1. Introduction
Glasses, which are flexible materials in terms of ease of production and structural variations to production, have vital roles in technology and research [
1]. Utilized as the primary raw materials, phosphorus pentoxide, boron oxide, and vanadium pentoxide are the most common compounds in the manufacture of glasses [
2,
3,
4]. Of these chemicals, B
2O
3 is regarded as the strongest glass former [
5,
6,
7]. Borate glasses in which B
2O
3 establishes the glass network are mostly used as optical materials because they have low melting points, high transmittance properties, and high thermal stability [
8,
9,
10]. They are widely used in the processing of dielectric materials, and used in electronic materials. In addition to their use as dielectric components, the presence of transition metal ions in the borate glass network results in a semiconducting character [
11,
12,
13,
14,
15]. Transition metals are used in glass science in different contexts because of their complex properties that emerge from several valence states [
16]. Zinc oxide/borax glasses are being used in plasma screens and displays for high definition and quality. They are chosen due to their ability to quickly pass energy in dielectric layers and their high transparency [
17]. With all of the qualities mentioned above, zinc borate glasses stand out among products for applications that are in doubt. Studies on vanadium have grown recently due to the material’s curious optical, electrical, and magnetic properties [
18,
19,
20,
21,
22,
23]. Though studies on transition-metal-doped glasses can frequently be found in the literature, there are still components, compositions, and properties that have not yet been studied. Despite the broad variety of papers researching transition-metal-doped glasses, many elements, formulations, and properties are not yet researched. On the other hand, analysis suggests that these glasses can be extremely protective against radiation [
24,
25,
26,
27,
28,
29,
30,
31,
32,
33]. The use of the glass material for radiation shielding is not limited to this kind of glass, but the frequency of experimental studies on the issue has been increasing daily as a hot topic. Any conventional materials such as lead and concrete used in nuclear fields do not possess superior material properties and have some features that can endanger health [
34]. Although this report does not say unequivocally that these new shielding materials are an insufficient radiation-shielding material, some organizations such as IAEA have direct incentives for researchers to study new-generation shielding materials. In this case, glasses suit the profile of these kinds of uses. For this aim, the compositions of a group of glasses encoded as ZBV1, ZBV2, ZBV3, and ZBV4 [
35] were tested and extensively researched for their capabilities in gamma-radiation attenuation.
In this study, gamma-attenuation properties of the ZnO-B
2O
3-V
2O
5 glass system were investigated in terms of the relationship between substitution-type (i.e., V
2O
5) changes in typical shielding behaviors of glass system. Previously, Kilic [
35] investigated the synthesis process and the optical, thermal, and structural properties of four different glasses based on zinc borate containing V
2O
5. His results showed that V
2O
5 enabled the glass-transition temperature of a sample to fall from 553 °C to 531 °C. Moreover, density declined with a rise in the quantity of V
2O
5. Volume improved as the V
2O
5 concentration increased. Compared with the earlier calculation, the refractive index improved. Their large refractive indices suggest that they may be strong optical materials that could be used in optical structures needing a high refractive index. These glasses may be used in many areas of optics, but in some sense are often innovative materials for solar-energy systems due to their semiconducting properties. However, those promising findings are worthy of continuous investigations of aspects such as resistance competencies against gamma rays. In fulfilment of international safety requirements, the value of alternate shielding materials is growing. Therefore, this paper simply focused on examining the interaction between nuclear-radiation-shielding properties in V
2O
5-reinforced ternary zinc borate glasses. This is because of glass materials’ potential as attenuator in industrial, medical, and research ionizing-radiation facilities. It is well known that material density has a remarkable impact on gamma-ray-shielding properties [
36,
37]. Therefore, the importance of traditional shields such as concrete and lead (Pb) is obvious in ionizing-radiation facilities. Since the glasses have been widely reported as alternative shields instead of the aforementioned conventional shields, this study aimed to characterize the material properties of a ZnO-B
2O
3-V
2O
5 system along with its gamma-shielding properties.
