Shielding characteristics of nanocomposites for protection against X- and gamma rays in medical applications: effect of particle size, photon energy and nano-particle concentration

Multi-nanoparticle-based composite for diagnostic X-ray shielding in computed tomography applications: a Monte Carlo study

While numerous studies have investigated the impact of various nanoparticles (NPs) in polymer matrices for radiation shielding, there is a notable gap in the literature regarding a comprehensive examination of both individual and combined selected NPs with functional polymers. This study aims to address this gap by systematically evaluating the synergistic potential of multiple high-Z NPs and specialized polymer matrices in radiation shielding design, particularly for computed tomography (CT) applications. A single and mixture range of NPs, including Gd2O3, Sm2O3, CeO2, HfO2, IrO2, Bi2O3, and WO3, were combined with polymers such as chlorinated polyvinyl chloride (CPVC), polychlorostyrene (PCS), polytrifluorochloroethylene (PTFCE), polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), and polyvinylidene chloride (PVDC) which served as matrices. By means of Geant4 Monte Carlo simulations, the study assessed the shielding effectiveness of these nanocomposites at various X-ray energies (80, 100, 120, and 140 kVp). The results revealed that nanocomposites containing Sm2O3 and Gd2O3 exhibited superior X-ray attenuation at 80 and 100 kVp, while the HfO2 nanocomposite demonstrated enhanced shielding at 120 and 140 kVp. Additionally, multi-filler nanocomposites with 30 wt% of Sm2O3 + HfO2 (SmHf) and Gd2O3 + Bi2O3 (GdBi) exhibited improved performance at 80 and 140 kVp, respectively. Notably, the 30 wt% Gd2O3 + IrO2 (GdIr) multi-filler nanocomposite outperformed others at 100 and 120 kVp. It is concluded that a combination of NPs with K-edge values close to the mean energy of the investigated X-ray spectra provide better shielding capabilities than single NPs, highlighting their potential for applications in radiation protection.

Promising application of nano-WO3/epoxy composite in intensity-modulated brachytherapy: a simulation study

PURPOSE

Implementing intensity-modulated brachytherapy (IMBT) techniques with high-energy sources like 60Co has always been challenging due to the clinical limitations of the applicator dimensions. This study aims to investigate using tungsten trioxide nanoparticles/epoxy composite as a shielding material to enhance the protective properties of a redesigned applicator.

MATERIALS AND METHODS

The Geant4 application to tomographic emission, the Geant4-based Monte Carlo dose calculation engine (version 9.0), was used to simulate the shielding composite and the IMBT technique with a voxelated patient-based phantom. To evaluate the effectiveness of the new shielding material, IMBT plans created with the redesigned applicator were compared with those with a conventional applicator. 60Co and 192Ir were utilized, and in the same high-risk clinical target volumes D90, the D2cc for the bladder and rectum were evaluated in 18 patients with vaginal cancer.

RESULTS

For the IMBT plans with the 60Co source, the use of the redesigned applicator decreased the D2cc of the bladder and rectum by 11.1% and 12.8%, respectively, while for those with the 192Ir source, the reduction was 16.6% and 18.7%, respectively. Nevertheless, there was an insignificant alteration in the absorbed dose parameter (D90) for the target using both sources.

CONCLUSION

This study demonstrates that tungsten trioxide nanoparticle/epoxy composite can be advantageous in tackling radiation shielding concerns. Enhancing the shielding properties of this composite, considering the size limitations of applicators, leads to improved protection of organs at risk, such as the bladder and rectum. This substance can be considered a promising shielding material in the construction of applicators.

Eggshell-derived particle composites with epoxy resin for enhanced radiation shielding applications

This study explores the development and efficacy of eggshell-derived particle composites with epoxy resin for enhanced radiation shielding applications. Eggshells, primarily composed of calcium carbonate, were processed into particles of three sizes: small, medium, and large. These particles were incorporated into epoxy resin at a 50% weight ratio and characterized using a Laser Particle Size Distribution Analyzer. Radiation shielding properties were determined using diagnostic X-ray equipment and a Radcal Accu-Gold detector, evaluating attenuation parameters such as the Half-Value Layer (HVL) and Linear Attenuation Coefficient (LAC). Mechanical testing revealed that composites with large particles exhibited the weakest performance, with a maximum force of 5674 N and stress of 52 MPa. In contrast, small particle composites demonstrated superior mechanical properties, achieving a maximum force of 9125 N and stress of 97 MPa. Additionally, small particle composites (S50%) displayed the highest LAC and lowest HVL, confirming their superior radiation shielding efficiency due to better dispersion and increased surface area. These findings highlight the potential of using finely ground eggshell particles to create cost-effective, environmentally friendly materials for radiation protection, underscoring the importance of particle size optimization in the development of advanced composite materials.

