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    Multifunctional GFRC composites: PEDOT: PSS-driven dielectric enhancement for energy storage and sensing applications
    (Elsevier Science Sa, 2026) Demir, Ahmet; Musatat, Ahmad Badreddin; Subasi, Azime; Ramazanoglu, Dogu; Dehgan, Haydar; Marasli, Muhammed; Gencel, Osman
    This study presents a comprehensive investigation into the development and characterization of multifunctional Glass Fiber Reinforced Cement (GFRC) composites enhanced with Poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT: PSS) to impart advanced electrical properties. We systematically analyzed the influence of PEDOT: PSS concentration (0-15 wt %) and curing age on the dielectric behavior of these novel composites, evaluating their capacitance, dielectric constant, loss factor, and electrical modulus across a broad frequency range (10 Hz-10 MHz). The integration of PEDOT: PSS significantly modified the material's electrical characteristics, demonstrating concentration-dependent variations and complex relaxation mechanisms dominated by Maxwell-Wagner interfacial polarization. The optimized P2 formulation (10 wt % PEDOT: PSS) exhibited superior electrochemical performance, maintaining the highest capacitance values and achieving a peak dissipation factor (tan delta) of 0.43 +/- 0.02 at day 15, representing a 185 % enhancement over unmodified GFRC. EDX analysis confirmed successful polymer incorporation, with P2 exhibiting the highest carbon content (5.8 wt %) and sulfur content (1.8 wt %), indicating optimal dispersion. Equivalent circuit models were established and validated (R2 > 0.98), providing insights into complex charge transport mechanisms within this hybrid material. Microstructural analyses via scanning electron microscopy revealed significant morphological modifications, including the formation of crystalline and plate-like structures, while complementary FT-IR and TGA analyses confirmed polymer-cement interaction stability and thermal stability up to 450 degrees C. These findings establish fundamental design principles for creating electrically conductive cementitious materials with tunable dielectric properties, enabling strategic deployment in innovative infrastructure systems, energy storage devices, and electromagnetic shielding technologies.
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    Polarization and relaxation mechanisms in glass fiber-reinforced LED-cured polyester composites incorporating graphene nanotubes
    (Elsevier, 2023) Subasi, Azime; Emiroglu, Mehmet; Demir, Ahmet
    The current research aimed to understand how the polarization and relaxation mechanisms in light-emitting diode (LED) cured glass fiber reinforced polyester (GFRP) composites change with graphene nanotubes (GNTs). In this context, the complex permittivity (?*), loss tangent (tan & delta;), AC electrical conductivity (& sigma;), and complex modulus (M*) features of the samples were measured via impedance spectroscopy. According to the virtual electrical modulus values, electrical polarization occurred after the first peak at 127 kHz. With increasing GNT ratio, a polarization mechanism was obtained at approximately 350 kHz as a result of a shift towards higher frequencies. Although a significant change was observed in the electrical conductivity value as the frequency increased depending on the GNT ratio, there was no change in the conductivity values up to 10 kHz. At high frequencies, dipole formation and orientation occurred, resulting in an increase in conductivity up to 150 kHz.