CN115197513B - Composite doped with two-dimensional material and preparation method thereof - Google Patents

Composite doped with two-dimensional material and preparation method thereof Download PDF

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CN115197513B
CN115197513B CN202210952656.8A CN202210952656A CN115197513B CN 115197513 B CN115197513 B CN 115197513B CN 202210952656 A CN202210952656 A CN 202210952656A CN 115197513 B CN115197513 B CN 115197513B
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CN115197513A (en
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丘陵
许兰淑
成会明
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Shenzhen International Graduate School of Tsinghua University
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    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
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    • C08J3/20—Compounding polymers with additives, e.g. colouring
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    • C08J2327/00—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers
    • C08J2327/02—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment
    • C08J2327/12—Characterised by the use of homopolymers or copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by a halogen; Derivatives of such polymers not modified by chemical after-treatment containing fluorine atoms
    • C08J2327/18—Homopolymers or copolymers of tetrafluoroethylene
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Abstract

The application provides a compound doped with a two-dimensional material and a preparation method thereof, comprising the following steps: providing a two-dimensional material dispersion; mixing the two-dimensional material dispersion liquid with the fiberized polymer dispersion liquid to obtain composite slurry; concentrating the composite slurry, wherein the solvent content in the composite slurry is 31-34 wt% to obtain a solid flexible product; rolling the solid flexible product to obtain a pre-rolling product; folding the pre-roll product, rolling again, and folding and rolling for more than 10 times to obtain the composite doped with the two-dimensional material, wherein the two-dimensional material is distributed in the composite in parallel in the horizontal direction. In the application, the solid flexible product is randomly processed in modes of kneading, mould pressing, rolling and the like, and the two-dimensional material is mechanically locked on the three-dimensional network structure by the fiberized polymer, so that aggregation and re-accumulation of the two-dimensional material are prevented. During the rolling process, the two-dimensional material gradually tends to align parallel and at a high level under the action of the drawing and rolling shafts of the fibrillated polymer to obtain a composite of high level thermal conductivity.

Description

Composite doped with two-dimensional material and preparation method thereof
Technical Field
The application relates to the technical field of nano materials and polymer composite materials, in particular to a composite doped with a two-dimensional material and a preparation method thereof.
Background
With the technical development of miniature electronic devices, electronic equipment and devices are gradually miniaturized and diversified, and with the increase of the working frequency, heat generated during working is rapidly accumulated, so that the environmental temperature of the electronic equipment or devices is continuously increased, and if the heat cannot be timely diffused outwards, the use reliability of the electronic equipment and devices is affected. Among them, the polymer-based heat conductive composite material has excellent processability and low cost, and is the most widely used heat dissipation material. However, due to the low thermal conductivity of the polymer properties, it is desirable to add thermally conductive fillers to increase the thermal conductivity of the composite.
The two-dimensional material has excellent physical and chemical properties, such as higher heat conductivity, lower dielectric constant and dielectric loss, and the defect of the performance of a pure polymer can be overcome by utilizing the performance advantages of the two-dimensional material, so that the heat conduction or electric conduction performance of the composite material is improved.
As a typical two-dimensional material graphene, a macroscopic assembly is generally designed and prepared using a graphene oxide dispersion liquid as a precursor, because graphene oxide has a rich functional group and excellent dispersibility in water. Generally, increasing the loading of the two-dimensional material in the polymer matrix enables more continuous heat or electrical conduction paths to be formed, thereby achieving improved thermal/electrical performance. However, at high loadings, two-dimensional materials are very prone to agglomerate formation. At the same time, these agglomerates can form mechanical stress concentrations that severely impact the mechanical properties and horizontal thermal conductivity of the composite.
Disclosure of Invention
In view of this, the present application provides a composite doped with a two-dimensional material and a method for preparing the same.
To achieve the above object, the present application provides a method for preparing a composite doped with a two-dimensional material, the method comprising: providing a two-dimensional material dispersion; mixing the two-dimensional material dispersion liquid with a fiberized polymer dispersion liquid to obtain composite slurry; concentrating the composite slurry to ensure that the solvent content in the composite slurry is 31-34 wt percent, thereby obtaining a solid flexible product; rolling the solid flexible product to obtain a pre-rolled product; folding the pre-roll product and rolling again, and obtaining the compound doped with the two-dimensional material after more than 10 times of folding and rolling, wherein the two-dimensional material is distributed in the compound in parallel in the horizontal direction.