Flexible and lead-free polymer composites for X-ray shielding: comparison of polyvinyl chloride matrix filled with nanoparticles of tungsten oxides

Polymer nanocomposites have been investigated as lightweight and suitable alternatives to lead-based clothing. The present study aims to fabricate flexible, lead-free, X-ray-shielding composites using a polyvinyl chloride (PVC) matrix and different nanostructures. Four different nanostructures containing impure tungsten oxide, tungsten oxide (WO3), barium tungstate (BaWO4), and bismuth tungstate (Bi2WO6) were synthesized through various methods. Subsequently, their morphological characteristics were determined by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Also, energy-dispersive X-ray spectroscopy (EDS) analysis was performed to establish the presence of the filler in the PVC matrix. Two different weight ratios of these nanostructures (20% wt and 50% wt) were used to produce the PVC composites. To investigate attenuation parameters, the prepared composites were irradiated with X-rays at tube voltages of 40, 80, and 120 kV. The results showed that the PVC composites containing 20% wt Bi2WO6 had the highest linear attenuation coefficient (µ) at all three voltages. Furthermore, they had the lowest half-value layer (HVL), tenth-value layer (TVL), and 0.5 mm equivalent lead thickness values at each of the three voltages. The PVC composites containing 50% wt Bi2WO6 had attenuation coefficients greater than those reported for PbO at all three X-ray voltages. Among the studied tungsten nanostructures, bismuth tungstate had the best attenuation performance for X-ray protection. Additionally, this composite is light, flexible, and non-toxic, making it a promising alternative to lead aprons.

Paraffin-based composites containing high density particles: lead and bismuth and its' oxides as γ-ray shielding materials: an experimental study

Shielding nano- and microcomposites have emerged as a promising solution in the constantly growing requirements and expectations in the field of radiological protection. The majority of gamma and X-ray shielding nanocomposites are based on polymers due to lightweight, low cost and flexibility as the inviting features in comparison to traditional lead shields. Taking this into consideration, the following study proposes gamma-ray shielding composites characterized by their susceptibility to shape change using the heat and manual pressure. The paraffin-based composites were filled with pure lead and bismuth particles (Bi and Pb, in one mass fraction: 10 wt%) as well as it's oxides: bismuth (III) oxide (Bi2O3) particles and lead (II,IV) oxide particles (Pb3O4) (manufactured in two concentrations: 10 and 50 wt%). Based on experimental studies utilizing 60Co the half-value layers were calculated approximately 13-14 cm and ca. 9 cm for 10 wt% and 50 wt% filler concentration, respectively. The relatively quick and straightforward manufacturing process, utilizing two commercially available components, allows for the production of a gamma-ray shielding composite featuring a variety of shape choices, facilitating its use in areas where acquiring complex shields remains problematic, or the desired shape development requires repetition of the production process, changes in some of its stages and modification of the composition.

Nanoscale dosimetry for a radioisotope-labeled metal nanoparticle using MCNP6.2 and Geant4

BACKGROUND

Metal nanoparticles (MNPs) labeled with radioisotopes (RIs) are utilized as radio-enhancers due to their ability to amplify the radiation dose in their immediate vicinity. A thorough understanding of nanoscale dosimetry around MNPs enables their effective application in radiotherapy. However, nanoscale dosimetry around MNPs still requires further investigation.

PURPOSE

This study aims to provide insight into the radio-enhancement effects of MNPs by elucidating nanoscale dosimetry surrounding MNPs labeled with Auger-emitting RIs. We particularly focus on distinguishing the respective dose contributions of photons and electrons emitted by Auger-emitting RIs in the context of dose enhancement.

