Development of SiO2-reinforced natural rubber vulcanizate composite with Gd2O3 additions for neutron shielding applications.

Flexible composite materials with excellent mechanical properties that exhibit neutron moderation and absorption are required for effective neutron shielding in various applications. However, the addition of neutron absorbers may be detrimental to the overall mechanical properties of the materials. In this study, SiO2-reinforced natural rubber (NR/SiO2) vulcanizate with addition of Gd2O3 (NR/SiO2-Gd2O3) was investigated to develop a flexible material with good mechanical and neutron attenuation properties. NR/SiO2 and NR/SiO2-Gd2O3with Gd2O3 concentrations of 5-15 phr were fabricated and characterized for their curing, mechanical, physicochemical, and thermal neutron attenuation properties. The results show that the vulcanizates retained acceptable hardness, tensile strength, elongation at break, and tear strength despite the addition of Gd2O3, with only moderate decreases observed. SEM-EDS mapping confirmed that Gd2O3 and SiO2 were dispersed within the vulcanizate, although micro-agglomeration of Gd2O3 was observed in all samples. The beam hardening correction was applied to estimate the effective neutron attenuation value (Σeff) by linear regression of the experimental values (Σexp) against sample thickness. The Σeff for NR/SiO2 was 2.02 cm-1, whereas the values for NR/SiO2-Gd2O3 were 5.20-9.33 cm-1. These values correspond to an increase in Σeff by a factor of 2.5-4.6 with the addition of Gd2O3 at the investigated concentrations. The value for NR/SiO2 was in close agreement with the theoretical total macroscopic cross section, whereas NR/SiO2-Gd2O3 exhibited smaller values, likely due to the micro-agglomeration of Gd2O3. Nevertheless, the Σeff values were still greater than those of other reported NR vulcanizates.