可用于3D打印的Zr-B-Si-C超高温陶瓷材料设计与原位合成研究

Ultra-high temperature ceramics (UHTCs) are considered as the potential candidate for high temperature structural parts in thermal protection systems of space vehicles. Due to the difficulty of casting or machining of ceramics, UHTCs are consolidated from powders by sintering which are difficult to be processed into complex shapes. 3D printing enables a leap in geometrical flexibility for manufacturing of UHTCs. However, the extremely high melting point of UHTCs adds challenges to 3D printing. The lack of printing raw materials, poor printing quality and properties of 3D-printed parts are still the limitation preventing the 3D printing from being widely used. Based on the stereo-lithography 3D printing, we provide pre-ceramic monomers which are photo-cured with ultraviolet light to form complex 3D polymer structures, and then these polymer structures can be pyrolyzed to a ceramic. The mechanisms of polymer-derived ceramics are clarified. The preparation process, microstructures, and comprehensive properties of 3D-printed UHTCs are investigated. Methods to overcome the physical-chemistry conflict between components are studied, and the key factors which affect the performance of materials are also discussed. The material system and process parameters are optimized in order to design ceramics with unique phase compositions and microstructures, and consequently with improved properties so that the 3D-printed materials can be used above the temperature of 1800 °C. The investigation presented here will enrich the design method of raw materials for 3D printing and point out a promising way for improving the properties of UHTCs. It also promotes the practical process of complex parts of UHTCs used in extremely harsh environments, and provides a theoretical basis and technical support to advance the development of weapons and equipment, such as hypersonic vehicle, deep space probe, aircraft engine and so on.

陶瓷的3D打印一体化成型是最有望突破传统粉末烧结工艺无法制备复杂结构超高温陶瓷热端部件的技术，然而可用于3D打印的超高温陶瓷材料选择局限性大、仅有的材料存在成型构件质量差和性能低下的缺点，这些问题一直制约其实际应用发展。基于此，本项目提出了光固化快速成型的聚合物转换法原位合成Zr-B-Si-C超高温陶瓷材料的学术思想，阐明光固化机理和陶瓷化转变机制，建立可用于超高温陶瓷3D打印的方法，分析制备工艺-微观组织-材料性能的关联关系，解决组分间物理/化学冲突，探究影响材料使役性能的关键控制因素，优化材料体系与制备工艺参数，获得满足1800 ℃使用性能的3D打印Zr-B-Si-C陶瓷材料，解决超高温陶瓷打印材料匮乏的瓶颈问题，为3D打印超高温陶瓷复杂构件提供基础，推进极端服役环境的复杂热端部件实用化进程，为新一代高超声速飞行器、深空探测、航空发动机等武器装备的跨越式发展提供理论依据和技术支撑。

陶瓷的3D打印是最有望突破复杂结构超高温陶瓷成型的技术，但是目前可用于3D打印的超高温陶瓷材料有限。本项目采用了光固化快速成型的聚合物转换法原位合成了Zr-B-Si-C超高温陶瓷材料，阐明了其光固化机理和陶瓷化转变机制；结合立体光刻快速成型技术验证了Zr-B-Si-C超高温陶瓷材料的精密打印，并分析了“材料组分–制备工艺–组织结构–材料性能”之间的关系，陶瓷的致密度以及微观结构影响了材料的宏观力学性能，其次，打印参数的设置也会间接影响材料性能，试验获得了较致密的陶瓷材料，其断裂韧性和弯曲强度分别能够达到4.65MPa·m1/2和834MPa；进一步优化了材料体系和制备工艺参数，大幅度提高了3D打印陶瓷材料的服役温度和综合性能，最终获得了可用于3D打印的高性能Zr-B-Si-C陶瓷材料，解决了超高温陶瓷打印材料匮乏的瓶颈问题，为进一步开发高性能的3D打印用超高温陶瓷材料提供了试验基础和技术指导。