Simultaneous dual pyrolysis synthesis of heterostructured FeCo/C porous hollow microspheres for high efficient microwave absorption

2022 ◽  
Author(s):  
Ran Liu ◽  
Gaiping Du ◽  
Bin Liao ◽  
Weixin Xiao ◽  
Zhenguo An ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Lightweight Design ◽  
Impedance Matching ◽  
Hollow Microspheres ◽  
Low Density ◽  
Hollow Structures ◽  
High Efficient ◽  
Pyrolysis Synthesis

Due to their multiple dissipation mechanisms, low density and easy tailored impedance matching, heterogeneous hollow structures are promising candidates for microwave absorbents towards wideband absorption and lightweight design. In this...

Silicate–CoNi–carbon triple shell sandwich structured composite hollow microspheres with low density boosted microwave absorption and high mechanical strength

2021 ◽  
Author(s):  
Zhenguo An ◽  
Jingjie Zhang
Keyword(s):  
Mechanical Strength ◽  
Microwave Absorption ◽  
Large Scale ◽  
Hollow Microspheres ◽  
Electromagnetic Properties ◽  
Low Density ◽  
High Mechanical Strength

Low density silicate–CoNi–carbon triple shell hollow microspheres with high mechanical strength and controllable electromagnetic properties were prepared on a large scale.

MIL-88B (Fe) driven Fe/Fe3C encapsulated in high-crystalline carbon for high-efficient microwave absorption and electromagnetic interference shielding

2021 ◽  
Author(s):  
Xianfeng Yang ◽  
You Zhou ◽  
Hongna Xing ◽  
Hongpeng Wang ◽  
Wei Feng ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Electromagnetic Interference ◽  
Magnetic Loss ◽  
Impedance Matching ◽  
Filling Ratio ◽  
Emi Shielding ◽  
Electromagnetic Interference Shielding ◽  
Dual Functional ◽  
High Efficient ◽  
Magnetic Dielectric

Abstract Dual-functional magnetic/dielectric Fe/Fe3C@C composites were fabricated by pyrolysis of MIL-88B (Fe) in Ar atmosphere, which was used for microwave absorption and electromagnetic interference (EMI) shielding. The Fe/Fe3C nanocrystals were completely encapsulated in crystalline carbon, which can improve the oxidation resistance capacity. Owing to the remarkable impedance matching and strong attenuation constants, Fe/Fe3C@C composites show an optimal RL value of -56.4 dB at 14.0 GHz and broad effective absorption bandwidth (RL ≤ -10 dB) of 4.8 GHz, when the filling ratio and absorber thickness are only 20 wt% and 1.9 mm, respectively. Resulted from the high conductivity of crystalline carbon, magnetic loss of Fe/Fe3C and core-shell structure, the Fe/Fe3C@C composites also show remarkable EMI shielding properties at X band, which are enhanced by increasing the filling ratio of Fe/Fe3C@C composites. When the filling ratio was 50 wt%, the EMI shielding efficiency can reach 35 dB. This work suggests that the magnetic/dielectric Fe/Fe3C@C is a good cadidate in microwave absorption and electromagnetic interference shielding.

scholarly journals Effect of Reaction Time on Microwave Absorption Properties of Fe3O4 Hollow Spheres Synthesized via Ostwald Ripening

Materials ◽  
2019 ◽  
Vol 12 (18) ◽  
pp. 2921 ◽  
Author(s):  
Wei Huang ◽  
Yujiang Wang ◽  
Shicheng Wei ◽  
Bo Wang ◽  
Yi Liang ◽  
...  
Keyword(s):  
Reaction Time ◽  
Microwave Absorption ◽  
Ostwald Ripening ◽  
Impedance Matching ◽  
Hollow Spheres ◽  
Absorption Properties ◽  
Microwave Absorption Properties ◽  
Magnetic Structures ◽  
Absorption Performance ◽  
Microwave Absorption Performance

Hollow magnetic structures have great potential to be used in the microwave absorbing field. Herein, Fe3O4 hollow spheres with different levels of hollowness were synthesized by the hydrothermal method under Ostwald ripening effect. In addition to their microstructures, the microwave absorption properties of such spheres were investigated. The results show that the grain size and hollowness of Fe3O4 hollow spheres both increase as the reaction time increases. With increasing hollowness, the attenuation ability of electromagnetic wave of Fe3O4 spheres increases first and then decreases, finally increases sharply after the spheres break down. Samples with strong attenuation ability can achieve good impedance matching, which it does preferentially as the absorber thickness increases. Fe3O4 hollow spheres show the best microwave absorption performance when the reaction time is 24 h. The minimum reflection loss (RL (min)) can reach −40 dB, while the thickness is only 3.2 mm.

