Browsing by Author "Bulut F."

Now showing 1 - 10 of 10

Characterization of the CoFe2O4/Cu displacement effect in the Y123 superconductor matrix on critical properties
(2020-11-01) Safran S.; Bulut F.; Nefrow A.R.A.; Ada H.; Ozturk O.
In this study, CoFe2O4 (x = 0, 5, 10 and 20 wt%) doped YBa2Cu3−x(CoFe2O4)xO7−δ bulk samples were produced using solid state reaction (SSR) method and sol–gel(SG) methods. Oxide-form and acetate-form powders were preferred for SSR method and SG method, respectively. The heat treatment of the produced samples was carried out in two stages. Firstly, the samples were annealed at 950 °C for 24 h, after which they were kept in oxygen at 500 °C for 5 h and allowed to be cooled down to room temperature. Characterization of all samples was performed using methods such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, temperature-dependent resistance measurement (R–T) and Vickers microhardness analysis. Superconducting behavior was observed in all the produced samples, but as a result of the addition, a decrease was observed with the increase of the doping ratio at the critical transition temperature. As a result of the characterization, it is concluded that the doping ions can be replaced with Cu atoms in Y123 structure. In addition, doping led to significant changes in Vickers microhardness results.
Comparison of the Dopant Effect and Sample Preparation Method on Y-123 Superconductors
(2021-11-01) Ozturk O.; Nefrow A.R.A.; Bulut F.; Kurnaz S.; Safran S.
The detailed comparison of the effects of Co and CoFe2O4 dopants and preparation methods (solid-state reaction method and sol–gel methods) have been studied on structural, electrical, superconducting, and mechanical properties of Y123 bulk superconductors. The doping amounts of Co and CoFe2O4 were chosen up to 0.10 wt. %. X-ray powder diffraction (XRD) method, temperature-dependent resistance measurement (R-T), and Vickers microhardness analyses were performed to characterize prepared samples. XRD analysis showed that all samples have Pmmm symmetry of orthorhombic crystal structure; intensities and width of the diffraction lines were affected by doping material, but, independent of the preparation method. Although all samples crystallize in orthorhombic structure and exhibit superconductivity behavior, with increasing doping rate the critical transition temperatures of the samples showed a significant decrease and broadened to superconducting temperature transition width. This is more evident in CoFe2O4-doped Y-123 samples produced by sol–gel method. As the applied force increased, it was observed that the microhardness values of the Co-doped samples increased while the CoFe2O4-doped samples decreased, regardless of the sample preparation method.
Effect of Co/Cu partial replacement on fundamental features of Y-123 ceramics
(2020-05-01) Ozturk O.; Nefrow A.R.A.; Bulut F.; Ada H.; Turkoz M.B.; Yildirim G.
This study is liable for the effect of sample production processes including the standard solid-state reaction (SSR) and classical sol–gel (SG) preparation methods on the fundamental characteristic features, namely electrical, superconducting, crystal structure quality, crystallinity, morphological, strength quality of grain boundary couplings, and interaction between the grains of YBa2Cu3−xCoxO7−δ (Y-123) advanced ceramic compounds within the weight ratio intervals x = 0–20%. The main heat treatments are exerted at two main steps: (I) annealing at 950 °C for 24 h in air medium conditions and (II) annealing at 500 °C during 5 h under the oxygen annealing ambient. The standard measurement methods such as powder X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, temperature-dependent electrical resistance, and Vickers hardness measurements are performed for the characterization of materials. It is found that the samples prepared at SSR route present much more superior characteristic features as compared to those fabricated at SG technique, being one of the most striking points deduced this work. In more detail, every material prepared crystallizes in the orthorhombic symmetry and exhibits the superconducting nature but considerable decrement in the critical transition temperatures. The onset and offset transition temperatures are noted to decrease regularly from 92.96 K (92.28 K) to 90.20 K (83.59 K); and 90.05 K (90.03 K) to 45.97 K (30.49 K) for the materials prepared by the SSR (SG) route. Similarly, the variation in the lattice cell and average grain size parameters confirm that the Co/Cu substitution damages Y-123 superconducting phase. Additionally, the Co/Cu partial replacement mechanism leads to increase significantly the Vickers hardness results. To sum up, the Co/Cu partial substitution (produced by either SSR or SG method) is plowed to improve the fundamental characteristic features for new, novel, and feasible market application areas of Y-123 cuprate ceramics in the universe economy.
