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Öğe Effect of Mn Addition on Structural and Superconducting Properties of (Bi, Pb)-2223 Superconducting Ceramics(Springer, 2012) Yildirim, G.; Bal, S.; Yucel, E.; Dogruer, M.; Akdogan, M.; Varilci, A.; Terzioglu, C.This study deals with the effect of Mn addition on the structural and superconducting properties of Bi1.8Pb0.4Sr2Mn (x) Ca2.2Cu3.0O (y) ceramics with x=0,0.03,0.06,0.15,0.3 and 0.6 by means of X-ray analysis (XRD), scanning electron microscopy (SEM), electron dispersive X-ray (EDX), resistivity, and transport critical current density (J (c)) measurements. Zero-resistivity transition temperatures (T (c)) of the samples produced via the standard solid-state reaction method are estimated from the dc resistivity measurements. Moreover, the phase fraction and lattice parameters are determined from XRD measurements while the microstructure, surface morphology and element composition analyses of the samples are investigated by SEM and EDX measurements, respectively. It is found that T (c) values are obtained to decrease from 109 K to 85 K; likewise, J (c) values are observed to reduce from 3200 A/cm(2) to 125 A/cm(2) with increasing Mn addition. According to the refinement of cell parameters done by considering the structural modulation, the Mn addition is confirmed by both an increase of the lattice parameter a and a decrease of the cell parameter c of the samples in comparison with that of the pure sample (Mn0). SEM measurements show that not only the surface morphology and grain connectivity are seen to degrade but the grain sizes of the samples are found to decrease with the increase of the Mn addition as well. The EDX results reveal that the elements used for the preparation of samples distribute homogeneously and the Mn atoms enter into the crystal structure by replacing Sr and Cu atoms. The possible reasons for the obtained degradation in microstructural and superconducting properties are also interpreted.Öğe Effects of different annealing atmospheres on the properties of cadmium sulfide thin films(Pergamon-Elsevier Science Ltd, 2015) Yucel, E.; Kahraman, S.; Guder, H. S.Cadmium sulfide (CdS) thin films were prepared on glass substrates by using chemical bath deposition (CBD) technique. The effects of different annealing atmospheres (air and sulfur) on the structural, morphological and optical properties of CdS thin films were studied at three different pH values. Compactness and smoothness of the films (especially for pH 10.5 and 11) enhanced after sulfur annealing. pH value of the precursor solution remarkably affected the roughness, uniformity and particle sizes of the films. Based on the analysis of X-ray diffraction (XRD) patterns of the films, micro-strain and dislocation density values of the sulfur-annealed films (pH 10.5 and 11) were found to be lower than those of air-annealed films. Air-annealed films (pH 10.5, 11 and 11.5) exhibited higher transmittance than sulfur-annealed films in the wavelength region of 550-800 nm. Optical band gap values of the films were found between 2.31 eV and 236 eV. (C) 2015 Elsevier Ltd. All rights reserved.Öğe Fabrication and Transport Critical Current Densities of MgB2/Fe/Cu Multifilament Tapes without Any Intermediate Annealing(Polish Acad Sciences Inst Physics, 2012) Yucel, E.; Terzioglu, C.; Varilci, A.; Gencer, A.; Belenli, I.We have fabricated superconducting 6 and 7 filaments MgB2/Fe/Cu tapes by ex situ powder-in-tube method using Cu-sheath without any intermediate annealing. Properties of two different multicore MgB2/Fe/Cu tapes annealed at 900 degrees C for 2 h in high purity argon gas atmosphere were compared. The samples were characterized using scanning electron microscope, X-ray diffraction, electron dispersive spectroscopy, optical microscopy, critical transition temperature, transport critical current density, and magnetic measurements. Transport critical current densities of the 6 and 7 filaments tapes were found to be 450 A/cm(2) and 190 A/cm(2) at 20 K, respectively. From X-ray diffraction measurements, lattice parameters a and c were determined. From dc resistivity measurements, the connectivity between grains was investigated by using Rowell's connectivity analysis.Öğe Ganglioglioma with lytic skull lesions(Sociedad Espanola Neurocirugia, 2007) Gurkanlar, D.; Kocak, H.; Yucel, E.; Aciduman, A.; Gunaydin, A.; Ekinci, Oe.; Keskil, S.Gangliogliomas represent only 0.4% of central nervous system neoplasms and 1.3% of brain tumors. They are benign neoplasms with low morbidity and mortality and the patients usually present with seizures, but there has been no adult ganglioglioma with lytic skull lesion. A 49-year-old right handed woman suffering from generalized epileptic seizures was admitted to our hospital. She had also left hemiparesis with 4/5 motor strength. Magnetic resonance imaging and immunohistochemical studies revealed WHO Grade 11 ganglioglioma. Skull X-ray showed the lytic skull lesions. We have to consider gangliogliomas in the differential diagnosis of lytic skull lesions.