METHODS

A 50 nm diameter NP of silver (Ag) core and gold (Au) shell (Ag@Au NP) was assumed to emit mono-energetic electrons and photons (3, 5, 10, 20, and 30 keV), or the energy spectrum corresponding to one of three Auger-emitting RIs (103Pd, 125I, and 131Cs) from the Ag core. Nanoscale radial dose distributions around a single radioactive Ag@Au NP were evaluated in spherical shells of water. Monte Carlo simulations were conducted using single-event and track structure transport methods implemented in MCNP6.2 and Geant4-DNA-Au physics, respectively. To evaluate the extent of radio-enhancement by the Ag@Au NP, two scenarios were considered: Ag@Au NPs (Au shell included) and Ag@water NPs (Au shell replaced by water).

RESULTS

The radial doses of 10, 20, and 30 keV electrons estimated by both codes were comparable. However, the radial doses of 3 and 5 keV electrons by MCNP6.2 were much larger near the NP surface than those by Geant4. There was a dose enhancement of a few % to tens % by the Au shell in the region of the NP surface to 10 µm, depending on the electron energy. The radial doses of photons with the Au shell were higher up to their secondary electron ranges than those without the Au shell. The maximum dose enhancement factor of photons occurred at 20 keV and was 63.4 by MCNP6.2 and 50.5 by Geant4. The overall radial doses of electrons were 1-2 orders of magnitude larger than those of photons. As a result, in cases of RIs emitting both electrons and photons, the radial doses up to electron ranges were dominantly governed by electrons. The dose enhancement estimated by both codes for the RIs ranged from a few % except in the immediate vicinity of the NP surface.

CONCLUSION

Given the dominant contribution of electrons to radial doses of MNP labeled with Auger-emitting RIs, physical dose enhancement expected by interactions with photons was hindered. Since there are no available RIs emitting exclusively photons, achieving enhanced physical doses within a cell through a combination of MNPs and RIs appears currently unattainable. The radial doses of photons near the NP surface exhibited considerable discrepancies between the codes, primarily attributed to low-energy electrons. The difference may arise from higher cross-sections of Au inelastic scattering in Geant4-DNA-Au compared to MCNP6.2.

Fabrication of polymeric shields to attenuation ionizing radiation and a flame retardant supported by nano-bismuth oxide prepared by co-deposition

The results of the preparation of protective shields from ionizing radiation, flame retardant from pure epoxy supported by nano-bismuth oxide, show that the protective shields supported by nanoparticles improve the attenuation properties, the thermal stability, the flame retardancy and mechanical properties. Also, the polymeric shield supported by Bi2O3 (Na2CO3) retardant the flame much better than supported by Bi2O3 (NaOH). Finally, the quality of the protective shields increased as the energy of the photons of the ionizing rays decreased.

Gamma rays and neutrons attenuation performance of a developed lead borate glass for radiotherapy room

The development of radiation therapy necessitated a continuous R&D for radiotherapy rooms' glass windows to reach the highest levels of protection for the staff of the radiotherapy facility. Therefore, in this article, a novel type of lead borate glass depending on parallel augmenting of lead and boron was produced to be used as gamma-rays and fast and thermal neutrons barriers in radiotherapy rooms. Neutrons and gamma rays' attenuation parameters, fast neutrons removal cross section ${\varSigma}_R$, thermal neutron total cross section ${\sigma}_T$, mass attenuation coefficient $\sigma$, linear attenuation coefficient μ, half-value layer, mean free path, effective atomic number Zeff, effective electron density Neff, and buildup factor for energy absorption (energy absorption buildup factor) and exposure (exposure buildup factor) were studied extensively. Three tools, Phy-X/PSD, EpiXS and XCOM computer programs and the standard mixture rules were utilized to estimate the attenuation parameters. The improvement caused by the augmentation of lead and boron in both gamma rays and neutrons attenuation was evident from the obtained results. The glass containing the highest lead and boron concentration PbB5, 40Pb-50B, which is the most efficient attenuator for gamma rays and both thermal and fast neutrons was recommended to be a distinguished choice as a shield in a radiotherapy room.

