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Article Citation - WoS: 4Citation - Scopus: 4Mixed Conduction and Anisotropic Single Oscillator Parameters in Low Dimensional Tlinse2 Crystals(Elsevier Science Sa, 2013) Qasrawi, A. F.; Gasanly, N. M.Due to the importance of the TlInSe2 crystal as neutron and gamma-ray detectors, its electrical and dispersive optical parameters have been investigated. Particularly, the anisotropic current conduction mechanism in the temperature region of 100-350 K and the room temperature anisotropic dispersive optical properties were studied by means of electrical conductivity and optical reflectance, respectively. It has been shown that the mixed conduction is the most dominant transport mechanism in the TlInSe2 crystals. Particularly, when the electric field is applied perpendicular to the crystal's c-axis, the main dominant current transport mechanism is due to the mixed conduction and the variable range hopping above and below 160 K, respectively. When the electric field is applied parallel to the crystal's c-axis, the electrical conductivity is dominated by the thermionic emission, mixed conduction and variable range hopping at high, moderate and low temperatures, respectively. The optical reflectivity analysis in the wavelength range 210-1500 nm revealed a clear anisotropy effect on the dispersive optical parameters. Particularly, the static refractive index, static dielectric constant, dispersion energy and oscillator energy exhibited values of 2.50, 6.24, 20.72 eV and 3.96 eV, and values of 3.05, 9.33, 39.27 eV and 4.72 eV for light propagation parallel and perpendicular to the crystal's c-axis, respectively. Moreover, the frequency dependence of the dielectric constant, epsilon(omega), reflected strong dielectric anisotropy that exhibit maximum epsilon(omega) value of 38.80 and 11.40 at frequencies of 11.07 x 10(14) Hz for light propagation parallel and perpendicular to the crystal's c-axis, respectively. The anisotropy in the epsilon(omega) makes the TlInSe2 crystals attractive to be used as nonvolatile static memory devices. (C) 2013 Elsevier B.V. All rights reserved.Article Citation - WoS: 6Citation - Scopus: 5Growth and Characterization of Pbmo0.75w0.25o4 Single Crystal: a Promising Material for Optical Applications(Elsevier Science Sa, 2023) Isik, M.; Gasanly, N. M.; Darvishov, N. H.; Bagiev, V. E.The present paper reports the structural and optical properties of PbMo0.75W0.25O4 single crystals grown by Czochralski method. XRD pattern of the crystal indicated well-defined two diffraction peaks associated with tetragonal crystalline structure. Raman and infrared spectra of the grown single crystals were presented to get information about the vibrational characteristics. Observed Raman modes were associated with modes of PbMoO4 and PbWO4. Eight bands were revealed in the infrared spectrum. The bands observed in the spectrum were attributed to multiphonon absorption processes. Transmission spectrum was measured in the 375-700 nm spectral region. The analyses of the spectrum resulted in direct band gap energy of 3.12 +/- 0.03 eV. The compositional dependent band gap energy plot was drawn considering the reported band gap energies of PbMoO4, PbWO4 and revealed band gap of PbMo0.75W0.25O4 single crystal. An almost linear behavior of composition-band gap energy was seen for PbMo1-xWxO4 compounds. Urbach energy was also found from the absorption coefficient analysis as 0.082 +/- 0.002 eV.Article Citation - WoS: 26Citation - Scopus: 28Utilization of Triso Fuel With Reactor Grade Plutonium in Candu Reactors(Elsevier Science Sa, 2010) Sahin, Suemer; Sahin, Haci Mehmet; Acir, AdemLarge quantities of plutonium have been accumulated in the nuclear waste of civilian LWRs and CANDU reactors. Reactor grade plutonium and heavy water moderator can give a good combination with respect to neutron economy. On the other hand. TRISO type fuel can withstand very high fuel burn-up levels. The paper investigates the prospects of utilization of TRISO fuel made of reactor grade plutonium in CANDU reactors. TRISO fuels particles are imbedded body-centered cubic (BCC) in a graphite matrix with a volume fraction of 68%. The fuel compacts conform to the dimensions of CANDU fuel compacts are inserted in rods with zircolay cladding. In the first phase of investigations, five new mixed fuel have been selected for CANDU reactors composed of (1) 4% RG-PuO2+ 96% ThO2; CD 6% RG-PuO2 + 94% ThO2; (3) 10% RG-PuO2+ 90% ThO2; 20% RG-PuO2+ 80% ThO2; (5) 30% RG-PuO2 + 70% ThO2. Initial reactor criticality (k(infinity,0) values) for the modes (1), (2), (3), (4) and are calculated as 1.4294, 1.5035, 1.5678, 1.6249, and 1.6535, respectively. Corresponding operation lifetimes are similar to 0.65, 1.1, 1.9.3.5, and 4.8 years and with burn ups of 30000, 60000, 100000. 