JP2007335100A - Manufacturing method of oxide superconducting wire and superconducting equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an oxide superconducting wire for improved superconducting characteristics. <P>SOLUTION: The manufacturing method of a metal-coated oxide superconducting wire includes a process in which material powder is packed in a metal pipe, a process in which the packed metal pipe is plastic-processed to form a metal-coated precursor wire, a process in which the metal-coated precursor wire is thermally processed to form (Bi, Pb)2223 superconducting phase, and a process for annealing in the atmosphere containing oxygen after the thermal process. During the annealing process, the partial pressure of oxygen is reduced by 1 kPa or more. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention is used for superconducting equipment such as superconducting cables, superconducting coils, superconducting transformers, superconducting power storage devices, etc. (Bi, Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O _{10 ± δ} (δ is a number of about 0.1) The following description relates to a method for manufacturing an oxide superconducting wire containing a phase (hereinafter referred to as (Bi, Pb) 2223), and more specifically, a method for manufacturing an oxide superconducting wire for the purpose of improving the critical current value of (Bi, Pb) 2223 superconducting wire It relates to superconducting equipment.

  An oxide superconducting wire mainly composed of (Bi, Pb) 2223 phase produced by a metal sheath method has a high critical temperature and a high critical current value even under relatively simple cooling such as liquid nitrogen temperature. It is a useful wire (for example, refer nonpatent literature 1). However, if further improvement in performance (critical current value) is realized, the range of practical use will expand.

In addition, it is considered that by using the (Bi, Pb) 2223 superconducting wire, it is possible to reduce energy loss far more than when using a conventional normal conductor. Therefore, development of superconducting application equipment such as a superconducting cable, a superconducting coil, a superconducting transformer, a superconducting power storage device using a (Bi, Pb) 2223 superconducting material wire as a conductor is being promoted at the same time.

  As a method for increasing the critical current value of a superconducting wire, a method of sintering a (Bi, Pb) 2223 series superconducting wire in a pressurized atmosphere is employed (see Patent Document 1 and Non-Patent Document 1). . As a result, the critical current value at the liquid nitrogen temperature is improved from about 100 A to 120 A class.

JP 2002-093252 A SEI Technical Review, March 2004, No. 164, p36-42

  The effect of improving the critical current value is also recognized by the above technique. However, considering the needs from the future market, further increase of the critical current value is desired. Therefore, an object of the present invention is to provide a method for producing an oxide superconducting wire having a higher critical current value.

  The present inventors have found that the critical current value is improved by examining the heat treatment step of the (Bi, Pb) 2223 wire, adding an annealing step thereto, and giving the annealing conditions characteristics.

  The present invention includes a step of filling a metal pipe with raw material powder, a step of plastically processing the metal pipe after filling to form a metal-coated precursor wire, and heat-treating the metal-coated precursor wire (Bi, Pb) 2223. A method for producing a metal-coated oxide superconducting wire comprising a step of forming a superconducting phase and a step of annealing in an atmosphere containing oxygen after the heat treatment, wherein the oxygen partial pressure is reduced by 1 kPa or more during the annealing step. It is the manufacturing method of the oxide superconducting wire characterized.

  In the present invention, it is preferable to lower the temperature of the atmosphere by 10 ° C. or more during the annealing step.

  In this invention, it is preferable that the said annealing process is performed under the pressure whose total pressure of atmosphere is 1 Mpa or more.

  In the present invention, it is preferable to reduce the oxygen partial pressure by 1 kPa or more during the annealing step so that the oxygen partial pressure is 5 kPa or more and less than 5 kPa.

  Furthermore, in the present invention, it is preferable to reduce the oxygen partial pressure during the annealing step so that the oxygen partial pressure becomes 5 kPa or more and 3 kPa or less.

  Moreover, this invention is a superconducting apparatus which contains the oxide superconducting wire manufactured by the manufacturing method in any one of said as a conductor.

According to the production method of the present invention, a (Bi, Pb) 2223 oxide superconducting wire having a high critical current value can be obtained. Moreover, by using the oxide superconducting wire of the present invention as a conductor, it is possible to realize superconducting equipment such as a high-performance superconducting cable, a superconducting coil, a superconducting transformer, and a superconducting power storage device.

