Crystallization of He in Aerogels

Static behaviors of crystallization of He in porous materials, such as the increase of melting pressure, have been studied extensively, but nonequilibrium dynamics of the phase transition is hardly known. Our interest was in how He crystals grow in a 90.4% porosity aerogel. Aerogels are transparent...

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Bibliographic Details
Published in:Journal of low temperature physics 2008-02, Vol.150 (3-4), p.499-504
Main Authors: Osawa, Aiko, Kato, Haruko, Mimori, Tomohiro, Nomura, Ryuji, Okuda, Yuichi
Format: Article
Language:English
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Summary:Static behaviors of crystallization of He in porous materials, such as the increase of melting pressure, have been studied extensively, but nonequilibrium dynamics of the phase transition is hardly known. Our interest was in how He crystals grow in a 90.4% porosity aerogel. Aerogels are transparent and the dynamics in them can be studied visually. A Pomeranchuk-type variable-volume cell was used to study crystallization at a fixed temperature with a blocked capillary condition. By continuously compressing a chamber, the pressure rose above the bulk melting pressure and at a pressure 1.7 bar above the bulk melting pressure these crystals began to invade the aerogel. A clear crystal-superfluid interface was moved smoothly by the steady compression. No macroscopic facets were observed in the aerogel well below the bulk roughening transition temperature.
ISSN:0022-2291
DOI:10.1007/s10909-007-9570-z