A method for preparing high-performance MgB2 bulk material by doping with bio-carbon

Abstract

The application discloses a method for preparing high-performance MgB2 bulk material by doping with biological carbon. Firstly, magnesium powder, boron powder and biological carbon powder are weighed, mixed, ground and pressed into tablets according to a certain stoichiometric ratio under a protective atmosphere to obtain a precursor bulk material; after vacuum sealing, the precursor bulk material is put into a heat treatment device for sintering, and after the temperature of the device decreases to room temperature, the bulk material is taken out, and the method is completed. The method can dope the MgB2 superconductor with novel high-activity biological carbon source, is simple in operation, low in cost, can effectively replace the boron position in the MgB2 superconductor lattice, form effective pinning centers, increase impurity scattering, and greatly improve the superconducting performance of the MgB2. Meanwhile, the biological carbon powder contains trace rare earth elements, can form additional pinning centers in the MgB2 superconductor, and further improves the current carrying capacity and application potential of the MgB2 superconductor.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of superconducting materials, and particularly relates to a method for preparing high-performance MgB2 bulk material by biological carbon doping. BACKGROUND

[0002] In 2001, the Akimitsu scientific group of Japan discovered the superconductivity of MgB2 superconductor and proved that the critical transition temperature T C reached 39K, which is very close to the limit of 40K in BCS theory. In subsequent studies, it was found that MgB2 superconductor, as a traditional BCS superconductor mediated by phonons, has smaller anisotropy and larger coherence length, which is more conducive to the introduction of magnetic flux pinning centers, and its structure is simpler; and compared with low-temperature superconductors, it has a higher application temperature range (20K~30K) which can greatly reduce the application cost. At present, the main method to improve the performance of MgB2 superconductor is still chemical doping, and the main dopants are amorphous carbon and its related compounds, metal elements, metal oxides, etc. Through further in-depth study, it is found that compared with other dopants, carbon doping can effectively improve the upper critical field and the rapid decay of critical current density under high field of MgB2 superconductor, making it a research hotspot in the field.

[0003] At present, the main forms of carbon elements as dopants are amorphous carbon, SiC, B4C, carbon nanotubes (CNT), etc. These carbon sources have been proven to form effective pinning centers or improve the grain boundary connectivity in MgB2 superconductors. However, these carbon sources are mainly artificially synthesized or obtained through secondary processing, which greatly increases the application cost and environmental pollution. At the same time, the storage of raw materials of some carbon sources requires a lot of manpower and resources, and some carbon sources need to be purchased from outside, which also increases the experimental cost and is not conducive to the further development of large-scale commercial application of MgB2 superconductors. At the same time, the pinning centers introduced by carbon atoms alone are too single, which may result in fewer effective pinning centers and cannot further improve the performance of MgB2 superconductors. Therefore, it is of great significance to find a sustainable and abundant existing resource that can introduce more effective pinning centers for improving MgB2 superconductors. SUMMARY

[0004] The present application aims at solving the existing problems of the carbon source doped in MgB2 superconductor, and provides a method for preparing high-performance MgB2 bulk material by biological carbon doping.

[0005] In order to achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

[0006] A method for preparing high-performance MgB2 bulk material by biological carbon doping, comprising the following steps:

[0007] Step 1: Under a protective atmosphere, magnesium powder, boron powder and biological carbon powder are weighed, mixed and ground for 45-70 minutes according to the stoichiometric ratio Mg:B:C=1:1.5-1.95:0.05-0.5 to obtain a mixed powder, so that the raw material powder is fully mixed and the particles are small enough. Finally, the mixed powder is pressed by a powder tablet press under a pressure of 10-20 MPa to press the mixed powder into a cylindrical block with a height of 5-10 mm and a diameter of 1-5 mm to obtain a precursor block.

[0008] The particle size of the magnesium powder is 100-200 mesh; the purity of the boron powder is ≥99%, and the particle size is ≤20 um; the biological carbon powder is formed by carbonizing organic biological matter under a protective atmosphere at high temperature or by other methods, and the biological carbon powder contains trace amounts of rare earth elements, including La series elements and S C , Y, etc.

[0009] It should be noted that the weighing should be accurate to the maximum accuracy of the instrument, and the powder weight can be read after the reading is stable.

[0010] Step 2: The precursor block is placed in a crucible under a protective atmosphere, the crucible is then placed in a quartz tube, and the quartz tube opening is sealed.

