Epitaxial Growth and Thermoelectric Measurement of Bi2Te3/Sb Superlattice Nanowires

Superlattice nanowires are expected to show further enhanced thermoelectric performance compared with conventional nanowires or superlattice thin films. We report the epitaxial growth of high density Bi₂Te₃/Sb superlattice nanowire arrays with a very small bilayer thickness by pulse electrodeposition. Transmission electron microscopy, selected area electron diffraction and high resolution transmission electron microscopy were used to characterize the superlattice nanowires, and Harman technique was employed to measure the figure of merit (ZT) of the superlattice nanowire array in high vacuum condition. The superlattice nanowire arrays exhibit a ZT of 0.15 at 330 K, and a temperature difference of about 6.6 K can be realized across the nanowire arrays.     

Electrochemical formation and composition analysis of Zn x Cd1-x Se solid solutions

The direct growth of ZnSe–CdSe solid solution onto metallic cathodes by electrodeposition from acidic aqueous sulphate solutions is described. The plating process is studied by simple voltammetry, while the structure and composition of the electrolytic deposits are investigated by X-ray diffraction. The experimental d-spacing values of the as-grown mixed lattice are compared to data from reference Zn _x Cd_1-x Se pellets of standard composition, produced by a sintering method. The findings are supplemented with energy-dispersive X-ray (EDX) elemental analysis. Thereupon, the variation of the mole fraction x in Zn _x Cd_1-x Se, and the solid phase constitution of the electrodeposits are determined and correlated to the electrochemical conditions of growth. The resulting films contain admixtures of CdSe compound and metallic Cd.     

悬浮粒子对电沉积Zn粉缓蚀性能的影响

在ＺｎＣｌ２镀槽中悬浮一定量的不溶性粒子，如石墨ＰｂＣ２，ＳｎＯ２，ＴｉＯ２，ＳｉＯ２等，电沉积制备Ｚｎ粉，并对其结构，形貌及腐蚀行为进行分析，ＳＥＭ的结果表明使用悬浮法可阻止Ｚｎ枝晶生长，悬浮ＰｂＯ２，ＳｎＯ２，ＴｉＯ２，ＳｉＯ２或Ｉｎ２Ｏ３等能明显地提高Ｚｎ粉在５ｍｏｌ／ＬＫＯＨ溶液中的缓蚀能力此外，文中还应用于分形理论对结果作了进一步讨论。     

Electrochemical characterization of Ni–Fe alloy codeposition under MHD control

The nickel–iron alloy electrodeposition is affected by a superimposed magnetic field. Some previous papers [Msellak et al., Magnetohydrodynamics, 39:487–493, 2003 and Msellak et al., J Magn Magn Mat, 281:295–304, 2004] have exhibited some dramatic changes in iron amount and morphology of these deposits. As it is usual for a magnetic field up to 1 T, no charge transfer effect can be expected, and the observed modifications can be explained by the magnetohydrodynamic convection that controls the iron species flux during the electrochemical reaction. By electrochemical impedance spectroscopy and physical investigations (scanning electron microscopy, X-ray diffraction, and inductively coupled plasma), the reduction process is analyzed, the characteristic parameters of the mechanism are determined, and the magnetic field effects can be quantified. Contribution to special issue on “Magnetic field effects in Electrochemistry”.     

(110)晶面全择优取向Cu镀层的制备及其条件优化

研究了添加剂聚乙二醇(PEG)、氯离子(Cl－)和电流密度对Cu的电沉积过程的影响, 着重探讨了制备(110)晶面全择优取向Cu镀层的电沉积条件及其形成机理. 循环伏安(CV)结果表明, PEG阻化Cu的电沉积, Cl－加快Cu的电沉积速率. XRD实验结果表明, PEG和Cl－在一定浓度范围有利于(110)晶面择优取向; 这两种不同特性的添加剂的协同作用可以制得(110)晶面全择优取向的较薄的Cu镀层; 所制备的全择优Cu镀层较稳定. 全择优取向Cu镀层形成的机理在于PEG和Cl－吸附过程联合起作用, 在不同晶粒的不同晶面进行选择吸附, 改变了晶面的生长速率及晶粒的快生长方向.     

