Experimental evaluation of gamma radiation shielding characteristics of Polyvinyl Alcohol/Tungsten oxide composite: A comparison study of micro and nano sizes of the fillers

Exploring green environmental composites as hosts for shielding materials using experimental, theoretical and Geant4 simulation methods

Rice straw is considered an agricultural waste harmful to the environment, which is abundant in most parts of the world. From this point, the present study is devoted to preparing new composites of two types of glue based on rice straw as a plentiful, low-cost matrix. Straw glue samples were prepared by mixing 20% wt. of rice straw with 80% wt. of animal glue (RS-An) and polyvinyl acetate (RS-PVAC) at different thicknesses of 1, 2, and 3 cm. The chemical composition of the prepared samples was identified by energy dispersive X-ray analysis and their morphology was examined using a scanning electron microscope. The mechanical test explored that RS-An and RS-PVAC respectively required a stress of 25.2 and 25.5 MPa before reaching the breaking point. γ-ray shielding performance was analyzed and determined at numerous photon energies from 0.059 to 1.408 MeV emitted from five-point γ-rays sources using NaI (Tl). Linear attenuation coefficient was calculated by obtaining the area under the peak of the energy spectrum observed from Genie 2000 software in the presence and absence of the sample. The experimental results of mass attenuation coefficient were compared with theoretical data of XCOM software with relative deviation ranging from 0.10 to 2.99%. Geant4 Monte Carlo simulation code was also employed to validate the experimental results. The relative deviation of XCOM and Geant4 outcomes was 0.09-1.77%, which indicates a good agreement between them. Other radiation shielding parameters such as half value layer (HVL), tenth value layer, and mean free path were calculated in three ways: experimentally, theoretically from the XCOM database, and by simulation using Geant4 code. Additionally, effective atomic number (Zeff), effective atomic number (Neff), equivalent atomic number (Zeq), and buildup factors were evaluated. It was confirmed that the γ-ray shielding properties were further boosted by mixing rice straw with the animal glue compared to the synthetic one.

Novel starch-tungsten (VI) oxide biocomposites: Preparation, characterization, and comparisons between experimental and theoretical photon attenuation coefficients

This study synthesized biocomposites containing starch and WO3 at varying ratios of 10 %, 20 %, 30 %, 40 %, and 50 % and assessed their thermal and radiation-shielding properties. These biocomposites were characterized using Fourier-transform infrared spectroscopy, X-ray diffraction (XRD) analysis, particle-size distribution assessments, scanning electron microscopy-energy dispersive X-ray spectroscopy, and thermogravimetric analysis-differential thermogravimetry measurements. Furthermore, the linear attenuation coefficients of the biocomposites were experimentally measured using an NaI(Tl) gamma spectrometry system and theoretically computed using XCOM and GAMOS simulations for comparisons. The XRD and particle-size distribution profiles of the WO3.2H2O powder, respectively, demonstrated evident diffraction peaks and favorable pore-size distributions. Morphological characterizations revealed that the WO3 particles were homogeneously dispersed throughout the starch matrix without any agglomeration. Comparisons of the thermal degradation rates revealed that the pure starch and starch +50%WO3 biocomposite began decomposing at approximately 200°Cand 300 °C, respectively, indicating that increasing WO3 proportions enhanced thermal stability. Furthermore, the starch +50%WO3 biocomposite demonstrated the highest experimental linear attenuation coefficient, with a value of 0.2510 ± 0.0848 cm-1 at a gamma energy of 662 keV. Meanwhile, XCOM and GAMOS simulations revealed theoretical attenuation coefficients of 0.1229 and 0.1213 cm-1 for pure starch and 0.2202 cm-1 and 0.2178 cm-1 for the starch +50%WO3 biocomposite at 662 keV, respectively.

Attenuation properties of poly methyl methacrylate reinforced with micro/nano ZrO2 as gamma-ray shields

This research aimed to examine the radiation shielding properties of unique polymer composites for medical and non-medical applications. For this purpose, polymer composites, based on poly methyl methacrylate (PMMA) as a matrix, were prepared and reinforced with micro- and nanoparticles of ZrO2 fillers at a loading of 15%, 30%, and 45% by weight. Using the high purity germanium (HPGe) detector, the suggested polymer composites' shielding characteristics were assessed for various radioactive sources. The experimental values of the mass attenuation coefficients (MAC) of the produced composites agreed closely with those obtained theoretically from the XCOM database. Different shielding parameters were estimated at a broad range of photon energies, including the linear attenuation coefficient (μ), tenth value layer (TVL), half value layer (HVL), mean free path (MFP), effective electron density (Neff), effective atomic number (Zeff), and equivalent atomic number (Zeq), as well as exposure buildup factor (EBF) and energy absorption buildup factor (EABF) to provide more shielding information about the penetration of γ-rays into the chosen composites. The results showed that increasing the content of micro and nano ZrO2 particles in the PMMA matrix increases μ values and decreases HVL, TVL, and MFP values. P-45nZ sample with 45 wt% of ZrO2 nanoparticles had the highest μ values, which varied between 2.6546 and 0.0991 cm-1 as γ-ray photon energy increased from 0.0595 to 1.408 MeV, respectively. Furthermore, the highest relative increase rate in μ values between nano and micro composites was 17.84%, achieved for the P-45nZ sample at 59.53 keV. These findings demonstrated that ZrO2 nanoparticles shield radiation more effectively than micro ZrO2 even at the same photon energy and filler wt%. Thus, the proposed nano ZrO2/PMMA composites can be used as effective shielding materials to lessen the transmitted radiation dose in radiation facilities.

