Titanium dioxide-based self-stripping insulating layer slurry as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation of insulating isolation materials, and discloses titanium dioxide-based self-stripping insulating layer slurry as well as a preparation method and application of the titanium dioxide-based self-stripping insulating layer slurry. 2, carrying out functionalization on the pretreated carbon black; 3, dispersing the titanium dioxide nano powder in a mixed solvent, and adding the functionalized carbon black powder and a plasticizer to prepare precursor slurry; during application, the precursor slurry is coated on a Bi-series wire rod to prepare a pretreatment film; and carrying out heat treatment on the pretreatment film step by step, and preparing the titanium dioxide-based self-stripping insulating layer on the surface of the Bi-series wire rod. According to the technical scheme, adhesion between Bi-series wires in the heat treatment process can be effectively prevented, and meanwhile the Bi-series wires can be easily stripped from the wires.

Description

Technical Field

[0001] This invention belongs to the field of insulating material preparation technology, specifically relating to a titanium dioxide-based self-peeling insulating layer slurry, its preparation method, and its application. Background Technology

[0002] High-temperature superconducting materials have important applications in superconducting magnet systems due to their high irreversible field and critical current density. Among them, Bi-2212 round wire, with its isotropic properties, is advantageous for applications requiring high-field, highly uniform magnetic fields and is easy to strand, making it a significant candidate material for manufacturing large, high-field magnets. However, when applied to magnet coils, overlapping contact of some superconducting wires can lead to adhesion between wires during sintering, resulting in wire damage and a decrease in yield. Therefore, there is an urgent need to develop a self-peelable insulating layer material and preparation method suitable for the wire winding process, providing insulation without affecting the wire's superconducting properties. This is of great significance for the large-scale application of bismuth-based wires.

[0003] TiO2 coatings have attracted widespread attention in the research of bismuth-based high-temperature superconducting insulating layers due to their high thermal conductivity, good thermal stability, and electrical insulation, as well as their sintering temperature being close to that of Bi-2212 wires and their good chemical compatibility with the metal sheath, which can avoid the impact of adverse reactions on wire performance. However, as an insulating layer, it faces the problem of difficult subsequent peeling, which limits its application. Summary of the Invention

[0004] To address the problems existing in the prior art, the present invention aims to provide a titanium dioxide-based self-peeling insulation layer slurry, its preparation method, and its application. The insulation layer obtained by the present invention can prevent the wires from sticking together during heat treatment, and the insulation layer can achieve complete self-peeling after heat treatment.

[0005] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a titanium dioxide-based self-peeling insulating layer paste includes the following steps: FCB powder (i.e., carbon black powder) is added to TiO2 nanopowder dispersion to mix the FCB powder evenly and obtain suspension A. The pH of suspension A is adjusted to 10-11 with ammonia water and stirred at 1500-2000 rpm for 10-15 h. Then, polyvinyl butyral, dibutyl phthalate, and butyl benzyl phthalate are added, and the mixture is heated and stirred at 40-60℃ for 10-30 min. After that, it is ultrasonically treated at an ultrasonic frequency of 30-100 kHz for 1-3 h to obtain a titanium dioxide-based self-exfoliating insulating layer slurry. In the titanium dioxide-based self-exfoliating insulating layer slurry, the mass fraction of FCB powder is 0.1%-0.5%, the mass fraction of TiO2 nanoparticles is 15%-20%, the mass fraction of polyvinyl butyral is 3%-10%, the mass fraction of dibutyl phthalate is 1%-2%, and the mass fraction of butyl benzyl phthalate is 1%-2%. The preparation process of FCB powder includes: Add carbon black powder to 1-3 mol·L -1 The carbon black powder was dissolved in a nitric acid solution, stirred until homogeneous, and then ultrasonically dispersed to obtain a carbon black powder dispersion. The dispersion was then heated and stirred at 80-100℃ for 18-22 hours, followed by cooling, solid-liquid separation, washing, drying, and grinding to obtain pretreated carbon black powder. The mass fraction of carbon black in the carbon black powder dispersion was 1%-3%. Pretreated carbon black powder was dispersed in an ethanol solution and ultrasonically dispersed. Then, polyethylene glycol was added, and the mixture was heated at 60-80°C and stirred at 1500-2000 rpm for 2-3 hours. Polyvinyl butyral was then added and stirring was continued for 2-3 hours to obtain mixture A. Solid-liquid separation, washing, and drying were then performed to obtain the FCB powder. In mixture A, the mass fraction of pretreated carbon black powder was 1%-5%, the mass fraction of polyethylene glycol was 0.5%-5%, and the mass fraction of polyvinyl butyral was 0.5%-5%.

[0006] Preferably, the solvent components in the TiO2 nanopowder dispersion include n-butanol, ethanol, xylene, and polyethylene glycol; wherein the content of n-butanol is 30%-33%, the content of ethanol is 16%-19%, the content of xylene is 21%-24%, and the content of polyethylene glycol is 1%-3%.

[0007] Preferably, the average molecular weight of the polyethylene glycol is 2000-8000.

