THE POSSIBLE ROLE OF THE PREEXPONENTIAL FACTOR IN EXPLAINING THE INCREASED REACTION-RATES OBSERVED DURING THE MICROWAVE SYNTHESIS OF TITANIUM CARBIDE

Reaction rates observed during the microwave synthesis of titanium carbide powder via the carbothermal reduction of the oxide are more than three times faster than those observed during conventional processing at the same temperature. Although not dissimilar to other reports of ''microwave effects'' in the literature, this result is of interest because the microwave heating mechanism is quite different compared to work using ionic ceramics. The initial powder mix consisted of low dielectric loss titania mixed intimately with very fine carbon black powder. It is the latter phase which couples with the microwaves via a conventional ohmic dissipation mechanism. Calculations have shown that the faster diffusion rates might be explained by an increase in the Arrhenius pre-exponential factor A, with no change in the activation energy.