Investigation on Physico Chemical and X-ray Shielding Performance of Zinc Doped Nano-WO3 Epoxy Composite for Light Weight Lead Free Aprons

This report addresses a way to reduce the usage of highly toxic lead in diagnostic X-ray shielding by developing a cost-effective, eco-friendly nano-tungsten trioxide (WO₃) epoxy composite for low-weight aprons. Zinc (Zn)-doped WO₃ nanoparticles of 20 to 400 nm were synthesized by an inexpensive and scalable chemical acid-precipitation method. The prepared nanoparticles were subjected to X-ray diffraction, Raman spectroscopy, UV-visible spectroscopy, photoluminescence, high-resolution-transmission electron microscope, scanning electron microscope, and the results showed that doping plays a critical role in influencing the physico-chemical properties. The prepared nanoparticles were used as shielding material in this study, which were dispersed in a non-water soluble durable epoxy resin polymer matrix and the dispersed materials were coated over a rexine cloth using the drop-casting method. The X-ray shielding performance was evaluated by estimating the linear attenuation coefficient (μ), mass attenuation coefficient (μ_m), half value layer (HVL), and X-ray percentage of attenuation. Overall, an improvement in X-ray attenuation in the range of 40-100 kVp was observed for the undoped WO₃ nanoparticles and Zn-doped WO₃ nanoparticles, which was nearly equal to lead oxide-based aprons (reference material). At 40 kVp, the percentage of attenuation of 2% Zn doped WO₃ was 97% which was better than that of other prepared aprons. This study proves that 2% Zn doped WO₃ epoxy composite yields a better particle size distribution, μ_m, and lower HVL value and hence it can be a convenient lead free X-ray shielding apron.

Computational prediction of electrical percolation threshold in polymer/graphene-based nanocomposites with finite element method

In this research work, a two-dimensional model to predict the electrical percolation threshold (EPT) of the polymer/graphene-based nanocomposites in different concentrations of the randomly dispersed inclusions in various polymer matrices is introduced using the finite element method (FEM). The predicted EPT values were validated by other experimental results for different nanocomposites. Results showed that the electrical conductivity of different nanocomposites is significantly related to the percentage weight of the reinforcing phase in the polymer matrix. Furthermore, the addition of graphene-based nano-fillers in the polymer matrix caused a decrease in the tunneling distance in nanocomposites.

Computational prediction of electrical percolation threshold in polymer/graphene-based nanocomposites with finite element method

In this research work, a two-dimensional model to predict the electrical percolation threshold (EPT) of the polymer/graphene-based nanocomposites in different concentrations of the randomly dispersed inclusions in various polymer matrices is introduced using the finite element method (FEM). The predicted EPT values were validated by other experimental results for different nanocomposites. Results showed that the electrical conductivity of different nanocomposites is significantly related to the percentage weight of the reinforcing phase in the polymer matrix. Furthermore, the addition of graphene-based nano-fillers in the polymer matrix caused a decrease in the tunneling distance in nanocomposites.

Evaluation of dosimetric characteristics of a ternary nanocomposite based on High Density Polyethylene/Bismuth Oxide/Graphene Oxide for gamma-rays

This research aims to investigate a ternary nanocomposite based on High Density Polyethylene/ Bismuth Oxide/Graphene Oxide (HDPE/Bi2O3/GO) at various concentrations. Solution method was used to fabricate the samples. FESEM-EDX mapping, AFM, TEM, XRD, XPS, FTIR, and TGA/DTG analyses were carried out on the samples. XRD analysis demonstrated a semi-crystalline behavior for the samples. TEM analysis exhibited a cauliflower-like structure of the material. The sample was irradiated by gamma-rays of 60Co source over the dose rate of 30–254 mGy/min and the electric current was measured as the response of the real-time dosimeter. Thus, various dosimetric characteristics were performed, namely linearity, angular dependence, energy dependence, bias-polarity, field size, and repeatability of the data. Results showed that response of the dosimeter was linear in the range of the investigated dose rate. The sensitivity of the 60 wt% Bi2O3 sample was measured as 3.4 nC·mGy−1. The angular response variation was 20% for normal beam incidence. The response of the dosimeter to assess the energy dependency was obtained as 2.2% at the radiation field of the 137Cs and 60Co beams. The dosimeter response was dependent on the bias-polarity, with maximum discrepancy of 11.1%. The dosimetry response was highly dependent upon the radiation field size. The repeatability of the dosimeter response was measured with standard deviation less than 1%. As well, the dosimeter response during the one-hour irradiation was stable with a standard deviation of 0.66%. Results showed that considering some correction factors, this material can be used for dosimetry of gamma-rays at the therapy level.