[0008] Preferably, FCB powder is added to TiO2 nanopowder dispersion, stirred at 1500-2000 rpm for 20-40 min at room temperature, and then ultrasonically treated at an ultrasonic frequency of 30-100 kHz for 40-60 min to make the FCB powder uniformly mixed and obtain suspension A. Add carbon black powder to 1-3 mol·L -1In a nitric acid solution, the mixture is stirred at 1500-2000 rpm for 20-60 min at room temperature, and then ultrasonically treated at an ultrasonic frequency of 30-100 kHz for 40-90 min to obtain a carbon black powder dispersion. The pretreated carbon black powder was dispersed in an ethanol solution and ultrasonically treated for 40-90 min at an ultrasonic frequency of 30-100 kHz, and then polyethylene glycol was added.

[0009] Preferably, the particle size of the carbon black powder is 30-80 nm; The TiO2 nanoparticles have a particle size of 20-100 nm.

[0010] The present invention also provides a titanium dioxide-based self-peeling insulating layer paste prepared by the above-described preparation method of the present invention.

[0011] The present invention also provides the application of the titanium dioxide-based self-peeling insulating layer slurry, characterized in that the titanium dioxide-based self-peeling insulating layer slurry is used to prepare an insulating layer on the surface of a high-temperature superconducting material.

[0012] Preferably, the process of preparing an insulating layer on the surface of a high-temperature superconducting material using the titanium dioxide-based self-peeling insulating layer slurry includes: The titanium dioxide-based self-peeling insulating layer slurry is coated onto the surface of a high-temperature superconducting material and then dried to form a pre-treatment film on the surface of the high-temperature superconducting material. The high-temperature superconducting material coated with the pretreated film is subjected to heat treatment. The specific heat treatment process includes: first, heating to 420-460℃ at a rate of 40-60℃ / h and holding at that temperature for 1.5-2h; then heating to 630-660℃ at a rate of 60-80℃ / h and holding at that temperature for 0.5-1h; then heating to 830℃ at a rate of 50-100℃ / h and holding at that temperature for 30-50h; then cooling to 800-810℃ at a rate of 1-5℃ / h and holding at that temperature for 10-20h; and finally cooling to room temperature in the furnace. Finally, a titanium dioxide-based self-peeling insulating layer is prepared on the surface of the high-temperature superconducting material.

[0013] Preferably, the titanium dioxide-based self-peeling insulating layer slurry is coated on the surface of the high-temperature superconducting material and then dried at 80-150°C to form a pre-treated film on the surface of the high-temperature superconducting material.

[0014] Preferably, the high-temperature superconducting material includes Bi-based superconducting wires.

[0015] The present invention has the following beneficial effects: Due to the difficulty in subsequent peeling of TiO2 coatings as insulating layers in existing technologies, this invention introduces modified carbon black into the TiO2 precursor dispersion. The modified carbon black powder (i.e., FCB powder) achieves a structural change compared to the unmodified carbon black powder: polymer molecules are chemically bonded to the carbon black surface, effectively improving its properties. Simultaneously, the polymer adsorption between the modified carbon black particles creates steric hindrance, inhibiting filler network formation and enhancing its dispersibility. When using the titanium dioxide-based self-peeling insulating layer slurry of this invention to prepare an insulating layer on the surface of a high-temperature superconducting material, the insulating coating obtained after high-temperature heat treatment has a loose, porous structure, providing oxygen diffusion channels for the superconducting core wire phase formation and effectively solving the problem of inter-turn adhesion during wire heat treatment. Furthermore, the titanium dioxide insulating coating prepared using the titanium dioxide-based self-peeling insulating layer slurry of this invention has increased brittleness and surface roughness, making it easier to peel off from the metal substrate, eliminating the need for subsequent manual peeling and effectively reducing costs.

[0016] According to the titanium dioxide-based self-peeling insulating layer slurry of the present invention, the present invention also controls the corresponding heat treatment process to realize the preparation of a self-peelable insulating layer on the surface of a high-temperature superconducting material. Attached Figure Description

[0017] Figure 1 This is a SEM image of the surface of the wire sample with the insulation layer covered in Embodiment 5 of the present invention.

[0018] Figure 2 This is a SEM image of the cross-section of the wire sample with the insulation layer covered in Embodiment 5 of the present invention. Detailed Implementation

[0019] The present invention will be further described clearly and in detail below with reference to specific embodiments and the accompanying drawings. Those skilled in the art will be able to implement the present invention based on these descriptions. Furthermore, the embodiments of the present invention described below are generally only some, not all, of the embodiments of the present invention. Therefore, all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0020] The preparation method of the titanium dioxide-based self-peeling insulating layer paste in this embodiment includes the following steps: Step 1: First, disperse a certain amount of raw carbon black (CB) powder in 1-3 mol·L⁻¹ -1In a nitric acid solution, the carbon black powder is stirred at 1500-2000 rpm for 20-60 min at room temperature, and then ultrasonically treated at an ultrasonic frequency of 30-100 kHz for 40-90 min to obtain a carbon black powder dispersion. The carbon black powder dispersion is then heated at 80-100℃ and stirred at 1500-2000 rpm for 18-22 h, then cooled to room temperature. The carbon black powder dispersion is then centrifuged, washed, dried, and ground to finally obtain pretreated carbon black powder (denoted as PTCB powder). The mass fraction of carbon black in the carbon black powder dispersion is 1%-3%, and the particle size of the carbon black powder is 30-80 nm.

