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Öğe Absorbing the entire X-band via conductive polymer polyaniline coated Y3Fe5O12/NiFe2O4 hybrid composites(Springer, 2023) Akyol, Mustafa; Aka, Cemal; Inozu, Onat; Alkurt, Fatih Ozkan; Karaaslan, MuharremConductive polymer coated Y3Fe5O12 (YIG)/NiFe2O4 (NFO) hybrid radar absorbing composites were studied in this work. The magnetic YIG and NFO particles were synthesized by sol-gel method, and then covered with a conductive PANI polymer by in-situ polymerization technique. The structural and magnetic properties of produced particles and hybrid composites were studied by XRD, SEM and VSM measurements. The microwave property of the hybrid composites reinforced in the epoxy matrix was studied in the X-band frequency range. The electromagnetic wave absorbing bandwidth in the X-band increases with the content of YIG in the hybrid composites. A broadband radar absorbing has been observed in EPYN08 and EPYN10 hybrid composites having entire X-band with an absorption criterion of - 10 dB. The maximum reflection loss (RL) value was found as - 35.1 dB at 10.8 GHz frequency in EPYN06 sample. The nanocomposite structures formed by combining magnetic and dielectric materials show better electromagnetic wave absorption properties rather than the each components in the composites. Hence, the experimental results of hybrid composites may be a promising candidate for radar and defense vehicles due to their fully absorbing property in the X-band.Öğe Broadband electromagnetic wave absorbing via PANI coated Fe3O4 decorated MoS2 hybrid nanocomposite(Elsevier Science Sa, 2023) Aka, Cemal; Akgol, Oguzhan; Karaaslan, Muharrem; Akyol, MustafaHigh performance electromagnetic wave (EMW) absorbing material systems are required for stealth applications and sensitive electronic devices. Absorbing of an incident EMW in a wide band range still has limitations in terms of materials system and engineering. It is required to extend the bandwidth and minimize the reflection from the material system for the next level stealth technologies. In this work, hybrid nanocomposite structures are developed by semiconductor flower-like MoS2 nanosheets, Fe3O4 magnetic nanoparticles and conductive poly aniline. A systematic study is presented by investigation the structural, magnetic, morphological, thermal, electronic and electromagnetic characteristic of hybrid nanocomposites (Fe3O4:MoS2, PANI@Fe3O4, PANI@MoS2 and PANI@Fe3O4:MoS2). EMW absorption characteristics results showed that Fe3O4:MoS2 and PANI@Fe3O4:MoS2 hybrid nanocomposites exhibit excellent EMW absorption characteristics. While the minimum reflection loss (RL) value was found as 54.97 dB at 15.99 GHz for the Fe3O4:MoS2 nanocomposite, the broad bandwidth (7.65 GHz) was observed in PANI@Fe3O4:MoS2 hybrid nanocomposite having 39.96 dB RL. According to the experimental results, a lightweight and high temperature resistance PANI@Fe3O4:MoS2 like hybrid nanocomposite can absorb almost 90% of incident EMW in a wide bandwidth.Öğe 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, MuharremY3Fe5O12(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.Öğe Interfacial effect on the microwave absorption properties in Y3Fe5O12/ Fe2O3(Elsevier, 2024) Altay, Melek; Teksen, Fikret Alpay; Karaaslan, Muharrem; Akyol, MustafaIn 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.Öğe Investigation of structural, magnetic and microwave absorption properties of NixCo1-xFe2O4/Ni:ZnO (x:0.0, 0.5, and 1.0) embedded epoxy composites(Springer Heidelberg, 2022) Kivrak, Burak; Tumen, Kutluhan Utku; Karaaslan, Muharrem; Akyol, MustafaIn this study, NixCo1-xFe2O4/Ni:ZnO (x:0.0, 0.5, and 1.0) epoxy-based composite structures were manufactured by sol-gel method. The structural, morphological and magnetic characteristics were investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). Electromagnetic wave (EMW) absorption measurements were carried out using a vector network analyzer (VNA) between 8 and 12 GHz (X band). Ni substitution with Co decreases the crystallite size, average particle size, magnetic saturation (M-s) and the coercive field (H-c) values of cobalt-ferrite spinel structure. EMW characterization results showed that minimum reflection loss (RL) - 30.91 dB (99.9% absorption) at 10.76 GHz, and the maximum bandwidth of 1.81 GHz were observed for the RAM1 composite. In addition, the substitution of Ni2+ into the cobalt-ferrite structure resulted in the shifting absorption peaks to the higher frequency region (towards K-u band).