近年来碳纳米管是一个重要的研究领域, 但研究重点主要是其电子、 光学和机械等特性。 尽管有关单壁碳纳米管的在远红外光谱已有诸多报道, 但多壁碳纳米管这方面的研究却较少。 试验采用太赫兹时域光谱系统对多壁碳纳米管进行表征, 同时也用扫描电镜对其进行形貌检测和微区成分分析, 以深入了解其特性。 检测结果显示, 在0.2～2.0 THz内, 样品折射率随着频率的增加而减小, 吸收系数却随着频率的增加而增加, 并可以拟合斜率为1.92的直线； 样品的内径为5～15 nm、 外径为15～25 nm, 且长度达到了微米级, 样品含C量大约为94%, 其他为O和Cl杂质元素。 根据泰勒扩展式和麦克斯韦方程, 得到了样品在该太赫兹频域内吸收的数学模型, 该数学模型基本上与检测结果一致。 该样品的太赫兹吸收特性主要取决于其化学组成和分子的大小, 含C量不同的碳纳米管预示着具有不同的太赫兹图谱和独特的功能。

In the present paper, the authors report the characterization of multiwalled carbon nanotube at terahertz (THz) frequency range using terahertz time-domain spectroscopy. The surface appearances and microanalysis of multiwalled carbon nanotubes were measured by scanning electron microscope in order to fully understand the unique features and applications of multiwalled carbon nanotube. The results show that the refractive indexes of the sample decrease with increasing frequency in the frequency range of 0.2 to 2 THz, while the absorption coefficients of the sample increase with increasing frequency. In addition, the curve of terahertz absorption coefficients can be fitted by a straight line with a slope of 1.92. From the results of scanning electron microscope, the ranges of inner diameter and outer diameters of the sample were from 5 to 15 nm and from 15 to 25 nm, respectively, and its length was in the order of micrometer. The results of microanalysis of its elemental composition showed that the content of element C was about 94% and the rest were O and Cl elements, which were impurity elements. Mathematical modes of terahertz absorption and refractive indexes in the frequency range of 0.2 to 2.0 THz were established after taking into account Taylor expansion and Maxwell’s equations, and the calculation was in relatively good agreement with the observed values of the sample in general. The terahertz refractive indexes and absorption properties of multiwalled carbon nanotube were mainly attributed to the chemical compositions and molecular weight, and carbon nanotubes with different content of carbon could show different terahertz absorption spectra and disclose different unique functions.