Multifunctional thermal conductive composite film of MXene-edge graphene oxide heterojunction / pbo fiber and preparation method thereof

Abstract

The application discloses a MXene-edge graphene oxide heterojunction / PBO fiber multifunctional heat-conducting composite film and a preparation method thereof. First, MXene and edge graphene oxide (EOG) are subjected to nucleophilic substitution and dehydration reaction to prepare MXene-edge graphene oxide (MEOG) heterojunction fillers, then the fillers are added into a dispersion solution of PBO fibers to prepare an acid gel, the acid gel is replaced by deionized water to prepare a water gel, and finally, the water gel is subjected to heat pressing to obtain the multifunctional heat-conducting composite film. The heat-conducting composite film comprises a PNF substrate and MEOG heterojunction fillers, covalent interaction between the fillers provides an effective way for phonon transmission, hydrogen bond and pi-pi interaction between the fillers and the substrate effectively reduce the interface thermal resistance, and the heat-conducting composite film can be widely used in EMI shielding performance and heat dissipation of electronic devices.

Description

Technical Field

[0001] The present invention relates to the technical field of composite materials, and in particular to a MXene-edge graphene oxide heterojunction / poly(p-phenylene benzobisoxazole) fiber multifunctional thermally conductive composite film and a preparation method thereof. Background Art

[0002] With the rapid development of high-tech technologies such as artificial intelligence, 5G communications, the Internet of Things, and big data, equipment is continuously moving towards miniaturization, integration, and intelligence. However, the increase in equipment power density leads to a rapid accumulation of heat generated by the equipment and components during operation, inevitably leading to heat accumulation problems, affecting the performance, lifespan, and reliability of the equipment and its components. Furthermore, the resulting electromagnetic radiation can interfere with the normal operation of surrounding equipment and components. Therefore, the design and development of multifunctional composite materials that integrate thermal conductivity and electromagnetic shielding is imperative.

[0003] Polymers filled with heterostructured thermally conductive fillers often have better thermal conductivity, which is mainly attributed to the fact that the construction of heterostructures can increase the contact between fillers, reduce interfacial thermal resistance and agglomeration. In addition, by designing heterostructures, the advantages of each material can be maximized, reflecting the functional synergistic effect of "1+1 is greater than 2". In previous research, the article "Multifunctional Thermally Conductive Composite Films Based on FungalTree-like Heterostructured Silver Nanowires@Boron Nitride NanosheetsandAramid Nanofibers" [1] The "fungus tree" heterostructured silver nanowires@boron nitride nanosheets (AgNWs@BNNS) thermal conductive filler was prepared by in situ growth method, and the thermal conductive AgNWs@BNNS / ANF composite film was obtained by "suction filtration self-assembly and hot pressing". When the mass fraction of AgNWs@BNNS is 50wt%, the AgNWs@BNNS / ANF composite film has a thermal conductivity of 9.44Wm -1 K -1 The article “Thermal conductivity enhancement of CNT / MoS2 / graphene-epoxy nanocomposites based on structural synergistic effects and interpenetrating network” [2]A carbon nanotube (CNT) / molybdenum disulfide (MoS2) / graphene heterostructured thermal conductive filler was synthesized using a hydrothermal method. During the hydrothermal reaction, MoS2 and graphene grew and wrapped around the CNT, ensuring better interfacial contact. The CNT acts as both a structural framework and a heat transfer channel, effectively collecting heat from the large surface area of ​​MoS2 and graphene nanosheets. The good wettability of MoS2 further reduces the interfacial thermal resistance between the heterostructured filler and the polymer matrix. The thermal conductivity can reach 4.6Wm -1 K -1 .

[0004] In the study of PBO as the matrix, the article "Mechanically strong and folding-endurance Ti3C2T x MXene / PBO nanofiber films for efficient electromagnetic interference shielding and thermal management” [3] In the process, f-Ti3C2T x As a composite material, a composite film is obtained by the preparation method of "sol-gel-film conversion". x When the content reaches 90%, the in-plane thermal conductivity is 5.82W m -1 K -1 Therefore, further improving the thermal conductivity of PBO films has become the focus of current research.

[0005] References:

[0006] [1]Han Y, Ruan K, Gu J.Multifunctional Thermally Conductive CompositeFilms Based on Fungal Tree-like Heterostructured Silver Nanowires@BoronNitride Nanosheets and Aramid Nanofibers[J]. Angewandte Chemie International Edition, 2022, 62: 1-7.

