甘油体系中不锈钢表面液相等离子体电解渗碳工艺

采用液相等离子体电解渗方法,在80%甘油水溶液中实现了304不锈钢表面快速渗碳。研究施加电压和放电时间对渗碳过程的影响,分析了渗碳层的显微组织,并比较了不同工艺条件下渗碳层显微硬度分布。结果表明:经过5 min的快速放电处理,渗碳层厚度接近100μm,硬度达到880 HV。在350 V和3 min渗透条件下渗碳层质量较好。     

Kinetics of electrochemical process of galena electrode in diethyldithiocarbamate solution

1　ＩＮＴＲＯＤＵＣＴＩＯＮＤｉｅｔｈｙｌｄｉｔｈｉｏｃａｒｂａｍａｔｅ (ＤＤＴＣ)ｉｓｏｎｅｏｆｔｈｅｍｏｓｔｆｒｅｑｕｅｎｔｌｙｕｓｅｄｃｏｌｌｅｃｔｏｒｓｆｏｒｆｌｏｔａｔｉｏｎｏｆｈｅａｖｙ ｍｅｔａｌｓｕｌｆｉｄｅｍｉｎｅｒａｌｓ ,ｓｕｃｈａｓｇａｌｅｎａ ,ｃｈａｌｃｏｐｙｒｉｔｅａｎｄｊａｍｅｓｏｎｉｔｅ ,ａｎｄｉｔｓｈｏｗｓｓｔｒｏｎｇｓｅｌｅｃｔｉｖｉｔｙ[1] .ＷｈｅｎＤＤＴＣｗａｓｕｓｅｄｉｎｈｉｇｈｌｙａｌｋａｌｉｎｅ (ｐＨ >11.4 )ｆｏｒｓｅｐａｒａｔｉｎｇｇａｌｅｎａｆｒｏｍｓ…     

Influence of process parameters on electrolytic plasma discharging behaviour and aluminum oxide coating microstructure

In this study, a plasma electrolytic oxidation process (PEO) was used to produce oxide coatings on commercially pure aluminum (Al 1100) at two different current modes, pulsed unipolar and bipolar modes. Optical emission spectroscopy (OES) in the visible and near ultraviolet (NUV) band (285 nm-800 nm) was employed to investigate the PEO plasma. The emission spectra were recorded and plasma temperature profile versus processing time was constructed using line intensity ratios method. Scanning Electron Microscopy (SEM) with energy dispersive x-ray analysis (EDS) was used to study the coating microstructure and coating cross section. It was found that the plasma discharge behavior significantly influenced the microstructure and the morphology of the oxide coatings. The main effect came from the strongest discharges which were initiated at the interface between the substrate and the coating. Through manipulation of process parameters to control or reduce the strongest discharge, the density and quality of the coating layers could be modified. This work demonstrated that by adjusting the ratio of the positive to negative pulse currents as well as their timing in order to eliminate the strongest discharges, the quality of the coatings was considerably improved.     

Effect of the electrolytic solution composition on the performance of micro-arc anodic oxidation films formed on AM60B magnesium alloy

Anodic oxidation in the micro-arc regime is one of the most investigated techniques used to coat magnesium alloys with ceramic coatings for protection from corrosion and wear. The composition of the electrolytic solution affects the anodic oxide layer morphology and composition and its behaviour in aggressive environments. In this paper the influence of the composition of the electrolytic solution on the anodic oxidation process of AM60B magnesium alloy and oxide properties is discussed. Scanning electron microscopy and x-ray diffraction were employed to assess morphology, crystallographic structure and composition of the anodic oxide. Electrochemical polarization tests were performed to evaluate the corrosion resistance behaviour of the coated magnesium alloys.     

Improving the electrolytic process magnesium production

Magnesium Corporation of America has completed a development program designed to improve the performance efficiency of the electrolysis system and eliminate operating chlorine losses. This work has culminated in the recent modernization of the process. The conversion has provided a number of operating benefits including significant reductions in labor costs, energy costs, maintenance costs, and environmental releases. This paper will review the development, design, environmental impact, and cost benefit of the project. For more information, contact R.L. Thayer, Magnesium Corporation of America, Operations Building, 238 North 2200 West, Salt Lake City, Utah 84116 USA; fax (801) 596-1132; e-mail rthayer@magnesiumcorp.com.     

