A method for preparing a dielectric composite film based on a layered structure

Abstract

This invention discloses a method for preparing a layered dielectric composite film, comprising the following steps: the layered dielectric composite film includes an upper layer, an intermediate layer, and a lower layer sequentially arranged; the upper layer is a BN / PI film; the intermediate layer is a PDA@CNT / PPI porous film; and the lower layer is a BN / PI film. The three sequentially arranged films are stacked under hot-pressing conditions and then hot-pressed for 30 min to obtain the BN / PDA@CNT / PI dielectric composite film. The beneficial effects are: the layered dielectric composite film prepared by this method has a high-density filler network distribution while also possessing excellent mechanical strength, high dielectric constant (dielectric constant of 7.57 and dielectric loss of 0.015 at 1 MHz), and high thermal conductivity (1.35 W·m). ‑ 1 K ‑1 The performance characteristics of ).

Description

Technical Field

[0001] This invention relates to the field of dielectric thin film technology, and more specifically to a method for preparing a dielectric composite thin film based on a layered structure. Background Technology

[0002] With the rapid development of modern electronic technology, fields such as electronic communication equipment, new energy vehicles, and artificial intelligence have experienced rapid growth, which in turn has driven the development of dielectric materials for film capacitors. Polymer film capacitors have attracted widespread attention due to their unique advantages, such as lightweight, low cost, compact structure, high portability, and excellent high operating temperature performance. Compared with traditional ceramic capacitors, polymer film capacitors also have advantages such as simple manufacturing process, high breakdown strength, and low dielectric loss. However, most polymers generally have low dielectric constants. Traditional methods of adding inorganic fillers can improve the dielectric properties of polymer composite films, but the development of composite films is also limited by the influence of filler agglomeration, leading to a decline in dielectric and mechanical properties.

[0003] The prior art, CN107474251A, discloses a method for preparing a composite dielectric film for a membrane capacitor, comprising five steps: (1) synthesizing a fluorinated phenolic hydroxyl polyimide precursor using a one-step method; (2) preparing high-dielectric oxide nanosheets using an intercalation-exfoliation method; (3) preparing a uniformly mixed solution of a two-phase polyimide / oxide nanosheet dielectric enhancer, or a uniformly mixed solution of a multiphase (three-phase) polyimide / oxide nanosheet dielectric enhancer / boron nitride nanosheet thermal conductivity enhancer; (4) drying to obtain a two-phase or multiphase (three-phase) fluorinated phenolic hydroxyl polyimide / nanosheet composite film; and (5) high-temperature treatment under a nitrogen atmosphere to obtain a two-phase or multiphase (three-phase) fluorinated polybenzoxazole high-temperature resistant aromatic heterocyclic / nanosheet composite dielectric film. The prepared composite dielectric film for a membrane capacitor exhibits excellent properties such as high temperature resistance, high breakdown strength, adjustable dielectric constant, and high energy storage density.

[0004] In existing technologies, polyimide (PI) has become a focus of research due to its excellent properties such as high heat resistance, high mechanical strength, and high insulation, and has been widely used in microelectronic devices. However, PI has a relatively low intrinsic dielectric constant (~3.4), which makes it difficult to meet the requirements of dielectric materials for capacitors in miniaturized electrical devices. Therefore, PI materials with higher dielectric constants are a hot topic in electrical materials research and development. At the same time, PI's inherently low thermal conductivity (~0.2) severely affects the stability of its dielectric properties at high temperatures, which greatly limits its application in the microelectronics field.

[0005] In summary, there is an urgent need to provide a method for preparing dielectric composite films based on layered structures. The dielectric composite films prepared by this method have a high-density filler network distribution and also possess excellent mechanical strength, high dielectric strength, and high thermal conductivity. Summary of the Invention

[0006] The purpose of this invention is to provide a method for preparing a layered dielectric composite film. The dielectric composite film prepared by this method has a high-density filler network distribution and also has excellent mechanical strength, high dielectric strength, and high thermal conductivity.

[0007] It effectively solves the problems in existing technologies.

[0008] More specifically: This invention improves the dielectric, thermal conductivity and mechanical properties of PI composite films by introducing low-content one-dimensional carbon nanotubes (CNTs) and two-dimensional boron nitride (BN) as dielectric and thermally conductive fillers, respectively, and by using a combination of multi-layer structure design and hot pressing process.

[0009] The preparation of polymer dielectric films based on the traditional blending method usually requires the addition of a large amount of inorganic filler with high dielectric constant. However, the addition of a large amount of filler will lead to agglomeration and a decrease in mechanical properties.

[0010] In this invention, in response to the dielectric performance requirements of flexible polymer film capacitors, a high-dielectric-and-thermal-conductivity PI composite film is prepared by leveraging the synergistic effect of one-dimensional filler CNT and two-dimensional filler BN, utilizing a porous structure to promote the concentrated distribution of low-content fillers, and simultaneously employing a multilayer hot-pressing process to produce a high-density filler network distribution with excellent mechanical strength.

