Method for preparing carbon-nanotube-modified natural graphite

Abstract

Disclosed in the present invention is a method for preparing a carbon-nanotube-modified natural graphite film. The method comprises the following steps: modifying carbon nanotubes; adding the modified carbon nanotubes to an ethanol / water mixed solution, so as to obtain a modified carbon nanotube dispersion; adding expanded graphite and a surfactant to an ethanol / water mixed solution, so as to obtain a graphite dispersion; adding the modified carbon nanotube dispersion to the graphite dispersion, so as to obtain a mixed slurry; ultrasonically dispersing and mixing same, and evaporating part of the solution while stirring, so as to obtain a concentrated slurry; sending the concentrated slurry to a forming fabric, and removing the solution under vacuum, so as to obtain a carbon-nanotube-modified natural graphite preform; and drying and compacting the preform, so as to obtain a carbon-nanotube-modified natural graphite film. In the present invention, by optimizing the modification process of carbon nanotubes and a preparation process for a composite material, the problems of poor dispersion, low interfacial bonding strength, etc., of carbon nanotubes are solved, thereby achieving the technical effect of the addition of a low proportion of carbon nanotubes to the natural graphite film significantly improving the thermal conductivity thereof.

Description

A method for preparing carbon nanotube-modified natural graphite Technical Field

[0001] This invention relates to the field of graphite film material technology, specifically to a method for preparing carbon nanotube-modified natural graphite. Background Technology

[0002] As electronic devices evolve towards miniaturization, integration, and high performance, the heat generated by chips and other electronic components continues to increase, making thermal management a growing concern. The development of efficient heat dissipation materials is crucial for ensuring the stable operation and lifespan of electronic devices.

[0003] Natural graphite possesses excellent thermal conductivity; its two-dimensional sheet structure gives it an in-plane thermal conductivity of approximately 700 W / m·K, making it widely used for heat dissipation in electronic products. However, with the increasing integration and power density of electronic devices, the thermal conductivity of natural graphite alone is no longer sufficient to meet the increasingly stringent heat dissipation requirements.

[0004] Carbon nanotubes have attracted much attention due to their unique one-dimensional structure and excellent thermal conductivity. At room temperature, the thermal conductivity of single-walled carbon nanotubes can reach 3980 W / m·K, while that of multi-walled carbon nanotubes is approximately 2860 W / m·K, significantly higher than that of traditional thermally conductive materials. This superior thermal conductivity makes carbon nanotubes an ideal additive for improving the performance of thermally conductive materials. Currently, scholars both domestically and internationally have conducted extensive research on carbon nanotube-modified thermally conductive materials. However, in existing technologies, the dispersion of carbon nanotubes in the matrix material is poor, and the interfacial bonding is not tight enough, resulting in the actual thermal conductivity of composite materials often falling short of theoretical expectations. To address these issues, many researchers have proposed different surface modification methods, including chemical modification and physical modification, aiming to enhance the compatibility and interfacial bonding between carbon nanotubes and the matrix material, thereby improving the dispersion and thermal conductivity of composite materials. Summary of the Invention

[0005] Based on the problems existing in the background technology, the present invention provides a method for preparing carbon nanotube-modified natural graphite. By optimizing the carbon nanotube modification process and the preparation process of the composite material, the problems of poor dispersion of carbon nanotubes and weak interfacial bonding are solved, thereby achieving the technical effect of significantly improving the thermal conductivity when a low proportion of carbon nanotubes is added to the natural graphite film.

[0006] This invention is implemented through the following technical solutions:

[0007] A method for preparing a carbon nanotube-modified natural graphite film includes the following steps:

[0008] S1. To modify carbon nanotubes, carbon nanotubes are ultrasonically dispersed in dimethyl sulfoxide, melamine is added, and ultrasonic dispersion is continued until the melamine dissolves. The temperature is raised to 60-65℃, and a dimethyl sulfoxide solution of o-phthalaldehyde is added dropwise. The reaction continues. After the reaction is completed, the mixture is filtered, washed, and dried to obtain modified carbon nanotubes.

[0009] S2. Add the modified carbon nanotubes to the ethanol / water mixed solution to obtain a modified carbon nanotube dispersion;

[0010] S3. Add expanded graphite and surfactant to an ethanol / water mixed solution to obtain a graphite dispersion;

[0011] S4. Add the modified carbon nanotube dispersion to the graphite dispersion to obtain a mixed slurry. Mix the slurry using an ultrasonic disperser, heat the mixed slurry, and stir to evaporate part of the solution to obtain a concentrated slurry.