[0007] [2] Ji C, Yan C, Wang Y, et al. Thermal conductivity enhancement of CNT / MoS2 / graphene-epoxy nanocomposites based on structural synergistic effects and interpenetrating network[J]. Composites Part B: Engineering, 2018, 163: 363-370.

[0008] [3] Wang L, Ma Z, Zhang Y, et al. Mechanically strong and folding-endurance Ti3C2Tx MXene / PBO nanofiber films for efficient electromagnetic interference shielding and thermal management[J]. Carbon Energy, 2022, 4: 200–210. Summary of the Invention

[0009] Based on the problems existing in the above-mentioned prior art, the present invention provides a MXene-edge graphene oxide heterojunction / poly(p-phenylene benzobisoxazole) fiber multifunctional thermal conductive composite film (MEOG / PNFs) and its preparation method. The present invention purposefully designs a lateral heterostructure filler, assembles edge graphene oxide (EOG) with MXene (MEOG), and uses covalent bond bridging between fillers to effectively reduce the interfacial thermal resistance ITR between fillers, reduce phonon scattering between fillers, and give full play to the intrinsic thermal conductivity of the filler. On the other hand, in response to the limitations of traditional graphene oxide (GO), the present invention maximizes the lattice integrity within the graphene surface by preparing EOG, which is conducive to the transmission of phonons. In addition, in order to better meet the application requirements of flexible electronic devices, the present invention adopts sol-gel-membrane conversion technology to introduce MEOG heterojunction fillers into poly(p-phenylene benzobisoxazole) nanofibers to prepare a multifunctional composite film, which is combined with PNFs through hydrogen bonds and π-π interactions on the filler surface to achieve the purpose of reducing the interfacial thermal resistance between the filler and the matrix, thereby further obtaining better thermal conductivity. This paper uses density functional theory (DFT) to explore the interface between heterojunction structure fillers and the bonding force between them and the matrix interface, and explores the formation of its heat conduction path. Heat transfer performance and molecular dynamics (MD) simulations verify the covalent bond of MEOG and its advantages in solving ITR. At the same time, in order to have a wider range of application scenarios, the system is designed based on the mechanical properties, electrical conductivity, electromagnetic shielding properties and flame retardancy of the composite material. This study provides a new idea for designing effective heterojunction structure multifunctional thermal conductive materials to reduce the ITR in thermal conductive composite materials.

[0010] To achieve the purpose, the present invention adopts the following technical solutions:

[0011] The present invention provides a method for preparing a MXene-edge graphene oxide heterojunction / PBO fiber multifunctional thermally conductive composite film. The method comprises the following steps: first, MXene and edge graphene oxide (EOG) are subjected to nucleophilic substitution and dehydration reactions to produce a MXene-edge graphene oxide heterojunction filler, referred to as MEOG filler; then, the MEOG filler is added to a PBO fiber dispersion to produce an acid gel, which is then replaced by deionized water to produce a hydrogel; and finally, the resulting hydrogel is hot-pressed to obtain the multifunctional thermally conductive composite film. The method specifically comprises the following steps:

[0012] Step 1: Preparation of MEOG filler

[0013] MXene is dispersed in deionized water at a concentration of 1 to 2 mg / mL to obtain a MXene dispersion; EOG is dispersed in deionized water at a concentration of 1 to 2 mg / mL to obtain an EGO dispersion; the MXene dispersion and the EOG dispersion are ultrasonically mixed uniformly according to a mass ratio of MXene to EOG of 10% to 50%:90% to 50%, and reacted at room temperature for 10 to 13 hours to allow the MXene and EOG to fully react, and then a solid is obtained by vacuum assisted filtration and centrifugation, and vacuum drying is performed to obtain MEOG filler.

[0014] Step 2: Preparation of PNFs

[0015] Methanesulfonic acid (MSA) and trifluoroacetic acid (TFA) are mixed uniformly in a mass ratio of 1:0.9 to 1.1 to obtain a mixed acid;

[0016] The PBO fibers were added to the mixed acid at a mass ratio of 1:95-105 and stirred at room temperature for 3-4 days to obtain a first PNFs dispersion. The mixed acid was then added to the first PNFs dispersion for dilution, yielding a second PNFs dispersion with a concentration of 0.1-0.15 wt%. The micron-sized PBO fibers were uniformly dispersed in the mixed acid to form nanofibers, designated PNFs.

