Browsing by Author "Rameshbabu, N."

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Assessment of corrosion and scratch resistance of plasma electrolytic oxidation and hard anodized coatings fabricated on AA7075-T6
(Transactions of the Indian Institute of Metals, 2021) Premchand, C.; Hariprasad, S.; Saikiran, A.; Lokeshkumar, E.; Manojkumar, P.; Ravisankar, B.; Venkataraman, B.; Rameshbabu, N.
Surface modification of high-strength aluminium alloy 7075-T6 by plasma electrolytic oxidation (PEO) and type II hard anodization (HA) is presented in the current work. PEO-based ceramic oxide coatings were fabricated by employing an alternating current (AC) power source with a current density of 300 mA/cm2. The concentration effect of electrolytes on the alumina coatings was investigated and optimized comprehensively. Three separate aqueous electrolytes with 1:3, 1:1 and 3:1 proportions of sodium silicate (Na2SiO3) and potassium hydroxide (KOH) were utilized to evaluate optimum electrolyte concentration for obtaining desired AC-PEO coatings. X-ray diffraction (XRD) was utilized to investigate the phase composition of the coatings. Field emission scanning electron microscopy (FESEM) was employed to investigate the surface and cross-sectional characteristics of oxide coatings. Scratch testing was used to assess the oxide coatings’ adhesion ability, and potentiodynamic polarization (PDP) was utilized to assess the coatings’ corrosion behaviour in a 3.5 wt% aqueous NaCl solution. Among the AC-PEO and HA coatings, the AC-PEO specimen fabricated with equal ratios of sodium silicate and KOH concentration (Na2- SiO3:KOH 1:1) showed excellent adhesion strength (critical load, Lc = 41.5 N) along with the remarkable corrosion resistance (corrosion current density, icorr = 5.63 9 10–6 mA/cm2).
Effect of frequency on plasma electrolytic oxidation of zirconium in pulsed unipolar mode
(IOP Conf. Series: Materials Science and Engineering, 2019) Parfenov, E. V.; Mukaeva, V. R.; Farrakhov, R. G.; Saikiran, A.; Hariprasad, S.; Manoj, P.; Lokesh, E.; Rameshbabu, N.
Using the method of in situ impedance spectroscopy, an optimization of plasma electrolytic oxidation (PEO) was performed, and the influence of the pulse frequency was evaluated for the coating of Zr-1Nb alloy. It was shown that the in situ impedance modulus decreased with increasing the pulse frequency in a pulsed unipolar mode. Also, the protective properties of the coating improved with frequency; this was attributed to the increase in the uniform distribution of the microdischarges over the sample surface. As a result, the optimal frequency range of PEO was justified based on the impedance spectroscopy studies.
Fabrication of ceramic coatings on the biodegradable ZM21 magnesium alloy by PEO coupled EPD followed by laser texturing process
(Journal of Magnesium and Alloys, 2020-11) Hariprasad, S.; Saikiran, A.; Premchand, C.; Lingamaneni, Rama Krishna.; Rameshbabu, N.
Zirconia (ZrO 2 ) incorporated ceramic coatings were fabricated on biodegradable ZM21 Mg alloy by the PEO coupled with EPD process. Subsequently, the sample surface was modified by laser texturing to improve the corrosion resistance, roughness and cell proliferation and growth properties. The corrosion performance of the fabricated samples along with the substrate was studied by electrochemical measurements under simulated body fluid (SBF) environment. The cell direct contact assay was conducted for the substrate and fabricated samples using L -929 mouse fibroblast cells for 24 h. The phase contrast images of cell direct contact assay revealed that fabricated samples exhibited better contact and response with the fibroblast cells, compared to the substrate. The addition of nanoparticles in the PEO process, called PEO coupled EPD process, resulted in attaining a higher thickness and improved corrosion performance of the samples than the PEO coated samples. Among all the samples, laser surface textured PEO, and PEO-EPD coated samples unveiled enhanced corrosion resistance, cell growth, thereby enabling it as a suitable prototype for biodegradable implant applications. © 2020 Published by Elsevier B.V. on behalf of Chongqing University. This is an open access article under the CC BY-NC-ND license ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ) Peer review under responsibility of Chongqing University
Facile preparation of immobilised visible light active W–TiO /rGOcomposite photocatalyst by plasma electrolytic oxidation process
(Physica B: Condensed Matter, 2022-04) Manojkumar, P.; Lokeshkumar, E.; Premchand, C.; Saikiran, A.; Lingamaneni, Rama Krishna.; Rameshbabu, N.
