石墨烯/高分子基多功能纳米复合材料的力学与电学性能研究

In recent years, due to the exceptional intrinsic mechanical, electrical and thermal properties of various nanomaterials, such as carbon nanotube (CNT), carbon nanofibre (CNF), nanowire, graphene, nanoclay, nanoparticle, etc., much attention has been paid to the fabrication of structural and functional nanocomposites with the use of these nanofillers in various matrix materials, such as polymer, metal and ceramics, to harness the above mentioned exceptional intrinsic properties of the nanofillers. These nanocomposites are very hopefully applied to various fields. For instance, with the outstanding mechanical properties, e.g., high strength and stiffness, carbon nanofillers are now being widely used as a hopeful mechanical reinforcement phase for polymer or ceramics-based structural nanocomposites with prospective application，such as, structural components in aerospace engineering, automotive industry, etc. Moreover, by using nanofiller's electrical, thermal and other physical properties, some matrices, e.g., polymers, with the incorporation of nanofillers show great potential as functional materials for electronic device applications, such as organic field emitting displays, photovoltaic cells, highly sensitive strain and temperature sensors, energy harvesting or conversion materials, electromagnetic interference materials, etc. To develop next generation, novel, highly efficient and multi-functional nanocomposites, in this research, graphene will be focused on since many recent research outcomes have shown its outstanding roles in development of various structural or functional nanocomposites. By employing: density function theory (DFT), molecular dynamics (MD), micromechanics, finite element modeling, 3D resistor network model, and some novel multi-scale modeling techniques by combing the above analysis techniques together, some important properties, e.g., the mechanical, electrical conductivity, piezoresistivity and piezoelectricity of graphene/polymer nanocomposites will be analyzed and evaluated with high accuracy. Uncovering the mechanisms of enhancement effects of graphene on the above properties of the nanocomposites will be the task of priority in this study. Thorough understanding of the mechanisms is very helpful to provide the valuable design guidelines of the nanocomposites under nano-, micro- and macro-scales. With the obtained design guidelines, the multi-functional nanocomposites can be effectively fabricated. Furthermore, the above mentioned properties of the nanocomposites will be experimentally evaluated and the corresponding results can be used to validate the proposed theoretical and numerical models, which can in turn guide us to choose appropriate fabrication conditions including dispersion techniques, surface treatment or functional techniques, etc., and consequently improve the fabrication process of the nanocomposites. Finally, the above properties of the nanocomposites can be significantly and comprehensively improved.

由于纳米碳管、纳米碳纤维、石墨烯等纳米材料具有出众的力学、电、热性能，利用这些纳米材料开发在许多领域具有广泛应用价值的结构型、功能型纳米复合材料的研究受到了广泛的关注。为了开发全新的高性能、多功能纳米复合材料，本项目将利用: 密度泛函理论(DFT)、分子动力学(MD)、细观力学、有限元模拟、3维电阻网络模型和由这些方法组合而成的全新的跨尺度模拟手段对石墨烯/高分子基多功能纳米复合材料的力学特性、导电特性、压电阻抗特性、压电特性等进行高精度的分析评价，揭示石墨烯的添加对上述各特性所发挥的增强效应的机理，从而提供在纳观、细微观、宏观等不同尺度下进行石墨烯纳米复合材料设计的指针。同时，利用这些设计指针改善石墨烯/高分子基多功能纳米复合材料的制备技术、进行上述材料特性的实验评价并对理论与数值计算模型的正确性进行验证，从而最终使石墨烯/高分子基多功能纳米复合材料的上述材料特性得到大幅度和全面的提高。

由于石墨烯等纳米材料具有出众的力学、电、热性能，利用这些纳米材料开发在许多领域具有广泛应用价值的结构型、功能型纳米复合材料的研究受到了广泛的关注。本项目通过实验和数值模拟的手段: 研究石墨烯单体、石墨烯/高分子基多功能纳米复合材料的力、电、热等特性，揭示石墨烯的添加对上述特性所发挥的增强效应的机理，从而提供石墨烯及其纳米复合材料的设计指针。同时，利用这些指针制备该类材料并使材料特性得到大幅度提高。本项研究获得的重要结果及其科学意义简单阐述如下.1、 由于纳米添加相和基体材料之间的界面力学、热学特性是决定纳米复合材料力学、热学性能的关键因素。我们用分子动力学方法计算了石墨烯及其三维杂化结构与高分子基体之间的界面力学性能、导热性能等，特别是研究了如：石墨烯的表面改性、石墨表面褶皱、石墨烯初始缺陷、拔出速度、石墨烯表面小官能团、杂化结构形式、高分子基体分子链长度、环境温度等条件和参数对界面力学、热学性能的影响，对制备高性能的石墨烯增强复合材料提供了指导意见。同时，基于细观力学的基础理论，我们还提出了一种基于平均场理论的评价弹塑复合材料宏观力学性能的Eshelby张量的新方法，这为后期评价基于石墨烯的纳米复合材料的宏观力学性能提供了基础。实验方面：我们利用石墨烯、纳米碳管、石墨烯/碳纳米管杂化纳米相对各类高分子基体、金属与纤维增强复合材料的层压材料的界面等进行增强，制备了相关的实验样件，并进行了力学性能的测试和分析，大幅度提高了相关材料的力学性能。.2、 在电学方面，我们研究了石墨烯、三维石墨烯气凝胶及其它纳米添加相对复合材料压阻性能、及其应变传感性能的影响，研制了如高性能柔性电子器件传感材料等。我们还发现还原氧化石墨烯的添加对增强PVDF的压电特性有更良好的效果，更容易起到结晶核的作用，从而促进PVDF中的压电相、即Beta相结晶形成。.上述研究在使用石墨烯对各类基体进行改性，提高材料的力、电、热性能有重要指导意义。