|Protecting astronauts and space crow from hazardous radiation is critical in space missions. Conventional metallic material such as aluminum (Al) and its alloys have been widely used for shielding the harmful space radiations, including high energy electrons. However, due to the issue of extra secondary radiation generation and heavy weight, metallic materials are not satisfying for modern applications and long-distance space missions. Among various materials for shielding the space radiations, low atomic-number materials, including hydrogen, are demonstrated as the most efficient materials; however, the feasibility and safety issues of these materials have limited their applications.
Employing hydrogen-rich polymer nanocomposites is one of the approaches to replace high atomic number metals. Polymer-based nanocomposites can provide enough shielding against hazardous radiations with less secondary radiation generation and lower weight, in addition to improved mechanical and physical properties. By reviewing literature, bismuth oxide (Bi2O3), multi-walled carbon nanotube (MWCNT), hexagonal-boron nitride (h-BN), and MXene nanomaterials were selected to enhance properties of polydimethylsiloxane (PDMS) polymer.
In first step, PDMS/Bi2O3 and PDMS/MWCNT nanocomposites with different weight percentages (wt.%) of nanofillers. Then, photon shielding effectiveness of fabricated nanocomposites were studied with utilizing diagnostic x-ray with 60, 70, 80, and 90 keV energies. Flexible thin multilayer nanocomposites with alternating PDMS/Bi2O3 and PDMS/MWCNT layers were fabricated and characterized.
Afterward, the role of nanofillers embedded in PDMS polymer matrix on shielding efficiency were studied by comparing the electron attenuation properties of PDMS/MWCNT, PDMS/Bi2O3, and PDMS/MWCNT/Bi2O3 nanocomposite with pure PDMS and Al. The results indicate that the addition of Bi2O3 and MWCNT in PDMS matrix can significantly improve the electron attenuation of the pure polymer. PDMS/MWCNT/Bi2O3 also has weight advantage in comparison with Al as it attenuates the same electron radiation energies with lower areal density. However, enhanced thermal and mechanical properties of the proposed nanocomposite are required to make it a promising candidate for electron radiation shielding in space applications. As a result, an optimization of nanocomposites has been accomplished by applying it in a layered structure. For this purpose, hydrogenated boron nitride (OHBN) and the novel 2D nanomaterials, MXene, were added to PDMS polymer matrix separately. A multilayer nanocomposite of PDMC/BN, PDMS/MXene, and PDMS/MWCNT/Bi2O3 layers were developed with enhanced thermal and shielding properties. The developed multilayer structure was fabricated with 5 different areal densities and studied for high energy electron radiation attenuation, under electron beam with energies of 9, 12, 16, and 20 MeV. According to the high ratio of radiation shielding effectiveness and weight of the developed nanocomposite, it is highly potential to be applied as the space shielding material.