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

## TL;DR

This paper studies new materials containing cadmium and heavy metals that can block gamma rays, charged particles, and neutrons more effectively than traditional materials like lead.

## Contribution

The study introduces Hf2CdC as a novel, high-density material with superior radiation shielding properties across multiple types of radiation.

## Key findings

- Hf2CdC outperforms lead in gamma-ray shielding with a lower half-value layer at 1173 keV.
- Hf2CdC has a high fast neutron removal cross section and excellent thermal neutron absorption due to cadmium.
- The material's high density contributes to its effectiveness in blocking charged particles and gamma rays.

## Abstract

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.