Showing papers on "Mean free path published in 2022"

Optical and radiation shielding effectiveness of a newly fabricated WO3 doped TeO2–B2O3 glass system

Abstract: The objective of this study is to investigate the effect of WO3 doping on optical and shielding properties of TeO2B2O3 glass system. A new glass series of [(TeO2)0.7(B2O3)0.3(ZnO)0.3]1-x(WO3)x had been synthesized through l melt-quenching method. Structurally, all glass samples are in long-range structural disorder which has an amorphic nature. The density of samples was seen to decrease as the concentration of WO3 and molar volume increases. In optical analysis, the values for direct and indirect optical band gaps were varied between 2.37 and 3.12 eV and between 2.27 and 2.58 eV respectively. The values of Urbach energy were found to lie within 0.35–1.33 eV. For radiation shielding features, linear attenuation coefficients obtained with FLUKA code and XCOM database are found to be in good harmony with relative difference <3%. Based upon mean free path, half value layer and linear attenuation coefficient, the glass sample ZnOB2O3TeO2WO3(0.00) having highest percentage of TeO2is found to be the most excellent shielding composition among the samples investigated in this study.

Structural, mechanical, radiation shielding properties and albedo parameters of alumina borate glasses: Role of CeO2 and Er2O3

Abstract: In this study, the effect of CeO2 and Er2O3 on the physical, structural and mechanical properties of the B2O3-Na2O-Al2O3 glass composition, according to the formula [75-(x+y)]B2O3-20Na2O-5Al2O3-x(CeO2)+y(Er2O3) (where x+y=1, mol %) were investigated. The half-value layer (HVL), neutron removal cross-section (R), effective atomic numbers (Zeff), mean free path (MFP), mass attenuation coefficients (MAC), and radiation safety efficiency (RPE) of the prepared glass structure were experimentally tested and theoretically determined for radiation shielding properties. The MCNP5 code was also used to measure the mass attenuation coefficients of glasses. At 59.54 keV, the glass system's albedo number, energy, and dose were determined by examining Compton and coherent peaks in XRF spectra. The XRD analyses showed that CeO2 and Er2O3 doped alumina borate glasses had a completely amorphous structure. Optical band gap ( E opt ) values decreased according to pure glass because of the replacement of RO oxides in the glass matrix. Luminescence spectra had red emission correspond to 640–690 nm region through 4F9/2→6H11/2 transition. Good agreements were also observed between WinXCOM and Monte Carlo simulation results for MAC values. It was observed that doping 1 mol% of Er2O3 decreased the reflectivity of the gamma rays of the alumina borate glass by 30.9% compared to the doping 1 mol% of CeO2. In addition, the structural and mechanical properties of the CeO2 and Er2O3 doped borate glasses were examined, and comparisons were made.

A detailed investigation on highly dense CuZr bulk metallic glasses for shielding purposes

Abstract: Abstract Gamma-ray shielding properties of eight different metallic glasses based on CuxZr100-x: x = 35 (Cu35Zr65) − 70 (Cu70Zr30) were determined using Monte Carlo simulations and Phy-X/PSD software. A typical gamma-ray transmission setup has been modeled in MCNPX Monte Carlo code. The general trend of the linear attenuation coefficients (μ) was reported as (μ)Cu35Zr65 < (μ)Cu40Zr60 < (μ)Cu45Zr55 < (μ)Cu50Zr50 < (μ)Cu55Zr45 < (μ)Cu60Zr40 < (μ)Cu65Zr35 < (μ)Cu70Zr30. In terms of half value layer (HVL) values, the Cu35Zr65 sample has the highest value (2.984 cm) and the Cu70Zr30 sample has the lowest value (2.769 cm) at 8 MeV photon energy. The mean free path (MFP) values were 4.305 and 3.995 cm for Cu35Zr65 and Cu70Zr30 samples, respectively. Generally, MFP and HVL values of the studied glasses were reported as (MFP,HVL)Cu35Zr65 > (MFP,HVL)Cu40Zr60 > (MFP,HVL)Cu45Zr55 > (MFP,HVL)Cu50Zr50 > (MFP,HVL)Cu55Zr45 > (MFP,HVL)Cu60Zr40 > (MFP,HVL)Cu65Zr35 > (MFP,HVL)Cu70Zr30 for all photon energy range. The Cu70Zr30 sample showed maximum values of both the effective conductivity (C eff) and effective electron density (N eff). In addition, the Cu70Zr30 sample has minimum exposure and energy absorption buildup factor (EBF and EABF) values at all studied gamma-ray energies. The results revealed that the Cu70Zr30 sample has superior attenuation properties among all studied samples.

