扩散过程强化超临界CO2技术制备石墨烯的基础研究

Owing to its various kinds of outstanding properties, graphene has been attracting great potential applications in the field of constructing new functional materials. Cheap ways to make high-quality graphene are urgently needed to meet its commercial applications. Up to now, the method of reduced graphene oxide has been widely used to synthesize graphene with low cost; however, the defects will be inevitably incorporated into the graphene crystal lattice during above synthesis process, which will lead to performance degradation of graphene. Therefore, it is still a bottleneck to effectively exfoliate graphite for high-quality, large-scale graphene synthesis. In the proposed research, a new technique combined both supercritical carbon dioxide and diffusion process intensification will be developed to directly convert graphite crystals into a high-yield of graphene sheets. High-speed fluid shear and rapid decompression technologies will be used to strengthen diffusivity and solvating of CO2 supercritical fluid between the graphite layers for graphite exfoliation. The relationships between the extent of graphite exfoliation and various kinds of conditions including the size of grain size of precursor graphite, level of fluid shear and the relief rate of CO2 will be clarified; as a result, a controllable synthesis route for graphene with different layers is expected to be achieved. The proposed study is helpful to develop a new way in large-scale production of high-quality, processable graphene sheets in China.

石墨烯在各方面所具有的优异性能使其在新材料领域具有广泛的应用前景，但如何制备高质量、低成本的石墨烯是实现其大规模应用前亟待解决的问题。目前普遍采用的氧化石墨还原法在氧化还原过程中石墨烯晶体的完整性容易受到破坏，进而影响石墨烯的性质。因此如何高效分离石墨片层而且又不破坏其晶型的完整性是石墨烯制备过程中的瓶颈难题。申请者提出通过扩散过程强化超临界CO2技术高效分离石墨片层制备石墨烯的工艺路线。本项目拟采用流体剪切技术强化超临界CO2分子在石墨片层间的扩散插层作用，并结合流体快速泄压技术发展一种清洁、高效剥离石墨片层制备石墨烯的方法。通过探索CO2分子在石墨片层间扩散传递的规律性，掌握石墨原料尺寸，流体剪切力大小及流体泄压速度对剥离石墨片层制备石墨烯的影响关系，从而得到不同层数石墨烯制备的调控方法。本项目所提出的扩散过程强化超临界CO2技术为我国高质量石墨烯低成本制备提供新的技术途径。

石墨烯在各方面所具有的优异性能使其在新材料领域具有广泛的应用前景，但如何制备高质量、低成本的石墨烯是实现其大规模应用前亟待解决的问题。本项目采用过程强化的超临界CO2剥离技术，利用廉价的石墨原料，包括鳞片石墨、膨胀石墨、膨胀石墨粉等成功制备出了少于10层的寡层石墨烯，并实现了石墨烯分散性能的改善以及其在散热、吸波方面的应用。通过流体剪切原位辅助CO2超临界剥离法以石墨为原料制备了层数少于10层的寡层石墨烯，发现制备过程中温度、压力和流体剪切速度是影响剥离效果的主要因素。制备的最佳条件是：反应温度：55度，反应压力：10 MPa。透射电镜及原子力显微镜表征结果显示制备的石墨烯主要分布在5-8层，拉曼光谱证实得到的石墨烯纳米片具有晶型程度高，缺陷少的特点。通过采用原位球磨辅助超临界剥离，通过不同添加剂，例如PVP，油氨，油酸等实现对石墨烯表面进行修饰或层间插层，得到了可以在水、乙醇等极性溶剂中稳定分散的石墨烯溶液，为后续石墨烯基水相导电浆料的研究奠定了基础。对制备所得石墨烯进行导热性能研究，发现超临界剥离石墨烯具备良好的导热性能，通过将石墨烯和纤维素复合，调控石墨烯和纤维素的比例，得到抗拉性能良好、面内和面间热导性能良好的复合导热膜，在横向热扩散应用方面有广泛的前景。通过将制备所得石墨烯与高分子材料复合，成功制备出了具有一定吸收电磁波效果的柔性吸波材料，其抗拉能力柔韧性能良好，并在一定频段内表现出良好的吸波效果。