Double-layer Microwave Research Articles

Development of high-efficient double layer microwave absorber based on Fe3O4/carbon fiber and Fe3O4/rGO

Recently, preparation of lightweight absorbers with high performance capability are urgently needed for practical demanded in order to solve the severe electromagnetic pollution. In the present study, two different composites (Fe3O4/carbon fiber and Fe3O4/rGO) were uniformly incorporated into resin epoxy matrix to obtain single and double layer X-band absorber with 20 wt% filler loading. Each of the composites were prepared via solvothermal process. According to the results, the minimum reflection loss values for each single layer Fe3O4/carbon fiber and Fe3O4/rGO absorber were −15 dB (3 mm thickness and 1.5 GHz bandwidth) and −50 dB (3 mm thickness and 4 GHz bandwidth) respectively. By assembling two-layer absorber in which Fe3O4/rGO composite placed at upper layer and Fe3O4/carbon fiber composite placed at bottom layer the minimum reflection loss reached to −52 dB (total thickness 2 mm and 4 GHz bandwidth). The special design of the absorber optimizes the thickness by improving the impedance matching characteristic. The results show that Fe3O4/rGO composite with high dielectric loss as an upper layer and Fe3O4/carbon fiber composite with high magnetic loss as bottom layer can be used as matching and absorber layer, respectively.

Electromagnetic wave absorption characteristics of single and double layer absorbers based on trimetallic FeCoNi@C metal−organic framework incorporated with MWCNTs

The present study focuses on the design of single and double layer microwave absorbers based on FeCoNi@C metal−organic framework incorporated with MWCNTs. FeCoNi@C metal−organic framework (MOF) and MWCNTs decorated with MOF (MW/MOF) were successfully synthesized via hydrothermal method and characterized with XRD, VSM and FESEM. The electromagnetic parameters of material (complex permittivity and permeability) of the as-prepared nanocomposites dispersing in paraffin (30 wt% powder, single layer) were evaluated by a vector network analyzer in X-band frequency range. The simulation of microwave absorption performance of single- and double-layer absorbers was performed via CST Studio software. The results indicate that the double layer absorber using M/MOF structure as matching layer and MOF structure as absorbing layer can increase the microwave absorption bandwidth up to 4 GHz and greatly decrease the reflection loss down to −36 dB for a total thickness of 2 mm. In contrast, the single layer microwave absorber consisting of 30 wt% M/MOF composite structure exhibited a minimum reflection loss of −18 dB at 9 GHz with 2 GHz bandwidth and 2.5 mm thickness. The better absorption performance of the double-layer absorber maybe attributed to the better impedance matching ability of M/MOF layer, coupling interactions between two distinctive layers (absorbing and matching layers) and excellent magnetic loss ability of MOF layer.

Double layer microwave absorber based on Cu dispersed SiC composites

The present work has been focused on designing an efficient and cost-effective double layer microwave absorber in 8.2–12.4 GHz frequency range. For the same, Cu particles were dispersed in SiC to achieve enhanced microwave absorption by combining the excellent dielectric characteristics of SiC with highly conductive Cu. Cu dispersed SiC composites were prepared by dispersing various weight fractions of Cu particles in the SiC matrix using planetary ball mill. The Cu dispersion in SiC yielded excellent relative complex permittivity values translating into a decrease in the reflection loss (RL) values of dispersed composites as compared to the pristine counterpart. The minimum RL of −17.18 dB has been observed for 2 wt% Cu dispersed SiC composite at 11.81 GHz with a thickness of 1.3 mm and bandwidth corresponding to −10 dB is 1.77 GHz. Genetic algorithm approach has been implemented to design double layer microwave absorber to further enhance the microwave absorption of the prepared composites for realizing a cost-effective solution. The optimum double layer results show the RL of −32.16 dB at 11.05 GHz with 1.67 mm total thickness and bandwidth corresponding to −10 dB is 2.35 GHz.

Development of Double Layer Microwave Absorber Using Genetic Algorithm

In this paper, an efficient two-layer microwave absorber at X-band is designed, optimized and implemented using the available materials with frequency dependent complex permittivity and complex permeability values as material database. The present work is focused on the design of a two-layer microwave absorber with good microwave absorption properties combined with broadband features at X-band. The optimization of various parameters such as materials, their sequence and thickness for obtaining better microwave absorption characteristics at X-band has been realized using Genetic Algorithm (GA). The optimized results were used to design a two-layer microwave absorber and experimentally tested using Attenuation Testing Device (ATD). Further verification of the experimentally obtained absorption results were simulated in High Frequency Structure Simulator (HFSS). The ATD result show that the maximum Reflection Loss (RL) for two-layer microwave absorber was -21.98 dB with 2.77 GHz bandwidth (corresponding to -10 dB) at 11.06 GHz for a total coating thickness of 1.5 mm.

