添加剂对氯化钾溶液中锌电沉积的影响

目前,添加剂对镀锌的作用及其机理说法不同.用线性扫描法、循环伏安法和计时电流法分别研究了聚乙二醇400(PEG400)及其与苄叉丙酮(BA)复配在氯化钾(KCl)溶液中对锌电沉积的影响;根据Scharifker-Hills成核模型拟合了电流-时间数据.结果表明:PEG400和BA混合比单加更能增大锌在KCl溶液中电沉积的过电位,能更有效地抑制析氢反应;锌的电沉积机理在一定程度上取决于所加入的添加剂,仅添加PEG400,锌电沉积机理与无添加剂的一样,都是晶核瞬时形成和成长的过程,PEG400和BA同时加入,锌的电沉积机理是晶核连续形成后转为晶核瞬时形成.本研究结果有助于氯化钾镀锌高效添加剂的开发.     

ChCl/CrCl3·6H2O体系中Cr(Ⅲ)的电化学成核机理

本文在ChCl/CrCl3.6H2O离子溶液体系中,采用循环伏安法和恒电位阶跃法研究了Cr(Ⅲ)在玻碳电极上的电化学成核机理。研究结果表明,Cr(Ⅲ)的电化学成核机理是三维成核并与过电位有关。当过电位较小时,Cr(Ⅲ)的电结晶过程为三维连续成核,其扩散系数为(2.56±0.33)×10-11m2/s。当过电位较大时,Cr(Ⅲ)的电结晶过程趋向于三维瞬时成核过程,其扩散系数和晶核数密度均与过电位无关,分别为(3.04±0.3)×10-11m2/s和(4.47±0.05)×1011/m2。两种成核方式的法向生长速率常数均与过电位成线性关系,晶体法向的生长没有受到任何阻滞。     

锌-铁合金异常共沉积中锌沉积机理的研究(Ⅰ)--Zn阴极沉积反应历程的拟定

为确定Zn-Fe合金异常共沉积过程中Zn的沉积机理,在机理研究的合理假设条件下,运用各种电化学测试方法研究了Zn-Fe合金异常共沉积中Zn的阴极沉积性质,将理论推导与试验数据相结合拟定出了电极反应历程.碱性锌酸盐电镀液中(pH＞13)锌离子主要是以四配位体Zn(OH)24-的形式存在;电极反应活化能为38.93kJ/mol,表明Zn(OH)24-在阴极放电受电化学极化控制,Zn(OH)24-在阴极放电首先经历前置化学转化反应,放电分两步进行,Zn(OH)24-的扩散系数为2.452×10-6cm2/s.体系中直接放电的配离子为Zn(OH)2.     

硫酸盐体系中铟在玻璃碳电极上的电化学成核机理

关于硫酸盐体系中镀铜的沉积机理少见报道,采用循环伏安法和计时电流法研究了铟在硫酸盐体系中电沉积的循环伏安特性与电结晶机理.通过分析恒电位暂态曲线,求出铟离子的扩散系数D和不同电压下的晶核密度N_0.结果表明:铟的电沉积没有经历欠电位沉积过程,而是经历了晶核形成过程,其电沉积反应是一个不可逆过程;在外加电位范围内铜的电结晶按照瞬时成核方式和三维生长方式进行.     

碱性锌酸盐体系Zn-Fe合金电镀异常共沉积研究

采用分电流曲线法研究了碱性锌酸盐体系Zn-Fe合金电镀异常共沉积的规律.研究发现:Zn-Fe合金共沉积在低电流密度下为正常共沉积,高电流密度下为异常共沉积,且存在一转换电流密度;锌铁离子摩尔比、NaOH、配合剂等影响锌铁离子阴极还原交换电流密度的因素均对转换电流密度有影响;Zn-Fe合金共沉积过程中锌发生了欠电势沉积.锌铁离子的交换电流密度不同是引起Zn-Fe合金异常共沉积的主要原因.     

