CN114456443B - Flexible cellulose/boron nitride/MXene sandwich structure composite membrane and preparation method and application thereof - Google Patents
Flexible cellulose/boron nitride/MXene sandwich structure composite membrane and preparation method and application thereof Download PDFInfo
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Abstract
The invention discloses a flexible cellulose/boron nitride/MXene sandwich structure composite membrane, a preparation method and application thereof, wherein the flexible cellulose/boron nitride/MXene sandwich structure composite membrane is prepared by adopting cellulose, boron nitride solution and MXene colloid solution, and the sandwich structure composite membrane formed by a heat conduction electric insulation cellulose/boron nitride outer layer and an electric conduction MXene interlayer is prepared by layer-by-layer self-assembly through an alternating vacuum auxiliary suction filtration method ‑1 K ‑1 The method comprises the steps of carrying out a first treatment on the surface of the The electromagnetic shielding effectiveness can reach 44.0dB, and the composite film can be used as a heat dissipation material and an electromagnetic shielding material in electronic devices.
Description
Technical Field
The invention relates to the technical field of heat conduction and electromagnetic shielding composite materials, in particular to a flexible cellulose/boron nitride/MXene sandwich structure composite film, and a preparation method and application thereof.
Background
With the rapid development of 5G communication, modern electronic devices are urgently needed to reduce heat accumulation and improve electromagnetic shielding performance, so as to meet the use requirements. When the electronic equipment is in operation, a large amount of heat can be generated, if the accumulated heat is not discharged in time, the electronic equipment can be caused to fail, natural self-explosion is caused, and the service life is shortened; on the other hand, the electronic equipment can generate electromagnetic radiation, so that the normal operation of surrounding electronic equipment is influenced, and meanwhile, the environment pollution and the human health are also caused. Therefore, the composite material with high heat conduction and high electromagnetic shielding performance has great research and application value in the field of electronic equipment and thermal management.
Cellulose is a natural polymer, has wide sources and low cost, and has many characteristics including biodegradability, reproducibility, processability, high strength and the like. Nanocellulose is derived from cellulose, which not only maintains the inherent properties of cellulose, but also has excellent properties of high aspect ratio, high specific surface area, and the like. Multifunctional nano cellulose-based composite materials are assembled by introducing fillers with different properties, so that the application field of the composite materials is expanded, and the maximum utilization value is realized.
Boron nitride is one of ceramic materials, and has electrical insulation property and high in-plane thermal conductivity (600 W.m -1 K -1 ) Good vertical plane thermal conductivity (30 W.m -1 K -1 ). Boron nitride is therefore often added to the matrix as a thermally conductive filler to enhance the thermal conductivity of the composite. In some cases, the addition of high levels of filler is unavoidable in order to obtain higher thermal conductivity. However, when the filler addition is too high, the mechanical properties of the composite material are sacrificed, so that it is important to design a flexible high-heat-conductivity composite material.
Recently, the emerging two-dimensional transition metal carbo/nitride (MXene) has excellent conductivity, abundant functional groups and unique dielectric properties, and has great application value in electromagnetic shielding, energy sources, catalysis and other aspects, and the MXene is usually obtained by selectively etching away the middle layer of MAX by an etchant. In addition, MXene is arranged by a plurality of elements according to a certain proportion and structure, and the physical and chemical properties of the MXene can be flexibly regulated through modification and functionalization of the surface terminal groups, so that the MXene is more beneficial to being compounded with other nano materials to obtain an ideal multifunctional composite material.
