Carbothermal Reduction and Nitridation of Çanakkale Origin Kaolin for SiAlON Powder Production

Abstract

SiAlON ceramics were successfully produced in the form of powders from high purity kaolin, a hydrated aluminium silicate, Al2Si2O5(OH)4 type of clay mineral (comprises 83.85% kaolinite, 13.59% quartz, 0.88% feldspar, 1.37% others) of Canakkale-Can origin. Factors affecting SiAlON powder production were temperature, holding time, gas-flow rate and preparation methods. System optimisation was achieved following the results succeeded from numerous testing and characterisation (with XRD, SEM, EDS, BET, etc.) of each test. Changing in gas flow rate, temperature and holding time at plateau temperature had influences on the final powder yield, their morphologies and phase formation. The best conversion of kaolin clay mineral to SiAlON ceramic powder was the test run at 1475oC for 4 hour under 1 lt/min N2-flow. Product after the process was mainly of β'- Si3Al3O3N5 (z=3) powder along with small amounts of Al2O3, mullite and AlN phases. Some powder product exhibits furry type of wiskers morphology, which may be useful for using as a reinforcing material in particulate composite bodies.