Search for a fluid phase in physisorbed hydrogen films

Thesis/Dissertation · Wed Jan 01 04:00:00 EST 1992

OSTI ID:7261152

Liu, FengChuan

Adsorption isotherms, heat capacity and quasi-elastic neutron scattering (QENS) techniques have been used to study H[sub 2], HD, H[sub 2]/NE and H[sub 2]/D[sub 2] films adsorbed on MgO or graphite. Two objectives are addressed: (1) For hydrogen films forming well defined molecular layers, as when adsorbed on MgO, is it known that a so called [open quotes]liquid[close quotes] phase is indeed liquid-like For reasons to be presented in chapter 2, HD films, rather than H[sub 2] films, adsorbed on MgO are studied with adsorption isotherms and QENS. Between 7K and 14.9K, adsorption isotherms show layer by layer growth from 1 to 5 layers, with approximately equal density among all layers. For HD coverages between 2 to 5 layers, the QENS measurements find liquid-like mobilities in various temperature regions. For a 4.9 layer film, a partial liquid-like layer (equivalent to 0.2 layers) remains even at 7K, with a translational diffusion rate about 1/4 that of bulk liquid HD at its triple point (T[sub t](3D) = 16.61K). (2) using graphite preplated with Ne, Ar and D[sub 2] as substrate, the author tries to find a single molecular layer of H[sub 2] film which stays in the liquid phase at temperatures lower than 5.96K. Successive lowering of this temperature may eventually lead to the discovery of superfluid H[sub 2] film, estimated to be in the neighborhood of 2K. For H[sub 2] adsorbed on Ne preplated graphite, evidence is found indicating that up to [approximately]80% of the Ne preplating is displaced by H[sub 2], followed by second layer H[sub 2] growing on itself. For H[sub 2] adsorbed on D[sub 2] preplated graphite, however, the D[sub 2] preplating is preserved. The phase diagram of first layer H[sub 2] on D[sub 2] preplated graphite is similar to that of the second layer H[sub 2] on bare graphite, but with a lower 2D triple point temperature at 5.74K.

• Research Organization: Washington Univ., Seattle, WA (United States)
• OSTI ID: 7261152
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360602 -- Other Materials-- Structure & Phase Studies
665430* -- Other Topics in Quantum Fluids & Solids-- (1992-)
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ADSORPTION ISOTHERMS
COHERENT SCATTERING
DEUTERIDES
DEUTERIUM
DEUTERIUM COMPOUNDS
DIFFRACTION
ELEMENTS
FILMS
HYDROGEN
HYDROGEN COMPOUNDS
HYDROGEN DEUTERIDE
HYDROGEN ISOTOPES
ISOTHERMS
ISOTOPES
LIGHT NUCLEI
NEUTRON DIFFRACTION
NONMETALS
NUCLEI
ODD-ODD NUCLEI
PHASE STUDIES
PHYSICAL PROPERTIES
SCATTERING
SPECIFIC HEAT
STABLE ISOTOPES
TEMPERATURE RANGE
TEMPERATURE RANGE 0000-0013 K
TEMPERATURE RANGE 0013-0065 K
THERMODYNAMIC PROPERTIES
THIN FILMS