Microwave absorption and mechanical properties of integrated glass-carbon hybrid composites: Co-design of weaving mode and frequency-selective surface for X-band applications

Effects of oxygen vacancy defect on microwave pyrolysis of biomass to produce high-quality syngas and bio-oil: Microwave absorption and in-situ catalytic.

Achieving broadband microwave absorption and excellent mechanical properties via constructing 3D reduced graphene oxide networks in glass fiber/epoxy resin composites

Honeycomb sandwich (HS) structures are important lightweight and load-bearing materials used in the aerospace industry. In this study, novel honeycomb-hollow pyramid sandwich (HPS) structures were manufactured with the help of fused deposition modeling techniques using PLA and PLA/CNT filaments. The microwave and mechanical energy absorption properties of the HPS structures with different geometry parameters were studied. Compared with the HS structure, the HPS structure enhanced both microwave absorption and mechanical properties. The HPS structures possessed both broadband and wide-angle microwave absorption characteristics. Their reflection loss at 8-18 GHz for incident angles of up to 45° was less than -10 dB. As the thickness of the hollow pyramid increased from 1.00 mm to 5.00 mm, the compressive strength of the HPS structure increased from 4.8 MPa to 12.5 MPa, while mechanical energy absorption per volume increased from 2639 KJ/m3 to 5598 KJ/m3. The microwave absorption and compressive behaviors of the HPS structures were studied.

Lightweight nitrogen-doped ordered mesoporous carbon (NOMC) with high specific surface area and pore volume have been prepared through self-assembly and subsequent heat treatment route. The spherical NOMC particles are decorated with CoFe2O4 nanoparticles via coprecipitation method to enhance their microwave absorption property. The electromagnetic parameters of the NOMC and CoFe2O4/NOMC composites are measured and the microwave reflection loss properties are evaluated in the frequency range of 0.5–18 GHz. The results show that both the real part and imaginary part of permittivity of NOMC totally decline and the real part of permeability increases with the introduction of ferrite. However, the negative values of the imaginary part of the complex permeability appear for the CoFe2O4/NOMC composites, which may be caused by enhanced eddy current effect due to the introduction of ferrite. The reflection loss results exhibit that the CoFe2O4/NOMC composites have excellent microwave absorption performances. The ...

Designing multifunctional integrated composites is a viable approach to meet the diverse requirements in complex environments. By incorporating microwave absorption capability into mullite insulation tiles, it becomes feasible to simultaneously achieve both microwave absorption and thermal insulation effectiveness within a single system, thereby enhancing the materials' adaptability and efficiency. In this study, mullite insulation tiles were utilized as support structures, and polymer‐derived SiCN (PDC‐SiCN) ceramic aerogel with microwave absorption properties was loaded onto the mullite through the high‐pressure impregnation‐pyrolysis technique to fabricate SiCN/mullite insulation tile composite (SM composite). With the inclusion of SiCN aerogel, the SM composite, after one impregnation‐pyrolysis cycle, exhibited exceptional microwave absorption performance, whose minimum reflection loss was −49.24 dB (99.99% microwave absorption) at 15.84 GHz, and effective absorption bandwidth was 9.23 GHz. Additionally, due to the synergistic effect between mullite and SiCN aerogel, the SM composite demonstrated significantly reduced thermal conductivity in 25–1000°C (.064–.086 W·m −1 ·K −1 ), much lower than that of mullite insulation tiles (.076–.156 W·m −1 ·K −1 ). The superior combination of excellent microwave absorption and low thermal conductivity properties makes the SM composite an ideal stealth/thermal insulation integrated material in a thermal protection system operating in a high‐temperature environment.

Efficient low-frequency microwave absorption and solar evaporation properties of γ-Fe2O3 nanocubes/graphene composites

Three-phase composites of poly(vinylidene fluoride)-BaFe12O19-reduced graphene oxide (PVDF–BFO-RGO) were synthesized by a facile wet chemical method and hot-pressing approach. The phase structure, topography of the hybrid materials were characterized by X-ray diffraction, scanning electron microscopy, and Raman spectra. Influence of RGO on their electromagnetic properties was investigated. Especially, improved microwave absorption and electromagnetic properties of BaFe12O19–PVDF composites by incorporating RGO were obtained and studied. The PVDF/BFO/RGO sample with m(RGO):m(BFO) = 5:100 shows the best microwave absorption properties with a minimum RL = −32 dB at 11 GHz and with the bandwidth less than −20 dB from 9.6 to 12.8 GHz. The composites were believed to have potential applications as the microwave absorber.

