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Access Right: info:eu-repo/semantics/closedAccessAuthor: Ucisik, A. Hikmet

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    Article
    Citation - WoS: 34
    Citation - Scopus: 37
    Characterization of Gas Tunnel Type Plasma Sprayed Hydroxyapatite-Nanostructure Titania Composite Coatings
    (Elsevier, 2015) Yugeswaran, S.; Kobayashi, A.; Ucisik, A. Hikmet; Subramanian, B.
    Hydroxyapatite (HA) can be coated onto metal implants as a ceramic biocompatible coating to bridge the growth between implants and human tissue. Meanwhile many efforts have been made to improve the mechanical properties of the HA coatings without affecting its bioactivity. In the present study, nanostructure titania (TiO2) was mixed with HA powder and HA-nanostructure TiO2 composite coatings were produced by gas tunnel type plasma spraying torch under optimized spraying conditions. For this purpose, composition of 10 wt% TiO2 + 90 wt% HA, 20 wt% TiO2 + 80 wt% HA and 30 wt% TiO2 + 70 wt% HA were selected as the feedstock materials. The phase, microstructure and mechanical properties of the coatings were characterized. The obtained results validated that the increase in weight percentage of nanostructure TiO2 in HA coating significantly increased the microhardness, adhesive strength and wear resistance of the coatings. Analysis of the in vitro bioactivity and cytocompatibility of the coatings were done using conventional simulated body fluid (c-SBF) solution and cultured green fluorescent protein (GFP) labeled marrow stromal cells (MSCs) respectively. The bioactivity results revealed that the composite coating has bio-active surface with good cytocompatibility. (C) 2015 Elsevier B.V. All rights reserved.
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    Citation - WoS: 95
    Citation - Scopus: 101
    Characterization of Az31 Mg Alloy Coated by Plasma Electrolytic Oxidation
    (Pergamon-elsevier Science Ltd, 2013) Durdu, Salih; Bayramoglu, Selin; Demirtas, Aysun; Usta, Metin; Ucisik, A. Hikmet
    In this study, AZ31 Mg alloy produced by twin roll casting was coated by a plasma electrolytic oxidation (PEO) in the solution, consisting of Na2SiO3 center dot 5H(2)O + KOH electrolyte at 0.085 A/cm(2) current density for 15, 30, 45 and 60 min. Thickness of the coated layer, surface morphology, phase structure, hardness, adhesion strength of the layer and wear resistance were analyzed by an eddy current, SEM, XRD, Vickers hardness, micro scratch tester and tribometer, respectively. The average coating thickness ranged from 17 to 56 mu m. A number of pores were formed on the coated layer. XRD revealed that Mg2SiO4 (Forsterite) and MgO (Periclase) phases were formed on the surface of the magnesium alloy. Average coating hardness was measured as 660 HV, while the hardness of the magnesium alloy was 72 HV. Adhesion strength of coatings was increased by increasing duration time. Wear resistances of coatings were higher than AZ31 Mg alloy. (C) 2012 Elsevier Ltd. All rights reserved.