Design and Study of Novel Composites Based on EPDM Rubber Containing Bismuth (III) Oxide and Graphene Nanoplatelets for Gamma Radiation Shielding

The mechanical, thermal and gamma radiation attenuation properties of ethylene-propylene-diene monomer (EPDM)-based composites containing graphene nanoplatelets (GNs) and bismuth (III) oxide nanoparticles (B) were investigated. The use of polyethylene glycol (PEG) as a compatibilizer to improve the dispersion of the fillers was also investigated. The results showed that the combined use of these fillers resulted in a drastic increase in mechanical properties, reaching 123% and 83% of tensile strength and elongation at break, respectively, compared to those of EPDM. In contrast, the addition of PEG to composites containing EPDM GNs and B resulted in composites with lower values of mechanical properties compared to the EPDM/B/GN-based composite. However, the presence of PEG leads to obtaining a composite (EPDM/B/GNP) with a mass attenuation coefficient to gamma radiation (137Cs, 662 keV) superior to that composite without PEG. In addition, the composite EPDM, B and PEG exhibited an elongation at break 153% superior to unfilled EPDM. Moreover, the binary filler system consisting of 100 phr of bismuth (III) oxide and 10 phr of GN leads to reaching 61% of the linear damping coefficient of the EPDM composite compared to that value of the unfilled EPDM. The study of the morphology and the state of filler dispersion in the polymer matrix, obtained using scanning electron microscopy and energy-dispersive X-ray spectroscopy, respectively, provides a useful background for understanding the factors affecting the gamma radiation attenuation properties. Finally, the results also indicated that by adjusting the formulation, it is possible to tune the mechanical and thermal properties of EPDM composites reinforced with bismuth oxide and graphene nanoplatelets.

Fabrication of cadmium chloride PVA polymer composite for γ-ray shielding

Reducing the effect of exposure to radiation in places such as radiation labs, nuclear reactors, radiotherapy facilities, industries involving radiation, etc., is essential for the health of radiation workers. In such cases materials having flexibility added with high attenuation coefficient of radiation is required for manufacturing wearables. Even though materials such as lead compounds, building materials, etc., have high attenuation coefficient, they are toxic and rigid, making them unsuitable for this purpose. In this regard, blending compounds with polymers would lead to flexible materials with high shielding capability. In the present work, 25 wt% cadmium chloride in polyvinyl alcohol (PVA) polymer composite has been prepared using solution casting method. The obtained polymer composite is characterised by energy dispersive X-ray spectroscopy. The mass attenuation coefficients (μ/ρ) and half value layer (HVL) of gamma radiations were measured at various energies 511, 661, 1173 and 1332 keV using calibrated gamma ray spectrometer with NaI(Tl) detector and compared to WinXCom-calculated theoretical values. The measured μ/ρ and HVL are 0.089, 0.078, 0.064, 0.061 cm2/g and 0.685, 0.778, 0.985, 1.003 cm, respectively. It is found that the obtained experimental values are in good agreement with theoretical values within the experimental errors. Also, it is observed that the μ/ρ decreases and HVL increases with increase in energy. Even though PVA is not radiation resistant, when it is blended with 25 wt% cadmium chloride it shows good shielding property. Thus, the fabricated cadmium chloride-PVA polymer composite can be used for radiation shielding instead of toxic and expensive materials.

Fe-nanoparticle effect on polypropylene for effective radiation protection: Simulation and theoretical study

An evaluation of the gamma-neutron shielding capabilities of polymer nanocomposite materials based on polypropylene and iron nanoparticles is presented in this study. The chemical composition of the materials is (100-x) PP-Fex, (where x = 0.1, 0.3, 0.5, 1, 2 and 5 wt percent). For the proposed polymer samples with photon energies ranging from 30 to 2000 KeV, the mass attenuation coefficient (MAC), a crucial parameter for studying gamma-ray shielding capability, was calculated using the Geant4 Monte Carlo code. Results were compared with those predicted by EpiXS. The values of the Geant4 code and the EpiXS software were both found to be in excellent agreement. Using the mass attenuation coefficient values, we determined the linear attenuation coefficients, electron density, effective atomic number, and half value layer for all the samples. The shielding properties of the polymer samples were also evaluated by estimating both the fast neutron removal cross-section and the mean free path of the fast neutron at energies between 0.25 and 5.5 keV. The study's findings indicate a positive correlation between the Fe nanoparticle content and the gamma-ray shielding performance of PP-Fe polymer samples. Out of the several glasses that were evaluated, it was found that the PP-Fe5 polymer sample demonstrates the highest efficacy in terms of gamma-ray shielding. Moreover, the polymer sample PP-Fe5, which consists of 5 mol% of iron (Fe), exhibits the highest value of ∑R (1.10650 cm-1) and the lowest value of the mean free path for fast neutrons. This indicates that the PP-Fe5 possesses better gamma-neutron shielding efficiency.

