Comparative X-ray Shielding Properties of Single-Layered and Multi-Layered Bi(2)O(3)/NR Composites: Simulation and Numerical Studies

This work theoretically compared the X-ray attenuation capabilities in natural rubber (NR) composites containing bismuth oxide (Bi(2)O(3)) by determining the effects of multi-layered structures on the shielding properties of the composites using two different software packages (XCOM and PHITS). The shielding properties of the single-layered and multi-layered Bi(2)O(3)/NR composites investigated consisted of the transmission factor (I/I(0)), effective linear attenuation coefficient (µ(eff)), effective mass attenuation coefficient (µ(m,eff)), and effective half-value layer (HVL(eff)). The results, with good agreement between those obtained from XCOM and PHITS (with less than 5% differences), indicated that the three-layered NR composites (sample#4), with the layer arrangement of pristine NR (layer#1)-Bi(2)O(3)/NR (layer#2)-pristine NR (layer#3), had relatively higher X-ray shielding properties than either a single-layer or the other multi-layered structures for all X-ray energies investigated (50, 100, 150, and 200 keV) due to its relatively larger effective percentage by weight of Bi(2)O(3) in the composites. Furthermore, by varying the Bi(2)O(3) contents in the middle layer (layer#2) of sample#4 from 10 to 90 wt.%, the results revealed that the overall X-ray shielding properties of the NR composites were further enhanced with additional filler, as evidenced by the highest values of µ(eff) and µ(m,eff) and the lowest values of I/I(0) and HVL(eff) observed in the 90 wt.% Bi(2)O(3)/NR composites. In addition, the recommended Bi(2)O(3) contents for the actual production of three-layered Bi(2)O(3)/NR composites (the same layer structure as sample#4) were determined by finding the least Bi(2)O(3) content that enabled the sample to attenuate incident X-rays with equal efficiency to that of a 0.5-mm lead sheet (with an effective lead equivalence of 0.5 mmPb). The results suggested that the recommended Bi(2)O(3) contents in layer#2 were 82, 72, and 64 wt.% for the combined 6 mm, 9 mm, and 12 mm samples, respectively.