Preparation method of large-size (Cu, C)-1234 superconducting material and superconducting material

Abstract

The invention provides a preparation method of a large-size (Cu, C)-1234 superconducting material and the superconducting material. The preparation method comprises the following steps: step 1, crushing a small-size (Cu, C)-1234 superconducting material into powder; 2, the small-size (Cu, C)-1234 superconducting powder is subjected to compression molding; and 3, carrying out hot pressed sintering on the block material obtained by compression molding to obtain the large-size (Cu, C)-1234 superconducting material. Wherein the pressure of hot pressing sintering is not less than 300 MPa, and the sintering temperature is 100-350 DEG C. Small-size (Cu, C)-1234 with the diameter smaller than 5 mm is used as a raw material, and the large-size (Cu, C)-1234 superconducting material with the diameter larger than 8 mm and the superconducting transmission performance is prepared through the low-temperature hot pressing sintering technology.

Description

Technical Field

[0001] The invention belongs to the technical field of superconducting material preparation, and in particular relates to a preparation method of a large-size (Cu, C)-1234 superconducting material and a superconducting material. Background Art

[0002] In 1986, with the discovery of Cu-based superconductors, the application of superconducting materials began to enter the liquid nitrogen temperature range. Today, four copper-based superconductors, Y series (Y-123, etc.), Bi series (Bi-2223, etc.), Tl series (Tl-2223, etc.) and Hg series (Hg-1234, etc.), have been confirmed to have superconducting transition temperatures T c Above 77 K, it has the prospect of practical application. Among them, the Y series is not suitable for the preparation of practical wire strips by the PIT technology route due to its small coherence length and extremely low grain boundary adaptation angle. It is difficult to prepare kilometer-level wire strips, and the cost is high. The Bi series is limited by the strong two-dimensionality of the material itself, resulting in the irreversible field (H2O) under liquid nitrogen (77 K). irr ) is extremely low and cannot be used under liquid nitrogen. The application of Tl and Hg series is limited by the highly toxic metals Tl and Hg in the raw materials. In 1994, Kawashima T et al. found that by replacing Hg in Hg-1234 with (Cu, C), T c Superconductors up to 118 K. Studies have shown that (Cu,C)-1234 still has a very high upper critical field above liquid nitrogen temperature (15 T at 86 K, 5 T at 98 K). At 77 K and 0 T, the critical current density of (Cu,C)-1234 can reach 6.5 × 10 5 A / cm 2 Therefore, (Cu,C)-1234, as a liquid nitrogen temperature zone superconductor with abundant raw materials and no toxicity, has great potential for practical application.

[0003] At present, the preparation of (Cu,C)-1234 superconducting materials adopts a six-sided top press, which is sintered at a pressure of about 4 GPa and a high temperature of 1100 °C. However, this high temperature and high pressure preparation method is difficult to prepare large-sized polycrystalline materials, which greatly limits the application scenarios of (Cu,C)-1234. Therefore, it is necessary to provide a method for preparing large-sized (Cu,C)-1234 superconducting materials. Summary of the invention

[0004] To solve the above problems, the present invention proposes a method for preparing a large-size (Cu, C)-1234 superconducting material. The method uses small-size (Cu, C)-1234 as raw material, adds metal dopants, and can realize low-temperature sintering to prepare large-size (Cu, C)-1234 superconducting material.

[0005] The chemical formula of (Cu,C)-1234 is (Cu,C)Ba2Ca3Cu4O 11+δ .

[0006] Another object of the present invention is to provide a large-size (Cu, C)-1234 superconducting material prepared by the above method.

[0007] The present invention adopts the following technical solutions:

[0008] A method for preparing a large-size (Cu, C)-1234 superconducting material comprises the following steps:

[0009] Step 1: crushing small-sized (Cu,C)-1234 superconducting material into powder;

[0010] Step 2: Pressing small-sized (Cu,C)-1234 superconducting powder into a shape;

[0011] Step 3: Hot-pressing and sintering the pressed block material to obtain a large-size (Cu, C)-1234 superconducting material; wherein the hot-pressing and sintering pressure is not less than 300 MPa, and the sintering temperature is 100-350 °C.

