Fig.1 Silver decoration observation with an optical microscope. Left : rolled vanadium. Right : coarse grains of vanadium.[1] T. Fujimaru et al., Vac. Surf. Sci., 66, 608-612 (2023). [2] A. N. Itakura et al., e-JSSNT, 22, 174–178 (2024).93Poster Award NomineePoster Award NomineeP5-25Differences in Hydrogen Behavior Depending on Vanadium Grain SizeSouta Miyai1, Tomoyasu Fujimaru2, Tomoharu Hirayama1, Eiji Tokumaru1, Kouta Miyanouchi1, Tomoko Kusawake3, Yoshihisa Matsumoto1, and Akiko N. Itakura31 National Institute of Technology, Oita College2 Interdisciplinary Graduate School of Engineering Sciences, Kyushu University3 Center for Basic Research on Materials, National Institute for Materials Science (NIMS)We have been studying vanadium as a material for hydrogen separation membranes that can extract high-purity hydrogen gas from gas mixtures. It has been found that the amount of hydrogen permeation varies depending on the crystal grains [1]. In this study, we report the hydrogen diffusion in a rolled vanadium with a thickness of 0.5mm by hydrogen visualization using the silver decoration method [2]. First, a speckled pattern of permeated hydrogen was observed (Fig.1 left). It was found that the pattern corresponds to the shape of crystal grains, size of around 73mm, and the orientation. Next, we observed around the triple junction of large crystal grains, prepared by the unidirectional solidification method. Black dots were distributed throughout the surface (see Fig.1 right), and no orientation difference was found. These results suggest that not only the crystal orientation but also the crystal size affects the hydrogen diffusion behavior.P5-26Energy Performance Advancement by Tuning Nanospace of Hollow Carbon Spheres Sabina Shahi1,2 and Lok Kumar Shrestha1,21 Department of Materials Science, Institute of Pure and Applied Sciences, University of Tsukuba2 Research Center for Materials Nanoarchitectonics, National Institute for Materials Science (NIMS)Hollow carbon spheres, with their unique structural properties; hollow space at the center and carbon shells due to which they exhibit high surface area, have emerged as promising materials for energy storage/conversion and catalysts to drug delivery and sensing [1,2]. However, optimizing these materials still remains a challenge. We aim to enhance ion transport within these spheres, by manipulating the hollow spaces and nanopore engineering in the porous shell, improving their energy density performance to contribute to next generation energy storage technologies. In this contribution, we have used fullerene as a carbon source due to its ability to self-assemble and ethylenediamine as a structure-directing agent to synthesize the hollow carbon spheres with uniform particle size by simple dynamic liquid-liquid interfacial precipitation (DLLIP) method [2]. Systematic control over the nanoscale dimensions of the hollow spaces can improve ion mobility. Considering this, we successfully synthesize spheres with tunable cavity size. Furthermore, we chemically activated these hollow spheres using KOH and then carbonized at 900 °C. The morphology was intact even after carbonizing at high temperature. Spheres with high surface area (2189 m2 g-1) along with micro-mesopores on the shell and cavity at the center has been obtained. Electrochemical studies are going on to evaluate their performance as advanced electrode materials. [1] Y. Sun, Carbon, 125, 139-145(2017). [2] L.K. Shrestha, Nanomaterials, 13, 946(2023).
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