Lightweight superconductive carbon fiber composite cable and preparation method thereof
By grafting multifunctional silane-polyamic acid nanocoatings onto the surface of carbon fiber bundles and employing a sol-gel process, lightweight superconducting cables were fabricated. This solved the problems of superconducting cable self-weight and interface stability, achieving efficient superconducting transmission and thermal management, and improving cable reliability and production efficiency.
Patent Information
- Application Number
- CN202511971077.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-12-25
- Publication Date
- 2026-03-20
AI Technical Summary
Existing superconducting cables are heavy, have poor flexibility, are prone to interface peeling and microcracks, and lack microchannel or heat-conducting network designs integrated with the cable structure, which limits their application in long-distance, high-power transmission and high-frequency fields.
A YBa2Cu3O7-x superconducting layer was prepared by in-situ grafting of multifunctional silane-polyamic acid nanocoating onto the surface of carbon fiber bundles, combined with sol-gel and supercritical CO2 drying processes. The layer was then integrated with insulation, shielding, and sheathing to form a continuous microchannel cooling network.
It achieves lightweight, high-strength superconducting transmission performance, improves current carrying capacity and thermal management efficiency, avoids local thermal collapse, and enhances the reliability and production efficiency of cables in low-temperature cycling.
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Figure CN121709347A_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of carbon fiber composite materials, specifically relating to a lightweight superconducting carbon fiber composite cable and its preparation method. Background Technology
[0002] With the increasing demands for efficiency and stability in modern energy transmission and high-frequency signal transmission, superconducting cables have attracted significant attention due to their near-zero resistance and lossless transmission capabilities in low-temperature environments. Existing superconducting cables typically employ metal or glass fiber reinforcement structures, covered with multiple layers of insulation and shielding materials, and then have a high-temperature ceramic superconducting layer attached to its surface or interior. However, these cables are heavy, lack flexibility, and are prone to delamination and microcracks at the interface, severely limiting the continuity and current-carrying capacity of the superconducting layer along its length. The mismatch in thermal expansion coefficients and chemical properties between the metal and ceramic superconducting phases further exacerbates the risk of interfacial fatigue failure during cyclic cooling. Furthermore, to ensure the safe operation of the power supply and the superconducting layer, an external liquid nitrogen or helium circulation system is required for cooling, but the lack of an integrated microchannel or heat-conducting network design within the cable structure leads to frequent localized "thermal collapse" phenomena, hindering the widespread application of superconducting cables in long-distance, high-power transmission and high-frequency fields.
[0003] Carbon fiber, as an advanced composite material with lightweight, high strength and excellent thermal conductivity, has been widely used in traditional fields, but its application in superconducting cables has not yet overcome key difficulties: surface chemical inertness leads to poor wetting and bonding performance with ceramic superconducting precursors, and conventional surface treatments cannot maintain interface stability during subsequent high-temperature heat treatment. Summary of the Invention
[0004] To address the shortcomings mentioned in the background art, the present invention aims to provide a lightweight superconducting carbon fiber composite cable and its preparation method. This method involves in-situ grafting a silane-polyamic acid nanocoating onto carbon fiber bundles, combined with a sol-gel and supercritical CO2 drying process to prepare YBa2Cu3O. 7-x The superconducting layer, along with integrated insulation, shielding, and sheathing, achieves lightweight, strong interfacial adhesion, and excellent superconducting transmission performance.
[0005] The objective of this invention can be achieved through the following technical solutions: A lightweight superconducting carbon fiber composite cable, comprising a carbon fiber bundle layer, a multifunctional composite coating, a superconducting functional layer, an insulation layer, a shielding layer, and a protective layer. The carbon fiber bundle layer is closely attached to the outside of the superconducting functional layer. The multifunctional composite coating covers the outside of the carbon fiber bundle layer. The insulation layer covers the outside of the multifunctional composite coating. The shielding layer surrounds the outer wall of the insulation layer. The protective layer covers the outside of the shielding layer. The multifunctional composite coating comprises the following raw materials in parts by weight: 60-65 parts of polyimide precursor; 8-12 parts of 4-aminopropyltrimethoxysilane; 1-2 parts of glutaraldehyde; 3-5 parts of graphene nanosheets; and YBa2Cu3O. 7-x 15-20 parts of precursor.