[0011] To achieve the above objectives, the following technical solutions are used: A method for preparing dielectric composite thin films based on layered structures. The preparation steps include the following: The layered dielectric composite film includes an upper layer, a middle layer, and a lower layer arranged sequentially. The upper layer is a BN / PI thin film; The intermediate layer is a PDA@CNT / PPI porous film; The lower layer is a BN / PI film.

[0012] The three layers of film that were set in sequence in the previous step were stacked under hot pressing conditions and then hot pressed for 30 min to obtain BN / PDA@CNT / PI dielectric composite film.

[0013] As a further improvement to this plan, The intermediate layer, a PDA@CNT / PPI porous film, was prepared as follows: (1) Preparation of polydopamine-coated CNTs: CNTs were ultrasonically dispersed in a mixture of ethanol and water. Dopamine hydrochloride was added and stirred evenly at room temperature. Then, an aqueous solution containing tris(hydroxymethyl)aminomethane was added and magnetically stirred at room temperature for 12 h. After centrifugation and washing with deionized water, PDA@CNT powder was obtained after drying. (2) Preparation of PDA@CNT / PPI porous films: 0.1-1 parts by weight of PDA@CNT were dispersed in N-methylpyrrolidone, 10 parts by weight of PI were added, and the mixture was stirred overnight. The mixture was then coated onto a glass plate. After removing the solvent at room temperature, the plate was demolded with deionized water and soaked for 1 hour. The plate was then transferred to a vacuum oven to remove the remaining solvent, thus preparing a PDA@CNT / PPI porous film, which served as the intermediate layer of the composite film. As a further improvement to this plan, The preparation of the upper and lower BN / PI films is as follows: (3) Preparation of BN / PI thin film 0.2-2 parts by weight of BN are dispersed in dichloromethane solvent, and 20 parts by weight of PI are added. The mixture is mechanically stirred at room temperature until completely dissolved. The mixture is then spin-coated into a film using a spin coater, dried at room temperature, and the remaining solvent is removed in a vacuum oven to obtain a BN / PI film. The BN / PI film obtained in this step is used as the upper and lower layers of the composite film.

[0014] As a further improvement to this scheme, in step (1), the mass ratio of CNT to dopamine hydrochloride is 5:1 to 1:5; The volume ratio of the ethanol and water mixture is 2:1 to 4:1. The mass ratio of the aqueous solution of tris(hydroxymethyl)aminomethane to CNT is 5:1 to 1:1.

[0015] As a further improvement to this scheme, in step (3), the mass ratio of BN to PI is 1:100 to 1:10; The spin coating conditions are: 1000~3000 rpm, 1 min; The solvent was removed in a vacuum oven, and the drying temperature was 80 ℃~160 ℃ for 12 hours.

[0016] As a further improvement to this solution, in step (2), the mass ratio of PDA@CNT to PI is 1:100~1:10. The drying conditions of the vacuum oven are 80 ℃~160 ℃ for 12 hours.

[0017] As a further improvement to this scheme, in step (4), the hot pressing conditions are 180 ℃~240 ℃ and 10~30KPa for 30 min to remove the holes and obtain the BN / PDA@CNT / PI dielectric composite film.

[0018] It has the following beneficial effects: 1) The fabrication principle of layered dielectric thin films The layered dielectric thin film of this invention is constructed through a layer-by-layer stacking structure, which allows for control over the material's thickness, interface structure, and properties. First, the upper and lower layers with a BN sheet orientation structure reduce dielectric loss and improve thermal conductivity. Second, a porous film with polymer-coated CNTs concentrated at the porous interface, after hot pressing, serves as an intermediate layer to further enhance the dielectric constant and thermal conductivity, making it suitable for preparing high-performance dielectric and thermally conductive thin film materials.

[0019] 2) The fabrication principle of high heat conduction network Hot pressing was performed on BN / PI non-porous films and PDA@CNT / PPI porous films. The BN sheet structure formed a highly oriented in-plane structure within the film, and together with the PDA@CNT network structure in the middle layer, a stacked structure of one-dimensional and two-dimensional nanomaterials was formed, which reduced the interfacial thermal resistance and improved the thermal conductivity and mechanical properties.

