石墨烯高频介电行为与调制方法

Graphene has attracted increasing attention due to its excellent optic, electric and mechanical properties. Recently, we found that graphene exhibited a novel dielectric properties at a high frequency of electromagnetic wave,i.e. high dielectric loss-low absorption characteristics, and the mechanism is still unclear. The explanation for its origin and the realization of the modulation of its dielectric properties will lead to the breakthrough in the field of electromagnetic absorption with lightweight and wide frequency characteristics. Therefore, in the prograpm, graphene with different specific surface area was prepared by simple chemical and physical methods, and the dielectric properties of graphene with different atomic layers, specific surface area and conductivity were investaged, and the physical mechanim of the high dielectric loss-low absorption characteristics and their effect factors would be carified; The graphene/organics and graphene/inorganics were synthesized by a controllable way; Through the analysis and characterization of structure, specific surface area and electric properties of graphene composites, the modulation means of the dielectric properties of graphene by the growing and dispersive situations of organics and inorganics would be given; The effect of keyfactors on the dielectric properties of graphene would be demonstrated by the dielectric relaxation and transmission line theories and numerical mode matching. The expected results above would provid the scientific basis for design and synthesis of graphene-based composites with wide-fruquency absorption and lightweight characteristics and thus promote the rapid development of the novle type of graphene-based dielectric materials.

石墨烯由于具有优异的光、电以及机械性能而受到广泛关注。近期，申请者发现石墨烯在高频电磁波范围内表现出全新的介电特性，即高介电损耗-低吸收特性。目前，其机制尚不清晰。该机理的阐明及其介电特性调制的实现可能在轻质、宽频电磁波吸收材料领域取得突破性进展。因此，本项目拟利用简单的物理化学方法，制备不同比表面积的石墨烯，研究不同比表面积以及不同电导率的石墨烯的介电特性，揭示石墨烯高介电损耗-低吸收介电行为的影响规律和物理本质；实现石墨烯/有机物和石墨烯/无机物的可控制备，通过对石墨烯复合物的微观结构、比表面积及电学性质的分析与表征，给出无机物、有机物在石墨烯表面生长情况、分散情况等因素对其介电行为的调控规律；利用介电弛豫理论、传输线理论，通过数值模拟计算揭示其介电行为对电磁波吸收的影响规律，从而为轻质、宽频吸收石墨烯复合结构的设计、可控制备与应用提供科学依据，推动新型石墨烯介电功能材料的快速发展。

近年来，石墨烯具有优异的光、电以及机械性能而受到广泛关注。同时，石墨烯的比表面积大，可用来构建超轻材料。石墨烯在高频电磁波辐射下，表现出较高的介电损耗特性；然而，其电磁波吸收特性却较差。为了解释其物理机制，使之能够满足与轻质电磁波吸收领域，本项目设计了石墨烯复合纳米结构，研究石墨烯异质结构的形成机制，探讨了其在轻质电磁波吸收等领域中能够实际应用的可能性。同时，对石墨烯纳米复合结构的电磁吸收特性增强机理进行了探讨。取得了如下研究成果；（1）石墨烯/特殊结构的有机物或无机物复合纳米结构的构建方法。发展了种子法制备了三维石墨烯磁性无机磁性纳米阵列结构；发展了柯肯达尔效应在石墨烯表面生长了中空磁性纳米颗粒，蛋黄蛋壳结构；发展了低温技术实现了三维石墨烯/有机纳米棒阵列的可控制备；采用了简单的溶剂热技术等，制备了石墨烯/双金属复合纳米材料以及石墨烯/无机物/有机物等多元复合纳米结构；为具有特殊结构的石墨烯复合纳米结构的制备提供了基本方法和调控手段，为开展这些具有特殊结构的复合纳米结构的物理化学特性奠定了物质基础；（2）石墨烯介电行为的调控及机制。利用传输线理论、介电弛豫理论，通过数值模拟计算揭示了这些石墨烯/特殊结构的介电行为可调控机制。其中，界面效应、几何效应（1/4波长匹配）以及阻抗匹配对石墨烯的介电行为起到关键的调控作用；而与之相关的协同效应（尺寸效应、界面耦合输特性以及特殊结构特性等）增强了其对电磁波的吸收特性。重要的是，这些石墨烯复合纳米结构在介质中的添加量均小于或等于20wt%, 从而为轻质、宽频石墨烯基复合电磁波吸收材料的应用提供了科学依据。