[0012] S5. The concentrated slurry is fed to the forming screen, and the solution is removed by vacuum to obtain carbon nanotube modified natural graphite preform. The carbon nanotube modified natural graphite preform is dried and compacted to obtain carbon nanotube modified natural graphite film.

[0013] Furthermore, in step S1, the mass ratio of carbon nanotubes to melamine is 1:(0.4-0.65).

[0014] Further, in step S1, the mass ratio of phthalaldehyde to melamine is 1:(1.4-1.7); the concentration of phthalaldehyde is 2-3 wt%.

[0015] Furthermore, in step S1, the dropping rate of the dimethyl sulfoxide solution of o-phthalaldehyde is 2-3 mL / min.

[0016] Furthermore, in step S2, the solid content of the modified carbon nanotube dispersion is 5-10%.

[0017] Furthermore, in step S3, the solid content of the expanded graphite is 8-12%.

[0018] Furthermore, in step S3, the surfactant is sodium dodecylbenzenesulfonate, and the amount of surfactant used is 2-5% of the amount of expanded graphite.

[0019] Further, in step S4, the mass ratio of modified carbon nanotubes to graphite in the mixed slurry is (3-6):(94-97).

[0020] Furthermore, in step S4, the heating temperature of the mixed slurry is 60°C, the stirring rate is 300-400 rpm, and the solid content of the concentrated slurry is 20-40%.

[0021] Furthermore, in step S5, the drying adopts a step-by-step drying method. First, it is pre-dried at 40°C for 40-60 minutes, then the temperature is raised to 60°C and dried for 30-40 minutes, and finally dried at 80°C for 20-30 minutes. The entire drying process is carried out in a vacuum environment.

[0022] Furthermore, in step S5, the compaction process uses a bidirectional press platen. At room temperature, a pressure of 5 MPa is applied for pre-compaction for 2-3 minutes, then the temperature is raised to 60°C, the pressure is increased to 15 MPa, and maintained for 8-12 minutes.

[0023] The beneficial effects of this invention are:

[0024] 1. This invention introduces modified carbon nanotubes into natural graphite. Carbon nanotubes themselves have extremely high thermal conductivity; adding them to a natural graphite film improves the thermal conductivity of the composite material at a macroscopic level. This invention enhances the dispersibility and interfacial bonding of carbon nanotubes through modification, achieving a more uniform heat conduction path and improving the overall thermal conductivity of the composite material.

[0025] 2. In this invention, carbon nanotubes are modified using melamine and phthalaldehyde. These two substances form a network structure with triazine rings as the core on the surface of the carbon nanotubes through a Schiff base reaction. The triazine ring network structure can not only form multiple interactions with carbon nanotubes and graphite through π-π interactions and hydrogen bonds, but also provide additional heat conduction channels as a rigid framework. The coating of the network structure can effectively prevent the aggregation of carbon nanotubes and improve their dispersibility in the graphite matrix. The planar structure of the triazine ring is conducive to the directional arrangement of carbon nanotubes between graphite layers, and this directional arrangement helps to form efficient heat conduction channels.

[0026] 3. In the composite membrane forming process, the present invention adopts a stepped drying process, which effectively prevents the membrane material from cracking and improves the product qualification rate; it adopts a bidirectional pressure compaction process to ensure the product density and mechanical strength; the overall process route is simple and controllable, and easy to realize industrial production. Attached Figure Description

[0027] The accompanying drawings are provided to further explain the invention and form part of the specification. They are used together with the embodiments of the invention to explain the invention and do not constitute a limitation thereof. In the drawings:

[0028] Figure 1 is a flowchart of the preparation process of the present invention;

[0029] Figure 2 is a schematic diagram of the first direction of the flat plate press used in step S5 of the present invention;

[0030] Figure 3 is a schematic diagram of the second direction of the flat plate press used in step S5 of the present invention;

[0031] Figure 4 is a schematic diagram of the hot pressing device used in the flat plate press in the first direction;

[0032] Figure 5 is a schematic diagram of the hot pressing device used in the flat plate press from the second direction.

