A composite film with electromagnetic shielding and thermal conductivity and a preparation method thereof

Abstract

The present invention belongs to the technical field of functional composite films, and specifically discloses a composite film with electromagnetic shielding and thermal conductivity and a preparation method thereof. First, Fe3O4 nanoparticles, Ti3C2T x MXene nanosheets and cobalt-multi-walled carbon nanotubes are prepared, and then Ti3C2T x MXene dispersion, Fe3O4 dispersion, cobalt-multi-walled carbon nanotube dispersion and glass fiber dispersion are prepared. Then, Fe3O4@Ti3C2T x MXene mixed dispersion and Co-MWCNTs mixed dispersion are obtained. Then, an electromagnetic shielding and thermal conductivity composite film is prepared by alternating suction filtration. The electromagnetic shielding material prepared by the present invention is not limited to the X band, and also has good electromagnetic shielding effect in the K u band, and has excellent heat dissipation performance and high strength, and can meet the current requirements for electromagnetic shielding materials.

Description

Technical Field

[0001] The present invention relates to the technical field of functional composite films, and particularly relates to a composite film with electromagnetic shielding and heat conduction properties and a preparation method thereof. Background Art

[0002] With the advent of the 5G era, the rapid replacement and large-scale popularization of electronic devices have generated a large amount of electromagnetic radiation. Excessive electromagnetic radiation will interfere with the normal operation of electronic devices and even cause health problems for the human body. However, due to the extensive application of centimeter waves and millimeter waves in the 5G field, higher requirements are put forward for the broadband of electromagnetic shielding materials. At the same time, due to the miniaturization and high integration of electronic devices, the problem of heat accumulation during their operation is becoming increasingly serious, and higher requirements are also put forward for the heat conduction performance and light weight of electromagnetic shielding materials. Common / Traditional traditional electromagnetic shielding materials have gradually been unable to meet the needs, and the design and development of lightweight and highly thermally conductive broadband electromagnetic shielding materials have become problems that need to be solved urgently at present.

[0003] In recent years, 2D (graphene, phosphorene, etc.) materials with high conductivity have become the most competitive and promising electromagnetic shielding materials due to their strong electromagnetic wave attenuation ability. MXene is a typical representative among them. MXene is a transition metal carbide, nitride or carbonitride with the general formula M n+ 1X n T x where M represents early transition metals (e.g., Ti, Zr, V, Nb, Ta or Mo), X represents carbon and / or nitrogen, and T x represents the functional groups (=O, -OH, and / or -F) on the surface of MXene. Its excellent properties make it an ideal candidate for novel electromagnetic shielding materials.

[0004] Gogotsi et al. found that the conductivity of Ti3C2T x MXene is about 2.4×10 5S / m, which is several times higher than the conductivity of graphene or carbon nanotubes. Therefore, MXene has high electromagnetic shielding capabilities due to its unique two-dimensional layered structure and high conductivity. And because of the high specific surface area and rich functional groups on the surface of MXene, it has the advantages of hydrophilicity and easy dispersion, which is conducive to the processing and design of MXene-based composite materials, and has great potential for application in the field of electromagnetic shielding. However, the high-temperature and easy oxidation characteristics of MXene can easily lead to phonon scattering and increased thermal resistance, reducing its heat dissipation performance. Secondly, the development of 5G technology requires that electromagnetic shielding materials have an effective action frequency band as wide as possible, but the current research on MXene-based electromagnetic shielding materials is still limited to the X-band, which is not conducive to its practical application. Therefore, MXene-based broadband electromagnetic shielding and thermal management materials still face great challenges.

[0005] Adding 1D materials with high electrical and thermal conductivity to the 2D MXene matrix is expected to solve the above problems. Due to the excellent intrinsic electrical and thermal conductivity of carbon nanotubes (CNTs), it is expected that the combination of carbon nanotubes (CNTs) and MXene as fillers can reduce phonon scattering while building an efficient conductive network, thereby improving the electromagnetic shielding performance and heat dissipation performance. However, the dispersibility of CNTs materials is extremely poor. Chemical functionalization or surfactants are often used in experiments to obtain uniformly dispersed carbon nanotubes, but this will inevitably reduce the intrinsic electrical and thermal conductivity of CNTs, resulting in a large difference between the performance of the composite material and expectations, limiting its application in composite materials. At the same time, adding 0D magnetic particles to electromagnetic shielding materials is conducive to reducing the impedance mismatch between the shielding material and the air interface, promoting the further attenuation of electromagnetic waves entering the material, reducing reflection losses, and effectively alleviating secondary electromagnetic pollution. However, due to the poor intrinsic thermal conductivity of magnetic particles, the addition will weaken the thermal conductivity of MXene-based composite materials.

