Preparation of Mortar with Fe₂O₃ Nanoparticles for Radiation Shielding Application

Abstract

The current study aims to investigate the radiation shielding properties of mortar samples with Fe₂O₃ nanoparticles for radiation protection applications. For the reference mortar (free Fe₂O₃ nanoparticles) and the mortar with different concentrations of Fe₂O₃ nanoparticles, we experimentally measured the transmission factor (I/I0) for four different thicknesses of the prepared mortar. The I/I₀ results indicated that the transmission of the photons through the mortars decreases with increases in the mortar’s thickness. The lowest TF was found for the mortar coded as MI-25 (contains 25 wt.% of Fe₂O₃ nanoparticles), which gives an indication about the development in the attenuation ability of the prepared mortar samples due to the addition of Fe₂O₃. Similarly, the linear attenuation coefficient (LAC) results showed an increasing trend with the addition of Fe₂O₃ nanoparticles for the four tested energies. These results confirm that increasing the ratio of Fe₂O₃ nanoparticles can lead to a remarkable improvement in the gamma ray shielding. We reported the half value layer (HVL) and we found that the HVL for the reference mortar at 0.06 MeV is 1.223 cm, while it changed from 1.19 to 1.074 cm for the mortar with 5 and 25 wt.% of Fe₂O₃ nanoparticles. The HVL results demonstrated that increasing the ratio of Fe₂O₃ nanoparticles can lead to a notable reduction in the HVL. The tenth value layer results proved that we can develop new mortars for radiation shielding applications by introducing more concentrations of Fe₂O₃ nanoparticles.

1. Introduction

Radiation offers many benefits when used in applications in the medical industry, energy generation, food processing, agriculture, and more. Radiation can save lives by eliminating tumors in radiotherapy and imaging using X-rays. However, despite these advantages, ionizing radiation can be very harmful to humans if they are exposed to these high-energy photons for long periods of time, as the radiation can rip electrons from atoms and cause permanent side effects [1,2,3]. Due to the naturally harmful nature of radiation, several methods are used in an attempt to reduce these effects. These include distancing oneself from the radiation source, minimizing the time exposed to radiation, and using radiation shields [4,5,6].

Radiation shields are materials that are placed between the radiation source and the human body and are specifically designed to absorb as many photons as possible for that specific application. Ideal radiation shields should be light, effective at absorbing a wide range of photons, thin, low cost, easy to manufacture, and have other factors. They vary from simple lead aprons to glasses, composites, polymers, alloys, and more. These materials are often enhanced using different micro- and nanoparticles, which are suited for the desired application [7,8,9,10,11,12].

One example of a radiation shielding material that is commonly used is concrete [13,14]. Nikbin, I. et al. [15] prepared heavy-weight concrete with varying amounts of nano bismuth oxide. Heavy-weight concrete aims to reduce the thickness of the shield by increasing the density of concrete through the use of heavy-weight aggregates. The mechanical and gamma ray shielding properties of the concretes improved when more bismuth oxide nanoparticles were added to the composition. Nikbin, I. et al. [16] studied the gamma ray shielding properties of introducing nanoparticle titanium oxide to heavy-weight concrete, finding a positive correlation between TiO₂ content and the attenuation abilities of the concretes. El-Sayed, T. [17] furthered previous research on heavy-weight concrete by analyzing the effect of adding rice straw ash on the shielding properties of the concretes, in an attempt to make use of a waste material. The study demonstrated that the sample with 3% polyethylene is the optimum concrete mix for shielding applications. El-Sayed, A. et al. [18] developed an artificial neural network to calculate radiation shielding parameters of concrete with different nanoparticle additives and then compared the predicted values with experimental results, finding a great agreement between the two methods, and proving the viability of the model.

Other materials, such as cements with different nanoparticles, are also being investigated for their radiation shielding potential. Abo-El-Enein, S. et al. [19] used hematite (Fe₂O₃) and ZnO nanoparticles to try to enhance the mechanical, thermal, and radiation shielding ability of ordinary Portland cement pastes. Additionally, mortar and concrete are being researched as a more environmentally friendly and cheaper alternative to ordinary Portland cement. Mortar by itself exhibits poor strength at ambient temperatures, but these properties can be greatly improved by adding different types of nanoparticles into the mix, as demonstrated by Seifan, M. et al. [20] when they introduced nanosilica and microsilica to fly ash mortar. Furthermore, Glinicki, M. et al. [21] evaluated the neutron shielding ability of mortar containing boron aggregates, discovering a positive linear relationship between the boron content of the samples and their shielding ability.

