Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1996-11-06
2001-04-24
Arbes, Carl J. (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C505S236000, C505S500000, C505S501000, C505S510000
Reexamination Certificate
active
06219901
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to novel precursor materials for the preparation of high T
c
oxide superconductors and superconducting composites. The invention further relates to the use of the novel precursor materials in the preparation of oxide superconductors and superconducting composites.
BACKGROUND OF THE INVENTION
The discovery of high transition temperature superconducting oxides over the past six years triggered an international race to develop high temperature superconducting (HTS) materials. For many applications, in particular electrical power generation, the required HTS materials must operate at high current densities in magnetic fields, and possess adequate robustness, flexibility and critical current tolerance of strain. The stringent performance requirements of the HTS materials has demanded the development of new processing materials and techniques which impart improved superconducting and mechanical properties to the material.
Any improvements in material or process that can beneficially affect the superconducting and mechanical properties of the HTS material are highly desirable.
SUMMARY OF THE INVENTION
The object of the present invention is to provide novel composite materials useful in the preparation of oxide superconducting composites. The novel composite of the present invention exhibits reduced segregation of copper into the matrix metal phase and preferential growth of oxide superconductor phase, both of which have a beneficial effect on the superconducting properties of the oxide superconducting composite.
It is another object of the present invention, to provide a method for preparing composite materials as precursors and intermediates to oxide superconducting composites.
It is yet another object of the present invention to provide a method for preparing an oxide superconductor composite to improve the superconducting characteristics of the composite.
In one aspect of the invention, a composite of the invention includes a primary alloy phase containing constituent elements of a desired oxide superconductor and a secondary phase containing copper. The secondary phase is supported by the primary alloy phase.
“Alloy” is used herein in the conventional sense to mean an intimate mixture of phases or solid solution of two or more elements. An alloy can be prepared by milling, cooling from a melt or any other conventional means.
In a preferred embodiment, the constituent elements of the primary alloy phase and the copper of the secondary phase, in combination, are present in an amount sufficient to form the desired oxide superconductor. Excess or deficiency of a particular element is defined by comparison to the ideal copper cation stoichiometry of the desired oxide superconductor. In some embodiments, the elements may be present in the stoichiometric proportions of the desired oxide superconductor. In other embodiments, there may be a stoichiometric excess or deficiency of any constituent element to accommodate the processing conditions used to form the desired oxide superconductor. In preferred embodiments, copper is present in stoichiometric excess in the range of 10% to 30% with respect to the ideal copper cation stoichiometry of the desired oxide superconductor.
In preferred embodiments, a noble metal may also be present in the primary alloy phase and/or the secondary phase. Noble metals may include, among others, silver, gold, palladium and platinum.
The primary alloy phase supports the secondary phase. In one preferred embodiment, the support may be accomplished by disposing the secondary phase within the primary alloy phase. By “disposed within”, as that term is used herein, it is meant that the secondary phase is embedded within the matrix material or substantially completely surrounded by the matrix material. The secondary phase preferably is in the form of a wire, rod, foil or particle.
In another preferred embodiment, the support is accomplished by contactingly surrounding at least a portion of an outer periphery of the primary alloy phase with the secondary phase. By “contactingly surrounding”, as that term is used within, it is meant that at least one surface of the secondary phase is in contact with an outer periphery of the primary alloy phase. The secondary phase preferably is in the form of a wire, rod, foil or particle.
In one embodiment of the present invention, substantially all of the constituent element, copper, is in the secondary phase. In another embodiment of the present invention, a portion of the constituent element, copper, is the secondary phase and the balance of the copper needed to form an oxide superconductor is in the primary alloy phase.
In another aspect of the present invention, a composite of the invention includes a primary alloy phase containing constituent elements of a desired oxide superconductor, a secondary phase containing copper, the secondary phase supported by the primary alloy phase, and a matrix material for supporting a primary alloy phase and secondary phase disposed therein.
By “matrix”, as that term is used herein, it is meant a material or homogeneous mixture of materials which supports and/or binds a substance disposed within or around the matrix.
In preferred embodiments, the matrix material is preferably a noble metal. The primary alloy phase and the secondary phase may also additionally comprise a noble metal. A noble metal is a material that is inert to chemical reaction and oxidation under the processing conditions used to form an oxide superconductor. Silver is a preferred noble metal.
In yet another aspect of the invention, an oxide composite includes a primary oxide phase comprising a sub-oxide of a desired oxide superconductor and a secondary silver phase disposed therein. By “sub-oxide”, as that term is used herein, it is meant one or more oxides selected from the group consisting of simple, binary and higher oxides of the constituent elements of a desired oxide superconductor.
In yet another aspect of the invention, an oxide composite includes a primary oxide phase comprising a sub-oxide of a desired oxide superconductor, a secondary silver phase disposed therein and a matrix material for supporting a primary oxide phase and secondary silver phase therein.
In yet another aspect of the invention, an oxide superconductor is prepared by oxidation of composite including a primary alloy phase comprising an alloy of constituent elements of a desired oxide superconductor and a secondary phase comprising copper, the secondary phase supported by the primary alloy phase.
In yet another aspect of the invention, an oxide superconductor is prepared by oxidizing a composite including a primary alloy phase comprising an alloy of constituent elements of a desired oxide superconductor, a secondary phase comprising copper, the secondary phase supported by the primary alloy phase and a matrix material for supporting the primary alloy phase and secondary phase disposed therein.
In yet another aspect of the invention, a metal oxide/silver composite is prepared. A composite comprising a primary alloy phase comprising the constituent elements of a desired oxide superconductor and silver and a secondary phase comprising copper, the secondary phase supported by the primary alloy phase is prepared. The composite is oxidized under conditions sufficient to oxidize the constituent elements of a desired oxide superconductor and under conditions which promote the diffusion of the silver of the primary alloy phase into the region of the secondary phase and under conditions to promote the diffuision of the copper of the secondary phase into the region of the primary alloy phase, so that a pure silver phase occupying substantially the secondary phase is formed.
In another aspect of the invention, an oxide superconductor is prepared. A composite is prepared which includes a primary alloy phase comprising silver and the constituent elements of a desired oxide superconductor and a secondary phase comprising copper. The secondary phase supported by the primary alloy phase. The composite is oxidized
Craven Christopher A.
Masur Lawrence J.
Otto Alexander
Podtburg Eric R.
Sandhage Kenneth H.
American Superconductor Corporation
Arbes Carl J.
Clark & Elbing LLP
Scozzafava Mary Rose
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