多孔金属连续电沉积数学模型

采用电沉积方法制备连续多孔金属,通过把电流密度随时间的变化转换为镀区内的位置分布,建立了稳恒状态下高孔率带状多孔金属连续电沉积动态模型,推导出表观电流密度分布的数学表达式.并在多孔金属镍实际制备过程中对模型进行了验证,结果表明带状多孔金属与阳极配置满足一定角度时,实现阴极表观电流密度恒定,镍的结晶细致.这一工作为电沉积法制备多孔金属的在线控制提供了理论依据.     

基于电沉积多孔碳修饰电极测定6-苄氨基嘌呤的研究

利用恒电位法沉积多孔碳固定于玻碳电极表面,构建多孔碳修饰电极,利用线性扫描伏安法和差分脉冲伏安法研究了标题化合物在多孔碳修饰电极上的电化学行为,建立了一种测定标题化合物的电化学分析方法。结果表明,与玻碳电极相比,多孔碳修饰电极能显著提高标题化合物的氧化峰电流。在优化的实验条件下,标题化合物的氧化峰电流与浓度在1. 0×10-7~4. 0×10-5mol/L范围内呈较好的线性关系,最低检出限为7. 6×10-8mol/L。本法用于黄豆芽中标题化合物的测定,效果良好。     

电沉积制备多孔铅电极及其对CO2的电还原性能

采用铜片为基底,利用其自身析出的氢气泡为模板,通过电沉积的方法合成了具有三维多孔结构的铅沉积层,并将其作为电极材料应用到CO2的电还原反应中.考察了不同沉积时间及不同沉积电流密度对电极形貌及电催化还原CO2性能的影响,得出在5℃下,沉积电流密度为-6 A/cm2,沉积时间为20 s时,电极催化效果最好,在施加电位为-1.7V时生成甲酸的最高电流效率可达96.8％.     

喷射电沉积块体多孔镍的研究

采用喷射电沉积方法制备块体多孔镍.分别选择不同的扫描方式、电流密度进行试验,分析了各试验参数对块体多孔镍形貌的影响规律,并应用图形处理软件ImageJ对多孔镍的孔隙率和相对密度进行分析,获得最佳试验参数.结果表明:采用扫描速率中间部位慢于边界部位、在块体各点均暂停的扫描方式,有利于多孔镍沉积均匀平整.随着电流密度的增加,镍沉积层明显变得致密,孔径减小,而孔隙率增大.     

流通型碳纤维电极的电沉积行为

研究了电极构型对流通型碳纤维电极从ＡｕＣｌ－４稀溶液中电沉积金行为的影响．在顺流操作方式下，整个电极能够在极限电流条件下工作，利用电沉积分布曲线计算了传质系数与流速的关系式．逆流方式可以使电沉积分布更为均匀，从而提高整个电极的利用效率．利用数学模型对各种实验曲线进行了模拟，计算结果与实验结果相符．     

扫描喷射电沉积制备多孔金属镍

采用扫描喷射电沉积制备具有一定厚度、孔隙率较高、组织较均匀的多孔金属镍;并研究了在不同扫描速率、喷嘴高度等实验条件下,多孔金属镍电沉积生长的行为特性;最后应用图形处理软件Image J对多孔金属镍的孔隙率和相对密度进行分析,得到了最佳实验参数.结果表明:采用扫描速率为4 mm/s时,孔隙结构相当完善;当喷嘴高度为6 mm时,孔隙率和相对密度比较适中.     

电沉积制备多孔Ni-Fe-Sn合金电极及其析氧性能

采用直流电沉积法在铜箔表面合成了多孔结构的Ni–Fe–Sn合金,用扫描电子显微镜、X射线能谱仪和X射线衍射仪对合金的微观组织形貌和相态进行了表征,用电化学工作站测试了合金电极在碱性环境中的析氧性能。结果表明,Ni–Fe–Sn合金电极主要由Ni3Sn2和FeNi3相组成,电极表面形成了多孔结构。在30wt% KOH溶液中,Ni–Fe–Sn合金的析氧过电位仅为261 mV(电流密度10 mA/cm2),Tafel斜率为69.9 mV/dec。电极在10 mA/cm2电流密度下能稳定工作12 h以上,具有良好的电化学稳定性。     

电流密度对电沉积锰结构及性能的影响

锰被广泛应用于钢材中,研究制备高质量的金属锰具有很重要的现实意义。采用石墨阳极,无硒硫氨酸盐电解液,在不锈钢表面电沉积金属锰,采用恒电流法研究了电流密度对电流效率以及镀层厚度的影响。利用X-射线衍射仪测试镀层结构,扫描电镜观察镀层表面形貌,维氏硬度计测试镀层硬度。结果表明,Jκ为14A/dm2时η达到57.63%,镀层δ为37.07μm,硬度为509.53HV,获得表面形貌和晶体结构较优的金属锰。     

电沉积铂研究Ⅰ--工艺条件与镀层性能

研制了2种新的电沉积铂镀液体系：新槽液Ⅰ号和Ⅱ号。通过实验研究了电流密度、温度和主盐含量对镀液电流效率的影响,并与常用的碱性P盐槽液、酸性P盐槽液和DNS槽液进行对比。结果发现：新槽液Ⅰ号在电流密度为2A／dm^2、工作温度为30～40℃以及主盐含量为4～10g/L时,电流效率较高,从而可以在较低的温度下实现光亮镀铂。分散能力实验表明,新槽液Ⅰ号具有良好的分散能力。扫描电镜(SEM)图和X射线晶体衍射(XRD)图也证明,与传统的可获得色泽最白、性能最优的镀层的DNS槽液相比,新槽液Ⅰ号获得的镀层对晶面的择优程度与DNS槽液相近,但其内应力更小、表面更平整、结晶更细致、厚度更大。     

