铝合金微弧氧化过程的特性研究及机理分析

在硅酸钠和氢氧化钾电解液中利用微弧氧化方法,在2024铝合金上制备了陶瓷膜层.测定了膜层的厚度,考察了微弧氧化过程中放电参数及形成陶瓷膜速率的规律,用X射线衍射仪(XRD)观察分析了其成分及组成,对陶瓷膜的摩擦性能进行了研究,推断了在电极上发生的反应,对陶瓷膜的成膜机理进行了分析.结果表明,随着时间的进行,阴阳极电压逐步升高,开始时膜厚增加较快,以后逐渐变慢,膜层厚度随时间变化不是简单的线性关系.陶瓷膜内含有γ-Al2O3和α-Al2O3相,膜层内外两相含量差异较大,主要是由于冷却速率不同的原因.陶瓷层表面经历了一个熔融、凝固和冷却的过程.陶瓷层由内向外可以分为过渡层、致密层和疏松层,陶瓷膜与基体的结合非常牢固,属于冶金结合.溶液内的Si、K元素和基体内的合金元素Cu在陶瓷膜中都有存在,阴极成分Fe也存在于陶瓷膜中,放电通道中在高的能量密度下生成了Si-Al-O三重复杂化合物.     

In‐situ investigation of the surface‐topography during anodic dissolution of copper under near‐ECM conditions

Electrochemical machining is characterized by deliberate high speed anodic dissolution. The distance between anode and cathode are only a few hundred microns. Additionally, the electrolyte flow rate is in the range of approximately meter/second. A special electrochemical cell design was developed to investigate the surface topography during the anodic dissolution simultaneously and in‐situ under near‐ECM conditions. The anode was directly placed under the cathode with a gap of 350 µm. We carried out pulse experiments at 15 A/cm² and 25 A/cm² with an electrolyte flow rate of 4m/s. First‐time it was possible to observe the surface changing of the anode directly during current pulses by using a video camera. Different stages e.g. roughening, film formation or gas evolution could be distinguished.     

氯盐体系锡隔膜电沉积仿真模拟

采用COMSOL多场耦合计算机仿真软件对氯盐体系锡隔膜电沉积进行了仿真模拟,研究锡隔膜电积时电解槽内离子浓度、流体密度、流体速度、电流密度等的分布特征及其随时间的变化规律。结果表明:锡隔膜电积时槽内离子浓度分布受到入口流速、电流密度、电积时间、槽内离子互相作用的影响而发生变化。增加进液速度及降低HCl浓度有利于提高电解液平均密度及阴极表面Sn^2+的最低浓度。电积时极板边缘发生离子对流,顶部对流速度高于边缘处对流速度,且流体密度梯度影响离子对流方式。极板周围电流密度分布呈非均匀分布,在电极边缘发生电流偏转。增加电流密度能降低阴极表面Sn^2+最低浓度及流体的平均密度,同时也将增加阴极表面流体的平均流速,并使得阴极产物厚度不均匀。     

基于渐变孔隙正极和叉指型流道主动式锂空气液流电池电化学性能理论研究

提出了具有渐变孔隙正极结构的主动式锂空气液流电池,利用溶液泵驱动电解液循环,结合渐变孔隙正极结构,强化电极内部Li^+和O2扩散和结合能力,减弱电极钝化。基于COMSOL Multiphysics 5.3,建立二维电化学模型,用Darcy定律、Butler-Volmer方程和组分输运公式描述在渐变孔隙正极结构(ε=0.55+αX等)下电极内部电解液流动、正负极电化学反应及电解液中Li^+和O2浓度场分布。由于Li2O2积聚在正极孔隙内,电极比表面积下降,采用Carman-Kozeny方程修正渗透率K。研究渐变孔隙率、压强差、氧气参数、正极厚度及动力学速率系数对该电池放电性能影响。结果表明:在放电电流密度0.1 mA/cm^2,电池比电容量是被动式结构的2.5倍;与ε=0.85-0.1X相比,采用ε=0.55+αX结构的电化学性能较佳;在放电电流密度0.1 mA/cm^2下,正极厚度为500^750μm,电池放电性能较好。     

Peculiarities of heat transfer at anodic plasma electrolytic treatment of cylindrical pieces

Heat transfer in a three-phase electrochemical system consisting of a metal cylindrical anode (a workpiece), a vapor-gas envelope, and an electrolyte solution is considered. The purpose of the study is to determine the effect of the length of the sample part contacting with the electrolyte on the distribution of the heating characteristics on its surface. It is established that the increase of the length of the part of the anode submerged into the electrolyte causes a decrease in the average current density, reduction in the vertical current density gradient, and a decrease in the density of the heat flux from the envelope to the sample. A model is proposed to calculate the stationary cylindrical anode temperature and the current in the system with the evaluation of the convective heat flux from the anode portion protruding above the electrolyte into the atmosphere. The influence of the electrolyte flow along the sample on its temperature and the average current density in the system is determined and attributed to the variation of the vapor-gas envelope thickness.     