M.A. Tunes et al. developed a computational model of a compact pressurized-water nuclear reactor to investigate the use of innovative materials to enhance the biological-shielding effectiveness. They used MCNP and GEM/EVENT codes to simulate the behavior of several materials and the shielding thickness for gamma and neutron radiation [
38]. J. Kaewkhao et al. investigated the mass attenuation coefficients and shielding parameters of borate-based glasses involving Bi
2O
3 and BaO. They established that the increment of the mass-attenuation coefficients was a function of the Bi
2O
3, BaO, and PbO contents. Furthermore, the half-value layers of investigated glasses were more favorable than normal concretes and marketable window glasses. These results reflect that the Bi-based glass can replace Pb in radiation-shielding glass [
39]. P. Limkitjaroenporn et al. prepared lead sodium borate glasses via melt-quenching and explored their optical, physical, structural, and gamma-ray-shielding properties. They recorded that the gamma-ray-shielding properties increased with an increase in PbO concentration [
40]. K. Kirdsiri et al. measured the radiation-shielding and optical properties of bismuth lead silicate and barium silicate glasses. They observed that total mass-attenuation coefficients of the glasses at 662 keV were enhanced by the increment of Bi2O3 and PbO, which elevated the photoelectric absorption in the glass networks [
41]. S. Kaewjang et al. fabricated and investigated the (80−x)B
2O
3-10SiO
2-10CaO-xGd
2O
3 (where x = 15, 20, 25, 30, and 35 mol%) for their radiation-shielding, physical, and optical properties. They found that the experimental values of the mass-attenuation coefficients, effective atomic number, and effective electron densities of the glasses increased with the increasing of Gd2O3 concentration, and also with the increasing of photon energy from 223 to 662 keV [
42]. N. Chanthima et al. investigated the impacts of BaO on the physical properties of zinc borate-based glasses. They recorded that the radiation-shielding parameters were enhanced as a function of BaO, and the decrement of γ-ray energy [
43]. K. Boonin et al. synthesized and inspected zinc barium tellurite glasses for their radiation-defense mechanism and structural behavior. They found that the effective atomic number and effective electron density decreased with the increase in γ-ray energies, which is in a good agreement with theoretical values attained using Geant4 and WinXCOM [
44]. W. Cheewasukhanont et al. studied the radiation-shielding parameters of bismuth borosilicate-based glasses. The outcomes revealed that the density of the glasses increased with the increase of Bi
2O
3 content, while the particle size did not account for the density. They found that the radiation-shielding parameters of these glasses were enhanced over those for traditional glass windows and for some types of concrete [
45]. S. Kaewjaeng et al. prepared and investigated (80−x)B
2O
3:10SiO
2:10CaO:xLa
2O
3 glass (where x = 10, 15, 20, 25, and 30 mol%) for x-ray-shielding, physical, and optical properties. The found that the half-value layer and tenth-value layer of the glass samples tended to decrease when the kVp of an x-ray instrument decreased and La
2O
3 concentrations increased [
46]. F. H. ElBatal et al. studied UV-Vis and FTIR absorption spectra of some prepared undoped and NdF3-doped borophosphate glasses, with varying dopant contents before and after gamma irradiation [
47]. H. ElBatal et al. prepared undoped and CuO-doped lithium phosphate, lead phosphate, and zinc phosphate glasses. The measured the UV–VIS and infrared absorption spectra of the prepared samples before and after successive gamma irradiation [
48].
This study aims to discuss the potential effects of V2O5 substitution on the nuclear-radiation-shielding properties of ZnO-B2O3-V2O5 glasses. The investigated radiation-attenuation parameters can be ordered as: linear-attenuation coefficients (LACs), mass-attenuation coefficients (MACs), effective electron density (Neff), half-value layer (T1/2), exposure buildup factor (EBF), energy-absorption buildup factor (EABF), tenth-value layer (TVL), mean free path (λ), and effective atomic number (Zeff). The obtained outcomes from the current investigation could be useful to understand the direct impact of glass structure, glass density, and replacement type on the radiation-shielding properties of ZnO-B2O3-V2O5 glasses. In this research report, all the investigated parameters will be discussed in terms of synergistic effect of substitution and changes in the resistance behavior against gamma radiation.
3. Results and Discussions
To determine the nuclear-radiation-shielding dynamics of V
2O
5-reinforced ZnO-B2O3 glasses, in silicon Monte Carlo simulation studies were performed. Accordingly, four separate glasses encoded as ZBV1, ZBV2, ZBV3, and ZBV4 based on a (100−x)(0.6ZnO-0.4B
2O
3)(x)(V
2O
5) (x = 1, 2, 3, 4 mol. %) glass system was checked for their potentials as possible materials for nuclear-radiation-shielding implementations. In this study, we used Monte Carlo simulations and Phy-X PSD [
53] code for determination of shielding parameters. First, linear-attenuation coefficients (LACs) were determined between 0.015–15 MeV gamma photon energy.
