Halloysite-based clay bricks as an efficient γ-ray protective material: Experimental evaluation for the structural, thermal, and γ-ray attenuation properties

The current study aims to fabricate brick series based on natural halloysite clay for radiation shielding applications. The brick series consists of six prepared brick samples that have the same halloysite chemical composition, but they were molded under various pressure rates that varied between 7.61 MPa and 114.22 MPa. The density of the prepared bricks based on halloysite increased from 2.123 g/cm 3 to 2.701 g/cm 3 when the pressure rate increased from 7.6 MPa to 11.22 MPa, respectively. X-ray diffraction, scanning electron microscopy, and energy-dispersive X-rays were utilized to examine the structural properties of the natural halloysite used in the brick's fabrication process. The thermal properties of the prepared samples were also investigated using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The obtained results showed that raising the temperature from 150 o C to 500 o C increases the mass loss in halloysite from 2 to 9 %. Then, the impact of pressure rate on the linear attenuation coefficient (LAC, cm −1 ) of prepared bricks was investigated experimentally using the NaI(Tl) detector and the narrow beam transmission method. The linear attenuation coefficient of prepared bricks increased from 0.176 cm −1 to 0.225 cm −1 (at 0.662 MeV), 0.135 cm −1 to 0.169 cm −1 (at 1.173 MeV), and 0.122 cm −1 to 0.153 cm −1 (at 1.332 MeV), respectively, when the fabrication pressure rate raised from 7.61 MPa to 114.22 MPa.