water molecules are not observed for -and λ-MnO 2,suggesting that these phases do not contain water.This is in agreement with the literature report that -and λ-MnO 2do not contain lattice water.22,32Figure 7.TEM images at different magnifications (δ1,δ2,and δ3)and HRTEM image (δ4)of δ-MnO 2.SAD pattern in given as an inset in δ1.Also shown are TEM images at different magnifications (λ1,λ2),FFT pattern (λ3),and EDAX spectrum (λ4)of λ-MnO 2.Effect of Crystallographic Structure of MnO 2J.Phys.Chem.C,Vol.112,No.11,200844133.5.Thermogravimetric Analysis.TGA thermograms of different crystallographic forms of MnO 2were recorded (see Supporting Information,Figure S3).Progressive weight loss from room temperature to 500°C is observed for R -,R (m)-,γ-,and δ-MnO 2samples.This is due to removal of water.13Weight loss is not observed in the case of -and λ-MnO 2samples because of the absence of water in these phases.22,32At around 550°C,a sudden weight loss is observed for all samples except for δ-MnO 2.This weight loss corresponds to the transformation of MnO 2to Mn 2O 3.41As δ-MnO 2prepared in the presence of excess of K +ions,these ions present between the layers of δ-MnO 2prevent the conversion of MnO 2to Mn 2O 3.The weight loss corresponding to this process is sharp in the case of -MnO 2as it has very narrow (1×1)tunnel in which no stabilizing ions are present.22The weight loss is much less (<2wt %)in the case of R -MnO 2because the stabilizing cations present at low concentration in its (2×2)tunnels prevent the transformation to a large extent.Weight loss values of about 2and 6wt %are observed for R -and R -MnO 2(m),respectively.This difference is ascribed to different amounts of K +ions present in their (2×2)tunnels.All crystallographic forms of MnO 2were annealed in air for 3h at various temperatures ranging from ambient to 800°C at intervals of 200°C,and powder XRD patterns were recorded (not shown).Conversion of MnO 2to Mn 2O 3is observed for all samples annealed at g 400°C except for δ-MnO 2,thus supporting the analysis of TGA data.3.6.Electrochemical Studies.There are two mechanisms proposed for charge storage in MnO 2.The first mechanism involves intercalation/extraction of protons (H 3O +)or alkali cations such as Li +,Na +,K +,and so forth into the bulk of oxide particles with concomitant reduction/oxidation of the Mn ion.10,23The second mechanism is a surface process,which involves the adsorption/desorption of alkali cations.17Although the bulk process (reaction 6)is anticipated to occur in crystalline samples of MnO 2,the surface process (reaction 7)occurs in amorphous samples.24Electrodes,which were fabricated with different crystal-lographic forms of MnO 2,were subjected to electrochemical studies in aqueous 0.1M Na 2SO 4electrolyte.Cyclic voltam-mograms recorded between 0and 1.0V at a sweep rate of 20mV s -1for all electrodes are shown in Figure 8.All voltam-mograms are nearly rectangular in shape.The rectangular shape of the voltammogram is a fingerprint for capacitance behavior.1-3Among all samples,the highest current density is obtained for R -MnO 2(m)(Figure 8),which is attributed to the higher porosity and greater surface area in relation to the rest of the samples.The voltammograms of R -and δ-MnO 2electrodes nearly overlap,suggesting that the SC values of R -and δ-MnO 2are comparable.The voltammetric current of the γ-MnO 2electrode (Figure 8)is lower than the currents of the R -,R (m)-,and δ-MnO 2electrodes.There is an increase in current near 0and also at 1V,suggesting that the overpotentials for the hydrogen evolution reaction (HER)as well as the oxygen evolution reaction (OER)are lower for γ-MnO 2.The current values(Figure 8)for the -and λ-MnO 2electrodes are very low,suggesting that the capacitance values of these samples are very small.Thus,the SC values of MnO 2samples qualitatively decrease in the following order:R (m)>R =δ>γ>λ> .Quantitatively,the SC values were evaluated from galvanostatic charge -discharge cycling as described below.The electrodes were subjected to galvanostatic charge -discharge cycling between 0and 1.0V in aqueous 0.1M Na 2-SO 4electrolyte at several current densities.The variations of potential with time during the first few charge -discharge cycles at a current density of 0.5mA cm -2are shown in Figure 9.Linear variation of potential during both charging and discharg-ing processes are observed for all MnO 2electrodes.The linear variation of potential during charging and discharging processes is another criterion for capacitance behavior of a material in addition to exhibiting rectangular voltammograms.1The dura-tions of charging and discharging are almost equal for each electrode,implying high columbic efficiency of charge -discharge cycling.However,the durations of charge and discharge cycles are different for different crystallographic forms of MnO 2,suggesting that the SC values are different similar to the observation made from cyclic voltammograms (Figure 8).The SC values were calculated from charge -discharge cycles using the following equationwhere,I is the discharge (or charge)current,t is the discharge (or charge)time,∆E ()1.0V)is the potential window of cycling,and m is the mass of MnO 2.The discharge SC values for all electrodes are presented in Figure 10.The variation of SC values follows the order R (m)>R =δ>γ>λ> .The SC values are 240F g -1for R -MnO 2and 236F g -1for δ-MnO 2.Alternatively,they are as low as 9F g -1for -MnO 2and 21F g -1for λ-MnO 2.The SC values are generally expected to follow the trend of surface area if capacitance is due to double-layer charging or adsorption of cations on the surface of active material.In recent studies,it is shown that the surface process is dominant in the amorphous sample of MnO 2.24Because all samples of MnO 2prepared in the present study are in the crystalline or poorly crystalline state of various structures,the low values of SC obtained are not due to the amorphous nature of the samples.In fact,λ-MnO 2has greater crystallinity than the rest of the samples (Figure 2)because of its larger particle size (Figure 4),but its SC is low.It is inferred that SC values largely depend on crystal structure and not on surface area while making comparisons among various structures (within thesameFigure 8.Cyclic voltammograms of R -,R (m)-, -,γ-,δ-,and λ-MnO 2recorded between 0and 1.0V vs SCE in aqueous 0.1M Na 2SO 4at a sweep rate of 20mV s -1.SC )It /(∆Em )(8)MnO 2+M ++e -h MnOOM (M +)Li +,Na +,K +,or H 3O +)(6)(MnO 2)surface +M ++e -h (MnOOM)surface (M +)Li +,Na +,K +,or H 3O +)(7)4414J.Phys.Chem.C,Vol.112,No.11,2008Devaraj andMunichandraiah。
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Modeling of morphology evolution in the injection moldingprocess of thermoplastic polymersR.Pantani,I.Coccorullo,V.Speranza,G.Titomanlio* Department of Chemical and Food Engineering,University of Salerno,via Ponte don Melillo,I-84084Fisciano(Salerno),Italy Received13May2005;received in revised form30August2005;accepted12September2005AbstractA thorough analysis of the effect of operative conditions of injection molding process on the morphology distribution inside the obtained moldings is performed,with particular reference to semi-crystalline polymers.The paper is divided into two parts:in the first part,the state of the art on the subject is outlined and discussed;in the second part,an example of the characterization required for a satisfactorily understanding and description of the phenomena is presented,starting from material characterization,passing through the monitoring of the process cycle and arriving to a deep analysis of morphology distribution inside the moldings.In particular,fully characterized injection molding tests are presented using an isotactic polypropylene,previously carefully characterized as far as most of properties of interest.The effects of both injectionflow rate and mold temperature are analyzed.The resulting moldings morphology(in terms of distribution of crystallinity degree,molecular orientation and crystals structure and dimensions)are analyzed by adopting different experimental techniques(optical,electronic and atomic force microscopy,IR and WAXS analysis).Final morphological characteristics of the samples are compared with the predictions of a simulation code developed at University of Salerno for the simulation of the injection molding process.q2005Elsevier Ltd.All rights reserved.Keywords:Injection molding;Crystallization kinetics;Morphology;Modeling;Isotactic polypropyleneContents1.Introduction (1186)1.1.Morphology distribution in injection molded iPP parts:state of the art (1189)1.1.1.Modeling of the injection molding process (1190)1.1.2.Modeling of the crystallization kinetics (1190)1.1.3.Modeling of the morphology evolution (1191)1.1.4.Modeling of the effect of crystallinity on rheology (1192)1.1.5.Modeling of the molecular orientation (1193)1.1.6.Modeling of theflow-induced crystallization (1195)ments on the state of the art (1197)2.Material and characterization (1198)2.1.PVT description (1198)*Corresponding author.Tel.:C39089964152;fax:C39089964057.E-mail address:gtitomanlio@unisa.it(G.Titomanlio).2.2.Quiescent crystallization kinetics (1198)2.3.Viscosity (1199)2.4.Viscoelastic behavior (1200)3.Injection molding tests and analysis of the moldings (1200)3.1.Injection molding tests and sample preparation (1200)3.2.Microscopy (1202)3.2.1.Optical microscopy (1202)3.2.2.SEM and AFM analysis (1202)3.3.Distribution of crystallinity (1202)3.3.1.IR analysis (1202)3.3.2.X-ray analysis (1203)3.4.Distribution of molecular orientation (1203)4.Analysis of experimental results (1203)4.1.Injection molding tests (1203)4.2.Morphology distribution along thickness direction (1204)4.2.1.Optical microscopy (1204)4.2.2.SEM and AFM analysis (1204)4.3.Morphology distribution alongflow direction (1208)4.4.Distribution of crystallinity (1210)4.4.1.Distribution of crystallinity along thickness direction (1210)4.4.2.Crystallinity distribution alongflow direction (1212)4.5.Distribution of molecular orientation (1212)4.5.1.Orientation along thickness direction (1212)4.5.2.Orientation alongflow direction (1213)4.5.3.Direction of orientation (1214)5.Simulation (1214)5.1.Pressure curves (1215)5.2.Morphology distribution (1215)5.3.Molecular orientation (1216)5.3.1.Molecular orientation distribution along thickness direction (1216)5.3.2.Molecular orientation distribution alongflow direction (1216)5.3.3.Direction of orientation (1217)5.4.Crystallinity distribution (1217)6.Conclusions (1217)References (1219)1.IntroductionInjection molding is one of the most widely employed methods for manufacturing polymeric products.Three main steps are recognized in the molding:filling,packing/holding and cooling.During thefilling stage,a hot polymer melt rapidlyfills a cold mold reproducing a cavity of the desired product shape. During the packing/holding stage,the pressure is raised and extra material is forced into the mold to compensate for the effects that both temperature decrease and crystallinity development determine on density during solidification.The cooling stage starts at the solidification of a thin section at cavity entrance (gate),starting from that instant no more material can enter or exit from the mold impression and holding pressure can be released.When the solid layer on the mold surface reaches a thickness sufficient to assure required rigidity,the product is ejected from the mold.Due to the thermomechanical history experienced by the polymer during processing,macromolecules in injection-molded objects present a local order.This order is referred to as‘morphology’which literally means‘the study of the form’where form stands for the shape and arrangement of parts of the object.When referred to polymers,the word morphology is adopted to indicate:–crystallinity,which is the relative volume occupied by each of the crystalline phases,including mesophases;–dimensions,shape,distribution and orientation of the crystallites;–orientation of amorphous phase.R.Pantani et al./Prog.Polym.Sci.30(2005)1185–1222 1186R.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221187Apart from the scientific interest in understandingthe mechanisms leading to different order levels inside a polymer,the great technological importance of morphology relies on the fact that polymer character-istics (above all mechanical,but also optical,electrical,transport and chemical)are to a great extent affected by morphology.For instance,crystallinity has a pro-nounced effect on the mechanical properties of the bulk material since crystals are generally stiffer than amorphous material,and also orientation induces anisotropy and other changes in mechanical properties.In this work,a thorough analysis of the effect of injection molding operative conditions on morphology distribution in moldings with particular reference to crystalline materials is performed.The aim of the paper is twofold:first,to outline the state of the art on the subject;second,to present an example of the characterization required for asatisfactorilyR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221188understanding and description of the phenomena, starting from material description,passing through the monitoring of the process cycle and arriving to a deep analysis of morphology distribution inside the mold-ings.To these purposes,fully characterized injection molding tests were performed using an isotactic polypropylene,previously carefully characterized as far as most of properties of interest,in particular quiescent nucleation density,spherulitic growth rate and rheological properties(viscosity and relaxation time)were determined.The resulting moldings mor-phology(in terms of distribution of crystallinity degree, molecular orientation and crystals structure and dimensions)was analyzed by adopting different experimental techniques(optical,electronic and atomic force microscopy,IR and WAXS analysis).Final morphological characteristics of the samples were compared with the predictions of a simulation code developed at University of Salerno for the simulation of the injection molding process.The effects of both injectionflow rate and mold temperature were analyzed.1.1.Morphology distribution in injection molded iPP parts:state of the artFrom many experimental observations,it is shown that a highly oriented lamellar crystallite microstructure, usually referred to as‘skin layer’forms close to the surface of injection molded articles of semi-crystalline polymers.Far from the wall,the melt is allowed to crystallize three dimensionally to form spherulitic structures.Relative dimensions and morphology of both skin and core layers are dependent on local thermo-mechanical history,which is characterized on the surface by high stress levels,decreasing to very small values toward the core region.As a result,the skin and the core reveal distinct characteristics across the thickness and also along theflow path[1].Structural and morphological characterization of the injection molded polypropylene has attracted the interest of researchers in the past three decades.In the early seventies,Kantz et al.[2]studied the morphology of injection molded iPP tensile bars by using optical microscopy and X-ray diffraction.The microscopic results revealed the presence of three distinct crystalline zones on the cross-section:a highly oriented non-spherulitic skin;a shear zone with molecular chains oriented essentially parallel to the injection direction;a spherulitic core with essentially no preferred orientation.The X-ray diffraction studies indicated that the skin layer contains biaxially oriented crystallites due to the biaxial extensionalflow at theflow front.A similar multilayered morphology was also reported by Menges et al.