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Cobalt doping-induced strong electromagnetic wave absorption in SiC nanowires
摘要： Understanding the electronic structure-property relationship in doped systems is a prerequisite to designing functional materials. We fabricated Co-doped SiC nanowires with different Co contents by a facile carbothermal reduction approach. The nanowires were characterized in terms of microstructure, electronic structure, and electromagnetic (EM) parameters to uncover the effect of Co dopants on enhancing the EM wave absorption ability. Microstructure analysis and density functional theory calculations verified that the doped Co species inhibited the formation of stacking faults and point defects and increased the conductivity of Co-doped SiC nanowires, which indicated the dominant role of conductivity in enhancing dielectric loss. The Co dopants also imparted the Co-doped SiC nanowires with distinct room-temperature ferromagnetic property, which led to enhanced magnetic loss and impedance matching. The induced synergism among SiC nanowires and Co dopants endowed Co-doped SiC nanowires with strong EM wave absorption ability. The minimum reflection loss of Co-doped SiC nanowires reaches (cid:1)50 dB, and the effective absorption bandwidth is 4.0 GHz with only 1.5 mm sample thickness. Thus, Co-doped SiC nanowires can be used as effective EM wave absorption materials. This study also provided a guideline for designing high-performance EM wave absorbers.
关键词： Dielectric loss,Doping,Density functional theory calculations,Electromagnetic wave absorption,Magnetic property
更新于2025-09-23 15:23:52
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Fabrication and electromagnetic wave absorption property of quartz ceramics with a gradient distribution of BaTiO3
摘要： Quartz ceramics with a uniform/gradient distribution of BaTiO3 (U/G–SO–BTO) are fabricated by cold pressing a powder blend with BTO followed by sintering and using a combined technique of spreading the powder blends with gradually increased BTO layer–by–layer and sintering. The electromagnetic wave absorption properties of these two ceramics are studied in detail. For U–SO–BTO samples, the primary electromagnetic re?ection is strong due to the aggravated impedance mismatch at their surfaces. The electromagnetic wave re?ectivity of U–SO–BTO could only reach ?7.0 dB when the sample thickness is 6 mm and the BTO content is 8.0 wt%, and it decreases slightly to ?8.1 dB when the sample thickness is increased to 10.0 mm and the BTO content is decreased to 5.0 wt% simultaneously. For G–SO–BTO samples, electromagnetic waves could enter with little re?ection due to the weak surface impedance mismatch, and the electromagnetic waves entering these samples could propagate forward while being absorbed gradually with little re?ection because of the weak impedance mismatch at the interfaces. The G–SO–BTO samples are promising excellent electromagnetic absorbing materials because their electromagnetic wave re?ectivity could reach a level lower than ?12.0 dB and could decrease further from –12.2 to ?13.1 dB as the layer thickness increases from 1.0 to 2.0 mm.
关键词： Impedance mismatch,Electromagnetic wave absorption,Quartz ceramics,Electromagnetic re?ection,Gradient distribution,BaTiO3
更新于2025-09-23 15:22:29
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[IEEE 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - Xuzhou (2018.7.21-2018.7.24)] 2018 Cross Strait Quad-Regional Radio Science and Wireless Technology Conference (CSQRWC) - The Design and Experimental Verification of Broadband Absorbing Structure Combined by A1<inf>2</inf>O<inf>3f</inf>/ Al<inf>2</inf>O<inf>3</inf>Compositesand Metamaterials
摘要： With the aim to design a particular electromagnetic (EM) wave absorbing structure for broadband frequency used at high temperature, a multi-layer structure was proposed by combing the dielectric materials and square patch metamaterial. The absorbing structure was fabricated by precursor infiltration and pyrolysis technique and screen printing process. The computational and experimental results showed that a maximum reflection loss could be lower than ?7dB at 2-18GHz with a total thickness of 9mm. This effective enhancement on EM wave absorption property was believed to be a consequence of multi-layer and resonance effect induced by combining the traditional EM absorbing materials with metamaterial structure.
