绿色制备柔性导热石墨烯-碳化宣纸复合膜

Green Fabrication of Flexible, Thermally Conductive Graphene-carbonized Chinese Art Paper Composite Film

基于柔韧吸水的天然宣纸和大球-小球复合球磨法剥离宏量高分散的水性石墨烯分散液,通过浸泡吸附-机械压缩-热处理路线,绿色制备了柔性导热石墨烯-碳化宣纸复合膜.该石墨烯-碳化宣纸复合膜的电导率和热导率分别高达568 S/cm和258 W/mK,其红外热成像图片展现了好的热传输性能.另外,该石墨烯-碳化宣纸复合膜具有良好的柔韧性,反复弯曲100次之后,其电阻基本不变.

Highly thermal conductive and flexible materials are urgently required in the heat management of high-power electronic devices. In this work, a composite film with these required properties, based on graphene and carbonized Chinese art paper, is prepared through a green route. Graphite is directly exfoliated in water in the presence of polyvinylpyrrolidone surfactant into high-quality graphene through a combination of large and small ball milling. The exfoliated graphene is filled into the porous network of the flexible superhydrophilic Chinese art paper through immersion absorption. After drying, the immersed Chinese art paper is mechanically compressed and carbonized at high temperature, leading to a composite film of graphene and carbonized Chinese art paper. TEM shows that the exfoliated graphene nanoplatelets is of layered structure and has a diameter in the range of several hundreds of nanometers to several micrometers. Raman spectroscopy proves that the exfoliated graphene nanoplatelet has a few defects with a low intensity ratio of D peak to G peak （0.25）. SEM image shows that the graphene nanoplatelets filled in Chinese art paper are interconnected, which provides continuous channels for phonon transport. Mechanical compression increases the mass density of the composite film and improves the contact between the graphene nanoplatelets. Raman spectroscopy proves that annealing at high temperature decreases the amount of SP3 hybrid carbon. As a result, the resultant composite film of graphene and carbonized Chinese art paper shows excellent thermal conductivity of 258 W/mK, superior to previously reported RGO- polymer composites （0.8 - 19.5 W/InK）. The interconnected three-dimensional microfiber network of the carbonized Chinese art paper imparts the composite film with good flexibility, superior to that of the pure graphene film. After 100 bending cycles, the electrical resistance of the composite film remains practically unchanged. Compared with the conventional chemical oxidation-thermal reduction, the present route is environment-friendly, which avoids the use of strong oxidizing acids and does not generate acidic waste water.