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Effect of sawdust kind on Si3 N4 powder prepared with SiO2 carbothermal reduction and nitridation method
Author(s): 
Pages: 96-100
Year: Issue:  2
Journal: Refractories

Keyword:  silicon nitridepine sawdusttung sawdustsilica solimmersion methodcarbothermal reduction and nitridation;
Abstract: 为了确定SiO2碳热还原氮化法制备氮化硅时合适的木屑种类,分别以松、桐两种木屑和SiO2质量分数为2.5%、5%、7.5%、10%、15%、20%的硅溶胶为原料,采用真空常压浸渍-碳热还原氮化法(成型压力10 MPa,氮气流量400 mL·min-,反应温度1 500℃,反应时间9h)制备了氮化硅粉体,并对采用本法制备Si3 N4粉体的传质机制进行了初步探讨.结果表明:松、桐两种木屑分别经w(SiO2)=7.5%的硅溶胶浸渍后,经碳热还原氮化反应均可制得高o-Si3 N4和β-Si3N4含量的混合粉体,但用松木屑制得的Si3N4粉体中α相含量明显较桐木屑的高,更适合用此法制备氮化硅粉体;本试验中碳热还原氮化反应采用的是形成气相中间产物的传质形式,C颗粒是氮化物颗粒的前驱物,其基本反应过程是:木屑炭化→原位还原SiO2→生成气体中间产物→N2参与反应→完成碳热还原氮化反应.
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