镍铁钨合金电沉积工艺

为获得性能良好的镍铁钨合金镀层,研究了电解液pH值、温度、电流密度、柠檬酸钠浓度对施镀阴极电流效率和镍铁钨合金镀层组分、表面形貌、显微硬度的影响.结果表明:镀液pH值对镀层形貌和阴极电流效率影响较大;随柠檬酸钠浓度增加,电流效率逐渐降低,镀层表面形貌更加粗糙.在镀液pH=8,温度70℃,电流密度7 A/dm2,柠檬酸钠...     

稀土添加剂对镀镍液性能的影响

为了将稀土引入电镀金刚石工具的生产之中,研究了稀土添加剂对镀镍液性能的影响.以普通镀镍液为基础,采用远近阴极法测定了不同稀土含量镀镍液的分散能力,用内孔法测定了其深镀能力,镀液及其底液的阴极极化性能.结果表明,稀土添加剂可以提高镀镍液的分散能力和电流效率,但对于镀液的深镀能力有不良影响,这可能与稀土阳离子的水解产物在阴极的吸附、提高了阴极极化有关.     

锌酸盐体系Zn-Fe合金电镀阴极电流效率的研究

对碱性锌酸盐体系电镀Zn-Fe合金阴极电流效率的影响因素进行了系统的研究,并分析了镀层中铁原子的引入对Zn-Fe合金电镀阴极电流效率的影响原因及合金镀层中铁含量与阴极电流效率的关系,以期通过控制镀液组成及工艺条件在一定程度上提高阴极电流效率.增加电镀液中锌铁离子总摩尔浓度,提高镀液中锌铁离子摩尔比,降低铁离子浓度,适当控制阴极电流密度,升高镀液温度均可提高锌铁合金电沉积的阴极电流效率.添加剂ZFA的加入使Zn-Fe合金电镀的阴极电流效率降低.合金镀层中引入Fe明显降低了电沉积的阴极电流效率,镀层中的Fe含量从0升高至0.73%,合金电沉积的阴极电流效率却从79.48%降低至68.23%.这是由于碱性溶液中,氢气在金属Fe上析出的过电势明显小于在金属Zn上的过电势,使析氢容易进行引起的.     

化学镀铜—锡—磷三元合金

采用化学镀技术，成功地在钢铁基体上制备了84．5%Cu、12％Sn、3．5%P的三元合金镀层，其沉积速度约为3μm/h。阐述了镀液关键组分的浓度和工艺参数对镀层中铜锡磷含量的影响，提出了获得良好镀层的最佳镀液组成及操作条件。     

阴离子膜不锈钢阳极锌锰合金电沉积的研究

研究了锌锰合金电沉积的工艺条件,镀液稳定性,镀层中锰含量和阴极电流效率的规律。采用阴离子膜作阳极隔膜,不锈钢作阳极,紫铜板为阴极,研究了硫酸盐－柠檬酸体系锌锰合金电沉积的工艺条件,讨论了阴极电流密度,镀液中锰离子的浓度,镀液中锌,锰离子的摩尔比,增效剂、电沉积温度等因素对镀层中锰含量和阴极电流效率的影响规律,探索了提高阴极电流效率的途径,改善了镀液的稳定性。本文所选工艺条件为：MnSO4.H2O 30-50g/L,ZrSO4.7H2O:5-10g/L,柠檬酸钠（二水）100－150g/L,增效剂0．083g/L,表面活性剂适量,ic 1.5-3.0A/dm^2,pH值5．6,t25-30℃。该工艺可得含锰量为50％左右的锌锰合金镀层,阴极电流效率约60％。镀液在该工艺条件下连续施镀90min镀层组成稳定。     

三价铬镀液中配体的作用

三价铬镀铬液中的配体对镀液的稳定性和沉积速度影响极大,从三价铬镀液的化学和电化学特性分析入手,介绍了镀液中所加配体(如羧酸、羟基羧酸、氨基羧酸及其盐)的作用:(1)与三价铬离子形成活性配位离子加快电沉积速度;(2)抑制Cr3 的羟桥化反应;(3)可以掩蔽杂质金属离子,减少杂质金属离子对镀层质量的干扰,使电镀能持续进行;(4)可以稳定镀液.特别指出,只有选用能形成活性配位离子的配体,使电镀能持续进行,才能获得性能良好的厚铬镀层.     

