ARC Research Hub for Graphene Enabled Industry Transformation publications

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Browsing ARC Research Hub for Graphene Enabled Industry Transformation publications by Author "Atiq, S."

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    Advancing dielectric and ferroelectric properties of piezoelectric polymers by combining graphene and ferroelectric ceramic additives for energy storage applications
    (MDPI, 2018) Ishaq, S.; Kanwal, F.; Atiq, S.; Moussa, M.; Azhar, U.; Imran, M.; Losic, D.
    To address the limitations of piezoelectric polymers which have a low dielectric constant andto improve their dielectric and ferroelectric efficiency for energy storage applications, we designed and characterized a new hybrid composite that contains polyvinylidene fluoride as a dielectric polymer matrix combined with graphene platelets as a conductive and barium titanite as ceramic ferroelectric fillers. Different graphene/barium titanate/polyvinylidene fluoride nanocomposite films were synthesized by changing the concentration of graphene and barium titanate to explore the impact of each component and their potential synergetic effect on dielectric and ferroelectric properties of the composite. Results showed that with an increase in the barium titanate fraction, dielectric efficiency ofthe nanocomposite was improved. Among all synthesized nanocomposite films, graphene/barium titanate/polyvinylidene fluoride nanocomposite in the weight ratio of 0.15:0.5:1 exhibited thehighest dielectric constant of 199 at 40 Hz, i.e., 15 fold greater than that of neat polyvinylidene fluoride film at the same frequency, and possessed a low loss tangent of 0.6. However, AC conductivity and ferroelectric properties of graphene/barium titanate/polyvinylidene fluoride nanocomposite films were enhanced with an increase in the graphene weight fraction. Graphene/barium titanate/polyvinylidene fluoride nanocomposite films with a weight ratio of 0.2:0.1:1 possessed a high AC conductivity of 1.2 × 10-4 S/m at 40 Hz. While remanent polarization, coercive field, and loop area of the same sample were 0.9 μC/cm², 9.78 kV/cm, and 24.5 μC/cm²·V, respectively. Our results showed that a combination of graphene and ferroelectric ceramic additives are an excellent approach to significantly advance the performance of dielectric and ferroelectric properties of piezoelectric polymers for broad applications including energy storage.
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    Dielectric and impedance spectroscopic studies of three phase graphene/titania/poly(vinyl alcohol) nanocomposite films
    (Elsevier, 2018) Ishaq, S.; Kanwal, F.; Atiq, S.; Moussa, M.; Azhar, U.; Gul, I.; Losic, D.
    Flexible dielectric polymer composites with high dielectric permittivity and low dielectric loss have many applications in different areas of electronic industry. In this paper, we propose synthesis of flexible dielectric materials with efficient dielectric properties. We increased dielectric efficiency of poly(vinyl alcohol) by reinforcement of conducting graphene and rutile titania fillers in different weight fractions. The superiority of this method is that synthesized three phase graphene/titania/poly(vinyl alcohol) nanocomposite films have high dielectric permittivity, low dielectric loss and are flexible. Our results show that graphene/titania/poly(vinyl alcohol) with weight/weight fraction of 3:20:100 bears dielectric permittivity of 330 at 20 Hz that is about 36 times larger than that of neat PVA at same frequency. At this frequency above mentioned graphene/titania/poly(vinyl alcohol) nanocomposite has loss tangent of 4.39 acceptable for dielectrics in embedded capacitors and AC conductivity of 1.6 × 10⁻⁶ Sm⁻¹ that is much greater than that of neat PVA i.e; 6.5 × 10⁻⁹ Sm⁻¹. Complex impedance spectroscopy, complex electric modulus and Cole-Cole plots of synthesized graphene/titania/poly(vinyl alcohol) nanocomposite films further confirm its better capacitive performance.
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    Dielectric properties of graphene/titania/polyvinylidene fluoride (G/TiO2/PVDF) nanocomposites
    (MDPI, 2020) Ishaq, S.; Kanwal, F.; Atiq, S.; Moussa, M.; Azhar, U.; Losic, D.
