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

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.

One-Dimensional Magnetic FeCoNi Alloy Toward Low-Frequency Electromagnetic Wave Absorption

Rational designing of one-dimensional(1D)magnetic alloy to facilitate electromagnetic(EM)wave attenuation capability in low-frequency(2-6 GHz)microwave absorption field is highly desired but remains a significant challenge.In this study,a composite EM wave absorber made of a FeCoNi medium-entropy alloy embedded in a 1D carbon matrix framework is rationally designed through an improved electrospinning method.The 1D-shaped FeCoNi alloy embedded composite demonstrates the high-density and continuous magnetic network using off-axis electronic holography technique,indicating the excellent magnetic loss ability under an external EM field.Then,the in-depth analysis shows that many factors,including 1D anisotropy and intrinsic physical features of the magnetic medium-entropy alloy,primarily contribute to the enhanced EM wave absorption performance.Therefore,the fabricated EM wave absorber shows an increasing effective absorption band of 1.3 GHz in the low-frequency electromagnetic field at an ultrathin thickness of 2 mm.Thus,this study opens up a new method for the design and preparation of high-performance 1D magnetic EM absorbers.

Silicon-coated fibrous network of carbon nanotube/iron towards stable and wideband electromagnetic wave absorption

Materials that can absorb electromagnetic(EM)wave have garnered increased attention in recent years due to their potential to mitigate the ever increasing environmental pollution by EM waves.Thanks to recent advances in micro/nanofabrication,a variety of magnetic metal-based EM absorbers have been reported.The design and synthesis of EM absorbers that exhibit efficient and wide-band absorption at small thicknesses,however,remains elusive.Here we report the design of fibrous nanostructures consisting of magnetic iron(Fe)nanoparticles and carbon nanotubes(CNTs),which exhibits a wide-band EM absorption(3.8 GHz)while maintain the thickness at 1.2 mm.In our work,we created a novel core-shell structure by immersing the highly fibrous CNT-Fe structure into solid-state silicon(SiO)matrix.Finally,the SiO-coated CNT-Fe structures exhibit good stability against air-induced oxidation and acid corrosion while maintaining high EM absorption.Overall,the results reported in this study present new avenues to absorb EM from ambient air.We believe that our work elevates the utility of EM absorbers to real-world applications such as anti-acid and oxidation ability.

Low-dimensional cobalt doped carbon composite towards wideband electromagnetic dissipation

Composites composed of a carbon matrix decorated with a metal or metal oxide derived from zeolitic imidazolate frameworks(ZIFs)have been widely applied as suitable electromagnetic wave absorbers due to their high porosity and controllable morphology.However,achieving ideal absorption performance remains a challenge owing to the inadequate conductivity and high density of the metal components.Therefore,a temperature-controlling treatment was employed for the bimetal ZIFs,and the corresponding derivatives exhibited an excellent dissipation ability with a minimum reflection loss value of−54.3 dB and an effective bandwidth of 7.0 GHz at a thickness of 2.4 mm,which resulted from the strong dipole polarization behavior.Furthermore,after successfully controlling the Zn/Co ratio,the attenuation capability was greatly enhanced at a thickness of 1.4 mm,with bandwidths of 13.0–18.0 GHz.Overall,this work provides an ameliorated strategy for microwave absorption performance of carbon-based materials.

An angle-insensitive electromagnetic absorber enabling a wideband absorption

Electromagnetic(EM)wave absorbers with wideband absorption capability are proposed as a strategy to mitigate environmental pollution by EM waves.However,designing an EM absorber with its performance capacity independent of the EM wave incident angle remains elusive to date.Resolving this challenge requires development of EM absorbers whose EM absorption performance is insensitive to the EM wave incident angle.Herein,we synthesized EM absorbers with a variety of structures with different symme-tries(including micro-/nanospheres,nanoflakes and nanotubes)to study the effect of the EM absorbers’structure and the EM wave incident angle on the EM absorption performance.Our analysis reveals that non-magnetic EM absorbers with spatially symmetric nanostructures exhibit excellent EM wave incident angle-insensitivity.Finally,we demonstrate that a class of non-magnetic EM absorbers made from bam-boo derived-carbon nanospheres exhibit EM incident angle-insensitivity and wideband EM absorption performance with an effective absorption band up to 3.5 GHz when the thickness is 1.4 mm,a signif-icant improvement from prior studies which used thicknesses as high as 3-4 mm for comparable EM absorption performance.