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    Electromagnetic wave absorption in polyaniline coated Y3Fe5O12/Carbon-Black hybrid composites
    (Elsevier Science Sa, 2024) Akyol, Mustafa; Altay, Melek; Parajuli, Saroj; Teksen, Fikret Alpay; Karaaslan, Muharrem
    Y3Fe5O12(YIG)(1-x)/Carbon-Black(CB)(x) (0.00 <= x <= 1.00; 0.25 steps) coated with polyaniline (PANI), forming a core-shell structure, were synthesized by in-situ polymerization following sol-gel and solid-state reactions. The crystalline, surface morphology and magnetic properties of YIG(1-x)/CBx and PANI@YIG(1-x)/CBx hybrid composites were studied using X-ray diffraction (XRD), scanning electron microscopy (SEM), and vibrating sample magnetometer (VSM), respectively. Electromagnetic wave (EMW) absorbing properties were investigated by measuring dielectric parameters in the 2-18 GHz frequency range. The reflection loss (RL), impedance matching, and loss tangent were studied in detail. The electromagnetic wave absorbing mechanisms were discussed by considering dielectric and magnetic losses, as well as microstructural properties of the samples. The EMW absorbing performance of the YIG(1-x)/CBx composites showed a broadband absorption property (7.0 GHz bandwidth at -10 dB reflection loss value) in YIG(0.75)/CB0.25 composite. When the composites are covered with conductive PANI, the EMW absorbing performance is enhanced in terms of RL (minimum -36.5 dB) and effective absorption bandwidth (EAB) (maximum 10.2 GHz at -10 dB) values due to increasing scattering probability, interfacial polarization and conduction loss of the penetrated EMW. The results showed that a wider absorption frequency range could be obtained by coating PANI on YIG/CB composite.
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    Öğe
    Interfacial effect on the microwave absorption properties in Y3Fe5O12/ Fe2O3
    (Elsevier, 2024) Altay, Melek; Teksen, Fikret Alpay; Karaaslan, Muharrem; Akyol, Mustafa
    In this work, the interfacial effect on the electromagnetic wave (EMW) absorbing performance in Y3Fe5O12 and Fe2O3 material system synthesized by one-step sol-gel method followed by various sintering temperature was studied. The synthesized samples were first characterized by performing x-ray diffraction (XRD), scanning electron microscope (SEM) and vibrating sample magnetometer (VSM) measurements. A linear dependence of the saturation magnetization with the YIG content in the samples was observed that the saturation magnetization increases from 4.18 to 20.2 emu/g when the YIG crystal content is increased from 43 % to 88 %. Then, the EMW absorbing performance were studied by measuring dielectric parameters of the samples in the X-band. The experimental results indicate that the higher sintering temperature reduce the intensity of Fe2O3 peaks and enhance the formation of YIG chemical structure. Due to the both Fe2O3 and YIG crystal phases, the Fe2O3/ Y3Fe5O12 interface enhances the EMW polarization and thus EMW absorbing performance. The minimum reflection loss was determined as -15.4 dB at 9.5 GHz frequency in YF1000 sample. The experimental results demonstrate that the sintering temperature has the prominent effect on the structural, magnetic and EMW absorbing properties of YIG. The results would be useful for the YIG-based microwave device applications.
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    Öğe
    Phase (1T/2H) dependent electromagnetic wave absorbing performance of flower-like MoS2 nanosheets
    (Elsevier, 2023) Aka, Cemal; Kivrak, Burak; Teksen, Fikret Alpay; Akyildiz, Hasan; Akgol, Oguzhan; Karaaslan, Muharrem; Akyol, Mustafa
    A study was carried out to determine the phase-dependent electromagnetic wave (EMW) absorption performance of MoS2 particles via systematically diversified hydrothermal synthesis conditions such as time, temperature, precursor molarity, and oxalic acid concentration. The formation of mixed-phase structure was verified depending on the presence of the characteristic diffraction peaks belong to 1T (trigonal, P3?m1 space group) and 2H (hexagonal, P63/mmc space group) phases in the X-ray diffraction (XRD) patterns. Phase-pure 2H-MoS2 was obtained at 200 degrees C after 12 h of reaction and using 5 mmol oxalic acid. Microscopic examinations indicate that MoS2 particles formed by assembling several nanosheets to create a flower-like morphology. The size, shape, and the distance between the nanosheets were observed to change with increasing temperature, time, and acid concentration. The band gap was found to be modified depending on the phase distribution and decreased from 1.54 eV (2H) to a minimum of 0.64 eV (1T/2H) with the formation of the 1T (metallic) phase. Finally, the minimum reflection loss was measured as -67.73 dB (99.9999 % of absorption at 9.05 GHz) with an effective absorption bandwidth (EAB) of 3.52 GHz for the sample composed of 1T/2H mixed-phased structure.