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Article Citation - WoS: 7Citation - Scopus: 9Electrochemical Copolymerization of 2-Substituted Thiophene Derivative Linked by Polyether Bridge With Thiophene(Elsevier Science Sa, 2005) Cihaner, A; Önal, AMNew conducting copolymers have been synthesized via electrochemical oxidation of thiophene (Th) in the presence of monomer bis(2-thienyl)ethyl (1). Cyclic voltammetry (CV) studies showed that the presence of monomer I in the electrolytic solution greatly changes the CV behaviour of the formation of the polythiophene films. It is found that the increasing ratio of I was found to decrease electroactivity of copoly(I-Th). Electrochemical synthesis of copolymer films was achieved via constant potential electrolysis (CPE) in an electrolytic solution containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF(6)) dissolved in CH3CN. Spectroelectrochemical (SPEL) properties of the films were investigated using UV-vis spectroscopic technique. (C) 2005 Elsevier B.V. All rights reserved.Article Citation - WoS: 18Citation - Scopus: 21Does Central Bank Independence Lower Inflation?(Elsevier Science Sa, 2004) Ismihan, M; Ozkan, FG; Gulcin Ozkan, F.This paper provides a potential explanation for the recent findings of no significant relationship between central bank independence (CBI) and lower inflation. We argue that although CBI delivers lower inflation in the short-term, it may reduce the scope for productivity enhancing public investment and so harm future growth potential. We also argue that the effects on growth make CBI less likely to achieve lower inflation in the long-term. (C) 2004 Elsevier B.V. All rights reserved.Article Citation - WoS: 15Citation - Scopus: 21Comparison of Various Preforms for Hot Forging of Bearing Rings(Elsevier Science Sa, 2005) Arbak, M; Tekkaya, AE; Özhan, FProduction of bearing rings by hot forging is investigated in this study. The aim of the study is to determine a feasible preform at the first station of the forming process such that the tool wear is prolonged and tool fracture is prevented. For this purpose, it is assumed that the contact pressure at the interface between tools and workpiece is the predominant process parameter. The contact pressures are determined by precise thermo-mechanical coupled finite element analyses based on elastic-plastic material description. Material flow curves for various temperatures and strain-rates are determined in velocity controlled upsetting tests. Cooling experiments are used to determine the heat transfer coefficients. Accuracy of the numerical models has been verified by extensive numerical convergence studies and finally by comparing with experimental measurements. The analysed preforms are evaluated using a scheme of weight-factors for the various tool parts. Finally, a preform is suggested for which the weighted total tool pressure could be reduced by 15%. (c) 2005 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: 1Citation - Scopus: 1Spectroelectrochemical Investigation of the Anodic Oxidation of Dibenzo-18(Elsevier Science Sa, 2004) Cihaner, A; Önal, AMPoly(dibenzo-18-crown-6) (poly-DB18C6) was synthesized by electrochemical oxidation of dibenzo-18-crown-6 (DB18C6) using a mixture of acetonitrile and dichloromethane as the solvent and tetrabutylammonium tetrafluoroborate (TBABF(4)) or tetrabutylammonium hexafluorophosphate (TBAPF(6)) as supporting electrolyte. The anodic polymerization of DB18C6 was investigated using in situ ESR and in situ UV-Vis spectroscopic techniques. Spectroelectrochemical (SPEL), properties and thermal analysis of the resulting polymers have been investigated using UV-Vis spectroscopy, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). (C) 2004 Elsevier B.V. All rights reserved.Article Citation - WoS: 5Citation - Scopus: 5Acoustic Phonons Scattering Mobility and Carrier Effective Mass in In6s7< Crystals(Elsevier Science Sa, 2006) Qasrawi, A. F.; Gasanly, N. M.Systematic dark electrical resistivity and Hall coefficient measurements have been carried out in the temperature range of 170-320 K on n-type In6S7 crystals. The analysis of the electrical resistivity and carrier concentration reveals the intrinsic type of conduction with an average energy band gap of similar to 0.75 eV The carrier effective masses of the conduction and valence bands were calculated from the intrinsic temperature-dependent carrier concentration data and were found to be 0.565m(0) and 2.020m(0), respectively. The temperature-dependent Hall mobility was observed to follow the mu alpha T-3/2 law and was analyzed assuming the domination of acoustic phonons scattering. The acoustic phonons scattering mobility was calculated from the crystal's structural data with no assumptions. The experimental Hall mobility data of In6S7 crystals coincides with the theoretical acoustic phonons scattering mobility data with acoustic deformation potential of 6.4 eV. (c) 2006 Elsevier B.V. All rights