Öğe Multi-band polarization independent cylindrical metamaterial absorber and sensor application(World Scientific Publ Co Pte Ltd, 2016) Dincer, Furkan; Karaaslan, Muharrem; Colak, Sule; Tetik, Erkan; Akgol, Oguzhan; Altintas, Olcay; Sabah, CumaliA multi-band perfect metamaterial absorber (MA) based on a cylindrical waveguide with polarization independency is numerically presented and investigated in detail. The proposed absorber has a very simple configuration, and it operates at flexible frequency ranges within the microwave frequency regime by simply tuning the dimensions of the structure. The maximum absorption values are obtained as 99.9%, 97.5%, 85.8%, 68.2% and 40.2% at the frequencies of 1.34 GHz, 2.15 GHz, 3.2 GHz, 4.31 GHz and 5.41 GHz, respectively. The numerical studies verify that the proposed model can provide multi-band perfect absorptions at wide polarization and incident angles due to its rotational symmetry feature. We have also realized sensor and parametric study applications in order to show additional features of the suggested model. The suggested MA enables myriad potential applications in medical technologies, sensors and in defense industry etc.Öğe Optimizing the Gain and Directivity of a Microstrip Antenna with Metamaterial Structures by Using Artificial Neural Network Approach(Springer, 2021) Sağık, Metin; Altıntaş, Olcay; Ünal, Emin; Özdemir, Ersin; Demirci, Mustafa; Çolak, Şule; Karaaslan, MuharremThe purpose of this study is to improve the gain and directivity of the microstrip patch antenna by means of metamaterial (MTM) structures. As it is known, antennas have power densities in a certain direction, and the radiation curves of the antennas are shaped by orienting them according to this power density. Based on this feature of the antennas, it is aimed to improve the gain and directivity of microstrip patch antennas with the most suitable structures thanks to metamaterial (MTM) structures. The MTM structures designed are interacted with the antenna. Then, the frequency, gain and directivity of the antenna are trained by the artificial neural network technique to estimate the most appropriate values. As a result, the gain and directivity of the antenna are improved by the interaction of microstrip patch antenna and MTM structures and the results are interpreted on the figures. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC part of Springer Nature.Öğe PANI-coated YIG/CFO hybrid composites as advanced electromagnetic wave absorber through X-band(Elsevier Science Sa, 2023) Kivrak, Burak; Sergun, Atalay; Karaaslan, Muharrem; Akyol, MustafaPolyaniline (PANI)-coated Y3Fe5O12(YIG)/CoFe2O4(CFO) hybrid composites were synthesized via sol-gel and oxidative polymerization methods to achieve advanced microwave absorption properties. The structural, morphological, magnetic, and microwave absorption characteristics of the resulting samples were analyzed by performing X-ray diffraction (XRD), scanning electron microscopy (SEM), vibration sample magnet-ometer (VSM), and vector network analyzer (VNA). XRD results revealed that CFO and YIG have cubic crystal structures with Fd3m and Ia3d space symmetry, respectively, with an average crystallite size of 35.3 nm and 42.9 nm. The Ferro/ferrimagnetic signals were detected from the ferrite samples' room temperature magnetic hysteresis loops. The incorporation of PANI and YIG into the composites resulted in a decrease in their magnetic saturation (Ms) and coercive field (Hc) values. VNA measurements demonstrated that nearly all samples achieved 90% absorption (& LE;-10 dB) of incident electromagnetic waves throughout the X-band frequency range. The minimum reflection loss (RLmin) value reaches - 47.34 dB at 8.14 GHz, with an effective bandwidth of 4.00 GHz, covering the entire X-band and beyond. These impressive absorption characteristics suggest that the manufactured composites possess potential as viable candidates for defense applications conducted at X-band frequency.& COPY; 2023 Elsevier B.V. All rights reserved.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, MustafaA 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.