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Öğe Characteristic Properties of Dy-Eu-Ag co-Doped TiO2 Nanoparticles Prepared by Electrospinning Processes(POLISH ACAD SCIENCES INST PHYSICS, 2015) Evcin, A.; Bezir, N. C.; Kayali, R.; Kasikci, M.; Oktay, A.TiO2 with high photoactive wide band gap energy semiconductor has been studied intensively for its attractive applications as photo catalyst and solar cell. TiO2 has three kinds of different crystal structures; anatase, brookite and rutile. TiO2-nanoparticles could become valuable light emitting materials when they are doped with highly luminescent rare earth ions. In this study, Dy-Eu-Ag co-doped TiO2 nano particles were prepared by electrospinning method. The crystal structures of nanofibers were determined X-Ray Diffraction device (XRD), morphology of the samples were analyzed by scanning electron microscope (SEM), and the optical properties of the samples were determined by ultraviolet/visible spectrometer (UV/VIS) measurements. Electrical and electronic properties of the sampled were determined using the data obtained from four point prob technique (FPPT).Öğe Characteristic Properties of Dy-Eu-Ce Co-Doped ZrO2 Nanofibers Fabricated via Electrospinning(POLISH ACAD SCIENCES INST PHYSICS, 2016) Bezir, N. Cicek; Evcin, A.; Kayali, R.; Ozen, M. Kasikci; Esen, K.; Cambaz, E. B.Zirconium oxide (ZrO2) is one of the widely studied oxide materials because of its excellent electrical, mechanical and optical properties. In this study, undoped and Dy-Eu-Ce co-doped ZrO2 nanofibers were fabricated by electrospinning method and their crystal structure, surface morphology, optical properties, electrical and electronic properties, and chemical properties have been analyzed using X-ray diffraction, scanning electron microscope (SEM), UV/VIS spectrometer, four point probe technique ( FPPT) energy dispersive X-ray (EDX) measurements, respectively.Öğe Comparison of Five-Layered ZrO2 and Single-Layered Ce, Eu, and Dy-Doped ZrO2 Thin Films Prepared by Sol-Gel Spin Coating Method(Polish Acad Sciences Inst Physics, 2017) Bezir, N. Cicek; Evcin, A.; Kayali, R.; Ozen, M. K.; Esen, K.In order to investigate the influence of the number of layers on the properties of ZrO2 thin films, we prepared one pure ZrO2 film sample with five layers and Ce, Eu, and Dy-doped ZrO2 samples with single layer, by spin-coating sol gel-method. The crystal structures of thin films were determined using X-ray diffraction, morphology of the samples was analyzed by scanning electron microscopy, and the optical properties of the samples were determined by ultraviolet/visible absorbance measurements. The results of these measurements have shown that the concentration of the dopants and the thickness of thin film layers play a vital role in the physical, chemical, and optical properties of the pure and doped ZrO2 thin films.Öğe Comparison of Pure and Doped TiO2 Thin Films Prepared by Sol-Gel Spin-Coating Method(Polish Acad Sciences Inst Physics, 2017) Bezir, N. Cicek; Evcin, A.; Kayali, R.; Ozen, M. K.; Balyaci, G.In this study, using spin-coating sol-gel method we fabricated TiO2 thin films, doped with different concentrations (1, 2, and 3 mole %) of Ce, Dy, and Eu. Characterization of the prepared samples was performed by means of the X-ray diffraction, scanning electron microscopy, ultraviolet visible absorption, and differential thermal and thermo gravimetric analysis. X-ray diffraction measurements have shown that in Eu and Dy-doped samples crystal structure consists of mixed rutile and the dominant anatase phases, however the Ce doped samples consist of anatase phase only. Scanning electron microscopy images have revealed that while average thin film thickness of the Dy-doped samples decreases with increasing concentration of Dy, the average film thicknesses of samples doped with Ce and Eu increases with increasing concentrations of these dopants. Ultraviolet visible absorption spectroscopy measurements have shown that while absorbances of the samples doped by 1 and 2 mole % of the dopants have nearly similar properties, these properties differ from each other for 3 mole % of the dopants. Finally, differential thermal and thermo gravimetric analyses have shown that the chemical reactions and weight losses of the samples have occurred at the expected temperatures.Öğe Dependence of electrical and thermal conductivity on temperature in directionally solidified Sn-3.5 wt% Ag eutectic alloy(SPRINGER, 2011) Cadirli, E.; Sahin, M.; Kayali, R.; Ari, M.; Durmus, S.Sn-3.5 wt% Ag alloy was directionally solidified upward with a constant growth rate (V = 16.5 mu m/s) and a temperature gradient (G = 3.3 K/mm) in a Bridgman-type growth apparatus. The variations of electrical resistivity (rho) with temperature in the range of 293-476 K for the directionally solidified Sn-3.5 wt% Ag eutectic alloy was measured. The measurements indicate that the electrical resistivity of the directionally solidified Sn-Ag eutectic solder increases with increasing temperature. The variations of thermal conductivity of solid phases versus temperature for the same alloy was determined from the Wiedemann-Franz and Smith-Palmer equations by using the measured values of electrical conductivity. From the graphs of electrical resistivity and thermal conductivity versus temperature, the temperature coefficient of electrical resistivity (alpha (TCR) ) and the temperature coefficient of thermal conductivity (alpha (TCT) ) for the same alloy were obtained. According to experimental results, the electrical and thermal conductivity of Sn-Ag eutectic solder linearly decrease with increasing the temperature. The enthalpy of fusion (Delta H) and the change of specific heat (Delta C (P) ) during the transformation at the studied alloy were determined from heating curve during the transformation from eutectic solid to eutectic liquid by means of differential scanning calorimeter (DSC).