Gamma, neutron, and heavy charged ion shielding properties of Er3+-doped and Sm3+-doped zinc borate glasses

Abstract: Abstract This study aimed to investigate the nuclear radiation shielding properties of erbium (Er)-reinforced and samarium (Sm)-reinforced borate glasses. In the 0.015–15 MeV photon energy range, attenuation coefficients, as well as half-value layer tenth-value layers, and the mean-free path have been calculated. Additionally, effective, and equivalent atomic numbers, effective atomic weight, electron density, and exposure and energy absorption build-up factors were also calculated. To evaluate the overall nuclear radiation attenuation competencies of Er-rich and Sm-rich glasses, effective removal cross-section values for fast neutrons and projected range/mass stopping power values for alpha and proton particles were also determined. The glass sample BZBEr2.0 had the highest linear and mass attenuation coefficients (µ and µ m), effective conductivity (C eff), the effective number of electrons (N eff), and effective atomic number (Z eff) values as well as the lowest half-value layer (T 1/2), tenth value layers (T 1/10), mean free path (λ), exposure build-up factor, and energy absorption build-up factor values. µ m values were reported as 2.337, 2.556, 2.770, 2.976, 2.108, 2.266, 2.421, 2.569, and 2.714 for BZBEr0.5, BZBEr1.0, BZBEr1.5, BZBEr2.0, BZBSm0.0, BZBSm0.5, BZBSm1.0, BZBSm1.5, and BZBSm2.0 glass samples at 0.06 MeV, respectively. The results showed that Er has a greater effect than Sm regarding the gamma-ray shielding properties of borate glasses. The results of this investigation could be used in further investigations and added to older investigations with the same aim, to aid the scientific community in determining the most appropriate rare-earth additive, to provide adequate shielding properties based on the requirement.

The Influence of Bi2O3 Nanoparticle Content on the γ-ray Interaction Parameters of Silicon Rubber

Abstract: In this study, synthetic silicone rubber (SR) and Bi2O3 micro- and nanoparticles were purchased. The percentages for both sizes of Bi2O3 were 10, 20 and 30 wt% as fillers. The morphological, mechanical and shielding properties were determined for all the prepared samples. The Linear Attenuation Coefficient (LAC) values of the silicon rubber (SR) without Bi2O3 and with 5, 10, 30 and 30% Bi2O3 (in micro and nano sizes) were experimentally measured using different radioactive point sources in the energy range varying from 0.06 to 1.333 MeV. Additionally, we theoretically calculated the LAC for SR with micro-Bi2O3 using XCOM software. A good agreement was noticed between the two methods. The NaI (Tl) scintillation detector and four radioactive point sources (Am-241, Ba-133, Cs-137 and Co-60) were used in the measurements. Other shielding parameters were calculated for the prepared samples, such as the Half Value Layer (HVL), Mean Free Path (MFP) and Radiation Protection Efficiency (RPE), all of which proved that adding nano-Bi2O3 ratios of SR produces higher shielding efficiency than its micro counterpart.

Assessment of the usability conditions of Sb2O3–PbO–B2O3 glasses for shielding purposes in some medical radioisotope and a wide gamma-ray energy spectrum

Abstract: Abstract We report some fundamental gamma-ray shielding properties and individual transmission factors (TFs) of five distinct glass samples with a nominal composition of xSb2O3·(40 − x)PbO·60B2O3·0.5CuO and (where; 0 ≤ x ≤ 40 mol%). Phy-X/PSD and MCNPX (version 2.7.0) Monte Carlo code are utilized to determine several critical parameters, such as cross-sections, attenuation coefficients, half and tenth value layers, build-up factors, and TFs. A general transmission setup is designed using basic requirements. Accordingly, TFs are evaluated for several medical radioisotopes. Next, the gamma-ray shielding parameters and TFs are assessed together in terms of providing the validity of the findings. Our results showed that there is a positive contribution of increasing Sb2O3 amount in the glass matrix owing its direct effect to the density increment as well. This positive effect on gamma-ray shielding properties is also observed for decreasing mean free path values from S1 to S5 samples. The exposure build-up factor (EBF) and energy absorption build-up factor (EABF) values, increasing the quantity of Sb2O3 supplementation, resulted in a general reduction in EBF and EABF values (i.e., from 0.5 to 40 mfp). When the quantity of Sb2O3 rises from S1 to S5, the collision rate of incoming gamma rays in glass samples increases significantly. The TF figures reveal that S5 showed the least transmission behavior across all the above-mentioned studied glass thicknesses. It can be concluded that increasing the Sb2O3 additive is a beneficial and monotonic technique, when the gamma-ray shielding qualities or TF values must be further enhanced.

