石墨烯及其衍生结构热输运性能及热管理模式的研究

Graphene, a representative two-dimensional carbon nanomaterials, has attracting enormous attention for its fascinating thermal properties. However, its allotrope, graphyne expresses significantly lower thermal properties. Specially, when the two nanomaterials are combined to be a composite structure, the thermal transport properties of the composite structure express obvious difference compared to that of graphene. Therefore, the investigations on the thermal transport properties of nanomaterials based on graphene are urgent. During the investigation process, the most important issues are to obtain the effect of bonding structures, the morphology of interface (heterojunction) and different defects on the phonon, electron thermal transport processes, and furthermore, to obtain the relationship between the mechanic properties and thermal transport properties of nanomaterials. With these aims, the non-equilibrium Green’s function method should be used to analyze the electron thermal transport processes, the morphology of heterojunction between graphene and graphyne should be rationally built by ab-initial theory, in addition, the multi-scale coupling algorithms combined with the first principle and molecular dynamics methods should be developed, the phonon theory and molecular dynamics method are also needed to combine. Thereby, based on the investigations above, it can be expected to obtain the effect mechanism of different bonding forms on the phonon and electron thermal transport process, the effect of heterojunction structure on the thermal transport properties of composite structure and the relationship between mechanical and thermal transport properties. Finally, an effectivelly controlable thermal management mode based on graphene and graphyne nanomaterials will be hopefully realized.

石墨烯是目前最受关注的纳米材料，具有优异的热输运性能，而其衍生结构石墨炔的热导率却显著地低于石墨烯，当两者相结合形成复合结构时，其热输运性能与石墨烯相比有明显的变化，因此，研究石墨烯基材料的热输运性能显得日趋迫切。其中核心问题是探明材料中成键结构、接触界面（异质结）形貌和诸多缺陷对模型热输运性能的影响机理以及纳米材料力学性能与热学性能之间的关系。因此，需用非平衡格林函数方法来分析模型的电子热输运过程；应用第一性原理搭建合理的异质结构型；构建第一性原理与分子动力学结合的多尺度耦合算法；实现声子理论与分子模拟方法相结合。进而获得石墨烯、石墨炔中多种杂化对模型电子和声子输运的影响机理、石墨烯/石墨炔异质结对模型热输运性能的影响以及纳米材料热、力性能的内在联系。最终基于上述结果提出一套针对石墨烯和石墨炔纳米材料的有效的热管理模式。

石墨炔的出现可克服石墨烯在电学领域的限制，扩展碳基纳米材料在热电领域的应用。尤其当两者形成异质结结构时，除优异的热电属性外，结构中的声子和电子输运往往还具有较好的可调节性。基于此，本课题主要以石墨炔为研究对象，搭建了稳定的石墨烯/石墨炔异质结，并构建了基于晶格动力学的多种声子计算方法。结合上述方法和模型，我们发现了缺陷分布对二维碳基纳米材料热导率有效的调节作用以及（14,14,14）型石墨炔显著的各向异性及其纳米管结构依赖于直径的各向异性。此外，还发现了异质结结构可将碳基纳米材料转变为热电材料这一现象并分析了其机理。进一步，研究了比异质结更具普遍意义的多晶化现象，发现多晶化是一种可极其有效提升热电属性的手段，其甚至可以将硅基纳米材料这种热电性能极弱的材料转变为热电材料，我们还在此基础上探讨了多晶化的影响机理。最后，研究了新型笼子结构这种具有优异可调节物理属性材料的热输运和热电性能。本课题的研究提出了多种可显著且有效调控碳基纳米材料传热属性以及优化其热电性能的手段，对提升碳基纳米材料在传热、热电和力学领域中的应用潜力有着积极的意义。