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Si3N4 grain size and phase composition of silicon nitride ceramic material as a synthesis of the two main quality indicators. SHS synthesis of silicon nitride with low power consumption , no pollution, high purity, low cost , etc., is one of the main methods Preparation of Silicon Nitride Powder . As a raw material in the synthesis of silicon nitride is silicon nitride diluent is added , therefore , there is accumulation of silicon nitride crystal grains growing phenomenon . Clarify the way the silicon nitride grain growth control its growth , reduce costs and post- grinding contamination has important theoretical and practical significance. Meanwhile, the self-propagating high temperature synthesis of silicon nitride having a fast response characteristics, how to effectively control the phase composition is also a key technical issues. SHS silicon nitride powder prepared containing α, β -phase . By adjusting the ratio of raw materials , particle size , reaction pressure and other parameters can be controlled in a silicon nitride powder, α, β phase ratio changes. In this paper, accumulating experimental design , layered fabrics, adding silica experiment , powder morphology by scanning electron microscopy , X diffraction analysis of the powder composition and content changes , discuss nitride α phase and β phase formation mechanism and the particle size variation . Stratified layers of fabric changes additive NH 4 Cl content, adding SiO 2 powder reaction system temperature changes , reducing the particle size increased α phase content . The results showed that: Thinner avoid powder agglomeration , reducing β -phase formation of nucleation process . α phase from the vapor phase growth method , hot promotion α-Si 3 N 4 into β-Si 3 N 4 . Meanwhile heat the powder to promote rapid growth . Layered fabric effectively reduce the temperature of the system self-propagating reaction , hindering powder grow , improve powders α phase content . When the intermediate layer additive content of 5% , the lower is 2.5%, α -phase increased to 50.34% . SHS powder to add SiO 2 increases the oxygen content of impurities , reducing the α phase content .
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