[0011] It should be noted that since part of the magnesium powder will volatilize during sintering, 1-2% of the total amount of magnesium powder used in step 1 is added to the crucible to supplement the raw materials.

[0012] Step 3: The quartz tube is taken out of the protective atmosphere and vacuum sealed by a vacuum sealing machine.

[0013] Specific operation is: first with cutting about 5cm section quartz tube connection valve one end and vacuum tube sealing machine joint, then use vacuum tube sealing machine first extraction located above the valve 5cm quartz tube to vacuum state, then open the valve switch, extraction lower quartz tube to vacuum state, keep the vacuum degree in 1.5x10 -3 ~2.5x10 -3 Pa after high temperature complete tube sealing.

[0014] It should be noted that: before taking out the quartz tube needs to be used with the valve has been closed double pagoda plug straight ball valve rubber ring seal quartz tube mouth, prevent the quartz tube into air before vacuum tube sealing, cause sample oxidation.

[0015] Step 4: the sealed quartz tube is placed in the heat treatment device, and the temperature in the heat treatment device is increased from room temperature to 700-1000 DEG C at a rate of 1-20 DEG C / min, and the temperature is kept for 1-10 hours to obtain the biological carbon doped MgB2 bulk material.

[0016] Step 5: after the temperature in the device decreases to room temperature, the biological carbon doped MgB2 bulk material is taken out and stored in a dry environment.

[0017] The protective atmosphere described in the application is an inert gas atmosphere such as argon, helium, nitrogen, etc., and the purity is 99.0-99.99%.

[0018] The heat treatment device includes a tubular furnace, a box furnace, a muffle furnace and other programmable heat treatment devices.

[0019] The application provides a method for preparing high-performance MgB2 bulk material by biological carbon doping based on the existing carbon source problem in carbon-doped MgB2 superconductor.

[0020] (1) the application provides a novel and effective doped carbon source for MgB2 superconductor by biological carbon doping MgB2 superconductor, enriches the existing carbon source reserve, and provides a novel, effective and sustainable way to solve the problems of carbon source cost and pollution.

[0021] (2) the application can form more pinning centers in MgB2 superconductor by introducing trace rare earth elements in biological carbon powder, effectively improves the superconducting performance of MgB2 bulk material, and greatly improves the practical value of MgB2 superconductor.

[0022] (3) the application can dope carbon atoms and trace rare earth elements in biological carbon powder into MgB2 superconductor by traditional solid phase sintering method, effectively improve the current carrying performance of MgB2 superconductor, the operation process is simple, the cost is low, and the performance is improved significantly. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 XRD diffractogram of the MgB2C0 bulk material prepared for Example 1.

[0024] Figure 2 Scanning electron microscope picture of the MgB2C0 bulk material prepared for Example 1 at 5000x magnification.

[0025] Figure 3 XRD diffractogram of the MgB 1.95 C 0.05 bulk material prepared for Example 2.

[0026] Figure 4 Scanning electron microscope picture of the MgB 1.95 C 0.05 bulk material prepared for Example 2 at 5000x magnification.

[0027] Figure 5 XRD diffractogram of the MgB 1.9 C 0.1 bulk material prepared for Example 3.

[0028] Figure 6 Scanning electron microscope picture of the MgB 1.9 C 0.1 bulk material prepared for Example 3 at 5000x magnification.

[0029] Figure 7 XRD diffractogram of the MgB 1.8 C 0.2 bulk material prepared for Example 4.

[0030] Figure 8 Scanning electron microscope picture of the MgB 1.8 C 0.2 bulk material prepared for Example 4 at 5000x magnification.

[0031] Figure 9 XRD diffractogram of the MgB 1.7 C 0.3 bulk material prepared for Example 5.

[0032] Figure 10 Scanning electron microscope picture of the MgB 1.7 C 0.3 bulk material prepared for Example 5 at 5000x magnification.

[0033] Figure 11 Critical current density plot at 10 K, 5 T of the products prepared for Examples 1-5.

[0034] Figure 12 Plot of the lattice parameter a and the lattice parameter c variation of the products prepared for Examples 1-5.

[0035] Figure 13 Magnetization versus temperature plots for the products prepared for Example 1 and Example 2 under zero field cooling and field cooling (20 oe) conditions. DETAILED DESCRIPTION

[0036] In order to make the objects, technical solutions and advantages of the present application clearer, further detailed description will be given below in combination with embodiments and drawings, and the schematic embodiments of the present application and the description thereof are only used to explain the present application, but not to limit the present application.

