Ultrafine $\alpha$-$\mathrm{Al}_2\mathrm{O}_3$. Explosive method of synthesis and properties

An explosive method for producing ultrafine $\alpha$-$\mathrm{Al}_2\mathrm{O}_3$ is developed and optimal synthesis parameters are determined. Particles of ultrafine $\alpha$-$\mathrm{Al}_2\mathrm{O}_3$ have a spherical shape and are separated from one another. The size distribution is log-normal (number-averaged size 70 nm and variance 1.9). Special features of phase transitions in ultrafine aluminum oxide under shock-wave action are studied. Results of x-ray phase analysis suggest stabilization of the new high-pressure phase $\delta'$-$\mathrm{Al}_2\mathrm{O}_3$ with a face-centered cubic lattice with a parameter $a=8,53\mathring{\mathrm{A}}$.