The current study aims to investigate the radiation shielding properties of mortar samples with Fe₂O₃ nanoparticles for various applications.

2. Materials and Methods

The mortar was prepared in the traditional way, and the same properties of cement and sand were published previously [22], where the cement was mixed with sand and then water was added, where the ratio of cement to water was 2:1, and stirred well to obtain a homogeneous mortar to obtain the control sample (MI-0), and then the Fe₂O₃ nanoparticles were added in proportions of 5, 10, 15, 20, and 25% of the amount of cement added to obtain the rest of the mortar samples as shown in

Table 1. The composition of the prepared mortar (Kg/m³).

Codes	Composition, Kg/m3				Density, g/cm−3
	Cement	Water	Sand	Fe2O3 Nanoparticles
MI-0	500	250	1375	—	2.241
MI-5	500	250	1375	25	2.256
MI-10	500	250	1375	50	2.270
MI-15	500	250	1375	75	2.285
MI-20	500	250	1375	100	2.300
MI-25	500	250	1375	125	2.314

. The samples were cut to fit the experimental measurement as shown in Figure 1. Fe₂O₃ nanoparticles were purchased from Nano-Tech Company in Egypt and their size was confirmed by photographing them using a transmission electron microscope (TEM). It was found that Fe₂O₃ nanoparticles are needles and rods with an average size of 100 ± 50 (length) and 15 ± 5 (width) nm as shown in Figure 2. The density was measured traditionally by the law of mass over volume, where samples are homogeneous in shape, the sample is weighed, and the volume is measured theoretically for a cylindrical sample [23].

The attenuation coefficient was measured experimentally only for the use of nanoparticles in the samples, but for the accuracy of the measurement by which the samples were measured, the control sample was compared with the XCOM program, and a very good agreement between the theoretical and experimental results was obtained. Three radioactive sources (Cs-137, Co-60, and Am-241) and an HPGe detector were used. The samples were placed as in Figure 3, and the counting rate was calculated using a program connected to the device (Genie 2000 program), where a sample of thickness t and counting rate N was calculated, then the sample was removed and the free counting rate was calculated (N₀) as shown in Figure 4 for the Cs-137 point source. From the count rate calculation, the linear attenuation coefficient (LAC) was calculated from the following formula [24,25,26,27].

$$\mathrm{L}\mathrm{A}\mathrm{C}=\frac{-1}{\mathrm{t}}\ln \frac{\mathrm{N}}{{\mathrm{N}}_0}$$

(1)

The other shielding parameters were calculated based on previous works [28,29,30,31,32,33], such as HVL, MFP, TF, TVL, and radiation absorption ration (RAR) by the following equations.

$$\mathrm{H}\mathrm{V}\mathrm{L}=\frac{\ln \left(2\right)}{\mathrm{L}\mathrm{A}\mathrm{C}}$$

(2)

$$\mathrm{M}\mathrm{F}\mathrm{P}=\frac{1}{\mathrm{L}\mathrm{A}\mathrm{C}}$$

(3)

$$\mathrm{T}\mathrm{V}\mathrm{L}=\frac{\ln \left(10\right)}{\mathrm{L}\mathrm{A}\mathrm{C}}$$

(4)

$$\mathrm{T}\mathrm{F}=\frac{\mathrm{I}}{{\mathrm{I}}_0}=\frac{\mathrm{N}}{{\mathrm{N}}_0}$$

(5)

$$\mathrm{R}\mathrm{A}\mathrm{R} \left(\%\right)=\left[1-\mathrm{T}\mathrm{F}\right]\times 100$$

(6)

