Synthesis of ultrafine Al2 O 3 is considered. An X-ray phase analysis indicates that ultrafine γ-Al 2 O 3 , (θ + α)-Al 2 O 3 , and α-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.

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