关键词： Electromagnetic wave absorption properties,Computation,Ceramic matrix composites
更新于2025-09-23 15:22:29
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Reduced Graphene Oxide Aerogels with Uniformly Self-Assembled Polyaniline Nanosheets for Electromagnetic Absorption
摘要： Reduced Graphene Oxide (RGO)/polyaniline (PANI) composite aerogels (GPA) with uniformly distributed PANI nanosheets were prepared by a facile self-assembly way. The fabricated hybrids present a cross-linked three-dimensional(3D) porous network and RGO sheets were covered by PANI sheets with controlled content. The unique architecture efficiently reduced agglomeration of RGO and enhanced the conductive loss of the material to incident wave. Specifically, the GPA composite with 50 wt% PANI showed excellent electromagnetic wave absorption capacity, the largest reflection loss (RL) value reached -48 dB with fill loading of only 3% and the qualified bandwidth (RL ≤-10 dB) covered the entire Ku band (12-18 GHz). The study is expected to pave the way to prepare wide qualified bandwidth and lightweight graphene-based electromagnetic wave absorption hybrids with controlled microstructure.
关键词： conductive network,3D porous structure,electromagnetic wave absorption,self-assembly,light weight
更新于2025-09-23 15:21:01
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Strain Improving the Performance of a Flexible Monolayer MoS <sub/>2</sub> Photodetector
摘要： Electromagnetic wave absorbing foamed ceramics (FCs) with high closed porosity and gradient SiC distribution were prepared from the powder blend containing quartz, talc, CaCO3, Si3N4 and SiC by sintering at 1200 °C for 1 h in air. The retention in the temperature holding process of the continuous and gradual SiC distribution arising from the inward oxidation of SiC in the temperature rising process is the formation mechanism of the gradient SiC distribution in FCs. As to the FC prepared from the powder blend with 3 wt% of SiC, it shows the best comprehensive performance with low bulk density of 0.48 g/cm3 and relatively high compressive strength of 9.6 MPa, good thermal insulation performance for its high total porosity of 82%, good water resistance performance for its high closed porosity of 80%, and excellent electromagnetic wave absorption performance for its low mean re?ectivity of ?11.9 dB in the frequency range of 8.0–18.0 GHz and especially low minimum re?ectivity of ?14.2 dB at 12.7 GHz. More importantly, it is also an excellent high temperature electromagnetic wave absorbing material for its little increased mean re?ectivity of ?11.3 dB after heat treating at 1000 °C for 20 h in air.
关键词： Electromagnetic wave re?ectivity,High closed porosity,Electromagnetic wave absorption performance,Foamed ceramics,Gradient distribution
更新于2025-09-19 17:13:59
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Three-dimensional architectures assembled with branched metal nanoparticle-encapsulated nitrogen-doped carbon nanotube arrays for absorption of electromagnetic wave
摘要： Three-dimensional magnetic metal nanoparticle-encapsulated nitrogen-doped carbon nanotube arrays (3D M@NCNTS) are fabricated through a facile method. The unique 3D architectures have abundant defects, various N dopants, numerous interfaces, and void spaces. Benefitting from the advantages above, our designed 3D M@NCNTSs exhibit excellent electromagnetic wave absorption properties including strong attenuation abilities, thin thickness of absorber film, and low filler mass loading, superior to most of reported magnetic metal-based absorbers. Typically, the minimal reflection loss of the optimized 3D architecture is – 49.82 dB at a frequency of 7.92 GHz, and efficient absorption bandwidth is 4 GHz as the thickness of the absorber film is merely 2 mm. Furthermore, we also find that the dielectric losses of the 3D architectures can be tuned by the metal composition. Thus, the controllable electromagnetic wave absorption properties can be achieved. Our strategy here may be extended to synthesize other types of 3D architectures as high-performance electromagnetic wave absorbers.
关键词： 3D architecture,bimetal-based nanoparticle,electromagnetic wave absorption,N doping
更新于2025-09-12 10:27:22
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Light and flexible composite nanofibrous membranes for high-efficiency electromagnetic absorption in a broad frequency
摘要： With the fast advancement of up-to-date communication technologies, electromagnetic wave (EMW) absorption materials are widely required for various applications. However, it is still a big challenge to produce lightweight, flexible and high efficiency EMW absorption materials in a broad-ranging frequency. Herein, we designed to fabricate the magnetic and dielectric nanofibrous membranes which can be effectively used as EMW absorption materials by facile electrospinning process. The as-fabricated composite carbon nanofibers (CNFs), which combined the components of nickel, cobalt antioxidant nanoparticles and carbon nanotubes, exhibited outstanding magnetic, dielectric properties and strong absorption ability in a wide frequency range. These nanoparticles encapsulated in CNFs are extremely beneficial to the electrical conductivity of the composites through decreasing the contact loss within the CNFs by formation the metal-metal interfaces. Correspondingly, the RL value of -46.60 dB was reached at 4.88 GHz frequency range with a layer thickness of 5.5 mm for these mechanically light and flexible membranes. The enhanced absorption performance (<?10 dB) in the wide frequency band (4.16-18 GHz) can be achieved by selecting a suitable thickness of the material. Results demonstrate that the permittivity and permeability of developed samples have been largely improved due to the integrated interaction of all introduced components in the structure. The composite membranes are a promising candidate for scalable, lightweight and high performance EMW absorption materials in the frequency range from C band to Ku band (4?18 GHz).