Effect of Ni and Al doping on structural, optical, and CO2 gas sensing properties of 1D ZnO nanorods produced by hydrothermal method
(2022-04-01) Bulut F.; Ozturk Ö.; Acar S.; Yildirim G.
In the present study, the one-dimensional ZnO nanorod structures are produced within the different nickel and aluminum molecular weight ratios of 0–7% using the hydrothermal method. It is found that the aluminum (Al) and nickel (Ni) impurities with different ionic radius, chemical valence, and electron configurations of outer shell cause to vary the fundamental characteristic features including the crystallinity quality, crystallite size, surface morphology, nanorod diameter, optical absorbance, energy band gap, resistance, gas response, and gas sensing properties. The structural analyses performed by powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) indicate that the samples are found to crystallize in the hexagonal wurtzite structure. The presence of optimum nickel and aluminum in the crystal system improves considerably the crystallinity quality and surface morphology. Additionally, the combination of electron dispersive X-ray (EDX) and XRD results declare that the Ni and Al impurities incorporate successfully into the ZnO crystal structure. Moreover, the diameters of nanorod structures in 1D orientation are determined to be 80 nm or below. The hexagonal wurtzite-type ZnO nanorod structure prepared by 5% Ni has more space between the nanorods and thus presents higher response to the CO2 detection. Further, the optical absorbance spectra display that the band gap value is observed to decrease regularly with the increment in the doping level as a result of band shrinkage effect depending on the enhancement of mobile hole carrier concentrations in the crystal structure. In other words, the doping mechanism leads to vary the homogeneities in the interfacial charges, nanorod diameters, ZnO oxide layer composition and thickness. The last test conducted in this study is responsible for the determination of CO2 gas sensing levels. The obtained gas sensing results are further compared with each other and literature findings. It is observed that 5% Ni-doped sample provides more successful results than other samples in the sensing CO2 gas at the different concentrations. All in all, the paper establishing a strong methodology between doping mechanism and change in the fundamental characteristic features of hexagonal wurtzite-type ZnO with the aid of advanced microscopy techniques will become pioneering research to answer key questions in materials sciences and electronic research.
Experimental and theoretical approaches for electrical, magnetic, micromechanical, and structural characterization of BSCCO ceramic superconductors
(2018-07-01) Safran S.; Ozturk H.; Bulut F.; Ozturk O.
This study investigates how the preparation and re-pelletization of BSCCO ceramic superconductors affects their structural, magnetic, electrical, and mechanical properties. Samples were prepared using conventional methods including the dry solid state (SS) reaction and wet ammonium nitrate (AN) precipitation, with three variations prepared for each technique. The fabricated samples were then characterized with X-ray powder diffraction (XRD) and scanning electron microscopy. The density, resistance vs. temperature characteristics, AC susceptibility vs. temperature characteristics, and magnetic hysteresis properties were measured. In addition, Vicker's microhardness was measured and revealed that all six samples exhibit the reverse indentation size effect (RISE). Microhardness modeling was also conducted. Calculations with Meyer's law, the Hays and Kendall model, and the proportional sample resistance model indicate that the samples are far from the plateau region, whereas the indentation-induced cracking model was consistent with the experimental results. The elastic modulus, Young's modulus, yield strength, and brittleness index were also calculated for each sample.
