βSi_3N_4在含碳材料中转化为SiC的研究

Phase transformation research of β-Si_3N_4 to SiC in carbon-containing refractories

以β-Si3N4及活性炭黑为原料,按照两者质量比为3: 1制成试样。在埋炭条件下,将试样分别在1480℃、1500℃、1550℃和1600℃保温3h热处理。利用SEM、EDS及XRD等检测方法,结合热力学分析,研究了高温状态下β- Si3N4在含碳耐火材料中的稳定性以及作为过渡相向碳化硅的转化。结果表明:在该试验条件下,β- Si3N4在含碳材料中将作为过渡相向SiC转化,明显的转化温度>1500℃, 1600℃仍存在较多未转化的氮化硅;氮化硅颗粒与炭黑的反应主要从接触面开始,然后向内逐步推进;β-Si3N4的粒度对其转化率影响较大。

The specimens were prepared using β-Si3N4 and active carbon black as starting materials (75 wt% β-Si3N4 and 25 wt% active carbon) and fired by flashing combustion process in air at temperatures of 1480°C, 1500°C, 1550°C and 1600°C for 3 h respectively, embedded in carbon. The stability of β-Si3N4 at high temperatures and its transformation as a transient phase to SiC were studied by SEM, EDS and XRD. The results show that: (1) β-Si3N4, as transient phase, transformed to SiC obviously at above 1500°C, and at 1600°C, there was still much Si3N4;(2)The reactions between Si3N4 grains and carbon started mainly from the interface and then to the interior gradually, and the grain size of Si3N4 had great effect on its transformation ratio.