Method for producing superconducting wire, method for modifying oxide-coated superconducting wire, and oxide-coated superconducting wire

FIELD: superconducting wire manufacture.

SUBSTANCE: proposed method for producing superconducting wire includes production of wire material in the form of source powdered metal-covered and oxide-coated superconducting material and heat treatment of wire material obtained in the process in high-pressure environment with total pressure maintained at 1 MPa or higher and below 50 MPa in the course of heat treatment; pressure rise is started with temperature at which 0.2% conventional yield point of metal becomes lower than total pressure in the course of heat treatment. Such procedure makes it possible to eliminate voids between oxide-coated superconducting material crystals and bulging of oxide-coated superconducting wire material, as well as to easily control oxygen partial pressure during heat treatment.

EFFECT: enhanced critical current density in wire material obtained.

22 cl, 27 dwg, 3 tbl

 

The technical field

The present invention relates to a method of manufacturing an oxide superconducting wire, the method of modifying an oxide superconducting wire and an oxide superconducting wire, and more specifically, it relates to a method of manufacturing an oxide superconducting wire capable of improving the critical current density, method of modifying an oxide superconducting wire and an oxide superconducting wire.

The level of technology

Generally speaking, as a method of manufacturing an oxide superconducting wire a method of obtaining an oxide superconducting wire by heat treatment of the wire formed by loading a metal tube with powder source material of the oxide superconductor and the subsequent drawing and rolling this metal tube, for sintering the powder source material of the oxide superconductor. However, in the above-mentioned stage heat treatment for sintering the wire is blown up, which is an undesirable manner reduces the superconductivity of the obtained oxide superconducting wire.

The publication of the patent application of Japan No. 5-101723 (patent document 1) proposes a method of manufacturing an oxide superconducting wire by heat treatment of a metal tube, zapolnenie the powder of the oxide superconductor or tapered body from him, in the atmosphere of increased pressure for sintering the powder of the oxide superconductor. In the above publication describes that when carrying out the heat treatment under pressure in this way we obtain a wire with excellent superconductivity.

More specifically, trying to hold the metal tube, loaded with powder of an oxide superconductor, a heat-resistant/Marostica a closed vessel to prevent swelling during sintering by increasing the internal pressure after (according to) the heating of the closed vessel. In the above publication describes that the current internal pressure can be obtained from the equation of state of gas or the like, and may be obtained from the internal pressure of approximately 4 atmospheres at a temperature of heating, for example, approximately 900°C.

In Japan patent No. 2592846 (publication of the Japan patent No. 1-30114) (patent document 2) proposes a method of manufacturing an oxide superconducting conductor by keeping a metal tube filled with an oxide superconducting powder or the like, in a state of high pressure, at least, either during the heat treatment or after the heat treatment. In the above publication describes that the premises of a metal tube in the condition with high blood pressure according to this method may be redetermine partial delamination at the interface between the oxide superconductor and the metal tube during sintering.

More specifically, a metal tube filled with an oxide superconducting powder, can be prepressure to the sintered body by keeping the metal tube in a state with a high pressure of from 500 to 2000 kg/cm2(approximately from 50 to 200 MPa), at least either during treatment or after the heat treatment. Thus, when the superconductor partially undergoes hardening, the heat released during this hardening can be quickly removed. In addition, you can also prevent deterioration of superconductivity arising from a section of the bundle forming a plot of the concentration causing distortion stresses.

Disclosure of invention

Problems to be solved by the invention of

According to the publication of the patent application of Japan No. 5-101723, however, the internal pressure obtained after heating in a closed vessel, is about 4 bar (0.4 MPa). Thus, when the sintering between the oxide superconducting crystals voids, unwanted way reduces the critical current density.

Moreover, the oxide superconducting wire can not be sufficiently protected from the formation of blisters during sintering due to internal pressure of about 4 bar (0.4 MPa), and therefore the critical current density also reduces unwanted.

In the method according to the Japan patent No. 2592846 it is difficult to regulate the partial pressure of oxygen during the heat treatment due to the use of excessively high pressure from 500 to 2000 kg/cm2(from about 50 MPa to 200 MPa), which reduces the critical current density.

Thus, the aim of the present invention is to provide a method of manufacturing an oxide superconducting wire capable of improving the critical current density by suppressing the formation of voids between the oxide superconducting crystals and swellings in the oxide superconducting wire, while simplifying the regulation of the partial pressure of oxygen during the heat treatment method of modifying an oxide superconducting wire and an oxide superconducting wire.

Means for solving problems

A method of manufacturing an oxide superconducting wire according to the present invention includes a stage for receiving a wire formed by covering the powder source material of an oxide superconductor with a metal, and the stage of heat treatment, which consists in heat treating the wire in an atmosphere of high pressure with the total pressure of at least 1 MPa and less than 50 MPa during heat treatment. During heating before heat treatment under heat treatment, the pressure increase starts the t temperature, a reduction of 0.2%conventional yield stress of the metal below the total pressure during the heat treatment.

Method of modifying an oxide superconducting wire according to the present invention includes a stage heat treatment which involves the heat treatment of the oxide superconducting wire formed by coating an oxide superconductor with a metal, in an atmosphere of high pressure with the total pressure of at least 1 MPa and less than 50 MPa during heat treatment. During heating before heat treatment under heat treatment, the pressure increase start with temperature, a reduction of 0.2%conventional yield stress of the metal below the total pressure.

According to the proposed in the present invention a method of manufacture or modification of the oxide superconducting wire pressure is applied to the wire in a state in which the 0.2%conventional yield stress of the metal is smaller than the total pressure in the atmosphere of heightened pressure during the heat treatment. Thus, the metal portion is easily compressed under the action of compressive forces occurring due to the increase of pressure due to the effect of such compression during hot processing. Therefore, the wire is compressed before creating high pressure gas penetrates into the wire through the surface pores, posredstwom the formation of voids and blisters can be sufficiently suppressed due to the increased pressure. As a result, the density of the oxide superconductor after sintering can be improved, and therefore, can be enhanced critical current density of the oxide superconducting wire.

Another method of manufacturing an oxide superconducting wire according to the present invention includes a stage for receiving a wire formed by covering the powder source material of oxide superconductor containing silver metal, and the stage of heat treatment, which consists in heat treating the wire in an atmosphere of high pressure with the total pressure of at least 1 MPa and less than 50 MPa during heat treatment. During heating before heat treatment under heat treatment, the pressure increase start after the temperature of the atmosphere exceeds 400°C.

Another method of modifying an oxide superconducting wire according to the present invention includes a stage heat treatment which involves the heat treatment of the oxide superconducting wire formed by coating an oxide superconductor containing silver metal in an atmosphere of high pressure with the total pressure of at least 1 MPa and less than 50 MPa during heat treatment. During heating before heat treatment under heat treatment, the pressure increase start after the temperature of the ATM the sphere will exceed 400° C.

According to that proposed in the present invention a method of manufacture or modification of the oxide superconducting wire, the pressure to the wire is applied in a state in which the 0.2%conventional yield strength containing silver metal is reduced to a level that is essentially identical to the total pressure in the atmosphere of heightened pressure during the heat treatment. Thus, the metal portion is easily compressed under the action of compressive forces occurring due to the increase of pressure due to the effect of such compression during hot processing. Therefore, the wire is compressed before creating high pressure gas penetrates into the wire through the surface pores, whereby the formation of voids and blisters can be sufficiently suppressed due to the increased pressure. As a result, the density of the oxide superconductor after sintering can be improved, and therefore, can be enhanced critical current density of the oxide superconducting wire.

Preferably, in the above-mentioned methods of making and modifying the pressure increase start after the temperature of the atmosphere exceeds 600°during heating before heat treatment under heat treatment.

Thus, the pressure to the wire is applied in a state in which the 0.2%-nylony yield strength containing silver metal is reduced to approximately half of the total pressure in the atmosphere of heightened pressure during the heat treatment. Therefore, the metal portion is more easily compressed under the action of compressive forces occurring because of the increased pressure. Therefore, the density of the oxide superconductor after sintering can be further improved, and therefore can be further improved critical current density of the oxide superconducting wire.

Preferably in the above-mentioned methods of making and modifying the rate of pressure increase is at least 0.05 MPa/min.

The authors of the present invention found that the penetration rate creates a high pressure gas in the wire through the surface pores on the stage of heat treatment is less than about 0.05 MPa/min. When the total pressure of the atmosphere is regulated to a continuous increase with the speed of at least 0.05 MPa/min during heating before heat treatment, the pressure in the atmosphere may be continuously maintained higher than the pressure in the wire. Thus, during heating before heat treatment to the wire can be applied compressive force regardless of whether or not the wire surface pores at the stage of heat treatment, resulting in suppressed the formation of voids and blisters. Therefore, the density of the oxide superconductor after sintering can be effectively improved through the I heat-treated in an atmosphere of high pressure of at least 1 MPa and less than 50 MPa, and therefore can be effectively improved critical current density of the oxide superconducting wire.

Preferably in the above-mentioned methods of making and modifying the rate of pressure increase is at least 0.1 MPa/min

Thus, the pressure in the atmosphere can be maintained higher than the pressure in the wire. Therefore, during heating before heat treatment to the wire can be applied even higher compressive force regardless of whether or not the wire surface pores at the stage of heat treatment, resulting in suppressed the formation of voids and blisters. Therefore, the density of the oxide superconductor after sintering can be more effectively improved by the heat treatment in the atmosphere of high pressure of at least 1 MPa and less than 50 MPa, and therefore can be more effectively improved critical current density of the oxide superconducting wire.

Preferably in the above-mentioned methods of manufacture and modification stage heat treatment is carried out in an oxygen atmosphere, and the partial pressure of oxygen is at least of 0.003 MPa and not more than 0.02 MPa.

When the partial pressure of oxygen during the heat treatment of the support in the range of at least of 0.003 MPa and not more than 0.02 MPa, formed tamilna oxide superconducting phase, and therefore the critical current density can be improved. If the partial pressure of oxygen greater than 0.02 MPa, formed a non-superconducting phase, whereas if the partial pressure of oxygen is less than 0,003 MPa, the oxide superconducting phase is formed with difficulty, and therefore the critical current density is reduced.

