共查询到19条相似文献,搜索用时 156 毫秒
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采用非平衡分子动力学方法研究了300 K和1000 K时(5,5)碳纳米管热导率随长度的变化.在室温下,碳纳米管长度小于40 nm时热导率与长度呈线性关系,此时导热处于弹道输运阶段,单位面积弹道热导为5.88×109 Wm-2K-1.随着碳纳米管长度的增加,其热导率逐渐增加,但增加速度随长度逐渐减小,此时导热处于弹道—扩散输运阶段,并随长度的增加从以弹道输运为主向以扩散输运为主转变.长度大于10 μm时由于弹道输运可以忽略,导热近似达到完全
关键词:
碳纳米管
热导率
弹道输运
低维导热 相似文献
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黄希 《原子与分子物理学报》2015,32(6)
通过非平衡态分子动力学方法,研究了锯齿形石墨烯纳米带中掺杂原子硼的两种不同位置排列(三角形硼掺杂和平行硼掺杂)对热导率和热整流的影响并从理论上分析了其变化的原因。研究表明这两种硼掺杂模型在不同温度下导致石墨烯纳米带热导率大约54%-63%的下降;同时发现平行硼掺杂结构对热传递的抑制作用强于三角形硼掺杂结构;硼掺杂结构降低热导率的作用随着温度的升高逐渐减小;三角形硼掺杂结构两个方向上的热导率值具有较大差异,这种结构下的热整流随着温度的上升呈现减弱的趋势;而平行硼掺杂结构两个方向上的热导率值近乎相等,热整流现象表现不明显. 相似文献
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通过非平衡态分子动力学方法,研究了锯齿形石墨烯纳米带中掺杂原子硼的两种不同位置排列(三角形硼掺杂和平行硼掺杂)对热导率和热整流的影响并从理论上分析了其变化的原因。研究表明这两种硼掺杂模型在不同温度下导致石墨烯纳米带热导率大约54%-63%的下降;同时发现平行硼掺杂结构对热传递的抑制作用强于三角形硼掺杂结构;硼掺杂结构降低热导率的作用随着温度的升高逐渐减小;三角形硼掺杂结构两个方向上的热导率值具有较大差异,这种结构下的热整流随着温度的上升呈现减弱的趋势;而平行硼掺杂结构两个方向上的热导率值近乎相等,热整流现象表现不明显。 相似文献
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基于线性波尔兹曼输运方程和碳纳米管的色散关系,本文研究了声子散射的Umklapp和Normal过程同时存在时单壁碳纳米管的晶格热导率,以及温度、管长和管径对它的影响.结果表明:N过程的影响在高温不能忽略;对(10,0)管而言,在低温下其导热率随温度升高迅速增大,在90 K附近达到最大值,然后逐渐开始下降;热导率与管长L的关系是κ∝ L1/2;在相同管长和温度下,热导率随管径的减小而增大. 相似文献
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热导率是表征物质导热性能的一个重要物性参数.通过分子模拟从微观角度揭示有机物分子液体导热机理并计算热导率具有重要的理论意义和应用价值.通过非平衡态分子动力学模拟方法,分别模拟了庚烷、己醛、2-己酮和己醇在263~363 K的热传导过程并得到了热导率.4种有机物在263~363 K下热导率的计算值与实验值的相对平均偏差分别小于5.40%,5.46%,4.29%和7.80%,表明模拟结果与实验结果基本一致.热流分解和原子热路径的结果表明,对总热流有显著贡献的库仑相互作用项、范德华相互作用项和扭转角项都随着温度的升高而减小,这使得4种有机物的热导率随着温度的升高而降低.同时研究表明温度的升高增大了分子的原子振动,加速了分子运动,降低了模拟体系的质量密度.本文为温度对液体热传导影响提供了微观解释和理论依据. 相似文献
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利用稳态电热拉曼技术测量了碳纳米管纤维对流换热环境下的导热系数. 该方法基于材料拉曼信号与温度之间的关系, 实时探测一维材料在不同电加热(内热源)下的中心点温度, 利用对流环境下的稳态导热模型推导出材料的导热系数, 实现了一维微纳材料热物性的无损化和非接触式测量. 实验发现: 碳纳米管纤维的导热系数远低于单根碳纳米管的导热系数, 但高于碳纳米管堆积床的导热系数. 这表明碳纳米管体材料的热物性主要取决于内部管束的列阵和管束间的接触热阻. 相似文献
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By using molecular-dynamics simulations, we demonstrate the existence of heat-pulse rectification in graphene Y junctions. Our results show that the heat pulse will separate into two parts when it flows from stem to branches. However, when it flows from branches to stem, substantial part of the heat pulse is reflected back into the branches with no separation. Moreover, we discuss rectification in different type of junctions and find that the preferred heat pulse transport direction depends on the structure of the junctions, which enable us to delicately control the heat rectification in graphene based structures. 相似文献
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Non-equilibrium molecular dynamics (NEMD) simulations are employed to investigate the longitudinal thermal conductivity of non-orthogonal extended X-junction (EX-junction) of single-walled carbon nanotubes (SWCNTs). Different from standard junctions of SWCNTs, two distinct jumps in the temperature profile around the EX-junction are observed, which are responsible for the larger temperature gradient and reduction in thermal conductivity when compared to standard X-junction. Quantum corrected results show that the longitudinal thermal resistance of the X-junction and EX-junction decreases monotonically with increasing temperature which makes the longitudinal thermal conductivity of the tube with junction less sensitive to temperature above 400 K comparing with the individual pristine tube. The origin of the significant decrease of thermal conductivity of EX-junction is discussed through phonon spectra analysis. 相似文献
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Based on Fourier's law for heat conduction, we investigate the asymmetric heat flow in two segment rods of nonmetallic materials. Specifically, we study the effect of the Kapitza resistance at the boundary of the segments on the thermal rectification. To understand basic features of the rectification, we first develop analytical calculation for the heat currents in an ideal rod of a macroscopic length. Explicitly, this is made by assuming that the thermal conductivity of each constituent has a power-law dependence on temperature and also assuming the continuity of temperature at the boundary. Then, we introduce the temperature jump at the boundary due to the Kapitza resistance and show that this effect on the thermal rectification becomes significant as the length of the rod decreases typically to submillimeters. In particular, we find that the temperature jump yields a finite rectification even when no asymmetry is predicted in the heat currents from the continuity of temperature at the junction. The obtained results have an important implication for the analysis of the thermal rectification of a rod consisting of semiconductors Ge and Si. 相似文献
