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Author: search.filters.author.Anandhan, S.Subject: search.filters.subject.Nanofibers

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    Parametric study of manufacturing ultrafine polybenzimidazole fibers by electrospinning
    (Springer, 2012) Anandhan, S.; Ponprapakaran, K.; Senthil, T.; George, G.
    Polybenzimidazole (PBI), a high performance polymer, was synthesized from 3,3?-diaminobenzidine (DAB) and isophthalic acid (IPA) through polycondensation. The chemical structure of PBI was confirmed by Fourier transform infrared spectroscopy. Thermal characterization of PBI was done by thermogravimetry and differential scanning calorimetry. PBI nanofibers were fabricated by electrospinning of N, N-dimethyl acetamide solutions of PBI of different solution concentrations, at different voltages. The effects of solution and process parameters (namely, solution concentration and DC voltage) on morphology and average diameter of electrospun PBI fibers were investigated. The electrospun ultrafine fibers' diameter and morphology were characterized by using scanning electron microscopy. Nanofibers were obtained only from PBI solutions of concentrations 12 and 14 % (w/v). At concentrations of 8, 10, and 16 %, fibers could not be obtained. The process parameters were optimized by using the statistical tool, factorial or two-way ANOVA (analysis of variance), DOE (design of experiments) and the results indicate that the applied voltage and the interaction of voltage and solution concentration are influential in determining the diameter and morphology of the electrospun ultrathin PBI fibers. Electrospun PBI fibers, as small as 56 nm, could be successfully produced by using the right combination of solution concentration and spinning voltage. © 2012 Central Institute of Plastics Engineering & Technology.
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    Structural characterization of nano-crystalline Co3O4 ultra-fine fibers obtained by sol-gel electrospinning
    (2013) George, G.; Anandhan, S.
    In this paper, we report the obtention of ultrafine fibers of cobalt oxide (Co3O4) by combining electrospinning method with high-temperature calcinations from the precursor sol of poly(2-ethyl-2- oxazoline) (PEtOx)/cobalt acetate tetrahydrate [Co(CH3COO) 2·4H2O] in water. The optimum electrospinning conditions for obtaining precursor composite nanofibers from PEtOx/Co(CH 3COO)2·4H2O solution in water, to produce ceramic nanofibers, were studied. The average fiber diameter of the precursor composite fibers measured by scanning electron microscopy (SEM) was approximately 200 nm. Thermogravimetric analysis of PEtOx was performed to estimate the suitable calcination temperature of the precursor fibers. SEM images of the ceramic fibers obtained after calcination revealed the shrinkage in diameter due to complete degradation of the polymer and Co(CH 3COO)2·4H2O. Fourier transform infrared spectroscopy was used to ensure the complete pyrolysis of polymer during calcinations of the composite fibers. Crystalline properties of the ceramic fibers were studied by X-ray diffraction and high resolution transmission electron microscopy. The ceramic fibers are polycrystalline with an average grain size of ?40 nm obtained at a calcination temperature of 773 K. It was observed that the grain sizes increased as the calcination temperature was increased, due to self assembly mechanism. © 2013 Springer Science+Business Media New York.
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    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.
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    Glass fiber-supported NiO nanofiber webs for reduction of CO and hydrocarbon emissions from diesel engine exhaust
    (Cambridge University Press, 2014) George, G.; Anandhan, S.
    In this study, nickel acetate tetrahydrate (NACTH)/poly(styrene-co-acrylonitrile) (SAN) sol was used for the fabrication of nanocrystalline NiO nanofibers. An indigenous setup was developed to use these nanofibers for the oxidation of carbon monoxide (CO) and unburnt hydrocarbons (HC) from diesel engine exhaust. The morphological, compositional, and crystalline properties of the NiO nanofibers obtained after calcination were studied by scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and x-ray diffraction (XRD). Clear evidence of defects in the fibers was observed in ultraviolet-visible-near infrared (UV-Vis-NIR) spectra, Raman spectra, and magnetic property measurements. The NiO nanofiber mats supported by glass fiber mats were efficient in oxidizing CO and HC from diesel engine exhaust, and the maximum efficiency was achieved by using NiO nanofibers with the maximum amount of defects. © © Materials Research Society 2014.
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    Glass fiber-supported NiO nanofiber webs for reduction of CO and hydrocarbon emissions from diesel engine exhaust
    (Cambridge University Press, 2014) George, G.; Anandhan, S.
    In this study, nickel acetate tetrahydrate (NACTH)/poly(styrene-co-acrylonitrile) (SAN) sol was used for the fabrication of nanocrystalline NiO nanofibers. An indigenous setup was developed to use these nanofibers for the oxidation of carbon monoxide (CO) and unburnt hydrocarbons (HC) from diesel engine exhaust. The morphological, compositional, and crystalline properties of the NiO nanofibers obtained after calcination were studied by scanning electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and x-ray diffraction (XRD). Clear evidence of defects in the fibers was observed in ultraviolet-visible-near infrared (UV-Vis-NIR) spectra, Raman spectra, and magnetic property measurements. The NiO nanofiber mats supported by glass fiber mats were efficient in oxidizing CO and HC from diesel engine exhaust, and the maximum efficiency was achieved by using NiO nanofibers with the maximum amount of defects. © © Materials Research Society 2014.
