高频等离子法制取超细Si_3N_4粉末

PREPARATION OF ULTRAFINE Si_3N_4 POWDER BY R. F. PLASMA

本文述及高频等离子法制取超细Si_3N_4粉末的原理、装置,工艺参数及粉末性能的一些检测结果。利用SiCl_4+NH_3气-气相反应,所得白色粉末含有NH_4Cl晶体,热重分析表明350℃失重停止,280℃失重速率最快,经400～700℃处理后的粉末仍为非晶,不含NH_4Cl,BET测得比表面积为75.8 m^2/g,X光小角度散射法测粒子半径分布主峰R为100～150,且符合正态对数分布规律,平均直径=527;1400℃处理后,X光衍射测得主相为α-Si_3N_4、次相为Si_2N_2O,粒径明显长大,平均直径达1700。

In this paper the principle, apparatus and technological parameters for preparing ultrafine Si3N4 powder by R. F. plasma were described and some properties of powder made by this process were introduced.The reaction between vapor phase SiCl4 and NH3 resulted in white powder containing NH4C1 crystals The thermogravimetric analysis shows that the weight loss rate appeared to be the highest at 280℃ and the weight kept constant above 350℃. After heat treatment in the range of 400-700℃, the Si3N4 powder structure still remains amorphous, no NH4Cl, its specific surface area is 75.8 m2/g by BET method. X-ray small angle scattering analysis shows that the distribution of Si3N4 particle size is in the form of logarithmic normal distribution with the average diameter D=527 , and the radius R corresponding to the primary peak is 100-150A.After heat treatment at 1400℃, X-ray diffraction has indicated that the primary phase is aaaaaaa-Si3N4, the second phase is Si2N2O, the particle size of Si3N4 powder grows obviously and its average diameter approaches to 1700.