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Article Citation - WoS: 77Citation - Scopus: 79Electrical Properties of Al/Pcbm:zno Heterojunction for Photodiode Application(Elsevier Science Sa, 2020) Gullu, H. H.; Yildiz, D. E.; Kocyigit, A.; Yildirim, M.In this paper, the electrical characteristics of spin-coated PCBM:ZnO interlayered Al/PCBM:ZnO/Si diode are investigated under the aim of photodiode application. Under dark condition, the diode shows about four orders in magnitude rectification rate and diode illumination results in efficient rectification with increase in intensity. The analysis of current-voltage curve results a non-ideal diode characteristics according to the thermionic emission model due to the existence of parasitic resistances and interface states. The measured current-voltage values are used to extract the barrier height and ideality factor under dark and illumination conditions. Under illumination, photo-generated carriers contribute to the current flow and linear photo-conductivity behavior in photo-current measurements with illumination shows the possible use of hybrid PCBM:ZnO layer in Si-based photodiodes. In addition, change in the series and shunt resistance values under illumination is found to be effective in this light-sensing behavior of the diode. This characteristic is also observed from the typical on/off illumination switching behavior for the photodiodes in transient photo-current, photo-capacitance and photo-conductance measurements with the quick response to the illumination. The deviations from ideality are also discussed by means of distribution of interface states and series resistance depending on the applied frequency and bias voltage. (C) 2020 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: 10Citation - Scopus: 12Influence of the Heat Treatment on the Microstructure, Mechanical and High-Temperature Oxidation Behavior of Hastelloy X Alloy Fabricated Via Laser Powder Bed Fusion(Elsevier Science Sa, 2025) Ozer, Seren; Yalcin, Mustafa Alp; Bilgin, Gueney Mert; Davut, Kemal; Esen, Ziya; Dericioglu, Arcan F.The effect of building direction and heat treatment on the microstructure, mechanical properties, and high- temperature oxidation behavior of Hastelloy X (HX) alloy fabricated by the laser powder bed fusion (L-PBF) method was studied. Electron backscatter diffraction analyses revealed that the development of textured columnar grains with varying average grain sizes, boundary fractions, and dislocation densities induced the mechanical anisotropy observed in both horizontally and vertically fabricated samples. The yield strength (YS) values of the horizontally and vertically as-fabricated samples were determined as 605.7 +/- 15.9 MPa and 552.3 +/- 8.5 MPa, respectively. The post-processing heat treatment increased the ductility remarkably and reduced YS value down to similar to 445 MPa for all samples by the elimination of microstructural anisotropy and increased grain size subsequent to recrystallization. Oxidation tests conducted at 900 degrees C up to 100 h on as- fabricated samples exhibited severe intergranular oxidation, which was accompanied by the formation of large voids and microcracks as well as spallation of the oxide layer. In contrast, the heat-treatment improved the oxidation resistance of the alloy possibly due to the formation of uniform and dense Cr2O3 layer on the substrate surface.Article Citation - WoS: 29Citation - Scopus: 29The investigation of electronic, anisotropic elastic and lattice dynamical properties of MAB phase nanolaminated ternary borides: M 2 AlB 2 ( M = Mn , Fe and Co ) under spin effects(Elsevier Science Sa, 2020) Surucu, Gokhan; Yildiz, Bugra; Erkisi, Aytac; Wang, Xiaotian; Surucu, Ozge[No Abstract Available]Article Citation - WoS: 9Citation - Scopus: 9Experimental and Theoretical Investigation of the Mechanical Characteristics of Sillenite Compound: Bi12geo20<(Elsevier Science Sa, 2021) Surucu, Gokhan; Isik, Mehmet; Gencer, Aysenur; Gasanly, NizamiThe present study reports the mechanical and elastic characteristics of Bi12GeO20 (BGO) compound by experimental nanoindentation measurements and density functional theory (DFT) calculations. X-ray diffraction pattern of BGO was plotted and revealed diffraction peaks were associated with Miller indices of cubic crystalline structure with lattice constant of a = 10.304 angstrom. Two- and three-dimensional representations of Young's modulus, linear compressibility, shear modulus and Poisson's ratio were presented according to DFT calculations. The calculated elastic constants pointed out the mechanically stable and anisotropic behavior of the BGO. The hardness and Young's modulus ranges of the BGO calculated from DFT studies were found as 3.7-6.3 GPa and 61.7-98.9 GPa, respectively. Hardness and