[0006] In addition, some existing MXene-based composite materials still have the problem of low strength, which limits the practical application of MXene-based composite materials. Therefore, how to develop a composite film with electromagnetic shielding and thermal conductivity, give full play to the synergistic advantages of each phase to build a good conductive and thermal network, so as to obtain a composite material with both broadband electromagnetic shielding performance and thermal conductivity, and ensure that the material has excellent strength is a difficult problem to be solved in this field. Summary of the invention

[0007] In view of this, the present invention provides a composite film with electromagnetic shielding and thermal conductivity properties and a preparation method thereof to solve the problems that existing electromagnetic shielding materials are limited to the X-band, are not conducive to practical applications, have poor heat dissipation performance and low strength.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A preparation method of a composite film with electromagnetic shielding and thermal conductivity performance, comprising the following steps:

[0010] 1) Prepare Ti3C2T x MXene nanosheets, Fe3O4 nanoparticles and cobalt-multi-walled carbon nanotubes;

[0011] 2) Respectively use Ti3C2T x MXene nanosheets, Fe3O4 nanoparticles, cobalt-multi-walled carbon nanotubes and glass fibers to prepare Ti3C2T x MXene dispersion, Fe3O4 dispersion, cobalt-multi-walled carbon nanotube dispersion and glass fiber dispersion;

[0012] 3) Mix the Ti3C2T x MXene dispersion and the Fe3O4 dispersion to obtain an Fe3O4@Ti3C2T x MXene mixed dispersion, mix the cobalt-multi-walled carbon nanotube dispersion and the glass fiber dispersion to obtain a Co-MWCNTs mixed dispersion;

[0013] 4) Filter the Fe3O4@Ti3C2T x MXene mixed dispersion to obtain the first layer of film, then add the Co-MWCNTs mixed dispersion and continue filtering to obtain the second layer of film, repeat the above steps to obtain a Co-MWCNTs@Fe3O4@Ti3C2T x MXene composite film with electromagnetic shielding and thermal conductivity performance.

[0014] Preferably, the preparation method of the cobalt-multi-walled carbon nanotubes includes: mixing multi-walled carbon nanotubes, Co3O4 nanoparticles and an organic solvent to obtain a mixed solution, and sintering the dried mixed solution to obtain cobalt-multi-walled carbon nanotubes.

[0015] Preferably, the mass-volume ratio of the multi-walled carbon nanotubes, Co3O4 nanoparticles and the organic solvent is 1 g: 0.8 - 1 g: 20 - 30 mL; the sintering temperature is 800 - 1200 °C, and the sintering time is 1.2 - 1.8 h; the organic solvent includes one or more of ethanol, propanol, aniline, acetonitrile and trifluoroacetic acid.

[0016] Preferably, the preparation method of the Ti3C2T x MXene nanosheets includes: mixing LiF and HCl solution to react to obtain a reaction solution; then reacting the reaction solution with Ti3AlC2 to obtain a reaction product; then dissolving and centrifuging the reaction product, and drying the supernatant to obtain Ti3C2T x MXene nanosheets.

[0017] Preferably, the mass-to-volume ratio of the LiF and the HCl solution is 2 g: 30 - 50 mL, and the concentration of the HCl solution is 10 - 13 mol / L; the mass ratio of LiF to Ti3AlC2 is 0.8 - 1.2:1; the reaction time of LiF and the HCl solution is 12 - 18 min, the reaction time of the reaction solution and Ti3AlC2 is 44 - 50 h, and the reaction temperature is 40 - 50 °C.

[0018] Preferably, the method for preparing the Fe3O4 nanoparticles includes: mixing FeCl3, NaAc and ethylene glycol to obtain a mixed solution, and then mixing and reacting the mixed solution with an ethylene glycol solution containing polyethylene glycol, and drying to obtain Fe3O4 nanoparticles.

[0019] Preferably, the mass-to-volume ratio of FeCl3, NaAc and ethylene glycol in the mixed solution is 0.7 - 1 g: 2.5 - 3 g: 40 mL; the mass-to-volume ratio of polyethylene glycol to ethylene glycol in the ethylene glycol solution containing polyethylene glycol is 1.2 - 1.8 g: 20 mL; the mass ratio of FeCl3 to polyethylene glycol is 0.7 - 1: 1.2 - 1.8; the reaction temperature is 180 - 220 °C, and the reaction time is 10 - 14 h.

[0020] Preferably, the Ti3C2T x MXene dispersion is Ti3C2T x MXene ethylene glycol dispersion, with a mass concentration of 5 - 35%; the Fe3O4 dispersion is Fe3O4 ethylene glycol dispersion, with a mass concentration of 10 - 40%; the cobalt-multi-walled carbon nanotube dispersion is cobalt-multi-walled carbon nanotube ethylene glycol dispersion, with a mass concentration of 3 - 15%; the glass fiber dispersion is glass fiber ethylene glycol dispersion, with a mass concentration of 5 - 20%.

[0021] Preferably, in step 3), the volume ratio of the Ti3C2T x MXene dispersion and the Fe3O4 dispersion is 1 - 8: 1 - 5;

[0022] In step 3), the volume ratio of the cobalt-multi-walled carbon nanotube dispersion and the glass fiber dispersion is 8 - 10: 2 - 3.

[0023] Another object of the present invention is to provide a composite film with electromagnetic shielding and heat conduction properties. The thickness of the composite film is 20 - 40 μm, and the number of layers of the composite film is 7 - 19 layers.

