基于纳米织构的氧化铝“形貌”复合陶瓷三维结构设计和力学性能研究

New structural design concepts are currently attempted for improving fracture toughness and mechanical reliability of alumina based ceramics in structural materials field. In this project, isotropic equiaxed alumina and anisotropic platelet nano-textured alumina with the same composition/single phase and different microstructures are chosen as the two components, respectively. Nano-texture, microstructural combination and 3D structural design etc. will be uniquely integrated together to form multistage toughening synergism. Firstly, the effects of matrix gel quality, template size/amount and growth aids on phase structure variation, densification behavior, texture fraction and microstructure evolution etc. of nano-textured alumina monolith will be studied. The strategy on how to tailor the grain sizes of nano-textured monolith will be explored. After that, the effects of monolith properties, 3D connectivity and its architectural parameters, interface adjustment and 3D processing techniques on residual stresses and their distributions, crack generation and propagation, fracture behavior, fatigue and thermal shock resistance etc. of the microstructural composites under service conditions will be studied. The mechanism on how to tailor mechanical properties of the composites will be clarified. Finally, we expect to achieve 3D microstructural alumina composites with high mechanical properties, good mechanical reliability and some new functional characteristics. This work will provide experimental support and theoretical basis for design, fabrication and property optimization of novel materials with high performance. Most importantly, it may represent a new investigation direction for the development of structural composites.

采用新设计概念提高氧化铝陶瓷的断裂韧性和可靠性，是当今国际上结构材料领域的研究前沿和热点之一。本项目选择组成相同但形貌不同的等轴状普通氧化铝和片状纳米织构氧化铝分别作为基本、增韧单体，拟将纳米织构、形貌复合与三维结构设计等结合形成多级增韧协同作用。首先研究凝胶性质、模板尺寸/含量、生长助剂等对单体纳米织构过程中的相结构变化、致密化行为、取向行为演变、微观形貌演变等影响规律，探讨高质量纳米织构单体的晶粒尺寸调控机制；然后研究单体性质、三维连通方式及结构参数、界面调控、3D合成技术等对复合陶瓷的残余应力、裂纹产生及扩张方式和服役条件下的断裂行为、抗疲劳行为及抗热冲击能力等影响规律，阐明其力学性能调控机理。最终获得高力学性能、高可靠性兼顾新功能的三维“形貌”复合氧化铝基材料。本研究可为新一代高性能材料的设计、制备技术和性能调控提供理论及实验依据，为结构复合材料的研究探索一个新发展方向。

采用新设计概念提高氧化铝陶瓷的断裂韧性和可靠性，是当今国际上结构材料领域的研究前沿和热点之一。本项目选择了等轴状普通陶瓷和片状纳米织构陶瓷分别作为基础、增韧单体，将纳米织构、形貌复合与三维结构设计等结合形成多级增韧协同作用来提高氧化铝陶瓷的力学性能。首先创建了沿[0001]c择优取向且粒径自500nm至10μm可控的片状氧化铝微晶模板的制备技术，阐明了片状籽晶的生长机理；随后，详细研究了纳米织构过程中的相结构变化、致密化行为、取向行为演变、微观形貌演变等规律，制备出了沿[0001]取向度高达93%以上的氧化铝织构陶瓷，提出了织构单体晶粒尺寸调控机制；然后，合成了具有不同连通方式（例如2-2、3-1等）的等轴普通-片状纳米织构“形貌”复合氧化铝陶瓷，系统研究了单体的选用方案、结构设计参数、工艺参数等对复合材料的共烧及致密化行为、微观形貌、复合界面的离子扩散行为等影响规律，以此指导了3-0连通的钛酸钡复合陶瓷合成；最后，深入研究了三维“形貌”复合氧化铝材料的残余应力、裂纹产生及扩张方式和服役条件下的断裂行为、抗疲劳行为及抗热冲击能力等影响规律，阐明了其力学性能调控机理，获得了高力学性能、高可靠性兼顾新功能的三维“形貌”复合氧化铝基材料，尤其是其断裂韧性和断裂功高达11.7MPa.m1/2和1540J/m2。本研究可为新一代高性能材料的设计、制备技术和性能调控提供理论及实验依据，为结构复合材料的研究探索一个新发展方向。