200000 and 290000 MW d/tonne, respectively. The higher initial plutonium charge is the higher burn ups can be achieved. In the second phase, a graphical-numerical power flattening procedure has been applied with radially variable mixed fuel composition in the fuel bundle. Mixed fuel fractions leading to quasi-constant power production are found in the 1st, 2nd. 3rd and 4th row to be as 100% PuO2, 80/20% PuO2/ThO2, 60/40% PuO2/ThO2, and 40/60% PuO2/ThO2, respectively. Higher plutonium amount in the flattened case increases reactor operation lifetime to >8 years and the burn up to 580 000 MW d/tonne. Power flattening in the bundle leads to higher power plant factor and quasi-uniform fuel utilization, reduces thermal and material stresses, and avoids local thermal peaks. Extended burn-up grade implies drastic reduction of the nuclear waste material per unit energy output for final waste disposal. (C) 2010 Elsevier BM. All rights reserved.Article Citation - WoS: 29Citation - Scopus: 29Public Debt and Financial Development: a Theoretical Exploration(Elsevier Science Sa, 2012) Ismihan, Mustafa; Ozkan, F. GulcinIn countries where the government is the major recipient of bank lending, public debt is likely to harm financial development. Moreover, the lower the financial depth, the greater the adverse effects of public borrowing on financial development and macroeconomic outcomes. (C) 2012 Elsevier B.V. All rights reserved.Article Citation - WoS: 6Citation - Scopus: 5Synthesis of a regular polymer containing pseudo-polyether cages(Elsevier Science Sa, 2005) Cihaner, A; Önal, AMA new compound consisting of 2-thienyl units linked by polyether bridge has been synthesized and its electrochemical polymerization was performed via constant potential electrolysis (CPE) in an electrolytic solution containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF(6)) dissolved in CH3CN. Chemical polymerization was carried out using FeCl3 as oxidizing agent. It is found that both methods gave the same polymer product without any cleavage of the polyether bridge between thiophene (Th) rings. Although as synthesized polymers exhibited no conductivity, they gain conductivity via chemical doping using 12 vapor exposure. The polymers were characterized using FTIR spectroscopic technique and 12 doping was monitored using in-situ electron spin resonance (ESR) spectroscopy. Thermal behavior of electrochemically prepared polymer was investigated using differential scanning calorimetry, DSC and thermogravimetric analysis, TGA. (c) 2005 Elsevier B.V. All rights reserved.Article Citation - WoS: 23Citation - Scopus: 27Nanocrystalline Metal Organic Framework (mil-101) Stabilized Copper Nanoparticles: Highly Efficient Nanocatalyst for the Hydrolytic Dehydrogenation of Methylamine Borane(Elsevier Science Sa, 2018) Baguc, Ismail Burak; Ertas, Ilknur Efecan; Yurderi, Mehmet; Bulut, Ahmet; Zahmakiran, Mehmet; Kaya, MuratThe copper nanoparticles stabilized by nanocrystalline MIL-101 framework (Cu/nano-MIL-101) was reproducibly prepared by following double solvent method combined with liquid phase chemical reduction technique. The characterization of the resulting new material was done by using various analytical techniques including ICP-OES, P-XRD, N-2-adsorption-desorption, XPS, FE-SEM, SEM-EDX, BFTEM and HAADF-STEM; the summation of their results reveals that the formation of well-dispersed and very small sized (0.8 nm) copper nanoparticles within nanocrystalline MIL-101 framework. The catalytic performance of Cu/nano-MIL-101 in terms of activity and stability was tested in the hydrolytic dehydrogenation of methylamine borane (CH3NH2BH3), which has been considered as one of the attractive materials for the efficient chemical hydrogen storage. Cu/nano-MIL-101 catalyzes the hydrolytic dehydrogenation of methylamine borane with high activity (turnover frequency; TOF = 257 mot H-2/mol Cu x h) and conversion ( > 99%) under air at room temperature. Moreover, these nano-MIL-101 framework stabilized copper nanoparticles show great durability against to sintering and leaching, which make Cu/nano-MIL-101 reusable nanocatalyst in the hydrolytic dehydrogenation of methylamine-borane. Cu/nano-MIL-101 nanocatalyst retains 83% of its inherent activity at complete conversion even at 10th recycle in the hydrolytic dehydrogenation of methylamine borane.Article Citation - WoS: 8Citation - Scopus: 9Electronic, Optical and Thermodynamic Characteristics of Bi12sio20 Sillenite: First Principle Calculations(Elsevier Science Sa, 2021) Isik, M.; Surucu, G.; Gencer, A.; Gasanly, N. M.Bi12XO20 (X: Si, Ge, Ti) ternary semiconducting compounds are known as sillenites and take