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Author: search.filters.author.Amudha, A.Subject: search.filters.subject.Alumina

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    Plasma-sprayed graphene oxide reinforced alumina composite coatings on low carbon steel with improved fracture toughness, brittleness index, and microhardness
    (Elsevier Ltd, 2020) Amudha, A.; Nagaraja, H.S.; Shashikala, H.D.
    In this work, the mechanical properties of atmospheric plasma-sprayed Al2O3and Al2O3-xGO (x = 0.5, 1.0, 1.5, and 2.0 wt%) coatings on low carbon steel was evaluated using the Vickers indentation technique, and the effects of GO addition in microhardness brittleness index and fracture toughness were investigated. The Fourier-transform infrared (FTIR) spectroscopy and Field Emission Scanning Electron Microscopy (FE-SEM) techniques were employed to analyze the microstructural characterization of the plasma-sprayed coatings and to confirm the retention of GO in the Al2O3-xGO composite after the plasma spray. It was found that the Vicker's microhardness of as-sprayed Al2O3is 4.148 GPa and it decreased with the increase in the addition of GO and for Al2O3-2.0GO, it is 3.305 GPa. The fracture toughness of Al2O3is 4.86 (MPa m1/2) whereas for Al2O3-2.0GO is 16.85 (MPa m1/2). The fracture toughness has increased whereas the brittleness index has decreased as the weight percentage of GO addition is increased in the Al2O3-GO composite. Thus, the plasma-sprayed Al2O3and Al2O3-xGO coatings suggest that 2 wt% GO addition helps in the improvement of brittleness, fracture toughness, and the microhardness. © 2020 Elsevier Ltd. All rights reserved.
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    Effect of graphene oxide loading on plasma sprayed alumina-graphene oxide composites for improved anticorrosive and hydrophobic surface
    (IOP Publishing Ltd custserv@iop.org, 2019) Amudha, A.; Shashikala, H.D.; Asiq Rahman, O.S.; Keshri, A.K.; Nagaraja, H.S.
    Alumina is a widely used anticorrosive coating material for protection of metal surfaces. The graphene oxide (GO)-Alumina composite coatings can enhance the anticorrosion property of carbon steel surfaces used in an industrial scale. In the present work, the spray dried graphene oxide nanoplatelets of 0, 0.5, 1, 1.5 and 2 wt% reinforced alumina (?-Al2O3) were deposited on the low carbon steel substrate by Atmospheric Plasma Spray (APS) technique. The GO-Alumina nanocomposite coatings are characterised using XRD, FE-SEM, HR-TEM and Raman Spectroscopy. The electrochemical corrosion behaviour of the coatings on carbon steel has been examined using three electrode electrochemical method in 3.5 wt% NaCl electrolyte. A remarkable improvement in the corrosion resistance (with a corrosion current density of 0.01 nAcm-2) of about six orders with respect to pristine alumina was observed. The wettability tests revealed that, with 1.5 and 2 wt% graphene oxide nanoplatelets addition, the surface coating turned out to be hydrophobic with contact angle of 127°, from hydrophilic with contact angle 36°, which complements the anticorrosion results. The in situ reduction of GO to r-GO by APS deposition and bridging of alumina splats by the GO sheets accounts for observing the superior performance of the composite coatings. © 2019 IOP Publishing Ltd.