[0006] More preferably, the method for preparing the polyimide precursor specifically includes the following steps: S101. Weigh out tetraphenyltetrahydride and p-phenylenediamine in a molar ratio of 1:1, dissolve them in N-methylpyrrolidone solvent, and obtain a homogeneous reaction mixture; S102. Under nitrogen protection, the mixture is stirred to allow tetraphenyltetrahydride and p-phenylenediamine to undergo a condensation reaction, generating a viscous and homogeneous polyamic acid solution, which can then be allowed to stand for a certain period of time. S103. The generated polyamic acid solution is filtered through a microporous membrane to remove unreacted dianhydride or diamine particles. The filtrate is concentrated in a vacuum container to remove some N-methylpyrrolidone. After a small amount of inert gas is introduced into the solution for protection, a stable polyamic acid precursor solution is obtained.
[0007] More preferably, YBa2Cu3O 7-x The preparation method of the precursor specifically includes the following steps: S201. Weigh out yttrium acetate, barium acetate and copper acetate in a molar ratio of Y∶Ba∶Cu = 1∶2∶3, and dissolve them in 2-methoxyethanol to obtain three homogeneous metal acetate solutions. S202. Mix the above metal acetate solutions, add an equimolar amount of citric acid and stir, then add an equal volume of ethylene glycol, and continue heating and stirring until the solution becomes clear and has a uniform viscosity, forming YBa2Cu3O. 7-x Precursor sol; S203. The obtained sol was allowed to stand at room temperature for several hours to mature, then filtered through a filter membrane to remove unreacted particles, yielding a transparent and stable YBa2Cu3O. 7-x Precursor.
[0008] More preferably, the thickness of the multifunctional composite coating is 50–300 nm.
[0009] More preferably, the superconducting functional layer is YBa2Cu3O deposited via a sol-gel method.7-x The precursor is a ceramic superconducting layer obtained by pre-firing, calcining and annealing heat treatment.
[0010] More preferably, the insulating layer is a polytetrafluoroethylene film, the shielding layer is an annular metal tube, and the protective layer is a polyurethane coating layer.
[0011] A method for preparing a lightweight superconducting carbon fiber composite cable includes the following steps: S1. The carbon fiber bundles are immersed in an organic solvent for ultrasonic cleaning, rinsed with deionized water and vacuum dried, then treated with oxygen plasma, purged with nitrogen and collected for later use. S2. Impregnate the carbon fiber bundles obtained in step S1 with a substrate containing polyamic acid precursor, 4-aminopropyltrimethoxysilane, glutaraldehyde, graphene nanosheets, and YBa2Cu3O. 7-x A multifunctional composite coating is formed in the composite solution of the precursor; S3. The carbon fiber bundles obtained in step S2 are subjected to sol-gel impregnation and heat treatment to obtain a superconducting functional layer; S4. Fix the composite unit obtained in step S3, spirally wrap it with a polytetrafluoroethylene insulation layer, braid a metal shielding layer, place the braided fiber bundle in a polyurethane extruder mold, extrude the polyurethane sheath, pass the extruded cable through a heating pipe, let it stand at room temperature, and cut the finished cable segment according to the design length to obtain the lightweight superconducting carbon fiber composite cable.
[0012] More preferably, after step S2, the multifunctional composite coating is subjected to nanoimprint microstructuring treatment to form parallel microgrooves on the coating surface, which are used to induce the directional growth of superconducting grains.
[0013] More preferably, the number of cycles of sol-gel impregnation and pre-calcination, calcination, and annealing heat treatment in step S3 is 3 to 5.
[0014] More preferably, in step S3, after each sol-gel impregnation, supercritical CO2 drying is performed first, followed by pre-calcination, calcination, and annealing cycles to generate a continuous microchannel cooling network within the superconducting functional layer.