[0020] The layered dielectric composite film of the present invention uses a multilayer structure and inorganic filler surface modification to solve the problem of poor dispersion of inorganic fillers, effectively improving the dielectric and thermal conductivity of PI dielectric films. Attached Figure Description

[0021] Figure 1 In the preparation method of a layered dielectric composite film of the present invention, the dielectric constant and dielectric loss diagrams of the composite films in Examples 3, 4 and 5 are shown. Figure 2 In the preparation method of a layered dielectric composite film of the present invention, the dielectric constant and dielectric loss diagrams of the composite films of Comparative Examples 3, 4 and 5 are shown. Figure 3 The present invention provides a method for preparing a layered dielectric composite film, showing the changes in storage modulus E' and loss factor tan δ of the composite films in Examples 3, 4, and 5 as a function of temperature. Figure 4 SEM images of BN, original CNT, and PDA@CNT; Figure 5 SEM images of SiC nanowires and g-C3N4 nanosheets; Figure 6 SEM images of the cross-sections of the composite films in Examples 1, 2, and 3. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below in conjunction with embodiments and accompanying drawings: In the following embodiments and comparative examples: Hexagonal boron nitride is abbreviated as "BN"; Multi-walled carbon nanotubes are abbreviated as "CNT"; Graphite-phase carbon nitride nanosheets are simply referred to as "g-C3N4"; Silicon carbide nanowires are abbreviated as "SiC"; Polydopamine-coated carbon nanotubes are abbreviated as "PDA@CNT"; Polyphosphazene-coated carbon nanotubes are abbreviated as "PZS@CNT"; Polyimide is abbreviated as "PI"; Porous polyimide is simply referred to as "PPI".

[0023] Example 1 This embodiment provides a method for preparing a layered dielectric composite thin film, including the following steps: (1) Preparation of polydopamine-coated CNTs: 100 mg of CNT was added to a mixture of 75 ml of ethanol and 25 ml of water and dispersed by sonication. Then, 50 mg of dopamine hydrochloride was added, and the mixture was stirred thoroughly at room temperature. An aqueous solution containing 300 mg of tris(hydroxymethyl)aminomethane was then added, and the mixture was magnetically stirred for 12 h at room temperature. The resulting PDA@CNT / water / ethanol mixture was centrifuged and washed three times with deionized water. After drying, PDA@CNT powder was obtained.

[0024] (2) Preparation of BN / PI thin films: 0.036 g of BN was dispersed in dichloromethane solvent, and 3.60 g of PI was weighed and added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixture was then spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 °C for 12 h to remove the remaining solvent, thus obtaining a BN / PI film, which served as the upper and lower layers of the composite film.

[0025] Preparation of PDA@CNT / PPI porous films: 0.108 g of PDA@CNT was dispersed in N-methylpyrrolidone, and 3.60 g of PI was added. The mixture was stirred overnight. The mixture was coated onto a glass plate, and after removing the solvent at room temperature, it was demolded with deionized water and soaked for 1 hour. The plate was then transferred to a vacuum oven at 100 °C for 12 hours to remove the remaining solvent, thus preparing a PDA@CNT / PPI porous film, which served as the intermediate layer of the composite film.

[0026] (4) Finally, the single-layer films obtained in steps (2) and (3) above are stacked and hot-pressed for 30 min at 200 ℃ and 20 kPa to obtain a BN / PDA@CNT / PI dielectric composite film. Among them, the BN / PI film is used as the upper and lower layers, and the PDA@CNT / PPI porous film is used as the middle layer.

[0027] Example 2 This embodiment provides a method for preparing a layered dielectric composite thin film, including the following steps: (1) Preparation of polydopamine-coated CNTs: 100 mg of CNTs were added to a mixed solution of 75 ml ethanol and 25 ml water and dispersed by ultrasonication. Then, 50 mg of dopamine hydrochloride was added, and the mixture was stirred evenly at room temperature. Then, an aqueous solution containing 300 mg of tris(hydroxymethyl)aminomethane was added, and the mixture was stirred magnetically for 12 h at room temperature. The resulting PDA@CNT / water and ethanol mixture was centrifuged and washed three times with deionized water. After drying, PDA@CNT powder was obtained.

[0028] (2) Preparation of BN / PI film: 0.108 g of BN was dispersed in dichloromethane solvent, and 3.60 g of PI was weighed and added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixture was then spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining the BN / PI film, which served as the upper and lower layers of the composite film.

[0029] (3) Preparation of PDA@CNT / PPI porous film: 0.108 g of PDA@CNT was dispersed in N-methylpyrrolidone, and 3.60 g of PI was added and stirred overnight. The mixed solution was coated onto a glass plate, and after removing the solvent at room temperature, it was demolded with deionized water and soaked for 1 h. It was then transferred to a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus preparing the PDA@CNT / PPI porous film, which served as the intermediate layer of the composite film.

[0030] (4) Finally, the single-layer films obtained in steps (2) and (3) above are stacked and hot-pressed for 30 min at 200 ℃ and 20 kPa to obtain a BN / PDA@CNT / PI dielectric composite film. Among them, the BN / PI film is used as the upper and lower layers, and the PDA@CNT / PPI porous film is used as the middle layer.

