六方氮化硼陶瓷的烧结及其结构与性能

Structure and Properties of Hexagonal Boron Nitride Ceramics by Different Sintering Methods

以亚微米级h-BN粉体为原料,在不添加任何烧结助剂的情况下,分别采用无压烧结、热压烧结和放电等离子烧结（SPS）制备h-BN陶瓷,采用X射线衍射和扫描电子显微镜对烧结后样品的物相组成和显微结构进行测试和观察,研究不同烧结方法对h-BN陶瓷的致密度、晶粒取向、显微形貌及力学性能的影响,对比分析了不同烧结方法下坯体初始致密度对h-BN陶瓷性能的影响。结果表明：无压烧结无法实现h-BN陶瓷烧结致密化,力学性能较差,而通过热压和放电等离子烧结的方法均能得到结构致密、力学性能较好的h-BN陶瓷。相比于传统的无压和热压烧结,放电等离子烧结方法制备的h-BN陶瓷具有更高的致密度和更好的力学性能,而且晶粒更均匀细小,烧结温度可降低200℃以上。此外,坯体初始致密度的提高能显著提高h-BN陶瓷的抗弯强度和断裂韧性,但对热压和放电等离子烧结制备的h-BN陶瓷致密化的影响较小。

h-BN ceramics were prepared via pressureless sintering, hot pressing sintering or spark plasma sintering（SPS） with submicron-sized h-BN powder as raw material without any sintering aids. The phase composition and microstructure of specimens were characterized by X-ray diffraction and scanning electronic microscopy. The effect of sintering method on the densification, grain orientation, microstructure and mechanical properties of h-BN ceramics was investigated. The influence of initial green density on the properties of h-BN ceramics was also analyzed. The results show that h-BN ceramics prepared by PLS have a lower density and poor mechanical properties, and h-BN ceramics with compact structure and good mechanical properties can be fabricated by HP and SPS. Compared to the conventional PLS and HP, however, h-BN ceramics prepared by SPS have a greater density and better mechanical properties, more uniform and fine grains, and the densification temperature is decreased by more than 200 ℃. Furthermore, increasing the initial green density can improve the flexural strength and fracture toughness of h-BN ceramics, and there is little impact on the densification of h-BN ceramics prepared by HP and SPS.