Gamma radiation effects on AG MP-50 cation exchange resin and sulfonated activated carbon for bismuth-213 separation

Medical 225Ac/213Bi radionuclide generators are designed to provide a local supply of the short-lived 213Bi for cancer treatment. However, radiation-induced damage to the sorbents commonly used in such radionuclide generators remains a major concern. In this study, the effects of gamma radiation on AG MP-50 cation exchange resin and sulfonated activated carbon (SAC) were studied by analyzing the changes in the morphological characteristics, functional groups, and the La3+/Bi3+ sorption performance, with La3+ being a suitable non-radioactive substitute for Ac3+. The surface sulfonic acid groups of AG MP-50 resin suffered from severe radiation-induced degradation, while the particle morphology was changed markedly after being exposed to absorbed doses of approximately 11 MGy. As a result, the sorption performance of irradiated AG MP-50 for La3+ and Bi3+ was significantly decreased with increasing absorbed doses. In contrast, no apparent changes in acquired morphological characteristics were observed for pristine and irradiated SAC based on SEM and XRD characterization. The surface oxygen content (e.g., O-C[double bond, length as m-dash]O) of irradiated SAC increased for an absorbed dose of 11 MGy due to free radical-induced oxidation. The sorption performance of pristine and irradiated SAC materials for La3+ and Bi3+ remained generally the same at pH values of 1 and 2. Furthermore, the applicability of AG MP-50 and SAC in the 225Ac/213Bi generators was illustrated in terms of their radiolytic stability. This study provides further evidence for the practical implementation of both AG MP-50 and SAC in 225Ac/213Bi radionuclide generators.

Metal Particle Pencil Beam Spray-Coating Method for High-Density Polymer-Resin Composites: Evaluation of Radiation-Shielding Sheet Properties

Medical shielding suits must be lightweight and satisfy the requirements of thin films to guarantee user mobility and safety. The thin film weight is related to the density and thickness, which are associated with the particle dispersion in shielding materials. An even distribution of metal particles in a polymer can maintain the spacing among them. This paper proposes a pencil beam spray-coating method that involves spraying a constant amount of a polyethylene and tungsten mixture in a thin beam onto a nonwoven fabric at a constant speed. This technique yields higher productivity than does the electrospinning method and is expected to produce materials with better shielding performance than that of materials obtained using the calender method. The shielding performance was evaluated by manufacturing shielding sheets (thickness: 0.48-0.54 mm) using the calender and pencil beam spray-coating methods under the same conditions. The densities and performances of the sheets differed significantly. The sheet manufactured using the proposed method had an even particle dispersion and exhibited 2-4% better shielding performance than did that manufactured using the calender method. Therefore, the pencil beam spray-coating method can effectively satisfy the requirements of thin films for medical radiation-shielding materials while increasing the material flexibility.

Shielding performance of multi-metal nanoparticle composites for diagnostic radiology: an MCNPX and Geant4 study

Lead-free polymer composite shields are used in diagnostic radiology to protect patients from unnecessary radiation exposure. This study aimed to examine and introduce the radiation-shielding properties of single- and multi-metal nanoparticle (NP)-based composites containing Bi, W, and Sn using Geant4, MCNPX, and XCom for radiological applications. The mass attenuation coefficients and effective atomic numbers of single- and multi-metal NP-loaded polymer composites were calculated using the Geant4 and MCNPX simulation codes for X-ray energies of 20-140 keV. The nano-sized fillers inside the polydimethylsiloxane (PDMS:C₂H₆SiO) matrix included W (K = 69.5 keV), Bi (K = 90.5 keV), and Sn (K = 29.20 keV). For single-metal shields, one filler was used, while in multi-metal shields, two fillers were required. The MCNPX and Geant4 simulation results were compared with the XCom results. The multi-metal NP composites exhibited higher attenuation over a larger energy range owing to their attenuation windows. In addition, Bi₂O₃ + WO₃ NPs showed a 39% higher attenuation at 100-140 keV, and that of Bi₂O₃ + SnO₂ NPs was higher at 40-60 keV. Meanwhile, the WO₃ + SnO₂ NPs exhibited lower attenuation. The difference between the results obtained using Geant4 and XCom was less than 2%, because these codes have similar simulation structures. The results show that the shielding performance of the Bi₂O₃ + WO₃ filler is better than that of the other single- and multi-metal fillers. In addition, it was found that the Geant4 code was more accurate for simulating radiation composites.

