Browsing by Author "Hariprasad, S."

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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
Synthesis and characterization of shape-stable bio-char composite PCM material for solar desalination application
(Materials Science Forum, 2023-10-05) Ravikumar, K.; Nagesh, G.V.; Venkestaswara Rao, R.; Saikiran, A.; Swapna, R.; Gunavardhana Naidu, T.; Hariprasad, S.
In the present study, three different D-Mannitol based activated bio-char composite shape-stable phase change materials (PCM) were developed for medium temperature energy storage applications like solar desalination, solar thermal storage and waste heat recovery with varying bio-char compositions. The activated bio-char (A-BC) composite-based samples were prepared from sawdust by using the pyrolysis method. The phase composition, morphology, latent heat capacity and phase change temperature of the fabricated samples were assessed by XRD, SEM, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The fabricated bio-char composite materials exhibited good thermal properties and structural stability compared to pure PCM. The phase change material with a blend of minimum 15 wt.% activated bio-char and 85% D-Mannitol was observed to be leak resistant. FTIR and XRD results confirm that the chemical properties of the bio-char composite remain the same as the pure PCM, which confirms that there are no chemical interactions between the PCM and bio-char. PCM sample with 15% activated bio-char exhibited an enhanced thermal stability compared to the pure PCM.
Synthesis and characterization of Shape-Stable Bio-Char composite PCM meterial for solar desalination application
(Trans tech publication ltd, 2023-10-05) Ravikumar, K.; Nagesh, G. V.; Rao, Venkateswara.; Saikiran, A.; Swapna, R.; Naidu, Gunavardhana.; Hariprasad, S.