纳米结构的热输运及热电性质

发布时间：2018-01-18 02:26

本文关键词：纳米结构的热输运及热电性质　出处：《湘潭大学》2015年硕士论文　论文类型：学位论文

【摘要】：近年来,对低维纳米材料热输运的研究已经成为目前凝聚态物理的前沿课题之一。声子学的提出使人们认识到可以像控制电子一样对声子的输运进行有目的的调控。同时,能源短缺和环境问题使具有热电转换功能的热电材料的研究日益引起人们的关注。本文从以下几个方面对纳米结构的热输运及其热电性质进行研究:(1)采用分子动力学方法研究了氢吸附折叠graphene‘纳米被’的结构形变、热稳定性及其热输运性质。研究结果表明,‘纳米被’的形状及其热导率都可以通过氢吸附的比例来进行调控。将单个‘纳米被’组合成多重‘纳米被’后,它具有比没有氢吸附的折叠graphene更高的热稳定性,同时通过结构的调控可以很好的调控其热输运能力。(2)在包括MoS2/Graphene纳米结在内的纳米功能器件中,热耗散问题是影响其结构稳定性和光电性能的关键问题。采用分子动力学方法研究了多种MoS2/Graphene复合纳米结构的热输运性质。在这些结构中发现了多样的、与结构特性相关的热输运过程,并且它们的热导率可以通过层间耦合、环境温度以及层间交叠方式进行调控。在室温下,复合结构最大的热导率可以达到单层MoS2的5倍。我们通过声子态密度、温度的空间分布以及层间热阻研究了热传导输运机制。(3)采用分子动力学方法研究了硅锥结构中的热整流现象。结果表明,整流效率并不是随着结构不对称性的增大而增大的。在顶角小于90°的时候,整流效率随着角度的增大而增大;但是,当顶角大于90°的时候,整流效率随着角度的增大而减小。这种转变是由热输运机制的变化造成的。在小角度,声子输运由局域态主导的,而在大角度的时候,局域模式消失,导致了整流效率减小。(4)采用格林函数方法研究了MoS2/WS2复合纳米条带的热电性质。研究发现热电转换效率在复合条带中得到了很大的提高。这主要是因为界面对热、电输运的不同影响导致的。复合结构的ZT值在300K下可以达到2.7,是MoS2的1.8倍、WS2的1.4倍。通过结构周期数的进一步调节,ZT值在室温下可以达到4.1、600K下可以达到5.6。
[Abstract]:In recent years. The study of thermal transport of low-dimensional nanomaterials has become one of the frontier topics in condensed matter physics. The introduction of phonon makes people realize that the phonon transport can be controlled purposefully just like controlling electrons. . Energy shortage and environmental problems make the study of thermoelectric materials with thermoelectric conversion function more and more concerned. In this paper, the thermal transport and thermoelectric properties of nanostructures are studied from the following aspects: 1). The structural deformation of hydrogen-adsorbed graphene 'nanocrystalline' was studied by molecular dynamics. Thermal stability and thermal transport properties. The results show that the shape and thermal conductivity can be controlled by the proportion of hydrogen adsorption. It has higher thermal stability than folded graphene without hydrogen adsorption. At the same time, the thermal transport ability can be well controlled by the structure regulation.) in the nanofunctional devices, including MoS2/Graphene nanojunctions. The thermal dissipation problem is the key problem affecting the structural stability and optoelectronic properties of MoS2/Graphene nanostructures. The thermal transport properties of various MoS2/Graphene nanostructures are studied by molecular dynamics method. Found a variety of. Thermal transport processes associated with structural properties, and their thermal conductivity can be regulated by interlaminar coupling, ambient temperature, and interlaminar overlap. The maximum thermal conductivity of the composite structure is 5 times that of the monolayer MoS2. We pass through the density of phonon states. The temperature spatial distribution and interlaminar thermal resistance are studied. The mechanism of heat conduction and transport is studied. (3) the phenomenon of thermal rectification in silicon cone structure is studied by molecular dynamics method. The results show that: 1. The rectifying efficiency does not increase with the increase of the structural asymmetry. When the vertex angle is less than 90 掳, the rectifying efficiency increases with the increase of the angle. However, when the vertex angle is greater than 90 掳, the rectifier efficiency decreases with the increase of angle. This change is caused by the change of thermal transport mechanism. At small angle, phonon transport is dominated by local state. At large angles, the local pattern disappears. Reduced rectifier efficiency. 4). The thermoelectric properties of MoS2/WS2 nanostrip were studied by Green's function method. It was found that the thermoelectric conversion efficiency was greatly improved in the composite strip, which was mainly due to the interface heat. The ZT value of composite structure can reach 2.7 at 300K, which is 1.4 times of that of MoS2. The ZT value can reach 4.1 ~ 600K at room temperature and up to 5.6 at room temperature.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TB383.1

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