Preferably in the aforementioned method of manufacturing a powder source material of oxide superconductor includes a Bi2223 phase, and thus the oxide superconducting wire is annealed in an oxygen-containing atmosphere at a temperature of at least 300°and not more than 600°at the stage of heat treatment.

Preferably in the aforementioned method of modifying an oxide superconducting wire includes a Bi2223 phase, and thus the oxide superconducting wire is annealed in an oxygen-containing atmosphere at a temperature of at least 300°and not more than 600°at the stage of heat treatment.

The authors of the present invention noticed that the oxide superconductor mainly consisting of a Bi2223 phase, included the Bi2212 phase, and conducted in-depth research, finding that the oxygen content in the Bi2212 phase changes when the oxide superconductor is annealed in an oxygen atmosphere, with the improvement of the critical current density at a low temperature of about 20 K. Now what describes the cause of improving the critical current density at a low temperature of about 20 K.

Oxide superconductor (fiber oxide superconductor) oxide superconducting wire includes the Bi2212 phase in addition to the main phase Bi2223 (not currently received wire from the oxide superconductor consisting of a Bi2223 phase at 100%). When this wire is annealed in an oxygen atmosphere so that the Bi2212 phase absorbs oxygen, low-temperature characteristics of the wire are improved due to the following properties:

(1) In respect of the Bi2212 phase

In the Bi2212 phase oxygen content significantly changes when the wire is annealed in an oxygen atmosphere. In other words, the value ofzin (BiPb)2Sr2Ca1Cu2O8+zchanges due to annealing in an oxygen atmosphere, with the change of the critical temperature (Twith) and the critical current density (Jwith) Bi2212 phase. More specifically, the critical temperature Twithdecreases (changes in the range from 70 To 90 K), when the value ofzincreases. Additionally, the critical current density Jcincreases at a low temperature of about 20 K, while the critical current density Jcat a high temperature of approximately 77 K decreases.

This change is due to the fact that the concentration providing the conductivity of carriers (holes) increases when increasing the oxygen content in f is ze Bi2212. In other words, the critical temperature Twithreduced if oxygen is introduced in excess, because there is an optimal concentration of holes, increasing Twithrelative to the critical temperature Twithwhile the critical current density Jcimproved in relation to the critical current density Jcat a much lower temperature than the critical temperature Twithas improving the electrical conductivity with increasing carrier concentration. As for the critical current density Jcat high temperature, the critical temperature Twith(for example, 77 K: since the critical temperature of the Bi2212 phase is close to or is not more than the temperature) is reduced and, consequently, the critical current density Jcalso reduced.

(2) In respect of the Bi2223 phase

The Bi2223 phase is extremely difficult absorbs or releases oxygen, and the oxygen content in it barely changes when the wire is annealed in an oxygen atmosphere. In other words, the value ofzin (BiPb)2Sr2Ca2Cu3O10+zessentially remains at zero. Therefore, the critical temperature Twithand the critical current density Jcthe Bi2223 phase remain unchanged, when the wire is annealed in an oxygen atmosphere.

As is clear from table 1, showing above the aforementioned results, properties of Bi2223 phase does not change with annealing in an oxygen atmosphere, while the Bi2212 phase includes oxygen change its properties, and therefore the critical current density Jcat a low temperature of about 20 K improves across the wire.

Table 1
Before annealingAfter annealing
(1)Characteristics of the Bi2223 phase

(Twithand Jcat high and low temperatures)
unchanged
(2)Twithphase Bi2212highlow
(3)Jcthe Bi2212 phase at high temperature (about 77 K)highlow (for the above reason (2))
(4)Jcthe Bi2212 phase at low temperature (20 K)lowhigh
(5)Jcjust wire at high temperature (about 77 K)highlow (for the above reasons(1) + (3))
(6)Jcjust wire at low temperature (20 K)lowhigh above the reasons(1) + (4))

The annealing temperature set at the level of at least 300°and not more than 600°so that the Bi2212 phase could effectively include oxygen and the decomposition of the Bi2223 phase can be prevented. In other words, if the annealing temperature is less than 300°s, the oxygen is not embedded in the Bi2212 phase/is not deleted from the Bi2212 phase, whereas if the annealing temperature exceeds 700°With, the Bi2223 phase decomposes.

Preferably the above-mentioned manufacturing method additionally includes the stage of twisting the wires at the stage of heat treatment. Thus, twisted oxide superconducting wire can be protected from the formation of blisters, and the critical current density can be improved.

Preferably in the aforementioned method of manufacturing the wire is not rolled. Thus, from the formation of swellings may be secured round the oxide superconducting wire.

Preferably in the aforementioned method of manufacturing at the stage of receiving the wire, which is formed by powder coating source material of oxide superconductor metal, get a wire formed by covering a metal coated with ceramic rod, obtained by powder coating source material ceramics. Thus, the oxide superconducting wire, have the second ceramic coating (protective) layer, can be protected from the formation of blisters.

Preferably the above-mentioned manufacturing method additionally includes the stage of forming the wire into a coil at the stage of heat treatment. Thus, deterioration in the value of the critical current in the coil of the oxide superconducting wire can be effectively suppressed with simultaneous protection of the wires of blistering.

Preferably in the aforementioned method of manufacturing a wire stand in an atmosphere of reduced pressure before starting the pressure increase at the stage of heat treatment.

Preferably in the aforementioned method of modifying an oxide superconducting wire is kept in the atmosphere of reduced pressure before starting the pressure increase at the stage of heat treatment.

Thus, in the condition before increasing the pressure during the heat treatment, the pressure in the atmosphere does not exceed the pressure in the wire, resulting in gas practically does not penetrate into the wire, and blistering on the wire can be suppressed even more.

In the oxide superconducting wire according to the present invention the density of the oxide superconductor after sintering is at least 95%, preferably at least 99%.

When applying the method of making hydroxy who aqueous superconducting wire or method of modifying an oxide superconducting wire according to the present invention, it is possible to obtain an oxide superconducting wire having an oxide superconductor, showing a high density after sintering, which is still usually not made. In addition, the critical current density of the oxide superconducting wire can be improved by increasing the density after sintering of the oxide superconductor in the oxide superconducting wire.

Throughout this description the term "Bi2223 phase" means the oxide superconducting phase in the Bi-Pb-Sr-Ca-Cu-O containing bismuth, lead, strontium, calcium and copper in an atomic relations (bismuth and lead):strontium:calcium:copper, approximately expressed as 2:2:2:3, more specifically the superconducting phase (BiPb)2Sr2Ca2Cu3O10+z.

In addition, the term "phase Bi2212" means an oxide superconducting phase in the Bi-Pb-Sr-Ca-Cu-O containing bismuth, lead, strontium, calcium and copper in an atomic relations (bismuth and lead):strontium:calcium:copper, approximately expressed as 2:2:1:2, more specifically the superconducting phase (BiPb)2Sr2Ca1Cu2O8+z.

The effects of the invention

According to the proposed in the present invention the method of manufacturing an oxide superconducting wire, the pressure to the wire put in the time to 0.2%conventional yield stress of the metal is smaller than the total pressure in the atmosphere of heightened pressure during the heat treatment. Thus, the metal portion is easily compressed under the action of compressive forces occurring due to the increase of pressure due to a similar effect during hot processing. Therefore, the wire is compressed before creating high pressure gas will penetrate into the wire through the surface pores, resulting in the formation of voids and blisters can be sufficiently suppressed due to the increased pressure. Therefore, the density of the oxide superconductor after sintering can be improved, and therefore, can be enhanced critical current density of the oxide superconducting wire.

Brief description of drawings

Figure 1 is a diagram showing a partial detail view in perspective, conceptually illustrating the structure of an oxide superconducting wire.

Figure 2 - chart showing the stage of manufacturing the oxide superconducting wire according to the first variant implementation of the present invention.

Figure 3 - schematic view in section of the apparatus of the hot isostatic pressing (CIP).

Figure 4(a)-(d) are conceptual diagrams Paladino showing the behavior of voids between the oxide superconducting crystals.

5 is a chart showing the ratio between the total pressure P (MPa) in the atmosphere of high pressure and the number is (/10 m) swellings on the wire.

6 is a chart showing the total pressure and the partial pressure of oxygen to the gas mixture containing about 80% nitrogen and about 20% oxygen.

Fig.7 is a graph showing the ratio between the total pressure and concentration of oxygen in the case of an assignment of oxygen partial pressure constant.

Fig is a partial detail view in perspective, conceptually showing the structure of an oxide superconducting wire having surface pores.

Figa is a chart showing the thickness of the oxide superconducting wire having no surface long before heat treatment and after heat treatment in the atmosphere of high blood pressure.

FIGU is a chart showing the thickness of the oxide superconducting wire having surface pores, before heat treatment and after heat treatment in the atmosphere of high blood pressure.

Figure 10 is a graph showing the relationship between temperature and pressure at the stage of heat treatment and time in the second embodiment of the present invention.

11 is a diagram showing the above as an example of the relationship between temperature, total pressure and partial pressures of oxygen during the heat before heat treatment and during heat treatment and time in the third embodiment, this is subramania.

Fig is a graph showing the relationship between velocity pressure and the density after sintering at different temperatures start increasing the pressure.

Fig is a graph showing the temperature dependence of 0.2%of the conventional yield strength of silver.

Fig - chart showing the relation between the densities of the oxide superconductors after sintering and values of the critical current of the oxide superconducting wires.

Fig - chart showing the above as an example of the relationship between temperature, total pressure and partial pressures of oxygen and time in case of carrying out annealing after heat treatment in the fourth embodiment of the present invention.

Fig is a graph showing the values of the critical currents of the oxide superconducting wires before annealing and after annealing at a temperature of 500°at appropriate temperatures.

Fig is a partial detail view in perspective, conceptually showing the structure of a twisted oxide superconducting wire.

Fig - chart showing the manufacturing stage twisted oxide superconducting wire.

Fig is a partial detail view in perspective, schematically showing the state of a twisted multi-fiber wire.

