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<p>This work reports the sustainable synthesis of iron-doped silica nanoparticles derived from waste concrete (Fe-doped WC NPs) via the sol–gel method, with Fe<sub>2</sub>O<sub>3</sub> doping levels ranging from 0 to 15 wt%. Structural analyses confirmed the presence of a hexagonal SiO<sub>2</sub> phase, along with the emergence of secondary phases, including sillimanite (Al<sub>2</sub>SiO<sub>5</sub>) and calcium iron oxide (CaFe<sub>2</sub>O<sub>4</sub>). The presence of such phases, originating from the intrinsic chemistry of waste concrete, influences both optical absorption and radiation shielding. The crystallite size, lattice strain, and dislocation density exhibited nonlinear trends, reflecting the dual role of Fe ions in defect formation and lattice relaxation. Transmittance spectra reveal a gradual decrease in transparency with increasing Fe content, with the direct band gap narrowing from 3.95&#xa0;eV (undoped) to 3.66&#xa0;eV (15 wt% Fe), accompanied by an increase in Urbach energy from 0.84 to 1.88&#xa0;eV, indicative of enhanced structural disorder. The effective refractive index, dielectric constant, and extinction coefficient increased with the Fe content, confirming improved polarizability and optical absorption. Radiation shielding simulations demonstrated that the Fe-rich samples, particularly WC-Fe-15, exhibited superior gamma-ray attenuation, achieving a high linear attenuation coefficient of 49.07&#xa0;cm<sup>–1</sup> at 0.015&#xa0;MeV, a low half-value layer of 0.014&#xa0;cm, and the highest effective atomic number (Z<sub>eff</sub> = 19.85). These findings highlight Fe-doped WC NPs as promising multifunctional materials for optical and eco-friendly radiation shielding applications.</p>

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Sustainable synthesis of Fe-enriched multiphase silica-based nanocomposites from concrete waste: optical property optimization and gamma-shielding efficiency

  • 期刊论文

  • 发表日期：

    2026年7月17日

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  • A. M. A. Mostafa,
  • Ahmed S. Ali,
  • Shams A. M. Issa,
  • Ahmed M. Hassan,
  • M. A. Uosif,
  • Ivan S. Zhidkov,
  • H. M. H. Zakaly

摘要

This work reports the sustainable synthesis of iron-doped silica nanoparticles derived from waste concrete (Fe-doped WC NPs) via the sol–gel method, with Fe2O3 doping levels ranging from 0 to 15 wt%. Structural analyses confirmed the presence of a hexagonal SiO2 phase, along with the emergence of secondary phases, including sillimanite (Al2SiO5) and calcium iron oxide (CaFe2O4). The presence of such phases, originating from the intrinsic chemistry of waste concrete, influences both optical absorption and radiation shielding. The crystallite size, lattice strain, and dislocation density exhibited nonlinear trends, reflecting the dual role of Fe ions in defect formation and lattice relaxation. Transmittance spectra reveal a gradual decrease in transparency with increasing Fe content, with the direct band gap narrowing from 3.95 eV (undoped) to 3.66 eV (15 wt% Fe), accompanied by an increase in Urbach energy from 0.84 to 1.88 eV, indicative of enhanced structural disorder. The effective refractive index, dielectric constant, and extinction coefficient increased with the Fe content, confirming improved polarizability and optical absorption. Radiation shielding simulations demonstrated that the Fe-rich samples, particularly WC-Fe-15, exhibited superior gamma-ray attenuation, achieving a high linear attenuation coefficient of 49.07 cm–1 at 0.015 MeV, a low half-value layer of 0.014 cm, and the highest effective atomic number (Zeff = 19.85). These findings highlight Fe-doped WC NPs as promising multifunctional materials for optical and eco-friendly radiation shielding applications.