钨酸盐与BTA对碳钢协同缓蚀作用的研究

采用电化学阻抗谱方法研究了钨酸盐和苯并三氮唑(BTA)对碳钢的协同缓蚀作用。两者单独使用时钨酸盐的缓蚀作用比BTA显著，复配使用时表现出协同缓蚀效应，升高pH对协同缓蚀作用有利。此外还用表面分析法分析了碳钢表面膜，证明Na2WO4和BTA参与了表面膜的形成。     

硝酸溶液中十二烷基苯磺酸钠对锌缓蚀作用的电化学研究

采用电化学极化曲线和电化学交流阻抗方法考察了在20℃～50℃温度的3%硝酸中不同浓度的十二烷基苯磺酸钠(SDBS)对锌的缓蚀作用.实验结果表明,SDBS能够同时抑制阳极和阴极反应起到缓蚀作用.通过增加锌电极表面膜的电阻,降低膜的电容,增加膜表面的覆盖度提高对锌的保护.用塔菲尔斜率外推法处理数据获得了电化学参数E,I和缓蚀率η,进而计算了动力学参数活化能.电化学交流阻抗方法可知锌电极表面膜电阻、电容与表面覆盖度,所得缓蚀率数据与电化学极化曲线所得数据相符.     

用交流阻抗谱研究活性砂浆胶结材料的电化学行为

海水环境潮差浪溅区钢筋混凝土结构易腐蚀破损,可采用锌网阳极与活性砂浆组成的牺牲阳极阴极保护系统进行修复保护.用交流阻抗谱方法对活性砂浆胶结材料的电化学性能进行了研究,并采用等效电路对阻抗谱进行拟合解析.结果表明:砂浆中掺入活性组分后,砂浆电阻显著降低,极化电阻与扩散阻抗系数也随活性组分的掺入大幅度降低；活性砂浆中阳极表面膜层不再是致密钝化的状态,表面易于进行阴极反应；活性组分同等掺量条件下,溴化锂更利于提高砂浆的电化学活性.     

复合材料低密度表面膜替代性研究

复合材料表面胶膜的面密度、结合力和最终产品的表观质量是影响表面膜工业化应用的关键因素。通过对比国内外常用FM99、J-266和EA9845系列表面膜的物理和工艺性能,从面密度、工艺性、结合力、脱模剂渗透性和最终表观质量等方面着手,研究进口低密度表面膜与国产低密度表面膜的替代性。经过多次、反复的工艺验证,确认了国产低密度表面膜与进口低密度表面膜的可替代性。     

复合材料表面膜的研究进展

复合材料表面膜因具有改善复合材料表面质量、减轻结构质量、节约制造成本等诸多优点,在航空航天复合材料构件制造中获得了广泛应用。总结了复合材料表面膜的研究历程,展望了复合材料表面膜研究发展方向。     

悬浮法聚氯乙烯树脂的形态结构

聚氯乙烯树脂形态的疏松与紧密对生产软质制品的加工和性能均有很大的影响。从树脂的形态结构着手,作者用电子显微镜观察了树脂的表面和剖面,用普通显微镜观察了树脂在增塑剂及溶剂中的行为,阐明了聚氯乙烯悬浮树脂的内外形态。提出了悬浮树脂形态结构的生成机理。认为明胶浮悬剂表面张力大,在聚合过程中料粒表面膜强韧,易生成单细胞颗粒(紧密型)。聚乙烯醇悬浮剂表面张力小,表面膜性碎易于兼并成多细胞颗粒(疏松型)。而后者比前者具有更大的空隙和更小的不均匀性。本文指出改变搅拌、界面张力及表面膜的稳定性有可能使单细胞树脂(紧密型)转化成多细胞树脂(疏松型)。     

复合材料表面膜的反应机理及固化行为研究

通过差示扫描量热仪(DSC)、红外光谱(FT-IR)、热失重分析仪(TGA)及流变仪对一种改性的环氧基复合材料表面膜的固化反应动力学、反应机理和热性能进行了研究。结果表明:表面膜的反应机理为环氧基与胺类的开环反应;确定了反应的固化工艺参数、反应的表观活化能Ea和频率因子A;表面膜在80~120℃呈低黏度平台区,具有较宽的加工工艺窗口;固化后表面膜的热失重温度约为347℃;此外,表面膜具有良好的悬垂性能。     

中性体系中MoO_4~(2-)对碳钢垢下局部腐蚀的抑制作用

设计了一种能够模拟垢下局部腐蚀自催化过程的闭塞电池,采用极化曲线和电化学阻抗方法研究了MoO42-对N80钢在近中性NaCl溶液中闭塞区内化学及电化学状态变化的影响。结果表明,MoO24-能有效地减缓闭塞区内pH值降低及Cl-浓集、减弱酸化自催化效应、抑制垢下局部腐蚀。MoO42-的作用机制在于使水合氧化铁腐蚀膜由阴离子选择性变为阳离子选择性,H 可以从膜下扩散出去,而Cl-难以扩散到膜下富集,抑制了腐蚀反应的阴极过程;同时MoO24-迁入闭塞区后增大了电极表面膜层阻抗,抑制了腐蚀反应的阳极过程。     

