Electric insulation type electromagnetic shielding-heat conduction multifunctional composite film and preparation method and application thereof

Abstract

The invention belongs to the technical field of electromagnetic shielding-heat management multifunctional materials, and discloses an electric insulation type electromagnetic shielding-heat conduction multifunctional composite film and a preparation method and application thereof. A metal phase / semiconductor vanadium oxide nanowire / sheet / belt prepared by adopting a one-step hydrothermal method is adopted, and then the vanadium oxide / polymer composite film is obtained by adopting a vacuum filtration-packaging and hot pressing process. The one-step hydrothermal method is adopted, operation is simple, and the obtained product is adjustable in morphology, phase structure and performance; the method has the advantages of cheap and easily available raw materials, low energy consumption, environmental protection, good repeatability, low requirement on instrument precision, high yield and good industrial application potential; the vacuum filtration-packaging and hot pressing process is simple to operate, low in cost and easy for large-scale production; and the obtained vanadium oxide / polymer composite film has good electromagnetic shielding, heat conduction and electrical insulation properties, and has good industrial application potential in the fields of electromagnetic shielding, heat management, sensors and the like.

Description

Technical Field

[0001] The present invention belongs to the technical field of electromagnetic shielding-thermal management multifunctional materials, and relates to a preparation and film-forming process of low-dimensional metal phase / semiconductor vanadium oxide fillers and their applications in the fields of electromagnetic shielding, thermal management, sensors, supercapacitors, photocatalysis, and batteries. Background Art

[0002] Among different new ceramic materials, heterostructured vanadium oxide nanowires / ribbons / sheets have low density, high specific surface area, large shape anisotropy, and unique mechanical, electrical, and thermal properties, showing good application prospects in the fields of thermal management, energy, electronic devices, and electromagnetic protection; vanadium ions have multiple oxidation states (+5, +4, +3, +2, +1), and can form different single-valence vanadium oxides (such as V 2 O 5 、VO 2 、V 2 O 3 、VO、V 2 O) and mixed-valence vanadium oxides, namely Magnéli phase V n O 2n-1 (3≤n≤9) and Wadsley phase V n O2 n+1 (n = 2, 3, 6). During the process of vanadium ions changing from high oxidation state to low oxidation state, oxygen vacancies and free electrons are usually generated, which is beneficial to dipole / defect polarization loss; therefore, VO 2 、V 2 O 3 、V 2 O 5 、VOOH and their composites have been studied as microwave absorbers.

[0003] At present, the reported vanadium oxides are mainly used as electromagnetic wave shielding, absorption and heat conduction materials in combination with other materials. Among them, Chinese Patent CN109502578A discloses a preparation method of a vanadium oxide-graphene intercalation composite material. This preparation method uses vanadium pentoxide and graphene as raw materials, and is obtained through an ice-water bath, pH adjustment, aging, and high-temperature calcination. Finally, it can be used as an electromagnetic shielding material. This method uses a relatively high temperature and a complex process; Chinese Patent CN119240788A discloses a microwave absorption material of nitrogen-doped vanadium oxide and its preparation method. This preparation method uses ammonium metavanadate, guanidine carbonate and glucose as raw materials, and subsequent steps such as pH adjustment, hydrothermal treatment, and calcination are required, and the process is cumbersome; Chinese Patent CN114574169A discloses a vanadium dioxide-boron nitride phase change heat conduction composite material, its preparation method and application. This method uses ammonium metavanadate, oxalic acid, hexagonal boron nitride, ammonium tungstate and / or tellurium dioxide as raw materials. This method is obtained through steps such as stirring, hydrothermal treatment, centrifugation, and calcination. This method is divided into two steps, with a long time, a high temperature, and a complex process.

[0004] Therefore, how to develop a process-simple, easy-to-industrialize, with controllable morphology and size, having a high specific surface area, and an electromagnetic shielding / wave absorption-heat conduction multifunctional material is an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide an electrically insulating electromagnetic shielding-heat conduction multifunctional composite film, its preparation method and application. The electromagnetic shielding-heat conduction multifunctional filler of this composite film is simple to operate and has a novel product morphology. The vanadium oxide / polymer composite film is obtained by vacuum filtration-encapsulation and hot pressing process, which overcomes the defects of harsh reaction conditions, difficult control of the morphology of reaction products, and poor experimental repeatability in the previous preparation process; the obtained vanadium oxide / polymer composite film has good electromagnetic shielding, heat conduction and electrical insulation properties, and has good industrial application potential in the fields of electromagnetic shielding, thermal management, sensors, etc.

