Reaction mechanism for in-situ β-Si Al ON formation in Fe3Si–Si3N4–Al2O3 composites

In this work,FeSi–SiN–AlOcomposites were prepared at 1300°C in an Natmosphere using fused corundum and tabular alumina particles,AlOfine 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–AlOcomposites 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~3 and 3.30 g/cm~3,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 SiAlONindicated that the ferrosilicon alloy accelerated the reactions between SiNand α-AlOfine powder and that Si in the ferrosilicon alloy was nitrided directly,forming β-Si Al ON simultaneously.In addition,fused corundum did not react directly with SiNbecause of its low reactivity.