[0021] Step 2: Disperse the prepared PTCB powder in an ethanol solution and sonicate it at an ultrasonic frequency of 30-100 kHz for 40-90 min to obtain a PTCB dispersion. Add polyethylene glycol (PEG, average molecular weight 2000-8000) to the PTCB dispersion and continue heating at 60-80℃ with stirring at 1500-2000 rpm for 2-3 h. Then add polyvinyl butyral (PVP) to the PTCB dispersion and stir under the same conditions for 2-3 h to obtain mixture A. Filter, wash, and dry mixture A to obtain functionalized carbon black powder (denoted as FCB powder). The mass fraction of PTCB in mixture A is 1%-5%, the mass fraction of PEG is 0.5%-5%, and the mass fraction of PVP is 0.5%-5%.

[0022] Step 3: Disperse TiO2 nanoparticles (particle size 20-100 nm) in a mixed solvent composed of n-butanol, ethanol, xylene, and polyethylene glycol (average molecular weight 2000-8000) to prepare a TiO2 nanoparticle suspension (also known as a TiO2 nanoparticle dispersion). The n-butanol content is 30%-33%, the ethanol content is 16%-19%, the xylene content is 21%-24%, and the polyethylene glycol content is 1%-3%. Add the FCB powder obtained in Step 2 to the TiO2 nanoparticle dispersion, stir at 1500-2000 rpm for 20-40 min at room temperature, and then sonicate at an ultrasonic frequency of 30-100 kHz for 40-60 min to obtain suspension A. Adjust the pH of suspension A to between 10 and 11 using ammonia. The mixture was stirred at 1500-2000 rpm for 10-15 h at room temperature. Then, polyvinyl butyral (PVB), dibutyl phthalate (DBP), and butyl benzyl phthalate (BBP) were added to suspension A to obtain mixture A. Mixture A was heated at 40-60 °C and stirred at 1500-2000 rpm for 10-30 min, followed by ultrasonic treatment at an ultrasonic frequency of 30-100 kHz for 1-3 h to finally obtain a well-dispersed TiO2 / FCB precursor slurry (i.e., the titanium dioxide-based self-peeling insulating layer slurry). In mixture A, the mass fraction of FCB powder was 0.1%-0.5%, the mass fraction of TiO2 nanoparticles was 15%-20%, the mass fraction of PVB was 3%-10%, and the mass fractions of DBP and BBP were 1%-2%.

[0023] This embodiment takes Bi-based superconducting wire as an example to illustrate the application (i.e., the method of use) of the titanium dioxide-based self-peeling insulating layer slurry obtained in the above embodiment. Specifically, the application method includes the following steps: S1: Immerse the cleaned Bi-based superconducting wire (such as Bi-2212 wire) in the TiO2 / FCB precursor slurry prepared above, and use the dip coating method to pull the wire out of the slurry at a retraction speed of 0.5-2m / s. Dry the Bi-based wire coated with the wet coating at 80-150℃ to obtain a pre-treated film on the surface of the Bi-based wire.

[0024] S2: The Bi-based wire with a pre-treated film on its surface is placed in a tube furnace for heat treatment. The specific heat treatment process includes: first, heating to 420-460℃ at a rate of 40-60℃ / h and holding at that temperature for 1.5-2h; then heating to 630-660℃ at a rate of 60-80℃ / h and holding at that temperature for 0.5-1h; then heating to 830℃ at a rate of 50-100℃ / h and holding at that temperature for 30-50h; then cooling to 800-810℃ at a rate of 1-5℃ / h and holding at that temperature for 10-20h; and finally cooling to room temperature with the furnace. Finally, a titanium dioxide-based self-peeling insulation layer is prepared on the Bi-based superconducting wire.

[0025] Example 1 The preparation method of the titanium dioxide-based self-peeling insulating layer paste in this embodiment includes the following steps: Step 1: First, disperse a certain amount of raw carbon black (CB) powder in 1 mol·L⁻¹ solution. -1 The carbon black powder dispersion was obtained by stirring the solution at 1500 rpm for 20 min at room temperature in nitric acid solution, followed by ultrasonic treatment at 30 kHz for 90 min. The carbon black powder dispersion was then heated at 80°C and stirred at 1500 rpm for 22 h, followed by cooling to room temperature. The dispersion was then centrifuged, washed, dried, and ground to obtain pretreated carbon black powder. The carbon black content in the dispersion was 1% by mass.