Pig - partial double the th perspective view, conceptually showing the structure of all of the oxide superconducting wire.

Fig is a view in section, conceptually showing the structure of an oxide superconducting wire with a ceramic coating layer.

Fig diagram schematically showing the first stage of the method of manufacturing an oxide superconducting wire according to the sixth variant of implementation of the present invention.

Fig diagram schematically showing the second stage of the method of manufacturing an oxide superconducting wire according to the sixth variant of implementation of the present invention.

Fig diagram schematically showing the third stage of the method of manufacturing an oxide superconducting wire according to the sixth variant of implementation of the present invention.

Fig is a perspective view showing the structure of the coils in the coil of the oxide superconducting wire.

Fig is a diagram showing a stage of manufacturing the oxide superconducting wire according to a seventh variant of implementation of the present invention.

List of reference numbers of positions

1, 1A, 1b oxide superconducting wire; 2, 2A, 2b, 2C fiber of oxide superconductor; 3, 3A, 3b, 3C - shell; 4 - gas inlet; 5 - upper lid; 6 - cylinder vessel high pressure; 7 - thermal barrier; 8 - processed the object; 9 - heater; 10 - bearing; 11 - bottom cover; 12 - superconducting crystal; 13 unit; 14 - surface time; 21 - ceramic coating layer; 22 - coated ceramic rod; 25 - pin.

The best ways of carrying out the invention

Now will be described embodiments of the present invention with reference to the drawings.

The first option exercise

Figure 1 is a partial detail view in perspective, conceptually showing the structure of an oxide superconducting wire.

Multi-fiber oxide superconducting wire, for example, described with reference to figure 1. The oxide superconducting wire 1 has many fibers 2 of oxide superconductor extending in the longitudinal direction, and covering their shell 3. The material of each of the multiple fibers 2 of oxide superconductor preferably has a composition, for example, Bi-Pb-Sr-Ca-Cu-O, and, in particular, the material comprising the Bi2223 phase with the atomic ratios of (bismuth and lead):strontium:calcium:copper, approximately expressed as 2:2:2:3 is optimal. The material for the shell 3 has, for example, of silver.

Although the above has been described a multi-fiber wire, alternatively, can be used an oxide superconducting wire with single-fibre structure of the wire containing a single the first fiber 2 of oxide superconductor, coated 3.

A method of manufacturing the above-mentioned oxide superconducting wire described below.

Figure 2 is a graph showing the stage of manufacturing the oxide superconducting wire according to the first variant implementation of the present invention.

Referring to figure 2, first, a powder source material of oxide superconductor is filled metal tube (stage S1). The powder source material of oxide superconductor is made of a material that includes, for example, the Bi2223 phase.

To perform a metal tube preferably use silver or silver alloy with high thermal conductivity. Thus, the heat generated at the moment when the superconductor partially undergoes rapid cooling (quenching), can quickly be removed from the metal tube.

Then the above-mentioned wire pull (subjected to drawing), thereby forming single-fibre wire having a core material of the precursor-coated metal, such as silver (stage S1). Then a large number of such single-fibre wires are collected in a bundle and placed in a metal tube made of metal, such as, for example, silver (multi-fiber Assembly: stage S1b). Thus, get the wire from the multi-fiber structure having a large kilometersof of cores from a powder source material. Then wire with a multi-fiber structure is subjected to drawing, thereby forming a multi-fiber wire from a powder source material contained within the shell of, for example, silver or the like (stage S2). Thus, receive a multi-fiber wire formed by powder coating source material of oxide superconductor metal.

This wire is subjected to the primary rolling (stage S3), followed by the first heat treatment (stage S4). Due to these operations from a powder source material is formed of an oxide superconducting phase. Heat-treated wire is subjected to secondary rolling (stage S5). This removes voids formed by the first heat treatment. The wire after the secondary rolling is subjected to a second heat treatment (stage S6). When the second heat treatment is sintering of the oxide superconducting phase, and at the same time the oxide superconducting phase is transformed into a single phase.

The oxide superconducting wire shown in figure 1, can be obtained, for example, according to the aforementioned manufacturing method.

In this embodiment, at least either the first heat treatment (stage S4)or the second heat treatment (stage S6) is carried out in an atmosphere of high pressure, which as a General pressure applied pressure is s, of at least 1 MPa and less than 50 MPa.

The heat treatment in the atmosphere of high pressure is carried out by, for example, hot isostatic pressing (CIP). This is the hot isostatic pressing is described below.

Figure 3 is a schematic view in section of apparatus for conducting a hot isostatic pressing (CIP).

Referring to figure 3, the apparatus 13 for conducting a hot isostatic pressing consists of a cylinder 6 of the vessel of high pressure, the top cover 5 and the bottom cover 11 covering both ends of the cylinder 6 of the vessel high pressure, input 4 gas provided on the top cover 5 for the introduction of gas into the cylinder 6 of the vessel high pressure heater 9 which heats the object to be processed 8, thermal barrier 7 and the bearing 10 supporting the object to be processed 8.

According to this variant implementation support 10 supports the wire is obtained by filling the powder source material metal tube and the subsequent drawing wire/rolling in the quality of the processed object 8 in the cylinder 6 of the vessel high pressure. In this state, the predetermined gas is introduced into the cylinder 6 of the vessel high pressure through the inlet 4 of the gas, creating an atmosphere of high pressure of at least 1 MPa and less than 50 MPa in the cylinder 6 of the vessel value is about pressure and heating the wire 8 through the heater 9 to a predetermined temperature, in this atmosphere of increased pressure. This heat treatment is preferably carried out in an oxygen atmosphere, and the partial pressure of oxygen therein is preferably at least of 0.003 MPa and not more than 0.02 MPa. Thus, the wire 8 is subjected to heat treatment by hot isostatic pressing.

Under this option the implementation of the heat treatment is carried out in an atmosphere of increased pressure which is at least 1 MPa and less than 50 MPa, as described above, to achieve, mainly the following three effects:

First, it can be reduced the number of voids formed between the oxide superconducting crystals during thermal treatment.

The authors of the present invention found that the number of voids formed between the oxide superconducting crystals, mainly during the heat treatment can be significantly reduced by conducting the heat treatment in the atmosphere of high pressure in at least 1 MPa, compared with the case where the pressure is less than 1 MPa.

Figure 4(a)-(d) are conceptual diagrams Paladino showing the behavior of voids between the oxide superconducting crystals.

According to figure 4(a)-(d), when the heat treatment is carried out in an atmosphere of high pressure, the contact area between the oxide superconducting crystals 12, education is chimica during heat treatment, increases due to plastic flow, reducing the number of voids with sizes ranging from several microns to several tens microns, present between the superconducting crystals 12 (figure 4(a) → figure 4(b)). When held in this state is called the creep strain, as shown in figure 4(C), so that these voids are present at the transition boundary, are reduced, and the contaminated area, such as an oxide film, partially destroyed/degraded, causing the diffusion of atoms and further course of sintering. The space between the superconducting crystals 12, in the end, essentially disappear, as shown in figure 4(d), and formed a stable transition boundary.

Passing current through a superconducting wire means passing current between the superconducting crystals that are part of the superconducting wire. It is the transition between the superconducting crystals in a state of weak superconductivity and superconducting crystals have stronger superconductivity than the transition between these crystals, usually limits the amount of current that can pass while maintaining the superconducting state (without any electrical resistance in the coolant (e.g. liquid nitrogen or helium, or refrigerator) in the case of the use of superconducting what the wires. In the case of sintering at normal atmospheric pressure at the transition between the superconducting crystals inevitably remain void. When the number of voids between the superconducting crystals decreases, the performance characteristics of the superconducting wire is improved so that it can be prevented by reducing the critical current density.

More specifically, the density after sintering of the oxide superconductor, heat-treated at atmospheric pressure, ranged from 80 to 90% in respect of the oxide superconducting wire containing a Bi2223 phase, whereas the density after sintering of the oxide superconductor obtained by setting the total pressure at 10 MPa, was from 93 to 96%, and there was a decrease in the number of voids formed between the oxide superconducting crystals.

Secondly, the oxide superconducting wire can be protected from bumps, formed during heat treatment.

The authors of the present invention investigated the number of swellings formed during heat treatment when the variation of the total pressure of the heat treatment of the oxide superconducting wire in an atmosphere of high pressure. Figure 5 is a graph showing the ratio between the total pressure P (MPa) in the atmosphere of high pressure and number (/10 m) swellings in the wire. Addressing Phi is .5, it is clear that the number of swellings in the oxide superconducting wire is markedly reduced when the total pressure in the atmosphere increased pressure greater than 0.5 MPa, and swelling in the oxide superconducting wire essentially disappear when the total pressure exceeds 1 MPa. These results were obtained, apparently, for the following reason.

The powder of the oxide superconductor is typically loaded into a metal tube with a fill factor of about 80% of theoretical density before sintering, and therefore, in the voids of the powder gas is present. The gas in the voids of the powder undergoes a volumetric expansion when reaching high temperatures during the heat treatment, causing swelling of the wire. According to this variant implementation, however, the heat treatment is carried out in an atmosphere of high pressure of at least 1 MPa, and therefore, the pressure on the outside of the metal tube can rise higher than in a metal tube. Thus, apparently, the wire is protected from the formation of swellings caused by gas in the voids of the powder.

The authors present invention further investigated the cause of blistering in the wire, finding that the adsorbates, such as carbon (C), water (H2O) and oxygen (O2), adhering to the powder source material of the oxide superconductor, and Parauta during sintering and increase in volume in a metal tube, so this gas forms a swelling in the wire. However, the formation of such swellings wire as a result of evaporation of adsorbates on the powder can also, apparently, to prevent, as far as the external pressure can be raised above the "intermetallic" internal pressure by conducting heat treatment in an atmosphere of high pressure of at least 1 MPa.

Thus, apparently, can essentially remove not only the bloating caused by gas present in the voids of the powder source material of an oxide superconductor, but also swelling caused by evaporation of adsorbates, adhering to the surface of its particles. Swellings in the oxide superconducting wire cause a reduction in the critical current density, and consequently, reduction of the critical current density can be prevented by preventing the formation of swellings in the wire.