ABSTRACTPolymeric composites filled with magnetic absorbents have been used extensively as microwave absorbing materials. However, their high filler content obstructed the application. In order to optimize the filler content and further improve the microwave absorbing properties, alternating multilayer carbonyl iron powder (CIP)/poly(vinyl chloride) (PVC) composites were designed and prepared by stacking neat PVC and CIP filled PVC alternately. The microwave absorbing properties were theoretically calculated by the transmission line theory and experimentally measured by the arch method, respectively. The experimental results were consistent with the calculated ones, which demonstrated that the alternating multilayer structure design can significantly improve the microwave absorbing property without increasing the filler content. The consistent results also demonstrated that the reflection loss (RL) of the multilayer composites was strongly dependent on the layer number and layer arranging sequence. The minimumRL(RL‐min) and effective bandwidth were exponentially dependent on the layer number. And the dependencies of theRL‐min and effective bandwidth on layer number exhibited a “regularity reversal” phenomenon when different layers faced to the incident wave. The mechanical property test showed that the alternating multilayer composites possessed enhanced tensile strength and elongation at break as the layer number increased. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci.2018,135, 45846.

The Mg2+ and Ti4+ ions substituted M-type Ca(MgTi)xFe12−2xO19 (x = 0, 0.3, 0.6, 0.9) hexagonal ferrites (x = 0, 0.3, 0.6, 0.9) were synthesized by the citrate sol–gel method. The microwave absorption, crystal structure, magnetic and morphology of the nanopowders were investigated with vector network analyzer, X-ray diffraction (XRD), vibrating sample magnetometer and transmission electron microscopy. XRD results verified the formation of M-type hexagonal structures. The particle size estimated by the Scherer formula. Results illustrated particles size is less 100 nm. The hysteresis loops showed saturation magnetization increased from 72 to 98 kA m−1 while coercive force decreased from 1710 to 428 Oe with Mg–Ti content. Microwave absorption properties measured by the standing-wave-ratio method in the Ku band frequency. The observations showed that Ca(MgTi)xFe12−2xO19 nanopowders have extraordinary microwave absorption properties. It is observed bandwidth 6.3 gigahertz (12.5–18.8 GHz with respect to − 15 dB reflection loss) for composite x = 0.6. Furthermore, the results showed a minimum reflection loss − 31.5 and − 39 dB for composites 0.6 and 0.9, respectively. It should be pointed out thickness of the composites are 1.9 mm.

In this present work, we offer the design of good, wideband microwave absorption materials (MAMs) based on CB/Mn0.1Ni0.5Zn0.4Fe2O4 (carbon black/MnNiZn ferrite). The ferrite is prepared by a self-combustion method using sucrose as fuel. The chemical is utilized for the synthesis of carbon black nanopowder is carbon black powder (2–8 μm). Then, the operation is continued via mixing carbon black and MnNiZn ferrite through the grinding balls. Four various weight ratios of CB/Mn0.1Ni0.5Zn0.4Fe2O4 (1:0, 1:1, 2:1, and 3:1) with various thicknesses (2–4–6 mm) are prepared. X-ray diffractometry and FTIR spectroscopy are utilized in order to characterize samples. The morphology of the powders is investigated by SEM. The electromagnetic interference (EMI) shielding and microwave absorption properties are measured in the frequency band of 8.8–12 GHz to accomplish the practical characterization. The MAMs show broad bandwidths under -10 dB in the range of 0.3–3.2 GHz and reasonable surface density in the range of 2.91–3.66 kg/m2 with a weight ratio within a paraffin matrix of 40% w/w. The MAM shows a minimal reflection loss of -18.3 dB at the frequency of 11.4 GHz for the thickness of 2 mm. The maximum shielding efficiency is 18.5 dB at 11.5 GHz for 2 mm thickness of the CB/F-21 nanocomposite sample.