[0024] Through the above technical solutions, compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. In the composite film material prepared by the present invention, Ti3C2Tx MXene and Co-MWCNTs together form a rich conductive network, which is conducive to the transmission of charges, thus generating ohmic losses. And when electromagnetic waves contact Fe3O4 and Co nanoparticles, hysteresis losses will also be generated. While Ti3C2T x The abundant functional groups and defects on the surface of MXene can also act as polarization centers to enhance dielectric losses, thereby absorbing part of the electromagnetic waves. The highly oriented and parallel arrangement of Fe3O4@Ti3C2T x The MXene layer and the Co-MWCNTs layer sandwiched therein extend the transmission path of electromagnetic waves inside the composite film. Fe3O4@Ti3C2T x The interfacial impedance mismatch between the MXene layer and the Co-MWCNTs layer leads to further reflection and attenuation of electromagnetic waves inside the composite film, greatly improving the multiple interface reflection effect, making the electromagnetic waves experience a continuous attenuation process of reflection and absorption inside the composite film and finally being converted into heat;

[0026] 2. Co-MWCNTs play a bridging role between adjacent Fe3O4@Ti3C2T x MXene layers, increasing the free path of phonon transmission, thus effectively reducing phonon scattering between interfaces and constructing an efficient heat conduction network, which improves the thermal conductivity and thermal diffusivity of the composite film; The present invention also incorporates a glass fiber dispersion, which is beneficial to improving the strength of the composite film material and avoiding the problem that the strength is too low to meet the application requirements. Specific Embodiments

[0027] The present invention provides a method for preparing a composite film with electromagnetic shielding and heat conduction properties, comprising the following steps:

[0028] 1) Prepare Ti3C2T x MXene nanosheets, Fe3O4 nanoparticles and cobalt-multi-walled carbon nanotubes;

[0029] 2) Respectively use Ti3C2T x MXene nanosheets, Fe3O4 nanoparticles, cobalt-multi-walled carbon nanotubes and glass fibers to prepare Ti3C2T x MXene dispersion, Fe3O4 dispersion, cobalt-multi-walled carbon nanotube dispersion and glass fiber dispersion;

[0030] 3) Mix the Ti3C2T x MXene dispersion and the Fe3O4 dispersion to obtain a Fe3O4@Ti3C2T x MXene mixed dispersion, mix the cobalt-multi-walled carbon nanotube dispersion and the glass fiber dispersion to obtain a Co-MWCNTs mixed dispersion;

[0031] 4) Filter the Fe3O4@Ti3C2T x MXene mixed dispersion to obtain the first-layer film, then add the Co-MWCNTs mixed dispersion and continue filtering to obtain the second-layer film. Repeat the above steps to obtain the Co-MWCNTs@Fe3O4@Ti3C2T x MXene composite film with electromagnetic shielding and thermal conductivity properties.

[0032] In the present invention, the preparation method of the cobalt-multi-walled carbon nanotubes includes: mixing multi-walled carbon nanotubes, Co3O4 nanoparticles and an organic solvent to obtain a mixed solution, and sintering the dried mixed solution to obtain cobalt-multi-walled carbon nanotubes.

[0033] In the present invention, the mass-volume ratio of multi-walled carbon nanotubes, Co3O4 nanoparticles and the organic solvent is 1 g: 0.8 - 1 g: 20 - 30 mL, preferably 1 g: 0.85 - 0.95 g: 22 - 28 mL, more preferably 1 g: 0.88 - 0.92 g: 24 - 26 mL, and still more preferably 1 g: 0.9 g: 25 mL; the mixing is preferably ultrasonic mixing, the ultrasonic power is 500 - 1000 W, specifically 600 W, 700 W, 800 W, 900 W; the ultrasonic time is 1 - 3 h, specifically 1.2 h, 1.5 h, 1.7 h, 2 h, 2.2 h, 2.4 h, 2.5 h, 2.8 h; the sintering temperature is 800 - 1200 °C, specifically 850 °C, 900 °C, 950 °C, 1000 °C, 1050 °C, 1100 °C, 1150 °C; the sintering time is 1.2 - 1.8 h, specifically 1.3 h, 1.4 h, 1.5 h, 1.6 h, 1.7 h; the organic solvent includes one or more of ethanol, propanol, aniline, acetonitrile and trifluoroacetic acid.

[0034] In the present invention, the Ti3C2T x The preparation method of MXene nanosheets includes: mixing LiF and HCl solution for reaction to obtain a reaction solution; then mixing the reaction solution with Ti3AlC2 for reaction to obtain a reaction product; and then dissolving and centrifuging the reaction product, and drying the supernatant to obtain Ti3C2T x MXene nanosheets.

[0035] In the present invention, the mass-volume ratio of LiF to the HCl solution is 2 g: 30 - 50 mL, preferably 2 g: 33 - 47 mL, more preferably 2 g: 37 - 43 mL, and still more preferably 2 g: 40 mL; the concentration of the HCl solution is 10 - 13 mol / L, specifically it can be 10.5 mol / L, 11 mol / L, 11.5 mol / L, 12 mol / L, 12.5 mol / L, and the reaction time of LiF and the HCl solution is 12 - 18 min, specifically it can be 13 min, 14 min, 15 min, 16 min, 17 min, 18 min.

