Silica-Modified Ordered Mesoporous Carbon for Optimized Impedance-Matching Characteristic Enabling Lightweight and Effective Microwave Absorbers

Enhanced microwave absorption performance of Fe3Al flakes by optimizing the carbon nanotube coatings

Fe3Al is a good magnetic loss absorber for microwave absorption. However, due to the relatively high density and poor impedance matching ratio, the potential of Fe3Al cannot be fully released. Herein, a dielectric loss absorber of carbon nanotubes (CNTs) is coupled with Fe3Al to form Fe3Al/CNTs composite absorbers. CNTs are randomly tangled and coated on the surface of the Fe3Al flakes, forming a connecting conductive network. By carefully tuning the content of CNTs, the optimized Fe3Al/CNTs composite absorber with 1.5% of CNTs can combine both magnetic loss and dielectric loss mechanisms, thus achieving an impedance matching ratio close to 1 while keeping strong attenuation for enhanced microwave absorption. As a result, an effective absorption bandwidth (RL ≤ -10 dB) of 4.73 GHz at a thickness of 2 mm is achieved.

Enhancement of microwave absorption performance of porous carbon induced by Ce (CO3) OH

In recent years, electromagnetic pollution has become more and more serious, resulting in a very negative impact on people's health. Therefore, it is important to develop efficient microwave absorbers to reduce electromagnetic pollution. Here, we construct a novel absorbing material of the polymer gel-derived porous carbon decorated by rare earth compounds (Ce (CO₃) OH). When the thickness is 2.2 mm, the composite exhibits excellent microwave absorption performance with the optimal RL_min value and EAB reached up to -47.67 dB and 5.52 GHz, respectively, covering the Ku band. The high-efficiency microwave absorption is mainly attributed to the synergistic effect of dipole polarization, defect polarization and interfacial polarization. This work not only provides a new view for designing superior absorber materials, but also lay a foundation for their real applications.

Liquid metal derived MOF functionalized nanoarrays with ultra-wideband electromagnetic absorption

Low melting point liquid metal alloys are progressively utilized in different research fields due to their unique physicochemical properties. Among them, EGaIn is liquid at room temperature with an excellent solubility for reactive metal atoms such as Al. Combined with their characteristic flexible surface, large area and atomically flat interfaces, a library of two-dimensional materials can be generated. Liquid metal synthesis routes provide a highly reproducible thickness of nanosheets with fast, simple, scalable, inexpensive, high yield and non-toxic methods, especially for Al oxides and hydroxides. At the same time, Al-based heterojunction structure also shows a good application prospect in the field of electromagnetic wave absorption, therefore, the use of liquid metal synthesis methods to find the synthesis methods of Al-based layered double hydroxide (LDH) and its derivatives remains to be explored. In this work, EGaIn was used as an aluminum reservoir to prepare LDH and metal organic framework (MOFs) nano-arrays. The prepared CoAl-LDH@ZIF 67 can be transformed into CoAl-LDO@Co-C in the subsequent annealing process performed under nitrogen environments. Interestingly, a series of samples with different morphologies can be obtained by changing the synthesis parameters. The excellent electromagnetic wave interactions are fully characterized. It has an effective absorption bandwidth of 8.48 GHz at 2.6 mm. The findings demonstrated in this work pave the way for the application of lightwave and ductile complex nanoarrays obtained from liquid metals.

High Performance Microwave Absorption of Lightweight and Porous Non-carbon-based Polymeric Monoliths via Gel Emulsion Template

A special porous non-carbon-based microwave-absorbing materials are designed and synthesized by bonding di(prop-1-en-2-yl) ferrocene into porous polymeric monoliths made by gel-emulsions as templates. In this study, a sequence of porous...

Fabrication of Hollow Cube Dual-Semiconductor Ln2O3/MnO/C Nanocomposites with Excellent Microwave Absorption Performance

Metal-organic frameworks (MOFs) have been verified as ideal precursors for preparing highly effective microwave absorbers. However, it is still challenging to fabricate a thin, lightweight, and well-organized nanostructure with strong microwave absorption (MA) capability and wide absorption bandwidth. In this study, hollow cube dual-semiconductor Ln₂O₃/MnO/C (Ln = Nd, Gd, Er) nanocomposites, which are effective microwave absorbers, have been fabricated via one-step high-temperature carbonization of Ln-Mn-MOFs. The effect of band gap on the MA performance of various nanocomposites synthesized at the same carbonization temperature is investigated. Gd₂O₃/MnO/C-800 shows superior MA capacity with maximum reflection loss (RL_max) of -64.4 dB at 12.8 GHz and 1.86 mm-thickness. When the thickness is 1.44 mm, the RL value is obtained as -52.7 dB at 16.8 GHz, and at a low frequency of 4.36 GHz and thickness of 4.59 mm, the RL value reaches -56.4 dB. Further, the effect of temperature on the MA properties of Gd₂O₃/MnO/C is examined. The results reveal that Gd₂O₃/MnO/C-700 has an ultrahigh MA bandwidth of 6.6 GHz, covering the entire Ku bands at 2.09 mm-thickness. Overall, this work demonstrates a facile strategy to construct hollow, homogeneous ternary composites with outstanding MA performance.