Effect of the anode material on the composition and dimensional characteristics of the nano-sized copper-bearing powders produced by the electrochemical method

The effect of the anode material on the dimensional characteristics and chemical composition of the ultradispersed copper-bearing powders produced by the electrochemical method from aqueous-organic solutions of copper sulphate has been investigated. A complex physical and chemical study of the produced powders has been carried out. The sizes of the particles of the produced powder have been determined according to the results of the examination of electron-microscopic photos. The electron-diffraction, radiographic, and thermogravimetric methods were used to determine the chemical composition of the powder.     

Effects of electrochemical process parameters on the synthesis and properties of polypyrrole coatings on steel

Polypyrrole coatings have been successfully formed on low carbon steel by aqueous electrochemical process. The effects of electrochemical process parameters such as pH of the reaction medium, applied current density and initial monomer and electrolyte concentrations on the formation process of polypyrrole coatings were systematically investigated. The composition and morphology of the coatings were studied by FT-IR, elemental analysis and scanning electron microscopy (SEM). Our results show that passivation of the steel, electropolymerization of pyrrole, the morphology and properties of the coatings were all dependent on the electrochemical process parameters. By proper choice of the electrochemical process parameters, the passivation of the steel could be established within a short time and smooth, uniform, strongly adherent coatings could be formed on the steel substrate.     

Influence of synthesis temperature on electrochemical polymerization of o-anisidine on low carbon steel

The influence of synthesis temperature on the electrochemical polymerization (ECP) of o-anisidine (OA) on low carbon steel (LCS) has been investigated. The ECP of OA was carried out on LCS substrate under galvanostatic conditions from aqueous solution of oxalic acid at various temperatures between 0 and 40 °C. The resulting poly(o-anisidine) (POA) coatings were characterized by potential–time (E–t) curves, UV–VIS absorption spectroscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements. The E–t curves reveal that the synthesis of POA coating at 0, 15 and 27 °C on LCS occurs in three stages, an induction time for ECP, passivation of LCS electrode surface via the formation of iron oxalate (FeC₂O₄·2H₂O) interphase and the dissolution of interphase and followed by ECP of OA. However, at 40 °C with an applied current density ∼0.66 mA/cm², the E–t curve shows the undesirable behavior which is attributed to non-decomposition of interphase during the third growth stage. As a consequence, at 40 °C the ECP of OA has not occurred on the LCS electrode surface. The XRD, SEM and optical absorption spectroscopy support this observation. It has been found that, as the synthesis temperature is increased, at low current densities, the induction time is observed to decrease, whereas it does not show any significant change at higher current densities. The optical absorption spectroscopy reveals the formation of mixed phase of emeraldine salt (ES) and pernigraniline base (PB) at 27 °C, whereas at lower temperatures the major portion of the coating constitutes the ES phase. The surface morphology, as revealed by SEM is observed to depend on the synthesis temperature.     

工艺参数对含钛高炉渣合成(Ca,Mg)α''-Sialon-AlN-TiN粉的影响

以含钛高炉渣、硅灰、高铝矾土熟料和炭黑为原料,采用碳热还原氮化法合成了(Ca,Mg)α'-SialonAlN-TiN粉.用X射线衍射法测定了产物相组成及相对含量,研究了合成温度和恒温时间对反应过程的影响,并对合成机理进行了探讨.结果表明:合成温度对(Ca,Mg)α'-Sialon-AlN-TiN粉的合成过程影响显著,随着合成温度升高,产物中α'-Sialon相含量增大,1 480℃时α'-Sialon含量达最大,是最佳的合成温度.恒温时间对产物相组成的影响不十分显著,但较长的恒温时间可使还原氮化反应进行得更充分,恒温8 h的试样中α'-Sialon含量最高,是较理想的恒温时间.合成过程中SiO的挥发导致试样较大的质量损失,且随着合成温度升高和恒温时间延长而增大.     

水雾化粉末状触媒中固溶碳对金刚石合成的影响初探

高压水雾化方法制备触媒粉末为降低粉末氧含量,实验中加入合成金刚石用高纯天然鳞片石墨粉,灰分含量小于20×10-6,制备成合成柱在六面顶压机上进行系列合成实验,合成腔体为φ41 mm,通过合成的金刚石结果,判断总结出最佳含碳量值.所制得FeNi30如触媒粉末中的碳有两种状态存在:固溶单质碳和Fe3C型碳化物.结果发现固溶单质碳的存在,促进碳在触媒合金中内外双向扩散.促进了金刚石成核和转化;另外,根据固体与分子经验电子理论,分别计算了Fe3C及(Fe,Ni)3C型碳化物内C-C键原子组成的晶面的共价电子密度与金刚石晶面的共价电子密度,发现二者之间具有连续性,说明Fe3C型碳的存在也很有可能是金刚石形核与生长的有效碳源.     