Figure 3 depicts the variation in the linear attenuation coefficients (µ) against photon energy for all glasses.
Figure 3 shows that the influence of the photoelectric effect, Compton scattering, and pair production processes on the LAC was variable depending on the incident energy zones (i.e., low, middle, and high energy). This finding follows as a result of the association of radiation with matter. At low energy values, the LAC is lost due to photo adsorption. Compton scattering accounted for the majority of the energy difference at the mid-energy area, while the lowest LAC was reported in the ZBV4 sample. In other words, the ZBV4 sample with the highest amount of V
2O
5 additive showed the lowest LAC values. In contrast, the ZBV1 sample showed the highest LAC values. In the low-energy region, LAC values were quite similar, whereas in the high-energy region, the differences were slightly higher. The importance of density and direct LAC relationship with density were dominant factors (
Figure 3). The mass-attenuation coefficient (MAC) of a material is a specific parameter that can be used in terms of density-independent categorizations of studied shielding materials.
Figure 4 illustrates the variations in the mass-attenuation coefficient (µ
m) against incident photon energy for all glasses at 0.015–15 MeV. The chemical structure of the attenuator glass altered the rate of variation of the calculated MAC values. The mathematical analysis of the MAC data show patterns in distinct regions. In the low-energy condition, in which the photoelectric effect is important, the absorption dramatically decreased. Compton-scattering superiority showing the total decrease from the MAC at the mid-energy region. The ZBV1 sample displayed very high atomic concentrations at all incident photon energies. The situation in both the low- and high-energy areas can be clarified by the presence of the highest volume of zinc (
Z = 30) in the glass structure, since it has a significant atomic number among the utilized composition elements (i.e., B, O, V, Zn).
HVL, which stands for “half-value layer” (T
1/2), is a valuable amount when measuring the thickness of a shielding material in order to minimize gamma rays. So, a smaller HVL may serve as a measure of a material’s capacity to shield incident gamma rays from a primary source. Using the calculated LAC values, the HVLs of the studied glasses were calculated.
Figure 5 demonstrates the association between photon energy and T
1/2 for all glass samples. In the low-energy spectrum, calculations of HVL values were reported smaller. This is a predictable result for shielding in materials that low-intensity gamma rays cannot move through almost completely. To learn more about the efficiency of the studied materials as gamma-ray absorbers, we found it useful to compare them with some of the materials most commonly used as shields against gamma rays. The HVL value for the best glass sample (ZBV4 = 8.13915 cm) at 15 MeV was compared with other shielding materials (lead= 1.08069 cm, ordinary concrete = 13.89992 cm, HSC = 11.63975 cm, ILC = 9.40269 cm, IL = 7.81848 cm, G1 = 15.25284 cm, and G2 = 10.53327 cm) glasses [
54,
55]. The comparison shows that the ZBV4 glass came third after lead, and with IL outperforming the other shield types. Considering its other distinguishing features, such as lack of toxicity risk and lower weight, this glass is recommended as the ideal choice in many applications that require gamma-ray shields with specific properties.
However,
Figure 5 shows that the HVL values were greater in the mid- as well as the high-energy field. This was attributed to the penetration property of gamma rays and how it changes with higher energy levels. Considering the direct impact of material densities, which were reported as 3.392 g/cm
3, 3.371 g/cm
3, 3.339 g/cm
3, and 3.329g/cm
3 for ZBV1, ZBV2, ZBV3, and ZBV4, respectively, the HVL values were changed in similar order. For example, HVL values of 1.109 cm HVL
ZBV1 < 1.121 cm HVL
ZBV2 < 1.136 HVL
ZBV3 < 1.143 cm HVL
ZBV4 were reported at 0.15 MeV. The initial difference in HVL values was 0.034 cm at 0.015 MeV. To confirm the previously mentioned interpretation of the changing trend of HVL values depending on energy region, it is favorable to order those HVL values in the high-energy region. Thus, 7.948 cm HVL
ZBV1 < 8.011 cm HVL
ZBV2 < 8.101 cm HVL
ZBV3 < 8.139 cm HVL
ZBV4 were also reported at 15 MeV. In this case, the difference in HVL values was 0.191 cm at 0.015 MeV. Therefore, one can say that the negative effect of V
2O
5 on HVL values was slightly lower at low energies. Accordingly, the aforementioned reinforcement type negativity can be tolerated at low energy values, considering the positive effects on optical, structural, and thermal properties. The effect of the mean free path (λ) is critical in the capacity of shielding materials to defend against gamma radiation. Glass samples were analyzed in terms of λ values, and details are summarized in
Figure 6. The λ values can fluctuate, similar to the shifting patterns in the HVL. The λ values of ZBV1 have been recoded as the minimum in the investigated energy range. Another main element to remember is the tenth-value layer (TVL). The TVL element is another critical criterion to verify the thickness of shields, minimizing gamma rays’ strength to 1/10 of their original intensity. The TVLs of the studied samples were calculated, and a graph was drawn showing their importance against incident photon energy (
Figure 7). In the lower-energy ranges, the TVL values were lower. Similar to the changing trend in HVL values, TVL values were registered as 3.685 cm HVL
ZBV1 < 3.722 cm HVL
ZBV2 < 3.772 cm HVL
ZBV3 < 3.797 cm HVL
ZBV4 at 0.15 MeV. The effective atomic number (Z
eff) of a substance used for gamma-ray exposure regulation would contribute to its photon-attenuation properties. The variation of effective atomic number (Z
eff) against photon energy for all glasses is shown in
Figure 8.