[3].Later on,Fujiyama et al.[4] investigated the skin–core morphology of injection molded iPP samples using X-ray Small and Wide Angle Scattering techniques,and suggested that the shear region contains shish–kebab structures.The same shish–kebab structure was observed by Wenig and Herzog in the shear region of their molded samples[5].A similar investigation was conducted by Titomanlio and co-workers[6],who analyzed the morphology distribution in injection moldings of iPP. They observed a skin–core morphology distribution with an isotropic spherulitic core,a skin layer characterized by afine crystalline structure and an intermediate layer appearing as a dark band in crossed polarized light,this layer being characterized by high crystallinity.Kalay and Bevis[7]pointed out that,although iPP crystallizes essentially in the a-form,a small amount of b-form can be found in the skin layer and in the shear region.The amount of b-form was found to increase by effect of high shear rates[8].A wide analysis on the effect of processing conditions on the morphology of injection molded iPP was conducted by Viana et al.[9]and,more recently, by Mendoza et al.[10].In particular,Mendoza et al. report that the highest level of crystallinity orientation is found inside the shear zone and that a high level of orientation was also found in the skin layer,with an orientation angle tilted toward the core.It is rather difficult to theoretically establish the relationship between the observed microstructure and processing conditions.Indeed,a model of the injection molding process able to predict morphology distribution in thefinal samples is not yet available,even if it would be of enormous strategic importance.This is mainly because a complete understanding of crystallization kinetics in processing conditions(high cooling rates and pressures,strong and complexflowfields)has not yet been reached.In this section,the most relevant aspects for process modeling and morphology development are identified. In particular,a successful path leading to a reliable description of morphology evolution during polymer processing should necessarily pass through:–a good description of morphology evolution under quiescent conditions(accounting all competing crystallization processes),including the range of cooling rates characteristic of processing operations (from1to10008C/s);R.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221189–a description capturing the main features of melt morphology(orientation and stretch)evolution under processing conditions;–a good coupling of the two(quiescent crystallization and orientation)in order to capture the effect of crystallinity on viscosity and the effect offlow on crystallization kinetics.The points listed above outline the strategy to be followed in order to achieve the basic understanding for a satisfactory description of morphology evolution during all polymer processing operations.In the following,the state of art for each of those points will be analyzed in a dedicated section.1.1.1.Modeling of the injection molding processThefirst step in the prediction of the morphology distribution within injection moldings is obviously the thermo-mechanical simulation of the process.Much of the efforts in the past were focused on the prediction of pressure and temperature evolution during the process and on the prediction of the melt front advancement [11–15].The simulation of injection molding involves the simultaneous solution of the mass,energy and momentum balance equations.Thefluid is non-New-tonian(and viscoelastic)with all parameters dependent upon temperature,pressure,crystallinity,which are all function of pressibility cannot be neglected as theflow during the packing/holding step is determined by density changes due to temperature, pressure and crystallinity evolution.Indeed,apart from some attempts to introduce a full 3D approach[16–19],the analysis is currently still often restricted to the Hele–Shaw(or thinfilm) approximation,which is warranted by the fact that most injection molded parts have the characteristic of being thin.Furthermore,it is recognized that the viscoelastic behavior of the polymer only marginally influences theflow kinematics[20–22]thus the melt is normally considered as a non-Newtonian viscousfluid for the description of pressure and velocity gradients evolution.Some examples of adopting a viscoelastic constitutive equation in the momentum balance equations are found in the literature[23],but the improvements in accuracy do not justify a considerable extension of computational effort.It has to be mentioned that the analysis of some features of kinematics and temperature gradients affecting the description of morphology need a more accurate description with respect to the analysis of pressure distributions.Some aspects of the process which were often neglected and may have a critical importance are the description of the heat transfer at polymer–mold interface[24–26]and of the effect of mold deformation[24,27,28].Another aspect of particular interest to the develop-ment of morphology is the fountainflow[29–32], which is often neglected being restricted to a rather small region at theflow front and close to the mold walls.1.1.2.Modeling of the crystallization kineticsIt is obvious that the description of crystallization kinetics is necessary if thefinal morphology of the molded object wants to be described.Also,the development of a crystalline degree during the process influences the evolution of all material properties like density and,above all,viscosity(see below).Further-more,crystallization kinetics enters explicitly in the generation term of the energy balance,through the latent heat of crystallization[26,33].It is therefore clear that the crystallinity degree is not only a result of simulation but also(and above all)a phenomenon to be kept into account in each step of process modeling.In spite of its dramatic influence on the process,the efforts to simulate the injection molding of semi-crystalline polymers are crude in most of the commercial software for processing simulation and rather scarce in the fleur and Kamal[34],Papatanasiu[35], Titomanlio et al.[15],Han and Wang[36],Ito et al.[37],Manzione[38],Guo and Isayev[26],and Hieber [25]adopted the following equation(Kolmogoroff–Avrami–Evans,KAE)to predict the development of crystallinityd xd tZð1K xÞd d cd t(1)where x is the relative degree of crystallization;d c is the undisturbed volume fraction of the crystals(if no impingement would occur).A significant improvement in the prediction of crystallinity development was introduced by Titoman-lio and co-workers[39]who kept into account the possibility of the formation of different crystalline phases.This was done by assuming a parallel of several non-interacting kinetic processes competing for the available amorphous volume.The evolution of each phase can thus be described byd x id tZð1K xÞd d c id t(2)where the subscript i stands for a particular phase,x i is the relative degree of crystallization,x ZPix i and d c iR.Pantani et al./Prog.Polym.Sci.30(2005)1185–1222 1190is the expectancy of volume fraction of each phase if no impingement would occur.Eq.(2)assumes that,for each phase,the probability of the fraction increase of a single crystalline phase is simply the product of the rate of growth of the corresponding undisturbed volume fraction and of the amount of available amorphous fraction.By summing up the phase evolution equations of all phases(Eq.(2))over the index i,and solving the resulting differential equation,one simply obtainsxðtÞZ1K exp½K d cðtÞ (3)where d c Z Pid c i and Eq.(1)is recovered.It was shown by Coccorullo et al.[40]with reference to an iPP,that the description of the kinetic competition between phases is crucial to a reliable prediction of solidified structures:indeed,it is not possible to describe iPP crystallization kinetics in the range of cooling rates of interest for processing(i.e.up to several hundreds of8C/s)if the mesomorphic phase is neglected:in the cooling rate range10–1008C/s, spherulite crystals in the a-phase are overcome by the formation of the mesophase.Furthermore,it has been found that in some conditions(mainly at pressures higher than100MPa,and low cooling rates),the g-phase can also form[41].In spite of this,the presence of different crystalline phases is usually neglected in the literature,essentially because the range of cooling rates investigated for characterization falls in the DSC range (well lower than typical cooling rates of interest for the process)and only one crystalline phase is formed for iPP at low cooling rates.It has to be noticed that for iPP,which presents a T g well lower than ambient temperature,high values of crystallinity degree are always found in solids which passed through ambient temperature,and the cooling rate can only determine which crystalline phase forms, roughly a-phase at low cooling rates(below about 508C/s)and mesomorphic phase at higher cooling rates.The most widespread approach to the description of kinetic constant is the isokinetic approach introduced by Nakamura et al.According to this model,d c in Eq.(1)is calculated asd cðtÞZ ln2ðt0KðTðsÞÞd s2 435n(4)where K is the kinetic constant and n is the so-called Avrami index.When introduced as in Eq.(4),the reciprocal of the kinetic constant is a characteristic time for crystallization,namely the crystallization half-time, t05.If a polymer is cooled through the crystallization temperature,crystallization takes place at the tempera-ture at which crystallization half-time is of the order of characteristic cooling time t q defined ast q Z D T=q(5) where q is the cooling rate and D T is a temperature interval over which the crystallization kinetic constant changes of at least one order of magnitude.The temperature dependence of the kinetic constant is modeled using some analytical function which,in the simplest approach,is described by a Gaussian shaped curve:KðTÞZ K0exp K4ln2ðT K T maxÞ2D2(6)The following Hoffman–Lauritzen expression[42] is also commonly adopted:K½TðtÞ Z K0exp KUÃR$ðTðtÞK T NÞ!exp KKÃ$ðTðtÞC T mÞ2TðtÞ2$ðT m K TðtÞÞð7ÞBoth equations describe a bell shaped curve with a maximum which for Eq.(6)is located at T Z T max and for Eq.(7)lies at a temperature between T m(the melting temperature)and T N(which is classically assumed to be 308C below the glass transition temperature).Accord-ing to Eq.(7),the kinetic constant is exactly zero at T Z T m and at T Z T N,whereas Eq.(6)describes a reduction of several orders of magnitude when the temperature departs from T max of a value higher than2D.It is worth mentioning that only three parameters are needed for Eq.(6),whereas Eq.(7)needs the definition offive parameters.Some authors[43,44]couple the above equations with the so-called‘induction time’,which can be defined as the time the crystallization process starts, when the temperature is below the equilibrium melting temperature.It is normally described as[45]Dt indDtZðT0m K TÞat m(8)where t m,T0m and a are material constants.It should be mentioned that it has been found[46,47]that there is no need to explicitly incorporate an induction time when the modeling is based upon the KAE equation(Eq.(1)).1.1.3.Modeling of the morphology evolutionDespite of the fact that the approaches based on Eq.(4)do represent a significant step toward the descriptionR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221191of morphology,it has often been pointed out in the literature that the isokinetic approach on which Nakamura’s equation (Eq.(4))is based does not describe details of structure formation [48].For instance,the well-known experience that,with many polymers,the number of spherulites in the final solid sample increases strongly with increasing cooling rate,is indeed not taken into account by this approach.Furthermore,Eq.(4)describes an increase of crystal-linity (at constant temperature)depending only on the current value of crystallinity degree itself,whereas it is expected that the crystallization rate should depend also on the number of crystalline entities present in the material.These limits are overcome by considering the crystallization phenomenon as the consequence of nucleation and growth.Kolmogoroff’s model [49],which describes crystallinity evolution accounting of the number of nuclei per unit volume and spherulitic growth rate can then be applied.In this case,d c in Eq.(1)is described asd ðt ÞZ C m ðt 0d N ðs Þd s$ðt sG ðu Þd u 2435nd s (9)where C m is a shape factor (C 3Z 4/3p ,for spherical growth),G (T (t ))is the linear growth rate,and N (T (t ))is the nucleation density.The following Hoffman–Lauritzen expression is normally adopted for the growth rateG ½T ðt Þ Z G 0exp KUR $ðT ðt ÞK T N Þ!exp K K g $ðT ðt ÞC T m Þ2T ðt Þ2$ðT m K T ðt ÞÞð10ÞEqs.(7)and (10)have the same form,however the values of the constants are different.The nucleation mechanism can be either homo-geneous or heterogeneous.In the case of heterogeneous nucleation,two equations are reported in the literature,both describing the nucleation density as a function of temperature [37,50]:N ðT ðt ÞÞZ N 0exp ½j $ðT m K T ðt ÞÞ (11)N ðT ðt ÞÞZ N 0exp K 3$T mT ðt ÞðT m K T ðt ÞÞ(12)In the case of homogeneous nucleation,the nucleation rate rather than the nucleation density is function of temperature,and a Hoffman–Lauritzen expression isadoptedd N ðT ðt ÞÞd t Z N 0exp K C 1ðT ðt ÞK T N Þ!exp KC 2$ðT ðt ÞC T m ÞT ðt Þ$ðT m K T ðt ÞÞð13ÞConcentration of nucleating particles is usually quite significant in commercial polymers,and thus hetero-geneous nucleation becomes the dominant mechanism.When Kolmogoroff’s approach is followed,the number N a of active nuclei at the end of the crystal-lization process can be calculated as [48]N a ;final Zðt final 0d N ½T ðs Þd sð1K x ðs ÞÞd s (14)and the average dimension of crystalline structures can be attained by geometrical considerations.Pantani et al.[51]and Zuidema et al.[22]exploited this method to describe the distribution of crystallinity and the final average radius of the spherulites in injection moldings of polypropylene;in particular,they adopted the following equationR Z ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi3x a ;final 4p N a ;final 3s (15)A different approach is also present in the literature,somehow halfway between Nakamura’s and Kolmo-goroff’s models:the growth rate (G )and the kinetic constant (K )are described independently,and the number of active nuclei (and consequently the average dimensions of crystalline entities)can be obtained by coupling Eqs.(4)and (9)asN a ðT ÞZ 3ln 24p K ðT ÞG ðT Þ 3(16)where heterogeneous nucleation and spherical growth is assumed (Avrami’s index Z 3).Guo et al.