Browsing by Author "Khalifa, M."

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A Facile Strategy to Achieve High Piezoelectric Performance in Electrospun Poly(Vinylidene Fluoride) Non-woven Nanofabrics
(Korean Institute of Electrical and Electronic Material Engineers, 2024) Khalifa, M.; Kumar, M.; Subramanian, G.; Anandhan, S.
Poly(vinylidene fluoride) (PVDF) with its piezoelectric characteristics holds the potential to be the promising candidate in microdevices, sensors and actuators. In this study, a facile strategy was adopted to augment the electroactive β-phase of electrospun PVDF non-woven nanofabric. Electrospun PVDF non-woven fabric was mechanically stretched at different strain rates. SEM images revealed that upon stretching the non-woven fabric, the fibers tend to orient along the stretching direction. The fibers from the necked region were characterized to understand effect of stretching on the polymorphism, crystallinity and piezoelectric performance. The β-phase content of PVDF increased upon increasing the strain rate, while the degree of crystallinity decreased slightly. The highest β-phase content of 79% was achieved for electrospun PVDF non-woven fabric stretched at 10 mm/min. Further, the piezoelectric performance of the stretched nanofabric was evaluated to assess its electroactive characteristics. The piezoelectric performance of electrospun PVDF fabric was studied by imparting the pressure/load by one-finger tapping, hand pressure and dropping weight. The highest output voltage and current of 8.4 V and 249 nA, respectively were obtained from the electrospun PVDF non-woven stretched at 10 mm/min, which is almost 8 times higher than that of the unstretched PVDF non-woven. Given the flexibility, lightweight with good piezoelectric performance these electrospun PVDF non-woven fabrics could be a potential material for energy harvesting and self-powered nano-electronic devices. Graphical Abstract: (Figure presented.) © The Korean Institute of Electrical and Electronic Material Engineers 2023.
A high thermally stable polyacrylonitrile (PAN)-based gel polymer electrolyte for rechargeable Mg-ion battery
(Springer, 2020) Singh, R.; Janakiraman, S.; Khalifa, M.; Anandhan, S.; Ghosh, S.; Adyam, A.; Biswas, K.
The ionic conductivity and thermal stability of the electrolyte-separator system is an essential parameter for improving battery performance and safety. The present work addresses the high thermally stable gel polymer electrolyte (GPE) using polyacrylonitrile (PAN) as a polymer membrane and magnesium perchlorate in propylene carbonate (Mg(ClO4)2-PC) as a liquid electrolyte. The PAN based polymer membrane is prepared by electrospinning process which produces a bead free and uniformly distributed nanofibers. The electrospun PAN based GPE is characterized by different physical and electrochemical techniques like X-ray diffraction, field emission scanning electron microscopy, thermogravimetric analysis, differential scanning calorimetry, ionic conductivity, linear sweep voltammetry, magnesium ion transference number and electrochemical impedance spectroscopy. The ionic conductivity of PAN is 3.28 mS cm?1, compared to that of PP Celgard is 1.97 × 10–4 mS cm?1 at 30 °C. The electrochemical stability of PAN is 4.6 V and also exhibits excellent interfacial stability with magnesium metal. The results showed that the PAN-based GPE has higher ionic conductivity and thermal stability than the polypropylene (PP) Celgard membrane. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.
A new multifunctional energy harvester based on mica nanosheet-dispersed PVDF nanofabrics featuring piezo-capacitive, piezoelectric and triboelectric effects
(Royal Society of Chemistry, 2023) Ekbote, G.S.; Khalifa, M.; Venkatesa Perumal, B.; Anandhan, S.
