Characteristics of Microwave Absorption of Ni-Zn-Ferrite/Sic Hemi-Crystallized Composites

2000 ◽  
Vol 656 ◽  
Author(s):  
Makoto Nakanishi ◽  
Tomonori Shibuya ◽  
Tatsuo Fujii ◽  
Jun Takada
Keyword(s):  
Absorption Spectrum ◽  
Dielectric Loss ◽  
Grain Growth ◽  
Magnetic Loss ◽  
Wide Band ◽  
Granular Structure ◽  
Dielectric Losses ◽  
Zn Ferrite ◽  
Band Absorption ◽  
Ferrite Composites

ABSTRACTIn order to develop wide-band microwave absorbers we tried to prepare composite absorbers between the magnetic loss (Ni-Zn-ferrite) and the dielectric loss (SiC) materials. The dry or wet mixtures of Ni-Zn-ferrite and polycarbosilane (PCS) were cured in air and were then subjected to pyrolysis forming of the ferrite composites. The composites produced by the wet mixing had granular structure: the PCS surrounding the ferrite particles suppressed the sintering and the grain growth of the ferrite composites during pyrolysis. The matching frequency due to the magnetic loss linearly increased with increasing the PCS content. Moreover the ferrite/SiC hemi-crystallized composite cured at 473 K for 24 hours showed wide-band absorption spectrum having the both magnetic and dielectric losses.

Magnetodielectric Ni ferrite ceramics with Bi2O3 additive for potential antenna miniaturizations

2009 ◽  
Vol 24 (2) ◽  
pp. 324-332 ◽  
Author(s):  
X.T. Liew ◽  
K.C. Chan ◽  
L.B. Kong
Keyword(s):  
Magnetic Properties ◽  
Dielectric Loss ◽  
Grain Growth ◽  
Sintering Temperature ◽  
Magnetic Loss ◽  
Liquid Phase Sintering ◽  
X Ray Diffraction ◽  
Low Dielectric ◽  
High Concentrations

This paper reports on the preparation and characterization of nickel ferrite (NiFe1.98O4) ceramics doped with Bi2O3 as sintering aid. Focus has been on the effects of concentration of Bi2O3 and sintering temperature on the densification, grain growth, dielectric, and magnetic properties of the NiFe1.98O4 ceramics, with an aim at developing magnetodielectric properties, with almost equal real permeability and permittivity, as well as sufficiently low magnetic and dielectric loss tangents, over 3 to 30 MHz (high frequency or HF band). X-ray diffraction results indicated that there is no obvious reaction between NiFe1.98O4 and Bi2O3, at Bi2O3 levels of up to 7 wt% and temperatures up to 1150 °C. The addition of Bi2O3 facilitated a liquid phase sintering mechanism for the densification of NiFe1.98O4 ceramics. The addition of Bi2O3 not only improved the densification but also promoted the grain growth of NiFe1.98O4 ceramics. To achieve sufficiently low dielectric loss tangent, the concentration of Bi2O3 should not be less than 5 wt%. The low dielectric loss tangents of the samples doped with high concentrations of Bi2O3 can be attributed to the full densification of the ceramics. Magnetic properties of the NiFe1.98O4 ceramics, as a function of sintering temperature and Bi2O3 concentration, can be qualitatively explained by the Globus model. Promising magnetodielectric properties have been obtained in the sample doped with 5% Bi2O3 and sintered at 1050 °C for 2 h. The sample has almost equal values of permeability and permittivity of ∼12, together with low dielectric and magnetic loss tangents, over 3 to 30 MHz. This material might be useful for the miniaturization of HF (3 to 30 MHz) antennas.

Preparation and Performance of Chiral Polyaniline/Cobalt Ferrite Composites

2016 ◽  
Vol 852 ◽  
pp. 342-345
Author(s):  
Juan Bi Li ◽  
Di Qiong Hu ◽  
Yu Huan Wang ◽  
Liang Chao Li ◽  
Yan Ding
Keyword(s):  
Dielectric Loss ◽  
Cobalt Ferrite ◽  
In Situ Polymerization ◽  
Optical Rotation ◽  
Magnetic Loss ◽  
And Performance ◽  
Ferrite Composites ◽  
Co Precipitation ◽  
Polymerization Method

The cobalt ferrite and chiral polyaniline/cobalt ferrite composites were synthesized by co-precipitation and in-situ polymerization method, respectively. The crystal structure and composition, electrical conductivity, optical rotation, dielectric loss and magnetic loss of the as-prepared samples were researched. It was found that the optical rotation (levorotation) of composites is less than that of chiral polyaniline (L-PANI), and increased with the increasing of L-PANI content. The conductivity of the composites with a mass ratio of L-PANI to cobalt ferrite above 0.4 was better than of pure L-PANI, and their dielectric loss was in accordance with the conductivity in variation trend.