Trade-off between breast dose and image quality using composite bismuth shields in computed tomography: A phantom study

INTRODUCTION

Many researchers have suggested that bismuth composite shields (BCS) reduce breast dose remarkably; however, the level of this reduction and its impact on image quality has not been assessed. This study aimed to evaluate the efficiency of nano- and micro- BCS in reducing the dose and image quality during chest computed tomography (CT) scans.

MATERIALS AND METHODS

Bismuth shields composed of 15 weighting percentage (wt%) and 20 wt% bismuth oxide (Bi₂O₃) nano- and micro-particles mixed in silicon rubber polymer were constructed in 1 and 1.5 mm thicknesses. The physical properties of nanoparticles were assessed using a scanning electron microscope (SEM), X-ray diffraction (XRD), and energy-dispersive X-ray (EDX). Breast radiation doses were measured experimentally during chest CT using PMMA standard dosimetry phantom (body phantom, 76-419-4150, Fluke Biomedical) in the presence of the shields. The image quality was assessed by calculating signal and noise values in different regions.

RESULTS

The SEM images showed that the average size of Bi₂O₃ nano- and micro-particles was about 70 nm and 150 μm, respectively. The breast doses were reduced by increasing the shield thickness/bismuth weight percentage. The maximum dose reduction was related to the 20% weight of Bi₂O₃ nano-particles and a thickness of 1.5 mm. The minimum dose reduction was related to the 15% weight of Bi₂O₃ micro-particles with a thickness of 1 mm. The mean noise was higher in nano-particle bismuth shields than in micro-particles.

CONCLUSION

Composite shields containing bismuth nano- and micro-particles can reduce the breast dose during chest CT examinations while negatively impacting diagnostic image quality. Several critical factors, such as bismuth concentration, particle size, and shield thickness, directly affect the efficiency.

Evaluation of silicone rubber-lead shield's effectiveness in protecting the breast during thoracic CT

Radiation of thoracic computed tomography (CT) involves the breast although it is not considered an organ of interest. According to the International Commission on Radiological Protection (ICRP) No. 103, the breast is an organ with a high level of sensitivity when interacting with x-rays, increasing the potential risk of breast cancer. Therefore, the radiation dose must be optimized while maintaining image quality. The dose optimization can be accomplished using a radiation shield. This study aims to determine the effect of silicone rubber (SR)-lead (Pb) in various thicknesses as an alternative protective material limiting dose and preserving the image quality of the breast in thoracic CT. SR-Pb was made from SR and Pb by a simple method. The SR-Pb had thicknesses of 3, 6, 9, and 12 mm. The breast dose was measured using a CT dose profiler on the surface of the breast phantom. The CT number and the noise level of the resulting image were determined quantitatively. The dose without the radiation shield was 5.4 mGy. The doses measured using shielding with thicknesses of 3, 6, 9, and 12 mm were 5.2, 4.5, 4.3, and 3.3 mGy, respectively. Radiation shielding with a thickness of 12 mm reduced breast surface dose by up to 38%. The CT numbers and noise levels for the left and right breast phantom images were almost the same as those ​​without radiation shields indicating there were only slight artifacts in the image. Therefore, SR-Pb is considered a good shielding material which can be pplied in a clinical setting by placing it directly on the breast surface for dose optimization.

