Yazar "Ibrahim, Jamal-Eldin F. M." seçeneğine göre listele

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    Eco-Friendly Synthesis of Geopolymer Foams from Natural Zeolite Tuffs and Silica Fume: Effects of H2O2 and Calcium Stearate on Foam Properties
    (MDPI, 2025) Sahin, Ethem Ilhan; Ibrahim, Jamal-Eldin F. M.
    The need for environmentally friendly and energy-efficient building materials has increased significantly. This study synthesizes geopolymer foams with enhanced thermal insulation properties using silica fume and natural zeolite tuff. Zeolite's porous structure and active sites improve polymerization and strengthen the foam, while silica fume reacts with NaOH to release sodium silicate, forming a durable geopolymer matrix. Foam porosity is introduced by generating oxygen gas from H2O2 and NaOH, with calcium stearate stabilizing the foam structure. Comparative analysis of the compressive strength, bulk density, porosity, and thermal conductivity shows that incorporating H(2)O(2 )and calcium stearate significantly reduces thermal conductivity (from 0.19 to 0.06 W/mK) while ensuring a highly porous system (66-82.6% porosity) with adequate mechanical strength (1.6-3.39 MPa). These findings highlight the potential of the developed geopolymer foam for sustainable insulation applications.
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    High-Performance NiO/PANI/ZnNb2O6 Composites for EMI Shielding: Structural Insights and Microwave Shielding Effectiveness in the Sub-8 GHz Range
    (MDPI, 2025) Emek, Mehriban; Sahin, Ethem Ilhan; Ibrahim, Jamal-Eldin F. M.
    The increasing demand for high-frequency applications and the widespread use of electromagnetic (EM) waves in communication systems necessitate the development of effective electromagnetic interference (EMI) shielding materials. This study investigates the structural and shielding effectiveness properties of novel polyaniline (PANI)-based NiO/ZnNb2O6 composites for sub-8 GHz applications. NiO and ZnNb2O6 were synthesized via conventional solid-state reactions and combined with PANI to form composites with varying compositions. X-ray diffraction (XRD) confirmed the successful formation of single-phase NiO and ZnNb2O6, while scanning electron microscopy (SEM) revealed well-defined microstructures, contributing to enhanced shielding efficiency. Shielding effectiveness (SE) measurements were performed across the 0-8 GHz frequency range using a vector network analyzer. Among the compositions tested, the epoxy-based NiO-ZnNb2O6 (75-25% by weight) with a 1:1 PANI ratio exhibited the highest SE value of -41.16 dB (decibels) at 6.24 GHz, demonstrating superior attenuation of EM waves. The observed shielding efficiency is attributed to multiple reflection effects, dipole interactions, and the conductive network formed by PANI. These findings highlight the potential of NiO/PANI/ZnNb2O6 composites as cost-effective, high-performance EMI shielding materials for next-generation microwave communication and electronic applications. Further optimization and hybridization approaches are recommended to enhance performance for broader frequency bands.
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    Structural and shielding effectiveness properties of (NiFe2O4/chopped strands) composites for 6.5-18 GHz applications
    (Springer, 2024) Sahin, Ethem Ilhan; Ibrahim, Jamal-Eldin F. M.; Emek, Mehriban; Sinsoysal, Bahaddin; Amanzholova, Alina
    In this research, a mixed oxide technique was employed to create composite materials comprising NiFe2O4-chopped strands, aimed at evaluating their structural properties and microwave shielding effectiveness. The composites, produced through a hot-pressing process with varying proportions of NiFe2O4 and chopped strands, were integrated with epoxy to enhance their shielding capabilities. X-ray diffraction confirmed the formation of single-phase NiFe2O4, free from secondary phases. Scanning electron microscopy analysis corroborated the presence of cubic crystalline NiFe2O4, without microstructural impurities. The microwave shielding performance of the composites was assessed within the 6.5-18 GHz frequency range using a network analyzer (NA), revealing a minimum shielding effectiveness of - 36.34 dB at 16.56 GHz for a 1.3 mm thick sample. These findings demonstrate the successful fabrication of NiFe2O4-chopped strands composites with tunable microwave shielding properties, achieved by adjusting the NiFe2O4 content, allowing for tailored performance across various frequency bands.
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    Öğe
    Structural and shielding effectiveness properties of (NiFe2O4/chopped strands) composites for 6.5-18 GHz applications (vol 35, 1407, 2024)
    (Springer, 2024) Sahin, Ethem Ilhan; Ibrahim, Jamal-Eldin F. M.; Emek, Mehriban; Sinsoysal, Bahaddin; Amanzholova, Alina
    [Abstract Not Available]