Comparative mechanical, self-healing, and gamma attenuation properties of PVA hydrogels containing either nano- or micro-sized Bi2O3 for use as gamma-shielding materials

This work investigated the gamma-shielding, mechanical, and self-healing properties of polyvinyl alcohol (PVA) hydrogels with the addition of varying bismuth oxide (Bi2O3) contents (0 wt%, 20 wt%, and 40 wt%) and particle sizes (nanoparticles and micro-particles) based on samples prepared using a one-cycle freezing/thawing method. The results indicated that the gamma-shielding properties of the hydrogels increased with increasing Bi2O3 content and that nanocomposites had a greater capability to attenuate incident gamma rays than micro-composites, determined at the same content and thickness. Furthermore, the developed hydrogels had excellent self-healing capabilities at their fractured surfaces, as seen by the percentage of recoverable strength (% Recovery) which was as high as 95.9% in 20 wt% nano-sized Bi2O3/PVA hydrogel after being self-healed within 1 min. In terms of mechanical properties, higher Bi2O3 contents led to increased tensile modulus at 100% elongation and tensile strength but elongation at break was relatively unchanged, with nanocomposites again having higher overall mechanical strength and self-healing capability than micro-composites. In summary, the overall properties suggested that autonomously self-healing Bi2O3/PVA hydrogels had great potential to be utilized as 'smart' gamma-shielding materials and that nanocomposites had higher overall gamma-shielding, mechanical, and self-healing properties.