Macrokinetic Principles of the Synthesis of Zirconium Carbonitrides from a Granular Charge during Combustion in a Nitrogen Flow
B. S. Seplyarskii, D. S. Vasil’ev, R. A. Kochetkov, V. V. Zakorzhevskii
Merzhanov Institute of Structural Macrokinetics and Materials Science, Russian Academy of Sciences, Chernogolovka, Russia
Keywords: combustion synthesis, SHS, zirconium carbonitrides, combustion patterns, combustion mechanism, granulation, X-ray phase analysis
Abstract
A study was conducted on the macrokinetic combustion of a granulated Zr + 0.5C mixture under nitrogen flow conditions. It was shown that the combustion rate increases nonlinearly with increasing gas flow rate, with the combustion process accompanied by sample shrinkage of up to 26%. Experimental data were analyzed using conductive and convective combustion models. Calculations showed that combustion in a nitrogen flow at gas flow rates exceeding 500 l/h occurs via the convective mechanism. It was established that longitudinal sample shrinkage is due to the presence of a significant amount of zirconium melt during combustion. According to X-ray diffraction analysis, the synthesis products are a mixture of zirconium carbonitrides ZrCxNy of variable composition. Chemical analysis of the synthesis products revealed that the degree of nitridation of the granulated mixtures is higher than that of the powder mixtures and increases with increasing nitrogen flow through the sample.
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