3. Results and Discussion

The effect of the addition of nanosized Fe₂O₃ particles on the radiation attenuation performance of the prepared mortars was examined by using experimental results (see Section 2). Additionally, the radiation shielding abilities of the prepared mortars with nanosized Fe₂O₃ were compared to each other and we reported the influence of different thicknesses on the transmission of the photons through each sample. For the reference mortar (free Fe₂O₃ nanoparticles) and the mortar with different concentrations of Fe₂O₃ nanoparticles, we experimentally measured the transmission factor (I/I₀) for each thickness of the prepared mortar. We plotted I/I₀ versus the thickness of the mortar samples at the tested energies (Figure 5a–d). These are very useful figures, since from these figures we can understand the influence of the thickness on the transmission factor. In addition, from this figure, we can estimate the LAC for the reference mortar and the mortar samples with Fe₂O₃ particles. In each figure, we included the straight line fit equation, and we can notice that the slope of each equation is negative, which indicates that the parameter on the Y-axis (which is the TF) decreases with increases in the mortars’ thickness. For the reference mortar, the straight line best fit equation at 0.060 MeV is y = −0.2868x + 0.8759. The absolute value of the slope represents the LAC at this energy (i.e., 0.06 MeV) which is equal to 0.5670 cm⁻¹. We can derive the MAC from the LAC. By dividing the LAC for each mortar by its individual density, we can derive the MAC at a given energy. All these critical parameters (i.e., TF, LAC, and MAC) have been determined for the reference mortar and mortar samples with Fe₂O₃ nanoparticles as we will discuss in the next paragraphs. It can be observed in Figure 5a–d that an increase in the thickness of the mortars led to a decrease in the TF and hence a decrease in the transmission of the photons through the prepared mortars under all the applied energies. Additionally, the lowest TF belongs to mortar coded as MI-25, which gives an indication about the development in the attenuation ability of the prepared mortar samples due to the addition of Fe₂O₃. In order to check the enhancement in the attenuation ability of these mortar samples due to the increase in the thickness and Fe₂O₃ contents, we will discuss the MAC and LAC, and other related parameters.

In Figure 6, we represented the LAC for the reference mortar and the samples with Fe₂O₃ nanoparticles as a function of Fe₂O_3. The LAC results display an increasing trend with the addition of Fe₂O₃ nanoparticles for the four tested energies. The lowest LAC has been reported for the reference mortar (free Fe₂O₃ nanoparticles) because it is composed of low atomic number elements. In contrast, the highest LAC is found for MI-25, which contains the maximum amount of Fe₂O₃. These results confirm that increasing the ratio of Fe₂O₃ nanoparticles can lead to a remarkable improvement in the gamma ray shielding. In addition to the impact of Fe₂O₃ nanoparticles on the LAC, we can see that the energy of the photons is another factor that changes the LAC values. When examining the LAC for a specific composition at 0.06 and 1.333 MeV, we can see a big difference in the LAC values between these two energies. The LAC for MI-10 (for example) at 0.06 MeV is 0.598 cm⁻¹, while it is only 0.1301 cm⁻¹ at 1.333 MeV. The LAC values at low and high energies for the reference mortar and other mortar samples with Fe₂O₃ nanoparticles have the same trend as the LAC reported in other studies and for different materials [34,35,36].

The experimental HVL values for the reference mortar and the mortar samples with Fe₂O₃ nanoparticles are given in Figure 7. It was found that the HVL values for the four tested energies decrease as the amount of Fe₂O₃ nanoparticles increases in the mortar. At 0.06 MeV, the HVL for the reference mortar is higher than the other mortar samples (it is 1.223 cm for the reference mortar and varied between 1.19 cm for MI-5 and 1.074 cm for MI-25). At 0.662 MeV, the HVL for the reference mortar is 4.002 cm and decreases to 3.898 cm due to the addition of 5% of Fe₂O₃ nanoparticles, and to 3.524 cm due to the addition of 25% of Fe₂O₃ nanoparticles. So, increasing the ratio of Fe₂O₃ nanoparticles can lead to a notable reduction in the HVL. As we found in the previous figure, the energy of the photons also affects the HVL. It can be seen that the HVL increases significantly due to the increase in the energy from 0.06 to 1.333 MeV. For instance, for MI-5, the HVL varied between 1.190 and 5.468 cm between the lowest and highest investigated energies. So, the HVL at 1.33 MeV is almost 4.5 times the HVL for the same sample (i.e., MI-5) at 0.06 MeV. This result is also valid for the other mortars, where the HVL for MI-15 at 1.333 MeV is almost 4.6 times the HVL of the same mortar at 0.06 MeV.

The radiation attenuation competences of the tested mortars have been examined in the context of the tenth value layer (TVL). The experimental results for the TVL have been graphed in Figure 8. According to the data given in this figure, the thinnest TVL and thus the superior radiation shielding competence (3.56, 11.69, 15.36, and 16.40 cm at the selected energies) have been found for the mortar with 25% of Fe₂O₃ nanoparticles. Additionally, the TVL values of the reference mortar were higher than the values predicted for all mortars with 2%–25% of Fe₂O₃ nanoparticles. According to the TVL results, we can develop new mortars for radiation shielding applications by introducing Fe₂O₃ nanoparticles.