Therefore, the invention discloses a flexible cellulose/boron nitride/MXene sandwich structure composite membrane, a preparation method and application thereof, wherein the flexible cellulose/boron nitride/MXene sandwich structure composite membrane is prepared by adopting cellulose, boron nitride solution and MXene colloid solution, and the sandwich structure composite membrane formed by a heat-conducting and electric-insulating cellulose/boron nitride outer layer and an electric-conducting MXene interlayer is prepared by layer-by-layer self-assembly through an alternating vacuum auxiliary suction filtration methodFlexibility, thermal conductivity up to 33.0Wm -1 K -1 The method comprises the steps of carrying out a first treatment on the surface of the The electromagnetic shielding effectiveness can reach 44.0dB, and the composite film can be used as a heat dissipation material and an electromagnetic shielding material in electronic devices.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a flexible cellulose/boron nitride/MXene sandwich structure composite membrane, a preparation method and application thereof, wherein the preparation of the flexible cellulose/boron nitride/MXene sandwich structure composite membrane adopts cellulose, boron nitride solution and MXene colloid solution, and the sandwich structure composite membrane consisting of a heat-conducting and electric-insulating cellulose/boron nitride outer layer and an electric-conducting MXene interlayer is prepared by layer-by-layer self-assembly through an alternating vacuum auxiliary suction filtration method, and the composite membrane provided by the invention can keep good flexibility and has a heat conductivity of 33.0Wm -1 K -1 The method comprises the steps of carrying out a first treatment on the surface of the The electromagnetic shielding effectiveness can reach 44.0dB, and the composite film can be used as a heat dissipation material and an electromagnetic shielding material in electronic devices.
In order to achieve the technical effects, the following technical scheme is adopted:
a flexible cellulose/boron nitride/MXene "sandwich" structured composite membrane having the structure:
the cellulose/boron nitride electric insulation heat conduction layer is used as a top layer and a bottom layer, the MXene electric conduction layer is used as a sandwich repeating unit structure of a middle layer, and the number of the repeating units is n, wherein n is more than or equal to 1;
the heat conductivity coefficient of the flexible cellulose/boron nitride/MXene sandwich structure composite film is more than 26.81 W.m -1 K -1 The average electromagnetic shielding effectiveness is greater than 28.1dB.
The preparation method of the flexible cellulose/boron nitride/MXene sandwich structure composite membrane comprises the following steps:
step S1: preparing a cellulose water dispersion liquid with a certain concentration; adding boron nitride into the cellulose water dispersion liquid, and stirring to prepare a cellulose/boron nitride mixed solution;
step S2: preparing a few-layer MXene colloidal solution by an in-situ HF etching method;
step S3: the cellulose/boron nitride mixed solution prepared in the step S1 and the MXene colloidal solution prepared in the step S2 are subjected to repeated alternating vacuum auxiliary suction filtration, and the single sandwich structure repeating unit alternating vacuum auxiliary suction filtration method comprises the following steps:
firstly, filtering the cellulose/boron nitride mixed solution prepared in the step S1 to serve as a bottom layer;
then, adding the less-layer MXene colloidal solution prepared in the step S2 as an intermediate layer when the bottom layer is pumped to a state that the surface is slightly moist;
finally, adding the cellulose/boron nitride mixed solution prepared in the step S1 when the intermediate layer is pumped to a state that the surface is slightly moist, and pumping to dryness to serve as a top layer;
repeating the alternating vacuum auxiliary suction filtration process for n times by using a single sandwich structure repeating unit to obtain the flexible cellulose/boron nitride/MXene sandwich structure composite film with the sandwich structure by using the cellulose/boron nitride electric insulation heat conduction layer as a top layer and a bottom layer and using the MXene electric conduction layer as a middle layer, wherein the number of the repeating units is n, and n is more than or equal to 1.
Step S4: and (3) drying at low temperature in vacuum, and removing the filter membrane to obtain the cellulose/boron nitride/MXene sandwich structure composite membrane.
Further, the filter paper used in the suction filtration process is an aqueous cellulose ester filter film.
Further, in the step S1, the mass fraction of boron nitride in the cellulose/boron nitride mixed solution is 20-60 wt% of the cellulose.
Further, the specific method for preparing the cellulose/boron nitride mixed solution in the step S1 is as follows:
dispersing high-concentration cellulose gel into deionized water to prepare cellulose aqueous dispersion, adding boron nitride powder into the cellulose aqueous dispersion, carrying out ultrasonic treatment, and stirring to prepare a milky cellulose/boron nitride cellulose mixed solution.