[0036] In the present invention, the mass ratio of LiF to Ti3AlC2 is 0.8 - 1.2:1, preferably 0.9 - 1.15:1, more preferably 0.95 - 1.1:1, and still more preferably 1:1.

[0037] In the present invention, the step of mixing the reaction solution with Ti3AlC2 is preferably adding Ti3AlC2 into the reaction solution in multiple times, and the number of adding times is preferably 3 - 8 times, specifically it can be 4 times, 5 times, 6 times, 7 times; the reaction time of the reaction solution and Ti3AlC2 is 44 - 50 h, specifically it can be 45 h, 46 h, 47 h, 48 h, 49 h; the reaction temperature is 40 - 50 °C, specifically it can be 41 °C, 42 °C, 43 °C, 45 °C, 46 °C, 47 °C, 48 °C, 49 °C.

[0038] In the present invention, the reaction of the reaction solution and Ti3AlC2 is preferably carried out under stirring conditions, and the stirring rate is preferably 400 - 600 rpm, specifically it can be 420 rpm, 440 rpm, 450 rpm, 460 rpm, 480 rpm, 500 rpm, 520 rpm, 540 rpm, 550 rpm, 560 rpm, 580 rpm.

[0039] In the present invention, the reaction product needs to be washed until neutral, and the washing method is preferably centrifugal washing, the centrifugal rate is 3000 - 4000 rpm, specifically it can be 3200 rpm, 3400 rpm, 3500 rpm, 3600 rpm, 3800 rpm, and the centrifugal time is 50 - 80 min, specifically it can be 55 min, 60 min, 65 min, 70 min, 75 min.

[0040] In the present invention, the re-dissolution of the reaction product is preferably carried out by ultrasonic dissolution in an ice bath under a protective atmosphere, and the protective atmosphere includes one or more of nitrogen, helium, neon, argon, krypton and xenon; the power of ultrasonic is preferably 500-1000W, specifically it can be 600W, 700W, 800W, 900W; the time of ultrasonic is 50-80min, specifically it can be 55min, 60min, 65min, 70min, 75min.

[0041] In the present invention, the rate of re-centrifugation is 3000-4000rpm, specifically it can be 3200rpm, 3400rpm, 3500rpm, 3600rpm, 3800rpm; the time of centrifugation is 50-80min, specifically it can be 55min, 60min, 65min, 70min, 75min.

[0042] In the present invention, the drying process of the supernatant is preferably freeze-drying, and the drying temperature is preferably -50 to -70°C, specifically it can be -55°C, -60°C, -65°C.

[0043] In the present invention, the preparation method of the Fe3O4 nanoparticles includes: mixing FeCl3, NaAc and ethylene glycol to obtain a mixed solution, and then mixing the mixed solution with an ethylene glycol solution containing polyethylene glycol for reaction, and drying to obtain Fe3O4 nanoparticles.

[0044] In the present invention, the mass-volume ratio of FeCl3, NaAc and ethylene glycol in the mixed solution is 0.7-1g: 2.5-3g: 40mL, preferably 0.75-0.95g: 2.6-2.9g: 40mL, further preferably 0.8-0.9g: 2.7-2.8g: 40mL, and still further preferably 0.81g: 2.71g: 40mL; the mass-volume ratio of polyethylene glycol to ethylene glycol in the ethylene glycol solution containing polyethylene glycol is 1.2-1.8g: 20mL, preferably 1.3-1.7g: 20mL, further preferably 1.4-1.6g: 20mL, and still further preferably 1.5g: 20mL; the mass ratio of FeCl3 to polyethylene glycol is 0.7-1: 1.2-1.8, preferably 0.75-0.95: 1.3-1.7, further preferably 0.8-0.9: 1.4-1.6, and still further preferably 0.81: 1.5; the reaction temperature is 180-220°C, specifically it can be 185°C, 190°C, 195°C, 200°C, 210°C; the reaction time is 10-14h, specifically it can be 10.5h, 11h, 11.5h, 12h, 12.5h, 13h, 13.5h.

[0045] In the present invention, the Ti3C2T xThe MXene dispersion is Ti3C2T x The MXene ethylene glycol dispersion has a mass concentration of 5 - 35%, specifically it can be 10%, 15%, 20%, 25%, 30%; the Fe3O4 dispersion is an Fe3O4 ethylene glycol dispersion with a mass concentration of 10 - 40%, specifically it can be 15%, 20%, 25%, 30%, 35%; the cobalt - multi - wall carbon nanotube dispersion is a cobalt - multi - wall carbon nanotube ethylene glycol dispersion with a mass concentration of 3 - 15%, specifically it can be 5%, 8%, 10%, 12%, 14%; the glass fiber dispersion is a glass fiber ethylene glycol dispersion with a mass concentration of 5 - 20%, specifically it can be 8%, 10%, 12%, 14%, 15%, 16%, 18%.

