Effect of the Addition of á-Si_3N_4 on the Direct Nitridation of Silicon Powder at Atmospheric Pressure

摘要

Effect of the addition of á-Si_3N_4 on the nitridation of silicon powder was studied at 1550°C and atmospheric pressure. Silicon powder of 2.2um in size and 99.99% in purity was adopted as experimental materials, á-Si_3N_4 powder of 2.2um in size and 99% in purity was used as diluent, and nitrogen of 99.9993% in purity was used as reaction gas. The morphologies and phase compositions of the products were analyzed by SEM and XRD respectively. The results show that the conversion of silicon is improved considerably by increasing the adding proportion of á-Si_3N_4 diluent. When the adding proportion of á-Si_3N_4 increases from 10% to 50%, the conversion of silicon powder increases from 38% to 92.55%. The content of ?-Si_3N_4 in product decreases, after an initial increase, with the adding proportion of á-Si_3N_4 increases, and it reaches the peak point when the adding proportion of á-Si_3N_4 was 30%. The sinterability of silicon nitride decreases as the content of ? phase increases, so the adding proportion of á-Si_3N_4 should be kept away from 30%.