Faculty Publications
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Item Synthesis and characterisation of nickel oxide nanofibre webs with alcohol sensing characteristics(Royal Society of Chemistry, 2014) George, G.; Anandhan, S.In this study, nickel oxide (NiO) nanofibres were obtained by a sol-gel electrospinning process followed by calcination from an aqueous sol of poly(2-ethyl-2-oxazoline)/nickel acetate tetrahydrate. Thermogravimetric analysis was used to determine the degradation temperature of the composite fibres, so as to get nickel oxide nanofibres. X-ray photoelectron spectroscopy and X-ray diffraction studies revealed the complete elimination of the organic phase from NiO fibres during calcination. The change in grain size with calcination temperature was determined by X-ray diffraction. The defects in fibres resulted in the modification of their Raman spectra as compared with that of a single crystal. The magnetic properties of the fibres were reduced as the calcination temperature was increased; this is due to the presence of non-stoichiometric defects. As the calcination temperature was increased, the amount of defects was reduced, which induced a difference in the band gap energy of the fibres. Sensitivity of the NiO fibres towards five different alcohols was studied, and the sensitivity towards ethanol was the highest. © The Royal Society of Chemistry 2014.Item Morphological and structural characterisation of sol-gel electrospun Co3O4 nanofibres and their electro-catalytic behaviour(Royal Society of Chemistry, 2015) George, G.; Elias, L.; Hegde, A.C.; Anandhan, S.Evolution of hydrogen and oxygen are a crucial part of many renewable energy systems. The replacement of the essential and expensive components in such systems can reduce the capital cost and improve the effectiveness of those systems. In this study, Co3O4 nanofibres were fabricated from sol-gel assisted electrospun poly(styrene-co-acrylonitrile)/cobalt acetate tetrahydrate precursor composite fibres. The morphological and compositional features of the Co3O4 nanofibres obtained after calcination of the precursor nanofibers were studied using scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy. The results of X-ray diffraction study and Raman spectroscopy revealed that the average grain size of the fibres increased with the calcination temperature. Clear evidence of defects in the fibres was observed in ultraviolet-visible-near infrared and energy dispersive spectroscopic measurements. The electrocatalytic behaviour of Co3O4 nanofibres obtained at different calcination temperatures was studied using them for the water splitting reaction in an alkaline medium. The maximum efficiency in the hydrogen evolution reaction was achieved using the Co3O4 nanofibres obtained at the lowest calcination temperature, which had the highest surface area and the smallest grain size. © The Royal Society of Chemistry 2015.Item Interparticle interactions and lacunarity of mechano-chemically activated fly ash(Elsevier, 2015) Patil, A.G.; Shanmugharaj, A.M.; Anandhan, S.A class F fly ash was subjected to high-energy ball milling-induced mechano-chemical activation aided by a surfactant. The resultant nanostructured fly ash was characterized by various techniques. X-ray fluorescence results showed that the amount of iron oxide was reduced from 4.39% to 2.75% after pre-treatment of fly ash by magnetic separation. Ethyl acetate as the milling medium, a ball to powder ratio of 12:1 and 2wt% of surfactant reduced the average particle size of fly ash to 329nm and led to a specific surface area of 8.73m2/g. The decrease in crystallite size of mechano-chemically activated fly ash was confirmed from a reduction in peak intensity with a broadened amorphous phase by X-ray diffraction studies. X-ray photoelectron spectroscopic characterization illustrated that peak area of major elements (O, Si and Al) increased after milling. Morphological and FTIR studies revealed that the smooth and inert surface of the fly ash was converted to a rough and more reactive one after mechano-chemical activation. The surface modification of fly ash with the surfactant