Study of polycarbonate–bismuth nitrate composite for shielding against gamma radiation

Physical, mechanical, and microstructural characterisation of tungsten carbide-based polymeric composites for radiation shielding application

Polymeric based composites have gained considerable attention as potential candidates for advanced radiation shielding applications due to their unique combination of high-density, radiation attenuation properties and improved mechanical strength. This study focuses on the comprehensive characterisation of polymeric based composites for radiation shielding applications. The objective of this study was to evaluate the physical, mechanical and microstructural properties of tungsten carbide-based epoxy resin and tungsten carbide cobalt-based epoxy resin for its efficiency in shielding against gamma-rays ranging from 0.6 up to 1.33 MeV. Polymeric composites with different weight percentages of epoxy resin (40 wt%, 35 wt%, 30 wt%, 25 wt%, 20 wt%, 15 wt% and 10 wt%) were fabricated, investigated and compared to conventional lead shield. The attenuation of the composites was performed using NaI (Tl) gamma-ray spectrometer to investigate the linear and mass attenuation coefficients, half value layer, and mean free path. High filler loadings into epoxy resin matrix (90% filler/10% epoxy) exhibited excellent gamma shielding properties. Mechanical properties, such as hardness were examined to assess the structural integrity and durability of the composites under various conditions. The fabricated composites showed a good resistance, the maximum hardness was attributed to composites with small thickness. The high loading of fillers in the epoxy matrix improved the microhardness of the composites. The distribution of the filler powder within the epoxy matrix was investigated using FESEM/EDX. The results revealed the successful incorporation of tungsten carbide and cobalt particles into the polymer matrix, leading to increased composite density and enhanced radiation attenuation. The unique combination of high-density, radiation attenuation, and improved mechanical properties positions polymeric based composites as promising candidates for radiation protection field.

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.

An alternative method for calculation of half-value layers without the knowledge of attenuation coefficient

Radiation protection is crucial for the safe utilization of ionizing radiation and minimizing the harmful effect upon exposure, hence some standards have been defined by some relevant organizations for the safe uses of radiation. One of the parameters relevant to the calculation of gamma ray shielding is the half-value layer (HVL), which is normally calculated using the knowledge of linear attenuation coefficient (μ). In this research, an attempt has been made to directly calculate HVL without the knowledge of μ via Monte Carlo simulation technique. For this purpose, in the Monte Carlo N-Particle eXtended (MCNPX) code, F1, F5 and Mesh Popul sequences tallies were defined and the optimal structure for the least measurement error was introduced. The MCNPX calculated values showed reasonable agreement with the experimental findings. According to the obtained results, it is suggested that in order to reduce the error of HVL calculations, in exchange for the MCNPX code, the values of the R parameter and the radiation angle of the source should be considered according to the calculations introduced in this plan. Because the results show that by considering the measurement error between 6 and 20%, the code output can be cited in different energy ranges.

Experimental investigation of the structural features of polycarbonate (PC) filled with bismuth nitrate pentahydrate (BNP) composite films in terms of free volume defects probed by positron annihilation lifetime spectroscopy

The effect of bismuth nitrate pentahydrate (BNP) on the properties and microstructural features of polycarbonate (PC) has been investigated using PALT, XRD, SEM, EDX, TG, ATR-FTIR and tensile mechanical measurements. Positron Annihilation Lifetime Spectroscopy reveals that the ortho-positronium lifetime and its corresponding intensity significantly decrease as the filler level of BNP in PC (in the composite) increases from 0.3 wt% up to 5.0 wt%. This is due to the increasing fraction of positrons that annihilate with the filler particles and also in the interfacial layers of the filler and the host polymer. Fourier Transform Infrared spectra show that there is no significant shift in the IR bands of the composite when compared to those of pure PC, and so there is little molecular level interaction between PC and BNP. The micrographs of SEM revealed a random distribution of filler particles in the composite, and there is the formation of agglomerates of BNP at higher filler levels. There is an increase in the degree of crystallinity of the composite films due to the addition of the crystalline filler, which was confirmed by XRD analysis. Tensile mechanical tests confirmed the improved tensile strength of prepared composites at lower and moderate filler levels, from 0.0 wt % up to 2.5 wt%. The free volume properties of the composite films are correlated with its tensile mechanical properties.

