Graphene aluminum-based alloy enameled wire and preparation method thereof

Abstract

This application relates to the field of conductor technology, specifically disclosing a graphene-based aluminum alloy enameled wire and its preparation method. This application optimizes the graphene content of the conductive core and limits the composition of the insulating varnish layer, improving the thermal conductivity and heat resistance of the enameled wire. Utilizing its excellent thermal conductivity, the aluminum alloy enameled wire of this application allows for a more uniform internal heat distribution, facilitating rapid heat dissipation. Furthermore, combined with its good thermal stability, the aluminum alloy enameled wire of this application effectively reduces damage to the insulating varnish layer under high-temperature conditions, thereby maintaining the effectiveness of insulation protection for a long time and contributing to improved reliability and stability of electronic equipment.

Description

Technical Field

[0001] This application relates to the field of conductor technology, and more specifically, to a graphene-aluminum-based alloy enameled wire and its preparation method. Background Technology

[0002] Enameled wire is a major type of winding wire, consisting of a conductor and an insulation layer. It is typically made by annealing and softening bare wire, then coating it with enamel and baking it. Currently, various motors and electrical appliances are developing towards miniaturization, lightweighting, and high performance, thus requiring increasingly finer enameled wire. Due to the shortage of copper raw materials, aluminum is used instead of copper in the enameled wire conductors of some electrical appliances.

[0003] One related technology involves a rare-earth aluminum alloy enameled wire, comprising a conductive core and an insulating varnish layer. The conductive core is made of rare-earth aluminum alloy, and the insulating varnish layer consists of a first varnish layer, a second varnish layer, and a third varnish layer sequentially coated onto the conductive core from the inside out. The first, second, and third varnish layers are all primarily composed of polyamic acid, with added fluorinated graphite powder, titanium dioxide, and silica sol, respectively. After coating and thermal imidization, the aforementioned varnishes form an insulating layer primarily composed of polyimide.

[0004] Regarding the aforementioned technologies, the inventors believe that although the rare-earth aluminum alloy conductive cores in the related technologies have good electrical and mechanical properties, the application of aluminum-based composite materials will lead to an increase in the heat load of the enameled wire compared with copper-based conductors. Furthermore, the heat resistance of current insulation materials is limited, and they cannot guarantee the effectiveness of insulation protection for a long time. Summary of the Invention

[0005] In related technologies, the application of aluminum-based composite materials leads to an increase in the heat load of enameled wires, while current insulation materials have limited heat resistance and cannot guarantee the effectiveness of insulation protection for extended periods. To address this deficiency, this application provides a graphene-aluminum-based alloy enameled wire and its preparation method.

[0006] In a first aspect, this application provides a graphene-aluminum-based alloy enameled wire, employing the following technical solution: A graphene-aluminum alloy enameled wire includes a conductive core and an insulating varnish layer. The conductive core is made of a graphene-aluminum alloy with a graphene content of 0.32-0.44 wt%. The insulating varnish layer comprises the following components in parts by weight: 100 parts polyimide, 8.6-9.8 parts heat-resistant additives, 0.44-0.48 parts hexagonal boron nitride nanosheets, and 0.36-0.40 parts fluorinated graphene. The polyimide is an imidized product of polyamic acid, and the heat-resistant additives include nanocellulose and hydroxyapatite nanowires. The polyimide contains o-carborane units and benzimidazole groups.

[0007] By adopting the above technical solution, this application optimizes the graphene content of the conductive core and defines the composition of the insulating varnish layer. Fluorinated graphene and hexagonal boron nitride nanosheets in the insulating varnish layer can synergistically conduct heat, which is beneficial for the uniform distribution of heat and effectively prevents localized heat accumulation. Furthermore, the addition of fluorinated graphene can effectively reduce the dielectric constant of the insulating varnish layer, compensating for the shortcomings of polyimide in electrical performance. The polyimide in this application contains o-carborane units, which have a cage-like rigid structure. The benzimidazole groups in the polyimide can associate with nanocellulose and hydroxyapatite nanowires to form a hydrogen bond network. The rigid structure and the hydrogen bond network synergistically improve the thermal stability of the insulating varnish layer. In addition, in the polyimide molecules of the insulating varnish layer, the o-carborane units can form a boron oxide passivation layer on the surface of the insulating varnish layer, thereby isolating oxygen and reducing high-temperature oxidation of the insulating varnish layer. Thanks to its excellent thermal conductivity, the aluminum alloy enameled wire of this application can distribute heat more evenly inside, which is conducive to rapid heat dissipation. In addition, with its good thermal stability, it can effectively reduce the damage to the insulating varnish layer under high temperature conditions, thereby maintaining the effectiveness of insulation protection for a long time and helping to improve the reliability and stability of electronic equipment.