[0006] In order to achieve the above purpose, the present invention discloses the following technical content:

[0007] The first technical purpose of the present invention is to provide an electrically insulating electromagnetic shielding-heat conduction multifunctional composite film, which is obtained by vacuum filtration-encapsulation and hot pressing process using an electromagnetic shielding-heat conduction multifunctional filler; the electromagnetic shielding-heat conduction multifunctional filler is metal-phase vanadium oxide / semiconductor vanadium oxide nanowires / nanoplates / nanobelts; the vanadium oxide is VO 2 (A), VO 2 (P), V 2 O 5 V 3 O 7; The average diameter of the nanowires / nanosheets / nanobelts is 51.2 - 798.0 nm, the average length is 35.8 - 1116.8 μm, and the aspect ratio is 50.4 - 13739.7. From the EDX pattern of the vanadium metal oxide / semiconductor vanadium oxide nanowires / nanosheets / nanobelts, it can be obtained that they contain V and O elements.

[0008] Furthermore, the multifunctional composite film has excellent thermal conductivity and shielding properties. The thermal conductivity is 2.36 - 4.25 W / (m·K); the electromagnetic interference shielding effectiveness is 12.1 - 46.9 dB, and the sample thickness is 3 mm.

[0009] It should be noted that VO 2 has ten phase structures (M1, M2, B, A, R, P, T, etc.). Among them, due to its high stability and metal-insulator transition characteristics, M1 and R phase VO 2 and their composites (VO 2 (M) / Ti 3 C 2 T x ), cellulose nanofibers / VO 2 (R), VO 2 / graphene, VO 2 / CNF) have been studied the most as intelligent electromagnetic wave absorption / shielding materials. VO 2 , V 2 O 5 and their composites have also been studied separately as thermal conductive fillers. Since the heterointerfaces are beneficial to microwave absorption / shielding, but the phonon mismatch at the heterointerfaces is not conducive to the heat conduction of the heterostructure materials. Therefore, we choose low-dimensional metal phase VO 2 (A) with good phonon matching and semiconductor vanadium oxide to construct a heterostructure nanofiber / band / sheet. As far as we know, currently, vanadium oxide is mainly studied separately as an electromagnetic wave absorption / shielding or thermal conductive material, while the study on VO 2 (A), especially the low-dimensional metal phase VO 2 (A) / semiconductor vanadium oxide composite film as an electromagnetic wave shielding-thermal conduction-electrical insulation multifunctional material is rarely reported, and the incompatibility of the electromagnetic wave shielding-thermal conduction-electrical insulation properties makes it face great challenges to improve their performance synergistically.

[0010] The second technical objective of the present invention is to provide a preparation method of the above-mentioned electrically insulating electromagnetic shielding-thermal conduction multifunctional composite film. The multifunctional composite film is prepared by a vacuum filtration-encapsulation and hot pressing process using electromagnetic shielding-thermal conduction multifunctional fillers. The specific steps are as follows:

[0011] (1) Vacuum filtration to form a film: Weigh a certain mass of the electromagnetic shielding-thermal conductivity multifunctional filler and add it to water, then ultrasonically disperse it for 10 - 30 minutes to obtain an aqueous solution of the multifunctional filler; pour the dispersed solution into a vacuum filtration device to filter it into a pure film, place the film between two glass slides, and dry it at 50 - 80 °C for 6 - 12 hours for later use;

[0012] (2) Film encapsulation process: thinly coat a solution of thermoplastic polyurethane (TPU) and 1,4-dioxane on one of the glass slides, then place the dried film between the two glass slides, evacuate the excess air bubbles in a vacuum drying oven, and evaporate the solvent to complete the TPU encapsulation of one side of the film; use the same method to encapsulate the other side of the film with TPU to obtain the electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film;

[0013] (3) Film hot pressing process: Place the obtained electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film between two glass slides, and then perform hot pressing treatment with an electric iron at 90 - 110 °C for 10 minutes.

[0014] Preferably, the electromagnetic shielding-thermal conductivity multifunctional filler is prepared by a hydrothermal method, that is: mix vanadium pentoxide, polyethylene glycol with different molecular weights and water, stir and pour it into a reaction kettle, react at 200 °C for 48 h, the mass ratio of vanadium pentoxide to surfactant is 11:18, and the mass ratio of vanadium pentoxide to water is 1:320 - 1:50; after the reaction is completed and naturally cooled to room temperature, wash the sample alternately with water and ethanol and filter it out, and dry it to obtain metal-phase vanadium oxide / semiconductor vanadium oxide nanowires / nanoplates / nanobelts with different aspect ratios, that is, the electromagnetic shielding-thermal conductivity multifunctional filler.

