Influence of NH4F additive on the combustion synthesis of β-SiAlON in air

Abstract

The preparation of β-SiAlON, Si6–zAlzOzN8–z (z = 1–4), was investigated using the combustion synthesis (CS) technique with Si, Al, and CO(NH2)2 as the main raw materials in air. Different amounts of NH4F were used as a low-melt additive to the raw materials to decrease the reaction temperature and promote β-SiAlON formation. Phase and microstructural analyses of the reaction products were performed by X-Ray diffraction (XRD) and FE-SEM/energy dispersive X-ray spectrometer techniques. FT-IR spectroscopy was also used to demonstrate the formation of β-SiAlON in the final product. The phase and microstructural analysis results showed that NH4F addition improved the exothermic reaction of β-SiAlON phase formation and increased its content in the final synthesized powders. Additional heat treatment of the sample at the optimum z-value (z = 4) and different percentages of NH4F revealed the positive effect of the low-melt additive on β-SiAlON phase formation under very low N2 pressure.