Surface functionalization of carbonyl iron with aluminum phosphate coating toward enhanced anti-oxidative ability and microwave absorption properties

The porous nickel film with agglomerate nanoparticles and 1.5~2.0 μm in thickness was used to enhance microwave absorption and ferromagnetic properties of nanowire-like copper oxide-covered carbon fiber composites. Firstly, the porous nickel film/carbon fiber composites were prepared by plating route, when the current intensity was 120 mA for 30 min (sample S1) and 40 min (sample S2), respectively. Then, the copper oxide/porous nickel/carbon fiber (CNCF1 and CNCF2) composites were synthetized by electroless deposition copper and thermal oxidation route (the sample S1 and sample S2), respectively. The microwave absorption properties of composites were investigated over frequency range, 1-18 GHz. The results showed that the strongest reflectivity loss (RL) values of CuO/carbon fiber (CCF) and CNCF1-2 composites were -25.93 dB at 3.59 GHz with a matching thickness layer of 2.4 mm, -27.87 dB at 6.67 GHz with a matching thickness layer of 2.5 mm, and -54.82 dB at 9.23 GHz with a matching thickness layer of 2.192 mm. When the RL values of CCF and CNCF1-2 composites were lower than -10 dB, the absorption frequency range from 8.12 to 9.64 GHz (1.52 GHz in absorption bandwidths, 1.5 mm in thickness), 6.45 to 8.81 GHz (2.36 GHz in absorption bandwidths, 2.4 mm in thickness) and 10.51 to 14.35 GHz (3.84 GHz in absorption bandwidths, 1.8 mm in thickness), respectively. Therefore, the CNCF2 composites showed more excellent microwave absorption properties, and are potential microwave absorption candidates for making a thin thickness, strong absorption and wide-frequency.

Biomass-derived graphene-like porous carbon nanosheets towards ultralight microwave absorption and excellent thermal infrared properties

Microwave absorbing materials plays a crucial role in reducing pollution created due to the electromagnetic radiation and several defence applications. This paper reports about the microwave absorption property of combined form of Carbon Nano fibres (CNF) and Ferric Oxide Nano powder (Fe2O3). Ferric Oxide Nano powder is deposited on the fibres of CNF using hydrothermal autoclave method. The samples of CNF- Ferric Oxide Nano powder with different weight percentages is fabricated and the microstructure and microwave absorbing properties are studied. By varying the amount of CNF and Ferric Oxide Nano powder the microwave absorbing and electromagnetic properties are modulated. For investigating the synergistic effects between CNF and ferric powders, different mass ratios of CNF to ferric oxide Nano powder have been synthesized and helped in enhancement of the effect between the magnetic loss and dielectric loss to achieve high microwave absorption. These results might be inspiration for the future to create microwave absorbing materials which are light weight.

The SiC fibers are essential for designing microwave absorption and mechanical properties of multifunctional composites. In this study, SiCf/SiC composites were fabricated by SLF, KD-II, and KD-S SiC fibers. The SLF fibers are composed by amorphous SiOC. The KD-II and KD-S fibers reveal higher crystallizations. The conductivity of SLF, KD-II, and KD-S SiC fibers are 0.0127, 1.184, and 0.1316 S/cm, respectively. The flexural strength of SLF, KD-II, and KD-S SiCf/SiC composites are 147.77, 322.57, and 248.16 MPa, respectively. With the thickness of 2.3 mm, the microwave absorption property of SLF SiCf/SiC composites is over − 25 dB in X band. Additionally, the effective absorption bandwidth (EAB) of SLF SiCf/SiC composites below − 10 dB reaches 3.72 GHz with the thickness of 2.7 mm. In contrast, the KD-II SiCf/SiC composites only reach − 3.6 dB in X band when the thickness varies from 2 to 2.9 mm. With the thickness of 2 mm, the microwave absorption property of KD-S SiCf/SiC composites is over − 9 dB. With the thickness of 2.2 mm, the EAB of KD-S SiCf/SiC composites below − 7 dB reaches 4.12 GHz. The mechanisms of mechanical, microwave absorption, and penitential applications for SiCf/SiC composites are also discussed.