Theoretical Investigation of Fast Neutron and Gamma Radiation Properties of Polycarbonate-Bismuth Oxide Composites Using Geant4

The gamma mass (µ_m) and linear (µ) attenuation coefficients of polycarbonate-bismuth oxide composites (PC-Bi₂O₃) with different bismuth oxide weight factors were investigated theoretically using EpiXS and a Monte Carlo simulation-based toolkit and Geant4 within an energy range between 0.1 and 2 MeV. The wide energy ranges of gamma rays and neutrons were chosen to cover as many applications as possible. The attenuation coefficients were then used to compute the half-value layers. The effective atomic numbers and effective electron densities of the studied samples obtained by EpiXS were compared as well. In order to further evaluate the shielding effectiveness of the studied samples, the thicknesses of all the investigated samples equivalent to 0.5 mm lead at a gamma energy of 511 keV were compared using a Geant4 code simulating a female numerical phantom with a gamma source placed facing the chest and a cylinder-shaped shield wrapped around the trunk area. The fast neutron removal cross sections of the investigated samples were studied to evaluate the effect of the weight factor of nanocomposites on the neutron shielding capabilities of the polymer as well.

Comparison of Shielding Material Dispersion Characteristics and Shielding Efficiency for Manufacturing Medical X-ray Shielding Barriers

During medical diagnoses, X-ray shielding barriers are used to protect against direct and indirect X-rays. Currently, lead is used as the primary material for shielding barriers; however, the demand for eco-friendly shielding barriers has been increasing. Conventionally, shielding barriers are manufactured using a mechanically bonded combination of lead and aluminum; however, in this study, a plastic-based injection-molded product was developed using tungsten as an eco-friendly alternative to lead. A new process technology was required for mixing tungsten-which can be difficult to process-with a polymer. Consequently, the mixing conditions within the injection molding machine and the related compounding technology factors were analyzed. The process technology considered the pre-mixing method using powdery polymer, particle dispersion method, number of screw rotations, and amount of filler input. The product's shielding performance was then analyzed. The tungsten content of the 2-mm thick barrier manufactured using the proposed method was 90 wt%, and the lead equivalent was 0.321 mmPb. To increase the effectiveness of injection molding in the manufacturing process, specific hourly compounding conditions were proposed. Consequently, the process technology method developed in this study can be considered suitable for manufacturing various shielding barriers.

Gamma radiation shielding performance and physico-chemical properties of poly (vinyl alcohol)/Cd(NO3)2 composite films

To improve a radiation shielding performance of the polymer composite, poly (vinyl alcohol) (PVA) was composited with cadmium nitrate. Its radiation shielding capabilities of PVA/Cd(NO3)2 composite films were investigated at three different Cd(NO3)2 concentration levels: 5, 10, and 15% wt. The structural, thermal, and optical properties of the synthesized composite films were examined. The addition of cadmium nitrate to the polymer worsened its thermal stability and improved its optical energy band gap by lowering its direct bandgap energy from 4.56 to 3.25 eV for PVA and PVA/15 wt% Cd(NO3)2 films, respectively. The gamma-ray shielding capacity of the composite was examined using radioactive sources including 241Am (59.5 keV),57Co (122 keV), 192Ir (346 keV) and 137Cs (662 keV). The Micro-Shielding program was used to compare the experimental results of gamma transmittance with theoretical calculations, and the results were found to be in good agreement. Radiation shielding performance of PVA/Cd(NO3)2 composite films was examined by the determination of the linear attenuation coefficient (µ), mass attenuation coefficient (µ m), half value layer (HVL) and exposure buildup factor (EBF). The reinforcement of PVA matrix with 15 wt% Cd(NO3)2 supported to increase the radiation shielding capacity by 13.7% for gamma photons of 57Co radioisotope.