[43]adopted this approach to describe the dimensions of spherulites in injection moldings of polypropylene.1.1.4.Modeling of the effect of crystallinity on rheology As mentioned above,crystallization has a dramatic influence on material viscosity.This phenomenon must obviously be taken into account and,indeed,the solidification of a semi-crystalline material is essen-tially caused by crystallization rather than by tempera-ture in normal processing conditions.Despite of the importance of the subject,the relevant literature on the effect of crystallinity on viscosity isR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221192rather scarce.This might be due to the difficulties in measuring simultaneously rheological properties and crystallinity evolution during the same tests.Apart from some attempts to obtain simultaneous measure-ments of crystallinity and viscosity by special setups [52,53],more often viscosity and crystallinity are measured during separate tests having the same thermal history,thus greatly simplifying the experimental approach.Nevertheless,very few works can be retrieved in the literature in which(shear or complex) viscosity can be somehow linked to a crystallinity development.This is the case of Winter and co-workers [54],Vleeshouwers and Meijer[55](crystallinity evolution can be drawn from Swartjes[56]),Boutahar et al.[57],Titomanlio et al.[15],Han and Wang[36], Floudas et al.[58],Wassner and Maier[59],Pantani et al.[60],Pogodina et al.[61],Acierno and Grizzuti[62].All the authors essentially agree that melt viscosity experiences an abrupt increase when crystallinity degree reaches a certain‘critical’value,x c[15]. However,little agreement is found in the literature on the value of this critical crystallinity degree:assuming that x c is reached when the viscosity increases of one order of magnitude with respect to the molten state,it is found in the literature that,for iPP,x c ranges from a value of a few percent[15,62,60,58]up to values of20–30%[58,61]or even higher than40%[59,54,57].Some studies are also reported on the secondary effects of relevant variables such as temperature or shear rate(or frequency)on the dependence of crystallinity on viscosity.As for the effect of temperature,Titomanlio[15]found for an iPP that the increase of viscosity for the same crystallinity degree was higher at lower temperatures,whereas Winter[63] reports the opposite trend for a thermoplastic elasto-meric polypropylene.As for the effect of shear rate,a general agreement is found in the literature that the increase of viscosity for the same crystallinity degree is lower at higher deformation rates[62,61,57].Essentially,the equations adopted to describe the effect of crystallinity on viscosity of polymers can be grouped into two main categories:–equations based on suspensions theories(for a review,see[64]or[65]);–empirical equations.Some of the equations adopted in the literature with regard to polymer processing are summarized in Table1.Apart from Eq.(17)adopted by Katayama and Yoon [66],all equations predict a sharp increase of viscosity on increasing crystallinity,sometimes reaching infinite (Eqs.(18)and(21)).All authors consider that the relevant variable is the volume occupied by crystalline entities(i.e.x),even if the dimensions of the crystals should reasonably have an effect.1.1.5.Modeling of the molecular orientationOne of the most challenging problems to present day polymer science regards the reliable prediction of molecular orientation during transformation processes. Indeed,although pressure and velocity distribution during injection molding can be satisfactorily described by viscous models,details of the viscoelastic nature of the polymer need to be accounted for in the descriptionTable1List of the most used equations to describe the effect of crystallinity on viscosityEquation Author Derivation Parameters h=h0Z1C a0x(17)Katayama[66]Suspensions a Z99h=h0Z1=ðx K x cÞa0(18)Ziabicki[67]Empirical x c Z0.1h=h0Z1C a1expðK a2=x a3Þ(19)Titomanlio[15],also adopted byGuo[68]and Hieber[25]Empiricalh=h0Z expða1x a2Þ(20)Shimizu[69],also adopted byZuidema[22]and Hieber[25]Empiricalh=h0Z1Cðx=a1Þa2=ð1Kðx=a1Þa2Þ(21)Tanner[70]Empirical,basedon suspensionsa1Z0.44for compact crystallitesa1Z0.68for spherical crystallitesh=h0Z expða1x C a2x2Þ(22)Han[36]Empiricalh=h0Z1C a1x C a2x2(23)Tanner[71]Empirical a1Z0.54,a2Z4,x!0.4h=h0Zð1K x=a0ÞK2(24)Metzner[65],also adopted byTanner[70]Suspensions a Z0.68for smooth spheresR.Pantani et al./Prog.Polym.Sci.30(2005)1185–12221193。
黏滞系数 英文
黏滞系数英文Title: The Viscosity CoefficientIntroduction:The viscosity coefficient is a fundamental property that characterizes the resistance of a fluid to flow. It plays a crucial role in various fields, such as physics, chemistry, engineering, and biology. Understanding the concept of viscosity and its coefficient is essential for comprehending fluid dynamics and its applications. In this article, we will explore the viscosity coefficient in detail, discussing its definition, factors affecting it, measurement techniques, and its significance in different industries.Body:1. Definition and Importance of Viscosity Coefficient:1.1 Definition of viscosity and its coefficient1.2 Newtonian and non-Newtonian fluids1.3 Significance of viscosity coefficient in fluid dynamics2. Factors Affecting Viscosity Coefficient:2.1 Temperature and its impact on viscosity2.2 Pressure and its influence on viscosity2.3 Composition and molecular structure of the fluid2.4 Shear rate and its effect on viscosity2.5 Relationship between viscosity and flow behavior3. Measurement Techniques for Viscosity Coefficient:3.1 Capillary viscometry method3.2 Rotational viscometry method3.3 Vibrational viscometry method3.4 Falling ball viscometry method3.5 Rheometer and its role in measuring viscosity coefficient4. Applications of Viscosity Coefficient:4.1 Industrial applications in manufacturing processes4.2 Importance in the petroleum and petrochemical industry4.3 Role in food and beverage production4.4 Significance in pharmaceutical and cosmetic industries4.5 Influence on biological systems and medical research5. Future Developments and Challenges:5.1 Advances in viscosity measurement techniques5.2 Exploration of new materials and their viscosity behavior5.3 Understanding the impact of nanoscale phenomena on viscosityConclusion:In conclusion, the viscosity coefficient is a vital parameter that characterizes the flow behavior of fluids. It is influenced by factors such as temperature, pressure, composition, and shear rate. Various measurement techniques, including capillary viscometry and rotational viscometry, are used to determine the viscosity coefficient accurately. The viscosity coefficient finds applications in diverse industries, including manufacturing, petroleum, food, pharmaceuticals, and biology. As research progresses, further developments and challenges lie ahead in the study of viscosity, including advancements in measurement techniques and the exploration of nanoscale phenomena. Understandingand utilizing the viscosity coefficient will continue to be of utmost importance in various scientific and industrial fields.。
Measurement_of_the_corrosion_rate_of_magnesium_alloys_using_Tafel_extrapolation
Measurement of the corrosion rate of magnesium alloys using Tafel extrapolationZhiming Shi,Ming Liu,Andrej Atrens *The University of Queensland,Division of Materials,Brisbane,Qld 4072,Australiaa r t i c l e i n f o Article history:Received 13July 2009Accepted 9October 2009Available online 6November 2009Keywords:A.Magnesium corrosionB.Weight lossB.Tafel extrapolation B.Hydrogen evolutiona b s t r a c tThe hypothesis that the corrosion of Mg alloys can be adequately estimated using Tafel extrapolation of the polarisation curve is termed herein the electrochemical measurement hypothesis for Mg.In principle,such a hypothesis can be disproved by a single valid counter example.The critical review of Mg corrosion by Song and Atrens in 2003indicated that,for Mg alloys,Tafel extrapolation had not estimated the cor-rosion rate reliably.This paper examines the recent literature to further examine the electrochemical measurement hypothesis for Mg.The literature shows that,for Mg alloys,corrosion rates evaluated by Tafel extrapolation from polarisation curves have not agreed with corrosion rates evaluated from weight loss and hydrogen evolution.Typical deviations have been $50–90%.These were much larger than the precision of the measurement methods and indicate a need for careful examination of the use of Tafel extrapolation for Mg.For research that nevertheless does intend to use Tafel extrapolation to elucidate corrosion of Mg associated with service,it is strongly recommended that these measurements be com-plemented by the use of at least two of the three other simple measurement methods:(i)weight loss rate,(ii)hydrogen evolution rate,and (iii)rate of Mg 2+leaving the metal surface.There is much better insight for little additional effort.Ó2009Elsevier Ltd.All rights reserved.1.IntroductionMagnesium (Mg)alloys are used in transport applications,such as in auto construction,because of their low density,adequate strength–weight ratio and excellent castability.However,an issue is their corrosion properties [1–5].As a consequence,there is much current research to understand Mg corrosion for such ser-vice applications.Some of this research relies on the measurement of the corrosion rate using Tafel extrapolation from polarisation curves.Such research relies on what is herein termed the electro-chemical measurement hypothesis for Mg,namely,that the corro-sion rate of Mg alloys can be adequately estimated using Tafel extrapolation of the polarisation curve.In principle,such a hypoth-esis can be disproved by a single valid counter example.The critical review of Mg corrosion by Song and Atrens [2]indicated that,for Mg alloys,Tafel extrapolation had not estimated the corrosion rate reliably.The scope of this paper is to examine the recent literature to further examine the electrochemical measure-ment hypothesis for Mg.A subsidiary aim is to facilitate research directed at Mg alloy development and at understanding corrosion of Mg in service applications to ensure such research is as effective as possible.2.Corrosion rate measurementThe simplest and most fundamental measurement of the corro-sion rate is the metal weight loss rate,D W (mg/cm 2/d).This can be converted to an average corrosion rate (mm/y)using [6–9]P W ¼3:65D W =qð1Þwhere q is the metal density (g/cm 3).For Mg alloys,q is 1.74g/cm 3,and Eq.(1)becomes:P W ¼2:10D W ð2ÞIn the overall corrosion reaction of pure Mg,one molecule of hydro-gen is evolved for each atom of corroded Mg.One mol (i.e.24.31g)of Mg metal corrodes for each mol (i.e.22.4L)of hydrogen gas pro-duced.Therefore,the hydrogen evolution rate,V H (ml/cm 2/d),is re-lated to the metallic weight loss rate,D W m (mg/cm 2/d),using [2,10–14]D W ¼1:085V H ð3ÞThe corresponding corrosion rate,P H ,is evaluated by substituting Eq.(3)into Eq.(2)to giveP H ¼2:279V Hð4ÞFor Mg corrosion,there is excellent agreement [2,10,13,15]between the corrosion rate measured by the weight loss rate and that eval-uated from the hydrogenevolution rate.Fig.1presents a cross plot0010-938X/$-see front matter Ó2009Elsevier Ltd.All rights reserved.doi:10.1016/j.corsci.2009.10.016*Corresponding author.Address:The University of Queensland,Division of Materials,St.Lucia,Brisbane,Qld 4072,Australia.Tel.:+61733653748;fax:+61733653888.E-mail address:andrejs.atrens@.au (A.Atrens).Corrosion Science 52(2010)579–588Contents lists available at ScienceDirectCorrosion Sciencej o ur na l h om e pa ge :w w w.e lse v ie r.c om /lo c at e /c or s c iof the independent measurements of the weight loss rate and the hydrogen evolution rate,for48h and96h immersion tests of castAZ91in1M NaCl solution[13].The line,in Fig.1,is a goodfit through the data.However,the line is not drawn as a line of best fit through the data.The line is actually the plot of the theoretical expectation of Eq.(3).This data shows that the corrosion rate eval-uated from weight loss agrees within an error of$±10%with the corrosion rate independently measured from hydrogen evolution, as also indicated by the review of Song and Atrens[2].In the Tafel extrapolation method for measuring the Mg corro-sion rate,the corrosion current density,i corr(mA/cm2)is estimated by Tafel extrapolation of the cathodic branch of the polarisation curve,and i corr is related to the average corrosion rate using [6–9,11,14]P i¼22:85i corrð5ÞReasons were given by Song and Atrens[2]why this electrochemi-cal technique might not give reliable values for Mg corrosion.Nev-ertheless the electrochemical technique of Tafel extrapolation is widely used for the evaluation of the corrosion of Mg alloys,at least partly,because it is a quick and easy technique.Therefore it is use-ful to review the literature on this technique for Mg alloys.It is useful to have quantitative measures of the quality of the corrosion rate evaluated by the Tafel extrapolation.One measure is to evaluate the relative deviation between the measured corro-sion rate and a standard corrosion rate.The corrosion rate evalu-ated from weight loss,P W,and the corrosion rate,P H,evaluated from the hydrogen evolution data,can each be used as a standard against which to compare the corrosion rate evaluated by Tafel extrapolation.Experimentally it has been shown that there is good agreement between measurements of P W and P H.The relative devi-ation for the corrosion rate determined from Tafel extrapolation was evaluated usinge i¼P iÀP WðÞ=P WðÞj jÂ100ð6Þore i¼P iÀP HðÞ=P HðÞj jÂ100ð7ÞAn alternative measure of quality is the ratio P W/P i.This ratio would be equal to unity if P i were a good estimate of P W.Mg corrosion has a strange phenomenon that anodic polarisation increases both the amount of Mg2+ions produced AND the amount of hydrogen evolved[1–3].This is summarised in the Section5.The most likely explanation is that part of the corrosion reaction is chemical rather than electrochemical.The consequence is that the ratio P W/P i would be expected to have a value between1and2,if P W is a good measure of the rate of the total corrosion reaction and if P i were a good measure of the rate of the electrochemical part of the total corrosion reaction.3.Corrosion rate measurements from Tafel extrapolation3.1.Pure Mg,AZ91and ZE41in1M NaClTable1[15]relates to the corrosion of pure Mg,AZ91and ZE41 in1M NaCl.All three alloys were as cast and all were high purity in that the concentration of the impurity was lower than the impurity tolerance limits[16].AZ91and ZE41are both two-phase alloys;in each case,the second phase was not continuous so there was no tendency for the second phase to provide a barrier effect [2,13,17].Samples were encapsulated in resin and only one surface was exposed to the solution.This approach facilitated the exami-nation of the corrosion morphology.The specimen surface was mechanically ground to1200grit on SiC paper,washed with dis-tilled water and dried.The hydrogen evolution was measured overa period of48h using duplicate specimens exposed horizontally to1.5L of1M NaCl.For ZE41the corrosion initiated as localized cor-rosion at some sites on the surface and subsequently expanded over the whole surface.The hydrogen evolution,after an initiation time of several hours,increased linearly with exposure time.The advance of the corrosion over the surface of AZ91was slower, although the corrosion also initiated as localized corrosion;there was corrosion on only part of the surface at the end of the48h per-iod.The hydrogen evolution,after an initiation time of several hours,increased with exposure time;the hydrogen evolution rate increased slightly with time.Nevertheless,the hydrogen evolution volume for AZ91was significantly lower than for ZE41.The corro-sion of the pure Mg was uniform over a macroscale in that there were no preferential sites for corrosion.At the end of the48h exposure,the corrosion was essentially uniform over