新型镍、银基仿生复合材料优化设计与制备

Biological materials, although built from a small palette of chemical components, have evolved unique combinations of properties to fulfill their specific functions through a series of ingenious designs, e.g., by forming hierarchical architectures with structural characteristics regulated at multiple length-scales coupled with exquisite gradients and interfaces. The translation of such design motifs into synthetic materials offers a spectrum of feasible pathways towards high performance for practical uses in a variety of fields. This project plans to strengthen and stiffen metals of nickel and silver by creating new metal-based composites using reinforcements of graphene and silicon carbide whiskers. Complex architectures mimicking those of biological materials, such as the brick-and-mortar structure of nacre and the helicoidally-arranged fibrous structure of crab exoskeleton, will be constructed in the composites through new materials processing techniques developed principally based on methods of freeze casting and vacuum filtration. By this means, potent toughening mechanisms that are unique to biological materials, e.g., crack deflection and un-cracked ligament bridging, can be replicated to improve the plasticity and toughness of the composites in addition to their enhanced strength and stiffness. The functional properties of electromagnetic shielding and electrical conductivity and the performance of the composites will be additionally optimized by modulating their phase constitution and architectures. The relationships between the processing, structure, and properties of the composites will be probed and established. As a result, novel nickel- and silver-based composite materials, which are expected to exhibit remarkable mechanical/functional properties and performance that orient for specific applications, will be developed by employing the bioinspired design. Besides, new materials design principles that are common among natural and man-made systems will be extracted by comparing such bioinspired materials to their biological models. The composite materials and corresponding processing techniques exploited by this project will be promising and competitive for uses in fields such as electromagnetic stealth and high voltage transmission so as to better fulfill the practical demands.

天然生物材料的组织结构在长期的自然选择与进化过程中得以持续优化，使其能够利用简单的化学组成实现优异的力学性能和功能，同时也为人造材料的组织结构和性能优化设计与制备提供了重要的启示和指导。本项目拟采用石墨烯和碳化硅晶须作为增强相，对镍、银体系进行仿生复合化设计与组织结构调控，并基于冰模板法等技术发展新型材料制备工艺，在材料中构筑类似鲍鱼壳珍珠层、螃蟹外壳等典型天然生物材料的组织结构，在实现材料刚化与强化的同时引入裂纹沿界面的偏转与桥连等高效增韧机制，从而达到优异的强度与塑/韧性匹配，并兼顾材料的电磁屏蔽、导电等功能。在此基础上，本项目将建立材料的制备工艺、组织结构与性能功能之间的系统关系，发展并完善从仿生角度进行复合化设计实现金属材料的组织结构优化与强韧化的策略和方法，并最终研发出综合性能优异的新型镍、银基仿生复合材料及相应的制备工艺，以更好地满足我国国民经济和国防建设的实际应用需求。

研制兼具优异力学性能与功能性质的新型金属基复合材料具有重要的科学意义和应用价值，天然生物材料具有复杂巧妙的组织结构和优异的力学性能，可为新型仿生材料设计与性能优化提供重要启示。高性能仿生材料的设计与制备首先依赖于对天然生物材料本身组织结构与强韧化机理的深入认识，在此基础上还需优化设计仿生结构，并且开发相应的材料制备工艺，实现所设计结构的有效构筑与调控。本项目首先从材料学与力学角度探究了典型天然生物材料的多级组织结构与强韧化机理，揭示了对生物生存至关重要的天然铠甲材料的三种典型生物力学效应，即梯度结构取向效应、原位结构再取向效应，以及多级缝合界面效应，从梯度、取向、界面三个方面阐明了其高效防护作用的本质；基于对天然生物材料强韧化机理的认识，设计了多种具有不同结构类型的仿生三维互穿结构，并采用熔体浸渗工艺实现了金属材料复杂仿生结构的有效构筑与调控，进而建立了能够定量描述仿生材料结构与力学性能之间关系的力学模型，为金属仿生材料的结构优化设计与强韧化提供了理论指导；在此基础上，通过模仿典型天然生物材料的微观三维互穿结构，利用仿生结构优化设计与熔体浸渗工艺，在以银、镍为主的材料体系中，研制了兼具高弹性、高电导率和高强度的银-镍钛仿生电接触材料、以MAX相陶瓷增强的高耐磨银基仿生电接触材料，以及高镍含量（体积分数大于40%）银-镍仿生电接触材料等多种高性能仿生材料，突破了现有材料在弹性、电导率、强度等方面的性能极限，获得了强度、硬度、弹性、耐磨性等力学性能与导电等功能性质的优异匹配。相关工作为克服材料的强度、断裂韧性、阻尼等不同性能之间的制约关系提供了新思路，有助于指导新型高性能金属仿生材料设计，研制的仿生材料由于性能优异有望在电气电路等领域获得应用。研究成果在Science Advances、Nature Communications、Advanced Materials、Materials Today、金属学报等期刊发表学术论文27篇，授权专利8项，得到Phys.org、Advances in Engineering、科技日报等媒体以及国内外研究学者的广泛报道与引用。