γ‑Ray, Charged Particle, and Neutron Attenuation Characteristics of Cadmium-Containing 211 MAX Phase Carbides, M2CdC (M = Ti, Zr, and Hf).

This study examines the attenuation behavior of γ rays and both charged (proton, α, electron) and uncharged (neutron) particles in cadmium-containing Group 4 MAX phase carbides: Ti2CdC, Zr2CdC, and Hf2CdC. Key parameters such as the linear attenuation coefficient (LAC), atomic cross section (ACS), electronic cross section (ECS), half-value layer (HVL), mean free path (MFP), effective atomic number (Z eff), and energy absorption buildup factor (EABF) were evaluated for γ-ray interactions. Among the studied materials, Hf2CdC, with a density of 12.67 g/cm3, exhibited superior γ-ray shielding performance, reflected in its high LAC and low HVL and MFP. Its effectiveness is comparable to that of conventional shielding materials such as lead (Pb). Notably, Hf2CdC demonstrated an HVL of 0.968 cm at 1173 keV, outperforming Pb (0.990 cm) at the same energy. This enhanced performance at γ energies dominated by Compton scattering is primarily attributed to its high density. For charged particles, Ti2CdC showed the highest mass stopping power for protons and α particles. However, due to its higher density, Hf2CdC resulted in the shortest penetration depths; for example, 10 MeV protons had a penetration range of only 1.77 μm in Hf2CdC. Additionally, Hf2CdC exhibited a high fast neutron removal cross section (FNRCS) of 0.163 cm-1, significantly outperforming common neutron shielding materials such as B4C, graphite, and concrete. Furthermore, all three compounds demonstrated excellent thermal neutron absorption due to the presence of cadmium (Cd), with Hf2CdC achieving the highest thermal neutron LAC of 43.38 cm-1. These results identify Hf2CdC as a strong candidate for integrated, multipurpose radiation shielding applications.