Further, the specific method for preparing the few-layer MXene colloidal solution in the step S2 by an in-situ HF etching method comprises the following steps:
step S21: 1-2 g of lithium fluoride is slowly dissolved in 20-40 mL of 9M hydrochloric acid and stirred for 20-30 min to obtain clarified etching solution;
step S22: slowly adding 1-2 g Ti into the etching solution 3 AlC 2 Stirring for 36-48 h at 35-40 ℃, washing and centrifuging for 4-6 times by using deionized water, wherein the centrifugal speed is 3500-4000 rpm, and each cycle is carried out for 10min, and the pH value of supernatant is about 6;
step S23: collecting sediment at the bottom of the centrifuge tube, adding 10-20 mL of deionized water, shaking up the mixed solution vigorously by hand, and performing ultrasonic treatment for 1-1.5 h;
step S24: centrifuging the mixed solution in the step S23 at 3500-4000 rpm for 10-30 min, collecting the upper dark green liquid which is the less-layer MXene colloidal solution, preparing 2-10 mg/mL less-layer MXene colloidal solution, and sealing and preserving in a refrigerator at 3-6 ℃ for standby.
Further, the low-temperature vacuum drying conditions in the step S4 are as follows: vacuum drying at 35-40 deg.c for 12-24 hr and pressure of 0.08-1MPa.
Further, the stirring in the step S2 adopts mechanical stirring or magnetic stirring, and the rotating speed is 1500-2000 rpm.
Further, when n is 1, the layer-by-layer suction filtration structure is a 3-layer symmetrical structure, the bottom layer and the top layer are both cellulose/boron nitride electric insulation heat conduction layers, and the middle interlayer is an MXene electric conduction layer.
The application of the cellulose/boron nitride/MXene sandwich structure composite membrane prepared by the preparation method according to any one of the above claims is characterized in that: the prepared composite film has excellent heat conducting performance, high electromagnetic shielding performance, surface electrical insulation performance and good flexibility, and is used as a heat dissipation material and an electromagnetic shielding material in electronic devices.
The beneficial effects of the invention are as follows:
the invention aims atThe invention provides a flexible cellulose/boron nitride/MXene sandwich structure composite membrane, a preparation method and application thereof, wherein the flexible cellulose/boron nitride/MXene sandwich structure composite membrane is prepared by adopting cellulose, boron nitride solution and MXene colloid solution, and the sandwich structure composite membrane formed by a heat-conducting and electric-insulating cellulose/boron nitride outer layer and an electric-conducting MXene interlayer is prepared by layer-by-layer self-assembly through an alternating vacuum auxiliary suction filtration method, and the composite membrane provided by the invention can keep good flexibility, and the heat conductivity can reach 33.0Wm -1 K -1 The method comprises the steps of carrying out a first treatment on the surface of the The electromagnetic shielding effectiveness can reach 44.0dB, and the composite film can be used as a heat dissipation material and an electromagnetic shielding material in electronic devices.
The invention has the advantages that:
1. the cellulose/boron nitride/MXene sandwich structure composite membrane provided by the invention has good flexibility and can be bent in practice; the thermal conductivity measured by the laser thermal conductivity meter can reach 33.0Wm -1 K -1 The method comprises the steps of carrying out a first treatment on the surface of the The electromagnetic shielding effectiveness measured by the microwave vector network instrument can reach 44.0dB.
2. The matrix of the invention is cellulose, and has wide sources and low cost, thus being suitable for mass use. The method for preparing the composite membrane provided by the invention has the advantages of simple process, easiness in operation, safety, no pollution and easiness in industrial production.
Drawings
FIG. 1 is a photograph of a composite membrane of a cellulose/boron nitride/MXene "sandwich" structure prepared in example 1 of the present invention;
FIG. 2 is an SEM image of a cellulose/boron nitride/MXene "sandwich" structured composite membrane prepared in example 1 of the present invention;
FIG. 3 is an EDS diagram of a cellulose/boron nitride/MXene "sandwich" structured composite membrane prepared in example 1 of the present invention;
FIG. 4 is a graph showing the comparison of the results of the thermal conductivity tests of different materials according to the embodiment of the present invention;
fig. 5 is a graph comparing electromagnetic shielding performance test results of different materials in the embodiment of the present invention.
