铜在磷酸溶液中的电化学抛光研究

通过阳极极化和电化学阻抗谱测试,研究了铜在磷酸溶液中进行电化学抛光的电化学行为。研究发现:随着磷酸浓度的增加,铜在0.2,0.4,0.6,0.8 V四个电位下电化学抛光后的粗糙度都呈现先减小、后增大的趋势,在磷酸质量分数为55%时达最低值;EIS图谱拟合的Rs值的变化反映了磷酸盐粘膜层电阻和铜表面氧化膜电阻的变化,此外,随着磷酸浓度的增加,EIS中第一个容抗半圆的弛豫时间延长,铜的溶解反应速度加快。     

氢氟酸-硝酸体系中Ti-6Al-4V的腐蚀加工溶解特征

利用E-t曲线、动电位极化曲线研究了氢氟酸-硝酸体系中溶液主体成分、温度对Ti-6Al-4V腐蚀加工溶解行为和特征的影响,通过测试阳极与阴极反应动力学揭示钛合金腐蚀加工动力学规律。研究结果表明,在该溶液体系中钛合金的腐蚀加工是侵蚀-溶解-钝化循环往复的过程,硝酸的钝化作用与氢氟酸的溶解作用同时存在,当钝化膜的生成速度和钛基体的溶解速度达到动态平衡时,腐蚀速度处于相对稳定的状态。腐蚀加工初期阶段氢氟酸浓度会影响钛合金表面氧化膜的破坏,浓度较低时,氧化膜较难破坏,自腐蚀电位正移;浓度较高时,氧化膜容易被腐蚀溶解,自腐蚀电位负移。氢氟酸浓度和温度增加,反应活化能减少,腐蚀溶解加剧。氢氟酸浓度较低时,温度对加工速度的影响占主导地位;浓度增加到80 m L/L,温度的影响减弱,氢氟酸起主要作用。硝酸的钝化作用在减少总体腐蚀速度的同时可有效改善微观表面的凹凸不平,使微观表面趋于平整。     

抛光液对304钢在模拟PEMFC阳极环境中电化学行为的影响

    利用电化学测试技术研究了304不锈钢经不同浓度的柠檬酸、硝酸、双氧水和硝酸铁四种溶液化学抛光后在模拟质子交换膜燃料电池(PEMFC)阳极环境中的电化学行为.结果表明,经上述四种溶液抛光后,304不锈钢在模拟PEMFC阳极环境中的耐蚀性均可提高一个数量级.即使极化到0.8 V,腐蚀电流密度分别降低到25.69、8.3、21.39和24.44 μA/cm2,接近美国能源部要求的16 μA/cm².硝酸和双氧水由于具有氧化作用使不锈钢表面钝化而降低腐蚀电流密度,而柠檬酸和硝酸铁能使不锈钢表面发生选择性溶解,形成富铬表面层而增强耐蚀性.     

合金元素对Al-Zn-In系牺牲阳极溶解行为的影响

通过电化学阻抗、扫描电子显微镜和能谱分析研究了三种不同元素含量的Al-Zn-In牺牲阳极在0.5mol/L NaCl溶液中的溶解行为和溶解形貌,对比不同合金元素含量牺牲阳极的电化学溶解特征表明,随着铁含量的增加,铝阳极的局部腐蚀敏感性增加,适当提高Zn的含量能有效改善铁含量增加引起的局部腐蚀,但阳极的自腐蚀速度增加.     

Q235-304L电偶对在Na2S溶液中的电偶腐蚀行为研究

用电化学法和浸泡法研究了Q235-304L电偶对在3种不同浓度的Na2S溶液中的电偶腐蚀行为,用SEM观察试样的表面形貌.结果表明:在3种溶液中Q235钢的阳极过程均为混合控制,而304L的阴阳极过程均为电化学控制;偶接后Q235钢表面阳极金属的溶解过程与阴极过程同时进行,其阳极溶解电流大于电偶电流值;电偶腐蚀效应随阴阳极面积比的增大而增大;随着S2-浓度的升高,电偶对中Q235钢的腐蚀速率减小,电偶腐蚀效应也随之降低.     