[0008] Preferably, the weight ratio of the nanocellulose and hydroxyapatite nanowires is 1:(8-10).

[0009] By adopting the above technical solution, this application optimizes the weight ratio of nanocellulose and hydroxyapatite nanowires, which helps to improve the high-temperature resistance of enameled wires.

[0010] Preferably, the hydroxyapatite nanowires are prepared according to the following method: Sodium oleate and deionized water were mixed and stirred to dissolve, resulting in a sodium oleate solution. Calcium chloride aqueous solution and sodium dihydrogen phosphate aqueous solution were added sequentially to the sodium oleate solution, and stirring was continued to obtain a suspension. The suspension was transferred to a hydrothermal reactor for reaction. The product was filtered to obtain a filter cake, which was then washed and dried to obtain hydroxyapatite nanowires.

[0011] By adopting the above technical solution, this application uses sodium oleate and calcium chloride to react and produce calcium oleate, and then carries out a hydrothermal reaction using calcium oleate as a precursor. Calcium oleate serves as both a precursor and a calcium source, and can slowly release calcium ions. During the hydrothermal reaction, the calcium ions combine with hydroxide ions and phosphate ions to obtain hydroxyapatite nanowires.

[0012] Preferably, the heat-resistant additive also includes halloysite nanotubes.

[0013] By adopting the above technical solution, halloysite nanotubes have a large number of silanol and aluminol groups on their walls, which can associate with benzimidazole groups, nanocellulose and hydroxyapatite nanowires to form a hydrogen bond network, increasing the complexity of the hydrogen bond network and improving the high temperature resistance of the enameled wire.

[0014] Preferably, the weight ratio of the nanocellulose and halloysite nanotubes is 1:(2.6-2.8).

[0015] By adopting the above technical solution, this application optimizes the weight ratio of nanocellulose and halloysite nanotubes, which helps to improve the high-temperature resistance of enameled wire.

[0016] Preferably, the polyamic acid is made from a diamine monomer and a dianhydride monomer, wherein the diamine monomer includes an o-carborane diamine monomer.

[0017] By adopting the above technical solution, this application has preferred the type of diamine monomer. By using a diamine monomer containing an ortho-carborane unit to prepare polyamic acid, a polyimide molecule containing an ortho-carborane unit can be obtained after the imidization reaction.

[0018] Preferably, the o-carborane diamine monomer is prepared according to the following method: (1) Add nitrate-sulfuric acid and DCM to DPCB under ice-water bath conditions, stir the reaction and then pour the mixture into ice water to quench it. Extract with DCM, wash and dry the organic phase, and then concentrate by rotary evaporation to obtain the dinitro intermediate. (2) The dinitro intermediate was reduced by using tin chloride as a reducing agent to obtain the ortho-carborane diamine monomer.

[0019] By adopting the above technical solution, this application first sulfonates DPCB with a mixture of nitric and sulfuric acids to obtain a dinitro intermediate, and then reduces the nitro group with tin chloride to an amino group, thereby obtaining the o-carborane diamine monomer.

[0020] Preferably, the diamine monomer further includes at least one of 2-(3,5-diaminophenyl)-benzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole.

[0021] By adopting the above technical solution, this application has selected the type of diamine monomer. The two diamine monomers mentioned above can introduce benzimidazole groups and phenyl groups into polyamic acid, which can effectively improve the heat resistance of aluminum alloy enameled wire.

