摘要：厚度达数百微米的高性能石墨烯薄膜具有更高的热传导能力，有望解决严峻的热管理需求。然而，厚石墨烯薄膜的导热系数有限，低于1000Wm-1K-1，这是由于薄膜内部的皱褶缺陷造成的。本文，浙江大学高超 教授、高微微 副教授、Peng Li、刘英军 教授等在《Smal

1成果简介

厚度达数百微米的高性能石墨烯薄膜具有更高的热传导能力，有望解决严峻的热管理需求。然而，厚石墨烯薄膜的导热系数有限，低于1000Wm-1K-1，这是由于薄膜内部的皱褶缺陷造成的。本文，浙江大学高超 教授、高微微 副教授、Peng Li、刘英军 教授等在《Small》期刊发表名为“Scalable High-Performance Graphene Films Over Hundreds Micrometer Thickness via Sheargraphy”的论文，研究提出了一种剪切方法，以精确调节液晶的薄片排列，从而获得厚度为215µm 的石墨烯薄膜，其平面内热导率达到创纪录的1380Wm-1K-1。水平移动的金属丝阵列产生的5µm 的微尺度剪切场可压平片状皱纹，并消除氧化石墨烯液晶的多晶性。

均匀的液晶赋予凝结的固体薄膜以高度有序性，从而形成致密平整的叠层石墨晶体。最高热通量（厚度乘以热导率）可达0.3WK-1，从而使厚膜具有长距离快速热传播能力和热传导路径的可设计性。这项工作提供了一种有效的方法来调节二维薄片的有序性，并生产出高热流石墨烯薄膜，以解决日益严峻的热管理挑战。

2图文导读

图1、通过剪切法制备厚石墨烯薄膜。

图2、The conformation evolution of solid film via sheargraphy. a) Influence of diameter (D) of microwire and spacing (S) of adjacent shearing fields on the ordering of GOLCs. b) A contour plot indicating the influence of D and S on the order parameter of GOLCs. c–f) Conformation evolution of GOLCs and corresponding solid condensed films prepared by different assembly processes, including random casting, blade coating, and sheargraphy. The first two rows were POM images of GOLCs from macro to micro. The third row was SEM images of different liquid crystals prepared by freeze-drying process and insert was corresponding Fourier–Transform diffraction patterns. The last two rows were surface roughness (Ra) and cross-sectional morphology of solid films. g) X-ray diffraction profiles of solid graphene oxide films via three different methods.

图3、Comprehensive properties of thick graphene films. a) SAXS and WAXS patterns of graphene films via sheargraphy (S-GFs) and the graphene films via blade coating (B-GFs), respectively. Both films had the same thickness of 215 µm. b) Raman spectra of S-GFs and B-GFs, respectively. The left was the Lorentzian fit of the 2D band. The right was the corresponding full width at half maximum (FWHM) of 2D1 and 2D2 subpeaks. c) In-plane thermal conductivity (K∥) of S-GFs and B-GFs with varying thickness. d) The comparison of K∥ between S-GFs and other graphite films. e) Through-plane thermal conductance (K⊥) of S-GFs and B-GFs, respectively. f) Electricity of S-GFs and B-GFs. g) Stress–strain curves of S-GFs and B-GFs.

图4、Multi-scale microstructure analysis for thermal enhancement mechanism of thick graphene film. a, c) Cross-sectional SEM morphologies for S-GFs and B-GF. b, d) 3D void microstructures reconstructed by X-ray microtomography for S-GFs and B-GFs. Blue denoted the voids. e) Corresponding void volume distribution. The insert was middle pore volume. f,g) Through-plane graphite grain of S-GFs and B-GFs, respectively. From left to right were cross-sectional bright-field TEM, high-angle annular dark-field scanning TEM, and high-resolution TEM. h) The corresponding grain band thickness (Lc) and graphite lamella thickness distributions of films via sheargraphy, blade coating, and random casting, respectively. i) An illustration of ordered crystallites inside thick graphene films via sheargraphy.

图5、Fast heat dissipation of thick graphene film via sheargraphy. a) Top-view infrared images of heat and cold conduction of thick (215 µm) and thin (20 µm) S-GFs, respectively. b) Corresponding temperature-distance variation diagram. c) Corresponding heat and cold conduction distance of different graphene films. d) Infrared image of heat dissipation capability of serpentine and straight pathways, respectively. Serpentine pathways were obtained by adjusting the curvature radius (r) from 0 to 0.25. e) Corresponding temperature-time profile of different pathways. Temperature was the average value within the dashed box at the same vertical distance of 60 mm from the heater edge. f) Scheme of a thermal management evaluation system. g) Surface temperature evolution of LED chip. The temperature was the average value within the dotted circle. C-GFs were the films via random casting. h) Resulting infrared images of LED chip from heating to cooling.

3小结

厚度达数百微米的高性能石墨烯薄膜具有更高的热传导能力，有望解决严峻的热管理需求。然而，厚石墨烯薄膜的导热系数有限，低于1000Wm-1K-1，这是由于薄膜内部的皱褶缺陷造成的。在此，我们提出了一种剪切策略，以精确调节液晶的薄片排列，从而获得厚度为215µm 的石墨烯薄膜，其平面内热导率达到创纪录的1380Wm-1K-1。水平移动的金属丝阵列产生的5µm 的微尺度剪切场可压平片状皱纹，并消除氧化石墨烯液晶的多晶性。均匀的液晶赋予凝结的固体薄膜以高度有序性，从而形成致密平整的叠层石墨晶体。最高热通量（厚度乘以热导率）可达0.3WK-1，从而使厚膜具有长距离快速热传播能力和热传导路径的可设计性。这项工作提供了一种有效的方法来调节二维薄片的有序性，并生产出高热流石墨烯薄膜，以解决日益严峻的热管理挑战。

文献：

来源：材料分析与应用

来源：石墨烯联盟