空位缺陷及Ni/Co/Ti掺杂对铜-石墨烯界面结合影响及其机理的第一性原理研究

The high strength high electrical copper-based material is an essential basic material for the modern industry. It has been a hot issue focused issues to prepare the high strength and high electrical material. It is an effective way to prepare graphene-copper (Cu-G) composite material by adding the graphene as reinforcements into the copper powder because of the excellent mechanical and electrical properties of graphene. A good Cu-G interfacial bonding is one of requirements to achieve the purpose of the high strength and high conductivity. In the project, based on first-principles calculation, the Cu-G interface is object and it is studied that how the possible factors, such as vacancy defect and Ni/Co/Ti doping, affect the Cu-G interfacial bonding, which affect the Cu-G interfacial bonding. The purpose of the work is to improve the Cu-G interfacial bonding. The Cu-G interface with C/Cu vacancy defects is built. The effect of vacancy defects on the Cu-G interfacial bonding and its mechanism are explored according to the microstructure and electronical structure. The Ni/Co/Ti is doped into the Cu-G interface and instead of Cu and C atom, respectively. By the calculation of microstructure and electronical structure of the doped Cu-G interface, the effect of Ni/Co/Ti doping on Cu-G interfacial bonding and its mechanism are studied. Based on the spark plasma sintering method, the Cu-G composites doped by Ni/Co/Ti is prepared and the mechanical properties and electronical properties are studied to test our calculation. The study provides theoretical guidance and experimental basis.

高强高导铜基材料是现代工业的重要材料，一直是研究的热点。以力电性能优异的石墨烯作为增强体，制备铜-石墨烯（Cu-G）复合材料是一条有效途径。良好Cu-G界面的形成是实现其高强高导目的的必要条件之一。本项目基于第一性原理计算，以Cu-G界面为研究对象，对影响界面结合的可能因素，如空位缺陷和Ni/Co/Ti掺杂，如何影响界面结合进行研究，以改进Cu-G界面结合。构建带有C/Cu空位缺陷的Cu-G界面，通过对其微观及电子结构分析，探索空位缺陷对界面结合的影响及其机理；将Ni/Co/Ti掺入Cu-G界面，分别代替界面处的Cu及C原子，计算掺杂界面的微观及电子结构，研究Ni/Co/Ti掺杂对界面结合的影响及其机理；基于放电等离子体烧结方法制备Ni/Co/Ti掺杂的Cu-G复合材料，并测试其力、电性能，以检验我们的计算结果。本研究为改进Cu-C界面结合，开发应用Cu-G复合材料提供理论指导及实验依据。

高强高导的铜基复合材料，是材料科研工作者们关注的热点和研究的重点。石墨烯具有优良的电子和力学性质，可以作为增强体，在保证铜基体的优良电学性质下，改进铜基体的力学性能。另外，石墨烯由于特殊的结构而具有优越的电子性质，带隙为零限制了它的应用。类石墨烯二维材料的结构与石墨烯相似也具有优越的电子性质，在高速低耗高密度的电子存储领域具有广泛地应用前景。基于以上背景及我们实验室的发展方向（石墨烯为主的低维纳米材料制备及其应用的相关研究），本项目做了以下工作。1.通过第一性原理计算，研究了Co、Ni掺杂对石墨烯/铜界面结合的影响及影响机理，模拟了石墨烯/铜复合材料的拉伸力学性能；2.通过SPS烧结技术，制备了石墨烯/铜复合材料、Co及Ni 掺杂石墨烯/铜复合材料，研究了球磨时间、石墨烯掺杂浓度、Co及Ni掺杂浓度对复合材料力学和电学性能的影响；3.基于第一性原理计算，预测了一族二维拓扑绝缘体类石墨烯Be3X2 (X = Si, Ge, Sn)并预测了二维半金属的潜在候选材料单层Mg3Si2。计算结果表明， Co低浓度掺杂更利于石墨烯/铜界面结合，进一步研究发现石墨烯/铜复合材料中的空位缺陷能够增强Co对界面结合的促进作用。综合实验结果发现， 0.4wt%石墨烯与铜混合，球磨时间为 6 h，石墨烯均匀分散，石墨烯/铜复合材料的抗压强度为601.88MPa，硬度为128HV与纯铜相比分别提高了3倍和42.2%，其IACS为79%；掺3wt%Co的复合材料抗压强度和硬度分别为571.32mpa和145hv，与纯铜相比分别提高了2.81倍和61.1%，其IACS为65%；预测的类石墨烯结构Be3X2 (X = Si, Ge, Sn)具有很小SOC带隙，被认为是二维狄拉克材料。预测的另外一种二维材料Mg3Si2在基态是一种AFM半导体。通过电子或空穴掺杂，其磁性基态将从AFM转换到FM状态。本项目的研究结果为高强高导复合材料的制备及应用提供了实验经验及理论支持，同时丰富了二维拓扑绝缘材料家族，为二维材料在自旋电子学领域的应用提供了可能。