单壁碳纳米管-石墨烯异质连接的机理与性能的理论研究

The single-walled carbon nanotubes and graphenes are the key materials of the future nanotechnology ages because of their outstanding physical properties. The nanocarbon hybrid materials and devices, composed of the two materials, have broad applied prospects for their peculiar properties. The effective connection is one of crucial projects in the field of nanocarbon hybrid materials and devices based on the single-walled carbon nanotubes and graphenes.The existing methods, such as electronic beams bombarding, metal connecting etc.,could not well localized connection points, and the connection structures and propertis are not stable enough. The project introduces the new idea that the microstructures, such as B/N/O radical and/or topological defects which have sufficient chemical activity, can be used to connect the two materials with hetero-covalent junctions. Using the first-principles calculation methods, the project aims at exploring the characteristic of the B/N/O atomic hetero-structures in the nanotubes and graphenes; The mechanism of the hetero-connection will be further investigated through the molecular dynamic theory, and the basic properties will be calculated for the connection systems; At last, we will give an reasonable way to build the hetero-connections in carbon nanotube-graphene systems according to the relationship of between the corresponding properties and the structures. In our methods, the connection is a self-assembled progress. The connections not only have strong structures and stable properties, but also can locate the connective position automatically and precisely. Besides, the electronic and optical properties of the substrates can be tuned by the doped atomic structures according the required. Therefore, our new method has more obvious advantages than the existed ones. We expect that the project can provide a new train of thought and theoretic references for the synthesis of complex three-dimensional carbon networks and the practicability of nanotube-graphene hybrid materials and devices.

石墨烯和单壁碳纳米管具有优异的物理特性，是未来纳米科技时代的关键材料。同时运用这两者构建的碳纳米复合材料及器件性能优良，前景广阔。两者间的有效连接是碳纳米复合材料及器件实用化的关键课题。目前的电子束照射、金属连接等方法有定位性低、结构及性能的稳定性不足等问题。本项目提出利用硼/氮/氧杂质与拓扑缺陷等具有一定化学活性的微结构作连接介质、对这两者进行异质连接的新方法：我们采用第一性原理的密度泛函理论算法，探索碳纳米管和石墨烯中的硼/氮/氧掺杂微结构特性；再结合分子动力学分析掺杂结构的异质连接机理，并计算连接体的基本物理性能；最后根据连接体结构与性能的内在联系，建立合理的碳管-石墨烯异质连接方法。这种方法的连接具有自组装特性，定位连接点能力强，连接结构与性能稳固，能灵活调控连接体的光电特性，优势突出。本项目将为复杂三维碳网络结构制备、碳管-石墨烯复合材料及器件的实用化提供新思路和理论参考。

利用基于第一性原理的密度泛函理论，我们针对碳纳米管和石墨烯的共价连接的可能构型和途径进行了探索性的研究。通过引入杂质、缺陷、小分子等多种元素，打破碳管和石墨烯的表面惰性。发现了几种可能的碳管石墨烯共价连接的途径，并针对相关结构体系的电子结构、电子输运等特性进行了研究。计算结果表明，硼氮共参杂能够在碳管和石墨烯中形成稳定硼氮链，并与氧分子进行自组装的共价连接。而拓扑缺陷和空位缺陷则能够在吸附一定能量的情况下在石墨烯和碳管间形成有效的共价结构。碳管和石墨烯上的空位缺陷则能够对小分子形成强烈的解离效应。而这些复合结构都对碳管和石墨烯的电子结构及输运特性形成了明显的调制及效果。这些结果对基于碳管和石墨烯的碳基电子器件的研制具有重要的理论参考价值。