Browsing by Author "Ramana Reddy, P.R."

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Contact angle measurement studies on porous anodic alumina membranes prepared using different electrolytes
(VBRI Press editorialoffice@vbripress.com, 2016) Ramana Reddy, P.R.; Ajith, K.M.; Udayashankar, N.K.
This paper investigates the effect of pore widening duration on the wetting properties of nanostructured porous anodic alumina (PAA) membranes fabricated using sulphuric and oxalic acid as electrolytes by two step anodization process. XRD analysis shows that prepared PAA membranes were amorphous in nature. With increasing of pore widening durations from 0 to 120 min, the contact angle of PAA membranes varied from 21 to 78°. It was noticed that PAA membranes were hydrophilic in nature in the present of water medium. In the presence of acetone medium, PAA membranes prepared with 1hr pore widening time showed super hydrophilic behaviour. © 2016 VBRI Press.
Micro and nanoindentation analysis of porous anodic alumina prepared in oxalic and sulphuric acid
(Elsevier Ltd, 2016) Ramana Reddy, P.R.; Ajith, K.M.; Udayashankar, N.K.
In this article, the mechanical behavior of porous anodic alumina (PAA) structures obtained from two different electrolytes (oxalic and sulphuric acids) was investigated using micro and nanoindentation techniques. Regularity ratio (RR) of PAA structures was calculated using WSxM software and it was found that strength of the PAA structures varies with the RR of the pores. Micro hardness of the PAA structures was studied using 0.98, 9.8 N loads and it was observed that surface ring cracks were generated for 9.8 N load in oxalic acid. PAA structures formed in sulphuric acid exhibits an extremely high hardness of 7.5 GPa and Young's modulus as 146.5 GPa compared with oxalic acid due to low porosity. Results indicate that the indentation modulus and hardness of the PAA structures decrease with increasing pore size. Further the effect of porosity and regularity ratio of pores on mechanical properties of PAA structures was studied in detail. © 2016 Elsevier Ltd and Techna Group S.r.l.
Morphological analysis and photoluminescence properties of hydrophilic porous anodic alumina formed in oxalic acid
(Springer New York LLC barbara.b.bertram@gsk.com, 2016) Ramana Reddy, P.R.; Ajith, K.M.; Udayashankar, N.K.
Porous anodic alumina (PAA) templates were prepared via two-step anodization process in 0.3 M oxalic acid for different anodization durations (2–10 h with a step of 2 h). In this article, we report our studies on the morphological analysis and photoluminescence (PL) properties of hydrophilic PAA templates prepared at 8 and 18 °C. Two-dimensional fast Fourier transform was used to study the regularity ratio of PAA. It was found that for a longer anodization time (6, 8 and 10 h) the better array of pores observed with anodization potential of 40 V. The effect of anodization duration on the structural aspects including pore diameter, interpore distance, porosity and pore density were investigated in detail. It was observed that increase in anodization duration led to an increase in pore diameter and porosity. Contact angle measurement of PAA templates was carried out to confirm the hydrophilic nature. The relationship between morphology of PAA and PL emission bands was studied. The PL spectra of PAA templates show two emission sub-bands, which can be ascribed to two luminescence centers, F+ (band-1) and F (band-2), respectively. © 2016, Springer Science+Business Media New York.
Optical and mechanical studies on free standing amorphous anodic porous alumina formed in oxalic and sulphuric acid
(Springer Verlag service@springer.de, 2018) Ramana Reddy, P.R.; Ajith, K.M.; Udayashankar, N.K.
Anodic porous alumina (APA) membranes with a uniform pore arrangement typically serve as an ideal template for formation of different types of nanostructured materials. In the present work, APA membranes were synthesized using two-step anodization in 0.3 M of oxalic and 0.3 M of sulphuric acid under the anodization potential of 40 V and 20 V respectively, at 8 °C. Alumina nanowires (ANW) were synthesized by the chemical etching of the APA membranes using phosphoric acid solution. The optical absorbance and reflectance measurements of APA membranes were performed on a spectrometer in the wavelength range of 200–600 nm. The band-gap energy (3.7 and 4.3 eV for oxalic and sulphuric acid) of APA membranes was determined from UV–visible absorption data. The photoluminescence (PL) investigations have revealed the presence of F and F+ defect centers, which could be attributes to oxygen vacancy-related defect centers in oxalic (483 and 466 nm) and sulphuric (423 and 421 nm) alumina. The mechanical properties of amorphous APA membranes were investigated by micro- and nanoindentation techniques. The results indicate that highest hardness (7.70 GPA) and Young’s modulus (138.80 GPA) for sulphuric alumina compared with oxalic alumina. In sulphuric alumina, more number of ANW were observed compared with oxalic alumina. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature.
Structural analysis of porous anodic alumina membranes using the dedicated executable software
(American Scientific Publishers order@aspbs.com, 2016) Ramana Reddy, P.R.; Udayashankar, N.K.; Ajith, K.M.
Porous Anodic Alumina (PAA) membranes with highly order array of nanopores were prepared by two-step self-organized anodization process. Structural properties of the prepared PAA membranes such as Pore diameter (Dp), Interpore distance (Dc), Porosity (P) and Pore density (n) were studied using Image J and SEM image analysis. X-ray diffraction analysis of the prepared PAA membrane was carried out. The pore arrangement regularity was analyzed for different anodization process durations. The effect of anodization process duration on structural features of PAA membranes was investigated. It was pointed out that interpore distance decrease with increase of anodization process duration. © 2016 American Scientific Publishers. All rights reserved.
Structural and wetting properties of porous anodic alumina templates prepared by different electrolytes
(American Institute of Physics Inc. subs@aip.org, 2016) Suchitra, S.M.; Ramana Reddy, P.R.; Udayashankar, N.K.
Porous anodic alumina (PAA) has been extensively studied in recent years due to their unique properties and applications for manufacturing nanostructured materials. In this article, we report our studies on structural and wetting properties of PAA membranes prepared using different electrolytes such as sulphuric, oxalic and phosphoric acids. The morphological parameters such as pore diameter and porosity were measured using SEM and analysed using image-J software. The structural investigation of PAA membranes was carried out through X-ray diffraction analysis and it was confirmed that PAA membranes were amorphous in nature. The wetting behaviour of PAA membranes were measured using contact angle measurement technique. The results show that PAA membranes were hydrophilic in nature with contact angles 26.03Â°, 35.21Â° and 42.0Â° for sulphuric, oxalic and phosphoric acids respectively. Â© 2016 Author(s).