Study of Patterns and Mechanisms of Combustion of a Powdered and Granulated Ti–C–B System

Abstract

Experimental studies of the combustion patterns of the ternary system (100 – x)(Ti + C) – x(Ti + 2B) of bulk density in the powder and granular form used for the synthesis of TiC–TiB₂ composite ceramics are carried out. The study shows that the dependence of the powder mixture’s combustion rate on the Ti + 2B content has a non-monotonic character, which is associated with the influence of the impurity gas (IG) release on the combustion process. By removing the influence of the IG by granulation, a monotonic dependence with two characteristic sections is obtained. For the granulated mixture, an increase in the Ti + 2B content to >60 wt % leads to a change from the conductive combustion mode to the convective one, accompanied by a sharp increase in the combustion rate. For the conductive combustion mode, the combustion rate of the substance inside the granule and the combustion transfer time from granule-to-granule are determined, which allows us to estimate the inhibitory effect of the IG release on the combustion rate of powder mixtures of different compositions. For the convective combustion mode, it is shown that a decrease in the content of the gasifying additive in the mixture (granulation with ethyl alcohol) leads to an unexpected result: an increase in the combustion rate of the mixture. For compositions with (Ti + 2B) > 60 wt %, the combustion rate with the counterfiltration of IGs is determined for the first time, which makes it possible to estimate the front rate increase according to the filtration combustion theory. According to the X-ray phase analysis (XPA), the combustion products of all compositions contain only two main phases: TiC and TiB₂