Yazar "Karahan, I. Hakki" seçeneğine göre listele

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    Different copolymer films on ZnFeCo particles: Synthesis and anticorrosion properties
    (Elsevier, 2014) Ozyilmaz, A. Tuncay; Avsar, Busra; Ozyilmaz, Gul; Karahan, I. Hakki; Camurcu, Taskin; Colak, Fatma
    Zinc-iron-cobalt (ZnFeCo) particles were electrochemically deposited on carbon steel (CS) electrode applying current of 3 mA with chronopotentiometry technique. ZnFeCo particles had homogenous, smooth with prismatic structure. It was shown that the ZnFeCo particles exhibited important barrier effect on CS substrate. Poly(aniline-co-o-anisidine), poly(aniline-co-pyrrole), poly(aniline-co-N-methylpyrrole) and poly(o-anisidine-co-pyrrole) copolymer films were obtained on CS/ZnFeCo electrode. Evaluation of anticorrosion performance of copolymer coatings in 3.5% NaCl solution was investigated by using AC impedance spectroscopy (EIS) technique, anodic polarization and the E-OCP-time curves. Copolymer films exhibited significant physical barrier behavior on ZnFeCo plated carbon steel, in longer exposure time. (C) 2014 Elsevier B.V. All rights reserved.
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    Electrochemical synthesis of polyaniline films on zinc-cobalt alloy deposited carbon steel surface in sodium oxalate
    (Elsevier Science Sa, 2014) Ozyilmaz, A. Tuncay; Akdag, Abdurrahman; Karahan, I. Hakki; Ozyilmaz, Gul
    Polyaniline (PANI) coatings were electropolymerized on zinc-cobalt alloy deposited carbon steel (CS/ZnCo) electrode from an aqueous sodium oxalate solution using three different scan rates in cyclic voltammetric technique. Scanning electron microscopy (SEM) was used to analyze the surface morphology of the polymer film. The SEM images showed that the increase in scan rate induced an increase in grain size of the PANI film. The corrosion behavior of CS/ZnCo electrodes with and without PANI film in 3.5% NaCl solution were investigated through electrochemical impedance spectroscopy (EIS) and anodic polarization studies. The results of the study showed that the PANI coatings provided significant and effective protection for the CS/ZnCo electrode, in preventing corrosion. In addition, the PANI film that was synthesized at a high scan rate, exhibited the best anti-corrosive performance due to the formation of protective oxide layers through its catalytic efficiency. (C) 2014 Elsevier B.V. All rights reserved.
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    Electronic Structure Study of Ni-B Alloy Coatings by XAFS Technique
    (Springer, 2021) Ozkendir, O. Murat; Cengiz, Erhan; Karahan, I. Hakki; Klysubun, Wantana
    The crystal and electronic structure properties of Ni-B (nickel-boron) alloy coatings produced by an electrodeposition method have been investigated. The crystal structures of the alloy coatings were determined by x-ray diffraction patterns and supported by extended x-ray absorption fine structure (EXAFS) spectroscopy. The local atomic structure around the Ni atom was obtained from EXAFS studies at the Ni K-edge, and the EXAFS data were fitted with theoretical calculations. With the addition of boron atoms in the nickel environment, NiB composite alloys were formed in the crystals with an orthorhombic Cmcm structure. The analysis revealed a limited effect of boron doping in the electronic structure of the nickel atoms. Boron atoms were determined as sitting between the Ni atoms and causing a disturbance in the crystal structure due to providing inhomogeneous interstitial potential and defects.
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    Electronic structure study of the bimetallic Cu1-xZnx alloy thin films
    (Taylor & Francis Ltd, 2018) Ozkendir, O. Murat; Cengiz, Erhan; Mirzaei, Mahmoud; Karahan, I. Hakki; Ozdemir, Rasim; Klysubun, Wantana
    A series of Zn doped copper materials were investigated upon their crystal and electronic structure with the general formula Cu1-xZnx. CuZn alloys were produced via electrodeposition method. Galvanostatic deposition was preferred for the deposition. Crystal properties of the samples were studied via X-ray diffraction (XRD) patterns and supported by the X-ray absorption fine structure spectroscopy (XAFS) data. According to the crystal structure analysis, crystal geometries of the substituted samples were mainly determined in bcc cubic. The study has revealed that, low amount of Zn substitution (0.1M) are inactive in the molecular interplays and treated as an impurity in fcc copper environment. However, higher Zn concentrations (> 0.1 M) have built bcc structure under the influence of the highly overlapped 4p levels wavefunctions of the neighbouring Cu and Zn atoms. Thus, 0.1 M zinc substitution has been determined as a threshold of the phase transition from fcc to the bcc structure.
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    Grain size calculation of Cu-Zn alloys using genetic programming; an alternative for Scherer's formula
    (Natl Inst Optoelectronics, 2015) Ozdemir, R.; Karahan, I. Hakki
    Genetic Programming (GP) was used as a new method for formulation of grain size of electrodeposited Cui_xZnx alloys as a function of Zinc and Copper content both electrolyte and the alloy films produced by electrodeposition technique. To predict grain size 48 different expression models were conducted. Each model differs from the other with their linking function, number of genes, head size, and chromosomes. To generate databases for the new grain size formulations, testing and training sets in total of 134 samples were selected at different Zn and Cu ratios of components. The testing and training sets consisted of randomly selected 106 and 28 for the proposed models. 6 different input parameters were selected as dspacing spacing, Zn and Cu % content in the electrolyte and thin films and the test FWHM of the thin films obtained by XRD results. The output parameter was grain size of the electrodeposited Cu-Zn alloys. All results in the models indicated an applicable performance for predicting grain size of the alloys and found reliable. The predicted model showed that all of the input parameters effected on the resulting grain size.
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    The influence of polyaniline (PANI) coating on corrosion behaviour of zinc-cobalt coated carbon steel electrode
    (Elsevier Science Sa, 2013) Ozyilmaz, A. Tuncay; Akdag, Abdurrahman; Karahan, I. Hakki; Ozyilmaz, Gul
    Zinc-cobalt alloy plating (ZnCo) was successfully deposited on carbon steel (CS) applying current of 2 mA with galvanostatic technique. Polyaniline film (PANI) was synthesized with cyclic voltammetry technique from 0.20 M aniline containing 0.20 M sodium tartrate solution on zinc-cobalt plated carbon steel (CS/ZnCo) electrode. PANI film characterized by scanning electron microscopy (SEM), was covered with a dark green-brown homopolymer film of strongly adherent homogeneous characteristic while the other one was plated with a porous light ZnCo one. The corrosion behaviour of zinc-cobalt deposited carbon steel electrodes with and without polyaniline (PANI) film in 3.5% NaCl solution was investigated with AC impedance spectroscopy (EIS) technique and anodic polarization curves. The results showed that PANI coating led to decrease of the permeability of metallic plating. The PANI homopolymer film provided an effective barrier property on zinc-cobalt coating and a remarkable anodic protection to substrate for longer exposure time. (C) 2012 Elsevier B.V. All rights reserved.