[0015] The beneficial effects of this invention are: This invention employs an innovative technique of in-situ grafting a multifunctional silane-polyamic acid nanocoating onto the surface of carbon fiber bundles. This significantly enhances the chemical bonding and interfacial wetting properties between the carbon fibers and the superconducting precursor, effectively eliminating the interfacial delamination and microcrack problems commonly found in traditional superconducting cables. Through a heat treatment process combining sol-gel and supercritical CO2 drying, YBa2Cu3O4 with oriented crystal structure and a continuous microchannel cooling network is generated in-situ on the coating. 7-xThe superconducting layer enables high critical current density and stable superconducting transmission. The carbon fiber composite material itself possesses high strength and low density, resulting in a significantly lower linear density and a much lighter weight than existing metal or glass fiber reinforced superconducting cables, greatly improving the ease of laying and maintenance. Furthermore, the parallel microgroove structure formed by nanoimprinting not only induces the orientation and growth of superconducting grains but also improves thermal management efficiency, preventing localized thermal collapse and enhancing the cable's reliability during low-temperature cycling. The overall process is highly integrated and structurally simple, eliminating segmented winding and multiple gluing processes, significantly shortening the production cycle and reducing manufacturing costs. Attached Figure Description
[0016] The invention will now be further described with reference to the accompanying drawings.
[0017] Figure 1 A bar chart comparing the thermal conductivity of cables prepared in Examples 1-3 and Comparative Examples 1-2; Figure 2 Line graphs showing the thermal cycling performance retention rate of cables prepared in Examples 1-3 and Comparative Examples 1-2. Detailed Implementation
[0018] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0019] Example 1 I. Preparation of polyimide precursors In a stirred, temperature-controlled, and nitrogen-protected reactor, 200 g of N-methylpyrrolidone was added, and nitrogen was purged for 30 min. Then, 10.80 g of p-phenylenediamine was added, and the mixture was stirred at room temperature for 15 min until completely dissolved, yielding a transparent homogeneous solution. The reactor was cooled to 2 °C in an ice-water bath, and while maintaining a temperature of 0–5 °C, 21.81 g of tetraphenyltetrahydric anhydride was slowly added to the solution in three portions. After each addition, the mixture was stirred for 5 min, and the total reaction time was maintained at 2 h to generate polyamic acid. After the reaction was completed, the cooling device was turned off and the system was allowed to rise to room temperature naturally. Stirring was continued for 4 hours to allow the high molecular weight segments to fully extend and stabilize. The resulting polyamic acid solution was filtered through a 0.45 μm polytetrafluoroethylene membrane. The filtrate was concentrated under reduced pressure at 30 mbar in a 50 ℃ water bath until the solid content in the solution reached 15 ± 1 wt%. A small amount of nitrogen was introduced into the concentrated polyamic acid solution for replacement. The solution was then transferred to a nitrogen-protected brown glass bottle and stored at 4 ℃ for later use. This is the polyimide precursor.
[0020] II. YBa2Cu3O 7-x Preparation of precursors Weigh 3.80 g of yttrium acetate, 9.60 g of barium acetate, and 14.40 g of copper acetate, and separately add them to 100 mL of 2-methoxyethanol. Stir at room temperature until completely clear and well mixed. Then add 9.00 g of citric acid, heat to 50 °C, and stir for 30 min to allow the metal ions to fully complex with the citric acid. Slowly add 50 mL of ethylene glycol to the system, maintaining the temperature at 50 °C and stirring for 20 min to form a homogeneous and transparent sol. Cool the resulting sol to room temperature and allow it to stand at room temperature for 4 h to stabilize the complex network. Filter the matured sol through a 0.45 μm PTFE membrane to remove undissolved impurities. Place the filtrate in a 60 °C water bath and evaporate under reduced pressure to a solution volume of approximately 80 mL to obtain YBa₂Cu₃O. 7-x Precursor sol.
