光导薄膜表面静电荷积累过程的动力学特征

本文对电照相用高分子光导材料薄膜涂层的表面电性能进行了研究,确定了表面充电过程宏观动力学的表征方法、动力学方程以及影响电荷沉积速度的因素。     

In-situ Study of Charge and Discharge of Ni-MH Battery Using the Combined Method of Electrochemistry and Microcalorimetry

An apparatus to study the battery system has been set up. The thermal effects of charge and discharge of Ni-MH batteries have been studied. The calorimetric measurements indicate that the net heat dissipation during charging is larger than that during discharging. It is observed that the ratio of heat dissipation to charging energy varies with charging capacity, and almost 90 percent of charging energy is lost as heat dissipation near the end of the charging process at 97.7 mA. A jump of thermal curve near the end of discharge due to a secondary electrode reaction has been observed.This revised version was published online in November 2005 with corrections to the Cover Date.     

铝在KOH溶液中的惰化

用恒电流充电曲线法研究了C_KOH、C_Al以及电流密度对铝电极惰化的影响,得到i～τ^-1/2之间符合如下的不稳定扩散方程: 曲线由不同斜率的两条直线组成,i_L系铝腐蚀产生H₂搅拌的影响。同时,还求得了几种KOH溶液中C_Al^S和D_Al的值。 实验结果表明:低电流密度区,惰化过程受Al(OH)₄^-扩散控制,由过饱和Al(OH)₄^-溶液中析出成相的Al(OH)₃或Al₂O₃膜,引起电极惰化。高电流密度区,除扩散外,还可能由电化学反应直接形成表面惰化层。     

超级电容器用聚吡咯纳米粒子的比容量衰减机理研究

基于化学氧化聚合法制备了粒径约为40nm的掺杂对甲苯磺酸(TSA)的聚吡咯(PPy)复合纳米粒子.采用XRD、EDS、SEM和TEM研究了产物的结构和形貌特征,并用循环伏安、恒流充放电等方法测试了纳米粒子的电化学性能.结果表明PPy/TSA具有良好的快速充放电能力,在10 mA/cm2时比容量达到268Fg-1,但在1000次循环后发现其比容量下降了25.5%.用CV测试了PPy/TSA电极在第一次循环和第1000次循环的伏安曲线图,发现经过1000次循环后PPy/TSA电极的氧化峰逐渐消失,并且非法拉第电流减小.交流阻抗测试表明,PPy/TSA纳米粒子在反复充放电循环后,其界面电荷传递电阻增加,高频段双层电容值降低,但低频段的赝电容值却有所增加.通过比表面积测量发现,聚合物链的反复氧化-还原过程还可导致平均孔径减小、比表面积下降.红外和拉曼光谱也证实PPy纳米粒子在充放电过程中会发生降解,生成一种含氧的醌式结构,这表明聚合物电极材料比容量的下降可能与PPy主链的不可逆氧化和结构碎片化有关.     

Discrete electrostatic charge transfer by the electrophoresis of a charged droplet in a dielectric liquid

We have experimentally investigated the electrostatic charging of a water droplet on an electrified electrode surface to explain the detailed inductive charging processes and use them for the detection of droplet position in a lab-on-a-chip system. The periodic bouncing motion of a droplet between two planar electrodes has been examined by using a high-resolution electrometer and an image analysis method. We have found that this charging process consists of three steps. The first step is inductive charge accumulation on the opposite electrode by the charge of a droplet. This induction process occurs while the droplet approaches the electrode, and it produces an induction current signal at the electrometer. The second step is the discharging of the droplet by the accumulated induced charge at the moment of contact. For this second step, there is no charge-transfer detection at the electrometer. The third step is the charging of the neutralized droplet to a certain charged state while the droplet is in contact with the electrode. The charge transfer of the third step is detected as the pulse-type signal of an electrometer. The second and third steps occur simultaneously and rapidly. We have found that the induction current by the movement of a charged droplet can be accurately used to measure the charge of the droplet and can also be used to monitor the position of a droplet under actuation. The implications of the current findings for understanding and measuring the charging process are discussed.     

