Yazar "Bayrakdar, H." seçeneğine göre listele
Listeleniyor 1 - 4 / 4
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Comparison effects and electron spin resonance studies of alpha-Fe2O4 spinel type ferrite nanoparticles(PERGAMON-ELSEVIER SCIENCE LTD, 2014) Bayrakdar, H.; Yalcin, O.; Cengiz, U.; Ozum, S.; Anigi, E.; Topel, O.alpha-Fe2O4 spinel type ferrite nanoparticles have been synthesized by cetyltrimethylammonium bromide (CTAB) and ethylenediaminetetraacetic acid (EDTA) assisted hydrothermal route by using NaOH solution. Electron spin resonance (ESR/EPR) measurements of alpha-Fe2O4 nanoparticles have been performed by a conventional x-band spectrometer at room temperature. The comparison effect of nanoparticles prepared by using CTAB and EDTA in different alpha-doping on the structural and morphological properties have been investigated in detail. The effect of EDTA-assisted synthesis for alpha-Fe2O4 nanoparticles are refined, and thus the spectroscopic g-factor are detected by using ESR signals. These samples can be considered as great benefits for magnetic recording media, electromagnetic and drug delivery applications. (C) 2014 Elsevier B.V. All rights reserved.Öğe Effect of different doping on the structural, morphological and magnetic properties for Cu doped nanoscale spinel type ferrites(ELSEVIER SCIENCE BV, 2013) Bayrakdar, H.; Yalcin, O.; Vural, S.; Esmer, K.CuxM1-xFe2O4 (M=Co, Mn and Ni; x=0.0, 0.6 and 1.0) spinel type ferrite nanoparticles have been synthesized by cetyltrimethylammonium bromide (CTAB) assisted hydrothermal route using NaOH solution. The purity, structural characterization and magnetic properties have been investigated using the scanning electron microscopy, x-ray diffraction analysis and a quantum design vibrating sample magnetometer depending on the temperature. The scanning electron microscopy imaging exhibits very powerful aspect. The average size of composite nanoparticles for all samples was determined. Diameter of the samples is synthesized in nanoscale. The x-ray diffraction results have indicated that these samples are high phase purity, crystalline and inverse spinel ferrites. The temperature evolution of the magnetic properties and different doping effects for the samples have been observed. The pseudo spin-valve behavior has been showed for Cu0.6Co0.4Fe2O4 and CoFe2O4 samples. These samples can be considered as promising materials for magnetic recording media and electromagnetic absorbing technologies applications. (C) 2013 Elsevier B.V. All rights reserved.Öğe Martensitic and austenitic transformations in core-surface cubic nanoparticles(ELSEVIER SCIENCE BV, 2015) Ozum, S.; Yalcin, O.; Erdem, R.; Bayrakdar, H.; Eker, H. N.As a continuation of our recently published work, we have used the pair approximation in Kikuchi version to investigate martensitic and austenitic transformations in homogeneous (HM) and composite (CM) cubic nanoparticles (CNPs) based on the Blume-Emery-Griffiths model. A single cubic nanoparticle made of a core surrounded by a surface is considered as shaped in two dimensional (2D) square arrays instead of hexagonal array. From the phase diagrams of HM and CM-CNPs it has been observed that the martensitic-austenitic transformations (MT-AT) occurred. The influence of the exchange coupling and single-ion anisotropy parameters in the model Hamiltonian on the MT-AT is studied and analyzed in comparison with the results for hexagonal nanoparticles. Significant changes of the phase transition points and hysteresis behaviours depending upon the particle structure have been discussed. (C) 2014 Elsevier B.V. All rights reserved.Öğe Origin of Cross-Over Phenomenon of Hysteresis Loops and High Absorption Loss Properties for Spinel Ferrite Nanoparticles(Polish Acad Sciences Inst Physics, 2021) Yalcin, O.; Bayrakdar, H.; Ozum, S.Spinel ferrite nanoparticles have been synthesized by the surfactant-assisted hydrothermal route using cetyltrimethylammonium bromide (CTAB) and ethylenediaminetetraacetic acid (EDTA) in the NaOH solution. Temperature evolution of magnetic hysteresis loops has been investigated in detail. The magnetic characterization of spinel nanoparticles has been measured by a quantum design vibrating sample magnetometer model 6000. The origin of a cross-over feature of ferrite nanoparticles has been observed at room temperature. Microwave properties of ferrites were investigated with the use of an Anritsu MS2028C VNA Master. The present studies also demonstrate that a microwave absorber can be fabricated within a ferrite polymer nanocomposite for technological applications up to 16 GHz, with the reflection loss of more than -60 dB and -50 dB by using CTAB and EDTA, respectively.
