Synthesis of Hollow Rod-like Hierarchical Structures Assembled by CoFe/C Nanosheets for Enhanced Microwave Absorption

2021 ◽  
Author(s):  
Susu Bao ◽  
Zhijia Song ◽  
Runjing Mao ◽  
Yue Li ◽  
Shuhong Zhang ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Synergistic Effects ◽  
Hierarchical Structures ◽  
Interfacial Polarization ◽  
Ferromagnetic Metal ◽  
Hybrid Structures

Composites of ferromagnetic metal and carbon with hierarchical structures are favoured for strengthening microwave absorption capability due to synergistic effects of hybrid structures and enhanced interfacial polarization. However, it remains...

scholarly journals Facile Synthesis of GNPs@NixSy@MoS2 Composites with Hierarchical Structures for Microwave Absorption

Nanomaterials ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1403 ◽  
Author(s):  
Wenfeng Zhu ◽  
Li Zhang ◽  
Weidong Zhang ◽  
Fan Zhang ◽  
Zhao Li ◽  
...  
Keyword(s):  
Magnetic Properties ◽  
Microwave Absorption ◽  
Reflection Loss ◽  
Skin Effect ◽  
Hydrothermal Reaction ◽  
Synergistic Effects ◽  
Hierarchical Structures ◽  
Dielectric Losses ◽  
Facile Synthesis ◽  
Molar Ratios

Graphene-based powder absorbers have been used to attain excellent microwave absorption. However, it is not clear if inferior microwave absorption by pure graphene materials can be attributed to impedance mismatching or inadequate attenuation capability. In this comparative study, we focus on these aspects. Graphene nanoplatelets (GNPs) multi-component composites (GNPs@NixSy@MoS2) were prepared by hydrothermal reaction with different S and Mo molar ratios. The morphologies, phase crystals, elemental composition, and magnetic properties of the composites were also analyzed. In addition, microwave absorption of the as-prepared samples was investigated and it revealed that the impedance mismatching could be responsible for inferior microwave absorption; higher conductivity can lead to skin effect that inhibits the further incidence of microwaves into the absorbers. Furthermore, the optimum reflection loss (RL) of GNPs@NixSy@MoS2-2 can reach −43.3 dB at a thickness of 2.2 mm and the corresponding bandwidth with effective attenuation (RL < −10 dB) of up to 3.6 GHz (from 7.0 to 10.6 GHz). Compared with the GNPs, the enhanced microwave absorption can be assigned to the synergistic effects of conductive and dielectric losses.

Carbon encapsulated nanoscale iron/iron-carbide/graphite particles for EMI shielding and microwave absorption

2017 ◽  
Vol 19 (34) ◽  
pp. 23268-23279 ◽  
Author(s):  
Rajeev Kumar ◽  
Harish Kumar Choudhary ◽  
Shital Patangrao Pawar ◽  
Suryasarathi Bose ◽  
Balaram Sahoo
Keyword(s):  
Microwave Absorption ◽  
Multiple Scattering ◽  
Metallic Iron ◽  
Iron Carbide ◽  
Interfacial Polarization ◽  
Emi Shielding ◽  
Graphite Particles ◽  
Iron Iron

Dispersed metallic-iron and dielectric-Fe3C nanoparticles in carbon globules facilitate multiple scattering and absorption of EM-waves through large interfacial polarization.

The synergistic effects of carbon coating and micropore structure on the microwave absorption properties of Co/CoO nanoparticles

2016 ◽  
Vol 18 (44) ◽  
pp. 30507-30514 ◽  
Author(s):  
Xiubo Xie ◽  
Yu Pang ◽  
Hiroaki Kikuchi ◽  
Tong Liu
Keyword(s):  
Microwave Absorption ◽  
Vapor Deposition ◽  
Carbon Coating ◽  
Synergistic Effects ◽  
Impedance Matching ◽  
Chemical Vapor ◽  
Absorption Properties ◽  
Microwave Absorption Properties ◽  
Micropore Structure ◽  
Coo Nanoparticles

Microporous Co/CoO/C nanoparticles prepared by combining chemical dealloying and chemical vapor deposition methods exhibited high microwave absorption properties due to the synergistic effects of the carbon coating and the micropore structure on the impedance matching of the absorber.

Dual-Interfacial Polarization Enhancement to Design Tunable Microwave Absorption Nanofibers of SiC@C@PPy

2020 ◽  
Vol 2 (6) ◽  
pp. 1505-1513 ◽  
Author(s):  
Chang Xu ◽  
Fan Wu ◽  
Liqun Duan ◽  
Ziming Xiong ◽  
Yilu Xia ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Interfacial Polarization ◽  
Tunable Microwave

scholarly journals Investigation of Microwave Absorption Performance of CoFe2O4/NiFe2O4/Carbon Fiber Composite Coated with Polypyrrole in X-Band Frequency

Micromachines ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 809
Author(s):  
Rozhin Sadeghi ◽  
Abbas Sharifi ◽  
Marta Orlowska ◽  
Isabelle Huynen
Keyword(s):  
Carbon Fiber ◽  
Microwave Absorption ◽  
In Situ Polymerization ◽  
Fiber Composite ◽  
Sol Gel ◽  
Interfacial Polarization ◽  
Microwave Absorber ◽  
Carbon Fiber Composite ◽  
Band Frequency ◽  
5 Ghz