In some embodiments, the concentration of the two-dimensional material dispersion is 5-100 mg/mL, and the two-dimensional material accounts for 10-40 wt% of the composite slurry.
In some embodiments, the two-dimensional material comprises graphene, boron nitride, mica, or MoS 2 One or more of the nanoplatelets.
In some embodiments, the fibrillated polymer includes one or more of dispersed polytetrafluoroethylene, aramid nanofibers, polyester fibers, polyamide fibers, polyvinyl alcohol fibers, polyacrylonitrile fibers, polypropylene fibers, or polyvinyl chloride fibers.
In some embodiments, the two-dimensional material dispersion comprises a two-dimensional material and a dispersant, the two-dimensional material being prepared from a feedstock by one of ball milling, sanding, grinding, mechanical stirring, high-speed shearing, sonication, high-pressure homogenization, chemical stripping, or microfluidics;
the dispersing agent comprises one of isopropanol, N-butanol, acetone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide or N-methylpyrrolidone.
In some embodiments, the method of concentrating the composite slurry includes one of heat evaporation, centrifugation, suction filtration, or precipitation.
In some embodiments, the rolling speed of the rolling treatment is 10-15 mm/s, the gap between the two rollers is 0.3-0.8 mm, the rolling time is 1-5 min, and the temperature is 20-40 ℃.
The application also provides a compound doped with the two-dimensional material, which is prepared by the preparation method of the compound doped with the two-dimensional material.
According to the preparation method of the compound doped with the two-dimensional material, the two-dimensional material dispersion liquid and the fiber polymer dispersion liquid are compounded in a liquid phase blending mode, and the two-dimensional material is mechanically locked on the three-dimensional network structure by the fiber polymer, so that aggregation and re-accumulation of the two-dimensional material can be prevented. The compound doped with the two-dimensional material can be obtained through more than 10 times of folding rolling, and the horizontal orientation degree of the two-dimensional material in the compound doped with the two-dimensional material can be adjusted through multiple times of folding rolling. In the rolling process, under the action of traction and stretching of the fiberized polymer and a roll shaft, the two-dimensional materials gradually tend to be arranged in parallel and in a high-level orientation in the horizontal direction, so that a compound with high mechanical property and high-level heat conductivity, which is doped with the two-dimensional materials, is obtained, and the compound can be used as an excellent material for heat dissipation by combining the high mechanical property and the high-level heat conductivity, such as a soaking plate or a soaking film. Meanwhile, the compound doped with the two-dimensional material prepared by the method has the advantages of good ductility, easiness in shaping and recycling and reprocessing.
Drawings
Fig. 1 is a scanning electron microscope image of a composite doped with a two-dimensional material prepared in example 1 in the present application.
In fig. 2, a is a cross-sectional scanning electron microscope image of a composite obtained by directly cutting and thinning a solid flexible product in comparative example 3, b is a cross-sectional scanning electron microscope image of a composite doped with a two-dimensional material in comparative example 2, c is a cross-sectional scanning electron microscope image of a composite doped with a two-dimensional material in comparative example 1, and d is a cross-sectional scanning electron microscope image of a composite doped with a two-dimensional material in example 1.
FIG. 3 is an X-ray diffraction pattern of the composites prepared in example 1, examples 5-7 and comparative example 4 of the present application.
FIG. 4 is a graph of the half-width values versus the composites prepared in example 1, examples 5-7, and comparative example 4 of the present application.
FIG. 5 is an X-ray diffraction pattern of the composites prepared in example 1 and comparative examples 1-3 of the present application.
FIG. 6 is a graph of the full width at half maximum (FWHM) and peak intensity ratio of the compounds prepared in example 1 and comparative examples 1-3 of the present application.
Fig. 7 is a vertical/horizontal thermal conductivity bar graph of the composites prepared in example 1 and comparative examples 1-3 of the present application.
FIG. 8 is a schematic representation of the two-dimensional material being composited with a fibrillated polymer in this application.
