Positronium Lifetimes and Gas Permeation in Aquivion® for Fuel Cells

Abstract

Variations of ortho-positronium (o-Ps) lifetime and gas permeability of the Aquivion® E8705 membrane were studied as functions of temperature under vacuum and relative humidity at room temperature. When the temperature was varied between 0 and 100 °C in vacuum, the hole volume of Aquivion® E8705, deduced from the ortho-positronium lifetime, gradually increased. However, when the relative humidity was changed at room temperature, the hole volume was essentially unchanged. Good linear correlations between the logarithm of permeabilities of O2 and H2 and reciprocal hole volume at different temperatures indicates the importance role of free volume in gas permeation in dry Aquivion® E8705. However, for hydrated Aquivion® E8705 the permeability less depends on hole volume.

Free Volume and Electrical Conductivity in Pure and Doped Polyvinyl Chloride with Al2O3

“…The general definition of the free volume is the open space that is freely moving in a medium [6][7][8]. In a series of experiments [9][10][11][12][13][14][15][16], the free volume mean size, fraction, and anisotropic structure in polymers as a function of sorption gas, permeability, doped concentration, time, electric field and temperature have been determined using the positron annihlation lifetime (PAL) technique. The sensitivity of PAL in probing free volume properties arises from the fact that Ps is preferentially trapped (localized) in atomic scale hole volume.…”