对惠斯顿电桥法离子电导测量电路的讨论

采用平衡假设法推导了几种不同惠斯登交流电桥电路在测量电解液离子电导时的电桥平衡条件;探讨了几种电路的优缺点以及实际测量过程中可变电容及可变电阻的取值原则;有助于本科生深入理解并掌握离子电导的测量原理与方法。     

对物理化学电导测量电路图的改进

通过电学理论对测试溶液电导的等效电路进行分析,并在测试电导的实验条件下进行了电化学阻抗测量,以所获得的电化学阻抗数据为依据,提出电导测量中正确的测量方法。     

电化学测试中溶液电阻的自动测量与补偿

由16位DAC器件作为分压器,设计了恒电位仪以及正反馈补偿电路,实现了对溶液电阻的自动测量和补偿,同时采用高阻抗体系对其溶液电阻测量的准确性和补偿效果进行了验证.结果表明,溶液电阻最高补偿值可达1.0×10(8)Ω,在可补偿电阻范围内,自动电阻测量误差最大不超过1.5%,平均误差小于0.5%.本实验设计的电路可以较精确...     

电导滴定

溶液电导的测定,可用来做酸碱滴定或沉淀滴定,以计算溶液的浓度。如在强碱溶液中,慢慢滴入强酸溶液,则OH~-渐渐减少,电导亦随之减少,至电导减至最小时,即表示OH~-已完全中和,再多加一滴酸则因H~+的生成又使电导加大。这样,假若我们在一定量的碱溶液内,慢慢的滴入酸溶液,在滴定的过程中,随时测定溶液的电导,将结果作图,用所加入的酸溶液的体积为横标,比电导为纵标,当得两个直线,这两个直线的交点,就是中和点。在实际做物理化学实验时,我们是用威斯登电桥,求溶液的电阻的,所以我们只须用威斯登电桥上的数为纵标作图即可。我们知道,为了避免电解作用或极化作用的发生,我们测电导时的电源一定要用交流电,而且因为我们要用耳机听音去找平衡点,所以     

示波电导滴定

通常的电导滴定用电导仪测量滴定过程中溶液电导率的变化;以电导值对滴定剂体积作图,将两条直线外推,其交点为等当点。本文提出的示波电导滴定法,利用示波图的突然收缩或扩张指示滴定终点,简便快速,终点直观,适用于各类滴定反应。 1 原理 当交流电源输出电压为V=V_0sinωt,交流电频率较高,溶液浓度较稀时,“E～t”曲线与“i～t”曲线的相位差接近0°,电解池的阻抗接近纯电阻。若溶液电阻为R_L、外加电阻为R_0,则流     

电化学合成聚苯胺粉末电极的电化学行为研究

我们曾用慢速动电位扫描法研究化学合成聚苯胺粉末的电化学行为.本文对恒电位电解合成聚苯胺粉末进行了研究.用这种方法制备的粉末由于合成溶液中不含氧化剂因而纯度高.本文还报导了这种聚苯胺粉末电极的交流阻抗测量结果.交流阻抗法曾用于聚苯胺膜的电导和化学合成聚吡咯的电阻测定. 所用盐酸、氟硼酸、硅氟酸、苯胺均为分析纯;苯胺经常压蒸馏提纯;硫酸为超纯;磷酸为分析纯;高氯酸为优级纯.溶液皆用两次蒸馏水配制.     

Ba12Y4.67Ti8O35的交流阻抗谱和氧浓差电势测量

用高温固体合成法制备了经验分子式为Ba12Y4.67Ti8O35的导电陶瓷.利用交流阻抗谱技术、氧浓差电势测量和热电效应测量等方法表征了材料的导电性能.研究指出, 该材料是一种氧离子/空穴混合导体.在700 ℃下，材料本体的电导约为2×10－3 Ω－1•cm－1，氧离子迁移数为0.35.对700 ℃下空气、O2和N2气氛中的交流阻抗谱数据进行了等效电路拟合.拟合指出，在空气和O2气氛中，氧离子的扩散阻抗谱不能明显地观察到是因为氧离子电导通路被空穴电导短路；而在N2气氛中，阻抗谱在低频段表现出特征的扩散阻抗.     

