KINETICS MODEL FOR THE GROWTH OF SILICON-CARBIDE BY THE REACTION OF LIQUID SILICON WITH CARBON

The kinetics and mechanism of reaction of glassy carbon with a pure silicon melt or a Si + Mo melt were investigated. The results showed that the growth of a continuous reaction-formed SiC layer followed a fourth-power rate law in the temperature range of 1430 degrees to 1510 degrees C. A model that could explain the fourth-power rate law was developed. In this model, an internal electric field was assumed to be set up over the reaction-formed SIC layer through a negative space charge, and then the diffusion of the carbon-ion vacancies across this layer, driven predominately by this electric field, was considered as the rate-limiting step for the SLC growth. Neither an increase in the processing temperature nor an addition of 10 wt% Mo into the silicon melt had a significant influence on the reaction kinetics. X-ray diffraction analysis revealed that the reaction products were beta-SiC, and beta-SiC + MoSi2, for the Si-C and Si-C-Mo reactions, respectively.