Reaction mechanism for in-situ β-SiAlON formation in FeSi-SiN-AlO composites.

In this work, FeSi-SiN-AlO composites were prepared at 1300°C in an N atmosphere using fused corundum and tabular alumina particles, AlO fine powder, and ferrosilicon nitride (FeSi-SiN) as raw materials and thermosetting phenolic resin as a binder. The effect of ferrosilicon nitride with different concentrations (0wt%, 5wt%, 10wt%, 15wt%, 20wt%, and 25wt%) on the properties of FeSi-SiN-AlO composites was investigated. The results show that the apparent porosity varies between 10.3% and 17.3%, the bulk density varies from 2.94 g/cm and 3.30 g/cm, and the cold crushing strength ranges from 67 MPa to 93 MPa. Under the experimental conditions, ferrosilicon nitride, whose content decreases substantially, is unstable; part of the ferrosilicon nitride is converted into FeC, whereas the remainder is retained, eventually forming the ferrosilicon alloy. Thermodynamic assessment of the SiAlON indicated that the ferrosilicon alloy accelerated the reactions between SiN and α-AlO fine powder and that Si in the ferrosilicon alloy was nitrided directly, forming β-SiAlON simultaneously. In addition, fused corundum did not react directly with SiN because of its low reactivity. [ABSTRACT FROM AUTHOR]