Faculty Publications
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Item Comparative Studies on Crystalline and Amorphous Vinylidene Fluoride Based Fibrous Polymer Electrolytes for Sodium-Ion Batteries(Springer Singapore, 2020) Janakiraman, S.; Khalifa, M.; Biswal, R.; Ghosh, S.; Anandhan, S.; Adyam, A.In the present work, electrospun poly (vinylidene fluoride) (PVDF) and poly (vinylidene fluoride-co hexafluropropylene) (P(VdF-co-HFP)) fibrous membranes have been compared. Porous homo and copolymer fiber-based membranes with an interconnected structure, high porosity, large electrolyte uptake were prepared by an electrospinning route. The effect of crystallinity in terms of X-ray diffraction (XRD) was investigated for the fibrous polymer membranes (FPMs). The surface morphology of the FPMs is evaluated by field emission scanning electronmicroscopy (FESEM). The FPMswere soaked in 1MNaClO4-ethylene carbonate (EC)/diethyl carbonate (DEC) (1:1, vol%) solution to form fibrous polymer electrolytes (FPEs). The ionic conductivity of copolymer showed 1.126 mS cm−1 under ambient temperature (at 28 °C) higher than the homopolymer (0.79 mS cm−1) because of HFP unit. The electrochemical stability window of the copolymer membrane also enhanced and stable up to 4.9 V versus Na+/Na suitable for high voltage sodium rechargeable batteries. When tested with Na066Fe0.5Mn05O2 as cathode and Na metal as an anode, the cycle performance significantly improved for the copolymer. © Springer Nature Singapore Pte Ltd. 2021.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 Synergism of Electrospinning and Nano-alumina Trihydrate on the Polymorphism, Crystallinity and Piezoelectric Performance of PVDF Nanofibers(Minerals, Metals and Materials Society 184 Thorn Hill Road Warrendale PA 15086, 2018) Khalifa, M.; Deeksha, B.; Mahendran, A.; Anandhan, S.Poly(vinlylidene fluoride) (PVDF) is known for its electroactive phases, which can be nucleated by incorporating nanoparticles into PVDF to enhance its piezoelectric performance. In this study, the synergistic effect of electrospinning and nano alumina trihydrate (ATH) filler was used to enhance the electroactive ? phase of PVDF. Electrospun nanofibers of PVDF/ATH nanocomposite (PANCF) were synthesized with different loadings of ATH. The presence of ATH enhances the surface charges of the electrospun droplets, leading to thinner fibers. The highest ?-phase content was found to be 70.1% for PANCF with 10% ATH. The piezoelectric performance of the nanofiber mats was studied using an indigenous setup. The highest voltage output of 840 mV was produced by PANCF with 10% ATH. These nanofibers could be a promising material in the field of sensors, actuators and energy-harvesting applications. © 2018, The Minerals, Metals & Materials Society.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/halloysite nanocomposite-based non-wovens as gel polymer electrolyte for high safety lithium ion battery(John Wiley and Sons Inc. cs-journals@wiley.com, 2019) Khalifa, M.; Janakiraman, S.; Ghosh, S.; Adyam, A.; Anandhan, S.Gel polymer electrolyte (GPE) based on electrospun poly(vinylidene fluoride) (PVDF)/halloysite nanotube (HNT) nanocomposite non-wovens was synthesized and its suitability as a separator in lithium-ion battery (LIB) was explored. In this study, HNT played a key role in reducing the average diameter of the electrospun fibers and uplifted the porosity of the non-wovens thereby improving their electrolyte uptake. Due to a reduction in crystallinity and increased % porosity of the PVDF/HNT non-wovens, the ionic conductivity (1.77 mScm?1) and ionic transport across the separator were improved. Moreover, this GPE separator exhibited high tensile and puncture strength with negligible thermal shrinkage and a higher melting temperature compared with a commercially available separator, which is vital from the safety perspective. The cycling performance of Li/GPE/LiCoO2 cell was evaluated and it exhibited a high capacity of 138.01 mAhg?1 with 97% coulombic efficiency for the initial cycle. The cell was stable and retained its high performance with little loss in capacity even after repeated charge–discharge cycles. Such a combination of high ionic conductivity, tensile strength with low thermal shrinkage is seen to be very rare in polymer-based separators. It is noteworthy that this novel GPE outperformed the commercial separator also in the cycle performance. POLYM. COMPOS., 40:2320–2334, 2019. © 2018 Society of Plastics Engineers. © 2018 Society of Plastics EngineersItem An electroactive ?