School of Mechanical Engineering and the Birck Nanotechnology Center, Purdue University , West Lafayette, Indiana 47907, United States.
Department of Mechanical Engineering, National University of Singapore , 9 Engineering Drive 1, EA-07-05, Singapore 117575, Singapore.
ACS Appl Mater Interfaces. 2016 Jul 13;8(27):17461-71. doi: 10.1021/acsami.6b04114. Epub 2016 Jun 30.
The production of continuous carbon nanotube (CNT) fibers and films has paved the way to leverage the superior properties of individual carbon nanotubes for novel macroscale applications such as electronic cables and multifunctional composites. In this manuscript, we synthesize fibers and films from CNT aerogels that are continuously grown by floating catalyst chemical vapor deposition (FCCVD) and measure thermal conductivity and natural convective heat transfer coefficient from the fiber and film. To probe the mechanisms of heat transfer, we develop a new, robust, steady-state thermal characterization technique that enables measurement of the intrinsic fiber thermal conductivity and the convective heat transfer coefficient from the fiber to the surrounding air. The thermal conductivity of the as-prepared fiber ranges from 4.7 ± 0.3 to 28.0 ± 2.4 W m(-1) K(-1) and depends on fiber volume fraction and diameter. A simple nitric acid treatment increases the thermal conductivity by as much as a factor of ∼3 for the fibers and ∼6.7 for the thin films. These acid-treated CNT materials demonstrate specific thermal conductivities significantly higher than common metals with the same absolute thermal conductivity, which means they are comparatively lightweight, thermally conductive fibers and films. Beyond thermal conductivity, the acid treatment enhances electrical conductivity by a factor of ∼2.3. Further, the measured convective heat transfer coefficients range from 25 to 200 W m(-2) K(-1) for all fibers, which is higher than expected for macroscale materials and demonstrates the impact of the nanoscale CNT features on convective heat losses from the fibers. The measured thermal and electrical performance demonstrates the promise for using these fibers and films in macroscale applications requiring effective heat dissipation.
连续碳纤维（CNT）纤维和薄膜的生产为利用单个 CNT 的优异性能开拓了新途径，可将其应用于新型宏观尺度领域，如电子电缆和多功能复合材料。在本文中，我们使用 CNT 气凝胶合成纤维和薄膜，该气凝胶是通过浮动催化剂化学气相沉积（FCCVD）连续生长的，并测量纤维和薄膜的导热系数和自然对流传热系数。为了探究传热机制，我们开发了一种新的、强大的、稳态热特性测试技术，可测量纤维的固有导热系数和纤维到周围空气的对流传热系数。所制备纤维的导热系数范围为 4.7±0.3 至 28.0±2.4 W m(-1) K(-1)，取决于纤维体积分数和直径。简单的硝酸处理可将纤维的导热系数提高约 3 倍，薄膜的导热系数提高约 6.7 倍。这些经酸处理的 CNT 材料的比热导率明显高于具有相同绝对热导率的常见金属，这意味着它们是相对较轻量、导热的纤维和薄膜。除了导热系数之外，酸处理还将电导率提高了约 2.3 倍。此外，所有纤维的对流传热系数范围为 25 至 200 W m(-2) K(-1)，高于宏观尺度材料的预期值，这表明 CNT 的纳米级特征对纤维的对流传热损失有影响。所测量的热性能和电性能表明，这些纤维和薄膜有望在需要有效散热的宏观尺度应用中得到应用。
