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1

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

Kaur Gurjit, Deep Aul Gagan

Composites Theory and Practice

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2020

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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.

2

Improvement of Microwave Absorption Characteristics by Coating Layer in Substituted U-Type Ferrites

Jeong Kwang-Pil, Kim Jeong-Gon, Yang Su-Won, Choi Jin-Hyuk, Park Seung-Young

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1287--1291

EN

The U-type ferrite is a kind of hexagonal ferrite, and it is known as a microwave absorber in the X-band. The magnetic and dielectric loss of the U-type ferrite change to the composition and coating layer, etc. In this study, the silicon oxide layer was coated on the substituted U-type ferrites to improve microwave absorption characteristics. The complex permittivity and complex permeability were measured using toroidal specimens that were press-molded and the measured frequency range was set from 2-18 GHz. The improvement of the microwave absorption rate was different according to the type of the substituted U-type ferrites. Only in the substituted U-type ferrites with nickel and zinc, an improvement in the microwave absorption rate due to enhancement of magnetic loss was confirmed. The highest microwave absorption was 99.9% at 9.6 GHz, which was S_Z0.5 U.

3

Enhanced Microwave Absorption of CNT Composites Mixing with Fe3O4 and Carbonyl Iron

Park J. H., Choi J., Lee K., Park J., Song J. K., Jeon E.

Archives of Metallurgy and Materials

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2018

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Vol. 63, iss. 3

1513--1516

EN

We fabricated two different kinds of composite materials for absorbing microwave in a frequency range of 2 to 18 GHz using coaxial airline and thru-reflect-line (TRL) method. The composite materials having carbon nanotube (CNT) with carbonyl iron (CI) or iron oxide (Fe3 O4 ) were fabricated by mixing each components. Magnetic properties were measured by SQUID equipment. Complex permittivity and complex permeability were also obtained by measuring S-parameters of the toroidal specimen dispersing CI/CNT and Fe3 O4 /CNT into the 50 weight percent (wt%) epoxy resin. The real permittivity was improved by mixing the CNT however, the real permeability was same as pure magnetic powders. The CI/CNT had a maximum value of real permittivity and real permeability, 11 and 1.4 at 10 GHz, respectively. The CNT composites can be adapted to the radar absorbing materials, band width 8-12 GHz.

4

Preparation and microwave absorption of M type ferrite nanoparticle composites

Shen G. Z., Cheng G. S., Cao Y., Xu Z.

Materials Science Poland

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2010

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Vol. 28, No. 1

327--334

EN

The sol-gel method was used to obtain M type BaFe12O19 ferrite nanoparticles. Rod like and flake like ferrite nanoparticles can be successfully fabricated by controlling the heating process of the precursor. The phase attributes, morphology and grain size of BaFe12O19 ferrite were characterized by TEM and XRD. The complex permittivity and permeability of ferrite epoxy resin composites were measured in the Ku waveband (12.4-18 GHz). Ferrite composites containing short carbon fibres have also been fabricated in order to obtain higher complex permittivities of the composites. The reflectivities of these ferrite composites were calculated according to the measured electromagnetic parameters. The results show that the microwave absorption properties of ferrite composites can be effectively improved by filling them with short carbon fibres.

5

Microwave absorption (MMMA) - a contactless method to study superconductors and magnetic nanostructures

Stankowski J.

Metrology and Measurement Systems

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2006

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Vol. 13, nr 2

125-135

EN

Magnetically Modulated Microwave Absorption (MMMA) is a sensitive differential method to study magnetoresistence related to the voltage fluctuation in nonhomogeneous superconducting systems with Josephson junctions (JS) and in magnetic systems exhibiting giant magnetoresistence (GMR). The MMMA method has been successfully established after the discovery of polycrystalline high temperature superconductors with high concentration of Josephson junctions. MMMA proved to be the third method besides resistivity and magnetic susceptibility measurements to determine critical temperature Tc. In magnetic nanostructures MMMA enables to determine GMR(H) and magnetization reversal.

PL

Magnetycznie modulowana mikrofalowa absorpcja - MMMA jest czułą metodą różniczkową badania magnetooporu związanego z fluktuacjami napięcia w niejednorodnych układach nadprzewodzących ze złączami Josephsona - JS i w układach magnetycznych wykazujących gigantyczny magnetoopór GMR. MMMA pojawiła się po odkryciu polikrystalicznych nadprzewodników wysokotemperaturowych, w których duża koncentracja złączy powoduje, że nadprzewodnik można traktować jako system Josephsona - JJS. MMMA okazuje się trzecią metodą, obok oporności i podatności wyznaczania temperatury krytycznej Tc. W nanostrukturach magnetycznych MMMA pozwala na wyznaczenie kształtu GMR(H) oraz pola przełączania namagnesowania w punktach osobliwych pętli histerezy, w których nachylenie M(H) ma największe wartości.