[0046] In the present invention, in step 3), the Ti3C2T x The volume ratio of the MXene dispersion to the Fe3O4 dispersion is 1 - 8:1 - 5, preferably 2 - 7:2 - 4, more preferably 3 - 6:2.5 - 3.5, and still more preferably 5:3.

[0047] In step 3), the volume ratio of the cobalt - multi - wall carbon nanotube dispersion to the glass fiber dispersion is 8 - 10:2 - 3, preferably 8.5 - 9.5:2.2 - 2.9, more preferably 8.8 - 9.2:2.4 - 2.8, and still more preferably 9:2.5.

[0048] In the present invention, in step 3), the mixing is carried out by ultrasonic mixing. The power of the ultrasonic wave is independently 500 - 1000W, specifically it can be 600W, 700W, 800W, 900W; the time of the ultrasonic wave is independently 50 - 80min, specifically it can be 55min, 60min, 65min, 70min, 75min.

[0049] Another object of the present invention is to provide a composite film with electromagnetic shielding and heat conduction properties.

[0050] In the present invention, the thickness of the composite film is 20 - 40μm, specifically it can be 22μm, 24μm, 25μm, 26μm, 28μm, 30μm, 32μm, 34μm, 35μm, 36μm, 38μm; the number of layers of the composite film is 7 - 19 layers, specifically it can be 9 layers, 10 layers, 11 layers, 12 layers, 13 layers, 15 layers.

[0051] In the present invention, the thickness difference between each layer of the composite film is controlled between 0 - 0.2μm, preferably 0 - 0.1μm, more preferably 0 - 0.05μm, and still more preferably 0μm (each layer of the composite film has the same thickness).

[0052] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0053] Example 1

[0054] Preparation of cobalt-multi-walled carbon nanotubes by the sintering method

[0055] Under magnetic stirring conditions, 1 g of multi-walled carbon nanotubes and 0.85 g of Co3O4 nanoparticles were added to 30 mL of propanol, and then ultrasonicated at 800 W for 1 h. After sufficient dispersion, it was dried and then placed in a muffle furnace and sintered at 1100 °C for 1.5 h. After cooling, cobalt-multi-walled carbon nanotubes were obtained.

[0056] Preparation of Ti3C2Tx MXene nanosheets by in-situ synthesis of HF etching Ti3AlC2 MAX phase

[0057] Under magnetic stirring conditions, 2 g of LiF was added to a polytetrafluoroethylene container containing 40 ml of HCl (12 mol / L) and reacted for 15 min; then 2 g of Ti3AlC2 powder was slowly added to the liquid-phase mixture in 4 portions, and magnetically stirred at 45 °C for 48 h at a rotation speed of 500 rpm; then, the obtained product was centrifugally washed with deionized water at a speed of 3500 rpm / min and washed multiple times until the pH of the mixture was neutral. Subsequently, the obtained product was ice-bath sonicated (800 W) for 1 h under an Ar gas protection atmosphere, and then the sonicated product was centrifuged at a speed of 3500 rpm for 1 h, and the deep green supernatant after centrifugation was collected to obtain Ti3C2T x MXene nanosheet suspension. Finally, Ti3C2T x The MXene nanosheet suspension was freeze-dried at -60 °C and collected for standby.

[0058] Preparation of Fe3O4 nanoparticles by solvothermal method

[0059] At 50 °C, 1.5 g of polyethylene glycol was heated and dissolved in 20 mL of ethylene glycol solution; then 1.35 g of FeCl3·6H2O and 4.5 g of NaAc·3H2O were added to 40 mL of ethylene glycol solution, and at the same time, the ethylene glycol solution after dissolving polyethylene glycol was added; the obtained mixed solution was magnetically heated and stirred for 30 min to form a uniform suspension; then it was reacted at 200 °C for 12 h. After the solution was cooled to room temperature, the obtained product was centrifugally washed with deionized water and absolute ethanol; subsequently, it was freeze-dried for 24 h to obtain Fe3O4 nanoparticles for standby.

[0060] Preparation of Dispersions

[0061] Ti3C2Tx MXene nanosheets, Fe3O4 nanoparticles, cobalt-multi-walled carbon nanotubes (MWCNTs), and glass fibers were separately added to ethylene glycol solution, and then sonicated at 600 W for 1 h respectively to obtain a Ti3C2T x MXene dispersion with a mass concentration of 30%, an Fe3O4 dispersion with a mass concentration of 25%, a cobalt-multi-walled carbon nanotube dispersion with a mass concentration of 12%, and a glass fiber dispersion with a mass concentration of 10% for standby.

[0062] Example 2

[0063] Preparation of Cobalt-Multi-Walled Carbon Nanotubes by Sintering Method

[0064] Under magnetic stirring conditions, 1 g of multi-walled carbon nanotubes and 1 g of Co3O4 nanoparticles were added to 25 mL of acetonitrile, then sonicated at 1000 W for 2 h, dried after sufficient dispersion, and then placed in a muffle furnace and sintered at 1000 °C for 1.5 h. After cooling, cobalt-multi-walled carbon nanotubes were obtained.