[0012] The (Cu, C)-1234 superconducting material is a small-sized (Cu, C)-1234 superconducting material prepared by a six-sided top press.

[0013] Wherein, the particle size of the (Cu, C)-1234 superconducting material powder is 2-20 μm.

[0014] Wherein, the heating rate of the hot pressing sintering is 3-10°C / min.

[0015] The hot pressing sintering is carried out in a hot pressing furnace, and the position of the pressing head is kept unchanged during the hot pressing sintering process.

[0016] The heat preservation time of the hot pressing sintering is 1-24 h, and the pressure holding time is 1-24 h.

[0017] Wherein, before step 2, the method further includes the step of adding a metal dopant into the small-sized (Cu, C)-1234 superconducting powder;

[0018] The metal dopant is Sn powder or Pb powder or a mixture of the two.

[0019] Wherein, the added amount of the metal dopant is 0-11% of the (Cu, C)-1234 superconducting material powder.

[0020] A large-size (Cu, C)-1234 superconducting material is prepared by the above-mentioned large-size (Cu, C)-1234 superconducting material preparation method, wherein the large-size (Cu, C)-1234 superconducting material has a diameter greater than 8 mm and a density greater than 4.0 g / cm 3 , density is greater than 80%, and Vickers hardness exceeds 300.

[0021] A large-size (Cu, C)-1234 superconducting material is prepared by the above-mentioned large-size (Cu, C)-1234 superconducting material preparation method, wherein the large-size (Cu, C)-1234 superconducting material has a diameter greater than 8 mm and a density greater than 4.0 g / cm 3 ; The large-size (Cu, C)-1234 superconducting material contains at least one element of Sn and Pb, wherein Sn and / or Pb are distributed in the pores of the grains.

[0022] The beneficial effects of the present invention are as follows:

[0023] (1) The present invention uses small-sized (Cu, C)-1234 with a diameter of less than 5 mm as raw material and utilizes a low-temperature hot pressing sintering process to prepare a large-sized (Cu, C)-1234 superconducting material with a diameter of more than 8 mm and superconducting transmission performance.

[0024] (2) The present invention dopes low-melting-point metal powder into small-sized (Cu, C)-1234 powder and uses the low-melting-point metal powder as a binder between (Cu, C)-1234 grains, thereby improving the densification of low-temperature sintered (Cu, C)-1234 superconducting materials.

[0025] (3) The present invention can prepare (Cu, C)-1234 superconducting materials in various shapes, which are suitable for various application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 The (Cu, C)-1234 superconducting material prepared in Example 1.

[0027] Figure 2 This is the MT curve of the (Cu, C)-1234 superconducting material prepared in Example 1.

[0028] Figure 3 This is the MH curve of the (Cu, C)-1234 superconducting material prepared in Example 1.

[0029] Figure 4 This is the SEM image of the (Cu, C)-1234 superconducting material prepared in Example 2.

[0030] Figure 5This is the EPMA element distribution diagram of the (Cu, C)-1234 superconducting material prepared in Example 2.

[0031] Figure 6 This is the MT curve of the (Cu, C)-1234 superconducting material prepared in Example 2.

[0032] Figure 7 This is the MH curve of the (Cu, C)-1234 superconducting material prepared in Example 2.

[0033] Figure 8 This is the MT curve of the (Cu, C)-1234 superconducting material prepared in Example 3.

[0034] Fig. 9 This is the MH curve of the (Cu, C)-1234 superconducting material prepared in Example 3. DETAILED DESCRIPTION

[0035] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0036] A method for preparing a large-size (Cu, C)-1234 superconducting material comprises the following steps:

[0037] Step 1: crushing small-sized (Cu,C)-1234 superconducting material into powder;

[0038] Step 2: Pressing small-sized (Cu, C)-1234 superconducting powder into a shape; in this step, the powder is placed in a mold and pre-pressed into a shape under a certain pressure; the mold can be selected according to actual needs, so that the method of the present invention can prepare superconducting materials of various shapes;

[0039] Step 3: The block material obtained by pressing and molding is subjected to hot pressing and sintering to obtain a large-sized (Cu, C)-1234 superconducting material; wherein the hot pressing and sintering pressure is not less than 300 MPa, and the sintering temperature is 300-350 °C.