Öğe Dynamics of ultrarelativistic jets(AMER INST PHYSICS, 2007) Doenmez, O.; Kayali, R.; Cetin, SA; Hikmet, IWe investigate the dynamics and morphology of jets propagating into the interstellar medium using 2D special relativistic hydrodynamics code. The calculations are performed assuming axisymmetric geometry and trace a long propagation of jets. The jets are assumed to be higher density than the ambient gas. The relativistic astrophysical jet is modeled for ultrarelativistic flow case. The dynamics of jet flowing is then determined by the ambient parameters such as densities, and velocities of the jets and the momentum impulse applied to the computational surface. We obtain solutions for the jet structure, propagation of jet during the time evolution, and variation in the Mach number, pressure and Lorentz factor on the computational domain at a fixed time.Öğe Effect of deposition conditions on the InP thin films prepared by spray pyrolysis method(SPRINGER, 2006) Oeztas, M.; Bedir, M.; Kayali, R.; Aksoy, F.InP thin films were prepared by spray pyrolysis technique using aqueous solutions of InCl3 and Na2HPO4, which were atomized with compressed air as carrier gas. The InP thin films were obtained on glass substrates. Thin layers of InP have been grown at various substrate temperatures in the range of 450-525 degrees C. The structural properties have been determined by using X-ray diffraction (XRD). The changes observed in the structural phases during the film formation in dependence of growth temperatures are reported and discussed. Optical properties, such as transmission and the band gap have been analyzed. An analysis of the deduced spectral absorption of the deposited films revealed an optical direct band gap energy of 1.34-1.52 eV for InP thin films. The InP films produced at a substrate temperature 500 degrees C showed a low electrical resistivity of 8.12 x 10(3) Omega cm, a carrier concentration of 11.2 x 10(21) cm(-3), and a carrier mobility of 51.55 cm(2)/Vs at room temperature.Öğe Effect of Layer Thickness on I-V Characteristics of GaInP Nanofibers Fabricated by Electrospinning on n-Si Substrates(Polish Acad Sciences Inst Physics, 2017) Bezir, N. Cicek; Evcin, A.; Okcu, H.; Kayali, R.; Kaleli, M.; Aldemir, D. A.GaInP nanofibers were formed on n-Si substrates by electrospinning method, using constant voltage (25 kV), height (6 cm), and flow rate (0.3 ml/h) during various process times (of 10, 20, 25 minutes). Characterization of the prepared samples was performed by X-ray diffraction, differential scanning calorimetry/thermal gravimetric analysis, scanning electron microscopy, and energy dispersive X-ray spectrometry. Furthermore, the current-voltage measurements of the GaInP/n-Si samples have been carried out. The obtained results show that I - V characteristics of all GaInP/n-Si samples fabricated with three thicknesses of GaInP layers are rather in a good agreement with the theory and that they exhibit rectifying properties.Öğe Influence of the annealing conditions on the properties of InP thin films(ELSEVIER SCIENCE SA, 2006) Oztas, M.; Bedir, M.; Kayali, R.; Aksoy, F.InP thin films were prepared on glass substrates by the spray pyrolysis technique. Results on structural, optical and electrical properties of the layers as a function of the thermal annealing are reported. XRD data indicates that samples show microstructural perfection improvement as a function of annealing time. The optical band-gap shows a dependence with the inverse of the squared crystallite size, suggesting that electron confinement has some effect. The lattice parameter and band-gap energy (BGE) of the samples annealed at 450 degrees C for 160 min (20-40-80-120-160-200) correspond to the reported values of InP thin films. In addition, the electrical resistivity measurement shows a slight decrease when annealing time is increased up to 80 min but it saturates annealing times between 80 and 160 min. Then it is slightly increased for larger times. (c) 2006 Elsevier B.V All rights reserved.