Nuclear shielding characteristics of Sm3+ doped borosilicate glasses containing Na2O, PbO and ZnO

Abstract: The aim of this paper is to investigate the photon, charged particles, fast and thermal neutrons absorption characteristics and dose rates of Sm3+ doped borosilicate glasses containing Na2O–PbO–ZnO via theoretical method and simulation code. The linear attenuation coefficients of SBNPZS4 glasses are the highest whereas the mass attenuation coefficients of SBNPZS1 glasses are the highest in the present SBNPZS glasses. The SBNPZS4 has the lowest half value layer and mean free path values among the SBNPZS glasses and compared standard shielding materials therefore SBNPZS4 has the better photon absorption characteristics. The effective atomic number, effective electron density, mass energy-absorption coefficient, specific gamma ray constant, and gamma dose rate values change as SBNPZS4

Experimental and FLUKA evaluation on structure and optical properties and γ-radiation shielding capacity of bismuth borophosphate glasses

Abstract: For 662, 1173, 1275, and 1333 keV gamma-ray energy, photon transmissions, linear attenuation coefficients, half value layer, tenth value layer, and mean free path values of bismuth-borophosphate glasses were measured experimentally. Then, the measured findings were compared to the FLUKA code. The FLUKA code findings agreed well with the experimental results. Furthermore, the findings show that adding Bi 2 O 3 to the glass network improves the shielding properties. The current data reveal that when the Bi 2 O 3 content rises, so does the absorbance. Furthermore, the optical constants of the present gasses, such as optical band gap, phonon energy, and tails of localized states, were examined. Fourier transform infrared (FTIR) spectrometer was used to analyze the Fourier transform infrared (FTIR) spectra of our samples at room temperature in the 4000–400 cm −1 wavenumber range. From a shielding standpoint, bismuth-borophosphate glasses offer excellent gamma-ray shielding properties.

Evaluation of structural, elastic properties and nuclear radiation shielding competence of Nd3+ doped lithium-zinc-phosphate glasses

Abstract: Nd3+ doped lithium-zinc-phosphate glasses were synthesized by melt-quenching technique. FTIR spectra were recorded in the wavenumber range of 400–4000 cm−1. Elastic parameters such as Debye temperature and fractal bond connectivity were calculated. The results revealed that these parameters were influenced by the glass system's composition and dopant concentration. The mass and linear attenuation coefficients (MAC, LAC) of gamma-ray photons at the energy range from 0.015 to 15 MeV have been investigated using the Phy-X/PSD software program as well as the XCOM database program. Both MAC and LAC increase with the increase in the amount of Nd2O3. Also, the mean free path values and the half-value layer decrease while the density increases with the increase of the Nd2O3 content. Moreover, the fast neutron removal cross section was also presented and the results were compared with the concrete and commercial shielding glasses.

Effect of B2O3 on the Radiation Shielding Performance of Telluride Lead Glass System

Abstract: This paper studies the role of B2O3 in the radiation shielding properties of (100-x)(60TeO2-40PbO)-xB2O3 glass systems where x = 0, 1, 2, 3, 4 and 5 mol%. Through the scanning electron microscope (SEM) and X-ray diffraction (XRD) tests of the glass, the structure of the glass was studied. Physical radiation sources (57Co, 60Co, 137Cs, 133Ba, and 241Am) and WinXCOM software were used to experimentally and theoretically calculate the radiation properties of the glass, respectively. The gamma shielding ability of the glass was evaluated using its mass decay coefficient (μm), half-value layer (HVL), mean free path (MFP) and effective atomic number (Zeff). The neutron shielding ability of the glass was evaluated by calculating the fast neutron removal cross-section (RCS) value. The glass’s gamma and neutron shielding properties were compared to various ordinary concrete and other tellurite glasses. The measured mass decay coefficients agree well with the theoretical values obtained using WinXCOM software. Low HVL, MFP, and high μm, Zeff, and RCS values indicate that this series of glass materials have good shielding properties. According to the obtained results, among the glass samples doped with B2O3, the TPB-1 glass sample showed the best radiation shielding performance.