[0040] The present invention uses small-sized (Cu, C)-1234 superconducting materials as raw materials and successfully prepares large-sized (Cu, C)-1234 superconducting materials by low-temperature hot pressing and sintering process, thereby realizing the industrial application of (Cu, C)-1234 superconducting materials. The (Cu, C)-1234 superconducting materials prepared by the six-sided top press are small in size, with a diameter of less than 5 mm and an overall mass of less than 10 g. The preparation method of the present invention can prepare (Cu, C)-1234 superconducting materials of any size, such as (Cu, C)-1234 targets or wire strips, so that they have higher industrial application value.

[0041] The (Cu, C)-1234 superconducting material is a small-sized (Cu, C)-1234 superconducting material prepared by a six-sided top press. The present invention uses the small-sized (Cu, C)-1234 superconducting material prepared by a six-sided top press as raw material; the small-sized (Cu, C)-1234 superconducting material prepared by the six-sided top press is ground and crushed into powder.

[0042] Preferably, the particle size of the (Cu, C)-1234 superconducting material powder is 2-20 μm.

[0043] Preferably, the heating rate of the hot pressing sintering is 3-10°C / min.

[0044] Preferably, the hot pressing sintering is carried out in a hot pressing furnace, and the position of the pressure head is kept unchanged during the hot pressing sintering process. The hot pressing sintering process only needs to maintain a pressure of not less than 300 MPa, so the position of the pressure head can be kept unchanged during the hot pressing sintering process, and the pressure can also be appropriately increased.

[0045] Preferably, the heat preservation time of the hot pressing sintering is 1-24 h, and the pressure holding time is 1-24 h.

[0046] As a more preferred embodiment, before step 2, a step of adding a metal dopant to the small-sized (Cu, C)-1234 superconducting powder is also included; the metal dopant is one of Sn powder or Pb powder or a mixture of the two. This embodiment mainly adds metal powder to the (Cu, C)-1234 superconducting material powder as a binder between (Cu, C)-1234 grains to further improve the density.

[0047] Wherein, the added amount of the metal dopant is 0-10% of the (Cu, C)-1234 superconducting material powder.

[0048] Example 1

[0049] Step 1: Powder preparation;

[0050] In dry air, the (Cu,C)-1234 single crystal block was placed in a mortar and ground for 30 min to grind the single crystal block into fine powder.

[0051] Step 2: Powder pre-compression;

[0052] About 0.5 g of (Cu,C)-1234 powder was placed in a φ 8 mm circular tableting mold, and a pressure of 50 MPa was applied to pre-compact the powder.

[0053] Step 3: hot pressing and sintering;

[0054] The mold filled with powder is placed in a hot pressing furnace with an air atmosphere. First, a pressure of 400 Mpa is applied at room temperature to compact the powder, and then the temperature is increased at a rate of 5 ℃ / min. The hot pressing sintering temperature is 300 ℃, and the holding time is 12 h. The holding time of the sample is synchronized with the holding time. During the heating process, the position of the pressure head is kept unchanged. Due to thermal expansion, the pressure of the powder rises to 600 Mpa. After the insulation is completed, the temperature is lowered by furnace cooling and the pressure is released at room temperature. After hot pressing and sintering, a (Cu, C)-1234 superconducting block with a size of φ 8 mm is prepared. It has been tested that the starting transition temperature T of the block is 200 °C. c,onset is 117 K.

[0055] Figure 1 The picture of the superconducting material prepared in Example 1 shows that the hot pressing sintering method of the present invention can be used to prepare a dense (Cu, C)-1234 superconducting material. The (Cu, C)-1234 superconducting material prepared in Example 1 is a circular block of φ 8 mm, with a density of 80% and a density of 4.0 g / cm 3 The average grain size is 10-20 μm, the Tc,onset is 117 K, and the superconducting transition of MT and the superconducting hysteresis loop of MH are measured.

