Enhanced Bentonite/PVA Matrix for Advanced Shielding Applications

The shielding characteristics of natural bentonite can be enhanced based on calcination and ball-milling processes for protection against gamma radiation. The calcination process increases the content of the oxide, which enhances the mass attenuation coefficient; however, the elimination of water and organic matter from bentonite clay structures increases the particle size, where large particle size has a negative effect on this mass attenuation coefficient. Therefore, the calcinated bentonite has been ball-milled to reduce the particle size and improve the attenuation properties of natural bentonite. Furthermore, the calcination process occurs at 700°C for 2 h because dehydration is completed above 500°C while dehydroxylation is observed at 700°C. Therefore, the shielding parameters have been determined for calcinated, ball-milled, pressed bentonite clay samples according to different gamma-ray energies (662, 1173, and 1332 keV), where the experimental setup is based on narrow beam transmission techniques with two sources (¹³⁷Cs and ⁶⁰Co). In addition, the particle size of bentonite clay has been characterized using X-ray diffraction patterns depending on two different methods: dynamic light scattering and Williamson-Hall size analyses. This study shows that the calcinated, ball-milled bentonite pressed at 150 bar has the highest linear and mass attenuation coefficients of μ = 0.13 cm⁻¹ and μ_m = 0.082 cm²/gm, respectively. Moreover, the experimental and theoretical investigation of the mass attenuation coefficient is in good agreement.