超轻、高强韧三维曲面微纳米点阵材料的序构设计、制备和力学性能研究

Three-dimensional (3D) micro-/nanolattices are a type of micro-/nanostructured materials. Owing to their unique geometric structures, these 3D micro-/nanolattices with characteristic size of hundreds of nanometers to several micrometers have exhibited some excellent mechanical properties. However, these 3D micro-/nanolattices are mainly composed of truss-based unit cells, and there exists an apparent conflict between their strength and ductility. To overcome the strength-ductility trade-off, this project plans to design the unit cell with the minimal surface and to replace the truss-based unit cell, which can reduce the stress concentration due to the continuity and smoothness of minimal surface and further enhance the strength of overall micro-/nanolattices. At the same time, the gradient and/or hierarchical structures are introduced into the micro-/nanolattices via bio-mimic design, in order to improve the ductility of overall structures. According to the designed structures, this project will use a combination of advanced 3D lithography techniques (two-photon lithography and projection micro-stereolithography), high-temperature pyrolysis and coating to fabricate the minimal-surface-based micro-/nanolattices with characteristic size of hundreds of nanometers. These minimal-surface-based micro-/nanolattices will achieve the low density, high strength and good ductility due to the advantages and effects of nanomaterials. The studies in this project will provide a guide for the design, fabrication and mechanics of high-performance materials.

三维微纳米点阵材料是一种典型的微纳米结构材料，由于具有特殊的几何结构，且结构的特征尺寸在几百纳米到几微米之间，因此呈现出一些优异的力学性能。然而，目前已有的三维微纳米点阵材料主要是由杆状胞元组成，其强度与韧性存在明显的矛盾。为了克服这一矛盾，本项目拟将利用力学原理序构设计连续光滑的曲面胞元结构，从而代替传统的杆状胞元结构，以减少应力集中，实现材料强度的提高；同时基于仿生设计，引入梯度结构及多层级结构，用以实现断裂韧性的提高。在序构设计的基础上，将采用先进的微纳米尺度的三维光刻技术（双光子光刻技术和面投影微立体光刻技术）与高温热解、镀膜等技术相结合，制备特征尺寸为几百纳米的三维微纳米曲面热解碳点阵材料，充分发挥纳米结构材料的优势，从而构建出超轻、高强韧的新型微纳米结构材料。本项目的研究拟将为功能基元序构的高性能材料的设计、制备和力学性能研究提供一定的指导。

做为一种新型的结构材料，三维微纳米点阵材料由于具有特殊的几何结构，且结构的特征尺寸在几百纳米到几微米之间，因此呈现出优异的力学性能。然而，目前已有的三维微纳米点阵材料主要是由杆状胞元组成，其强度与韧性存在明显的矛盾。为了克服这一矛盾，在本项目执行过程中，我们利用力学原理序构设计了连续光滑的基于极小曲面的胞元，代替了传统的杆状胞元结构，从而避免了应力集中，提高了点阵材料的强度；同时设计了杆板混合的多层级点阵材料、双稳态曲面胞元以及具有多层级结构的多稳态力学结构。随后，我们采用双光子光刻技术与高温热解相结合的方法，制备了曲壳厚度为177-333 nm的三维曲面热解碳纳米点阵材料。进一步的力学测试结果表明：当密度为0.53-0.80g/cm3时，曲面纳米点阵材料的强度达到了多孔材料强度的理论极限，最高强度可达3.52 GPa，其断裂应变可达20%。在项目执行过程中，项目负责人以通讯作者在PNAS、PRL、Nature Commu、EML等期刊上发表5篇SCI论文，并授权获得2项国家发明专利。这些研究成果将会功能基元序构的高性能结构材料的设计、制备和力学性能研究提供一定的指导。