(Embodiment)
FIG. 1 is a partial cross-sectional perspective view schematically showing the configuration of an oxide superconducting wire. For example, a multi-core oxide superconducting wire will be described with reference to FIG. The oxide superconducting wire 11 has a plurality of oxide superconductor filaments 12 extending in the longitudinal direction and a sheath portion 13 covering them. The material of each of the plurality of oxide superconductor filaments 12 is preferably a Bi—Pb—Sr—Ca—Cu—O based composition, and in particular, the atomic ratio of (Bi, Pb): Sr: Ca: Cu is approximately 2. The material including the (Bi, Pb) 2223 phase expressed by the ratio of 2: 2: 3 is optimal. The material of the sheath part 13 is comprised from metals, such as silver and a silver alloy, for example.

  Next, the manufacturing method of said oxide superconducting wire is demonstrated.

  FIG. 2 is a flowchart showing a manufacturing process of the oxide superconducting wire in the embodiment of the present invention. 3 to 7 are diagrams showing each step of FIG.

Referring to FIGS. 2 and 3, first, oxide superconductor precursor powder 31 is filled into metal tube 32 (step S1). This oxide superconductor precursor powder 31 is, for example, a (Bi, Pb) ₂ Sr ₂ Ca ₁ Cu ₂ O _{8 ± δ} (δ is a number close to 0.1: hereinafter referred to as (Bi, Pb) 2212) phase. (Bi, Pb) 2223 phase, alkaline earth oxides (for example, (Ca, Sr) CuO ₂ , (Ca, Sr) ₂ CuO ₃ , (Ca, Sr) ₁₄ Cu ₂₄ O ₄₁ etc.) , And a Pb oxide (for example, Ca ₂ PbO ₄ , (Bi, Pb) ₃ Sr ₂ Ca ₂ Cu ₁ O _z ). The metal tube 32 is preferably made of silver or a silver alloy. This is to prevent compositional deviation of the precursor powder due to the reaction between the precursor powder and the metal tube to form a compound.

  Next, as shown in FIG. 2 and FIG. 4, the metal tube 41 filled with the precursor powder is drawn to a desired diameter, and the precursor 42 is used as a core material and coated with a metal such as silver. The core wire 43 is produced (step S2).

  Next, as shown in FIGS. 2 and 5, a large number of single core wires 51 are bundled and fitted into a metal tube 52 made of, for example, silver (multi-core fitting: step S3). Thereby, the multi-core structure material which has many precursor powders as a core material is obtained.

  Next, as shown in FIGS. 2 and 6, the multi-core structural member 61 is drawn to a desired diameter, the precursor powder 62 is embedded in the metal sheath portion 63, and the cross-sectional shape is circular or polygonal. An isotropic multi-core bus 64 is produced (step S4). Thereby, an isotropic multi-core bus 64 having a form in which the precursor powder 62 of the oxide superconducting wire is covered with a metal is obtained.

  Next, as shown in FIGS. 2 and 7, the isotropic multi-core bus bar 71 is rolled (primary rolling: step S5). Thereby, the tape-shaped precursor wire 72 is obtained.

  Next, the tape-shaped precursor wire is heat-treated (primary heat treatment: step S6). This heat treatment is performed at a temperature of about 830 ° C., for example, under atmospheric pressure or in a pressurized atmosphere of 1 MPa to 50 MPa. The target (Bi, Pb) 2223 superconducting phase is generated from the precursor powder by heat treatment.

  Thereafter, the wire is rolled again (secondary rolling: step S7). In this way, voids generated by the primary heat treatment are removed by performing the secondary rolling.

  Subsequently, for example, the wire is heat-treated at a temperature of 830 ° C. (secondary heat treatment: step S8). Also at this time, heat treatment is performed under atmospheric pressure or in a pressurized atmosphere. The oxide superconducting wire shown in FIG. 1 is obtained by the above manufacturing process.

  The oxide superconducting wire which does not perform an annealing process is obtained by the above manufacturing process. The oxide superconducting wire obtained at this stage also has a critical current value of 120 A class, but a higher critical current value is desired.

  Therefore, in this embodiment, an annealing step (step S9) is further performed on the oxide superconducting wire obtained above.

