Hybrids of Reduced Graphene Oxide and Hexagonal Boron Nitride: Lightweight Absorbers with Tunable and Highly Efficient Microwave Attenuation Properties

Abstract

Sandwichlike hybrids of reduced graphene oxide (rGO) and hexagonal boron nitride (h-BN) were prepared via heat treatment of the self-assemblies of graphene oxide (GO) and ammonia borane (AB). TG-DSC-QMS analysis indicate a mutually promoted redox reaction between GO and AB; 900 °C is a proper temperature to transfer the hybrids into inorganic sandwiches. XRD, XPS, and Raman spectra reveal the existence of h-BN embedded into the rGO frameworks. High-resolution SEM and TEM indicate the layer-by-layer structure of the hybrids. The content of h-BN can be increased with increase of the mass ratio of AB and the highest heat treatment temperature. The complex permittivity and the microwave absorption are tunable with the variation of the content of h-BN. When the mass ratio of GO/AB is 1:1, the microwave absorption of the hybrid treated at 900 °C is preferable in the range of 6-18 GHz. A minimum reflection loss, -40.5 dB, was observed at 15.3 GHz for the wax composite filled with 25 wt % hybrids at the thickness of 1.6 mm. The qualified frequency bandwidth reaches 5 GHz at this thickness with a low surface density close to 1.68 kg/m. The layer-by-layer structure of the hybrid makes great contributions to the increased approaches and possibilities of electron migrating and hopping, which has both highly efficient dielectric loss and excellent impedance matching for microwave consumption.

Enhanced Microwave Absorption Bandwidth in Graphene-Encapsulated Iron Nanoparticles with Core–Shell Structure

“…This material consisted of a metal nanoparticle inner core and a carbon outer shell. Materials of the carbon shells include graphite [13], amorphous carbon [14], and graphene [15], while metals include Ni [14], Co [16], FeNi [17], FeCo [18], FeSn 2 [19], and TiO 2 [20], among others. As we all know, controlling the composition and structure of the composite core and shell can make the dielectric and magnetic properties of these materials more conducive to impedance matching [21].…”

Implementation of Atomically Thick Graphene and Its Derivatives in Electromagnetic Absorbers

“…The measured RL exhibits a minimum of −46 dB at 9.1 GHz for d 1 = 1.4 mm and d 2 = 2.2 mm. Meanwhile, the device demonstrates excellent microwave absorption (RL < 10 dB) over the whole measurement range (8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18), as shown in Figure 10b. The authors attribute the advantage of using rGO-FSS to the polarization and conduction losses induced by abundant micro-defects and hopping of charge carriers in their multilayer rGO, respectively.…”

“…In addition, graphene-based beem-steering devices operating at mid-infrared frequency have also been proposed, demonstrating effective control over the reflection angle of the incident wave [12,13]. Moreover, graphene and its derivatives such as reduced graphene oxide (rGO) have also been utilized along with other materials to realize EM absorbers with fixed wave absorption and operation frequencies [14][15][16][17][18][19]. Meanwhile, graphene-based reconfigurable EM absorbers have also been proposed, paving the way for the development of smart EM absorbing materials.…”

Progress on microwave absorption materials with core-shell structure

“…受此启发, 研究者将其与碳纳米管进行复合(图7(a), (b)) [49] , 制成吸收剂, 但其吸收性能表现却不尽如人 [24] ; 直接使用石墨烯泡沫结构, 使得吸收剂 的密度进一步降低, 石墨烯泡沫内部存在丰富的界 面结构, 能够形成多重散射, 有效提升了微波吸收效 果(图7(c), (d)) [50] . 但是, 以上材料由于刻蚀了内部 的磁核或者未引入磁损耗, 综合表现并不十分突出, 另一种有效的办法是刻蚀部分磁核, 在降低密度的 同时, 保留磁损耗, 是一种折衷的调节手段 [28] .…”