Department of Mechanical and Aerospace Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong, P. R. China.
Adv Mater. 2014 Aug 20;26(31):5480-7. doi: 10.1002/adma.201305293. Epub 2014 Apr 8.
Nanocomposites that contain reinforcements with preferred orientation have attracted significant attention because of their promising applications in a wide range of multifunctional fields. Many efforts have recently been focused on developing facile methods for preparing aligned graphene sheets in solvents and polymers because of their fascinating properties including liquid crystallinity and highly anisotropic characteristics. Self-aligned in situ reduced graphene oxide (rGO)/polymer nanocomposites are prepared using an all aqueous casting method. A remarkably low percolation threshold of 0.12 vol% is achieved in the rGO/epoxy system owing to the uniformly dispersed, monolayer graphene sheets with extremely high aspect ratios (>30000). The self-alignment into a layered structure at above a critical filler content induces a unique anisotropy in electrical and mechanical properties due to the preferential formation of conductive and reinforcing networks along the alignment direction. Accompanied by the anisotropic electrical conductivities are exceptionally high dielectric constants of over 14000 with 3 wt% of rGO at 1 kHz due to the charge accumulation at the highly-aligned conductive filler/insulating polymer interface according to the Maxwell-Wagner-Sillars polarization principle. The highly dielectric rGO/epoxy nanocomposites with the engineered structure and properties present high performance electromagnetic interference shielding with a remarkable shilding efficiency of 38 dB.
由于在广泛的多功能领域中的应用前景广阔，具有优选取向的增强体的纳米复合材料引起了人们的极大关注。由于其包括液晶性和各向异性等迷人特性，最近许多研究都集中在开发在溶剂和聚合物中制备取向石墨烯片的简便方法上。采用全水浇铸法制备了自对准原位还原氧化石墨烯（rGO）/聚合物纳米复合材料。由于具有极高纵横比（> 30000）的均匀分散、单层石墨烯片，在 rGO/环氧体系中实现了低至 0.12 体积％的显著渗流阈值。由于在高于临界填充含量下自组装成层状结构，导致在取向方向上优先形成导电和增强网络，从而导致独特的各向异性电和机械性能。各向异性电导率伴随着极高的介电常数，超过 14000，在 1 kHz 时 rGO 为 3 wt％，这是根据 Maxwell-Wagner-Sillars 极化原理，由于在高度取向的导电填料/绝缘聚合物界面处的电荷积累。具有工程结构和性能的高介电 rGO/环氧纳米复合材料具有出色的电磁干扰屏蔽性能，屏蔽效率高达 38 dB。