[0017] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0018] The MEOG filler obtained in step 1 is added to the second PNFs dispersion and ultrasonicated for 2 to 2.5 hours to form a viscous sol, and then the first PNFs dispersion is added and stirred evenly, and then Na2SO4 is added and stirred for 3 to 3.5 hours to obtain an acid sol; the acid sol is poured into a mold and solidified at 0 to 6°C for 12 to 16 hours to form an acid gel;

[0019] Immersing the acid gel in deionized water to exchange the solvent for 1 to 3 hours, then changing the water and exchanging the solvent again, repeating the exchange 10 to 12 times to obtain a hydrogel;

[0020] The hydrogel is hot-pressed to obtain a MEOG / PNFs multifunctional thermally conductive composite film.

[0021] Furthermore, in step 1, the vacuum drying temperature is 55-65° C. and the time is 11-13 hours.

[0022] Furthermore, in step 3, the volume ratio of the second PNFs dispersion to the first PNFs dispersion is 1.5 to 2.5:1.

[0023] Furthermore, in step 3, the ratio of the amount of Na2SO4 added to the total volume of the second PNFs dispersion and the first PNFs dispersion is 1 to 3 g / 60 mL.

[0024] Furthermore, the mass percentage of MEOG filler in the MEOG / PNFs multifunctional thermally conductive composite film is 10 to 50%.

[0025] The beneficial effects of the present invention are embodied in:

[0026] This invention prepares edge-carboxylated graphene using a modified Hummers method, imparting a complete in-plane structure to the material, reducing in-plane phonon scattering and improving its thermal conductivity. A MEOG heterojunction thermally conductive filler is prepared through nucleophilic substitution and dehydration reactions, creating covalent bonds between MXene and EOG to reduce the interfacial thermal resistance between the filler and the filler. Furthermore, the filler is composited with a PNFs matrix, providing additional thermal bridges through π-π and hydrogen bonding interactions between the filler and the matrix, thereby improving the material's thermal conductivity. A hydrogel is then prepared by displacement, and a thin film with a layered stacking structure is obtained by hot pressing. The abundant interfaces within the film's layered structure enhance multiple reflections and scattering of electromagnetic waves, thereby strengthening their reabsorption and attenuation, resulting in excellent electromagnetic shielding performance. The well-defined layered structure of MEOG / PNFs further facilitates interactions between the filler and the matrix. Hydrogen bonds, π-π interactions, and van der Waals forces serve as bridges between the one-dimensional PNFs and the two-dimensional MEOG nanosheets, also contributing to improved mechanical properties of the film. When the filler content is 40 wt%, the maximum in-plane thermal conductivity of the film is 22.2 ± 0.4 W m -1 K -1 , a 900% improvement over the blank PNFs sample. The film's electromagnetic shielding performance reached 59.8dB at a thickness of 72μm, with a maximum tensile strength of 176.3±1.3MPa and an elongation at break of 36.9±1.0%. It can be widely used in electronic devices for EMI shielding and heat dissipation. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the preparation process of MEOG / PNFs multifunctional thermal conductive composite film.

[0028] Figure 2 Comparison of thermal conductivity of MEOG / PNFs composite films prepared from MEOG heterojunction fillers with different MXene:EOG ratios in Examples 1 to 5 and Comparative Examples 1 to 2.

[0029] Figure 3 The thermal conductivity of the MEOG / PNFs composite films with different MEOG filler contents prepared in Examples 6 to 10 and Comparative Examples 3 to 4 is compared.

[0030] Figure 4 Schematic diagram of molecular dynamics simulation data of MEOG and PNFs, where: (a) is the molecular dynamics model diagram of MEOG; (b) is the steady-state temperature distribution diagram; (c) is the interface heat transfer data diagram; (de) is the phonon state density of filler and PNFs.

[0031] Figure 5 Schematic diagram of the thermal conduction mechanism of MEOG / PNFs composite film.

[0032] Figure 6 The electromagnetic shielding performance of the MEOG / PNFs composite films prepared in Examples 6 to 10 and Comparative Examples 3 to 4, wherein (a) is SE T , (b) is SE A , (c) is SE R .

[0033] Figure 7 Schematic diagram of the electromagnetic shielding mechanism of MEOG / PNFs composite film.