    Flexible electronics have gained eminent importance in recent years due to their high mechanical strength and resistance to environmental conditions, along with their effective energy storage and energy generating abilities. In this work, graphene/ceramic/polymer based flexible dielectric nanocomposites have been prepared and their dielectric properties were characterized. The composite was formulated by combining graphene with rutile and anatase titania, and polyvinylidene fluoride in different weight ratios to achieve optimized dielectric properties and flexibility. After preparation, composites were characterized for their morphologies, structures, functional groups, thermal stability and dielectric characterizations by using scanning electron microscopy, X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, thermal gravimetric analysis and impedance spectroscopy. Dielectric results showed that prepared flexible composite exhibited dielectric constant of 70.4 with minor leakage current (tanδ) i.e., 0.39 at 100 Hz. These results were further confirmed by calculating alternating current (AC) conductivity and electric modulus which ensured that prepared material is efficient dielectric material which may be employed in electronic industry for development of next generation flexible energy storage devices.
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    Enhancement of dielectric and ferroelectric properties in flexible polymer for energy storage applications
    (Elsevier, 2020) Ishaq, S.; Kanwal, F.; Atiq, S.; Noreen, S.; Moussa, M.; Azhar, U.; Losic, D.
    In the present paper, synthesis and characterizations of flexible dielectric and ferroelectric polymer films combining different ratios of graphene, barium titanate and polydimethylsiloxane are presented. Broad range of characterization techniques were carried out to confirm their, morphological, structural, chemical, thermal and mechanical (flexibility, stretching, bending and twisting) characteristics. Dielectric studies showed that a high dielectric constant of the nanocomposite was dependent on the ratio of graphene:bariumtitanate: polydimethylsiloxane, showing that ratio of 15:25:100 had a high dielectric constant at high frequency range and the ratio 15:30:100 at the low frequency range. At 2 Hz the ratio 15:30:100 showed a dielectric constant of 116.9 which decreased to 30.6 at 2 MHz, thus showing capacitive nature at full frequency range. Meanwhile dielectric loss was very low i.e., 1.3 at 20 Hz and 0.02 at 2 MHz and AC conductivity was 1.6 × 10−7 S/m. Ferroelectric properties like energy density, energy loss and efficiency were calculated and compared. At an electric field of 0.92 kV/cm, remanant polarization and coercive field were 3.9×10−4 μC/cm2 and15.82 kV/cm, respectively. Energy density of 0.64 J/m3, energy loss 0.358 J/m3 and efficiency 64.2% were confirmed respectively. Results indicate that the nanocomposite films having desirable performances such as flexibility, thermal stability, high dielectric constant, high energy density are good candidates to be considered in energy storage and memory device applications.
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    Synthesis of three phase graphene/titania/polydimethylsiloxane nanocomposite films and revealing their dielectric and impedance properties
    (Elsevier, 2019) Ishaq, S.; Kanwal, F.; Atiq, S.; Moussa, M.; Losic, D.
    Compounds and composites with high dielectric performance are in high demand in electronic industry due to their ability to store more charge and lower energy dissipation. In this paper we present synthesis of flexible three phase nanocomposite films of graphene/titania/polydimethylsiloxane with reasonably high real part of permittivity and very low imaginary part of permittivity. Dielectric permittivity of polydimethylsiloxane was raised by addition of graphene and rutile titania used as conducting and ceramic additives, respectively added in various weight ratios. Dielectric studies of synthesized three phase graphene/titania/polydimethylsiloxane nanocomposite films with weight/weight of 2:15:20 exhibits dielectric permittivity of 34.8 even at very high frequency of 2 MHz. While loss tangent of the same three phase graphene/titania/polydimethylsiloxane nanocomposite film is as low as 0.01 and its AC conductivity is 4.3 × 10⁻⁵ Sm⁻¹. Complex impedance and complex electric modulus of three phase graphene/titania/polydimethylsiloxane nanocomposite films also confirm its capacitive behaviour. Based on these properties and results we propose that these type of three phase graphene/titania/polydimethylsiloxane nanocomposite films can be used as useful dielectric materials in energy storage devices.