Fe2 O3 对碳热还原氮化SiO2 合成Si2 N2 O的催化效应及机理

采用碳热还原氮化SiO2的方法在1 500℃制备了Si2N2O,并通过XRD和热失重分析,研究了Fe2O3对合成Si2N2O的催化作用及机理。Fe2O3对Si2N2O的合成具有显著的催化作用,加入少量Fe2O3可以使SiO2的转化率达到100%。Fe2O3的催化机理为:一方面,Fe2O3被C还原为纳米铁单质,并与Si形成Fe-Si液相,该Fe-Si液相可溶解SiO2和C颗粒,促使SiOC中间相在较低温度下形成,从而显著降低碳热还原反应的开始温度。另一方面,Fe-Si液相中的CO2与FeSi反应,通过形成SiO和CO而加速碳热还原反应的进行。

Catalytic Effect and Mechanism of Fe2 O3 on Synthesis of Si2 N2 O byCarbothermal Reduction and Nitridation of SiO2

Si2N2O was prepared by carbothermal reduction and nitridation of SiO2 at 1 500℃.The catalytic effect and mechanism of Fe2O3 on synthesis of Si2N2O were investigated by XRD and thermogravimetry.Fe2O3 had a remarkable catalytic effect on synthesis of Si2N2O.A 100% conversion ratio of SiO2 could be achieved when adding a little Fe2O3.The catalytic mechanism of Fe2O3 could be concluded as:on the one hand,the Fe2O3 can be reduced to nanosized Fe by C,which may form Fe-Si liquid with Si.The Fe-Si liquid can dissolve SiO2 and C particles and promote formation of the intermediate phase SiOC at a lower temperature,leading to a significantly decrease of the starting temperature of carbothermal reduction.On the other hand,the CO2 can react with Fe-Si liquid to form SiO and CO,which may enhance the reaction rate of carbothermal reduction.