[0015] It should be noted that the electromagnetic shielding-thermal conductivity multifunctional filler prepared by the hydrothermal method disclosed in the present invention not only has a novel structure and formation mechanism, but also can prepare a series of metal-phase vanadium oxide / semiconductor vanadium oxide nanowires / nanoplates / nanobelts by changing the hydrothermal reaction time, and the prepared nanowires / nanoplates / nanobelts show great potential in the field of electromagnetic shielding; moreover, the electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film prepared by the present invention has excellent thermal conductivity-shielding characteristics.

[0016] In addition, the preparation method disclosed in the present invention is simple to operate and the product morphology is novel, overcoming the defects of harsh reaction conditions, difficult control of the morphology of reaction products, and poor experimental repeatability in the previous preparation process, and has good potential for industrial application.

[0017] Furthermore, the molecular weights of the polyethylene glycol are 400 g / mol, 2000 g / mol, 6000 g / mol, 10000 g / mol and 20000 g / mol.

[0018] Furthermore, the reaction temperature is 120 - 220°C, the stirring time is 0.5 - 1.0 h, and the reaction time is 3 - 72 h.

[0019] Preferably, in step (1), the concentration of the multifunctional filler aqueous solution is 0.019 mol / L - 0.076 mol / L; in step (2), the concentration of the solution of thermoplastic polyurethane (TPU) in 1,4 - dioxane is 0.083 - 0.125 g / mL.

[0020] The third technical object of the present invention is to provide the application of the above - mentioned electrically insulating electromagnetic shielding - thermal conductivity multifunctional composite film in the fields of electromagnetic shielding, thermal management, sensors, supercapacitors, photocatalysis, and batteries.

[0021] It can be seen from the above - mentioned technical solutions that, compared with the prior art, the present invention provides an electrically insulating electromagnetic shielding - thermal conductivity multifunctional composite film, its preparation method and application, and has the following excellent effects:

[0022] 1) The present invention uses water as a solvent, vanadium pentoxide as a raw material, and polyethylene glycol as a surfactant, and prepares metal - phase vanadium oxide / semiconductor vanadium oxide nanowires / nanoplates / nanobelts with unique morphologies by a one - step hydrothermal method. This synthesis method is simple, has a high yield, and the morphology, phase structure, and properties of the obtained products can be adjusted.

[0023] 2) The electrically insulating electromagnetic shielding - thermal conductivity multifunctional composite film prepared by the present invention has good electrical insulation, excellent thermal conductivity, hydrophobicity, electromagnetic shielding, Joule heat, and sensing characteristics, and shows great application potential in the fields of electromagnetic shielding, thermal management, and sensing, especially in extreme environments.

[0024] 3) The vacuum filtration - encapsulation and hot - pressing process of the electrically insulating electromagnetic shielding - thermal conductivity multifunctional composite film of the present invention is simple and unique, and the raw materials are cheap and easily available. The reaction process is simple, time - consuming short, energy - consuming small, dangerous low, green and environmentally friendly, has good repeatability, low requirement for instrument precision, and has a considerable output, and has good industrial application potential. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only the embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained according to the provided drawings.

[0026] Figures 1 to 3 They are respectively the phase and morphology of the product obtained in Example 1 of the present invention measured by XRD, EDX, and scanning electron microscopy.

[0027] Figures 4 to 6 They are the phases and morphologies of the product obtained in Example 2 of the present invention measured by XRD, EDX, and scanning electron microscopy respectively.

[0028] Figures 7 to 9 They are the phases and morphologies of the product obtained in Example 3 of the present invention measured by XRD, EDX, and scanning electron microscopy respectively.

[0029] Figure 10 It is the morphology of the product obtained in Example 4 of the present invention measured by scanning electron microscopy.

[0030] Figure 11 It is the morphology of the product obtained in Example 5 of the present invention measured by scanning electron microscopy.

[0031] Figure 12 It is the morphology of the product obtained in Example 6 of the present invention measured by scanning electron microscopy.

[0032] Figure 13 It is the morphology of the product obtained in Example 7 of the present invention measured by scanning electron microscopy.

