Combustion macrokinetics of titanium containing mixtures: effect of mixture structure and titanium particle size

For the first time, experimental dependences of the combustion rate of powder and granular mixtures 5Ti + 3Si, Ti + C$^{am}$, (Ti + C$^{am}$) + 20% Cu, (Ti + C$^{am}$) + 20% Ni, Ti + C$^{cr}$ (with amorphous carbon in the form of soot and crystalline carbon in the form of graphite) on the size of titanium particles are discussed using different models of combustion front propagation in a condensed medium. The theory of gasless combustion (taking into account the mechanism of capillary spreading and without it), microheterogeneous models do not even qualitatively explain the difference in the dependences of the combustion rate on the size of titanium particles for powder mixtures of titanium with soot and with graphite or the increase in the combustion rate of powder mixtures Ti + C$^{am}$ when diluted with nickel and copper, accompanied by a decrease in combustion temperature. Changing the structure of the medium – granulation of powder mixtures – leads to a change in the combustion rate without changing the phase composition of the synthesis products. Within the framework of the convective-conductive combustion model, all these results are explained uniformly by the inhibitory influence of impurity gases released ahead of the combustion front in powder mixtures when the conditions for heating the component particles are met. The influence of impurity gas release on the combustion rate of powder mixtures can be assessed for each composition by the difference in the combustion rates of granular and powder samples. For all studied compositions of granular mixtures, where the influence of impurity gases on the combustion rate is leveled, the analytical approximation of the experimental dependence of the combustion rate on the size of titanium particles showed qualitative agreement with the dependence that follows from the convective-conductive combustion model.