Öğe Investigation of Structural and Electrical Properties of (Bi2O3)1-x-y(CeO2)x(Eu2O3)y Electrolytes for Solid Oxide Fuel Cells(Polish Acad Sciences Inst Physics, 2019) Islek, Y.; Ozen, M. Kasikci; Kayali, R.; Ari, M.In the present study, CeO2 and Eu2O3 doped Bi2O3 composite materials for solid oxide fuel cells were investigated. (Bi2O3)(1-x-y)(CeO2)(x) (Eu2O3)(y) ternary systems (x = 0.01, 0.03, 0.05, 0.07, 0.09, 0.11 and y = 0.11, 0.09, 0.07, 0.05, 0.03, 0.01 dopant concentrations) were fabricated at different temperatures (650, 700, 750, and 800 degrees C) using conventional solid-state synthesis techniques. Characterization of these electrolyte samples were carried out by X-ray powder diffraction, differential thermal analysis/thermal gravimeter, and the four-point probe technique measurements. X-ray powder diffraction measurements showed that nearly all the samples have alpha+beta+gamma phase except the samples with tetragonal beta-phase sintered at 700, 750 degrees C and 750, 800 degrees C with the dopant ratios (x = 0.07, y = 0.05) and (x = 0.09, y = 0.03), respectively. Four-point probe technique measurements showed that the measured ionic conductivity of the stable samples vary in the range 1.05 x 10(-1)-4.76 x 10(-1) S/cm. Additionally, the activation energy values of the samples were calculated with the help of the Arrhenius equation adapted to the logs graphics versus 1000/T varying in the range 0.7799-0.8746 eV. This result shows that there is a good relationship between the activation energy values and conductivity values.Öğe Performance of a salt gradient solar pond with reflective covered surface and derivation of analytic functions for air and soil temperatures for isparta region(AMER INST PHYSICS, 2007) Bezir, N. C.; Oezek, N.; Kayali, R.; Oeztuerk, M.; Cetin, SA; Hikmet, IIn this study, salt gradient solar pond having a surface area of 3.5x3.5 m(2) and depth of 2 m has been constructed in Isparta/Turkiye and a computer software, capable of giving the temporal temperature variation at any point inside or outside a insulated solar pond at any time is presented. Hourly average values of air temperature and daily average soil temperature for the site were used as input parameters. These parameters have been calculated from analytical functions derived by using the hourly and daily temperature values for air and soil data obtained from the local meteorological station in Isparta region, respectively. The results obtained using analytic functions were in good agreement with the experimental results. Performance of the pond has been investigated theoretically and experimentally.Öğe Synthesizing of (Bi2O3)(1-x-y)(Ho2O3)(x)( Dy2O3)(y) Electrolytes for Intermediate-Temperature Solid Oxide Fuel Cells(POLISH ACAD SCIENCES INST PHYSICS, 2016) Ozen, M. Kasikci; Kayali, R.; Bezir, N. Cicek; Evcin, A.In present study, Ho2O3 and Dy2O3 doped Bi2O3 composite materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs) were investigated. (Bi2O3)(1-x-y)(Ho2O3)(x)(Dy2O3)(y) ternary systems (x = 0.11, 0.13, 0.15 and y = 0.01, 0.03, 0.05, 0.07) were fabricated using conventional solid-state synthesis techniques. The samples were characterized by means of X-ray powder diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy, differential thermal analysis/thermal gravimeter, and the four-point probe technique. X-ray powder diffraction measurements indicated that all samples have the stable fluorite type face centered cubic (fcc) delta-Bi2O3 phase. Scanning electron microscopy micrographs of all of the samples showed that grain size distribution was uniform. Four-point probe technique measurements showed that the conductivity of the samples increase with increase of temperature. Additionally, it has been found that the maximum conductivity values of all samples fall in a range 8.4 4 x 10(-2)-4.60 x 10(-1) S cm(-1) and their conductivity values corresponding to the intermediate-temperature region vary in the range 1.65 x 10(-3)-2.30 x 10(-1) S cm(-1). The activation energy values of the samples were calculated from log sigma graphics versus 1000/T using the Arrhenius equation. It was found that there is a good agreement between the activation energy values and conductivity values.Öğe Theoretical and Experimental Analysis of a Salt Gradient Solar Pond with Insulated and Reflective Covers(TAYLOR & FRANCIS INC, 2009) Bezir, N. C.; Ozek, N.; Kayali, R.; Yakut, A. K.; Sencan, A.; Kalogirou, S.In this study, a salt gradient solar pond having a surface area of 3.5 3.5 m2 and depth of 2 m has been built for supplying hot water to a leather workshop on the campus area of Vocational College of Isparta/Yalvac. A cover system was used on the surface of the pond to reduce the thermal losses from the top to air and to increase the thermal efficiency of the pond. Such an arrangement is used for the very first time. The system is composed of two covers that can be rotated between 0 and 180 degrees by a controlled electric motor and has insulation and reflection properties, i.e., the covers function as insulators when closed and as reflectors when opened. The pond's thermal analysis has been carried out theoretically and experimentally for different operating conditions. Results obtained from this study show that salt gradient solar ponds can be used as a source of warm water required at the leather workshop and for suitable domestic applications. The covers were effective both for reducing the night thermal losses and for increasing the daytime performance, although the former effect is negligible.
