Permittivity-Regulating Strategy Enabling Superior Electromagnetic Wave Absorption of Lithium Aluminum Silicate/rGO Nanocomposites

Abstract

Lithium aluminum silicate (LAS) nanoparticles have been successfully loaded on graphene nanosheets by adding a silane coupling agent KH-550 by sol–gel process, hydrothermal reaction, and heat treatment process. By regulating the complex permittivity of reduced graphene oxide (rGO) by LAS nanoparticles and KH-550, LAS/rGO-KH-550 possesses excellent microwave absorption performance. The maximum reflection loss of LAS/rGO-KH-550 reaches −62.25 dB at 16.48 GHz with thickness of only 2.7 mm, and the widest bandwidth is up to 6.64 GHz below −10 dB. The LAS/rGO-KH-550 has effective absorption (99.9%) below −20 dB at all X and Ku bands (8–18 GHz). Also, the added quantity of composites in the paraffin matrix is only 20 wt %. The results demonstrate that the interfacial polarization, the Debye dipolar relaxation, the well-matched characteristic impedance, and the quarter-wavelength matching all play important roles in improving the microwave absorption properties of LAS/rGO-KH-550 nanocomposites. Consequently, the LAS/rGO-KH-550 nanocomposites can be readily applied as an ultra-wide-band, light weight, and ultra-high-performance microwave-absorbing material.

Enhanced Electromagnetic Absorption Properties of Commercial Ni/MWCNTs Composites by Adjusting Dielectric Properties

“…The increase is mainly determined by the interfacial polarization and enhanced conductivity resulted from the gradually establishment of a large conductive networks as the increasing filler loading (Figure S5), which is beneficial for electron transport and space charge polarization (Xu W. et al, 2018;Wu et al, 2019). Based on the free electron theory (Liang et al, 2016;Guan et al, 2018;Lu et al, 2019): σ = 2πf ε ′′ ε 0 , the frequency-dependent conductivity profiles were characterized in Figure S3. The conductivity values of 0.04-0.73 S/m are obtained for the Ni/MWCNTs composite with the loading of 1, 5, and 10 wt% in 2-18 GHz.…”

A review on the pursuit of an optimal microwave absorber

“…Unfortunately, the direct application of graphene in EM absorption is restricted due to its high εr value which causes impedance mismatch [25,26]. Efforts have been made to improve matching by mixing them with different magnetic fillers [27] and by using modified graphene (RGO).…”

Photocatalytic Application of Ag-Decorated CuS/BaTiO3 Composite Photocatalysts for Degrading RhB

“…These nanosized carbon and noble metal materials are particularly interesting and have received much attention due to their fascinating physical properties and potential technological applications in many fields. [17][18][19][20] Moreover, the excellent electron-trapping ability of these nanosized materials makes it easier for them to trap the photoproduced electrons, thus reducing the e À /h + recombination probability. These nanomaterials can also act as interesting co-catalysts.…”