Abstract
A broadband microwave absorbing composite with a multi-scale layered structure is proposed, in which a reduced graphene oxide (RGO) film sandwiched between two layers of epoxy glass fiber laminates serves as the frequency selective surface (FSS). RGO films with the desired electrical properties were synthesized directly by hydrothermal reaction, vacuum filtration, and heat treatment without subsequent processing. With the novel layer-by-layer structure ranging from micro to macro scale, the optimized composite exhibits excellent microwave absorption performance with a total thickness of 3.2 mm. Its reflection coefficient (RC) is less than −10 dB in the entire X and Ku band, reaching a minimum value of −32 dB at 10.2 GHz and an average RC of −22.8 dB from 8 to 18 GHz. Enhanced microwave absorption of the composites is achieved through the optimization of layer thickness in the sandwich structure to promote destructive interference. Improved impedance matching by the introduction of FSS along with the polarization and conduction loss of layered graphene films also contribute to the increased absorption.
Highlights
Extensive use of portable electronic instruments and wireless communication has resulted in a serious electromagnetic (EM) interference pollution
The composite with reduced graphene oxide (RGO) frequency selective surface (FSS) films sandwiched between two dielectric FR4 layers
Integration simulations, the composite with films waswas found to exhibit Through excellent finite
Summary
Extensive use of portable electronic instruments and wireless communication has resulted in a serious electromagnetic (EM) interference pollution. Broadening the absorption bandwidth of reflection coefficient (RC) to under −10 dB always comes with the unavoidable increase in thickness of the composites [11,12]. It is still a challenging issue in the design of broadband absorbers with low thickness. Loaded with lumped components like resistors and capacitors, FSS is usually fabricated with highly conductive materials such as metals with periodic patterns and specific sheet resistances. These materials are usually thick and Materials 2018, 11, 1771; doi:10.3390/ma11091771 www.mdpi.com/journal/materials
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