Journal Articles
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Item 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.Item Dual electrochemical application of r-GO wrapped ZnWO4/Sb nanocomposite(Institute of Physics Publishing helen.craven@iop.org, 2019) Brijesh, K.; Bindu, K.; Amudha, A.; Nagaraja, H.S.ZnWO4/Sb nanorods and r-GO-ZnWO4/Sb nanocomposite have been prepared using a single step solvothermal method. The prepared nanocomposites have been characterized using x-ray diffractometer (XRD), Scanning Electron Microscope (SEM), High Resolution Transmission Electron Microscope (HR-TEM), Raman and Brunauer-Emmett-Teller (BET). The x-ray photoelectron spectroscopy (XPS) technique was used to determine the elemental composition of ZWS-5 (5 mg r-GO-ZnWO4/Sb) composite. The XRD reveals the monoclinic wolframite structure of ZnWO4/Sb and r-GO-ZnWO4/Sb. SEM and HRTEM confirms that the ZnWO4/Sb has been decorated on the r-GO sheets. The electrochemical performance of the prepared samples towards the Hydrogen Evolution Reaction (HER) and dopamine sensing has been tested using electrochemical techniques. Onset potential of 265 mV @10 mA cm-2, lower Tafel slope (95 mV dec-1), high electrochemical surface area (1383.216 m2g-1) and high specific site density (18.551 06 × 1021 g-1) of ZWS-5 reveals the high electrocatalytic activity of the composite towards HER. Chronoamperometric dopamine sensing shows that ZWS-5 has the superior sensing performance with highest specific sensitivity (723 ?A ?M-1 ?g-1), lowest limit of detection (0.9624 ?M), along with a good selectivity. Results suggest that the r-GO-ZnWO4/Sb nanocomposite is a good candidate for the HER and electrochemical dopamine sensor. The incorporation of r-GO nanosheets with ZnWO4/Sb (ZWS) nanorods enhances the specific and electrochemical surface area, which accounts for the high electrocatalytic activity of the composite. © 2019 IOP Publishing Ltd.Item Finite element analysis of thermal residual stresses in SS-309Mo and Inconel-625 multilayer weld deposition on low carbon steel(Elsevier Ltd, 2019) Amudha, A.; Nagaraja, H.S.; Shashikala, H.D.ANSYS Finite Element Analysis is adopted for simulation of SS-309Mo and Inconel-625 deposition in single and double layers, on IS-2062 Grade-B low carbon steel base metal. The Von-Mises residual stress distribution is obtained for twelve different combinations of weld deposition techniques and weld materials. Aim is to obtain a combination with minimum residual stress, using a technique of alternate skip weld deposition and base metal preheating. Also, the effect of change in the thickness of the base metal on coating residual stress is studied. The best model has 18 MPa surface residual stress. The very low values of residual stress obtained in the top layer of the multilayer deposition is helpful in preventing corrosion problems like stress corrosion cracking and corrosion fatigue, resulting in lower equipment downtime and losses to industry. © 2019 Elsevier LtdItem Enhanced corrosion resistance of atmospheric plasma-sprayed zirconia–GNP composite by graphene oxide nanoplatelet encapsulation(Springer, 2020) Amudha, A.; Hosakoppa S, N.; Holavanahalli Doraiswamy, S.The unique natural diffusion barrier property of graphene plays a crucial role in protecting the carbon steel substrates from corrosion, particularly using graphene oxide nanoplatelets (GNP)–zirconia (ZrO2) composites. In the present work, atmospheric plasma spraying (APS) technique has been used to coat both the spray-dried pristine ZrO2 and ZrO2–(0.5, 1.0, 1.5 and 2) wt% GNP composite on the carbon steel substrate. The retention of GNPs in the coating was confirmed using XRD, Raman spectroscopy, TEM, FE-SEM, and EDAX techniques. The corrosion properties of the coatings in 3.5 wt%NaCl electrolyte were studied using linear polarization resistance and electrochemical impedance spectroscopy technique. This reveals the enhanced charge transfer resistance, decreased corrosion current density and corrosion rate of ZrO2–GNP composite. Further, the corrosion rate of ZrO2–2 wt% GNP coating is 130 times less than the plasma-sprayed ZrO2. Compared to 0.5, 1.0 and 1.5 wt% GNP added zirconia coatings, ZrO2–2 wt% GNP displayed the highest stability up to 14 days in 3.5% NaCl electrolyte. © 2020, Springer-Verlag GmbH Germany, part of Springer Nature.Item Mechanical and wetting properties of 25%NiCr-75%Cr2C3 cermet coated on low carbon steel using HVOF thermal spray technique(Elsevier B.V., 2021) Amudha, A.; Nagaraja, H.S.; Shashikala, H.D.The hydrophobic ceramic–metal composites with enhanced mechanical properties will have longer durability because of the embedded liquid-repellent properties, with low water and salt absorption. In this work, the 25%NiCr-75%Cr2C3 cermet powder has been coated on low carbon steel substrate, using High Velocity Oxy-fuel thermal spray technique. The SEM is employed to analyse the morphological characterization of the coating. The mechanical