[0034] Figure 8 2 are stress-strain curves of the MEOG / PNFs composite films prepared in Examples 6 to 10 and Comparative Example 4. DETAILED DESCRIPTION

[0035] The following is a detailed description of an embodiment of the present invention. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiment.

[0036] In the following examples, the preparation method of the MXene used is as follows: 2g Ti3AlC2 powder is slowly added to a mixed solution containing 2g LiF and 40mL 9mol / L HCl. The mixture is then stirred and reacted at 35°C for 24h. After the reaction is completed, the obtained product is centrifuged and washed with deionized water several times until the pH is ~6. The washed sediment is dispersed in 100mL deionized water and ultrasonicated in an ice bath for 1h. It is then centrifuged at 4000rpm for 8min to separate the unetched Ti3AlC2. Finally, the supernatant is freeze-dried to obtain Ti3C2T x MXene nanosheets.

[0037] In the following examples, the EOG used was prepared as follows: 3.0 g of graphite was dispersed in 138 mL of 98% concentrated sulfuric acid, maintaining the system temperature at 0°C. After complete dispersion, 50 mL of deionized water was slowly added dropwise, maintaining the system temperature below 70°C, to obtain Solution A. 18.0 g of potassium permanganate was dissolved in 200 mL of deionized water to obtain Solution B. Solution B was slowly added dropwise to Solution A, the temperature was raised to 70°C, and the reaction was stirred for 24 hours. The mixture was then centrifuged, washed, and freeze-dried to obtain the EOG sample.

[0038] In the following examples, the thermal conductivity was measured using a thermal conductivity meter (Hot Disk TP3500, Kegonas Instrument Trading Shanghai Co., Ltd.), the mechanical properties of the composite materials were measured using a universal material testing machine (Instron 5967, USA), and the electromagnetic interference shielding performance was measured using a vector network analyzer (Anritsu MS46322B, Japan).

[0039] 1. Effect of the mass ratio of MXene to EOG in MEOG filler on the properties of composite films

[0040] Example 1

[0041] In this example, the MEOG / PNFs multifunctional thermally conductive composite film was prepared according to the following steps:

[0042] Step 1: Preparation of MEOG filler

[0043] MXene was dispersed in deionized water at a concentration of 1 mg / mL to obtain a MXene dispersion; EOG was dispersed in deionized water at a concentration of 1 mg / mL to obtain an EGO dispersion; the MXene dispersion and the EOG dispersion were ultrasonically mixed evenly according to a mass ratio of MXene to EOG of 4:6, and reacted at room temperature for 12 hours to allow MXene and EOG to fully react, and then a solid was obtained by vacuum filtration and centrifugation, and vacuum dried at 60°C for 12 hours to obtain MEOG filler.

[0044] Step 2: Preparation of PNFs

[0045] Methanesulfonic acid (MSA) and trifluoroacetic acid (TFA) were mixed uniformly in a mass ratio of 1:1 to obtain a mixed acid;

[0046] According to the mass ratio of PBO fiber to mixed acid being 1:100, PBO fiber was added to the mixed acid and stirred at room temperature for 3 days to obtain a first PNFs dispersion; mixed acid was added to the first PNFs dispersion for dilution to obtain a second PNFs dispersion with a concentration of 0.1 wt%.

[0047] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0048] The MEOG filler obtained in step 1 was added to 40 mL of the second PNFs dispersion and sonicated for 2 h to form a viscous sol. Then, 20 mL of the first PNFs dispersion was added and stirred evenly. Then, 2 g of Na2SO4 was added and stirred for 3 h to obtain an acid sol. The acid sol was poured into a mold and solidified at 5°C for 12 h to form an acid gel.

[0049] The acid gel was immersed in deionized water to exchange the solvent for 1 h, and then the water was changed and exchanged again, and the exchange was repeated 12 times to obtain a hydrogel;

[0050] The hydrogel was hot-pressed (60° C., 15 KPa) to obtain a MEOG / PNFs multifunctional thermally conductive composite film with a filler content of 5%.

[0051] Example 2

[0052] In this example, the MEOG / PNFs multifunctional thermally conductive composite film was prepared according to the following steps:

[0053] Step 1: Preparation of MEOG filler

[0054] MXene was dispersed in deionized water at a concentration of 1 mg / mL to obtain a MXene dispersion; EOG was dispersed in deionized water at a concentration of 1 mg / mL to obtain an EGO dispersion; the MXene dispersion and the EOG dispersion were ultrasonically mixed evenly according to a mass ratio of MXene to EOG of 1:9, and then reacted at room temperature for 12 hours to allow MXene and EOG to fully react, and then a solid was obtained by vacuum filtration and centrifugation, and vacuum dried at 60°C for 12 hours to obtain MEOG filler.

