Carbothermal Reduction and Nitridation of Quartz Mineral for the Production of Alpha Silicon Nitride Powders

摘要

In this study, α-Si_3N_4 powder was produced by carbothermal reduction and nitridation (CRN) of quartz from Can-Canakkale. Carbon with a specific surface area of 110 m~2g~(-1) and quartz powders were mixed then the powder mix was placed in an alumina tube furnace and reacted in between 1300-1500℃ for 4 hours under nitrogen flow. The quartz powder was carbothermally reduced and nitrided to form silicon nitride powders. XRD results showed that the reaction product was mainly α-Si_3N_4 and contained some β-Si_3N_4 and residual quartz. In order to reduce amount of unreacted quartz, the raw materials mixture was grinded either with carbon black or with no carbon. After CRN reactions of separate grinded quartz powders with carbon, residual quartz was disappeared, reaction temperature was decreased and α-Si_3N_4 rate was increased. Hence, a better mixing of carbon and fine silica enhanced the a phase formation. SEM images and XRD pattern showed that sub micron particles (0.6-0.8μm), high α-phase content Si_3N_4 powders can be produced at 1450℃ for 4 h in flowing nitrogen gas during the CRN process.