Effects of surface site distribution and dielectric discontinuity on the charging behavior of nanoparticles: a grand canonical Monte Carlo study

The surface site distribution and the dielectric discontinuity effects on the charging process of a spherical nanoparticle (NP) have been investigated. It is well known that electrostatic repulsion between charges on neighbouring sites tends to decrease the effective charge of a NP. The situation is more complicated close to a dielectric breakdown, since here a charged site is not only interacting with its neighbours but also with its own image charge and the image charges of all its neighbours. Coexistence of opposite charges, titration sites positions, and pH dependence are systematically studied using a grand canonical Monte Carlo method. A Tanford and Kirkwood approach has been applied to describe the interaction potentials between explicit discrete ampholytic charging sites. Homogeneous, heterogeneous and patch site distributions were considered to reproduce the titration site distribution at the solid/solution interface of natural NPs. Results show that the charging process is controlled by the balance between Coulomb interactions and the reaction field through the solid-liquid interface. They also show that the site distribution plays a crucial role in the charging process. In patch distributions, charges accumulate at the perimeter of each patch due to finite size effects. When homogeneous and heterogeneous distributions are compared, three different charging regimes are obtained. In homogeneous and heterogeneous (with quite low polydispersity indexes) distributions, the effects of the NP dielectric constant on Coulomb interactions are counterbalanced by the reaction field and in this case, the dielectric breakdown has no significant effect on the charging process. This is not the case in patch distributions, where the dielectric breakdown plays a crucial role in the charging process.     

THE CHEMILUMINESCENCE OF CERTAIN INDOLES*

Abstract— A series of twenty-four indoles and related compounds have been examined for chemiluminescent activity in aqueous solution and in dimethylsulfoxide. Seven compounds were found to chemiluminesce in the presence of base and peroxydisulfate in aqueous solution and eleven compounds gave chemiluminescence in dimethylsulfoxide with base using oxygen as the oxidizing agent. The relative intensities have been determined. There is no clear correlation between substitution patterns and the presence of chemiluminescence in either series. Some preliminary kinetic studies have been made on the indole system. Product studies indicate that the indole is degraded by at least two different pathways and that chemiluminescent process is probably only a small fraction of the total chemical change occurring.     

THE INFLUENCE OF FLUORESCENCE CONCENTRATION QUENCHING ON THE EMISSION ANISOTROPY OF FLAVINS IN GLYCERINE-WATER SOLUTIONS

The measurements of the emission anisotropy r/r0 of flavomononucleotide (FMN) within a range of concentrations of 10(-5)-10(-1) mol/L in glycerine-water solutions of different viscosities--0.056 Pa/s (system I) and 0.256 Pa/s (system II) have been carried out. In the range of high concentrations the repolarization effect due to the sharp drop of the quantum yield has been observed. The experimental results have been compared with theoretical expressions evaluated by taking into account both concentration and rotation depolarization. A good agreement on the values of the theoretical parameters obtained from independent measurements has been found. It has been stated that in the investigated systems the excitation energy transfer may be treated as a Markov process.     

Interaction of activated carbon electrodes with sulfuric acid solutions

Impedance and potentiodynamic studies have been carried out to investigate reversible processes on the surface of electrodes based on activated carbon (AC). Relationships have been found between the reversible capacity and true resistance, on the one hand, and the potential, on the other. Stoichiometric characteristics of AC charging in sulfuric acid have been obtained. A mechanism of the reversible surface process is suggested. It is concluded that Faraday pseudocapacity makes a considerable contribution to charging of AC electrolytes. The amount of gas liberated in the course of AC wetting in electrolyte has been measured. It is assumed that the amount of liberated gas depends on the amount of active oxygen involved in the current-forming reaction. Based on the data obtained, a redox surface reaction is substantiated in general form.     

