Application of chemical thermodynamics to the description of processes of special inorganic materials preparation

Abstract

The paper reviews the possibilities of chemical thermodynamics for the description of processes for preparing special inorganic materials with exactly defined final properties. The first part is devoted to general conditions of thermodynamic equilibrium, and describes a procedure for calculating the equilibrium composition of multiphase and multicomponent systems by minimizing the total Gibbs energy of the system while satisfying mass balance conditions. A stoichiometric algorithm convenient especially for equilibrium composition calculations of simple systems is described. Special attention is paid to input data needed for equilibrium calculations. Data characterizing the thermodynamic properties of individual pure substances are discussed, as are data describing the nonideal behaviour of multicomponent condensed phases. The second part of the paper gives a summary of some applications of chemical thermodynamics to the description of processes of special inorganic materials preparation. Case studies on thermodynamic analysis are described for three industrial processes: (1) chemical vapour deposition of titanium carbonitride, (2) growth of Si-doped GaAs single crystals by Bridgman's method, and (3) refining of technical boron nitride by reductive chlorination. The results of equilibrium calculations for all the three systems are in very good agreement with available experimental data.