[0033] Figure 14 It is the morphology of the product obtained in Example 8 of the present invention measured by scanning electron microscopy.

[0034] Figure 15 It is the morphology of the product obtained in Example 9 of the present invention measured by scanning electron microscopy. Detailed implementation manners

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] The embodiments of the present invention disclose an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film with simple process, controllable size and good electromagnetic shielding characteristics, and its preparation method and application.

[0037] To better understand the present invention, the following embodiments are used to further specifically illustrate the present invention, but it should not be construed as a limitation to the present invention. For those skilled in the art, some non-essential improvements and adjustments made according to the above invention content are also considered to fall within the protection scope of the present invention.

[0038] Next, the technical solutions of the present invention will be further described in conjunction with specific embodiments.

[0039] Example 1

[0040] A preparation method of an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film specifically includes the following steps:

[0041] Add 0.55 g of vanadium pentoxide and 0.9 g of PEG 2000 to 80 mL of water, stir magnetically at room temperature for 1 h, and the solution turns bright orange; then place the solution in a high-pressure reaction kettle and carry out hydrothermal reaction at 200 °C for 48 h; after the reaction is completed, cool to room temperature and then filter out the sample by suction filtration under the condition of alternating washing with water and ethanol several times, and dry it in an oven at 60 °C for 12 h to obtain the electromagnetic shielding-thermal conductive multifunctional filler;

[0042] Take 0.5 g of the dried sample and add it to 100 mL of water for ultrasonic dispersion for 30 mins, pour the dispersed solution into a vacuum filtration device and filter it into a pure film, place it between two glass slides and bake it at 60 °C for 6 hours; thinly coat a solution of thermoplastic polyurethane (TPU) and 1,4-dioxane on one of the glass slides, then place the dried film between two glass slides, evacuate the excess bubbles in a vacuum drying oven, and evaporate the solvent at 60 °C to complete the TPU encapsulation of one side of the film; use the same method to encapsulate the other side of the film with TPU, and finally obtain an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film;

[0043] Place the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film between two glass slides, and then carry out hot pressing treatment at about 100 °C for 10 minutes; this hot pressing process promotes the full infiltration of the TPU matrix and penetration into the filler gaps and makes the composite film smoother, thereby effectively improving the thermal conductivity of the composite film.

[0044] The phase, composition, and morphology of the obtained filler measured by XRD, EDX, and scanning electron microscopy are respectively as Figures 1 to 3 shown.

[0045] The product is V 3 O 7 ·H 2 O and VO 2 (A) nanowires / nanobelts with an average length of 567.3 μm and an average diameter of 116 nm. It can be obtained from the EDX diagram that it contains V and O elements.

[0046] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film has excellent electromagnetic shielding characteristics. Among them, the thickness is 3 mm, and the electromagnetic interference shielding effectiveness SE in the range of 2 - 18 GHz T ≥20 dB, and the maximum SE T is 46.9 dB; the thermal conductivity is 3.22 W / (m·K).

[0047] Example 2

[0048] A preparation method of an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film. With other conditions unchanged, on the basis of Example 1, the molecular weight of polyethylene glycol was changed to 400 g / mol.

[0049] The phase, composition, and morphology of the obtained filler measured by XRD, EDX, and scanning electron microscopy are respectively as Figures 4 to 6 shown.

[0050] The product is V 3 O 7 ·H 2 O and VO 2 (A) nanobelts with an average length of 40.2 μm and an average diameter of 798.0 nm. It can be concluded from the EDX pattern that it contains V and O elements.

[0051] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film has excellent electromagnetic shielding properties. Among them, the thickness is 3 mm, and the electromagnetic interference shielding effectiveness SE in the range of 5.8 - 18 GHz T ≥20 dB, and the maximum SE T is 33.3 dB; the thermal conductivity is 2.89 W / (m·K).

[0052] Example 3

[0053] A preparation method of an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film. With other conditions unchanged, on the basis of Example 1, the molecular weight of polyethylene glycol was changed to 20000 g / mol.

[0054] The phase, composition, and morphology of the obtained filler measured by XRD, EDX, and scanning electron microscopy are respectively as Figures 7 to 9 shown.

[0055] The product is V 2 O 5 ·1.6H 2 O and V 3 O 7 ·H 2 O nanowires / nanobelts with an average length of 1116.8 μm and an average diameter of 92 nm. It can be concluded from the EDX pattern that it contains V and O elements.

