Ni-SiC电结晶沉积层的阻抗谱及SiC颗粒对Ni沉积的影响

Electrochemical Impedance Spectra of Electrodeposited Ni-SiC Composite Coating and Effect of SiC on Deposition of Nickel

前期研究发现,SiC颗粒在阴极有利于Ni结晶形核,为此研究了在电位-250～-1 050 mV(vs SCE)下,Ni-SiC复合体系电沉积阻抗谱特征,利用扫描电镜(附能谱仪)观察了Ni-SiC体系复合沉积初期的表面形貌。结果表明:Ni-SiC体系Nyquist谱主要表现为一个压扁的容抗半圆,随着电位负移,Ni-SiC沉积的电化学阻抗值基本呈下降趋势。在电位-750～-1050 mV,Nyquist谱低频段还伴随一个感抗弧,Ni-SiC沉积的阻抗显著减小,反映Ni在铜基体上开始电结晶形核/生长;在低过电位(-250～-650 mV)下,SiC颗粒明显降低了Ni-SiC体系Ni沉积还原反应的电荷转移电阻;分析认为:SiC微粒在阴极表面上对镍的中间产物生成起到了活化作用。

The co-deposition behavior of electrodeposited Ni-SiC on copper substrate was investigated u-sing electrochemical impedance spectroscopy ( EIS). Thus the EIS feature of Ni-SiC system under applied potentials from —250 mV to-1 050 mV was measured. The morphologies of Ni-SiC coatings deposited on copper substrate in the early stage of depo-sition were observed using a scanning electron microscope e-quipped with an attachment for energy dispersive spectrometric ( EDS) analysis. Results show that the Nyquist spectra of Ni-SiC system are characterized by depressed capacitance semicircle. In a potential range of-250～-1050 mV, the electrochemical impedance of Ni-SiC co-deposition gradually decreased. Within apotential range of- 750 ～-1050 mV, an inductive reactance arc occurred in the low frequency section of Nyquist spectrum, and the impedance value significantly descended, reflecting the occurrence of nickel electro-crystallization on copper electrode. It was also found that the charge transfer resistance of Ni- SiC co-deposition was apparently lower than that of pure Ni deposition in a lower over-potential range (-250 ～-650 mV). It was sup-posed that SiC particles on the cathode surface might activate the formation of Ni intermediates.