Combustion modes of mixtures of copper (II) oxide with aluminum and titanium

The influence of the ratio of the initial components on the combustion parameters and modes of mixtures of aluminum with copper oxide has been studied. It has been shown that under normal conditions, such mixtures can burn steadily when they contain not less than $30\%$ copper oxide. Moreover, as the content of copper oxide increases to the stoichiometric ratio, the combustion mode changes in the following sequence: self-oscillatory combustion, spin combustion, a combination of convective and multi-hotspot combustion, flame, and fireball. In addition, the effect of the ratio of the components on the combustion of ternary mixtures of copper oxide-aluminum-titanium was studied, and the concentration regions were determined for four main modes of their combustion: self-oscillatory, hotspot, flame, and fireball. It has been shown that the hotspot combustion mode of such mixtures can exist in five different forms: spin, multi-hotspot, a combination of convective and multi-hotspot modes, a multi-hotspot mode with the formation of an opposed front, and a multi-hotspot mode with a periodic separation of combustion products. Depending on the ratio of the initial components, the condensed combustion products of mixtures of copper oxide with aluminum and titanium were found to contain copper, intermetallic compounds $\mathrm{Al}_3\mathrm{Ti}$, $\mathrm{Ti}_3\mathrm{Al}$, and $\mathrm{Cu}\mathrm{Al}_5\mathrm{Ti}_2$ and oxides $\mathrm{Al}_2\mathrm{O}_3$, $\mathrm{TiO}_2$, $\mathrm{TiO}$, $\mathrm{Cu}_2\mathrm{O}$, $\mathrm{Al}_2\mathrm{TiO}_5$, and $\mathrm{Cu}_3\mathrm{Ti}_3\mathrm{O}$.