[0031] Example 3 This embodiment provides a method for preparing a layered dielectric composite thin film, including the following steps: (1) Preparation of polydopamine-coated CNTs: 100 mg of CNTs were added to a mixed solution of 75 ml ethanol and 25 ml water and dispersed by ultrasonication. Then, 50 mg of dopamine hydrochloride was added, and the mixture was stirred evenly at room temperature. Then, an aqueous solution containing 300 mg of tris(hydroxymethyl)aminomethane was added, and the mixture was stirred magnetically for 12 h at room temperature. The resulting PDA@CNT / water and ethanol mixture was centrifuged and washed three times with deionized water. After drying, PDA@CNT powder was obtained.

[0032] (2) Preparation of BN / PI film: 0.180 g of BN was dispersed in dichloromethane solvent, and 3.60 g of PI was weighed and added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixture was then spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining the BN / PI film, which served as the upper and lower layers of the composite film.

[0033] (3) Preparation of PDA@CNT / PPI porous film: 0.108 g of PDA@CNT was dispersed in N-methylpyrrolidone, and 3.60 g of PI was added and stirred overnight. The mixed solution was coated onto a glass plate, and after removing the solvent at room temperature, it was demolded with deionized water and soaked for 1 h. It was then transferred to a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus preparing the PDA@CNT / PPI porous film, which served as the intermediate layer of the composite film.

[0034] (4) Finally, the single-layer films obtained in steps (2) and (3) above are stacked and hot-pressed for 30 min at 200 ℃ and 20 kPa to obtain a BN / PDA@CNT / PI dielectric composite film. Among them, the BN / PI film is used as the upper and lower layers, and the PDA@CNT / PPI porous film is used as the middle layer.

[0035] Example 4 This embodiment provides a method for preparing a layered dielectric composite thin film, including the following steps: (1) Preparation of polydopamine-coated CNTs: 100 mg of CNTs were added to a mixed solution of 75 ml ethanol and 25 ml water and dispersed by ultrasonication. Then, 50 mg of dopamine hydrochloride was added, and the mixture was stirred evenly at room temperature. Then, an aqueous solution containing 300 mg of tris(hydroxymethyl)aminomethane was added, and the mixture was stirred magnetically for 12 h at room temperature. The resulting PDA@CNT / water and ethanol mixture was centrifuged and washed three times with deionized water. After drying, PDA@CNT powder was obtained.

[0036] (2) Preparation of BN / PI film: 0.180 g of BN was dispersed in dichloromethane solvent, and 3.60 g of PI was weighed and added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixture was then spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining the BN / PI film, which served as the upper and lower layers of the composite film.

[0037] (3) Preparation of PDA@CNT / PPI porous film: 0.036 g of PDA@CNT was dispersed in N-methylpyrrolidone, and 3.60 g of PI was added and stirred overnight. The mixed solution was coated onto a glass plate, and after removing the solvent at room temperature, it was demolded with deionized water and soaked for 1 h. It was then transferred to a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus preparing a PDA@CNT / PPI porous film, which served as the intermediate layer of the composite film.

[0038] (4) Finally, the single-layer films obtained in steps (2) and (3) above are stacked and hot-pressed for 30 min at 200 ℃ and 20 kPa to obtain a BN / PDA@CNT / PI dielectric composite film. Among them, the BN / PI film is used as the upper and lower layers, and the PDA@CNT / PPI porous film is used as the middle layer.

[0039] Example 5 This embodiment provides a method for preparing a layered dielectric composite thin film, including the following steps: (1) Preparation of polydopamine-coated CNTs: 100 mg of CNTs were added to a mixed solution of 75 ml ethanol and 25 ml water and dispersed by ultrasonication. Then, 50 mg of dopamine hydrochloride was added, and the mixture was stirred evenly at room temperature. Then, an aqueous solution containing 300 mg of tris(hydroxymethyl)aminomethane was added, and the mixture was stirred magnetically for 12 h at room temperature. The resulting PDA@CNT / water and ethanol mixture was centrifuged and washed three times with deionized water. After drying, PDA@CNT powder was obtained.

[0040] (2) Preparation of BN / PI film: 0.180 g of BN was dispersed in dichloromethane solvent, and 3.60 g of PI was weighed and added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixture was then spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining the BN / PI film, which served as the upper and lower layers of the composite film.

[0041] (3) Preparation of PDA@CNT / PPI porous film: 0.180 g of PDA@CNT was dispersed in N-methylpyrrolidone, and 3.60 g of PI was added and stirred overnight. The mixed solution was coated onto a glass plate, and after removing the solvent at room temperature, it was demolded with deionized water and soaked for 1 h. It was then transferred to a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus preparing the PDA@CNT / PPI porous film, which served as the intermediate layer of the composite film.

[0042] (4) Finally, the single-layer films obtained in steps (2) and (3) above are stacked and hot-pressed for 30 min at 200 ℃ and 20 kPa to obtain a BN / PDA@CNT / PI dielectric composite film. Among them, the BN / PI film is used as the upper and lower layers, and the PDA@CNT / PPI porous film is used as the middle layer.

