Superconductor technology: apparatus – material – process – Processes of producing or treating high temperature...
Reexamination Certificate
2002-03-13
2003-01-28
Kopec, Mark (Department: 1751)
Superconductor technology: apparatus, material, process
Processes of producing or treating high temperature...
C420S402000, C420S901000, C252S521400, C423S289000, C423S155000, C505S100000, C505S430000, C505S490000, C505S500000, C505S736000, C505S805000
Reexamination Certificate
active
06511943
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a process for synthesis of high quality superconducting magnesium diboride (MgB
2
) powders.
BACKGROUND OF THE INVENTION
Recently, magnesium diboride (MgB
2
) was found to exhibit superconducting properties. It is thought that MgB
2
may be an alternate to conventional superconductors such as NbTi or BSCCO in the 20-30K and 0-1T range for the fabrication of conductor tapes or wires. That has naturally lead to investigation into optimal processes for preparing this material. Prior processes for producing MgB
2
powders generally have described the use of stoichiometric amounts of magnesium and boron, i.e., Mg:B of 1:2 (e.g., Cunningham et al., Physica C, v. 353, pp. 5-10 (2001)), have heated such mixtures under vacuum or under a hydrogen/argon mix, have used quartz tubes, or have required high pressure techniques to obtain the desired MgB
2
.
Other prior processes have included a process wherein boron filaments are exposed to magnesium vapor and processes involving deposition of magnesium diboride via magnetron sputtering, pulsed laser deposition and the like. Just recently, Aswal et al. (Physica C, v. 363(#3) pp. 149-154, Nov. 15, 2001) have described a process that involves Mg excess to avoid Mg loss during the synthesis. However, they mixed boron and magnesium powders and pressed the mixture into pellets and did not produce MgB
2
powder with good superconductive properties.
Despite these prior processes, an improved process for preparing magnesium diboride powder has been desired. After extensive and careful investigation, a process has now been found in the preparation of magnesium diboride powder. In particular, the present process involves heating amorphous boron powder pressed in pellets and solid magnesium under an inert atmosphere in a Mg:B ratio larger than about 0.6:1 at temperatures and for a time sufficient to form superconducting magnesium diboride. Note that the solid magnesium pieces (e.g. turnings or shavings) were not mixed with the boron powder in this invention. This leads to high quality MgB
2
superconducting powders since the impurities and MgO in the magnesium metal would not be left inside the MgB
2
powder after its synthesis.
It is an object of the present invention to provide a process of preparing high quality superconducting magnesium diboride.
It is another object of the present invention to provide stable superconducting magnesium diboride compositions.
It is another object of the present invention to provide a process, which allows the formation of Mg(B,O) precipitates inside MgB
2
grains that act as flux pinning centers in magnetic field.
SUMMARY OF THE INVENTION
To achieve the foregoing and other objects, and in accordance with the purposes of the present invention, as embodied and broadly described herein, the present invention provides a process of preparing superconducting magnesium diboride powder by heating amorphous boron powder and solid magnesium under an inert atmosphere in a Mg:B ratio greater than about 0.6:1 at temperatures and for time sufficient to form said superconducting magnesium diboride.
REFERENCES:
patent: CN 1329370 (2002-01-01), None
Nagamatsu et al, “Superconductivity at 39K in Magnesium Boride”, Nature, 410, 63-64, 2001.*
Aswal et al, “Synthesis and Characterization of MgB2 Superconductor”, J. Physica. C., 363, 149-154, (2001).*
Christen et al, “Superconducting magnesium diboride films with Tc=24K grown by pulsed laser deposition with in situ anneal”, J. Physica. C. 353, 157-161, 2001.*
Eom et al, “High critical density and enhanced irreversibility field in superconducting MgB2 thin films”, Nature, 411, 558-560, 2001.*
Cunningham et al, “Synthesis and processing of MgB2 powders and wires”, J. Physica. C. 353, 5-10, 2001.*
Bud'ko et al, “Boron Isotope Effect in Superconducting MgB2”, Phys. Rev. Lett. 86(9), 1877-1880, 2001.*
Aswal et al., “Synthesis and Characterization of MgB2Superconductor,” Physica C 363, pp. 149-154, 2001.
Frederick et al., “Improved Superconducting Properties of MgB2,” Physica C 363, pp. 1-5, 2001.
Cunningham et al., “Synthesis and Processing of MgB2Powders and Wires,” Physica C 353, pp. 5-10, 2001.
Bud'ko et al., “Boron Isotope Effect in Superconducting MgB2,” Physical Review Letters, vol. 86, No. 9, pp. 1877-1880, Feb. 2001.
Serquis et al., “Effect of Lattice Strain and Defects on the Superconductivity of MgB2,” Applied Physics Letters, vol. 79, No. 26, pp. 4399-4401, 2001.
Canfield, “Superconductivity in Dense MgB2Wires,” Physical Review Letters, vol. 86, No. 11, pp. 2423-2426, 2001.
Larbalestier et al., “Strongly Linked Current Flow in Polycrystalline Forms of the Superconductor MgB2,” Nature, vol. 410, pp. 186-189, 2001.
Liao Xiao Zhou
Mueller Frederick M.
Peterson Dean E.
Serquis Adriana C.
Zhu Yuntian T.
Cottrell Bruce H.
Kopec Mark
The Regents of the University of California
Vijayakumar Kallambella M
LandOfFree
Synthesis of magnesium diboride by magnesium vapor... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Synthesis of magnesium diboride by magnesium vapor..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Synthesis of magnesium diboride by magnesium vapor... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3050702