[0037] In the following examples, the biochar powder is provided by Chen Zuliang's research group of the College of Environment and Resources, Fujian Normal University. The preparation method is mainly as follows: collecting organic plants of mangrove in abandoned rare earth mine area of Changting County in Fujian Province, and then obtaining high-quality biochar powder through high-temperature calcination and extraction under the protection of inert gas. The total weight of lanthanide elements Sc and Y in the biochar powder accounts for about 0.34wt% of the total amount of the biochar powder.

[0038] Example 1

[0039] Preparation method of MgB2C0 bulk material

[0040] Step 1: Under a protective atmosphere, magnesium powder, boron powder and biochar powder are accurately weighed and mixed according to the stoichiometric ratio Mg:B:C=1:2:0, wherein the particle size of the magnesium powder is 100-200 mesh, the purity of the boron powder is ≥99%, and the particle size is ≤20um. Then, the original powder is ground for 45min to fully mix the powder and make the particles small enough. Finally, the mixed powder is pressed into a tablet by a powder tablet press under a pressure of 14MPa, and the mixed powder is pressed into a cylindrical bulk body with a height of 6mm and a diameter of 1mm to obtain a precursor bulk material.

[0041] Step 2: The precursor bulk material is placed in a crucible under a protective atmosphere, and at the same time, in order to make up for the loss of magnesium caused by the volatilization of magnesium powder, 1.5% of the total amount of magnesium powder used in step 1 is additionally added near the sample in the crucible. Then the crucible is placed in a quartz tube, and the quartz tube is sealed by a double-pot insertion straight ball valve with a rubber ring which has been closed.

[0042] Step 3: The quartz tube is taken out from the protective atmosphere and vacuum sealed by a vacuum sealing machine. The specific operation is as follows: first, a part of the quartz tube with a length of about 5cm is connected to the end of the valve and the connector of the vacuum sealing machine, and then the 5cm quartz tube above the valve is first extracted to a vacuum state by the vacuum sealing machine, and then the valve switch is opened and the lower quartz tube is extracted to a vacuum state. The vacuum degree is maintained at about 2.3×10 -3 Pa, and then high temperature is used for complete sealing.

[0043] Step 4: Put the sealed quartz tube into the muffle furnace, and increase the temperature of the furnace from room temperature to 750°C at a rate of 5°C / min, and keep the temperature for 2 hours.

[0044] Step 5: After the temperature in the device drops to room temperature, take out the block, and store it in a dry environment.

[0045] Figure 1 Figure 1 is an XRD diffraction pattern of the MgB2C0 block prepared in Example 1, which can see that the purity of the block is high, except for a small amount of MgO peak caused by oxidation of magnesium powder at 2θ = 60° ~ 65°, there is no other obvious impurity phase. Figure 2 Figure 2 is a scanning electron microscope picture of the MgB2C0 block prepared in Example 1, which can be found that although the grain boundary is complete, due to the undoped biological carbon, the grain is large. Figure 11 It can be seen that the critical current density of the MgB2C0 block prepared in Example 1 is 1.68×10 4 A / cm 2 . Figure 12 Figure 3 shows the lattice parameters a and c of the MgB2C0 block prepared in Example 1. Figure 13 Figure 4 is the M-T curve of the MgB2C0 block prepared in Example 1 under zero field cooling (ZFC) and field cooling (FC, 20Oe) conditions, at this time the sample is pure, the critical transition temperature T C reached 38.3K and has a narrow transition width, ΔT C 1.1K.

[0046] Example 2

[0047] Preparation method of MgB 1.95 C 0.05 block

[0048] Step 1: Under a protective atmosphere, magnesium powder, boron powder, and biological carbon powder are accurately weighed, mixed according to the stoichiometric ratio Mg:B:C = 1:1.95:0.05, wherein the particle size of the magnesium powder is 100-200 mesh, the purity of the boron powder is ≥99%, and the particle size is ≤20um. Then grind for 45min to fully mix the original powder and make the particles small enough. Finally, use a powder tablet machine to press the mixed powder under a pressure of 14MPa, and press the mixed powder into a cylindrical block with a height of 6mm and a diameter of 1mm, to obtain a precursor block.

