Yazar "Sahin, Ethem Ilhan" seçeneğine göre listele

Listeleniyor 1 - 11 / 11
  • [ X ]
    Öğe
    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.
  • [ X ]
    Öğe
    Electromagnetic shielding effectiveness of Ba(Zn1/3Nb2/3)O3: chopped strands composites for wide frequency applications
    (Korean Assoc Crystal Growth, Inc, 2023) Sahin, Ethem Ilhan
    In this work, the conventional mixed oxide process was used to form Ba(Zn1/3Nb2/3)O-3-chopped strands composites. The single phase compound with the chemical equation Ba(Zn1/3Nb2/3)O-3 was generated after sintering at 1250 degrees C for 4 h. Varied amounts of Ba(Zn1/3Nb2/3)O-3-chopped strands were fabricated for the structural examination. X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) were carried out for the structural analysis, and the results showed that the second phase did not form in Ba(Zn1/3Nb2/3)O-3. In addition to, the Ba(Zn1/3Nb2/3)O-3-strands composites were created by hot pressing using the compositions of Ba(Zn1/3Nb2/3)O-3-chopped strands in various rates and epoxy. The Ba(Zn1/3Nb2/3)O-3-chopped strands compound created in varied weights, and epoxy powder were utilized to manufacture microwave shielding effect composites. Using a two-port vector network analyser (VNA) device, the microwave shielding effect of Ba(Zn1/3Nb2/3)O-3-chopped strands composites was examined in a range of 0-8 GHz. A minimal of -44.75 dB shielding effectiveness value was reached at 6.24 GHz and 1.4 mm in thick. The Ba(Zn1/3Nb2/3)O-3-chopped strands were fabricated as composite and their properties were defined characterized for shielding effectiveness. To modify microwave shielding effectiveness, the content of components in the specimens may be adjusted for the wider and required frequency ranges.
  • [ X ]
    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, Mesut
    This 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.
  • [ X ]
    Öğe
    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.
  • [ X ]
    Öğe
    Production and microwave electromagnetic shielding effectiveness of polyaniline-La2Ti2O7:Er,Yb composites
    (Korean Assoc Crystal Growth, Inc, 2021) Sahin, Ethem Ilhan; Canturk, Selim Burak; Emek, Mehriban; Genc, Seval; Kartal, Mesut
    In this research, La2Ti2O7 doped with erbium-ytterbium was produced by using solid state technique. A series of compounds with the chemical equation (La1-x-yREx-y)(2)Ti2O7 were doped with (Er3+, x = 0.025, 0.050) and (Yb3+ y = 0.02) rare earth ions prepared by conventional solid state reaction method at 1350 degrees C for 24 h. X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) were carried out for the structural analysis, which showed that second phase did not form in (La1-x-yREx-y)(2)Ti2O7. Additionally, the polyaniline- erbium, ytterbium doped La2Ti2O7 composites were fabricated via hot pressing using the compositions of (La0.955Yb0.02Er0.025)(2)Ti2O7, (La0.93Yb0.02Er0.05)(2)Ti2O7 and aniline. The weight ratios of erbium-ytterbium doped lanthanum titanate and aniline were 1:1 and 1:3 respectively, and epoxy resin was utilized to develop microwave shielding effectiveness composites. The microwave shielding effectiveness performances of polyaniline- La2Ti2O7: erbium-ytterbium composites were examined by shielding effect in 0-8 GHz using two-port vector network analyzer. A minimum of - 34.37 dB shielding effect performance was obtained in 6.27 GHz at the thickness of 2.0 mm. This shielding effect performance can be adjusted easily by managing the content of polyaniline in the composites for the needed frequency bands.
  • [ X ]
    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.
  • [ X ]
    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, Mesut
    Herein, 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.
  • [ X ]
    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]
  • [ X ]
    Öğe
    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.
  • [ X ]
    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]
  • [ X ]
    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, Istvan
    The 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.