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Öğe Corrosion behavior of galvanized steel exposed to fusarium oxysporum f. sp. cumini isolated from a natural biofilm(Maik Nauka/Interperiodica/Springer, 2022) Kadaifçiler, Duygu; Danışman, Merve; Arslan Vatansever, D.; Cansever, Nurhan; İlhan Sungur, EsraFusarium spp. are prevalent fungi in water systems and also in biofilm layers developing upon metal surfaces associated with these systems. The present study investigated (i) the presence of Fusarium sp. in biofilms on galvanized steel surface exposed to potable water, and (ii) the effect of Fusarium sp. on corrosion behaviour of galvanized steel by electrochemical methods. The natural biofilm was formed on the galvanized steel surface in a laboratory-scaled test system. Molecular characterization of the tentative Fusarium isolate was carried out by sequencing of the internal transcribed spacer (ITS) regions. The metal coupons were exposed for 336 h to potato dextrose broth medium inoculated with Fusarium sp. The biofilm formation and corrosion products on the metal surfaces were investigated by scanning electron microscopy. The ITS sequences showed that the Fusarium sp. isolate was closely related to Fusarium oxysporum f. sp. cumini (98.97%). The electrochemical analysis revealed that although the test medium was corrosive for the metal, the presence of F. oxysporum f. sp. cumini accelerated the corrosion of galvanized steel. According to the results, this is the first study showing the presence of Fusarium sp. in the natural biofilm formed on the galvanized steel surface and also the effect of Fusarium sp. on corrosion behavior of the galvanized steel in aqueous environment.Öğe Crystallization of TiO2 on sputter deposited amorphous titanium thin films(Elsevier Science Sa, 2022) Tepe, Seda Aysel; Danışman, Murat; Cansever, NurhanTitanium and titanium dioxide are both very well-known and commonly used materials in today's world. They would also be very promising materials for years to come as their more novel properties are continued to be investigated. For meeting the demands of today's technology and to fine tune its properties, titanium dioxide is still in the scope of scientists from different branches of science. In our study, sputter deposited amorphous titanium thin films on glass substrates were anodically oxidized at 0.7 V for 250, 750, 1250 s in 0.5 M H2SO4 solution to observe their crystalline structure and electrochemical properties. X ray diffraction analysis revealed rutile and anatase crystalline peaks on 250 s and 1250 s anodized samples. Additionally, electrochemical impedance spectroscopy and atomic force microscopy analysis were carried out for investigating the effect of anodization on electrochemical and surface properties of amorphous titanium thin films. Both analysis showed compressive stress related findings in oxide films due to crystallization process.Öğe Diffusion characteristics of plasma nitrided hard chromium on AISI 1010 steel(Walter de Gruyter GmbH, 2015) Danışman, Murat; Kocabaş, Mustafa; Cansever, NurhanIn order to investigate the different Cr-N formation characteristics of plasma nitrided hard Cr coatings, Cr was electrodeposited on AISI 1010 steel and plasma nitrided at 600, 700 and 800 degrees C for 3 h, 5 h and 7 h, respectively. Phase analyses of resulting Cr-N phases and grain size of Cr layer before and after nitriding process were calculated by X-ray diffraction analysis. Structure of nitride layer and its thickness were analyzed using scanning electron microscopy micrographs. The micrographs indicated that samples consisted of three distinctive layers. In order to distinguish these layers, scanning electron microscopy and energy dispersive spectroscopy (EDX) analysis were used as well as elemental distribution versus depth was plotted. The Cr-N diffusion was investigated by layer thickness measurements, and diffusion coefficient as well as activation energies were calculated.Öğe Effect of plasma nitriding time on surface properties of hard chromium electroplated AIS1 1010 steel(Carl Hanser Verlag, 2015) Kocabaş, Mustafa; Danışman, Murat; Cansever, Nurhan; Ülker, ŞükrüProperties of steel can be enhanced by surface treatments such as coating. In some cases, further treatments such as nitriding can also be used in order to get even better results. In order to investigate the properties of nitride layer on hard Cr coated AISI 1010 steel, substrates were electroplated to form hard Cr coatings. Then hard Cr coatings were plasma nitrided at 700°C for 3 h, 5 h and 7 h and nitride phases on the coatings were investigated by X-ray diffraction analysis. The layer thickness and surface properties of nitride films were investigated by scanning electron microscopy. The hardness and adhesion properties of Cr-N phases were examined using nano indentation and Daimler-Benz Rockwell C adhesion tests. The highest measured hardness was 24.1 GPa and all the three samples exhibited poor adhesion.Öğe Investigation of porous anodic film formation on AA1050 by electrochemical impedance spectroscopy(World Scientific Publishing Company Pte Ltd, 2020) Danışman, Murat; Kocabaş, Mustafa; Curioni, Michele; Cansever, NurhanIn this study, the formation of porous Al2O3 on commercial 1050 aluminium alloy (AA1050) in 2 M sulfuric acid (H2SO4) electrolyte was investigated. Anodization was performed at 12 V and 15 V specimens for a charge density of 757 mC/cm(2) and 3231 mC/cm(2). The resulting oxides were analyzed using scanning electron microscopy (SEM). According to analysis, a hexagonal oxide formation containing more than one nano pore was observed on the surface of the specimen. The structural properties of the porous oxide film were analyzed with electrochemical impedance spectroscopy (EIS) analysis and film-related features such as thickness of the porous and the barrier layer were obtained.