Supercapacitor carbon electrodes with high capacitance

Electrochemical behavior of electrodes on the basis of CH900-20 activated carbon (AC) cloth has been studied in concentrated sulfuric acid solution. Cyclic voltammetric curves have been studied in the reversibility range (from 0.1 to 0.9 V RHE) and in the deep cathodic charging potential range (from –0.8 to 1 V RHE). It has been shown that electric double layer (EDL) charging occurs in the reversibility range, while faradaic processes of hydrogen intercalation into AC carbon take place in the range of negative potentials (←0.1 V). The intercalation process is governed by slow solid-phase hydrogen diffusion. The specific charge value grows at an increase in concentrated sulfuric acid solution. The mechanism of double intercalation of sulfuric acid and hydrogen into the AC material is suggested. On the basis of the reached specific discharge capacitance of 1,560 C/g (or 1,110 F/g) and Faraday's law, it has been concluded that the compound of C₆H is formed in the limiting case of deepest cathodic charging. The obtained data have been used in a mathematical charge–discharge model for an AC electrode taking into account the EDL charging and the hydrogen intercalation. The galvanostatic recharge curves have been calculated in the diapason of currents by the developed model.     

电渗析法再生离子交换树脂的进展

文章介绍了电渗析法再生离子交换树脂原理和适用的工艺流程。长期以来此法因电流效率低下而阻碍了其工业应用。最近此法在流程上作了变化，并在处理含铜废液的实验设备上取得了成功，电流效率提高到30～40％。这是进一步推广应用此法的可喜进展。     

气氛对尼龙1010热降解的影响

利用ＴＧ和ＤＴＡ研究了尼龙１０１０在Ｎ２气和空气流巾的降解过程和动力学，考察了反应气氛对降解步骤．降解温度、降解率和动力学参数的影响，分析了两者降解机理的可能差别．发现空气中的热氧降解为多步反应，而Ｎ２气中的热降解为一步反应Ｚ降解温度和降解率，Ｎ２气中均高于空气中；表观反应级数Ｎ２气中为１．０，空气中为１．１级．     

THE pH DEPENDENCE OF TRANSIENT CHANGES IN THE CURVATURE OF THE PURPLE MEMBRANE*

Abstract– We have observed transient changes in the curvature of purple membrane fragments upon photoexcitation as a function of the pH of the suspending medium. The room temperature suspensions have low ionic strengths, and the bending is observed by changes in the scattered light at 320 nm. The photoexcitation is from a 20 ns laser pulse at 532 nm. We use a simple first-order approximation to subtract any changes in the scattered light associated with transient absorption changes during the photocycle. The resultant scattering curves are then fitted to the sum of three fundamental bending processes. Each process has an exponential rise, an exponential decay and an amplitude. We model two of the processes as transient forces correlated with the charge motion during the photocycle. The third process is probably cuased by local changes in the pH as the protein pumps protons. However, this is not proved rigorously. Additional experiments are proposed.     

硼特效树脂吸附硼的动力学研究

采用动边界模型对硼特效树脂XSC-800吸附模拟废水中硼酸根离子的动力学进行了描述.采用有限浴方法考察了体系温度、搅拌速度、树脂粒径及溶液中硼酸根离子浓度对交换过程的影响,并得到了交换动力学总方程.确定了硼酸根离子的交换过程属颗粒扩散控制,交换过程的表现活化能为20.38kJ/mol,表观反应级数为1.661.     

