SINGLE-CRYSTAL ALN FIBERS OBTAINED BY SELF-PROPAGATING HIGH-TEMPERATURE SYNTHESIS (SHS)

Single crystal AIN fibers [1(1) over bar0$] elongated up to 20 mm leng th and up to 40 mu m diameter were obtained by self-propagating high-t emperature synthesis (SHS) starting from a mixture of Al, AlN and NH4C l under 100 atm. of N-2. TWO types of fibers were obtained: (i) long, thin fibers with smooth surfaces and diameter <20 mu m; and (ii) long, thick fibers (d > 20 mu m) of ''banderilla-type'' having scores of cr ystalline ear-like projections aligned along generator lines on the fi ber surfaces. The fibers grew by a vapor-solid mechanism in the axial geode-like region of the cylindrical AlN cake obtained after the SHS. (C) 1997 Acta Metallurgica Inc.