Abstract
This work theoretically determined the high-energy photon shielding properties of high-density polyethylene (HDPE) composites containing rare-earth oxides, namely samarium oxide (Sm2O3), europium oxide (Eu2O3), and gadolinium oxide (Gd2O3), for potential use as lead-free X-ray-shielding and gamma-shielding materials using the XCOM software package. The considered properties were the mass attenuation coefficient (µm), linear attenuation coefficient (µ), half value layer (HVL), and lead equivalence (Pbeq) that were investigated at varying photon energies (0.001–5 MeV) and filler contents (0–60 wt.%). The results were in good agreement (less than 2% differences) with other available programs (Phy-X/PSD) and Monte Carlo particle transport simulation code, namely PHITS, which showed that the overall high-energy photon shielding abilities of the composites considerably increased with increasing rare-earth oxide contents but reduced with increasing photon energies. In particular, the Gd2O3/HDPE composites had the highest µm values at photon energies of 0.1, 0.5, and 5 MeV, due to having the highest atomic number (Z). Furthermore, the Pbeq determination of the composites within the X-ray energy ranges indicated that the 10 mm thick samples with filler contents of 40 wt.% and 50 wt.% had Pbeq values greater than the minimum requirements for shielding materials used in general diagnostic X-ray rooms and computerized tomography rooms, which required Pbeq values of at least 1.0 and 1.5 mmPb, respectively. In addition, the comparisons of µm, µ, and HVL among the rare-earth oxide/HDPE composites investigated in this work and other lead-free X-ray shielding composites revealed that the materials developed in this work exhibited comparable X-ray shielding properties in comparison with that of the latter, implying great potential to be used as effective X-ray shielding materials in actual applications.
Highlights
High-energy photon technologies, especially those related to X-rays and gamma rays, have been extensively used in several applications such as X-ray and gamma imaging for medical diagnostic and material characterization [1,2,3,4], gamma-induced mutation breeding in plants [5,6], quality control and quality assurance for industrial products [7], and gemstone irradiation for color enhancement [8,9]
The μm values for the Sm2O3/highdensity polyethylene (HDPE), Eu2O3/HDPE, and Gd2O3/HDPE composites at photon energies of 0.001–5 MeV and filler contents of 0, 20, 40, and 60 wt.% are shown in Figure 1
This work determined the theoretical high-energy photon shielding properties for Sm2O3/HDPE, Eu2O3/HDPE, and Gd2O3/HDPE composites with filler contents in the range 0–60 wt.% and photon energies in the range 0.001–5 MeV for the development of Pb-free materials to shield against X-rays and gamma rays with exceptional strength and rigidity
Summary
High-energy photon technologies, especially those related to X-rays and gamma rays, have been extensively used in several applications such as X-ray and gamma imaging for medical diagnostic and material characterization [1,2,3,4], gamma-induced mutation breeding in plants [5,6], quality control and quality assurance for industrial products [7], and gemstone irradiation for color enhancement [8,9]. Examples of rare-earth-oxide-containing materials, previously developed for use as high-energy photon shielding materials, are TeO2-ZnF2As2O3-Sm2O3 glasses [26], waste soda-lime glass doped with La2O3 and Gd2O3 [27], Eu2O3-reinforced zinc-borate glasses [28], erbium (III)- and terbium (III)-containing silicatebased bioactive glass [29], and rare-earth/glassy alloys [30], which all had highly promising photon shielding ability Another important advantage of rare-earth oxides (Sm2O3, Eu2O3, and Gd2O3) over the common Pb, Bi2O3, WO3, and Fe2O3 fillers is that the former are able to attenuate high-energy photons and thermal neutrons with exceptional efficiency (even higher than common borated materials) [31]. The outcomes of this work should reveal theoretically the effectiveness of rare-earth oxides to attenuate high-energy photons and increase the availability of the currently limited information on the use of rare-earth oxides for radiation protection
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