the whole exposed surface area.The hydrogen evolution,after an initiation time of several hours,increased linearly with exposure time.The hydrogen evolution volume for pure Mg was significantly lower than for the two alloys,consistent with the general observation that the lowest corrosion rate is produced by pure Mg[1,2]and that the higher corrosion rates of the two alloys was in each case due to micro-galvanic acceleration of the corrosion by the second phase.The average hydrogen evolution rate over the exposure period is reported in Table1[15].At the end of the exposure per-iod,the corrosion products were removed by the standard cleaning solution,and the weight loss evaluated.The weight loss rate is also contained in Table1.There was good agreement between the corrosion rate evaluated from the hydrogen evolution rate and that evaluated from the weight loss rate,as expected from Fig.1and from the review of Song and Atrens[2].The polarisation curves were measured in a standard three-electrode glass cell with a standard scan rate of0.2mV/s.The reference electrode was a saturated calomel electrode(SCE).The specimen configuration was the same as that used in the immer-sion experiments,which measured the hydrogen evolution and the weight loss.Duplicate polarisation curves were essentially identical.In each case the cathodic branch provided an extensive linear Tafel region,the evaluated i corr value is included in Table1 as is the corresponding corrosion rate.The corrosion rate values derived from Tafel extrapolation were quite different to those derived from the hydrogen evolution rate and from the weight loss data.The lower derived corrosion rates for ZE41and AZ91might be attributed to the incubation of corrosion as shown by the lower hydrogen evolution rates at the beginning of the immersion tests.Fig. 1.Cross plot of the independent measurements of weight loss rate andhydrogen evolution rate,for48h and96h immersion tests of cast AZ91in1M NaClsolution.The line is a plot of the theoretical expectation;it is not simply a linethrough the experimental data points.580Z.Shi et al./Corrosion Science52(2010)579–588The corrosion rate for pure Mg from the Tafel extrapolation was about three times that measured by weight loss or hydrogen evolution.This might be associated with the transformation of an air formedfilm to the steady statefilm for Mg exposed to water [18].However,the hydrogen evolution data did not show any analogous feature,the hydrogen evolution was low and,as far as could be discerned,the hydrogen evolution was linear with time.The data of Table1relates to the corrosion rate,P W and P H,mea-sured over48h and P i measured soon after specimen immersion in the solution.For all three Mg alloys,there was a large relative deviation for the corrosion rate determined from Tafel extrapola-tion compared with the weight loss rate.The relative deviation for the corrosion rate determined from Tafel extrapolation was calculated using Eq.(6).This large relative deviation is in agree-ment with the observations of the review of Song and Atrens[2].3.2.Heat Treated Mg–10Gd–3Y–0.4Zr in5%NaClTable2relates to the study of Peng et al.[19];they studied the corrosion of Mg alloy Mg–10Gd–3Y–0.4Zr,in the as cast(F),solu-tion treated(T4)and aged(T6)conditions,in5%NaCl solution, by immersion tests and potentiodynamic polarisation curves.The corrosion rate was measured using three or four replicate speci-mens,for each microstructure condition,immersed for3days at 25±2°C in5wt.%NaCl aqueous solution,prepared with AR grade NaCl and distilled water.Each specimen was polished successively on320grit waterproof abrasive paper and three grit metallo-graphic paper,washed with distilled water,dried in warmflowing air and weighed to determine the original weight.During thefirst few hours of immersion,the solution pH increased from neutral to pH$11due to the precipitation of Mg(OH)2because of its low solubility.Thereafter the pH remained constant at$11.Because the time of the initial increase in pH was short(a few hours)com-pared with the test duration(3days)the corrosion rates measured were essentially the same as measured in a solution saturated with Mg(OH)2.After the immersion test,each specimen was washed with distilled water and dried.One sample was used for the corro-sion product analysis.The other samples were used to determine the corrosion rate by means of the metal weight loss.The corrosion products were removed by sample immersion in a solution of 200g LÀ1CrO3+10g LÀ1AgNO3at ambient temperature for 7min.Separate experiments demonstrated that this treatment re-moves all the corrosion products without removing any Mg metal. Each specimen was then washed with distilled water,dried in the warmflowing air and weighed to determine the weight after cor-rosion.The corrosion rate,P W(mm/y),is presented in Table2[19].Potentiodynamic polarisation curves were measured with metallographic polished specimens in5%NaCl saturated with Mg(OH)2that gave a stable pH of$11,using a three-electrode elec-trochemical cell and a scanning rate of1mV sÀ1.After immersion for1h,the polarisation was started from a potential ofÀ250mV SCE (cathodic)relative to the open circuit potential and was stopped at an anodic potential where the anodic current increased dramati-cally.At least two tests were conducted for each microstructure condition;these confirmed the reproducibility of the polarisation curves.The polarisation curves were used to evaluate the corrosion density,i corr,by Tafel extrapolation of the cathodic branch to the corrosion potential,E corr.The corresponding corrosion rate,P i,is included in Table2.Table2presents i corr,P i,E corr and b c values for GWK103in the as cast(F),solution treated(T4)and aged(T6)conditions,evaluated from polarisation curves measured in5%NaCl saturated with Mg(OH)2.Also listed for comparison are P W,P W/P i,and the relative deviation calculated using Eq.(6).The cathodic Tafel slope,b c,was similar for all conditions,indicating similar electrochemical reac-tions for hydrogen evolution;however,the values did have signif-icant variation larger than experimental scatter,which could indicate that there was more than one hydrogen evolution reac-tion.The values of i corr,and the corresponding corrosion rate,P i, for the different microstructure conditions correlated with the corrosion rates measured from weight loss,P W,but did not agree in magnitude.Moreover the ratio P W/P i was not constant,and the relative deviations were large,indicating that the electrochemical method based on Tafel extrapolation of the cathodic polarisation curve did not provide a good measurement of the corrosion rate, in agreement with Song and Atrens[2].The data of Table2relates to the corrosion rate,P W,measured over3days and P i measured soon after specimen immersion(1h)in the solution.3.3.AZ91in3.5%NaClTable3relates to the study by Candan et al.[20]of the corrosion of AZ91alloys,containing0–1wt%Pb,in3.5%NaCl.The corrosion rate was measured by weight loss for72h immersion in3.5%NaCl, P W,and the corrosion rate,P i,evaluated by Tafel extrapolation from polarisation curves measured with a scan rate of1mV SCE/s after 1h immersion in3.5%NaCl.Specimens were polished to1l m diamond,washed with alcohol and washed with distilled water. There were large differences between the two measures of corro-sion rate.The values of the corrosion rate measured by weight loss,P W, given in Table3,are larger than expect for AZ91in3.5%NaCl asTable2i corr,P i,E corr and b c values for GWK103(Mg–10Gd–3Y–0.4Zr)in the F,T4and T6 conditions,evaluated from polarisation curves measured in5%NaCl saturated with Mg(OH)2after solution equilibration for1h.Also presented are values for P W,P W/P i and e i.P W is the corrosion rate measured from the weight loss for immersion in5% NaCl solution for3days.e i was evaluated using Eq.(6).Material i corr(l A cmÀ2)P i(mm/y)E corr(V SCE)b c(V SCE)P W(mm/y)P W/P ie i(%)GWK103–F50 1.1À1.6700.230 3.0 2.763 GWK103–T4240.54À1.7100.1700.390.7138 GWK103–T6–16h310.71À1.6900.200 2.0 2.865GWK103–T6–500h 300.67À1.6800.190 1.7 2.661Table3Corrosion rates(mm/y)for AZ91base alloys containing0–1%Pb,measured by weightloss,P W,for72h immersion in3.5%NaCl;and P i,evaluated by Tafel extrapolationfrom polarisation curves measured after1h immersion in3.5%NaCl.Alloy P W P i P W/P iAZ91160 3.545AZ91+0.2%Pb110 2.055AZ91+0.5%Pb900.20450AZ91+1.0%Pb800.071140Table1Measurements related to corrosion rate in1M NaCl at room temperature.Hydrogen evolution rate,V H,and weight loss rate,D W,was measured using48h immersion. Tafel extrapolation evaluated i corr from polarisation curves measured using as-polished specimens soon after solution immersion.Also given is the relative deviation for the corrosion rate determined from Tafel extrapolation,e i,compared with the weight loss rate,calculated using Eq.(6).Alloy V H(ml/cm2/d)P H(mm/y)D W(mg/cm2/d)P W(mm/y)i corr(mA/cm2)P i(mm/y)e i(%)P W/P iZE41 5.914 5.7120.09 2.183 5.7 AZ91D 3.17.1 3.0 6.20.040.9185 6.8PureMg 0.44 1.00.430.900.12 2.72000.33Z.Shi et al./Corrosion Science52(2010)579–588581is evident by a comparison of the data of Table 3and those in Tables 1,4and 8.However,the higher values of corrosion rate are plausible because a small amount of Fe (above the tolerance limit)would cause these higher corrosion rates and such Fe contents could easily arise in their alloy production using raw material ingots from a commercial company.It is plausible that the corrosion rate mea-sured over 72h in the immersion tests becomes manifest during the 72h of the test,whereas a significantly lower corrosion rate was present during the first hour of immersion and measured by the corrosion rate,P i ,evaluated by Tafel extrapolation.Table 4relates to the study of Zhou et al.[21]of the corrosion of AZ91alloys,containing Ca,Sb and Bi Pb,in 3.5%NaCl.The corro-sion rate,P W ,was measured by weight loss for 6days immersion in 3.5%NaCl;and the corrosion rate,P i ,evaluated by Tafel extrap-olation from polarisation curves measured with a scan rate of 1mV SCE /s in 3.5%NaCl.Specimens were polished to 6l m diamond,washed with acetone and washed with distilled water.There were large differences between the two measures of corrosion rate.The relative deviations ranged from 30%to 97%.3.4.AZ91in 0.1M NaClTable 5presents corrosion rates [22,23]for AZ91in 0.1M NaCl measured using weight loss for 100h solution immersion in 0.1M NaCl,P W (mm/y);and corrosion rates,P i -10h ,P i -30h and P i -100h ,cal-culated using Eq.(5)in the present work from the values presented in [22,23]of i corr-10h ,i corr-30h and i corr-100h ,estimated in [22,23]by Tafel extrapolation,from polarisation curves measured after solu-tion exposure of 10h,30h and 100h.The authors indicated that ‘‘there appears to be a direct correlation between the weight loss data and the data collected using electrochemical techniques”,although they did not report the actual numerical values of the cor-rosion rates associated with their electrochemical measurements in their papers [22,23].The samples were ground to 1200grit,cleaned,weighted and introduced into the solution.Potentiody-namic polarisation curves were measured at a relatively rapid scan rate of 4mV SHE /s.The agreement between P W and P i -10h ,P i -30h and P i -100h was not good.This is further explored in Table 6,which pre-sents the ratios P W /P i -10h ,P W /P i -30h and P W /P i -100h ;these ratios should be equal to unity for good agreement.There was not good agreement.The experimental description for the weight loss determination [22,23]indicates that there might have been some corrosion prod-ucts on the specimen surface.That might explain the low reported corrosion rates from weight loss,P W .The values for P W for as cast AZ91in Table 5are significantly lower than the values of P W or P H in Tables 1,3and 8and for P W for comparable alloys in Table 4.The authors [22,23]attributed the low corrosion rates,P W ,to the fact that the tests were carried out in a relatively mild solution.The authors recognized that the corrosion rates measured by Tafel extrapolation were typically much greater than the corrosion rates measured by weight loss,P W .They [22,23]attributed the difference between the two techniques to the fact that the corrosion was local-ized.This issue is dealt with in Section 5.2of the discussion.3.5.Secondary AZ91alloysScharfe et al.[24]carried out a large number of corrosion tests on AZ91base alloys with the addition of extra alloying.For the al-loy designated as ‘‘25”(consisting of AZ91+0.5%Cu),they carried out electrochemical tests and hydrogen evolution measurements under nearly similar conditions so that a comparison is possible.Samples were ground to 1200grit and cleaned with ethanol.Polar-isation curves were measured 0.5h after immersion in 5%NaCl,with starting pH 11.The corrosion rate,calculated from the polar-isation curve was reported as 2.19mm/y [24].The corrosion rate was evaluated to be 5.28mm/y from hydrogen evolution data for this alloy in a nearly similar solution (3.5%NaCl,pH 10)between 70and 90h [24].They attributed the difference in corrosion rate to the possibility that the polarisation curve gave a measurement related to the early stages of corrosion whereas the hydrogen evo-lution data related to long-term steady state corrosion.3.6.Mg–6Zn–Mn–(0.5–2)Si–(0–0.2)CaFig.2relates to the study by Lisitsyn et al.[25]on the corrosion of Mg–6Zn–Mn–(0.5–2)Si–(0–0.2)Ca alloys in 3.5%NaCl saturated with Mg(OH)2.The immersion tests were carried out for 72h and the weight loss was converted to a corrosion rate,P W .Also mea-sured was the corrosion rate from polarisation curves at 1h and 4h (labelled as PD test t =1,and PD test 4h).There was some agreement between P W and the corrosion rate measured from the polarisation curves at 4h (PD test 4h)for some alloys,but poor agreement for the other cases.In general,the corrosion rate mea-sured from the immersion tests,P W gave lower values which may be due to the film tendencies of this testing solution.Table 4Corrosion rates (mm/y)for AZ91base alloys,measured by weight loss,P W ,for 6days immersion in 3.5%NaCl;and P i ,evaluated by Tafel extrapolation from polarisation curves measured in 3.5%NaCl.e i was evaluated using Eq.(6).AlloyP W i corr (mA/cm 2)P i e i (%)P W /P i Mg–9Al–0.6Zn–0.2Mn8.60.0110.259734Mg–9Al–0.8Zn–0.2Mn–0.14Ca 8.80.271 6.230 1.4Mg–9Al–0.8Zn–0.2Mn–0.4Sb 19.90.207 4.776 4.2Mg–9Al–0.8Zn–0.2Mn–0.4Sb–1Bi38.00.76217.4552.1Table 5Corrosion rates (mm/y)for AZ91in 0.1M NaCl measured by weight loss over 100h solution immersion,P W ,and,P i -10h ,P i -30h and P i -100h ,evaluated using Eq.(5)from i corr-10h ,i corr-30h and i corr-100h ,estimated by Tafel extrapolation,from polarisation curves measured after solution exposure of 10h,30h and 100h.Alloy100h 10h30h100hP W (mm/y)i corr-10h (mA/cm 2)P i -10h (mm/y)i corr-30h (mA/cm 2)P i -30h (mm/y)i corr-100h (mA/cm 2)P i -100h (mm/y)As cast 0.350.73170.9321 1.0424T40.290.15 3.40.44100.9021T6–10h 0.310.48110.6415 1.0624T6–16h 0.440.08 1.80.8419 2.2351T6–19h0.620.173.90.77184.43101Table 6Ratios P W /P i -10h ,P W /P i -30h and P W /P i -100h from the data of Table 5.Alloy P W /P i -10h P W /P i -30h P W /P i -100h As cast 0.0210.0170.015T40.850.0290.014T6–10h 0.0280.0210.013T6–16h 0.240.0230.0086T6–19h0.160.0340.0061582Z.Shi et al./Corrosion Science 52(2010)579–5883.7.ZE41in 0–1M NaCl,pH 3–11Table 7relates to the work of Zhao etal.