Detailed Description
The present invention will now be described further with reference to the accompanying drawings, wherein the embodiments described are only some, but not all embodiments of the invention. The following description of the exemplary embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. All other embodiments, which can be made by one of ordinary skill in the art without undue burden on the person of ordinary skill in the art based on embodiments of the present invention, are within the scope of the present invention.
Techniques, methods, and apparatus known to those skilled in the art may not be discussed in detail, but are intended to be part of the specification where appropriate.
The test materials used in the examples described below, unless otherwise specified, are all conventional in the art and are commercially available or prepared by conventional techniques.
The nanocellulose gel used in the examples below was purchased from new material of nanofibrillar, inc, middle mountain, guangdong at a concentration of 4.5% ± 0.5%.
The nano boron nitride powder used in the following examples was purchased from Shanghai A Ding Keji Co., ltd, and was less than 150nm in size.
MAX (Ti) 3 AlC 2 ) Purchased from Jilin, a technology Co., ltd, with a particle size of 400 mesh.
In order to better understand the technical scheme of the application, the embodiment uses a cellulose/boron nitride electric insulation heat conduction layer as a top layer and a bottom layer, uses an MXene conductive layer as a sandwich repeating unit structure of a middle layer, and has the number of repeating units of n, wherein n is 1, and when n is greater than 1, the method is consistent with the preparation method of the embodiment, and the multilayer repeating unit structure can be formed by alternately repeating vacuum auxiliary suction filtration according to the requirement.
When n is 1, the layer-by-layer suction filtration structure is a 3-layer symmetrical structure, the bottom layer and the top layer are both cellulose/boron nitride electric insulation heat conduction layers, and the middle interlayer is an MXene electric conduction layer.
Example 1
(1) 1.0g of lithium fluoride is dissolved in 20mL of 9M hydrochloric acid and stirred for 30min to obtain clear etching solution; 1.0g MAX powder was slowly added and stirred at 35℃for 48h. After the reaction is finished, the precipitate is centrifugally collected and centrifugally washed by deionized water for 5 times (3500 rpm,10 min) until the pH value of the supernatant is more than 6. Dissolving the precipitate in a centrifuge tube containing 15mL, shaking the mixed solution vigorously by hand for 5min, and then performing ultrasonic treatment for 1h; centrifuging the mixed solution at 3500rpm for 10min, collecting upper dark green liquid, circulating for 2-3 times, preparing into 10mg/mL small-layer MXene colloidal solution, and sealing in a refrigerator at 4deg.C for use.
(2) Dispersing high-concentration cellulose gel into deionized water to prepare a cellulose water dispersion with the concentration of 2mg/mL, taking 30mL of cellulose water dispersion into a beaker, adding 0.024g of boron nitride powder into the beaker, carrying out ultrasonic treatment for 1h (240W), and stirring for 2h (1500 rpm) to prepare a cellulose/boron nitride cellulose mixed solution with the concentration of boron nitride of 40wt% (the boron nitride content accounts for the mass fraction of the total cellulose).
(3) And (3) uniformly dividing 30mL of cellulose/boron nitride cellulose mixed solution with the boron nitride content of 40wt% into 2 parts, and alternately carrying out vacuum filtration with 10mL of MXene colloidal solution through a water-based cellulose ester filter membrane with the pore diameter of 0.22 mu m to obtain the symmetrical 3-layer composite gel.
(4) And (3) vacuum drying the gel at 35 ℃ and 0.08MPa for 24 hours to obtain the cellulose/boron nitride/MXene sandwich structure composite membrane.
Fig. 1 is a photograph of a composite film of cellulose/boron nitride/MXene "sandwich" structure prepared in example 1, which shows that the composite film has good flexibility and can be bent.
