The method of obtaining long-length conductors based on high-temperature superconducting compounds
(57) Abstract:The invention relates to the technical superconductivity, in particular to a technology for long composite superconductors on the basis of high-temperature superconducting compounds, designed to create electrical devices. The invention is: to obtain a superconductor in an electrically insulated metal pipe filled with the powder HTSC compounds, subjecting it to deformation and heat treatment and applied vinyl coating by pyrolysis of ORGANOMETALLIC compound on the surface of the conductor before the final high-temperature treatment, and the coating carried out over several cycles, immersing the conductor in the solution of metal-containing organic compounds on the basis of a mixture of salts of carboxylic acids and thermoablative at 400 - 650oC, while the layers of the coating form both of the oxide of one metal, and oxides of various metals, which can significantly reduce the thickness of the electrically insulating coating and to increase its adhesion to the Explorer shell. 1 C.p. f-crystals, 1 Il, 1 table. The invention relates to the technical superconductivity in frequent is rprovides compounds, designed to create electrical devices.The use of high-temperature superconductors in various electrical devices involves the use of electrical insulation, which presented a number of specific requirements.Such isolation must retain their electrical insulating properties at operating temperatures of the product, not to reduce the critical characteristics of the conductor when it is applied and does not significantly increase the size of the product. In some cases applied insulation in addition to the above must withstand prolonged high temperature processing, preserving electrical insulating properties. In addition, the insulating coating must be permeable to oxygen during the heat treatment, since the formation of the superconducting properties of the conductor it is necessary to maintain the appropriate coloradohomes ceramic core with the environment annealing.At the present time in the development of electrical devices such as a magnetic coil (solenoid) tasted two ways. The first of them, the so-called winding-annealing is in the manufacture of blanks, filled with powder HTSC compounds, it is Yesenia on the surface of the Explorer shell ceramic powder mixed with an organic binder. From the thus obtained of the conductor is wound a solenoid and is subjected to the final annealing, in which the organic adhesive fade.This method has some significant drawbacks:
floor to create electrical properties must be significant, more than 20 μm, the thickness of which increases the dimensions of the solenoid;
low adhesion strength of the coating with the Explorer shell;
the unevenness of the coating thickness.In the second method, the so-called method of annealing-winding, the magnetic coil is wound from a superconductor after all heat treatments. At the same time as electrical insulation use widely known in the electrical engineering materials, such as polymer film thickness of several μm, wound (laid) between the coils of the solenoid. In this case, between the conductor and the insulation is only a mechanical contact, which can impede heat transfer between the cryogenic environment and the superconductor.The invention is illustrated in the drawing.The invention is aimed at obtaining guides on the basis of high-temperature compounds with an insulating coating, the thickness of which is and increase adhesion to the Explorer shell.This is achieved by the fact that in the manufacture of the conductor forming the workpiece in the form of sealed capsules made of metal or alloy, fill it with the powder of the superconducting compound, such as oxide ceramics, bismuth system bismuth-lead-calcium-strontium-copper-oxygen Pb Bi Ca Sr Cu O, or semi-finished products, carry out the deformation obtained billet to the desired size, thermoablative received the Explorer, and before the final heat treatment is applied insulating coating on the Explorer shell by dipping in a solution of ORGANOMETALLIC compounds (MOS) on the basis of a mixture of salts of carboxylic acids (carboxylates), and then thermoablative in air and (or) in an inert gas environment at amounts to 400-650oC, not winding the conductor in the solenoid. In the heating process is thermal decomposition (pyrolysis) of metal-containing organic compounds on the basis of a mixture of salts of carboxylic acids (carboxylates) Me(COOH)nwhere, for example IU-zirconium, aluminium, yttrium, in accordance with reaction