Thirdly, the partial pressure of oxygen can be easily adjusted during the heat treatment.

The authors of the present invention found that the phase 2223 oxide superconductor based on Bi stably formed in the case, when the oxygen partial pressure is regulated at the level at least of 0.003 MPa and not more than 0.02 MPa, regardless of the total pressure. If the partial pressure of oxygen greater than 0.02 MPa, a non-superconducting f is for, such as Ca2PbO4whereas, if the partial pressure of oxygen is less than 0,003 MPa, practically does not form a Bi2223 phase, and the critical current density is reduced.

6 is a graph showing the total pressure and the partial pressure of oxygen to the gas mixture containing about 80% nitrogen and about 20% oxygen. Fig.7 is a graph showing the ratio between the total pressure and concentration of oxygen in the case of an assignment of oxygen partial pressure constant.

Referring to Fig.6, the Bi2223 phase stably formed without regulation of the partial pressure of oxygen, when the total pressure in the atmosphere of high pressure corresponds to, for example, atmospheric pressure is 1 ATM (0.1 MPa), because the partial pressure of oxygen equivalent to 0.2 ATM (0.02 MPa), shown by the dashed line. However, when the total pressure in the atmosphere increased pressure is increased to 2 ATM, 3 ATM, etc., the partial pressure of oxygen is also increased, exceeding the level at 0.2 ATM, shown by the dashed line. Therefore, the Bi2223 phase is not formed stably. Therefore, the oxygen partial pressure must be regulated at the level at least of 0.003 MPa and not more than 0.02 MPa by varying the proportion of oxygen in the gas mixture when mixing,as shown in Fig.7. The dotted line in figure 7 shows the level at 0.2 ATM (0.02 MPa), like the dashed line in Fig.6.

In practice, the partial pressure of oxygen regulate when tracking (monitoring) of the total pressure and oxygen concentration. In other words, the partial pressure of oxygen is determined by multiplying the total pressure on the oxygen concentration. Therefore, if the total pressure is, for example, 50 MPa, the oxygen concentration is 0.01% in the case where heat treatment is conducted at a partial oxygen pressure of 0.005 MPa. Consequently, the composition of the input gas mixture must be adjusted to measure the oxygen concentration of 0.01%. However, the oxygen concentration of 0.01% is essentially identical to the measurement error, and therefore difficult to control gaseous oxygen in the input gas mixture using the correct measuring the concentration of oxygen. According to this variant implementation, the total pressure in the atmosphere of high pressure set at less than 50 MPa, so that the concentration of oxygen in the input gas mixture, you can save high to some extent in reducing the impact of measurement error on the concentration of oxygen, resulting in oxygen partial pressure can be easily adjusted.

Although this alternative implementation is shown for the case when the atmosphere is as high pressure consists of nitrogen and oxygen, the atmosphere of high pressure may consist of noble (inert) gas and oxygen. Therefore, the atmosphere of high pressure may consist of, for example, of argon and oxygen.

The second option exercise

It was found that the formation of voids and blisters can be effectively suppressed when carrying out the heat treatment in the aforementioned pressure range (at least 1 MPa and less than 50 MPa), when the wire is formed by coating the metal powder source material of an oxide superconductor, has no surface pores, whereas the formation of voids and blisters cannot be sufficiently suppressed only by conducting the heat treatment in the above pressure range, when the wire has a surface pores.

Fig is a partial detail view in perspective, conceptually showing the structure of an oxide superconducting wire having surface pores (point pinholes). Addressing pig, surface pores 14 are formed so that they pass to the outside of the fibers 2 of oxide superconductor. The rest of the structure shown in Fig, is essentially identical to the structure shown in figure 1, and therefore, identical elements are denoted by identical reference numbers, and redundant description is not repeated.

Figa is sonographic, showing the thickness of the oxide superconducting wire having no surface long before and after the stage of heat treatment in the atmosphere of high pressure, and FIGU is a graph showing the thickness of the oxide superconducting wire having surface pores, before and after the stage of heat treatment. Conditions of heat treatment on figa and 9B are as follows: the total pressure is 20 MPa, the partial pressure of oxygen - 0,008 MPa, temperature - 825°in the atmosphere, and the heat treatment time is 50 hours.

Addressing figa, the thickness of the oxide superconducting wire having no surface pores decreases by approximately 0,006 mm to 0.01 mm after heat treatment. This is due to the fact that suppress the formation of voids between the oxide superconducting crystals and swellings of the oxide superconducting wire due to heat treatment in an atmosphere of high pressure with the total pressure of 20 MPa.

Addressing figv, on the other hand, the thickness of the oxide superconducting wire having surface pores, decreases only by about from 0.002 mm to 0.005 mm after heat treatment, and the formation of voids between the oxide superconducting crystals and swellings of the oxide superconducting wire is suppressed enough. The thickness of one plot (plot A), having surface pores in the wire Uwe is aceveda after heat treatment compared to the thickness before heat treatment.

Thus, it was found that the formation of voids and blisters can be effectively suppressed by conducting the heat treatment in the aforementioned pressure range (at least 1 MPa and less than 50 MPa), when the surface pores are absent, whereas the formation of voids and blisters cannot be sufficiently suppressed only by conducting the heat treatment in the above pressure range, when the surface pores are present.

During the heat treatment in the atmosphere of high pressure according to the present invention formed by heat treatment of the superconducting crystals are plastic flow and creep data arising from high pressure in at least 1 MPa outside of the wire, which suppresses the voids formed between the heat treatment of the oxide superconducting crystals. Additionally, due to the pressure on the outside of the metal tube can be prevented expansion during heat treatment gas in the voids of the powder formed during heat treatment of the oxide superconducting crystals, or gas, adhering to the powder resulting from the heat treatment of the oxide superconducting crystals, resulting in the oxide superconducting wire is protected from the formation of swellings. SL is therefore prevents the reduction of the critical current density arising from voids and blisters.

However, in the case of a wire having surface pores, creating a high pressure gas enters the wire through these surface pores also, when the above-mentioned heat treatment is carried out in an atmosphere of high pressure. Therefore, there is difference between internal and external pressure wire, and the formation of voids and blisters is not suppressed sufficiently by heat treatment in an atmosphere of high pressure. As a result, the effect of preventing the reduction of the critical current density decreases.

Addressing pig, the thickness W of the shell 3 can be increased so that there are no surface pores 14, passing to the outside of the fibers 2 of oxide superconductor. However, if the thickness W of the shell 3 is increased, the proportion of fibers 2 of oxide superconductor in the oxide superconducting wire 1 is reduced, reducing the amount of current flowing per unit area. Therefore, the authors of the present invention conducted in-depth research, finding that the formation of voids and blisters can be suppressed to improve the critical current density without increasing the thickness W of the shell 3 in the case of wires having surface pores by applying the methods described below.

According to the this method, the pressure increase is carried out with a speed of at least 0.05 MPa/min during heating before heat treatment in the course, at least either the first heat treatment (stage S4)or the second heat treatment (stage S6). During heat treatment the total pressure in the atmosphere to regulate its continuous increase. During cooling immediately after heat treatment also carry out the regulation in order to compensate for the pressure drop caused by lowering the temperature (by adding the pressure).

Figure 10 is a graph showing the relationship between temperature and pressure at the stage of heat treatment and time in the second embodiment of the present invention.

Referring to figure 10, the pressure increases gradually in accordance with the equation of state of gas during heating before heat treatment, if the temperature of the atmosphere is, for example, not more than 700°C. When the temperature of the atmosphere is essentially exceeds 700°C, the pressure in the atmosphere increases to about 10 MPa. At this time the pressure in the atmosphere increases abruptly with the speed increase pressure of at least 0.05 MPa/min.

The authors of the present invention found that the rate of penetration creates high pressure gas in the wire through the surface of the pores is less than about 0.05 MPa/min, when the oxide superconducting wire having surface pores, heat-treated in the atmosphere p is increased pressure. Therefore, during the heat-up time before the heat treatment, the pressure in the atmosphere can be maintained higher than the pressure in the wire, by adjusting the total pressure of the atmosphere for continuous improvement with a speed of at least 0.05 MPa/min during heating before heat treatment.

After that, the temperature of the support at the level of, for example, 830°during heat treatment. On the other hand, the pressure in the atmosphere continuously improve. Although the rate of increase of pressure during the heat treatment is preferably as high as possible, the total pressure exceeds 50 MPa, if the rate of increase of pressure is excessively high, and therefore the pressure must continuously increase with an appropriate rate of increase of pressure to the total pressure during the heat treatment does not exceed 50 MPa. Referring to figure 10, the pressure increased to about 30 MPa. Therefore, the time when the pressure in the wire and the pressure in the atmosphere are equal to each other, may be delayed from time t1before time t2in comparison with the case where the pressure constant support during heat treatment. Thus, the condition in which the pressure in the atmosphere is higher than the pressure in the wire, can continuously be maintained longer during heat treatment.

After that, during ohla the Denia immediately after heat treatment, the pressure begins to decrease in accordance with the equation of state of gas, followed by decrease of temperature in the atmosphere. At this time, the pressure is adjusted so as to compensate for the pressure drop caused by lowering the temperature (by adding the pressure). In order to form a stable oxide superconducting phase, the partial pressure of oxygen is adjusted so that it was constantly in the range from 0.003 to 0.02 MPa.

According to this method, the pressure in the atmosphere increases above the pressure in the wire during heating before heat treatment, resulting in the wire can be applied compressive force. In addition, in a state where the pressure in the atmosphere is higher than the pressure in the wire can be continuously maintained during the heat treatment for a longer period of time. Therefore, the formation of voids and blisters is suppressed during heating before heat treatment and during heating, resulting in a reduction of the critical current density can be effectively suppressed due to heat treatment in an atmosphere of high pressure of at least 1 MPa and less than 50 MPa.

A third option exercise

The authors present invention additionally has conducted in-depth research and came to the conclusion that the critical current density in the oxide superconducting wire can be further improved through the use of techniques, opisyvaemuyu.