中性体系中MoO2-4对碳钢垢下局部腐蚀的抑制作用

设计了一种能够模拟垢下局部腐蚀自催化过程的闭塞电池,采用极化曲线和电化学阻抗方法研究了MoO2-4对N80钢在近中性NaCl溶液中闭塞区内化学及电化学状态变化的影响.结果表明,MoO2-4能有效地减缓闭塞区内pH值降低及Cl-浓集、减弱酸化自催化效应、抑制垢下局部腐蚀.MoO2-4的作用机制在于使水合氧化铁腐蚀膜由阴离子选择性变为阳离子选择性,H+可以从膜下扩散出去,而Cl-难以扩散到膜下富集,抑制了腐蚀反应的阴极过程;同时MoO2-4迁入闭塞区后增大了电极表面膜层阻抗,抑制了腐蚀反应的阳极过程.     

用椭圆偏光法研究玻璃表面膜的性质

本文介绍了利用椭圆偏光法测量玻璃表面膜的厚度和折射率;以观察玻璃风化过程中的表面膜做为例子,说明了本方法的实际应用。     

Electrochemical performances of lithium ion battery using alkoxides of group 13 as electrolyte solvent

Tris(methoxy polyethylenglycol) borate ester (B-PEG) and aluminum tris(polyethylenglycoxide) (Al-PEG) were used as electrolyte solvent for lithium ion battery, and the electrochemical property of these electrolytes were investigated. These electrolytes, especially B-PEG, showed poor electrochemical stability, leading to insufficient discharge capacity and rapid degradation with cycling. These observations would be ascribed to the decomposition of electrolyte, causing formation of unstable passive layer on the surface of electrode in lithium ion battery at high voltage. However, significant improvement was observed by the addition of aluminum phosphate (AlPO₄) powder into electrolyte solvent. AC impedance technique revealed that the increase of interfacial resistance of electrode/electrolyte during cycling was suppressed by adding AlPO₄, and this suppression could enhance the cell capabilities. We infer that dissolved AlPO₄ components formed electrochemically stable layer on the surface of electrode.     

Preparation, electrochemical characterization and charge–discharge of reticulated vitreous carbon/polyaniline composite electrodes

Polyaniline was electrodeposited onto reticulated vitreous carbon – RVC – in order to obtain a tridimensional composite electrode. Three variations of these electrodes were analysed: a small-anion-doped polyaniline (RVC/Pani), a polyanion-doped polyaniline (RVC/PaniPSS) and a bi-layer type formed by an inner layer of the first electrode and an outer layer of the second one (RVC/Pani/PaniPSS). These composites were characterized by cyclic voltammetry, scanning electronic microscopy and electrochemical impedance spectroscopy. Photomicrographies, voltammetric profiles and impedance data pointed to different morphological and electrochemical characteristics for polyaniline doped with small or large anions, and a mixed behavior for the bi-layer electrodes. Charge–discharge tests for these tridimensional (3D) electrodes, employed as the cathode in lithium batteries, indicated better performance for the RVC/Pani electrode. These RVC composites presented higher specific capacities when compared with those obtained for Pani deposited onto bidimensional substrates.     

Application of pulse methods to the determination of the electrochemical characteristics of lithium intercalates

The transfer processes proceeding in insertion electrodes with surface control on the application of a potential or current step are considered theoretically. The theoretical relationships have been verified by the determination of the kinetic and diffusion parameters of electrochemical lithium intercalation into thin carbon films. The overall electrode polarization is divided, both theoretically and experimentally, into the kinetic component, related to hindered ion transfer in the passive surface layer, and the diffusion one, related to decelerated lithium diffusion in the carbon matrix. The polarization dependence of kinetic current is shown to obey the same regularities that the current-potential function of the lithium electrode. The concentration dependences of the surface layer parameters and the diffusion coefficient of lithium in carbon have been determined.     

Reprint of “Suppressing propylene carbonate decomposition by coating graphite electrode foil with silver”

A method has been developed to suppress the decomposition of propylene carbonate (PC) by coating graphite electrode foil with a layer of silver. Results from electrochemical impedance measurements show that the Ag-coated graphite electrode presents lower charge transfer resistance and faster diffusion of lithium ions in comparison with the virginal one. Cyclic voltammograms and discharge-charge measurements suggest that the decomposition of propylene carbonate and co-intercalation of solvated lithium ions are prevented, and lithium ions can reversibly intercalate into and deintercalate from the Ag-coated graphite electrode. These results indicate that Ag-coating is a good way to improve the electrochemical performance of graphitic carbon in PC-based electrolyte solutions.     

