Papers by Keyword: Absorbing Materials

Abstract: The aim of the presented work is to study polymer ceramic-inorganic composites for electromagnetic radiation absorbing. Epoxy-based polymer composites modified with ceramic-inorganic graphite-ferromagnetic (CIGF) fillers were first obtained: silicon carbide, chromium oxide Cr₂O₃, graphite, humic substances and potassium titanate. As polymer matrix epoxy resin based on Epikote Resin MGS LR 285 and Epikure Curing Agent MGS LH 285 was studied. Primary research was directed to study humic substance, silicon carbide SiC, chromium oxide Cr₂O₃, graphite and potassium titanate nanoparticles introduction impact on polymer ceramic-inorganic composites strength and technological properties. Complex of technological and strength characteristics were researched and compositions with humic substances 0.5 wt%, a higher silicon carbide SiC – 10 wt% content were studied, while chromium oxide Cr₂O₃, graphite content in 5–25 % wt. range was optimized. Results shows, that addition of humic substances, silicon carbide SiC, chromium oxide Cr₂O₃, graphite and potassium titanate nanoparticles into the epoxy resin up to 20 wt% filler content increases the composite impact strength and breaking stress during bending. The CIGF fillers complex system using advantage is proven by studying the nature of modification effect on ceramic-ferromagnetic-graphite polymer composites for electromagnetic radiation absorption.

Abstract: Honeycomb absorbing materials are anisotropic structural materials. Depending on the size of honeycomb lattices, the absorbent content of the impregnated layer is different, the thickness of the impregnated layer is different, and the absorbing function of the impregnated honeycomb absorbing materials is also different. For the characterization of electromagnetic parameters of honeycomb absorbing materials, this paper adopts free space method for testing, uses CST software for modeling, and inverts the electromagnetic parameters of honeycomb absorbing structures. The absorbing performance of single-layer and double-layer honeycomb sandwich structures was simulated by RAM Optimizer software. The research shows that the height of the single-layer honeycomb absorbing material is 22mm. When the absorber content is 65%, 75% and 85% respectively, the harmonic peak moves slightly to the low frequency electromagnetic wave with the increase of the absorber content, but the absorbing strength decreases with the increase of the absorber content. For the double-layer honeycomb sandwich structure, the difference of absorber content in the upper and lower honeycomb absorbing materials is smaller, and the absorbing performance is stronger. When the thickness of the wave-transparent panel is thinner, the harmonic peak of the absorbing curve moves slightly to the high frequency.

Abstract: From actual conditions, this paper emphatically introduces the concept of electromagnetic wave and the influence of electromagnetic wave to human body health and damage, which leads to the introduction of electromagnetic wave absorption materials and the application of electromagnetic wave absorption materials. Although time and research scope is limited, but I hope this paper can give readers bring enlightenment and help.

Abstract: Graphite-FeSi absorbents were fabricated by mechanical milling method. The complex permittivity and permeability were measured in frequency 1-4 GHz, and then reflection loss (RL) and shielding effectiveness (SE) were calculated. It was obtained that the graphite was bonded to the surface of FeSi by X-ray diffraction (XRD) patterns and scanning electron microscopy (SEM) images. The permittivity and permeability could be enlarged as graphite added in the milling process. It was attributed to the excellent conductivity of graphite and interactions of the two particles. The graphite-FeSi composites had a better shielding property (maximum 25.93 dB) in 1-4 GHz as well as the absorbing property at 1GHz than FeSi composites.

Abstract: In order to compare the absorbing properties of different microwave-absorbing agents and their mixture, this paper has selected two typical microwave-absorbing agents which respectively are carbon fiber resistance microwave-absorbing agents and ferrite magnetism microwave-absorbing agents, and took them as monolayer absorbing materials. Then used MG formula to calculate the effective electromagnetic parameter of their mixture under different proportion at X band, and finally analyzed their absorbing properties separately. Then through contrasting the impedance matching characteristic and attenuation coefficient of the materials, it is proved that adding carbon fiber in ferrite can not improve absorption properties. Although the ability of attenuating electromagnetic wave would be enhanced when resistance materials and magnetism materials are blend with each other, doping will destroy the materials’ impedance matching characteristic because most resistance materials have high permittivity. It makes reflection strengthen and can not improve absorbing properties.

Abstract: In order to improve absorbing properties of material effectively, enhance the ability of attenuating electromagnetic wave, and at the same time, make the impedance matching with air to the most extent, this paper mixed ferrite magnetism microwave-absorbing agents with semiconductor particulates. We got the effective EM parameter of the mixture using effective EM parameter model, and then analyzed absorption properties. As the result, it figured out the cubage proportion and conductance of semiconductor particulates based on the resistance matching principle. Through calculating the reflection ratio、impedance matching characteristic and attenuation coefficient of the material, it is proved that mixing ferrite magnetism microwave-absorbing agents with semiconductor particulate which has less permittivity could reduce real complex permittivity and increase imaginary complex permittivity of the composite material. It was able to enhance the ability of attenuating electromagnetic wave, improve absorbing properties, and meanwhile do not destroy the impedance matching characteristic with air.

Abstract: The three common frequency selective surface (FSS) structure, i.e. ring, crosses and Y-aperture which have the same center frequencies are designed, then the three FSS structures are placed at absorbing materials to form complex absorbing structures which are simulated by means of spectral domain approach. Therefore, the effects of different FSS on the characteristics of absorbing materials are studied and the influence laws are given. This research offers reference to element selection for the application of common FSS to absorbing materials.

Abstract: Microwave absorbing material is currently being more and more widely applied in the world. However, conventional absorbent coating material cannot fulfill the complex current requirements of science and technology to have a wide absorption frequency band, and high absorption. This paper describes composite material plates with a multi-layer absorbing structure designed according to impedance-matching and attenuation principles, producing two- and three-layer absorbing structures. Twelve samples were made, containing graphite powder and manganese dioxide at varying concentrations. The results show that in the frequency range 8-18 GHz, the peak absorption of double-layer samples is -12.3dB, the effective bandwidth (R < -10 dB) is 1.8GHz. The absorption peak of three-layer samples is -18 dB, and the effective bandwidth (R < -10 dB) is 8GHz. The findings of this research are useful in improving the absorption bandwidth of absorbing material.