Abstract: The effects of surface oxygen content on the nitridation of high-purity silicon powders were studied, high-α phase silicon nitride was prepared via direct nitridation process of silicon powders in the N2/H2 atmosphere.The results show that the content of α-Si3N4 in nitridation products tended to increase first and then decrease with the increase of the oxygen content on the silicon surface. When the surface oxygen content of silicon powders was 3.91%, the α-Si3N4 content of nitridation products could reach 97%, the residual silicon content was lower than 1% and the oxygen content in central region was 1.71%, the micrograph morphology of nitridation products mainly composed of rod shaped α-Si3N4 whisker which was formed by chemical vapor deposition at 1 350 ℃ for 3 hours in the N2/H2 atmosphere. When the surface oxygen content of silicon powders was lower than 4.38%, all the content of the α-Si3N4 in nitridation products was over 95%, a small amount of β-Si3N4 and residual silicon phase, which was examined by XRD, can be observed, but no silicon oxynitride. While the oxygen content of silicon powders was higher than 5.61%, the content of silicon oxynitride increased obviously with the increase of oxygen content. While the oxygen content of silicon powders was lower than 5.61%, the residual silicon of nitridation products decreased significantly with the increase of oxygen content, which showed that the increase of oxygen in silicon powders could accelerate the nitridation rate significantly and then reduce the content of residual silicon in nitridation products.
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2018, Vol. 32 
