A process for reducing carbon content of REBCO powder

Abstract

The application discloses a treatment method for reducing carbon content of REBCO powder, and relates to the technical field of superconducting material preparation. The treatment method is that the REBCO powder is placed in an ozone-containing atmosphere for heat treatment. The core principle of the treatment method is that the strong oxidizing property of ozone and active oxygen atoms generated by the decomposition of ozone are used to directly oxidize carbon impurities in the REBCO powder into CO2 gas at a lower temperature, and meanwhile, the superconducting phase is avoided from being damaged. It is verified by a carbon analyzer that the carbon reduction efficiency of the powder after ozone heat treatment is several times higher than that of the powder after traditional oxygen atmosphere treatment.

Description

Technical Field

[0001] This invention relates to the field of superconducting material preparation technology, and in particular to a method for reducing the carbon content of REBCO powder. Background Technology

[0002] REBCO-coated conductors are the core material of second-generation high-temperature superconducting tapes, possessing a high critical current density (J / L). c Due to its excellent performance under strong magnetic fields and potential for lower manufacturing costs, REBCO coatings are widely used in fields such as strong magnets, power transmission, and nuclear fusion devices. Plasma-assisted pulsed laser deposition (PLD) is one of the main preparation routes for REBCO coated conductors. Its main principle is to focus a laser onto a target material, using high energy density to evaporate and ionize the target material, forming a plasma plume. This plume is then transferred to the substrate for deposition, thus forming a thin film. Therefore, the interaction between the target material and the laser has a crucial impact on the final film quality. The density, grain size, and thermal conductivity of the target material are key factors affecting the plasma plume dynamics. Current technologies can flexibly control these three factors; however, there is still room for improvement in the texture, density, and crystallinity of REBCO films prepared by PLD.

[0003] In the preparation of REBCO high-temperature superconducting materials, carbon content is one of the key factors affecting quality. Carbon impurities can lead to problems such as decreased purity of the superconducting phase, grain boundary contamination, and reduced current carrying capacity after coating. Industrially, barium carbonate (BaCO3) is commonly used as the barium source due to its low cost and good chemical stability. However, barium carbonate is difficult to completely decompose at conventional sintering temperatures (700-950℃), resulting in significant carbon impurity issues. To avoid carbon contamination, industrial processes often employ prolonged high-temperature vacuum annealing to reduce carbon content by extending the heat treatment time. However, this method is inefficient and energy-intensive, significantly increasing preparation costs and time. While directly using barium oxide (BaO) to replace barium carbonate can avoid carbon introduction, BaO readily absorbs moisture at room temperature and forms barium hydroxide, posing serious safety hazards and operational difficulties.

[0004] Therefore, there is an urgent need for a rapid, efficient, and low-temperature treatment method to reduce the carbon content of REBCO powder. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides a method for reducing the carbon content of REBCO powder. This method can achieve a carbon removal rate of at least 50%.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A method for reducing the carbon content of REBCO powder involves heat-treating the REBCO powder in an ozone atmosphere. The core principle of this method is to utilize the strong oxidizing properties of ozone and the active oxygen atoms produced by its decomposition to directly oxidize the carbon impurities in the REBCO powder into CO2 gas at a relatively low temperature, while avoiding damage to the superconducting phase.

[0008] The heat treatment temperature is 300-500℃, and the heat treatment time is 0.5-3 hours.

[0009] Among them, the ozone concentration in the ozone-containing atmosphere is 10-300 g / m³. 3 .

[0010] Among them, REBCO powder is REBa2Cu3O 7-δ , where RE is one of Y, Eu, Gd or Yb, 0<δ<1, and δ is the oxygen vacancy parameter, which indicates the degree to which the oxygen content deviates from the stoichiometric ratio 7.

[0011] The heat treatment is carried out in a closed furnace or an ozone annealing furnace.

[0012] The oxygen pressure in the ozone-containing atmosphere is controlled at 0.02-5 MPa.

[0013] The oxygen pressure in the ozone-containing atmosphere is controlled at 0.1-5 MPa.

[0014] The ozone concentration in the ozone-containing atmosphere is 30-100 g / m³. 3 .

[0015] The heating rate for heat treatment is 2-10℃ / min.

[0016] The beneficial effects of this invention are as follows:

[0017] (1) High efficiency in carbon reduction: Ozone has strong oxidizing properties at low temperatures and can effectively decompose carbon impurities such as barium carbonate, reducing the carbon content from 1100 ppm to below 500 ppm. Verified by a carbon analyzer, the carbon reduction efficiency of powder after ozone heat treatment is several times higher than that of traditional oxygen atmosphere treatment, directly proving the high efficiency of this method in removing carbon impurities.

[0018] (2) Short processing time: Compared with traditional vacuum annealing (tens of hours), the processing time of this invention can be shortened to 0.5-3 hours.

[0019] (3) Low temperature process: The processing temperature is as low as 300-500℃ to avoid grain coarsening and phase decomposition caused by high temperature and maintain powder activity.

[0020] (4) Operational safety: Avoid using barium oxide with strong hygroscopicity. The process is safe and controllable, and is suitable for industrial promotion. Attached Figure Description

[0021] Figure 1 This is a flowchart of the method for reducing the carbon content of REBCO powder according to the present invention.

[0022] The attached diagram is labeled as follows: 100-Ozone annealing furnace; 200-Ozone generator; 300-Dust filtration device. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] See Figure 1 The method for reducing the carbon content of REBCO powder according to the present invention is carried out in a closed furnace or ozone annealing furnace 100. The closed furnace or ozone annealing furnace 100 is provided with an ozone inlet, which is connected to an ozone generator 200. A dust filter device 300 is also connected to the closed furnace or ozone annealing furnace 100.

