Browsing by Subject "Electrospun nanofibers"

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    Comparative evaluation of PVDF based piezoelectric nanogenerator (PNG) under various resistive loads for energy harvesting applications
    (Institute of Electrical and Electronics Engineers Inc., 2020) Parali L.; Koc M.; Sari A.
    Piezoelectric nanogenerator (PNG) is a type of sensor that converts mechanical energy to electrical energy by detecting small-scale physical deformation. In this study, to realize a PNG, firstly polyvinylidene difluoride (PVDF) based electrospun nanofiber film is produced through electrospinning system. The obtained nanofiber film was characterized by X-ray powder diffraction (XRD), Scanning Electron Microscopy (SEM), and Fourier Transform Infrared spectroscopy (FTIR). After that, the PNG device was built as the capacitor by locating the PVDF electrospun nanofiber between two aluminum conductive plates and cabled. The piezoelectric energy harvesting analyses of the PNG was defined by taking measurements under various resistive loads. At a vibration frequency of 15 Hz, the effective voltage value of the PNG reached the maximum voltage of 62.6 mV under the resistive load of 750 KΩ while its electrical power was around 5.23 μ W under the same load. The PNG based energy harvesting system aims to obtain electrical energy from the natural vibrational sources for mobile microelectronics. © 2020 IEEE.
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    Structural and luminescent properties of Er3+ and Tb3+-doped sol–gel-based bioactive glass powders and electrospun nanofibers
    (Springer, 2021) Deliormanlı A.M.; Rahman B.; Oguzlar S.; Ertekin K.
    In this study, sol–gel-based erbium (Er3+), terbium (Tb3+) and Er3+: Tb3 co-doped 1393 bioactive glass powders and electrospun nanofibers were prepared. Structural and morphological properties of the bioactive glasses as well as the photoluminescence characteristics were investigated in detail. The median particle size and average diameter of the prepared glass powders and fibers were in the range of ~ 1.5–3.5 μm and 280–660 nm, respectively. The steady-state photoluminescence and decay kinetics of the samples were investigated under excitation (374 nm) where only Er3+ and Tb3+ ions close to Si nanoclusters can be excited. All the samples prepared in the study exhibited bright green emission upon excitation at 374 nm. Results showed that the dopant concentration and the sample morphology have significant influence on the photoluminescence and decay properties of the glasses. Sol–gel-derived bioactive glass particles exhibited stronger emission intensity, whereas electrospun nanofibers showed extended decay times. In vitro bioactivity experiments revealed that Er3+ and Tb3+ doping did not inhibit the conversion of the glass samples to hydroxyapatite treated in simulated body fluid for 30 days. It was concluded that Er3+ and Tb3+-containing 1393 bioactive glasses have a potential to be used in tissue engineering applications as well as bioimaging studies. © 2021, The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature.
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    Piezoelectric and magnetoelectric properties of PVDF/NiFe2O4 based electrospun nanofibers for flexible piezoelectric nanogenerators
    (Elsevier B.V., 2022) Paralı L.; Demirci Dönmez Ç.E.; Koç M.; Aktürk S.
    In this study, flexible piezoelectric nanogenerators (PNGs) were fabricated using the composite fibers which were prepared by combining polyvinylidene difluoride (PVDF) and nickel ferrite (NiFe2O4) nanoparticles (NPs) at a concentration of 1, 3, 5, 7, and 10 wt%. The piezoelectric properties of PNG indicate that the PVDF/NiFe2O4 fibers containing NiFe2O4 NPs at a concentration of 10 wt% has a higher power efficiency of 5.4% at 20 Hz compared to that of the pure PVDF fibers at 10 Hz, under the same resistive load of 2.5 MΩ. The magnetoelectric properties of PNG show that the PNG with PVDF+7 wt%NiFe2O4 supplied the highest electrical power of 0.40 μW under a resistive load of 750KΩ while it reached a maximum voltage value of 17.50 mV at the same load resistive load for a low-level magnetic field of 50 Hz frequency. © 2022 Korean Physical Society