A Study on the Gamma Radiation Protection Effectiveness of Nano/Micro-MgO-Reinforced Novel Silicon Rubber for Medical Applications

Abstract: In this work, we examined novel polymer composites for use in radiation protection applications. These prepared polymers are non-toxic compared with lead and show potential to be used as protective gear in different medical applications where low-energy photons are utilized. We prepared silicon rubber (SR) with different concentrations of micro- and nano-sized MgO. We used a HPGe detector to measure radiation attenuation factors at different photon energies, ranging from 59.6 to 1333 keV. We reported the effect of particle size on the attenuation parameters and found that the linear attenuation factors for SR with nano-MgO were higher than for SR with micro-MgO. The mean free path (MFP) for pure SR and SR with micro- and nano-sized MgO were determined, and we found that silicon rubber with MgO (both micro- and nano-sized) has a lower MFP than pure SR. The linear attenuation coefficient results show the importance of using SR with high MgO content for low-energy radiation protection applications. Moreover, the half-value layer (HVL) results demonstrate that we need a certain thickness of SR with nano-MgO to effectively reduce the intensity of the low-energy photons.

Comparative assessment of fast and thermal neutrons and gamma radiation protection qualities combined with mechanical factors of different borate-based glass systems

Abstract: Adequate shielding from ionizing radiations is essential in nuclear facilities because of such radiations’ adverse effects on humans in the event of unwanted or accidental exposure. In the current work, for four distinct compositions of B2O3-Li2O, Li2O-Na2O-K2O-B2O3, Gd2O3-SiO2-B2O3, and Bi2O3-Li2O-ZnO-B2O3 glass systems, neutron and γ-ray attenuation competencies combined with elastic features have been examined for feasible nuclear radiation protection purposes. ΣR (fast neutron removal cross-section) and for thermal energy neutrons σT (total cross-section) and SP (shielding percentage) were estimated. Comparably, in all samples, 50B2O3-10K2O-40Li2O (mol%) glass possesses larger ΣR (=0.11755 cm−1), whereas 25B2O3-37.5Si2O-37.5Gd2O3 (mol%) glass shows large σT (=646.171 cm−1) and SP for thermal neutrons at minimal thickness, indicating the included Gd2O3’s positive effect as element Gd has a high neutron absorption capacity. Employing the Phy-X/PSD program and MCNPX code, μ/ρ (mass attenuation coefficient) of all selected glasses is calculated for a γ-ray energy span of 0.015 – 15 MeV. Gd2O3 or Bi2O3 addition improved μ/ρ, and such increment is significant at low energies owing to PEA (photoelectric absorption) dominance and Gd or Bi K-edges. Also, for 15B2O3-10ZnO-5Li2O-70Bi2O3 (mol%) glass, μ/ρ has been derived by the WinXCOM program and FLUKA, Geant4, and PHITS codes, and a good accord between such simulated and theoretical μ/ρ outcomes is noticed following the calculated relative differences. Next, linear attenuation coefficient, effective atomic number and electron density, MFP (mean free path), TVL (tenth-value layer), HVL (half-value layer), and RPE (radiation protection efficiency) have also been evaluated. Comparatively, at 1.25, 0.662, and 0.2 MeV energies, 15B2O3-10ZnO-5Li2O-70Bi2O3 (mol%) sample possesses lower MFP and HVL than five SCHOTT AG commercial glass shields. Approximated RPE results affirmed all Gd2O3-SiO2-B2O3 and Bi2O3-Li2O-ZnO-B2O3 samples’ potent absorption (almost 100%) ability for lower energy γ-rays. Moreover, equivalent atomic number, and by geometric progression fitting process, within energy 15 keV–15 MeV extent for ten different penetration depths at 1–40 mfp span buildup factors have been assessed. 15B2O3-10ZnO-5Li2O-70Bi2O3 (mol%) glass exhibits better gamma-ray shielding effectiveness in all chosen samples, specifying Bi2O3’s favorable impact. Changes in photon shielding factors were interpreted following pair production, Compton scattering, and PEA processes. Later, elastic (Young’s (Y), bulk (K), shear (S), and longitudinal (L)) moduli and Poisson’s ratio values have been calculated for all inspected glasses. BC (bond compression) and M-M (Makishima–Mackenzie) models were utilized for such elastic traits reckoning. All K, Y, S, and L values’ trends for binary B2O3-Li2O glasses were identical in both BC and M-M models, and Kbc was found to be raised from 73.63 to 89.89 GPa, while KM–M increased from 75.35 to 180.53 GPa accordingly when Li2O content improved from 9.6 to 39.9 mol% in the chemical composition.

