THEORY OF THE OSTWALD RIPENING IN MULTICOMPONENT SYSTEMS UNDER NONISOTHERMAL CONDITIONS

The Ostwald ripening of a new phase during decomposition and crystalli zation in multicomponent and multiphase solutions and melts is investi gated. Both conservative and open systems under non-isothermal conditi ons are considered. It is shown that heat of chemical reaction will be liberated during the Ostwald ripening of new phase nuclei, and the he at liberated will increase the temperature of the system, leading to a change in the equilibrium composition of the components. Under these conditions some of the nuclei of the new phase will be unstable, and t he diffusion and thermal fields will become self-consistent. A set of equations describing the evolution of such systems is derived and solv ed. It is shown that the size distribution functions for nuclei of the new phases are universal; as for the types of phases, these are deter mined by the relation between the quantities of dissolved substances, temperature and chemical reaction constants. An algebraic set of equat ions determining the types of co-existing phases of chemical compounds is obtained, and for each phase the size distribution function at a g iven time interval is found. General equations are also derived defini ng the regions of phase coexistence in the space of concentration and temperature. The formation or removal of a substance, and cooling or h eating of a system lead to a redistribution of the size and compositio n of nuclei of the new phase. It is shown that there is an opportunity to control the structure and composition of a decomposed multicompone nt solid solution, and the crystallization of a multicomponent melt.