Reaction Processes and Thermodynamic Modeling for SiAlON Structural Ceramic Powders Synthesized from Nonmetallic Mine
SiAlON family matrix materials have been fabricated from nonmetallic mine. The process of Carbothermal Reduction and Nitridation (CRN) is selected on the basis of raw rocks containing various Si/Al ratios. Thermodynamic analysis of Si-Al-O-N system at different sintering temperatures indicates once the temperature is above 1673 K, a series of chemical reactions occur in sequence, SiO2, SiO, Si2N2O, SiO2+Al2O3, mullite, X-SiAlON, O′-SiAlON, β-SiAlON, SiAlON- polytypiods and Si3N4+AlN. Moreover, most of the reactions are exothermal and are promoted by further heating. The adding or in-situ formed SiC can reduce mullite and Al2O3 to produce O′- or β-SiAlON, and its reaction is surprisingly endothermic and is inhibited when further heated. Also, atmosphere is essential to affect the sintering process. Either raising N2 partial pressures or reducing CO partial pressures can accelerate CRN progress. Correspondingly, phase content and microstructure of the product converted from nonmetallic ore are in detail investigated via X-ray diffraction (XRD) and scanning electron microscopy (SEM).
Wei Pan and Jianghong Gong
L. H. Xu et al., "Reaction Processes and Thermodynamic Modeling for SiAlON Structural Ceramic Powders Synthesized from Nonmetallic Mine", Key Engineering Materials, Vols. 368-372, pp. 1564-1567, 2008