添加剂对Cu/Co多层膜电结晶成核机理及磁性的影响

在硼酸镀液中以单晶S i(111)为基底用双槽法制备Cu/Co多层膜,在镀液中分别加入了镀铜添加剂2000#和镀钴添加剂5#。探讨了镀层电结晶成核机理,在基础镀液中铜电结晶为三维连续成核过程,钴电结晶在较低电位下为三维连续成核,在较高电位下为三维瞬时成核过程。加入添加剂后,铜、钴电结晶均为三维瞬时成核过程。测试了Cu/Co多层膜的磁性能;添加剂能提高多层膜的磁性能,无添加剂的Cu/Co多层膜的巨磁阻(GMR)值约为5%,而在加入了添加剂后,其GMR值高达52%。     

流动槽滴入法电结晶制备铜钴纳米多层膜

在硼酸镀液体系中采用流动槽滴入法电结晶制得Cu/Co纳米多层膜,通过循环伏安法确定Cu、Co电结晶电位,分别为-0.55V和-1.05V(vs.SCE),通过X射线衍射技术(XRD)和X射线荧光光谱法(XRF)对Cu/Co纳米多层膜的结构、成份进行了分析.并用物性测量系统PPMS测试了Cu/Co多层膜的磁性能,结果表明:电结晶制备的Cu/Co多层膜的矫顽力比较小,仅为34 Oe,适合作巨磁阻磁头材料,其磁电阻随磁场强度的增大而减小,且约在3000 Oe时磁电阻趋于饱和,此时的巨磁阻效应GMR值达到了14%.     

Electrochemical nucleation and growth of poly-N-Methylpyrrole on copper

The potentiostatic electropolymerization of poly-N-Methylpyrrole on Cu at 1.5 V, 2.0 V and 2.5 V vs saturated calomel electrode potentials has been carried out to establish the successive steps of polymer coating generation. The chronoamperograms obtained allow the different steps of the nucleation and growth mechanism to be analyzed by fitting the experimental data to the mathematical equations established in the electrocrystallization theory. In all cases a mechanism consisting of a two-dimensional growth at short time followed by a three-dimensional diffusion controlled growth and at longer times a subsequent two-dimensional growth mechanism, with progressive nucleation, is suggested. Scanning electron microscopy micrographs support this mechanism.     

Effect of 2-butyne-1, 4-diol on silver electrodeposition from 5, 5-dimethyl hydantoin solutions

The effect of 2-butyne-1, 4-diol on silver electrodeposition process from 5, 5-dimethyl hydantoin solutions was investigated by means of cyclic voltammetric measurement, scanning electron microscopy (SEM) and X-ray diffraction (XRD).Cyclic voltammetric studies indicate that the reduction process of silver electrodeposition is influenced by adding 2-butyne-1, 4-diol.Owing to its adsorption on the electrode surface, 2-butyne-1, 4-diol moderately hinders the mass transfer of the silver complexed ions from the bulk solution to the outer limit of the electrode double layer and affects the electrocrystallization step.Scanning electron microscopy analysis reveals that the presence of 2-butyne-1, 4-diol in the electrolyte is beneficial and the silver deposits obtained are smoother, more compact and more leveled.X-ray diffraction analysis of the silver deposits obtained at 0.5 g·L-1 2-butyne-1, 4-diol indicated that the (110) plane is the most preferred plane and is not affected by the presence of 2-butyne-1, 4-diol in the electrolyte.     

氯化物三价铬电镀的电化学形核机理

为研究Cr³⁺在金属电极表面的电结晶行为,在氯化物三价铬电镀溶液中,采用电化学工作站测试了Cr³⁺沉积的时间电流曲线,并利用扫描电镜(SEM)分析镀层形貌。结果表明:在镍电极、铜电极和铬电极表面,Cr³⁺的电沉积均经历了成核过程;铜电极和镍电极表面表现为连续成核转为瞬时成核的机理,铬电极的(I/Im)2-t/tm曲线偏离理论曲线较大,但其表现出较正的形核阶跃电位(-1.1 V);随着阶跃电位的负移,3种电极电沉积的电流极大值逐渐增加,电结晶的扩散速率增加,成核数密度减少,镀层由平整光滑逐渐转变为球状晶胞紧密堆砌,晶胞尺寸逐渐增大;在相同的阶跃电位下,铬电极的沉积电流值更小,成核数密度更大,晶胞尺寸更小。     

