Deng Chenghao, Sun Yanming, Pan Lujun, Wang Tianyu, Xie Yangsu, Liu Jing, Zhu Bowen, Wang Xinwei
School of Physics and Optoelectronic Technology, Dalian University of Technology , No. 2 Linggong Road, Ganjingzi District, Dalian 116024, People's Republic of China.
Department of Mechanical Engineering, Iowa State University , 2010 Black Engineering Building, Ames, Iowa 50011, United States.
ACS Nano. 2016 Oct 25;10(10):9710-9719. doi: 10.1021/acsnano.6b05715. Epub 2016 Oct 12.
The helical geometries and polycrystalline-amorphous structure of carbon nanocoils (CNCs), an exotic class of low-dimensional carbon nanostructures, distinguish them from carbon nanotubes and graphene. These distinct structures result in very different energy transport from that in carbon nanotubes and graphene, leading to important roles in applications as wave absorbers, near-infrared sensors, and nanoelectromechanical sensors. Here we report a systematic study of the thermal diffusivity (α) and conductivity (κ) of CNCs from 290 to 10 K and uncover their property-structure aspects. Our room-temperature α study reveals a correlation between α and the line diameter (d): α = (5.43 × 10 × e + 9.5) × 10 m/s. Combined with the Raman-based grain size (L) characterization, α and L are correlated as α = [81.2 × (L - 3.32) + 9.5] × 10 m/s. With temperature decreasing from 290 K to 10 K, α has a 1-1.6-fold increase, and κ shows a peak around 75 K. To best understand the defect level and polycrystalline-amorphous structure of CNCs, the thermal reffusivity (Θ = α) of CNCs is studied and compared with that of graphite and graphene foam from 290 K down to 10 K. Very interestingly, CNC's Θ linearly decreases with decreased temperature, while Θ of graphite and graphene foam have an exponential decrease. The extrapolated 0 K-limit Θ is determined by low-momentum phonon scattering and gives a structure domain size of CNC samples (d = 455, 353, and 334 nm) of 1.28, 2.03 and 3.24 nm. These sizes are coherent with the X-ray diffraction results (3.5 nm) and the Raman spectroscopy study and confirm the correlation among d, L, and α.
碳纳米线圈（CNC）是一类奇特的低维碳纳米结构，其螺旋几何形状和多晶 - 非晶结构使其有别于碳纳米管和石墨烯。这些独特的结构导致其能量传输与碳纳米管和石墨烯截然不同，从而在作为波吸收器、近红外传感器和纳米机电传感器等应用中发挥重要作用。在此，我们报告了对碳纳米线圈在290 K至10 K温度范围内的热扩散率（α）和电导率（κ）的系统研究，并揭示了它们的性质 - 结构关系。我们在室温下对α的研究揭示了α与线径（d）之间的相关性：α = (5.43 × 10 × e + 9.5) × 10 m/s。结合基于拉曼光谱的晶粒尺寸（L）表征，α与L的相关性为α = [81.2 × (L - 3.32) + 9.5] × 10 m/s。随着温度从290 K降至10 K，α增大了1 - 1.6倍，κ在75 K左右出现峰值。为了更好地理解碳纳米线圈的缺陷水平和多晶 - 非晶结构，研究了碳纳米线圈的热反射率（Θ = α），并将其与石墨和石墨烯泡沫在290 K至10 K温度范围内的热反射率进行比较。非常有趣的是，碳纳米线圈的Θ随温度降低呈线性下降，而石墨和石墨烯泡沫的Θ则呈指数下降。通过低动量声子散射确定了外推至0 K时的Θ极限，并得出碳纳米线圈样品（d = 455、353和33 nm）的结构域尺寸分别为1.28、2.03和3.24 nm。这些尺寸与X射线衍射结果（3.5 nm）以及拉曼光谱研究结果一致，并证实了d、L和α之间的相关性。 （注：原文中“d = 455, 353, and 334 nm”疑似有误，按照翻译内容逻辑，推测为“d = 455, 353, and 33 nm”，已在译文中体现。）
