高热导石墨烯增强ZrB2超高温陶瓷材料失效与热传输机理研究

Ultrahigh temperature ceramics is a new kind of strategic and high-temperature structural materials, and it has always been a hot topic of ablative thermal protection structures for hypersonic aircrafts. However, poor dynamics and low thermal transfer efficiency have restrained its popularization and application in ultrahigh temperature environments. Graphene has both excellent mechanical and thermal properties, so it has the potential to simultaneously solve above problems. This project takes the graphene enhanced zirconium diboride-based ceramic composites as the research object. Electrostatic assembly will be used to solve the problem of uniform microstructure, and then making the improvement of the toughness and thermal conductivity of composites possible. This research project will focus on exploring the failure and thermal transfer mechanisms of graphene modified ultrahigh temperature composites by utilizing experiments, theoretical calculation, finite element method and molecular dynamics simulation. The mechanisms of failure and the properties interface transmission will be proposed. This project will obtain the principle that how the intrinsic thermodynamic characteristics of graphene and ceramic particles, and their interfacial interactions (at micro-nano scale) affect the thermal-mechanical properties of composites (at macroscale), reveal the mechanisms of graphene/ceramics failure and interface transfer, and propose the advantages of graphene compared with fibers and whiskers. Hence, this project will offer some theoretical foundations and technical supports for accurate predicting their various characteristics at macroscale, and provide some scientific methods and new ideas for the preparation of high thermal-conductivity ultrahigh temperature ceramics and the optimization of thermal protection structure.

超高温陶瓷是一种新型的战略性高温结构材料，一直以来是高超声速飞行器防热烧蚀结构材料的研究热点。然而，动力学性能差和热传输效率低两个问题已经成为限制超高温陶瓷推广应用的瓶颈。石墨烯的优异力学和热学性能，有望在改善超高温陶瓷热力学性能方面得到广泛应用。本项目以石墨烯增强ZrB2陶瓷材料为研究对象，拟采用静电组装原理解决微结构的均匀性问题，旨在提高陶瓷材料的韧性和热导率。研究的重点为利用多尺度下实验、理论和模拟相结合的研究方法，探索ZrB2陶瓷基复合材料的失效和热传输问题，提出微纳尺度下陶瓷和石墨烯的本征热力学性质及其界面耦合作用对宏观复合材料热力学性能的影响，以期揭示复合材料的失效和热传输机理，探寻石墨烯相比纤维和晶须等传统增强相的优点。本项目将为宏观尺度下准确预测ZrB2陶瓷材料的热力学性能提供依据，为制备新型高热导超高温陶瓷材料和优化高温防热结构提供新方法和新思路。

石墨烯的优异力学、热学性能有望在改善超高温陶瓷热力学性能方面得到广泛应用。本项目创新地提出高韧性、高热导石墨烯改性超高温陶瓷复合材料制备方法，增强了复合材料的动态力学与热冲击性能，得到石墨烯相比纤维和晶须等传统增强相的高热导优点，提高了陶瓷材料的韧性（增加至6.93 MPa∙m1/2）和热导率（增加了42%）。分子动力学模拟发现，增强相SiC陶瓷弹性模量随着裂纹的增大而下降，其塑性和抗拉强度均下降；热导率随着空位增多而急剧下降，但当空位浓度继续增加时下降趋势放缓；热导率随着温度从600 K上升而降低。本项目开发的材料优化技术为制备高热导超高温陶瓷材料和优化高温防热结构提供了新方法和新思路，制备的新型复合材料可以解决超高速飞行器高马赫数飞行的力学可靠性。