Simultaneous calcination and spheroidization of gibbsite powders in an RF thermal plasma

Thermal treatment of gibbsite (Al(OH)(3)) powders of different particle siz e was studied in inductively coupled thermal plasma operating at normal pre ssure. Calcination and spheroidization took place simultaneously although s pheroidization did not occur with coarse feed particles. Microsized or nano sized Al2O3 particles of different phase composition were produced dependin g on the size of injected grains. The microsized powders were mainly formed by melt solidification. In the formation of nanopowders, however, evaporat ion of small grains followed by homogeneous nucleation from the vapor phase and grain growth seem to be the dominant processes. (C) 2000 Elsevier Scie nce S.A. All rights reserved.