[0025] The REBCO powder to be treated is placed in a sealed furnace or ozone annealing furnace 100 and then heat-treated by introducing ozone. The heat treatment temperature is 300-500℃, and the time is 0.5-3 hours. The heat treatment mainly utilizes the strong oxidizing property of ozone and the active oxygen atoms (O) produced by its decomposition. The carbon impurities in the REBCO powder are directly oxidized into CO2 gas and escape. That is, CO2 and O2 enter the dust filtration device 300.

[0026] Example 1:

[0027] EuBa2Cu3O was selected 7-δ The powder being processed had an initial carbon content of 1100 ppm.

[0028] A method for reducing the carbon content of REBCO powder, specifically involving: removing EuBa2Cu3O powder with an initial carbon content of 1100 ppm... 7-δ The powder is evenly spread in the ozone annealing furnace 100, and ozone concentration of 50 g / m³ is introduced through the ozone generator 200. 3 The atmosphere was controlled so that the oxygen pressure inside the furnace was 0.03 MPa, and the temperature was increased to 400°C at a rate of 5°C / min, and held for 0.5 hours. After the treatment, the furnace was cooled to room temperature.

[0029] Test results showed that the carbon content of the powder decreased to 480 ppm after treatment, and the carbon removal rate was 56%.

[0030] Example 2:

[0031] YBa2Cu3O was selected 7-δ Powder with an initial carbon content of 1300 ppm.

[0032] A method for reducing the carbon content of REBCO powder, specifically involving: removing YBa2Cu3O powder with an initial carbon content of 1300 ppm... 7-δ The powder is placed in an ozone annealing furnace 100, and ozone is introduced through an ozone generator 200 at a concentration of 200 g / m³. 3 The atmosphere was controlled with oxygen pressure at 0.5 MPa, and the temperature was increased to 500℃ at a rate of 10℃ / min, and held for 2 hours. After treatment, the furnace was cooled to room temperature.

[0033] Test results showed that the carbon content dropped to 300 ppm after treatment, with a carbon removal rate of 77%.

[0034] Example 3:

[0035] GdBa2Cu3O was selected. 7-δ Powder with an initial carbon content of 900 ppm.

[0036] A method for reducing the carbon content of REBCO powder, specifically involving: removing GdBa2Cu3O powder with an initial carbon content of 900 ppm... 7-δ The powder is placed in an ozone annealing furnace 100, and ozone is introduced through an ozone generator 200 at a concentration of 300 g / m³. 3 The atmosphere was controlled with an oxygen pressure of 2 MPa, and the temperature was increased to 350°C at a rate of 2°C / min, and held for 3 hours. After treatment, the furnace was cooled to room temperature.

[0037] Test results showed that the carbon content dropped to 250 ppm after treatment, with a carbon removal rate of 72%.

[0038] Example 4:

[0039] YbBa2Cu3O was selected. 7-δ Powder with an initial carbon content of 1100 ppm.

[0040] A method for reducing the carbon content of REBCO powder, specifically involving: removing YbBa2Cu3O powder with an initial carbon content of 1100 ppm... 7-δ The powder is placed in an ozone annealing furnace 100, and ozone is introduced through an ozone generator 200 at a concentration of 80 g / m³. 3The atmosphere was controlled with oxygen pressure at 0.02 MPa, and the temperature was increased to 300°C at a rate of 5°C / min, and held for 2.5 hours. After treatment, the furnace was cooled to room temperature.

[0041] Test results showed that the carbon content dropped to 450 ppm after treatment, and the carbon removal rate was 59%.

[0042] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A method for reducing the carbon content of REBCO powder, characterized in that, The specific treatment method involves placing REBCO powder in an ozone-containing atmosphere for heat treatment. This method utilizes the strong oxidizing properties of ozone and the active oxygen atoms produced by its decomposition to directly oxidize the carbon impurities in the REBCO powder into CO2 gas at a preset temperature, while avoiding damage to the superconducting phase.

2. The method for reducing the carbon content of REBCO powder according to claim 1, characterized in that, The preset temperature for heat treatment is 300-500℃, and the heat treatment time is 0.5-3 hours.

3. The method for reducing the carbon content of REBCO powder according to claim 1, characterized in that, The ozone concentration in an ozone-containing atmosphere is 10-300 g / m³ 3 .

4. The method for reducing the carbon content of REBCO powder according to claim 1, characterized in that, REBCO powder is REBa2Cu3O 7-δ , where RE is one of Y, Eu, Gd or Yb, and 0 < δ < 1.

5. The method for reducing the carbon content of REBCO powder according to claim 1, characterized in that, Heat treatment is carried out in a closed furnace or an ozone annealing furnace.

6. The method for reducing the carbon content of REBCO powder according to claim 1, characterized in that, The oxygen pressure in the ozone-containing atmosphere is controlled at 0.02-5 MPa.

7. The method for reducing the carbon content of REBCO powder according to claim 6, characterized in that, The oxygen pressure in the ozone-containing atmosphere is controlled at 0.1-5 MPa.

8. The method for reducing the carbon content of REBCO powder according to claim 3, characterized in that, The ozone concentration in an ozone-containing atmosphere is 30-100 g / m³. 3 .

9. The method for reducing the carbon content of REBCO powder according to claim 2, characterized in that, The heating rate for heat treatment is 2-10℃ / min.

Images