Coating of polyester fabrics with micro-particles of Bi2O3 and BaO for ionization ray shielding

The aim of the present study is to fabricate an economical, environmentally friendly, easily workable, light-weight and comfortable textile-based radiation shield. At first, polyester fabrics were coated with PVA resin that contained bismuth micro-particles (Bi₂O₃) and barium oxide (BaO) powder in two different weight ratios. Then, the fabric samples were exposed to a source of ²²⁶Ra. Attenuation characteristics such as linear attenuation coefficient (μ), half-value layer (HVL) and tenth-value layer (TVL) were calculated for the individual samples. Their morphological properties were also examined through SEM analyses. Moreover, evaluations were performed of the weight, thickness, crease recovery angle, and air permeability of the modified polyester fabrics as well as the water drop absorption time on their surface. As the results showed, the sample with 30% BaO had the highest rate of attenuation, and the attenuation coefficients would increase with an increase of barium and bismuth oxides in the samples. The lowest HVL and TVL values belonged to the sample with 30% BaO.

Ultralight and Superelastic Gd2O3/Bi2O3 Nanofibrous Aerogels with Nacre-Mimetic Brick-Mortar Structure for Superior X-ray Shielding

The widespread use of X-rays has prompted a surge in demand for effective and wearable shielding materials. However, the Pb-containing materials currently used to shield X-rays are commonly bulky, hard, and biotoxic, severely limiting their applications in wearable scenarios. Inspired by the nacre, we report on ultralight, superelastic, and nontoxic X-ray shielding nanofibrous aerogels with microarch-engineered brick/mortar structure by combining polyurethane/Bi₂O₃ nanofibers (brick) and Gd₂O₃ nanosheets (mortar). The synergistic attenuation effect toward X-rays from the reflection of microarches and absorption of Bi/Gd elements significantly enhances the shielding efficiency of aerogels, and microarches/robust nanofibrous networks endow the materials with superelasticity. The resultant materials exhibit integrated properties of superior X-ray shielding efficiency (91-100%), ultralow density (52 mg cm^-3), large stretchability of 800% reversible elongation, and high water vapor permeability (8.8 kg m^-2 day^-1). The fabrication of such novel aerogels paves the way for developing next-generation effective and wearable X-ray shielding materials.

Assessment of new composites containing polyamide-6 and lead monoxide as shields against ionizing photonic radiation based on computational and experimental methods

This study aimed to introduce new composites, containing polyamide-6 (PA6) and lead monoxide (PbO), to protect against ionizing photon sources used for diagnostic and therapeutic purposes. Five composites, containing various weight percentages of PbO filler (0, 5, 10, 20, and 50%), were developed in this study. Initially, the numerical attenuation value was estimated using the XMuDat program by calculating the mass attenuation coefficients at different energy levels. Next, the samples were synthesized based on the melt-mixing method in a laboratory mixing extruder. Their characteristics were also determined by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Finally, experimental radiation attenuation tests were carried out. Based on the SEM results, the acceptable filler weight percentage was up to 20%. However, substantial aggregates were formed at the highest weight percentage. The results of XRD analysis showed a higher tendency for crystallization by decreasing the amorphous area while increasing the filler weight percentage. Moreover, the mass loss rate was monitored at different temperatures, revealing that the filler incorporation improved the thermal durability of the samples. The radiation results showed a good agreement between the experimental and computational data, except when aggregates formation was substantial. The experimental data revealed that when the lead weight percentage increased from 0% (crude PA6) to 50%, the half-value layer decreased from 3.13 to 0.17 cm at an energy level of 59 keV and from 7.28 to 4.97 cm at an energy level of 662 keV. Following the studied mechanism, the superiority of lead/polyamide composites can be found in the high adsorption of photon radiation at low energies (E < 0.20 MeV) and significant attenuation at medium and higher energies. Considering these promising results, the shielding properties of these composites can be further analyzed via more practical investigations.

Assessment of new composites containing polyamide-6 and lead monoxide as shields against ionizing photonic radiation based on computational and experimental methods