[0026] Step 2: The PTCB powder prepared above was dispersed in an ethanol solution and ultrasonically treated for 40 min at an ultrasonic frequency of 30 kHz to obtain a PTCB dispersion. Polyethylene glycol (PEG-8000) was then added to the PTCB dispersion, and the mixture was heated at 60°C and stirred at 2000 rpm for 2 h. Polyvinyl butyral (PVP) was then added to the PTCB dispersion, and the mixture was stirred for 2 h under the same conditions to obtain mixture A. Mixture A was filtered, washed, and dried to obtain functionalized carbon black powder. In mixture A, the mass fraction of PTCB was 1%, and the mass fractions of PEG and PVP were both 0.5%.

[0027] Step 3: Disperse TiO2 nanoparticles in a mixed solvent composed of n-butanol, ethanol, xylene, and polyethylene glycol (PEG-8000) to prepare a TiO2 nanoparticle suspension. The content of n-butanol is 30%, the content of ethanol is 17%, the content of xylene is 22%, and the content of polyethylene glycol is 1%. Add the FCB powder prepared in Step 2 to the TiO2 nanoparticle suspension, stir at 2000 rpm for 20 min at room temperature, and then sonicate at 30 kHz for 60 min to obtain suspension A. Adjust the pH of suspension A to 10 with ammonia. The mixture was stirred at 2000 rpm for 10 h at room temperature. Then, polyvinyl butyral (PVB), dibutyl phthalate (DBP), and butyl benzyl phthalate (BBP) were added to suspension A to obtain mixture A. Mixture A was heated at 40 °C and stirred at 2000 rpm for 10 min, followed by ultrasonic treatment at 30 kHz for 1 h to finally obtain a well-dispersed TiO2 / FCB precursor slurry. In mixture A, the mass fraction of FCB powder was 0.1%, the mass fraction of TiO2 nanoparticles was 15%, the mass fraction of PVB was 3%, and the mass fractions of DBP and BBP were 2%.

[0028] This embodiment uses Bi-2212 wire as the high-temperature superconducting material. The application of the titanium dioxide-based self-peeling insulating layer slurry obtained in the above preparation process is explained. Specifically, the application method includes the following steps: S1: Immerse the cleaned Bi-2212 wire in the TiO2 / FCB precursor slurry prepared above, and pull the wire out of the slurry at a retraction speed of 0.5m / s using the dip coating method. Dry the Bi-2212 wire coated with the wet coating at 120°C to obtain a pretreated film on the Bi-2212 wire.

[0029] S2: The Bi-2212 wire with a pre-treated film on its surface is placed in a tube furnace for heat treatment. The specific heat treatment process includes: first, heating to 420℃ at a rate of 40℃ / h and holding at that temperature for 2 hours; then heating to 630℃ at a rate of 60℃ / h and holding at that temperature for 0.5 hours; then heating to 830℃ at a rate of 50℃ / h and holding at that temperature for 30 hours; then cooling to 800℃ at a rate of 1℃ / h and holding at that temperature for 20 hours; and finally cooling to room temperature with the furnace. Finally, a titanium dioxide-based self-peeling insulating layer is prepared on the Bi-based superconducting wire.

[0030] The insulating layer prepared in this embodiment exhibits a loose and porous structure, which can provide oxygen diffusion channels for the full phase formation of the superconducting core wire; on the other hand, it can also increase the brittleness of the coating, making it easier to peel off from the substrate.

[0031] Example 2 The preparation method of the titanium dioxide-based self-peeling insulating layer paste in this embodiment includes the following steps: Step 1: First, disperse a certain amount of raw carbon black (CB) powder in 1.5 mol·L⁻¹ -1 In a nitric acid solution, the mixture was stirred at 1600 rpm for 30 min at room temperature, followed by ultrasonic treatment at 50 kHz for 60 min to obtain a carbon black powder dispersion. The carbon black powder dispersion was then heated at 80℃ and stirred at 1600 rpm for 20 h, followed by cooling to room temperature. The dispersion was then centrifuged, washed, dried, and ground to obtain pretreated carbon black powder. The carbon black content in the dispersion was 2% by mass.

[0032] Step 2: The PTCB powder prepared above is dispersed in an ethanol solution and ultrasonically treated at a frequency of 50 kHz for 60 min to obtain a PTCB dispersion. Polyethylene glycol (PEG-6000) is then added to the PTCB dispersion, and the mixture is heated at 70°C and stirred at 1800 rpm for 2 h. Polyvinyl butyral (PVP) is then added to the PTCB dispersion, and the mixture is stirred for 2 h under the same conditions to obtain mixture A. Mixture A is filtered, washed, and dried to obtain functionalized carbon black powder. In mixture A, the mass fraction of PTCB is 1%, and the mass fractions of PEG and PVP are both 1.5%.