In recent years, there has been a significant rise in the popularity of piezoelectric and triboelectric nanogenerators as alternative power sources for miniature devices and internet of things devices (IoT). Herein, piezoelectric nanogenerators (PNG) and triboelectric nanogenerators (TENG) based on mica nanosheet (MNS)-infused poly(vinylidene fluoride) (PVDF) composite nanofabrics were developed. The morphology, crystallinity, and polymorphism of PVDF/MNS composite nanofabrics were studied using different characterization techniques. The incorporation of MNS into PVDF resulted in enhanced electroactive β-phase content, reaching a maximum of 84.3% in the composite nanofabric containing 0.75 wt% of MNS. The same nanofabric exhibited a dielectric constant ∼1.64 times that of pure PVDF nanofabric, substantially enhancing the capacitive sensing capability by ∼4.4 times. The PNG developed using the nanofabric containing 0.75 wt% of MNS displayed an open-circuit voltage (VOC) of ∼8.4 V and a power density of ∼3 μW cm−2 when subjected to 8 N force. The TENG based on the aforementioned nanofabric produced a maximum VOC of ∼163 V and a power density of ∼585 μW cm−2 when subjected to one-finger tapping. With the same TENG upon one-finger tapping, 35 LEDs were illuminated. A fluttering-driven TENG utilizing the same nanofabric generated a maximum VOC of ∼70 V when exposed to a wind speed of 7 m s−1. The results indicate that the nanofabrics developed herein could potentially be utilized to fabricate energy harvesting devices to power health monitoring sensors, IoT and nano/micro devices. © 2023 RSC.
A study on electroactive PVDF/mica nanosheet composites with an enhanced ?-phase for capacitive and piezoelectric force sensing
(Royal Society of Chemistry, 2021) Khalifa, M.; Schoeffmann, E.; Lammer, H.; Mahendran, A.R.; Wuzella, G.; Anandhan, S.
Herein, a multifunctional poly(vinylidene fluoride) (PVDF)/mica nanosheet composite (PMNC) thin film was developed for preparing a capacitive and piezoelectric force sensor. A high electroactive ?-phase content (89%) of PVDF was achieved through a facile rapid cooling process of PMNC films. The crystallinity of PVDF decreased upon the addition of mica nanosheets, while the dielectric constant increased significantly (?300%). The capacitance-based PMNC pressure sensor was found to be sensitive to the applied pressure. On the other hand, piezoelectric voltages of 18 V (single layer) and 32 V (multi-layer) were generated for PMNCs loaded with 1% mica nanosheets. Furthermore, a PMNC based nanogenerator generated a power density of 8.8 ?W cm?2and showed excellent durability (>60?000 cycles). High flexibility, lightweight and skin-friendly PMNCs could be a potential material in applications such as energy harvesting, energy storage, actuators, and self-powered and smart wearable electronic devices. © The Royal Society of Chemistry 2021.
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.
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.
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.
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
Durable, efficient, and flexible piezoelectric nanogenerator from electrospun PANi/HNT/PVDF blend nanocomposite
(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
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
An electroactive ?-phase polyvinylidene fluoride as gel polymer electrolyte for magnesium ion battery application
(2019) Singh, R.; Janakiraman, S.; Khalifa, M.; Anandhan, S.; Ghosh, S.; Venimadhav, 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.
Graphene-based elastomer nanocomposites: A fascinating material for flexible sensors in health monitoring
(CRC Press, 2022) Khalifa, M.; SelvaKumar, S.; Anandhan, S.
[No abstract available]
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.
Ionic Surfactant-Assisted PVDF Nanofabrics with High Dielectric and Excellent Piezoelectric Performance
(Korean Fiber Society, 2024) Khalifa, M.; Lammer, H.; Anandhan, S.
Flexible dielectrics and piezoelectric sensors have attracted a number of applications in advanced electronic systems. In this regard, poly(vinylidene fluoride) (PVDF) is considered as a promising option due to its flexibility and ferroelectric properties. In this study, a highly flexible non-woven fabric was developed from electrospun PVDF nanofibers containing cationic and anionic surfactants. Cetrimonium bromide (CTAB) was used as a cationic surfactant, while sodium lauryl sulfate (SLS) was used as an anionic surfactant. The presence of cationic and anionic surfactants played a pivotal role in the production of finer fibers. PVDF-SLS nano-fabric exhibited oriented fibers, while PVDF-CTAB nano-fabric displayed randomly arranged fibers. PVDF-SLS-based nano-fabric displayed the highest β-phase content of 98.2%, while PVDF-CTAB non-woven showed a β-phase content of 91.6%. A significant improvement in the dielectric properties of PVDF nano-fabric was observed upon the addition of cationic and anionic surfactants. Furthermore, PVDF-SLS nano-fabric demonstrated exceptional dielectric and piezoelectric properties, generating a piezoelectric voltage of ~ 19 V. In comparison, PVDF-CTAB nano-fabric exhibited a piezoelectric voltage of 12.5 V. The power density of PVDF improved significantly upon the addition of SLS surfactant. Such attributes position PVDF-SLS nanofabrics as valuable candidates for diverse applications, particularly in the field of piezoelectric sensors and energy storage devices. The research not only advances the understanding of optimizing PVDF nanofabrics, but also establishes a foundation for future exploration in the realm of flexible electronics. Graphical Abstract: (Figure presented.) © The Author(s), under exclusive licence to the Korean Fiber Society 2024.
