Utilizing ammonium persulfate assisted expansion to fabricate flexible expanded graphite films with excellent thermal conductivity by introducing wrinkles
Utilizing ammonium persulfate assisted expansion to fabricate flexible expanded graphite films with excellent thermal conductivity by introducing wrinkles
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利用过硫酸铵辅助膨胀通过引入褶皱制备具有优异导热性的柔性膨胀石墨薄膜
DOI：
10.1016/j.carbon.2019.07.079
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发表时间：
2019-11-01
期刊：
影响因子：
10.9
通讯作者：
Chen, Feng
中科院分区：
文献类型：
--
作者：
Liu, Yuhang;Qu, Bingxin;Chen, Feng
传统的膨胀石墨（EG）薄膜由于氧化程度较弱，缺陷密度较低，因此具有优异的导电性和导热性。然而，刚性片材结构使得EG膜非常脆，这极大地限制了其在下一代柔性电子器件中的应用。为了克服这一挑战，采用过硫酸铵（（NH 4）（2）S2 O 8）作为膨胀剂和弱氧化剂。结果表明，弱氧化能有效降低EG与水的表面能失配，使EG在水中高速剪切结合超声处理剥离成为可能。最特别地，膨胀步骤将大量褶皱引入EG片材中，这显著地改善了EG膜的柔性。此外，采用较大横向尺寸的石墨原料和较少的（NH_4）_2S_2O_（8），可以大大提高最终的综合性能。制备的EG薄膜具有良好的电导率和热导率，分别为2977 S/cm，854 W/mK。33.1膜厚仅为10 μ m，就可获得dB EMI屏蔽性能。此外，可以克服800次的直接弯曲而没有任何结构断裂。这种大规模、环境友好的制备方法使薄膜在柔性电子器件中具有巨大的应用潜力。(C)2019爱思唯尔有限公司版权所有。
Traditional expanded graphite (EG) films exhibit excellent electric and thermal conductivities, due to weak oxidation degree induced low defect density. However, the stiff sheet structure makes EG films very brittle, which greatly limits its applications in next generation flexible electric devices. To overcome this challenge, ammonium persulfate ((NH4)(2)S2O8) is employed as both expansion agent and weak oxidation agent. As a result, the weak oxidation can effectively reduce the surface energy mismatching between EG and water, making it possible for EG to be exfoliated in water by high-speed shearing combined with sonication. Most particularly, the expansion step introduces plenty of wrinkles into the EG sheets, which notably improve the flexibility of EG films. Besides, using raw graphite with large lateral size and less (NH4)(2)S(2)O(8 )can greatly improve the final overall performances. The prepared EG films exhibit good electric and thermal conductivities of 2977 S/cm, 854 W/mK, respectively. 33.1 dB EMI shielding property is obtained with the film thickness of only 10 mu m. Moreover, 800 times direct bending can be overcome without any structure break. This facial large scale and environmentally friendly method endows the films with great potential applications in flexible electric devices. (C) 2019 Elsevier Ltd. All rights reserved.