[0033] Step 3: Disperse TiO2 nanoparticles in a mixed solvent composed of n-butanol, ethanol, xylene, and polyethylene glycol (PEG-6000) to prepare a TiO2 nanoparticle suspension. The content of n-butanol is 31%, the content of ethanol is 18%, the content of xylene is 22%, and the content of polyethylene glycol is 2%. Add the FCB powder prepared in Step 2 to the TiO2 nanoparticle suspension, stir at 1900 rpm for 30 min at room temperature, and then sonicate at 50 kHz for 50 min to obtain suspension A. Adjust the pH of suspension A to 10.5 with ammonia. The mixture was stirred at 1800 rpm for 12 h at room temperature. Then, polyvinyl butyral (PVB), dibutyl phthalate (DBP), and butyl benzyl phthalate (BBP) were added to suspension A to obtain mixture A. Mixture A was heated at 50 °C and stirred at 1600 rpm for 20 min, followed by ultrasonic treatment at 50 kHz for 2 h to finally obtain a well-dispersed TiO2 / FCB precursor slurry. In mixture A, the mass fraction of FCB powder was 0.2%, the mass fraction of TiO2 nanoparticles was 16%, the mass fraction of PVB was 5%, and the mass fractions of DBP and BBP were 1.5%.

[0034] This embodiment uses Bi-2212 wire as the high-temperature superconducting material. The application of the titanium dioxide-based self-peeling insulating layer slurry obtained in the above preparation process is explained. Specifically, the application method includes the following steps: S1: Immerse the cleaned Bi-2212 wire in the TiO2 / FCB precursor slurry prepared above, and pull the wire out of the slurry at a retraction speed of 1m / s using the dip coating method. Dry the Bi-2212 wire coated with the wet coating at 100°C to obtain a pretreated film on the Bi-2212 wire.

[0035] S2: The Bi-2212 wire with a pre-treated film on its surface is placed in a tube furnace for heat treatment. The specific heat treatment process includes: first, heating to 430℃ at a rate of 50℃ / h and holding for 2 hours, then heating to 640℃ at a rate of 70℃ / h and holding for 0.5 hours, then heating to 830℃ at a rate of 60℃ / h and holding for 40 hours, then cooling to 800-810℃ at a rate of 3℃ / h and holding for 15 hours, and then cooling to room temperature with the furnace. Finally, a titanium dioxide-based self-peeling insulating layer is prepared on the Bi-based superconducting wire.

[0036] The insulating layer prepared in this embodiment exhibits a loose and porous structure, which can provide oxygen diffusion channels for the full phase formation of the superconducting core wire; on the other hand, it can also increase the brittleness of the coating, making it easier to peel off from the substrate.

[0037] Example 3 The preparation method of the titanium dioxide-based self-peeling insulating layer paste in this embodiment includes the following steps: Step 1: First, disperse a certain amount of raw carbon black (CB) powder in 2.0 mol·L⁻¹ -1 In a nitric acid solution, the mixture was stirred at 1700 rpm for 40 min at room temperature, followed by ultrasonic treatment at 70 kHz for 70 min to obtain a carbon black powder dispersion. The carbon black powder dispersion was then heated at 90°C and stirred at 1700 rpm for 18 h, followed by cooling to room temperature. The dispersion was then centrifuged, washed, dried, and ground to obtain pretreated carbon black powder. The carbon black content in the dispersion was 3% by mass. Step 2: The PTCB powder prepared above is dispersed in an ethanol solution and ultrasonically treated for 70 min at an ultrasonic frequency of 70 kHz to obtain a PTCB dispersion. Polyethylene glycol (PEG-6000) is then added to the PTCB dispersion, and the mixture is heated at 70°C and stirred at 1700 rpm for 2 h. Polyvinyl butyral (PVP) is then added to the PTCB dispersion, and the mixture is stirred for 2 h under the same conditions to obtain mixture A. Mixture A is filtered, washed, and dried to obtain functionalized carbon black powder. In mixture A, the mass fraction of PTCB is 1%, and the mass fractions of PEG and PVP are both 3%.

[0038] Step 3: Disperse TiO2 nanoparticles in a mixed solvent composed of n-butanol, ethanol, xylene, and polyethylene glycol (PEG-6000) to prepare a TiO2 nanoparticle suspension. The content of n-butanol is 31%, the content of ethanol is 17%, the content of xylene is 23%, and the content of polyethylene glycol is 2%. Add the FCB powder prepared in Step 2 to the TiO2 nanoparticle suspension, stir at 1800 rpm for 40 min at room temperature, and then sonicate at 70 kHz for 60 min to obtain suspension A. Adjust the pH of suspension A to 11 with ammonia. The mixture was stirred at 1700 rpm for 13 h at room temperature. Then, polyvinyl butyral (PVB), dibutyl phthalate (DBP), and butyl benzyl phthalate (BBP) were added to suspension A to obtain mixture A. Mixture A was heated at 60 °C and stirred at 1900 rpm for 10 min, followed by ultrasonic treatment at 70 kHz for 2 h to finally obtain a well-dispersed TiO2 / FCB precursor slurry. In mixture A, the mass fraction of FCB powder was 0.3%, the mass fraction of TiO2 nanoparticles was 18%, the mass fraction of PVB was 7%, and the mass fractions of DBP and BBP were 1.5%.

