Phase transitions and dimensional and morphological changes in an “aluminum hydroxide-alumina” system under a shock-wave action

A method is proposed to study the sequence of phase transitions in powdered materials under a shock-wave action. It is shown that the “aluminum hydroxide-alumina” system has the following sequence of phase transformations under a shock-wave action: bayerite $\to$ boehmite $\to$ $\gamma$-Al$_2$O$_3$ $\to$ $\alpha$-Al$_2$O$_3$. It is found that there are no transitional high-temperature modifications of alumina. A method is developed for obtaining a submicron alumina powder, which allows obtaining materials with a controlled phase composition, including a thermodynamically stable $\alpha$-modification of Al$_2$O$_3$. The specific features of the morphological structure and the phase and structural characteristics of powders after a shock-wave action are considered.