CNTs-SiC增强铝基复合材料中CNTs/SiC/Al复合界面调控及其强化机理

Aiming to solve the key scientific problems such as carbon nanotubes (CNTs) dispersion, Al/CNTs interfacial reaction and interfacial bonding which restrict the exertion of the compound effect of CNTs reinforced aluminum matrix composites (AMCs). Proceeding from the design of composite configuration and interface structures, a new thought to be used to improve the interfacial bonding and prevent the chemical reaction between CNTs and Al matrix by introducing SiC as a transition layer is proposed. In the mastery of the thermodynamic and kinetic mechanisms for CNTs-Si and CNTs-SiO2, the advanced preparation technology is employed to synthesis the nano CNTs-SiC composite reinforcement and the interfacial structure and the chemical reaction of the nano CNTs-SiC composite reinforcement are regulated and controlled in order to reduce the surface energy of CNTs, weaken its own agglomeration trend and improve the dispersion and the wettability of CNTs with the aluminum substrate. On this basis, the study focuses on the influence disciplinary of the microstructure and contents of nano CNTs-SiC composite reinforcement on microstructure, interfacial structure of AMCs and the interrelation of microstructure and macro-mechanical properties of AMCs, building collaborative strengthening model for nano CNTs-SiC composite reinforcements strengthened AMCs, clarifying the intrinsic strengthening mechanism of nano CNTs-SiC reinforcement and the matching between strength-plastic/toughness of AMCs, realizing the controllable preparation of nano CNTs-SiC reinforced AMCs and solving the current existing common problems in which the composition effect of CNTs in AMCs is difficult to be effectively exerted. It also provides experimental basis and theoretical reference for the development of CNTs reinforced AMCs with high strength and high conductivity and to promote its engineering application.

针对碳纳米管（CNTs）增强铝基复合材料（AMCs）研究中Al/CNTs界面结合及界面反应等制约CNTs在AMCs中复合效应发挥的关键科学问题，本申请从AMCs的复合构型和界面结构设计出发，提出在Al/CNTs界面间引入SiC过渡层的新思路。在明确CNTs与Si及SiO2的反应热-动力学机理的基础上，制备合成纳米CNTs-SiC复合增强相，并对其界面结构和界面反应进行调控，以降低CNTs比表面能，改善CNTs的分散性及与铝基体润湿性。在此基础上重点研究CNTs-SiC复合相结构和含量对AMCs微观组织，界面结构和宏观力学性能的影响，构建CNTs-SiC增强AMCs的强化模型，阐明其强度−塑/韧性匹配的内在协同强化机制，实现CNTs-SiC增强AMCs的可控性制备，解决CNTs在AMCs中复合效应难以有效发挥的共性瓶颈问题，为CNTs增强AMCs的研制和应用提供实验参考和理论依据。

碳纳米管（CNTs）增强铝基复合材料因具有轻质、高强度高模量、高导电导热以及良好的耐蚀性等优点，在快速发展的航空航天、交通运输及电力电子构件轻量化等领域展现出广阔的应用前景。本项目针对CNTs增强铝基复合材料研究中所面临的诸如CNTs易团聚、CNTs/Al界面润湿性差、界面反应难以控制等瓶颈问题，从铝基复合材料的界面结构设计出发，提出在CNTs/Al界面引入纳米SiC层以改善其界面润湿性和界面结合、调控二者界面反应，充分发挥CNTs在铝基体中强化效果的新思路。本研究结合变速球磨─粉末冶金─热挤压工艺在制备纳米SiC层包覆CNTs增强铝基复合材料的基础上，针对增强相的含量、结构以及制备工艺对复合材料的微观组织、界面结构以及力学和电学性能的影响展开了系统研究，揭示了增强相含量、结构、分布等与强化效果的关系，阐明了其强/韧化机理。结果表明，CNTs-SiC复合相的合成过程为Si原子在真空下通过扩散和蒸发─凝聚，优先在CNTs表面缺陷处形核生成SiC，其反应过程依赖C原子的间隙扩散和Si原子的空位迁移。SiC层的引入使得CNTs-SiC复合相在基体中的分散性得到改善，同时阻碍了CNTs/Al的直接接触，从而调控了界面反应。SiC过渡层的引入将CNTs/Al4C3/Al反应界面结构转变为CNTs/SiC/Al复合界面结构，在保证复合界面结构稳定性的前提下，提升了CNTs/Al界面间及CNTs层间的界面结合强度，使得载荷传递效率及CNTs承载性能得到提升。复合材料的界面润湿性及界面结合强度随SiC过渡层占比的增加而提升，充分发挥了CNTs在基体中的承载作用。CNTs-SiC增强铝基复合材料的强度和强化效率达到212 MPa和157，强度较纯铝、CNTs-Al和SiC-Al复合材料分别提升了66.9%、43.2%和35.0%，展现出显著的协同强化效果，伸长率和电导率仍保持在18.8%和48%IACS。在复合界面的连接作用下，载荷传递强化机制对复合材料强度的贡献逐渐增加，由增强相与基体热错配引起的位错强化、Orowan强化以及细晶强化等机制协同作用，使得铝基复合材料的综合性能得到显著提升。本项目的实施为高强韧、高可靠铝基复合材料的研制和应用提供了理论依据和实验参考。