[0043] Comparative Example 1 Using Example 5 as the standard, Comparative Example 1 was a pure PI film, and the preparation process was consistent with that of the Example, but without the addition of CNT and BN fillers.

[0044] This comparative example provides a method for preparing a dielectric thin film, comprising the following steps: (1) Take 3.60 g of PI and N-methylpyrrolidone solvent and place them in a three-necked flask. Stir mechanically at room temperature until completely dissolved to obtain PI solution.

[0045] (2) The PI solution was placed on a glass slide and spin-coated to form a film using a spin coater. The spin coating conditions were 2000 rpm, room temperature drying for 1 day, vacuum oven at 100 ℃ for 12 h to remove the remaining solvent and obtain the PI film, which served as the upper and lower layers of the composite film.

[0046] (3) The mixed solution was coated onto a glass plate. After removing the solvent at room temperature, it was demolded with deionized water and soaked for 1 hour. It was then transferred to a vacuum oven at 100 °C for 12 hours to remove the remaining solvent, thus preparing a PPI porous film as the intermediate layer of the composite film.

[0047] (4) The film obtained in step (2) is used as the upper and lower layers, and the film obtained in step (3) is used as the middle layer. After stacking the three layers, the film is hot-pressed at 200℃ and 20 kPa for 30 min to obtain the PI dielectric film.

[0048] Comparative Example 2 Using Example 5 as the standard, the intermediate layer of Example 5 is a porous film, while the intermediate layer of Comparative Example 2 is a non-porous film.

[0049] This comparative example provides a method for preparing a dielectric thin film, comprising the following steps: (1) Preparation of polydopamine-coated CNTs: 100 mg of CNTs were added to a mixed solution of 75 ml ethanol and 25 ml water and dispersed by ultrasonication. Then, 50 mg of dopamine hydrochloride was added, and the mixture was stirred evenly at room temperature. Then, an aqueous solution containing 300 mg of tris(hydroxymethyl)aminomethane was added, and the mixture was stirred magnetically for 12 h at room temperature. The resulting PDA@CNT / water and ethanol mixture was centrifuged and washed three times with deionized water. After drying, PDA@CNT powder was obtained.

[0050] (2) Preparation of BN / PI film: 0.180 g of BN was dispersed in dichloromethane solvent, and 3.60 g of PI was weighed and added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixture was then spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining the BN / PI film, which served as the upper and lower layers of the composite film.

[0051] (3) Preparation of PDA@CNT / PI film: 0.180 g of PDA@CNT was dispersed in N-methylpyrrolidone, and 3.60 g of PI was added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixture was then spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining the PDA@CNT / PI film, which served as the intermediate layer of the composite film.

[0052] (4) Finally, the single-layer films obtained in steps (2) and (3) above are stacked and hot-pressed for 30 min at 200 ℃ and 20 kPa to obtain a BN / PDA@CNT / PI dielectric composite film. Among them, the BN / PI film is used as the upper and lower layers, and the PDA@CNT / PI film is used as the middle layer.

[0053] Comparative Example 3 Using Example 5 as the standard, the CNTs in Comparative Example 3 are unmodified CNTs.

[0054] This comparative example provides a method for preparing a dielectric thin film, comprising the following steps: (1) Preparation of unmodified CNTs: 100 mg of CNTs were added to a mixed solution of 75 ml of ethanol and 25 ml of water, ultrasonically dispersed, and magnetically stirred at room temperature for 12 h. The resulting CNT / water and ethanol mixed solution was centrifuged and washed three times with deionized water, and dried to obtain CNT powder.

[0055] (2) Preparation of BN / PI film: 0.180 g of BN was dispersed in dichloromethane solvent, and 3.60 g of PI was weighed and added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixture was then spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining the BN / PI film, which served as the upper and lower layers of the composite film.

[0056] (3) Preparation of CNT / PPI porous film: 0.180 g of CNT was dispersed in N-methylpyrrolidone, and 3.60 g of PI was added and stirred overnight. The mixed solution was coated onto a glass plate, and after removing the solvent at room temperature, it was demolded with deionized water and soaked for 1 h. It was then transferred to a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining a CNT / PPI porous film, which served as the intermediate layer of the composite film.

[0057] (4) Finally, the single-layer films obtained in steps (2) and (3) above are stacked and hot-pressed for 30 min at 200 ℃ and 20 kPa to obtain a BN / CNT / PI dielectric composite film. Among them, the BN / PI film is used as the upper and lower layers, and the CNT / PPI porous film is used as the middle layer.

[0058] Comparative Example 4 Using Example 5 as a standard, the CNTs in Comparative Example 4 were coated with PZS.

