Faculty Publications
Permanent URI for this communityhttps://idr.nitk.ac.in/handle/123456789/18736
Publications by NITK Faculty
Browse
19 results
Search Results
Item Electrospun PVDF-based composite nanofabrics: An emerging trend toward energy harvesting(Elsevier, 2021) Shetty, S.; Anandhan, S.Poly(vinylidene fluoride) (PVDF) has gained attention in energy-related applications, due to its ferroelectric, piezoelectric, and pyroelectric properties. PVDF is a semicrystalline fluoropolymer having different phase domains based on its chain conformations. The polar domains contribute to its ferroelectric and piezoelectric characteristics. Electrospinning is a facile nanofabrication technique used to produce ultrafine fibers that self-integrates into functional webs/nanofabrics. This chapter emphasizes the electrospinning/filler route to tune the electroactive properties of PVDF-based composite nanofabrics and their applicabilities toward energy-related systems. The influence of various fillers/additives on the structure, morphology, and electroactive response of PVDF composite nanofabrics, including their incorporation into energy-related systems, is described in detail. Understanding the interplay between the filler and PVDF matrix coupled with electrospinning could contribute toward the fabrication of scalable and practical energy systems. © 2021 Elsevier Inc.Item Miscibility of poly(vinylidene fluoride) and cellulose acetate blends in dimethyl formamide(Chemical Publishing Co., 2011) Muthu, M.S.; Bhat, D.K.The miscibility of poly(vinylidene fluoride) (PVDF) and cellulose acetate blends in dimethyl formamide has been investigated by viscosity, density, refractive index and ultrasonic velocity studies. The polymer-solvent and blend-solvent interaction parameters and heat of mixing have been calculated using the viscosity, density and ultrasonic velocity data. The results indicated the existence of positive interactions in the blend polymer solutions and that they are miscible in dimethyl formamide in the entire composition range between 303-323 K. The study also revealed that the variation in the temperature does not affect the miscibility of poly(vinylidene fluoride) and cellulose acetate blends in DMF significantly. The presence of hydrogen bonding in the blends in the solid state has also been indicated by FTIR studies. SEM images also supported the miscibility of blends.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.Item Electroactive poly(vinylidene fluoride) fluoride separator for sodium ion battery with high coulombic efficiency(Elsevier B.V., 2016) Janakiraman, S.; Surendran, A.; Ghosh, S.; Anandhan, S.; Adyam, A.Electroactive separators are recent interest in self-charging rechargeable batteries. In this study, electrospun polyvinylidene fluoride (PVDF) is characterized as an electroactive separator for Na-ion batteries. The intrinsic ?-phase with high porosity of the separator is confirmed from X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Field emission scanning electron microscopy (FESEM) and Atomic Force Microscopy (AFM) studies. The electroactive separator is immersed in 1M NaClO4-ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1 by weight) solution. The physicochemical characteristics of electroactive separator electrolyte (EaSE) were investigated using sodium ion conductivity, ion transference number and contact angle measurements. Linear and cyclic voltammetry studies were also carried out for the electrolyte system to evaluate oxidation stability window. The inherent ?-phases of the separator as obtained by electrospinning has an ionic conductivity of ~ 7.38 × 10- 4 S cm- 1 under ambient condition. Sodium ion cell made from EaSE with Na0·66Fe0.5Mn0·5O2 as cathode and Na metal as anode has displayed a stable cycle performance with a coulombic efficiency of 92% after 90 cycles. © 2016 Published by Elsevier B.V.Item Electrochemical characterization of a polar ?-phase poly (vinylidene fluoride) gel electrolyte in sodium ion cell(Elsevier B.V., 2019) Janakiraman, S.; Surendran, A.; Biswal, R.; Ghosh, S.; Anandhan, S.; Adyam, A.A polar ?