The microwave-absorption properties and mechanism of phenyl silicone rubber/CIPs/graphene composites after thermal-aging in an elevated temperature

Abstract

Recently, the application and development of flexible microwave-absorption composites based on silicone rubber have gradually become a research hot spot. In this study, methyl vinyl phenyl silicone rubber (MPVQ)/carbonyl iron particles (CIPs)/graphene (GR) composites were prepared by mechanical blending, and the effects of thermal-ageing temperature on the microwave-absorption properties of the composites were investigated. The mechanism of the thermal-ageing temperature’s effects on microwave-absorption behaviour was identified. The results show that unaged composites have superior microwave-absorption properties, with a minimum reflection loss (RLmin) of − 87.73 dB, a lowest thickness of 1.46 mm, and an effective absorption bandwidth (EAB, RL < − 10 dB) reaching 5.8 GHz (9.9–15.7 GHz). With ageing at 240 °C for 24 h, the RLmin at a frequency of 5.48 GHz is − 45.55 dB with a thickness of 2.55 mm, and the EAB value reaches 2 GHz (range 4.6–6.6 GHz). In the thermal-ageing process, a crosslinking reaction occurs in MPVQ with an increase in crosslinking density from 5.88 × 10−5 mol g−1 (unaged) to 4.69 × 10−4 mol g−1 (aged at 240 °C). Simultaneously, thermal degradation of the composites leads to a reduction in the rubber concentration. In addition, a small amount of CIPs are oxidized to Fe3O4, and the remaining CIPs aggregate to generate more electrically conductive pathways. Consequently, the dielectric loss of the composites will be significantly improved, resulting in poor impedance matching. The microwave-absorption properties of the composites gradually decrease with increasing thermal-ageing temperature from 200 to 240 °C.

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

“…The occurrence of polar organic ligands and structural defects in the milled materials at high energy are other absorbing mechanisms that may help obtain a superior attenuation. , The two groups alter in the electrical charge distribution of the absorbing material and lead to the formation of scattering centers, undergoing interfacial polarization, dipolar polarization, and/or associated relaxation phenomena when the EM wave contacts them. ,, The nature of the organic ligands and the oxidation state evolution of the milled carbon is studied by IRAS (Figure a) and optical absorbance (Figure b) measurements in the transmission mode.…”

“…The minimum value found is −87.73 dB obtained for carbonyl iron particles [50 vol % + graphene (0.8 wt %) embedded in Epilox (resin)]. 17 In particular, that result is very interesting from the point of view of technological applicability, as well as all the strategies carried out to obtain values higher than |−60 dB|. However, only a V f,TOTAL of 1.67% (V f,MWs = 0.37%, V f,DFLGMs = 1.30%) with an RL min of −53.08 dB is employed in this work, and a frequency tunability is obtained by varying the V f,MWs , maintaining similar attenuation values above |−44.06| dB (composite MW− DFLGM-1).…”

“…Numerous powerful microwave absorbing composite designs and fabrication strategies are available, including Fe 3 O 4 @N-doped carbon nanochains, carbonyl iron particles + graphene, dumbbell-like Fe 3 O 4 @N-doped carbon@2H/1T-MoS 2 , and trimetallic FeCoNi@C nanocomposite hollow spheres, in which the minimum reflection loss coefficient (RL min ) is below −60 dB with a filling content of at least 20% and thicknesses in the order of millimeters. At those percentages, large changes in permittivity and permeability are obtained, due to both dielectric and magnetic losses. − It is worth mentioning that there are other parameters to be adjusted as the matching thickness and impedance matching to determine the optimal RL min conditions at a given frequency located in the GHz range . However, those parameters can become very restrictive and limiting, which could be counteractive in terms of multifunctionality, frequency tunability, and applicability to any electronic system or device.…”

Oleaster seed-derived activated carbon/ferrite nanocomposite for microwave absorption in the X-band range

“…Carbon is useful for forming conductive paths. The ε and μ values of the sample show oscillation, and the resonance peak appears in the frequency range because more holes and defects (Yan et al, 2022). Optimal impedance matching occurs where the relative complex permittivity and permeability are close enough and have an appropriate paradigm.…”

Radar Absorbing Properties of Barium Hexaferrite Accompanying with Cu Powders in Polymer Composite Coatings

“…This means that their electromagnetic waves are absorbed by electrons in the metal or propagated back in the same direction. At the same time, some of its electromagnetic energy is lost as heat [19][20][21].…”