Journal Articles
Permanent URI for this collectionhttps://idr.nitk.ac.in/handle/123456789/19884
Browse
35 results
Search Results
Item 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.Item Solution electrospinning of styrene-acrylonitrile random copolymer from dimethyl sulfoxide(Springer India sanjiv.goswami@springer.co.in, 2013) Senthil, T.; Anandhan, S.Electrospinning is an efficient and versatile technique for the fabrication of ultrafine fibers having diameters ranging from nano to sub-micron level for various potential applications. In this study, we have investigated the influence of process and solution parameters, such as solution concentration, flow rate and applied voltage, on the morphology of electrospun poly(styrene-co-acrylonitrile) (SAN) fibers. Morphology and average diameter (Davg.) of the electrospun SAN fibers were characterized by scanning electron microscopy (SEM). The SEM results reveal that concentration, applied voltage and flow rate of solution are strongly associated with formation of defects, such as beads, in the fibers. Ultrafine SAN fibers with Davg. in the range of 96-872 nm were obtained by controlling the experimental parameters. The Davg. of electrospun fibers increased with increasing solution concentration, applied voltage and flow rate. Also, the Davg. exhibits a power law relationship with the solution concentration. © 2013 Central Institute of Plastics Engineering & Technology.Item Chemical-resistant Ultrafine Poly(styrene-co-acrylonitrile) Fibers by Electrospinning: Process Optimization by Design of Experiment(2013) Senthil, T.; George, G.; Anandhan, S.The effects of solution and processing parameters on the morphology and diameter of electrospun poly(styrene-co-acrylonitrile) fibers were investigated by design of experiment. Morphology of the electrospun fiber mats were investigated by scanning electron microscopy. With increasing solution concentration, fiber morphology changed from that of a spindle-like beaded one to smooth, and the average fiber diameter increased from 96 to 876 nm. Average fiber diameter gradually increased with applied voltage; however, fiber morphology was only slightly influenced by flow rate. Regression analysis results reveal that solution concentration has the most significant impact on the average and standard deviation of fiber diameter. © 2013 Copyright Taylor and Francis Group, LLC.Item 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.Item 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.Item 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.Item 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.Item 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.Item A comparative study on the physico-chemical properties of sol-gel electrospun cobalt oxide nanofibres from two different polymeric binders(Royal Society of Chemistry, 2015) George, G.; Anandhan, S.In this study, two different sacrificial polymeric binders, namely poly(2-ethyl-2-oxazoline) (PEtOx) and poly(styrene-co-acrylonitrile) (SAN) along with cobalt acetate tetrahydrate (CATH), as the metal oxide precursor, were used for the fabrication of Co3O4 nanofibres through sol-gel electrospinning. It was observed that the degradation behaviour and physical properties of SAN and PEtOx influenced the structure, morphology and spectral properties of Co3O4 nanofibres, as the properties of the nanofibres obtained from the aforementioned systems were compared with each other. The grain size, shape and the activation energies for grain growth of Co3O4 nanofibres obtained from these two polymeric systems were different. This difference in grain size and shape caused a difference in the optical band gap energies and the magnetic properties of the Co3O4 nanofibres. This study reveals that one can tailor the characteristics of cobalt oxide nanofibres by an appropriate selection of polymeric binders for sol-gel electrospinning. © The Royal Society of Chemistry.Item Probing the synergism of halloysite nanotubes and electrospinning on crystallinity, polymorphism and piezoelectric performance of poly(vinylidene fluoride)(Royal Society of Chemistry, 2016) Khalifa, M.; Mahendran, A.; Anandhan, S.Poly(vinylidene fluoride) (PVDF) nanofibers have tremendous potential in nano-sensing and energy scavenging applications. In this study, uniaxially aligned nanofibers were developed from halloysite nanotubes (HNT)/PVDF nanocomposite using electrospinning technique. Incorporation of HNT into PVDF not only reduced the diameter of the electrospun nanofibers, but, also improved their morphology. Fourier transform infrared spectroscopy, wide angle X-ray diffraction and differential scanning calorimetry techniques were used to characterize the crystallinity, polymorphism and polymer-filler interaction in the nanocomposite nanofibers. A force sensor was indigenously designed to study the piezoelectric responses of the nanocomposite nanofibers. At 10 wt% of HNT loading, the sensor produced the highest voltage output, which can be ascribed to its highest ?-phase content. Incorporation of HNT and use of electrospinning synergistically enhanced the ?-phase content and hence the piezoelectric behavior of PVDF. Hence, these nanofibers could be promising and prominent materials in sensor and actuator applications. © The Royal Society of Chemistry.