[0059] This comparative example provides a method for preparing a dielectric thin film, comprising the following steps: (1) Preparation of polyphosphazene (PZS) coated CNTs: 100 mg of CNTs were added to a mixed solution of 90 ml acetonitrile and 90 ml tetrahydrofuran, followed by 3 ml of triethylamine. The mixture was ultrasonically dispersed, and then 600 mg of hexachlorocyclotriphosphazene and 428 mg of 4,4'-diaminodiphenyl ether were added. The mixture was ultrasonically dispersed at 60 °C, stirred, and refluxed for 24 h. The product was filtered to obtain PZS@CNTs, washed with a mixed solution of water and ethanol, centrifuged three times, and dried to obtain PZS@CNT powder.

[0060] (2) Preparation of BN / PI film: 0.180 g of BN was dispersed in dichloromethane solvent, and 3.60 g of PI was weighed and added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixture was then spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining the BN / PI film, which served as the upper and lower layers of the composite film.

[0061] (3) Preparation of PZS@CNT / PPI porous film: 0.180 g of PZS@CNT was dispersed in N-methylpyrrolidone, and 3.60 g of PI was added and stirred overnight. The mixed solution was coated onto a glass plate, and after removing the solvent at room temperature, it was demolded with deionized water and soaked for 1 h. It was then transferred to a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus preparing the PZS@CNT / PPI porous film, which served as the intermediate layer of the composite film.

[0062] (4) Finally, the single-layer films obtained in steps (2) and (3) above are stacked and hot-pressed for 30 min at 200 ℃ and 20 kPa to obtain a BN / PZS@CNT / PI dielectric composite film. Among them, the BN / PI film is used as the upper and lower layers, and the PZS@CNT / PPI porous film is used as the middle layer.

[0063] Comparative Example 5 Using Example 5 as the standard, BN in Comparative Example 5 was replaced with graphitic carbon nitride g-C3N4 nanosheets.

[0064] This comparative example provides a method for preparing a dielectric thin film, comprising the following steps: (1) Preparation of polydopamine-coated CNTs: 100 mg of CNTs were added to a mixed solution of 75 ml ethanol and 25 ml water and dispersed by ultrasonication. Then, 50 mg of dopamine hydrochloride was added, and the mixture was stirred evenly at room temperature. Then, an aqueous solution containing 300 mg of tris(hydroxymethyl)aminomethane was added, and the mixture was stirred magnetically for 12 h at room temperature. The resulting PDA@CNT / water and ethanol mixture was centrifuged and washed three times with deionized water. After drying, PDA@CNT powder was obtained.

[0065] (2) Preparation of g-C3N4 / PI film: 0.180 g of graphitic carbon nitride nanosheets (g-C3N4) were dispersed in dichloromethane solvent, and 3.60 g of PI was weighed and added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixed solution was spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining the g-C3N4 / PI film, which served as the upper and lower layers of the composite film.

[0066] (3) Preparation of PDA@CNT / PPI porous film: 0.180 g of PDA@CNT was dispersed in N-methylpyrrolidone, and 3.60 g of PI was added and stirred overnight. The mixed solution was coated onto a glass plate, and after removing the solvent at room temperature, it was demolded with deionized water and soaked for 1 h. It was then transferred to a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus preparing the PDA@CNT / PPI porous film, which served as the intermediate layer of the composite film.

[0067] (4) Finally, the single-layer films obtained in steps (2) and (3) above are stacked and hot-pressed for 30 min at 200 ℃ and 20 kPa to obtain g-C3N4 / PDA@CNT / PI dielectric composite film. Among them, g-C3N4 / PI film is used as the upper and lower layers, and PDA@CNT / PPI porous film is used as the middle layer.

[0068] Comparative Example 6 Using Example 5 as the standard, BN in Comparative Example 6 was replaced with silicon carbide nanowires (SiC).

[0069] This comparative example provides a method for preparing a dielectric thin film, comprising the following steps: (1) Preparation of polydopamine-coated CNTs: 100 mg of CNTs were added to a mixed solution of 75 ml ethanol and 25 ml water and dispersed by ultrasonication. Then, 50 mg of dopamine hydrochloride was added, and the mixture was stirred evenly at room temperature. Then, an aqueous solution containing 300 mg of tris(hydroxymethyl)aminomethane was added, and the mixture was stirred magnetically for 12 h at room temperature. The resulting PDA@CNT / water and ethanol mixture was centrifuged and washed three times with deionized water. After drying, PDA@CNT powder was obtained.

[0070] (2) Preparation of SiC / PI thin film: 0.180 g of silicon carbide nanowires (SiC) were dispersed in dichloromethane solvent, and 3.60 g of PI was weighed and added. The mixture was mechanically stirred at room temperature until completely dissolved. The mixture was then spin-coated into a film using a spin coater at 2000 rpm. After drying at room temperature for 1 day, the film was dried in a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus obtaining the SiC / PI thin film, which served as the upper and lower layers of the composite film.

