Explosive synthesis of ultrafine Al$_2$O$_3$ and effect of temperature of explosion

Synthesis of ultrafine Al$_2$O$_3$ is considered. An X-ray phase analysis indicates that ultrafine $\gamma$-Al$_2$O$_3$, $(\theta + \alpha)$-Al$_2$O$_3$, and $\alpha$-Al$_2$O$_3$ are synthesized by explosion of water-gel explosives with a zero oxygen balance, prepared by mixing aluminum nitrate, RDX, and carbamide. All granules of ultrafine Al$_2$O$_3$ are spherical and homogeneous, and the granule size varies from 10 to 30 nm. The average crystal sizes of ultrafine Al$_2$O$_3$ are calculated by the Scherrer equation. The temperatures of explosion of water-gel explosives are found by a simplified approach. A comparison indicates that the higher the temperature of explosion, the greater the average nanocrystal size.