Yazar "Onar, K." seçeneğine göre listele
Listeleniyor 1 - 6 / 6
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Characterization of Fe3O4 Nano Particles for Biomedical Applications(Ieee, 2015) Onar, K.; Yakinci, M. E.Nano particles of Fe3O4 with the range of 30 and 60 nm were synthesized by using chemical coprecipitation method. Particle size effects according to magnetic properties were investigated together with the constant reaction and crystallization temperature. According to calculations peaks were indexed as cubic Fe3O4 for all samples. The hysteresis loops shows superparamagnetic behavior. It was found that when Fe2+/Fe3+ ratio increase to 50% the particle size increases approximately one fold. We realized that chemical coprecipitation method is suitable for biomedical applications of Fe3O4 nano particles.Öğe Effect of grain size on the electrical and magnetic properties of MgB2 thick films deposited on the Al2O3 single crystal substrates(Springer, 2014) Onar, K.; Balci, Y.; Yakinci, M. E.MgB2 films having thicknesses of approximately 10 mu m have been prepared on the Al2O3 single crystal substrates by using ultrasonic spray pyrolysis technique. The films fabricated were then analyzed by means of microstructural, structural, transport and magnetic properties. The influence of grain size, depending on the ex-situ and in situ heating, were investigated. The results obtained showed that the size of MgB2 grains has an effect on the transport and magnetic properties of the films. Films prepared with in situ heating have small particle size (< 50 nm) and were found to be much better properties than the films prepared ex-situ heating, which have larger grains (similar to 1 mu m). The best T (c) value and critical current density, J (c) (mag) , were obtained to be similar to 36 K and 9.88 x 10(5) A cm(-2) respectively for the films prepared with small grains. The results were showed that the smaller grain size and in situ heating cycles are essential points for quality thick film MgB2 fabrication.Öğe Enhanced physical properties of single crystal Fe0.99Te0.63Se0.37 prepared by self-flux synthesis method(Elsevier Science Sa, 2016) Onar, K.; Oezcelik, B.; Guler, N. K.; Okazaki, H.; Takeya, H.; Takano, Y.; Yakinci, M. E.In this study, we have systemically studied the physical, electrical and magnetic properties of Fe0.99Te0.63Se0.37 single crystalline samples prepared by self-flux method. We found that the self-flux method is a suitable synthesis technique for this alloys if setting of experimental parameters made carefully. The M-H curve affirms that samples are typical type-II superconductor. Strong sign of bulk superconductivity, even after high field measurements, were seen. Calculated J(c)(mag) values, at zero field, were found to be 7.7 x 10(5) Acm(-2) and 2.6 x 10(4) Acm(-2) for 5 K and 10 K respectively. The upper critical field H-c2(0) has been determined with the magnetic field parallel to the sample surface and yielding a maximum value of 65 T. At the zero field coherence length, xi, value was calculated to be 2.24 nm for 10% T-c(offset) which is significantly larger (approximately 6 fold) than the unit cell, a, and indicating the absence of weak link behavior in the sample. Calculated mu H-0(c2)(0)/k(B)T(c) rate indicated comparably higher value (3.66 T/K) than the Pauli limit (1.84 T/K) and obtained results were suggested unconventional nature of superconductivity in our samples. (C) 2016 Elsevier B.V. All rights reserved.Öğe Solid state synthesis and characterization of bulk ?-FeSe superconductors(Elsevier Science Sa, 2015) Onar, K.; Yakinci, M. E.Polycrystalline FeSe0.88 was synthesized by solid-state reaction method in sealed quartz tube at different heat heating cycles. The identification and characterization of FeSe0.88 samples were determined by X-ray Diffraction (XRD), Scanning Electron Microscope (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). The electrical transport, magnetic and thermal transport properties of the obtained samples were also investigated. The results showed that the sensitivity of resistivity and magnetic susceptibility depends on heating cycles while the structural formation of samples does not. The upper critical field H-c2(0) has been determined with the magnetic field parallel to the sample surface and yielding a maximum value of 23.2 T. At the zero field coherence length, xi, value was calculated to be 3.33 nm. Calculated mu H-0(c2)(0)/k(B)T(c) rate indicated comparably higher value (3.17 T/K) than the Pauli limit (1.84 T/K) and obtained results were suggested unconventional nature of superconductivity in our samples. (C) 2014 Elsevier B.V. All rights reserved.Öğe Solid state synthesis and characterization of bulk FeTe0.5Se0.5 superconductors(Iop Publishing Ltd, 2016) Onar, K.; Yakinci, M. E.FeTe0.5Se0.5 polycrystalline superconductor samples were synthesized by solid-state reaction method at different heating temperatures. The morphological and structural characterization of FeTe0.5Se0.5 samples were carried out by X-rays Diffraction, Scanning Electron Microscope and Energy Dispersive X-ray Spectroscopy. The electrical, magnetic and thermal transport properties were investigated up to 8 T by using physical property measurement system. The results reveal that the sensitivity of electrical and magnetic properties strongly depends on the heat treatment cycles. The upper critical field, H-c2(0), was determined with the magnetic field parallel to the sample surface. It gives a maximum value of 36.3 T. The lower critical field, H-c1(T), was obtained as 210, 140 and 70 Oe at 5, 8 and 12 K, respectively. The coherence length, xi, at the zero field, was calculated to be 1.94 nm and suggested a transparent intergrain boundaries peculiarity. The mu H-0(c2)(0)/k(B)T(c) rate shows higher value (3.36 T/K) than the Pauli limit (1.84 T/K) which suggests unconventional nature of superconductivity for the polycrystalline FeTe0.5Se0.5 superconducting samples.Öğe Synthesis of Fe3O4 nanoparticles for biomedical applications(Iop Publishing Ltd, 2016) Onar, K.; Yakinci, M. E.Nano particles of Fe3O4 with the range of 6.9 and 14.2 nm. By using chemical coprecipitation method. Particle size effect according to magnetic properties were investigated together with the constant reaction and crystallization temperature. According to calculations peaks were indexed as cubic Fe3O4 for all samples. The hysteresis loops shows superparamagnetic nature. It was found that when Fe2+/Fe3+ ratio increase 50% the particle size increases approximately one fold. We also realized that chemical coprecipitation method is suitable for biomedical applications of Fe(3)O(4)nano particles.