Unraveling Heat Transport and Dissipation in Suspended MoSe2 from Bulk to Monolayer

Abstract: Understanding heat flow in layered transition metal dichalcogenide (TMD) crystals is crucial for applications exploiting these materials. Despite significant efforts, several basic thermal transport properties of TMDs are currently not well understood, in particular how transport is affected by material thickness and the material's environment. This combined experimental–theoretical study establishes a unifying physical picture of the intrinsic lattice thermal conductivity of the representative TMD MoSe2. Thermal conductivity measurements using Raman thermometry on a large set of clean, crystalline, suspended crystals with systematically varied thickness are combined with ab initio simulations with phonons at finite temperature. The results show that phonon dispersions and lifetimes change strongly with thickness, yet the thinnest TMD films exhibit an in‐plane thermal conductivity that is only marginally smaller than that of bulk crystals. This is the result of compensating phonon contributions, in particular heat‐carrying modes around ≈0.1 THz in (sub)nanometer thin films, with a surprisingly long mean free path of several micrometers. This behavior arises directly from the layered nature of the material. Furthermore, out‐of‐plane heat dissipation to air molecules is remarkably efficient, in particular for the thinnest crystals, increasing the apparent thermal conductivity of monolayer MoSe2 by an order of magnitude. These results are crucial for the design of (flexible) TMD‐based (opto‐)electronic applications.

Superdiffusion of cosmic rays in compressible magnetized turbulence

Abstract: Owing to the complexity of turbulent magnetic fields, modeling the diffusion of cosmic rays is challenging. Based on the current understanding of anisotropic magnetohydrodynamic (MHD) turbulence, we use test particles to examine the cosmic rays' superdiffusion in the direction perpendicular to the mean magnetic field. By changing Alfven Mach number $M_A$ and sonic Mach number $M_S$ of compressible MHD simulations, our study covers a wide range of astrophysical conditions including subsonic warm gas phase and supersonic cold molecular gas. We show that freely streaming cosmic rays' perpendicular displacement increases as 3/2 to the power of the time traveled along local magnetic field lines. This power-law index changes to 3/4 if the parallel propagation is diffusive. We find that the cosmic rays' parallel mean free path decreases in a power-law relation of $M_A^{-2}$ in supersonic turbulence. We investigate the energy fraction of slow, fast, and Alfvenic modes and confirm the dominance of Alfvenic modes in the perpendicular superdiffusion. In particular, the energy fraction of fast mode, which is the main agent for pitch-angle scattering, increases with $M_A$ but is insensitive to $M_S \ge 2$. Accordingly, our results suggest that the suppressed diffusion in supersonic molecular clouds arises primarily due to the variations of $M_A$ instead of $M_S$.

Performance of newly developed concretes incorporating WO3 and Barite as radiation shielding material

Abstract: The preparation of suitable materials with satisfactory nuclear and mechanical properties to shield the ionizing radiation is a major concern in design the radiation protection. In this work, a group of heavy concrete samples were prepared containing varying concentrations of Tungsten oxide, and the mechanical and radiation shielding properties of the resulting samples was studied using theoretical and experimental techniques. Good agreement between the experimental test and the theoretical data was confirmed at all examined energies. Using WO3 in the present concretes increases the density of specimens as well as the photons shielding capability. The increase in the amount of WO3 caused a reduction in the half value layer and an increase in the radiation protection efficiency for the prepared concretes. The linear attenuation coefficient (LAC) for the control concrete reduces from 0.665 to 0.127 cm−1 over the selected energy range, while it is reduced from 1.803 to 0.134 cm−1 and from 2.014 to 0.138 cm−1 for Conc-1 and Conc-2 samples. The mean free path results demonstrated that all the specimens with additive materials (i.e. WO3 and barite) have lower MFP than the control concrete. Thus, incorporating WO3 and barite into the concrete significantly decreases the MFP of the specimens. The high-density concrete (i.e. Conc-5) absorbs gamma photons more efficaciously than the lower density samples. The radiation protection efficiency (RPE) for Concr-5 is 99% at 0.122 MeV, which suggests that this concrete can stop almost all the incoming photons with low energy.