FIG. 2 is a microscopic SEM image of a cross section of the cellulose/boron nitride/MXene "sandwich" structured composite membrane prepared in example 1, demonstrating the "sandwich" structure of the composite membrane.
FIG. 3 is a cross-sectional EDS image corresponding to the cellulose/boron nitride/MXene "sandwich" structured composite membrane prepared in example 1, further demonstrating the "sandwich" structure of the above composite membrane, wherein the Ti element map demonstrates the middle interlayer as the MXene layer.
Example 2:
(1) 2.0g of lithium fluoride is dissolved in 40mL of 9M hydrochloric acid and stirred for 30min to obtain clear etching solution; 2.0g of MAX powder was slowly added and stirred at 38℃for 40h. After the reaction, the precipitate was collected by centrifugation, and washed with deionized water for 6 times (3500 rpm,10 min) to a supernatant pH of greater than 6. Dissolving the precipitate in a centrifuge tube containing 20mL, shaking the mixed solution vigorously by hand for 5min, and then performing ultrasonic treatment for 1.5h; centrifuging the mixed solution at 3500rpm for 20min, collecting upper dark green liquid, circulating for 2-3 times, preparing into 10mg/mL small-layer MXene colloidal solution, and sealing in a refrigerator at 4deg.C for use.
(2) Dispersing high-concentration cellulose gel into deionized water to prepare a cellulose water dispersion with the concentration of 2mg/mL, taking 30mL of cellulose water dispersion into a beaker, adding 0.012g of boron nitride powder into the beaker, carrying out ultrasonic treatment for 1h (240W), and stirring for 2h (1500 rpm) to prepare a cellulose/boron nitride cellulose mixed solution with the concentration of 20wt% of boron nitride.
(3) And (3) uniformly dividing 30mL of cellulose/boron nitride cellulose mixed solution with the boron nitride content of 20wt% into 2 parts, and alternately carrying out vacuum filtration with 10mL of MXene colloidal solution through a water-based cellulose ester filter membrane with the pore diameter of 0.22 mu m to obtain the symmetrical 3-layer composite gel.
(4) And (3) vacuum drying the gel at 35 ℃ and 1MPa for 16 hours to obtain the cellulose/boron nitride/MXene sandwich structure composite membrane.
Example 3:
(1) 2.0g of lithium fluoride is dissolved in 40mL of 9M hydrochloric acid and stirred for 30min to obtain clear etching solution; 2.0g MAX powder was slowly added and stirred at 40℃for 36h. After the reaction, the precipitate was collected by centrifugation, and washed with deionized water for 6 times (3500 rpm,10 min) to a supernatant pH of greater than 6. Dissolving the precipitate in a centrifuge tube containing 20mL, shaking the mixed solution vigorously by hand for 5min, and then performing ultrasonic treatment for 1.5h; centrifuging the mixed solution at 3500rpm for 30min, collecting upper dark green liquid, circulating for 2-3 times, preparing into 10mg/mL small-layer MXene colloidal solution, and sealing in a refrigerator at 4deg.C for use.
(2) Dispersing high-concentration cellulose gel into deionized water to prepare a cellulose water dispersion with the concentration of 2mg/mL, taking 30mL of cellulose water dispersion into a beaker, adding 0.036g of boron nitride powder into the beaker, carrying out ultrasonic treatment for 2h (240W), and stirring for 3h (2000 rpm) to prepare a cellulose/boron nitride cellulose mixed solution with the concentration of 60wt% of boron nitride.
(3) And (3) uniformly dividing 30mL of cellulose/boron nitride cellulose mixed solution with the boron nitride content of 60wt% into 2 parts, and alternately carrying out vacuum filtration with 10mL of MXene colloidal solution through a water-based cellulose ester filter membrane with the pore diameter of 0.22 mu m to obtain the symmetrical 3-layer composite gel.
(4) And (3) vacuum drying the gel at 35 ℃ and 0.08MPa for 18 hours to obtain the cellulose/boron nitride/MXene sandwich structure composite membrane.
