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根据Si—N—O三元系热力学的计算,讨论在混合气体N_2-H_2-H_2O产中生成氮化硅的条件及氧对氮化过程的影响。用光学显微镜、扫描电子探针和x射线衍射分析方法检验氮化硅试样的显微组织,确定为:α-Si_3N_4,β-Si_3N_4,残余硅和孔隙。 采用热重分析方法研究1603-1675K 范围的混合气体 N_2-H_2-H_2O(P_(N_2)=8×10~(-1)atm,P_(H_2)=2×10~(-1)atm,P_(H_2O)=2×10~(-7)atm)中硅氮化反应的动力学。 认为:氮化过程的限速步骤是氮气通过在硅表面上的氮化物壳层的扩散,并提出一种解释扩散机理的模型。计算得扩散活化能为148.000Cal/mol。
According to the thermodynamics calculation of Si-N-O ternary system, the conditions of forming silicon nitride in N_2-H_2-H_2O mixed gas and the effect of oxygen on the nitriding process are discussed. The microstructure of Si3N4 samples was examined by optical microscope, scanning electron probe and X-ray diffraction analysis. The results were as follows: α-Si_3N_4, β-Si_3N_4, residual silicon and pores. The thermogravimetric method was used to study the gas mixtures of N_2-H_2-H_2O (P_ (N_2) = 8 × 10 -1 atm, P_2 (H_2) = 2 × 10 -1 atm, P_ (H_2O) = 2 × 10 ~ (-7) atm). It is believed that the rate-limiting step in the nitridation process is the diffusion of nitrogen through the nitride shell on the silicon surface and proposes a model to explain the diffusion mechanism. The calculated activation energy for diffusion was 148,000 cal / mol.