As electromagnetic absorbers with wide absorption bandwidth are highly pursued in the cutting-edge electronic and telecommunication industries, the traditional dielectric or magnetic bulky absorbers remain concerns of extending the effective absorption bandwidth. In this work, a dual-principle strategy has been proposed to make a better understanding of the impact of utilizing conductive absorption fillers coupled with implementing artificial structures design on the absorption performance. In the comparison based on the microscopic studies, the carbon nanotubes (CNTs)-based absorbers are confined to narrow operating bandwidth and relatively fixed response frequency range, which can not fulfill the ever-growing demands in the application. With subsequent macroscopic structure design based on the CNTs-based dielectric fillers, the artificial patterns show much more broadened absorption bandwidth, covering the majority of C-band, the whole X-band, and Ku-band, due to the tailored electromagnetic parameters and more reflections and scatterings. The results suggest that the combination of developing microscopic powder/bulky absorbers and macroscopic configuration design will fundamentally extend the effective operating bandwidth of microwave.

https://link.springer.com/content/pdf/10.1007/s12274-020-3208-8.pdf

From intrinsic dielectric loss to geometry patterns: Dual-principles strategy for ultrabroad band microwave absorption

Porous carbon materials have been widely reported on dealing with the electromagnetic (EM) wave interference. However, monotonous EM loss mechanism still performed an obstacle to achieve exceptional absorption. In this paper, a series of three-dimensional porous carbon·@PANI (polyaniline) composites were synthesized via facile roasting and subsequent coating process. The morphology, nanostructure and EM wave absorption properties of porous carbon@PANI (PC@PANI) were discussed in detail. Obviously, porous carbon derived from EDTA-2Na coated by PANI (PC@PANI-2) composites exhibited significantly enhanced EM wave absorption performance compared to pure porous carbon. The widest absorption bandwidth (RL

Morphology-control synthesis of polyaniline decorative porous carbon with remarkable electromagnetic wave absorption capabilities

Electromagnetic absorption materials: current progress and new frontiers

MXene-based accordion 2D hybrid structure with Co9S8/C/Ti3C2Tx as efficient electromagnetic wave absorber

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

Although advances in wireless technologies such as miniature and wearable electronics have improved the quality of our lives, the ubiquitous use of electronics comes at the expense of increased exposure to electromagnetic (EM) radiation. Up to date, extensive efforts have been made to develop high-performance EM absorbers based on synthetic materials. However, the design of an EM absorber with both exceptional EM dissipation ability and good environmental adaptability remains a substantial challenge. Here, we report the design of a class of carbon heterostructures via hierarchical assembly of graphitized lignocellulose derived from bamboo. Specifically, the assemblies of nanofibers and nanosheets behave as a nanometer-sized antenna, which results in an enhancement of the conductive loss. In addition, we show that the composition of cellulose and lignin in the precursor significantly influences the shape of the assembly and the formation of covalent bonds, which affect the dielectric response-ability and the surface hydrophobicity (the apparent contact angle of water can reach 135°). Finally, we demonstrate that the obtained carbon heterostructure maintains its wideband EM absorption with an effective absorption frequency ranging from 12.5 to 16.7 GHz under conditions that simulate the real-world environment, including exposure to rainwater with slightly acidic/alkaline pH values. Overall, the advances reported in this work provide new design principles for the synthesis of high-performance EM absorbers that can find practical applications in real-world environments.

Biomass-Derived Carbon Heterostructures Enable Environmentally Adaptive Wideband Electromagnetic Wave Absorbers.

https://www.techscience.com/jrm/v9n5/41556/pdf

Fabrication of Crack-Free Flattened Bamboo and Its Macro-/MicroMorphological and Mechanical Properties

Rational design of low-dimensional, core-shell nanocrystals with superior synergistic dimensional-interfacial effect is promising to address the growing electromagnetic (EM) pollution challenge. Particularly, the monodispersed and core/shell component-controllable nanocrystal is highly desirable but remains challenging. Herein, a monodispersed core-shell nanocrystal consisting of a magnetic iron-based core and graphitized carbon (g-C) shell is synthesized via the in-situ pyrolysis of bamboo-derived lignin modified Fe3O4 (Fe3O4-lignin). The component of core can be controllably manipulated by altering the amount of lignin and a variety of iron-based cores, such as Fe3O4/Fe3C, Fe3C/Fe, Fe3O4/Fe3C/Fe and so forth, can be obtained using this in-situ pyrolysis approach. The result revealed that the optimized sub-13-nm-sized Fe–C nanocrystal displayed an ultra-wide EM absorption range (8.4–18.0 GHz) and the minimum reflection loss (RLmin) value was even reached as low as −47.11 dB at 8.0 GHz. The correlation of component-structure-dielectric or magnetic loss was further well investigated to reveal the EM dissipation mechanism. This novel method for sub-13-nm-sized magnetic nanocrystals is of great significance for the synthesis and design of nanocrystals and the mechanism study shed new sights for future high-performance electromagnetic absorbers.

In-situ formation of low-dimensional, magnetic core-shell nanocrystal for electromagnetic dissipation

Regulating lignin content to obtain excellent bamboo-derived electromagnetic wave absorber with thermal stability

With the rapid growth of China’s economy and people’s high-level pursuit of life, eco-friendly materials are gradually used in home decoration, furniture and construction industries. Compared to wood, bamboo has its own advantages such as large strength, good toughness, and great abrasion resistance when it is applied as a material to structural engineering or home decor. However, bamboo also has several limitations, for example, a small diameter, a longitudinal difference in diameter, thin and hollow walls, and a disposition to corrosion and cracking. Therefore, there is an urgent need to develop a new efficient and high-value utilization technology of bamboo. “Bamboo flattening” is a kind of high-efficiency utilization technology adopted to construct flattened bamboo boards from bamboo tubes or pre-softened arc-shaped bamboo sheets. Prior to flattening, pretreatments are requested, including softening, outer layer removal, and inner layer removal. For the bamboo tubes, penetrating grooves are requested to be created which are supposed to be widened during the saturated steam heat treatment and are conducive for the tubes to enter into the flattening machine. Moreover, tapered, rectangular or “V”-shaped protrusions nails with uniform dispersions, or diamond-shaped line grooves with a width, depth and spacing of 1.5–2.0 mm, 2.0–4.0 mm and 5.0–8.0 mm are always created to release the generated internal stress during the flattening processes. For the arc-shaped bamboo slices, a non-notched flattening method is introduced with a machine equipped with the unfolding rolling component, the flattening component, and the reverse roller component. There are no grooves, nails or guide lines on the inside surface of the obtained bamboo board. It is worth mentioning that all boards obtained should be treated by cooling, shaping and drying. Bamboo flattening technology can increase the utilization rate of bamboo resource from the original 30–55 %, reduce the amount of adhesive by 30 %, and increase the added value by more than 20 %. Herein, the achievements in bamboo flattening technology based on published papers and patents are described, along with their underlying physicochemical mechanisms.

Qiuyi Wang

Papers

Biomass-Derived Carbon Heterostructures Enable Environmentally Adaptive Wideband Electromagnetic Wave Absorbers.

Fabrication of Crack-Free Flattened Bamboo and Its Macro-/MicroMorphological and Mechanical Properties

In-situ formation of low-dimensional, magnetic core-shell nanocrystal for electromagnetic dissipation

Regulating lignin content to obtain excellent bamboo-derived electromagnetic wave absorber with thermal stability

Bamboo flattening technique: a literature and patent review