According to this method, the pressure increase start when the temperature of the atmosphere exceeds 400°C, preferably 600°during heat before heat treatment during at least either the first stage heat treatment (stage S4), or the second stage heat treatment (stage S6)shown in figure 2. The pressure increase is preferably carried out with a speed of at least 0.05 MPa/min, more preferably at least 0.1 MPa/min

11 is a diagram showing the above as an example of the relationship between temperature, total pressure and partial pressures of oxygen and time during heat before heat treatment and during the heat treatment in the third embodiment of the present invention.

Referring to 11, the temperature in the atmosphere gradually increased to 820°C. the Pressure in the atmosphere increases gradually in accordance with the equation of state of gas, when the temperature is less than 600°C. the pressure Increase start after the temperature in the atmosphere will reach 600°and continue to about 25 MPa at a speed of increase of pressure of about 0.1 MPa/min oxygen Partial pressure maintained within the range at least of 0.003 MPa and less than 0.02 MPa. The critical current density of the oxide superconducting wire can be advanced at the of Oksana by conducting the heat treatment under these conditions.

To confirm the influence of the aforementioned method of heat treatment, the authors of the present invention conducted the following experiment.

Fig is a graph showing the relationship between velocity pressure and the density after sintering at different temperatures start increasing the pressure.

Addressing pig, the fibre density of the oxide superconductor (oxide superconductors) after sintering is about 93 to 96% at speeds increase the pressure of at least 0.05 MPa/min. in case of pressure increase, when the temperature of the atmosphere is 30°C. on the other hand, in case the pressure increase after the temperature of the atmosphere reaches 400°C, the fibre density of the oxide superconductor after sintering is at least about 95%, at speeds increase the pressure of at least 0.05 MPa/min. moreover, in case the pressure increase after the temperature of the atmosphere reaches 600°C, the fibre density of the oxide superconductor after sintering is at least about 97%, at speeds increase the pressure of at least 0.05 MPa/min, and the density of the fibers of the oxide superconductor after sintering is at least about 98%, at speeds increase the pressure of at least 0.1 MPa/min Dopolnenie to this, in both cases, the beginning of the pressure increase after the temperature of the atmosphere reaches respectively 400°and 600°C, the fibre density of the oxide superconductor after sintering is at least about 99%, at speeds increase the pressure of at least 0.15 MPa/min. Density after sintering is improved when the speed of pressure increase of at least 0.05 MPa/min, apparently, because the penetration rate creates a high pressure gas in the wire through the surface of the pores is less than about 0.05 MPa/min, and therefore the pressure in the atmosphere can be permanently maintained higher than the pressure in the wire as the wire is compressed with greater speed than the speed of penetration. From the results shown in Fig, it is clear that the density after sintering of the fibers of the oxide superconductor is improved when the pressure increase start after the temperature of the atmosphere exceeds 400°C, preferably 600°C. it is Also clear that the density after sintering of the fibers of the oxide superconductor is additionally improved, when the rate of increase of pressure is preferably set at the level of at least 0.05 MPa/min, more preferably at least 0.1 MPa/min. It is, apparently, happens for the following reason.

Fig is a chart that shows the General temperature dependence of 0.2%of the conventional yield strength of silver.

Addressing pig, 0,2%conditional yield of silver is about 370 MPa, when the atmosphere is at room temperature, and decreases with increasing temperature of the atmosphere. In other words, 0,2%conditional yield strength is reduced to about 50 MPa when the temperature of the atmosphere reaches 400°S, and 0.2%conventional yield strength is reduced to about 25 MPa when the temperature of the atmosphere reaches 600°C. Thus, the 0.2%conditional yield of silver is reduced to a level that is essentially identical to the total pressure of at least 1 MPa and less than 50 MPa above atmospheric high pressure, when the temperature of the atmosphere is equal to 400°C. in Addition, 0,2%conditional yield of silver is reduced to approximately half of the total pressure (at least 1 MPa and less than 50 MPa) in the above atmosphere of high pressure, when the temperature of the atmosphere is equal to 600°C. According to the above-mentioned method, it is necessary that the pressure applied to the wire, when the strength of the casing is reduced to a level that is essentially identical to the total pressure in the atmosphere of high pressure. Therefore, the membrane can be easily compressed under the action of compressive force due to increasepressure due to the effect similar to the effect of hot working. Therefore, the wire si is moved before as creating the high pressure gas enters the wire through the surface pores, resulting in the formation of voids and blisters can be sufficiently suppressed by increasing pressure, and the density after sintering of the oxide superconducting fibers can be improved. Values of 0.2%of the conventional yield stress shown in Fig, represent values obtained during the burst test according to Industrial Standards of Japan (JIS) on the wires of pure silver with a diameter of 1.5 mm.

Density after sintering of the fibers of the oxide superconductor shown in Fig calculated by the following method. First, from each of the oxide superconducting wire cut to 5 g (= Mt(g)). Then cut off the oxide superconducting wire was immersed in alcohol for measuring mass (W (g)) the wires in alcohol and calculate the buoyancy acting on the oxide superconducting wire. Volume (Vt(cm3)) the oxide superconducting wire was calculated using the known density of alcohol (ρ=0,789 g/cm3). More specifically, the volume Vtwas calculated by the following equations (1) and (2), provided that Ftrepresents buoyancy:

Ft= Mt- W(1)

Vt= Ft(2)

Then the oxide superconducting wire was dissolved in nitric acid, and Orebro were determined using emission spectroscopy with an induction-coupled plasma (ICP) for this solution to calculate the proportion (Y) of silver in the mass of the oxide superconducting wire. Mass (Mf(g)fibre) of the oxide superconductor and the mass (Ms(g)) of the membrane was calculated from the mass of the oxide superconducting wire according to the following equations (3) and (4):

Ms= Mt× Y(3)

Mf= Mt- Ms(4)

Further, the volume (Vs(cm3the membrane was calculated from the known density of silver is 10.5 g/cm3), and volume (Vf(cm3)) fibers oxide superconductor was calculated from the volume of the shell. Density ρffibers of the oxide superconductor was calculated from the volume of the fibers of the oxide superconductor. More specifically, density ρfwas calculated by the following equations(5)-(7):

Vs= Ms/10,5(5)

Vf= Vt- Vs(6)

ρf= Mf/Vf(7)

On the other hand, as theoretical density of the fibers of the oxide superconductor used a value of 6.35 g/cm3. This value was calculated by the following method. The atomic ratio of the Bi2223 phase in the fibers of the oxide superconductor was calculated using the method of emission spectroscopy with an induction-coupled plasma (ICP) method and energy dispersive x-ray fluorescence analysis (EDX). Constant of the crystal lattice of the Bi2223 phase were obtained using x-ray diffraction analysis to calculate the greates the n - and C-axes. theoretical density was calculated based on these values.

The density after sintering of the fibers of the oxide superconductor was calculated as the ratio between the density of the fibers of the oxide superconductor obtained by the aforementioned method, and theoretical density of the fibers of the oxide superconductor. More specifically, the density after sintering was calculated by the following equation (8):

The density after sintering (%)=(ρf/6.35mm)×100(8)

Fig is a graph showing a relationship between densities after sintering of oxide superconductors and values of the critical current of the oxide superconducting wires.

Addressing pig can be seen that the values of the critical current of the oxide superconducting wire having a density after sintering is not more than about 95%, less than 80 And, while the values of the critical current of the oxide superconducting wire having a density after sintering, at least about 95%, are mainly in the range of larger than 80 A. the Value of the critical current was obtained by multiplying the critical current density on the cross section of the fibers of the oxide superconductor, and therefore the critical current density is proportional to the value of the critical current. Therefore, the critical current density is improved in the oxide with erprobte wire, with a high density after sintering. This, apparently, is due to the large amount of current flows in the superconducting fibers in the oxide superconducting wire having a high density after sintering, due to the small number of voids between the crystals of the superconducting fibers.

From the above results, shown in Fig and 14, it is clear that the density after sintering of the fibers of the oxide superconductor is improved, as well as improving the critical current density of the oxide superconducting wire, when the pressure increase start after the temperature of the atmosphere exceeds 400°C, preferably 600°S, with a speed component preferably at least 0.05 MPa/min, more preferably at least 0.1 MPa/min

According to the method of manufacturing an oxide superconducting wire described in this embodiment, pressure is applied to the wire when the 0.2%conventional yield strength of the shell is reduced to a level that is essentially identical to the total pressure in the atmosphere of heightened pressure during the heat treatment. Thus, the membrane can be easily compressed under the action of compressive force due to increasepressure due to the effect similar to the effect of hot working. Therefore, the wire is compressed before the AK creating high pressure gas enters the wire through the surface pores, resulting in the formation of voids and blisters can be effectively suppressed by increasing the pressure. Therefore, the density after sintering of the fibers of the oxide superconductor can be improved, and therefore, can be enhanced critical current density of the oxide superconducting wire.

Preferably in the aforementioned method of manufacturing the pressure increase start after the temperature of the atmosphere exceeds 600°during heating before heat treatment under heat treatment.

Thus, pressure is applied to the wire when the 0.2%conventional yield strength of the shell is reduced to approximately half of the total pressure in the atmosphere of heightened pressure during the heat treatment. Therefore, the shell is more easily compressed under the action of compressive efforts, the resulting pressure increase. Therefore, the density after sintering of the fibers of the oxide superconducting wire can be further improved, and in addition, can be enhanced critical current density of the oxide superconducting wire.

Preferably in the aforementioned method of manufacturing the rate of pressure increase is at least 0.05 MPa/min, more preferably at least 0.1 MPa/min

Thus, the density after sintering of oxide fibers CBE is Provodnik can be further improved, and therefore can be further improved critical current density of the oxide superconducting wire.

Preferably in the aforementioned method of manufacturing stage heat treatment is carried out in an oxygen atmosphere, and the partial pressure of oxygen is at least of 0.003 MPa and not more than 0.02 MPa.

