Modifying irregular titania powders in a low power microwave plasma torch

Abstract

Rapid passage of titania powder as an aerosol through a plasma generated with a low power microwave torch, resulted in many changes to the powder. Some or all of the titania became spherical, its phase changed, the level of carbon impurity changed, and its surface area declined. The final state of the titania depended on plasma operating conditions. For example, all of the titania became spherical and converted to the rutile phase, only if the processing rate remained low. Complete spherodization occurred only if the energy absorbed by the particles was <2.5% of the total power applied. Excess solid loading reduced the fraction spherodized or otherwise modified, as well as the net rate of conversion. Passing titania through an oxygen plasma removed virtually all the carbon impurity. This process is similar to alumina studies in the same apparatus and suggests that many refractory oxides can be modified by low-power plasmas. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2090–2100, 2004