[0021] III. Preparation of Lightweight Superconducting Carbon Fiber Composite Cables A lightweight superconducting carbon fiber composite cable includes a carbon fiber bundle layer, a multifunctional composite coating, a superconducting functional layer, an insulation layer, a shielding layer, and a protective layer. The carbon fiber bundle layer is closely attached to the outside of the superconducting functional layer. The multifunctional composite coating covers the outside of the carbon fiber bundle layer. The insulation layer covers the outside of the multifunctional composite coating. The shielding layer surrounds the outer wall of the insulation layer. The protective layer covers the outside of the shielding layer.
[0022] The multifunctional composite coating comprises the following raw materials in parts by weight: 60 parts polyimide precursor; 8 parts 4-aminopropyltrimethoxysilane; 1 part glutaraldehyde; 3 parts graphene nanosheets; and YBa2Cu3O. 7-x 15 parts of precursor.
[0023] The preparation method of the lightweight superconducting carbon fiber composite cable includes the following steps: S1. Take the carbon fiber bundle, first immerse it in ethanol for ultrasonic cleaning, rinse it three times with deionized water, and then dry it in a vacuum drying oven; then place the carbon fiber bundle in a plasma etching chamber, use oxygen as the working gas, treat it for 10 minutes, then purge it with nitrogen and collect it for later use. S2. Add N-methylpyrrolidone to a stirred tank, stir, and then sequentially add polyamic acid precursor, 4-aminopropyltrimethoxysilane, glutaraldehyde, graphene nanosheets, and YBa2Cu3O. 7-x Precursor sol, continue stirring; immerse carbon fiber bundles in it, take them out and spin dry, then transfer them to an oven for crosslinking for 4 h to form a multifunctional composite coated carbon fiber bundle with a coating thickness of about 100 nm. S3, Impregnate composite coated carbon fiber bundles with YBa2Cu3O 7-xThe precursor sol was spun dry and then subjected to the following steps in sequence: pre-calcination at 620 °C for 30 min, calcination at 780 °C for 1 h, and annealing at 850 °C for 10 h. After cooling to room temperature, the "impregnation-pre-calcination-calcination-annealing" cycle was repeated 3 times to obtain a dense and oriented superconducting functional layer. S4. The composite unit obtained in S3 is clamped in a winding machine at a tension of 5 N and a linear speed of 0.5 m / s, and spirally wound with a polytetrafluoroethylene film; then a stainless steel shielding mesh is woven on the outside of the insulation layer; the woven fiber bundle is fed into a polyurethane extruder, cured in a 60°C water bath, and then left to stand at room temperature for 1 h to obtain the lightweight superconducting carbon fiber composite cable.
[0024] Example 2 Polyimide precursor and YBa2Cu3O 7-x The preparation method of the precursor is the same as in Example 1.
[0025] A lightweight superconducting carbon fiber composite cable includes a carbon fiber bundle layer, a multifunctional composite coating, a superconducting functional layer, an insulation layer, a shielding layer, and a protective layer. The carbon fiber bundle layer is closely attached to the outside of the superconducting functional layer. The multifunctional composite coating covers the outside of the carbon fiber bundle layer. The insulation layer covers the outside of the multifunctional composite coating. The shielding layer surrounds the outer wall of the insulation layer. The protective layer covers the outside of the shielding layer.
[0026] The multifunctional composite coating comprises the following raw materials in parts by weight: 65 parts polyimide precursor; 12 parts 4-aminopropyltrimethoxysilane; 2 parts glutaraldehyde; 5 parts graphene nanosheets; and YBa2Cu3O. 7-x 20 parts of precursor.
[0027] The preparation method of the lightweight superconducting carbon fiber composite cable is the same as that in Example 1.
[0028] Example 3 Polyimide precursor and YBa2Cu3O 7-x The preparation method of the precursor is the same as in Example 1.