制备条件对纳米镍粉电化学性能的影响

在水、乙二醇和1,2丙-二醇3种溶液中,以NiSO4.6H2O为主盐、水合肼为还原剂制备纳米镍粉,然后将镍粉压制成片状电极。采用X射线衍射分析镍粉的成分,SEM和TEM表征其微观形貌,XPS研究片状镍电极表面的化学状态,并在碱性溶液中进行循环伏安测试。结果表明:纳米镍粉的制备条件对其电化学性能存在明显的影响,在乙二醇溶液中制得的镍粉呈分散状态,且颗粒尺寸分布均匀,直径为30~100 nm,较在其它两种溶液中制备的镍粉电极具有更高的氧化还原电流密度,即具有更高的电化学活性。     

退火加热过程对高压电解电容器阳极铝箔立方织构的影响

采用织构定量检测、 EBSD微取向分析、晶粒尺寸分析等手段研究了退火加热过程对高压电解电容器阳极铝箔立方织构的影响. 结果表明 铝箔在最终退火加热中分别经历了初次再结晶和晶粒长大两个主要过程, 两过程互有重叠, 其中在300℃适当完成初次再结晶并在500℃促使立方取向晶粒长大有利于提高最终的立方织构量; 在500℃长时间加热有可能诱发晶粒异常长大, 并降低立方织构量.     

Influence of the experimental parameters on the synthesis process of yttria-doped zirconia sol-gel films

The influence of the alcohol solvent (methanol, ethanol, propanol, isopropanol or buthanol) and the proportion used in the preparation of precursor solutions to obtain ZrO₂-3 mol% Y₂O₃ sol-gel films are investigated. In particular, the effect of the aging process of the solutions on the porosity and critical thickness of the films is analysed. Implications for the preparation of zirconia sol-gel films by the dip-coating technique are also discussed.Other aspects of the process such as the aging of the solutions, the evolution of the dimensionless parameter J, the porosity, P, and the fully dense critical thickness, t_cd, are also investigated and discussed. This allows one to understand the behaviour of the precursor solutions, and to obtain dense coatings and crack-free films. The results reveal a significant influence of the alcohol used as the main solvent in the first densification stages of the films (100 °C-500 °C). Likewise, the type and amount of alcohol used also notably influence the aging process of the solution, the porosity and the fully dense critical thickness finally obtained with each solution.     

不同氧化剂对单镍盐电解着色的影响

研究了不同氧化剂对单镍盐电解着色的影响。结果表明,无钠宽温氧化剂与常温氧化剂对单镍盐电解着色影响甚微,可以生产稳定的香槟色铝型材料,但含钠宽温氧化助剂对单镍盐电解着色影响较大,不易得到均匀稳定的香槟色铝型材料。     

Frequency response studies for the plasma electrolytic oxidation process

This paper introduces a methodology for obtaining a fundamental characteristic of the plasma electrolytic process — that is the frequency response (magnitude and phase angle). A methodology is developed for plasma electrolytic oxidation (PEO) of aluminium; however, it can be applied to any plasma electrolytic process. For PEO the frequency response was evaluated as a complex impedance of the electrolyser. It was found that the impedance magnitude decreases with frequency growth from 10³-10⁴ to 10-10² Ω and the phase angle decreases from 0 to − 70 − 80°. This fact appears to be consistent with a hypothesis of active-capacitive load behaviour for the PEO process. Evolution of the frequency response during PEO is consistent with that of the surface state; therefore, it can be used for process diagnostics and control. Frequency response adds a new dimension to the investigation of plasma assisted electrochemical processes. Major benefits of this approach are expected in the field of the process automation and the development of new pulsed plasma electrolytic technologies.     