[0071] (3) Preparation of PDA@CNT / PPI porous film: 0.180 g of PDA@CNT was dispersed in N-methylpyrrolidone, and 3.60 g of PI was added and stirred overnight. The mixed solution was coated onto a glass plate, and after removing the solvent at room temperature, it was demolded with deionized water and soaked for 1 h. It was then transferred to a vacuum oven at 100 ℃ for 12 h to remove the remaining solvent, thus preparing the PDA@CNT / PPI porous film, which served as the intermediate layer of the composite film.

[0072] (4) Finally, the single-layer films obtained in steps (2) and (3) above are stacked and hot-pressed for 30 min at 200 ℃ and 20 kPa to obtain SiC / PDA@CNT / PI dielectric composite film. Among them, SiC / PI film is used as the upper and lower layers, and PDA@CNT / PPI porous film is used as the middle layer.

[0073] Analysis of experimental results: Figure 1 The dielectric constant and dielectric loss diagrams for the composite films of Examples 3, 4, and 5 are shown in 10... 2 ~10 6 Within the Hz range, by increasing the content of the intermediate layer PDA@CNT, the relative permittivity of the dielectric composite film gradually increases; Figure 2 The dielectric constant and dielectric loss diagrams are for comparative examples 3, 4, and 5 of the composite films.

[0074] Example 5 shows that the intermediate layer has the highest PDA@CNT content and the highest dielectric constant, with a dielectric constant of 7.57 and a dielectric loss of 0.015 at 1 MHz.

[0075] Example 4 has the lowest PDA@CNT content in the intermediate layer, and its dielectric constant is the lowest, with a dielectric constant of 7.01 and a dielectric loss of 0.038 at 1 MHz.

[0076] In Example 3, the content of PDA@CNT in the intermediate layer is moderate, with a dielectric constant of 7.46 and a dielectric loss of 0.018 at 1 MHz.

[0077] Example 5 showed a 127% improvement in dielectric constant (3.33@1MHz) compared to the original PI without filler in Comparative Example 1, while maintaining a low dielectric loss (~0.01@1MHz).

[0078] Compared to Comparative Example 3, the dielectric loss of the composite film with added original CNTs was reduced by 70-80% at 0.05@1MHz, while Comparative Example 3 had a dielectric constant of 7.49 at 1MHz.

[0079] Comparative Example 4, compared to Example 5, has an interlayer filler replaced with PZS@CNT, which has a dielectric constant of 7.31 and a dielectric loss of 0.036 at 1 MHz.

[0080] Compared to Example 5, Comparative Example 5 uses thermally conductive g-C3N4 nanosheets as the upper and lower fillers, which have a dielectric constant of 6.95 and a dielectric loss of 0.015 at 1 MHz.

[0081] Compared to Example 5, Comparative Example 6 uses thermally conductive SiC nanowires as the upper and lower fillers, achieving a dielectric constant of 7.6 and a dielectric loss of 0.15 at 1 MHz.

[0082] Figure 3 The energy storage modulus of the composite thin films in Examples 3, 4, and 5 E 'and loss factor tan δThe graph shows the change with temperature. When the BN content in both the upper and lower layers is 5 parts by weight, the energy storage modulus increases from 915 MPa to 1364 MPa and the glass transition temperature increases from 217 ºC to 225 ºC as the PDA@CNT content in the middle layer increases.

[0083] The volume resistivity of Examples 1-5 and Comparative Examples 1, 2, and 4-6 is all above 10. 14 ~10 15 Within this range, it falls under the category of insulating materials.

[0084] This indicates that the polydopamine-coated carbon nanotube filler within the PI matrix did not reach the percolation threshold for conductivity. The volume resistivity of Comparative Example 3 was 2 × 10⁻⁶. 10 The lack of PDA coating on CNTs resulted in a certain loss of insulation in the composite film.

[0085] The thermal conductivity (TC) of the composite films in Examples 1-5 is 0.52 W·m. -1 K -1 0.57 W·m -1 K -1 0.68 W·m -1 K -1 0.53 W·m -1 K -1 1.35 W·m -1 K -1 .

[0086] In Example 5, the composite material system achieved a TC of 1.35 W·m³ when both BN and PDA@CNT were filled in 5 parts by weight. -1 K -1 It is a pure PI thin film TC (0.15 W·m -1 K -1 ) 9 times (Comparative Example 1).

[0087] The TC of the composite film in Comparative Example 2 was 1.15 W·m. -1 K -1 It is evident that simply changing the intermediate layer to a non-porous film does not improve thermal conductivity as efficiently as the hot pressing method with porous films.

[0088] The TC of the composite film in Comparative Example 3 was 1.03 W·m. -1 K -1 The dispersion of CNTs without PDA coating in porous films is poor, and the improvement in TC is not as good as that after hot pressing of porous intermediate layers.

[0089] The TC of the composite film in Comparative Example 4 was 1.33 W·m. -1 K -1PZS@CNT / PPI serves as the intermediate layer, and the thermal conductivity of the composite film is similar to that of Example 5.