It is also important to examine the radiation absorption ratio (RAR) and to check the impact of the thickness of the mortars on this quantity as shown in Figure 9. So, we selected two thicknesses from each mortar (2 cm and 5 cm) and evaluated the RAR for the mortars with these two thicknesses. If we look at the RAR values for MI-0 at 0.06 MeV, we can see that the RAR is 67.82% for a thickness of 2 cm, but it is 94.13% for MI-0 with a thickness of 5 cm. For MI-10, the RAR at 0.06 MeV is 69.76% for a thickness of 2 cm, and increases to 94.97% for a thickness of 5 cm. At this energy, we noticed that the RAR for MI-0 and MI-10 with a thickness of 5 cm is higher than that of 2 cm, and this is correct for the other mortars. Hence, the thickness of the mortar plays a major role in attenuating the incoming photons. An interesting result is the RAR for MI-25 with a thickness of 5 cm. For this mortar, the RAR at 0.06 MeV is 96.03% which means that this mortar can block almost all the incoming photons with low energy (less than 0.1 MeV). MI-15 and MI-20 with a thickness of 5 cm are also effective mortars in low-energy applications. The results proved that if the space is available, preparing mortar with Fe₂O₃ nanoparticles with a thickness of 5 cm is very useful in radiation shielding applications. When we look at the RAR for both thicknesses at 1.333 MeV, we found that the RAR values reduce to around half, varying between 21.88% (for the reference mortar with a thickness of 2 cm) and 24.46% for MI-25 with the same thickness. Meanwhile, it varied between 46.04 for the reference mortar at 5 cm and 50.40% for MI-25. The mortar at 2 cm has weak attenuation ability for the radiation with energy of 1.333 MeV, while the same mortars with a 5 cm thickness can block about 50% of the radiation with energy higher than 1 MeV.

The present prepared mortars were compared with other related literature, including mortar-based ball clay (M1), mortar-based barite (M3) [22], and mortars with ores and minerals additives (MOS30, MOPr30, MOCr30, and MOMg30) [37]. Figure 10 shows the MFP (which equals the reciprocal of LAC and represents the path length without any collisions inside the absorber) of this mortar, and the results indicated that the MI-25 mortar had the lowest MFP compared to the rest of the mortars, for which the MFP was 5.324, 5.135, 5.564, 5.323, 5.279, 5.195, 5.342, 5.209, and 5.084 cm for M1, M3, MOS30, MOPr30, MOCr30, MOMg30, MI-15, M1-20, and MI-25, respectively.

4. Conclusions

We experimentally reported the attenuation factors for some mortar samples with Fe₂O₃ nanoparticles. We studied the impact of Fe₂O₃ nanoparticles by comparing the reference mortar with the other samples which contain nano-Fe₂O₃. From the relation between the transmission factor (I/I₀) and the thickness of the prepared mortar, we calculated the LAC and, from this parameter, we derived other important factors such as HVL. When we examined the impact of the thickness of the prepared mortars on the attenuation performance of the newly developed samples, we found that increasing the thickness of the mortars led to a decrease in the TF and hence a decrease in the transmission of the photons through the prepared mortars under all the applied energies. Among the different prepared mortars, the lowest TF belongs to the mortar coded as MI-25, which gives an indication about the development in the attenuation ability of the prepared mortar samples due to the addition of Fe₂O₃. When we examined the impact of Fe₂O₃ nanoparticles on the attenuation performance of these samples, we found that the lowest LAC belongs for the reference mortar (free Fe2O₃ nanoparticles). On the contrast, the highest LAC is found for MI-25, which contains the maximum amount of Fe₂O₃. Hence, we can draw a conclusion that increasing the ratio of Fe₂O₃ nanoparticles can lead to a remarkable improvement in the gamma ray shielding. When we examined the impact of the energy of the radiation on the attenuation performance of the newly prepared mortars, we found a high difference in the LAC as well as HVL values between the lowest and highest energies. From the RAR results, we found that MI-25 can block almost all the incoming photons with low energy (less than 0.1 MeV). The RAR results also demonstrated that a mortar of a thickness of 5 cm can be used effectively in radiation shielding applications.