[0022] Preferably, the polyamic acid is prepared according to the following method: Diamine monomer and DMAC were mixed and stirred under nitrogen protection to obtain a diamine solution. Dianhydride monomer and DMAC were added to the diamine solution under ice-water bath conditions, and stirring was continued under nitrogen atmosphere to obtain polyamic acid.

[0023] By adopting the above technical solution, this application has selected a preferred method for preparing polyamic acid. Through the above method, polyamic acid with good fluidity can be synthesized, which is convenient for coating onto the surface of conductive wire core.

[0024] Secondly, this application provides a method for preparing graphene-aluminum-based alloy enameled wire, which adopts the following technical solution.

[0025] A method for preparing graphene-aluminum-based alloy enameled wire includes the following steps: (1) Mix polyamic acid, hexagonal boron nitride nanosheets, fluorinated graphene and heat-resistant additives to obtain insulating varnish for later use; clean the conductive wire core and send it into an annealing furnace for annealing, then clean and dry it for later use. (2) Apply insulating varnish to the surface of the conductive core, cure the insulating varnish into an insulating varnish layer by baking, and then wait for the conductive core to cool down; (3) Apply lubricating oil to the surface of the insulating varnish layer, dry it, and then take the wire to obtain graphene aluminum-based alloy enameled wire.

[0026] By adopting the above technical solution, this application first prepared an insulating varnish and annealed the conductive core. Then, the insulating varnish was coated onto the surface of the conductive core. After thermal imidization, the conductive core was cured into a film. Then, lubricating oil was applied to obtain a graphene aluminum-based alloy enameled wire with high heat resistance.

[0027] In summary, this application has the following beneficial effects: 1. This application optimizes the graphene content of the conductive core and limits the composition of the insulating varnish layer, thereby improving the thermal conductivity and heat resistance of the enameled wire. Utilizing its excellent thermal conductivity, the aluminum alloy enameled wire of this application allows for a more uniform internal heat distribution. This facilitates rapid heat dissipation, and combined with its good thermal stability, effectively reduces damage to the insulating varnish layer under high-temperature conditions. This ensures the effective maintenance of insulation protection over a longer period, contributing to improved reliability and stability of electronic equipment.

[0028] 2. Halloysite nanotubes are preferred as the third component of the heat-resistant additive in this application. Halloysite nanotubes have a large number of silanol and aluminol hydroxyl groups on their tube walls, which can associate with benzimidazole groups, nanocellulose and hydroxyapatite nanowires to form a hydrogen bond network, increasing the complexity of the hydrogen bond network and improving the high-temperature resistance of the enameled wire.

[0029] 3. In the polyimide molecules of the insulating varnish layer, the ortho-carborane unit can form a boron oxide passivation layer on the surface of the insulating varnish layer, thereby isolating oxygen and reducing the high-temperature oxidation of the insulating varnish layer. Detailed Implementation

[0030] The present application will be further described in detail below with reference to the embodiments, preparation examples and comparative examples. The raw materials involved in the present application can all be obtained commercially.

[0031] Preparation example of hydroxyapatite nanowires The following explanation uses Preparation Example 1 as an example.

[0032] Preparation Example 1 In this preparation example, hydroxyapatite nanowires were prepared according to the following method: 2.44 g of sodium oleate and 25 g of deionized water were mixed and stirred to dissolve, resulting in a sodium oleate solution. 25 mL of calcium chloride aqueous solution (containing 0.22 g of anhydrous calcium chloride) and 25 mL of sodium dihydrogen phosphate aqueous solution (containing 0.28 g of sodium dihydrogen phosphate dihydrate) were added sequentially to the sodium oleate solution. After stirring for 35 min, a suspension was obtained. The suspension was transferred to a hydrothermal reactor lined with polytetrafluoroethylene and reacted at 200 °C for 36 h. The product was filtered to obtain a filter cake, which was then washed and dried to obtain hydroxyapatite nanowires.

[0033] Preparation example of polyamic acid The following explanation uses Preparation Example 2 as an example.