[0065] Preparation of Ti3C2Tx MXene Nanosheets by In-Situ Synthesis of HF-Etched Ti3AlC2 MAX Phase

[0066] Under magnetic stirring conditions, 2 g of LiF was added to a polytetrafluoroethylene container containing 30 ml of HCl (13 mol / L) and reacted for 12 min; then 2 g of Ti3AlC2 powder was slowly added to the liquid-phase mixture in 5 portions and magnetically stirred at 40 °C for 50 h at a rotation speed of 590 rpm; then, the obtained product was centrifugally washed with deionized water at a speed of 3000 rpm / min and washed multiple times until the pH of the mixture was neutral. Subsequently, the obtained product was sonicated in an ice bath (600 W) for 80 min under an Ar gas protection atmosphere, and then the sonicated product was centrifuged at a speed of 3000 rpm for 80 min, and the deep green supernatant after centrifugation was collected to obtain Ti3C2T x MXene nanosheet suspension. Finally, the Ti3C2T x MXene nanosheet suspension was freeze-dried at -50 °C and collected for standby.

[0067] Preparation of Fe3O4 Nanoparticles by Solvothermal Method

[0068] 1.2 g of polyethylene glycol was heated and dissolved in 20 mL of ethylene glycol solution at 50°C; then 1.35 g of FeCl3·6H2O and 4.5 g of NaAc·3H2O were added to 40 mL of ethylene glycol solution, and the ethylene glycol solution after the polyethylene glycol was dissolved was added at the same time; the obtained mixed solution was magnetically heated and stirred for 30 minutes to form a uniform suspension; then the mixture was reacted at 180°C for 14 hours, and after the solution was cooled to room temperature, the product was centrifugally washed with deionized water and anhydrous ethanol; then it was freeze-dried for 24 hours to obtain Fe3O4 nanoparticles for use.

[0069] Preparation of dispersion

[0070] Ti3C2Tx MXene nanosheets, Fe3O4 nanoparticles, cobalt-multi-walled carbon nanotubes (MWCNTs) and glass fibers were added to ethylene glycol solution, and then ultrasonicated at 900 W for 1 h to obtain Ti3C2Tx with a mass concentration of 20%. x A MXene dispersion, a Fe3O4 dispersion with a mass concentration of 15%, a cobalt-multi-walled carbon nanotube dispersion with a mass concentration of 8%, and a glass fiber dispersion with a mass concentration of 15% are set aside.

[0071] Example 3

[0072] Preparation of Cobalt-Multi-Walled Carbon Nanotubes by Sintering

[0073] Under magnetic stirring conditions, 1 g of multi-walled carbon nanotubes and 0.9 g of Co3O4 nanoparticles were added to 20 mL of acetonitrile, and then ultrasonicated at 600 W for 3 h. After being fully dispersed, they were dried and then placed in a muffle furnace and sintered at 800 ° C for 1.8 h. After cooling, cobalt-multi-walled carbon nanotubes were obtained.

[0074] Preparation of Ti3C2T by in-situ synthesis of HF-etched Ti3AlC2 MAX phase x MXene nanosheets

[0075] Under magnetic stirring conditions, 2g LiF was added to a polytetrafluoroethylene container containing 50ml HCl (10mol / L) and reacted for 18min; then 2g Ti3AlC2 powder was slowly added to the liquid mixture in 4 times, and magnetic stirring was carried out at 50°C for 44h at a speed of 400rpm; then, the obtained product was centrifuged and washed with deionized water at a speed of 4000rpm / min, and washed multiple times until the pH of the mixture was neutral. Subsequently, the obtained product was ultrasonicated (700W) in an ice bath under an Ar gas protective atmosphere for 50min, and then the ultrasonicated product was centrifuged at a speed of 4000rpm for 50min, and the dark green supernatant after centrifugation was collected to obtain Ti3C2T x MXene nanosheet suspension. Finally, Ti3C2Tx The MXene nanosheet suspension was freeze-dried at -70 °C and collected for later use.

[0076] Preparation of Fe3O4 nanoparticles by solvothermal method

[0077] At 50 °C, 1.8 g of polyethylene glycol was heated and dissolved in 20 mL of ethylene glycol solution; then 1.35 g of FeCl3·6H2O and 4.5 g of NaAc·3H2O were added to 40 mL of ethylene glycol solution, and at the same time, the ethylene glycol solution after dissolving polyethylene glycol was added; the obtained mixed solution was magnetically heated and stirred for 30 min to form a uniform suspension; then it was reacted at 220 °C for 10 h. After the solution was cooled to room temperature, the obtained product was centrifugally washed with deionized water and absolute ethanol; subsequently, it was freeze-dried for 24 h to obtain Fe3O4 nanoparticles for later use.

[0078] Preparation of dispersion

[0079] Ti3C2Tx MXene nanosheets, Fe3O4 nanoparticles, cobalt-multi-walled carbon nanotubes (MWCNTs) and glass fibers were respectively added to ethylene glycol solution, and then sonicated at 700 W for 1 h to obtain a Ti3C2T x MXene dispersion with a concentration of 35%, an Fe3O4 dispersion with a concentration of 40%, a cobalt-multi-walled carbon nanotube dispersion with a concentration of 12% and a glass fiber dispersion with a concentration of 5% for later use.

