金属—石墨烯层状复合材料的缺陷性能研究

发布时间：2018-10-24 20:59

【摘要】：在核反应过程中,堆芯结构材料在高强度的辐照下产生的空位和间隙会随时间演变成缺陷团簇、位错和晶界,最终导致材料肿胀、高温晶界脆化、表面粗化和起泡,从而力学性能降低。所以,研发能够适应核能系统发展的抗辐照材料是有必要的。石墨烯以其良好性能使有的石墨烯复合材料具有卓越的性质和广阔的应用前景。有研究表明,金属-石墨烯层状复合材料中的石墨烯可以阻碍位错的扩展,因而铜-石墨烯层状复合材料可能具有良好的抗辐照性。为了全面了解金属-石墨烯层状复合材料的抗辐照性能,需要深入研究金属/石墨烯/金属界面附近的点缺陷行为。本文采用第一性原理,利用VASP软件包,研究了金属/石墨烯/金属界面附近点缺陷的形成和迁移行为。主要内容和结论如下:1.采用第一性原理研究了铜/石墨烯/铜层状复合材料(Cu/Gr/Cu)中点缺陷的特性,并与本征石墨烯和纯铜中的点缺陷比较,分析了石墨烯对点缺陷行为的影响范围及其影响机理。计算结果表明Cu/Gr/Cu中的碳空位形成能较本征石墨烯的空位形成能偏小。界面处的铜和碳间隙都是在fcc间隙位置最稳定。Cu/Gr/Cu界面对铜间隙原子的影响远大于对碳间隙原子的影响,铜的点缺陷会被界面捕获,且界面对铜缺陷的捕获范围约为15?。2.采用CI-NEB方法计算了Cu/Gr/Cu中点缺陷的迁移机制。结果表明:Cu/Gr/Cu中的碳空位迁移能垒较本征石墨烯要小。界面附近的铜空位可能朝着界面中心迁移。铜和碳间隙在最稳定的俩近邻fcc间隙位置之间的迁移需经过hollow位置。铜间隙原子在界面中比在纯铜中更容易迁移。3.采用第一性原理研究了镍/石墨烯/镍层状复合材料(Ni/Gr/Ni)中点缺陷的特性。计算结果表明碳空位的形成能在Ni/Gr/Ni中比在本征石墨烯中显著降低。界面处镍间隙在hollow位置最稳定。相对于碳间隙原子,镍间隙原子受到界面的影响更为明显。界面可以捕获镍的空位和间隙,且对镍点缺陷的捕获范围约为12.5?。4.采用CI-NEB方法计算了Ni/Gr/Ni中点缺陷的迁移机制。结果表明:Ni/Gr/Ni中的碳空位迁移较本征石墨烯中更难。镍间隙在两个近邻hollow间隙位置之间的迁移时,可能会经过fcc位置跳跃到近邻的hollow位置,或者直接在两近邻hollow间隙位置间迁移。镍间隙原子在界面中比在纯镍中更难迁移。5.对于Cu/Gr/Cu和Ni/Gr/Ni,虽然碳空位的形成能在两种复合结构中都低于本征石墨烯的空位形成能,但两者的原因是不同的。金属-石墨烯复合结构中不同金属对碳空位迁移的影响也不同。在Cu/Gr/Cu中,最稳定的间隙位置是fcc位置,而在Ni/Gr/Ni中,最稳定的间隙位置则是hollow位置。两种金属-石墨烯复合结构的界面对碳间隙的影响很小,但对金属的点缺陷具有很强的捕获作用,缺陷被捕获湮灭,导致缺陷减少,从而证实了金属-石墨烯复合材料的抗辐照能力。
[Abstract]:During the process of nuclear reaction, the vacancies and gaps produced by the core structure materials under high intensity irradiation will evolve over time into defect clusters, dislocations and grain boundaries, resulting in material swelling, high temperature grain boundary embrittlement, surface coarsening and foaming. As a result, the mechanical properties are reduced. Therefore, it is necessary to develop anti-radiation materials that can adapt to the development of nuclear energy systems. Some graphene composites have excellent properties and wide application prospects because of their good properties. Some studies have shown that graphene in metal-graphene laminated composites can hinder the expansion of dislocation, therefore, Cu-graphene laminated composites may have good radiation resistance. In order to understand the radiation resistance of metal-graphene laminated composites, it is necessary to study the point defect behavior near the metal / graphene / metal interface. In this paper, the formation and migration behavior of point defects near the metal / graphene / metal interface are studied by using the first principle and VASP software package. The main contents and conclusions are as follows: 1. The characteristics of point defects in copper / graphene / copper laminated composites (Cu/Gr/Cu) were studied by first principle. Compared with the point defects in graphene and pure copper, the influence range and mechanism of graphene on the behavior of point defects were analyzed. The results show that the formation energy of carbon vacancy in Cu/Gr/Cu is smaller than that of graphene. The effect of Cu/Gr/Cu interface on copper interstitial atoms is much greater than that on carbon interstitial atoms, and the point defects of copper are trapped by the interface, and the trapping range of copper defects at the interface is about 150.2. The migration mechanism of point defects in Cu/Gr/Cu is calculated by CI-NEB method. The results show that the carbon vacancy migration barrier in Cu/Gr/Cu is smaller than that in intrinsic graphene. The copper vacancy near the interface may migrate towards the interface center. The migration of copper and carbon gap between the most stable two nearest neighbors of fcc is required to pass through the hollow position. Copper interstitial atoms are easier to migrate at the interface than in pure copper. The characteristics of point defects in nickel / graphene / nickel layered composites (Ni/Gr/Ni) were investigated by first principles. The results show that the formation of carbon vacancy in Ni/Gr/Ni is significantly lower than that in intrinsic graphene. The nickel gap at the interface is the most stable in the hollow position. Compared with the carbon gap atom, the nickel gap atom is affected more obviously by the interface. The interface can capture the vacancy and gap of nickel, and the trapping range of nickel point defects is about 12.5. 4. The migration mechanism of point defects in Ni/Gr/Ni is calculated by CI-NEB method. The results show that the migration of carbon vacancies in Ni/Gr/Ni is more difficult than that in graphene. When the nickel gap migrates between the two adjacent hollow gap positions, it may jump through the fcc position to the nearest neighbor hollow position, or move directly between the two nearest neighbor hollow gap positions. Nickel interstitial atoms are more difficult to migrate at the interface than in pure nickel. For Cu/Gr/Cu and Ni/Gr/Ni, the formation energy of carbon vacancy is lower than that of graphene, but the reasons are different. The effect of different metals on the migration of carbon vacancy is also different in the metal-graphene composite structure. In Cu/Gr/Cu, the most stable gap position is the fcc position, while in Ni/Gr/Ni, the most stable gap position is the hollow position. The interface of two kinds of metal-graphene composite structure has little influence on the carbon gap, but it has a strong trapping effect on the point defect of the metal, and the defect is captured and annihilated, which leads to the reduction of the defect. Therefore, the radiation resistance of metal-graphene composite was confirmed.
【学位授予单位】：电子科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TB33

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