电沉积Ni—Cr合金工艺

给出了三价铬体系电镀Ｎｉ－Ｃｒ合金工艺的配方，通过实验表明，镀液的稳定性高，分散能力和覆盖能力好。温度１０－７０℃，ｐＨ值１－５，阴极电流密度－１４Ａ／ｄｍ＾２，阴极电流效率最高可达到７０５以上。镀层外观明亮如镜，可用于防护及装饰镀层。     

电流密度对甲基磺酸盐电沉积亚光锡的影响

在甲基磺酸盐电镀溶液中进行恒电流电沉积亚光锡镀层实验,考察电流密度对镀液极化性能、阴极过电位、电流效率、沉积速率及镀液分散能力的影响。利用SEM和XRD分析不同电流密度所得锡镀层的表面形貌和结晶取向。结果表明:随着电流密度增大(0.5～4A.dm-2),镀液的阴极极化增大,电流效率先增加后降低,沉积速率不断加快,但镀液分散能力有所下降;晶体由"向上生长"模式逐渐转变为"侧向生长"模式,择优取向由(321),(431)晶面转变为(112),(332)晶面;添加剂吸附在晶体表面,降低了被吸附晶面的表面自由能,使这些晶面的生长速率下降,从而改变了镀层择优取向和晶体生长的方式。     

稀土在镍铁合金电沉积中的作用

通过赫尔槽实验、微分电容曲线和极化曲线测定等方法，研究了几种稀土元素对Ｎｉ－Ｆｅ合金镀液和镀层性能的影响。结果表明，在Ｎｉ－Ｆｅ合金镀液中加入少量稀土化合物后，稀土能吸附在阴极表面，使阴极极化作用增强，从而使镀液的光亮电流密度范围增宽，使镀液的分散能力、电流效率和镀液的稳定性等都得到改善和提高，同时还增强了镀层的耐蚀性。     

镍钴合金电沉积中硫酸钴影响的探讨

电沉积镍层硬度低,耐磨性差,在瓦特型镀镍液中加入硫酸钴可以提高镀层的抗热性能、耐蚀性能和韧性.采用硫酸盐电解液电沉积镍钴合金,研究了电解液中硫酸钴浓度与镀液分散能力、深镀能力的关系及其对镀层显微硬度、孔隙率和内应力的影响.同时,利用扫描电子显微镜分析了沉积层的表面形貌.结果表明:随着镀液中硫酸钴浓度的增大,镀液的分散能力下降,深镀能力升高;镀层显微硬度显著提高,内应力和孔隙率也有所增加.镍钴合金沉积层比纯镍镀层更细致、结晶均匀.     

Polynitroaniline as brightener for zinc-nickel alloy plating from non-cyanide sulphate bath

Electro-polymerization of orthonitroaniline was carried out on graphite electrode in hydrochloric acid medium. Zinc-nickel alloy deposition was carried out in the presence of polynitroaniline in acid sulphate bath. The bath constituent and bath variables were optimized through Hull cell experiments. The current efficiency and throwing power were measured. High shift of potential towards more cathodic direction was observed in presence of addition agent. Corrosion resistance test revealed good protection of base metal by zinc-nickel coating obtained from the developed electrolyte. SEM photomicrograph shows fine-grained deposit in the presence of addition agent. The consumption of brightener in the lab-scale was 0·01 gL⁻¹ for 1000 amp-h.     

Study on the behaviour of ZnCoCu alloy electroplating

Ternary zinc–cobalt–copper alloys of wide range composition were deposited on to steel substrates from dilute metal sulphate bath. The bath consisted of 1–20 g dm⁻³ CuSO₄·5H₂O, 1–30 g dm⁻³ CoSO₄·7H₂O, 1–50 g dm⁻³ ZnSO₄·7H₂O, 20 g dm⁻³ Na₂SO₄ and 150–200 g dm⁻³ NH₂CH₂COOH. The effect of bath composition, current density and temperature on the cathodic potential, cathodic current efficiency and composition of the deposits were investigated. The codeposition of ZnCoCu alloys from these solutions can be classified as regular. Increasing current density enhances the rate of Zn deposition but suppresses that of Cu deposition. However, increasing the bath temperature favours Cu deposition. Co content in the deposits is hardly affected by changing these variables. Increasing Cu content in the bath or increasing the applied current density greatly improves the cathodic efficiency for the alloy deposition. X-ray diffraction studies showed that the deposits obtained at high current density (Zn-rich alloy) consisted of a cubic CuZn₂ phase, while that obtained at high temperature (Cu-rich alloy) consisted of a face, centred cubic CuCo phase. The structure and morphology of the deposited alloys were characterised by anodic stripping and SEM.     

Oxygen Coefficient of Uranium Oxides and Current Efficiency as Influenced by Electrolysis Parameters and Composition of Molten Salt Electrolytes in the Na2WO4-Na2W2O7-UO2WO4 System

The oxygen coefficient of uranium oxides, their structure, and current efficiency were studied as influenced by the electrolyte composition, deposition potential, and temperature of electrolysis. On passing from Na₂WO₄-UO₂WO₄ binary system to lower-melting ternary systems the dependences of the oxygen coefficient in the cathodic product on the electrolyte composition and electrolysis parameters remain essentially similar. Significant deviation of the experimental current efficiency with respect to uranium oxides from the theoretical value suggests significant chemical interaction between the cathodic product and electrolyte. The corrosion rate increases and the current efficiency decreases with increasing temperature and concentration of W₂O₇ ^2- ions. The structure of the resulting cathodic deposits is predominantly determined by their specific electrical conductivity, which is a function of the chemical composition of the electrolyte. The dendrite structure is typical for higher oxides.     

