CS271520B1 - Method of superconductor preparation with critical temperature above 30k - Google Patents

Abstract

The solution concerns the method of preparation of a superconductor with a junction temperature above 30 K to the bases of an alloy of the general formula(Re-D)xM1-x,where (Re) stands for the element from the group of rare earths or the element (3a) of the sub group of the periodic system as (Y, Sc); (0) is the element (2a) of the sub group of the periodic system; (M) is metal and (x) is of the value in the range between 10<4> to 5.10<-1>, which is prepared from melting by rapid cooling, with the advantage of a discharge to the cooled rotating metal disc or roller, at simultaneous formation into the shape of a ribbon, wire or powder, while the speed of the cooling is higher than 10<3> K s<-1>. The superconducting layer is created by the subsequent annealing of the alloy at a temperatures of 600 K to 900 K in the atmosphere containing oxygen until the creation of an oxide coating with the concentration of the elements (Re, D, M) corresponding to the superconducting phase. The superconductor prepared by this method can be used in such an engineering practice, where the superconductors with the junction temperature under 30 K are hitherto used.

Description

The present invention relates to a process for preparing a superconductor having a critical temperature above 30 K.

Technically useful superconductors are prepared mainly in the form of wires (NbTi monofilament or many filamentary) or in the form of tapes (eg Nb ^ Sn, NB ^ Ge). The technology of preparation consists mainly in technological processing of cold melt eg. by melt extrusion through a die or by molding (rolling and drawing). The superconductors prepared in this way reach a length of several kilometers and are mainly made of superconducting magnets. The temperatures of transition from superconducting to normal state, critical temperatures, above superconductors described above reach values up to 23 K.

At the beginning of 1986, superconductors in the form of so-called superconductors were prepared. rare earth ceramic discs.

The preparation process consists of sintering the rare earth oxides, barium and media in air or oxygen atmosphere. The main disadvantages of this method of preparation are the high proportion of expensive raw materials (up to 50%) and the resulting product in the form of a sintered superconductor is less suitable in practice, although a critical temperature above 30 K is very attractive for use in technical practice.

A different way of preparing superconductors is used in MS. author certificate no. (PV 4040-87), which consists in the preparation of a rare earth melt. Superconductors with a critical temperature above 30 K are prepared from the melt by cold forming and further heat treatment. The superconductors thus prepared can be used wherever a high current carrying capacity is not required due to a small proportion of the superconducting phase.

The above-mentioned drawbacks are solved by the process of preparing a superconductor with a critical temperature above 30 K according to the invention, which is based on the fact that the alloy of the formula (Re - D) _{x M1} . _x where Re stands for a rare-earth element or a 3a sub-group element of the periodic table as 2 »Sc:

means element 2a of the sub-periodic table of the elements;

M is metal and x. value in the range of 10 ^ ¹ to 5.10 from the molten state whilst forming, particularly in the form of strips, or Hold the powder cools at a rate of more than 10 ^ ks ^first The melt is cooled by firing on a cooled rotating metal disk or cylinder, or between cooled metal plates.

Upon cooling of the melt, an alloy is formed which is annealed at temperatures of 600K to 900K in an oxygen-containing atmosphere until a concentrate oxide layer is formed. elements of Re, D, M corresponding to the superconducting phase.

In the above-described process, a superconductor is formed in the form of tape, foil, wire, or powder with 50% to 99.9% metal content. From the point of view of costs and technical parameters, it is most desirable to choose a metal with 95% of the alloy.

In particular, the advantages of the process for preparing a superconductor according to the invention: the superconductor formed having a critical temperature above 30 K is in the form applicable to technical practice (tape, foil, wire, powder);

the current load of the superconductor is at least 10 times higher compared to the superconductor prepared by the oxidation of a platelet or prism alloy.

The invention is illustrated by the following examples:

Example 1

Preparation of the portion (in percentage by weight):

3 % la lanthanum 2 % ba barium 95 % Cu honey

Chemical purity of the elements is at least 3N (ie 99.9%) _w Alloy preparation:

The melt is formed by melting the charge in an inert atmosphere (spectral pure argon) at a pressure of 0.03 MPa and a temperature of 1430 K for 5 minutes by induction heating. This is followed by pouring into a copper mold and cooling to room temperature. This results in a master alloy which is subsequently melted by induction heating (temperature 1450 K) in an atmosphere of spectral pure argon and fired through a nozzle onto the surface of a rotating metal disk. In such an arrangement, the cooling rate of the melt is greater than 10 ³ K s -1. Depending on the nozzle dimensions, an alloy is formed in the form of a tape, unit widths up to tens of mm, depths of 25-60 µm and lengths of tens of meters.

Superconducting layer formation:.

The alloy is placed in an annealing furnace and annealed in air at 600 K for 6 hours.

The superconducting transition temperature is 31 K.

Example 2 '

Preparation of the portion (in percentage by weight):

3 % la lanthanum 2 % ba barium 95 % Cu honey

Chemical purity of elements is at least 3N (ie 99.9%)

Alloy preparation:

The melt is formed by melting the charge in an inert atmosphere (spectral pure argon) at a pressure of 0.03 MPa and a temperature of 1430 K for 5 minutes by induction heating. This is followed by pouring into a copper mold and cooling to room temperature. This results in a master alloy which is subsequently melted by induction heating (temperature 1450 K) in an atmosphere of spectral pure argon and fired through a nozzle onto the surface of a rotating metal disk. In such an arrangement, the cooling rate of the melt is greater than 10 ³ K s -1. Depending on the dimensions of the nozzle, an alloy is formed in the form of a tape of unit widths of up to tens of mm, thickness of 25-60 [mu] m and lengths of tens of meters.

