材料期刊网

用氮化硼纳米管（BNNT）增强氮化硅（Si3N4）陶瓷制备了BNNT／Si3N4复合材料，利用三点弯曲强度及单边切口梁（SENB）法测定了BNNT／Si3N4复合材料的弯曲强度和断裂韧性。通过SEM观察了BNNT／Si3N4复合材料微观形貌。基于BNNT增强Si3N4陶瓷复合材料的裂纹扩展阻力计算公式，构建了BNNT对Si3N4陶瓷裂纹屏蔽区的裂纹扩展阻力的数学模型。用该模型的计算结果与Si3N4陶瓷的裂纹扩展阻力进行了对比。结果表明：BNNT／Si3N4复合材料的弯曲强度和断裂韧性明显高于Si3N4陶瓷，说明BNNT对Si3N4陶瓷的裂纹扩展有阻力作用，摩擦拔出是Si3N4陶瓷抗裂纹扩展能力提高的主要原因；BNNT对Si3N4陶瓷有明显的升值阻力曲线行为。通过有限元模拟裂纹尖端应力分布，发现BNNT使Si3N4陶瓷裂纹尖端的最大应力转移到纳米管上，而且BNNT降低了Si3N4陶瓷裂纹尖端的应力，对Si3N4陶瓷尖端的裂纹有屏蔽作用，从而提高了Si3N4陶瓷的裂纹扩展阻力。

BNNT/Si3N4 composites were prepared with Si3N4 ceramics enhanced by BN nanotubes (BNNT). Bending strength and fracture toughness of BNNT/Si3 N4 composites were tested by three point bending strength and SENB method. BNNT/Si3N4 composite microstructures were observed by SEM. The mathematical model of the crack propagation resistance of Si3N4 ceramics crack shielding region enhanced by BNNT was constructed, which was based on the crack propagation resistance formula of BNNT reinforcing Si3N4 ceramics. The calculated results used this model were compared with crack propagation resistance of Si3 N4 ceramics. The results show that bending strength and fracture toughness of BNNT/Si3 N4 composites are obviously higher than those of pure Si3 N4 ceramics and BNNT increases the crack propagation resistance of Si3 N4 ceramics. It can be seen that the friction resistance to pull out is the main reason of reducing the Si3 N4 ceramics crack propagation capability and that Si3 N4 ceramics added BNNT has clear appreciation of the resistance curve behavior. The finite element simulation results on the crack tip stress indicate that BNNT makes maximum stress of the crack tip to deflect nanotubes and reduce stress of the Si3 N4 ceramics crack tip, which can improve the crack propagation resistance behavior of Sis N4 ceramics.