喷射速度对喷射电沉积多孔金属镍的影响

借助电化学技术,采用喷射电沉积的方法,直接制备出具有一定厚度、孔隙率较高、组织较均匀的多孔金属镍,并研究了不同喷射速度对喷射电沉积直接制备多孔金属镍的表面形貌和结构特征的影响。研究结果表明,多孔金属镍的孔隙率随喷射速度的增加先减小后增加。     

多孔泡沫金属及其在化工设备中的应用

介绍了多孔泡沫金属的结构特征与力学、热物理、渗透、电学和声学等性能,重点讨论了它在化工生产装置中的应用状况,并对其在研究中存在的问题和应用前景作了评述。     

海水组成的变化对海水直接电解的影响

主要讨论了海水组成的变化对海水直接电解过程的影响。海水的组成随季节、地点的变化而变化。当海水中氯离子浓度下降时,阳极的电极电位上升,同时电解过程的电流效率下降。当海水中钙镁离子浓度增加时,电流效率上升。     

The electrochemical generation of ferrate at porous magnetite electrode

In this work, ferrate(VI) was generated by the electrochemical oxidation of porous magnetite electrodes, made by melting pure magnetite grains. Pretreatment of the anode by cathodic polarization was necessary for ferrate(VI) generation and the achievement of high current efficiency. A electrolyte composition was found to be 16 M NaOH. In this electrolyte, the effect of anode current density J on Fe(VI) synthesis rate, current efficiency, and internal cell temperature were studied. An optimum result was obtained at J=3.3 mA cm⁻², 30 °C in 16 M NaOH for 5 h.     

Bi electrodeposition under magnetic field

Bi was galvanostatically electrodeposited in a hydrochloric acid solution in the presence and absence of a 0.5 T field. The effects of magnetohydrodynamics (MHD) convection were focused on the concentration overpotential as well as the current efficiency. The morphological and microstructural variation of electrodeposited Bi thin film was also investigated. Dendritic growth enhanced at higher current density was considerably suppressed by superimposition of a 0.5 T field, while the effect on the crystal microstructure was not confirmed.     

Role of Mo<Superscript>6+</Superscript> during nickel electrodeposition from sulfate solutions

The effect of Mo⁶⁺ on the current efficiency, deposit quality, surface morphology, crystallographic orientations and polarisation behaviour of the cathode during electrodeposition of nickel from sulfate solutions was investigated. Mo⁶⁺ did not have a significant effect on current efficiency over the concentration range 2–100 mg dm⁻³. However; a decrease in current efficiency by a magnitude of more than 20% was seen at 500 mg dm⁻³. The quality of the nickel deposit with reference to the visual appearance and contamination level varied with varying concentration of Mo⁶⁺; this was also reflected in the morphology and crystallographic orientations of the deposits. Addition of Mo⁶⁺ to the electrolyte introduced two new crystal planes i.e., (220) and (311). Depolarisation of the cathode was noted at lower concentrations of Mo⁶⁺ (2–40 mg dm⁻³) whereas polarisation of the cathode was observed at Mo⁶⁺ concentration >40 mg dm⁻³ .The effect of Mo⁶⁺ on parameters such as Tafel slope (b), transfer coefficient (α) and exchange current density (i ₀) were also determined.     

Transient surface photovoltage studies of bare and Ni-filled porous silicon performed in different ambients

Mesoporous silicon and porous silicon/Ni nanocomposites have been investigated in this work employing light-dark surface photovoltage (SPV) transients to monitor the response of surface charge dynamics to illumination changes. The samples were prepared by anodization of a highly n-doped silicon wafer and a subsequent electrodepositing of Ni into the pores. The resulting pores were oriented towards the surface with an average pore diameter of 60 nm and the thickness of the porous layer of approximately 40 μm. SPV was performed on a bare porous silicon as well as on a Ni-filled porous silicon in vacuum and in different gaseous environments (O₂, N₂, Ar). A significant difference was observed between the ‘light-on’ and ‘light-off’ SPV transients obtained in vacuum and those observed in gaseous ambiences. Such behavior could be explained by the contribution to the charge exchange in gas environments from chemisorbed and physisorbed species at the semiconductor surface.

PACS

81.05.Rm; 73.20.-r; 75.50.-y; 82.45.Yz     

Foam gel-casting preparation of SiC bonded ZrB2 porous ceramics for high-performance thermal insulation

Lightweight SiC-ZrB₂ porous ceramics is of great potential as thermal insulation material used in aerospace, chemical and energy industries. In this work, a series of SiC bonded ZrB₂ (SiC_b-ZrB₂) porous ceramics with porosity high up to 86.9% were prepared by a simple foam gel-casting method. The SiC_b-ZrB₂ porous ceramic prepared at 1573 K exhibited a low thermal conductivity of 0.280 W/(m?K) and a reasonable compressive strength of 0.52 MPa. It could maintain the original geometric shape and microstructure after a secondary heat treatment at 1473 K in inert atmosphere. When heating the samples with thickness of 30 mm for 12 min with an alcohol spray lamp (～1273 K), the temperatures of the cold sides of SiC_b-ZrB₂ ceramics were all lower than 432 K, demonstrating their exceptional insulation capabilities. The present work provides a simple route to produce robust and thermally-insulating non-oxide porous ceramics for use under high temperature.