Superconducting layer formation:

The alloy is placed in an annealing furnace in a spectral pure oxygen atmosphere at 600 K for 2 hours. ·

The superconducting transition temperature is 36 K.

I

Example 3

Preparation of the portion (in percentage by weight):

3 % sm samarium 2 % ba barium 95 % Cu mEO

The chemical purity of the elements is at least 3N (ie 99.9%).

Alloy preparation:

The melt is formed by melting the charge in an inert atmosphere (spectral pure argon) at a pressure of 0.03 MPa and a temperature of 1430 K for 5 minutes by induction heating. This is followed by pouring into a copper mold and cooling to room temperature. This produces a pre-alloy which is subsequently melted by induction heating (temperature 1450 K) in an atmosphere of spectral pure argon and fired through a nozzle onto the surface of a rotating metal disk. In such an arrangement, the melt cooling rate is greater than 10 * ⁵ K s · ² . Depending on the nozzle dimensions, an alloy in the form of a tape, unit widths up to tens of mm, depths of 25 - 60 µm and lengths of tens of meters is produced.

Superconducting layer formation:

The alloy is placed in an annealing furnace in an atmosphere of spectral pure oxygen at temperature

800 K for 2 hours.

The superconducting transition temperature is 63 K.

Example 4

- Preparation of the weighed portion (referred to weight percent) 3% Y yttrium 2% Ba barium 95% Cu mEO

The chemical purity of the elements is at least 3N (ie 99.9%).

Alloy preparation:

The melt is formed by melting the charge in an inert atmosphere (spectral pure argon) at a pressure of 0.03 MPa and a temperature of 1430 K for 5 minutes by induction heating. This is followed by pouring into a copper mold and cooling to room temperature. This results in a master alloy which is subsequently melted by induction heating (temperature 1450 K) in an atmosphere of spectral pure argon and fired through a nozzle onto the surface of a rotating metal disk. In such an arrangement, the melt cooling rate is greater than 10 ° C s ² . Depending on the dimensions of the nozzle, an alloy is formed in the form of a tape of unit widths up to tens of mm, depths of 25-60 µm and lengths of tens of meters.

Superconducting layer formation:

The alloy is placed in an annealing furnace in a spectral pure oxygen atmosphere at 900 K for 3 hours. '

The superconducting transition temperature is 07 K.

CS 271520 01

Example 5

Preparation of the portion (in percentage by weight):

% Y% Ba% Cu yttrium barium med

The chemical purity of the elements is at least 3N (ie 99.9%).

Alloy preparation:

The melt is formed by melting the charge in an inert atmosphere (spectral pure argon) at a pressure of 0.03 MPa and a temperature of 1430 K for 5 minutes by induction heating. This is followed by pouring into a copper mold and cooling to room temperature. This results in a master alloy which is subsequently melted by induction heating (temperature 1450 K) in an atmosphere of spectral pure argon and fired through a nozzle onto the surface of a rotating metal disk. In such an arrangement, the rate of cooling of the melt is greater than 10 ³ K s. Depending on the nozzle dimensions, an alloy is formed in the form of a tape, unit widths up to tens of mm, depths of 25 - 60 µm and lengths of tens of meters.

Superconducting layer formation:

The alloy is placed in an annealing furnace and annealed in air at 650 K for 2 hours, followed by annealing in spectral pure oxygen at 850 K for 3 hours.

The superconducting transition temperature is 91 K.

Example 6

Preparation of the portion (in percentage by weight):

2 % Y уtriům 1 % Sc skandlum 2 % ba barium $ 9 % Cu honey

The chemical purity of the elements is at least 3N (ie 99.9%).

Alloy preparation:

The melt is formed by melting the charge in an inert atmosphere (spectral pure argon) at a pressure of 0.03 MPa and a temperature of 1430 K, for 5 minutes by induction heating. This is followed by pouring into a copper mold and cooling to room temperature. This results in a master alloy which is subsequently melted by induction heating (temperature 1450 K) in an atmosphere of spectral pure argon and fired through a nozzle onto the surface of a rotating metal disk. In such a saving, the cooling rate of the melt is greater than 10 ³ K s ^-1 . Depending on the nozzle dimensions, an alloy is formed in the form of a tape, unit widths up to tens of mm, depths of 25 to 60 µm and lengths of tens of meters.

Superconducting layer formation:

The alloy is placed in an annealing furnace in an atmosphere of spectral pure oxygen at temperature

850 K for 3 hours.

The superconducting transition temperature is 87 K.

Claims (2)

A method for preparing a superconductor having a critical temperature above 30 K, characterized in that the alloy of the general formula ^(Re - ^D \ ^M 1x) wherein (Re) is an element from the group of rare earth elements or element (3a) yttrium (Y), scandium (Sc), (0) means element (2a) below: the group of the periodic table of elements, (M) is a metal, preferably a sword, (X) is a value in the range: 104 and 5.10 ¹ , is cooled from the molten state while being formed, in particular in the form of a strip, wire or powder, at a rate greater than 1 ° C, then annealed at temperatures of 600 to 900 K in an oxygen-containing atmosphere until forming an oxide layer with a concentration of elements (Re, D, M) corresponding to the superconducting phase. 2. A process for preparing a superconductor according to claim 1, characterized in that the melt is cooled by firing on a cooled rotating metal disk or cylinder, or between cooled metal plates. ·