-phase polyvinylidene fluoride as gel polymer electrolyte for magnesium–ion battery application(Elsevier B.V., 2019) Singh, R.; Janakiraman, S.; Khalifa, M.; Anandhan, S.; Ghosh, S.; Adyam, A.; Biswas, K.The gel polymer electrolytes (GPEs) are currently interesting research area in rechargeable batteries. In the present study, synthesis and characterization of electroactive gel polymer electrolyte (EGPE) for Mg-ion batteries application have been investigated. The bead free electroactive polyvinylidene fluoride (PVDF) with high porosity is achieved by an electrospinning process. The ?-phase of PVDF is polar and electroactive with a high dipole moment. Electroactive ?-phase is confirmed by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). Field emission scanning electron microscopy (FESEM) study is done to analyze the structure and morphology of the electroactive membrane. The electroactive gel polymer electrolyte is formed by immersing an electroactive PVDF membrane in 0.3 M magnesium perchlorate (MgClO4) and propylene carbonate (PC) solution. The ionic conductivity of electroactive ?-phase PVDF membrane is achieved to be 1.49 mS cm?1 at 30 °C, which is higher than commercial available polypropylene (PP) Celgard. Tortuosity of electroactive gel polymer electrolyte is found to be 1.44. The voltage stability of the EGPE is stable up to a high voltage of 5.0 V against Mg+2/Mg. The total ionic transference number and magnesium ion transference number of EGPE are also investigated to confirm high ionic conductivity. © 2019 Elsevier B.V.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 Highly sensitive and wearable NO2gas sensor based on PVDF nanofabric containing embedded polyaniline/g-C3N4nanosheet composites(IOP Publishing Ltd, 2021) Khalifa, M.; Anandhan, S.In this study, a highly flexible and wearable nitrogen dioxide (NO2) gas sensor was fabricated based on electrospun poly(vinylidene fluoride) (PVDF)/polyaniline (PANi)/graphitic-carbon nitride (g-C3N4) blend nanocomposite (EBNC). g-C3N4/PANi nanocomposite (GPC) was synthesized by in situ polymerization technique prior to its incorporation into PVDF nanofibers, which ensured uniformity of dispersion. For the comparison study, PVDF/GPC nanocomposite film was fabricated using doctor blade technique. EBNC sensor exhibited high sensitivity, selectivity, reproducibility along with quick response and complete recovery. Electrospinning and GPC synergistically improved the performance of the EBNC based gas sensor. The superior gas sensing ability along with its low cost and the use of scalable electrospinning technique could make this system a promising one for the detection of gaseous NO2. © 2021 IOP Publishing Ltd.Item Piezoelectric Energy Harvesting Using Flexible Self-Poled Electroactive Nanofabrics Based on PVDF/ZnO-Decorated SWCNT Nanocomposites(Springer, 2022) Khalifa, M.; Peravali, S.; Varsha, S.; Anandhan, S.This study probes the synergism of electrospinning and zinc oxide-decorated single-walled carbon nanotubes (ZCNT) in enhancing the β-phase nucleation and piezoelectric performance of PVDF. The nanofibers were spun in the form of nonwoven fabrics and characterized for their morphology, crystallinity, polymorphism, and tensile properties. Inclusion of ZCNT significantly promoted the β-phase (~95%) and tensile properties of PVDF, while the total degree of crystallinity was reduced. The highest voltage output of 15.5 V, which is 15 times more than that of the pristine PVDF nanofabrics, and a power density of 8.1 μWcm−2 was attained for the nanogenerator based on 0.75 wt.% ZCNT/PVDF nanofabrics. Implementation of electrospinning process and ZCNT proved to be beneficial in fabricating a flexible, lightweight, and robust nanogenerator for electronic devices. © 2022, The Minerals, Metals & Materials Society.