Outstanding comprehensive performance versus facile synthesis: Constructing core and shell-interchangeable nanocomposites as microwave absorber

Noticeably enhanced microwave absorption performance via constructing molecular-level interpenetrating carbon network heterostructure

Microwave absorption properties of the nanocrystalline strontium ferrite (SrFe12O19) and iron (α-Fe) microfibers for single-layer and double-layer structures are investigated in a frequency range of 2 GHz–18 GHz. For the single-layer absorbers, the nanocrystalline SrFe12O19 microfibers show some microwave absorptions at 6 GHz–18 GHz, with a minimum reflection loss (RL) value of −11.9 dB at 14.1 GHz for a specimen thickness of 3.0 mm, while for the nanocrystalline α-Fe microfibers, their absorptions largely take place at 15 GHz–18 GHz with the RL value exceeding −10 dB, with a minimum RL value of about −24 dB at 17.5 GHz for a specimen thickness of 0.7 mm. For the double-layer absorber with an absorbing layer of α-Fe microfibers with a thickness of 0.7 mm and matching layer of SrFe12O19 microfibers with a thickness of 1.3 mm, the minimum RL value is about −63 dB at 16.4 GHz and the absorption band width is about 6.7 GHz ranging from 11.3 GHz to 18 GHz with the RL value exceeding −10 dB which covers the whole Ku-band (12.4 GHz–18 GHz) and 27% of X-band (8.2 GHz–12.4 GHz).

Microwave absorption materials are of great importance in various application nowadays. In this article, a new type of metal–organic framework (MOF)-based Fe/C@Co3O4 core–shell nanocomposites is introduced for microwave absorption coating applications, via a simple and low-cost fabrication process. The nanocomposites have been successfully synthesized via a controlled high-temperature treatment of a PB@Co(OH)2 precursor, which was prepared earlier by a solvent-thermal method. The nanocomposites have excellent microwave absorption properties, and the maximum reflection loss (RL) value and effective bandwidth (RL < − 10 dB) can be tuned by the fabrication parameters. The results show that the different nanostructures and electromagnetic properties of the Fe/C@Co3O4 nanocomposites can be obtained by the heat treatments with different temperatures. With an excellent attenuation performance and distinguished impedance matching properties, the nanocomposite processed by a heat treatment at 700 °C (ICCO-700) has the best microwave absorption results. The maximum RL value reaches − 58.5 dB at 4.57 GHz, which is a remarkable valley in the low frequency range, when the absorber thickness is 2.5 mm. The effective bandwidth can be as wide as 11.0 GHz, when the sample thickness is 5.0 mm, which covers three quarters of the S band, one half of the C band, one half of the X band and the whole Ku band.

A generalizable strategy for constructing ultralight three-dimensional hierarchical network heterostructure as high-efficient microwave absorber

The elevated levels of electromagnetic (EM) radiation released by electronic instruments, communication devices, and information processing technologies are becoming a major concern nowadays. Consequently, great effort has been made to develop unique nanomaterials to enhance the electromagnetic absorption properties of microwave-absorbing materials. These materials should have superior reflection loss (RL), thin thickness, wide absorption bandwidth, low density, and light weightiness. This article discusses the electromagnetic microwave absorption basic theory, the materials and the performance will be highlighted. The strategies scheme to enhance the absorption properties of microwave absorbing materials (MAMs) will be elaborated. Metal-based composites often exhibit high efficiency to fulfill coveted magnetic and dielectric characteristics. This review provides a brief presentation of the useful theory of some selected microwave absorbers of ferrites and composites of carbon-based materials. In addition, the classifications of microwave absorbers according to important parameters for the fundamental microwave absorption property of the substance are discussed. The effect of great potential application in microwave absorbing materials (MAMs) with thin thicknesses was also investigated. Furthermore, this paper provides a comprehensive review study on several microwave absorption materials and their fundamental mechanisms of microwave absorption, dielectric loss, magnetic loss, dielectric/magnetic loss coupling, absorption bandwidth, and the reflection loss (RL) values of nanomaterials. The electromagnetic and microwave absorption properties of sandwich absorbers by the single- and double-layer microwave absorber, are studied intensively.

Microwave absorption is a critical challenge with progression in electronics, where fine structural designing of absorbent materials plays an effective role in optimizing their microwave absorption properties. Here, we have developed Fe3O4@C (FC) and Fe-Fe3O4@C (FFC) hybrid nanorings via a hydrothermal method coupled with a chemical catalytic vapor deposition technique. FC and FFC hybrid nanorings have fine carbon coating while their size can easily be tunable in a certain range from 80-130 to 90-140 nm. The optimized FC and FFC hybrid nanorings bear minimum reflection loss (RL) values of -39.1 dB at 15.9 GHz and -32.9 dB at 17.1 GHz, respectively, whereas FFC shows an effective absorption bandwidth (RL values < -10 dB) ranged from 5.2 to 18 GHz. Such an enhanced microwave absorption performance of hybrid nanorings is mainly due to the suitable impedance characteristics, multilevel interfaces, and polarization features in nanorings. This work provides an approach to design hybrid materials having a complex structure to enhance the microwave absorption properties.