Investigation of structural, superconducting and mechanical properties of Co/Cu substituted YBCO-358 ceramic composites
(2019-01-01) Ozturk O.; Arebat R.; Nefrow A.; Bulut F.; Guducu G.; Asikuzun E.; Celik S.
In this study, we have examined the structural, superconducting and mechanical properties of Y 3 Ba 5 Cu 8−x Co x O 18 − δ system (x = 0, 0.05, 0.1, 0.15, 0.2 and 0.5), which is produced by conventional solid-state reaction method. Produced samples have been examined using X-ray diffraction (XRD), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), Vicker’s hardness (H v ) and electrical resistance measurement (R–T). According to the XRD patterns, we have obtained that the Co nanopowder doping has been caused some changes on the average grain size, characteristic peak intensities and lattice parameters of the Y 3 Ba 5 Cu 8 O 18 − δ crystal system. Furthermore, according to the electrical resistance measurements, the critical temperature (T c ) values of all the samples have tended to decrease constantly with the increment in the doping ratio in the Y358 crystal structure. As for the variation in the microhardness parameters of superconducting materials, the H v parameters and other related computations (Young’s modulus and yield strengths) have been found to increase regularly with the Co/Cu substitution level. Besides, the characteristic H v curves have confirmed that the whole bulk of Bi-2212 samples showed untypical reverse indentation size effect (RISE) behavior.
Nanostructural characterization and defect-mediated room temperature ferromagnetism of Zn1−xFexO (x = 0.00–0.07) nanorods prepared via hydrothermal method
(2021-11-05) Kaya S.; Ozturk O.; Arda L.; Bulut F.
The effect of Iron (Fe) doping on crystal structure, morphology, optical behavior, and magnetism of Zn1−xFexO (x = 0.00, 0.01, 0.03, 0.05, 0.07) nanorods prepared via a hydrothermal method was investigated. According to the X-ray diffraction results, Fe ions were incorporated successfully into the Zn ions sites without any deterioration in the wurtzite crystal structure. According to the photoluminescence spectra, a relative increment was observed in the intensity of the near band edge emissions as the Fe concentration increased. Deep level emissions showed that the yellow-orange and violet emissions, corresponding to the oxygen vacancies and zinc interstitials, respectively, increased with the Fe doping. Magnetic measurement results indicated that the undoped ZnO nanorods are diamagnetic. Room temperature ferromagnetism was observed in the Fe doped ZnO nanorods regardless of the doping rate. Although there was no logical relationship between the saturated magnetic moments and the Fe concentration, an obvious correlation was observed between the concentration of point crystal defects including oxygen vacancies, zinc interstitials, and the ferromagnetic parameters. The defect-mediated interactions and the bound polarons effect are suggested for the possible origins of room temperature ferromagnetism in Fe doped ZnO nanorods. The results of the study also provide detailed data for the production method of the ZnO nanorods with enhanced structural, optical and ferromagnetic properties, which are promising candidates for spintronic device applications in nanoelectronics.
The influence of re-pelletization and heat treatment on physical, superconducting, magnetic and micro-mechanical properties of bulk BSCCO samples prepared by ammonium nitrate precipitation method
(2017-12-01) Safran S.; Ozturk H.; Bulut F.; Ozturk O.
The influence of re-pelletization and annealing time on the structural, magnetic, electrical and mechanical properties of Bi-based high temperature bulk superconductor have been investigated. All samples used in this study have been prepared by a wet technique denoted as ammonium nitrate precipitation method. The samples have been characterized by X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), resistance vs. temperature (R-T), magnetic hysteresis (M-H) and hardness vs. applied load (Hv-F) measurements. Bi-2223 and Bi-2212 peaks as major phases have been observed with small amounts of impurities from XRD results. The microstructures of most samples show a plate-like granular form. The grain sizes have been investigated by SEM and XRD. The critical transition temperature (Tc) has been obtained from resistivity measurements in the range of 99–110 K, depending on the annealing time and re-pelletization. The calculated maximum critical current density (Jc), using Beans’ model, is around 12,000 A/cm2 at 10 K ∼ 0.2 T. Moreover, all prepared samples exhibit reverse indentation size effect (RISE) behavior and hardness increased with re-pelletization according to results obtained from mechanical measurements.