  The annealing process performed by the inventors of the present application reduces the oxygen partial pressure by 1 kPa or more during the process. As a result, it was found that a superconducting wire having a high critical current value can be obtained. Below, the aspect and effect of this annealing process are demonstrated.

  Heat treatment in ceramic materials such as oxide superconductors can be broadly classified into three. The first is heat treatment that promotes a large phase change. For example, in the (Bi, Pb) 2223 wire, the (Bi, Pb) 2212 phase that is the precursor is transformed into the target (Bi, Pb) 2223 phase, which is formed before and after the heat treatment. The chemical composition of the compound is greatly changed. In the manufacturing process of (Bi, Pb) 2223 wire, primary heat treatment (step S6) corresponds to this.

  The second is a heat treatment generally referred to as “sintering”, which is performed for the purpose of firmly bonding the particles of the compound, although the chemical composition of the existing compound itself does not change. This heat treatment greatly changes from an isolated grain state in which electrical and mechanical bonds are disjoint and thin to a structure in which they are integrally bonded. In the manufacturing process of the (Bi, Pb) 2223 wire, secondary heat treatment (step S8) corresponds to this.

The “annealing” or “annealing” of the present invention, unlike the above two, has little change in macro viewpoint and promotes micro change. Therefore, in terms of temperature, the heat treatment is performed at such a low temperature that the two heat treatments do not occur. In the case of the (Bi, Pb) 2223 phase, the oxygen content δ or the Pb content of (Bi, Pb) ₂ Sr ₂ Ca ₂ Cu ₃ O _{10 ± δ} can be changed by annealing. As a result, the amount of carriers such as electrons and holes responsible for electrical conduction in the (Bi, Pb) 2223 phase increases and decreases, and the superconducting characteristics change.

  In addition to the increase / decrease in the amount of cations such as Pb and the amount of oxygen as anions in the superconducting phase as described above, there is an effect of inducing uniform dispersion of these ion components. There is also an effect of relaxing the strain introduced in the cooling process of the immediately preceding heat treatment. By increasing the uniformity of these ionic components and relaxing the strain, scattering of carriers responsible for electrical conduction is suppressed, the conductivity is improved, and the critical current value is improved.

The present invention mainly focuses on changing the Pb content of the (Bi, Pb) 2223 phase among the above-described annealing actions. At a temperature of about 800 ° C., the Pb element contained in the ceramic material such as the (Bi, Pb) 2223 phase tends to exist as Pb ⁴⁺ ions on the high oxygen partial pressure side. On the other hand, it tends to exist as Pb ²⁺ ions on the low oxygen partial pressure side.

In the (Bi, Pb) 2223 phase, it is considered that the Pb element is present in a Pb ²⁺ ion state in a large proportion. Therefore, on the high oxygen partial pressure side where the Pb ⁴⁺ ion state is stable, the solid solubility of the Pb element in the (Bi, Pb) 2223 phase becomes low, and the Pb element is discharged from the (Bi, Pb) 2223 phase, and Ca ₂ PbO ₄ , (Bi, Pb) ₃ Sr ₂ Ca ₂ Cu ₁ O _z , such as a compound in which Pb is tetravalent (hereinafter referred to as Pb tetravalent compound) is likely to precipitate.

  These Pb tetravalent compounds precipitated on the high oxygen partial pressure side decompose, for example, by lowering only the oxygen partial pressure by exposing them to a constant temperature, and the Pb element in the (Bi, Pb) 2223 phase is decomposed. The solid solubility increases, and a phenomenon occurs in which the Pb element is taken into the (Bi, Pb) 2223 phase. The present inventors have found that this phenomenon leads to an improvement in the critical current value.

  In other words, in a certain high oxygen partial pressure state, the Pb element is once present as a Pb tetravalent compound, and from that state, the oxygen partial pressure is lowered, the Pb tetravalent compound is decomposed and the Pb element is taken into the (Bi, Pb) 2223 phase. It is an operation. At this time, if the change in oxygen partial pressure is less than 1 kPa, the amount of decomposition of the Pb tetravalent compound and the change in solid solubility of the Pb element in the (Bi, Pb) 2223 phase are not sufficient, so the change in critical current value is also small.