[0056] Figure 2 This is the MT curve of the (Cu, C)-1234 superconducting material prepared in Example 1. Figure 2 It can be seen that the initial transition temperature of the sample is T c is 117 K.

[0057] Figure 3 This is the MH curve of the (Cu,C)-1234 superconducting material prepared in Example 1. It can be seen that the sample has an obvious superconducting hysteresis loop at 4.2 K, indicating that there is a superconducting loop current inside the sample at 4.2 K.

[0058] Example 2

[0059] Step 1: Powder preparation

[0060] In dry air, the (Cu, C)-1234 single crystal block was placed in a mortar and ground for 30 min to grind the single crystal block into fine powder. Sn powder with a mass ratio of 10% was weighed and placed in the ground (Cu, C)-1234 powder, and ground again for 30 min to mix the (Cu, C)-1234 powder and the doped Sn powder evenly.

[0061] Step 2: Powder pre-pressing

[0062] About 0.5 g of Sn-doped (Cu,C)-1234 powder was placed in a φ 8 mm circular tableting mold, and a pressure of 50 MPa was applied to pre-compact the powder.

[0063] Step 3: Hot Pressing and Sintering

[0064] The mold containing the powder is placed in a hot pressing furnace with an air atmosphere. First, a pressure of 400 Mpa is applied at room temperature to compact the powder, and then the temperature is increased at a rate of 5 ℃ / min. The hot pressing sintering temperature is 300 ℃ and the holding time is 12 h. During the heating process, the position of the pressure head is kept unchanged. Due to thermal expansion of the powder, the pressure rises to 600 Mpa. The holding time of the sample is synchronized with the holding time. After the holding is completed, the temperature is lowered by furnace cooling and the pressure is released at room temperature. After hot pressing and sintering, a high-density (Cu, C)-1234 superconducting block is prepared.

[0065] Figure 4 This is a SEM image of the (Cu, C)-1234 superconducting bulk material prepared in Example 2. Figure 4 It can be seen that the 10% Sn-doped (Cu,C)-1234 bulk material has a very high density and there are no gaps between the grains.

[0066] Figure 5 EPMA element distribution diagram of 10% Sn-doped (Cu,C)-1234 bulk prepared in Example 2. Figure 5 It can be seen that Sn is doped in the grain gaps of (Cu, C)-1234, which improves the density of the (Cu, C)-1234 bulk material.

[0067] Figure 6 This is the MT curve of the sample prepared in Example 2. It can be seen that the sample initial transition temperature T c is 110K.

[0068] Figure 7 From the MH curve of the sample prepared in Example 2, it can be seen that the sample has an obvious superconducting hysteresis loop at 4.2 K, indicating that there is a superconducting loop current inside the sample at 4.2 K.

[0069] The (Cu,C)-1234 superconducting material prepared in Example 2 is a circular block of φ 8 mm, and its density is close to the theoretical density, which is 98%, and the density is 5.0 g / cm 3 ,T c,onset is 110K.

[0070] Example 3

[0071] Step 1: Powder preparation

[0072] In dry air, a (Cu, C)-1234 single crystal block was placed in a mortar and ground for 30 min to grind the single crystal block into fine powder. Pb powder with a mass ratio of 10% was weighed and added to the ground (Cu, C)-1234 powder, and ground again for 30 min to mix the (Cu, C)-1234 powder and the doped Pb powder evenly.

[0073] Step 2: Powder pre-pressing

[0074] About 0.5 g of 10% Pb-doped (Cu,C)-1234 powder was placed in a φ 8 mm circular tableting mold, and a pressure of 50 MPa was applied to pre-compact the powder.