[0056] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film has excellent electromagnetic shielding properties. Among them, the thickness is 3 mm, and the electromagnetic interference shielding effectiveness SE in the range of 4.4 - 18 GHz T ≥20 dB, and the maximum SE T is 40.1 dB; the thermal conductivity is 4.25 W / (m·K).

[0057] Example 4

[0058] A preparation method of an electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film, with other conditions unchanged, the hydrothermal time was changed to 3 h on the basis of Example 1.

[0059] The morphology of the obtained filler measured under a scanning electron microscope is as Figure 10 shown.

[0060] The product is V 2 O 5 ·1.6H 2 O, V 3 O 7 ·H 2 O and V 2 O 5 ·H 2 O nanowires / nanobelts, with an average length of 147.7 μm and an average diameter of 118 nm.

[0061] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film has excellent electromagnetic shielding properties, with a thickness of 3 mm, and the electromagnetic interference shielding effectiveness SE T ≥20 dB in the range of 16 - 18 GHz, and the maximum SE T is 23.1 dB; the thermal conductivity is 2.37 W / (m·K).

[0062] Example 5

[0063] A preparation method of an electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film, with other conditions unchanged, the hydrothermal time was changed to 72 h on the basis of Example 1.

[0064] The morphology of the obtained filler measured under a scanning electron microscope is as Figure 11 shown.

[0065] The product is V 3 O 7 ·H 2 O and VO 2 (A) nanowires / nanobelts, with an average length of 584.9 μm and an average diameter of 106 nm.

[0066] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film has excellent electromagnetic shielding properties, with a thickness of 3 mm, and the electromagnetic interference shielding effectiveness SE T ≥20 dB in the range of 2 - 18 GHz, and the maximum SE T is 43.7 dB; the thermal conductivity is 3.86 W / (m·K).

[0067] Example 6

[0068] A preparation method of an electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film. With other conditions unchanged, based on Example 1, the hydrothermal temperature is changed to 120 °C.

[0069] The morphology of the obtained filler measured under a scanning electron microscope is as Figure 12 shown.

[0070] The product is V 2 O 5 ·1.6H 2 O nanosheets with an average diameter of 522.9 nm.

[0071] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film has excellent electromagnetic shielding properties. Among them, the thickness is 3 mm, and the maximum SE T is 12.1 dB; the thermal conductivity is 2.36 W / (m·K).

[0072] Example 7

[0073] A preparation method of an electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film. With other conditions unchanged, based on Example 1, the hydrothermal temperature is changed to 220 °C.

[0074] The morphology of the obtained filler measured under a scanning electron microscope is as Figure 13 shown.

[0075] The product is V 3 O 7 ·H 2 O and VO 2 (A) nanowires / nanobelts with an average length of 22.9 μm and an average diameter of 280 nm.

[0076] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film has excellent electromagnetic shielding properties. Among them, the thickness is 3 mm, and in the range of 4.8 - 18 GHz, the electromagnetic interference shielding effectiveness SE T ≥20 dB, and the maximum SE T is 37.7 dB; the thermal conductivity is 2.90 W / (m·K).

[0077] Example 8

[0078] A preparation method of an electrically insulating electromagnetic shielding-thermal conductivity multifunctional composite film. With other conditions unchanged, based on Example 1, the mass ratio of vanadium pentoxide to water is changed to 11:3200.

[0079] The morphology of the obtained filler measured under a scanning electron microscope is as Figure 14 shown.

[0080] The product is V 3 O 7 ·H2 O and VO 2 (A) Nanowires / nanobelts with an average length of 477.4 μm and an average diameter of 144 nm.

[0081] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film has excellent electromagnetic shielding properties, with a thickness of 3 mm, and an electromagnetic interference shielding effectiveness SE in the range of 5.6 - 18 GHz T ≥20 dB, and the maximum SE T is 39.3 dB; the thermal conductivity is 3.12 W / (m·K).

[0082] Example 9

[0083] A preparation method of an electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, with other conditions unchanged, based on Example 1, the mass ratio of vanadium pentoxide to water is changed to 11:800.

[0084] The morphology of the obtained filler measured under a scanning electron microscope is as Figure 15 shown.

[0085] The product is V 3 O 7 ·H 2 O and VO 2 (A) Nanowires / nanobelts with an average length of 703.5 μm and an average diameter of 51.2 nm.

