摘要:
理论分析了声子和电子输运对Cu, Ag金属纳米线热导率的贡献。采用镶嵌原子作用势模型描述纳米尺寸下金属原子间的相互作用,应用平衡分子动力学方法和Green-Kubo函数模拟了金属纳米线的声子热导率；采用玻尔兹曼输运理论和Wiedemann-Franz定律计算电子热导率；并通过散射失配模型和Mayadas-Shatzkes模型引入晶界散射的影响。在此基础上,考察分析了纳米线尺度和温度的影响。研究结果表明： Cu, Ag纳米线热导率的变化规律相似；电子输运对金属纳米线的导热占主导地位,而声子热导率的贡献也不容忽视；晶界散射导致热导率减小,尤其对电子热导率作用显著；纳米线总热导率随着温度的升高而降低；随着截面尺寸减小而减小,但声子热导率所占份额有所增加。
关键词:
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纳米线
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热导率
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表面散射
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晶界散射
Abstract:
The contributions of phonon and electron transport to the thermal conductivities of Cu and Ag nanowires are studied theoretically. The effects of surface and grain boundary scatterings are involved. The embeded atom method is employed to express the interatomic potential of nanowires. While the molecular dynamic simulation and Green-Kubo formulation are used to obtain the lattice thermal conductivity, a model derived from Boltzmann transport equation and the Wiedemann-Franz relation are used to calculate electronic thermal conductivity. In addition, diffuse mismatch model is used to calculate thermal resistance of grain boundary to modify the lattice thermal conductivity, meanwhile, Mayadas-Shatzkes model is used to consider the influence of grain boundary scattering on the electronic thermal conductivity. By coupling the lattice and electronic thermal conductivity, the effective thermal conductivity of nanowire is obtained. On this base, the influences of size and temperature are analyzed. It turns out that Cu and Ag nanowires have a similar tendency in the thermal conductivity. The contribution of electron transport to the thermal conductivity of nanowire is dominated, but the contribution of phonon transport cannot be ignored on the nanoscale. The thermal conductivity of nanowire decreases due to the grain boundary scattering. And it decreases with temperature increasing or size decreasing. The contribution of phonon transport becomes more important in the case of smaller size.
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