Öğe Ganglioglioma with lytic skull lesions: A case report(Sociedad Espanola de Neurocirugia, 2007) Gürkanlar, Do?a; Kocak, H.; Yucel, E.; Aciduman, A.; Gunaydin, A.; Ekinci, Ö.; Keskil, S.Gangliogliomas represent only 0.4% of central nervous system neoplasms and 1.3% of brain tumors. They are benign neoplasms with low morbidity and mortality and the patients usually present with seizures, but there has been no adult ganglioglioma with lytic skull lesion. A 49-year-old right handed woman suffering from generalized epileptic seizures was admitted to our hospital. She had also left hemiparesis with 4/5 motor strength. Magnetic resonance imaging and immunohistochemical studies revealed WHO Grade II ganglioglioma. Skull X-ray showed the lytic skull lesions. We have to consider gangliogliomas in the differential diagnosis of lytic skull lesions.Öğe Influence of diffusion-annealing temperature on physical and mechanical properties of Cu-diffused bulk MgB2 superconductor(Springer, 2013) Dogruer, M.; Zalaoglu, Y.; Gorur, O.; Ozturk, O.; Yildirim, G.; Varilci, A.; Yucel, E.This study reports not only the effect of Cu diffusion on physical and mechanical properties of bulk MgB2 superconductors with the aid of Vickers microhardness (H-v) measurements but also the diffusion coefficient and the activation energy of copper (Cu) in the MgB2 system using the resistivity measurements for the first time. Cu diffusion is examined over the different annealing temperature such as 650, 700, 750, 800 and 850 A degrees C via the successive removal of thin layers and resistivity measurement of the sample. Further, Vickers microhardness, elastic modulus, yield strength, fracture toughness and brittleness index values of the samples studied are evaluated from microhardness measurements. It is found that all the results obtained depend strongly on the diffusion annealing temperature and applied load. The microhardness values increase with ascending the annealing temperature up to 850 A degrees C owing to the increment in the strength of the bonds between grains but decreasing with the enhancement in the applied load due to Indentation Size Effect behaviour of the bulk samples. Moreover, the diffusion coefficient is observed to enhance from 2.84 x 10(-8) to 3.22 x 10(-7) cm(2) s(-1) with the increase of the diffusion-annealing temperature, confirming that the Cu diffusion is more dominant at higher temperatures compared to lower ones. Besides, temperature dependence of the Cu diffusion coefficient is described by the Arrhenius relation D = 2.66 x 10(-3) exp(-1.09 +/- A 0.05 eV/k(B)T) and the related activation energy of the Cu ions in the MgB2 system is obtained to be about 1.09 eV. Based on the relatively low value of activation energy, the migration of the Cu ions primarily proceeds through defects such as pore surfaces and grain boundaries in the polycrystalline structure, resulting in the improvement of the physical and mechanical properties of the bulk MgB2 samples.Öğe Primary spinal cord oligodendroglioma. : Case illustration(Sociedad Espanola Neurocirugia, 2006) Gurkanlar, D.; Kocak, H.; Aciduman, A.; Yucel, E.; Ekinci, Ö.Spinal cord oligodendrogliomas are rare pathologies of the spinal cord, and their location at conus and/or filum terminale is even rarer. There are only 7 spinal cord oligodendrogliomas reported in the literature. Our case is the eighth spinal cord oligodendrogliomas at this location.Öğe Primary spinal cord oligodendroglioma. Case illustration(Sociedad Espanola de Neurocirugia, 2006) Gürkanlar, Do?a; Koçak, H.; Aciduman, A.; Yucel, E.; Ekinci, Ö.Spinal cord oligodendrogliomas are rare pathologies of the spinal cord, and their location at conus and/or filum terminale is even rarer. There are only 7 spinal cord oligodendrogliomas reported in the literature. Our case is the eighth spinal cord oligodendrogliomas at this location.Öğe Production of p-CuO/n-ZnO:Co nanocomposite heterostructure thin films: An optoelectronic study(Elsevier Sci Ltd, 2023) Kahveci, O.; Akkaya, A.; Yucel, E.; Aydin, R.; Sahin, B.The p-n junction is the principal mode of optoelectronic semiconductor material. At present, we submit a solution-based attempt at the synthesis of nanostructured p-type CuO and n-type ZnO nanocomposite (NC) heterostructure films. Bare and Cobalt (Co)-doped CuO-ZnO NC films have been produced on glass slides using the SILAR (Successive Ionic Layer Adsorption and Reaction) method. The influence of Co-doping concentration on the physical characteristics of CuO-ZnO NC heterostructure films was investigated. XRD spectrums indicated the phase and structural purity of solution-based synthesized CuO-ZnO NC samples. The surface topographical, as well as optical and electrical properties of heterostructure films were, also investigated. While the bare CuO-ZnO NC film has a-38% transmission near 1000 nm wavelength region, the 2.0% Co-doped CuO-ZnO NC film has-31% of optical transmission. The sheet resistance value of the grown 2.0% Co:CuO-ZnO NC sample is almost 13 times lower than that of the bare CuO-ZnO NC sample at 400 K temperature. As a consequence, our attempt ensures a novel strategy for the production and performance optimization of CuO-ZnO NC hetero-structures in the implementation of optoelectronics.