  Here, the annealing process will be described. FIG. 8 is a diagram schematically showing temperature and oxygen partial pressure profiles in several annealing processes. Both the points A and B in the temperature pattern are room temperature. The (Bi, Pb) 2223 phase undergoes chemical reactions such as the entry and exit of oxygen and the entry and exit of Pb elements at a temperature of 300 ° C. or higher. However, the temperature increasing process from room temperature to 300 ° C. and the temperature decreasing process from 300 ° C. to room temperature are inevitable additional elements in actual processes. Therefore, reducing the oxygen partial pressure by 1 kPa or more during the annealing step in the present invention is performed in a region of 300 ° C. or more. That is, the change in oxygen partial pressure in a state of 300 ° C. or higher is targeted.

  In addition, as shown in FIG. 8, various patterns such as isothermal (pattern 1), constant speed change (pattern 2), step change (pattern 3) can be adopted as the temperature change pattern. Similarly, the oxygen partial pressure change can also be a constant rate pressure reduction (pattern A), stepped pressure reduction (pattern B), etc., and the temperature and oxygen partial pressure change pattern can be appropriately selected by a combination thereof.

In the present invention, it is also preferable to lower the ambient temperature by 10 ° C. or more during the annealing step. This is because the stability of the Pb tetravalent compound also depends on the temperature. In the region where the (Bi, Pb) 2223 phase does not melt, the Pb tetravalent compound tends to exist stably on the high temperature side. On the other hand, it is unstable on the low temperature side. Therefore, in order to promote the decomposition of the Pb tetravalent compound, it is preferable to decrease the temperature as the oxygen partial pressure decreases. In that case, it is more effective if there is a temperature drop of 10 ° C. or more.

  It has also been found effective to perform annealing while applying a total pressure of 1 MPa or more. During the annealing process, the bonding between (Bi, Pb) 2223 phase grains may be loosened due to the entry and exit of gas components, the relaxation of strain, and the precipitation of minute components. By performing the annealing while applying pressure, the (Bi, Pb) 2223 intergranular bond can be maintained in the state before annealing. Thereby, the bond between grains is maintained, the effect introduced by annealing is added as it is, and there is a larger improvement in critical current value.

It is more effective to reduce the oxygen partial pressure by 1 kPa or more so that the oxygen partial pressure is 5 kPa or more and less than 5 kPa. In the temperature range applied to annealing, the inventors have defined a Ca ₂ PbO ₄ phase and (Bi, Pb) ₃ Sr ₂ Ca ₂ Cu ₁ O _z phase defined as the same Pb tetravalent compound at an oxygen partial pressure of around 5 kPa. It was found that there was a phase transition between. It is more effective to incorporate the Pb element into the (Bi, Pb) 2223 phase across the phase transition boundary.

  Furthermore, it has also been found that when the oxygen partial pressure is decreased so that the oxygen partial pressure is 5 kPa or more and 3 kPa or less, the amount of Pb absorbed is increased and a remarkable effect is obtained.

In addition, the inventors have performed the annealing process after the (Bi, Pb) 2223 superconducting phase contained in the wire is maximized in the heat treatment process for forming the (Bi, Pb) 2223 superconducting phase. Has also been found to be preferable.

  As described above, the (Bi, Pb) 2223 wire is subjected to heat treatment to transform the precursor (Bi, Pb) 2212 phase into the desired (Bi, Pb) 2223 phase. This heat treatment is performed at a temperature of about 840 ° C. for about 30 to 100 hours so that the ratio of the (Bi, Pb) 2223 superconducting phase in the wire is maximized. If the heat treatment time is too short, the transformation does not proceed sufficiently to the (Bi, Pb) 2223 phase, and the process stops with a small proportion of the (Bi, Pb) 2223 superconducting phase. On the other hand, if the heat treatment time is too long, the completed (Bi, Pb) 2223 superconducting phase is decomposed, and the existing ratio of the (Bi, Pb) 2223 superconducting phase is reduced.

  Further, as described above, since annealing is usually set at a temperature at which phase transformation and grain bonding do not occur, phase transformation to the (Bi, Pb) 2223 superconducting phase and grain bonding reaction are not completed by annealing alone. . Therefore, it is preferable that phase transformation and grain bonding are completed before annealing.