properties of the 25%NiCr-75%Cr2C3 coating is evaluated using the Vickers micro-indentation technique. The micro-hardness, fracture toughness and brittleness index of the coatings are obtained. Also, the wetting property of the coating in 3.5% NaCl salt solution is investigated using the contact angle measured by sessile drop method. The contact angle of the coating is observed to be hydrophobic in nature with a contact angle of 98.14?. Thus, 25%NiCr-75%Cr2C3 hydrophobic coatings helps in the improvement of brittleness, fracture toughness, and the microhardness. © 2020 Elsevier B.V.Item Mesoporous NiWO4@rGO nanoparticles as anode material for lithium-ion battery(Taylor and Francis Ltd., 2023) Brijesh, B.; Amudha, A.; Mukesh, M.P.; Sagar, L.; Moolayadukkam, S.; Nagaraja, H.S.Herein, we have tried to explore the charge storage properties of mesoporous NiWO4 as an anode in lithium-ion batteries (LIB). A one pot-solvothermal synthesis is used to tweak the properties of mesoporous NiWO4 nanoparticles with reduced graphene oxide (rGO) for the first time and explored the LIB anode applications. Materials are well characterised using structural and morphological characterisations to corroborate the relation between the electrochemical properties and the graphene addition. At 100 mA g−1, the NiWO4@rGO (NWZC) exhibits initial discharge capacity of 1439 mAh g−1, which is more than that of NiWO4 (NWZ). Both NWZ and NWZC display initial coloumbic efficiency of 91.65% and 62.1%. After 500 cycles, the coloumbic efficiency of the NWZ and NWZC is above 99%. The improved lithium-ion storage characteristics of the NWZC may be from the synergetic effect between NiWO4 and r-GO. © 2023 Informa UK Limited, trading as Taylor & Francis Group.Item Enhanced Electrochemical Performance of Low-Content Graphene Oxide in Porous Co3O4 Microsheets for Dual Applications of Lithium-Ion Battery Anode and Lithium-Ion Capacitor(Springer, 2024) Lakshmi Sagar, G.; Brijesh, K.; Mukesh, P.; Amudha, A.; Bhat, K.S.; Nagaraja, H.S.The enhancement of electrochemical performance in lithium-ion battery (LIB) anode materials through nanostructures is of paramount importance, facilitated by the synergistic integration of these unique architectures with active materials, which increases the availability of active sites and decreases the diffusion path for lithium ions. In this investigation, we successfully synthesized cobalt oxide (Co3O4) microsheets composed of small nanoparticles (measuring 28–33 nm), employing a straightforward hydrothermal process followed by annealing. Furthermore, to enhance the composite’s ability to endure volume changes and increase its electrical conductivity, we created a Co3O4/reduced graphene oxide (rGO) composite embedding a judicious amount of graphene oxide (GO). This engineered composite exhibited remarkable specific discharge capacity of 1081 mAh g−1 at 100 mA g−1, a substantial improvement over the pristine material’s capacity of 718 mAh g−1. The composite demonstrated reduced irreversible capacity loss relative to the pristine counterpart and approached a reversible capacity of nearly 99%. Even after 400 cycles under the demanding conditions of high current density of 500 mA g−1, the composite managed to retain 81% of its initial capacity, underscoring its exceptional cycling stability. Moreover, the application of the Co3O4/rGO//carbon black (CB) assembly in lithium-ion capacitors (LIC) yielded notable energy density of 15.6 Wh kg−1 at elevated power density of 1007 W kg−1. These LIC devices demonstrated robust cyclic stability across extended cycles, sustaining 56% of their initial capacity after 2000 cycles while operating at a current density of 2 A g−1. Graphical Abstract: [Figure not available: see fulltext.]. © 2024, The Minerals, Metals & Materials Society.Item Efficient removal of toxic dyes and nitrophenol using Graphene Oxide-ZrO2 hybrid catalysts(Elsevier Ltd, 2025) Amudha, A.; Mahendra, K.; Yashodhara, I.; Pattar, J.; Anil Rao, H.N.; Shashikala, H.D.; Hosakoppa, S.N.In the current study, efficient removal of industrial dyes and nitrophenol by ZrO2–GO catalyst has been reported. ZrO2–GO nanoparticles were prepared using the hydrothermal technique and are characterized using X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), Transmission Electron Microscopy (TEM), Photoluminescence (PL), Raman, and UV–visible spectroscopy techniques. The ability of the nanoparticles to degrade Methylene Blue (MB), Crystal Violet (CV), and Nitrophenol (NP) was examined for their photocatalytic activities. Results revealed that there is an increase in the crystallite size and pore size increased almost 2 times after adding 2 % GO in ZrO2. The addition of GO into ZrO2 also caused a decrease in the PL intensity and energy gap indicating an increase in the charge carriers. ZrO2–GO nanoparticles showed photocatalytic degradation of 90 % (70 min), 98 % (90 min), and 70 % (120 min) for MB, CV, and NP respectively. © 2025 Elsevier B.V.