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Öğe Electromagnetic Shielding Performance of Ta-Doped NiFe2O4 Composites Reinforced with Chopped Strands for 7-18 GHz Applications(MDPI, 2025) Emek, Mehriban; Sahin, Ethem Ilhan; Ibrahim, Jamal Eldin F. M.; Kartal, MesutThis study reports the synthesis, structural characterization, and electromagnetic shielding performance of tantalum (Ta)-doped nickel ferrite (NiFe2O4) composites reinforced with chopped strands. Ta-doped NiFe2O4 powders were prepared via the conventional mixed-oxide route and sintered at 1200 degrees C for 4 h, resulting in a well-crystallized single-phase spinel structure. Comprehensive structural and chemical analyses were carried out using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), confirming the successful incorporation of Ta into the NiFe2O4 lattice and the uniform microstructural distribution. The ferrite powders were subsequently embedded with chopped strands and epoxy resin through hot pressing to fabricate composites with varying filler contents. The electromagnetic interference (EMI) shielding effectiveness (SE) of the composites was systematically evaluated in the 7-18 GHz frequency range using a network analyzer (NA). The optimized composite, with a thickness of 1.2 mm, demonstrated a maximum SE of 34.74 dB at 17.4 GHz, primarily attributed to interfacial polarization, dipolar relaxation, and multiple scattering effects induced by the chopped strands. The results indicate that the shielding performance of the composites can be precisely tuned by modifying the filler concentration and microstructural characteristics, enabling selective frequency-band applications. Overall, this work highlights the potential of Ta-doped NiFe2O4/chopped strand composites as lightweight, cost-effective, and high-performance candidates for advanced microwave absorption and electromagnetic shielding applications in defense, and next-generation communication technologies.Öğe Glass-ceramic foams produced from zeolite-poor rock (Tokaj)(Akademiai Kiado ZRt., 2023) Ibrahim, Jamal Eldin F. M.; Tihtih, Mohammed; Kurovics, Emese; Şahin, Ethem Ilhan; Gömze, László A.; Kocserha, IstvánThis study evaluated the possibility of producing innovative glass-ceramic foams from zeolite-poor rock (Tokaj, Hungary) using alkali-activation and reactive sintering techniques. The composition and morphology of the samples were studied using X-ray diffraction, X-ray fluorescence, scanning electron microscope, and computed tomography techniques. The influence of various sintering temperatures on glass-ceramic foams was examined. It has been observed that zeolite-poor rock has a self-foaming capability. The heat treatment temperature affects the pore size and distribution as well as the technical characteristics of the obtained samples. The resulting glass-ceramic foams possess moderate thermal conductivity ranging from 0.11 to 0.17 W mK-1 and good compressive strength (1.5-4.4 MPa). The produced samples might be utilized for thermal insulation, which would have both economic and environmental advantages. © 2022 The Author(s).Öğe Production and Shielding Effectiveness Features of Chopped Strands Backed-GdMnO3 Composites for 6.5-17.5 GHz Applications(MDPI, 2025) Emek, Mehriban; Sahin, Ethem Ilhan; Ibrahim, Jamal Eldin F. M.This research investigates the synthesis and characterization of GdMnO3/chopped strands composites using the conventional oxide mixing technique. A single-phase GdMnO3 compound was successfully formed through sintering at 1350 degrees C for 20 h. Structural analysis using X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) confirmed phase purity and uniform grain morphology. The microwave shielding effectiveness of GdMnO3/chopped strands composites was evaluated within the 6.5-17.5 GHz frequency range using a network analyzer (NA). The GdMnO3/chopped strands composite with a 60-40% weight ratio exhibited superior shielding performance, achieving a minimum shielding effectiveness of -35.61 dB at 6.9 GHz, while the 80-20% composite reached -32.54 dB at 16.74 GHz. Both compositions demonstrated shielding effect values below -10 dB across wide frequency bands, with significant attenuation below -20 dB at various GHz ranges. The study demonstrates that by adjusting the content of the components in the samples, the microwave shielding effect performance of the GdMnO3/chopped strands composites can be easily controlled to meet the requirements of specific frequency bands. These findings highlight the potential of GdMnO3-based composites for tailored microwave shielding applications, particularly in the military, aerospace, and telecommunication industries.