National University of Science and Technology “MISiS”, Moscow, Russia:
I. V. Iatsyuk, Post-Graduate Student of a Chair “Powder Metallurgy and Functional Coatings”, e-mail: ivansvoy@mail.ru

Scientific and Education Center of Self-Spreading High-Temperature Synthesis “MISiS – ISMAN”, Moscow, Russia:
Yu. S. Pogozhev, Senior Researcher of the Scientific and Education Center, e-mail: yspogozhev@mail.ru
A. V. Novikov, Senior Researcher of the Scientific and Education Center, e-mail: avnovikov@inbox.ru

The work is devoted to obtaining high-temperature ceramic composition ZrB₂ — 25% SiC by the self-propagating high-temperature synthesis (SHS). In order to increase the heat release during the combustion of the elemental reaction mixture, the two-stage scheme of its preparation with preliminary mechanical activation (MA) of the Si + C mixture in a planetary centrifugal mill (PCM) and subsequent admixing of Zr and B powders in the ball mill (BM) was used. The effect of the initial temperature of the SHS process (T₀) on the main combustion parameters is determined. The T_c (T₀) and U_c (T₀) dependencies are linear in nature, indicating that the stages of chemical reactions of formation of ZrB₂ diboride and SiC carbide are unchanged. The value of the effective activation energy of the combustion process E_eff turned out to be small, which is characteristic for systems in which the processes of liquid-phase interaction exert a determining influence on the kinetics of combustion. The results of dynamic X-ray diffraction showed sequential formation of phase constituents when, first of all, ZrB₂ phase forms from Zr –Si melt saturated with boron, and SiC is formed with an insignificant temporal separation after 0.5 s due to the interaction of the Si melt with the carbon black particles. The SHS method has been successfully used to produce both compact and powder ceramics. In both cases the structure of the products of synthesis is two-phase and consists of the homogeneously distributed in volume ZrB₂ and SiC grains, the size of which is commensurable and varies within the range of 1–5 μm. The powder particles have a round and polyhedral form. The obtained SHS ceramics possesses low residual porosity, high hardness, elastic modulus, elastic recovery, and also thermal conductivity and can be used as a structural material for high-temperature applications.

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