[0029] A lightweight superconducting carbon fiber composite cable includes a carbon fiber bundle layer, a multifunctional composite coating, a superconducting functional layer, an insulation layer, a shielding layer, and a protective layer. The carbon fiber bundle layer is closely attached to the outside of the superconducting functional layer. The multifunctional composite coating covers the outside of the carbon fiber bundle layer. The insulation layer covers the outside of the multifunctional composite coating. The shielding layer surrounds the outer wall of the insulation layer. The protective layer covers the outside of the shielding layer.
[0030] The multifunctional composite coating comprises the following raw materials in parts by weight: 62.5 parts polyimide precursor; 10 parts 4-aminopropyltrimethoxysilane; 1.5 parts glutaraldehyde; 4 parts graphene nanosheets; and YBa2Cu3O.7-x 17.5 parts of precursor.
[0031] The preparation method of the lightweight superconducting carbon fiber composite cable is the same as that in Example 1.
[0032] Comparative Example 1 Polyimide precursor and YBa2Cu3O 7-x The preparation method of the precursor is the same as in Example 1.
[0033] A lightweight superconducting carbon fiber composite cable includes a carbon fiber bundle layer, a multifunctional composite coating, a superconducting functional layer, an insulation layer, a shielding layer, and a protective layer. The carbon fiber bundle layer is closely attached to the outside of the superconducting functional layer. The multifunctional composite coating covers the outside of the carbon fiber bundle layer. The insulation layer covers the outside of the multifunctional composite coating. The shielding layer surrounds the outer wall of the insulation layer. The protective layer covers the outside of the shielding layer.
[0034] The multifunctional composite coating does not contain graphene nanosheets, and the other components and contents are the same as in Example 3. The lightweight superconducting carbon fiber composite cable is prepared according to the method in Example 3.
[0035] Comparative Example 2 Polyimide precursor and YBa2Cu3O 7-x The preparation method of the precursor is the same as in Example 1.
[0036] A lightweight superconducting carbon fiber composite cable includes a carbon fiber bundle layer, a multifunctional composite coating, a superconducting functional layer, an insulation layer, a shielding layer, and a protective layer. The carbon fiber bundle layer is closely attached to the outside of the superconducting functional layer. The multifunctional composite coating covers the outside of the carbon fiber bundle layer. The insulation layer covers the outside of the multifunctional composite coating. The shielding layer surrounds the outer wall of the insulation layer. The protective layer covers the outside of the shielding layer.
[0037] The multifunctional composite coating contains no glutaraldehyde, and the other components and contents are the same as in Example 3. The lightweight superconducting carbon fiber composite cable is prepared according to the method in Example 3.
[0038] Performance testing 1. Lightweight performance test Take 5 m of cable segments from each of Examples 1-3 and Comparative Examples 1-2, and weigh three segments from each example on a precision balance to measure their actual length and calculate the linear density (g / m). Then, clamp the same cable segment in a room temperature universal tensile testing machine with a clamping distance of 100 mm at both ends, and load it at a rate of 10 mm / min until fracture, recording the breaking load (N). Calculate the specific strength = breaking load / linear density (N·m / g). The results are shown in Table 1 below.
[0039] Table 1 Lightweight performance results
[0040] As shown in Table 1, the linear densities of Examples 1–3 were all below 0.8 g / m, while the breaking loads were significantly increased, with final specific strengths reaching 538, 544, and 571 N·m / g, respectively, representing an improvement of over 20% compared to Comparative Examples 1 and 2. This indicates that the carbon fiber matrix, in-situ grafted silane-polyamic acid network, nanoimprinted microgrooves, and graphene filler in this invention work together to not only ensure excellent interfacial adhesion between the coating and the superconducting layer, but also to construct a highly efficient thermally conductive and cross-linked support structure in the extremely thin coating. Compared to the comparative samples lacking graphene or cross-linking agents, the examples exhibit significantly enhanced load-bearing capacity with similar or lower weight.