Young's modulus of BGO single crystal were also obtained by analyzing force-dependent nanoindentation experimental data. It was observed that hardness and Young's modulus decrease with increase of load in the low applied loads and then reaches saturation in the high applied loads. This behavior is known as indentation size effect. True hardness value was determined from proportional specimen resistance model as 4.1 GPa. The force independent region presented the Young's modulus as 114 GPa. (C) 2021 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: 22Citation - Scopus: 25Thermal Comfort Analysis of Historical Mosques. Case Study: the Ulu Mosque, Manisa, Turkey(Elsevier Science Sa, 2021) Diler, Yusuf; Turhan, Cihan; Arsan, Zeynep Durmus; Akkurt, Gulden GokcenMosques are sanctuary places for Muslims where they can perform their religious activities and also can communicate with each other. On the other hand, historical mosques may contain artworks which have cultural heritage values. These mosques originally have not any Heating, Ventilating and Air Conditioning systems. For this reason, obtaining thermal comfort becomes a significant issue. In this study, a systematic approach on monitoring and evaluating thermal comfort of historical mosques were developed. As a case study, The Ulu Mosque, Manisa/Turkey was monitored from 2015 to 2018, and thermal comfort evaluation of the mosque was conducted during prayer times based on the method provided by ISO 7730. A dynamic Building Energy Performance Software, DesignBuilder, was used to model the mosque, and the model was calibrated by using hourly indoor temperature data. The calibrated model was then used to evaluate existing conditions of the mosque and develop retrofitting scenarios in order to increase thermal comfort of prayers. Thirteen different scenarios were proposed to improve thermal comfort of prayers during worship periods. The results were evaluated according to EN 16883 for conservation of cultural heritage of the mosque. Electrical radiator heating with intermittent operating schedules was obtained as the best scenario to protect cultural heritage via artworks, while decreasing disssatisfaction level of the prayers from 45% to 10% in winter months. Additionally, intermittent operation saved 46.9% of energy compared to continuous operating schedule. (C) 2021 Elsevier B.V. All rights reserved.Article Citation - WoS: 32Citation - Scopus: 28Photocatalytic activity of hydroxyapatite-precipitated potassium titanate whiskers(Elsevier Science Sa, 2010) Park, JongeePhotocatalytic properties of hydroxyapatite (HAP)-precipitated multifunctional potassium titanate (KT) whiskers were investigated in terms of the decomposition of methylene blue (MB) in aqueous solution under UV irradiation. Hydroxyapatite was formed on the surface of KT whiskers through a biomimetic process in simulated body fluid (SBF). The SBF used in this investigation had concentrations of calcium and phosphate ions 10 times greater than those of human plasma. Results revealed that hydroxyapatite precipitation enhanced the photocatalytic activity of the KT whiskers. In the case of unreacted KT whisker, complete degradation of methylene blue took 5.5 h, on the other hand degradation time decreased to 3.5 h when the whisker was precipitated with hydroxyapatite. (C) 2009 Elsevier B.V. All rights reserved.Article Citation - WoS: 18Citation - Scopus: 19Effect of Furan, Thiophene and Selenophene Donor Groups on Benzoselenadiazole Based Donor-Acceptor Systems(Elsevier Science Sa, 2016) Karabay, Lutfiye Canan; Karabay, Bads; Karakoy, Merve Serife; Cihaner, AtillaA series of the monomers called 4,7-di(furan-2-yl)benzo[c][1,2,5]selenadiazole (OSeO), 4,7-di(thiophen-2-yl)benzo[c]11,2,5]selenadiazole (SSeS) and 4,7-di(selenophen-2-yl)benzo[c][1,2,5]selenadiazole (SeSeSe) was synthesized via a donor-acceptor-donor (D-A-D) approach. Benzoselenadiazole was used as an acceptor unit and furan, thiophene and selenophene were used as donor units. The effects of chalcogen atoms (0, S, and Se) in furan, thiophene and selenophene were investigated systematically on the properties of the monomers and their corresponding polymers (POSeO, PSSeS and PSeSeSe, respectively), which were polymerized electrochemically via potentiodynamic or potentiostatic methods. The monomers OSeO, SSeS and SeSeSe exhibited low oxidation potentials of 1.15, 1.25 and 1.19 V vs. Ag/AgCl, respectively. Intramolecular charge transfer interaction between donor and acceptor units was demonstrated from the emission spectra of the monomers. Also, the optical studies showed that the ambipolar and electrochromic polymers POSeO, PSSeS and PSeSeSe have low band gaps of 1.57, 1.47 and 1.45 eV, respectively. (C) 2016 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.