[0049] Step 2: Put the precursor block into the crucible under the protection atmosphere, and add 1.5% of the total amount of magnesium powder used in step 1 near the sample in the crucible to compensate for the loss of magnesium due to magnesium powder evaporation. Then put the crucible into the quartz tube and seal the quartz tube opening with a double-pyramid plug straight ball valve with a rubber ring.

[0050] Step 3: Take the quartz tube out of the protection atmosphere and vacuum seal it with a vacuum sealing machine. First, connect the end of the 5 cm cut quartz tube with the valve to the connector of the vacuum sealing machine, then use the vacuum sealing machine to extract the 5 cm quartz tube above the valve to a vacuum state, then open the valve switch and extract the lower quartz tube to a vacuum state, maintaining a vacuum degree of 2.3 x 10 -3 Pa or so, and then completely seal the tube with high temperature.

[0051] Step 4: Put the sealed quartz tube into the muffle furnace, and increase the temperature in the furnace from room temperature to 750°C at a rate of 5°C / min, and keep the temperature for 2 hours.

[0052] Step 5: After the temperature in the device drops to room temperature, take out the block and store it in a dry and suitable environment.

[0053] Figure 3 is the XRD diffraction pattern of the MgB 1.95 C 0.05 block prepared in Example 2. It can be seen that the block also has a small amount of MgO peak at 2θ = 60° ~ 65°, and no other obvious impurity phase, and the quality is good. Figure 4 is the scanning electron microscope picture of the sample of Example 2. It can be found that the grain boundary is complete, and due to the doping of biological carbon, the grain size begins to decrease, which is beneficial to the improvement of the grain boundary pinning force. Figure 11 It can be seen that the critical current density of the sample of Example 2 at 10K@5T is 5.57 x 10 4 A / cm 2 , which is 3.3 times that of the product of Example 1. Figure 12 is the lattice parameter a and lattice parameter c graph of the sample of Example 2. Due to the doping of biological carbon, the B layer is distorted, but the Mg layer is little affected, so the lattice parameter a decreases, but the lattice parameter c remains basically unchanged. Figure 13 is the M-T curve of the sample of Example 2 under ZFC and FC (20Oe) conditions. Due to the doping of biological carbon, it can inhibit the T C , increase the ∆T C , and thus the T C drops to 37.7K, and the ∆T C increases to 1.5K.

[0054] Example 3

[0055] MgB 1.9 C 0.1 Method for preparing bulk material

[0056] Step 1: Under a protective atmosphere, accurately weigh and mix magnesium powder, boron powder and biochar powder according to the stoichiometric ratio Mg:B:C = 1:1.9:0.1, wherein the particle size of the magnesium powder is 100-200 mesh, the purity of the boron powder is ≥99%, and the particle size is ≤20um. Then grind for 45min to fully mix the original powder and make the particles small enough. Finally, use a powder tablet press to press the mixed powder at a pressure of 14MPa to press the mixed powder into a cylindrical bulk material with a height of 6mm and a diameter of 1mm, obtaining a precursor bulk material.

[0057] Step 2: Put the precursor bulk material into the crucible under a protective atmosphere, and at the same time, in order to make up for the loss of magnesium due to the volatilization of magnesium powder, 1.5% of the total amount of magnesium powder used in step 1 is added near the sample in the crucible. Then put the crucible into a quartz tube and seal the quartz tube port with a double-pot insertion straight ball valve with a rubber ring.

[0058] Step 3: Take the quartz tube out of the protective atmosphere and vacuum seal it with a vacuum sealing machine. The specific operation is as follows: first connect the one end of the cut-off 5cm quartz tube with the valve and the joint of the vacuum sealing machine, then use the vacuum sealing machine to extract the 5cm quartz tube above the valve to a vacuum state, then open the valve switch and extract the lower quartz tube to a vacuum state, keep the vacuum degree at about 2.3×10 -3 Pa, and then completely seal the tube with high temperature.

[0059] Step 4: Put the sealed quartz tube into a muffle furnace, and increase the temperature in the furnace from room temperature to 750°C at a rate of 5°C / min, and keep the temperature for 2 hours.

[0060] Step 5: After the temperature in the device decreases to room temperature, take out the bulk material and store it in a dry and suitable environment.