Example 4:
(1) 1.5g of lithium fluoride is dissolved in 30mL of 9M hydrochloric acid and stirred for 30min to obtain clear etching solution; 1.5g MAX powder was slowly added and stirred at 35℃for 48h. After the reaction, the precipitate was collected by centrifugation, and washed with deionized water for 6 times (3500 rpm,10 min) to a supernatant pH of greater than 6. Dissolving the precipitate in a centrifuge tube containing 20mL, shaking the mixed solution vigorously by hand for 5min, and then performing ultrasonic treatment for 1.5h; centrifuging the mixed solution at 3500rpm for 30min, collecting upper dark green liquid, circulating for 2-3 times, preparing into 10mg/mL small-layer MXene colloidal solution, and sealing in a refrigerator at 4deg.C for use.
(2) Dispersing high-concentration cellulose gel into deionized water to prepare a cellulose water dispersion with the concentration of 1mg/mL, taking 60mL of cellulose water dispersion into a beaker, adding 0.024g of boron nitride powder into the beaker, carrying out ultrasonic treatment for 1h (240W), and stirring for 2h (1500 rpm) to prepare a cellulose/boron nitride cellulose mixed solution with the concentration of 40wt% of boron nitride.
(3) And (3) uniformly dividing 60mL of cellulose/boron nitride cellulose mixed solution with the boron nitride content of 40wt% into 2 parts, and alternately carrying out vacuum filtration with 12.5mL of the MXene colloidal solution through a water-based cellulose ester filter membrane with the pore diameter of 0.22 mu m to obtain the symmetrical 3-layer composite gel.
(4) And (3) vacuum drying the gel at 40 ℃ and 1MPa for 12 hours to obtain the cellulose/boron nitride/MXene sandwich structure composite membrane.
Example 5:
(1) 2g of lithium fluoride is dissolved in 40mL of 9M hydrochloric acid and stirred for 30min to obtain clear etching solution; 2g of MAX powder was slowly added and stirred at 38℃for 40h. After the reaction, the precipitate was collected by centrifugation, and washed with deionized water for 6 times (3500 rpm,10 min) to a supernatant pH of greater than 6. Dissolving the precipitate in a centrifuge tube containing 20mL, shaking the mixed solution vigorously by hand for 5min, and then performing ultrasonic treatment for 1.5h; centrifuging the mixed solution at 3500rpm for 30min, collecting upper dark green liquid, circulating for 2-3 times, preparing into 10mg/mL small-layer MXene colloidal solution, and sealing in a refrigerator at 4deg.C for use.
(2) Dispersing high-concentration cellulose gel into deionized water to prepare a cellulose water dispersion with the concentration of 1mg/mL, taking 30mL of cellulose water dispersion into a beaker, adding 0.024g of boron nitride powder into the beaker, carrying out ultrasonic treatment for 1.5h (240W), and stirring for 2.5h (2000 rpm) to prepare a cellulose/boron nitride cellulose mixed solution with the concentration of 40wt% of boron nitride.
(3) And (3) uniformly dividing 30mL of cellulose/boron nitride cellulose mixed solution with the boron nitride content of 40wt% into 2 parts, and alternately carrying out vacuum filtration with 15mL of MXene colloidal solution through a water-based cellulose ester filter membrane with the pore diameter of 0.22 mu m to obtain the symmetrical 3-layer composite gel.
(4) And (3) vacuum drying the gel at 40 ℃ and 1MPa for 12 hours to obtain the cellulose/boron nitride/MXene sandwich structure composite membrane.
Comparative example 1:
uniformly dispersing nano cellulose gel by deionized water, filtering the solution into a cellulose film by adopting a vacuum auxiliary filtering method, and drying to obtain the pure cellulose film.
Fig. 4 is a graph comparing the thermal conductivity of pure cellulose films and examples 1-3. As is clear from FIG. 4, the in-plane thermal conductivity of the pure cellulose film was 1.40 W.multidot.m -1 K -1 The in-plane thermal conductivity of examples 1 to 3 was 31.18 W.multidot.m in order -1 K -1 ，26.81W·m - 1 K -1 ，33.05W·m -1 K -1 The thermal conductivity of the composite membrane is far higher than that of a pure cellulose membrane, and the composite membrane with a cellulose/boron nitride/MXene sandwich structure has excellent thermal conductivity.
