Abstract: The present invention relates to a process for preparing a high-T.sub.c superconductor as a precursor material for the oxide-powder-in-tube method, which involves mixing the oxides of the elements Bi, Sr, Ca and Cu and completely melting them at temperatures of .gtoreq.1000.degree. C., then casting the melt onto a substrate which is kept at room temperature, and disintegrating the cooled melt block and grinding it into a powder.

Abstract: In order to produce tubular moldings of high-temperature superconducting material based on oxides of bismuth, calcium, strontium, copper and optionally lead, a homogeneous melt of the oxide mixture in a predefined stoichiometry having temperatures from 900 to 1300.degree. C. is made to flow into a casting zone. The casting zone, as a function of its internal diameter, rotates at from 200 to 1500 rpm about its axis which is inclined by at least 15.degree. with respect to the horizontal. The solidified molding is taken from the casting zone and annealed for from 4 to 150 hours at from 700 to 900.degree. C. in an oxygen-containing atmosphere.

Abstract: Process for preparing a high-T.sub.c superconductor as a precursor material for the oxide-powder-in-tube method (OPIT). The present invention relates to a process for preparing a high-T.sub.c superconductor as a precursor material for the oxide-powder-in-tube method, which involves mixing the oxides of the elements Bi, Sr, Ca and Cu and completely melting them at temperatures of >1000.degree. C., then casting the melt onto a substrate which is kept at room temperature, and disintegrating the cooled melt block and grinding it into a powder.

Abstract: Process for preparing a high-T.sub.c superconductor as a precursor material for the oxide-powder-in-tube method (OPIT). The present invention relates to a process for preparing a high-T.sub.c superconductor as a precursor material for the oxide-powder-in-tube method, which involves mixing the oxides of the elements Bi, Sr, Ca and Cu and completely melting them at temperatures of .gtoreq.1000.degree. C., then casting the melt onto a substrate which is kept at room temperature, and disintegrating the cooled melt block and grinding it into a powder.

Abstract: The invention relates to solid bodies made of high-temperature superconducting material to which contact is made by solid, compact metallic conductors.To produce said solid bodies, high-temperature superconducting material is either melted completely or a melt is obtained from the oxides of bismuth, strontium, calcium and copper, and, optionally, of antimony and lead. The solid, compact metallic conductors made of silver, gold, a platinum metal or an alloy containing said metals are then partially encased in the melt and the melt is allowed to solidify. Finally, the solid body obtained is annealed together with the conductors in a first stage at temperatures of from 710.degree. to 810.degree. C. and in a second stage in an oxygen-containing atmosphere at temperatures of from 750.degree. to 880.degree. C.

Abstract: To produce a high-temperature superconductor of the composition Bi.sub.2 (Sr,Ca).sub.3 Cu.sub.2 O.sub.8+x having a strontium to calcium ratio of 5:1 to 2:1 and a value of x between 0 and 2, the oxides and/or carbonates of bismuth, strontium, calcium and copper are vigorously mixed in a stoichiometric ratio. The mixture is heated at a temperature of 870.degree. to 1100.degree. C. until a homogeneous melt is obtained. The melt is poured into mold and allowed to solidify in them. The cast bodies removed from the molds are annealed for 6 to 30 hours at 780.degree. to 850.degree. C. Finally, the annealed cast bodies are treated for at least 6 hours at temperatures of 600.degree. to 820.degree. C. in an oxygen atmosphere. The cast bodies can be converted into shaped bodies of the desired sizes by mechanical processes before they are annealed. The shape and size of the shaped bodies may also be determined by the shape and dimensioning of the mold used in producing the cast bodies.

Abstract: To produce tubular molded parts made of high-temperature superconductor oxide material based on bismuth, calcium, strontium and copper, a homogeneous melt of the oxide with a specified stoichiometry is allowed to run at temperatures of 900.degree. to 1100.degree. C. into a casting zone rotating about its horizontal axis. The solidified molded part is removed from the casting zone and it is annealed for 4 to 150 hours at 700.degree. to 900.degree. C. in an oxygen-containing atmosphere. A plant for producing tubular molded parts includes a rotatably arranged mold (4, 9) which is provided at least at one end face with a front plate 6 which reduces its free cross section, a runner 7 extending into the interior of the mold (4, 9) and a crucible 8 arranged above the runner 7 which is capable of feeding the runner 7 with melt (cf. FIG. 2 A).

