Mixed Oxides Prepared with an Induction Plasma Torch Part 2 Chromia/Titania

Pure and mixed titania and chromia have been prepared and characterised by methods described in the previous paper [1]. The titania and chromia/titania contained mostly spherical particles in the size range 0.01 to 0.15 mu m. The pure titania was mainly the metastable phase, anatase, but the proportions of rutile and of stacking faults in the rutile structure increased with increasing chromium concentration. A high degree of solid solution was achieved for the mixed oxides, a result which accords with the proximity of the temperature ranges for condensation, predictable from thermodynamic data. This is the chief factor which distinguishes the behaviour of the chromia/titania from that of the chromia/alumina system. It is concluded that reference to such data should enable processes in the gas phase to be predicted and controlled. Processes in the condensed phase are governed as much by kinetic as equilibrium factors.