[12];they used the same ZE41and the same procedures as in the research summarised in Section 3.1[15].The hydrogen evolution volume was measured as a function of immersion time,for ZE41immersed in 0M,0.1M and 1M NaCl solutions with pH 3,7and 11.The solutions desig-nated as 0M NaCl consisted of distilled water plus zero added NaCl,adjusted to the desired pH value with HCl and NaOH.The evolved hydrogen volume was essentially zero for the 48h immer-sion in 0M NaCl solutions with pH 7and pH 11,which indicated that there was a low corrosion rate for ZE41in neutral or alkaline solutions without chloride ions.For all other solutions,after an incubation period during which there was a low hydrogen evolu-tion rate,there was an increase in hydrogen evolution volume with increasing immersion time.The incubation period and rate of hydrogen evolution depended on the solution.The incubation per-iod decreased and the hydrogen evolution rate increased with increasing chloride ion concentration at each pH and with decreas-ing pH for each chloride ion concentration.The average corrosion rate,P H (mm/y),evaluated over 48h from the average hydrogen evolution rate for cast ZE41immersed in the various NaCl solutions is presented in Table 7.Potentiodynamic polarisation curves were measured for freshly prepared ZE41samples immediately after immersion in 0M,0.1M and 1M NaCl solutions with pH 3,7and 11.The polarisation curves were used to estimate the corrosion current density ,i corr ,at E corr ,by Tafel extrapolation of the cathodic branch and the cor-responding corrosion rates,P io (mm/y),are presented in Table 7.A comparison of these values from Tafel extrapolation with those calculated from the hydrogen evolution data indicated that (i)the corrosion rates were much higher when estimated from the hydrogen evolution rate and (ii)the corrosion rate estimated from the Tafel extrapolation showed the same trends in influence of pH and chloride ion concentration.The reason for the difference may be that different types of corrosion were measured.The corrosion rate from the Tafel extrapolation may relate to the onset of corro-sion,whereas the corrosion rate from the hydrogen evolution mea-surements relates to corrosion averaged over a considerable time period and includes corrosion some considerable time after corro-sion onset,when the corrosion is well established.Polarisation curves were also measured after 48h immersion in some of the solutions.There were large differences compared with the curves measured immediately after solution immersion for each solution.Tafel extrapolation was used to evaluate i corr and the corresponding corrosion rates have been designated,P i-ss ,to indicate that steady state corrosion conditions had been estab-lished.The corrosion rate,P i-ss ,was always greater than the corro-sion rate,P io ,but the difference was small for the 0.1M NaCl solutions whereas the difference was larger in the 1M NaCl solu-tion.The trends for the corrosion rate,P i-ss (related to pH and chlo-ride concentration)were similar to those for the corrosion rate,P H ;but any similarity of the numerical value of P i-ss and P H appears fortuitous.Table 7showed that the corrosion rate determined from the current at the free corrosion potential,did not agree with direct measurements evaluated from the evolved hydrogen.Of most con-cern may be that there did not appear to be any relation between P i-ss and P H .Any similarity of the numerical value of P i-ss and P H ap-pears fortuitous;the ratio P H /P i-ss varied seemingly randomly be-tween 5.0and 1.2.In most cases the relative deviation was large.3.8.Mg alloys in 1M NaClTable 8relates to the work of Zhao et al.[14].The corrosion rates of common Mg alloys (pure Mg,AZ31,AZ91,AM30,AM60,ZE41)immersed in 3wt.%NaCl for 12days were evaluated by mea-suring the hydrogen evolution.The corrosion rate was also esti-mated using Tafel extrapolation of the cathodic branch of the polarisation curve measured soon after specimen immersion in the solution,after 1day and after 7days immersion in the solution.The pure Mg,AZ91,AM60and ZE41were from cast ingot whereas AZ31and AM30were from extrusions.These alloys were high pur-ity and so were suitable for the study of the influences on corrosion other than the effect of the impurity elements.The hydrogen evolution was measured for two samples each of each Mg alloy immersed in 3%NaCl.For pure Mg and the Mg alloys (with the exception of AZ31),there was initially an incubation per-iod during which there was a small rate of hydrogen evolution.The incubation period was quiet long for pure Mg,there was essentially no incubation period for ZE41.Thereafter there was an increase in hydrogen evolution with increasing immersion time.For most al-loys,the rate of hydrogen evolution initially increased with increasing exposure time,which is attributed to corrosion occur-ring over increasing fractions of the surface as was observed in our prior work [12,15].Nevertheless,it should also be noted that the increase in hydrogen evolution could also be associated with the increased actual surface area;the actual surface area of a corroded surface is larger than the original surface area due to anTable 7The corrosion rate (mm/y),P i-ss (estimated from i corr from polarisation curves measured for ZE41after reaching steady state corrosion conditions,i.e.after 48h immersion)compared with the corrosion rate,P io (estimated from i corr measured from polarisation curves for freshly prepared cast ZE41)and the corrosion rate,P H (evaluated over 48h from the average hydrogen evolution rate)for cast ZE41immersed in various NaCl solutions.The units for the corrosion rate were mm/y.(The relative deviation,calculated using Eq.(7)is given in the brackets in each case,%.)NM indicates not measured.pH0.1M NaCl 1M NaCl P HP ioP i-ss P H P ioP i-ss39.7 3.7(62%) 4.5(54%)20 5.0(75%)17.0(4%)7 2.30.63(73%)NM14 1.6(89%) 3.2(77%)111.50.22(85%)0.3(80%)8.00.6(93%)NMFig.2.Corrosion rate data from the study by Lisitsyn et al.[25]on the corrosion of Mg–6Zn–Mn–(0.5–2)Si–(0–0.2)Ca alloys in 3.5%NaCl saturated with Mg(OH)2.The immersion tests were carried out for 72h and the weight loss was converted to a penetration rate,P W .Also measured was the corrosion rate from polarisation curves at 1h and 4h (labelled as PD test t =1,and PD test 4h).There was some agreement between P W and the corrosion rate measured from the polarisation curves at 4h (PD test 4h)for some alloys,but poor agreement for the other cases.In general,the corrosion rate measured from the immersion tests,P W gave lower values which may be due to the film tendencies of this testing solution.Z.Shi et al./Corrosion Science 52(2010)579–588583。
New Perspectives on the Structure of Graphitic Carbons
Critical Reviews in Solid State and Materials Sciences,30:235–253,2005 Copyright c Taylor and Francis Inc.ISSN:1040-8436printDOI:10.1080/10408430500406265New Perspectives on the Structure of Graphitic CarbonsPeter J.F.Harris∗Centre for Advanced Microscopy,University of Reading,Whiteknights,Reading,RG66AF,UKGraphitic forms of carbon are important in a wide variety of applications,ranging from pollutioncontrol to composite materials,yet the structure of these carbons at the molecular level ispoorly understood.The discovery of fullerenes and fullerene-related structures such as carbonnanotubes has given a new perspective on the structure of solid carbon.This review aims toshow how the new knowledge gained as a result of research on fullerene-related carbons canbe applied to well-known forms of carbon such as microporous carbon,glassy carbon,carbonfibers,and carbon black.Keywords fullerenes,carbon nanotubes,carbon nanoparticles,non-graphitizing carbons,microporous carbon,glassy carbon,carbon black,carbonfibers.Table of Contents INTRODUCTION (235)FULLERENES,CARBON NANOTUBES,AND CARBON NANOPARTICLES (236)MICROPOROUS(NON-GRAPHITIZING)CARBONS (239)Background (239)Early Models (241)Evidence for Fullerene-Like Structures in Microporous Carbons (242)New Models for the Structure of Microporous Carbons (242)Carbonization and the Structural Evolution of Microporous Carbon (243)GLASSY CARBON (244)CARBON FIBERS (245)CARBON BLACK (248)Background (248)Structure of Carbon Black Particles (249)Effect of High-Temperature Heat Treatment on Carbon Black Structure (250)CONCLUSIONS (250)ACKNOWLEDGMENTS (251)REFERENCES (251)INTRODUCTIONUntil quite recently we knew for certain of just two allotropes of carbon:diamond and graphite.The vast range of carbon ma-∗E-mail:p.j.f.harris@ terials,both natural and synthetic,which have more disordered structures have traditionally been considered as variants of one or other of these two allotropes.Because the great majority of these materials contain sp2carbon rather than sp3carbon,their struc-tures have been thought of as being made up from tiny fragments235236P.J.F.HARRISFI G.1.(a)Model of PAN-derived carbon fibres from the work of Crawford and Johnson,1(b)model of a non-graphitizing carbon by Ban and colleagues.2of crystalline graphite.Examples of models for the structures of carbons in which the basic elements are graphitic are reproduced in Figure 1.The structure shown in Figure 1(a)is a model for the structure of carbon fibers suggested by Crawford and Johnson in 1971,1whereas 1(b)shows a model for non-graphitizing car-bon given by Ban and colleagues in 1975.2Both structures are constructed from bent or curved sheets of graphite,containing exclusively hexagonal rings.Although these models probably provide a good first approximation of the structures of these car-bons,in many cases they fail to explain fully the properties of the materials.Consider the example of non-graphitizing carbons.As the name suggests,these cannot be transformed into crystalline graphite even at temperatures of 3000◦C and above.I nstead,high temperature heat treatments transform them into structures with a high degree of porosity but no long-range crystalline order.I n the model proposed by Ban et al.(Figure 1(b)),the structure is made up of ribbon-like sheets enclosing randomly shaped voids.It is most unlikely that such a structure could retain its poros-ity when subjected to high temperature heat treatment—surface energy would force the voids to collapse.The shortcomings of this and other “conventional”models are discussed more fully later in the article.The discovery of the fullerenes 3−5and subsequently of re-lated structures such as carbon nanotubes,6−8nanohorns,9,10and nanoparticles,11has given us a new paradigm for solid car-bon structures.We now know that carbons containing pentago-nal rings,as well as other non-six-membered rings,among the hexagonal sp 2carbon network,can be highly stable.This new perspective has prompted a number of groups to take a fresh look at well-known forms of carbon,to see whether any evidence can be found for the presence of fullerene-like structures.12−14The aim of this article is to review this new work on the structure of graphitic carbons,to assess whether models that incorporate fullerene-like elements could provide a better basis for under-standing these materials than the conventional models,and to point out areas where further work is needed.The carbon ma-terials considered include non-graphitizing carbon,glassy car-bon,carbon fibers,and carbon black.The article begins with an outline of the main structural features of fullerenes,carbon nanotubes,and carbon nanoparticles,together with a brief dis-cussion of their stability.FULLERENES,CARBON NANOTUBES,AND CARBON NANOPARTICLESThe structure of C 60,the archetypal fullerene,is shown in Figure 2(a).The structure consists of twelve pentagonal rings and twenty hexagons in an icosahedral arrangement.I t will be noted that all the pentagons are isolated from each other.This is important,because adjacent pentagonal rings form an unstable bonding arrangement.All other closed-cage isomers of C 60,and all smaller fullerenes,are less stable than buck-minsterfullerene because they have adjacent pentagons.For higher fullerenes,the number of structures with isolated pen-tagonal rings increases rapidly with size.For example,C 100has 450isolated-pentagon isomers.16Most of these higher fullerenes have low symmetry;only a very small number of them have the icosahedral symmetry of C 60.An example of a giant fullerene that can have icosahedral symmetry is C 540,as shown in Figure 2(b).There have been many studies of the stability of fullerenes as a function of size (e.g.,Refs.17,18).These show that,in general,stability increases with size.Experimentally,there is evidence that C 60is unstable with respect to large,multiwalled fullerenes.This was demonstrated by Mochida and colleagues,who heated C 60and C 70in a sublimation-limiting furnace.19They showed that the cage structure broke down at 900◦C–1000◦C,although at 2400◦C fullerene-like “hollow spheres”with diameters in the range 10–20nm were formed.We now consider fullerene-related carbon nanotubes,which were discovered by Iijima in 1991.6These consist of cylinders of graphite,closed at each end with caps that contain precisely six pentagonal rings.We can illustrate their structure by considering the two “archetypal”carbon nanotubes that can be formed by cutting a C 60molecule in half and placing a graphene cylinder between the two halves.Dividing C 60parallel to one of the three-fold axes results in the zig-zag nanotube shown in Figure 3(a),whereas bisecting C 60along one of the fivefold axes produces the armchair nanotube shown in Figure 3(b).The terms “zig-zag”and “armchair”refer to the arrangement of hexagons around the circumference.There is a third class of structure in which the hexagons are arranged helically around the tube axis.Ex-perimentally,the tubes are generally much less perfect than the idealized versions shown in Figure 3,and may be eitherNEW PERSPECTIVES ON GRAPHITIC CARBONS STRUCTURE237FI G.2.The structure of (a)C 60,(b)icosahedral C 540.15multilayered or single-layered.Figure 4shows a high resolu-tion TEM image of multilayered nanotubes.The multilayered tubes range in length from a few tens of nm to several microns,and in outer diameter from about 2.5nm to 30nm.The end-caps of the tubes are sometimes symmetrical in shape,but more often asymmetric.Conical structures of the kind shown in Fig-ure 5(a)are commonly observed.This type of structure is be-lieved to result from the presence of a single pentagon at the position indicated by the arrow,with five further pentagons at the apex of the cone.Also quite common are complex cap struc-tures displaying a “bill-like”morphology such as thatshownFI G.3.Drawings of the two nanotubes that can be capped by one half of a C 60molecule.(a)Zig-zag (9,0)structure,(b)armchair (5,5)structure.20in Figure 5(b).21This structure results from the presence of a single pentagon at point “X”and a heptagon at point “Y .”The heptagon results in a saddle-point,or region of negative curvature.The nanotubes first reported by Iijima were prepared by va-porizing graphite in a carbon arc under an atmosphere of helium.Nanotubes produced in this way are invariably accompanied by other material,notably carbon nanoparticles.These can be thought of as giant,multilayered fullerenes,and range in size from ∼5nm to ∼15nm.A high-resolution image of a nanopar-ticle attached to a nanotube is shown in Figure 6(a).22In this238P.J.F.HARRISFI G.4.TEM image of multiwalled nanotubes.case,the particle consists of three concentric fullerene shells.A more typical nanoparticle,with many more layers,is shown in Figure 6(b).These larger particles are probably relatively im-perfect instructure.FI G.5.I mages of typical multiwalled nanotube caps.