A highly efficient immobilised W–TiO/rGO composite photocatalyst was prepared as a coating on titaniumusing plasma electrolytic oxidation (PEO) with particle addition. The high dopant concentration in TiO resulted in smaller crystallite size , increased lattice strain, and dislocation density. The optimum Wcontaining G6W sample has improved electron mobility, higher charge carrier separation efficiency, andlower electron-hole recombination rate. This can be ascribed to the number of different defect centresemerging from tungsten interstitials and higher oxygen vacancies in the TiO structure. The catalystexhibited enhanced photocatalytic degradation efficiency (93%) of methylene blue dye than the pure TiO ,which was attributed to the synergetic effect of 2-D structured rGO and the changes incorporated upon tungsten interstitials in the TiO. The present research concludes that W–TiO/rGO photocatalyst by PEOprocess can be a good candidate for efficient, low cost, reusable, and visible-light-driven immobilisedphotocatalyst for textile wastewater treatment.
Superior properties and behaviour of coatings produced on nanostructured titanium by PEO coupled with the EPD process
(Surface Topography: Metrology and Properties, 2022-02-18) Lokeshkumar, E.; Saikiran, A.; Ravisankar, B.; Krishna, Rama.; Parfenova, L. V.; Parfenov, E. V.; Valiev. R. Z.; Rameshbabu, N.
Surface modification of commercially pure Grade 4 coarse-grained titanium (CG-Ti) and nano-grained titanium (n-Ti) by plasma electrolytic oxidation (PEO) and plasma electrolytic oxidation conjugated with electrophoretic deposition (PEO-EPD) processes is reported in the present study. Two different coatings were developed on each CG-Ti and n-Ti in phosphate-based electrolytes without and with the incorporation of hydroxyapatite (HA) nanoparticles. The phase composition, morphology (surface and cross-sectional), corrosion resistance, surface roughness, and scratch-resistance of the fabricated coatings were thoroughly studied and analysed. The L-929 fibroblast cells were used for assessing the in-vitro cell viability. The L-929 cells cultured on PEO-EPD treated CG-Ti, and n-Ti samples exhibited higher cell growth than PEO treated CG-Ti and n-Ti samples. Among all the PEO and PEO-EPD treated samples, the PEO-EPD treated n-Ti sample showed significantly better corrosion resistance (icorr = 8.85 × 10−7 mA cm−2 ), lower contact angle (40°), and good adhesion strength (Lc = 29 N), demonstrating the importance of the nanostructuring of the titanium substrate for the properties of the coating. The origin of the discovered enhancement in the properties of the modified PEO coating produced on nanostructured titanium was examined and discussed. After soaking in SBF for 14 days, the PEO-EPD treated sample is wholly covered with apatite layer indicating its good bioactivity
Surface modification of CP-Ti metallic implant material by plasma electrolytic oxidation
(IOP Conf. Series: Materials Science and Engineering, 2019) Rameshbabu, N.; Ravisankar, B.; Saikiran, A.; Parfenov, E. V.; Valiev, R. Z.
Plasma electrolytic oxidation (PEO) is a relatively new and environmentally friendly process for development of thick and adherent oxide coatings on conventional and nanostructured metallic implant materials. The PEO process involves anodic oxidation of metals or alloys in aqueous solutions at voltages higher than the breakdown voltage of the oxides present on its surfaces. Currently, the PEO process is gaining increased attention as a novel technique for the fabrication of corrosion resistant, bioactive and functionally modulated composite coatings on commercial pure titanium (Cp-Ti) and Ti based alloys for orthopedic and dental applications. The PEO process coupled with the electrophoretic deposition (EPD) technique is used for the fabrication of TiO2/hydroxyapatite (HA) composite coating on a Cp-Ti implant material in a single step. This paper briefly reviews the properties of the coatings produced on Cp-Ti by PEO and PEO coupled EPD processes.