Journal Articles
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Item Preparation and performance studies of polysulfone-sulfated nano-titania (S-TiO2) nanofiltration membranes for dye removal(Royal Society of Chemistry, 2015) Pereira, V.R.; Isloor, A.M.; Bhat, K.U.; A.F., A.F.; AlObaid, A.; Fun, H.-K.Polysulfone nanofiltration membranes containing sulfated nano-titania (S-TiO2) were fabricated, with the aim to enhance the membrane properties along with the possible rejection of Methylene Blue (MB) dye by membranes. Initially S-TiO2 was synthesized from nano TiO2 by the action of sulfuric acid. The synthesized S-TiO2 was characterized by Fourier Transform Infrared spectroscopy (FT-IR), Energy Dispersive Spectrophotometry (EDS) and Transmission Electron Microscopy (TEM) analysis. S-TiO2 was added in increasing concentrations into the membranes and its effect on the performance of the membranes was evaluated. The synthesized membranes were characterized by Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (AFM). Polysulfone membranes containing S-TiO2 showed enhancement in properties in terms of hydrophilicity, water uptake, mechanical strength, improved pure water flux (PWF), antifouling nature and high Flux Recovery Ratio (FRR). The polysulfone membranes with S-TiO2 showed 99% rejection for BSA (Bovine Serum Albumin) protein molecules during BSA filtration. The prepared membranes were used for the removal of MB dye from aqueous solutions. A maximum of 90.4% rejection was obtained for MB for the membrane having 2.0 wt% of S-TiO2 under UV light radiation. This approach showed that polysulfone-S-TiO2 membranes displayed good efficiency for dye removal and can be effectively used for the removal of MB dye from aqueous solutions under suitable conditions. © The Royal Society of Chemistry.Item Optimised microwave-assisted biosynthesis of silver nanoparticles from Nothapodytes foetida leaf extracts and its anti-microbial activities(Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2016) Roopesh, R.; Geedhika, G.; D'Souza, J.; Anandhan, S.; Bhat, K.U.; Jaya M, J.; Fathima B, S.; Mohan Balakrishnan, R.M.The present investigation reports the biogenesis of silver nanoparticles (Ag NPs) using extracts of a medicinal plant Nothapodytes foetida. Total phenolic content (TPC) and ferric reducing antioxidant power (FRAP) assay were carried out for the microwave-assisted extract (MAE) of N. foetida using methanol as solvent and the conditions for extraction were optimised by response surface methodology (RSM). The effects of operating variables such as extraction time, temperature and ratio of sample to solvent were studied using central composite design (CCD). A mathematical model with a high determination coefficient (R2) for TPC (0.991) and FRAP (0.995) was obtained. The optimal conditions of extraction for TPC were 48.6 ºC, 23.15 min and 2.04:30 (g/mL) and for FRAP 52.31ºC, 12.32 min and 1.67: 30 (g/mL). Under these conditions, the experimental yields of TPC and FRAP were 2.426 mg gallic acid equivalents (GAE)/g dry powder and 14.985mg of FeSO4·7H2O/g of dry powder, respectively. Ag NPs were characterised using UV–Vis spectroscopy, transmission electron microscopy (TEM), X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The synthesised Ag NPs have also shown potent activity against the human pathogenic Staphylococcus aureus. © 2016 Informa UK Limited, trading as Taylor & Francis Group.Item Microstructural characterization of low temperature plasma-nitrided 316L stainless steel surface with prior severe shot peening(Elsevier Ltd, 2016) Jayalakshmi, M.; Huilgol, P.; Badekai Ramachandra, B.R.; Bhat, K.U.Surface nanocrystallization by severe deformation has proven beneficial as pre-treatment to plasma nitriding. It aids in achieving thicker nitride layers at lower temperatures thus making the process more economical. In austenitic stainless steels, severe deformation leads to formation of strain induced martensite on the surface while plasma nitriding alone forms expanded austenite. However, structural characteristics of surface layer of pre-deformed steel after plasma nitriding is still a matter of debate. In present study, 316L stainless steel was subjected to severe shot peening: followed by plasma nitriding at 400 °C for 4 h. Characteristics of sample surface before and after treatment were analyzed by scanning electron microscopy, X-ray diffractometry and transmission electron microscopy techniques. Results showed that, this duplex treatment leads to formation of about 45 ?m thick nitride layer; without CrN precipitation. This is significantly high compared to reported data considering the temperature and duration of nitriding treatment employed. Selected area electron diffraction pattern from topmost surface confirmed the co-existence of austenite and martensite while subsurface layer was predominantly consisting of lath martensite. This indicates that major phase in the nitrided layer is martensitic in nature and nitrogen supersaturation leads to transformation of small fraction of martensite to expanded austenite. © 2016 Elsevier LtdItem Metastable microstructures at the interface between AISI 321 steel and molten aluminum during hot-dip aluminizing(Elsevier B.V., 2018) Huilgol, P.; Udupa, K.R.; Bhat, K.U.The microstructure at the interface between AISI 321 stainless steel and molten aluminum was investigated which occurs during the process of hot-dip aluminizing. Microstructural characterization was carried out by scanning electron microscopy, transmission electron microscopy and X-ray diffraction. The study revealed the formation of metastable FeAlm and multiple twinned Al13Fe4 phases at the interface between steel and aluminum. Multiple twinned Al13Fe4 phase exhibits pseudo tenfold electron diffraction pattern. Another metastable phase Al3(NiFe) with an orthorhombic structure was formed as one of the eutectic phase mixture in the solidified aluminum topcoat. The Al3(NiFe) phase in the eutectic shares crystallographic orientation relationship with the Al matrix. Metastable intermetallic phases are being reported for the first time during hot-dip aluminizing. © 2018 Elsevier B.V.Item Microstructural investigations on the hot-dip aluminized AISI 321 stainless steel after diffusion treatment(Elsevier B.V., 2019) Huilgol, P.; Udupa, K.R.; Bhat, K.U.The microstructure of the hot-dip aluminized AISI 321 stainless steel was studied after diffusion treatment at 900 °C for 3 h. The microstructural characterization was carried out by scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry. The microstructure of the as aluminized steel consisted of two regions, viz.; aluminum topcoat and aluminide layer. During the diffusion treatment, the coating transformed into a layered structure consisting of four layers. The Fe2Al5 phase was formed in the outermost layer and the presence of Al13Fe4 quasicrystalline approximant phase was observed. The innermost layer adjacent to the base metal transformed to ferrite phase with NiAl precipitates. Next, to this layer, a disordered FeAl phase was observed. The lattice parameter of the disordered FeAl phase was found to be larger than that of the ordered B2 FeAl phase. The layer between outer Fe2Al5 phase and disordered FeAl phase consists of a mixture of three phases, namely Fe2Al5, disordered FeAl and a new phase with the simple cubic structure. The phase with simple cubic structure shares cube on cube crystallographic orientation relationship with the disordered FeAl phase. © 2019 Elsevier B.V.