Development of nano-sized graphene flowers as neutron reflectors: Structural control of nano-sized graphene and application as neutron reflectors

To enhance the intensity of neutron beams, attention has been focused on the coherent scattering caused by nano-sized particle ensembles, and the use of nano-diamonds has been actively considered. Graphene, which has an sp 2 carbon crystal structure, has a larger van der Waals force compared to sp 3 carbon crystal structure such as nano-diamonds. Additionally, the bonding force between carbon atoms in graphene is strong, which makes it easier to mold into a large block and plate and to adapt to higher radiation fields. However, graphene is easily to cause aggregation due to its large van der Waals force, making it difficult to form a nano-sized three-dimensional structure. To address this problem, we focused on the hot isostatic pressing (HIP) method, which uses resin powder as the raw material and produces vapor-phase-grown graphene through HIP treatment. We have reported a method for producing free-standing, three-dimensional graphene called “graphene flower” made of nano-sized graphene and a method for controlling the nano-size of graphene. Additionally, we presented a prototype of a graphene neutron reflector and measured the coherent scattering of neutrons by graphene for the first time. In this paper, we will report on the optimization of the graphene manufacturing method using the HIP process to improve the coherent scattering performance of neutrons.