[0034] Preparation Example 2 In this preparation example, the molar ratio of diamine monomer to dianhydride monomer is 1:1.02. The diamine monomer is a mixture of o-carborane diamine monomer and benzimidazole monomer in a weight ratio of 1:3. The benzimidazole monomer is 2-(3,5-diaminophenyl)-benzimidazole. The dianhydride monomer is BTDA.

[0035] The o-carborane diamine monomer is prepared according to the following method: (1) Add 10 mL of 65 wt% nitric acid and 30 mL of 98 wt% sulfuric acid to 6.77 mmol of diphenyl o-carborane (DPCB) and 30 mL of dichloromethane (DCM) under ice-water bath conditions. After stirring for 3 h, the mixture was quenched in 250 mL of ice water and extracted with DCM. The organic phase was washed with saturated sodium bicarbonate solution and saturated sodium chloride solution in sequence, and dried with anhydrous sodium sulfate for 6 h. The dried product was then concentrated by rotary evaporation to obtain the dinitro intermediate. (2) Under a nitrogen atmosphere, 4.82 mmol of dinitro intermediate, 48.77 mmol of tin chloride, 40 mL of anhydrous ethanol, 40 mL of ethyl acetate and 4 mL of 36.5 wt% hydrochloric acid were mixed and heated under reflux at 80 °C for 6 h. After the reaction was completed, the pH of the product solution was adjusted to 8 with sodium bicarbonate, extracted with ethyl acetate, and the organic phase was washed with saturated sodium chloride solution. The resulting solution was dried with anhydrous sodium sulfate for 6 h and concentrated by rotary evaporation to obtain the o-carborane diamine monomer.

[0036] This preparation example provides a polyamic acid, prepared according to the following method: Diamine monomer and DMAC were mixed at a ratio of 1g:2.5mL and stirred under nitrogen protection to obtain a diamine solution. Dianhydride monomer and DMAC (the same amount of DMAC used to prepare the diamine solution) were added to the diamine solution under ice-water bath conditions. After stirring for 24h under nitrogen atmosphere, polyamic acid was obtained.

[0037] Preparation Example 3 The difference between this preparation example and Preparation Example 1 is that the benzimidazole monomer is prepared by mixing 2-(3,5-diaminophenyl)-benzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole in a weight ratio of 1:1.5.

[0038] Preparation example of fluorinated graphene The following explanation uses Preparation Example 4 as an example.

[0039] Preparation Example 4 This preparation example provides a fluorinated graphene, prepared according to the following method: Fluorinated graphite and NMP were mixed to obtain a 5 mg / mL fluorinated graphite solution. The solution was heated and refluxed at 55 °C for 2.5 h, and then ultrasonically exfoliated at 300 W for 4 h to remove the solvent NMP, thus obtaining fluorinated graphene.

[0040] Example of conductive wire core preparation The following explanation uses Preparation Example 5 as an example.

[0041] Preparation Example 5 In this preparation example, the conductive wire core is made of graphene-aluminum based alloy, and the elemental weight composition of the graphene-aluminum based alloy is as follows: silicon 0.14%, iron 0.9%, copper 0.4%, vanadium 0.08%, graphene 0.32%, zirconium 0.06%, boron 0.08%, lanthanum 0.02%, scandium 0.01%, with the balance being aluminum and impurities that have no effect on performance.

[0042] This preparation example provides a conductive wire core, which is prepared according to the following method: (1) Smelting: Weigh the raw materials corresponding to the composition of the aluminum-based composite conductor, put the aluminum raw materials into a crucible, heat to 730°C, add the remaining raw materials and stir continuously to form a uniform melt; (2) Refining: Maintain the temperature at 730℃ and add refining agent under an inert protective atmosphere Ar. During the refining process, permanent magnet stirring is performed every 10 minutes for 3 minutes each time. After refining, slag removal is performed. (3) Degassing in the holding furnace: Under the holding condition, a mixed gas is introduced into the melt for degassing treatment. The mixed gas is 60 vol% Ar and 40 vol% Cl2. (4) Casting and continuous casting: The molten material is cast and continuously cast to obtain aluminum-based alloy rods. The total cooling rate during the casting process is controlled at 10℃ / s. (5) Toughening treatment: The aluminum-based alloy rod is placed in a toughening furnace for treatment. The toughening temperature is 340℃ and the toughening time is 4h. (6) Wire drawing and aging treatment: The toughened aluminum alloy rod is drawn into wire and then put into an aging furnace for aging treatment; in this step, the wire diameter is φ0.2mm, the aging treatment temperature is 165℃ and the aging treatment time is 4h. (7) Bundling and re-twisting: Aluminum-based alloy wires are bundled and re-twisted to finally obtain conductive wire cores. Example

[0043] Examples 1-3 The following description uses Example 1 as an example.