Microwave wide band absorption by carbon from Corn cob-1

2016 ◽  
Vol 12 (2) ◽  
pp. 4204-4212 ◽  
Author(s):  
Maheshwar Sharon ◽  
Ritesh Vishwakarma ◽  
Abhijeet Rajendra Phatak ◽  
Golap Kalita ◽  
Nallin Sharma ◽  
...  
Keyword(s):  
Microwave Absorption ◽  
Agricultural Waste ◽  
Wide Band ◽  
Nickel Nitrate ◽  
Equivalent Amount ◽  
Frequency Range ◽  
Corn Cob ◽  
Different Temperatures ◽  
Band Absorption ◽  
5 Ghz

Corn cob, an agricultural waste, is paralyzed at different temperatures (700oC, 800oC and 900oC). Microwave absorption of carbon in the frequency range of 2 GHz to 8 GHz is reported. Carbon activated  with 5%  nickel nitrate showed more than 90% absorption of microwave in the frequency range from 6 GHz to 8 GHz, while carbon activated  with 10% Nickel nitrate treated corn cob showed 90% absorption  in the frequency range of 2.5 GHz to 5 GHz. Carbon showing the best absorption are characterized by XRD, Raman spectra and SEM . It is suggested that corn cob treatment   alone with KOH did not improve the microwave absorption, whereas treatment along with nickel nitrate improved the absorption property much better. It is proposed that treatment with nickel nitrate helps in creating suitable pores in carbon   which improved the absorption behavior because while treating carbon with 1N HCl helps to leach out nickel creating equivalent amount of pores in the carbon.

scholarly journals Independently Tunable Multipurpose Absorber with Single Layer of Metal-Graphene Metamaterials

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 284
Author(s):  
Chen Han ◽  
Renbin Zhong ◽  
Zekun Liang ◽  
Long Yang ◽  
Zheng Fang ◽  
...  
Keyword(s):  
Energy Harvesting ◽  
Fermi Level ◽  
Potential Application ◽  
Single Layer ◽  
Wide Band ◽  
Metamaterial Absorber ◽  
Unit Cell ◽  
Perfect Absorption ◽  
Solar Energy Harvesting ◽  
Band Absorption

This paper reports an independently tunable graphene-based metamaterial absorber (GMA) designed by etching two cascaded resonators with dissimilar sizes in the unit cell. Two perfect absorption peaks were obtained at 6.94 and 10.68 μm with simple single-layer metal-graphene metamaterials; the peaks show absorption values higher than 99%. The mechanism of absorption was analyzed theoretically. The independent tunability of the metamaterial absorber (MA) was realized by varying the Fermi level of graphene under a set of resonators. Furthermore, multi-band and wide-band absorption were observed by the proposed structure upon increasing the number of resonators and resizing them in the unit cell. The obtained results demonstrate the multipurpose performance of this type of absorber and indicate its potential application in diverse applications, such as solar energy harvesting and thermal absorbing.

scholarly journals Short-Time Photodissociation Dynamics of 1-Chloro-2-Iodoethane From Resonance Raman Spectroscopy

1999 ◽  
Vol 19 (1-4) ◽  
pp. 71-74 ◽  
Author(s):  
Xuming Zheng ◽  
David Lee Phillips
Keyword(s):  
Raman Spectroscopy ◽  
Absorption Spectrum ◽  
Raman Spectra ◽  
Resonance Raman Spectroscopy ◽  
Resonance Raman ◽  
Time Dependent ◽  
Internal Excitation ◽  
Band Absorption ◽  
Resonance Raman Spectra ◽  
Short Time

We have obtained A-band absorption resonance Raman spectra of 1-chloro-2- iodoethane in cyclohexane solution. We have done preliminary time-dependent wavepacket calculations to simulate the resonance Raman intensities and absorption spectrum in order to learn more about the short-time photodissociation dynamics. We compare our preliminary results for 1-chloro-2-iodoethane with previous resonance Raman results for iodoethane and find that there appears to be more motion along non- C—I stretch modes for 1-chloro-2-iodoethane than for iodoethane. This is consistent with results of TOF photofragment spectroscopy experiments which indicate much more internal excitation of the photoproducts from 1-chloro-2-iodoethane photodissociation than the photoproducts from iodoethane photodissociation.

