Cubic Si6-zAlzOzN8-z (z=1.8 and 2.8) spinels formed by shock compression

We present the formation of cubic Si6-zAlzOzN8-z (z = 1.8 and 2.8) spinels by shock compressions from the corresponding P-sialon. Formed sialon spinel s coexist with considerable amounts of the amorphous phase. The amorphizati on is considered to be a solid-solid reaction due to the sluggish phase tra nsition under shock compression. The lattice parameter of the spinel increa ses and the density decreases with increasing z parameter. Shock-synthesize d sialon spinels are nanocrystals with most grain sizes less than 30 nm and consist of main units of SiN4, SiN6 and AlO6. (C) 2001 Elsevier Science B. V. All rights reserved.