Study on Kinetics of Crystal Dissolution

点击翻译按钮获取中文摘要

The Cu (111) surface was etched by a potentiostatic electrolysis and the effects of applied potential, etching temperature and inhibitor concentration in an electrolyte on the dissolution at edge dislocations and matrix surface were investigated. The composition of the standard electrolyte was 5 kmol・m^<-3>NaCl, 0.25 kmol・m^<-3>NaBr, 10^<-4> kmol・m^<-3>CuCl. The dislocation etch pits formed a slightly rounded triangular pyramid. From the variation of the size of these etch pits and the dissolved depth of matrix surface with an etching time, the vertical dissolution rate along a dislocation line, Vd, the lateral one, Vh, and the vertical one of matrix surface,Vs, were determined.1. Effect of applied potential : Etching was carried out in the standard electrolyte at 298 K under constant potentials of 0,10,20 and 30 mV vs SHE. The values of Vd, Vh and Vs became large as the applied potential increased. The rate of increase in Vd was slightly larger than that in Vh and Vs.2. Effect of etching temperature : Etching was carried out in the standard electrolyte at 268,283,298 and 308 K under overpotential of 176 mV. The rise of temperature increased the values of Vd, Vh and Vs. The rate of increase in Vd was smaller than that in Vh and Vs.3. Effect of inhibitor concentration : Etching was carried out at 298 K under overpotential of 176 mV in electrolytes containing 0.1, 0.25, 0.4 and 0.5 kmol・m^<-3>NaBr besides 5 kmol・m^<-3>NaCl and 10^<-4> kmol・m^<-3>CuCl. The values of Vd, Vh and Vs decreased at a low concentration of inhibitor and increased slightly at its high concentration. The rate of decrease in Vd was smaller than that in Vh and Vs.4. It was shown that these results could be explained qualitatively on the basis of the two dimensional nucleation theory of crystal dissolution.