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Numerical investigation on thermal conductivity and thermal rectification in graphene through nitrogen-doping engineering 总被引:1,自引:0,他引:1
Ping Yang Xialong Li Haiying Yang Xuenan Wang Yunqing Tang Xiaomin Yuan 《Applied Physics A: Materials Science & Processing》2013,112(3):759-765
The aim of this article is to provide a systematic evaluation to perform characteristics on the thermal conductivity and thermal rectification of nitrogen-doped graphene (NDG). Two different structural models about nitrogen-doped graphene (NDG) are constructed by considering nitrogen atomic arrangement. It indicates that thermal conductivity of the graphene decreases because of N-doping and different doped configurations. Thermal rectification of the triangular single-nitrogen-doped graphene (SNDG) decreases with an increasing temperature. However, thermal rectification of the parallel various–nitrogen-doped graphene (VNDG) remains unchanged. The phenomenon of thermal rectification exits in SNDG. It implies that the SNDG might be a potential promising structure for thermal rectifier by controlling the nitrogen-doped model. 相似文献
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任何的非平面连接,材料连接处的材料失配都能导致材料局部或整体性质的改变.本文以纵向拉开的碳纳米管(CNT)为研究对象,采用非平衡态分子动力学(NEMD)的模拟方法,通过改变CNT纵向拉开的剧烈程度,即CNT向石墨烯纳米带(GNR)过渡转变的开角大小,研究其力学稳定性和热传导性质的变化.结果表明,CNT到GNR的过渡越剧烈,连接处的开角越大,其局部热导率越高,单位长度的热阻越小;对于不同管径的CNT来说,连接处的最大开角恒定不变,为16.3°. 相似文献
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Xueming Yang Albert C. To Mesut Kirca 《Physica E: Low-dimensional Systems and Nanostructures》2011,44(1):141-145
Recent studies on intramolecular junctions of silicon nanowires and carbon nanotubes have revealed a wealth of intriguing phenomena. However, the thermal properties of the intramolecular junctions of silicon nanowires (SiNWs) are not yet well understood. In this study periodic arrays of intramolecular junctions with different lattice orientations are investigated, and their thermal conductivities are calculated using nonequilibrium molecular dynamics (NEMD) simulations. Different from the X-shaped and Y-shaped junctions of carbon nanotubes, no distinct jump is found in the temperature profile at the junctions. Compared with straight pristine SiNWs of the same length, the thermal conductivity of the periodic array of intramolecular junctions is reduced. The underlying mechanism of the observed behavior is analyzed by the phonon spectral density of the atomic velocities. The dependence of temperature on the thermal conductivity of this junction array structure is discussed. 相似文献
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Quantum conductivity of single-wall carbon nanotube Y-junctions is calculated. The current versus voltage characteristics of these junctions show asymmetry and rectification, in agreement with recent experimental results. Furthermore, rectification is found to be independent of the angle between the branches of these junctions, indicating this to be an intrinsic property of symmetric Y-junctions. The implications for the Y-junction to function as a nanoscale molecular electronic switch are investigated. 相似文献
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建立了考虑变截面、变热导率及界面接触热阻效应的组合热整流结构的温度场及热整流系数的理论模型和有限元解.数值算例证明了本文模型及算法的可靠性,进而通过参数影响研究确定了若干几何及材料参数对结构热整流系数的影响规律,揭示界面接触热阻对热整流效果的影响机理.研究结果表明长度比、截面半径变化率、热导率、边界条件温差和界面接触热阻等因素必须通过优化设计才能得到最大的热整流系数,同时界面接触热阻的引入也为调控热整流系数提供了一条新的途径. 相似文献
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Thermal conductivity of metallic zigzag carbon nanotube is investigated in the context of Holstein model. Green's function approach is implemented to calculate the electronic contribution of thermal conductivity as a function of radius of carbon nanotube, temperature and electron phonon coupling strength. Our results show that electronic thermal conductivity increases as a function of temperature at low temperature and gets a maximum value then decays at high temperature. Also the effect of radius of both metallic and semiconductor zigzag carbon nanotube on the thermal conductivity is studied. Our results show thermal conductivity increases when CNT diameter increases and decreases with electron phonon interaction strength. 相似文献