Evaluation of dosimetric characteristics of a ternary nanocomposite based on High Density Polyethylene/Bismuth Oxide/Graphene Oxide for gamma-rays

This research aims to investigate a ternary nanocomposite based on High Density Polyethylene/ Bismuth Oxide/Graphene Oxide (HDPE/Bi₂O₃/GO) at various concentrations. Solution method was used to fabricate the samples. FESEM-EDX mapping, AFM, TEM, XRD, XPS, FTIR, and TGA/DTG analyses were carried out on the samples. XRD analysis demonstrated a semi-crystalline behavior for the samples. TEM analysis exhibited a cauliflower-like structure of the material. The sample was irradiated by gamma-rays of ⁶⁰Co source over the dose rate of 30-254 mGy/min and the electric current was measured as the response of the real-time dosimeter. Thus, various dosimetric characteristics were performed, namely linearity, angular dependence, energy dependence, bias-polarity, field size, and repeatability of the data. Results showed that response of the dosimeter was linear in the range of the investigated dose rate. The sensitivity of the 60 wt% Bi₂O₃ sample was measured as 3.4 nC·mGy^-1. The angular response variation was 20% for normal beam incidence. The response of the dosimeter to assess the energy dependency was obtained as 2.2% at the radiation field of the ¹³⁷Cs and ⁶⁰Co beams. The dosimeter response was dependent on the bias-polarity, with maximum discrepancy of 11.1%. The dosimetry response was highly dependent upon the radiation field size. The repeatability of the dosimeter response was measured with standard deviation less than 1%. As well, the dosimeter response during the one-hour irradiation was stable with a standard deviation of 0.66%. Results showed that considering some correction factors, this material can be used for dosimetry of gamma-rays at the therapy level.

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.

Introducing a novel beta-ray sensor based on polycarbonate/bismuth oxide nanocomposite

In this research, for the first time, the polycarbonate/bismuth oxide (PC-Bi₂O₃) composite was studied as a beta-ray sensor using a pure beta-emitter ⁹⁰Sr source. Firstly, the range and stopping power of the electrons in the composite at various loadings of 0, 10, 20, 30, 40, and 50 wt% were calculated using the ESTAR program. Results of simulation demonstrated that the concentration of the heavy metal oxide particles into the polymer matrix played an important role in evaluating the range and stopping power of the electrons in the composite. Secondly, at the experimental phase, the pure Polycarbonate and 50 wt% PC-Bi₂O₃ nanocomposite with dimensions of 4 × 4 × 0.1 cm³ were prepared and irradiated by ⁹⁰Sr. Also, current-voltage (I-V) plot exhibited linear response ranging from 100 to 1000 V at the fixed source-to-surface distance (SSD). Then the amount of electric current as the sensor response was measured in various dose rates at the fixed voltage of 400 V for the pure Polycarbonate and 50 wt% PC-Bi₂O₃ nanocomposite using an electrometer, in which results showed that the sensitivities were found as 20.3, and 33.3 nC mSv^-1 cm^-3, respectively. This study showed that this composite could serve as a novel beta-ray sensor.

Introducing a novel beta-ray sensor based on polycarbonate/bismuth oxide nanocomposite

In this research, for the first time, the polycarbonate/bismuth oxide (PC–Bi2O3) composite was studied as a beta-ray sensor using a pure beta-emitter 90Sr source. Firstly, the range and stopping power of the electrons in the composite at various loadings of 0, 10, 20, 30, 40, and 50 wt% were calculated using the ESTAR program. Results of simulation demonstrated that the concentration of the heavy metal oxide particles into the polymer matrix played an important role in evaluating the range and stopping power of the electrons in the composite. Secondly, at the experimental phase, the pure Polycarbonate and 50 wt% PC–Bi2O3 nanocomposite with dimensions of 4 × 4 × 0.1 cm3 were prepared and irradiated by 90Sr. Also, current–voltage (I–V) plot exhibited linear response ranging from 100 to 1000 V at the fixed source‐to‐surface distance (SSD). Then the amount of electric current as the sensor response was measured in various dose rates at the fixed voltage of 400 V for the pure Polycarbonate and 50 wt% PC–Bi2O3 nanocomposite using an electrometer, in which results showed that the sensitivities were found as 20.3, and 33.3 nC mSv−1 cm−3, respectively. This study showed that this composite could serve as a novel beta-ray sensor.