(a)cap with asymmetric cone structure,(b)cap with bill-like structure.21Single-walled nanotubes were first prepared in 1993using a variant of the arc-evaporation technique.23,24These are quite different from multilayered nanotubes in that they generally have very small diameters (typically ∼1nm),and tend to be curledNEW PERSPECTIVES ON GRAPHITIC CARBONS STRUCTURE239FI G.6.I mages of carbon nanoparticles.(a)small nanoparticle with three concentric layers on nanotube surface,22(b)larger multilayered nanoparticle.and looped rather than straight.They will not be considered further here because they have no parallel among well-known forms of carbon discussed in this article.The stability of multilayered carbon nanotubes and nanopar-ticles has not been studied in detail experimentally.However,we know that they are formed at the center of graphite electrodes during arcing,where temperatures probably approach 3000◦C.I t is reasonable to assume,therefore,that nanotubes and nanopar-ticles could withstand being re-heated to such temperatures (in an inert atmosphere)without significant change.MICROPOROUS (NON-GRAPHITIZING)CARBONS BackgroundIt was demonstrated many years ago by Franklin 25,26that carbons produced by the solid-phase pyrolysis of organic ma-terials fall into two distinct classes.The so-called graphitizing carbons tend to be soft and non-porous,with relatively high den-sities,and can be readily transformed into crystalline graphite by heating at temperatures in the range 2200◦C–3000◦C.I n con-trast,“non-graphitizing”carbons are hard,low-densitymateri-FI G.7.(a)High resolution TEM image of carbon prepared by pyrolysis of sucrose in nitrogen at 1000◦C,(b)carbon prepared bypyrolysis of anthracene at 1000◦C.I nsets show selected area diffraction patterns.30als that cannot be transformed into crystalline graphite even at temperatures of 3000◦C and above.The low density of non-graphitizing carbons is a consequence of a microporous struc-ture,which gives these materials an exceptionally high internal surface area.This high surface area can be enhanced further by activation,that is,mild oxidation with a gas or chemical pro-cessing,and the resulting “activated carbons”are of enormous commercial importance,primarily as adsorbents.27−29The distinction between graphitizing and non-graphitizing carbons can be illustrated most clearly using transmission elec-tron microscopy (TEM).Figure 7(a)shows a TEM image of a typical non-graphitizing carbon prepared by the pyrolysis of sucrose in an inert atmosphere at 1000◦C.30The inset shows a diffraction pattern recorded from an area approximately 0.25µm in diameter.The image shows the structure to be disordered and isotropic,consisting of tightly curled single carbon layers,with no obvious graphitization.The diffraction pattern shows symmetrical rings,confirming the isotropic structure.The ap-pearance of graphitizing carbons,on the other hand,approxi-mates much more closely to that of graphite.This can be seen in the TEM micrograph of a carbon prepared from anthracene,240P.J.F.HARRI Swhich is shown in Figure 7(b).Here,the structure contains small,approximately flat carbon layers,packed tightly together with a high degree of alignment.The fragments can be considered as rather imperfect graphene sheets.The diffraction pattern for the graphitizing carbon consists of arcs rather than symmetrical rings,confirming that the layers are preferentially aligned along a particular direction.The bright,narrow arcs in this pattern correspond to the interlayer {0002}spacings,whereas the other reflections appear as broader,less intense arcs.Transmission electron micrographs showing the effect of high-temperature heat treatments on the structure of non-graphitizing and graphitizing carbons are shown in Figure 8(note that the magnification here is much lower than for Figure 7).I n the case of the non-graphitizing carbon,heating at 2300◦C in an inert atmosphere produces the disordered,porous material shown in Figure 8(a).This structure is made up of curved and faceted graphitic layer planes,typically 1–2nm thick and 5–15nm in length,enclosing randomly shaped pores.A few somewhat larger graphite crystallites are present,but there is no macroscopic graphitization.n contrast,heat treatment of the anthracene-derived carbon produces large crystals of highly or-dered graphite,as shown in Figure 8(b).Other physical measurements also demonstrate sharp dif-ferences between graphitizing and non-graphitizing carbons.Table 1shows the effect of preparation temperature on the sur-face areas and densities of a typical graphitizing carbon prepared from polyvinyl chloride,and a non-graphitizing carbon prepared from cellulose.31It can be seen that the graphitizing carbon pre-pared at 700◦C has a very low surface area,which changes lit-tle for carbons prepared at higher temperatures,up to 3000◦C.The density of the carbons increases steadily as thepreparationFI G.8.Micrographs of (a)sucrose carbon and (b)anthracene carbon following heat treatment at 2300◦C.TABLE 1Effect of temperature on surface areas and densities of carbonsprepared from polyvinyl chloride and cellulose 31(a)Surface areas Specific surface area (m 2/g)for carbons prepared at:Starting material 700◦C 1500◦C 2000◦C 2700◦C 3000◦C PVC 0.580.210.210.710.56Cellulose 4081.601.172.232.25(b)Densities Helium density (g/cm 3)for carbons prepared at:Starting material 700◦C 1500◦C 2000◦C 2700◦C 3000◦C PVC 1.85 2.09 2.14 2.21 2.26Cellulose1.901.471.431.561.70temperature is increased,reaching a value of 2.26g/cm 3,which is the density of pure graphite,at 3000◦C.The effect of prepara-tion temperature on the non-graphitizing carbon is very different.A high surface area is observed for the carbon prepared at 700◦C (408m 2/g),which falls rapidly as the preparation temperature is increased.Despite this reduction in surface area,however,the density of the non-graphitizing carbon actually falls when the temperature of preparation is increased.This indicates that a high proportion of “closed porosity”is present in the heat-treated carbon.NEW PERSPECTIVES ON GRAPHITIC CARBONS STRUCTURE241FI G.9.Franklin’s representations of(a)non-graphitizing and(b)graphitizing carbons.25Early ModelsThefirst attempt to develop structural models of graphitizingand non-graphitizing carbons was made by Franklin in her1951paper.25In these models,the basic units are small graphitic crys-tallites containing a few layer planes,which are joined togetherby crosslinks.The precise nature of the crosslinks is not speci-fied.An illustration of Franklin’s models is shown in Figure9.Using these models,she put forward an explanation of whynon-graphitizing carbons cannot be converted by heat treatmentinto graphite,and this will now be summarized.During car-bonization the incipient stacking of the graphene sheets in thenon-graphitizing carbon is largely prevented.At this stage thepresence of crosslinks,internal hydrogen,and the viscosity ofthe material is crucial.The resulting structure of the carbon(at ∼1000◦C)consists of randomly ordered crystallites,held to-gether by residual crosslinks and van der Waals forces,as inFigure9(a).During high-temperature treatment,even thoughthese crosslinks may be broken,the activation energy for themotion of entire crystallites,required for achieving the struc-ture of graphite,is too high and graphite is not formed.Onthe other hand,the structural units in a graphitizing carbon areapproximately parallel to each other,as in Figure9(b),and thetransformation of such a structure into crystalline graphite wouldbe expected to be relatively facile.Although Franklin’s ideason graphitizing and non-graphitizing carbons may be broadlycorrect,they are in some regards incomplete.For example,thenature of the crosslinks between the graphitic fragments is notspecified,so the reasons for the sharply differing properties ofgraphitizing and non-graphitizing carbons is not explained.The advent of high-resolution transmission electron mi-croscopy in the early1970s enabled the structure of non-graphitizing carbons to be imaged directly.n a typical study,Ban,Crawford,and Marsh2examined carbons prepared frompolyvinylidene chloride(PVDC)following heat treatments attemperatures in the range530◦C–2700◦C.I mages of these car-bons apparently showed the presence of curved and twistedgraphite sheets,typically two or three layer planes thick,enclos-ing voids.These images led Ban et al.to suggest that heat-treatednon-graphitizing carbons have a ribbon-like structure,as shownin Figure1(b).This structure corresponds to a PVDC carbonheat treated at1950◦C.This ribbon-like model is rather similar to an earlier model of glassy carbon proposed by Jenkins andKawamura.32However,models of this kind,which are intendedto represent the structure of non-graphitizing carbons follow-ing high-temperature heat treatment,have serious weaknesses,as noted earlier.Such models consist of curved and twistedgraphene sheets enclosing irregularly shaped pores.However,graphene sheets are known to be highlyflexible,and wouldtherefore be expected to become ever more closely folded to-gether at high temperatures,in order to reduce surface energy.Indeed,tightly folded graphene sheets are quite frequently seenin carbons that have been exposed to extreme conditions.33Thus,structures like the one shown in Figure1(b)would be unlikelyto be stable at very high temperatures.It has also been pointed out by Oberlin34,35that the modelsput forward by Jenkins,Ban,and their colleagues were basedon a questionable interpretation of the electron micrographs.In most micrographs of partially graphitized carbons,only the {0002}fringes are resolved,and these are only visible when they are approximately parallel to the electron beam.Therefore,such images tend to have a ribbon-like appearance.However,because only a part of the structure is being imaged,this appear-ance can be misleading,and the true three-dimensional structuremay be more cagelike than ribbon-like.This is a very importantpoint,and must always be borne in mind when analyzing imagesof graphitic carbons.Oberlin herself believes that all graphiticcarbons are built up from basic structural units,which comprisesmall groups of planar aromatic structures,35but does not appearto have given a detailed explanation for the non-graphitizabilityof certain carbons.The models of non-graphitizing carbons described so farhave assumed that the carbon atoms are exclusively sp2and arebonded in hexagonal rings.Some authors have suggested thatsp3-bonded atoms may be present in these carbons(e.g.,Refs.36,37),basing their arguments on an analysis of X-ray diffrac-tion patterns.The presence of diamond-like domains would beconsistent with the hardness of non-graphitizing carbons,andmight also explain their extreme resistance to graphitization.Aserious problem with these models is that sp3carbon is unsta-ble at high temperatures.Diamond is converted to graphite at1700◦C,whereas tetrahedrally bonded carbon atoms in amor-phousfilms are unstable above about700◦C.Therefore,the242P.J.F.HARRI Spresence of sp 3atoms in a carbon cannot explain the resistance of the carbon to graphitization at high temperatures.I t should also be noted that more recent diffraction studies of non-graphitizing carbons have suggested that sp 3-bonded atoms are not present,as discussed further in what follows.Evidence for Fullerene-Like Structures in Microporous CarbonsThe evidence that microporous carbons might have fullerene-related structures has come mainly from high-resolution TEM studies.The present author and colleagues initiated a series of studies of typical non-graphitizing microporous carbons using this technique in the mid 1990s.30,38,39The first such study in-volved examining carbons prepared from PVDC and sucrose,after heat treatments at temperatures in the range 2100◦C–2600◦C.38The carbons subjected to very high temperatures had rather disordered structures similar to that shown in Figure 8(a).Careful examination of the heated carbons showed that they often contained closed nanoparticles;examples can be seen in Figure 10.The particles were usually faceted,and often hexagonal or pentagonal in shape.Sometimes,faceted layer planes enclosed two or more of the nanoparticles,as shown in Figure 10(b).Here,the arrows indicate two saddle-points,similar to that shown in Figure 5(b).The closed nature of the nanoparticles,their hexagonal or pentagonal shapes,and other features such as the saddle-points strongly suggest that the parti-cles have fullerene-like structures.I ndeed,in many cases the par-ticles resemble those produced by arc-evaporation in a fullerene generator (see Figure 6)although in the latter case the particles usually contain many more layers.The observation of fullerene-related nanoparticles in the heat treated carbons suggested that the original,freshly prepared car-bons may also have had fullerene-related structures (see next section).However,obtaining direct evidence for this is diffi-cult.High resolution electron micrographs of freshly prepared carbons,such as that shown in Figure 7(a),are usuallyratherFI G.10.(a)Micrograph showing closed structure in PVDC-derived carbon heated at 2600◦C,(b)another micrograph of same sample,with arrows showing regions of negative curvature.38featureless,and do not reveal the detailed structure.Occasion-ally,however,very small closed particles can be found in the carbons.30The presence of such particles provides circumstan-tial evidence that the surrounding carbon may have a fullerene-related structure.Direct imaging of pentagonal rings by HRTEM has not yet been achieved,but recent developments in TEM imaging techniques suggest that this may soon be possible,as discussed in the Conclusions.As well as high-resolution TEM,diffraction methods have been widely applied to microporous and activated carbons (e.g.,Refs.40–44).However,the interpretation of diffraction data from these highly disordered materials is not straightforward.As already mentioned,some early X-ray diffraction studies were interpreted as providing evidence for the presence of sp 3-bonded atoms.More recent neutron diffraction studies have suggested that non-graphitizing carbons consist entirely of sp 2atoms.40It is less clear whether diffraction methods can establish whether the atoms are bonded in pentagonal or hexagonal rings.Both Petkov et al .42and Zetterstrom and colleagues 43have interpreted neutron diffraction data from nanoporous carbons in terms of a structure containing non-hexagonal rings,but other interpreta-tions may also be possible.Raman spectroscopy is another valuable technique for the study of carbons.45Burian and Dore have used this method to analyze carbons prepared from sucrose,heat treated at tem-peratures from 1000◦C–2300◦C.46The Raman spectra showed clear evidence for the presence of fullerene-and nanotube-like elements in the carbons.There was also some evidence for fullerene-like structures in graphitizing carbons prepared from anthracene,but these formed at higher temperatures and in much lower proportions than in the non-graphitizing carbons.New Models for the Structure of Microporous Carbons Prompted by the observations described in the previous section,the present author and colleagues proposed a model for the structure of non-graphitizing carbons that consists ofNEW PERSPECTIVES ON GRAPHITIC CARBONS STRUCTURE243FI G.11.Schematic illustration of a model for the structure of non-graphitizing