Öğe Polyaniline-Functionalized Nanosized Cobalt Ferrite-Decorated MoS2 Composites for Broadband Electromagnetic Wave Absorption(Amer Chemical Soc, 2024) Kivrak, Burak; Akyildiz, Hasan; Akgol, Oguzhan; Karaaslan, Muharrem; Akyol, MustafaThis study presents the synthesis of polyaniline (PANI)-coated cobalt ferrite-decorated molybdenum disulfide (MoS2@CoFe2O4); a composite architecture engineered to combine unique morphological, magnetic, and dielectric properties for the electromagnetic wave/radar absorption applications. MoS2 and CoFe2O4 were produced separately using a one-step hydrothermal process. Then, the CoFe2O4 nanoparticles were integrated into the flower-like MoS2 nanosheets using the sonication method. Finally, PANI was synthesized through in situ polymerization of aniline on the surface of MoS2@CoFe2O4 to create the final design as well as to boost the dielectric performance. Structural analysis confirmed the existence of the 2H phase and a minor trace of the 1T phase in MoS2, while CoFe2O4 displayed a cubic structure without any detectable impurities. Scanning electron microscopy verified the successful distribution of CoFe2O4 particles within the MoS2 nanosheets, aligning with the design's intended configuration. The electromagnetic wave (EMW) characteristics of the composites were analyzed by using a vector network analyzer. The MoS2@CoFe2O4 demonstrated a broad effective absorption bandwidth, spanning from the X-band to the Ku-band with a minimum matching thickness of just 2 mm. The reflection loss minimum value (RLmin) reached -22.82 dB at 8.96 GHz, corresponding to a 99.47% absorption of the incident EMWs. The addition of PANI at 50% by weight further increased the RLmin value to approximately 99.999% absorption (-50 dB), indicating enhanced impedance matching and absorption efficiency.Öğe Synthesis and characterization of nanoparticles reinforced epoxy based advanced radar absorbing composites(Springer, 2021) Tümen, Kutluhan Utku; Kıvrak, Burak; Alkurt, Fatih Özkan; Akyol, Mustafa; Karaaslan, Muharrem; Ekicibil, AhmetIn this study, the structural and magnetic properties of NixCo1?xFe2O4 (0.0? x? 1.0) and ZnO nanoparticles synthesized by the sol-gel method were investigated. The microwave property of the composite structures produced from the combination of ZnO and NixCo1?xFe2O4 nanoparticles dispersed in the epoxy matrix property was studied in the X-band frequency range. The crystal structures of NixCo1?xFe2O4 have not been disrupted by Ni substitution, however, the lattice parameters of samples decrease due to the smaller ionic radii of Ni+2 compared to Co+2 ions. The magnetic saturation (Ms) and remanence magnetization (Mr) decreased with an increasing amount of Ni in NixCo1?xFe2O4 structure. According to the microwave absorption properties of samples, the maximum reflection loss (RL) value was found as ?28.10 dB at 10.23 GHz frequency in RAC4 sample. On the other hand, maximum bandwidth was found at 2.95 GHz around ?10 dB for RAC5 sample. All composites exhibit efficient RL in the X-band indicating that they can be used in potential applications in aviation, radar, and defense vehicles. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.Öğe Tunable left-hand characteristics in multi-nested square-split-ring enabled metamaterials(Central South University of Technology, 2020) Abdulkarim, Yadgar. I.; Deng, Lian-wen; Yang, Jun-liang; Çolak, Şule; Karaaslan, Muharrem; Huang, Sheng-xiang; He, Long-huiLeft-hand materials have drawn increasing attention from many disciplines and found widespread application, especially in microwave engineering. A sandwiched metamaterial consisting of multi-nested square-split-ring resonators on the top side and a set of wires on the back side is proposed. Scattering parameters are retrieved by high-frequency structure simulator (HFSS) software based on the finite element method. Effects of square-split-ring number on the left-hand characteristics containing negative values of permittivity, permeability, and refractive index have been intensively investigated. Simulated results show that obvious resonant left-hand characteristics could be observed within 8–18 GHz, and the resonant frequency counts are inclined to be in direct proportion to the square-split-ring number over 8–18 GHz. Besides, the proposed sandwiched metamaterial with three square-split-ring resonators and three wires presents the widest frequency band of left-hand characteristics in a range of 8–18 GHz. Further, electromagnetic field distributions demonstrated that the induced magnetic dipole dominates the resonant absorption. The multi-peak resonance characteristics of square-split-ring resonant structure are considered to be a promising candidate for selective-frequency absorption or modulation toward microwave frequency band. © 2020, Central South University Press and Springer-Verlag GmbH Germany, part of Springer Nature.