[0044] Example 1 This embodiment provides a graphene-aluminum alloy enameled wire, comprising a conductive core and an insulating varnish layer with a thickness of 40 μm. The conductive core is prepared according to the method of Preparation Example 5. The insulating varnish layer comprises the following components in parts by weight: 100 parts polyimide, 8.6 parts heat-resistant additives, 0.44 parts hexagonal boron nitride nanosheets, and 0.36 parts fluorinated graphene. The polyimide is made from polyamic acid as described in Preparation Example 2. The heat-resistant additives include nanocellulose and hydroxyapatite nanowires, with a weight ratio of nanocellulose to hydroxyapatite nanowires of 1:12. The specific surface area of ​​the hexagonal boron nitride nanosheets is 82 m². 2 / g, fluorinated graphene was prepared according to the method of Preparation Example 4.

[0045] This embodiment provides a method for preparing graphene-aluminum-based alloy enameled wire, including the following steps: (1) Mix polyamic acid, hexagonal boron nitride nanosheets, fluorinated graphene and heat-resistant additives to obtain insulating varnish for later use; clean the conductive wire core and send it into an annealing furnace for annealing, then clean and dry it for later use. (2) Apply insulating varnish to the surface of the conductive core and bake it to cure it into an insulating varnish layer. Then wait for the conductive core to cool down. In this step, the amount of coating is 12. After each coating is completed, a baking is performed. The baking procedure is as follows: start from 25°C, raise the temperature to 130°C in 1 hour, keep it at the temperature for 1 hour, raise the temperature to 300°C in 2 hours, keep it at the temperature for 1 hour, raise the temperature to 350°C in 50 minutes, keep it at the temperature for 2 hours, and then let it cool naturally. (3) Apply lubricating oil to the surface of the insulating varnish layer, dry it, and then take the wire to obtain graphene aluminum-based alloy enameled wire.

[0046] As shown in Table 1, the main differences between Examples 1-3 are the composition of the insulating varnish layer and the graphene content of the conductive wire core.

[0047] Table 1. Composition of the insulating varnish layer (by weight) and graphene content of the conductive core. Polyimide / part 100 100 100 Heat-resistant additives / part 8.6 9.2 9.8 Hexagonal boron nitride nanosheets / part 0.44 0.46 0.48 Fluorinated graphene / part 0.36 0.38 0.40 Graphene content of conductive wire core / % 0.32 0.38 0.44 Example 4 The difference between this embodiment and Embodiment 3 is that the weight ratio of nanocellulose and hydroxyapatite nanowires is 1:10.

[0048] Example 5 The difference between this embodiment and Embodiment 3 is that the weight ratio of nanocellulose and hydroxyapatite nanowires is 1:9.

[0049] Example 6 The difference between this embodiment and Embodiment 3 is that the weight ratio of nanocellulose and hydroxyapatite nanowires is 1:8.

[0050] Example 7 The difference between this embodiment and Embodiment 6 is that the heat-resistant additive also includes halloysite nanotubes, and the weight ratio of nanocellulose and halloysite nanotubes is 1:2.1.

[0051] Example 8 The difference between this embodiment and Embodiment 7 is that the weight ratio of nanocellulose and halloysite nanotubes is 1:2.6.

[0052] Example 9 The difference between this embodiment and Embodiment 7 is that the weight ratio of nanocellulose and halloysite nanotubes is 1:2.7.

[0053] Example 10 The difference between this embodiment and Embodiment 7 is that the weight ratio of nanocellulose and halloysite nanotubes is 1:2.8.

