Thermal oxidation of SiAlON powders synthesized from coal gangue

Abstract

The oxidation behavior of different SiAlON phases (β-SiAlON, X-phase SiAlON and 12H powders) synthesized from coal gangue in air atmosphere was investigated using isothermal thermogravimetry (TG) and field-emission scanning electron microscopy (FE-SEM). The effect of ferric oxide impurities in coal gangue was studied. The results show that ferric oxide contributes to the growth of SiAlON crystalline during the synthesis process. In the oxidation experiment, the existence of ferric oxide decreases the oxidation resistance of SiAlON. The reason is that the impurity causes the formation of a liquid phase at a higher temperature. At 1423-1623 K, the oxidation of SiAlON powders is diffusion controlled and it can be described by Chou's model. A fair agreement is found between theoretical calculations and the experimental data.

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“…β-SiAlONs are isostructural with β-Si 3 N 4 . β-SiAlON ceramics are promising materials for applications involving high temperatures, highly corrosive environments, and high mechanical stress because they exhibit high strength retention and high thermal shock resistance at elevated temperatures and good erosion resistance and low creep [148][149][150][151][152]. Compared with Si 3 N 4 , β-SiAlON ceramics are easily sintered and fabricated and can be easily combined with other materials to strengthen or improve the properties of ceramics [153,154].…”

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“…The use of cubic boron nitride (CBN) as a cutting tool in the processing of heat-resistant nickel alloys is poorly understood. Basically, CBN used in the treatment of increased material hardness (45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59)(60), such as hardened steel [33] or ductile iron [34,35].…”

“…β-SiAlONs are isostructural with β-Si3N4. β-SiAlON ceramics are promising materials for applications involving high temperatures, highly corrosive environments, and high mechanical stress because they exhibit high strength retention and high thermal shock resistance at elevated temperatures as well as good erosion resistance and low creep [44][45][46][47][48]. Compared with Si3N4, β-SiAlON ceramics are not only easily sintered and fabricated but also can be easily combined with other materials to strengthen or improve the properties of ceramics [49][50].…”