Interfacially Engineered Sandwich‐Like rGO/Carbon Microspheres/rGO Composite as an Efficient and Durable Microwave Absorber

Abstract

EM pollution, because they can convert the EM energy into thermal energy or dissipate the EM waves through interference. [ 4,5 ] Among many kinds of microwave absorbers, carbon materials are always the most attractive candidates due to their tunable properties, relative low density, abundant resource, easy preparation, and low cost. Various carbon materials, e.g., carbon nanotubes (CNTs), carbon nanofi bers (CNF), carbon nanocoils, and mesoporous carbon, have been utilized to construct highly effective microwave absorbers in the past decades. [6][7][8][9][10][11][12] Although these carbon-based materials have made signifi cant progress in the fi eld of microwave absorption, some elaborate innovations on structure and components are still paving the way for exciting performance to satisfy the requirements of practical applications.Recently, graphene appeared as a fascinating material and grabbed worldwide attention, whose unprecedented physical and chemical properties derived from its unique 2D structure have promised great potential in many research fi elds. [ 13 ] Notably, high charge carrier mobility, extraordinary electrical and thermal conductivity also rendered graphene as a new microwave absorber, and it was found that reduced graphene oxide (rGO) provided superior microwave absorption to graphene oxide (GO). [ 14,15 ] However, sole graphene material suffers from limited loss mechanism caused by interfacial impedance mismatching, [ 15,16 ] thus it is usually employed as EM interference shielding material rather than EM absorbing material. [17][18][19] Incorporation of other lossy materials, especially magnetic metal and metal oxides, has been widely studied as the imperative solution to improve the matching of characteristic impedance and enhance the microwave absorption performance. [20][21][22][23][24][25][26][27][28][29] For example, graphene-coated Fe nanocomposites and Ni/graphene composites showed enhanced microwave absorption due to the charge transfer at metal/graphene interface and the polarization of free carriers; [ 20,21 ] Fe 3 O 4 /graphene, rGO-Fe 2 O 3 , and rGO/CNT-Fe 3 O 4 materials demonstrated optimum characteristic impedance and compatible dielectric and magnetic loss, which resulted in their strong refl ection loss in the frequency range of 12.0-16.0 GHz; [21][22][23] Graphene decorated with coreshell Fe@Fe 3 O 4 @ZnO nanoparticles was also fabricated, and Graphene-based composites offer immense potential for overcoming the challenges related to the performance, functionality, and durability in microwave absorption. In this study, a sandwich-like graphene-based composite is successfully fabricated by an interfacial engineering of amorphous carbon microspheres (ACMs) and reduced graphene oxide (rGO), with a structure of rGO/ACMs/rGO. The as-prepared rGO/ACMs/rGO composite presents comparable/superior refl ection loss characteristics in the frequency range of 2.0-18.0 GHz to previous composites of graphene and high-density magnetic particles. Electromagnetic parameters and simulation resu...

Optically Transparent Broadband Microwave Absorption Metamaterial By Standing‐Up Closed‐Ring Resonators

“…Microwave absorbers (MAs) are widely used in a variety of fields ranging from military, aerospace to consumer electronics, for eliminating unwanted electromagnetic (EM) radiation or scattering so as to improve the performance or reduce the EM pollution . With the extensive investigation in the past decades, various types of MAs have been developed and widely applied.…”

MWCNTs as Conductive Network for Monodispersed Fe3O4 Nanoparticles to Enhance the Wave Absorption Performances

“…Thus, according to Figure c, the dielectric loss of the Fe 3 O 4 /MWCNTs composite makes a major contribution as the loss tangent of Fe 3 O 4 /MWCNTs is higher than that of Fe 3 O 4 NPs. Besides magnetic loss also influences the EM wave absorption . Magnetic tangent loss (tan δ µ = µ″ nne ) shows a similar trend with imaginary part of permeability versus frequency, as shown in Figure d.…”

Graphene‐Based Materials toward Microwave and Terahertz Absorbing Stealth Technologies

“…Liu and co‐workers also demonstrated that the 3D graphene networks benefit from the advantage of more effective electrical loss in terms of dissipating induced currents at very low densities. [20b] Recently, monolithic 3D graphene‐based composite foams prepared by Gao and co‐workers exhibited ultralow percolation thresholds of 0.006 vol% . The skeleton‐assisted bicontinuous microstructure endowed the composite foam with a conductive graphene framework and a mechanically robust sponge‐like skeleton of melamine.…”

“…Graphene hybrid absorbers possess relatively larger qualified absorption bandwidths compared with those of EAMs based on RGO, but the graphene/magnetic hybrid absorbers have the disadvantages of poor temperature and corrosion tolerance. Monolithic 3D graphene‐based foams demonstrate wider qualified absorption bandwidths than those of other kinds of graphene‐based absorbers,[7h,11a,15a,20b,55] indicating the superiority of these highly porous and hierarchical structures of graphene. Nevertheless, their mechanical strengths are still a problem for their practical application.…”

“…By assembling graphene units into well‐designed hierarchical structures, such as sandwich‐like and porous structures, enhanced electromagnetic interactions for graphene absorbers or graphene‐based absorbers can be achieved. [9a,20] These interactions include giant cross‐linked electric loss networks, multiple internal reflections, scattering, capacitor‐like interactions, etc., that contribute to increasing the attenuation of incident electromagnetic waves. Meanwhile, benefiting from the 2D nanostructure of graphene, the absorbing component can be maintained at a relatively low level to facilitate the application of graphene‐based stealth materials in a greater number of fields.…”