以三乙醇胺为辅助配位剂碱性电沉积锌镍合金的电化学行为

碱性镀液中镍离子的配位剂对镀层影响很大,目前对其多种配位剂共同使用的研究较少。研究了以四乙烯五胺为镍离子的主配位剂,三乙醇胺(TEA)为镍离子辅助配位剂的锌镍合金碱性电沉积体系,在不同三乙醇胺含量和电流密度下在Q235低碳钢表面电沉积锌镍合金的电化学过程。结果表明:随着镀液中三乙醇胺含量增加,电流效率和沉积速率下降,溶液电阻、电荷传递电阻和电感先增加后降低,在n(TEA)∶n(Ni2+)=2.0时阴极极化最大;增加阴极电流密度使镀液的沉积电位变负,阴极极化增大,同时使电荷传递电阻和电感变小;该碱性电沉积锌镍合金的过程受电化学步骤和扩散步骤混合控制。     

阴极偏压对Zn-Ni合金镀层电沉积行为的影响

碱性锌酸盐体系电沉积Zn-Ni合金镀层的研究还不系统。采用扫描电子显微镜(SEM)、能量色散谱仪(EDX)、电化学阻抗谱(EIS)等研究了碱性锌酸盐体系中A3钢表面Zn-Ni合金镀层的共沉积行为,考察了阴极偏压对Zn-Ni合金镀层成核/生长速率的影响规律。结果表明:通过恒电流电沉积技术得到的Zn-Ni合金镀层表面平整光亮,镀层中Ni含量为10.6%;Zn-Ni合金镀层的沉积过程遵循异常共沉积机制,镀液中的Zn2+阻碍了Ni2+的阴极还原反应过程;Zn-Ni合金镀层的沉积速率随着阴极偏压的变负而呈指数规律提高。     

碱性锌酸盐体系锌钴合金电镀工艺研究

目前国内对碱性锌酸盐体系电镀锌钴合金的研究较少。研究了碱性锌酸盐Zn-Co合金电镀体系中合金镀液组成及工艺条件对镀层Co含量的影响,得到了最佳镀液组成及工艺条件:锌钴离子总浓度0.3 mol/L,锌钴离子摩尔比9∶1,150 g/L氢氧化钠,15.0 m L/L添加剂A,1.0 m L/L添加剂B,电流密度Jc3 A/dm2,温度25~30℃。在最佳工艺条件下可得到Co含量为2.0%~2.2%的Zn-Co合金镀层。结果表明:Zn-Co金的沉积表现为异常共沉积;在一定范围内,镀层中钴含量的变化会影响镀层光亮度的变化;钴配位剂对Zn-Co合金的共沉积电化学行为不造成影响。     

氨络合物体系中镍在玻璃碳上的电化学成核机理

采用循环伏安法和计时电流法研究了氨络合物体系中镍在玻璃碳上电结晶的初期行为。结果表明．镍在该基体上的沉积没有经历UPD过程，镍的电沉积经历了晶核形成过程，在所研究的外加电位范围内其电结晶按连续成核和三维生长方式进行，外加电位对晶体生长具有显著的影响。通过分析恒电位暂态曲线，求出镍离子的扩散系数D，以及不同外加电位下的饱和晶核数密度Nsat，探讨了外加电位对成核作用的影响。     

耐高温碱性锌酸盐镀锌光亮剂的应用

介绍了碱性锌酸盐环保镀锌的新工艺，对镀液，镀层性能等进行了试验及生产实践，可见该光亮剂能使碱性锌酸盐镀锌工艺得到改善，表现为耐高温，出光快，结晶细，镀层光亮，均，深镀能力好，能抑制气雾等，它还解决了碱性锌酸盐镀锌在60℃高温时，不能正常生产的技术难题。     

Bi3+和四丁基溴化铵对碱性可充锌电极枝晶生长行为的影响*

采用电流－时间曲线、极化曲线和扫描电子显微镜等方法,研究了Bi^3 与四丁基溴化铵（TBAB）对可充锌电极在碱性锌酸盐溶液中枝晶生长行为的影响。实验结果表明,Bi^3 和TBAB对锌电极的枝晶生长均有一定的抑制作用,但在高阴极过电位下TBAB不能有效地抑制锌枝晶的生长。在实验过程中还发现,Bi^3 和TBAB对锌枝晶的抑制具有明显的协同作用,且对锌电极的放电行为几乎不产生影响。     

Investigation of the nucleation mechanism in bias-enhanced diamond deposition on silicon and molybdenum

Polycrystalline diamond films were deposited on Si and Mo substrates in a microwave plasma-enhanced chemical vapour deposition reactor employing bias-enhanced nucleation. The deposition process was subdivided into two consecutive steps: the pretreatment (bias-enhanced nucleation) and the diamond growth step. To investigate the nucleation process we kept the deposition parameters during the diamond growth step constant and only changed the parameters during the pretreatment. The methods employed to analyze the deposited films after the pretreatment step were electron energy loss spectroscopy (EELS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy.