Öğe Shielding effectiveness performance of polyaniline-NiFe2O4:Cu composites for sub-8 GHz applications(Springer, 2023) Sahin, Ethem Ilhan; Emek, Mehriban; Ibrahim, Jamal Eldin F. M.; Yumusak, Goerkem; Kartal, MesutHerein, NiFe2O4 doped Cu was synthesized using a mixed-oxide method to investigate its potential for creating composites with high microwave shielding effectiveness. The compound NiFe2-xCuxO4 was synthesized with x values of 0.1, 0.3 and 0.5, respectively. After sintering at 1250 degrees C for 4 h, single-phase Ni ferrite was formed. To analyze the phase composition and the structure of the synthesized compound, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were employed. The study's findings showed that NiFe2-xCuxO4 did not exhibit a second phase. To create composites with high microwave shielding effectiveness, polyaniline-NiFe2O4:Cu composites were fabricated using a hot-pressing technique, with compositions of NiFe1.9Cu0.1O3.95, NiFe1.7Cu0.3O3.85 and NiFe1.5Cu0.5O3.75 with the aniline, The weight ratios of Cu-added nickel ferrite and aniline were changed from 1:1 to 1:3, and epoxy resin was used. Using a two-port vector network analyzer, the polyaniline-NiFe2O4:Cu composites' microwave shielding effectiveness performance was examined in the range between 0 and 8 GHz. The study found that the shielding effect of the composites could be easily modified by changing the amount of polyaniline present in the specimens for the appropriate frequency bands. At 6.82 GHz, using a sample with a thickness of 2.0 mm, a minimum shielding effect performance of - 29.74 dB was achieved. Overall, the results of this study demonstrate the potential of polyaniline-NiFe2O4:Cu composites as effective microwave shielding materials.Öğe Shielding effectiveness performance of polyaniline-NiFe2O4:Cu composites for sub-8 GHz applications (vol 55, 500, 2023)(Springer, 2023) Sahin, Ethem Ilhan; Emek, Mehriban; Ibrahim, Jamal Eldin F. M.; Yumusak, Goerkem; Kartal, Mesut[Abstract Not Available]Öğe Sustainable zeolitic tuff incorporating tea waste fired ceramic bricks: Development and investigation(Elsevier, 2023) Ibrahim, Jamal Eldin F. M.; Tihtih, Mohammed; Sahin, Ethem Ilhan; Basyooni, Mohamed A.; Kocserha, IstvanThe present research examines the development of new porous ceramic bricks from Hungarian zeolitic tuff and tea waste as building materials. Recycling waste materials as a pore-forming agent in brick-making is a promising solution to environmental and economic challenges. Several zeolitic tuff/tea waste admixtures were milled in the planetary ball milling to produce homogenous powders. The substitution ratios were maintained as 0 %, 2 %, 4 %, 6 %, 8 %, 10 %, and 12 % by wt of zeolitic tuff. The ceramic disks were produced from the prepared mixtures via dry pressing and sintering at various temperatures (950-1250 degrees C) for consolidation. The produced bricks were investigated based on bulk density, apparent porosity, water absorption, volume shrinkage, thermal conductivity and compressive strength, as well as mineralogical, chemical, and morphological studies. The mineralogical determination confirms the existence of clinoptilolite, montmorillonite, cristobalite and illite as major phases in zeolite tuff. The experimental results reveal that the addition of tea waste produces hybrid bricks with better thermal insulation (0.17-0.504 W/m K), lighter weight (1.37-1.81 g/cm3), and lower compressive strength (5.52-34.4 MPa). However, the compressive strength value still lies within the range required by the standards. The production of burned bricks containing up to 10 wt% tea waste is viable without causing major changes in their technical characteristics. Developing new porous bricks using waste materials can help expand the application of sustainable and cost-effective insulation bricks in the construction industry.
