Intercrystallite Diffusion and Segregation of ~(57)Co Atomic Probes at Grain Boundaries in Polycrystals of Noble Metals: Palladium, Platinum and Gold

摘要

A two-dimensional diffusion flow takes place in high-purity polycrystalline noble metals even at extremely low temperatures of diffusion annealing. This flow arises because any polycrystal has segregations of "intrinsic" vacancies on GB's and/or segregations of vacancy-impurity complexes. The analysis of types of diffusion profiles in polycrystals, which was made using a new function J(y_0,t), confirmed the absence of the one-dimensional ICD flow at low temperatures. Measured values of the segregation enthalpy of ~(57)Co AP's on GB's in noble metals proved to be proportional to calculated values of the binding energy of these AP's on the surfaces of the metals studied.