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    Structure-property relationship of sol-gel electrospun ZnO nanofibers developed for ammonia gas sensing
    (Academic Press Inc. apjcs@harcourt.com, 2014) Senthil, T.; Anandhan, S.
    Zinc oxide (ZnO) based nanomaterials have been used in various gas sensors due to the wide band gap (3.37. eV), large exciton binding energy and high mobility of charge carriers of ZnO. In this work, nanocrystalline ZnO nanofiber mats were synthesized through combined sol-gel electrospinning techniques followed by calcination, in which poly(styrene- co-acrylonitrile) and zinc acetate were used as the binder and precursor, respectively. Average diameter of the ZnO nanofibers decreased from 400 to 60. nm, while their grain size and crystallinity were enhanced by increasing the calcination temperature. Morphology and structure of the ZnO nanofiber mats were characterized by high resolution transmission electron microscopy, scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction. ZnO nanofiber mats were found to be superhydrophilic (contact angle was close to 0°) by contact angle measurements. The sensitivity of these ZnO nanofibers in detecting gaseous ammonia was tested using an indigenous set up. Due to their high surface area and superhydrophility, these ZnO nanofiber mats were highly sensitive in sensing gaseous ammonia and the sensitivity of these mats increased as a function of their calcination temperatures. © 2014 Elsevier Inc.
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    Comparison of structural, spectral and magnetic properties of NiO nanofibers obtained by sol-gel electrospinning from two different polymeric binders
    (Elsevier Ltd, 2015) George, G.; Anandhan, S.
    NiO is a p-type semiconductor with wide band gap energy. In this study, nickel oxide nanofibers were fabricated by sol-gel electrospinning followed by high temperature calcination, using two sacrificial polymeric binders. Poly(2-ethyl-2-oxazoline) (PEtOx) in water and styrene-acrylonitrile random copolymer (SAN) in N,N- dimethylformamide (DMF) along with nickel (II) acetate tetrahydrate (NATH), as metal oxide precursor, were the two distinct polymeric systems used in this study. The morphological and structural properties of NiO fibers obtained from the aforementioned systems were compared with each other. The degradation behavior of the sacrificial polymeric binder imparted a significant effect on the properties of the obtained NiO fibers. The grain sizes and the activation energies for grain growth of NiO fibers from two systems were different. The non-stoichiometric NiO fibers obtained from the SAN/NATH system had a better ferromagnetic behavior as compared with that produced from the PEtOx/NATH system. This non-stoichiometry made a difference also in the optical band gap energies of the NiO nanofibers. © 2015 Elsevier Ltd.
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    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.
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    Electrospinning of non-woven poly(styrene-co-acrylonitrile) nanofibrous webs for corrosive chemical filtration: Process evaluation and optimization by Taguchi and multiple regression analyses
    (Elsevier, 2015) Senthil, T.; Anandhan, S.
    Nano-fibrous ultra-filtration membranes of poly(styrene- co-acrylonitrile) were produced from n-butanone solution by electrospinning. Effects of governing parameters on morphology and variation in diameter of the electrospun fibers were experimentally investigated by orthogonal experimental design. The process parameters were selected by Taguchi's method. Multiple regression analysis was used to obtain a quantitative relationship between selected electrospinning parameters and average fiber diameter and ANOVA was used to identify the statistically significant parameters and set the optimal level for each parameter. Confirmation experiment revealed a good agreement between the predicted values of the response obtained from optimum level parameters and the observed experimental values. © 2014 Elsevier B.V.
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    Fabrication of styrene-acrylonitrile random copolymer nanofiber membranes from N,N-dimethyl formamide by electrospinning
    (SAGE Publications Ltd info@sagepub.co.uk, 2015) Senthil, T.; Anandhan, S.
    Ultrafine styrene-acrylonitrile random copolymer (SAN) nanofiber-based membranes were produced from N,N-dimethyl formamide solution by electrospinning. The purpose of this study was to find the optimum values of the electrospinning parameters and the influence of major significant parameters on the electrospun fiber morphology and the average fiber diameter (Davg) and its standard deviation using design of experiment. A backward elimination model for multiple regression analysis was employed to obtain quantitative interactions among selected electrospinning parameters and the final fiber diameter. The dependence of the Davg and morphology on the critical entanglement concentration was also studied. Morphology of the electrospun nanofiber mats were examined by scanning electron microscopy. Davg of electrospun SAN fibers increased considerably with increasing solution concentration. Fibers with diameters ranging from 40 to 650 nm were obtained. Analysis of variance was utilized to identify the statistically significant parameters (p < 0.05) and error variance. © The Author(s) 2013.