[0039] This embodiment uses Bi-2212 wire as the high-temperature superconducting material. The application of the titanium dioxide-based self-peeling insulating layer slurry obtained in the above preparation process is explained. Specifically, the application method includes the following steps: S1: Immerse the cleaned Bi-2212 wire in the TiO2 / FCB precursor slurry prepared above, and pull the wire out of the slurry at a retraction speed of 1.5m / s using the dip coating method. Dry the Bi-2212 wire coated with the wet coating at 150°C to obtain a pretreated film on the Bi-2212 wire.

[0040] S2: The Bi-2212 wire with a pre-treated film on its surface is placed in a tube furnace for heat treatment. The specific heat treatment process includes: first, heating to 450℃ at a rate of 60℃ / h and holding at that temperature for 1.5h; then heating to 650℃ at a rate of 80℃ / h and holding at that temperature for 1h; then heating to 830℃ at a rate of 80℃ / h and holding at that temperature for 40h; then cooling to 810℃ at a rate of 5℃ / h and holding at that temperature for 10h; and finally cooling to room temperature with the furnace. A titanium dioxide-based self-peeling insulating layer is then prepared on the Bi-based superconducting wire.

[0041] The insulating layer prepared in this embodiment exhibits a loose and porous structure, which can provide oxygen diffusion channels for the full phase formation of the superconducting core wire; on the other hand, it can also increase the brittleness of the coating, making it easier to peel off from the substrate.

[0042] Example 4 The preparation method of the titanium dioxide-based self-peeling insulating layer paste in this embodiment includes the following steps: Step 1: First, disperse a certain amount of raw carbon black (CB) powder in 2.5 mol·L⁻¹ -1 The carbon black powder dispersion was obtained by stirring the solution at 1900 rpm for 60 min at room temperature in nitric acid solution, followed by ultrasonic treatment at 100 kHz for 40 min. The carbon black powder dispersion was then heated at 100°C and stirred at 1800 rpm for 18 h, then cooled to room temperature. After centrifugation, washing, drying, and grinding, pretreated carbon black powder was finally obtained; the carbon black content in the dispersion was 3% by mass.

[0043] Step 2: The PTCB powder prepared above is dispersed in an ethanol solution and ultrasonically treated at a frequency of 100 kHz for 40 min to obtain a PTCB dispersion. Polyethylene glycol (PEG-4000) is then added to the PTCB dispersion, and the mixture is heated at 80°C and stirred at 1600 rpm for 2 h. Polyvinyl butyral (PVP) is then added to the PTCB dispersion, and the mixture is stirred for 2 h under the same conditions to obtain mixture A. Mixture A is filtered, washed, and dried to obtain functionalized carbon black powder. In mixture A, the mass fraction of PTCB is 1%, and the mass fractions of PEG and PVP are both 5%.

[0044] Step 3: Disperse TiO2 nanoparticles in a mixed solvent composed of n-butanol, ethanol, xylene, and polyethylene glycol (PEG-4000) to prepare a TiO2 nanoparticle suspension. The content of n-butanol is 32%, the content of ethanol is 18%, the content of xylene is 23%, and the content of polyethylene glycol is 3%. Add the FCB powder prepared in Step 2 to the TiO2 nanoparticle suspension, stir at 1900 rpm for 40 min at room temperature, and then sonicate at 100 kHz for 40 min to obtain suspension A. Adjust the pH of suspension A to 11 with ammonia. The mixture was stirred at 1500 rpm for 15 h at room temperature. Then, polyvinyl butyral (PVB), dibutyl phthalate (DBP), and butyl benzyl phthalate (BBP) were added to suspension A to obtain mixture A. Mixture A was heated at 60 °C and stirred at 2000 rpm for 10 min, followed by ultrasonic treatment at 100 kHz for 1 h to finally obtain a well-dispersed TiO2 / FCB precursor slurry. In mixture A, the mass fraction of FCB powder was 0.4%, the mass fraction of TiO2 nanoparticles was 20%, the mass fraction of PVB was 3%, and the mass fractions of DBP and BBP were 1%.

[0045] This embodiment uses Bi-2212 wire as the high-temperature superconducting material. The application of the titanium dioxide-based self-peeling insulating layer slurry obtained in the above preparation process is explained. Specifically, the application method includes the following steps: S1: Immerse the cleaned Bi-2212 wire in the TiO2 / FCB precursor slurry prepared above, and pull the wire out of the slurry at a retraction speed of 2m / s using the dip coating method. Dry the Bi-2212 wire coated with the wet coating at 80°C to obtain a pretreated film on the Bi-2212 wire.

[0046] S2: The Bi-2212 wire with a pre-treated film on its surface is placed in a tube furnace for heat treatment. The specific heat treatment process includes: first, heating to 460℃ at a rate of 60℃ / h and holding at that temperature for 1.5h; then heating to 660℃ at a rate of 80℃ / h and holding at that temperature for 0.5h; then heating to 830℃ at a rate of 100℃ / h and holding at that temperature for 30h; then cooling to 810℃ at a rate of 5℃ / h and holding at that temperature for 10h; and finally cooling to room temperature with the furnace. A titanium dioxide-based self-peeling insulating layer is then prepared on the Bi-based superconducting wire.