Physicochemical characteristics of bio-based thermoplastic polyurethane/graphene nanocomposite for piezoresistive strain sensor
(John Wiley and Sons Inc. P.O.Box 18667 Newark NJ 07191-8667, 2020) Khalifa, M.; Ekbote, G.S.; Anandhan, S.; Wuzella, G.; Lammer, H.; Mahendran, A.R.
Herein, we report the physicochemical characteristics and piezoresistive strain sensing performance of flexible thin film comprising graphene and bio-based thermoplastic polyurethane (TPU) prepared by solution cast method. A detailed analysis was carried to study the influence of graphene nanoplatelets on the morphological, thermal, mechanical, and electrical properties of TPU nanocomposite. Upon increasing the graphene nanoplatelets loading, the thermal stability and tensile properties improved remarkably, while glass transition temperature decreased slightly. Owing to better dispersion of graphene, the electrical conductivity was significantly increased, which broaden the utilization of the nanocomposite for various applications. The piezoresistive sensor was able to respond to various stress modes such as tapping, bending, and finger touch. The piezoresistive sensor was sensitive and achieved a gauge factor of 11. Sensor attached to finger, showed distinctive response upon bending at different angles and showed high stability and reproducibility even after >10,000 cycles under repetitive constant load. Also, the nanocomposite was able to detect any breakage or fracture in the form of change in electrical resistance. A combination of bio-based TPU and graphene offered improved physical properties and high sensing performance, which could be a potential material in flexible electronics and structural health monitoring systems. © 2020 Wiley Periodicals, Inc.
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.
Polymer Electrolytes and Separators for Magnesium-Ion Batteries
(CRC Press, 2024) Singh, R.; Khalifa, M.; Janakiraman, S.; Adyam, V.; Anandhan, S.; Biswas, K.
Magnesium (Mg)-ion-based rechargeable batteries are attractive because magnesium is bivalent, abundant, non-toxic, and inexpensive. In the development of Mg-ion batteries (MIBs) with high energy densities, their ionic conductivity and safety have become important features. The most commonly used cathodes are Mo6S8, MoO3, V2O5, MnO2, and TiO2, but they are limited due to low voltages (<2.0 V) and low specific capacities. Therefore, electrolytes are needed to improve the voltage stability and ease of synthesis. In this chapter, polymer electrolytes and separators in MIBs with liquid or gel electrolytes are briefly outlined. Polymer electrolytes are classified into two categories, namely solid polymer electrolytes and gel polymer electrolytes (GPEs). Solid polymer electrolytes have several advantages such as high safety, lightweight, and favorable mechanical properties, but their weakness is their relatively lower ionic conductivity. To overcome these issues, GPE, which is a combination of liquid electrolyte and a polymer matrix, is explored. Poly(vinylidene fluoride)-based gel electrolytes showed a high ionic conductivity of the order of 10−3 S cm−1 at room temperature. In GPEs, an electrolyte is used as an ion transport medium between the electrodes, whereas a polymer membrane acts as a separator, thereby eliminating the physical contact between the electrodes. © 2025 selection and editorial matter, Prasanth Raghavan, Akhila Das, and Jabeen Fatima M. J.
Probing the synergism of halloysite nanotubes and electrospinning on crystallinity, polymorphism and piezoelectric performance of poly(vinylidene fluoride)
(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.
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.
PVDF Nanofibers with Embedded Polyaniline-Graphitic Carbon Nitride Nanosheet Composites for Piezoelectric Energy Conversion
(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.