织构h-BN基复合陶瓷的显微结构调控及定向导热微观机理研究

The hexagonal Boron Nitride (h-BN) has a lamellar structure similar to graphite, B and N atoms in the layer are combined by strong covalent bonds, while the layers are bonded by the weak Van der Waals forces. If the c-axis of the h-BN grains are arranged along a fixed direction by the preferred orientation growth or grain deflection during the sintering process, the h-BN matrix composite ceramics with texture characteristics and anisotropic properties are obtained, which can further extend the applications. The purpose of our application is to systematically investigate the mechanisms of atom diffusion, grain growth and crystal orientation during the sintering procedures by designing and optimizing material compositions, sintering method and process parameters. Through the characterization of microstructures and directional thermal conductive properties of composite ceramics, the influence of grain size, crystallization degree, grain arrangement direction, interface bonding and defects on the thermal conductivity properties are to be revealed, the relationship between the components, preparation parameters, microstructures and directional thermal conductivity features are to be clarified, then the h-BN matrix composite ceramics with obviously directional thermal conductivity can be obtained. This study can enrich and improve the basic theory on the manufacturing, characterization and properties of textured ceramics, which can build a solid foundation for popularization and application of h-BN matrix composite ceramics. Thus, it has important academic value and potential engineering application prospects.

六方氮化硼(h-BN)具有类似石墨的层状结构，其层片内的B和N原子通过强共价键结合，而层间则通过较弱的范德华力结合。如能在烧结过程中通过取向生长或晶粒偏转而使h-BN晶粒的c轴沿固定方向排列，就可以形成具有各向异性的织构h-BN基复合陶瓷，进一步扩展其应用领域。本项目拟通过材料成分设计、烧结方法和工艺参数优化，系统研究烧结过程中原子扩散、晶粒生长、晶体定向排布的机理。通过显微组织结构以及复合陶瓷定向导热性能的表征，揭示织构复合陶瓷中晶粒尺寸、结晶程度、晶粒排布方向、界面结合、缺陷等对其导热性能的影响规律，阐明织构h-BN基复合陶瓷成分-制备工艺-显微结构-定向导热性能间的内在联系，优化出具有显著定向导热特性的h-BN基复合陶瓷。本项目研究，将进一步丰富和完善织构陶瓷材料制备、表征及其性能等方面的基础理论，为h-BN基复合陶瓷的推广应用打下坚实的基础，具有重要的学术价值和潜在的工程应用前景。

六方氮化硼(h-BN)具有类似石墨的层状结构，如能在烧结过程中通过取向生长或晶粒偏转而使h-BN晶粒的c轴沿固定方向排列，就可以形成具有定向导热功能的织构h-BN基复合陶瓷，结合其耐高温、透波及绝缘特性，可用作航天器天线窗盖板、微电子行业用导热基片等定向热疏导材料。.本项目系统研究了原材料与制备工艺对h-BN及其复相陶瓷的组织结构演化与定向导热性能的影响规律，得到了以下结果：1) 热压烧结h-BN陶瓷的显微组织结构与烧结温度和压力密切相关：较高的烧结压力更有利于片状h-BN晶粒沿压力方向的择优取向生长，从而形成h-BN晶粒c轴沿垂直烧结压力方向排列的择优取向，然而具有该取向特征的结构只有在适当的烧结温度下才能获得；2) h-BN晶粒在热压烧结过程中存在“多区域共生长”，该现象也导致烧结后结晶完好的h-BN晶粒中存在一些层错；3) h-BN陶瓷的热导率与其晶粒取向程度、结晶化程度、晶粒尺寸均有关系，其中受晶粒取向程度的影响最甚，晶粒尺寸细小且结晶度较差的h-BN陶瓷热导率可能随测试温度的升高而有所提高；4) 对h-BN原料粉体的球磨处理可以在一定程度上提高液相烧结h-BN基复相陶瓷的织构化程度和定向导热性能，然欲进一步提高陶瓷的定向导热性能，则需要使用粒径较大的片状h-BN粉体；5) 3Re2O3-5Al2O3可以作为制备高度织构化h-BN陶瓷的有效烧结助剂，该体系复相陶瓷沿片层方向的热导率最高可达118.58W/(m·K)。.本项目的研究进一步丰富和完善了热压烧结h-BN陶瓷的组织结构演化理论，建立了h-BN陶瓷组织结构与其定向导热性能之间的内在联系，揭示了热压烧结过程中h-BN晶粒的生长机制，对未来h-BN陶瓷在定向导热材料方面的应用打下了坚实的理论和实验基础。.本项目实施期间，发表SCI检索论文15篇，获授权国家发明专利1项，主编专著1部，参加国内外学术交流5次（其中大会报告1次、邀请报告3次），获中国建材联合会中国硅酸盐学会技术发明一等奖1项。