Abstract: In the process for producing molded bodies from precursors of oxidic high-temperature superconductors a copper mold of the desired shape which encloses a solidified bismuth strontium calcium cuprate melt is treated with a solution of a soluble compound containing sulfate anions, an aqueous mineral acid and an oxidizing agent until the copper mold is dissolved. A protective layer of at least one of strontium sulfate or calcium sulfate is formed on the solidified melt.

Abstract: To produce more complex molded bodies from precursors of high-temperature superconductors based on the oxides of bismuth, strontium, calcium and copper, the homogeneous melt of these oxides is cast in molds at temperatures of 870.degree. to 1000.degree. C. In this process, the geometrically appropriately shaped molds are composed of a material having a melting point of at least 1000.degree. C. Finally, the molds containing solidified melt of the oxides of bismuth, strontium, calcium and copper are treated with dilute hydrofluoric acid at temperatures of 20.degree. to 90.degree. C. until the molds are dissolved.

Abstract: The invention relates to a high-temperature superconductor composed of the oxides of bismuth, strontium, calcium and copper and, optionally, of lead, and having the composition Bi.sub.2-a+b+c Pb.sub.a (Sr, Ca).sub.3-b-c Cu.sub.2+d O.sub.x, where a=0 to 0.7; b+c=0 to 0.5; d=-0.1 to 0.1 and x=7 to 10 and a Sr:Ca ratio of 2.8:1 to 1:2.8 as well as of strontium and/or barium sulfates. Said superconductor can be prepared by intimately mixing the oxides of bismuth, strontium, calcium and copper and optionally of lead with strontium and/or barium sulfates, melting the mixture by heating to temperatures of 870 to 1300.degree. C., higher temperatures being required for higher strontium and/or barium sulfate contents, pouring the melt into molds and allowing it to solidify slowly therein and subjecting the moldings removed from the molds to a heat treatment at temperatures of 700 to 900.degree. C. in an oxygen-containing atmosphere.

Abstract: In the process for producing molded bodies from precursors of oxidic high-temperature superconductors of the BSCCO type, a copper mold of the desired shape which encloses a solidified bismuth strontium calcium cuprate melt is wired as anode in a direct current circuit composed of anode, cathode and an electrolyte, a dilute sulfuric acid is used as electrolyte and the electrolyte is subjected to a direct current of 1 to 50 mA.cm.sup.-2 until the copper mold wired as anode is dissolved and the BSCCO molded body is laid bare.

Abstract: Method for joining parts of ceramic high-temperature superconductor material of the composition Bi.sub.(2+a-b) (Sr.sub.1-c) Ca.sub.c) .sub.(3-a) Pb.sub.b Cu.sub.(2+d) O.sub.x, where a is 0 to 0.3, b is 0 to 0.5, c is 0.1 to 0.9 and d is 0 to 2 and x has a value depending on the state of oxidation of the metals present, the end faces of the parts located at a gap spacing apart from one another are heated by means of a fuel gas/oxygen flame to temperatures from 750.degree. to 875.degree. C. Simultaneously, a rod of the same material above the spacing gap is heated until the melt thereof drips off into the gap between the end faces of the two parts, completely filling the gap. At least the joint region between the two parts is then heat-treated for 7 to 100 hours at temperatures between 780.degree. and 850.degree. C.

Abstract: The invention relates to a resistive current limiter having at least one conductor of a superconductive high-temperature material, carrying the rated current. The electrically active length of said conductor is at least three times greater than its linear extent.

Abstract: A resistive current limiter takes the form of a hollow cylinder and is composed of high-temperature superconducting material. In this connection, the high-temperature superconducting material may be a polynary oxide.To produce said resistive current limiter, a homogeneous melt is prepared from an oxide mixture, suitable for forming high-temperature superconductors, in a specified stoichiometry and said melt is allowed to run, at temperatures above 900.degree. C., into a casting zone which rotates about its horizontal axis. The molding, solidified as a cylinder, is removed from the casting zone. The cylinder is sawn so as to produce a gap extending parallel to its axis. Furthermore, a multiplicity of slits are sawn into the cylinder parallel to the gap. Finally, the cylinder is heat-treated for up to 150 hours at 700.degree. to 900.degree. C. in an oxygen-containing atmosphere.