[0055] Step 2: Preparation of PNFs

[0056] Same as Example 1.

[0057] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0058] Same as Example 1.

[0059] Example 3

[0060] In this example, the MEOG / PNFs multifunctional thermally conductive composite film was prepared according to the following steps:

[0061] Step 1: Preparation of MEOG filler

[0062] MXene was dispersed in deionized water at a concentration of 1 mg / mL to obtain a MXene dispersion; EOG was dispersed in deionized water at a concentration of 1 mg / mL to obtain an EGO dispersion; the MXene dispersion and the EOG dispersion were ultrasonically mixed evenly according to a mass ratio of MXene to EOG of 2:8, and then reacted at room temperature for 12 hours to allow MXene and EOG to fully react, and then a solid was obtained by vacuum assisted filtration and centrifugation, and vacuum dried at 60°C for 12 hours to obtain MEOG filler.

[0063] Step 2: Preparation of PNFs

[0064] Same as Example 1.

[0065] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0066] Same as Example 1.

[0067] Example 4

[0068] In this example, the MEOG / PNFs multifunctional thermally conductive composite film was prepared according to the following steps:

[0069] Step 1: Preparation of MEOG filler

[0070] MXene was dispersed in deionized water at a concentration of 1 mg / mL to obtain a MXene dispersion; EOG was dispersed in deionized water at a concentration of 1 mg / mL to obtain an EGO dispersion; the MXene dispersion and the EOG dispersion were ultrasonically mixed evenly according to a mass ratio of MXene to EOG of 3:7, and then reacted at room temperature for 12 hours to allow MXene and EOG to fully react, and then a solid was obtained by vacuum filtration and centrifugation, and vacuum dried at 60°C for 12 hours to obtain MEOG filler.

[0071] Step 2: Preparation of PNFs

[0072] Same as Example 1.

[0073] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0074] Same as Example 1.

[0075] Example 5

[0076] In this example, the MEOG / PNFs multifunctional thermally conductive composite film was prepared according to the following steps:

[0077] Step 1: Preparation of MEOG filler

[0078] MXene was dispersed in deionized water at a concentration of 1 mg / mL to obtain a MXene dispersion; EOG was dispersed in deionized water at a concentration of 1 mg / mL to obtain an EGO dispersion; the MXene dispersion and the EOG dispersion were ultrasonically mixed evenly according to a mass ratio of MXene to EOG of 5:5, and then reacted at room temperature for 12 hours to allow MXene and EOG to fully react, and then a solid was obtained by vacuum filtration and centrifugation, and vacuum dried at 60°C for 12 hours to obtain MEOG filler.

[0079] Step 2: Preparation of PNFs

[0080] Same as Example 1.

[0081] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0082] Same as Example 1.

[0083] Comparative Example 1

[0084] In this comparative example, an EOG / PNFs composite film with a filler content of 5% was prepared according to the same method as in Example 1, except that the MEOG filler in step 3 of Example 1 was replaced with an equal amount of EOG filler (i.e., the mass ratio of MXene to EOG was 0:10).

[0085] Comparative Example 2

[0086] In this comparative example, a MXene / PNFs composite film with a filler content of 5% was prepared according to the same method as in Example 1, except that the MEOG filler in step 3 of Example 1 was replaced with an equal amount of MXene filler (i.e., the mass ratio of MXene to EOG was 10:0).

[0087] Figure 2 The thermal conductivity of the MEOG / PNFs composite films prepared by using MEOG heterojunction fillers with different MXene:EOG ratios in Examples 1 to 5 and Comparative Examples 1 to 2 at the same content (5%) is shown. It can be seen that when the ratio of MXene to EOG in MEOG is 2:8, the material has the highest thermal conductivity of 7.6 W m -1 K -1 .