[0041] 2. Critical current density test The cable sample to be tested was cut into straight segments of 50 mm in length, ensuring that the superconducting layer was exposed and the contact area with the probes was flat and undamaged. The sample was fixed in a liquid nitrogen cooling bath at 77 K, maintaining an external magnetic field, with four probes contacting the surface of the superconducting layer at equal intervals. A gradually increasing current was applied externally through a constant current source, and the corresponding voltage drop was recorded simultaneously using a high-sensitivity voltmeter. The current used when the voltage per unit electrical length corresponding to the spacing between the center probes reached the criterion of 1 μV / cm was taken as the critical current Ic. The average value of three tests was taken, and the critical current density Jc was calculated based on the cross-sectional area of the superconducting layer (approximately 0.01 cm²), as shown in Table 2 below.
[0042] Table 2 Critical Current Density Results
[0043] As shown in Table 2, the average critical current density of Examples 1–3 is 1.40 × 10⁻⁶. 5 1.45×10 5 and 1.50×10 5 A / cm² was significantly higher than that of Comparative Example 1 (1.00 × 10⁻⁶). 5 A / cm²) and Comparative Example 2 (1.05×10 5 A / cm²). The silane-polyamic acid network grafted in the interfacial nanocoating effectively enhances the chemical bonding and thermal expansion matching between the carbon fibers and the superconducting precursor, making YBa₂Cu₃O₂... 7-x The superconducting layer maintains its structural integrity and continuity after high-temperature heat treatment. Furthermore, the parallel microgrooves formed by nanoimprinting and the graphene nanofiller together construct highly efficient thermally conductive and grain-oriented growth channels, promoting uniform orientation of the superconducting phase and tight grain boundary connections, thereby significantly improving current-carrying capacity. In contrast, the comparative sample, lacking graphene network or cross-linking agent reinforcement, exhibits uneven grain distribution and interfacial delamination within the superconducting layer, limiting its current-carrying capacity.
[0044] 3. Interface peel strength test The interfacial bond strength between the carbon fiber bundle and the superconducting functional layer was evaluated using a single-fiber peel test. Carbon fiber bundles with the superconducting layer were cut into 30 mm long specimens, with adhesive pads attached to the ends to ensure uniform loading. The specimens were fixed in a universal tensile testing machine with a 10 mm gap between the clamps at both ends and a tensile rate of 1 mm / min until interface failure. The maximum peel load was recorded, and the interfacial peel strength τ = maximum peel load / (width × length) (MPa) was calculated based on the specimen width and superconducting layer length. Five specimens for each sample were tested, and the average value was taken. The tests were conducted under room temperature and drying conditions. The results are shown in Table 3 below.
[0045] Table 3 Interfacial Peel Strength
[0046] As shown in Table 3, the interfacial peel strengths of Examples 1–3 reached 2.50, 2.63, and 2.75 MPa, respectively, representing increases of over 25% and 30% compared to Comparative Example 1 (2.00 MPa) and Comparative Example 2 (2.13 MPa). In the multifunctional nanocoating grafted in situ onto the carbon fiber bundle surface, the silane-polyamic acid network chemically bonds the carbon fibers, strengthening the interfacial adhesion between the matrix and the superconducting precursor. Simultaneously, the glutaraldehyde crosslinking agent forms a stable crosslinked structure within the coating, further improving the coating's mechanical integrity and heat resistance. In contrast, Comparative Example 1 lacks thermal management and stress dispersion channels from graphene nanosheets, leading to a higher likelihood of stress concentration and premature failure during tensile peeling. Comparative Example 2, lacking a crosslinking agent, suffers from an insufficiently dense network structure, limiting its interfacial strength.
[0047] 4. Thermal conductivity measurement Each sample cable was cut into a 10 mm diameter, 1 mm thick sheet, encapsulated with epoxy resin, and polished flat. The specimen was placed in a liquid nitrogen-cooled laser flash measurement instrument, and one side of the sample was heated by a laser pulse. An infrared detector recorded the transient response curve of the back side temperature over time. The thermal diffusivity α = 0.1388·L² / τ½ (L is the thickness) was obtained from the half-peak width time τ½. Then, the thermal conductivity was calculated using the independently measured specific heat capacity Cp (J / kg·K) and density ρ (kg / m³) according to the formula k = α·Cp·ρ. Each sample was measured 3 times and the average value was taken. The results are shown in Table 4 below.
