Freezing of molecular hydrogen and its isotopes in porous Vycor glass

Journal Article · Tue Oct 01 04:00:00 EDT 1996 · Journal of Low Temperature Physics

DOI:https://doi.org/10.1007/BF00754630· OSTI ID:482496

Beaudoin, G; Haljan, P; Paetkau, M; Beamish, J R ^[1]

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1. Univ. of Alberta, Edmonton (Canada)

The authors have made a detailed ultrasonic study of freezing and melting of molecular H{sub 2}, HD and D{sub 2} in the pores of Vycor glass. The behavior was similar to that seen in previous measurements with argon and helium. The hydrogen liquids undercooled about 2.5 K below their bulk triple points before freezing began and there was substantial hysteresis between freezing and melting. The velocity and attenuation began to increase suddenly at the onset of freezing. The velocity continued to increase to the lowest temperatures (2K) and the attenuation had a broad peak at about two thirds of the freezing temperature. The authors attribute these effects to stress relaxation via thermally activated vacancy motion in the solid hydrogen, an interpretation confirmed by looking at the frequency dependence of the velocity and attenuation. The magnitude of the velocity and attenuation changes increased in going from H{sub 2} to HD to D{sub 2}, as expected based on their increasing densities and elastic constants. However, there were no qualitative differences between the boson (H{sub 2} and D{sub 2}) and fermion (HD) cases nor, for that matter, between hydrogen and argon. The authors believe that essentially all the hydrogen was frozen a few tenths of a kelvin below T{sub F}, at the point where the melting;freezing hysteresis began. If even a few per cent of the hydrogen had remained liquid and become superfluid at some lower temperature, it would have been seen as a further increase in the velocity and a critical attenuation peak. The sensitivity of the ultrasonic measurements allowed the authors to make accurate measurements of the freezing and melting temperatures of the different liquids in Vycor. They found that the fractional undercooling, (T{sub B} {minus} T{sub F})/T{sub B}, increased as the molecular mass decreased which may indicate the importance of quantum effects on the liquid-solid interfacial energy {sigma}{sub Is}.

• Sponsoring Organization: USDOE
• OSTI ID: 482496
• Journal Information: Journal of Low Temperature Physics, Journal Name: Journal of Low Temperature Physics Journal Issue: 1-2 Vol. 105; ISSN 0022-2291; ISSN JLTPAC
• Country of Publication: United States
• Language: English

Related Subjects

66 PHYSICS
DEUTERIUM
FREEZING
HYDROGEN
HYDROGEN DEUTERIDE
MELTING
PHASE TRANSFORMATIONS
POROUS MATERIALS
ULTRASONIC TESTING
VYCOR