Sintered material, superconducting tape, and reinforcing layer for superconducting tape

Abstract

To provide a sintered material and a reinforcing layer for a superconducting tape having a large Young's modulus and high electrical conductivity, and to provide a superconducting tape having a reinforcing layer having a large Young's modulus and high electrical conductivity.SOLUTION: A sintered material includes tungsten carbide particles and brass particles. For example, the sintered material has a sheet-like form. For example, the ratio m / M of the mass of tungsten carbide (m) to the total mass M of tungsten carbide and brass (M) is 0.088 or more and 0.245 or less. For example, the Young's modulus of the sintered material is 110 GPa or more and 225 GPa or less. For example, the electrical conductivity of the sintered material is 2.1 μ Ω cm or more and 3.0 μ Ω cm or less. For example, the thermal expansion coefficient of the sintered material is 11×10-6 / K or more and 21×10-6 / K or less.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to sintered materials, superconducting tapes, and reinforcing layers for superconducting tapes. [Background technology]

[0002] The superconducting tape includes a superconducting layer, metal layers disposed on both sides of the superconducting layer, and reinforcing layers disposed outside the metal layers. The structure of the superconducting tape is disclosed in Patent Documents 1 and 2. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5040668 [Patent Document 2] Patent No. 5326573 Summary of the Invention [Problem to be solved by the invention]

[0004] In addition to having a large Young's modulus, the reinforcing layer preferably has high electrical conductivity. The reason for this is as follows: To manufacture a long superconducting tape, multiple superconducting tapes must be joined together. Two adjacent superconducting tapes are joined via a reinforcing layer. Therefore, it is preferable that the reinforcing layer have high electrical conductivity.

[0005] Furthermore, if the superconducting layer breaks due to a problem or other reason, a large current will flow into the reinforcing layer. In this case, it is preferable that the reinforcing layer has high electrical conductivity to prevent heat generation in the reinforcing layer. Conventionally, the materials used for the reinforcing layer have been SUS304, Hastelloy C276, etc. Conventional reinforcing layers have low electrical conductivity.

[0006] In one aspect of the present disclosure, it is preferable to provide a sintered material and a reinforcing layer for a superconducting tape having a high Young's modulus and high electrical conductivity, and a superconducting tape having a reinforcing layer having a high Young's modulus and high electrical conductivity. [Means for solving the problem]

[0007] One aspect of the present disclosure is a sintered material including tungsten carbide particles and brass particles. The sintered material of one aspect of the present disclosure has a high Young's modulus and high electrical conductivity. Another aspect of the present disclosure is a superconducting tape including a superconducting layer, metal layers disposed on both sides of the superconducting layer, and reinforcing layers disposed outside the metal layers. The reinforcing layers are layers containing a sintered material that includes tungsten carbide particles and brass particles. The reinforcing layers of the superconducting tape according to another aspect of the present disclosure have a large Young's modulus and high electrical conductivity.

[0008] Another aspect of the present disclosure is a reinforcing layer for a superconducting tape, the reinforcing layer including a sintered material containing tungsten carbide particles and brass particles. The reinforcing layer for a superconducting tape according to another aspect of the present disclosure has a large Young's modulus and high electrical conductivity. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 2 is a cross-sectional side view showing the configuration of a superconducting tape. [Figure 2] 1 is a photograph of a sintered material taken using a scanning electron microscope. [Figure 3] 1 is a graph showing the relationship between stress R and strain A measured for a sintered material. [Figure 4] 1 is a graph showing the relationship between current I and voltage V measured for a sintered material. [Figure 5] 1 is a graph showing thermal distortion of a sintered material measured at various temperatures. [Figure 6] FIG. 10 is a perspective view showing the configuration of a superconducting tape of another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0010] Exemplary embodiments of the present disclosure will be described with reference to the drawings. 1. Composition of sintered material The sintered material contains tungsten carbide particles and brass particles. The average particle size of the tungsten carbide particles is preferably 0.45 μm or more and 0.75 μm or less. The average particle size of the brass particles is preferably 1 μm or more and 15 μm or less. When the average particle sizes of the tungsten carbide particles and the brass particles are within the above ranges, the tungsten carbide particles and the brass particles tend to be uniformly dispersed in the sintered material.