[0048] Table 4 Thermal conductivity
[0049] As shown in Table 4, the thermal conductivity of Examples 1–3 are 4.00, 4.17, and 4.33 W / m·K, respectively, which are much higher than those of Comparative Examples 1 and 2 (2.83 and 3.00 W / m·K). This demonstrates the uniformly dispersed graphene nanosheets and microchannel cooling structure in the multifunctional composite coating of this invention: graphene itself has extremely high room temperature thermal conductivity, and the heat conduction network constructed at the nanoscale can rapidly transfer heat from the superconducting layer to the external cooling medium, while the built-in microchannel structure provides a continuous fluid pathway in the liquid nitrogen environment, further reducing thermal resistance. In contrast, Comparative Example 1, lacking graphene, cannot form an efficient heat conduction channel, resulting in a decrease in thermal diffusivity; the microchannel structure in Comparative Example 2, lacking a crosslinking agent, also cannot maintain a stable cooling network due to the loose coating interface.
[0050] 5. Thermal cycling stability test Each sample was cut into 50 mm straight segments. First, the initial critical current density Jc0 and interfacial peel strength τ0 were measured. Then, the specimens were placed in a thermal cycling device, switching back and forth between liquid nitrogen and room temperature for 100 cycles, holding each temperature stage for 5 minutes. After the cycles were completed, the samples were allowed to return to room temperature, and the critical current density Jc0 was measured again. 100 and interfacial peel strength τ 100 ; respectively according to Jc retention rate = Jc 100 / Jc0×100% and τ retention rate = τ 100 The performance retention rate was calculated as τ0×100%, and the average value of three tests was taken. The results are shown in Table 5.
[0051] Table 5 Thermal Cycling Stability
[0052] As shown in Table 5, Examples 1–3 maintained 97%, 98%, and 99% of the critical current density and 96%, 97%, and 98% of the interfacial peel strength, respectively, after 100 thermal cycles. In contrast, Comparative Examples 1 and 2 maintained only 85%–88% and 87%–89%, respectively, demonstrating the reliability of the nanogroove structure and the continuous microchannel network formed by supercritical CO2 drying under cyclic thermal shock. The nanoimprinted microgrooves not only induced the YBa2Cu3O... 7-x The directional growth of grains during heat treatment also provides stress release channels during low-temperature shrinkage and warm-up expansion; the microchannel cooling network generated by supercritical CO2 drying enables efficient heat exchange between the coating and the refrigerant, reducing the accumulation of interfacial thermal stress.
[0053] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0054] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.
Claims
1. A lightweight superconducting carbon fiber composite cable, characterized in that, The lightweight superconducting carbon fiber composite cable comprises a carbon fiber bundle layer, a multifunctional composite coating, a superconducting functional layer, an insulation layer, a shielding layer, and a protective layer. The carbon fiber bundle layer is closely attached to the outside of the superconducting functional layer. The multifunctional composite coating covers the outside of the carbon fiber bundle layer. The insulation layer covers the outside of the multifunctional composite coating. The shielding layer surrounds the outer wall of the insulation layer. The protective layer covers the outside of the shielding layer. The multifunctional composite coating comprises the following raw materials in parts by weight: 60-65 parts of polyimide precursor; 8-12 parts of 4-aminopropyltrimethoxysilane; 1-2 parts of glutaraldehyde; 3-5 parts of graphene nanosheets; YBa2Cu3O 7-x 15-20 parts of precursor.