[0080] Example 4

[0081] The Ti3C2T x MXene dispersion prepared in Example 1 and the Fe3O4 dispersion were mixed at a volume ratio of 7:3 and sonicated at 800 W for 1 h to obtain an Fe3O4@Ti3C2T x MXene mixed dispersion; the cobalt-multi-walled carbon nanotube dispersion and the glass fiber dispersion were mixed at a volume ratio of 9:2 and sonicated at 800 W for 1 h to obtain a Co-MWCNTs mixed dispersion.

[0082] First, the Fe3O4@Ti3C2T x MXene mixed dispersion was poured into a glass sand core funnel and filtered with a 0.45 μm nylon filter membrane. Subsequently, the Co-MWCNTs mixed dispersion was poured into the glass sand core funnel for filtration. In this way, a composite film with a 7-layer structure was prepared repeatedly; finally, the obtained composite film was freeze-dried at -60 °C for 24 h and then peeled off from the filter membrane to obtain a self-supporting Co-MWCNTs@Fe3O4@Ti3C2T x MXene composite film (containing 4 layers of Fe3O4@Ti3C2T xMXene and 3-layer Co-MWCNTs / fiberglass, denoted as C-MFT7).

[0083] Example 5

[0084] The difference between this example and Example 4 is only that a composite film with an 11-layer structure is prepared, denoted as C-MFT11.

[0085] Example 6

[0086] The difference between this example and Example 4 is only that a composite film with a 15-layer structure is prepared, denoted as C-MFT15.

[0087] Example 7

[0088] The difference between this example and Example 4 is only that a composite film with a 19-layer structure is prepared, denoted as C-MFT19.

[0089] Comparative Example 1

[0090] The difference between this comparative example and Example 7 is only that a multi-walled carbon nanotube dispersion is used instead of the Co-MWCNTs mixed dispersion, and the mass concentration of the multi-walled carbon nanotubes is the same as that of the multi-walled carbon nanotubes in the Co-MWCNTs mixed dispersion. The obtained composite film is denoted as MFT19.

[0091] Experimental Example 1

[0092] The composite films prepared in Examples 4 to 7 were subjected to relevant tests on thickness and electromagnetic interference shielding performance. The electromagnetic reflection loss (SE u ) and electromagnetic absorption loss (SE R ) in the X-band and K A band were detected respectively. The test results are shown in Table 1:

[0093] Table 1 Test Results of Electromagnetic Interference Shielding Efficiency

[0094]

[0095] It can be seen from Table 1 that the composite films prepared by the present invention have high electromagnetic reflection loss and electromagnetic absorption loss. The reason is that interfacial polarization, natural resonance and multiple internal reflections occur inside the composite film, increasing the electromagnetic interference shielding efficiency of the composite film, and good electromagnetic shielding effects are demonstrated in both the X-band and Ku-band.

[0096] Experimental Example 2

[0097] The thermal conductivity of the composite films prepared in Examples 4-7 was detected. The thermal conductivity of the composite films was detected according to the method of GB / T 10294-2008, and the thermal conduction coefficient of the composite films was detected according to the ASTM D5470 steady-state hot plate method. The detection results are shown in Table 2:

[0098] Table 2 Detection Results of Thermal Conductivity

[0099]

[0100] As can be seen from Table 2, the composite films prepared by the present invention have relatively high thermal conductivity and thermal conduction coefficient. With the increase of the number of layers, the thermal conductivity and thermal conduction coefficient show a significant upward trend. In the voids of the composite films, Fe3O4 and Co particles can jointly construct a thermal conduction path to reduce the interfacial thermal resistance, while the addition of glass fibers and multi-walled carbon nanotubes promotes the thermal conduction along the layer direction and improves the thermal conductivity of the composite films.

[0101] Experimental Example 3

[0102] A pressure of 1.5 bar was uniformly applied to the composite film prepared in Example 7 along the direction perpendicular to the layer for 30 minutes, and then the X-band electromagnetic reflection loss and electromagnetic absorption loss of the composite film were detected. The results were 26.8 dB and 28.7 dB respectively, and there was not much change in the electromagnetic reflection loss and electromagnetic absorption loss compared with the original.

[0103] Tensile forces were uniformly applied to the composite films prepared in Example 7 and Comparative Example 1 along the layer direction, and the tensile forces at the moment when the composite films cracked were recorded and the tensile strength was calculated. The test was repeated 3 times. The detection results are shown in Table 3:

[0104] Table 3 Detection Results of Tensile Strength

[0105]

[0106] As can be seen from Table 3, the tensile strength of the composite films prepared by the present invention has been significantly improved, and it can meet the higher strength requirements of electromagnetic shielding materials in many fields.

[0107] In this specification, each embodiment is described in a progressive manner. The key points of each embodiment are the differences from other embodiments. For the same or similar parts between the embodiments, reference can be made to each other.