关键词： Magnetic and dielectric properties,permeability,permittivity,carbon nanotubes,electromagnetic wave absorption
更新于2025-09-10 09:29:36
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Iron ions doping enhanced electromagnetic wave absorption properties of tin dioxide/reduced graphene oxide nanocomposites
摘要： Herein, the iron ions doped tin dioxide/reduced graphene oxide (Fe-doped SnO2/RGO) nanocomposites were fabricated by a facile one-step hydrothermal strategy. The structure, composition, micromorphology, and electromagnetic parameters of the obtained nanocomposites were systematically investigated by various analysis techniques. Results revealed that the doping of Fe3+ ion had notable effect on the structure and electromagnetic wave (EMW) absorption properties of SnO2/RGO nanocomposites. The as-prepared Fe-doped SnO2/RGO nanocomposites showed the minimum reflection loss (RLmin) of ?29.0 dB and effective absorption bandwidth (EAB, RL ≤ ?10 dB) of 2.7 GHz. Significantly, the dual-waveband absorption characteristic almost covering the C and Ku bands was observed. Besides, the possible EMW absorption mechanism was further proposed. Our results could be helpful for the designing and developing novel graphene-based nanocomposites as the high-performance EMW absorbers.
关键词： Electromagnetic wave absorption,Doping,Tin dioxide,Reduced graphene oxide,Hydrothermal
更新于2025-09-10 09:29:36
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Preparation and electromagnetic attenuation properties of MoS2–PANI composites: a promising broadband absorbing material
摘要： As an ideal electromagnetic (EM) wave absorber, it is prone to possess lightweight, thin matching thickness, broad absorption bandwidth and strong absorption performance. In this work, MoS2–PANI composites were prepared by situ chemical oxidative polymerization method, and the crystal structure, morphology, composition and EM properties were characterized. The microwave absorption properties of MoS2–PANI composites could be tuned by changing the PANI content to reach the best impedance match. The minimum reflection loss (RL) value of MoS2–PANI was ? 40.79 dB at 14.01 GHz with the thickness of 2.0 mm, and the maximum effective absorption bandwidth was 5.02 GHz ranging from 11.88 to 16.90 GHz with a thickness of 2.0 mm. Moreover, the RL value of MoS2–PANI composites could reach under ? 10 dB in a wide frequency range of 4.74–18 GHz with a thickness of 1.5–4.5 mm. In particular, the 3 mm wave attenuation properties of MoS2–PANI composites were investigated for the first time, and the maximum attenuation value reached 15.45 dB. As a result, MoS2–PANI composites are promising to be excellent EM wave absorption materials in broadband.
关键词： Electromagnetic wave absorption,Broadband absorbing material,MoS2–PANI composites,Chemical oxidative polymerization,Impedance match
更新于2025-09-10 09:29:36
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Metal-Organic Framework Derived Hierarchical Co/C@V2O3 Hollow Spheres as a Thin, Lightweight and High-Efficiency Electromagnetic Wave Absorber
摘要： Developing high-efficiency electromagnetic (EM) wave absorbing materials with light weight, thin thickness and wide absorption bandwidth is highly desirable for ever-developing electronic and telecommunication devices. Herein, hierarchical metal-organic framework (MOF)-derived Co/C@V2O3 hollow spheres were designed and synthesized through a facile hydrothermal, precipitation and pyrolysis method. The composite exhibits both excellent impedance matching and light weight due to the rational combination of hollow V2O3 spheres and porous Co/C. Additionally, multiple components enable a large dielectric and magnetic loss of the composite, giving rise to enhanced EM wave absorption performance with a maximum reflection loss (RL) of -40.1 dB and a broad effective absorption bandwidth (RL < -10 dB) of 4.64 GHz at a small thickness of 1.5 mm. This work provides insights into the design of hierarchical hollow and porous composites as a thin and lightweight EM wave absorbers with efficient absorption, which can also be extended to energy storage, catalysis and sensing.
关键词： Co/C@V2O3 composites,metal-organic framework,hierarchical hollow spheres,dielectric/magnetic composites,electromagnetic wave absorption
更新于2025-09-09 09:28:46