Person: SARIOĞLU, CEVAT
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SARIOĞLU
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CEVAT
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Publication Metadata only Residual stresses in (Zr,Hf)N films (up to 11.9 at.% Hf) measured by X-ray diffraction using experimentally calculated XECs(ELSEVIER SCIENCE SA, 2005) SARIOĞLU, CEVAT; Atar, E; Sarioglu, C; Cimenoglu, H; Kayali, ESIn the present work, the residual stresses of (Zr,Hf)N films were measured using X-ray diffraction (XRD) fixed incident multiplane technique (FIM) for varying amounts of Hf addition by assuming the film was isotropic and anisotropic (Kronel model). The residual stress values calculated according to isotropic and anisotropic models were almost the same (-6 GPa). Addition up to 11.9 at.% Hf into ZrN films did not affect the level of residual stress. (C) 2004 Elsevier B.V. All rights reserved.Publication Metadata only Fast and low-cost fabrication of 1D hematite photoanode in pure water vapor and air atmosphere: Investigation the effect of the oxidation atmosphere on the PEC performance of the hematite photoanodes(PERGAMON-ELSEVIER SCIENCE LTD, 2017) SARIOĞLU, CEVAT; Demirci, Selim; Sarioglu, CevatIn this study, hematite photoanodes were successfully fabricated by thermal oxidation of the commercial cold-rolled steel at 500 degrees C in pure water vapor and air atmosphere. The crystal phase structure, surface morphology, and optical properties of the hematite photoanodes were characterized using an X-ray diffractometer (XRD), field emission scanning electron microscopy (FESEM) and UV-VIS spectrophotometer, respectively. The results showed that hematite photoanodes had high crystalline phase and the annealing atmosphere influenced the morphology of the hematite photoanodes. Moreover, nanowhisker and nanorod shaped nanostructures were observed on the substrate. The optical band gap values of the hematite photoanodes varied between 2.38 and 2.70 eV. Photoelectrochemical (PEC) studies of the hematite photoanodes were assessed in the 0.1 M NaOH electrolyte solution using the Mott-Schottky analysis and electrochemical impedance spectroscopy techniques. The PEC findings exhibited that the hematite photoanode annealed 15-min in water vapor had best PEC performance achieving photocurrent density 0.244 mA/cm(2) at 1.6 V vs. V-RHE and highest carrier density value (N-D = 1.15 x 10(21) cm(-3)). Furthermore, the photoanodes annealed in water vapor atmosphere revealed at least three times higher PEC performance than that of photoanodes annealed in air. Thermal oxidation method in water vapor is an efficient methods for fabrication of hematite photoanodes. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Publication Metadata only The effect of anisotropy on residual stress values and modification of Serruys approach to residual stress calculations for coatings such as TiN, ZrN and HfN(ELSEVIER SCIENCE SA, 2006) SARIOĞLU, CEVAT; Sarioglu, CevatThe residual stresses in literature on hard coatings (e.g., TiN, CrN, HfN and ZrN) are usually calculated using the mechanical elastic constants often determined by indentation technique by assuming isotropic behavior. The effect of anisotropy of the hard coatings on residual stress values such as TiN, ZrN and HfN has been documented using classical technique and Thin Film techniques (fixed incidence multiplane (FIM) Technique). Due to lack of the single crystal data, the anisotropy of coatings has been taken into account through XECs determined experimentally for ZrN, HfN and TiN films. Recently, single crystal elastic constants of the ZrN, HfN and NbN have been measured. In the light of single crystal elastic constant data, residual stresses reported in the literature were reevaluated according to Reuss, Voigt, Hill (or mixed) and Kroner models using the best fitting approach after modifying Serruys approach. The modified Serruys approach captures the anisotropic behavior of coatings such as ZrN and Zr(Hf)N. The residual stress calculations were improved and the residual stress values were significantly increased as high as 30% compared to the previously published data. The best fitting approach (modified Serruys approach) was compared to the procedure used by Perry using experimentally determined XECs. (c) 2006 Elsevier B.V. All rights reserved.Publication Metadata only Measurement of residual stresses by X-ray diffraction techniques in MoN and Mo2N coatings deposited by arc PVD on high-speed steel substrate(ELSEVIER SCIENCE SA, 2005) SARIOĞLU, CEVAT; Sarioglu, C; Demirler, U; Kazmanli, MK; Urgen, MPolycrystalline MoN and Mo2N films have promising physical and mechanical properties, which made them candidates for wear- and corrosion-resistant coatings and diffusion barriers in microelectronics. The residual stresses in MoN and Mo2N films consist of thermal and growth stresses or intrinsic stress generated during deposition. Residual stresses in the MoN and Mo2N coatings deposited by arc PVD techniques on HSS substrate were measured by XRD using the Rocking and the Fixed Incidence Multiplane (FIM) techniques. Residual stresses measured by both techniques in Mo2N (face center cubic, f.c.c.) and in MoN (hexagonal) films were about 5 and 10 GPa (compressive), respectively. These results indicated that residual stresses in the MoN film was two times greater than the residual stresses in the Mo2N film. (C) 2004 Elsevier B.V. All rights reserved.