[0075] Step 3: Hot Pressing and Sintering

[0076] The mold filled with powder is placed in a hot pressing furnace with an air atmosphere. First, a pressure of 400 Mpa is applied at room temperature to compact the powder, and then the temperature is increased at a rate of 5 ℃ / min. The hot pressing sintering temperature is 350 ℃ and the holding time is 12 h. During the heating process, the position of the pressure head is kept unchanged. Due to thermal expansion of the powder, the pressure rises to 600 Mpa. The pressure holding time of the sample is synchronized with the holding time. After the insulation is completed, the temperature is lowered by furnace cooling and the pressure is released at room temperature. After hot pressing and sintering, a high-density (Cu, C)-1234 superconducting block is prepared. It has been tested that the starting transition temperature T of the block is 200 °C. c,onset is 110K.

[0077] The (Cu,C)-1234 superconducting material prepared in Example 3 is a circular block of φ 8 mm, with a density of 95% and a density of 4.7 g / cm 3 ,T c,onset The superconducting transition of MT and the superconducting hysteresis loop of MH were measured.

[0078] Figure 8 This is the MT curve of the sample prepared in Example 3. It can be seen that the sample initial transition temperature T c is 110K.

[0079] Fig. 9 From the MH curve of the sample prepared in Example 3, it can be seen that the sample has an obvious superconducting hysteresis loop at 4.2 K, indicating that there is a superconducting loop current inside the sample at 4.2 K.

[0080] Example 4

[0081] Step 1: Powder preparation

[0082] In dry air, the (Cu, C)-1234 single crystal block was placed in a mortar and ground for 30 minutes to grind the single crystal block into fine powder. Pb powder with a mass ratio of 5% and Sn powder with a mass ratio of 6% were weighed and placed into the ground (Cu, C)-1234 powder, and ground again for 40 minutes to mix the (Cu, C)-1234 powder and the doped Pb powder and Sn powder evenly.

[0083] Step 2: Powder pre-pressing

[0084] About 0.5 g of 10% Pb-doped (Cu,C)-1234 powder was placed in a φ 8 mm circular tableting mold, and a pressure of 50 MPa was applied to pre-compact the powder.

[0085] Step 3: Hot Pressing and Sintering

[0086] The mold containing the powder is placed in a hot pressing furnace with an air atmosphere. First, a pressure of 400 Mpa is applied at room temperature to compact the powder, and then the temperature is increased at a rate of 5 ℃ / min. The hot pressing sintering temperature is 350 ℃ and the holding time is 12 h. During the heating process, the position of the pressure head is kept unchanged. Due to thermal expansion of the powder, the pressure rises to 600 Mpa. The holding time of the sample is synchronized with the holding time. After the holding is completed, the temperature is lowered by furnace cooling and the pressure is released at room temperature. After hot pressing and sintering, a high-density (Cu, C)-1234 superconducting block is prepared.

[0087] Example 5

[0088] Step 1: Powder preparation

[0089] In dry air, the (Cu, C)-1234 single crystal block was placed in a mortar and ground for 30 min to grind the single crystal block into fine powder. Sn powder with a mass ratio of 1% was weighed and placed in the ground (Cu, C)-1234 powder, and ground again for 30 min to mix the (Cu, C)-1234 powder and the doped Sn powder evenly.

[0090] Step 2: Powder pre-pressing

[0091] About 0.5 g of Sn-doped (Cu,C)-1234 powder was placed in a φ 8 mm circular tableting mold, and a pressure of 50 MPa was applied to pre-compact the powder.

[0092] Step 3: Hot Pressing and Sintering

[0093] The mold containing the powder is placed in a hot pressing furnace with an air atmosphere. First, a pressure of 400 Mpa is applied at room temperature to compact the powder, and then the temperature is increased at a rate of 3 ℃ / min. The temperature of hot pressing sintering is 100 ℃, the holding time is 24 h, and the holding time is 24 h. During the heating process, the position of the pressure head is kept unchanged. Due to thermal expansion, the pressure of the powder rises to 600 Mpa. The holding time of the sample is synchronized with the holding time. After the holding is completed, the temperature is lowered by furnace cooling and the pressure is released at room temperature. After hot pressing and sintering, a high-density (Cu, C)-1234 superconducting block is prepared.