-phase poly (vinylidene fluoride) (PVDF) membrane is developed through the electrospinning method. PVDF gel electrolyte for sodium ion batteries was obtained by saturating the bare porous membrane in a liquid electrolyte, 1 M NaClO4 in EC: DEC (1:1 vol%). The physical and electrochemical characteristics of the polar ?-phase PVDF membrane are explored by X-ray diffraction (XRD), Field emission scanning electron microscopy (FESEM), Atomic force microscope (AFM), sodium ion conductivity, linear sweep voltammetry (LSV) and sodium ion transference number. The ionic conductivity of a polar ?-phase PVDF gel electrolyte exhibited 9.2 × 10?4 S cm?1, higher than the commercially used Celgard® 2400 membrane 0.36 × 10?4 S cm?1 at ambient temperature. The electrochemical expolarations of the sodium ion half-cell (Na2/3Fe1/2Mn1/2O2) as a cathode and sodium metal as a counter electrode) conducted from PVDF gel electrolyte are analysed by cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). CV of the battery showed a pseudo capacitive nature. The equivalent circuit model of the sodium ion cell brought out the effect of dipole moments in the polymer chains on the battery performance. © 2018 Elsevier B.V.Item Synergism of graphitic-carbon nitride and electrospinning on the physico-chemical characteristics and piezoelectric properties of flexible poly(vinylidene fluoride) based nanogenerator(Springer Netherlands rbk@louisiana.edu, 2019) Khalifa, M.; Mahendran, A.; Anandhan, S.Herein, we investigated the piezoelectric performance of electrospun poly(vinylidene fluoride)/graphitic carbon nitride (PVDF/g-C 3 N 4 ) nanocomposite fibers (PGN-X). Addition of g-C 3 N 4 nanosheets improved the spinnability of nanofibers and augmented the ?-phase content of PVDF. The synthesized PGN non-woven mats were flexible and easily deformable without disrupting the continuity of fibers. Upon the addition of g-C 3 N 4 , tensile strength and thermal stability of nanocomposite fibers improved significantly. A maximum voltage output of ~7.5 V was generated for PGN nanogenerator which is ~8 times more than that of PVDF nanogenerator. Also, the PGN-X nanogenerator generated current output of 0.23 ?A and a power density of 0.22 ?W/cm ?2 . Improved physico-chemical characteristics and piezoelectric performance of PGN nanogeneratoris promising and makes it suitable for portable electronic and wearable devices. © 2019, The Polymer Society, Taipei.Item PVDF Nanofibers with Embedded Polyaniline-Graphitic Carbon Nitride Nanosheet Composites for Piezoelectric Energy Conversion(American Chemical Society service@acs.org, 2019) Khalifa, M.; Anandhan, S.Herein, a facile approach was used to synthesize an ultrasensitive, durable, and flexible electrospun poly(vinylidene fluoride) (PVDF)/polyaniline (PANI)/graphitic carbon nitride nanosheets (g-C3N4) blend nanocomposite fibers (PPBF) based piezoelectric nanogenerator. PANI/g-C3N4 nanocomposite (PGNC) was prepared prior to its dispersal in PVDF. This unpretentious synthesis approach exploited the ?-nucleating activity of g-C3N4 along with the enhancement of electrical conductivity due to a network of PANI within individual PVDF nanofibers. Addition of PGNC and electrospinning synergistically enhanced the ?-phase content (?97%) of PVDF. The PPBF nanogenerator displayed remarkable improvement in the voltage and current output compared to pristine PVDF nanofibers (?1300%). The nanogenerator generated a voltage output of ?30 V and current output of 3.7 ?A with high stability and reproducibility (>50※000 cycles). The PPBF nanogenerator exhibited high-power density and conversion efficiency and was able to light up 70 commercial LEDs. The newly developed high performance nanogenerator could be a potential material in smart, self-powered wearable devices. © 2019 American Chemical Society.Item Effect of polarization switching on piezoelectric and dielectric performance of electrospun nanofabrics of poly(vinylidene fluoride)/Ca–Al LDH nanocomposite(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2020) Shamitha, C.; Mahendran, A.R.; Anandhan, S.At present, highly flexible, durable, and lightweight piezoelectric nanogenerators with high-power density and energy conversion efficiency are of great interest. The present study reports a new synthetic route for Ca–Al layered double hydroxide (LDH) nanosheets and incorporation of these two-dimensional nanosheets as filler material into poly(vinylidene fluoride) (PVDF) to produce composite nanofabrics by electrospinning. The polymorphism, crystallinity, and the interaction between PVDF and LDH were studied by Fourier transform infrared spectroscopy, X-ray diffraction, and differential scanning calorimetry techniques. The synergetic effect of PVDF–LDH interaction and in situ stretching due to electrospinning facilitates the nucleation of electroactive ? phase up to 82.79%, which makes it a suitable material for piezoelectric-based nanogenerators. The piezoelectric performance of PVDF/Ca–Al LDH composite nanofabrics was demonstrated by hand slapping and frequency-dependent mechanical vibration mode, which delivered a maximum open circuit output voltage of 4.1 and 5.72 V, respectively. Moreover, the composite nanofabrics exhibited a high dielectric constant and low dielectric loss due to superior interfacial polarization at low-frequency region with LDH loading, promising its potential applications in electronic devices. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 137, 48697. © 2019 Wiley Periodicals, Inc.Item Development of a new flexible nanogenerator from electrospun nanofabric based on PVDF/talc nanosheet composites(Royal Society of Chemistry, 2020) Shetty, S.; Mahendran, A.R.; Anandhan, S.Herein, a flexible piezoelectric nanogenerator composed of electrospun talc/PVDF [poly(vinylidene fluoride)] nanocomposite fabrics has been developed. These nanocomposite fabrics demonstrated enhanced mechanical and piezoelectric properties compared with pristine PVDF nanofabrics. In particular, nanocomposite fabrics with 0.50 wt% talc yielded 89.6% of polar ?-phase in the PVDF matrix, thereby augmenting its piezoelectric response. X-ray diffraction, Fourier transform infrared spectroscopy, and differential scanning calorimetry conclusively affirmed the promotion of polar ?-phase in the talc/PVDF nanocomposite fabrics. The 0.50 wt% talc/PVDF nanocomposite fabric based nanogenerator produced an open-circuit voltage and power density of 9.1 V and 1.12 ?W cm-2, respectively, under repetitive finger tapping mode (under a load of 3.8 N). Furthermore, the nanogenerator was also subjected to frequency modulated-shaker mode, wherein an output voltage of 8.9 V was produced. Improved flexibility, mechanical robustness, and enhanced piezoelectric responsiveness of this nanogenerator could possibly pave the way for its use in portable self-powered devices. This journal is © 2020 The Royal Society of Chemistry.Item Physico-chemical and piezoelectric characterization of electroactive nanofabrics based on functionalized graphene/talc nanolayers/PVDF for energy harvesting(Springer Science and Business Media B.V., 2021) Shetty, S.; Shanmugharaj, A.M.; Anandhan, S.Poly(vinylidene fluoride) (PVDF) is a versatile polymer, whose dielectric, piezoelectric and ferroelectric properties can be augmented by a range of processing routes and/or additives. We developed a flexible nanogenerator using electrospun PVDF/COOH-functionalized graphene nanosheet (FGNS)/talc nanosheet (TNS) hybrid nanocomposites. TNS loading was fixed at 0.50 wt% while FGNS loading was varied (0.05, 0.10, 0.15, and 0.20 wt %) in these nanofabrics and their structure–property relationship was explored. Incorporation of FGNS led to formation of an electrically conductive network in the polymer matrix aided by TNS and electrospinning. The uniform dispersion of the filler nanosheets led to effective enhancement of the electroactive ?-phase of the PVDF matrix. Crystallinity and polymorphism in these systems were explored by FTIR spectroscopy, X-ray diffraction and differential scanning calorimetry. A nanogenerator made of the nanofabric containing 0.5 wt% of TNS and 0.10 wt% of FGNS was mechanically impacted by pneumatic actuator (operating pressure 0.4 MPa), resulting in an output voltage of 12.9 V and a power density of 1.72 µW/cm2, respectively. The piezoelectric coefficient (d33) of this nanofiber system was 61 pm/V as revealed by piezoelectric force microscopy. These novel nanocomposites could be used in flexible energy-harvesting devices. © 2021, The Polymer Society, Taipei.