高温氮气气氛下硅–氮化硅–氧氮化硅体系的稳定性

Stability of Si–Si3N4–Si2N2O Complex at High-temperature with N2-blowing

硅粉生坯经过初次氮化制得硅–氮化硅–氧氮化硅体系的试样,分别于1 500和1 600℃氮气气氛下进行重烧实验,研究了高温稳定性。结果表明：在Si2N2O（s）与Si（l）两相接触的界面处,两者反应生成Si3N4（s）和介稳态SiO（g）。1 500℃重烧时体系氧分压[p（O2）]处于Si2N2O相稳定存在的区间,故1 500℃重烧试样中Si2N2O相含量高;1 600℃重烧时体系p（O2）小于Si3N4相能够稳定存在的临界值,Si（l）直接氮化生成Si3N4（s）,故1 600℃重烧试样中β-Si3N4相是主要物相。体系中的SiO（g）与CO（g）反应生成纤维状SiC,由于SiO分压[p（SiO）]与温度T负相关,因此1 500℃重烧试样中SiC相的含量高于1 600℃重烧试样的。试样随炉冷却过程中,部分介稳态SiO（g）会与N2（g）反应生成α-Si3N4（s）。

Si-Si3N4-Si2N20 complexes were fabricated via nitridation of silicon powder green bodies. The stability of the complexes was analyzed after re-sintering process in N2-blowing at 1 500 and 1 600 ℃, respectively. The results show that Si3Na（S） and metastable SiO（g） generate at the interface between Si2N2O（s） and Si（1）. For the samples re-sintered at 1 500 ℃, the partial pressure of oxygen [p（O2）] of the system is located in the stable section for SizN20 in the Si-N-O phase diagram, resulting in a higher content of Si2N2O. For the samples re-sintered at 1 600 ℃, the p（O2） is lower than the critical value for Si3N4（s） converting to SizNzO（s）, and Si3N4（s） generates directly from Si（1） since β-Si3N4 is the main phase. In the complexes, SiO（g） reacts with CO（g）, thus generating fibrous SiC, and the partial pressure of SiO [p（SiO）] is negatively related to the temperature. As a result, the content of SiC in the samples at 1 500 ℃ is greater than that at 1 600 ℃. In the process of furnace cooling, a part of the metastable SiO（g） reacts with N2（g）, thus generating a-Si3N4（s）.