纯钛表面微米级多孔TiO_2薄膜的制备及形成机制

研究了阳极氧化电压、氧化时间和电解液的浓度对纯钛表面形成的阳极氧化薄膜形貌的影响。在氧化电压为20V,HF溶液浓度为0．5％（质量分数,下同）,氧化时间为60min的条件下,可在纯钛表面获得分布比较均匀的微米级多孔氧化膜,孔径为1．5-2．2μm。经500℃,1h处理后,该薄膜成为锐钛矿结构的TiO2。可以通过控制工艺参数,使得TiO2钝化膜的局部溶解速率大于形成速率来获取这种微米级多孔TiO2薄膜。     

NiW合金基带电化学抛光过程研究

采用硫酸溶液作为抛光液对轧制辅助双轴织构技术制备的Ni5W合金基带进行电化学抛光,在不同的抛光液浓度下获得了表面状态不同的基带。利用X射线光电子能谱(XPS)、X射线衍射(XRD)、扫描电镜(SEM)等手段研究了抛光过程中表面物质相成分及成因。结果表明:抛光液浓度较低时基带表面会形成过量的氧化物和H2WO4,造成表面选择性溶解过程紊乱,导致无法抛光。通过优化抛光液浓度可在基带表面获得适当厚度的固体层和粘液层,电流通过时可获得良好的抛光效果。     

N80碳钢CO2／HAc腐蚀电化学过程

采用动电位扫描、恒电位极化和电化学交流阻抗测试技术,研究了乙酸(HAc)对N80碳钢在50℃、饱和CO2的1%NaCl溶液中的电化学腐蚀行为的影响,并讨论了阴极、阳极的反应机理.研究表明:HAc能够直接在电极表面还原,使阴极极限电流增加.HAc未改变阳极反应机理,但能够加速中间产物的形成/溶解过程,从而加速阳极溶解过程.在饱和CO2溶液体系,乙酸盐易与碳酸生成HAc,而参与电化学反应.因此,无论是HAc还是乙酸盐均能够加速N80碳钢电极的CO2腐蚀.     

Cu-20Zr合金在盐酸溶液中的脱合金腐蚀历程

采用电化学方法、化学分析和表面分析技术,系统研究了Cu-20Zr双相铸态合金和磁控溅射Cu-20Zr纳米薄膜在HCl溶液中的脱合金腐蚀规律.对Cu-20Zr双相铸态合金的研究表明,铸态Cu-20Zr合金中的双相为富Zr的Cu51Zr14相,及Cu与Cu9Zr2的共晶组织;在低阳极极化电位条件下,Cu51Zr14相因富含活性组元Zr而优先溶解,说明双相合金的溶解行为首先决定于合金的相及其本身的活性.对溅射Cu-20Zr纳米薄膜腐蚀规律的研究表明,在不同电极电位下,薄膜中各元素的溶解规律不同.当电极电位低于Cu的标准电极电位时,材料的腐蚀以富Zr相中Zr组元的优先溶解为主;但当电极电位高于Cu的标准电极电位后,薄膜中Cu、Zr元素同时溶解;随后,由于Cu2 与溶液中的Cl-反应,生成氯化铜或氯化亚铜腐蚀产物覆盖于薄膜表面,使Cu的溶解过程受到抑制,但Zr元素却仍然随电极电位的增加而快速溶解.     

低驱动电位Al-Ga合金牺牲阳极及其活化机制

采用恒电流试验评价了不同Ga含量的Al-Ga二元合金牺牲阳极的电化学性能,并通过X射线衍射、扫描电镜及能谱分析、回沉积等实验探讨了阳极的活化溶解机制。结果表明,采用高纯铝锭炼制的Al-0.07%Ga 二元合金工作电位在-0.820 V~-0.876 V（vs.Ag/AgCl海水）之间,而用工业铝锭Al99.85炼制的Al-0.1%Ga二元合金阳极工作电位在 -0.802 V~-0.818 V之间,基本满足低驱动电位牺牲阳极的要求,但局部腐蚀溶解均较严重,溶解性能有待改善;Al-Ga合金腐蚀产物中的 Ga含量随基体中Ga含量的增加而增加,但远小于基体中的Ga含量;溶解后阳极表面的Ga含量大于基体中Ga含量,原因是溶解在溶液中的 Ga³⁺回沉积到阳极表面,使得阳极表面Ga含量增加;Al-Ga阳极的活化符合溶解-再沉积机理。     

Reactivity of the surface of zirconium during pickling in nitric-hydrofluoric acid

The behaviour of zirconium in hydrofluoric-nitric acid pickling solutions has been studied using electrochemical methods, X-ray diffraction and Raman spectrometry. During a pickling experiment the depletion of the solutions could be correlated with the consumption of hydrofluoric acid to form metal oxo- or oxofluorocomplexes. The role of nitric acid added to the hydrofluoric acid for pickling has been discussed after replacing it by other strong acids or by hydrogen peroxide. It appears that the zirconium dissolution rate only depends on the hydrofluoric acid concentration, but that the properties of the oxide film are determined by the nature of the strong acid added to HF; it can be assumed that metal dissolution occurs through the oxide film and that ionic diffusion through the film is a rate determining step.     