[0108] 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. A preparation method of a composite film with electromagnetic shielding and thermal conductivity properties, characterized in that, It includes the following steps: 1) Preparation of Ti3C2T x MXene nanosheets, Fe3O4 nanoparticles, and cobalt-multi-walled carbon nanotubes; 2) Respectively use Ti3C2T x MXene nanosheets, Fe3O4 nanoparticles, cobalt-multi-walled carbon nanotubes and glass fibers to prepare Ti3C2T x MXene dispersion, Fe3O4 dispersion, cobalt-multi-walled carbon nanotube dispersion and glass fiber dispersion; 3) Mix the Ti3C2T x MXene dispersion and the Fe3O4 dispersion to obtain the Fe3O4@Ti3C2T x MXene mixed dispersion, mix the cobalt-multi-walled carbon nanotube dispersion and the glass fiber dispersion to obtain the Co-MWCNTs mixed dispersion; 4) Filter the Fe3O4@Ti3C2T x MXene mixed dispersion to obtain the first layer of film, then add the Co-MWCNTs mixed dispersion and continue filtering to obtain the second layer of film. Repeat the above steps to obtain the Co-MWCNTs@Fe3O4@Ti3C2T x MXene composite film; The preparation method of the cobalt-multi-walled carbon nanotubes includes: mixing multi-walled carbon nanotubes, Co3O4 nanoparticles and an organic solvent to obtain a mixed solution, drying the mixed solution and then sintering to obtain cobalt-multi-walled carbon nanotubes; The mass-volume ratio of the multi-walled carbon nanotubes, Co3O4 nanoparticles and the organic solvent is 1 g: 0.8 - 1 g: 20 - 30 mL; the sintering temperature is 800 - 1200 °C, and the sintering time is 1.2 - 1.8 h; the organic solvent includes one or more of ethanol, propanol, aniline, acetonitrile and trifluoroacetic acid; In step 3), the volume ratio of the cobalt-multi-walled carbon nanotube dispersion liquid to the glass fiber dispersion liquid is 8 - 10: 2 - 3.

2. The preparation method of a composite film with electromagnetic shielding and heat conduction properties according to claim 1, characterized in that, The Ti3C2T x The preparation method of MXene nanosheets includes: mixing and reacting LiF and HCl solution to obtain a reaction solution; then mixing and reacting the reaction solution with Ti3AlC2 to obtain a reaction product; dissolving and centrifuging the reaction product, and drying the supernatant to obtain Ti3C2T x MXene nanosheets.

3. The preparation method of a composite film with electromagnetic shielding and heat conduction performance according to claim 2, characterized in that, The mass-volume ratio of the LiF and HCl solution is 2 g: 30 - 50 mL, and the concentration of the HCl solution is 10 - 13 mol / L; the mass ratio of LiF to Ti3AlC2 is 0.8 - 1.2: 1; the reaction time of LiF and the HCl solution is 12 - 18 min, the reaction time of the reaction liquid and Ti3AlC2 is 44 - 50 h, and the reaction temperature is 40 - 50 °C.

4. The preparation method of a composite film with electromagnetic shielding and thermal conductivity according to claim 3, characterized in that, The preparation method of the Fe3O4 nanoparticles includes: mixing FeCl3, NaAc and ethylene glycol to obtain a mixed solution, and then mixing and reacting the mixed solution with an ethylene glycol solution containing polyethylene glycol, and drying to obtain Fe3O4 nanoparticles.

5. The preparation method of a composite film with electromagnetic shielding and heat conduction properties according to claim 4, characterized in that, The mass-volume ratio of FeCl3, NaAc and ethylene glycol in the mixed solution is 0.7 - 1 g: 2.5 - 3 g: 40 mL; the mass-volume ratio of polyethylene glycol to ethylene glycol in the ethylene glycol solution containing polyethylene glycol is 1.2 - 1.8 g: 20 mL; the mass ratio of FeCl3 to polyethylene glycol is 0.7 - 1: 1.2 - 1.8; the reaction temperature is 180 - 220 °C, and the reaction time is 10 - 14 h.

6. The preparation method of a composite film with electromagnetic shielding and thermal conductivity according to any one of claims 3 to 5, characterized in that, The Ti3C2T x MXene dispersion is Ti3C2T x MXene ethylene glycol dispersion with a mass concentration of 5 - 35%; the Fe3O4 dispersion is Fe3O4 ethylene glycol dispersion with a mass concentration of 10 - 40%; the cobalt-multi-walled carbon nanotube dispersion is cobalt-multi-walled carbon nanotube ethylene glycol dispersion with a mass concentration of 3 - 15%; the glass fiber dispersion is glass fiber ethylene glycol dispersion with a mass concentration of 5 - 20%.

7. The preparation method of a composite film with electromagnetic shielding and heat conduction performance according to claim 6, characterized in that, In step 3), the volume ratio of the Ti3C2T x MXene dispersion to the Fe3O4 dispersion is 1 to 8: 1 to 5.

8. The composite film with electromagnetic shielding and heat conduction properties prepared by the preparation method according to any one of claims 1 to 7, characterized in that, The thickness of the composite film is 20 - 40 μm, and the number of layers of the composite film is 7 - 19 layers.

Images