The current research reports the preparation of a microwave absorber containing CoFe2O4/NiFe2O4/Carbon fiber (H/S/CF) coated with polypyrrole polymer (PPy@H/S/CF) through sol-gel and in-situ polymerization processes. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), vibrating sample magnetometer (VSM), and a vector network analyzer (VNA) are utilized to evaluate the features of the prepared composite. The microstructure analysis results revealed carbon fibers well decorated with submicron-size particles having hard/soft magnetic phases and thoroughly coated with polymer. The paraffin-based microwave absorber sample filled with 45 wt.% of PPy@H/S/CF has simultaneously both magnetic and dielectric losses in the 8.2–12.4  GHz frequency range. The absorber is used in a Salisbury screen configuration aiming at reducing the radar cross-section of objects. A minimum reflection loss of −55  dB at 10.6 GHz frequency with 5 GHz bandwidth is obtained for the sample with a 2  mm thickness. Different mechanisms, such as interfacial polarization, ferromagnetic resonance, and electron hopping, are the main factors for achieving such an appropriate microwave absorption. These results suggest that the PPy@H/S/CF composite is an ideal candidate for microwave absorption applications requiring high performance and low thickness.

scholarly journals Enhanced Microwave Absorption and Electromagnetic Properties of Si-Modified rGO@Fe3O4/PVDF-co-HFP Composites

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 933 ◽  
Author(s):  
Yuexuan Li ◽  
Yugang Duan ◽  
Chengmeng Wang
Keyword(s):  
Microwave Absorption ◽  
Reflection Loss ◽  
High Efficiency ◽  
Vinylidene Fluoride ◽  
Synergistic Effects ◽  
Electromagnetic Properties ◽  
Absorption Mechanism ◽  
Simple Method ◽  
Absorption Frequency ◽  
Enhanced Absorption

Graphene has been regarded as one of the most promising two-dimensional nanomaterials. Even so, graphene was still faced with several key issues such as impedance mismatching and narrow bandwidth, which have hindered the practical applications of graphene-based nanocomposites in the field of microwave absorption materials. Herein, a series of Si-modified rGO@Fe3O4 composites were investigated and fabricated by a simple method. On one hand, the degree of defects in graphene carbon could be tuned by different silane coupling reagents, which were beneficial to enhancing the dielectric loss. On the other hand, the spherical Fe3O4 nanoparticles provided the magnetic loss resonance, which contributed to controlling the impedance matching. Subsequently, the electromagnetic absorption (EMA) properties of Si-modified rGO@Fe3O4 composites with poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-co-HFP) were investigated in this work. As a result, the Si(2)-rGO@Fe3O4/PVDF-co-HFP composite exhibited the excellent EMA performance in the range of 2–18 GHz. The maximum reflection loss (RLmax) reached −32.1 dB at 3.68 GHz at the thickness of 7 mm and the effective absorption frequency bandwidth for reflection loss (RL) below −10 dB was 4.8 GHz at the thickness of 2 mm. Furthermore, the enhanced absorption mechanism revealed that the high-efficiency absorption performance of Si(2)-rGO@Fe3O4/PVDF-co-HFP composite was attributed to the interference absorption (quarter-wave matching model) and the synergistic effects between Si(2)-rGO@Fe3O4 and PVDF-co-HFP. This work provides a potential strategy for the fabrication of the high-performance EMA materials.

Synthesis and Excellent Microwave Absorption Properties of ZnO/Fe3O4/MWCNTs Composites

NANO ◽  
2016 ◽  
Vol 11 (12) ◽  
pp. 1650139 ◽  
Author(s):  
Lei Wang ◽  
Honglong Xing ◽  
Zhenfeng Liu ◽  
Ziyao Shen ◽  
Xiang Sun ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Microwave Absorption ◽  
Photoelectron Spectroscopy ◽  
Wave Attenuation ◽  
Impedance Matching ◽  
Interfacial Polarization ◽  
X Ray Diffraction ◽  
X Ray ◽  
Zno Nanocrystals ◽  
Transmission Electron

ZnO nanocrystals were introduced into Fe3O4/MWCNTs composites to improve the impedance matching and electromagnetic (EM) wave attenuation of the system. The as-synthesized ZnO/Fe3O4/MWCNTs composites were characterized by X-ray diffraction, vibrating sample magnetometer, field-emission scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy. SEM and TEM images showed that Fe3O4 microspheres 100–200[Formula: see text]nm in size connected MWCNTs. Analysis of EM parameters revealed that the impedance matching of the ZnO/Fe3O4/MWCNTs composites was considerably improved after ZnO nanocrystals were introduced. The ZnO/Fe3O4/MWCNTs composites exhibited a highly efficient microwave absorption (MA) capacity within the tested frequency range of 2–18[Formula: see text]GHz. The optimal reflection loss of EM waves was [Formula: see text][Formula: see text]dB at 6.08[Formula: see text]GHz with an absorber thickness of 3.5[Formula: see text]mm. The excellent MA properties of the composites could be attributed to the improved impedance matching, interfacial polarization, and combined effects of dielectric and magnetic losses.

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