Positron annihilation lifetime spectroscopy of nano/macroporous bioactive glasses

摘要

Positron annihilation lifetime measurements are performed for sol-gel-derived 70 mol% SiO_2-30 mol% CaO bioactive glass. Strong positronium formation processes are shown to be an inherent feature for these kinds of materials. Observed orthopositronium (o-Ps) lifetimes show a three-modal distribution with lifetime values weighed at ～2, ～18, and ～70 ns. The exposure of the investigated sol-gel-derived bioactive glasses to water vapor significantly modifies o-Ps lifetime distribution due to the penetration of water molecules into the nanopores, indicating high ratio of their interconnectivity. Classic Tao-Eldrup equation is used to relate the o-Ps lifetimes with the size of nanopores, whose distribution is verified by nitrogen adsorption porosimetry.