β-Si3N4 whiskers preparation from Si3N4@MgSiN2 core-shell structure powders
WANG Weide1,2, LIU Yiming2, PAN Yong3, MO Yong2, WANG Weiming2, MA Qingsong2
1. College of Advanced Interdisciplinary Studies, National University of Defense Technology, Changsha 410073, China; 2. Science and Technology on Advanced Ceramic Fibers and Composites Laboratory, College of Aerospace Science and Engineering, National University of Defense Technology, Changsha 410073, China; 3. Science and Technology on Space Physics Labrotary, China Academy of Launch Vehicle Technology,Beijing 100076, China
Abstract：One dimensional single crystal β-Si3N4 whiskers possess excellent thermal, mechanical, high- temperature and corrosion resistance properties, and are widely used as resin based, metal based, and ceramic based reinforcement materials. β-Si3N4 whiskers prepared with oxides as sintering aids have shortcomings such as high residual impurities and low aspect ratio, which limit their reinforcement effect. This study utilized the molten salt synthesis to prepare Si3N4@MgSiN2 core-shell structured powders with controllable shell thickness at lower temperature, and further prepared β-Si3N4 whiskers from this powder through sintering. The phase composition and microstructure of powders and whiskers were studied using X-ray diffractometer, energy dispersive spectrometer, and scanning electron microscope. The results show that at high temperatures, α-Si3N4 undergoes a phase transformation and Ostwald ripening in the liquid phase formed by the shell MgSiN2 through a “dissolution-precipitation” mechanism, resulting in the formation of β-Si3N4 whiskers with high aspect ratio. Raising the sintering temperature and increasing the Mg/Si3N4 mass ratio in the raw material can enhance the diffusion mass transfer in the liquid phase, which is beneficial for the growth of whiskers along the [001] direction, manifest as an increase in whisker length and aspect ratio. At the same time, the unstable nature of MgSiN2 at high temperature promotes its decomposition into Mg, N2, and Si3N4, ensuring the high purity of the whiskers. Therefore, high-purity, high aspect ratio, and easily dispersible β-Si3N4 whiskers are prepared by sintering at 1 750 ℃ for 1 h. The new preparation strategy of whiskers proposed in this study is economically feasible and provides a new approach for the preparation of high-performance β-Si3N4 whiskers.
王为得, 刘一铭, 潘勇, 莫勇, 王伟明, 马青松. 基于Si3N4@MgSiN2核壳结构粉体制备β-Si3N4晶须[J]. 粉末冶金材料科学与工程, 2025, 30(1): 1-10.
WANG Weide, LIU Yiming, PAN Yong, MO Yong, WANG Weiming, MA Qingsong. β-Si3N4 whiskers preparation from Si3N4@MgSiN2 core-shell structure powders. Materials Science and Engineering of Powder Metallurgy, 2025, 30(1): 1-10.
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2025, Vol. 30 