[0094] Example 6

[0095] Step 1: Powder preparation

[0096] In dry air, the (Cu, C)-1234 single crystal block was placed in a mortar and ground for 30 min to grind the single crystal block into fine powder. Sn powder with a mass ratio of 5% was weighed and placed in the ground (Cu, C)-1234 powder, and ground again for 30 min to mix the (Cu, C)-1234 powder and the doped Sn powder evenly.

[0097] Step 2: Powder pre-pressing

[0098] About 0.5 g of Sn-doped (Cu,C)-1234 powder was placed in a φ 8 mm circular tableting mold, and a pressure of 50 MPa was applied to pre-compact the powder.

[0099] Step 3: Hot Pressing and Sintering

[0100] The mold containing the powder is placed in a hot pressing furnace with an air atmosphere. First, a pressure of 500 Mpa is applied at room temperature to compact the powder, and then the temperature is increased at a rate of 10 ℃ / min. The hot pressing sintering temperature is 200 ℃, the holding time is 1 h, and the holding time is 1 h. During the heating process, the position of the pressure head is kept unchanged. Due to thermal expansion, the pressure rises to 600 Mpa. The holding time of the sample is synchronized with the holding time. After the holding is completed, the temperature is lowered by furnace cooling and the pressure is released at room temperature. After hot pressing and sintering, a high-density (Cu, C)-1234 superconducting block is prepared.

[0101] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

[0102] The parts not elaborated in detail in the description of the present invention belong to the known technology in the art. The above embodiments are provided only for the purpose of describing the present invention, and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. Various equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A method for preparing a large-size (Cu, C)-1234 superconducting material, characterized in that: The steps include: Step 1: crushing small-sized (Cu,C)-1234 superconducting material into powder; Step 2: Pressing small-sized (Cu,C)-1234 superconducting powder into a shape; Step 3: Hot-pressing and sintering the pressed block material to obtain a large-sized (Cu, C)-1234 superconducting material; wherein the hot-pressing and sintering pressure is not less than 300 MPa, and the sintering temperature is 100-350°C.

2. The preparation method according to claim 1, characterized in that: The (Cu, C)-1234 superconducting material is a small-sized (Cu, C)-1234 superconducting material prepared by a six-sided top press.

3. The preparation method according to claim 1, characterized in that: The particle size of the (Cu, C)-1234 superconducting material powder is 2-20 μm.

4. The preparation method according to claim 1, characterized in that: The heating rate of the hot pressing sintering is 3-10°C / min.

5. The preparation method according to claim 1, characterized in that: Hot pressing sintering is carried out in a hot pressing furnace, and the position of the pressing head is kept unchanged during the hot pressing sintering process.

6. The preparation method according to claim 1, characterized in that: The heat preservation time of the hot pressing sintering is 1-24 h, and the pressure preservation time is 1-24 h.

7. The preparation method according to any one of claims 1 to 6, characterized in that: Before step 2, the method further includes the step of adding a metal dopant into the small-sized (Cu, C)-1234 superconducting powder; The metal dopant is Sn powder or Pb powder or a mixture of the two.

8. The preparation method according to claim 7, characterized in that: The added amount of the metal dopant is 0-11% of the (Cu, C)-1234 superconducting material powder.

9. A large-size (Cu, C)-1234 superconducting material, characterized in that: The large-size (Cu, C)-1234 superconducting material is prepared by the preparation method of any one of claims 1 to 6, wherein the large-size (Cu, C)-1234 superconducting material has a diameter greater than 8 mm and a density greater than 4.0 g / cm 3 , density is greater than 80%, and Vickers hardness exceeds 300.

10. A large-size (Cu, C)-1234 superconducting material, characterized in that: The large-size (Cu, C)-1234 superconducting material is prepared by the preparation method of the large-size (Cu, C)-1234 superconducting material according to claim 7 or 8, wherein the large-size (Cu, C)-1234 superconducting material has a diameter greater than 8 mm and a density greater than 4.0 g / cm 3 ; The large-size (Cu, C)-1234 superconducting material contains at least one element of Sn and Pb, wherein Sn and / or Pb are distributed in the pores of the grains.

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