  Moreover, since the superconducting device according to the present invention is composed of the superconducting wire having a high critical current value as described above, it has excellent superconducting characteristics. Here, the superconducting device is not particularly limited as long as it includes the superconducting wire, and examples thereof include a superconducting cable, a superconducting coil, a superconducting transformer, and a superconducting power storage device.

Example 1
Hereinafter, based on an Example, this invention is demonstrated further more concretely.

Raw material powder (Bi ₂ O ₃ , PbO, SrCO ₃ , CaCO ₃ , CuO) is Bi: Pb: Sr: Ca: Cu = 1.8: 0.3: 1.9: 2.0: 3.0 And are subjected to heat treatment at 700 ° C. for 8 hours, pulverization, heat treatment at 800 ° C. for 10 hours, pulverization, heat treatment at 840 ° C. for 4 hours, and pulverization in the air to obtain a precursor powder. In addition, by injecting a nitric acid aqueous solution in which five types of raw material powders are dissolved into a heated furnace, the water content of the metal nitrate aqueous solution particles evaporates, the thermal decomposition of the nitrate, and the reaction and synthesis of metal oxides. Precursor powder can also be produced by a spray pyrolysis method that instantly raises. The precursor powder thus produced is a powder mainly composed of the (Bi, Pb) 2212 phase.

  The precursor powder produced as described above is filled into a silver pipe having an outer diameter of 25 mm and an inner diameter of 22 mm, and drawn to a diameter of 2.4 mm to produce a single core wire. The single core wires are bundled into 55, inserted into a silver pipe having an outer diameter of 25 mm and an inner diameter of 22 mm, and drawn to a diameter of 1.5 mm to obtain a multi-core (55 core) wire. This multi-core wire is rolled and processed into a tape-like wire having a thickness of 0.25 mm. The obtained tape-shaped wire is subjected to primary heat treatment at 840 ° C. for 30 to 50 hours in an atmosphere having a total pressure of 1 atm (0.1 MPa) and an oxygen partial pressure of 8 kPa.

  The tape-shaped wire after the primary heat treatment is re-rolled to a thickness of 0.23 mm. The tape-shaped wire after re-rolling is subjected to a secondary heat treatment at 830 ° C. for 50 to 100 hours in a pressurized atmosphere containing an oxygen partial pressure of 8 kPa and a total pressure of 30 MPa. Some finished the process in this state and measured the critical current value (Ic). Some of them were then subjected to an annealing process under various conditions of temperature, total pressure, and oxygen partial pressure, and the characteristics were evaluated. The annealing conditions and evaluation results are shown in Table 1.

For the critical current value, a current-voltage curve was measured by a four-terminal method at a temperature of 77 K and in a zero magnetic field, and a current that generates a voltage of 1 × 10 ⁻⁶ V per 1 cm of wire was defined as the critical current value.

  The annealing start temperature in Table 1 is the highest temperature reached from room temperature. Thereafter, the temperature is maintained or controlled and the temperature is lowered. The annealing starting oxygen partial pressure is the oxygen partial pressure at the annealing starting temperature. The annealing end temperature is the final temperature lowered while being controlled. After that, naturally cool. The annealing end oxygen partial pressure is the oxygen partial pressure at the time of annealing end temperature.

  The annealing pattern applied to the samples in Table 1 was set so that the start point shown in FIG. 8 corresponds to the start of annealing shown in Table 1 and the end point in FIG. 8 corresponds to the end of annealing in Table 1. These samples were subjected to an annealing process by a combination of isothermal or constant speed temperature change and constant speed depressurization.

Sample No. 1 (Comparative Example) is not subjected to the pressure annealing of the present invention because the process is completed by the secondary heat treatment. Sample No. 2 (Comparative Example) has a change in oxygen partial pressure of 0.5 kPa. Sample No. 1 that has not been annealed has a critical current value of 120A. In Sample No. 2 (Comparative Example) in which the change in oxygen partial pressure was small, no improvement in the critical current value was observed. On the other hand, in Sample Nos. 3 to 8 in which the change in oxygen partial pressure was set to 1 kPa or more according to the present invention, the critical current value was improved.