Detailed Description
Embodiments of the present invention are described in detail below. The embodiments described below by referring to the drawings are illustrative only and are not to be construed as limiting the invention.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
The application provides a preparation method of a compound doped with a two-dimensional material, which comprises the following steps:
s1, providing a two-dimensional material dispersion liquid.
In some embodiments, the two-dimensional material dispersion includes a two-dimensional material and a dispersant, the two-dimensional material graphene, boron nitride, mica, or MoS 2 One or more of the nanoplatelets. The two-dimensional material is dispersed in a dispersing agent to improve the dispersibility of the two-dimensional material.
In some embodiments, the dispersant comprises one of isopropanol, N-butanol, acetone, dimethyl sulfoxide, dimethylformamide, dimethylacetamide, or N-methylpyrrolidone.
In some embodiments, the two-dimensional material is prepared from a commercially available feedstock by one of ball milling, sanding, grinding, mechanical agitation, high-speed shearing, sonication, high-pressure homogenization, chemical stripping, or microfluidization.
S2, mixing the two-dimensional material dispersion liquid with the fiberized polymer dispersion liquid to obtain composite slurry.
The fibrillated polymer comprises one or more of dispersed polytetrafluoroethylene, aramid nanofibers, polyester fibers, polyamide fibers, polyvinyl alcohol fibers, polyacrylonitrile fibers, polypropylene fibers, or polyvinyl chloride fibers. The fibrillated polymer dispersion includes a fibrillated polymer and the dispersant, which may be the same as the dispersant in the two-dimensional material dispersion. The fiberized polymer dispersion liquid can be obtained by directly mixing the fiberized polymer and the dispersing agent, and has stronger universality.
Wherein the polytetrafluoroethylene is fibrillated under mechanical agitation and forms a wire mesh structure of considerable strength. In addition, the fibrous polymer can be prepared by adding aramid nanofiber, polyester fiber, polyamide fiber, polyvinyl alcohol fiber, polyacrylonitrile fiber, polypropylene fiber or polyvinyl chloride fiber substances into a dispersing agent. The fibrillated polymer may form a network backbone structure.
For many two-dimensional materials, such as boron nitride, mica, moS 2 Nanoplates and the like are difficult to highly functionalize the surfaces of the nanoplates and the like, which means that strong valence bond connection is difficult to realize between the two-dimensional filler and the polymer matrix, so that effective load transfer cannot be carried out on the composite doped with the two-dimensional material in the mechanical deformation process, and the thermal, mechanical, electrical and other performances of the composite doped with the two-dimensional material are seriously affected.
The two-dimensional material is compounded with the fiberized polymer, the fiberized polymer provides a network skeleton and mechanically locks the two-dimensional material on the network skeleton, so that the two-dimensional material is connected with the fiberized polymer in a bonding way, the aggregation and the re-accumulation of the two-dimensional material are prevented, and the two-dimensional material still maintains high dispersibility under high filling quantity (the ratio of the two-dimensional material in the composite slurry is more than 10 percent) (see figure 8).
In some embodiments, the two-dimensional material dispersion has a concentration of 5 to 100mg/mL, which may be 5mg/mL, 15mg/mL, 25mg/mL, 35mg/mL, 60mg/mL, 70mg/mL, or 80mg/mL. The mass ratio of the two-dimensional material to the composite slurry is 10-40 wt%. May be 10wt%, 25wt%, 30wt%, 35wt% or 40wt%.
S3, concentrating the composite slurry to ensure that the solvent content in the composite slurry is 31-34 wt% so as to obtain a solid flexible product.
By concentrating the composite slurry to reduce the solvent, a solid flexible product with good flexibility and easy processing can be prepared. The solid flexible product can be shaped like a dough, has strong flexibility, can be shaped at will by kneading, mould pressing, rolling and the like, is very easy and suitable for being processed into a compound with a three-dimensional structure and doped with a two-dimensional material, and can also meet the processing of some complex surfaces. In addition, the solid flexible product can be recycled. This recyclability feature may reduce raw material costs and make it more functional.
In some embodiments, the method of concentrating the composite slurry includes one of heat evaporation, centrifugation, suction filtration, or precipitation. The application preferably employs heating evaporation to facilitate handling.