Öğe Role of diffusion-annealing temperature on the microstructural and superconducting properties of Cu-doped MgB2 superconductors(Springer, 2012) Dogruer, M.; Yildirim, G.; Yucel, E.; Terzioglu, C.This study deals with not only investigate the effect of the copper diffusion on the microstructural and superconducting properties of MgB2 superconducting samples employing dc resistivity as a function of temperature, scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements but also calculate the diffusion coefficient and the activation energy of copper for the first time. Electrical-resistivity measurements indicate that both the room-temperature resistivity value and zero resistivity transition temperatures (T (c) ) increase with increasing the diffusion-annealing temperature from 650 to 850 A degrees C. SEM measurements show that not only the surface morphology and grain connectivity improve but also the grain size of the samples increases with the increase in the diffusion-annealing temperature up to 850 A degrees C. As for the XRD results, all the samples contain the MgB2 phase only and exhibit the polycrystalline superconducting phase with more intensity of diffraction lines, leading to the increasement in the lattice parameter a and c. Additionally, the diffusion coefficient is observed to increase from 6.81 x 10(-8) to 4.69 x 10(-7) cm(2) s(-1) as the diffusion-annealing temperature increases, confirming that the Cu diffusion at lower temperatures is much less significant. Temperature dependence of the Cu diffusion coefficient is described with the aid of the Arrhenius relation D = 3.75 x 10(-3) exp (-1.15 +/- A 0.10 eV/k (B) T) and the corresponding activation energy of copper in MgB2 system is found to be about 1.15 eV. The possible reasons for the observed improvement in microstructural and superconducting properties of the samples due to Cu diffusion are also discussed.Öğe Soil-plant interactions in the monumental plane trees (Platanus orientalis) grove-Canakkale-Turkey(Triveni Enterprises, 2017) Ozturk, M.; Uysal, I.; Yucel, E.; Altay, Volkan; Karabacak, E.Aim : To study ecological features of monumental plane trees. Evaluate soil-plant interactions and mineral nutrition status of 150 to 800 year-old-chosen trees. Methodology : Soil and plant samples were collected and analysed using Kjeldahl, spectrophotometer, Flame photometer and ICP-OES. Results : The pH, electrical conductivity, calcium carbonate, organic matter, total nitrogen, phosphorus, sodium, potassium, calcium, magnesium, iron, manganese, zinc and copper values in the soil samples ranged between 6.6-7.4, 0.58-1.26 (dS. m(-1)), 0.00-1.52%, 1.55-5.05%, 0.08-0.29%, 4-28 ppm, 20-33 ppm, 50-314 ppm, 1086-3041 ppm, 54-302 ppm, 3.57-15.30 ppm, 3.37-13.29 ppm, 1.84-4.17 ppm, and 0.411.48 ppm, respectively. The mineral element values in young root, young stem, elderly stern, stem bark and leaf showed normal range.A strong relation has been noted among the Mg, P, Na, Mn, Fe, total N and Zn. Interpretation : Excess amount of Fe and Ca get accummulated in different plant parts.Öğe Use of Anionic Surfactant Sodium Lauryl Ether Sulfate as a Capping Agent in Metal-Chalcogenide PbS Thin Film Production(Polish Acad Sciences Inst Physics, 2023) Yucel, E.In this paper, nanostructured semiconductor PbS metal-chalcogenide thin films were fabricated by the chemical bath deposition method in a surface active agent environment. The structural, morphologi-cal, and optical properties of PbS thin films were characterized by X-ray diffraction, scanning electron microscopy, scanning probe microscope and ultraviolet-visible spectroscopy analyses. These analyses reveal that surfactant sodium lauryl ether sulphate plays a key role in modifying the surface roughness and optical properties of PbS thin films. The average surface roughness decreased from 87.9 to 42.8 nm after adding sodium lauryl ether sulfate to the chemical bath solutions. With the increasing sodium lauryl ether sulfate content, the optical band gaps of the PbS thin films increased from 2.10 to 2.52 eV. Additionally, the optical transmittance value of the 3% sodium lauryl ether sulfate added sample in-creased by approximately 37% compared to the pure sample.
