Micro and nano Bi₂O₃ filled epoxy composites: Thermal, mechanical and γ-ray attenuation properties

Polymer composites have attracted considerable attention as potential light-weight and cost-effective materials for radiation shielding and protection. In view of this, the present work focusses on development of lead-free composites of diglycidyl ether of bisphenol A (DGEBA) epoxy resin with micro (~ 10 μm) and nano (~ 20 nm) bismuth (III) oxide (Bi₂O₃) fillers, using solution casting technique. Thermal, mechanical and γ-ray attenuation properties of the composites were studied by varying the filler loading. Inclusion of the fillers into epoxy matrix was confirmed both structurally and morphologically by XRD and SEM, respectively. Thermogravimetric analysis (TGA) showed the thermal stability of composites to be as high as 400 °C. The nanocomposites exhibited relatively higher thermal stability than their micro counterparts. Among the composites, 14 wt% nano-Bi₂O₃/epoxy composites showed highest tensile strength of 326 MPa, which is about 38% higher than 30 wt% micro Bi₂O₃/epoxy composites. Mass attenuation coefficients (μ/ρ) of the composites were evaluated at γ-ray energies ranging from 0.356 to 1.332 MeV. Nanocomposites showed better γ-ray shielding at all energies (0.356, 0.511, 0.662, 1.173, 1.280 and 1.332 MeV) than micro composites with same filler loading. These studies revealed the significance of nano-sized fillers in enhancing overall performance of the composites.