[0054] Example 11 The difference between this embodiment and Example 10 is that the polyamic acid was prepared according to the method of Preparation Example 3.

[0055] Comparative Example Comparative Example 1 This comparative example provides a rare earth aluminum alloy enameled wire, including a conductive core and an insulating varnish layer with a thickness of 40 μm. The conductive core is made of rare earth aluminum alloy and has the same dimensions and specifications as in Example 1. The raw material components in the conductive core are, by weight, 0.245% copper, 0.1% zinc, 0.005% cerium, with the balance being aluminum and impurities that do not affect performance. The insulating varnish layer consists of a first varnish layer, a second varnish layer, and a third varnish layer sequentially coated on the conductive core from the inside out.

[0056] In this comparative example, the first paint layer, the second paint layer, and the third paint layer are all made from polyamic acid precursor, which is prepared according to the following method: Dissolve 3,3,4,4-benzophenone tetracarboxylic dianhydride and 4,4′-diaminodiphenyl ether together in N, at a molar ratio of 1.02:1. When N-dimethylacetamide is continuously stirred until the solution is encapsulated, a polyamic acid precursor is obtained.

[0057] The first paint is prepared according to the following method: Fluorinated graphite powder was added to N-methylpyrrolidone solvent to prepare a solution with a concentration of 4 mg / mL. The solution was heated to 55°C and refluxed for 60 minutes. After cooling, the solution was centrifuged and the supernatant was collected. The supernatant was mixed with the polyamic acid precursor solution at a volume ratio of 1:10 and mechanically stirred for 4 hours to obtain the first paint.

[0058] The second paint is prepared according to the following method: Titanium dioxide was baked at 100℃ for 120 minutes and then added to a polyamic acid precursor solution at a mass fraction of 5%. The mixture was ultrasonically vibrated for 30 minutes and then mechanically stirred for 60 minutes to obtain the second paint. The titanium dioxide was a mixed-crystalline fumed nano-titanium dioxide particle with an average particle size of 22 nm and a specific surface area of ​​[missing information]. 56m 2 / g, of which the mass ratio of anatase to rutile is 7:2.

[0059] The third paint is prepared according to the following method: Add 0.1 mol / L sodium hydroxide solution to the polyamic acid precursor solution until the pH is 8.5, then add 10% silica sol by mass of the solution, and stir at 40°C for 2 hours to obtain the third paint.

[0060] The preparation method of rare earth aluminum alloy enameled wire is as follows: (1) After cleaning the conductive core, send it into the annealing furnace for annealing, cool the core with 50°C clean water and then dry it quickly. (2) The annealed wire core is sent into the painting area of ​​the oven. The first paint, the second paint and the third paint are applied to the surface of the conductive wire core in sequence using the painting mold to form the first paint layer, the second paint layer and the third paint layer. During the painting process, the first paint is applied in 6 coats, the second paint in 2 coats and the third paint in 4 coats. After each coat is applied, a baking is performed. The baking procedure is as follows: starting from 25°C, the temperature is raised to 130°C in 1 hour, held for 1 hour, then raised to 300°C in 2 hours, held for 1 hour, then raised to 350°C in 50 minutes, held for 2 hours and then cooled naturally. (3) After the coated conductive core is cooled, a layer of lubricating oil is coated on the surface, and after drying, the wire is wound up to obtain rare earth aluminum alloy enameled wire.

[0061] Comparative Example 2 The difference between this comparative example and Example 1 is that the insulating varnish layer does not contain nanocellulose.

[0062] Comparative Example 3 The difference between this comparative example and Example 1 is that the insulating varnish layer does not contain hydroxyapatite nanowires.

[0063] Comparative Example 4 The difference between this comparative example and Example 1 is that the insulating varnish layer does not contain fluorinated graphene.

[0064] Comparative Example 5 The difference between this comparative example and Example 1 is that the insulating varnish layer does not contain hexagonal boron nitride nanosheets.

[0065] Comparative Example 6 The difference between this comparative example and Example 1 is that the diamine monomer used to synthesize polyamic acid does not include the o-carborane diamine monomer.