镀液中Ce^3＋离子对锡镀层结构缺陷和可焊性的影响

应用荧光分析法、X光电子能谱法(XPS)及正电子湮没寿命谱法(PALS)等研究了从含硫酸铈添加剂的酸性光亮锡镀液获得的锡镀层结构缺陷与可焊性的关系。结果表明,电镀时Ce与Sn不发生共沉积,Ce~(3+)的主要作用是阻化Sn~(2+)的水解和氧化使镀液稳定,因而使锡镀层纯度提高、结构致密、表层氧含量减少,有利于提高镀层的可焊性。当Ce~(3+)浓度控制在3.5g/L左右时,可使镀层结构缺陷较少,可焊性较佳,说明结构缺陷是影响锡镀层可焊性的直接原因。     

镧与镍共沉积的研究

由于含稀土的合金新材料具有多种特殊功能，因此，其制备技术已为人们所关注．制备含稀土合金的方法有高温烧结法、真空蒸发法、离子溅射法及电化学法等．其中电化学法设备简单，容易获得不同组份的表层材料，但是，由于稀土元素的电位很负，从电解质水溶液中沉积稀土及其合金是相当困难的，以往曾有采用熔融盐电解质或非水电解质制备稀土合金的一些报导[1，2]，而从电解质水溶液中电沉积稀土合金的报导甚少．本研究采用适宜的络合剂，实现了从电解质水溶液中电沉积Ni－La合金，镀层中钠含量最高达22．58％（质量分数，下同）．通过XPS及…     

在LiCl-KCl-NaCl熔盐体系中碳的阴极还原的研究

用循环伏安法和电位阶跃法研究了LiCl-KCl-NaCl熔盐体系中碳的阴极还原机理。在钨、铂、不锈钢等微电极上得到的伏安图表明碳的还原是由CO_3~(2-)离子经一步电化学反应实现的,电极反应速度控制步骤为CO_3~(2-)离子向阴极的扩散过程,还原过程具有反应物吸附特征。碳在W、Pt、不锈钢电极上析出电位分别为-2.05V、-1.745V和-1.90V(均相对于Ag/AgCl参比电极)。     

Electrochemical Study of Indium in a Water‐Stable 1‐Ethyl‐3‐Methylimidazolium Chloride/Tetrafluoroborate Room Temperature Ionic Liquid

The electrochemistry of indium species was investigated at glassy carbon, tungsten and nickel electrodes in a basic 1‐ethyl‐3‐methylimidazolium chloride/tetrafluoroborate ionic liquid. Amperometric titration experiments suggest that In(III) chloride is complexed as [InCl₅]^2? in this ionic liquid. The electrochemical reduction of [InCl₅]^2? to indium metal is preceded by overpotential driven nucleations. The effective anodic dissolution of indium to indium(III) requires, however, the presence of sufficient chloride ions at the electrode surface. The electrodeposition of indium at glassy carbon and tungsten electrodes proceeds via three‐dimensional instantaneous nucleation with diffusion‐controlled growth of the nuclei. At the nickel electrode, the deposition proceeds via three‐dimensional progressive nucleation with diffusion‐controlled growth of the nuclei. Raising the deposition temperature decreases the average radius of the individual nuclei, r. Scanning electron microscopic and x‐ray diffraction data indicated that bulk crystalline indium electrodeposits could be prepared on nickel substrates within a temperature range between 30 and 120 °C.     

Electrochemical technique for the determination of fractal dimension of dental surfaces

Fractal dimension of a carious tooth surface was determined using an electrochemical method. The method was based on time-dependent diffusion towards electrode surfaces, which is one of the most useful and reliable methods for the determination of fractal dimension of electrode surfaces. For this purpose, the tooth was covered with a gold layer, which acted as an electrode in electrochemical experiments. It is suggested that the fractal dimension can be used as a quantitative measure of the state of dental surfaces. The method presented demonstrates the power of electrochemical techniques for the determination of fractal dimension of surface of non-conducting objects.