Study of Salt Precipitation in Polymer Electrolytes Based on Poly(ethylene oxide) and EMImTf Ionic Liquid

Origin of enhanced boric acid adsorption in light-burned magnesium oxide

Light-burned magnesium oxide (MgO) possesses a high surface area and has attracted interest as a promising candidate for boron adsorption materials; however, the detailed molecular structures decisive for enhancing the adsorption performance have not yet been elucidated. Here, the origin of enhanced boric acid adsorption for the light-burned MgO is studied by multiple probes, including positronium (Ps) annihilation spectroscopy, Fourier transform infrared spectroscopy, and sorption experiments coupled with molecular simulations. The state-of-the-art technique of open space analysis using Ps revealed the detailed structure of the interfaces between MgO nanograins: ∼10 Å and ∼30 Å open spaces, participating in the chemisorption of B(OH)₄ ^- and BO₃ ^3- simultaneously with the physisorption of neutral B(OH)₃ molecules. Furthermore, in addition to the fraction of open spaces, a proton quasi-layer formed on the interior surfaces of the above-mentioned angstrom-scale open spaces was identified to be attributable for enhancing both the chemisorption and physisorption.

Evaluation methodology of diffusion coefficient of guest substances associated with angstrom-scale open spaces in materials by slow positron beam

The knowledge of elemental migration associated with angstrom-scale open spaces is a prerequisite for sophisticated material design with respect to nanodispersion as well as a better understanding of molecular migration in a geological environment. Here, we show the methodology for evaluating the diffusion coefficient of guest substances focusing on angstrom-scale open spaces, where the depth-variation of open spaces caused by elemental diffusion in the micrometer-scale surface region is examined by the variable-energy slow positron beam. The present methodology determines a low diffusion coefficient of ∼10^-14 cm² s^-1 for potassium at 533 K in SiO₂ glass within the framework of Fick's principle providing the evidence that ∼2.5 Å open spaces intrinsically present in the glass matrix govern the diffusion process.