Fast and thermal neutrons attenuation through micro-sized and nano-sized CdO reinforced HDPE composites

doi:10.1016/j.radphyschem.2020.109245

Radiation Physics and Chemistry

Volume 180, March 2021, 109245

https://doi.org/10.1016/j.radphyschem.2020.109245 Get rights and content

Highlights

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Fast and thermal neutron attenuation properties through polymer composites.
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High density polyethylene (HDPE) reinforced by micro-sized and nano-sized Cadmium Oxide (CdO).
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Nano CdO particles will enhance the shielding properties of the HDPE against fast neutrons.
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Capture of thermal neutrons inside the micro CdO/HDPE composites is more probable than that in nano CdO/HDPE composites.
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Particle addition percentage and size have significant effect on the mechanical properties of composites.

Abstract

The fast and thermal neutron attenuation properties through polymer composites based on high density polyethylene (HDPE) reinforced by micro-sized and nano-sized Cadmium Oxide (CdO) particles with weight fractions of 10% and 40% have been investigated. This study was carried out to present a new composite material based on HDPE filled with CdO in the form of micro and nano particles to be used as a promising neutron radiation shielding material. The composites were fabricated by compression molding technique and characterized by a scanning electron microscope (SEM). The composites were subjected to fast neutrons generated from ²³⁸Pu–Be neutron source with activity 12 × 10⁹ Bq and detected by a Stilbene scintillator. The fast neutron shielding properties were determined in terms of the fast neutron transmission fractions of the composites. The neutron activation method was applied by using Indium foils and Indium foils covered with Cadmium as a detector to study the properties of the thermal and epithermal neutron fluxes of the composites upon exposure to neutron flux generated from ²⁴¹Am–Be neutron source. It is clear from this study that the transmitted fractions for fast neutron in case of nano CdO/HDPE composites are less than the case of micro CdO/HDPE composites, however, the capture of thermal neutrons inside the micro CdO/HDPE composites is more probable than that in nano CdO/HDPE composites at the same weight fraction. Tensile mechanical testing has been conducted and showed that particle addition percentage and size have significant effect on the mechanical properties of composites. Nano CdO/HDPE composites showed more superior mechanical properties compared to micro CdO/HPDE composites at the same particle addition level.

Introduction

Due to the utilization of neutron radiation in many fields such as nuclear reactors, synthesis of radioisotopes, health care and aerospace (Cucinotta et al., 2006), it is important to shield against neutron radiation to protect workers and the environment (Zhang et al., 2017). The most common substances in shielding neutrons are boron and cadmium due to their higher absorption cross sections (Celli et al., 2006). Polymers, which are hydro carbonic materials, are suitable for neutron moderation (Abdo et al., 2003b). There are various studies in the literature investigating the neutron shielding properties of polymer composites filled with boron and boron compounds. Harrison et al. fabricated HDPE/boron nitride composites and tested for mechanical and space-radiation shielding properties (Harrison et al., 2008). Shin et al. developed HDPE/silane-treated mBN composites which showed better neutron shielding properties compared with the HDPE/BN and HDPE/B₄C composites (Shin et al., 2014). Özdemir et al. reported a flexible and effective neutron shielding composite of EPDM containing boron trioxide (Özdemir et al., 2017). Many scientists have studied the effect of using metal oxide nanoparticles in the polymeric matrix to enhance the radiation shielding characteristics of polymer nanocomposites (İrim et al., 2018). Theoretical simulation of thermal neutron-shielding properties of HDPE composites filled with metal oxides such as B₂O₃, Sm₂O₃, Gd₂O₃, or CdO at different concentrations was also reported using a Monte Carlo Code of PHITS (Particle and Heavy Ion Transport code System) (Poltabtim et al., 2019).