The short ionizing photon mean free path at z=6 in Cosmic Dawn III, a new fully-coupled radiation-hydrodynamical simulation of the Epoch of Reionization

Abstract: Recent determinations of the mean free path of ionising photons (mfp) in the intergalactic medium (IGM) at $\rm z=6$ are lower than many theoretical predictions. In order to gain insight, we investigate the evolution of the mfp in our new massive fully coupled radiation hydrodynamics cosmological simulation of reionization: Cosmic Dawn III (CoDa III). CoDa III’s scale ($\rm 94^3 \, cMpc^3$) and resolution ($\rm 8192^3$ grid) make it particularly suitable to study the IGM during reionization. The simulation was performed with RAMSES-CUDATON on Summit, and used 131072 processors coupled to 24576 GPUs, making it the largest reionization simulation, and largest ever RAMSES simulation. A superior agreement with global constraints on reionization is obtained in CoDa III over CoDa II, especially for the evolution of the neutral hydrogen fraction and the cosmic photo-ionization rate, thanks to an improved calibration, later end of reionization ($\rm z=5.6$), and higher spatial resolution. Analyzing the mfp, we find that CoDa III reproduces the most recent observations very well, from $\rm z=6$ to $\rm z=4.6$. We show that the distribution of the mfp in CoDa III is bimodal, with short (neutral) and long (ionized) mfp modes, due to the patchiness of reionization and the co-existence of neutral versus ionized regions during reionization. The neutral mode peaks at sub-kpc to kpc scales of mfp, while the ionized mode peak evolves from $\rm 0.1 Mpc/h$ at $\rm z=7$ to ∼10 Mpc/h at $\rm z=5.2$. Computing the mfp as the average of the ionized mode provides the best match to the recent observational determinations. The distribution reduces to a single neutral (ionized) mode at $\rm z>13$ ($\rm z<5$).

Ecofriendly and radiation shielding properties of newly developed epoxy with waste marble and WO3 nanoparticles

Abstract: Research into protection techniques from harmful effects of gamma radiation have increased contemporarily. The development of radiation-resistant materials having a high radiation resistance and absorption of different types of ionizing radiation could offer promising solutions to this matter. For this purpose, the preparation and examination of a novel type of polymer doped with various WO3 concentrations are presented in this study. To accomplish our main objective, we evaluated the effectiveness of their radiation shielding against gamma radiation from 137Cs, 60Co, and 241Am. At all investigated energies, the measured and theoretical linear attenuation coefficient (LAC) values are highly similar, proving that the experimental LAC values can be used to reliably predict other radiation shielding characteristics. The half value layer (HVL) values decreased as the samples' WO3 level rises indicating that increasing the amount of WO3 in these samples increases their radiation shielding effectiveness. In addition, it was found a positive correlation between radiation energy and the mean free path (MFP) values. At 0.060 MeV, the MFP values are equal to 1.374 cm, 0.691 cm, 0.521 cm, and 0.369 cm at concentrations of 0, 10, 20, and 25% WO3, respectively reflecting that the MFP is reduced by 3.7 times due to the addition of 20% WO3 nanoparticles. From the transmission factor, it was found that improving the shielding ability of the proposed materials could be achieved by increasing and adjusting the thickness of the absorber depending on the required energy range used. It is noteworthy that the present studied samples (epoxy + waste marble + nano-WO3) that have exhibited a greater shielding ability than other nanoparticles added polymers like (Epoxy + nano-MgO30), and (silicone rubber + nano-WO330).