[0088] 2. Influence of filler content ratio on composite film properties

[0089] Example 6

[0090] In this example, the MEOG / PNFs thermally conductive multifunctional film was prepared according to the following steps:

[0091] Step 1: Preparation of MEOG filler

[0092] MXene was dispersed in deionized water at a concentration of 1 mg / mL to obtain a MXene dispersion; EOG was dispersed in deionized water at a concentration of 1 mg / mL to obtain an EGO dispersion; the MXene dispersion and the EOG dispersion were ultrasonically mixed evenly according to a mass ratio of MXene to EOG of 2:8, and then reacted at room temperature for 12 hours to allow MXene and EOG to fully react, and then a solid was obtained by vacuum assisted filtration and centrifugation, and vacuum dried at 60°C for 12 hours to obtain MEOG filler.

[0093] Step 2: Preparation of PNFs

[0094] Same as Example 1.

[0095] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0096] 1.623 g of the MEOG filler obtained in step 1 was added to 40 mL of the second PNFs dispersion and sonicated for 2 h to form a viscous sol. 20 mL of the first PNFs dispersion was then added and stirred evenly. 2 g of Na2SO4 was then added and stirred for 3 h to obtain an acid sol. The acid sol was poured into a mold and solidified at 5°C for 12 h to form an acid gel.

[0097] The acid gel was immersed in deionized water to exchange the solvent for 1 hour, and then the water was changed and exchanged again, and the exchange was repeated 12 times to obtain a hydrogel; the hydrogel was hot pressed (60°C, 15KPa) to obtain a MEOG / PNFs multifunctional thermal conductive composite film with a filler content of 40%.

[0098] Example 7

[0099] In this example, the MEOG / PNFs thermally conductive multifunctional film was prepared according to the following steps:

[0100] Step 1: Preparation of MEOG filler

[0101] Same as Example 6.

[0102] Step 2: Preparation of PNFs

[0103] Same as Example 6.

[0104] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0105] 0.26 g of the MEOG filler obtained in step 1 was added to 40 mL of the second PNFs dispersion and sonicated for 2 h to form a viscous sol. 20 mL of the first PNFs dispersion was then added and stirred evenly. 2 g of Na2SO4 was then added and stirred for 3 h to obtain an acid sol. The acid sol was poured into a mold and solidified at 5°C for 12 h to form an acid gel.

[0106] The acid gel was immersed in deionized water to exchange the solvent for 1 hour, and then the water was changed and exchanged again, and the exchange was repeated 12 times to obtain a hydrogel; the hydrogel was hot pressed (60°C, 15KPa) to obtain a MEOG / PNFs multifunctional thermal conductive composite film with a filler content of 10%.

[0107] Example 8

[0108] In this example, the MEOG / PNFs thermally conductive multifunctional film was prepared according to the following steps:

[0109] Step 1: Preparation of MEOG filler

[0110] Same as Example 6.

[0111] Step 2: Preparation of PNFs

[0112] Same as Example 6.

[0113] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0114] 0.60 g of the MEOG filler obtained in step 1 was added to 40 mL of the second PNFs dispersion and sonicated for 2 h to form a viscous sol. 20 mL of the first PNFs dispersion was then added and stirred evenly. 2 g of Na2SO4 was then added and stirred for 3 h to obtain an acid sol. The acid sol was poured into a mold and solidified at 5°C for 12 h to form an acid gel.

[0115] The acid gel was immersed in deionized water to exchange the solvent for 1 hour, and then the water was changed and exchanged again, and the exchange was repeated 12 times to obtain a hydrogel; the hydrogel was hot pressed (60°C, 15KPa) to obtain a MEOG / PNFs multifunctional thermal conductive composite film with a filler content of 20%.

[0116] Example 9

[0117] In this example, the MEOG / PNFs thermally conductive multifunctional film was prepared according to the following steps:

[0118] Step 1: Preparation of MEOG filler

[0119] Same as Example 6.

[0120] Step 2: Preparation of PNFs

[0121] Same as Example 6.

[0122] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0123] 1.03 g of the MEOG filler obtained in step 1 was added to 40 mL of the second PNFs dispersion and sonicated for 2 h to form a viscous sol. 20 mL of the first PNFs dispersion was then added and stirred evenly. 2 g of Na2SO4 was then added and stirred for 3 h to obtain an acid sol. The acid sol was poured into a mold and solidified at 5°C for 12 h to form an acid gel.

[0124] The acid gel was immersed in deionized water to exchange the solvent for 1 hour, and then the water was changed and exchanged again, and the exchange was repeated 12 times to obtain a hydrogel; the hydrogel was hot pressed (60°C, 15KPa) to obtain a MEOG / PNFs multifunctional thermal conductive composite film with a filler content of 30%.

