Temperature Influence on the Properties of Freely Poured Nano-Sized Inorganic Oxide Powders

A comparative investigation was performed on the possibility of controlling the average sizes of nano-sized powders of silicon dioxide and aluminum oxide, obtained by electron-beam evaporation and by pyrogenic, liquid chemical, and plasma chemical methods, by keeping them in the temperature range 800 - 1300 degrees C in an air atmosphere. The average sizes of the resulting particles were estimated from measurements of the specific surface area using the Brunauer-Emmett-Taylor (BET) adsorption method at liquid nitrogen temperature. The crystallographic parameters in the treated powders were assessed by means of x-ray diffraction analysis. It is shown that by making a suitable choice of temperatures and initial powder it is possible to achieve in the resulting powder the phase composition and an average particle size close to a specified value.