低能量链端对聚苯乙烯薄膜铺展和润湿行为的影响

通过低能量功能端基的表面富集作用,研究了聚苯乙烯（ＰＳ）薄膜在聚甲基丙烯酸甲酯（ＰＭＭＡ）表面上的铺展和润湿动力学．用光学显微镜跟踪了ＰＳ薄膜的润湿行为,并对高分子熔体膜中非连续部分尺寸的增大速率进行了测定．分别用ＸＰＳ和ＡＦＭ对ＰＳ薄膜的表面组成和ＰＳ液滴的平衡接触角进行了测定．发现具有低表面能的氟碳端基在薄膜表面富集使ＰＳ薄膜的表面张力下降,并使ＰＳ液滴在ＰＭＭＡ表面上的平衡接触角减小,从而使高分子熔体膜中非连续部分尺寸的增长速率下降,得到了与液液界面铺展和润湿理论一致的实验结果．     

Hydrogen absorption kinetics of V–Al alloy

The vanadium–aluminum alloy has been prepared by aluminothermy process. The alloy ingot obtained was refined by electron beam melting and homogenized by vacuum arc melting technique. The refined alloy was crushed into small pieces. These pieces were kept isothermally in a thermobalance attached to the Sieverts apparatus for the hydrogen charging. Reacted fraction α was calculated using isothermal thermo-gravimetry method. The reacted fraction α–t data thus obtained have been linearly fitted over a suitable reaction mechanism function. Rate constants at different temperatures are determined using slope of these linearly fitted curves. Activation energy of hydrogen charging has been calculated using Arrhenius equation.     

共聚物铑配合物催化甲醇羰基化制备醋酸的反应动力学分析

以共聚物铑配合物催化甲醇羰基化经醋酸甲酯到醋酸的反应，具有高稳定性、高活性的特点．本文通过对作者近期研究工作的总结，绘出此催化反应全过程的循环图，并在此基础上求出有关动力学参数，结果计算值与实验值相符，证明此机理的合理性，并讨论了几种共聚物配体之间的差异．     

GRAFT COPOLYMERIZATION OF ACRYLAMIDE ONTO THE UV-RAY IRRADIATED FILM OF POLYESTER-POLYETHER

In this paper the Ce(Ⅳ) salt initiated graft copolymerization of acrylamide onto the film of polyesterpolyether block copolymer irradiated by UV-ray was reported. The UV-irradiation of the film and its graft process have been investigated by UV spectrum, ESR and ESCA and the influence of other factors on the graft copolymerization has been discussed.     

离子交换法从醋酸溶液中提取脯氨酸的研究

本文研究了脯氨酸在732,DO01,DH-8三种阳离子交换树脂上的静态吸附特性,发现732树脂的吸附容量最大,速度最快。并选用732树脂,研究了它从醋酸脯氨酸水溶液中吸附脯氨酸的动态过程。最后,以氨水为洗脱剂,考察了不同氨水浓度,洗脱速度对洗脱过程的影响。     

Characterization of Langmuir-Blodgett film using differential charging in X-ray photoelectron spectroscopy

Differential charging is often regarded as a problem in X-ray photoelectron spectroscopy (XPS) studies, especially for insulating or partially conducting samples. Neutralization techniques have been developed to circumvent this effect. Instead of neutralizing the positive charge, which is often the technique to obtain good quality data, it is possible to exploit this phenomenon to get useful information about the sample. An attempt is made here to use this differential charging to study the mono- and multilayer Langmuir-Blodgett (LB) films of cadmium arachidate on silicon substrate. The surface potential was probed by measuring XPS line shift with respect to their neutral position and was found to have correlation with the thickness of the films. No differential charging was observed in the monolayer LB film where there was only one layer of cadmium headgroup. Significant differential charging was observed for multilayer films, the total charging as well as the differential charging in these films increase with increasing number of layers. Angle-resolved XPS measurements were performed to obtain additional information about the structure of the films. Charging of the upper layer of the films close to the vacuum interface was found to be less compared to that of the interior. The discrete cadmium layers were found to be more differentially charged compared to the continuous hydrocarbon stacks in the multilayer LB films. Charging of the discrete cadmium layers has been utilized to obtain quantitative information of the multilayer LB films.