Nitrogen and sulfur co-doped graphene oxide (NS-GO) is obtained using a simple hydrothermal method using thiourea as nitrogen source and sulfur source, and then nitrogen and sulfur co-doped graphene/Fe3O4 (NS-rGO/Fe3O4) composite is synthesized by a solvent method. On this basis, nitrogen and sulfur co-doped graphene/Fe3O4/C nanocomposite (NS-rGO/Fe3O4/C) is obtained using a solvent method combined with a high temperature calcination process using pitch as carbon source. When the matching thickness is 2.7 mm, the NS-rGO/Fe3O4/C has a reflection loss peak at 10.56 GHz, the value of which is − 46.33 dB, and the effective absorption (RL ≤ − 10 dB) bandwidth of the nanocomposite is 5.04 GHz. Compared with NS-rGO/Fe3O4, the NS-rGO/Fe3O4/C shows higher reflection loss (RL) value, thinner matching thickness and wider effective absorption (RL ≤ − 10 dB) bandwidth. The presence of amorphous carbon regulates the dielectric parameters of the material and increases the interface of the material. Sulfur and nitrogen diatoms regulate the band gap of graphene, and the composite material has good impedance matching characteristics and multiple interface effects.

Hollow Ni/C microsphere@graphene foam with dual-spatial and porous structure on the microwave absorbing performance

Multi-dimensional ordered mesoporous carbon/silica@Ni composite with hierarchical nanostructure for strong and broadband microwave absorption

Increasing efforts have recently been devoted to the artificial design and function of nanostructures for their application prospects in catalysis, drug delivery, energy storage, and microwave absorption. With the advantages of natural abundance, low cost, and environment friendliness, a one-dimensional (1D) MnO2 nanowire (MW) is the representative dielectric-loss absorber for its special morphology and crystalline structure. However, its low reflection loss (RL) value due to its thin thickness limits its wide development and application in the microwave absorption field. In this work, artificially designed MnO2@AIR@C (MCs), namely, 1D hollow carbon nanotubes filled with nano-MnO2, were designed and synthesized. It is found that the RL value of the MC is almost lower than −10 dB. Furthermore, the RL value was able to achieve −18.9 dB with an effective bandwidth (−10 dB) of 5.84 GHz at 2.25 mm. Simultaneously, the dielectric and interfacial polarization became stronger while the impedance matching was much better than in the single MWs. Hence, the rational design and fabrication of micro-architecture are essential and MC has great potential to be an outstanding microwave absorber.

Boosted electromagnetic wave absorption performance from multiple loss mechanisms in flower-like Cu9S5/RGO composites

Polymer-blend-based nanocomposites incorporating carbon nanomaterials hold significant potential for microwave absorption materials (MAM) applications. This study investigates the microwave absorption response of hybrid nanocomposites composed of multiwalled carbon nanotubes (MWCNT) and nanographite, prepared using industrial-like melt-mixing masterbatch strategies in a polycarbonate/acrylonitrile-butadiene-styrene copolymer (PC/ABS) blend matrix with varying blend ratios (100/0, 80/20, 60/40, 50/50, 40/60, 20/80, and 0/100) and a constant filler content (2 wt % MWCNT and 2 wt % nanographite). Furthermore, the PC/ABS (40/60) blend-based nanocomposite was prepared with the addition of a compatibilizer, 5 wt % of maleic anhydride grafted ABS (ABS-g-MAH), to verify possible changes in morphology. Morphology, rheology, mechanical, electrical, and electromagnetic properties were correlated. From a morphological perspective, a preferential distribution of MWCNTs within the PC phase was observed, with the different blend ratios leading to a transition from a dispersed matrix morphology in 80/20 and 20/80 (PC/ABS) to cocontinuous morphologies in the intermediate blends (60/40, 50/50, and 40/60). The addition of ABS-g-MAH as a compatibilizer resulted in significant morphological refinement. Electromagnetic properties, evaluated using both X-band rectangular waveguide and broadband coaxial airline techniques, as well as electrical conductivity, were found to be strongly influenced by the varying morphologies. The nanocomposite PC/ABS/ABS-g-MAH with a thickness of 3.0 mm presented a Reflection Loss (RL) of -29.4 dB at 9.44 GHz, with a bandwidth of 3 GHz. Across the broadband spectrum, RL values below -10 dB were observed, including at lower frequencies around 3.70 GHz. These findings suggest that morphological tuning of the polymer matrix offers a promising pathway for optimizing microwave absorption in hybrid nanocomposites.

MOF-derived Co/CoO particles prepared by low temperature reduction for microwave absorption

Synergistically assembled nitrogen-doped reduced graphene oxide/multi-walled carbon nanotubes composite aerogels with superior electromagnetic wave absorption performance

Enhanced microwave absorption properties and mechanism of core/shell structured magnetic nanoparticles/carbon-based nanohybrids