Faculty Publications
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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 Organoclay enabled nanofiber formation from a polyolefin elastomer(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2018) Kumar, B.; Prakrthi, A.N.; Senthil, T.; Bhat, K.; Anandhan, S.The solution electrospinning of polyolefins has not been deeply studied mainly due to the difficulty in dissolving these polymers in appropriate solvents. In this study, composite nanofibers of organically modified montmorillonite/ethylene-octene random copolymer were produced for the first time with a mixture of cyclohexane and xylene as a solvent by solution electrospinning. Montmorillonite was used as an additive to increase the electrical charge density of the polymer solution. The influence of solution and process parameters on the electrospun ethylene-octene copolymer fibers' morphology and diameter was investigated using the design of experiment. Multiple regression analysis was used for the optimization of the electrospinning parameters. Ultrafine fibers, with diameters in the range of 150–350 nm were obtained; these nanofibers exhibited an excellent hydrophobicity over a period of 10 min as revealed by contact angle measurements. © 2016 Wiley Periodicals, Inc.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.Item Understanding the interplay of solution and process parameters on the physico-chemical properties of ZnO nanofibers synthesized by sol-gel electrospinning(Institute of Physics, 2023) Prabhu, N.N.; Rajendra, B.V.; Anandhan, S.; Murthy, K.; Jagadeesh Chandra, R.B.; George, G.; Kumar, B.; Shivamurty, B.Aging populations and the increase in chronic diseases worldwide demand efficient healthcare tools for simple, rapid, and accurate diagnosis and monitoring the human health. In this context, gas sensors are used to analyze the type of gas in the breath to diagnose chronic diseases. Metal oxide and ceramic nanofibers (NFs) produced by the electrospinning (ES) method have been investigated for potential use as gas sensors in the engineering and medical sectors. The material and process parameters are the main influencing factors on the functional performance of electrospun metal oxide NFs. Zinc oxide (ZnO) based NFs are used in various gas sensors due to the wide band gap (3.37eV), large exciton binding energy, and high mobility of charge carriers of ZnO. In this research, we made an attempt to study the effect of poly(vinyl alcohol) (PVA) and zinc acetate dihydrate (ZnAc2) concentrations and feed rate, voltage, spinneret tip-to-collector distance (TCD), and pyrolysis temperature on the physical properties of ZnO NFs. An average fiber diameter of 119 nm was obtained after pyrolysis at 600 °C of electrospun fiber produced from an aqueous PVA solution of concentration 15 w% with 7.5 w% ZnAc2 based on the weight of PVA. The grain size, transmittance, structural defects, and band gap energy of NFs were found to increase as a function of the pyrolysis temperature, which could be beneficial for the functional applications of these NFs. © 2023 The Author(s). Published by IOP Publishing Ltd