复杂型面电铸不溶性组合阳极优化设计

提出了一种电铸阳极优化设计方法,采用多个不溶性阳极单元组合成阳极轮廓,通过调整各阳极单元与阴极表面上各对应点的间距,以及对特殊部位进行局部修正,使阴极表面电场分布的均匀性得到改善。利用该方法对喷管模拟件的电铸阳极进行设计,结果表明,阴极各点电场强度最大与最小比值从2.19减小到1.15。     

气体流量和耦合度对GPCA-TIG焊电弧特性影响的数值模拟

根据磁流体动力学理论和组分守恒建立气体熔池耦合活性TIG焊电弧二维数学模型,采用简化阴极边界层模型将阴极与电弧耦合求解,计算得到了不同外层氧气流量与耦合度下电弧等离子的温度、氧气分布、阳极表面电流密度和热流密度等特征参数。结果表明,与TIG电弧相比,气体熔池耦合活性TIG电弧收缩,流速增大,阳极表面电弧压力升高;增大外层氧气流量或增大耦合度,电弧最高温度均上升,氧气向电弧区域扩散趋势更明显,电弧形貌略有收缩,阳极表面电流密度与热流峰值均略有增大。     

Contact Displacement of Copper at Copper Plating of Carbon Steel Parts

The process of the contact displacement of copper by the carbon steel surface in a low-concentrated sulfate electrolyte and in electrolytes containing copper complexes with glycine, tartrate, and ethylenediaminetetraacetate is studied. The method of analyzing the particular reactions of interaction between a steel surface and copper-containing electrolytes in the absence of current is applied. The parameters of the contact exchange kinetics are determined with computer processing of the arrays of the coordinates of the particular polarization dependences of cathodic copper deposition in the electrolytes and the anodic dissolution of steel in the corresponding background solutions, as well as of the chronopotentiograms of steel samples in the electrolytes under study. The values of the contact exchange current density and the relation between the areas of the cathode and anode surface sections are calculated as a function of the steel substrate potential and the steel–electrolyte contact time. The influence of the nickel sublayer thickness on the kinetics of the contact exchange in a low-concentrated sulfate electrolyte is shown.     

ZL115铸铝合金和C41500海军黄铜电偶腐蚀的边界元仿真研究

通过电化学实验测得ZL115铸铝合金和C41500海军黄铜的极化曲线。基于边界元法,以极化数据作为边界条件,建立了铝合金表面涂层损伤后与黄铜接触时的电偶腐蚀模型并进行仿真。结果表明:铸铝合金活性随电解液浓度的升高而增加,耐蚀性降低;相同条件下,黄铜变化微弱。电解液浓度和液膜厚度的增加均会加剧电偶腐蚀,相较而言,液膜厚度的影响更为强烈;阴阳极面积比的增加会明显增大电偶腐蚀中阳极处的局部腐蚀电流,即加剧阳极损耗;阴阳极间距的增加会在一定程度上削弱电偶腐蚀,但这种削弱效果十分有限。     

镍-氧化锆纳米复合电铸层微观形貌影响因素的分析

用SEM分析了诸如电铸时间、电流密度、镀液中纳米ZrO2颗粒悬浮量、电流形式和阴极表面粗糙度等因素对Ni-ZrO2纳米复合电铸层微观形貌的影响.结果表明,电铸时间、阴极电流密度以及镀液中纳米ZrO2悬浮量对纳米复合电铸层微观形貌有一定程度的影响,采用脉冲电沉积工艺有助于获得表面光滑平整、显微组织均匀致密的纳米复合电铸层.     