[0066] Comparative Example 7 The difference between this comparative example and Example 1 is that the diamine monomer used to synthesize polyamic acid does not include benzimidazole monomer.

[0067] Performance testing methods I. Heat Resistance of Insulating Varnish Following the methods described in the various embodiments and comparative examples, insulating varnish was coated onto the surface of a glass plate. The glass plate was pre-cleaned with deionized water, acetone, dichloromethane, and isoacetone, and then ultrasonically treated in deionized water for 15 minutes. After coating, the varnished glass plate was placed in a clean bench and subjected to thermal imidization after 24 hours to obtain the sample film.

[0068] In a nitrogen atmosphere, the temperature was increased at a rate of 10℃ / min, ranging from 25℃ to 800℃. The temperature at which the film lost 5% weight was recorded as the 5% weight loss temperature. The results are shown in Table 2.

[0069] II. Creep Variables The tests were conducted according to Appendix B of GB / T 30552 "Aluminum Alloy Wire for Cable Conductors". The test objects were the conductive wire cores of Examples 1-3 and Comparative Example 1. The test conditions were: creep temperature of 200℃, stress of 60MPa, and 100h. The results are shown in Table 2.

[0070] Table 2 Relative weight loss temperature Example 1 565.2 Example 10 574.5 Example 2 565.7 Example 11 577.3 Example 3 566.4 Comparative Example 1 518.4 Example 4 567.1 Comparative Example 2 539.8 Example 5 568.5 Comparative Example 3 542.5 Example 6 570.3 Comparative Example 4 553.2 Example 7 571.0 Comparative Example 5 548.4 Example 8 572.4 Comparative Example 6 546.4 Example 9 572.8 Comparative Example 7 541.9 Table 2. Creep Variables Example 1 0.18 Example 2 0.17 Example 3 0.16 Comparative Example 1 0.23 Combining Examples 1-3 and Comparative Example 1 with Tables 2 and 3, it can be seen that the 5% weight loss temperature measured in Examples 1-3 is relatively high. This is because this application optimizes the graphene content of the conductive core and limits the composition of the insulating varnish layer, thereby improving the thermal conductivity and heat resistance of the enameled wire. The creep measured in Examples 1-3 is relatively small, indicating that the conductive core also possesses good stability. With its excellent thermal conductivity, the aluminum alloy enameled wire of this application can distribute heat more evenly internally. This characteristic facilitates rapid heat dissipation, and combined with good thermal stability, effectively reduces damage to the insulating varnish layer under high-temperature conditions, thus maintaining the effectiveness of insulation protection for a long time and contributing to improving the reliability and stability of electronic equipment.

[0071] Based on Example 1 and Comparative Examples 2-3, and in conjunction with Tables 2 and 3, it can be seen that when nanocellulose and apatite nanowires are not used together, they cannot associate through hydrogen bonds. The lack of hydrogen bonds leads to poor heat resistance of the insulating varnish layer, and thus the insulating varnish layer will experience a 5% mass loss at a relatively low temperature.

[0072] Based on Examples 1 and Comparative Examples 4-5, and in conjunction with Tables 2 and 3, it can be seen that when fluorinated graphene and hexagonal boron nitride nanosheets are not used together, the poor thermal conductivity of the insulating varnish layer leads to localized temperature buildup, resulting in a premature 5% mass loss. Based on Examples 1 and Comparative Examples 6-7, and in conjunction with Tables 2 and 3, it can be seen that when either a carborane unit or a benzimidazole group is missing from the polyimide, the synergistic effect is affected, thus the heat resistance of the insulating varnish layer decreases, reaching a 5% mass loss at a relatively low temperature.

[0073] As can be seen from Examples 3 and 4-6 and Tables 2 and 3, when the weight ratio of nanocellulose and hydroxyapatite nanowires is 1:(8-10), the heat resistance of the insulating varnish layer is relatively good, and thus the enameled wire can resist high temperature for a longer period of time.

