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Double-layer microwave absorber based on nanocrystalline CoFe2O4 and CoFe2O4/PANI multi-core/shell composites

100%

Xu Y. , Shen G. , Wu H. , Liu B. , Fang X. , Zhang D. , Zhu J.

Materials Science Poland

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2017

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tom Vol. 35, No. 1

94--104

EN

Organic-inorganic nano-CoFe2O4/PANI (polyaniline) multi-core/shell composites have been successfully synthesized by chemical oxidative polymerization of aniline. The characterization results showed that the ferrite nanocrystals were efficiently embedded in PANI. The electromagnetic parameters of the composites were measured by a vector network analyser in the frequency range of 2 GHz to 18 GHz. Double-layer absorbers based on the CoFe2O4/PANI composite (matching layer) and calcined CoFe2O4 ferrite (absorbing layer) have been designed. The reflection loss of the microwave absorbers of both single layer and double-layer with a total thickness of 2.0 mm and 2.5 mm was calculated according to transmission-line theory. The results indicated that the minimum reflection loss of the CoFe2O4/PANI composite was −19.0 dB at 16.2 GHz at the thickness of 2.0 mm and −23.6 dB at 13.1 GHz at the thickness of 2.5 mm, respectively. The minimum reflection loss for double-layer absorbers reached −28.8 dB at 16.2 GHz at the total thickness of 2.0 mm, and −31.1 dB at 12.8 GHz at the total thickness of 2.5 mm. The absorption bandwidth under −10 dB was 4.2 GHz (13.8 GHz to 18.0 GHz) and 5.5 GHz (10.3 GHz to 15.8 GHz), respectively. The results show that the reflection loss and absorption bandwidth of the double-layer absorbers are obviously enhanced compared to corresponding single layer absorbers.

2

Influence of Substituted Elements on Reflection Loss of Ba-Ferrite Nanoparticle

88%

Yang S. , Jeong K.-P. , Park S.-Y. , Kim J.-G.

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tom Vol. 62, iss. 2B

1201--1204

EN

Due to the rapid development of the information communication industries, it is expected that next-generation mobile communication devices in the data communication environment will be used at the same time in the L~X band (1–12 GHz). To mutual electric wave interference prevention, research on wave absorbers in L~X band is needed. In this paper, barium ferrite was researched as L~X band wave absorber. The Barium ferrite (BaM, Ba ferrite) substituted by divalent ions (Co2+, Cu2+, Ni2+, Zn2+) and tetravalent ion (Ti4+). The substituted Ba ferrite nanoparticles were fabricated by sol-gel process. Lattice parameter, particle size, magnetic properties, and reflection loss were analyzed by X-ray diffraction (X-RD), a Vibrating Sample Magnetometer (VSM), and a Network Analyzer. Lattice parameter of Ba ferrite was changed 0.0005 to 0.0078 Å in a-b direction, and 0.0187 to0.0445 Å in c-direction by substituted elements, and it influenced on magnetic anisotropy. In addition, Co-Ti substitution elements influenced that coercive force decrease 5,739 to 2,240 Oe. Moreover, reflection loss frequencies were shifted from 16.3 GHz to 14.4 and 17.4 GHz by substituted elements Co-Ti and Zn-Ti.

3

Fabrication and characterization of iron coated carbon nanotubes/polymer composite for microwave absorption

63%

Kaur G. , Deep Aul G.

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2020

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tom R. 20, nr 3-4

111--117

EN

Electrical characteristics of iron coated multi-walled carbon nanotubes (MWNTs) along with ferromagnetic properties are very interesting nanomaterial for microwave absorption. In this research work, surface morphology, compositions and microwave absorption properties of polymer containing iron coated MWNTs have been investigated. Iron coated multi-walled carbon nanotubes composite were prepared by two simple steps method. In addition, microstructure and microwave absorption properties under frequency range 8÷13 GHz by means of FESEM, EDX &Vector network analyzer had shown. The maximum reflection loss is observed for Fe-coated MWNTs/polymer sample B is –20.86 dB and –18.13 dB at frequency 8.1 and 10.75 GHz respectively. And the maximum bandwidth window is available for sample C is 3.25 GHz from frequency 8.45 to 11.7 GHz with 3 mm thickness, which can be attributed to synergistic effect of improved impedance matching characteristic and superior microwave attenuation characteristic of the absorber. The reflection properties of the material enhanced with variations in the wt.% of Fe-coated MWNTs and polymer. In this research paper, Fe-coated MWNTs are analyzed as promising microwave absorbing material and combined utilization of dielectric loss and magnetic loss absorbent design shows great design flexibility and diversity in the frequency range 8÷13 GHz.

4

Influence of the Content of Nickel Powders on the Electromagnetic Properties of SingleLayer Coated Polyester-Cotton Plain Weave Fabric

63%

Liu Y. , Xue H. , Wang C. , Han X. , Zhao X.

Fibres & Textiles in Eastern Europe

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2022

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tom Vol. 30, no. 5

47--52

EN

A coated composite was prepared on polyester-cotton plain weave fabric, using PU2540 polyurethane as the matrix. The influences of the content of nickel powders on the dielectric constant (the real and imaginary parts and loss tangent value), reflection loss and shielding effectiveness of single-layer coated composites were mainly investigated. The results showed that within the frequency range of 1-1000 MHz, the value of the real part of the dielectric constant of the coated composites was the largest, and the polarisation ability with regard to electromagnetic waves was the strongest when the content of nickel powders was 40%. Within the frequency range of 15-225 MHz, the value of the imaginary part of the dielectric constant of the coated composites was the largest and the loss ability with regard to electromagnetic waves was the strongest when the content of nickel powders was 40%. Within the frequency range of 250-800 MHz, the loss tangent value of the dielectric constant of coated composites was the largest, and the attenuation ability with regard to electromagnetic waves was the strongest when the content of nickel powders was 40%. Within the frequency range of 1220-3000 MHz, the reflection loss value was the smallest when the content of nickel powders was 40%, and its absorption ability with regard to electromagnetic waves was the strongest. Within the frequency range of 760-3000 MHz, the shielding effectiveness of the coated composite was the largest when the content of nickel powders was 40%.