Suppressing propylene carbonate decomposition by coating graphite electrode foil with silver

A method has been developed to suppress the decomposition of propylene carbonate (PC) by coating graphite electrode foil with a layer of silver. Results from electrochemical impedance measurements show that the Ag-coated graphite electrode presents lower charge transfer resistance and faster diffusion of lithium ions in comparison with the virginal one. Cyclic voltammograms and discharge-charge measurements suggest that the decomposition of propylene carbonate and co-intercalation of solvated lithium ions are prevented, and lithium ions can reversibly intercalate into and deintercalate from the Ag-coated graphite electrode. These results indicate that Ag-coating is a good way to improve the electrochemical performance of graphitic carbon in PC-based electrolyte solutions.     

The effects of oxidation on the surface properties of MCMB-6-28

Graphite is an important active material for lithium ion battery anode. In the present paper, a kind of graphitized MCMB (MCMB-6-28) was oxidized at 600 or 700 °C, and the effects of the oxidation were investigated by cyclic voltammetry (CV) method, electrochemical impedance spectroscopy (EIS), and rectangular potential technique. It was found that the specific surface area of the electrode made of the graphite can be increased notably by the oxidative treatment. Meanwhile, after oxidation, the electrochemical impedance of the graphite electrode is reduced, and the reaction reversibility is improved.     

The effect of an irreversible homogeneous reaction on finite-layer diffusion impedance

The mass-transfer boundary layer adjacent to an electrode can contribute to the measured AC impedance of the electrode. Simple diffusion of the reactant across a stagnant diffusion layer can be analyzed exactly, but complications arising from homogeneous reactions, variable properties, or ionic migration can modify the impedance, and more detailed analysis is required. This paper presents a computational method to handle such cases, particularly where non-linearity appears in the diffusion problem. The method involves both orthogonal collocation and matrix transformations to compute approximate concentration profiles and impedance behavior. An example of the method is given for the case of a catalytic EC mechanism, where a homogeneous reaction in the diffusion layer is coupled with the electrode process. The analysis shows how the reaction decreases the impedance of the diffusion layer by regenerating the electroactive reactant.     

储氢合金粉表面包覆镍硼合金的研究

储氢合金是影响镍氢电池性能的主要因素,对储氢合金进行表面处理可以有效提高镍氢电池的性能。本文对储氢合金表面进行包覆镍硼合金处理,通过扫描电镜(SEM)及X射线衍射分析(XRD)对电极表面进行了表征,测定了包覆前后镍氢电池的大电流放电性能,以交流阻抗法和循环伏安法对电极进行了评价。结果表明,包覆镍硼合金后,电化学阻抗减小,电极的大电流放电性能有所提高,循环寿命增长,对储氢合金表面包覆镍硼合金可有效提高镍氢电池性能。     

柠檬酸钠体系中Ni・Fe合金的电沉积行为

采用循环伏安曲线、电化学阻抗谱、计时电流曲线等方法对柠檬酸钠体系中Ni-Fe合金的电沉积行为进行了研究。结果表明:柠檬酸钠体系中Ni-Fe合金电沉积是一个受扩散控制的不可逆过程。随着电位的增大,电沉积依次经历了电化学活化阶段、电结晶成核阶段、动力学-扩散混合控制阶段和扩散控制阶段。阴极附近未被及时消耗的FeOH+会覆盖在电极表面,阻碍金属离子扩散到电极表面放电,使电化学阻抗谱低频端存在阻挡层扩散阻抗特征。随着电位的增大,Ni-Fe合金的成核速率逐渐加快。Ni-Fe合金的成核机制在低电位下表现为连续成核,在高电位下表现为瞬时成核。     

Electrochemical stability of thin film LiMn2O4 cathode in organic electrolyte solutions with different compositions at 55 °C

A survey of the electrochemical stability of electrostatic spray deposited thin film of LiMn₂O₄ was performed in LiClO₄-EC-PC, LiBF₄-EC-PC, and LiPF₆-EC-PC solutions at 55 °C. The solution resistance, the surface film resistance, and the charge-transfer resistance were all found to depend on the electrolyte composition. Among the LiX-salts studied, the lowest charge transfer-resistance, and surface layer resistance were obtained in LiBF₄-EC-PC solution. There is no major influence of the electrolyte solution compositions upon lithium ion transport in the LiMn₂O₄ bulk at 55 °C. The diffusion coefficient of lithium in the solid phase varied within 10⁻¹⁰-10⁻⁸ cm² s⁻¹ in the three solutions. In general, it seems that in LiBF₄ solutions, the surface chemistry is the most stable in the three solutions examined, and hence the electrode impedance in LiBF₄ solutions was the lowest. In LiPF₆ solutions, HF seems to play an important role, and thus, the electrode impedance is relatively high due to the precipitation of surface LiF.