Tarannum Fatema, Danayat Swapneel S, Nayal Avinash, Muthaiah Rajmohan, Annam Roshan Sameer, Garg Jivtesh
School of Aerospace and Mechanical Engineering, University of Oklahoma, Norman, OK 73019, USA.
Nanomaterials (Basel). 2022 May 30;12(11):1877. doi: 10.3390/nano12111877.
We demonstrate in this work that expanded graphite (EG) can lead to a very large enhancement in thermal conductivity of polyetherimide-graphene and epoxy-graphene nanocomposites prepared via solvent casting technique. A value of 6.6 W⋅m⋅K is achieved for 10 wt% composition sample, representing an enhancement of 2770% over pristine polyetherimide (0.23 W⋅m⋅K). This extraordinary enhancement in thermal conductivity is shown to be due to a network of continuous graphene sheets over long-length scales, resulting in low thermal contact resistance at bends/turns due to the graphene sheets being covalently bonded at such junctions. Solvent casting offers the advantage of preserving the porous structure of expanded graphite in the composite, resulting in the above highly thermally conductive interpenetrating network of graphene and polymer. Solvent casting also does not break down the expanded graphite particles due to minimal forces involved, allowing for efficient heat transfer over long-length scales, further enhancing overall composite thermal conductivity. Comparisons with a recently introduced effective medium model show a very high value of predicted particle-particle interfacial conductance, providing evidence for efficient interfacial thermal transport in expanded graphite composites. Field emission environmental scanning electron microscopy (FE-ESEM) is used to provide a detailed understanding of the interpenetrating graphene-polymer structure in the expanded graphite composite. These results open up novel avenues for achieving high thermal conductivity polymer composites.
我们在这项工作中证明，膨胀石墨（EG）能够极大地提高通过溶液浇铸技术制备的聚醚酰亚胺 - 石墨烯和环氧 - 石墨烯纳米复合材料的热导率。对于10 wt% 组成的样品，热导率达到了6.6 W⋅m⁻¹⋅K⁻¹，相较于原始聚醚酰亚胺（~0.23 W⋅m⁻¹⋅K⁻¹）提高了约2770%。热导率的这种显著提高归因于长尺度上连续的石墨烯片网络，由于石墨烯片在这些连接处共价键合，使得在弯曲/转折处的热接触电阻较低。溶液浇铸具有保留复合材料中膨胀石墨多孔结构的优点，从而形成上述由石墨烯和聚合物组成的高导热互穿网络。溶液浇铸还由于涉及的力最小而不会破坏膨胀石墨颗粒，允许在长尺度上进行有效的热传递，进一步提高了复合材料的整体热导率。与最近引入的有效介质模型的比较显示，预测的颗粒 - 颗粒界面电导率值非常高，为膨胀石墨复合材料中的有效界面热传输提供了证据。场发射环境扫描电子显微镜（FE - ESEM）用于详细了解膨胀石墨复合材料中互穿的石墨烯 - 聚合物结构。这些结果为实现高导热聚合物复合材料开辟了新途径。