[0125] Example 10

[0126] In this example, the MEOG / PNFs thermally conductive multifunctional film was prepared according to the following steps:

[0127] Step 1: Preparation of MEOG filler

[0128] Same as Example 6.

[0129] Step 2: Preparation of PNFs

[0130] Same as Example 6.

[0131] Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film

[0132] 2.41 g of the MEOG filler obtained in step 1 was added to 40 mL of the second PNFs dispersion and sonicated for 2 h to form a viscous sol. 20 mL of the first PNFs dispersion was then added and stirred evenly. 2 g of Na2SO4 was then added and stirred for 3 h to obtain an acid sol. The acid sol was poured into a mold and solidified at 5°C for 12 h to form an acid gel.

[0133] The acid gel was immersed in deionized water to exchange the solvent for 1 hour, and then the water was changed and exchanged again, and the exchange was repeated 12 times to obtain a hydrogel; the hydrogel was hot pressed (60°C, 15KPa) to obtain a MEOG / PNFs multifunctional thermal conductive composite film with a filler content of 50%.

[0134] Comparative Example 3

[0135] In this comparative example, an EOG / PNFs composite film with a filler content of 40% was prepared according to the same method as in Example 6, except that the MEOG filler in step 3 of Example 6 was replaced with an equal amount of EOG filler.

[0136] Comparative Example 4

[0137] In this comparative example, a MEOG / PNFs composite film with a filler content of 0% was prepared according to the same method as in Example 6, except that the amount of MEOG filler added in step 3 of Example 6 was 0.

[0138] Figure 3 The thermal conductivity of the composite materials obtained in Examples 6 to 10 of the present invention and Comparative Examples 3 to 4 is compared. It can be seen from the figure that when the MEOG content is 40 wt%, the thermal conductivity of the obtained material is increased by 900% to 22.2 W m -1 K -1 By comparing with the single filler EOG / PNFs film, it is shown that the formation of MEOG heterojunction can introduce multiple interactions, which is beneficial to the improvement of thermal conductivity.

[0139] Figure 4 Schematic diagram of molecular dynamics simulation data for MEOG and PNFs. M-EOG, used for comparison, is a blend of MXene and EOG in a mass ratio of 2:8. (a) shows the molecular dynamics model of MEOG; (b) shows the steady-state temperature distribution; (c) shows the interfacial heat transfer data; and (d) shows the phonon density of states (pDOS) between the filler and PNFs. The low phonon transport resistance reflects the highest interfacial thermal conductivity and energy transfer capability between the EOG and MXene layers. Phonon density of states (pDOS) matching is used to determine the phonon energy transfer efficiency at the interface between MEOG, M-EOG, and PNFs. Compared to M-EOG, MEOG exhibits the highest peak pDOS and the highest relative optical spectral overlap (ORIL) with PNFs, confirming the positive impact of multiple non-covalent interactions on reducing ITRf-m. In the in-depth study of the heat conduction mechanism of MEOG heterojunction, in order to verify the role of covalent bonds in MEOG in bridging the phonon transmission, the MEOG and M-EOG models were established to analyze the heat transfer. Figure 4 As shown in (ac), due to the strong covalent interaction between the materials, a more efficient horizontal heat transfer interface structure is formed between the MEOG interface compared with the M-EOG model without interaction. When the heat flux in the system is in a steady state, the temperature gradient between the adjacent EOG and MXene layers in MEOG is the smallest (ΔT = 35.9K) compared with M-EOG, as shown in Figure 4(b) As shown. Because the strong interaction of covalent bonds strengthens the bonding between different interfaces, it effectively promotes phonon transmission. Compared with the forces between materials in the control sample, covalent interactions make the materials have stronger bonding forces, which is also reflected by the DFT binding energy calculation. The role of covalent bonds is more directly reflected in the heat transfer between MEOG layers. The interfacial thermal conductivity (ITC) of MEOG is 3.23GWm -2 K -1 , far exceeding M-EOG.

[0140] Figure 5 Schematic diagram of the thermal conductivity mechanism of MEOG / PNFs composite film, where heat flow is transmitted along the filler distribution direction. Inside the filler, the tightly bound covalent bonds (Ti-OC) and π-π and hydrogen bonds interact to promote the further transmission of phonons, which is beneficial to the improvement of the thermal conductivity of the film.

