Reaction kinetics of phase formation in Nb-Al powder metallurgy processed wire
The sequence of phases formed in the low temperature reaction of niobium and aluminum to form the A15 superconductor, Nb/sub 3/Al, was studied in high areal reduction powder metallurgy processed wire samples. The reaction path observed was the same as that reported previously for multilayer Nb/Al thin films. The reaction proceeds without the formation of the sigma phase, Nb/sub 2/Al, resulting in a metastable A15 of higher Al concentration. The extent of this metastable extension is estimated to be 22-24 atomic percent Al based upon the resistive T/sub c/ of 17.0 K observed. The reaction kinetics of the wire samples were examined by scanning heat flux calorimetry, and the activation energy of A15 formation was found to be 3.1 eV. The formation of NbAl/sub 3/ and dissolution of Al into the Nb lattice were both observed as precursor reactions with much lower activation energies.
- Research Organization:
- 9510048; 9502899
- OSTI ID:
- 6086552
- Report Number(s):
- CONF-880812-
- Journal Information:
- IEEE Trans. Magn.; (United States), Journal Name: IEEE Trans. Magn.; (United States) Vol. 25:2; ISSN IEMGA
- Country of Publication:
- United States
- Language:
- English
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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
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71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
ACTIVATION ENERGY
ALLOYS
ALUMINIUM
ALUMINIUM ALLOYS
CHEMICAL REACTION KINETICS
DISSOLUTION
ELECTRIC CONDUCTIVITY
ELECTRICAL PROPERTIES
ELEMENTS
ENERGY
ENERGY LEVELS
EXCITED STATES
KINETICS
LATTICE PARAMETERS
LOW TEMPERATURE
METALLURGY
METALS
METASTABLE STATES
NIOBIUM ALLOYS
NIOBIUM BASE ALLOYS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
POWDER METALLURGY
PRECURSOR
REACTION KINETICS
SUPERCONDUCTING WIRES
SUPERCONDUCTIVITY
WIRES