carbons based on fullerene-like elements.discrete fragments of curved carbon sheets,in which pentagons and heptagons are dispersed randomly throughout networks of hexagons,as illustrated in Figure11.38,39The size of the micropores in this model would be of the order of0.5–1.0nm, which is similar to the pore sizes observed in typical microp-orous carbons.The structure has some similarities to the“ran-dom schwarzite”network put forward by Townsend and col-leagues in1992,47although this was not proposed as a model for non-graphitizing carbons.I f the model we have proposed for non-graphitizing carbons is correct it suggests that these carbons are very similar in structure to fullerene soot,the low-density, disordered material that forms on walls of the arc-evaporation vessel and from which C60and other fullerenes may be ex-tracted.Fullerene soot is known to be microporous,with a sur-face area,after activation with carbon dioxide,of approximately 700m2g−1,48and detailed analysis of high resolution TEM mi-crographs of fullerene soot has shown that these are consis-tent with a structure in which pentagons and heptagons are dis-tributed randomly throughout a network of hexagons.49,50It is significant that high-temperature heat treatments can transform fullerene soot into nanoparticles very similar to those observed in heated microporous carbon.51,52Carbonization and the Structural Evolutionof Microporous CarbonThe process whereby organic materials are transformed into carbon by heat treatment is not well understood at the atomic level.53,54In particular,the very basic question of why some organic materials produce graphitizing carbons and others yield non-graphitizing carbons has not been satisfactorily answered. It is known,however,that both the chemistry and physical prop-erties of the precursors are important in determining the class of carbon formed.Thus,non-graphitizing carbons are formed, in general,from substances containing less hydrogen and more oxygen than graphitizing carbons.As far as physical properties are concerned,materials that yield graphitizing carbons usu-ally form a liquid on heating to temperatures around400◦C–500◦C,whereas those that yield non-graphitizing carbons gen-erally form solid chars without melting.The liquid phase pro-duced on heating graphitizing carbons is believed to provide the mobility necessary to form oriented regions.However,this may not be a complete explanation,because some precursors form non-graphitizing carbons despite passing through a liquid phase.The idea that non-graphitizing carbons contain pentagons and other non-six-membered rings,whereas graphitizing car-bons consist entirely of hexagonal rings may help in understand-ing more fully the mechanism of carbonization.Recently Kumar et al.have used Monte Carlo(MC)simulations to model the evo-lution of a polymer structure into a microporous carbon structure containing non-hexagonal rings.55They chose polyfurfuryl al-cohol,a well-known precursor for non-graphitizing carbon,as the starting material.The polymer was represented as a cubic lattice decorated with the repeat units,as shown in Figure12(a). All the non-carbon atoms(i.e.,hydrogen and oxygen)were then removed from the polymer and this network was used in the。
响应面法优化芦荟中抗氧化活性成分的提取工艺_唐远谋
第9卷第1期2011年1月生 物 加 工 过 程Ch i nese Journa l o f B ioprocess Eng i neer i ng V o.l 9N o .1Jan .2011do:i 10.3969/.j issn .1672-3678.2011.01.006收稿日期:2010-07-14作者简介:唐远谋(1986 ),男,四川南充人,硕士研究生,研究方向:食品营养与安全;焦士蓉(联系人),副教授,硕士生导师,E-m ai:lj s -rong2004@163.co m响应面法优化芦荟中抗氧化活性成分的提取工艺唐远谋1,焦士蓉1,冷 鹂2,唐鹏程1,刘 佳1,冯 慧1(1.西华大学生物工程学院,成都610039;2.四川大学生命科学学院,成都610064)摘 要:对芦荟中抗氧化活性物质提取工艺及其成分进行研究,通过单因素实验和响应面优化,以提取物对DPPH 自由基的清除率为抗氧化的考察指标,得到芦荟中抗氧化活性成分的提取工艺条件:提取温度29 、料液比(g /mL)1 33、提取时间107s 、微波功率500W,微波辅助水提,此条件下得到的提取物对DPPH 自由基的清除率达91 414%。
提取物活性成分分析表明:提取物中芦荟甙含量为1 5m g /g 、黄酮为1 13mg /g 、多酚为4 33m g /g 、多糖为126 36mg /g 。
关键词:芦荟;抗氧化物质;DPPH 自由基;提取;响应曲面法中图分类号:TS201.1 文献标志码:A 文章编号:1672-3678(2011)01-0024-05Opti m izati on of process para m eters of extraction antioxi dantsfro m A loe usi ng response surface m ethodol ogyTANG Yuan m ou 1,JI A O Sh irong 1,LENG L i 2,TANG Pengcheng 1,LI U Jia 1,FENG Hu i1(1.Schoo l o f B i oeng i neer i ng,X i hua U niversity ,Chengdu 610039,China ;2.Schoo l o f L ife Sc i ences ,Sichuan U ni v ers it y ,Chengdu 610064,Chi na)Abst ract :The process para m eters for extraction o f antiox i d ants fro m Aloe w ere opti m ized and the co m po -nents w ere analyzed .The opti m al process conditi o ns w ere attained by sing le factor m ethod and response surface m e t h odogy .Anti o x idant ab ilicy w as evalvated on the scaveng ing rate o fDPP H free radica.l M icro -w ave assisted ex traction(MAE )by w ater w as chosed and t h e solid -li q u i d ratio w as 1 33,m icro w ave po w -er w as 500W at 29 for 107s .Under t h ese conditi o ns ,the re m ova l rate of DPP H w as 91 414%.The resu lts o f co m ponent analysis for antiox idants show ed that the y ie l d of a l o in ,flavono i d s ,po l y pheno ls ,and po l y sacchari d e w ere 1 5m g /g ,1 13m g /g ,4 33m g /g ,and 126 36m g /g ,respectively .K ey w ords :A loe ;anti o x i d ants ;DPP H free rad ica;l extracti o n ;response surface m ethod 芦荟系百合科(L iliaceae )芦荟属(A loe )多年生的常绿、肉质草本植物,原产于非洲[1]。
Distillation11
9
• on the diagram, then on heating at constant pressure the following changes will occur • a) When T reaches T2, the liquid will boil, as shown by point B, and some vapor of composition y2 , shown by point E, is formed. • b) On further heating, the composition of the liquid will change because of the loss of the more volatile component to the vapor and the boiling point will therefore rise to some t’. At this temperature the liquid will have a composition represented by L, and the vapor a composition represented by N. The mass ratio of liquid remained to the vapor formed is (lever rule)
11
• any other single stage of vaporisation. • Starting with superheated vapor represented by H, on cooling to D condensation will commence, and the first drop of liquid will have a composition of K. Further cooling to temperature t’ will give liqu -id L and vapor N. Thus partial condensation brin -gs about enrichment of the vapor in the more vol -atile component in the same manner as partial va –porisation. The industrial distillation column is. in essence, a series of units in which these two pr -ocesses of partial vaporisation and condensation are effected simultaneously.
安东尼·普尔Viscosity Measurement of Raw Materials for C
Viscosity Measurement of Raw Materials for Cosmetic Products Cosmetic industry, pharmaceutical industry, clean oil producers, testing labsProducers of oil-based cosmetic products receive pure and clean oils as raw materials which are further processed to the final product. For handling, processing, and transportation, viscosity is a crucial parameter. The Anton Paar SVM™ 2001 is the optimum solution for viscositymeasurement throughout production.1 Why measure viscosity?For producers of oil-based cosmetic products, the viscosity is an essential parameter to be determined. The pure oils are used as raw materials and further checked in quality control, transported, stored, and processed. Since many pure oils show a freezing point close to ambient conditions, their viscosity has a crucial influence on the handling and processing of the ingredients. Moreover, finished retail products, such as creams or balsam oils, require a convenient application by customers at any time.This report describes how to test various types of pure oils used as ingredients as well as oil-based finished products at the following temperatures which are relevant for storage, transportation, processing and final application: 40, 25, 20 , and 15 °C(104, 77, 68 and 59 °F).2 Which instrument is used?For the test of oil samples, the SVM™ 2001 is used. The SVM™ 2001 features a viscosity measuring cell and a density measuring cell which are filled in one go. The instrument's internal software provides single point measurements with or without automatic repetition in three different precision classes from…P recise‟to …U ltrafast‟, while each class corresponds to defined stability criteria for temperature, viscosity and density.For measurements with automatic repetition, the software features default deviation criteria for the repeatability depending on the selected precision class:▪for viscosity from 0.1 to 2.5 %▪for density from 0.0002 to 0.0010 g/cm³3 Which samples are tested?Oil-based cosmetic products have a curing effect for all skin types and help to protect the skin against harmful issues. Modern beauty oils are a combination of different types of oils and extracts mixed in such a way to trigger the desired effects of the finished product.The scope of tested samples covers pure oil samples used as raw materials as well as oil-based finished products.Table 1: Tested samples4 How to measure the samples? 4.1Instrument preparationFor samples that are solid at ambient conditionspreheating to 50 °C is necessary for proper filling. For these samples the accessory Hot Filling Attachment is used to ensure a stable temperature in the syringe and connections throughout the whole measuring and cleaning cycle.The Hot Filling Attachment can easily be mounted on the instrument. 4.2 Instrument settings▪ Measuring mode: …R epeated Mode ‟ (automatic repetition)▪ Precision class: …P recise ‟ ▪ Automatic prewetting: yes ▪ Filling temperature: yes▪ Equilibration time: 180 s for preheated samples4.3CalibrationBefore the measurement of the samples, it isadvisable to perform a calibration. Use one or more standards in the viscosity range of your oil samples. This can be a certified standard or a house-internal standard with kinematic viscosity values. In any case you need reliable kinematic viscosity values at the measuring temperatures. If required, apply acalibration correction to improve the reproducibility. To perform a calibration, refer to the SVM ™ X001 Instruction Manual. 4.4Sample preparationIf the sample is not freshly drawn from a productionline or another reservoir, you can improve the repeatability by homogenizing the sample before taking the test specimen.Any sample that crystallizes at ambient conditions should be preheated to a temperature at which the sample shows a homogeneous liquid phase.4.5FillingSingle-use syringes are recommended. Never use syringes with a rubber sealing, as the rubber is chemically not resistant and these syringes tend to draw bubbles. For preheated samples, always use syringes with a Luer-Lock connector. The typical sample volume is 5 mL. 4.6 Cleaning 4.6.1SolventsIt is essential to use a solvent that dries up completely without residues even at low measuring temperatures. For most of the pure oils samples, cleaning with only one solvent is sufficient.So-called petroleum benzine (hydrocarbon solvent, blend of mainly C7, C8, C9 n-alkanes) with a boiling range of 100 °C to 140 °C (212 °F to 284 °F) is the best choice and a universal solvent for cleaning over a wide temperature range. Since the cleaning effect is accelerated at increasing temperatures, the pre-set filling temperature of 50 °C (104 °F) for preheated samples enhances the cleaning speed.For oil-based final products, it is recommended to use two cleaning agents: Isopropanol (Isopropylalcohol) to pre-clean and petroleum benzine for final cleaning and as drying solvent. 4.6.2 Procedure▪ To avoid spillage, remove the sample from the cell by drawing it back into the syringe.▪Fill approx. 2 mL of solvent(s) with a disposable syringe. Mix solvent and sample residues in the viscosity using the motor speed button . Fill approx. 1 mL more solvent, move the plunger several times forth and back, and remove the sample from the cell. The generated air bubbles improve the cleaning action. Repeat this procedure once.▪ Flush the cells with approx. 3 mL of fresh solvent. ▪Connect the air pump hose respectively clean compressed air to dry the cell.5 Results For each temperature, up to three measurementcycles with automatic repetition are conducted. Based on the valid results (n), the mean value and standard deviation is calculated and displayed in the tables below.5.1 Pure oils as raw materials 5.1.1Sunflower oil, olive oil and coconut oilAs their freezing points are below 0 °C (32 °F), olive oil and sunflower oil do not require any preheating. Viscosity measurements show a standard deviation between ± 0.01 % to ± 0.27 % for all measuring points.Since coconut oil has a freezing point between23 to 26 °C (73 to 79 °F), the sample is preheated to 50 °C (122 °F) to ensure a homogeneous, liquidsample. Due to the long solidification time of coconut oil, the SVM ™ 2001 gives stable measuring results for 25 °C and 20 °C (77 °F and 68 °F) at precision class …Precis e‟. For measurements at 15 °C (59 °F), the enhanced crystallization does not allow valid viscosity measurement any more.Table 2: Kinematic viscosity of sunflower, olive, and coconut oil at different temperatures 5.1.2 Red palm oilThe sample is preheated to 50 °C (122 °F) before filling. At 40 °C (104 °F) the sample is still liquid, but the crystallization process begins already and the sample is not ideally homogeneous anymore. M easurements with precision class …P recise‟ and measuring mode …R epeated M ode‟do not deliver results within the predefined repeatability range. Consequently, this sample can only fulfill precision class 'Ultrafast'.Due to enhanced crystallization in the measuring cell and syringe at 25 °C (77 °F), refilling out of the syringe is not possible anymore. Therefore, the measurement mode …S tandard‟ is selected. After filling at the same filling temperature of 50 °C (122 °F), the sample is cooled down to the 25 °C (77 °F).For measurements at 20 °C (68 °F) and 15 °C (59 °F), the advanced solidification process significantly limits the repeatability of measurements.Table 3: Kinematic viscosity of red palm oil at different temperatures5.1.3Shea butterThe sample is preheated to 50 °C (122 °F) before filling. For analysis of shea butter with a freezing point in a range from 35 to 42 °C (95 to 108 °F), measurements with the precision class …P recise‟ are only possible at 40 °C (104 °F).Table 4: Kinematic viscosity of shea butter at different temperaturesFor 25 °C (77 °F), the precision class is changed to …Ultrafast‟. Whereas at 25 °C (77 °F) measurements with measuring mode …Repeated M ode‟ are completed, the increasing crystallization limitsrepeatable results at 20 °C (68 °F) and doesn‟t allow any valid determination at 15 °C (59 °F).5.2 Oil-based finished productsFor all tested cosmetic products, measuring results with measuring mode …R epeated M ode‟ at highest precision class …P recise‟ are obtained. The standard deviation of kinematic viscosity results for the tested beauty oil, the make-up remover oil as well as the body care oil range from ± 0.04 % to ± 1.50 % at maximum.Table 5: Kinematic viscosity of finished cosmetic products atdifferent temperatures6 ConclusionThe SVM™ 2001 is perfectly suited for determiningthe kinematic viscosity of pure oils used for theproduction of cosmetic products as well as for finishedoil-based cosmetic products, provided that equipmentand settings are in accordance with this report(see 4 “How to measure the samples?”). Results areobtained at highest precision class and show goodrepeatability.For the viscosity measurements close to a knownfreezing point, the SVM™ 2001 gives successfulmeasuring result as single point measurement with orwithout automatic repetition. If an automatictemperature scan is desired for measurements atvarious temperatures, consider also the SVM™ 3001,as it offers a specific measuring mode as well as fastheating and cooling rates.Contact Anton Paar GmbH****************************。