Abstract: To produce a high-temperature superconductor of the composition Bi.sub.(2+a) (Sr.sub.(1-b) Ca.sub.b).sub.(3-a) Cu.sub.(2+c) O.sub.(8+x), where a is from 0 to 0.3, b is from 0.1 to 0.9 and c is from 0 to 2, and x has a value which depends on the oxidation state of the metals contained, oxides and/or carbonates of bismuth, strontium, calcium and copper are thoroughly mixed. In this process, the copper compound is used as a mixture of copper(I) oxide and copper(II) oxide. Then the mixture of oxides and/or carbonates is first allowed to react mutually in an inert gas atmosphere at temperatures from 700.degree. to 800.degree. C. for 0.5 to 36 hours before subsequently treating the mixture in an oxygen-containing atmosphere at temperatures from 700.degree. to 875.degree. C. for 3 to 60 hours.

Abstract: To produce a high-temperature superconductor of the composition Bi.sub.2 (Sr,Ca).sub.3 Cu.sub.2 O.sub.8+x having a strontium to calcium ratio of 5:1 to 2:1 and a value of x between 0 and 2, the oxides and/or carbonates of bismuth, strontium, calcium and copper are vigorously mixed in a stoichiometric ratio. The mixture is heated at temperatures of 870.degree. to 1100.degree. C. until a homogeneous melt is obtained. The melt is poured into molds and allowed to solidify in them. The cast bodies removed from the molds are annealed for 6 to 30 hours at 780.degree. to 850.degree. C. Finally, the annealed cast bodies are treated for at least 6 hours at temperatures of 600.degree. to 820.degree. C. in an oxygen atmosphere.The cast bodies can be converted into shaped bodies of the desired sizes by mechanical processes before they are annealed.The shape and size of the shaped bodies may also be determined by the shape and dimensioning of the molds used in producing the cast bodies.

Abstract: The present invention relates to a method for the preparation of electrolytic manganese dioxide in which flocculent nuclei of a manganese oxide hydrate is dispersed in the electrolyte.

Abstract: The disclosure relates to activated metal anodes consisting essentially of zirconium, niobium, tantalum or titanium and having its surface area activated by means of metallic manganese; the manganese content at the anode surface area of more than 16 weight % decreases towards the interior of the anode, reaching 0 weight % along a path corresponding to 1/4 of the thickness of the anode material, measured from the anode surface area.The disclosure also relates to a process for making these metal anodes.

Abstract: The disclosure relates to a process for removing molybdenum from aqueous manganese(II)salt solutions by adsorbing the molybdenum on manganese dioxide and separating adsorbend and adsorbate from the purified manganese(II)salt solution. To this end, the disclosure provides for a pH value lower than 5 to be established in the manganese salt solution; for an oxidant capable of oxidizing manganese(II)compounds to manganese(IV)compounds to be added at temperatures between 50.degree. and 80.degree. C., so as to effect oxidation of a small proportion of dissolved manganese(II)salt to manganese dioxide; for resulting precipitate to be allowed to remain in contact over a period of at least 15 minutes with the manganese(II)salt solution, and for the precipitate to be separated from said solution at said temperatures.

Abstract: The disclosure provides an electrolytic cell sealed in gas-tight and liquid-tight fashion. The cell is comprised of a box-shaped cell tank open at its top and provided with at least one intake duct, at least one overflow duct and at least one discharge duct. A cover is placed on the cell tank and two opposed flanges receiving electrode supporting frames are secured to the inside of the cell tank near the upper end thereof. A chemically resistant and electrically insulating coating is applied to the inside of the cover and cell tank and a plurality of semi-circular recessed grooves spaced apart from each other are formed in the upper rim portion of at least one of the side walls of the cell tank, the recessed grooves receiving semi-circular current beams projecting outwardly.