Thermodynamic study of some chemical reactions in the reaction spark-plasma synthesis of a multicomponent TiN—ZrN—HfN— TiB₂—ZrB₂—HfB₂ composites

Abstract

A thermodynamic study of the nature of some chemical reactions possible during intensive milling and reaction spark plasma synthesis of ceramic TiN—ZrN—HfN— TiB₂—ZrB₂—HfB₂ compositions in the temperature range from 300 to 2000—2300 K was carried out. The study was conducted on the basis of the temperature dependence analysis of the change in Gibbs free energy. The probability of the formation of oxides, beads, nitrides and carbides in the series of the corresponding initial metals Ti—Zr—Hf increased, and in the decarbidization, the reverse sequence was observed as a result of interaction with oxygen dissolved in the crystal lattice of carbides. In the range from 500 to 1800—2000 K, the studied refractory compounds could be located in the following order in the probability of formation: oxides-borides-nitrides-carbides. At temperatures below 500 K, the formation of nitrides was more thermodynamically advantageous than that of borides, and above 1800—2000 K, the formation of carbides was more advantageous than that of nitrides.