[0141] Figure 6 The electromagnetic shielding performance of the composite films obtained in Examples 6 to 10 of the present invention and Comparative Example 4 is shown in the figure. When the content of MEOG is 40 wt%, SE T 59.8dB, SE A Much higher than SE R , indicating that the absorption of electromagnetic waves is the main shielding mechanism of MEOG / PNFs films.

[0142] Figure 7 Schematic diagram of the electromagnetic shielding mechanism of MEOG / PNFs composite films. Electromagnetic wave absorption is the primary shielding mechanism of MEOG / PNFs films. When an incident electromagnetic wave reaches the surface of the MEOG / PNFs film, due to the impedance mismatch between air and the conductive MEOG / PNFs film, part of the electromagnetic wave is directly reflected, while the remainder enters the MEOG / PNFs interior. The abundant interfaces within the layered structure of the MEOG / PNFs film enhance multiple reflections and scattering of the electromagnetic wave, thereby increasing its reabsorption and attenuation.

[0143] Figure 8 The stress-strain curves of the composite materials obtained in Examples 6 to 10 of the present invention and Comparative Example 4 show that when the MEOG content is 40 wt %, the maximum tensile strength reaches 176.3 MPa and the elongation at break is 35.9%.

[0144] The above are merely exemplary embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing a MXene-edge graphene oxide heterojunction / PBO fiber multifunctional thermally conductive composite film, characterized by: First, MXene and edge graphene oxide (EOG) are reacted through nucleophilic substitution and dehydration to prepare a MXene-edge graphene oxide heterojunction filler, which is recorded as MEOG filler; then the MEOG filler is added to a dispersion of PBO fibers to prepare an acid gel, which is then replaced by deionized water to prepare a hydrogel; finally, the obtained hydrogel is hot-pressed to obtain the multifunctional thermally conductive composite film; specifically, the process comprises the following steps: Step 1: Preparation of MEOG filler MXene is dispersed in deionized water at a concentration of 1-2 mg / mL to obtain a MXene dispersion; EOG is dispersed in deionized water at a concentration of 1-2 mg / mL to obtain an EGO dispersion; the MXene dispersion and the EOG dispersion are ultrasonically mixed in a mass ratio of MXene to EOG of 10%-50%:90%-50%, reacted at room temperature for 10-13 hours, and then a solid is obtained by vacuum assisted filtration and centrifugation, and vacuum dried to obtain MEOG filler; Step 2: Preparation of PNFs Methanesulfonic acid and trifluoroacetic acid are mixed uniformly in a mass ratio of 1:0.9-1.1 to obtain a mixed acid; The PBO fibers were added to the mixed acid at a mass ratio of 1:95-105 and stirred at room temperature for 3-4 days to obtain a first PNFs dispersion; the mixed acid was added to the first PNFs dispersion for dilution to obtain a second PNFs dispersion with a concentration of 0.1-0.15 wt%; Step 3: Preparation of MEOG / PNFs multifunctional thermal conductive composite film The MEOG filler obtained in step 1 is added to the second PNFs dispersion and ultrasonicated for 2-2.5 hours to form a viscous sol. The first PNFs dispersion is then added and stirred evenly. Then, Na2SO4 is added and stirred for 3-3.5 hours to obtain an acid sol. The acid sol is poured into a mold and solidified at 0-6°C for 12-16 hours to form an acid gel. Immersing the acid gel in deionized water to exchange the solvent for 1 to 3 hours, then exchanging the water again, and repeating the exchange 10 to 12 times to obtain a hydrogel; The hydrogel is hot-pressed to obtain a MEOG / PNFs multifunctional thermally conductive composite film.

2. The preparation method according to claim 1, wherein: In step 1, the vacuum drying temperature is 55-65° C. and the time is 11-13 h.

3. The preparation method according to claim 1, wherein: In step 3, the volume ratio of the second PNFs dispersion to the first PNFs dispersion is 1.5-2.5:

1.

4. The preparation method according to claim 1, wherein: In step 3, the ratio of the amount of Na2SO4 added to the total volume of the second PNFs dispersion and the first PNFs dispersion is 1-3 g / 60 mL.

5. The preparation method according to claim 1, wherein: The mass percentage of MEOG filler in the MEOG / PNFs multifunctional thermal conductive composite film is 10-50%.

6. A MEOG / PNFs multifunctional thermally conductive composite film prepared by the preparation method according to any one of claims 1 to 5.

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