VALUES IN THE NOVELS OF ÖZGÜR ARAS TÜFEK'S TÜRKÇENİN MUHAFIZLARI SERİSİ (SERIES OF CONSERVERS OF TURKISH)
(2021-01-01) Bulut F.; ŞİMŞEK Ş.
The values that facilitate the adaptation of the human beings to the society, create a balance in the society by contributing to the distinction of good and bad, right and wrong, and enable individuals to live in peace, trust and harmony. Values education, which has gained importance in our country in recent years, has been an issue emphasized in educational practices. Özgür Aras Tüfek, one of the names that included values education in his novels, brought the first works of Islamic Turkish Literature to the world of fiction and wrote a different series of children's novels. In the first work titled Bir Kelime Seyyahı (A Word Traveler) of the series named “Türkçenin Muhafızları” (Turkish Conservers), Kaşgarlı Mahmut; Ali Şîr Nevâî in Simurg'a Yolculuk (Journey to Simurg); Mutluluk Bilgisi (In the Knowledge of Happiness), Yusuf Has Hacib's; He also described the life of Edip Ahmet Yüknekî's Kelimelerin Işığı (The Light of Words). These four books contain many values that can be used in values education beyond novelizing the life stories of great personalities of the Turkish language. The main purpose of this research is to examine the contribution of Özgür Aras Tüfek novels to children's literature and values education. In the research using the case study design one of the qualitative research methods, the “Conservers of Turkish” series was examined according to the 6-value classification of Allport, Lindzey and Vernon (1960) and how the values were processed was revealed. According to this classification, it has been determined that the works of Özgür Aras Tüfek mostly include social values, at least aesthetic and political values. The values of love for learning and love of teaching were intensively studied in the novels; It has been observed that there are many values that should be given to students such as kindness, solidarity, natural awareness, justice, righteousness, diligence, love of the country and nation, respect and humility.
Vibrational assignments, spectroscopic investigation (FT-IR and FT-Raman), NBO, MEP, HOMO-LUMO analysis and intermolecular hydrogen bonding interactions of 7-fluoroisatin, 7-bromoisatin and 1-methylisatin - A comparative study
(2015-12-05) Polat T.; Bulut F.; Arican I.; Kandemirli F.; Yildirim G.
In this comprehensive study, theoretical and experimental studies were carried out on 7-fluoroisatin, 7-bromoisatin and 1-methylisatin using FT-Raman and FT-IR spectra. The optimized geometrical parameters and theoretical vibrational frequencies were calculated by means of density functional theory (DFT/B3LYP) with 6-311++G(d,p) basis set based on scaled quantum mechanical (SQM) method for the first time. The relative abundances of the possible tautomers or conformers found were calculated with respect to the Boltzmann distribution. Moreover, the harmonic vibrational frequencies including IR and Raman intensities, thermodynamic and electronic parameters were computed in detail. The effects of substituents -F, -Br and -CH3 on the crucial characteristics pertaining to the title compound of isatin were investigated, and the obtained data were compared with each other. Natural bond orbital (NBO) analysis was applied to study the stability arising from charge delocalization along with the compound. The chemical reactivity parameters (chemical hardness and softness, electronegativity, chemical potential and electrophilicity index) were discussed clearly. The HOMO and LUMO energies determined showed that the serious charge transfer occurs in the title molecules studied. Furthermore, the size, shape, charge density distributions and chemical reactivity sites belonging to the molecules were obtained by mapping electron density isosurface with electrostatic potential surfaces (ESP). Additionally, the hydrogen-bonded complexes were simulated to describe the roles of intermolecular hydrogen bonding on the molecular structures and vibrational frequencies.