< / BR>with education on the Explorer shell is thin (about 0.1-0.3 μm) film of oxide of the metal. The operation of applying the MOS and heat treatment, unlike the prototype method, repeat several times in zavisimosti processing for forming superconducting properties when 815-900oC. Obtained in this way electroconductive oxide coating has an adjustable thickness of 0.1 to 6 μm while maintaining the electrical properties and good contact between the coating and the conductor. In addition, due to the application in each cycle of deposition of the layers of the MOS containing various metals, for example, the first layer of zirconium oxide, the second layer of aluminum oxide, and due to the amorphous structure of the layers is achieved by a substantial increase in resistance of the film to the Flexural deformation of the conductor when it is wound into a coil.The uniformity of coating thickness is achieved by the fact that the solutions of MOS have low viscosity and good wetting of the substrate in contrast to viscous powder mixtures with organic binder used in the method prototype.Thus, comparison of the proposed method with the method of the prototype shows that the distinctive features of this method are the use of mixtures of metal-containing organic compounds for applying for several cycles insulating coating by pyrolysis at 400 650oC to the winding of the conductor in the coil prior to its final high-temperature treatment, which suggests that proposed the storage of its electrical insulating properties, to increase the uniformity and thickness and increase adhesion to the Explorer shell.An example of the method. Insulating coating was applied on the composite tape conductors on the basis of the phase bismuth system Pb Bi Ca Sr Cu O (Bi-2223) in a silver shell cross section 0,23,4 mm2and a length of 60 mm as MOS used a mixture of zirconium carboxylates with the content of Zr=50 g/L. the coating was carried out for 15 cycles dive guides in the solution of MOS and heat treatment in a stream of argon at 550oC. After coating the conductors were subjected to final annealing at 840oC for 50 hours a Critical transition temperature was measured by an inductive method at a frequency of 300 Hz. As shown by the results of the measurements (table), an insulating coating on the basis dioxide ZrO2did not reduce the values of the critical temperature of transition in comparison with the conductor without insulation.Tests were dying to break showed that the coated samples can withstand up to 10 cycles without appreciable deformation of the coating flaking off. The study of the microstructure showed(drawing) that the floor is uneven in thickness not more than 3% from the average, well attached to the substrate men cryogenic environment. Also the layers of the coating was applied using MOS containing zirconium, and yttrium, which reduced the pyrolysis temperature of 400oC, and the number of cycles of application of the coating to reduce to 10 with the same thickness 6 microns.When researching the insulating properties of the coating thickness of 6 μm using amperometry throughout the length of the conductor conductive areas have been identified. Thus, sharing in the proposed method, the above-mentioned well-known and distinctive features will help to get a new technical result consists in obtaining a coating thickness of 0.1 to 6 μm, while maintaining its electrical insulating properties, ensuring uniformity in its application and increase the adhesion to the Explorer shell. The method of obtaining dinomania conductors based on high-temperature superconducting compounds, for example based on bismuth oxide ceramics system, in which form the workpiece in the form of sealed capsules made of metal or alloy, fill it with the powder of the superconducting compound or semi-finished products, carry out the deformation obtained billet to the required size and subjecting it to high-temperature treatment for forming Sverak cycles electrically insulating coating from a solution containing organic compounds on the basis of a mixture of salts of carboxylic acids, containing metals zirconium, aluminum, yttrium, and produce heat treatment in air or in inert gas in the temperature range 400 650oC.2. The method according to p. 1, characterized in that the coating layers formed during each cycle of the oxides of various metals.
FIELD: powder metallurgy.
SUBSTANCE: starting powders of silicon, 40 to 400 mcm, and niobium, below 63 mcm, are taken in proportion (1.33-1.38):1 to form monophase product and in proportion (1.44-1.69):1 to form multiphase product. Powders are subjected to mechanical activation in inert medium for 0.5 to 2 min, ratio of powder mass to that of working balls being 1:20. Resulting powder is compacted and locally heated under argon atmosphere to initiate exothermal reaction producing niobium silicide under self-sustaining burning conditions. Process may be employed in metallurgy, chemistry, mechanical engineering, space, nuclear, and semiconductor engineering, and in electronics.
EFFECT: found conditions for monophase and multiphase crystalline niobium silicide preparation.