钒液流电池用石墨毡电极电化学活化机理的交流阻抗研究

研究了不同氧化程度下的石墨毡在钒溶液中的吸附性、润湿性及其交流阻抗图谱(EIS), 结果发现随着氧化程度增加, 吸附性和润湿性增强; 交流阻抗谱包括两个半圆和一条直线, 高频半圆对应离子的吸脱附反应, 低频半圆对应电化学反应, 直线对应离子在溶液中的扩散过程. 随石墨毡氧化程度的增加, 低频半圆显著减小, 通过等效电路拟合及动力学参数计算, 发现电荷传递电阻显著减小.     

电化学阻抗谱研究铈盐转化膜形成过程中的影响因素

应用电化学阻抗谱(EIS)连续测试B95铝合金在0.01 mol·L-1CeCl3溶液中铈盐转化膜的形成过程,通过成膜过程中交流阻抗值的变化研究了温度,溶解氧O2的变化对B95铝合金稀土转化膜成膜过程的影响机制,采用等效电路的方式对测试的EIS进行了解析.结果表明:温度在20,25,30 ℃时B95铝合金在0.01 mol·L-1CeCl3溶液中的阻抗谱等效电路与成膜形成阶段的相同;温度为35,40,45℃B95铝合金的阻抗谱与成膜成长阶段的等效电路相同,表明升高温度缩短了稀土膜形成阶段的时间,铝合金基体溶解迅速被抑制;升高温度有利于铈盐氧化膜的形成;通O2对稀土Ce转化膜的形成无明显促进作用,O2参与的反应不是Ce转化膜形成的决速步骤.     

电化学交流阻抗复数平面图和电容复数平面图上相似图 …

提出并证明等效电路中含有Ｗａｒｂｕｒｇ阻抗的电化学交流阻抗复数平面图和电容复数平面图上相似图形效电路的变换规则。推而广之，对任意包含有Ｗａｒｂｕｒｇ阻抗或其变换的效电路，有着同样的变换规则。     

拉氏变换阻抗分析测量CdSe薄膜电极的表面态

在光电化学光能转换的研究中,由于多种因素在半导体/溶液界面形成了各种性质和作用不同的表面态,在界面的电荷和能量转移中起着重要作用,对光电转换性能产生较大的影响。对于多晶半导体——作为具有实用前景和目前深受重视的光电转换材料,由于存在较多的晶格缺陷和晶粒界面,在表面形成了浓度较高的表面态,这些表面态可作为光生电子空穴的复合中心,是造成多晶材料光电转换效率低于单晶材料的主要原因。因此测量和研究半导体/溶液界面的表面态能量分布,性质及作用对研究光电转换过程的机理,特别是对改善多晶半导体的性能都具有直接的重要意义。     

The use of electrochemical impedance spectroscopy (EIS) in the evaluation of the electrochemical properties of a microbial fuel cell

Electrochemical impedance spectroscopy (EIS) has been used to determine several electrochemical properties of the anode and cathode of a mediator-less microbial fuel cell (MFC) under different operational conditions. These operational conditions included a system with and without the bacterial catalyst and EIS measurements at the open-circuit potential of the anode and the cathode or at an applied cell voltage. In all cases the impedance spectra followed a simple one-time-constant model (OTCM) in which the solution resistance is in series with a parallel combination of the polarization resistance and the electrode capacitance. Analysis of the impedance spectra showed that addition of Shewanella oneidensis MR-1 to a solution of buffer and lactate greatly increased the rate of the lactate oxidation at the anode under open-circuit conditions. The large decrease of open-circuit potential of the anode increased the cell voltage of the MFC and its power output. Measurements of impedance spectra for the MFC at different cell voltages resulted in determining the internal resistance (R(int)) of the MFC and it was found that R(int) is a function of cell voltage. Additionally, R(int) was equal to R(ext) at the cell voltage corresponding to maximum power, where R(ext) is the external resistance that must be applied across the circuit to obtain the maximum power output.     

A Contactless Impedance Probe for Simple and Rapid Determination of the Ratio of Liquids with Different Permittivities in Binary Mixtures

Simple contactless cells with planar or tubular electrodes have been designed for measurement of the permittivity of solutions. The cells, connected to an integrated circuit of astable multivibrator, respond primarily to the capacitance component of the cell impedance, the multivibrator frequency depends in a defined manner on the solution permittivity and is readily used as the analytical signal in determinations of the ratios of components in binary liquid mixtures; water solution of methanol, ethanol and dioxane have been tested. The response of the cell with planar electrodes satisfies well the simple theoretical model and both the cells provide results with a sufficient sensitivity, a low LOD value (units of %vol) and a good precision (around 1%rel). The cell simplicity, small dimensions, long‐term stability and the possibility of powering them from a battery make them suitable for hand‐held meters. As an example of application in practice, the content of ethanol was determined in the car fuel petrol.     