The self-diffusivity of natural gas in the organic nanopores of source rocks

Abstract: Natural gas stored in source rocks has become a significant contributor to supply the energy demand. Source rocks are a special subclass of sedimentary rocks where the matrix serves as both the source and the reservoir at the same time. Attributed to their complex mineralogy and multi-scale pore systems, source rocks exhibit transport and storage processes that are not within the continuum framework. Significant portion of source rocks pores is of few nanometers in size. These nanopores offer large surface area to host hydrocarbons in the free and sorbed forms. Our ability to model the mechanisms by which hydrocarbons are stored and transported is, however, at infancy stages. In this paper, representative organic nanopores were formed from kerogen at different thermal maturation states. Free molecular diffusion was found to be the dominant mechanisms based on the calculated Knudsen number. Furthermore, diffusivity analysis was performed using molecular dynamics for some range of pressure that is typically encountered during the production span. The results revealed some deviation of the diffusivity coefficient from the value calculated theoretically. The deviation was even more pronounced for the post-mature case. The gap between the theoretically calculated and molecularly simulated diffusivity coefficients was found to reduce with increasing the pressure and the pore size. The sorption and diffusion data were coupled to redefine the mean free path for gas transport in organic nanopores. The reported values can serve as input for better description of the hydrocarbons transport in source rocks.

A Novel Epoxy Resin-Based Composite with Zirconium and Boron Oxides: An Investigation of Photon Attenuation

Abstract: We have attempted to develop the gamma radiation shielding abilities of newly prepared epoxy composites by introducing ZrO2. The radiation shielding parameters are experimentally reported below. The experimental setup included an HPGe detector and different radioactive point sources which emitted photons with energies of 0.06, 0.662, 1.173, and 1.333 MeV. The gamma radiation shielding abilities of the epoxy composites were examined in the context of the linear attenuation coefficient (LAC), half-value layer (HVL), radiation absorption ratio, and other factors. The experimental and Phy-X results for the LAC were compared, and acceptable consistency was reported. The lowest LAC values were reported for EBZr-0 (free of ZrO2), and we found that the photon attenuation competence of the present epoxy improved as a result of increasing the ZrO2 content. We compared the LAC values for the present epoxy composites with other samples, and we found that the prepared composites with 20% to 40% ZrO2 had higher LAC values than epoxy with 30% Yahyali Stone. The HVL lengths of the epoxy composites reduced with the addition of ZrO2 for the four selected energies, which confirmed that introducing ZrO2 improves the radiation absorption abilities of epoxy composites. At 0.06 MeV, the HVL for the ZrO2-free epoxy was 2.60 cm, which fell to 0.23 cm after adding 40% ZrO2. The mean free path (MFP) for the prepared composites was less than 1 cm at 0.06 MeV (standard for EBZr-0), while it was 1.32 cm for EBZr-10. For the other energies, it was higher than 6 cm, and became higher than 10 cm at 1.333 MeV for all composites. The obtained results suggest that non-toxic, natural, and cheap epoxy composites with high ZrO2 content have the potential to improve the gamma ray shielding competence of epoxy composites for low energy radiation applications.

High density binary TeO2-Bi2O3 glasses: Strong potential as a nontoxic and environmentally friendly glass shields for photons/charged particles

Abstract: Ionizing radiation/charged particles shielding capacity of high density bismuth tellurite based glasses: (100-x)TeO2+xBi2O3 with x = 5(TB5), 8(TB8), 10(TB10), 12(TB12), and 15 (TB15) mol% have been examined. New Phy-X/PSD software has been applied to achieve this aim. The gamma radiation shielding parameters such as mass/linear attenuation coefficients (MAC/LAC), half value thickness (HVT), effective atomic number/electron density (Zeff/Neff) and mean free path (MFP) were estimated for thirteen (13) energies in the range of 0.2835–2.506 MeV associated with 60Co, 137Cs, 131I, and 22Na sources. Comparatively, the obtained values revealed that (MAC/LAC)TB5 < (MAC/LAC)TB8 < (MAC/LAC)TB10 < (MAC/LAC)TB12 < (MAC/LAC)TB15. The Zeff and Neff varies from 25.01 to 43.96 and 2.69–4.25 × 1023 electrons/gram. The (HVT/MFP)TB15 < (HVT/MFP)TB12 < (HVT/MFP)TB10 < (HVT/MFP)TB8 < (HVT/MFP)TB5. The variation of the total stopping power (SP) of electron was obeyed the trend: (SP)TB5 < (SP)TB8 < (SP)TB10 < (SP)TB12 < (SP)TB15. Results revealed that the increase in the Bi2O3 content of the glasses has a positive influence on their photon absorbing ability.