[0047] The insulating layer prepared in this embodiment exhibits a loose and porous structure, which can provide oxygen diffusion channels for the full phase formation of the superconducting core wire; on the other hand, it can also increase the brittleness of the coating, making it easier to peel off from the substrate.

[0048] Example 5 The preparation method of the titanium dioxide-based self-peeling insulating layer paste in this embodiment includes the following steps: Step 1: First, disperse a certain amount of raw carbon black (CB) powder in 3.0 mol·L⁻¹ -1 In a nitric acid solution, the mixture was stirred at 2000 rpm for 30 min at room temperature, followed by ultrasonic treatment at 50 kHz for 60 min to obtain a carbon black powder dispersion. The carbon black powder dispersion was then heated at 80℃ and stirred at 2000 rpm for 18 h, followed by cooling to room temperature. The dispersion was then centrifuged, washed, dried, and ground to obtain pretreated carbon black powder. The carbon black content in the dispersion was 2% by mass.

[0049] Step 2: The PTCB powder prepared above is dispersed in an ethanol solution and ultrasonically treated at a frequency of 50 kHz for 60 min to obtain a PTCB dispersion. Polyethylene glycol (PEG-2000) is then added to the PTCB dispersion, and the mixture is heated at 60°C and stirred at 1500 rpm for 3 h. Polyvinyl butyral (PVP) is then added to the PTCB dispersion, and the mixture is stirred for 3 h under the same conditions to obtain mixture A. Mixture A is filtered, washed, and dried to obtain functionalized carbon black powder. In mixture A, the mass fraction of PTCB is 1%, and the mass fractions of PEG and PVP are both 3%.

[0050] Step 3: Disperse TiO2 nanoparticles in a mixed solvent composed of n-butanol, ethanol, xylene, and polyethylene glycol (PEG-2000) to prepare a TiO2 nanoparticle suspension. The content of n-butanol is 33%, the content of ethanol is 19%, the content of xylene is 24%, and the content of polyethylene glycol is 3%. Add the FCB powder prepared in Step 2 to the TiO2 nanoparticle suspension, stir at 2000 rpm for 30 min at room temperature, and then sonicate at 50 kHz for 60 min to obtain suspension A. Adjust the pH of suspension A to 10.5 with ammonia. The mixture was stirred at 1900 rpm for 12 h at room temperature. Then, polyvinyl butyral (PVB), dibutyl phthalate (DBP), and butyl benzyl phthalate (BBP) were added to suspension A to obtain mixture A. Mixture A was heated at 60 °C and stirred at 1500 rpm for 30 min, followed by ultrasonic treatment at 50 kHz for 2 h to finally obtain a well-dispersed TiO2 / FCB precursor slurry. In mixture A, the mass fraction of FCB powder was 0.5%, the mass fraction of TiO2 nanoparticles was 18%, the mass fraction of PVB was 10%, and the mass fractions of DBP and BBP were 1%.

[0051] This embodiment uses Bi-2212 wire as the high-temperature superconducting material. The application of the titanium dioxide-based self-peeling insulating layer slurry obtained in the above preparation process is explained. Specifically, the application method includes the following steps: S1: Immerse the cleaned Bi-2212 wire in the TiO2 / FCB precursor slurry prepared above, and pull the wire out of the slurry at a retraction speed of 0.5m / s using the dip coating method. Dry the Bi-2212 wire coated with the wet coating at 150°C to obtain a pretreated film on the Bi-2212 wire.

[0052] S2: The Bi-2212 wire with a pre-treated film on its surface is placed in a tube furnace for heat treatment. The specific heat treatment process includes: first, heating to 450℃ at a rate of 60℃ / h and holding for 2 hours, then heating to 650℃ at a rate of 80℃ / h and holding for 0.5 hours, then heating to 830℃ at a rate of 60℃ / h and holding for 36 hours, then cooling to 810℃ at a rate of 2℃ / h and holding for 12 hours, and then cooling to room temperature with the furnace. Finally, a titanium dioxide-based self-peeling insulation layer is prepared on the Bi-based superconducting wire.

[0053] See Figure 1 and Figure 2 In this embodiment, the titanium dioxide-based self-peeling insulation layer prepared on the surface of Bi-2212 wire can completely cover the surface of Bi-2212 wire. Microscopically, it exhibits a loose and porous structure with relatively uniform grain size and no obvious silver leakage. On the other hand, after the heat treatment, some insulation layers have fallen off, and their adhesion to the metal sheath is significantly weakened, making it easy to achieve self-peeling.

[0054] Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort should fall within the scope of protection of the present invention.

