Sustainable hybrid epoxy composites with natural fillers for radiation shielding applications

This study presents the systematic development and in-depth characterization of novel, sustainable, and lightweight hybrid epoxy composites reinforced with mahogany wood, periwinkle shell, and granite particles. These composites were specifically engineered for dual-function gamma-ray and fast neutron shielding applications. The materials were synthesized using varying filler mass fractions (10-20 wt%) and particle sizes (100 mu m and 700 mu m) under a Taguchi L4 orthogonal design to ensure optimized performance. FTIR spectroscopy confirmed that the chemical treatment of mahogany wood successfully removed organic compounds such as lignin, cellulose, and hemicellulose, thereby enhancing the interfacial bonding between fillers and the epoxy matrix. SEM and EDX analyses showed uniform filler distribution with minimal voids and revealed elemental contributions from high-Z elements like calcium and silicon, which are critical for radiation attenuation. Gamma-ray shielding performance was evaluated using a calibrated Ba-133 radioactive source covering energies from 81 to 383 keV. Among all tested samples, the A4 composite (700 mu m, 20 wt%) displayed the best performance, achieving mass attenuation coefficients (MAC) ranging from 0.1939 to 0.0984 cm2/g. This composite also demonstrated the lowest half-value layer (HVL) and buildup factors, along with the highest effective atomic number (Zeff), confirming its superior photon attenuation efficiency. These results highlight the impact of both high-Z content and optimized particle size on enhancing photon interaction probabilities and reducing secondary radiation hazards. In addition, neutron shielding capability was assessed using a 4.5 MeV Am-Be neutron source. The removal cross sections (Sigma R) for composites A3 and A4 were found to be 0.08313 cm(-)1 and 0.0758 cm(-)1, respectively, values that approach those of standard materials like graphite (0.07773 cm(-)1) and water (0.1023 cm(-)1). Furthermore, absorbed neutron dose measurements demonstrated a significant increase from 5.92% in A1 to 22.08% in A4, indicating enhanced neutron attenuation due to the synergistic effects of hydrogen-rich wood and calcium-rich shell fillers. These findings suggest that integrating both organic and inorganic bio-based fillers yields environmentally friendly composites with excellent gamma and neutron shielding properties. The combination of radiation attenuation efficiency, lightweight nature, cost-effectiveness, and sustainability makes these composites attractive candidates for practical applications in nuclear medicine, aerospace systems, radiological protection, and industrial shielding.