Faculty Publications

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Author: search.filters.author.Khalifa, M.Subject: search.filters.subject.Nanogenerators

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    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.
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    Durable, efficient, and flexible piezoelectric nanogenerator from electrospun PANi/HNT/PVDF blend nanocomposite
    (John Wiley and Sons Inc. cs-journals@wiley.com, 2019) Khalifa, M.; Mahendran, A.; Anandhan, S.
    Currently, there is considerable research focus on portable, lightweight, shock-resistant, and inexpensive wearable devices that are ideally powered by harvesting abundant mechanical or vibration energy, making battery or related wiring superfluous. In this study, piezoelectric nanogenerator was electrospun from PANi (polyaniline)/HNT (halloysite nanotube)/PVDF (poly[vinylidene fluoride]) blend nanocomposite. Polymorphism, crystallinity and morphology of the nanogenerator were explored in detail. HNT and PANi acted as a nucleating agent and conductive filler, respectively in PVDF; their synergism helps improve the piezoelectric performance of PVDF. The piezoelectric performance of the nanogenerator patch was studied under various external mechanical stresses, such as pressure, tapping, and impact. A maximum voltage output of approximately 7.2 V was generated by the nanogenerator under impact. The nanogenerator patch attached to human arm exhibited not only excellent piezoelectric response during arm movements, but, also proved to be flexible, highly sensitive and durable. This nanogenerator could possibly be used in wearable piezoelectric energy conversion application for self-powered devices. POLYM. COMPOS., 40:1663–1675, 2019. © 2018 Society of Plastics Engineers. © 2018 Society of Plastics Engineers
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    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.
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    Cationic surfactant assisted enhancement of dielectric and piezoelectric properties of PVDF nanofibers for energy harvesting application
    (Royal Society of Chemistry, 2021) Ekbote, G.S.; Khalifa, M.; Mahendran, A.; Anandhan, S.
    Poly(vinylidene fluoride) (PVDF) is among the most versatile polymers due to its wide range of properties, including dielectric, piezoelectric and ferroelectric properties. However, more frequently than not a range of processing routes and/or additives have been used to enhance such properties. In this study, PVDF nanofibers were electrospun from PVDF solution that contained tetra-n-butyl ammonium chloride (TBAC) at different loadings (1, 2, 3, and 5 wt%). The effect of TBAC on the morphology, crystallinity, and polymorphism of PVDF was studied using various characterization techniques. Addition of TBAC significantly improved the electroactive ?-phase of PVDF. The highest ?-phase content of 89% was attained at a TBAC loading of 3 wt%. Consequently, the dielectric and piezoelectric properties of the PVDF nanofibers improved significantly. A nanogenerator fabricated using 3 wt% TBAC/PVDF nanofibers exhibited the maximum voltage output of 17.2 V (under 5 N force) and the maximum power density of ?1.4 ?W cm?2(under 3 N force). Improved dielectric and piezoelectric properties of PVDF upon the addition of a small amount of TBAC could be useful for researchers in upbringing the material for flexible electronic devices. © The Royal Society of Chemistry 2021.
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    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.
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    Development of a flexible piezoelectric and triboelectric energy harvester with piezo capacitive sensing ability from barium tungstate nanorod-dispersed PVDF nanofabrics
    (Institute of Physics, 2023) Ekbote, G.S.; Khalifa, M.; Venkatesa Perumal, B.; Anandhan, S.
    Lead-free flexible piezoelectric nanogenerator (PNG) and triboelectric nanogenerator (TENG) are sought after due to their ability to produce electricity by harnessing wasteful mechanical energy. A comprehensive understanding of additives and processing techniques is crucial for fine-tuning the performance of such energy systems. We have investigated in detail the effect of the addition of reverse microemulsion synthesized barium tungstate nanorods (BWN) on morphology, crystallinity, polymorphism of electrospun nanofabrics of poly(vinylidene fluoride) (PVDF). The electroactive phase content of the nanofabrics was enhanced upon the addition of BWN and the highest electroactive phase content of 86.5% was observed in the nanofabric containing 3 wt% of BWN. The dielectric constant of the nanofabric containing 5 wt% BWN was ∼1.96 times higher than that of pristine electrospun PVDF nanofabric (EPVDF). The ratio of relative change in the capacitance to initial capacitance of the sensor fabricated from the same system was ∼4 times greater than that of EPVDF. Consequently, its piezoelectric and triboelectric performances were improved. The PNG fabricated using the nanofabric containing 3 wt% BWN produced the highest open-circuit voltage of 8 V under an applied load of 8 N. A TENG made using the same system was able to produce a voltage output of 200 V, which was 1.77 times as high as that of EPVDF under one-finger tapping in contact-separation mode. The same composite nanofabric produced piezoelectric and triboelectric power densities of 4.3 µW cm−2 and 646 µW cm−2, respectively. The TENG was able to light 40 LEDs under one finger tapping. Fluttering-driven TENG fabricated using the aforementioned nanofabric was able to produce a triboelectric voltage of 84 V at a wind speed of 7 m s−1. Overall, these nanofabrics could be a potential material for energy harvesting devices for powering wearable devices, environmental sensors, and internet of things. © 2023 IOP Publishing Ltd