reserved.Article Citation - WoS: 6Citation - Scopus: 6Synthesis and Polymerization of 2-And 3-Substituted Thiophene Derivatives Linked by Polyether Bridges(Elsevier Science Sa, 2004) Tirkes, S; Cihaner, A; Önal, AMNew compounds consisting of 2- and 3-thienyl units linked by polyether bridges have been synthesized and their electrochemical polymerization was performed via constant potential electrolysis (CPE) in an electrolytic solution containing 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF(6)) dissolved in CH3CN. 2-Thienyl monomers (I and II), but not 3-thienyl monomers (III and IV), were also polymerized via chemical oxidation, which yielded broken pi-conjugated polymer products. The polymers were characterized using H-1 NMR and FT-IR spectroscopic techniques. It was found that both chemical and electrochemical oxidation of 2-thienyl monomers gave mainly poly(2,2'-bithiophenemethylene) due to elimination of polyether chains during the polymerization reaction. On the other hand, electrochemical oxidation of 3-thienyl monomers resulted in corresponding polymers without any cleavage of polyether bridges. Spectroelectrochemical (SPEL) properties of the products were investigated using UV-Vis spectroscopic techniques. (C) 2004 Elsevier B.V. All rights reserved.Article Citation - WoS: 18Citation - Scopus: 19Temperature Dependence of the Direct Allowed Transitions Band Gap and Optical Constants of Polycrystalline Α-in2se3< Thin Films(Elsevier Science Sa, 2006) Qasrawi, A. F.Polycrystalline alpha-In2Se3 thin films were obtained by the thermal evaporation of alpha-In2Se3 crystals onto glass substrates kept at temperature of 200 degrees C. The temperature dependence of the optical band gap in the temperature region of 300-480 K and the room temperature refractive index, it (lambda), of these films have been investigated. The absorption edge shifts to lower energy values as temperature increases. The fundamental absorption edge corresponds to a direct allowed transitions energy gap that exhibits a temperature coefficient of -8.51 x 10(-4) (eV/K). The room temperature n(lambda) which was calculated from the transmittance data allowed the identification of the oscillator strength and energy, static dielectric constant and static refractive index as 20.7 and 2.15 eV, 10.70 and 3.26, respectively. (c) 2006 Elsevier B.V. All rights reserved.Article Citation - WoS: 6Citation - Scopus: 8Temperature and Magnetic Field Effects on the Carrier Density and Hall Mobility of Boron-Doped Tl-Ba Superconductor(Elsevier Science Sa, 2005) Kayed, TS; Qasrawi, AFBoron-doped T1-based superconductor was prepared by adding an amount of 1 wt.% B to the Tl1.8Ba2Ca2.2Cu3Ox, compound. The usual solid-state reaction method has been applied under optimum conditions. The X-ray data of the sample show a tetragonal structure with a high ratio of T1-2223 superconducting phase. The sample showed a transition at 125 K and the zero resistance was observed at 120 K. The magnetic field and temperature effects on the normal state electrical resistivity, carrier density, and Hall mobility have been investigated. Both temperature and magnetic field significantly affect the resistivity behavior. The zero field resistivity was found to vary exponentially with temperature with a slope revealing activation energy of 27.5 meV. When the magnetic field is applied, the resistivity varied up-normally in the temperature region of 160-240 K. The temperature dependent carrier concentration calculated from the Hall coefficient data varied linearly with the applied magnetic field. This effect was attributed to the increase in the hole effective mass upon field increment. The temperature-dependent carrier concentration data at several applied fields were analyzed by the single donor-single acceptor model to obtain the values of effective masses. The temperature and magnetic field dependent normal state Hall mobility was found to be limited by the scattering of acoustic phonons. (c) 2005 Elsevier B.V. All rights reserved.Article Citation - WoS: 28Citation - Scopus: 31Electrochemical Polymerization of 9-Fluorenone(Elsevier Science Sa, 2004) Cihaner, A; Tirkes, S; Önal, AMElectrochemical polymerization of 9-fluorenone, FO, was studied in CH2Cl2 solution with tetrabutylammonium tetrafluoroborate, TBABF(4), as the electrolyte, via constant potential electrolysis, CPE. Prior to CPE, the redox behavior of FO was investigated in the same solvent/electrolytic medium using cyclic voltammetry, CV. CPE of FO yielded an insoluble polymer deposit on the electrode surface. The product was characterized by FTIR spectroscopy techniques. The redox and spectroelectrochernical, SPEL, behavior of the polymer were studied by CV and in situ UV-Vis spectrophotometric techniques at various potentials, respectively. The conductivity was measured using a two-probe technique and the paramagnetic behavior of the polymer was monitored using in situ ESR spectroscopy. (C) 2004 Elsevier B.V. All rights reserved.
