Browsing by Author "Senol S."

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Effect of boron doping on the structural, optical and electrical properties of ZnO nanoparticles produced by the hydrothermal method
(2015-11-01) Senol S.; Ozturk O.; Terzioğlu C.
The effect of boron doping with 0–11 at% concentration on structural, optical and electrical properties of zinc oxide nanopowder synthesized by a hydrothermal method has been reported. We have performed X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), optical, Hall and resistivity measurements on the samples. XRD results reveal that all B doped ZnO nanopowders have single phase hexagonal (Wurtzite) structure without any impurity. But the positions of main diffracted peaks of ZnO shifted slightly towards small (2θ) angle and grain size decreases from 60.75 nm to 34.34 nm with an increase of B doping concentrations. SEM analysis indicates that the doping concentration of B affected the surface morphology of ZnO nanostructures. Optical properties were examined by UV–vis absorption/diffuse reflectance spectroscopy. The optical band gap of Zn1−xBx O nanostructures increased from 3.27 eV to 3.30 eV with increasing doping from x=0 to x=0.11. The role of doping concentrations of B on the transport properties was searched by temperature dependent Hall measurements in 180–350 K temperature range. The carrier concentration of the samples increased from 0.11×1014 cm−3 to 4.08×1014 cm−3, the Hall mobility decreased from 5.61 cm2 V−1 s−1 to 1.22 cm2 V−1 s−1 and electrical resistivity decreased from 10.89×104 Ω cm to 1.25×104 Ω cm with the increase of the B doping concentrations at room temperature. The electrical resistivity is observed to decrease with both the increase in dopant concentration and the temperature in the range of 180–350 K.
Preparation, structural and micromechanical properties of (Al/Mg) co-doped ZnO nanoparticles by sol–gel process
(2015-10-22) Asikuzun E.; Ozturk O.; Arda L.; Akcan D.; Senol S.; Terzioglu C.
Zn0.90Mg0.10−xAlxO (x = 0.0, 0.1, 0.2, 0.3, 0.4, 0.5 and 0.10) nanoparticles were prepared by using sol–gel technique. The effects of Al and Mg doping on the structural and mechanical properties were investigated by using X-Ray diffraction (XRD), scanning electron microscopy (SEM) and digital micro-hardness tester, respectively. The grain size, a and c lattice parameters and morphology of nanoparticles were characterized by XRD and SEM measurements. The grain sizes of Al/Mg co-doped ZnO nanoparticles were also calculated by Scherrer–Warren equation. a and c lattice parameters are calculated from XRD peaks. According to the results it was observed that the grain sizes increased with increasing the Al doping. c lattice parameter partially decreased with Al doping. The experimental results of hardness measurements were analyzed using Meyer’s law, proportional specimen resistance model, elastic/plastic deformation model, and Hays–Kendall (HK) approach. It was observed that HK approach is the most successful model for the micro-hardness analysis of Al/Mg co-doped ZnO materials.
The influence of boron doping on the structural and mechanical characterization of ZnO
(2019-08-15) Senol S.; Terzioglu R.; Ozturk O.
In this study, we have reported the structural and mechanical properties of B-doped ZnO (Zn1-xBxO, x = 0.00, 0.05, 0.07, 0.09, 0.11)by using XRD, SEM, EDS and static Vickers micro-hardness measurements. All nanopowder samples were prepared by hydrothermal method. From the XRD measurements, we have found that all the samples crystalize in hexagonal wurtzite structure and crystallite sizes were found to be 61.50, 36.97, 36.65, 36.59 and 34.85 nm for x = 0.00, 0.05, 0.07, 0.09, 0.11 samples, respectively. From the SEM measurements, the irregular appearance and size distribution of the particles were observed for all samples. The chemical composition of Zn1-xBxO nanopowders were investigated by EDX spectroscopy. Zn,O and B peaks are clearly seen and the content of Zn, O and B are consistent with preparation of samples. From the load dependent indentation diagonal length measurements, load dependent (apparent)hardness, elastic modulus, yield strength, and fracture toughness values of the samples were computed. The hardness values increase with increasing the boron content and the applied load. In addition, the apparent hardness values were analyzed by using the various theoretical models to evaluate the load independent (true)hardness values. The IIC model was found to be sufficient for our investigations. The possible reasons for the observed changes in mechanical, structural properties due to B-doping in ZnO were discussed.
Theoretical investigations of α,α,α-trifluoro-3, -p and o-nitrotoluene by means of density functional theory
(2012-01-01) Yildirim G.; Senol S.; Dogruer M.; Ozturk O.; Senol A.; Tasci A.; Terzioglu C.
This study reports the optimized molecular structures, vibrational frequencies including Infrared intensities and Raman activities, corresponding vibrational assignments, 1H and 13C NMR chemical shifts, the magnitudes of the JCH and JCC coupling constants, Ultraviolet-visible (UV-vis) spectra, thermodynamic properties and atomic charges of the title compounds, α,α,α-trifluoro-3, -p and o-nitrotoluene, in the ground state by means of the density functional theory (DFT) with the standard B3LYP/6-311++G(d,p) method and basis set combination for the first time. Theoretical vibrational spectra were interpreted by normal coordinate analysis based on scaled density functional force field. The results show that the vibrational frequencies and chemical shifts calculated were obtained to be in good agreement with the experimental data. Based on the comparison between experimental results and theoretical data, the calculation level chosen is powerful approach for understanding the identification of all the molecules studied. In addition, not only were frontier molecular orbitals (HOMO and LUMO), molecular electrostatic potential (MEP) and electrostatic potential (ESP) simulated but also the dipole moment, softness, electronegativity, chemical hardness, electrophilicity index, transition state and energy band gap values were predicted. According to the investigations, all compounds were found to be useful to bond metallically and interact intermolecularly; however, the thermodynamic properties confirm that the α,α,α-trifluoro-p- nitrotoluene was more reactive and more polar than the others. © 2011 Elsevier B.V. All rights reserved.