S4, rolling the solid flexible product to obtain a pre-rolled product, folding the pre-rolled product, rolling again, and obtaining the composite doped with the two-dimensional material after more than 10 times of folding and rolling, wherein the two-dimensional material is distributed in the composite in parallel in the horizontal direction.
By the roll-pressing method, the two-dimensional material in the solid flexible product tends to be aligned in the horizontal direction by the axial extrusion of the roll shaft and the fiber traction of the fibrillated polymer. The horizontal orientation degree of the boron nitride nano-sheet can be regulated and controlled by repeatedly folding, repeatedly rolling and repeatedly stretching the compound doped with the two-dimensional material. After more than 10 folds and rolls of the pre-roll product, it is ensured that the two-dimensional material tends to be parallel and aligned in the horizontal direction, thereby improving the horizontal thermal conductivity. In the present application, folding and rolling means that each pair of pre-rolled products is folded once and rolled once.
In some embodiments, the rolling speed of the rolling treatment is 10-15 mm/s, the gap between the two rollers is 0.3-0.8 mm, the rolling time is 1-5 min, and the temperature is 20-40 ℃. Under the rolling condition, the acting force applied to the solid flexible product in the rolling treatment process can be ensured, so that the orientation of the two-dimensional material in the solid flexible product can be regulated and controlled.
The application also provides a compound doped with the two-dimensional material, which is prepared by the preparation method of the compound doped with the two-dimensional material.
According to the preparation method of the compound doped with the two-dimensional material, the two-dimensional material dispersion liquid and the fiber polymer dispersion liquid are compounded in a liquid phase blending mode, and the two-dimensional material is mechanically locked on the three-dimensional network structure by the fiber polymer, so that aggregation and re-accumulation of the two-dimensional material can be prevented. The compound doped with the two-dimensional material can be obtained through more than 10 times of folding rolling, and the horizontal orientation degree of the two-dimensional material in the compound doped with the two-dimensional material can be adjusted through multiple times of folding rolling. In the rolling process, under the action of traction and stretching of the fiberized polymer and a roll shaft, the two-dimensional materials gradually tend to be arranged in parallel and in a high-level orientation in the horizontal direction, so that a compound with high mechanical property and high-level heat conductivity, which is doped with the two-dimensional materials, is obtained, and the compound can be used as an excellent material for heat dissipation by combining the high mechanical property and the high-level heat conductivity, such as a soaking plate or a soaking film. Meanwhile, the compound doped with the two-dimensional material prepared by the method has the advantages of good ductility, easiness in shaping and recycling and reprocessing.
The scheme of the present invention will be explained below with reference to examples. It will be appreciated by those skilled in the art that the following examples are for illustrative purposes only and are not to be construed as limiting the invention. Unless otherwise indicated, the reagents, software and instrumentation involved in the examples below are all conventional commercial products or open source.
Example 1
Providing ball-milled and stripped boron nitride nano-sheets and preparing the boron nitride nano-sheet dispersion liquid with the concentration of 80mg/mL in an isopropanol system, wherein the boron nitride nano-sheet dispersion liquid contains isopropanol and boron nitride nano-sheets with the sheet diameter of 0.2-1.5 mu m.
8.0g of polytetrafluoroethylene nanoparticles (FC-2121, da Jin Fuhua (China)) were provided and fully fibrillated by magnetic stirring in 100mL of isopropanol solvent for 24 h.
And measuring 25mL of boron nitride nano-sheet dispersion liquid, and slowly adding the boron nitride nano-sheet dispersion liquid into the 100mL of polytetrafluoroethylene dispersion liquid under continuous stirring to obtain composite slurry, wherein the mass ratio of the boron nitride nano-sheets is 20wt%. Concentrating the composite slurry, heating and evaporating the solvent on a hot table at 80 ℃ and continuously stirring to obtain a solid flexible product with the solvent content of 32wt%, rolling the solid flexible product, and repeatedly folding and rolling for ten times to obtain the composite doped with the boron nitride nano-sheets.
Example 2
Providing ball-milled and exfoliated graphene, and preparing graphene dispersion liquid with the concentration of 20mg/mL in an isopropanol system, wherein the graphene dispersion liquid contains isopropanol and graphene nano sheets with the sheet diameter of 0.8 mu m.
