FEATURES OF PRODUCTION AND HIGH-TEMPERATURE OXIDATION OF SHS-CERAMICS BASED ON ZIRCONIUM BORIDE AND ZIRCONIUM SILICIDE

Abstract

The paper is dedicated to the study of kinetics and combustion mechanism of reaction mixtures in Zr–Si–B and Zr–B systems, production of compact ceramic materials in a process of SHS compaction, as well as studying their heat resistance. The paper demonstrates that temperature and combustion speed dependencies of compounds in the Zr–Si–B system on the initial temperature (T 0 ) are linear, i.e. with a rise in T 0 , staging of chemical reactions of zirconium diboride and disilicide formation does not change. The paper calculates values of the effective SHS process activation energy, which demonstrate the crucial role of the reaction interaction between zirconium and boron and silicon in a melt. The paper studies the staging of chemical reactions in a mixture Zr–Si–B combustion wave: initially, the ZrB 2 phase is formed from the melt by crystallization, then the ZrSi 2 phase appears with a delay of 0,5 s and 1 second later unreacted Si crystallizes. The paper studies the phase composition of synthesis products with diboride ZrB 2 as a main component and zirconium disilicide ZrSi 2 , Si and boride ZrB 12 depending on the initial reaction charge composition. The new compact samples characterized by high hardness and low residual porosity were produced in the process of power SHS compaction. Formation of oxide films SiO 2 –ZrO 2 –B 2 O 3 along with the complex oxide ZrSiO 4 , which serve as an effective diffusion barrier and reduce the oxidation rate, occurs on the surface of SHS-samples in response to their high-temperature oxidation and depending on their composition.