Comparing sample number 3 without temperature change during the annealing process with sample number 4 subjected to annealing with temperature change, it can be seen that the annealing process with temperature change has a great effect. Moreover, when comparing sample numbers 4, 5, and 6, it can be seen that the higher the total pressure in the annealing atmosphere, the higher the critical current value. Further, from the comparison of Sample Nos. 6 and 7, the annealing process in which the oxygen partial pressure is changed so as to cross 5 kPa is more effective even when the pressure is reduced by the same oxygen partial pressure of 1 kPa. From Sample No. 8, it can be seen that the step of reducing the oxygen partial pressure from 5 kPa to 3 kPa is more preferable.

(Example 2)
In Example 1, an annealing process accompanied by a larger oxygen partial pressure change and a larger annealing temperature change was performed on the wire subjected to the secondary heat treatment. At this time, the total pressure was fixed at 30 MPa, the annealing time was fixed at 200 hours, and both temperature and oxygen partial pressure were changed at a constant rate. The critical current values of these samples were measured in the same manner as in Example 1.

  The annealing conditions shown in Table 2 are shown in FIG. In FIG. 9, the horizontal axis represents oxygen partial pressure, and the vertical axis represents temperature. The annealing start in Table 2 is the high oxygen partial pressure and the high temperature side annealing starting point in FIG. 9, and the annealing end is the annealing end point in FIG. In this example, the critical current value is significantly increased in any sample, and a critical current value of 150 A or more is obtained.

  From these results, the relationships between (oxygen partial pressure (kPa) and heat treatment temperature (° C.)) in FIG. 9 are (0.5, 680), (0.5, 790), (7, 810), (7, 780). ) In the range surrounded by four points, it can be seen that the annealing conditions in which the oxygen partial pressure and temperature shift from the high oxygen partial pressure and high temperature side to the low oxygen partial pressure and low temperature side are effective.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a partial section perspective view showing typically the composition of an oxide superconducting wire. It is a flowchart which shows the manufacturing process of the oxide superconducting wire in embodiment of this invention. It is a figure which shows S1 step in FIG. It is a figure which shows S2 step in FIG. It is a figure which shows S3 step in FIG. It is a figure which shows S4 step in FIG. It is a figure which shows S5 step in FIG. It is the figure which represented the annealing process heat treatment pattern typically. It is a figure which shows the annealing conditions of Table 2 in Example 2. FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Oxide superconducting wire, 12 Oxide superconducting filament, 13 Sheath part, 31 Precursor powder, 32 Metal tube 41 Metal tube filled with precursor powder, 42 Precursor, 43 Single core wire, 51 Single core wire, 52 Metal tube 61 multi-core structural material, 62 precursor raw material powder, 63 metal sheath part, 64 isotropic multi-core bus bar, 71 isotropic multi-core bus bar, 72 tape-shaped precursor wire.

Claims (6)

  A step of filling a raw material powder into a metal pipe, a step of forming a metal-coated precursor wire by plastic processing of the metal pipe after filling, and heat-treating the metal-coated precursor wire (Bi, Pb) 2223 to form a superconducting phase A method for producing a metal-coated oxide superconducting wire comprising a step of annealing in an atmosphere containing oxygen after the heat treatment, wherein the oxygen partial pressure is reduced by 1 kPa or more during the annealing step Manufacturing method of superconducting wire.   The method for producing an oxide superconducting wire according to claim 1, wherein the temperature of the atmosphere is lowered by 10 ° C or more during the annealing step.   3. The method for producing an oxide superconducting wire according to claim 1, wherein the annealing step is performed under a pressure of an atmosphere of 1 MPa or more. 4.   The oxide superconducting wire according to any one of claims 1 to 3, wherein the oxygen partial pressure is reduced by 1 kPa or more so that the oxygen partial pressure is 5 kPa or more and less than 5 kPa during the annealing step. Method.   The method for producing an oxide superconducting wire according to any one of claims 1 to 4, wherein the oxygen partial pressure is reduced so that the oxygen partial pressure is 5 kPa or more and 3 kPa or less during the annealing step. A superconducting device comprising, as a conductor, an oxide superconducting wire manufactured by the manufacturing method according to any one of claims 1 to 5.

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