The Z
eff values for ZBV1 glass were the best. For example, a Z
eff value of 14.01 was found for the ZBV1 sample at 0.15 MeV. However, the maximum Z
eff values recorded for samples were 28.42, 28.30, 28.19, and 28.07 for ZBV1, ZBV2, ZBV3, and ZBV4, respectively. The average photon flux was measured in the detection field by using an F4 tally mesh (
Figure 2). Then, an absorption coefficient was used to compensate for a scattering of the radiation. Excess radiation required the cumulative measurement of radiation buildup. The attenuation component was multiplied by the photon’s attenuation rate to measure the photon’s overall attenuation. The moderator attenuates the penetration of photons of varying intensities such that they both achieve the same reception. In this case, buildup factors can be classified as exposure buildup factor (EBF) and energy-absorption buildup factor (EABF).
In this analysis, a G-P fitting method was utilized for determination of EBF and EABF values. The fitting parameters’ calculated numerical values are displayed in
Table 3,
Table 4,
Table 5 and
Table 6 along with equivalent atomic numbers (Zeq).
Figure 9a–d and
Figure 10a–d illustrate the measured EBF and EABF values for studied glasses at various mean free paths from 0.6 to 40 mfp.
Figure 9 and
Figure 10 express the concentration of the different layers of EBF and EABF owing to irradiation by gamma rays. We shall explain the changing trend of EBF and EABF values at different energy values. Due to the photoelectric influence being neglected in regions with large atomic numbers, one may see smooth increments in the first region (
Table 3,
Table 4,
Table 5 and
Table 6). In addition, the third section of the sample was the most interesting during pair growth due to its absorption processes, which resulted in the decline in its value.
Figure 9 and
Figure 10 depict the changes in EBF and EABF values of ZBV1, ZBV2, ZBV3, and ZBV4 glass samples for different mean free path (mfp) values (i.e., 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 20, 25, 30, 35, and 40 mfp). These figures demonstrate the reliance of the EBF and EABF values upon the glass structure. The obtained EBF and EABF values showed that ZBV1 had the lowest EBF and EABF levels, and was superior to all other glasses.
Figure 11 and
Figure 12 show the differing energy-absorption buildup factors (EABF) and exposure buildup factors (EBF) at 0.4 MeV along with 10, 20, 30, and 40 mfp values for all glasses. It can be seen that the ZBV1 sample showed the minimum EBF and EABF values at the studied mfp values. From ZBV1 to ZBV4, EBF and EABF values showed an increasing trend. This can be explained by decreasing gamma-ray-attenuation competencies with a V
2O
5 reinforcement amount from 1 to 4 mol.%. As a last analysis of EBF and EABF values,
Figure 13 shows the variations in the energy-absorption buildup factor (EABF) and exposure buildup factor (EBF) against effective atomic number (Z
eff) for all glasses at 1 MeV/5 mfp. This is another sign of the synergistic effect of V
2O
5 reinforcement, which caused a decrement in densities of glasses, and in gamma-ray-shielding competencies accordingly. As illustrated in
Figure 13, EBF values increased gradually from ZBV1 to ZBV4. This trend was a natural consequence of variations in effective atomic numbers, which was discussed in previous sections.