[0086] As shown in Table 1, the obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film has excellent electromagnetic shielding properties, with a thickness of 3 mm, and an electromagnetic interference shielding effectiveness SE in the range of 4.2 - 18 GHz T ≥20 dB, and the maximum SE T is 44.2 dB; the thermal conductivity is 3.49 W / (m·K).

[0087] Table 1 shows the electromagnetic shielding-thermal conductive properties of the products obtained in Examples 1 - 9 of the present invention

[0088]

[0089] By analyzing the above data, it can be seen that the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film prepared by the present invention has good thermal conductive and shielding properties.

[0090] The foregoing description of the disclosed embodiments enables those skilled in the art to practice or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. An electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film, characterized in that: The composite film is obtained by using a vacuum filtration-packaging and hot pressing process to process an electromagnetic shielding-thermal conductive multifunctional filler; the electromagnetic shielding-thermal conductive multifunctional filler is a metal phase vanadium oxide / semiconductor vanadium oxide nanowire / sheet / belt; the vanadium oxide is VO2(A), VO2(P), V2O5, V3O7; the average diameter of the nanowire / sheet / belt is 51.2-798.0nm, the average length is 35.8-1116.8μm, and the aspect ratio is 50.4-13739.

7.

2. The electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 1, characterized in that: The multifunctional composite film has excellent thermal conductivity and shielding properties, with a thermal conductivity of 2.36 to 4.25 W / (m·K); an electromagnetic interference shielding effectiveness of 12.1 to 46.9 dB, and a sample thickness of 3 mm.

3. A method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film as claimed in claim 1, characterized in that: The multifunctional composite film is prepared by using a vacuum filtration-packaging and hot pressing process to prepare an electromagnetic shielding-heat conducting multifunctional filler, and the specific steps are as follows: (1) Vacuum filtration film formation: Weigh a certain mass of electromagnetic shielding-thermal conductive multifunctional filler and add it to water, and ultrasonically disperse it for 10 to 30 minutes to obtain a multifunctional filler aqueous solution; pour the dispersed solution into a vacuum filtration device and filter it into a pure film, and place the film between two glass sheets and dry it at 50 to 80° C. for 6 to 12 hours for use; (2) Film encapsulation process: a thin layer of thermoplastic polyurethane (TPU) and 1,4-dioxane solution is coated on one of the glass sheets, and then the dried film is placed between two glass sheets, and vacuum is drawn in a vacuum drying oven to remove excess bubbles and evaporate the solvent to complete TPU encapsulation of one side of the film; the other side of the film is encapsulated with TPU using the same method to obtain the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film; (3) Film hot pressing process: The obtained electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film is placed between two glass sheets, and then hot pressed at 90-110° C. for 10 minutes; 4. The method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 3, characterized in that: The electromagnetic shielding-thermal conductive multifunctional filler is prepared by a hydrothermal method, and the specific steps are as follows: Vanadium pentoxide, a surfactant and water are mixed, stirred and reacted at a certain temperature for different times; after the reaction is completed, the mixture is naturally cooled to room temperature, washed alternately with water and ethanol, and the sample is filtered out, and dried to obtain metal phase vanadium oxide / semiconductor vanadium oxide nanowires / sheets / belts with different aspect ratios, namely the electromagnetic shielding-thermal conductive multifunctional filler.

5. The method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 4, characterized in that: The surfactant is polyethylene glycol with molecular weights of 400 g / mol, 2000 g / mol, 6000 g / mol, 10000 g / mol and 20000 g / mol; the mass ratio of vanadium pentoxide to surfactant is 11:18, and the mass ratio of vanadium pentoxide to water is 1:320-1:

50.

6. The method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 4, characterized in that: The reaction temperature is 120-220° C., the stirring time is 0.5-1.0 h, and the reaction time is 3-72 h.

7. The method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 3, characterized in that: In step (1), the concentration of the multifunctional filler aqueous solution is 0.019 mol / L to 0.076 mol / L.

8. The method for preparing the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film according to claim 3, characterized in that: In step (2), the concentration of the 1,4-dioxane solution of the thermoplastic polyurethane (TPU) is 0.083 to 0.125 g / mL.

9. An application of the electrically insulating electromagnetic shielding-thermal conductive multifunctional composite film as claimed in claim 1 or the electromagnetic shielding-thermal conductive multifunctional filler prepared by the method as claimed in any one of claims 3 to 8 in the fields of electromagnetic shielding, thermal management, sensors, supercapacitors, photocatalysis, and batteries.

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