由稻壳制备氮化硅的动力学研究

Kinetics of Si_3N_4 Formation from Rice Hull

Coking the green rice hull can give silica and carbon,and this silica can reactwith N_2 at a certain temperature to produce Si_3N_4.In this paper,the kinetic prob-lem in preparing Si_3N_4 from rice hulls was investigated by means of thermogravime-tric analysis.Experimental results indicate that the reaction rate controlling steps inthe overall process are the diffusion of SiO gas and/or CO gas through the stagnantgas film around the carbon particle,the activation energy is less than 41.868 kJ/mole.Adding some Fe_O_3 and NaF as catalyst to the rice hulls can increase the nitri-ding percent.The optimum amount of Fe_2O_3 and NaF added to rice hulls are 0.224wt% and 0.1 mo1% respectively.The catalytic action of NaF is better than Fe_2O_3.