a remarkable attention thanks to their attractive photorefractive properties. The present paper reports electronic, optical and thermodynamic characteristics of Bi12SiO20 by means of density functional theory (DFT) calculations. The crystalline structure of the compound was revealed as cubic with lattice constant of 10.135 angstrom. XRD pattern obtained from DFT calculations were compared with experimental data and there is a good consistency between them. The electronic band structure and density of state plots were presented in detail. The band gap energy of the compound was determined from electronic band structure and spectra of optical constants. The spectral dependencies of real and imaginary components of dielectric function, refractive index, extinction coefficient, absorption coefficient and loss function were plotted in the 0-12 eV spectral range. The revealed structural, electronic and optical characteristics were discussed taking into account the previously reported theoretical and experimental studies on the Bi12SiO20 sillenite.Article Citation - WoS: 28Citation - Scopus: 30Composition-tuned band gap energy and refractive index in GaSxSe1-x layered mixed crystals(Elsevier Science Sa, 2017) Isik, Mehmet; Gasanly, NizamiTransmission and reflection measurements on GaSxSe1-x mixed crystals (0 <= x <= 1) were carried out in the 400-1000 nm spectral range. Band gap energies of the studied crystals were obtained using the derivative spectra of transmittance and reflectance. The compositional dependence of band gap energy revealed that as sulfur (selenium) composition is increased (decreased) in the mixed crystals, band gap energy increases quadratically from 1.99 eV (GaSe) to 2.55 eV (GaS). Spectral dependencies of refractive indices of the mixed crystals were plotted using the reflectance spectra. It was observed that refractive index decreases nearly in a linear behavior with increasing band gap energy for GaSxSe1-x mixed crystals. Moreover, the composition ratio of the mixed crystals was obtained from the energy dispersive spectroscopy measurements. The atomic compositions of the studied crystals are well-matched with composition x increasing from 0 to 1 by intervals of 0.25. (C) 2016 Elsevier B.V. All rights reserved.Article Citation - WoS: 47Citation - Scopus: 53Synthesis of Α-fe2o3< Heterogeneous Composites by the Sol-Gel Process and Their Photocatalytic Activity(Elsevier Science Sa, 2020) Bouziani, Asmae; Park, Jongee; Ozturk, Abdullahalpha-Fe2O3/TiO2 heterogeneous composites were synthesized by the sol-gel process to increase the photocatalytic activity of TiO2. The structural, morphological, and optical characteristics of the composites were determined by X-ray diffraction, scanning electron microscope, and UV-vis diffuse reflectance spectroscopy. Results revealed that the incorporation of alpha-Fe2O3 to TiO2 widened the visible light absorption ability of TiO2. It was realized that the calcination temperature plays a crucial role in morphology development hence photocatalytic activity of the alpha-Fe2O3/TiO2 heterogeneous composites. The photocatalytic activity of the composites calcined at various temperatures was evaluated for the degradation of Methylene Blue (MB) and Phenol (Ph) in aqueous medium under UV and sun-like illuminations. The alpha-Fe2O3-TiO2 composites exhibits superior photocatalytic efficiency to degrade both MB and Ph as compared to both pristine TiO2 and pristine alpha-Fe2O3 under sun-like illumination. The alpha-Fe2O3/TiO2 composite degraded approximately 90 % of MB and 50 % of Ph in 180 min sun-like illumination. Improvement in photocatalytic activity is attributed to the separation of photogenerated electron/hole pairs through the interaction of alpha-Fe(2)O(3 )and TiO2.Article Citation - WoS: 9Citation - Scopus: 10Characterization of Properties of Vanadium, Boron and Strontium Addition on Hpdc of A360 Alloy(Elsevier Science Sa, 2021) Gursoy, Ozen; Colak, Murat; Tur, Kazim; Dispinar, DeryaThe demand for lighter weight decreased thickness and higher strength has become the focal point in the automotive industry. In order to meet such requirements, the addition of several alloying elements has been started to be investigated. In this work, the additions of V, B, and Sr on feedability and tensile properties of A360 has been studied. A mold design that consisted of test bars has been produced. Initially, a simulation was carried out to optimize the runners, filling, and solidification parameters. Following the tests, it was found that V addition revealed the highest UTS but low elongation at fracture, while B addition exhibited visa verse. On the other hand, impact energy was higher with B additions.
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