Generation of Defective Few-Layered Graphene Mesostructures by High-Energy Ball Milling and Their Combination with FeSiCuNbB Microwires for Reinforcing Microwave Absorbing Properties

Abstract

Defective few-layered graphene mesostructures (DFLGMs) are produced from graphite flakes by high-energy milling processes. We obtain an accurate control of the generated mesostructures, as well as of the amount and classification of the structural defects formed, providing a functional material for microwave absorption purposes. Working under far-field conditions, competitive values of minimum reflection loss coefficient (RLmin) = −21.76 dB and EAB = 4.77 dB are achieved when DFLGMs are immersed in paints at a low volume fraction (1.95%). One step forward is developed by combining them with the excellent absorption behavior that offers amorphous Fe73.5Si13.5B9Cu1Nb microwires (MWs), varying their filling contents, which are below 3%. We obtain a RLmin improvement of 47% (−53.08 dB) and an EAB enhancement of 137% (4 dB) compared to those obtained by MW-based paints. Furthermore, a f min tunability is demonstrated, maintaining similar RLmin and EAB values, irrespective of an ideal matching thickness. In this scenario, the Maxwell-Garnet standard model is valid, and dielectric losses mainly come from multiple reflections, interfacial and dielectric polarizations, which greatly boost the microwave attenuation of MWs. The present concept can remarkably enhance not only the MW attenuation but can also apply to other microwave absorption architectures of technological interest by adding low quantities of DFLGMs.

Flexible, Stretchable, and Lightweight Hierarchical Carbon-Nanotube-Decorated Carbon Fiber Structures for Microwave Absorption

“…The reflection was measured from the simulation at different thicknesses, which are shown in Figure 8. The shifting of the minimum R L peak toward the lower frequency is observed when the nanocomposite thickness increases from 2.1 to 2.5 mm, which can be understood by the eq 3 of the quarter wavelength 20,23,26,61,65…”

“…The reflection was measured from the simulation at different thicknesses, which are shown in Figure . The shifting of the minimum R L peak toward the lower frequency is observed when the nanocomposite thickness increases from 2.1 to 2.5 mm, which can be understood by the eq of the quarter wavelength ,,,, t normalm = italicnc 4 f m ε normalr μ normalr 0.25em ( n = 1 , 3 , 5 , ··· ) where ε r and μ r are permittivity and permeability, respectively, matching thickness and frequency are t m and f m , respectively, and c is the speed of light. The best result is obtained for CFCNT0.35 at a 2.4 mm thickness, showing a minimum R L value of 52.53 dB covering 100% X band below 10 dB, i.e., an EAB of 4.2 GHz varying from 8.2 to 12.4 GHz and the EAB 20 dB bandwidth of 1.93 GHz is observed from the frequency ranging from 8.58 to 10.51 GHz (∼46% of the X band).…”

Graphene in rubber formulations: a comprehensive review and performance optimization insights

“…However, due to its hydrophobic surface 6 and lack of functionalities, 7 pristine graphene tends to agglomerate in rubber matrices, 8,9 which can have adverse effects on the properties of rubber nanocomposites. 10,11 To address this issue, various intense agitation techniques such as mechanical blending, 12,13 mechanical grinding, 14,15 and sonication 54 have been used to modify graphene and disrupt the π-π interactions between graphene sheets. Moreover, graphene has been integrated with other materials, such as carbon nanotubes, 18,19 metals, 20 nanocellulose, 21 and nanocrystals, 22 to form hybrid fillers that improve its dispersibility in rubber matrices and create new value in rubber nanocomposites.…”