Expanded graphite—Phenolic resin composites based double layer microwave absorber for X-band applications

In this investigation, double layer microwave absorbers are designed and developed with paired combination of 5 wt. %, 7 wt. %, 8 wt. %, and 10 wt. % expanded graphite-novolac phenolic resin (EG-NPR) composites, in the frequency range of 8.2–12.4 GHz. The thickness and compositional combination of the two layers constituting the absorber are optimized to achieve minimum value of reflection loss (dB) and a broad microwave absorption bandwidth. Double layer combinations showing −25 dB absorption bandwidth >2 GHz and −30 dB absorption bandwidth >1 GHz are chosen for fabrication. The total thickness of the fabricated double layer microwave absorber is varied from 3 mm to 3.4 mm. Absorption bandwidths at −10 dB, −20 dB, −25 dB and −30 dB are determined for the fabricated structure. The maximum −25 dB and −30 dB absorption bandwidth of 2.47 GHz and 1.77 GHz, respectively, are observed for the double layer structure with (5 wt. %–8 wt. %) EG-NPR composites with total thickness of 3.2 mm, while −10 dB bandwidth covers the entire X-band range.

High-temperature microwave bilayer absorber based on lithium aluminum silicate/lithium aluminum silicate-SiC composite

The microwave absorbing properties of lithium aluminum silicate (LAS) and LAS–SiC double layer composite absorbers were investigated within the frequency range of 8.2–12.4 GHz at 300–500 °C. The composite absorbers for use as high-temperature radar wave-absorbing materials were developed by hot-pressing LAS glass–ceramic and LAS–SiC composite, which were used as the impedance transformer layer and the low-impedance resonator layer, respectively. Nanometer-size β-SiC powders were fabricated at the relatively low sintering temperature of 1450 °C in argon atmosphere. The structure and morphology of the SiC powders were characterized using thermogravimetry-differential scanning calorimetry (TG-DSC), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The electromagnetic absorbing properties of the double layer at different temperatures and SiC contents were measured at normal temperature (27 °C) and high temperature by a vector network analyzer. The results indicate that the contents of nanometer-size β-SiC can increase the relative permittivity and dielectric loss of the double layer microwave absorbers. At high temperatures, the microwave absorber consisting of a 2-mm-thick layer of LAS ceramic and a 2-mm-thick layer of LAS–SiC composite with 10 wt% SiC content exhibited excellent performance with a minimum absorption at −42.8 dB at 10.5 GHz and the absorption bandwidth (reflection loss less than −10 dB) of 3.5 GHz in the X-band. The minimum reflection loss measured at 300–500 °C was less than −24 dB.

Double-layer type microwave absorber made of magnetic-dielectric composite material

Changing the combination of 2nd layer in a double-layer type microwave absorber, the matching frequency (8.10–10.88 GHz), maximum reflection loss and matching thickness at the matching frequency could be systematically controlled and compared with those of single-layer type microwave absorber.

Double-Layer Type Microwave Absorber Made of Magnetic-Dielectric Composite Material

Changing the combination of 1 st and 2 nd layer in a double-layer type microwave absorber, the matching frequency (5∼14GHz), the maximum reflection loss and matching thickness at the matching frequency could be systematically controlled and compared with those of single-layer type microwave absorber.

Development and Characterization of Hexagonal Ferrite based Microwave Absorbing Paints at Ku-Band

This paper deals with the development of single and double layer microwave absorbing paints using Mn-substituted Barium hexagonal ferrite. The comparative studies of both theoretical and experimental results at Ku-band have been reported. It has been found that the single layer absorbing paint exhibits peak absorption of 12.3 dB at 17.4 GHz for a thickness of 1.12 mm. Double layer absorbing paint with each layer of different composition of ferrite gives a broad band characteristics, but at the cost of lowered absorption.

Very high current ECR ion source for an oxygen ion implanter

A very high current ECR ion source is developed for a 50–100 mA oxygen ion implanter used for making SIMOX (separation by implanted oxygen) substrates with high production throughput. This newly developed ECR ion source achieves a 160 mA ion current with 20 mm beam diameter, that is, a very high-density ion current of 120 mA/cm 2. It also has a high desired O + to total ion ratio as well as having stability with reactive gas due to its no filament structure. To obtain high ion current density and maintain reliable operation, this source has a double layer microwave introduction window, an optimized axial magnetic field intensity and a short axis plasma chamber.