Sintering of Si3N4 powder synthesised from quartz mineral via carbotermal reducing and nitridation process and sintering

Keywords: Quartz, silicon nitride, powder metalurgy, carbothermal reductionnitridation, sintering Silicon nitride have high strength, hardness, wear resistance, fatigue life, thermal stability up to 1800ºC, because of low thermal expansion coefficient, excellent thermal shock resistance. In the last 30 years, this material have had a great interest. However, the main problem is production of bulk material, has high density, from silicon nitride powder. Properties of silicon nitride ceramic mentioned above are related to density of produced part. Due to the fact that Si3N4 has covalent bond, during sintering proses, diffusing each other of Si3N4 powders is difficult. Thus, hot pressing, hot isostatic pressing or pressureless sintering with various oxide additives (MgO, Y2O3, Al2O3 and CeO) as sintering aids are needed for sintering of Si3N4 powders. The object of this study is Si3N4 powder production from quartz mineral via carbothermal reducing and nitridation proces (CRN). After powders produced by CRN proces were grinded, effect of grinding on - Si3N4 transformation was investigated. Additives as sintering aids were added to Si3N4 powders produced and densificaton behavior of these mixtures were investigated.