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.
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