[0011] The sintered material has, for example, a sheet-like form. When the sintered material has a sheet-like form, the sintered material can be used, for example, as a reinforcing layer for a superconducting tape, a lead frame for bonding a semiconductor element, etc.

[0012] The total mass of the tungsten carbide contained in the sintered material and the brass contained in the sintered material is defined as M. The mass of the tungsten carbide contained in the sintered material is defined as m. The ratio of mass m to the total mass M, m / M, is, for example, 0.088 or more and 0.245 or less. m / M is the value obtained by dividing m by M. When m / M is within the above range, the Young's modulus of the sintered material is larger, the electrical conductivity of the sintered material is higher, and the thermal expansion coefficient of the sintered material is smaller.

[0013] The Young's modulus of the sintered material is, for example, 110 GPa or more and 225 GPa or less. The electrical conductivity of the sintered material is, for example, 2.1 μΩcm or more and 3.0 μΩcm or less. The thermal expansion coefficient of the sintered material is, for example, 11×10 -6 / K or more 21×10 -6 / K or less.

[0014] The sintered material can be used, for example, as a reinforcing layer for a superconducting tape, where the reinforcing layer for the superconducting tape comprises particles of tungsten carbide and particles of brass.

[0015] 2. Manufacturing method of sintered material The sintered material can be produced, for example, by the following method. (1) Tungsten carbide powder and brass powder are separately weighed. (2) Next, the tungsten carbide powder and the brass powder are mixed to obtain a mixed powder. For example, a vibrating disk mill is used for mixing. The mixing time is, for example, 10 minutes or more.

[0016] (3) Next, the mixed powder is sintered. For example, a vacuum hot press is used for sintering. Sintering is performed under high temperature and high pressure. For example, sintering can be performed under vacuum. Of the molds used for sintering, the parts that come into contact with the mixed powder are preferably made of a material other than metal. Examples of non-metallic materials include carbon. When the parts of the molds that come into contact with the mixed powder are made of a material other than metal, diffusion bonding between the mold and the sintered material can be suppressed. The sintering temperature is preferably 550°C or higher. The sintering pressure is preferably 4 tons or higher. The sintering time is preferably 30 minutes or longer. The sintered material is obtained through the above process.

[0017] (4) For example, the sintered material can be rolled. For example, the sintered material can be wrapped in a thin copper plate and hot-rolled together with the copper plate. As a result, a sheet-shaped sintered material can be obtained. By wrapping the sintered material in a thin copper plate, it is possible to prevent the sintered material from tearing during rolling. The thickness of the sheet-shaped sintered material is, for example, 150 μm or more and 200 μm or less.

[0018] 3. Superconducting tape 1 1 shows an example of a superconducting tape 1. The superconducting tape 1 includes a superconducting layer 3, a metal layer 5, a reinforcing layer 7, and a solder layer 8. The superconducting layer 3 includes, for example, a bismuth-based superconductor (BSCCO) 9 and silver 11.

[0019] The metal layers 5 are disposed on both sides of the superconducting layer 3 in the thickness direction of the superconducting tape 1. Examples of metals contained in the metal layers 5 include alloys containing silver. The reinforcing layers 7 are disposed outside the metal layers 5 in the thickness direction of the superconducting tape 1. The reinforcing layers 7 are layers containing a sintered material containing tungsten carbide particles and brass particles. The solder layer 8 is provided between the metal layers 5 and the reinforcing layers 7 in the thickness direction of the superconducting tape 1.

[0020] 4. Effects of sintered material and superconducting tape 1 (1A) Sintered materials have a high Young's modulus, high electrical conductivity, and a low coefficient of thermal expansion. (1B) The reinforcing layer 7 of the superconducting tape 1 is a layer containing a sintered material. The reinforcing layer 7 has a large Young's modulus, high electrical conductivity, and a small thermal expansion coefficient.

[0021] 5. Working Example (1) Manufacturing of sintered materials (i) Tungsten carbide powder and brass powder were prepared. The average particle size of the tungsten carbide powder was 0.45 μm. The average particle size of the brass powder was 5 μm. The average particle sizes were measured by observation using a scanning electron microscope.

