Effect of dilution and additive on direct nitridation of ferrosilicon

Ferrosilicon nitrides were fabricated by direct nitridation of ferrosilicon, and the effects of ferrosilicon nitride and α-Si3N4 dilution and ammonium chloride (NH4Cl) additive on characteristics of the nitride products were investigated. The phases of final nitride products consist of α-Si3N4, β-Si3N4 and iron silicides with various compositions. Long columnar crystals, equiaxed crystals and flower-like crystals were observed in the final products, and fiber or whisker-like crystals with a low degree of crystallization were also found in the nitrides. Both the diluents and additive can improve the nitridation degree, but only the additive can increase the content of α-Si3N4 in the nitride products. As a diluent, ferrosilicon nitride can decrease the cost of nitride products, and increase their nitridation degree more than α-Si3N4. NH4Cl made the products fluffy and expansive, while the dimensions of the compact without addition of NH4Cl remain unchanged during nitridation.