2. The lightweight superconducting carbon fiber composite cable according to claim 1, characterized in that, The preparation method of the polyimide precursor specifically includes the following steps: S101. Weigh out tetraphenyltetrahydride and p-phenylenediamine in a molar ratio of 1:1, dissolve them in N-methylpyrrolidone solvent, and obtain a homogeneous reaction mixture; S102. Under nitrogen protection, the mixture is stirred to allow tetraphenyltetrahydride and p-phenylenediamine to undergo a condensation reaction, generating a viscous and homogeneous polyamic acid solution, which can then be allowed to stand for a certain period of time. S103. The generated polyamic acid solution is filtered through a microporous membrane, the filtrate is concentrated in a vacuum container to remove some N-methylpyrrolidone, and a small amount of inert gas is introduced into the solution for protection to obtain a stable polyamic acid precursor solution.
3. The lightweight superconducting carbon fiber composite cable according to claim 1, characterized in that, The YBa2Cu3O 7-x The preparation method of the precursor specifically includes the following steps: S201. Weigh out yttrium acetate, barium acetate and copper acetate in a molar ratio of Y∶Ba∶Cu = 1∶2∶3, and dissolve them in 2-methoxyethanol to obtain three homogeneous metal acetate solutions. S202. Mix the above metal acetate solutions, add an equimolar amount of citric acid and stir, then add an equal volume of ethylene glycol, and continue heating and stirring until the solution becomes clear and has a uniform viscosity, forming YBa2Cu3O. 7-x Precursor sol; S203. The obtained sol was allowed to stand at room temperature for several hours to mature, then filtered through a filter membrane to remove unreacted particles, yielding a transparent and stable YBa2Cu3O. 7-x Precursor.
4. The lightweight superconducting carbon fiber composite cable according to claim 1, characterized in that, The thickness of the multifunctional composite coating is 50–300 nm.
5. The lightweight superconducting carbon fiber composite cable according to claim 1, characterized in that, The superconducting functional layer is YBa2Cu3O deposited via the sol-gel method. 7-x The precursor is a ceramic superconducting layer obtained by pre-firing, calcining and annealing heat treatment.
6. The lightweight superconducting carbon fiber composite cable according to claim 1, characterized in that, The insulating layer is a polytetrafluoroethylene film, the shielding layer is an annular metal tube, and the protective layer is a polyurethane coating.
7. A method for preparing a lightweight superconducting carbon fiber composite cable, wherein the lightweight superconducting carbon fiber composite cable is as described in any one of claims 1-6, characterized in that, Includes the following steps: S1. The carbon fiber bundles are immersed in an organic solvent for ultrasonic cleaning, rinsed with deionized water and vacuum dried, then treated with oxygen plasma, purged with nitrogen and collected for later use. S2. Impregnate the carbon fiber bundles obtained in step S1 with a substrate containing polyamic acid precursor, 4-aminopropyltrimethoxysilane, glutaraldehyde, graphene nanosheets, and YBa2Cu3O. 7-x A multifunctional composite coating is formed in the composite solution of the precursor; S3. The carbon fiber bundles obtained in step S2 are subjected to sol-gel impregnation and heat treatment to obtain a superconducting functional layer; S4. Fix the composite unit obtained in step S3, spirally wrap it with a polytetrafluoroethylene insulation layer, braid a metal shielding layer, place the braided fiber bundle in a polyurethane extruder mold, extrude the polyurethane sheath, pass the extruded cable through a heating pipe, let it stand at room temperature, and cut the finished cable segment according to the design length to obtain the lightweight superconducting carbon fiber composite cable.
8. The method for preparing the lightweight superconducting carbon fiber composite cable according to claim 7, characterized in that, After step S2, the multifunctional composite coating is subjected to nanoimprint microstructuring treatment to form parallel microgrooves on the coating surface, which are used to induce the directional growth of superconducting grains.
9. The method for preparing the lightweight superconducting carbon fiber composite cable according to claim 7, characterized in that, The number of cycles of sol-gel impregnation and pre-calcination, calcination, and annealing heat treatment in step S3 is 3 to 5.
10. The method for preparing the lightweight superconducting carbon fiber composite cable according to claim 7, characterized in that, In step S3, after each sol-gel impregnation, supercritical CO2 drying is performed first, followed by pre-calcination, calcination, and annealing cycles to generate a continuous microchannel cooling network within the superconducting functional layer.