纳米-Al2O3颗粒对镍电结晶初期阶段的影响

利用循环伏安(CV)、计时安培(CA)和电化学阻抗(EIS)研究了纳米Al2O3颗粒在不同电位(vs.SCE)下对Ni自硫酸盐镀液在铜基体上电沉积的影响。结果表明,Ni-Al2O3体系共沉积的起始电位为:–740mV左右;在不同的电位下,纳米-Al2O3颗粒对镍沉积过程的影响有所差别;在电位–740～–830mV范围,与纯Ni沉积相比较,Ni-Al2O3体系沉积的峰电流所对应的孕育期tm明显缩短,反映Al2O3颗粒在阴极表面有利于镍沉积成核,且促进了电结晶成核。Al2O3颗粒吸附在阴极表面可能会阻碍部分离子电荷放电和物质传输过程,尤其在电位–250～–650mV范围,致使Ni-Al2O3体系沉积阻抗增加。在较高的过电位下,Al2O3颗粒的促进作用有所减弱,许多颗粒堆积在电极表面上还可能减小Ni-Al2O3沉积的还原反应电流。在电位–890mV,Ni-Al2O3体系电沉积初期阶段的成核过程基本遵循三维的Scharifker-Hill瞬时成核模式。     

STUDY THE INFLUENCE OF H3BO3 ON THE ZINC ELECTROPLATING USING ELECTROCHEMICAL NOISE TECHNIQUE

The influence of H3BO3 on the zinc electroplating was studied using electrochemical noise technique, cyclic voltammetry and steady-state polarization method. The results showed that,under the experimental conditions, the deposition of zinc followed the mechanism of two-dimensional nucleation and subsequent grain growth. The addition of H3BO3 into the electroplating solution prominently changes the nucleation and growth kinetics of zinc deposits, which is directly related to the features of electrocrystallization noise and the corresponding structure of the electrodeposits. The results also shown that the electrochemical noise (EN) technique can give more information about the electrodeposits structure and electroplating mechanism than other normal electrochemical measurements can give, such as steady-state polarization method and cyclic voltammetry technique.     

电解银粉的制备及其电结晶

采用恒电流电解法,以HNO3+AgNO3体系为电解液制备银粉。通过X射线衍射(XRD)分析和电化学测试,研究电解液组份、沉积电位、电解温度以及添加剂等因素对银粉电结晶过程的影响。结果表明,电解液中HNO3浓度过大或过小都不利于获得细小晶粒,在硝酸质量浓度为10g/L时可制备晶粒尺寸相对较小(56.4 nm)的银粉;AgNO3质量浓度在10～20 g/L范围内,对晶核的形成速率和晶粒尺寸影响不大;较低的沉积电位和较高的电解温度均有利于提高银粉的电沉积速率;在电解液中加入含酸性基团的烷烃基铵盐添加剂(质量浓度0.5 g/L),可大大促进新的晶核形成速率,有利于制备更细的电解银粉。     

铈离子对镍电结晶过程的影响

为了解铈离子对镍电沉积电极过程的影响,采用线性扫描伏安法、单电位阶跃计时电流法、交流阻抗谱等方法,对镍在玻碳电极上的电沉积进行了研究。实验结果表明：CeCl3的加入使镍离子的扩散系数下降、电荷传递电阻增大,加大了镍沉积的阴极极化,同时使电结晶成核速率常数增大,晶体向外生长速度下降。这些变化可能与Ce^3＋及在沉积过程中形成的Ce^3＋多核配离子吸附在阴极表面有关。但铈离子的加入没有改变镍在玻碳电极上的电结晶成核机理。     

镍铁钨合金的电沉积行为研究

应用电化学方法研究了Ni-Fe-W合金的电沉积机理,并对Ni-Fe-W合金镀层的微观形貌和组成成分进行了表征.循环伏安测试表明,Ni-Fe-W合金电沉积是不可逆电极过程,且WO42-浓度的变化不改变电沉积机理;计时电流法研究表明,Ni-Fe-W合金在铜电极上的电结晶过程符合三维瞬时成核的生长机理;SEM和EDS结果表明,Ni-Fe-W合金镀层由纳米级的小颗粒组成,合金的组成为Ni 58.76%,Fe 32.72%,W 8.52%(原子数分数,后同).