Superconductor technology: apparatus – material – process – Processes of producing or treating high temperature... – With melting
Reexamination Certificate
2002-05-31
2003-10-07
Kopec, Mark (Department: 1751)
Superconductor technology: apparatus, material, process
Processes of producing or treating high temperature...
With melting
C505S500000, C423S289000
Reexamination Certificate
active
06630427
ABSTRACT:
BACKGROUND OF THE INVENTION
Magnesium diboride (MgB
2
) has recently been found to be superconducting at the critical temperature T
c
of ~40 K, much higher than the best low-temperature intermetallic superconductors (T
c
~23 K). See, Nagamatsu J, Nakagawa N, Muranaka T, et al., Superconductivity at 39 K in magnesium diboride, NATURE 410 (6824): 63-64 Mar. 1, 2001. While its critical temperature is lower than for the cuprate superconductors, MgB
2
is a classical superconductor behaving according to the BCS theory, like the existing low-temperature intermetallic superconductors. Unlike cuprates, however, MgB
2
shows excellent conduction across grain boundaries and it is a simple, stoichiometric compound, very easy and inexpensive to synthesize. In the few months since discovery of its superconductive properties, MgB
2
has generated a tremendous amount of research and interest.
Several factors would, however, seem to preclude widespread use of MgB
2
as a superconducting material. Because it is a brittle ceramic, MgB
2
is difficult to use in bulk form as a single phase. For instance, any cracks in the diboride phase will interrupt the superconducting pathway. The ceramic could be embedded in a tough, robust metallic matrix. This approach has been used with brittle cuprate superconductors (typically mixed and sintered with silver) and for the brittle, low-temperature intermetallic superconductor Nb
3
Sn (encapsulated in copper and cold-drawn as a Nb precursor). Such an approach would be difficult to achieve with MgB
2
.
The consensus is that the prior art relating to diboride superconducting materials has associated with it a number of problems and deficiencies, most of which relate to the structural and/or mechanical limitations of the superconducting phase. Accordingly, there is a need for one or more process and/or fabrication techniques, as well as related compositions of matter, to better utilize and benefit from the superconductivity of such materials.
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Kopec Mark
Northwestern University
Reinhart Boerner Van Deuren sc
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