was determined from FTIR spectroscopy. Also, a fractal approach was used to characterize the lacunarity of the agglomerates in the nanostructured fly ash. © 2014 Elsevier B.V.Item Some new observations on the structural and phase evolution of nickel titanate nanofibers(Elsevier Ltd, 2017) Kumar, B.S.; Shanmugharaj, A.M.; Kalpathy, S.K.; Anandhan, S.In this study, we report for the first time the synthesis of nickel titanate (NTO) nanofibers containing a mixture of ilmenite and spinel phases of NTO, at an atypical low temperature. Precursor nanofibers produced by sol-gel electrospinning were calcined at three different temperatures to produce the NTO nanofibers. Thermal analysis along with X-ray photoelectron spectroscopy confirmed the formation of non-crystalline stable phases of TiN and Ti-O-N that restrained the formation of ilmenite NTO, and the Ni-rich environment pushed the Ti atoms to tetrahedral sites to form a defective spinel structure. The crystallite size of spinel NTO was observed to increase as a function of the calcination temperature above 700 °C, as the activation energy for coalescence and growth of spinel NTO was favorable. NTO nanofibers obtained above the calcination temperature of 700 °C exhibited new band gap energy around 2.5 eV in Tauc plot. Oxygen vacancies in these ceramic nanofibers decreased as the calcination temperature was increased. A hypsochromic shift of 20 nm in the photoluminescence spectra suggested that the material had a Ni2+ rich NTO (spinel). © 2017 Elsevier Ltd and Techna Group S.r.l.Item Sol–gel electrospun mesoporous ZnMn2O4 nanofibers with superior specific surface area(Springer New York LLC barbara.b.bertram@gsk.com, 2017) Shamitha, C.; Senthil, T.; Wu, L.; Kumar, B.; Anandhan, S.ZnMn2O4 has application potential in lithium ion batteries, supercapacitors, sensors, and thermistors. In this study, mesoporous spinel ZnMn2O4 nanofibers were synthesized by sol–gel assisted electrospinning combined with calcination, using poly(styrene-co-acrylonitrile) as sacrificial polymeric binder. Structural, morphological and optical properties of these ceramic nanofibers were characterized. X-ray diffraction and X-ray photoelectron spectroscopy results revealed the presence of hexagonal ZnMnO3 and MnO phases in the ZnMn2O4 nanofibers produced. Based on these observations we propose a plausible mechanism of formation of ZnMn2O4 nanofibers. The nanofibers calcined at 773 K exhibit a specific surface area of 79.5 m2 g?1, which is higher than that of the zinc manganite nanofibers synthesized hitherto by sol–gel electrospinning. Moreover, this material exhibits four bandgaps, which is believed to be the first observation in ZnMn2O4 nanofibers. © 2017, Springer Science+Business Media, LLC.Item A Mechanistic Study on the Structure Formation of NiCo2O4 Nanofibers Decorated with In Situ Formed Graphene-Like Structures(Springer New York LLC barbara.b.bertram@gsk.com, 2018) Kumar, B.; Gudla, V.C.; Ambat, R.; Kalpathy, S.K.; Anandhan, S.Nickel cobaltite (NCO) nanofibers were synthesized using poly(styrene-co-acrylonitrile) (SAN) as the polymeric binder through sol–gel assisted electrospinning. Defect-free precursor nanofiber mats were pyrolyzed at 773 K at three different pyrolysis soaking times t = 2, 4, and 6 h. The SAN present in the precursor nanofibers caused morphological changes in the NCO nanofibers during their thermochemical degradation. Consequently, fractal aggregates of NCO nanoparticles were formed along the length of the nanofibers. X-ray photoelectron spectroscopy (XPS) revealed both + 2 and + 3 oxidation states for Ni and Co, with spinel crystal defects due to oxygen rich atmosphere. XPS, high-resolution transmission microscopy, and optical analysis showed graphene-like structures embedded within the NCO nanofibers. With increase in pyrolysis soaking time, the morphology of the NCO particles markedly changed from spherical to rod-like. We propose a mechanism for the morphological change of NCO nanoparticles on the basis of crystallite splitting accompanied by particle splitting and reordering. © 2018, Springer Science+Business Media, LLC, part of Springer Nature.