[0090] The TC of the composite film in Comparative Example 5 was 0.95 W·m. -1 K -1 When g-C3N4 / PI films are used as the upper and lower layers, g-C3N4 tends to agglomerate, and its efficiency in improving thermal conductivity is not as good as that of oriented BN nanosheets.

[0091] The TC of the composite film in Comparative Example 6 was 0.87 W·m. -1 K -1 When SiC / PI films are used as the upper and lower layers, the efficiency of improving the thermal conductivity of nanowires is not as good as that of oriented BN nanosheets.

[0092] This invention resolves the technical contradiction of simultaneously achieving high thermal conductivity and low dielectric loss / insulation through a specific combination of processes, achieving a balanced performance improvement through structural optimization. The key process step lies in the combination of "non-solvent-induced phase separation (NIPS) preparation of a porous interlayer + hot pressing to construct a sandwich structure." Using the NIPS method, PDA@CNT fillers are uniformly anchored onto the pore walls of a PPI porous framework, forming a three-dimensional percolation network. Hot pressing significantly shrinks the pore structure of the originally porous interlayer, but retains the three-dimensional percolation network of PDA@CNTs constructed by the NIPS method, avoiding the problem of CNT agglomeration. Compared with simple blending or simple three-layer stacking, this invention achieves a significant reduction in dielectric loss and a substantial improvement in thermal conductivity while simultaneously increasing the dielectric constant.

[0093] The above description is only a preferred embodiment of the present invention and does not limit the patent scope of the present invention. All equivalent modifications made using the present invention are within the patent protection scope of the present invention.

Claims

1. A method for preparing a dielectric composite thin film based on a layered structure, characterized in that, The preparation steps include the following: The layered dielectric composite film includes an upper layer, a middle layer, and a lower layer arranged sequentially. The upper layer is a BN / PI thin film; The intermediate layer is a PDA@CNT / PPI porous film; The lower layer is a BN / PI thin film; The three layers of film that were set in sequence in the previous step were stacked under hot pressing conditions and then hot pressed for 30 min to obtain BN / PDA@CNT / PI dielectric composite film.

2. The method for preparing a layered dielectric composite thin film according to claim 1, characterized in that, The intermediate layer, a PDA@CNT / PPI porous film, was prepared as follows: (1) Preparation of polydopamine-coated CNTs: CNTs were ultrasonically dispersed in a mixture of ethanol and water. Dopamine hydrochloride was added and stirred evenly at room temperature. Then, an aqueous solution containing tris(hydroxymethyl)aminomethane was added and magnetically stirred at room temperature for 12 h. After centrifugation and washing with deionized water, PDA@CNT powder was obtained after drying. (2) Preparation of PDA@CNT / PPI porous films: 0.1-1 parts by weight of PDA@CNT were dispersed in N-methylpyrrolidone, 10 parts by weight of PI were added, and the mixture was stirred overnight. The mixture was then coated onto a glass plate. After removing the solvent at room temperature, the plate was demolded with deionized water and soaked for 1 hour. The plate was then transferred to a vacuum oven to remove the remaining solvent, thus preparing a PDA@CNT / PPI porous film, which served as the intermediate layer of the composite film.

3. The method for preparing a layered dielectric composite thin film according to claim 1, characterized in that, The preparation of the upper and lower BN / PI films is as follows: (3) Preparation of BN / PI thin film 0.2-2 parts by weight of BN are dispersed in dichloromethane solvent, and 20 parts by weight of PI are added. The mixture is mechanically stirred at room temperature until completely dissolved. The mixture is then spin-coated into a film using a spin coater, dried at room temperature, and the remaining solvent is removed in a vacuum oven to obtain a BN / PI film. The BN / PI film obtained in this step is used as the upper and lower layers of the composite film.

4. The method for preparing a layered dielectric composite thin film according to claim 1, characterized in that, In step (1), the mass ratio of CNT to dopamine hydrochloride is 5:1 to 1:5; The volume ratio of the ethanol and water mixture is 2:1 to 4:

1. The mass ratio of the aqueous solution of tris(hydroxymethyl)aminomethane to CNT is 5:1 to 1:

1.

5. The method for preparing a layered dielectric composite thin film according to claim 1, characterized in that, In step (3), the mass ratio of BN to PI is 1:100 to 1:10; The spin coating conditions are: 1000~3000 rpm, 1 min; The solvent was removed in a vacuum oven, and the drying temperature was 80 ℃~160 ℃ for 12 hours.

6. The method for preparing a layered dielectric composite thin film according to claim 1, characterized in that, In step (2), the mass ratio of PDA@CNT to PI is 1:100 to 1:

10. The drying conditions of the vacuum oven are 80 ℃~160 ℃ for 12 hours.

7. The method for preparing a layered dielectric composite thin film according to claim 1, characterized in that, In step (4), the hot pressing conditions are 180 ℃~240 ℃ and 10~30 KPa for 30 min to remove the pores and obtain the BN / PDA@CNT / PI dielectric composite film.

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