Fig. 5 is a graph of electromagnetic shielding effectiveness of pure cellulose films and examples 1, 4 and 5 at the X-band (frequency 8.2-12.4 GHz). As can be seen from fig. 5, the average electromagnetic shielding effectiveness of the pure cellulose film is almost zero, which is only 0.07dB; the average electromagnetic shielding effectiveness of examples 1, 4 and 5 were 24.7dB, 28.1dB and 43.86dB, respectively, all meeting the commercial use requirements (SE T >20dB)。
In summary, the invention provides a flexible cellulose/boron nitride/MXene sandwich structure composite membrane, a preparation method and application thereof, the flexible cellulose/boron nitride/MXene sandwich structure composite membrane is prepared by adopting cellulose, boron nitride solution and MXene colloid solution, and the sandwich structure composite membrane formed by a heat-conducting and electric-insulating cellulose/boron nitride outer layer and an electric-conducting MXene interlayer is prepared by layer-by-layer self-assembly through an alternating vacuum auxiliary suction filtration method, and the composite membrane provided by the invention can keep good flexibility, and the heat conductivity can reach 33.0Wm -1 K -1 The method comprises the steps of carrying out a first treatment on the surface of the The electromagnetic shielding effectiveness can reach 44.0dB, and the composite film can be used as a heat dissipation material and an electromagnetic shielding material in electronic devices.
The cellulose/boron nitride/MXene sandwich structure composite membrane provided by the invention has good flexibility and can be bent in practice; the thermal conductivity measured by the laser thermal conductivity meter can reach 33.0Wm -1 K -1 The method comprises the steps of carrying out a first treatment on the surface of the The electromagnetic shielding effectiveness measured by the microwave vector network instrument can reach 44.0dB.
The matrix of the invention is cellulose, and has wide sources and low cost, thus being suitable for mass use. The method for preparing the composite membrane provided by the invention has the advantages of simple process, easiness in operation, safety, no pollution and easiness in industrial production.
So far, those skilled in the art will recognize that while embodiments of the present invention have been shown and described in detail herein, many other variations or modifications that are in accordance with the principles of the present invention may be directly ascertained or inferred from the present disclosure without departing from the spirit and scope of the present invention. Accordingly, the scope of the present invention should be understood and deemed to cover all such other variations or modifications.
Claims (8)
1. The flexible cellulose/boron nitride/MXene sandwich structure composite membrane is characterized in that the structure of the flexible cellulose/boron nitride/MXene sandwich structure composite membrane is as follows:
the cellulose/boron nitride electric insulation heat conduction layer is used as a top layer and a bottom layer, the MXene electric conduction layer is used as a sandwich repeating unit structure of a middle layer, and the number of the repeating units is n, wherein n is more than or equal to 1;
the heat conductivity coefficient of the flexible cellulose/boron nitride/MXene sandwich structure composite film is more than 26.81W m -1 K -1 The average electromagnetic shielding effectiveness is greater than 28.1dB;
the preparation method of the composite film comprises the following steps:
step S1: preparing a cellulose water dispersion liquid with a certain concentration; adding boron nitride into the cellulose water dispersion liquid, and stirring to prepare a cellulose/boron nitride mixed solution;
step S2: preparing a few-layer MXene colloidal solution by an in-situ HF etching method;
step S3: the cellulose/boron nitride mixed solution prepared in the step S1 and the MXene colloidal solution prepared in the step S2 are subjected to repeated alternating vacuum auxiliary suction filtration, and the single sandwich structure repeating unit alternating vacuum auxiliary suction filtration method comprises the following steps:
firstly, filtering the cellulose/boron nitride mixed solution prepared in the step S1 to serve as a bottom layer;
then, adding the less-layer MXene colloidal solution prepared in the step S2 as an intermediate layer when the bottom layer is pumped to a state that the surface is slightly moist;
finally, adding the cellulose/boron nitride mixed solution prepared in the step S1 when the intermediate layer is pumped to a state that the surface is slightly moist, and pumping to dryness to serve as a top layer;
repeating the alternating vacuum auxiliary suction filtration process of a single sandwich structure repeating unit for n times to obtain a flexible cellulose/boron nitride/MXene sandwich structure composite film with a sandwich structure taking a cellulose/boron nitride electric insulation heat conduction layer as a top layer and a bottom layer and an MXene electric conduction layer as a middle layer, wherein the number of the repeating units is n, and n is more than or equal to 1;
step S4: drying under low temperature and vacuum, removing the filter membrane to obtain a cellulose/boron nitride/MXene sandwich structure composite membrane;
and in the step S1, the mass fraction of the boron nitride in the cellulose/boron nitride mixed solution is 20-60 wt% of the cellulose.