Metal-assisted etching of p-silicon—Pore formation and characterization

Etching of silicon and formation of definite porous surfaces can be carried out by different methods. Metal-assisted etching represents a convenient method for the application of induced etching for beneficial applications. Porous silicon layers (PSL) on Si are useful and important in solar energy conversion and optoelectronics. Porous silicon on silicon increases the effective area and thus higher optical absorption as well as solar conversion efficiency can be achieved. The effective optical properties of PSL have found great interest in optoelectronics. In the last few years PSL of definite pore structures have been prepared by metal-assisted etching of p-Si in aqueous hydrofluoric acid solutions containing different oxidizing agents. Potassium dichromate, at definite concentration and after optimum etching time of p-Si on which Pt nuclei were electroless deposited, has shown promising effects. The effect of etching time, K₂Cr₂O₇ concentration and HF concentration on the main characteristics of the porous structure was investigated and discussed. In this respect electrochemical impedance spectroscopy (EIS) was used. The experimental data were fitted to theoretical data according to a proposed electrical equivalent circuit model. The morphology of the formed layers and surface contaminations were investigated by scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques.The results have shown that PSL with nano and micro pores were formed on p-Si when etched in HF-K₂Cr₂O₇ aqueous solutions. At 22.0 mol L⁻¹ HF and relatively high concentration of K₂Cr₂O₇ [>0.05 mol L⁻¹] a passive K₂SiF₆ layer was formed on the Si surface with a thickness that is affected by the concentrations of both HF and K₂Cr₂O₇. The passive K₂SiF₆ layer reduces the effectiveness of the PSL in both the solar conversion process and also its electrical and optical characteristics.     

Regularities of electrochemical dissolution of Cu 62 Zn alloy in chloride solutions

The pattern of the electrochemical ionization and passivation of Cu 62 Zn brass in chloride solutions with different compositions is studied. The electrochemical dissolution of Cu 62 Zn alloy is shown to be controlled by ionization of the copper component in the alloy. The dissolution selectivity of the brass Cu 62 Zn components and the modification of the surface of the alloy during electrochemical etching in chloride solutions are studied. The uniform electrochemical dissolution of α-brass in an acid medium was found to occur in the presence of chlorine ions and an Fe³⁺ oxidizing agent.     

不锈钢双相焊缝选择性腐蚀研究

采用动电位扫描,恒电位浸蚀以及金相检测等方法,研究了不锈钢双相组织在酸性介质中发生选择性腐蚀的机理。研究发现,选择性腐蚀与体系所处的氧化-还原电位有关。在活化区的低电位段发生铁素体相的选择性腐蚀,较高电位段则发生奥氏体相的选择性腐蚀,两者之间存在一个两相腐蚀区;在过钝化区和近过钝化区,腐蚀优先发生在铁素体相上,然后向奥氏体相扩展。     

Anisotropic etching and electrochemical etch-stop properties of silicon in TMAH:IPA:pyrazine solutions