Properties of the Contactless Impedance Detector with Insulated Wire Electrodes Placed Inside the Flowing Liquid Stream

The behavior of a flow cell, in which the impedance is measured between two insulated wire electrodes located within the stream of the test liquid, is described and compared with that of a semi‐quantitative theoretical model. A new approach is used to the monitoring of the impedance signal, based on connecting the cell as the input impedance of an operational amplifier in the differentiating circuit. A triangular AC voltage is fed to one of the electrodes and the other electrode is connected to the amplifier input. The square‐wave voltage at the amplifier output depends at low frequencies (from hundreds of Hz to several kHz) on the capacitive component of the overall impedance. The basic analytical parameters are in satisfactory agreement with the model and are comparable to those obtained with common contactless impedance detectors operating at higher frequencies of hundreds of kHz to a few MHz and monitoring primarily the conductance component of the impedance. The system described offers new detection possibilities, mainly for nonionic analytes of varying polarities.     

Protective Properties of Zinc-Rich Coatings: An Impedance Method Estimate

The impedance of zinc-rich polymer coatings on steel in a 3-% NaCl solution is studied. The electrochemical behavior of the electrode is satisfactorily described by an equivalent circuit that contains a constant-phase element, which reflects fractal properties of the zinc surface in the binder. From the results of calculations of the circuit elements for metal-rich electrodes with different zinc contents computed are fractions of the active area of the surface of the coating and its fractal dimensionality.     

Mg-Li电极在NaCl溶液中的电化学行为

应用熔炼法制备含Li量为8.5%和14%的两种Mg-Li合金,分别由电势线性扫描、计时电流、交流阻抗和失重法等检测Mg-Li电极在NaCl溶液中的电化学特性,SEM观察其放电表面形貌.结果表明:Mg-14Li电极比Mg-8.5Li电极有较负的开路电位、更大的放电电流和较高的放电效率,但附着电极表面的疏松产物易于脱落.Mg-8.5Li电极的放电效率高于Mg-14Li电极的放电效率.两种电极在低恒电位放电电流效率均高于较高恒电位的放电电流效率.     

Electrochemical Impedance Characterization of Nafion‐Coated Carbon Film Resistor Electrodes for Electroanalysis

Carbon film disk electrodes with Nafion coatings have been characterized by electrochemical impedance spectroscopy (EIS) with a view to a better understanding of their advantages and limitations in electroanalysis, particularly in anodic stripping voltammetry of metal ions. After initial examination by cyclic voltammetry, spectra were recorded over the full potential range in acetate buffer solution at the bare electrodes, electrodes electrochemically pretreated in acid solution, and Nafion‐coated pretreated electrodes in the presence and absence of dissolved oxygen. EIS equivalent circuit analysis clearly demonstrated the changes between these electrode assemblies. In order to simulate anodic stripping voltammetry conditions, spectra were also obtained in the presence of cadmium and lead ions in solution at Nafion‐coated electrodes, both after metal ion deposition and following re‐oxidation. Permanent changes to the structure of the Nafion film occurred, which has implications for use of these electrode assemblies in anodic stripping voltammetry at relatively high trace metal ion concentrations.     

An investigation of lithium intercalation into the carbon nanotubes by a.c. impedance

The closed and open carbon nanotube electrodes have been studied as a function of frequency and the open circuit cell potential. A comparison of these spectra reveals different behaviors depending on the form of the carbon nanotubes: for the closed carbon nanotubes the impedance spectra consists of only one arc in the high frequency, for the open carbon nanotubes the impedance spectra consists of two separated semicircles in the high frequency. Analysis based on plausible equivalent circuit models for the carbon nanotubes lead to evaluation the kinetic parameters for the various physicochemical processes occurring at the electrode/electrolyte interface.     

Impedance method of zone localization for paper chromatography which obviates the need for preliminary spraying

In 1936, Blake suggested and then applied radio-frequency currents to chemical analysis. He demonstrated that when a Rf current pulses through a solution from which the electrodes are separated by an insulator the impedance of the circuit is comparable to that of a condenser bridged by a resistance. The author again makes use of such a circuit in his radio-frequency zone locator for paper chromatographs. Details of the circuits are given together with illustrative diagrams. A feature of this method is that the need for spraying the chromatographs is obviated. It is also suggested that a technique for quantitative measurement of the contents of each zone may be developped.