DIFFUSIVE PROPERTIES OF TiC AT HIGH TEMPERATURES

摘要

In highly defective solids, in which the concentration of point defects is higher than 0.1at.%, interactions between defects become important and have influence on many macroscopic structure sensitive properties of these compounds. For a description of interactions between defects, it is necessary to introduce new terms in the diffusion theory that characterize the influence of the interaction energy between defects. These interactions affect the dependence of compound components activity on defect concentration and temperature and, as a result, the effective activation energy of diffusion of defects, atoms or ions and all related macroscopic properties of a given compound. As an example, the influence of interactions between defects on structure sensitive properties of TiC_(1-x) at high temperatures will be discussed. Especially: the dependence of carbon vacancy mobility on temperature and defect concentration, the effective activation energy of carbon diffusion, the enthalpy of carbon mobility, the free energy of repulsive interactions between carbon vacancies and attractive interactions between titanium ions. These properties give new information on the mechanism of carbon and titanium diffusion in the crystallographic lattice of TiC_(1-x).