[0055] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing a titanium dioxide-based self-peeling insulating layer paste, characterized in that, The process includes the following: FCB powder was added to TiO2 nanoparticle dispersion to mix the FCB powder evenly, resulting in suspension A. The pH of suspension A is adjusted to 10-11 with ammonia water and stirred at 1500-2000 rpm for 10-15 h. Then, polyvinyl butyral, dibutyl phthalate, and butyl benzyl phthalate are added, and the mixture is heated and stirred at 40-60℃ for 10-30 min. After that, it is ultrasonically treated at an ultrasonic frequency of 30-100 kHz for 1-3 h to obtain a titanium dioxide-based self-exfoliating insulating layer slurry. In the titanium dioxide-based self-exfoliating insulating layer slurry, the mass fraction of FCB powder is 0.1%-0.5%, the mass fraction of TiO2 nanoparticles is 15%-20%, the mass fraction of polyvinyl butyral is 3%-10%, the mass fraction of dibutyl phthalate is 1%-2%, and the mass fraction of butyl benzyl phthalate is 1%-2%. The preparation process of FCB powder includes: Add carbon black powder to 1-3 mol·L -1 The carbon black powder was dissolved in a nitric acid solution, stirred until homogeneous, and then ultrasonically dispersed to obtain a carbon black powder dispersion. The dispersion was then heated and stirred at 80-100℃ for 18-22 hours, followed by cooling, solid-liquid separation, washing, drying, and grinding to obtain pretreated carbon black powder. The mass fraction of carbon black in the carbon black powder dispersion was 1%-3%. Pretreated carbon black powder was dispersed in an ethanol solution and ultrasonically dispersed. Then, polyethylene glycol was added, and the mixture was heated at 60-80°C and stirred at 1500-2000 rpm for 2-3 hours. Polyvinyl butyral was then added and stirring was continued for 2-3 hours to obtain mixture A. Solid-liquid separation, washing, and drying were then performed to obtain the FCB powder. In mixture A, the mass fraction of pretreated carbon black powder was 1%-5%, the mass fraction of polyethylene glycol was 0.5%-5%, and the mass fraction of polyvinyl butyral was 0.5%-5%.

2. The method for preparing a titanium dioxide-based self-peeling insulating layer paste according to claim 1, characterized in that, The solvent components in the TiO2 nanopowder dispersion include n-butanol, ethanol, xylene, and polyethylene glycol; wherein the content of n-butanol is 30%-33%, the content of ethanol is 16%-19%, the content of xylene is 21%-24%, and the content of polyethylene glycol is 1%-3%.

3. The method for preparing a titanium dioxide-based self-peeling insulating layer paste according to claim 1 or 2, characterized in that, The average molecular weight of the polyethylene glycol is 2000-8000.

4. The method for preparing a titanium dioxide-based self-peeling insulating layer paste according to claim 1, characterized in that, Add FCB powder to TiO2 nanopowder dispersion, stir at 1500-2000 rpm for 20-40 min at room temperature, and then sonicate at an ultrasonic frequency of 30-100 kHz for 40-60 min to mix the FCB powder evenly and obtain suspension A. Add carbon black powder to 1-3 mol·L -1 In a nitric acid solution, the mixture is stirred at 1500-2000 rpm for 20-60 min at room temperature, and then ultrasonically treated at an ultrasonic frequency of 30-100 kHz for 40-90 min to obtain a carbon black powder dispersion. The pretreated carbon black powder was dispersed in an ethanol solution and ultrasonically treated for 40-90 min at an ultrasonic frequency of 30-100 kHz, and then polyethylene glycol was added.

5. The method for preparing a titanium dioxide-based self-peeling insulating layer paste according to claim 1, characterized in that, The particle size of the carbon black powder is 30-80 nm; The TiO2 nanoparticles have a particle size of 20-100 nm.

6. A titanium dioxide-based self-peeling insulating layer paste prepared by any one of the preparation methods of claims 1-5.

7. The application of the titanium dioxide-based self-peeling insulating layer paste according to claim 6, characterized in that, The titanium dioxide-based self-peeling insulating layer slurry is used to prepare an insulating layer on the surface of a high-temperature superconducting material.

8. The application according to claim 7, characterized in that, The process of preparing an insulating layer on the surface of a high-temperature superconducting material using the aforementioned titanium dioxide-based self-peeling insulating layer slurry includes: The titanium dioxide-based self-peeling insulating layer slurry is coated onto the surface of a high-temperature superconducting material and then dried to form a pre-treatment film on the surface of the high-temperature superconducting material. The high-temperature superconducting material coated with the pretreated film is subjected to heat treatment. The specific heat treatment process includes: first, heating to 420-460℃ at a rate of 40-60℃ / h and holding at that temperature for 1.5-2h; then heating to 630-660℃ at a rate of 60-80℃ / h and holding at that temperature for 0.5-1h; then heating to 830℃ at a rate of 50-100℃ / h and holding at that temperature for 30-50h; then cooling to 800-810℃ at a rate of 1-5℃ / h and holding at that temperature for 10-20h; and finally cooling to room temperature in the furnace. Finally, a titanium dioxide-based self-peeling insulating layer is prepared on the surface of the high-temperature superconducting material.

9. The application according to claim 8, characterized in that, The titanium dioxide-based self-peeling insulating layer slurry is coated onto the surface of a high-temperature superconducting material and then dried at 80-150°C to form a pre-treated film on the surface of the high-temperature superconducting material.

10. The application according to claim 7, characterized in that, The high-temperature superconducting material includes Bi-based superconducting wires.

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