原位引入BN-SiC燃烧合成Si3N4-BN-SiC复合材料

Si₃N₄-BN-SiC复合材料以其良好的力学性能和抗氧化性能而具有良好的工程应用前景。本研究以Si、Si₃N₄稀释剂、B₄C和Y₂O₃为原料, 采用燃烧合成法成功制备了Si₃N₄-BN-SiC复合材料。通过Si、B₄C和N₂气之间的反应, 在Si₃N₄陶瓷中原位引入BN和SiC, 制备的Si₃N₄-BN-SiC复合材料由长棒状的β-Si₃N₄和空心球形复合材料组成。实验研究了空心球微结构的形成机理, 结果表明, 生成的SiC、BN颗粒及玻璃相覆盖在原料颗粒上, 当原料颗粒反应完全时, 形成空心球形微结构。并进一步研究了B₄C含量对Si₃N₄-BN-SiC复合材料力学性能的影响。原位引入SiC和BN在一定程度上可以提高复合材料的力学性能。当B₄C添加量为质量分数0~20%时, 获得了抗弯强度为28~144 MPa、断裂韧性为0.6~2.3 MPa·m ^1/2, 杨氏模量为17.4~54.5 GPa, 孔隙率为37.7%~51.8%的Si₃N₄-BN-SiC复合材料。

Combustion Synthesis of Si3N4-BN-SiC Composites by in-situ Introduction of BN and SiC

Si₃N₄-BN-SiC composites present desirable potential for engineering applications because of their improved mechanical properties and oxidation resistance. In present work, Si₃N₄-BN-SiC composites were successfully fabricated by combustion synthesis using Si, Si₃N₄ diluent, B₄C, and Y₂O₃ as initial powders. BN and SiC were in situ introduced into Si₃N₄ ceramics by the reaction between Si, B₄C, and N₂ gas. The obtained Si₃N₄-BN-SiC composites were composed of elongated β-Si₃N₄ matrix and hollow spherical composites. The formation mechanism of the hollow spherical microstructure was investigated. The results show that the generated SiC and BN particles and glass phase cover on the raw materials, and hollow spherical microstructure is formed when raw particles are depleted. Furthermore, the impacts of B₄C content on the mechanical properties of Si₃N₄-BN-SiC composites were investigated in detail. The in-situ introduction of BN and SiC is beneficial to improving mechanical properties of the composites to some extent. Finally, Si₃N₄-BN-SiC composites with bending strength of 28-144 MPa, fracture toughness of 0.6-2.3 MPa·m ^1/2, Young's modulus of 17.4-54.5 GPa, and porosity of 37.7%-51.8% were obtained for the samples with 0-20% (in mass) B₄C addition.