Faculty Publications
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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 Anti-biofouling evaluation of vacuum-assisted hydrophobic ytterbium oxide (Yb2O3) coating on stainless steel by facile spray combustion(Springer, 2024) Karle, S.S.; Kailasam, K.; Vardhan, R.V.; Praveen, L.L.; Gautam, V.; Mandal, S.Despite the development of numerous coating techniques and materials, today’s anti-biofouling applications require coatings that are facile and mechanically robust in nature. Studies on the hydrophobicity of rare-earth oxides have risen due to their unusual chemical properties; ytterbium oxide is one such oxide substance. In this study, spray combustion was used to create a hydrophobic coating of ytterbium oxide (Yb2O3) on a stainless steel (SS) substrate, which was then vacuum-treated. GI-XRD analysis confirmed the sesquioxide cubic crystalline structure of Yb2O3. FESEM images displayed an underneath wavy morphological coating with discrete particles on the surface. The thickness and roughness were ~12 and ~0.17 µm, respectively. When 5 and 10 N loads were applied, the coating showed better scratch hardness than uncoated SS. Water contact angle (WCA) <10° indicated superhydrophilicity in the fabricated coating. After vacuum treatment, it became hydrophobic, and the WCA was 128°; because of the increment in the relative area fraction of the C–H bond. The proportion of area covered by blue–green algae (Phormidium sp.) on vacuum-treated Yb2O3 coating was only 3% compared to uncoated SS samples, 80%. © Indian Academy of Sciences 2024.Item Fabrication and Characterization of Silicon Dioxide-Reinforced Polydimethylsiloxane Composite Coating for Corrosion Protection of Galvanized Iron(SAE International, 2024) Kumar, P.; Ramesh, M.R.; Doddamani, M.The present work highlights the significance of nanocomposite coatings for their ease of processing and applicability in combating corrosion. Ongoing research is dedicated to the development of an effective nanocomposite hydrophobic coating. A hydrophobic nanocomposite coating was deposited on galvanized iron (GI) using a sol-gel route with polymethylsiloxane (PDMS) reinforced with nano-SiO2. Surface morphology and chemical composition analysis, conducted with scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDAX) and Fourier transform infrared spectroscopy (FTIR), revealed the coating's structural and compositional attributes. The resulting hydrophobic coating exhibits a water contact angle (WCA) of 104.1°, indicating a 30.45% increase compared to bare GI. Subsequent to these characterizations, the adhesion of the coated GI, rated as 4B per ASTM D3359, is followed by commendable resistance to corrosion, as evidenced by electrochemical tests. The corrosion rate for the coated GI sheet is notably low, at 62.78 × 10-3 mpy, underscoring its anti-corrosive efficacy. © 2024 SAE International.Item Exploring the protection of spray-pyrolysed tungsten oxide hydrophobic coating on stainless steel in a marine environment(Springer, 2024) Gautam, V.; Praveen, L.L.; Vardhan, R.V.; Mandal, S.Tremendous potential in the field of anti-biofouling coatings to prevent stainless steel (SS)-based underwater pipelines, sea vessels and other marine structures have been recognized to protect from biofouling, which is often initiated by algae attachment over the surface. In this work, hydrophobicity in spray-pyrolysed tungsten oxide (TO) coating on SS-316 substrate has been reported for the first time, via post-processing treatment using octadecyltrimethoxysilane (ODTMS) to induce self-assembled monolayer (SAM). Initially, structural and vibrational characteristics of ODTMS and ODTMS-treated TO (OTO) coating on SS were analysed using X-ray diffraction (XRD), Fourier transform infrared (FTIR) and Raman spectroscopies. OTO-coating depicted a water contact angle (WCA) of 121°, revealing its hydrophobic nature, with further affirmation from X-ray photoelectron spectroscopy (XPS). Durability of the TO-coating was explored using the scratch hardness (Hs) test at different loading conditions (5, 10 and 15 N). Biofouling study was conducted by culturing blue-green algae (BGA, Phormidium sp.) in an in-house laboratory setup for 40 days, using seawater (collected from the Arabian Sea, Karnataka). The SS, TO- and OTO-coatings were immersed for 14 days in a controlled sea-water environment in the laboratory with the presence of BGA. A comparative study on the areal-algae attachment was keenly analysed over SS-, TO- and OTO-coatings. This work can be projected as a promising application providing multi-dimensional solutions in creating scratch-resistant and anti-biofouling coatings on SS in the shipbuilding industry. © Indian Academy of Sciences 2024.Item Enhanced Anti-corrosion and Anti-fouling Properties of Galvanized Iron Using Nanocomposite Hydrophobic Coatings(Springer, 2025) Kumar, P.; Ramesh, M.R.; Doddamani, M.; Narendranath, S.Nanocomposite hydrophobic coatings have garnered substantial interest in recent times due to their remarkable anticorrosion and antifouling attributes. These coatings are designed to repel water and thwart the adherence of contaminants, rendering them valuable for an array of applications, including self-cleaning surfaces, anti-icing coatings, marine protection, and biomedical uses. This study delves into the fabrication of nanocomposite coatings, incorporating mixed oxide nanoparticles of CuO-MgO, MgO-ZnO, and CuO-ZnO at varying weight percentages within a poly (lactic acid) (PLA) matrix. Surface morphology and elemental composition were examined through Field Emission Scanning Electron Microscope (FESEM) and Energy-Dispersive x-ray Analysis (EDAX). The chemical composition of the coatings was assessed using Fourier Transform Infrared Spectroscopy (FTIR), revealing structural changes specific to PLA with Mg-Zn nanocomposite coating. The wettability studies indicate that the PLA/Cu-Mg coated sample exhibits superior hydrophobic properties, with a water contact angle (CA) of 98.2°. This value represents a remarkable 48.7 % increase compared to the bare Galvanised iron (GI) substrate. The coating's mechanical properties were assessed using scratch and adhesion tests. The efficacy of these coatings for anticorrosion and antifouling applications was gauged through comprehensive evaluations, in-vitro corrosion studies, egg white tests, and antibacterial tests. PLA/Mg-Zn nanocomposite coating exhibited exceptional performance in terms of scratch hardness and adhesion strength, whereas PLA/Cu-Zn nanocomposite coating exhibited better anticorrosion and antifouling properties. © ASM International 2024.