石墨烯/镁仿生微纳米层状复合材料的制备及其结构效应研究

The nano/micro-laminated architecture of nacre makes its optimal matching between strength and toughness. This proposal plans to use graphene as nano-reinforced layer to construct the graphene/Mg bioinspired nano/micro-laminated architecture to solve the inverse relationship between strength and ductility of Mg matrix composites. The bioinspired architecture can make the composites exhibit the excellent comprehensive mechanical properties, so a novel bioinspired Mg matrix composites will be developed. Firstly, a new processing for constructing the bioinspired nano/micro-laminated architecture will be developed through integrating the electrophoretic deposition and laminate processing. The electrophoretic deposition processing was used to disperse graphene and simultaneously construct “graphene/Mg” laminated units, which overcome the shortcomings of the single laminate processing that is very difficult to disperse nano-reinforcements. The evolution mechanisms for the bioinspired nano/micro-laminated architecture will be revealed during the fabrication processing. Secondly, the effects of the laminated architecture parameters on the microstructure and mechanical properties will be studied, and then the tailoring theory for the bioinspired nano/micro-laminated architecture will be built. Finally, the effects of the bioinspired nano/micro-laminated architecture on the local strain distribution, plastic deformation and fracture behaviors in the composites will be studied by jointly using DIC technique and the in-situ tensile technique of electron microscopes. Based on this results, the effect of nano/micro-laminated architecture will be revealed, and its strengthening and toughness models will be built. Through the above research, the design and fabrication theories for the graphene/Mg bioinspired nano/micro-laminated composites will be promoted, and the design theory for Mg matrix composites will also be improved and perfected.

贝壳的“微纳米层状”生物构型造就了其强度和塑韧性的最优匹配。针对镁基复合材料强度和塑韧性倒置的问题，本项目将以石墨烯作为纳米强化层，构建石墨烯/镁仿生微纳米层状结构，利用其结构效应开发一种综合力学性能优良的石墨烯/镁仿生复合材料。首先，将电泳沉积和叠层技术有机结合，有效分散石墨烯并同时构建“石墨烯/镁”层状基元，克服单一叠层技术对纳米增强体分散差的缺点，开发一种仿生微纳米层状复合材料的新型制备技术，揭示仿生微纳米层状结构的构建机理。其次，研究层状结构参数对复合材料显微组织和力学性能的影响规律，建立仿生微纳米层状结构的调控理论。最后，联合运用DIC技术和电镜原位拉伸技术，对比研究结构参数对复合材料的局域应变分布、塑性变形行为、断裂行为的影响规律，揭示仿生微纳米层状结构的结构效应，建立其强韧化模型。上述研究将有助于建立石墨烯/镁仿生微纳米层状复合材料的设计与制备理论，完善镁基复合材料设计理论。

本项目将贝壳的“微纳米层状”结构应用于镁基复合材料，探索石墨烯/镁微纳米层状复合材料的制备技术，研究微纳米层状石墨烯/镁复合材料的宏观及微观塑性变形行为及断裂行为，探明石墨烯和层状构型对复合材料的强化及韧化机制。通过系统的研究和分析，成功探索出利用电泳沉积构建微纳米层状基元，利用真空热压烧结和热轧制成功制备出层间结合紧密、层状结构参数可控的微纳米石墨烯/镁复合材料。实现了石墨烯/镁复合材料强韧性的协同提升。.通过OM与SEM下的原位拉伸，结合DIC技术，从宏-微观角度分析了纯镁与石墨烯/镁层状复合材料中的局域应变演化过程。从宏观上，提出石墨烯层能有效的缓解局域应力集中，并防止复合材料的提前失效。微观上，结合DIC分析与对数正态分布统计结果，提出石墨烯层的引入引起了局部的高应力状态，这种可控的局域高应力为<c+a>位错滑移提供了有利条件。石墨烯层引入的宏观均匀而微观不均匀的应变状态有效的提高了镁基体的宏观均匀塑性变形能力。.通过分子动力学模拟，定量研究了不同应力状态下的<c+a>交滑移能量势垒，提出了复杂应力状态下<c+a>交滑移能力势垒的解析表达式。此外，分子动力学研究还表明石墨烯层与裂纹尖端的交互作用能够缓解裂纹尖端应力集中并钝化裂纹，改变镁基体的应力分配，从而增大裂纹扩展所需驱动力以及钝化裂纹。钝化的裂纹尖端有利于位错发射的产生，并能促进镁基体由脆性断裂向韧性断裂的转变。.本项目研究的主要成果为开发了制备具有微纳米层状结构的石墨烯/镁复合材料，阐明了石墨烯/镁微纳米层状复合材料的强韧化机制，为轻质高强金属基复合材料的设计与制备提供了可借鉴的技术手段和理论依据。.项目执行期间发表了SCI学术论文19篇，获得授权国家发明专利1项，培养了硕士研究生2名。