This study aimed to introduce new composites, containing polyamide-6 (PA6) and lead monoxide (PbO), to protect against ionizing photon sources used for diagnostic and therapeutic purposes. Five composites, containing various weight percentages of PbO filler (0, 5, 10, 20, and 50%), were developed in this study. Initially, the numerical attenuation value was estimated using the XMuDat program by calculating the mass attenuation coefficients at different energy levels. Next, the samples were synthesized based on the melt-mixing method in a laboratory mixing extruder. Their characteristics were also determined by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), and thermogravimetric analysis (TGA). Finally, experimental radiation attenuation tests were carried out. Based on the SEM results, the acceptable filler weight percentage was up to 20%. However, substantial aggregates were formed at the highest weight percentage. The results of XRD analysis showed a higher tendency for crystallization by decreasing the amorphous area while increasing the filler weight percentage. Moreover, the mass loss rate was monitored at different temperatures, revealing that the filler incorporation improved the thermal durability of the samples. The radiation results showed a good agreement between the experimental and computational data, except when aggregates formation was substantial. The experimental data revealed that when the lead weight percentage increased from 0% (crude PA6) to 50%, the half-value layer decreased from 3.13 to 0.17 cm at an energy level of 59 keV and from 7.28 to 4.97 cm at an energy level of 662 keV. Following the studied mechanism, the superiority of lead/polyamide composites can be found in the high adsorption of photon radiation at low energies (E < 0.20 MeV) and significant attenuation at medium and higher energies. Considering these promising results, the shielding properties of these composites can be further analyzed via more practical investigations.

A comprehensive Monte Carlo study to design a novel multi-nanoparticle loaded nanocomposites for augmentation of attenuation coefficient in the energy range of diagnostic X-rays

Introduction: The present study aimed to investigate the radiation protection properties of silicon-based composites doped with nano-sized Bi2O3, PbO, Sm2O3, Gd2O3, WO3, and IrO2 particles. Radiation shielding properties of Sm2O3 and IrO2 nanoparticles were investigated for the first time in the current study.

Material and methods: The MCNPX (2.7.0) Monte Carlo code was utilized to calculate the linear attenuation coefficients of single and multi-nano structured composites over the X-ray energy range of 10–140 keV. Homogenous distribution of spherical nanoparticles with a diameter of 100 nm in a silicon rubber matrix was simulated. The narrow beam geometry was used to calculate the photon flux after attenuation by designed nanocomposites.

Results: Based on results obtained for single nanoparticle composites, three combinations of different nano-sized fillers Sm2O3+WO3+Bi2O3, Gd2O3+WO3+Bi2O3, and Sm2O3+WO3+PbO were selected, and their shielding properties were estimated. In the energy range of 20-60 keV Sm2O3 and Gd2O3 nanoparticles, in 70-100 keV energy range WO3 and for photons energy higher than 90 keV, PbO and Bi2O3 nanoparticles showed higher attenuation. Despite its higher density, IrO2 had lower attenuation compared to other nanocomposites. The results showed that the nanocomposite containing Sm2O3, WO3, and Bi2O3 nanoparticles provided better shielding among the studied samples.

Conclusions: All studied multi-nanoparticle nanocomposites provided optimum shielding properties and almost 8% higher attenuation relative to single nano-based composites over a wide range of photon energy used in diagnostic radiology. Application of these new composites is recommended in radiation protection. Further experimental studies are suggested to validate our findings.

Monte Carlo Calculation of linear attenuation coefficients and photon scattering properties of novel concretes loaded with Osmium, Iridium and Barite nanoparticles

Introduction: Recent studies have shown that the use of high-density nanoparticles (NPs) in concrete composition improves its radiation shielding properties. In the present study, the linear attenuation coefficients and photon scattering properties of newly developed high-density Nano-concretes have been calculated using the MCNPX Monte Carlo code.

Material and methods: The shielding properties of Nano-concretes containing 10%, 20%, and 30% weight percentage of Osmium, Iridium and Barite NPs (100 nm) as well as ordinary concrete were investigated. The 6 and 18 MV photon beams of Varian Linac and 60 Co photons were used for simulation. Photon scattering flux was calculated for all Nano-concretes with 30 wt% of NPs and ordinary concrete at different angles.

Results: In general, by adding Iridium, Osmium and Barite NPs to ordinary concrete, the linear attenuation coefficients increased. Despite a lower density relative to Iridium and Osmium, Nano-concretes containing Barite exhibited a higher linear attenuation coefficient due to their higher electron density.

Conclusions: The results revealed a dependence between the scattered photon flux and the effective atomic number of Nano-concretes. With increasing the atomic number of fillers, the intensity of the scattered photon flux enlarged. Also, the scattered flux was higher for all types of concretes at 180 degrees relative to other angles.