以铁合金行业的副产物-硅微粉(SiO_2≥90%,质量分数)和闪速燃烧合成的β-Si_3N_4(β-Si_3N_4≥95%,质量分数)为原料,按质量分数β-Si_3N_4:SiO_2=2:1的比例,分别将比表面积为1.19, 1.67, 2.48 m~2/g的β-Si_3N_4与SiO_2均匀混合、成型,分别经1300、1400、1500、1600 ℃,3 h埋碳(不接触碳)热处理,并对自然冷却后试样进行XRD、SEM分析.结果表明,β-Si_3N_4与SiO_2从1300 ℃开始缓慢反应生成Si_2N_2O,随温度升高到1500 ℃以上时Si_2N_2O反应速度明显加快;在1300、1400 ℃,反应以固-固反应为主,β-Si_3N_4的比表面积对Si_2N_2O生成量的影响越大,比表面积大则Si_2N_2O生成量较高;在1500 ℃以上时,随着硅微粉收缩、液化,将β-Si_3N_4包裹、胶结到一起,反应方式以固-液反应为主,反应速度明显加快,加速了Si_2N_2O的形成,β-Si_3N_4的比表面积对Si_2N_2O生成量的影响不明显.
Utilizing the ferroalloy industry by-products--Silica fume (SiO_2≥90%, mass fraction) and β-Si_3N_4 synthesized through flashing combustion process as raw materials, according to the mass content of β-Si_3N_4: SiO_2 = 2:1, β-Si_3N_4 with specific surface area of 1.19, 1.67, and 248 m~2/g and SiO_2 were mixed, molded, and sintered at 1300, 1400, 1500 and 600 ℃ with buried carbon (non-contact with carbon) for 3 h, and then analyzed through XRD and SEM. The results show that, the reaction of β-Si_3N_4 and SiO_2 slowly occured from the beginning at 1300 ℃, and at 1500 ℃ increases obviously; at 1300 and 1400 ℃, the reaction belongs to solid-solid type and the specific surface area of β-Si_3N_4 significantly affects the producing amount of Si_2N_2O; the sample containing Si_3N_4 with the larger specific surface area produces more amount of Si_2N_2O; and at 1500 and 1600 ℃, the specific surface area have relatively small impact.
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