THE DIFFUSION OF HYDROGEN AND HELIUM THROUGH SILICA GLASS AND OTHER GLASSES1

Chemical Analysis for Alkali Ion-exchanged Glass Using Atom Probe Tomography

The developing flexible ultrathin glass for use in foldable displays has attracted widespread attention as an alternative to rigid electronic smartphones. However, the detailed compositional effects of chemically strengthened glass are not well understood. Moreover, the spatially resolved chemistry and depth of the compression layer of tempered glass are far from clear. In this study, commonly used X-ray spectroscopy techniques and atom probe tomography (APT) were used comparatively to investigate the distribution of constituent elements in two representative smartphone glass samples: non- and chemically tempered. APT has enabled sub-nanoscale analyses of alkali metals (Li, Na, K, and Ca) and this demonstrates that APT can be considered as an alternative technique for imaging the chemical distribution in glass for mobile applications.

Determination of permeation properties of hydrogen gas in sealing rubbers using thermal desorption analysis gas chromatography

Permeation properties of hydrogen gas (H₂) into nitrile butadiene rubber (NBR), ethylene propylene diene monomer (EPDM), and fluoroelastomer (FKM) which are the strong candidates for sealing material in H₂ energy infrastructures, was quantified using a thermal desorption analysis gas chromatography (TDA GC) and a self-developed diffusion-analysis program. The samples were charged with H₂ in a high-pressure chamber for 24 h then decompressed into atmosphere, and the mass of H₂ released from the sample was measured as a function of elapsed time after decompression. The developed program calculated the total charging amount C₀ and diffusivity D, which were then used to calculate the H₂ solubility S and permeability P for variation of pressure. The samples were polymerized with and without carbon black (CB) filler in cylindrical shapes with different diameters. There was no appreciable pressure up to 12 MPa or diameter dependence investigated in this study on D, S and P. NBR and EPDM showed dual hydrogen diffusion with fast and slow diffusion behaviors caused by CB, whereas FKM showed a single diffusion behavior. The determined D are D_{fast, NBR} = (1.55 ± 0.28) × 10^–10 m²/s, D_{slow, NBR} = (3.1 ± 0.5) × 10^–11 m²/s, D_{fast, EPDM} = (3.65 ± 0.66) × 10^–10 m²/s, D_{slow, EPDM} = (3.3 ± 0.5) × 10^–11 m²/s, D_FKM = (7.7 ± 0.8) × 10^–11 m²/s. It appeared that the filler contributes to increase S and decrease D. The uncertainty analysis against the evaluated data was carried out, too, in order that the method could be applicable as a standard test for the permeation properties of various polymer membranes.