The nucleation density (N_D) on Si following the complete deposition cycle (pretreatment and diamond growth step) increases considerably from 5 × 10⁸ cm⁻² to 5 × 10¹⁰ cm⁻² with an increase in the substrate temperature during the pretreatment (T_p) in the temperature range from 680 to 750 °C. For T_p ≥ 770 °C continuous films are formed. The structure of the pretreatment deposit undergoes likewise considerable changes: if T_p exceeds 770 °C the appearance of an intense diamond plasmon at 34 eV is observed, indicative of an increase in the concentration of diamond crystallites embedded in an otherwise amorphous carbon matrix. Our experiments suggest that diamond crystallites formed during the pretreatment serve as nucleation centres for the subsequent diamond growth.

The same deposition parameters which result in the formation of a continuous diamond film on Si, yield only low nucleation densities on Mo. An increase in N_D from 6 × 10⁶ cm⁻² to 2 × 10⁸ cm⁻² can be achieved by raising the methane concentration [CH₄] in the gas phase during the pretreatment from 5 to 50% (T_p = 820 °C). The carbon concentration at the surface for the pretreatment deposit, determined by XPS analysis, increases likewise with [CH₄]. According to the EELS analysis the structure of the pretreatment deposit is comparable with disordered graphite or a-C and no diamond plasmon is observed. The high [CH₄] is required to form the Mo-carbide interface and balance the diffusion of carbon into the metal before the a-C layer can be formed.

The formation of nucleation centres during the bias-enhanced nucleation seems under these deposition conditions to proceed via different pathways on Si and Mo. While the nucleation on Si appears to be linked to the formation of diamond nanocrystals during the pretreatment, this is not the case for Mo.     

Microstructural characterization of pulsed electrodeposited Au/Sn alloy thin films

Based on previous work that identified an electrodeposited composite, multi-layer structure as a viable method of producing eutectic Au/Sn alloys for solder applications, a study of individual phase formation was undertaken. The AuSn phase, because of its higher deposition current (>2.0 mA cm⁻²), has a much faster deposition rate than Au₅Sn, which is deposited at <1.0 mA cm⁻². AuSn formation is growth controlled, while Au₅Sn formation is nucleation controlled. The AuSn forms a continuous layer within 60 s with a grain size of 50–75 nm. Because of the high deposition current, the dominant formation mechanism is two-dimensional nucleation, resulting in a relatively rough surface finish. Au₅Sn, on the other hand, forms a continuous layer within 600 s with an average grain size of 200 nm. Because of the significantly lower deposition current, the dominant formation mechanism is lateral spreading instead of two-dimensional nucleation. The result is a very smooth finish on the deposit surface.     

Structure, nucleation and Eu luminescence in alkaline earth rare earth borate glass

In La₂O₃-MO-B₂O₃ ternary system, various glasses/ glass ceramics with M=Ca, Sr and Ba have been prepared. In this ternary system, homogeneous nucleation occuring in the B₂O₃ melt appears to be the cause for the formation of nanocrystallites, hence glass ceramics. The nucleation process is very much dependent on the alkaline earth used viz., with smaller alkaline earths like Ca, boron prefers (BO₄)⁵⁻ tetrahedral coordination with oxygen, while in the case of bigger alkaline earths like Ba and Sr, (BO₃)³⁻ triangular coordination seems to be predominant. Eu³⁺ in this glass system yields intense ⁵D₀→⁷F_j emission. A cursory view on the dependence of the various Judd-Ofelt parameters (Ω_k) indicates that Ω₂ parameter is very much dependent on the immediate vicinity of the luminescent ion (Eu³⁺) while Ω₄ is not. Various results based on these are discussed.     

The process of electrochemical deposition of zinc in the presence of boron-doped detonation nanodiamonds

The influence of detonation of nanodiamonds doped with boron during the detonation synthesis (DND-boron) on the process of electrochemical deposition of zinc from a zincate electrolytic solution is investigated. It is shown that the throwing power (the coating uniformity) increases 2to 4-fold depending on the DND–boron concentration, the electrolytic conductivity remains unchanged, the corrosion resistance (as measured by the corrosion currents) of the Zn–DND-boron coating grows 2.6 times when tested in the 3% NaCl solution and 3 times in the climatic chamber.     