[0022] (ii) The tungsten carbide powder prepared in (i) above was mixed with brass powder to obtain a mixed powder. In the mixed powder, the volume ratio of the tungsten carbide powder was 10 volume %. In addition, in the mixed powder, the volume ratio of the brass powder was 90 volume %. A vibrating disk mill manufactured by Kawasaki Heavy Industries was used for mixing. The vibration frequency of the vibrating disk mill was 700 rpm. The mixing time was 10 minutes. After mixing for 10 minutes, the tungsten carbide powder and brass powder were uniformly dispersed in the mixed powder.

[0023] (iii) First, the mold used in sintering was manufactured as follows. A through hole with a diameter of 35 mm was drilled in the center of a disk-shaped steel plate with a diameter of 100 mm and a thickness of 30 mm. Next, a circular jig with an outer diameter of 35 mm, an inner diameter of 25 mm, and a length of 30 mm was pressed into the through hole. The jig was made of carbon. Through the above process, the mold was obtained.

[0024] Next, an appropriate amount of the mixed powder prepared in (ii) above was placed inside the annular jig in the mold. The mixed powder was in contact only with the jig, not with the steel plate. Next, the mixed powder was sintered. A vacuum hot press made by Daia Vacuum was used for sintering. Sintering was carried out under high temperature and high pressure. During sintering, a carbon member with a diameter of 25 mm was used as a piston. The sintering temperature was 550°C. The sintering pressure was 4 tons. The sintering time was 30 minutes. A sintered material was obtained through the above process.

[0025] (iv) The sintered material obtained in (iii) above was wrapped in a thin copper plate and hot-rolled together with the copper plate. A small, general-purpose manual rolling mill for experimental use was used for hot-rolling. As a result, a sheet-like sintered material was obtained. The thickness of the sheet-like sintered material was 150 to 200 μm.

[0026] (2) Evaluation of sintered materials The produced sintered materials were evaluated as follows. (i) Microstructure observation The surface of the sintered material was observed using a scanning electron microscope. The photograph obtained using the scanning electron microscope is shown in Figure 2. In the sintered material, the tungsten carbide particles and brass particles were uniformly dispersed.

[0027] (ii) Measurement of Young's modulus A stress R was applied to the sintered material using a tensile tester, while the strain A of the sintered material was measured using a strain gauge. The relationship between stress R and strain A is shown in Figure 3. The Young's modulus of the sintered material was calculated from the linear portion of this graph. The Young's modulus of the sintered material was 126 GPa.

[0028] (iii) Measurement of electrical conductivity The current I and voltage V of the sintered material were measured. The measurement results are shown in Figure 4. The electrical conductivity of the sintered material was calculated from the measurement results of the current I and voltage V. The electrical conductivity of the sintered material was 2.9 μΩcm.

[0029] (iv) Measurement of thermal expansion coefficient Using a tensile tester, a strain gauge, and a heating cell, the thermal strain of the sintered material was measured at various temperatures. The measurement results of the thermal strain of the sintered material are shown in Figure 5. The thermal expansion coefficient of the sintered material was calculated from the gradient of the portion of the graph shown in Figure 5 near room temperature. The thermal expansion coefficient of the sintered material was 12.3 x 10 -6 / K. Figure 5 also shows the measurement results for Comparative Examples 1 and 2. Comparative Example 1 is a test piece made only of brass. Comparative Example 2 is a test piece made only of copper.

[0030] 6. Other Embodiments Although the embodiments of the present disclosure have been described above, the present disclosure is not limited to the above-described embodiments and can be implemented in various modified forms.

[0031] (1) Sintered materials can be used, for example, as lead frames for bonding semiconductor elements. Sintered materials are suitable for lead frames because they have a high Young's modulus and high electrical conductivity. Conventional lead frames are made of copper or copper alloys. Sintered materials have high electrical conductivity and a higher Young's modulus than copper and copper alloys.

[0032] (2) The superconducting tape 1 may have the configuration shown in Fig. 6. In this superconducting tape 1, a first layer 23, a second layer 25, a third layer 27, a fourth layer 29, a fifth layer 31, a sixth layer 33, a seventh layer 35, and an eighth layer 37 are laminated in this order on one side of a substrate 21. In addition, a ninth layer 39 is provided on the opposite side of the substrate 21.

