Modification of dielectric properties of porous glass by adsorption of hydrogen

Abstract

We have investigated the dielectric properties of a porous glass ͑Vycor 7930, typical pore radius: Ϸ3 nm͒ with submonolayer coverages of H 2 , HD, or D 2 on the pore surface by means of a capacitive technique between 5 and 20 K. The adsorption of hydrogen influences, depending on the hydrogen species as well as on the coverage, the dielectric glass properties. We discuss our observations in terms of the thermally activated dynamics of atoms in the combined glass/hydrogen system, where atoms denote atoms which build the porous glass as well as adsorbed hydrogen molecules.

Freezing and Pressure-Driven Flow of Solid Helium in Vycor

“…Also, solid argon and krypton have been seen [12] to migrate out of the pores well below their freezing temperatures. Such effects can change the oscillator's moment of inertia and mimic superfluid decoupling, as was shown for hydrogen [13,14] where a dewetting transition expelled mass from the Vycor. In the experiments described in this paper, we used a capacitive technique to study the density changes associated with freezing of helium in Vycor and at the lower temperatures where Kim and Chan observed supersolidity.…”

Surface rearrangement at complex adsorbate–substrate interfaces

“…The latter appears as a consequence of the surface disorder, heterogeneity [6] or polydispersity. Glassy [7], granular, amorphous [8], or porous materials, like aerogels [9,10], could serve as examples. The morphology of such materials is conventionally specified by a probability distribution (e.g.…”