1.5g of polytetrafluoroethylene nanoparticles (Jin Fuhua (China) Inc., FC-2121) was provided and added to 20mL of isopropanol solvent and magnetically stirred for 24h to allow sufficient fibrillation.
50mL of graphene dispersion is measured and slowly added into 20mL of polytetrafluoroethylene dispersion under continuous stirring, so as to obtain composite slurry. The polytetrafluoroethylene is subjected to fibrosis under the mechanical action, a silk screen structure with considerable strength is formed, graphene sheets are dispersed in the silk screen structure, and the mass ratio of the graphene is 40wt%.
Concentrating the composite slurry, heating and evaporating on a hot table at 80 ℃, continuously stirring to obtain a solid flexible product with the solvent content of 32wt%, and repeatedly folding and rolling for ten times to obtain the graphene-doped composite.
Example 3
Providing ball-milled and peeled mica nano-sheets and preparing the mica nano-sheet dispersion liquid with the concentration of 5.0mg/mL in an isopropanol system, wherein the mica nano-sheet dispersion liquid contains isopropanol and mica nano-sheets with the average sheet diameter of 0.82 mu m.
1.5g of polytetrafluoroethylene nanoparticles (Jin Fuhua (China) Inc., FC-2121) was provided and fully fibrillated by magnetic stirring in 75mL of isopropanol solvent for 24 h.
100mL of mica nano-plate dispersion is measured and slowly added into 75mL of polytetrafluoroethylene dispersion under continuous stirring, so as to obtain composite slurry. Wherein, the polytetrafluoroethylene is fibrillated under the mechanical action and forms a silk screen structure with considerable strength, and the mica nano-sheet layer is dispersed in the silk screen structure formed by the polytetrafluoroethylene, and the mass ratio of the mica nano-sheet is 25wt%.
Concentrating the composite slurry, heating on a hot stage at 80 ℃, evaporating the solvent and continuously stirring to obtain a solid flexible product with the solvent content of 32wt%, and repeatedly folding and rolling the solid flexible product for ten times to obtain the composite doped with the mica nano-plate.
Example 4
Providing ball-milled and stripped boron nitride nano-sheets and preparing the boron nitride nano-sheet dispersion liquid with the concentration of 20mg/mL in an isopropanol system, wherein the boron nitride nano-sheet dispersion liquid contains isopropanol and boron nitride nano-sheets with the sheet diameter of 0.2-1.5 mu m.
Providing 10mg/mL of aramid nanofiber dispersion, wherein the aramid nanofiber dispersion comprises aramid fibers (1414) and dimethyl sulfoxide, and continuously stirring for 2 hours to uniformly disperse the aramid fibers.
10mL of boron nitride nanosheet dispersion is measured and slowly added into 60mL of aramid nanofiber dispersion under continuous stirring, so as to obtain composite slurry. Wherein, the aramid nanofiber can form a network skeleton to wind two-dimensional boron nitride nano sheets, and the mass ratio of the boron nitride nano sheets is 25wt%.
And placing the composite slurry in deionized water for protonation treatment, wrapping the obtained slurry with dust-free paper to further concentrate the solvent, and kneading to obtain a solid flexible product with the solvent content of 33 wt%. The boron nitride nano-sheets in the solid flexible product are wrapped by aramid nano-fibers layer by layer to form an assembly with certain processability, and the composite doped with the boron nitride nano-sheets is obtained through twelve repeated folding and rolling.
Example 5
Example 5 is different from example 1 in that 11mL of boron nitride nanosheet dispersion was measured and slowly added to 8g of polytetrafluoroethylene dispersion with continuous stirring to obtain a composite slurry, wherein the mass ratio of the boron nitride nanosheets was 10wt%, and the rest steps were the same as in example 1.
Example 6
Example 6 is different from example 1 in that 43mL of the boron nitride nanosheet dispersion was measured and slowly added to 8g of the polytetrafluoroethylene dispersion with continuous stirring to obtain a composite slurry, wherein the mass ratio of the boron nitride nanosheets was 30wt%, and the rest steps were the same as in example 1.
Example 7
Example 7 is different from example 1 in that 67mL of boron nitride nanosheet dispersion was measured and slowly added to the 8g of polytetrafluoroethylene dispersion with continuous stirring to obtain a composite slurry, wherein the mass ratio of the boron nitride nanosheets was 40wt%, and the rest steps were the same as in example 1.
