Abstract
Hydrogen reduction of germanium dioxide was studied by means of a thermobalance in pure hydrogen, a mixture of hydrogen and argon, and cracked ammonia gas. The initiation temperature was about 450°C and sublimation of GeO was increased remarkably above 650°C. The reduction curves were the sigmoid type characteristic of the autocatalytic reaction.
The incubation time was shortened with increase in temperature and partial pressure of hydrogen. In the main reduction period ranging about 10 to 90% reduction, the formula of interface reaction {1−(1-R)1⁄3}=Kt was valid, and the activation energy was 18.4 kcal/mol. According to the dimensionless time analysis, the effect of gas diffusion through the product layer was found to be added in the final period.
A linear relation was obtained between reduction rate and partial pressure of hydrogen, and a slower reaction rate than in the mixture of hydrogen and argon was found in cracked ammonia gas. Furthermore, the experimental results were in good agreement with the Eyring theory.
