EFFECTS OF HYDROGEN AND TEMPERATURE ON THE KINETICS OF THE FLUIDIZED-BED NITRIDATION OF SILICON

Silicon nitride was produced via direct nitridation of silicon powder, using nitrogen with 10-40 vol% hydrogen, in a fluidized-bed reactor, 55 mm in diameter, operated at temperatures in the range of 1200-1390-degrees-C. Hydrogen enhanced the nitridation of silicon toward its completion. The overall conversion of silicon as well as the yield of alpha-silicon nitride increased with an increase in reaction temperature, while the yield of beta-silicon nitride decreased. In nitridation at 1300-degrees-C with 40 vol% hydrogen in nitrogen, 99% of silicon was nitrided in 24 h with a yield of alpha-silicon nitride of about 90% in the product. When the reactor temperature was raised stepwise from 1300-degrees to 1390-degrees-C along with the progress of nitridation, 99% of silicon was nitrided in 2.5 h and 85% of the product was a-form.