Comparative example 1
Comparative example 1 differs from example 1 in that the solid flexible product was rolled and rolled repeatedly five times to obtain a composite doped with a two-dimensional material.
Comparative example 2
Comparative example 2 differs from example 1 in that the solid flexible product is rolled, and the rolling is repeated once to obtain a composite doped with a two-dimensional material.
Comparative example 3
Comparative example 3 differs from example 1 in that the solid flexible product was not rolled, cut directly to thin to give a composite doped with two-dimensional material.
Comparative example 4
Comparative example 4 is different from example 1 in that 2.5mL of the boron nitride nanosheet dispersion was measured and diluted to 100mL, 3.8g of polytetrafluoroethylene nanoparticles were slowly added and stirred uniformly to obtain a composite slurry of unfibrated polytetrafluoroethylene and boron nitride nanosheets, wherein the mass ratio of the boron nitride nanosheets was 5wt%.
The present application also conducted scanning electron microscope testing of the two-dimensional material doped composites prepared in example 1 and comparative examples 1-3. Referring to fig. 1, it can be seen from fig. 1 that the boron nitride nano-sheets in the composite are bound together by the polytetrafluoroethylene fiber chains, and the mechanical chain locking effect provided by the polytetrafluoroethylene fibers can prevent the agglomeration and re-accumulation of the boron nitride nano-sheets.
Referring to fig. 2, a of fig. 2 is a scanning electron microscope image of a cross section obtained by directly cutting a solid flexible product, and b, c, and d of fig. 2 are cross section scanning electron microscope images of a composite in which the solid flexible product is repeatedly rolled 1 time, 5 times, and 10 times, respectively (dotted line parts in the figures represent oblique directions of boron nitride nanoplatelets on the cross section). As can be seen from fig. 2 a, the boron nitride nanoplatelets exhibit a randomly oriented distributed state in the fibrous network of polytetrafluoroethylene. Compared to fig. 2 a, the boron nitride nanoplatelets in the composite doped with a two-dimensional material prepared after one rolling tend to be horizontally aligned (e.g., fig. 2 b), and more boron nitride nanoplatelets exhibit horizontal orientation as the number of rolling increases (e.g., fig. 2 c, d). This means that the boron nitride nano-sheets gradually tend to be aligned in a high level orientation by repeated axial extrusion of the roll shaft and traction and stretching of the polytetrafluoroethylene fiber through multiple rolling.
Referring to fig. 3 and 4, the present application also performed an X-ray diffraction test on the two-dimensional material doped composites prepared in example 1, examples 5 to 7, and comparative example 4, and the diffraction peak occurring around 26.7 ° in the X-ray diffraction spectrum in fig. 3 corresponds to the (002) crystal plane of the boron nitride nanosheets. The application uses the full width at half maximum (FWHM) of the (002) peak in X-ray diffraction spectrum (XRD) to evaluate the degree of agglomeration of two-dimensional boron nitride nanoplatelets in polytetrafluoroethylene matrices. (002) The intensity of the peaks increases with increasing loading of the two-dimensional boron nitride nanoplatelets from 10wt% to 40wt% (see fig. 3). The calculated half-width of (002) peak is as high as 0.334 at 20wt% loading, and as the loading of the boron nitride nano-sheet increases, the half-width thereof decreases, but still maintains high dispersibility (see fig. 4).
Referring to fig. 5 and 6, the present application also performed X-ray diffraction tests on the composites prepared in example 1 and comparative examples 1-3. In fig. 5, diffraction peaks occurring in the vicinity of 26.7 ° and 41.6 ° correspond to (002) and (100) crystal planes of the boron nitride nanoplatelets, respectively, and represent the horizontal and vertical alignment orientations of the boron nitride nanoplatelets, respectively, and the corresponding peak intensity ratios may illustrate the degree of horizontal or vertical alignment. By calculating (I 002 /I 100 ) The peak intensity ratio of (I) can be found if (I 002 /I 100 ) The greater the peak intensity ratio of (c), the more parallel the horizontal orientation of the two-dimensional material will be. With continued reference to FIG. 5, comparative example 3 shows a composite (I) obtained by direct cutting of a thinned solid flexible product 002 /I 100 ) The peak intensity ratio of (2) is only 4.89. With increasing number of rolls, the corresponding compound (I 002 /I 100 ) This may indicate that as the number of rolls increases, the fibrillated polymer gradually pulls the two dimensional material toward parallelism in the horizontal direction, such that the horizontal orientation of the two dimensional material in the composite gradually increases.