电解抛光法制备铝合金EBSD试样方法研究

目的 为在导电单相金属中获得高质量EBSD试样表面,研究电解抛光法制备铝合金试样的方法,并提供理论支持。方法 基于Jacquet黏膜模型和金属阳极原理,提出利用阳极极化曲线、电流-时间曲线和扫描电镜二次电子图像获得电解抛光工艺参数,批量制备铝合金EBSD试样的理论方法。采用恒电位法中的静态法记录稳定的电压-电流走势,以获得电流稳定的实验时间,在90 s内进行各电压下的电解抛光实验,获得电压与稳定电流的对应关系,并绘制阳极极化曲线。电流由持续稳定转至持续上升后的斜率与电压横坐标相交处为理论最低分解电压值。结合扫描电镜二次电子图像在最低分解电压以上观察抛光表面。结果 获得最优抛光电压值为31 V。利用电流随时间的变化曲线,结合黏膜模型分析,并通过扫描电镜二次电子图像验证,最优电压下的最佳抛光时间为12 s,该值是电流-时间曲线中的电流最低点。此工艺使制备的铝合金EBSD样品标定率为97%,是理想的电解抛光工艺。结论 采用阳极极化曲线获得的最优电压和最优电压下的最小电流规律由Jacquet黏膜模型支持,其所获得的电解抛光工艺能够制备出优质的样品表面,也能够为其他金属块体导电材料和其他需要电解抛光的实验类型提供获得最佳电解抛光工艺值的理论方法。     

双丝夹角对双丝间接电弧特性的影响

建立了双丝间接电弧的三维有限元数学模型,分析了不同双丝夹角对双丝间接电弧特性的影响.利用高速摄像机拍摄电弧图片与计算结果对比,以验证计算结果的准确性.结果表明,双丝间接电弧的温度、速度和电流密度等电弧参数在阴极区和阳极区较高,在弧柱区较低,弧柱区下端最低;随着双丝夹角的增加,双丝间接电弧的温度、速度、电流密度在阴极区、阳极区以及弧柱区上端增加,在弧柱区下端下降;上述电弧参数的变化率在阴极区和阳极区大于弧柱区,阳极区大于阴极区,弧柱区上端大于弧柱区下端;双丝间接电弧的偏转程度随着双丝夹角的增加而增加.     

RuOx-PdO/Ti电极上活性氯的生成及甲基橙模拟废水降解研究

以钛基RuOx-PdO为阳极,钛网为阴极,Na2SO4和NaCl为支持电解质,研究了NaCl质量浓度、电流密度和pH对活性氯生成的影响及活性氯的生成与甲基橙模拟废水降解之间的关系.实验发现,以Na2SO4为支持电解质时,甲基橙模拟废水的有限降解是该阳极直接电催化氧化作用的结果.NaCl质量浓度和电流密度对活性氯的生成有明显的影响,酸性溶液中活性氯的生成量直接决定了甲基橙模拟废水的脱色程度,两者之间呈现较好的线性关系,碱性条件下不仅不利于活性氯的生成而且活性氯物种对甲基橙模拟废水的降解基本不起作用.     

C/LiFePO4动力蓄电池的热行为

为了明确圆柱形C/LiFePO4动力蓄电池放电过程中的温度特性及其产热机理,利用自动充放电仪对其在不同倍率放电过程中表面温度的变化进行研究,并对该电池在放电过程中的产热率进行计算。结果表明:相同放电时间的表面温度增加与放电电流呈抛物线关系,放电结束时表面温度增加则与放电电流呈线性关系;电池内部的热效应主要为不可逆阻抗热和电池反应的可逆热效应,0.3C、1C、2C和3C放电时,不可逆阻抗热的平均产热率分别是总平均产热率的85.0%、98.0%、99.4%和99.6%,电池反应的可逆热效应所占比例很小;小电流放电时,电池表面温度的下降与电池反应的可逆热效应有关。     

Fabrication of microprism mould by electroforming with high electrolyte flowrate

Abstract

Electroforming is applied to fabricate microprism moulds, however only low working current density is employed because the higher current density at the edge limits the usable value of the working current density. Reduction of current density at the edge is a key in the enhancement of the working current density. In this paper, a secondary cathode was introduced to lower the edge current density. By this technique, the edge current density of the primary cathode surface is not only weakened obviously but can be even lower than that of the others. In addition, a high electrolyte flow rate has been introduced to improve working current density. Experimental results show that both the microhardness and tensile strength of the electroformed layer increase with electrolyte flowrate. By using both secondary cathode and high speed electrolyte flow, the electroforming time could be reduced significantly and mechanical properties of the electroformed layer are not adversely affected in electroforming of microprism moulds.     