Position Selective Dielectric Polarization Enhancement in CNTs Based Heterostructures for High-Efficient Microwave Absorbing

Nanoscale ◽  
2021 ◽  
Author(s):  
Haihua Hu ◽  
Yun Zheng ◽  
Kun Ren ◽  
Jieying Wang ◽  
Yanhui Zhang ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Microwave Absorption ◽  
Dielectric Polarization ◽  
High Efficient ◽  
Microwave Absorbing

Constructing carbon nanotubes (CNTs) based on heterostructures have been proved to be an effective way to improve microwave absorption (MA) capability of the materials, regardless of the inner wall or...

CNT@NiO/natural rubber with excellent impedance matching and low interfacial thermal resistance toward flexible and heat-conducting microwave absorption applications

2021 ◽  
Author(s):  
Maofan Zhou ◽  
Gengping Wan ◽  
Pengpeng Mou ◽  
Shengjie Teng ◽  
Shiwei Lin ◽  
...  
Keyword(s):  
Natural Rubber ◽  
Thermal Resistance ◽  
Microwave Absorption ◽  
Impedance Matching ◽  
Interfacial Thermal Resistance ◽  
Heat Conducting ◽  
Rubber Composites ◽  
Natural Rubber Composites

Herein, CNT@NiO/natural rubber composites were fabricated to apply as flexible and heat-conducting microwave absorption materials.

scholarly journals Structural Engineering of Hierarchical Aerogels Comprised of Multi-dimensional Gradient Carbon Nanoarchitectures for Highly Efficient Microwave Absorption

2021 ◽  
Vol 13 (1) ◽  
Author(s):  
Yongpeng Zhao ◽  
Xueqing Zuo ◽  
Yuan Guo ◽  
Hui Huang ◽  
Hao Zhang ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Structural Engineering ◽  
Carbon Nanomaterials ◽  
Wave Attenuation ◽  
Impedance Matching ◽  
Chemical Vapor ◽  
Electromagnetic Properties ◽  
Effective Bandwidth ◽  
Carbon Aerogels ◽  
Chemical Vapor Deposition Method

AbstractRecently, multilevel structural carbon aerogels are deemed as attractive candidates for microwave absorbing materials. Nevertheless, excessive stack and agglomeration for low-dimension carbon nanomaterials inducing impedance mismatch are significant challenges. Herein, the delicate “3D helix–2D sheet–1D fiber–0D dot” hierarchical aerogels have been successfully synthesized, for the first time, by sequential processes of hydrothermal self-assembly and in-situ chemical vapor deposition method. Particularly, the graphene sheets are uniformly intercalated by 3D helical carbon nanocoils, which give a feasible solution to the mentioned problem and endows the as-obtained aerogel with abundant porous structures and better dielectric properties. Moreover, by adjusting the content of 0D core–shell structured particles and the parameters for growth of the 1D carbon nanofibers, tunable electromagnetic properties and excellent impedance matching are achieved, which plays a vital role in the microwave absorption performance. As expected, the optimized aerogels harvest excellent performance, including broad effective bandwidth and strong reflection loss at low filling ratio and thin thickness. This work gives valuable guidance and inspiration for the design of hierarchical materials comprised of dimensional gradient structures, which holds great application potential for electromagnetic wave attenuation. "Image missing"

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.

Microwave absorption of NdFe magnetic powders tuned with impedance matching

2018 ◽  
Vol 449 ◽  
pp. 385-389 ◽  
Author(s):  
Lei Wang ◽  
Qichen Quan ◽  
Lili Zhang ◽  
Lichun Cheng ◽  
Peihao Lin ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Impedance Matching

Collision induced microwave absorption in N2, CH4, and CF4 in the gaseous and liquid phases

1977 ◽  
Vol 55 (6) ◽  
pp. 496-505 ◽  
Author(s):  
J. L. Urbaniak ◽  
I. R. Dagg ◽  
G. E. Reesor
Keyword(s):  
Liquid Phase ◽  
Microwave Absorption ◽  
Low Density ◽  
Temperature Range ◽  
Liquid Phases ◽  
Gas To Liquid

Measurements of collision induced microwave absorption at 2.3 cm−1 have been carried out on gaseous N2 in the temperature range from 124 to 156 K and on liquid N2 in the temperature range from 77 to 125 K. The low density gaseous measurements have been found to agree well with the previous microwave and infrared results and with existing theories. The dependence of the absorption on density has been obtained at 156 K up to a density of 400 amagat and the results compared with the absorption in the liquid at the same density. The absorption is found to be a function of temperature and density but does not depend on the molecules being in a gas or liquid phase. Results for liquid CH4 and CF4 are reported and compared with previous microwave gaseous results. In contrast to the results for N2 the dependence on the square of the density changes by a relatively small amount in going from the low density gas to liquid densities.

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