Thus, to form a stable oxide superconducting wire, the critical current density can be improved. If the partial pressure of oxygen greater than 0.02 MPa, formed heterophase, while, if the partial pressure of oxygen is less than 0,003 MPa, the oxide superconducting phase is formed with difficulty, and the critical current density decreases.

Each of the embodiments from the first to the third has been described with reference to the method for improving the critical current density (a method of manufacturing an oxide superconducting wire by a specified method of heat treatment on at least either the first stage heat treatment (stage S4)or the second-stage heat treatment (stage S6)shown in figure 2. Alternative instead of the above-mentioned case the present invention is also applicable as a stage heat treatment is carried out on already made an oxide superconducting wire (i.e. the oxide superconducting wire after completed the I stages S1-S6 in figure 2), i.e. a way of modifying an oxide superconducting wire. In other words, the oxide superconducting wire having a density after sintering less than 95%, can be modified, for example, by applying heat treatment according to the present invention, however, the effect of the modification is achieved also in the case of applying the heat treatment according to the present invention to an oxide superconducting wire having a density after sintering at least 95% and less than 99%. Thus, the critical current density of the oxide superconducting wire can be improved also in the case where the heat treatment according to the present invention is used as a method of modifying an oxide superconducting wire.

In addition, each of the embodiments from the first to the third has been described with reference to the case of heat treatment of the oxide superconducting wire having a sheath of silver, in an atmosphere of high pressure with the total pressure of at least 1 MPa and less than 50 MPa during heat treatment, and thus the pressure increase start after the temperature of the atmosphere exceeds 400°during heating before heat treatment under heat treatment. However, the present invention is not limited to this case and applicable to all of the oxide superconducting the wires, formed by coating an oxide superconductor metals. In this case, the heat treatment is carried out in an atmosphere of high pressure with the total pressure of at least 1 MPa and less than 50 MPa during heat treatment, and during the heat before heat treatment under heat treatment, the pressure increase start temperature, a reduction of at least 0,2%conditional yield strength of the metal below the total pressure of at least 1 MPa and less than 50 MPa) during heat treatment. Thus, pressure is applied to the wire in a state where the 0.2%conventional yield stress of the metal is less than the total pressure in the atmosphere of heightened pressure during the heat treatment, resulting metal part is easily compressed under the action of compressive forces in the pressure increase. Thus, the density after sintering of the oxide superconductor can be improved, and the critical current density of the oxide superconducting wire can be improved for the same reasons as in the above-mentioned oxide superconducting wire having a coating of silver.

The fourth option exercise

Generally speaking, the oxide superconducting wire based on bismuth (Bi) is known as one of the oxide superconducting wires. This oxide superconducting wire on the basis of i is used at the temperature of liquid nitrogen and can provide a relatively high critical current density. In addition, it is expected that this oxide superconducting wire based on Bi, which is relatively easily extended (stretched), will find application in superconducting cable or magnet. However, conventional oxide superconducting wire based on Bi still was, unfortunately, not suitable for applications requiring high performance at low temperature, due to the low critical current density (Jc) at a low temperature of about 20°K.

In this regard, the authors of the present invention have found that the critical current density of the oxide superconducting wires based on Bi at a low temperature of about 20 To may be improved by combining the following methods with the methods according to each of embodiments one through three. This technique is described below.

According to this method, the wire is annealed in an oxygen-containing atmosphere at a temperature of at least 300°and not more than 600°on at least either the first stage heat treatment (stage S4), or the second stage heat treatment (stage S6)shown in figure 2.

Fig is a diagram showing the above as an example of the relationship between temperature, total pressure, partial pressures of oxygen and time in case of carrying out annealing after termio the processing in the fourth embodiment of the present invention.

Addressing pig, the oxide superconducting wire is kept in an atmosphere having a temperature of 820°and the total pressure of 25 MPa, for a constant time, and then the temperature of the lower atmosphere. At this time the total pressure of the atmosphere is also gradually reduced. When the temperature and pressure of the atmosphere reaches, respectively, about 300°and about 16 MPa, the oxide superconducting wire is maintained at a constant temperature and annealed for 30 hours. Although the wire is maintained at a constant temperature, the total pressure on continuously and smoothly decreases. The temperature of the atmosphere decreases again after annealing. The partial pressure of oxygen is approximately 0,008 MPa during heat treatment and increases to about 0,024 MPa during annealing. After annealing the oxygen partial pressure decreases along with the total pressure.

In order to confirm the influence of the aforementioned annealing, the authors of the present invention conducted the following experiment.

The authors of the present invention investigated the degree of improvement of the values of the critical current Icat 20 K as in the case of annealing, and in the case without carrying out annealing on the stages of heat treatment. Annealing was carried out for different times of annealing at different partial pressures of oxygen. Table 2 a which shows the average coefficients of increasing values of the critical current at 22 K (I c(22)) and the values of the critical current at 77 K (Ic(77 K)) stages after heat treatment of the respective samples. Values of the critical current were measured in a magnetic field of 3 T.

Table 2
Sample< / br>
No.
TemperatureTimeThe partial pressure of oxygenAverage: Ic(20K)/< / br>
Ic(77 K)
1Neotony1,6
2Neotony1,7
3Neotony1,5
4Annealed300°C30 h24 kPa2,1
5Annealed300°C30 h12 kPa1,9
6Annealed300°C40 h20 kPa2

Referring to table 2, it is seen that the average coefficient values increase kriticheskogo current at 22 To the case without carrying out annealing, respectively 1,6, of 1.7 and 1.5. On the other hand, the average coefficients of increasing values of the critical current at 22 K in the case of annealing, respectively of 2.1, 1.9 and 2. Thus, it is clear that the value of the critical current at 20 K can be improved in the case of annealing in comparison with the case without carrying out annealing.

To confirm the effect of annealing the wire in oxygen-containing atmosphere at a temperature of at least 300°and not more than 600°With the authors of the present invention conducted the following experiment.

First received ribbon-like oxide superconducting wire Bi based multi-fiber structure with 61 fiber, with external dimensions of 4.2 mm and 0.24 mm in thickness, and with a bit of silver and 1.5. Further, this oxide superconducting wire was subjected to heat-treated and annealed during this heat treatment. Annealing was performed in a stream of oxygen during the time of annealing for 20 hours at different temperatures of annealing, are shown in table 3. The number of Bi2212 phase in the oxide superconductor is also varied. Table 3 also shows the corresponding values of the critical current Icat 77 K and 20 K before annealing and the corresponding values of the critical current Icat 77 K and 20 K after annealing of the respective samples.

Wire to be used were chosen from the same set (the party is), and it was assumed that the cross-sectional area of the superconducting parts of the respective wires are identical to each other. Therefore, the magnitude of the value of the critical current Icin the following table 3 is proportional to the critical current density Jc(Jc=Ic/cross-section of the superconducting part).

td align="center"> 82
Table 3
Sample No.The number of Bi2212 phase< / br>
(%)
Before annealing< / br>
Ic(A) at 77 K
Before annealing< / br>
Ic(A) at 20 K (1)
The temperature of annealing (°C)After annealing< / br>
Ic(A) at 77 K
After annealing< / br>
Ic(A) at 20 To< / br>
(2)
(2)/(1)
7995500No---
8995500100955001,0
9995500200955001,0
10995500 300945121,02
11995500400925301,06
12995500500905551,11
13995500600895501,1
14995500700704800,96
15995500800603450,69
162100527500995281,0
17597511500965431,06
18995500500905551,11
191392485500885401,11
2019904745005301,12
212583437500755001,14
225060316500504101,3

From the results shown in table 3, it is clear that the value of the critical current Ic(density Jcthe critical current) at low temperature (20 K) is improved compared with that before annealing due to the annealing is conducted in an oxygen atmosphere at a temperature of at least 300°and not more than 600°C. it is Also clear that the value of the critical current Icafter annealing exceeds 530 A, and the absolute value of the values of the critical current Ic(density Jcthe critical current) increases, due to the amount of the Bi2212 phase in the oxide superconductor, corrected at the level of at least 5 mol.% and not more than 20 mol.%.

The authors present invention also investigated the values of the critical current Icoxide superconducting wires at appropriate temperatures (in K) before annealing and after annealing at a temperature of 500°C. On Fig presents the results.

From the results presented on Fig, it is clear that the value of the critical value is th current I cthe annealed sample is higher than that at geotagging sample to a temperature not more than about 20 K.

In the method of manufacturing an oxide superconducting wire according to this variant implementation of the oxide superconducting wire includes a Bi2223 phase, and it is annealed in an oxygen-containing atmosphere at a temperature of at least 300°and not more than 600°C. Thus improving the critical current density of the oxide superconducting wire at a low temperature of about 20 K.

This option has been described with reference to the method for improving the critical current density by carrying out a specified method of heat treatment on at least either the first stage heat treatment (stage S4), or the second stage heat treatment (stage S6), presented in figure 2. Instead of this case, however, the present invention is also applicable to the stage of heat treatment carried out on already made an oxide superconducting wire (i.e. the oxide superconducting wire after completion of stages S1-S6 in figure 2), i.e. as a method of modifying an oxide superconducting wire. The critical current density of the oxide superconducting wire can also be improved when the heat treatment according to the present invention is used as a way of modifying the hydroxy is tion of the superconducting wire.

The fifth option exercise

Each variant of the implementation of the first to fourth has been described with reference to the manufacturing method in the case when the fibers 2 superconductor extend in the longitudinal direction of the oxide superconducting wire 1, and the oxide superconducting wire 1 is made in the form of a tape, as shown in figure 1. The oxide superconducting wire shown in figure 1, has a high critical current density. However, the method of manufacturing according to the present invention is also applicable, for example, to the method of manufacturing twisted oxide superconducting wire instead of the method of manufacturing an oxide superconducting wire shown in figure 1.

Fig is a partial detail view in perspective, conceptually showing the structure of a twisted oxide superconducting wire. As shown in Fig twisted oxide superconducting wire 1A has many fibers 2A oxide superconductor extending in the longitudinal direction, and covering their shell 3A. Fiber 2A of the oxide superconductor twisted spirally along the longitudinal direction of the oxide superconducting wire 1A. The method of manufacturing of this twisted oxide superconducting wire 1A is described next.

