Equilibrium involving selected LaNi/sub x/ and LaCo/sub 5-x/M/sub x/ hydrides: phase transformations and related studies
Phase transformations of LaNi/sub 5/, La/sub 2/Ni/sub 3/, LaNi, and La/sub 7/Ni/sub 3/ at H/sub 2/ pressures and temperatures up to 700 atm and 550/sup 0/C are investigated for the first time. At 525/sup 0/C and pressures less than 60 atm LaNi/sub 5/ exists as ..cap alpha.. phase LaNi/sub 5/. Higher pressures cause the formation of phase f nominal composition LaNiH/sub approx. 3.5/ together with LaNi/sub 13/H/sub approx. 3.5/ or Ni. LaNi at 525/sup 0/C and intermediate pressures less than 9 atm exists as LaH/sub 3-x/ and LaNi/sub 5/. At higher pressures only the LaNiH/sub approx. 3.5/ phases are observed. Desorption isotherms for the first order transition from these high pressure phases into the low pressure phases are obtained for the starting materials LaNi/sub 5/ and LaNi. Kinetic results for the LaNi phase transformation are also obtained and a mechanism suggested. Equipment designed for conduction of these experiments is described. Also the complications due to the non-ideality of H/sub 2/ gas under such conditions are considered. The hydriding characteristics of LaCo/sub 4/ /sub 4/Al/sub 0/ /sub 6/ and LaCo/sub 4/ /sub 4/Ga/sub 0/ /sub 6/ are examined in order to determine the effect of substitutions upon the high pressure phase LaCo/sub 5/H/sub 9/. As contracted with LaCo/sub 5/H/sub z/ at pressures of order 100 atm, the substitution of Al and Ga increases the hydrogen storage capacity. During studies of the effect of O/sub 2/ upon the metal hydride LaCo/sub 5/H/sub z/, three reactions are observed: (1) H/sub 2/O formation by the metal hydride with a first order type dependence upon z, (2) H/sub 2/ gas phase reaction with O/sub 2/, and (3) at temperatures greater than 40/sup 0/C, a matrix oxidation reaction. Results of a study are presented which determines the superconducting T/sub c/ of several A15 type metal hydrides (Nb/sub 3/Au/sub 0/ /sub 75/Ir/sub 0/ /sub 25/H/sub z/ and Nb/sub 3/Au/sub 1-x/Ge/sub x/H/sub z/). T/sub c/ is observed to decrease with H content.
- Research Organization:
- California Univ., San Diego (USA)
- OSTI ID:
- 6171217
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ALUMINIUM ALLOYS
HYDRIDATION
COBALT ALLOYS
GALLIUM ALLOYS
GERMANIUM HYDRIDES
SUPERCONDUCTIVITY
GOLD HYDRIDES
HYDROGEN
PHASE TRANSFORMATIONS
IRIDIUM HYDRIDES
LANTHANUM ALLOYS
NICKEL ALLOYS
NIOBIUM HYDRIDES
COBALT HYDRIDES
INTERMETALLIC COMPOUNDS
LANTHANUM HYDRIDES
OXIDATION
ALLOYS
CHEMICAL REACTIONS
COBALT COMPOUNDS
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
GERMANIUM COMPOUNDS
GOLD COMPOUNDS
HYDRIDES
HYDROGEN COMPOUNDS
IRIDIUM COMPOUNDS
LANTHANUM COMPOUNDS
NIOBIUM COMPOUNDS
NONMETALS
PHYSICAL PROPERTIES
RARE EARTH ALLOYS
RARE EARTH COMPOUNDS
TRANSITION ELEMENT COMPOUNDS
080201* - Hydrogen- Chemisorption Storage
360204 - Ceramics
Cermets
& Refractories- Physical Properties
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Electronic
Magnetic
Optical
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