Bismuth oxide (Bi 2 O 3 ) reinforced PDMS composites for gamma-ray shielding: experimental NaI (Tl) spectroscopy and Phy-X/WinXCom validation

Lightweight, non-toxic radiation shielding materials are increasingly required for terrestrial applications where conventional lead-based shields are limited by mass and toxicity. This study investigates polydimethyl-siloxane (PDMS) composites loaded with bismuth oxide (Bi2O3) as flexible gamma-ray attenuators. Four samples were fabricated: neat PDMS and PDMS filled with 20, 30, and 40 wt% Bi2O3. Gamma-ray attenuation was evaluated experimentally using NaI (Tl) spectroscopy with Ba-133, Cs-137, and Co-60 sources, and compared against simulation outputs from Phy-X and WinXCom. Key shielding parameters were derived, including the mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), and half value layer (HVL), tenth value layer (TVL), and mean free path (MFP). Increasing Bi2O3 loading consistently enhanced attenuation, yielding higher MAC and LAC and lower HVL, TVL, and MFP across measured energies. Experimental extremes ranged from MAC = 0.04876 cm2/g (neat PDMS at 1332 keV) to MAC = 0.162 cm2/g (40 wt% Bi2O3 at 356 keV), and from LAC = 0.04706 cm−1 (neat PDMS at 1332 keV) to LAC = 0.6680 cm−1 (40 wt% Bi2O3 at 356 keV). Simulations reproduced experimental trends closely, generally predicting slightly higher attenuation. These results support Bi2O3-PDMS composites as promising lead free candidate shields where reduced toxicity, and weight savings are critical.