[0033] The substrate 21 is made of, for example, Hastley. The thickness of the substrate 21 is, for example, 50 μm. The first layer 23 is made of, for example, alumina. The thickness of the first layer 23 is, for example, 75 nm or less. The second layer 25 is made of, for example, yttria. The thickness of the second layer 25 is, for example, 7 nm or less.

[0034] The third layer 27 is made of, for example, magnesium oxide formed by an ion beam assisted method. The thickness of the third layer 27 is, for example, 10 nm or less. The fourth layer 29 is made of, for example, homoepitaxially grown magnesium oxide. The thickness of the fourth layer 29 is, for example, 30 nm or less. The fifth layer 31 is, for example, an LMO layer. The thickness of the fifth layer 31 is, for example, 30 nm or less.

[0035] The sixth layer 33 is, for example, a layer made of a high-temperature superconductor. The thickness of the sixth layer 33 is, for example, 1 μm. The seventh layer 35 is, for example, a layer made of silver. The thickness of the seventh layer 35 is, for example, 2 μm. The eighth layer 37 is a reinforcing layer including the sintered material of the present disclosure. The thickness of the eighth layer 37 is, for example, 20 μm. The ninth layer 39 is, for example, a layer made of copper. The thickness of the ninth layer 39 is, for example, 20 μm.

[0036] (3) The function of one component in each of the above embodiments may be shared among multiple components, or the functions of multiple components may be performed by one component. Also, part of the configuration of each of the above embodiments may be omitted. Furthermore, at least part of the configuration of each of the above embodiments may be added to or substituted for the configuration of another of the above embodiments.

[0037] (4) In addition to the sintered material described above, the present disclosure can also be realized in various forms, such as a system including the sintered material as a component, a method for manufacturing a sintered material, etc.

[0038] [Technical idea disclosed in this specification] [Item 1] A sintered material comprising particles of tungsten carbide and particles of brass. [Item 2] The sintered material according to item 1, having a sheet-like form, Sintered material. [Item 3] Item 1 or 2, a sintered material, The ratio m / M of the mass of tungsten carbide m to the total mass M of tungsten carbide and brass is 0.088 or more and 0.245 or less. Sintered material. [Item 4] The sintered material according to any one of items 1 to 3, The Young's modulus of the sintered material is 110 GPa or more and 225 GPa or less, The electrical conductivity of the sintered material is 2.1 μΩcm or more and 3.0 μΩcm or less, The thermal expansion coefficient of the sintered material is 11 x 10 -6 / K or more 21×10 -6 / K or less, Sintered material. [Item 5] a superconducting layer; metal layers disposed on both sides of the superconducting layer; a reinforcing layer disposed outside the metal layer; A superconducting tape comprising: The reinforcing layer is a layer containing a sintered material including tungsten carbide particles and brass particles. Superconducting tape. [Item 6] A reinforcing layer for a superconducting tape comprising a sintered material including particles of tungsten carbide and particles of brass. [Explanation of symbols]

[0039] 1...superconducting tape, 3...superconducting layer, 5...metal layer, 7...reinforcing layer, 8...solder layer, 9...bismuth-based superconductor, 11...silver, 21...substrate, 23...first layer, 25...second layer, 27...third layer, 29...fourth layer, 31...fifth layer, 33...sixth layer, 35...seventh layer, 37...eighth layer, 39...ninth layer

Claims

1. A sintered material comprising particles of tungsten carbide and particles of brass.

2. The sintered material according to claim 1, having a sheet-like form, Sintered material.

3. The sintered material according to claim 1 or 2, The ratio m / M of the mass m of tungsten carbide to the total mass M of tungsten carbide and brass is 0.088 or more and 0.245 or less; Sintered material.

4. The sintered material according to claim 1 or 2, The Young's modulus of the sintered material is 110 GPa or more and 225 GPa or less, The electrical conductivity of the sintered material is 2.1 μΩcm or more and 3.0 μΩcm or less, The thermal expansion coefficient of the sintered material is 11×10 －６ / K or more 21×10 －６ / K or less, Sintered material.

5. a superconducting layer; metal layers disposed on both sides of the superconducting layer; a reinforcing layer disposed outside the metal layer; A superconducting tape comprising: The reinforcing layer is a layer containing a sintered material including tungsten carbide particles and brass particles. Superconducting tape.

6. A reinforcing layer for a superconducting tape comprising a sintered material including particles of tungsten carbide and particles of brass.

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