[0061] Figure 5 is the MgB 1.9 C 0.1 XRD diffraction pattern of the bulk material, it can be seen that the bulk material has a small amount of MgO peaks, and no other obvious impurity phases. Figure 6 is the scanning electron microscope picture of the sample of example 3, the grain size is further reduced, which shows that biochar doping can effectively refine the grain size and further improve the pinning force. Figure 11 It can be seen that the critical current density of the sample of example 3 at 10K@5T is 4.19×10 4 A / cm 2is 2.49 times of the sample of Example 1. Figure 12 The lattice parameter a of the sample of Example 3 is further reduced, while the lattice parameter c is almost unchanged.

[0062] Example 4

[0063] MgB 1.8 C 0.2 Method for preparing bulk material

[0064] Step 1: Under a protective atmosphere, accurately weigh and mix magnesium powder, boron powder and biochar powder according to the stoichiometric ratio Mg:B:C = 1:1.8:0.2, wherein the particle size of the magnesium powder is 100-200 mesh, the purity of the boron powder is ≥99%, and the particle size is ≤20um. Then grind for 45 minutes to fully mix the original powder and make the particles small enough. Finally, use a powder tablet press to press the mixed powder at a pressure of 14 MPa to press the mixed powder into a cylindrical bulk body with a height of 6 mm and a diameter of 1 mm, obtaining a precursor bulk material.

[0065] Step 2: Put the precursor bulk material into the crucible under a protective atmosphere, and at the same time, in order to make up for the loss of magnesium due to the volatilization of magnesium powder, 1.5% of the total amount of magnesium powder used in step 1 is added to the sample in the crucible. Then put the crucible into a quartz tube and seal the quartz tube port with a double-pot insertion straight ball valve with a rubber ring.

[0066] Step 3: Take the quartz tube out of the protective atmosphere and vacuum seal it with a vacuum sealing machine. The specific operation is as follows: first connect the end of the valve with a cutting part of about 5 cm of the quartz tube to the connector of the vacuum sealing machine, then use the vacuum sealing machine to extract the 5 cm quartz tube above the valve to a vacuum state, then open the valve switch and extract the lower quartz tube to a vacuum state, keep the vacuum degree at about 2.3x10 -3 Pa, and then completely seal the tube with high temperature.

[0067] Step 4: Put the sealed quartz tube into a muffle furnace, and increase the temperature in the furnace from room temperature to 750°C at a rate of 5°C / min, and keep the temperature for 2 hours.

[0068] Step 5: After the temperature in the device decreases to room temperature, take out the bulk material and store it in a dry and suitable environment.

[0069] Figure 7 is the MgB 1.8 C 0.2 XRD diffraction pattern of the bulk material, it can be seen that the bulk material also has a small amount of MgO peaks, the reason is the same as Examples 1, 2 and 3, and no other obvious impurity phases are produced. Figure 8is a scanning electron microscope picture of the sample of Example 4. Figure 11 It can be seen that the critical current density of the sample of Example 4 at 10K@5T is 1.79x10 4 A / cm 2 , which is still higher than that of the sample of Example 1. Figure 12 shows the lattice parameter a versus lattice parameter c graph of the sample of Example 4, which shows that the lattice parameter a continues to decrease as the amount of biocarbon doping increases, while the lattice parameter c still does not change much.

[0070] Example 5

[0071] MgB 1.7 C 0.3 Method for preparing the bulk material

[0072] Step 1: Under a protective atmosphere, accurately weigh and mix magnesium powder, boron powder and biocarbon powder according to the stoichiometric ratio Mg:B:C=1:1.7:0.3, wherein the particle size of the magnesium powder is 100-200 mesh, the purity of the boron powder is ≥99%, and the particle size is ≤20um. Then grind for 45min to fully mix the original powder and make the particles small enough. Finally, use a powder tablet press to press the mixed powder at a pressure of 14MPa to press the mixed powder into a cylindrical bulk material with a height of 6mm and a diameter of 1mm, obtaining a precursor bulk material.

[0073] Step 2: Put the precursor bulk material into the crucible under a protective atmosphere, and at the same time, in order to make up for the loss of magnesium due to the volatilization of magnesium powder, 1.5% of the total amount of magnesium powder used in Step 1 needs to be added near the sample in the crucible. Then put the crucible into a quartz tube and seal the quartz tube port with a double-pyramid plug straight ball valve with a rubber ring.

[0074] Step 3: Take the quartz tube out of the protective atmosphere and vacuum seal it with a vacuum sealing machine. The specific operation is as follows: first connect the end of the 5cm cut quartz tube with the valve and the connector of the vacuum sealing machine, then use the vacuum sealing machine to extract the 5cm quartz tube above the valve to a vacuum state, then open the valve switch and extract the lower quartz tube to a vacuum state, keep the vacuum degree at about 2.3x10 -3 Pa, and then completely seal the tube with high temperature.