Research on Electrochemical Behavior of Ti-Ir-Ru Anode Coating in Electrolytic Antifouling of Flowing Brine

By electrochemical techniques, the electrochemical behavior of Ti-Ir-Ru anode coating was studied in electrolytic antifouling of flowing brine. The effect of the brine’s flow rate and the anode/cathode interval on electrolysis was also considered. The results indicated that the brine’s flow rate had remarkable effect on the characteristic of the Ti-Ir-Ru anode. The electrolytic voltage and the evolved active chlorine concentration of Ti-Ir-Ru anode increased with increasing flow rate. Its energy consumption displayed the same variable rule as the electrolytic voltage. But the current density reduced with increasing flow rate. Increasing flow rate favored attenuation of the thickness of mass-transfer control layer and expediting the oxygen’s mass transfer, which accelerated the cathode polarization and the oxygen absorption reaction. The maximal current efficiency for Ti-Ir-Ru anode was obtained at the anode/cathode interval of 5 cm with the current density of 60 mA/cm². At this point, Ti-Ir-Ru anode also had relatively low electrolytic voltage. The above operating procedure was ideal for electrolyzing flowing brine using Ti-Ir-Ru anode coating.     

葡萄糖对铝合金电极电化学活性及自腐蚀的影响

针对铝-空气电池放电时铝合金阳极自腐蚀严重的问题,利用失重法、线性扫描伏安法等电化学方法研究了葡萄糖作为铝合金阳极缓蚀剂的缓蚀效果,以及葡萄糖对铝合金阳极电化学性能、空气电极电化学性能的影响,并利用XRD及金相组织形貌对放电后的铝合金阳极表面进行葡萄糖的缓蚀机理分析。结果表明,添加葡萄糖能够使铝合金阳极利用率由45%提高至90%,能适当提高铝合金阳极的电流密度约12 mA/cm2,且几乎不影响空气阴极的电化学性能。XRD及金相组织表明,添加葡萄糖能够促使铝合金阳极表面放电过程中产生的氢氧化铝脱落而使铝合金表面光滑平整。     

Galvanic Corrosion of a Carbon Steel-Stainless Steel Couple in Sulfide Solutions

The galvanic corrosion behavior of carbon steel-stainless steel couples with various cathode/anode area ratios was investigated in S ²⁻-containing solutions, which were in equilibrium with air, by electrochemical measurements, immersion test, and surface characterization. It is found that the galvanic corrosion effect on carbon steel anode increases with the cathode/anode area ratios, and decreases with the increasing concentration of S²⁻ in the solution. A layer of sulfide film is formed on carbon steel surface, which protects it from corrosion. When the cathode/anode area ratio is 1:1, the potentiodynamic polarization curve measurement and the weight-loss determination give the identical measurement of the galvanic corrosion effect. With the increase of the cathode/anode area ratio, the electrochemical method may not be accurate to determine the galvanic effect. The anodic dissolution current density of carbon steel cannot be approximated simply with the galvanic current density.     

Current density limitation and diffusion boundary layer calculation using CFD method

The knowledge of limiting current density and thickness of diffusion boundary layer is particularly important in improving space-time-yield of electrolysis and especially of high current-density electrolysis. Both natural and forced convection of electrolyte flow are considered in the presented computational fluid dynamics model for calculation of these values. Natural convection is modeled by implementation of a source term at the cathode surface for copper concentration according to Faraday’s law, which allows calculation of electrolyte density for each volume cell of the grid. Forced convection is considered as flow of electrolyte through the cell generated by electrolyte inlet and outlet. By variation of current density, the limiting current density can be calculated with a copperion concentration of zero at the cathode surface after reaching the steady-state conditions in electrolyte. Time dependency of diffusion boundary layer thickness is shown for a chosen cell geometry. Literature data and measured and calculated values of both quantities are in good agreement.     

海水中钢的电偶腐蚀研究

获取了不同电位差的钢偶对在海水吧不同面积比偶合的腐蚀结果,讲座了海水中钢偶对的电偶腐蚀行为;对文献中推导的海水中钢偶对的腐蚀速度公式进行了检验和简化,海水中钢偶对阳极的腐蚀速度随阴、阳极自腐蚀电极差和阴／阳极面积比的增大而增大,阳极的腐蚀速度与阴／阳极面积比的关系是非线性的,且阳极的腐蚀速度随阴／阳极面积比的增大有一个极限值,阴极的腐蚀速度随阴／阳极面积比减小和阴／阳极电位差增大而减小,简化的海水中钢偶对的腐蚀速度公式与试验结果符合较好。