Influence of the duty cycle on structural and mechanical properties of oxide layers on Al-1050 by a plasma electrolytic oxidation process

Oxide layers were prepared on Al-1050 substrates by an environmentally friendly plasma electrolytic oxidation process using an alkaline solution of Na₂SiO₃ (8 g/L) and NaOH (3 g/L) as the electrolyte. The effects of three different duty cycles (20%, 40%, and 60%) on the structure and hardness of the oxides were investigated. XRD analysis revealed that the oxides were mainly composed of α-Al₂O₃, γ-Al₂O₃, and mullite. The proportion of each phase depended on various electrical parameters, such as the duty cycle and frequency. The morphology, thickness, and the elemental distribution of the oxides were examined by scanning electron microscopy and energy dispersive spectroscopy. The thicknesses of the oxides were found to vary from 20 μm to more than 60 μm for various duty cycles, when identical treatment durations were used. The oxidation treatment also resulted in good adhesion between the oxide layer and the substrate. SEM images indicated that the oxide layers formed at the 60% duty cycle exhibited relatively coarser surfaces with larger pore sizes and sintering particles, and slower growth rates than did those formed at the 20% duty cycle, under identical treatment durations. The oxides prepared at the 20% duty cycle showed smooth surfaces. The oxides layers were found to improve the micro-hardness of Al-1050. In particular, the oxide layers formed at the 40% duty cycle exhibited relatively better micro-hardness owing to their compact microstructures.     

Effects of heat treatment scheme on the photocatalytic activity of TiO2 nanotube powders derived by a facile electrochemical process

TiO₂ nanotubes (NTs) in powder form were synthesized by a facile electrochemical process in a perchlorate-containing electrolyte. Transmission electron microscopy results indicate that the TiO₂ NT-powder is in an amorphous structure and has outer diameter of 20 nm and tube-wall thickness of 5 nm. X-ray diffraction analysis reveals that phase composition of the annealed TiO₂ NT-powders is related to the heat treatment scheme. Methyl orange was employed as a representative dye pollutant to evaluate the ultraviolet photocatalytic activity of the TiO₂ NT-powders. It was found that different post heat treatment schemes affect greatly the photocatalytic activities of the TiO₂ NT-powders, which should be ascribed to the changes in phase structural and morphological properties of the TiO₂ NT-powders. These results indicate that there should be a balance between crystal phase and nanotubular configuration for achieving the best photocatalytic activity of the TiO₂ nanotube powders.     

弱碱性溶液中硫砷铜矿的电化学氧化过程及表面相构成

采用循环伏安(CV)和X射线光电子能谱(XPS)对硫砷铜矿在pH值为9.2溶液中的电化学氧化过程以及电位对硫砷铜矿表面氧化相的构成影响进行研究。结果表明:硫砷铜矿在电位0.17 V(氧化峰A1电位范围)氧化,主要发生Cu部分离开矿物表面进入溶液形成缺铜硫化物(Cu3 xAsS4)的初步氧化过程,表面不存在Cu(Ⅱ)的氧化相,S氧化形成少量的S2 n,As不发生氧化。当氧化电位提高到0.3 V(氧化峰A2电位范围),大量的Cu离开矿物表面进入溶液,表面仍然不存在Cu(Ⅱ)的氧化相,可能存在少量的CuSO4,但处于检测下限,表面存在一定量的Sn^2-,不存在As的氧化相。当电位提高到0.5 V(氧化峰A2电位范围),发生Cu和As的氧化沉积过程,分别在矿物表面形成Cu(Ⅱ)氧化相(Cu(OH)2,CuSO4)和As2O3氧化相。此外,表面还存在一定的Sn^2-相。当电位提高到0.8V(氧化峰A3电位范围),表面形成一定量的Cu(Ⅱ)氧化相(Cu(OH)2和CuSO4),As仍然以As2O3的形式存在,S除形成CuSO4外,部分仍以Sn^2-的形式存在。     

镀液配比对金刚石微粉化学镀镍增重率的影响

通过正交试验探究络合剂、分散剂、稳定剂的浓度对金刚石微粉镀镍增重率的影响。结果表明:影响镀镍增重率因素的主次排序为:氨水> 柠檬酸> 柠檬酸钠> 硫脲> 十二烷基苯磺酸钠。综合考虑增重率、漏镀、连晶等情况,金刚石微粉表面化学镀镍的最优配方为:硫酸镍25 g/L,次亚磷酸钠33 g/L,氨水10～15 mL/L,柠檬酸15～20 g/L,柠檬酸钠10～15 g/L,硫脲1.3～2.1 mg/L,十二烷基苯磺酸钠1.6～2.4 g/L。