Anisotropic etching and electrochemical etch-stop properties of single-crystal silicon in tetramethylammonium hydroxide (TMAH): isopropyl alcohol (IPA) solutions containing pyrazine were investigated. With the addition of IPA to TMAH solution, an improvement in flatness on the etching front and a reduction in undercutting were observed, but the etch rate on (100) silicon decreased. However, the (100) silicon etch rate is improved by the addition of pyrazine. An etch rate of 0.8 μm/min on (100) silicon, which is faster by 13% than a 20 wt.% solution of pure TMAH, is obtained using 20 wt.% TMAH:0.005g/ml pyrazine solutions, but the etch rate on (100) silicon is decreased if there is an increase in the amount of pyrazine in the solution. With the addition of pyrazine to a 25 wt.% TMAH solution, no significant variations in flatness on the etching front were observed and the undercutting ratio was reduced by 30∼50%. The addition of pyrazine to TMAH:IPA solutions increased the etch rate of (100) silicon, thus the time required by the etch-stop process was shortened. The current-voltage (I–V) characteristics of n- and p-type silicon in TMAH:IPA:pyrazine solutions were obtained. The passivation potential (PP) of n- and p-type silicon was obtained and the applied potential was selected between n- and p-type silicon PPs. The electrochemical etch-stop method was applied to the fabrication of 801 silicon microdiaphragms of 20 μm thickness on a 5-inch silicon wafer. The average thickness of fabricated 801 microdiaphragms on one wafer was 20.03 μm and the standard deviation was ±0.26 μm. The silicon surface of the etch-stopped microdiaphragms was extremely flat with no noticeable taper or non-uniformity. The benefits of the electrochemical etch-stop method for the anisotropic etching of silicon in TMAH:IPA:pyrazine solutions become apparent when reproducibility of silicon microdiaphragm thickness for mass production is realized. The results indicate that use of the electrochemical etch-stop method for the anisotropic etching of silicon in TMAH:IPA:pyrazine solutions provides a powerful and versatile alternative process for fabricating high-yield silicon microdiaphragms.     

锌在KOH溶液中的腐蚀电化学行为

用电化学方法研究了锌在浓ＫＯＨ溶液中的电化学行为，得出了锌在浓碱液中的电化学反应机理。利用弱极化曲线拟合法得出了锌的腐蚀速度与ＫＯＨ浓度的关系。     

The effect of purine on the corrosion of copper in chloride solutions

The influence of the concentration of purine (PU) on the corrosion and spontaneous dissolution of copper in 1.0 M NaCl solutions (pH 6.8) was studied. The investigations involved electrochemical polarization methods as well as weight-loss measurements, electrochemical quartz crystal microbalance (EQCM) techniques and scanning electron microscopy (SEM). The inhibition efficiency (IE) increases with an increase in the concentration of PU. An adherent layer of inhibitor is postulated to account for the protective effect. The adsorption of PU has been found to occur on the surface of copper according to the Langmuir isotherm. Purine is chemically adsorbed on the copper surface.     

Kinetics and mechanism of the nickel electrode—II. Acid solutions containing a high concentration of sulphate and nickel ions

The kinetics of the Ni electrode in acid solutions with a high sulphate and nickel ion concentration has been investigated in the range of 25–75°C. The active dissolution and the passive regions and the active-passive transition phenomena have been studied employing different potential perturbation techniques using both still and stirred solutions.Two electrochemical processes are competing within the prepassive film potential region, namely, the active Ni dissolution to Ni(II) ions and the Ni(OH)₂ film formation. Nickel passivation is explained by reaction pathways involving successive electrochemical and chemical steps implying the occurrence of hydroxo- and oxo-species as reactions intermediates. The advanced mechanism is based upon a positively charged Ni surface structure and attributes the onset of the complete passivity to a particular surface oxide species.     

氯离子浓度对AZ63镁合金初始腐蚀的影响

采用腐蚀电位、线极化、电化学阻抗谱和极化测量等方法研究AZ63镁合金在1％、3％、5％和7％NaCl(质量分数)腐蚀介质中的初始腐蚀行为.结果表明,随着氯离子浓度的增加,腐蚀速率加快.基于得到的动力学参数,讨论了阳极溶解和析氢反应的机理,并建立了动力学模型.结果显示,阳极溶解是发生在Temkin条件下,析氢反应取决于M...     

H2S浓度对35CrMo钢应力腐蚀开裂的影响

用电化学技术研究了35CrMo钢在含有不同浓度H₂S溶液中的腐蚀行为,通过慢应变速率拉伸实验研究了35CrMo钢在不同浓度H₂S介质中的应力腐蚀开裂 (SCC) 行为与机理。结果表明：35CrMo钢在pH值为5的H₂S环境下存在SCC敏感性,H₂S浓度升高,SCC敏感性增加,H₂S浓度为200 mg/L时有明显的SCC敏感性。H₂S浓度达到200 mg/L时,能明显促进35CrMo钢腐蚀电化学过程进行。在pH值为5的H₂S环境下,35CrMo钢的SCC机制是以氢脆 (HE) 为主,阳极溶解(AD)为辅的协同机制。