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Dynamic response of graphene to thermal impulse

机译：石墨烯对热冲击的动态响应

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摘要

A transient molecular dynamics technique is developed to characterize the thermophysical properties of two-dimensional graphene nanoribbons (GNRs). By directly tracking the thermal-relaxation history of a GNR that is heated by a thermal impulse, we are able to determine its thermal diffusivity quickly and accurately. We study the dynamic thermal conductivity of various length GNRs of 1.99 nm width. Quantum correction is applied in all of the temperature calculations and is found to have a critical role in the thermal-transport study of graphene. The calculated specific heat of GNRs agrees well with that of graphite at 300.6 and 692.3 K, showing little effect of the unique graphene structure on its ability to store thermal energy. A strong size effect on GNR's thermal conductivity is observed and its theoretical values for an infinite-length limit are evaluated by data fitting and extrapolation. With infinite length, the 1.99-nm-wide GNR has a thermal conductivity of 149 W m~(-1) K~(-1) at 692.3 K, and 317 W m~(-1)K~(-1) at 300.6 K. Our study of the temperature distribution and evolution suggests that diffusive transport is dominant in the studied GNRs. Non-Fourier heat conduction is observed at the beginning of the thermal-relaxation procedure. Thermal waves in GNR's in-plane direction are observed only for phonons in the flexural direction (ZA mode). The observed propagation speed (c = 4.6 km s~(-1)) of the thermal wave follows the relation of c = v_g/2~(1/2) (v_g is the ZA phonon group velocity). Our thermal-wave study reveals that in graphene, the ZA phonons transfer thermal energy much faster than longitudinal (LA) and transverse (TA) modes. Also, ZA↔ZA energy transfer is much faster than the ZA↔LA/TA phonon energy transfer.
机译：开发了一种瞬态分子动力学技术来表征二维石墨烯纳米带（GNR）的热物理性质。通过直接跟踪由热脉冲加热的GNR的热松弛历史，我们能够快速，准确地确定其热扩散率。我们研究了1.99 nm宽度的各种长度GNR的动态热导率。量子校正应用于所有温度计算中，并且发现在石墨烯的热传输研究中具有关键作用。 GNR的计算比热与石墨在300.6和692.3 K时的比热非常吻合，显示出独特的石墨烯结构对其热能存储能力的影响很小。观察到了对GNR的热导率有很大的尺寸影响，并通过数据拟合和外推评估了其对无限长极限的理论值。无限长的1.99nm宽的GNR在692.3 K时的热导率为149 W m〜（-1）K〜（-1），在317 W时的热导率为317 W m〜（-1）K〜（-1） 300.6K。我们对温度分布和演化的研究表明，在研究的GNR中，扩散传输占主导。在热松弛过程开始时观察到非傅立叶热传导。仅在弯曲方向（ZA模式）的声子上观察到GNR平面内方向的热波。观测到的热波传播速度（c = 4.6 km s〜（-1））遵循c = v_g / 2〜（1/2）的关系（v_g是ZA声子群速度）。我们的热波研究表明，在石墨烯中，ZA声子传递热能的速度比纵向（LA）和横向（TA）模式快得多。同样，ZA↔ZA能量传递比ZA↔LA/ TA声子能量传递快得多。

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  • 来源
    《Physical review》 |2011年第23期|p.235416.1-235416.12|共12页
  • 作者

    Jingchao Zhang; Xiaopeng Huang; Yanan Yue; Jianmei Wang; Xinwei Wang;

  • 作者单位

    (2010 Black Engineering Building, Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011, USA;

    (2010 Black Engineering Building, Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011, USA;

    (2010 Black Engineering Building, Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011, USA;

    Department of Energy and Power Engineering, Wuhan University, Wuhan 430072, People's Republic of China;

    (2010 Black Engineering Building, Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011, USA,School of Environmental and Municipal Engineering, Qingdao Technological University, Qingdao 266033, People's Republic of China;

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  • 正文语种 eng
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  • 关键词

    thermal diffusivity; phonons in crystal lattices;

    机译：热扩散率晶格中的声子;

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