二元配合物中电镀锌镍合金的结构与抗腐蚀性

为深入了解碱性锌酸盐体系的工艺参数对锌镍合金镀层结构和耐蚀性的影响,在以四乙烯五胺(TEPA)为镍离子主络合剂、三乙醇胺(TEA)为辅助络合剂的碱性镀液中电沉积制备了锌镍合金镀层,利用电子能谱、X射线衍射、极化曲线和电化学阻抗谱等方法表征镀层的组成结构和在氯化钠溶液中的耐腐蚀性.结果表明:镀层含镍原子数分数11.54%~20.12%,为γ-Ni2Zn11+纯Zn两相结构(低含镍原子数分数时)或单一γ相结构(较高含镍原子数分数时),γ相晶粒在(600)方向上具有不同程度的择优取向性;随着镀液中镍原子数分数的提高,镀层的腐蚀电位正移,阻抗增加,耐蚀性提高;当电流密度为2 A/dm2时,镀层的腐蚀电位和电荷传递电阻最高,耐蚀性最好.     

脉冲电沉积法制备Al基Pb—WC—Ce02复合惰性阳极

为了制备性能优良的Al基Pb—WC—CeO：惰性阳极材料,考察了WC、CeO：颗粒浓度对阴极极化的影响,正向脉冲参数、温度和搅拌对沉积速率以及复合镀层表面形貌的影响,并研究了其在锌电解液中的耐蚀性能,确定了脉冲电沉积制备Al基Pb-WC-C02复合镀层的最佳工艺条件：基础镀铅液中添加40g／LWC（粒径1斗m）,30g...     

Influence of the cohesive behaviour of small particles on the solid-state photolytic degradation of furosemide

The effect of the cohesive behaviour of small particles on the solid-state photochemical degradation of furosemide is reported. Samples of agglomerated and recrystallised separated particles were exposed to direct sunlight for up to 240 hours, and the furosemide content measured with time. The solid-state photolytic degradation of furosemide proceeds from a nucleation period, through a growth period and eventual deceleration of the reaction. The kinetic process was best described by a power law dependence of the fraction degraded on time for the nucleation period and first order kinetics with asymptote, Prout-Tompkins equation, for the growth of the nuclei. The first order rate constants for the degradation of the agglomerated and the separated particles were 1.20 × 10^-2 hour^-1 and 1.48 × 10^-2 hour^-1 respectively for the nucleation period and 2.85 × 10² hour^-1 and 2.45 × 10^-2 hour^-1 for the growth period. Although the mean particle size of the particles which made up the agglomerates was significantly smaller (2.5 μm) than the separated particles (22 μm), the separated particles degraded more than the agglomerates. The maximum, infinite, fraction degraded ($aL∞,) was 0.450 for the agglomerates and 0.660 for the separated particles. It seemed as though nucleation depended on the surface area exposed to irradiation. Agglomeration decreased the surface area available and therefore nucleation was less. Degradation during the growth period appeared to occur inside the particles and was limited by the extent of nucleation.     

碱性锌酸盐镀锌液中辅助光亮剂苄基吡啶鎓-3-羧酸盐的紫外吸收分光光度法测定

为测定碱性锌酸盐镀锌液中辅助光亮剂苄基吡啶鎓-3-羧酸盐(BPC)的浓度,采用紫外分光光度法,确定了锌酸盐镀锌辅助光亮剂BPC的最大紫外吸收波长,探讨了光亮剂聚胺、氢氧化钠浓度对测定的影响。结果表明:光亮剂聚胺、氢氧化钠浓度对测定的影响较小。在BPC浓度为1~10 mg/L的条件下,测定相对误差在2%以内。由实际电镀过程分析得知,BPC的消耗量为0.45 g/(k A·h)。该方法简便、准确、快速,可作为锌酸盐镀锌液中辅助光亮剂BPC的检测方法。     

锻态TB6钛合金β相区压缩变形行为和动态再结晶

使用圆柱形试样在Thermecmaster-Z型热模拟试验机上进行锻态TB6钛合金β相区的热压缩实验(变形温度950~1100℃,应变速率0.001~1 s^-1),研究了合金的高温压缩变形和动态再结晶行为。结果表明,这种合金在β相区的变形激活能为246.7 kJ/mol,其热变形机制是动态再结晶,动态再结晶新晶粒的主要形核机制是弓弯形核。当应变速率为0.01~0.1 s^-1、变形温度为<1000℃时动态再结晶的发展比较充分,变形组织明显细化;当变形温度高于1000℃、应变速率低于0.001 s^-1时,动态再结晶的晶粒明显粗化。在动态再结晶的晶粒尺寸D与Z参数之间存在着相关性,其函数关系为D=6.44×10²·Z^-0.1628。