Flexible, Ultralight, and Mechanically Robust Waterborne Polyurethane/Ti3C2Tx MXene/Nickel Ferrite Hybrid Aerogels for High-Performance Electromagnetic Interference Shielding

Flexible, ultralight, and mechanically robust electromagnetic interference (EMI) shielding materials are urgently demanded to manage the increasing electromagnetic radiation pollution, but it remains a great challenge to simultaneously achieve ultralight yet mechanically robust properties while retaining high-efficiency EMI shielding performance. Herein, we fabricate a novel waterborne polyurethane/Ti₃C₂T_x MXene/nickel ferrite (WPU/MXene/NiFe₂O₄) hybrid aerogel by constructing a strong chemical bonding interaction between an NCO-terminated WPU prepolymer and hydroxyl functionalized MXene nanosheets. The resultant aerogels exhibit remarkable lightweight and mechanical properties, particularly high compressive stress far exceeding that of other MXene-based and WPU-based porous materials. Furthermore, synergistic effects of the oriented porous architecture and the multiphase skeleton endow the hybrid aerogels with a high X-band EMI shielding effectiveness (SE) of 64.7 dB at a low density of ∼38.2 mg/cm³. The corresponding specific SE value achieves 1694-3124 dB·cm³/g, and the SSE/d is up to 15,620 dB·cm²/g, surpassing that of most reported EMI shielding materials. Importantly, this aerogel, with excellent electromagnetic radiation protection effects and shielding reliability, is highly promising for long-term and effective EMI shielding service in various application environments.

Synthesis and microwave absorption properties of coralloid core-shell structure NiS/Ni3S4@PPy@MoS2 nanowires

Herein, coralloid core-shell structure NiS/Ni₃S₄@PPy@MoS₂ nanowires were elaborately designed and successfully synthesized through a three-step route to obtain exceptional microwave absorption (MA) properties. Ni nanowires were first fabricated, and then used as the substrate to be coated with a layer of PPy. Ni chalcogenides were obtained by using Ni nanowire as sacrificial templates while growing MoS₂ nanorods by hydrothermal method. Both the one-dimensional (1D) core-shell structure and the coralloid surface generated by MoS₂ nanorods were beneficial for the attenuation of microwaves. After investigating the electromagnetic properties of different loading content absorbers (30 wt.%, 40 wt.% and 50 wt.%), it is found that the 50 wt.% loading absorber has the optimal MA performance. The minimum reflection loss (RL_min) value can reach -51.29 dB at 10.1 GHz with a thickness of 2.29 mm, and the corresponding effective absorption bandwidth (EAB, RL < -10 dB) can be up to 3.24 GHz. This research provides a reference for exploiting novel high-efficient 1D absorbers in the field of MA.

Modulating dielectric loss of mesoporous carbon fibers with radar cross section reduction performance via computer simulation technology

Mesoporous carbon fibers, a kind of light weight microwave absorbing material, are prepared by electrospinning, through which the pore structure and microwave absorbing properties are influenced by the addition of tetraethyl orthosilicate.

Extending effective microwave absorbing bandwidth of CoNi bimetallic alloy derived from binary hydroxides

Effectively broadening microwave absorbing frequency of pure magnetic substances remains a huge challenge. Herein, micro-perspective structures can be controlled through a calcination route. Satisfactorily, the composites prepared at the calcination temperature of 900 °C exhibit excellent microwave attenuation performance with a broad working frequency and appropriate paraffin filling ratio. Remarkably, the composites can reach an extremely high reflection loss (RL) value of - 49.79 dB, and the extended effective working frequency range (RL < - 10 dB) of 6.84 GHz can also be obtained. Superb magnetic loss, admirable dielectric loss, sufficient dipole polarization, as well as superior impedance matching should be band together for obtaining ideal microwave absorbers. The CoNi hydroxides derived bimatallic alloy composites were fabricated via a cost-effective and facile synthesis process, and this work aroused inspirations of designing high-performance microwave absorbers for mataining the sustainable development.