Micro and nano Bi2O3 filled epoxy composites: Thermal, mechanical and γ-ray attenuation properties

Polymer composites have attracted considerable attention as potential light-weight and cost-effective materials for radiation shielding and protection. In view of this, the present work focusses on development of lead-free composites of diglycidyl ether of bisphenol A (DGEBA) epoxy resin with micro (~ 10 μm) and nano (~ 20 nm) bismuth (III) oxide (Bi₂O₃) fillers, using solution casting technique. Thermal, mechanical and γ-ray attenuation properties of the composites were studied by varying the filler loading. Inclusion of the fillers into epoxy matrix was confirmed both structurally and morphologically by XRD and SEM, respectively. Thermogravimetric analysis (TGA) showed the thermal stability of composites to be as high as 400 °C. The nanocomposites exhibited relatively higher thermal stability than their micro counterparts. Among the composites, 14 wt% nano-Bi₂O₃/epoxy composites showed highest tensile strength of 326 MPa, which is about 38% higher than 30 wt% micro Bi₂O₃/epoxy composites. Mass attenuation coefficients (μ/ρ) of the composites were evaluated at γ-ray energies ranging from 0.356 to 1.332 MeV. Nanocomposites showed better γ-ray shielding at all energies (0.356, 0.511, 0.662, 1.173, 1.280 and 1.332 MeV) than micro composites with same filler loading. These studies revealed the significance of nano-sized fillers in enhancing overall performance of the composites.

Introducing a novel low energy gamma ray shield utilizing Polycarbonate Bismuth Oxide composite

The fabrication of different weight percentages of Polycarbonate-Bismuth Oxide composite (PC-Bi2O3), namely 0, 5, 10, 20, 30, 40, and 50 wt%, was done via the mixed-solution method. The dispersion state of the inclusions into the polymeric matrix was studied through XRD and SEM analyses. Also, TGA and DTA analyses were carried out to investigate the thermal properties of the samples. Results showed that increasing the amount of Bi2O3 into the polymer matrix shifted the glass transition temperature of the composites towards the lower temperatures. Then, the amount of mass attenuation coefficients of the samples were measured using a CsI(Tl) detector for different gamma rays of 241Am, 57Co, 99mTc, and 133Ba radioactive sources. It was obtained that increasing the concentration of the Bi2O3 fillers in the polycarbonate matrix resulted in increasing the attenuation coefficients of the composites significantly. The attenuation coefficient was enhanced twenty-three times for 50 wt% composite in 59 keV energy, comparing to the pure polycarbonate.

Introducing a novel low energy gamma ray shield utilizing Polycarbonate Bismuth Oxide composite

The fabrication of different weight percentages of Polycarbonate-Bismuth Oxide composite (PC-Bi₂O₃), namely 0, 5, 10, 20, 30, 40, and 50 wt%, was done via the mixed-solution method. The dispersion state of the inclusions into the polymeric matrix was studied through XRD and SEM analyses. Also, TGA and DTA analyses were carried out to investigate the thermal properties of the samples. Results showed that increasing the amount of Bi₂O₃ into the polymer matrix shifted the glass transition temperature of the composites towards the lower temperatures. Then, the amount of mass attenuation coefficients of the samples were measured using a CsI(Tl) detector for different gamma rays of ²⁴¹Am, ⁵⁷Co, ^99mTc, and ¹³³Ba radioactive sources. It was obtained that increasing the concentration of the Bi₂O₃ fillers in the polycarbonate matrix resulted in increasing the attenuation coefficients of the composites significantly. The attenuation coefficient was enhanced twenty-three times for 50 wt% composite in 59 keV energy, comparing to the pure polycarbonate.

Polymeric composite materials for radiation shielding: a review

The rising use of radioactive elements is increasing radioactive pollution and calling for advanced materials to protect individuals. For instance, polymers are promising due to their mechanical, electrical, thermal, and multifunctional properties. Moreover, composites made of polymers and high atomic number fillers should allow to obtain material with low-weight, good flexibility, and good processability. Here we review the synthesis of polymer materials for radiation protection, with focus on the role of the nanofillers. We discuss the effectivness of polymeric materials for the absorption of fast neutrons. We also present the recycling of polymers into composites.