PREPARATION OF ULTRAFINE SiO_2 POWDER WITH A MICROWAVE INDUCED PLASMA

摘要

Ulttafine SiO_2 powder with high purity has been prepared with a microwave induced plasma in a reaction system of SiCl_4-O_2-Ar. The oxidation process is accomplished by utilizing a 2.45 GHz frequency and 5 kW power microwave generator which can create a microwave plasma column with a few centimeter diameter at 2500-3000 K temperatures. The preparation capacity of the experimental apparatus employed in the present study is 200 g/hr. The new powder product is characterized with amorphous crystalline type, as indicated in X-ray diffraction analysis, over 99.9% high purity determined by plasma spectrometry analysis, and 0.033 μm average particle size(110 m~2/g specific surface area). It is. observed from transmission electron microscope photographs that the powder has a particle size rang from 0.01 to 0.2 μm in diameter, some particles with 0.1-0.2 μm diameter in a perfectly round shape, and the other large amount of much smaller particles with sizes below 0.05 μm in irregular shapes.