Macrokinetic Regularities of the Synthesis of Zirconium Carbonitrides from a Granular Charge during Combustion in a Co-Flowing Nitrogen Stream

A study was conducted on the macrokinetic regularities of combustion of a granulated mixture Zr + 0.5C under conditions of a coflow of nitrogen. It has been shown that with an increase in the volumetric gas flow rate, the combustion rate increases nonlinearly and the combustion process is accompanied by shrinkage of the samples by up to 26%. The experimental data were analyzed within the framework of models of conductive and convective combustion mechanisms; the calculations showed that combustion in a nitrogen flow at a gas flow rate of more than 500 L/h occurs via a convective mechanism. It has been established that the longitudinal shrinkage of the sample is associated with the presence of a significant amount of zirconium melt during the combustion process. According to X-ray phase analysis data, the synthesis products are a mixture of zirconium carbonitrides ZrCxNy of variable composition. Chemical analysis of the synthesis products showed that the degree of nitriding of granulated mixtures is higher than that of powder mixtures and increases with the increase of the coflow of nitrogen passing through the sample.