Abstract:
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.
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