| Carbon nanomaterial has been the hot topic of frontier research since 1990 s, owing to its unique molecular structure and outstanding property in physics and chemistry. Carbon nanomaterials mainly include the zero-dimension fullerene, the unidimensional carbon nanotubes(CNTs) and the two-dimension graphene. They all have broad application prospects in high-tech fields such as new functional materials and nano electronics. For example, the decreasing of performance and lifetime of nuclear batteries caused by irradiation damage continue to be a thorny problem in the new energy field. Liviu Popa-Simil has proposed a designing scheme of nuclear batteries based on the composite material of CNTs and metal. Making use of the irradiation tolerance property of CNTs, this design is going to make the conversion efficiency from nuclear energy to electicity higher than 50 percentage. Based on this design, in our work, we used molecular dynamics to investigate factors influencing the irradiation tolerance of multiwalled carbon nanotubes with metal inside. Besides, we took the point defects produced in the process of irradiation into consideration and investigated how they affect the stability of composite materials of graphene and metal.In the first place, using molecular dynamics, we built a model of three-walled carbon nanotubes with copper inside, and simulated a carbon atom bombarding the system in a energy range of 100-1000 eV. Afterwards, we counted the coordination defects, perfect structure defects(pst defects), sputtered atoms as well as the total damage. Then we compared it with that of a independent three-walled CNT. The results show that with copper inset, the total damage of system is reduced obviously. So that the irradiation tolerance of the composite material system is enhanced. Also, this showed the feasibility of using carbon nanomaterials in nuclear batteries.With the use density functional theory, we investigated the mechanism of point defects influencing the composite material of graphene and metal, as well as the effect of defects in different relative positions. In our calculation, we chose the metal nickel which matches graphene in a 1×1 structure. We built a system of 4×4 monolayer graphene and six layers of nickel below. The system included four basic structures according to the relative position between graphene and the first layer of nickel substrate. We calculated the optimizing process of these structures after introducing a point defect in graphene. Results show that with a point defect introduced, the adsorption between graphene and the first-layer nickel is enhanced, so that the stability of the whole system is increased. Also, point defects in different relative positions have different influences, with a top-site defect enhances the adsorption more than a hollow-site defect.In conclusion, based on molecular dynamics we investigated the system of carbon atoms bombarding MCNT with metal inside and obtained preliminary result of the change of structure defects according to irradiation damage. Based on density functional theory, we investigated the mechanism of single vacancy affecting the combination between carbon atoms and nickel atoms and the differences of different vacancy sites. These research results can provide some theoretical reference for the study of interfaces between graphene and metal. Based on our current work, more systematic work can be started such as the combination between metal atoms and graphene materials besides copper and nickel and the influence caused by defects. |
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