2. The method for preparing the flexible cellulose/boron nitride/MXene sandwich structure composite membrane as claimed in claim 1, wherein the filter paper used in the suction filtration process is a water-based cellulose ester filter membrane.
3. The method for preparing the flexible cellulose/boron nitride/MXene "sandwich" structured composite film according to claim 1, wherein the specific method for preparing the cellulose/boron nitride mixed solution in step S1 is as follows:
dispersing high-concentration cellulose gel into deionized water to prepare cellulose aqueous dispersion, adding boron nitride powder into the cellulose aqueous dispersion, carrying out ultrasonic treatment, and stirring to prepare a milky cellulose/boron nitride cellulose mixed solution.
4. The method for preparing the flexible cellulose/boron nitride/MXene "sandwich" structured composite film according to claim 1, wherein the specific method for preparing the few-layer MXene colloidal solution by in-situ HF etching in step S2 is as follows:
step S21: 1-2 g of lithium fluoride is slowly dissolved in 20-40 mL of 9M hydrochloric acid and stirred for 20-30 min to obtain clarified etching solution;
step S22: slowly adding 1-2 g Ti into the etching solution 3 AlC 2 Stirring at 35-40 deg.c for 36-48 hr with deionized waterWashing and centrifuging for 4-6 times, wherein the centrifugal speed is 3500-4000 rpm, and each cycle is carried out for 10min, and the pH value of supernatant is 6;
step S23: collecting sediment at the bottom of the centrifuge tube, adding 10-20 mL of deionized water, shaking up the mixed solution vigorously by hand, and performing ultrasonic treatment for 1-1.5 h;
step S24: centrifuging the mixed solution in the step S23 at 3500-4000 rpm for 10-30 min, collecting the upper dark green liquid which is the less-layer MXene colloidal solution, preparing 2-10 mg/mL less-layer MXene colloidal solution, and sealing and preserving in a refrigerator at 3-6 ℃ for standby.
5. The method for preparing the flexible cellulose/boron nitride/MXene "sandwich" structured composite film according to claim 1, characterized in that the low temperature vacuum drying condition in step S4 is: vacuum drying at 35-40 deg.c for 12-24 hr and pressure of 0.08-1MPa.
6. The method for preparing a flexible cellulose/boron nitride/MXene sandwich composite membrane according to claim 4, wherein the stirring in the step S2 is mechanical stirring or magnetic stirring, and the rotating speed is 1500-2000 rpm.
7. The method for preparing the flexible cellulose/boron nitride/MXene sandwich structure composite membrane as claimed in claim 1, wherein when n is 1, the layer-by-layer suction filtration structure is a 3-layer symmetrical structure, the bottom layer and the top layer are both cellulose/boron nitride electric insulation heat conduction layers, and the middle interlayer is an MXene electric conduction layer.
8. Use of a cellulose/boron nitride/MXene "sandwich" structured composite membrane made by the preparation method according to any one of the claims from 1 to 7, characterized in that: the prepared composite film has excellent heat conducting performance, high electromagnetic shielding performance, surface electrical insulation performance and good flexibility, and is used as a heat dissipation material and an electromagnetic shielding material in electronic devices.
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