高温域におけるCr<SUB>2</SUB>O<SUB>3</SUB>の炭素還元

Abstract

The rate of reduction of Cr2O3 by solid carbon has been investigated at high temperature from 1743 to 1993 K, and under an argon atmosphere. The rate of reduction has been determined from the mass loss measured by means of the thermo-balance. The physical situation of the reduction product has been examined by microscopic observation.The powder of Cr2O3 in a graphite crucible as a reductant was hardly reduced, when the reduction product was solid carbide. The reduction was accelerated by continuous formation of Cr-C melt at high temperatures.The reduction rate of Cr3O3 by powdered graphite decreased with increasing the particle sizes of both Cr2O3 and graphite. In the case of fine powder of Cr2O3, the reduction product was formed around the graphite particle. The reduction was controlled by the diffusion of carbon or chromium in the product layer. The reduction of coarse particle of Cr2O3 proceeded topochemically and the graphite particle was not coated by the product. The reduction rate was analysed by means of the equation for rate controlled by gas diffusion through the porous product layer formed around Cr2O3.