A Multiple-Bands Metamaterial Absorber Based in X, Ku and K-Band

2021 ◽  
Author(s):  
Muhammad Fahim Zafar ◽  
Usman Masud
Keyword(s):  
Single Layer ◽  
Wide Band ◽  
Metamaterial Absorber ◽  
Basic Unit ◽  
Frequency Range ◽  
Structure Form ◽  
Perfect Absorption ◽  
Polarization Insensitive ◽  
Band Absorption ◽  
K Band

Abstract Developing a highly efficient and multiple-bands metamaterial absorber is a hot issue in recent era. In this paper, A multiple-bands metamaterial absorber has been presented which is based in X, Ku and K-band. Firstly, we have designed two single layer basic unit cell of X-shape and cross-shape, then they are arranged in the multi-layers structure form for the purpose of obtaining multiple- bands and wide band absorption. The proposed absorber is able to work in multiple bands because it has six peaks in the frequency range of 8–24 GHz with having near perfect absorption. Moreover, the sixth peak has a wideband absorption which is 2.93 GHz. Furthermore, the proposed absorber is also tested for polarization insensitivity and also for oblique incidence. Absorption was found polarization insensitive with almost perfect absorption.

Synergetic dielectric loss and magnetic loss towards superior microwave absorption through hybridization of few-layer WS2 nanosheets with NiO nanoparticles

2020 ◽  
Vol 65 (2) ◽  
pp. 138-146 ◽  
Author(s):  
Deqing Zhang ◽  
Yingfei Xiong ◽  
Junye Cheng ◽  
Jixing Chai ◽  
Tingting Liu ◽  
...  
Keyword(s):  
Dielectric Loss ◽  
Microwave Absorption ◽  
Magnetic Loss ◽  
Nio Nanoparticles ◽  
Ws2 Nanosheets

scholarly journals Microwave Absorption of Crystalline Fe/MnO@C Nanocapsules Embedded in Amorphous Carbon

2020 ◽  
Vol 12 (1) ◽  
Author(s):  
Gaihua He ◽  
Yuping Duan ◽  
Huifang Pang
Keyword(s):  
Dielectric Loss ◽  
Amorphous Carbon ◽  
High Performance ◽  
Magnetic Loss ◽  
Synthesis Method ◽  
Domain Size ◽  
Carbon Matrix ◽  
Effective Bandwidth ◽  
General Duty ◽  
Enhanced Absorption

AbstractCrystalline Fe/MnO@C core–shell nanocapsules inlaid in porous amorphous carbon matrix (FMCA) was synthesized successfully with a novel confinement strategy. The heterogeneous Fe/MnO nanocrystals are with approximate single-domain size which gives rise to natural resonance in 2–18 GHz. The addition of MnO2 confines degree of graphitization catalyzed by iron and contributes to the formation of amorphous carbon. The heterogeneous materials composed of crystalline–amorphous structures disperse evenly and its density is significantly reduced on account of porous properties. Meanwhile, adjustable dielectric loss is achieved by interrupting Fe core aggregation and stacking graphene conductive network. The dielectric loss synergistically with magnetic loss endows the FMCA enhanced absorption. The optimal reflection loss (RL) is up to − 45 dB, and the effective bandwidth (RL < − 10 dB) is 5.0 GHz with 2.0 mm thickness. The proposed confinement strategy not only lays the foundation for designing high-performance microwave absorber, but also offers a general duty synthesis method for heterogeneous crystalline–amorphous composites with tunable composition in other fields.

scholarly journals Improvement of Microwave Absorbance of Polymer Composites of W-Type Hexaferrite Powders by Attachment of Frequency Selective Surface

2017 ◽  
Vol 62 (2) ◽  
pp. 1325-1328
Author(s):  
H.-S. Cho ◽  
S.-S. Kim
Keyword(s):  
Reflection Loss ◽  
Electromagnetic Waves ◽  
Polymer Matrix Composites ◽  
Magnetic Loss ◽  
Frequency Selective Surface ◽  
Substrate Material ◽  
Matrix Composites ◽  
Frequency Selective ◽  
Ferrite Composites ◽  
Minimum Reflection Loss

AbstractThis work investigates the effect of a frequency selective surface (FSS) composed of a regular array of square loop elements on the absorption properties of grounded ferrite composites. Polymer matrix composites of CoZnW hexaferrite powders having small magnetic loss were used as the substrate material. Computational tools were used to model the interaction between electromagnetic waves and materials and determine the reflection coefficient. Reflection loss and bandwidth were greatly improved by attaching an FSS with controlled electrical resistance (R) onto the grounded ferrite composites. For the FSS withR= 800 Ω, the minimum reflection loss decreased to −25 dB at 10 GHz and the bandwidth was broadened to 7.5-12.5 GHz with respect to −10 dB reflection loss.

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