Ultrafine oxide powders prepared by inert gas evaporation

Abstract

Ultrafine amorphous (Al 2O 3, SiO 2) and crystalline (Y 2O 3) oxide powders have been prepared by direct evaporation of the bulk oxides via electron beam heating in an inert gas atmosphere. The powders were nearly stoichiometric, strongly agglomerated via sintering necks and had a very low apparent density of about 1% wt. The primary particle size of 4–6nm is rather insensitive to variations in gas pressure and evaporation rate. Water vapor is physisorbed only and can be desorbed readily below about 400°C.