Growth and characterization of electrosynthesised zinc oxide thin films

Zinc oxide (ZnO) films have been electrodeposited from an aqueous solution containing 0.1 M zinc nitrate as the electrolyte with pH around 5±0.1. The deposition was carried out by galvanostatic reduction with an applied cathodic current density in the range between 5 and 20 mA cm⁻². The influence of bath composition on the preparation of ZnO films is studied. The effects of zinc nitrate concentration and cathodic current density on the deposition rate of ZnO films were also studied. An optimum current density of 10 mA cm⁻² is identified for the growth of ZnO film with improved crystallinity and optical transmittance. The crystalline structure of the deposits studied by X-ray diffraction reveals the possibility of growing hexagonal ZnO films under suitable electrochemical conditions. The surface morphological studies by scanning electron micrographs revealed the presence of nodular appearance for films deposited at 800 °C bath temperatures.     

稀土在氯化物体系电沉积锌-铁合金中的作用

为了研究稀土在电沉积锌-铁合金中对镀层和镀液的作用,通过在镀液中添加LaCl3后,对镀层组分、厚度、耐蚀性的改变,镀液稳定性、分散力以及阴极极化作用的影响进行了研究.结果发现,稀土的加入有利于提高镀液稳定性、分散能力和减薄镀层,使锌-铁合金镀层的耐蚀性在中性5%NaCl溶液中有较大提高.研究表明,稀土盐的加入能改善镀液性能,改变镀层成分和锌-铁合金电沉积的阴极极化行为,同时提高镀层的耐腐蚀性.     

化学镀Ni-Co-W-P及其析氢性能的研究

用化学镀方法制备出Ni-Co-W-P合金电极,测量了其在1 mol/L NaOH溶液中的阴极极化曲线并研究了其析氢电催化活性.试验表明,在相同的电流密度下,Ni-Co-P,Ni-W-P和Ni-Co-W-P合金电极的析氢过电位较Fe电极降低,其中Ni-Co-W-P的析氢过电位降低约230 mV,XRD试验显示其镀层为非晶态.并进一步测试了其在7 mol/L KOH中的连续电解曲线.结果表明:Ni-Co-W-P合金电极比Ni-Co-P,Ni-W-P合金电极具有更好的析氢电催化活性和电化学稳定性,有利于降低槽压,减少能耗.     

采用电化学法研究Fe-W-P合金化学沉积工艺

通过偶接金属铝,采用化学沉积方法制备Fe-W-P三元合金镀层,用电化学方法研究了镀液组成对Fe-W-P化学沉积行为的影响,并分析了偶接金属铝对合金沉积的诱导作用,对合金沉积的机理进行了初步探讨.结果表明,改变镀液组成和沉积工艺,沉积电位和沉积电流随之变化,增大镀液中NaOH和还原剂NaH2PO2·H2O的浓度,沉积电位负移,沉积速率增大,而随着钨酸钠的加入镀层的沉积速率稍有下降,表明钨酸钠对Fe-W-P的化学沉积有一定的抑制作用.偶接金属铝使体系的电位负移,降低了阴阳极极化电阻,诱导了Fe-W-P三元合金的共沉积.     

碱性条件下Fe-P-B合金电镀

研究了碱性溶液中镀液组成、阴极电流密度、温度、pH值对Fe-P-B合金电镀层沉积速率和组成的影响,优化了工艺,在最佳工艺条件下获得Fe-P-B镀层,并对镀层的耐腐蚀性、结构和结合力进行了分析.结果表明:提高镀液中硫酸亚铁铵含量、溶液pH值、温度和电流密度,镀层沉积速率增加;提高镀液中次亚磷酸钠、丙二酸和硼氢化钠含量,镀层沉积速率先增后降低,出现一个极大值;镀层中B含量的增加会使P含量降低,但提高电流密度和镀液温度时二者都有所增加;在最佳工艺条件下获得的Fe-P-B合金镀层为非晶态结构,和基体结合力优良,耐蚀性良好,在15%NaoH溶液中的耐腐蚀性优于在5%NaCl溶液中.     

Electrodeposition of hard nanocrystalline chrome from aqueous sulfate trivalent chromium bath

A sulfate trivalent chromium bath is described which contains chromium(III) salt, sodium sulfate, aluminum sulfate, boric acid, formic acid, carbamide and surfactant. The bath is operated using either titanium-manganese dioxide anodes or platinized titanium anodes without separation of anodic and cathodic compartments. Effect of bath composition and electrolysis conditions on current efficiency of chromium electrodeposition was studied. At optimal bath composition and electrolysis conditions, the deposition rate does not practically change during electrolysis time; it is close to 0.8 μm min⁻¹. The nanocrystalline coatings with a thickness of several tens of micrometers are bright and smooth. The value of Cr-coatings hardness does not substantially differ from that observed in case of Cr(VI)-based baths. The possibility of continuous service of the proposed trivalent chromium bath was confirmed by means of a durational electroplating test (~ 2 months).