在角质细胞和EpiSkin表皮模型上测试化妆品原料对CD44蛋白表达的影响
Day6-5X
Day6-10X
Day6-20X
图 1 角质细胞在接种不同时间后的细胞形态
1.3.2 2D 人角质细胞的培养及原料处理
人 角 质 细 胞 在 含 10% FBS（Gibco）的 DMEM/
3.25
3.25
3.25
3.25
3.25
表 3 三维测试体系分组处理
分组 培养基加入的原料 原料在培养基中从终浓度
模型涂抹处理 每孔培养基体积 /mL
NT 0.01%Pro-VB5 0.03%Pro-VB5 0.1%HA+0.01%Pro-VB5
/ Pro-VB5
Pro-VB5
HA 和 Pro-VB5
和 HA 单独处理组和联合配伍组的二维细胞系统中
CD44 蛋白表达都有显著增加。
a.CD44 蛋白的表达
注：放大倍数为 40 倍 图 2 CEpiSkin 人表皮模型上的表达 如 图 4 和 图 5 所 示，各 处 理 组 相 比 对 照 组，
ZHOU Ming1,2, WANG Ping2, ZHU Yan1, QIU Jie2, DING Chunmei2, WANG Wei2 (1. School of life sciences, Fudan University, Shanghai 200433; 2. L'Oreal R&I Center, Shanghai 201206)
0.01%Pro-VB5 Pro-VB5 0.01% 3.25
0.03%Pro-VB5 0.1%HA+0.01%Pro-VB5 1.0%HA+0.01%Pro-VB5 DMSO 10 μmol/L RA
安东尼·巴尔产品说明书：SVM 3001或SVM 4001金属制造流体可见性仪器
Viscosity of Metalworking Fluids in Cutting ProcessesDetermined with SVM™ 3001 or SVM™ 4001 Viscometer Relevant for: machine shops for industrial production, manufacturing workshops,cutting fluid R&D, QC in cutting fluid productionMetalworking fluids are a vital part of manufacturing processes. Viscosity influences the liquid’s performance and the manufacturing quality. SVM™ is a fast and precise solution to measure viscosity and density, which are quality relevant parameters.Figure 1: Cutting fluid – essential for perfect surface quality1 IntroductionMetal working fluids (MWF) are complex mixtures of base liquids and additives, carefully selected and blended to provide optimum performance in a given application. There are different types: straight oils, oil-based water miscible fluids (emulsions, semi-synthetic fluids), and synthetic fluids.Metalworking fluids in cutting processesWater miscible fluids are one main group used in cutting processes such as drilling, milling, or turning, while oils are often used for grinding, honing, or threading. Their main function is to lubricate and cool the contact zone between a machine tool and a work piece. Depending on the combination of work piece and tool, but also on the cutting speed, different fluid compositions are required. Straight oils and oil concentrate are evaluated for viscosity and density, further for pour point, flash point and other parameters. When mixing concentrates with water, the correct dilution ratio can be checked with a refractometer. 2 Why measure viscosity?Viscosity has considerable influence on the properties of a cutting fluid. Higher viscosity improves the lubrication abilities of the fluid, but decreases the cooling performance. Lower viscosity provides better cooling performance and easier removal of solid particles. On the other hand, this may lead to a lack of lubrication between tool edge and work piece, especially at higher production speed. Poor surface quality and increased tool wear can occur. So viscosity affects the speed, at which the liquid fills the contact zone between cutting tool and work piece, and the thickness of the liquid film. Viscosity measurement helps to find a balance between fastest possible machine parameters and best possible surface quality of the work piece.The viscosity of cutting oils is typically specified and measured at 40 °C. Some manufacturers test the oil additionally at 100 °C and state the viscosity index. Other test the kinematic viscosity at 100 °F (37.78 °C) or state Saybolt viscosity (SSU – Saybolt Seconds Universal) at 100 °F (and 210 °F). Density is stated at 15 °C or 20 °C.Which samples are tested?Two different cutting oils were tested:Sample nameSample typeJokisch Monos Atos N3S(Special cutting oil S91)Cutting oil, free of mineral oilCastrol Honilo 980 Cutting fluid, hydrocarbon based,water insoluble3 Which instruments apply?The samples were tested with SVM™ 3001. This instrument serves for viscosity measurement according to ASTM D7042 and simultaneous density measurement according to ASTM D4052(ISO 12185). Additionally, the instrument can determine API density, Saybolt Viscosity and otherparameters. SVM™ 3001 also provides temperature and time scans for testing viscosity at different temperatures or over time.If viscosity index determination according to ASTM D2270 is required, SVM™ 4001 is suitable. It provides two measuring cells for simultaneous measurement with repeated determinations at two different temperatures.For quality control of kinematic viscosity at a single temperature only without the need of API density, SVM™ 2001 can be used.SVM™ can test all grades and types of cutting fluids with Newtonian properties.4 Measurement of cutting fluidsGenerally, the procedure is the same as for base oils or lube oils. Refer also to the Anton Paar Application Report “Viscosity of Lube Oils” (Doc. No. D89IA007EN) available on the Anton Paar Extranet.4.1 SettingsFor measurements according to ASTM D7042: •Method: Standard•Precision class: Precise•Automatic repetitions: 5•RDV limit: 0.10 %•RDD limit: 0.0002 g/cm³•Automatic prewetting: yes4.2 CalibrationUse only a calibrated instrument. The calibration shall be performed periodically using certified reference standards. According to ASTM D7042, the reference standards shall be certified by a laboratory, which meets the requirements of ISO/IEC 17025 or a corresponding national standard. Viscosity standards should be traceable to master viscometer procedures. The uncertainty for density standards must not exceed 0.0001 g/cm³. For each certified value. Theuncertainty should be stated (k = 2; 95 % confidence level). Use one or more standard(s) in the viscosity range of your oil sample(s). If required, apply a calibration correction to improve the reproducibility. To perform the calibration and to apply the correction,refer to the SVM™ X001 Reference Guide.4.3 Sample preparationIf the sample is not freshly drawn from a productionline or other reservoir, homogenizing the testspecimen may improve the measurement repeatability. For some samples, degassing may be required. Refer to the SVM™ X001 Reference Guide. 4.4 Filling5 mL single-use plastic syringes are recommended. Never use syringes with rubber seals, as the rubber is chemically not resistant to most oils. Further these syringes tend to suck bubbles. For SVM™ 4001, use a 10 mL syringe.Ensure that the system (measuring cells and hoses) is leak tight, clean and dry.Inject approximately 1.5 mL as first filling. After prewetting refill at least 1 mL or until the sample in the waste hose is free of bubbles. The typical amount for valid results is 4 to 5 mL for SVM™ 3001. The volume can vary depending on the sample.4.5 Cleaning4.5.1 SolventsPetroleum benzine 100/140 (aliphatic hydrocarbon solvent, blend of mainly C7, C8, C9 n-alkanes with a boiling range of 100 °C to 140 °C respectively 212 °F to 284 °F) was appropriate for the tested fluids. Depending on the chemical composition of cutting fluids, other solvents may be required. Some fluids may require an aromatic solvent, as they are not completely soluble in petroleum benzine. In that case, use toluene or xylene as first solvent and an aliphatic hydrocarbon solvent (e.g. n-Heptane) as drying solvent.Others may need an alcoholic component. In this case, a mixture of toluene and isopropyl alcohol can be a suitable solvent.The typical solvent amount was 6 to 8 mL per sample. For details, see the SVM™ X001 Reference Guide.4.5.2 Cleaning procedure•Tap the cleaning button to open the cleaning screen. Observe it during the cleaning procedure to get information on the cleaning status of theSVM™.•Remove the sample from the cells (push through using an air-filled syringe).•Fill approximately 2 mL of solvent using a syringe and leave the syringe connected.•For sticky or highly viscous oils: Tap the motor speed button to improve the cleaning performance in the viscosity cell. The cleaning screen shows the mixing of solvent and sample residue by change of viscosity. The density value indicates whether the cell is filled properly with solvent. Stop the motoragain.•Move the plunger of the syringe several times back and forth (motor at filling speed) to improve thecleaning performance in the cells.•Blow air through the cells for some seconds to remove the sample-solvent-mixture.•Repeat the procedure until the liquid has reached approximately the solvent’s viscosity while themotor is turning at high speed.•Perform a final flush with a drying solvent to remove any residues.•Observe the cleaning screen. Dry the measuring cells until the cleaning value turns green and stays steadily green.For details, see the SVM™ X001 Reference Guide.5 ResultsThis report compares results measured withSVM™ 3001 (ASTM D7042) with typical values from the product data sheets of the cutting fluids. The results of SVM™ 3001 are mean values obtained from a series (n = 12) of repeat measurements (cleaning in between the valid results).There are no specific standards available for cutting fluids. The viscosity specifications of industrial oils are more or less related to ISO 3448, which states a tolerance of ± 10 % to the specified kinematic viscosity at 40 °C. Manufacturer standards (OEM standards) may state more rigorous limits.ASTM D 7042 (and either ASTM D445) do not state any data for precision and bias of cutting fluids. Viscosity at 40 °CN3S (S91) 31.75 30 5.83 OK Honilo 980 4.281 4.5 -4.87 OK Table 1: Kinematic viscosity and deviation to typical valuesPrecision data of viscosity measurement:N3S (S91) 0.07 0.14Honilo 980 0.02 0.04Table 2: Standard deviation and repeatability of the measured oilsDensityMeasured density at 40 °CSample Density[g/cm³] Std. deviation[g/cm³]Repeatability(r; 2 σ)[g/cm³]N3S (S91) 0.9060 0.00005 0.00009 Honilo 980 0.8083 0.00003 0.00005 Table 3: Density, measured results and precision data N3S (S91) oil - API density at 20 °Typical value(Data sheet)[g/cm³]Dev. totypical value[g/cm³]0.9187 0.9 0.0187 Table 4: Jokisch N3S (S91) – determ. API density vs. typical value Honilo 980 oil - API density at 15 °Typical value(Data sheet)[g/cm³]Dev. totypical value[g/cm³] 824.11 824 0.11Table 5: Castrol Honilo 980 – determ. API density vs. typical value 6 ConclusionSVM™ 3001 is perfectly suited for determining the viscosity of cutting fluids, provided that all requirements according to section 4 “Measurement of cutting fluids” are fulfilled.Figure 2: SVM™ 3001 and SVM™ 4001Contact Anton Paar GmbH****************************7 Literature•Anton Paar Application Report: “Viscosity of lube oils” (Doc. No. D89IA007EN)•ASTM D7042: Standard Test Method for Dynamic Viscosity and Density of Liquids by StabingerViscometer™ (and the Calculation of KinematicViscosity)•EN ISO 3104: Petroleum products - Transparent and opaque liquids - Determination of kinematicviscosity and calculation of dynamic viscosity •ASTM D445: Standard Test Method for Kinematic Viscosity of Transparent and Opaque Liquids (and the Calculation of Dynamic Viscosity)•ISO 3448: Industrial liquid lubricants – ISO viscosity classificationAPPENDIX Appendix A. About cutting fluidsCutting is a chip-removing metalworking process using tools to shape a work piece. Main processes are e.g. turning, drilling, milling, grinding, or honing.Fluid typesCutting fluids can be:•Straight oils, which can be mineral oils, synthetic, vegetable, or animal oils. They provide very good lubricity properties, but are not designed for highmachining speeds. They consist mainly of a base oil with additives.•Emulsions, which are soluble oils mixed with water and other additives like corrosion protectors,surfactants, pH regulators, wear protectors, andbiocides. Such emulsions contain only a lowpercentage of the concentrate, the maincomponent is water. They have less lubricationproperties and their main field is cooling. They are suited for high machining speeds, where theworking zone is flooded with the liquid.•Semi-synthetic fluids containing small amounts of oil plus additives. They provide lower lubricity than oils, but high cooling performance.•Synthetic fluids, which are blended from different coolants, containing no oil. They are designed toprovide the properties of all other cutting fluids.They have high cooling performance, but notequally good lubricity as oils, produce no smoke,provide low surface tension and thus quick wetting properties. They are mainly used in high-speedturning of hard materials and for grindingprocesses.Importance of viscosityViscosity is important for:•Cutting oils, synthetic and semi-synthetic fluids.Further for concentrates before mixing them withwater.•Selection of the appropriate size and type of the fluid application system (pumps and nozzles). •The design of bulk storage and delivery system for cutting oils, coolant concentrates and othercompounds.Manufacturers state viscosity and density in various notations in their data sheets:•Kinematic viscosity at 40 °C, 100 °F (37.78 °C), sometimes at 100 °C, sometimes with VI •Dynamic viscosity at 25 °C•Saybolt Universal Seconds (SUS; SSU) •Density at 15 °C or 20 °C•Specific gravity at 20 °C or 25 °CAll these parameters can be determined using the suitable instrument of the SVM™ X001 series.Water diluted liquids (emulsions) have a low viscosity close to water and are normally not viscosity tested. However, the measuring results in Table 6 give an idea for the viscosity and density values of of an emulsion.Measured at 20 °CKin. Vis.[mm²/s]r; ( 2 σ)[%]Density[g/cm³]r; (2 σ)[g/cm³] Hi-Speed415(approx.conc. 5 %)1.374 0.9 1.0002 0.00017 Table 6: Kinematic viscosity and density of a cutting emulsion Cutting fluid monitoringTo extend the service lifetime of cutting fluids, they need to be checked regularly. Although contamination and degradation of the liquid also have effects on the viscosity, this parameter usually is not monitored.To check the concentration of the cutting fluid, refractometers are used.The content of tramp oil (unwanted lube oil which has leaked into the cutting fluid system) is analyzed by titration.Further pH-level and alkalinity are tested.。
重组人皮肤模型评价化妆品皮肤腐蚀性_刺激性替代方法的建立
LIU Zhen, LIU Junping, XU Guifeng, WANG Fei, et al.
The Second Military Medicine University, Shanghai 200433, China
Abstract: Objective Constructing reconstituted human engineered skin model, to establish an alternative approach for evaluating cosmetics skin corrosion and irritation. Methods A cut of human dermal tissue was taken, and the epidermis and dermis were separated respectively for primary cell culture. The reconstituted skin models were onstructed with rat tail collagen. Then, the models under air- liquid face were cultured. Skin models were affected by Chemicals for 3min or 1h in corrosivity test, and the models were affected for 15min in irritation test following with 42h culture. Then, the cytoactive were detected by MTT essay and IL- 1A releases level were detected by ELISA. Results In corrosion test, the cytoactive was declined < 50% ( 3min) and 15% ( 1h) after giving three corrosive chemicals. However, the cytoactive wasn. t change for two un- corrosive chemicals. In irritation test, three of four irritation chemicals caused cytoactive less than 50% , and another one made the IL-1Arelease more than 60pgPml in ELISA test. It seemed that all of four chemicals were irr itations. Conclusion It was suggested that constructing reconstituted human engineered skin model could be established as an alternative approach for predicting skin corrosion and irritation as possible.