Fig is a chart that shows the expansion of manufacturing a twisted oxide superconducting wire. Addressing pig, in the method of manufacturing twisted oxide superconducting wire 1A, the wire is twisted so that the steps of twisting comprise, for example, respectively, 500 mm, 100 mm, 50 mm and 10 mm, to the state round wire (stage S2) after drawing the wire will form a multi-fiber wire (stage S2), and before the primary rolling (stage S3). Fig shows the state after the twisting. Rest in this method of manufacture is essentially similar to the method of manufacturing according to the first variant of implementation, and therefore redundant description is not repeated.

Twisted oxide superconducting wire can effectively reduce the loss of AC. When the present invention is applied to a method of manufacturing twisted oxide superconducting wire, then twisted oxide superconducting wire can be suppressed blistering, and the critical current density can be improved.

The authors of the present invention was tested to confirm the above effect. This test is described below.

The powder having the composition ratio of Bi:Pb:Sr:Ca:Cu=1,82:0,33:1,92:2,01:3,02, prepared from Bi2O3, PbO, SrCO3, CaCO3and CuO. This powder was subjected to heat treatment at a temperature of 750°C for 10 hours, and then subjected is whether the heat treatment at a temperature of 800° C for 8 hours. After that, the sintered mass obtained through these treatments, rasmalai in the powder in an automatic mortar. The powder obtained after grinding was subjected to heat treatment at 850°C for 4 hours, and sintered mass obtained by this heat treatment, rasmalai in the powder in an automatic mortar. The powder obtained after grinding was subjected to heat treatment, and then they filled out a silver tube with an external diameter of 36 mm and an inner diameter of 30 mm (stage S1). Then the silver tube filled with the powder was subjected to wire drawing to obtain single-fibre wire (stage S1a). Next 61 this single-fibre wire gathered together in a bundle and inserted into a silver tube with an external diameter of 36 mm and an inner diameter of 31 mm (stage S1b). Then the silver tube inserted in her many unifiber wires were subjected to wire drawing to obtain a multi-fiber wire with a diameter of 1.5 mm (stage S2). Then, the multi-fiber wire twisted with steps of twisting of 20 mm, 15 mm, 10 mm and 5 mm (stage S2a). This was followed by primary rolling (stage S3) to get the wire in the form of a tape having a thickness of 0.26 mm, a width of 3.7 mm and a length of 100 m, Then this wire is subjected to heat treatment at a temperature of 840&x000B0; C in an atmosphere with oxygen concentration of 8% for 30 hours as a first heat treatment (stage S4). This was followed by a secondary rolling (stage S5) for crimping wires 8%. Then this wire is subjected to heat treatment at a temperature of 820°in an atmosphere having a total pressure of 25 MPa and the partial oxygen pressure of 8 kPa for 50 hours as a second heat treatment (stage S6). During heating before the second heat treatment (stage S6), the pressure increase is started with the temperature, a reduction of 0.2%conditional yield silver tube below 25 MPa. Sample 1 was obtained from twisted oxide superconducting wire 1A, obtained through the above steps.

On the other hand, stages S1-S5 shown in Fig, conducted under conditions identical to the above, and the wire is subjected to heat treatment at a temperature of 820°in the atmosphere with atmospheric pressure and the oxygen partial pressure of 8 kPa for 50 hours as a second heat treatment (stage S6) to obtain twisted oxide superconducting wire of comparative example 1. We measured the critical current density and explored a number of the resulting warping, as in the sample 1 and comparative example 1. As a result, the critical current density of the sample of comparative example 1 was 2.0 kA/with the 2, while the critical current density of the sample 1 was 2.6 kA/cm2that was an improvement of approximately 1.3 times. While the sample of comparative example 1 underwent 30 swellings at 100 m, the sample 1 has not undergone absolutely no swellings. Thus, it is clear that the formation of swellings on twisted oxide superconducting wire can be suppressed, and the critical current density can be improved in accordance with the proposed in the present invention a method of manufacture.

Proposed in the present invention, the manufacturing method is also applicable, for example, to the method of manufacturing round of the oxide superconducting wire.

Fig is a partial detail view in perspective, conceptually showing the structure of all of the oxide superconducting wire. As shown in Fig, all of the oxide superconducting wire 1b has many fibers 2b oxide superconductor extending in the longitudinal direction, and covering their shell 3b. The oxide superconducting wire 1b is a cross-sectional shape close to a perfect circle.

All of the oxide superconducting wire 1b is made without conducting primary rolling (stage S3) and secondary rolling (stage S5) in the method of manufacturing an oxide superconducting wire shown in F. the Data2. The rest of this method of manufacture is essentially the same as the method of manufacturing according to the first variant of implementation, and therefore redundant description is not repeated.

All of the oxide superconducting wire can effectively reduce the loss of AC. When the present invention is applied to a method of manufacturing round of the oxide superconducting wire, in this round of the oxide superconducting wire can be suppressed blistering, and the critical current density can be improved.

The sixth option exercise

Each of the embodiments from the first to the fourth has been described with reference to the manufacturing method in the case when the fibers superconductor extend along the longitudinal direction of the oxide superconducting wire, and the oxide superconducting wire 1 has a ribbon-like shape. The fifth option has been described with reference to the method of manufacture in the case where the oxide superconducting wire is a stranded wire or round wire. Instead of these methods of manufacturing oxide superconducting wires, proposed in the present invention, the manufacturing method is also applicable to the method of manufacturing an oxide superconducting wire having a ceramic coating layer.

Fig is the Oh view in section, conceptually showing the structure of an oxide superconducting wire having a ceramic coating layer. As shown in Fig, the oxide superconducting wire 1C, having a ceramic coating layer, has a lot of fibers 2c oxide superconductor extending in the longitudinal direction (the direction perpendicular to the plane of the figure), and a ceramic coating layer 21 covers a multitude of fibers 2C oxide superconductor, and the shell 3 covers the ceramic coating layer 21. Ceramic coating layer 21 is, for example, of a metal oxide and becomes networkprovider at the operating temperature of the oxide superconducting wire 1C. The following describes a method of manufacturing an oxide superconducting wire 1C, having a ceramic coating layer 21.

First, the powder source material molded to form the rod 25 from the powder source material, as shown in Fig. Then ring the periphery of the rod 25 cover compacted ceramic powder using an extruder or the like for forming coated with ceramic rod 22 having a ceramic coating layer 22 covering the rod 25, as shown in Fig. Then the lot covered by ceramic rods 22 are tightly inserted into the casing 3, as shown in Fig. Thus, the receive wire megavol the horse patterns, having a large number of fibers from a powder source material. Then this wire multi-fiber structure is subjected to wire drawing to the formation of the multi-fiber wire sealed in a silver sheath 3C of the source material. So, get a wire formed by covering a metal coated with ceramic rods obtained powder coating source material ceramics. Then spend the stages S3-S6 shown in figure 2, to complete the fabrication of the oxide superconducting wire 1C according to this variant implementation, shown in Fig.

The oxide superconducting wire having a ceramic coating layer, can effectively reduce the loss of AC. When the present invention is applied to a method of manufacturing an oxide superconducting wire having a ceramic coating layer, this oxide superconducting wire with a ceramic coating layer can be suppressed blistering, and the critical current density can be improved.

To confirm the above effect, the authors of the present invention obtained oxide superconducting wire having a ceramic coating layer, by using the manufacturing method according to this variant implementation and measured the critical current density. In is the result, the critical current density was improved by 1.4 times compared with the case of conducting both heat treatments in the atmosphere.

The seventh option exercise

If the oxide superconducting wire is used in the magnets or the like, then use body obtained by winding the oxide superconducting wire in the form of coils tightly wound coils, as shown in Fig. The oxide superconducting wire can be formed into a coil with a winding technology and response.

Fig is a diagram showing a stage of manufacturing the oxide superconducting wire according to a seventh variant of implementation of the present invention. As shown in Fig, winding technology and response is a method of forming the wire into a coil (stage S5a) immediately after the second rolling (stage S5), and after the second heat treatment (stage S6).

Wire, not yet subjected to the second heat treatment (stage S6), has a greater bending strength than that of the oxide superconducting wire, past the second heat treatment (stage S6). The load on the bending was applied to the wire at the stage of forming the wire into a coil, so the coil of the oxide superconducting wire obtained by using the techniques of coiling and response, best way had less deterioration in the value of Crete is as current as compared with the coil, molded after the completion of manufacturing an oxide superconducting wire. Deterioration in the value of the critical current can be effectively suppressed by the use of technologies winding and response, in particular, when receiving coil of the oxide superconducting wire having a diameter of not more than 100 mm.

On the other hand, the winding technology and response has the disadvantage that the finished coil of the oxide superconducting wire can not be used if the wire has acquired swellings during the second heat treatment (stage S6). Therefore, the winding technology and response is not often used in practice for the manufacture of coils of the oxide superconducting wire.

However, when proposed in the present invention a method of heat treatment applied during the second heat treatment (stage S6), the coil of the oxide superconducting wire can be obtained using the techniques of coiling and response, with simultaneous suppression of swellings in the wire. Thus, deterioration in the value of the critical current can be effectively suppressed in the case of forming the wire into a coil. The rest of this method of manufacturing an oxide superconducting wire is identical to the method of manufacturing an oxide superconducting wire according to the first variant implementation, shown in figure 2, and so the WMD redundant description is not repeated.

The eighth option exercise

The first version of the implementation has been described with reference to the case of smooth increase of pressure in the atmosphere, starting from atmospheric pressure, in accordance with the equation of state of gas before pressure increase during heat treatment (figure 11), as shown in figure 11. However, the authors of the present invention found that the number of bumps formed on the wire, can be further reduced by keeping the wire in an atmosphere of reduced pressure before increasing the pressure during the heat treatment (figure 11). The reason for this is described later.

As described in the first embodiment, in the atmosphere, the gas penetrates into the wire through the surface pores, when the pressure in the atmosphere exceeds the pressure in the wire. Therefore, before you start increasing the pressure during the heat treatment, the wire is kept in the atmosphere of reduced pressure so that the pressure in the atmosphere does not exceed the pressure in the wire. Thus, the gas practically does not penetrate into the wire also in a state before starting the pressure increase during heat treatment, and blistering of the wire can be further suppressed.