Cadmium has been used efficiently because of its high thermal neutron absorption cross section. The prominent 0.178 eV resonance in ¹¹³Cd isotope gives rise to the large thermal cross section. The peak cross section of ¹¹³Cd, 12.22% abundant in natural Cd, is 2 × 10⁴ barns (Toth et al., 2020). Flex-boron, gadolinium, and samarium were examined as possible replacements for cadmium as a thermal neutron filter (D’Mellow et al., 2007). Although the low cost flex-boron was suitable in some applications and gadolinium had absorption properties similar to cadmium, the study reported that cadmium to be unsurpassed in its performance as a thermal neutron filter. In our previous work, we demonstrated that CdO nanoparticles have a better γ-radiation shielding ability than micro-CdO in HDPE based radiation shielding material (El-Khatib et al., 2019). The survey of the literature reveals that there is no available study that deals with the use of CdO as a filler in the polymeric matrix to attenuate neutrons. Therefore, the present work is devoted to developing a novel neutron protective HDPE-based composites reinforced with CdO particles. Hence, this study aims to investigate the effect of incorporating both micro-sized and nano-sized CdO particles on the fast and thermal neutron radiation shielding ability of CdO/HDPE composites.

The mechanical behavior of filled polymer composites can be greatly affected by the type, the concentration, the size, the shape, and the orientation of the reinforcing particles. In addition, the strength of the adhesive bond between particles and polymer matrix, the type of dispersion, and the extent of particle agglomeration have significant effects (Tavman, 1996). These important factors must be taken into account in determining the mechanical properties of the particle reinforced polymer composites. To make adequate study of the CdO/HDPE composites as shielding materials, the variation of mechanical properties with the size and percentage of CdO reinforcing particles must be known. Therefore, mechanical tensile tests were also conducted to investigate how the presence of either micro or nano CdO reinforcing particles can affect the mechanical properties of HDPE-based shielding composites.

Section snippets

Materials

HDPE (HD5403EA grade) with a melt flow index of 0.35 g/10 min and a density of 0.955 g/cm³ was a commercial product and supplied by Sidpec (Sidi Kerir Petrochemicals Company), Egypt. CdO micro filler in powder form with average particle size in the range of 0.5–1.0 μm was purchased from Loba Chemie, India. CdO nanoparticles with average particle size of 50 nm were procured from Nanotech Company (Egypt). Pure HDPE and HDPE composites sheets reinforced by micro-sized and nano-sized CdO particles

Scanning electron microscope (SEM)

A SEM (JSM-6010LV, JEOL) was utilized to observe the shape of micro-sized and nano-sized CdO particles and the morphological features of CdO/HDPE composites. Before SEM observation, all the samples were gold-coated using a low-vacuum sputtering coating device (JEOL-JFC-1100E). The SEM images were acquired at magnification order of 5,000x at 20 KV.

Fig. 5 shows the SEM images of pure HDPE, micro CdO particles, nano CdO particles, HDPE filled with 10 wt% micro CdO, 10 wt% nano CdO, 40 wt% micro

Conclusions

This work presents the preparation of new composite material based on HDPE filled with CdO in the form of micro and nanoparticles to be used as a neutron radiation shielding material. The study aims to investigate the effect of incorporation of micro-sized and nano-sized CdO particles on the fast and thermal neutron radiation shielding ability of CdO/HDPE composites. According to the results, it is found that the transmitted fractions for fast neutron in the case of nano CdO/HDPE composites are

Authors’ contribution statements

Ahmed M. El-Khatib and Mahmoud I. Abbas Conception and design of study, Mohamed S. Hamada, Mahmoud T. Alabsy, Yehia Mohamed Youssef Mohamed Abd Elzaher worked out almost all of the technical details, and performed the experiment, and wrote the manuscript Mohamed S. Badawi, M. Fayez-Hassan, Yuri N. Kopatch, Ivan N. Ruskov, data interpretation.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgements

The authors would like to acknowledge the Experimental Nuclear Physics Laboratory, Nuclear Research Center, Egyptian Atomic Energy Authority for their contribution in the experiment of thermal neutrons attenuation. The authors are also grateful to the Sector of Investigations of Neutron-Nuclear Interactions, Frank Laboratory of Neutron Physics, JINR, Dubna, Russia where the experiment of fast neutrons attenuation was carried out due to a governmental agreement between Russia and Egypt.

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Fast and thermal neutrons attenuation through micro-sized and nano-sized CdO reinforced HDPE composites

Highlights

Abstract

Introduction

Section snippets

Materials

Scanning electron microscope (SEM)

Conclusions

Authors’ contribution statements

Declaration of competing interest

Acknowledgements

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Ann. Nucl. Energy

Compos. B Eng.

Radiat. Phys. Chem.

J. Saudi Chem. Soc.

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Thermochim. Acta

Radiat. Phys. Chem.

Geochem. Cosmochim. Acta

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