Desilicating Zircon with Plasma Heating and Phase Equilibrium Analyses

摘要

Desilicated zirconia has a great variety of applications. The maximum SiO_2 content in desilicated zirconia is 91.54 mass percent ZrO_2, <5.39 mass percent MgO) were produced successfully from zircon using a 150 kW plasma rotating furnace. The effects of time and carbon content on the desilication degree were investigated. The mixture treated in the plasma furnace included condensed phases Zr, ZrC, ZrN, ZrO_2, C, Si, SiC, SiO_2 and gaseous phases SiO, O_2, N_2, CO. The established phase equilibrium diagrams of the Si-C-N-O and Zr-C-N-O systems suggest that the formation of Si_3N_4 is thermodynamically impossible, and the formation of ZrC and ZrN is thermodynamically possible in the central high-temperature region of the plasma furnace. Experimental results supported the analyses.