Referring to fig. 6, the dispersion state of the two-dimensional boron nitride nanosheets in the polytetrafluoroethylene matrix through different rolling times was evaluated using the full width at half maximum (FWHM) of the (002) peak in the X-ray diffraction spectrum (XRD). The (002) peak width at half height of the composite obtained by directly cutting and thinning the solid flexible product in comparative example 3 is 0.335, which shows that the two-dimensional boron nitride nano-sheet in the solid flexible product still maintains high dispersibility. As the number of rolling times increases, the half-width of the composite decreases from 0.335 to 0.222, which indicates that the uniformly dispersed two-dimensional boron nitride nano-sheets are gradually arranged in a horizontal orientation, so that the two-dimensional boron nitride nano-sheets are stacked and overlapped with each other, and a continuous conductive/thermal path is formed.
Meanwhile, referring to fig. 7, the vertical and horizontal thermal conductivity test was also performed on the composites doped with two-dimensional materials prepared in example 1 and comparative examples 1 to 3. From the data in fig. 7, the solid flexible product has similar vertical thermal conductivity and horizontal thermal conductivity, further illustrating that the boron nitride nanoplatelets exhibit a random oriented arrangement in polytetrafluoroethylene, and that the composite of the near-isotropic boron nitride nanoplatelets and polytetrafluoroethylene doped with a two-dimensional material is expected to be a material for preparing a heat sink (soaking plate or film). As the number of rolls increases, the horizontal thermal conductivity of the composite increases significantly, while the corresponding vertical thermal conductivity decreases gradually. After 10 times of rolling, the horizontal thermal conductivity of the compound is 2.5 to 2.5W m -1 K -1 Lifting to 11Wm -1 K -1 . The composite with high-level heat conductivity can be used as an excellent material for preparing a soaking plate or a soaking film.
The above embodiments are only for illustrating the technical solution of the present invention and not for limiting the same, and it should be understood by those skilled in the art that modifications and equivalents may be made thereto without departing from the spirit and scope of the technical solution of the present invention.

Claims (4)

1. A method of preparing a composite doped with a two-dimensional material, the method comprising:
providing ball-milled and stripped boron nitride nano-sheets and preparing a boron nitride nano-sheet dispersion liquid with the concentration of 80mg/mL in an isopropanol system, wherein the boron nitride nano-sheet dispersion liquid contains isopropanol and boron nitride nano-sheets with the sheet diameter of 0.2-1.5 mu m;
providing 8.0g of polytetrafluoroethylene nano particles, adding the nano particles into 100mL of isopropanol solvent, and magnetically stirring for 24 hours to obtain fully fibrillated polytetrafluoroethylene dispersion;
measuring 25mL of the boron nitride nanosheet dispersion liquid, and slowly adding the boron nitride nanosheet dispersion liquid into 100mL of the polytetrafluoroethylene dispersion liquid under continuous stirring to obtain composite slurry;
concentrating the composite slurry to ensure that the solvent content in the composite slurry is 32 weight percent, thereby obtaining a solid flexible product;
rolling the solid flexible product to obtain a pre-rolled product;
folding the pre-roll product and rolling again to obtain a compound doped with the two-dimensional material after 10 times of folding and rolling, wherein the two-dimensional material is distributed in the compound in parallel in the horizontal direction.
2. The method of preparing a composite doped with a two-dimensional material according to claim 1, wherein the method of concentrating the composite slurry comprises one of thermal evaporation, centrifugation, suction filtration, or precipitation.
3. The method of preparing a composite doped with a two-dimensional material according to claim 1, wherein the rolling speed of the rolling treatment is 10 to 15mm/s, the gap between the two rolls is 0.3 to 0.8mm, the rolling time is 1 to 5min, and the temperature is 20 to 40 ℃.
4. A composite doped with a two-dimensional material, characterized in that it is produced by a method for producing a composite doped with a two-dimensional material according to any one of claims 1 to 3.
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