[0075] Step 4: Put the sealed quartz tube into a muffle furnace, increase the temperature in the furnace from room temperature to 750°C at a rate of 5°C / min, and keep the temperature for 2 hours.

[0076] Step 5: After the temperature in the device decreases to room temperature, take out the bulk material and store it in a dry and suitable environment.

[0077] Figure 9 is the MgB1.7 C 0.3 The XRD diffraction pattern of the bulk material, it can be seen that at high doping concentration of bio-carbon, in addition to a small amount of MgO, a spurious phase peak also appears at about 40°. The analysis of the appearance of the spurious phase is due to the excessive dopant gathering with other elements inside the superconductor, but the overall sample is still dominated by MgB2 phase, and the spurious phase is still a small amount. Figure 10 is a scanning electron microscope picture of the sample of example 5. Figure 11 It can be seen that the critical current density of the sample of example 5 at 10K@5T is 2.49x10 2 A / cm 2 Due to excessive bio-carbon doping, the critical current density is significantly lower than examples 1-4. Figure 12 The lattice parameter a and lattice parameter c diagram of the sample of example 5, the lattice parameter a continues to decline, but the lattice parameter c still has not changed too much.

[0078] The above examples further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only a specific implementation of the present application and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method of producing high performance MgB2 bulk material by doping with biochar, characterized in that, The method comprises the following steps: Step 1: under a protective atmosphere, magnesium powder, boron powder and biochar powder are weighed, mixed and ground according to a stoichiometric ratio of Mg:B:C = 1:1.5-1.95:0.05-0.5 to obtain a mixed powder, and then the mixed powder is pressed into a tablet by a powder tablet press at a pressure of 10-20 MPa to obtain a precursor block; The biological carbon powder is obtained by collecting organic plants of Miscanthus sinensis in rare earth mining area, high-temperature calcination and extraction under the protection of inert gas, and contains trace rare earth elements, including lanthanide series elements and S C , Y, wherein the total weight of lanthanide series elements, Sc and Y accounts for 0.34wt% of the total weight of the biological carbon powder. Step 2: the precursor block is placed in a crucible under a protective atmosphere, the crucible is then placed in a quartz tube, and the mouth of the quartz tube is sealed; Step 3: the quartz tube is taken out from the protective atmosphere and vacuum sealed by a vacuum sealing machine; Step 4: the sealed quartz tube is placed in a heat treatment device, the temperature in the heat treatment device is raised from room temperature to 700-1000°C, and the temperature is kept for 1-10 hours to obtain a biochar-doped MgB2 block; Step 5: after the temperature in the device decreases to room temperature, the biochar-doped MgB2 block is taken out and stored in a dry environment.

2. The method of claim 1, wherein the method is characterized by: The protective atmosphere is an inert gas atmosphere of argon, helium or nitrogen, and the purity is 99.0-99.99%.

3. The method of claim 1, wherein the carbon-doped preparation of high performance MgB2 bulk material is characterized by, The particle size of the magnesium powder is 100-200 mesh, and the purity of the boron powder is greater than or equal to 99% and the particle size is less than or equal to 20 um.

4. The method of claim 1, wherein the method is characterized by: In step 1, the grinding time is 45-70 min.

5. The method of claim 1, wherein the carbon-doped preparation of high- performance MgB2 bulk material is characterized by, In step 1, the precursor block is a cylindrical block with a height of 5-10 mm and a diameter of 1-5 mm.

6. The method of claim 1, wherein the carbon-doped preparation of high performance MgB2 bulk material is characterized by, In step 2, 1%-2% of the total amount of magnesium powder used in step 1 is additionally added to the crucible to supplement the magnesium powder volatilized during sintering.

7. The method for preparing high-performance MgB2 bulk material by bio-carbon doping according to claim 1, characterized in that, In step 3, the vacuum degree is maintained at 1.5 x 10 -3 2.5 x 10 -3 Pa when vacuum sealing.

8. The method for preparing high-performance MgB2 bulk material by bio-carbon doping according to claim 1, characterized in that, In step 4, the heat treatment device includes a tube furnace and a box furnace, and the heating rate of the heat treatment device is 1-20°C / min.

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