[0074] As can be seen from Examples 6 and 7-10 and Tables 2 and 3, when the weight ratio of nanocellulose to halloysite nanotubes is 1:(2.6-2.8), the hydrogen bonds associated with the heat-resistant filler are more complete, so the heat resistance of the insulating varnish layer is relatively good, and the enameled wire can resist high temperature for a longer period of time.

[0075] As can be seen from Examples 10 and 11, and Tables 2 and 3, when the diamine monomer includes both 2-(3,5-diaminophenyl)-benzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole, the insulating varnish layer has good heat resistance and strong resistance to high temperatures.

[0076] The above embodiments are merely explanations of this application and are not intended to limit it. After reading this specification, those skilled in the art can make modifications to the embodiments of this application without contributing any inventive step, but such modifications are protected by patent law as long as they are within the scope of the claims of this application.

Claims

1. A graphene-aluminum-based alloy enameled wire, characterized in that, The device comprises a conductive core and an insulating varnish layer. The conductive core is made of a graphene-aluminum based alloy with a graphene content of 0.32-0.44 wt%. The insulating varnish layer comprises the following components in parts by weight: 100 parts polyimide, 8.6-9.8 parts heat-resistant additives, 0.44-0.48 parts hexagonal boron nitride nanosheets, and 0.36-0.40 parts fluorinated graphene. The polyimide is an imidized product of polyamic acid, and the heat-resistant additives include nanocellulose and hydroxyapatite nanowires. The polyimide contains o-carborane monophosphate. The polyamic acid contains a benzimidazole group; the weight ratio of the nanocellulose and hydroxyapatite nanowires is 1:(8-10); the heat-resistant additive also includes halloysite nanotubes; the weight ratio of the nanocellulose and halloysite nanotubes is 1:(2.6-2.8); the polyamic acid is made from a diamine monomer and a dianhydride monomer, the diamine monomer including o-carborane diamine monomer; the diamine monomer also includes at least one of 2-(3,5-diaminophenyl)-benzimidazole and 2-(4-aminophenyl)-5-aminobenzimidazole.

2. The graphene-aluminum-based alloy enameled wire according to claim 1, characterized in that, The hydroxyapatite nanowires were prepared according to the following method: Sodium oleate and deionized water were mixed and stirred to dissolve, resulting in a sodium oleate solution. Calcium chloride aqueous solution and sodium dihydrogen phosphate aqueous solution were added sequentially to the sodium oleate solution, and stirring was continued to obtain a suspension. The suspension was transferred to a hydrothermal reactor for reaction. The product was filtered to obtain a filter cake, which was then washed and dried to obtain hydroxyapatite nanowires.

3. The graphene-aluminum-based alloy enameled wire according to claim 1, characterized in that, The o-carborane diamine monomer is prepared according to the following method: (1) Add nitric acid and dichloromethane to diphenylo-borane under ice-water bath conditions. After stirring the reaction, pour the mixture into ice water to quench it. Extract with dichloromethane, wash and dry the organic phase, and then concentrate by rotary evaporation to obtain the dinitro intermediate. (2) The dinitro intermediate was reduced by using tin chloride as a reducing agent to obtain the ortho-carborane diamine monomer.

4. The graphene-aluminum-based alloy enameled wire according to claim 1, characterized in that, The polyamic acid is prepared according to the following method: Diamine monomer and DMAC were mixed and stirred under nitrogen protection to obtain a diamine solution. Dianhydride monomer and DMAC were added to the diamine solution under ice-water bath conditions, and stirring was continued under nitrogen atmosphere to obtain polyamic acid.

5. The method for preparing graphene-aluminum-based alloy enameled wire according to any one of claims 1-4, characterized in that, Includes the following steps: (1) Mix polyamic acid, hexagonal boron nitride nanosheets, fluorinated graphene and heat-resistant additives to obtain insulating varnish for later use; clean the conductive wire core and send it into an annealing furnace for annealing, then clean and dry it for later use. (2) Apply insulating varnish to the surface of the conductive core, cure the insulating varnish into an insulating varnish layer by baking, and then wait for the conductive core to cool down; (3) Apply lubricating oil to the surface of the insulating varnish layer, dry it and then take it out to obtain graphene aluminum-based alloy enameled wire.