瞬间液相合金渗入法低温制备Cf/(Hf,Si)C复合材料机理研究

Because of combination of high mechanical performance of C/C composites at elevated temperatures and excellent anti-ablation property of ultrahigh temperature ceramics (UHTCs), the carbon fiber reinforced UHTCs-based composites (Cf/UHTCs) have been widely studied in recent years. Among different kinds of UHTCs, the HfC ceramic possesses an even better anti-ablation property at ultrahigh temperatures. However, due to the difficulties of preparation, more creative and innovative research is needed to develop carbon fiber reinforced HfC-based composites (Cf/HfC). Different with the reactive melt infiltration method, by which the metal or alloy has to be melted at a very high temperature and then infiltrates into C/C preform, our research group prepared the Cf/HfC composites by instantaneous liquid infiltration (ILI) at a relative low temperature below the alloy melting point. Based on alloy design, the alloy reacts selectively with the carbon in the surface layer of C/C preform, generating Hf-rich liquid which infiltrates into C/C preform below alloy melting point. The infiltrated liquid reacts with the carbon matrix of C/C preform and the Cf/HfC composite is obtained. The prepared composites possess a good anti-ablation property. This project is to conduct further research on alloy design and the mechanism of alloy infiltration at low temperature, reveal the infiltration process and the formation of composite structure, and solve the key scientific problems during the preparation and application of Cf/HfC composites. By the implement of this project, the ultrahigh temperate performance of Cf/UHTCs is expected to be improved to a higher level, creating a more substantial material base for the development of advanced aerocraft and space power system.

由于碳化铪熔点高、抗高温氧化烧蚀性能突出，碳纤维增强碳化铪基复合材料近年来日益受到重视。但是由于铪基合金熔点过高，采用熔渗法制备碳化铪基复合材料，工艺难度大，且过高的工艺温度会对碳纤维力学性能造成损伤，因此要发展碳纤维增强碳化铪基复合材料并实现其应用还需要更具创新性的研究。本课题组率先提出基于合金设计、在低于铪合金熔点的较低温度下通过选择性界面碳化反应触发瞬间液相产生并渗入碳碳预制体、合金液相与基体碳反应制得碳纤维增强碳化铪基复合材料的设想，并已取得了初步的研究成果。本项目旨在进一步深入开展合金设计及合金瞬间液相产生及渗入机理的研究，揭示合金渗入过程及材料组织的形成机理，解决碳纤维增强碳化铪基复合材料的制备和应用中的关键科学问题，有望将超高温陶瓷基复合材料的综合性能再提高一个台阶，为先进飞行器和空间动力系统的发展提供更为优异的超高温材料。

由于碳化铪熔点高、抗高温氧化烧蚀性能突出，碳纤维增强碳化铪基复合材料近年来日益受到重视。但是由于铪基合金熔点过高，采用熔渗法制备碳化铪基复合材料，工艺难度大，且过高的工艺温度会对碳纤维力学性能造成损伤，因此要发展碳纤维增强碳化铪基复合材料并实现其应用还需要更具创新性的研究。本项目提出基于合金设计、在低于铪合金熔点的较低温度下通过选择性界面碳化反应触发瞬间液相产生并渗入碳碳预制体、合金液相与基体碳反应制得碳纤维增强碳化铪基复合材料的设想，开展了合金成分理论设计与实验研究、瞬间液相产生机理与渗入过程研究、复合材料微观多层碳化物陶瓷结构的形成机理研究等。项目研究结果揭示了在低于合金熔点的工艺温度下瞬间液相产生及渗入机理，建立了合金瞬间液相渗入模型，为采用该方法制备Cf/HfC 复合材料提供了理论指导。在低于合金熔点的较低工艺温度下实现高熔点铪合金渗入碳/碳预制体以制备碳化铪基复合材料的方法，突破了反应熔渗法要求合金熔化后渗入预制体、工艺温度在合金熔点以上的制约，为碳纤维增强碳化铪基超高温复合材料的制备提供了新思路、新方法；利用不同合金组分碳化物形成能力的差异，创新性地把合金设计的思想引入到陶瓷基复合材料的制备方法中，并通过合金设计来调控复合材料的组织与性能，这种思想可为其他材料体系提供借鉴；与其他可能的制备碳化铪基复合材料的方法如CVD、PIP 方法相比，瞬间液相合金渗入法制备周期短、工艺成本低。