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Öğe A novel lanthanum hexaboride-modified cementitious composites: evolution and microstructural architecture of LaB6-integrated GFRC systems with enhanced dielectric response(Elsevier Science Sa, 2026) Demir, Ahmet; Subasi, Serkan; Dehgan, Haydar; Ramazanoglu, Dogu; Marasli, Muhammed; Aksu, Mecit; Subasi, AzimeThis study investigates the integration of lanthanum hexaboride (LaB6) microparticles into glass fiber-reinforced concrete (GFRC) to improve its dielectric and microstructural properties. GFRC mixtures with 1-3 % LaB6 replacement were characterized for capacitance, impedance, dielectric constant (epsilon ' and epsilon ''), dissipation factor (tan delta), electrical modulus (M ' and M ''), and Cole-Cole diagrams across varying frequencies (20 Hz-5 MHz) and hydration times (7-58 days). Comprehensive Microstructural, Thermal Stability, and Chemical Characterization analyses were also performed. Results demonstrate that LaB6 significantly improves GFRC's capacitance, conductivity, and dielectric properties. Specifically, L2 and L3 samples exhibited capacitance values approximately 100 times higher than the reference and L1 samples after 56 days, and approximately 25 times greater capacitance behavior across the tested frequency spectrum. The real dielectric constant (epsilon ') reached 250-fold, decreasing by about 10 times with LaB6 addition in L2 and L3, indicating improved insulation. Dielectric losses (epsilon '') were also markedly higher for L2 and L3, approaching 100 times greater than R and L1, implying favorable conductive functionality. Cole-Cole analysis indicated minimal dielectric dispersion for L2 and L3, suggesting near-ideal polarizable interfaces. Equivalent circuits were fitted, demonstrating that LaB6 significantly influences the electrical transport and storage mechanisms within the GFRC composites, leading to improved dielectric performance. Scanning electron microscopy (SEM) revealed denser microstructures, while thermogravimetric analysis (TGA), differential thermal analysis (DTA), and Fourier-transform infrared spectroscopy (FTIR) corroborated enhanced thermal stability, bond strength, and favorable microstructural interactions. These findings highlight LaB6 as a promising additive for developing high-performance cementitious composites with tailored electrical responses for smart concrete applications.Öğe Electrical and dielectric tailoring of glass fiber-reinforced concrete using ZnO-based hybrid nanocomposites(Springer, 2026) Ramazanoglu, Dogu; Musatat, Ahmad Badreddin; Subasi, Azime; Demir, Ahmet; Subasi, Serkan; Marasli, MuhammedThis study investigates frequency-dependent dielectric and electrical transport properties of glass fiber-reinforced concrete (GFRC) systematically doped with ZnO-based hybrid composite (ZnO-@) nanoparticles at 1%, 2%, and 3% mass fractions. Electrical impedance spectroscopy (20 Hz-5 MHz) coupled with microstructural characterization (SEM-EDX, FTIR) and mechanical validation establishes concentration-dependent polarization mechanisms governing electromagnetic property modulation. The 2% ZnO-@ formulation exhibits optimal dielectric enhancement with maximum real permittivity (epsilon '), superior AC conductivity (100 Hz-10 kHz domain), and 100% imaginary modulus augmentation (M ''), attributed to Maxwell-Wagner-Sillars interfacial polarization at ZnO-cement matrix boundaries. Equivalent circuit modeling reveals that grain boundary resistance escalates to 5.8 M Omega at optimal doping, and constant phase element (CPE) exponent values (P = 0.77-0.84) confirming non-Debye relaxation due to hierarchical microstructural heterogeneity. The critical percolation threshold, between 2% and 3% ZnO concentration, demarcates the transition from capacitive to conductive behavior, where specimens at 3% exhibit dielectric parameter regression toward baseline values due to nanoparticle agglomeration and the formation of conductive pathways. Spectroscopic validation confirms the integration of wurtzite-phase ZnO (Zn-O: 474 cm(-)1) with preserved calcium silicate hydrate phases, while post-aging Leeb hardness measurements demonstrate 171-176% mechanical reinforcement (387-456 HLD), validating the retention of structural durability. These findings establish quantitative compositional guidelines for engineering multifunctional construction composites with tailored electromagnetic response characteristics for interference shielding, capacitive energy storage, and electromagnetically compatible innovative infrastructure applications.Öğe 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, OsmanThis 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.Öğe Polarization and relaxation mechanisms in glass fiber-reinforced LED-cured polyester composites incorporating graphene nanotubes(Elsevier, 2023) Subasi, Azime; Emiroglu, Mehmet; Demir, AhmetThe 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.
