Interface-mediated extremely low thermal conductivity of graphene aerogel
Interface-mediated extremely low thermal conductivity of graphene aerogel
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DOI：
10.1016/j.carbon.2015.11.033
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发表时间：
2016-03-01
期刊：
影响因子：
10.9
通讯作者：
Wang, Xinwei
中科院分区：
文献类型：
--
作者：
Xie, Yangsu;Xu, Shen;Wang, Xinwei
由于石墨烯的超高热导率（k），石墨烯基材料有望成为良好的热导体。然而，在这里，我们发现了极低k的超轻石墨烯气凝胶（GAs）。虽然我们的GA（类似于4 mg cm（-3））比空气（类似于1.2 mg cm（-3））重约两倍，但在室温（RT）下的k（4.7 x 10（-3）-5.9 x 10（-3）W m（-1）K-1）比空气（在20 ℃下为0.0257 W m（-1）K-1）低约80%。在低温下，GA的k达到2 × 10（-4）-4 × 10（-4）W m（-1）K-1的较低水平。这是我们所知的最低k值。通过研究GA的k、热扩散率（α）和比热（c（p））从室温到低至10.4K的温度变化来探索这种极低k的机制。未被覆盖的小但正的偏导数α/偏导数T揭示了热传输中占主导地位的界面接触热阻。对于具有声子-声子散射维持的热输运的正常材料，偏导数α/偏导数T总是保持为负。对c（p）的研究表明，GAs具有高度无序和无定形的结构，这也是超低k的原因之一。这使得GA成为一种非常有前途的隔热材料，特别是在真空条件下（例如，隔热区域）。(C)2015爱思唯尔有限公司版权所有。
Due to the ultra-high thermal conductivity (k) of graphene, graphene-based materials are expected to be good thermal conductors. Here, however, we uncovered extremely low k of ultralight graphene aerogels (GAs). Although our GA (similar to 4 mg cm(-3)) is about two times heavier than air (similar to 1.2 mg cm(-3)), the k (4.7 x 10(-3)-5.9 x 10(-3) W m(-1) K-1) at room temperature (RT) is about 80% lower than that of air (0.0257 W m(-1) K-1 at 20 degrees C). At low temperatures, the GA's k reaches a lower level of 2 x 10(-4)-4 x 10(-4) W m(-1) K-1. This is the lowest k ever measured to our best knowledge. The mechanism of this extremely low k is explored by studying the temperature variation of GA's k, thermal diffusivity (alpha) and specific heat (c(p)) from RT to as low as 10.4 K. The uncovered small, yet positive partial derivative alpha/partial derivative T reveals the dominant interface thermal contact resistance in thermal transport. For normal materials with thermal transport sustained by phonon-phonon scattering, partial derivative alpha/partial derivative T always remains negative. The study of c(p) suggests highly disordered and amorphous structure of GAs, which also contributes to the ultralow k. This makes the GA a very promising thermal insulation material, especially under vacuum conditions (e.g. astronautics areas). (C) 2015 Elsevier Ltd. All rights reserved.