Superconductor technology: apparatus – material – process – High temperature – per se – Having tc greater than or equal to 150 k
Patent
1990-10-01
1992-10-06
Lieberman, Paul
Superconductor technology: apparatus, material, process
High temperature , per se
Having tc greater than or equal to 150 k
505734, 505725, 505735, 252521, H01B 1200
Patent
active
051531720
DESCRIPTION:
BRIEF SUMMARY
h iodine, because of its high solubility in alcohols and other organic solvents.
The hydrolysis reaction step may use any suitable quantity of water. In general, excellent results are obtained with from about two to ten (2-10) equivalents of water.
The concentrated viscous mass or dry resin mass of pre-ceramic material, which results from concentration after the addition of the iodine solution, may be redissolved in any suitable non-polar solvent. Typical solvents include binary mixtures of isopropanol and benzene, xylene, toluene, hexane, cyclohexane, pentane, isopentane or octane. Generally, a weight ratio of isopropanol to the non-polar solvent of about one to six (1:6) to one to thirty (1:30) may be used. The solvent quantity is adjusted to provide the desired fiber drawing or film forming characteristics, or to provide desired characteristics for other methods of producing a shaped product.
Any suitable method may be used for the conversion of the pre-ceramic shapes into superconductors. Initially, the pre-ceramic resin is heated to a temperature that is sufficient to form gamma copper iodide. Preferably, the resin is heated for about two to sixteen (2-16) hours at a temperature from about 100.degree. to 200.degree. C. Then, the temperature is increased to gradually decompose the copper iodide to copper oxide. Preferably, the resin is heated to about 250.degree. to 450.degree. C. for about two to twenty-four (2-24) hours. The resin material is then heated to a much higher temperature to convert it to the superconducting ceramic, preferably to about 800.degree. to 900.degree. C. for about two to ten (2-10) hours. Finally, the material is sintered, preferably at about 920.degree. to 1,000.degree. C. for about two to thirty (2-30) hours, to improve product physical characteristics. In order to maximize oxygen content, the product is then preferably annealed at a temperature of about 360.degree. to 500.degree. C. for a few hours.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Details of the present invention will be further understood upon reference to the following examples, which disclose preferred embodiments of this invention. All parts and percentages are by weight, unless otherwise indicated.
EXAMPLE I
Initially, the required starting materials are prepared. An about three tenths molar (0.3M) solution of yttrium isopropoxide solution in isopropanol is prepared by reacting yttrium metal chips in dry isopropanol with a small amount of mercuric chloride and refluxing for about three (3) days at about 82.degree. C., followed by filtering to obtain clear solution. An about three tenths molar (0.3M) solution of barium isopropoxide in isopropanol is prepared by adding barium metal to dry isopropanol and filtering the solution. Copper ethylhexanoate is mixed in dry isopropanol to produce an about three tenths molar (0.3M) solution. An iodine/isopropanol solution is prepared by dissolving iodine crystal flakes into dry isopropanol. These solutions are stored under dry nitrogen until used.
Stoichiometric amounts of the barium isopropoxide/isopropanol solution and the yttrium isopropoxide/isopropanol are calculated to give a final ceramic composition of YBa.sub.2 Cu.sub.3 O.sub.y. Those amounts are pipetted into a round bottom flask. The solution is refluxed at its boiling point under nitrogen for about one (1) hour. The stoichiometric amount of copper ethylhexanoate/isopropanol solution is then added. A green precipitate forms and is kept at the boiling temperature for an additional eight (8) hours under dry nitrogen. The temperature of the precipitated solution is then reduced to about 60.degree. C. A water/isopropanol solution is prepared using four (4) equivalents of water per mole of yttrium isopropoxide. This solution is added to the flask, gradually dissolving the precipitate and forming a dark green homogeneous solution. This solution is stirred for about four (4) hours at about 60.degree. C. To this solution is then added a quantity of the iodine starting solution sufficient to provide about o
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Chen Kuo-Chun
Mazdiyasni Khodabakhsh S.
General Atomics
Lieberman Paul
Swope Bradley A.
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