FREEZING AND MELTING OF HELIUM IN DIFFERENT POROUS-MEDIA

Citation
Eb. Molz et Jr. Beamish, FREEZING AND MELTING OF HELIUM IN DIFFERENT POROUS-MEDIA, Journal of low temperature physics, 101(5-6), 1995, pp. 1055-1077
Citations number
39
Categorie Soggetti
Physics, Applied
ISSN journal
00222291
Volume
101
Issue
5-6
Year of publication
1995
Pages
1055 - 1077
Database
ISI
SICI code
0022-2291(1995)101:5-6<1055:FAMOHI>2.0.ZU;2-R
Abstract
We have studied the freezing and melting of He-4 confined in several p orous media with very different structures. These include Vycor glass, which has very small pores with a rather narrow, size distribution, a silica aerogel with a much more open geometry and a wider range of po re sizes, and art alumina membrane with larger but non-intersecting po res. We measured the velocity and attenuation of ultrasonic waves, whi ch allowed us to detect the decoupling of any superfluid in the pores as well as the modulus changes associated with freezing and melting. W e find that the shift of the melting curve due to confinement is small er in the aerogel than in Vycor, but the hysteresis between freezing a nd melting is similar. The effects of confinement are very small for t he alumina membrane and hysteresis is only observed at the lowest pres sures.