The authors of the present invention have examined the effect of keeping the wire in an atmosphere of reduced pressure before the avicenia pressure during heat treatment. More specifically, they received an oxide superconducting wire, by setting the pressure level respectively about 0.1 MPa (atmospheric pressure) and 10 PA before increasing the pressure during the heat treatment. These oxide superconducting wire was immersed in a container of liquid nitrogen under a pressure of 1 MPa, and left for 24 hours. Then determine the number of bumps formed on the respective oxide superconducting wires. As a result, the oxide superconducting wire obtained by setting the pressure of about 0.1 MPa (atmospheric pressure) before pressure increase during heat treatment, education has undergone one puff at 1000 m on the other hand, the oxide superconducting wire obtained when setting a pressure of about 10 PA before increasing the pressure during the heat treatment, demonstrated an absolute lack of swellings. Thus, it is clear that the swelling of the oxide superconducting wire can be further suppressed by keeping the wire in an atmosphere of reduced pressure before increasing the pressure during the heat treatment.

This option has been described as a method of manufacturing an oxide superconducting wire with reference to the case of keeping the wire in an atmosphere of reduced pressure before p is increasing pressure during the heat treatment. Instead of this case, however, the present invention is also applicable as a stage heat treatment is carried out on already made an oxide superconducting wire, i.e. as a method of modifying an oxide superconducting wire. Also in the case when proposed in the present invention the heat treatment is applied as a method of modifying an oxide superconducting wire can be enhanced critical current density of the oxide superconducting wire.

Disclosed above are embodiments of should be considered in all respects as illustrative and not restrictive. Scope of the present invention is defined not by the above-mentioned variants of the implementation and the framework of the patent claims set forth in the claims, and it is covering all the refinements and modifications within the entity and the amount equivalent to the framework of the patent claims set forth in the following claims.

1. A method of manufacturing an oxide superconducting wire, comprising a stage (S1, S2) to obtain a wire formed by covering the powder source material of an oxide superconductor with a metal, and the stage (S4, S6) heat treatment, which consists in heat treating the said wire in an atmosphere of high pressure with bsim pressure of at least 1 MPa and less than 50 MPa during heat treatment, while heat before heat treatment at the above-mentioned stage (S4, S6) heat treatment, the pressure increase start with temperature, a reduction of 0.2%conventional yield stress of the above-mentioned metal (3) the below mentioned General pressure in the above-mentioned heat treatment.

2. A method of manufacturing an oxide superconducting wire according to claim 1, in which the speed of the above-mentioned pressure increase is at least 0.05 MPa/min.

3. A method of manufacturing an oxide superconducting wire according to claim 2, in which the speed of the said increase of pressure is at least 0.1 MPa/min

4. A method of manufacturing an oxide superconducting wire according to claim 1, in which the mentioned stage (S4, S6) of the heat treatment performed in an oxygen atmosphere with a partial pressure of oxygen of at least of 0.003 MPa and not more than 0.02 MPa.

5. A method of manufacturing an oxide superconducting wire according to claim 1 in which the said powder source material mentioned oxide superconductor includes a Bi2223 phase, and at the said stage (S4, S6) of the heat treatment mentioned wire is annealed in an oxygen-containing atmosphere with a temperature of at least 300°and not more than 600°C.

6. A method of manufacturing an oxide superconducting wire according to claim 1, further comprising a stage (S2a) curl mentioned wire ZAR is mentioned it to the stage (S4, S6) heat treatment.

7. A method of manufacturing an oxide superconducting wire according to claim 1 in which the said wire is rolled.

8. A method of manufacturing an oxide superconducting wire according to claim 1, in which the above mentioned stages (S1, S2) to obtain the above-mentioned wire receive a wire formed by covering the said metal (3C) is covered with a ceramic rod (22), obtained by coating the above-mentioned powder (25) source material ceramics (21).

9. A method of manufacturing an oxide superconducting wire according to claim 1, further comprising a stage (S5a) forming the said wire into a coil before mentioned stage (S4, S6) heat treatment.

10. A method of manufacturing an oxide superconducting wire according to claim 1, in which before starting the above-mentioned pressure increase on said stage (S4, S6) of the heat treatment, the wire is kept in the atmosphere of reduced pressure.

11. A method of manufacturing an oxide superconducting wire, comprising

stage (S1, S2) to obtain a wire formed by covering the powder source material of oxide superconductor containing silver metal, and the stage (S4, S6) heat treatment, which consists in heat treating the said wire in an atmosphere of high pressure with the total pressure of at least 1 MPa and less than 50 MPa is during the heat treatment, while heat before heat treatment at the above-mentioned stage (S4, S6) heat treatment, the pressure increase start after the mentioned temperature of the atmosphere exceeds 400°C.

12. A method of manufacturing an oxide superconducting wire according to claim 11, in which during heating before heat treatment at the above-mentioned stage (S4, S6) heat-treating the above-mentioned pressure increase start after the mentioned temperature of the atmosphere exceeds 600°C.

13. Method of modifying an oxide superconducting wire, comprising a stage (S4, S6) heat treatment, which consists in heat treating the oxide superconducting wire (1)formed by coating an oxide superconductor (2) metal (3), in the atmosphere of high pressure with the total pressure of at least 1 MPa and less than 50 MPa during the heat treatment, while during heating before heat treatment at the above-mentioned stage (S4, S6) heat treatment, the pressure increase start with temperature, a reduction of 0.2%conventional yield stress of the above-mentioned metal below mentioned General pressure in the above-mentioned heat treatment.

14. Method of modifying an oxide superconducting wire according to item 13, in which the speed of the above-mentioned pressure increase is at least 0.05 MPa/min.

15. The method of inoculation oxide surprosed the total wire 14, in which the speed of the said increase of pressure is at least 0.1 MPa/min

16. Method of modifying an oxide superconducting wire according to item 13, in which the mentioned stage (S4, S6) of the heat treatment performed in an oxygen atmosphere with a partial pressure of oxygen of at least of 0.003 MPa and not more than 0.02 MPa.

17. Method of modifying an oxide superconducting wire according to item 13, in which the mentioned oxide superconducting wire (1) includes the Bi2223 phase and at the said stage heat treatment (S4, S6) of the said oxide superconducting wire (1) annealed in oxygen-containing atmosphere at a temperature of at least 300°and not more than 600°C.

18. Method of modifying an oxide superconducting wire according to item 13, in which before starting the above-mentioned pressure increase in the above-mentioned stage (S4, S6) of the heat treatment mentioned oxide superconducting wire (1) stand in an atmosphere of reduced pressure.

19. Method of modifying an oxide superconducting wire, comprising a stage (S4, S6) heat treatment, which consists in heat treating the wire formed by coating an oxide superconducting wire (2) containing silver metal (3), in the atmosphere of high pressure with the total pressure of at least 1 MPa and less than 50 MPa during thermobreak is, while heat before heat treatment at the above-mentioned stage (S4, S6) heat treatment, the pressure increase start after the mentioned temperature of the atmosphere exceeds 400°C.

20. Method of modifying an oxide superconducting wire according to claim 19, in which during heating before mentioned heat treatment at the above-mentioned stage (S4, S6) heat-treating the above-mentioned pressure increase start after the mentioned temperature of the atmosphere exceeds 600°C.

21. The oxide superconducting wire (1), contains many of oxide superconductors (2)extending in the longitudinal direction, and a shell (3)covering mentioned many of oxide superconductors (2), each of these sets of oxide superconductors (2) has a density after sintering at least 95%.

22. The oxide superconducting wire (1) according to item 21, in which each of the said sets of oxide superconductors (2) has referred to the density after sintering at least 99%.



 

Same patents:

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13 cl, 5 dwg, 1 tbl

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6 cl, 27 dwg, 4 tbl, 6 ex

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2 cl, 1 dwg

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3 cl 1 tbl

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Daubing material // 2316520

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2 tbl, 1 ex

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4 ex

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6 cl

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21 cl, 2 ex, 6 dwg

FIELD: chemical technology, materials technology.

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1 ex

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6 cl, 4 ex, 3 dwg

FIELD: chemical industry; other industries; production of the superfine-grained diamond sintered articles of the high purity and high hardness.

SUBSTANCE: the invention is pertaining to the production of the superfine-grained diamond sintered articles of the high purity and high hardness, which is intended for usage in the capacity of the wear-resistant material capable to let the light go through it, and may be used in production of jewels. The article has the size of the grain equal to 100 nanometers or less. For its manufacture the superfine-grained natural diamond powder having the granulometric spread of values from null up to 0.1 microns is subjected to desiliconization, to sublimation drying in the solution, inclusion into the tantalum or molybdenum capsule without the sintering additive, heating and application of the excessive pressure to the capsule using the device for the synthesis at the super-high pressure at the temperature of 1700°С or more and under pressure of 8.5 GPa or more, which meet the conditions of the thermodynamic stability of the diamond. The technical result of the invention is realization of the synthesis of the diamond sintered article at the more low pressure, than in the standard method and without usage of any sintering additive. The article has hardness according to Vickers - 80 GPa and more and is excellent concerning resistance to the tear and wear and the thermal resistance.

EFFECT: the invention ensures realization of the synthesis of the diamond sintered article at the more low pressure, than in the standard method, and without usage of any sintering additive, ensures its hardness of 80 GPa and more according to Vickers and the excellent properties concerning resistance to the tear and wear and the thermal resistance.

4 cl, 5 ex, 3 dwg

FIELD: ceramics, building industry and materials.

SUBSTANCE: invention relates to compositions of ceramic masses used in manufacturing brick. Proposed ceramic mass comprises the following components, wt.-%: refractory clay, 30-40; quartzites, 50.0-65.0; lime, 4.8-9.8, and sulfite-alcoholic distillery grains, 0.1-0.2. Invention provides enhancing strength of brick.

EFFECT: improved and valuable property of brick.

1 tbl

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.

2 ex

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