[0033] Figure 6 is a third-direction schematic diagram of the hot pressing components used in the flat plate press;

[0034] Figure 7 is a schematic diagram of the transmission slide used in the flat plate press;

[0035] Figure 8 is a schematic diagram of the stripping auxiliary device used in the flat plate press. Detailed Implementation

[0036] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0037] Example 1

[0038] A method for preparing a carbon nanotube-modified natural graphite film includes the following steps:

[0039] S1. To modify carbon nanotubes, 5g of carbon nanotubes were ultrasonically dispersed in 500mL of dimethyl sulfoxide, 2.5g of melamine was added, and ultrasonic dispersion was continued until the melamine dissolved. The temperature was raised to 60℃, and a dimethyl sulfoxide solution of phthalaldehyde (phthalaldehyde concentration of 2wt% and phthalaldehyde amount of 4g) was added dropwise. The reaction was continued. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified carbon nanotubes.

[0040] S2. Add the modified carbon nanotubes obtained in S1 to an ethanol / water (volume ratio 4:1) mixed solution to obtain a modified carbon nanotube dispersion with a solid content of 10%.

[0041] S3. Add 95g of expanded graphite and 3.8g of surfactant to an ethanol / water (volume ratio 4:1) mixed solution to obtain a graphite dispersion with a solid content of 10% for the expanded graphite.

[0042] S4. Add the modified carbon nanotube dispersion to the graphite dispersion to obtain a mixed slurry. Mix the slurry using an ultrasonic disperser, heat the mixed slurry to 60°C, set the stirring speed to 300 rpm, and stir to evaporate part of the solution to obtain a concentrated slurry with a solid content of 30%.

[0043] S5. The concentrated slurry is fed to a forming screen, and the solution is removed under vacuum to obtain a carbon nanotube-modified natural graphite preform. The carbon nanotube-modified natural graphite preform is then dried and compacted.

[0044] The drying process employs a stepped drying method: first, pre-drying at 40℃ for 40 minutes; then, heating to 60℃ and drying for 40 minutes; finally, drying at 80℃ for 20 minutes. The entire drying process is carried out under vacuum.

[0045] The compaction process employed a bidirectional pressure platen press. Pre-compaction was initiated at room temperature with a pressure of 5 MPa for 2 minutes, followed by heating to 60°C, increasing the pressure to 15 MPa, and maintaining this pressure for 10 minutes.

[0046] A carbon nanotube-modified natural graphite film with a thickness of 0.25 mm was obtained.

[0047] Example 2

[0048] The difference between this comparative example and Example 1 is that the amounts of melamine and phthalaldehyde were adjusted in the carbon nanotube modification step. The specific steps are as follows:

[0049] S1. To modify carbon nanotubes, 5g of carbon nanotubes were ultrasonically dispersed in 500mL of dimethyl sulfoxide, 3g of melamine was added, and ultrasonic dispersion was continued until the melamine dissolved. The temperature was raised to 60℃, and a dimethyl sulfoxide solution of phthalaldehyde (phthalaldehyde concentration of 2wt% and phthalaldehyde amount of 4.8g) was added dropwise. The reaction was continued. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified carbon nanotubes.

[0050] The remaining steps are the same as in Example 1.

[0051] Comparative Example 1

[0052] The difference between this comparative example and Example 1 is that the carbon nanotubes were not modified. The specific steps are as follows:

[0053] S1. Add 5g of carbon nanotubes to a mixed solution of ethanol / water (volume ratio 4:1) to obtain a carbon nanotube dispersion with a solid content of 10%.

[0054] S2. Add 95g of expanded graphite and 3.8g of surfactant to an ethanol / water (volume ratio 4:1) mixed solution to obtain a graphite dispersion with a solid content of 10% for the expanded graphite.

[0055] S3. Add the carbon nanotube dispersion to the graphite dispersion to obtain a mixed slurry. Mix the slurry using an ultrasonic disperser, heat the mixed slurry to 60°C, set the stirring speed to 300 rpm, and stir to evaporate part of the solution to obtain a concentrated slurry with a solid content of 30%.

[0056] S4. The concentrated slurry is fed to a forming screen, and the solution is removed under vacuum to obtain a carbon nanotube-modified natural graphite preform. The carbon nanotube-modified natural graphite preform is then dried and compacted.

[0057] The drying process employs a stepped drying method: first, pre-drying at 40℃ for 40 minutes; then, heating to 60℃ and drying for 40 minutes; finally, drying at 80℃ for 20 minutes. The entire drying process is carried out under vacuum.

[0058] The compaction process employed a bidirectional pressure platen press. Pre-compaction was initiated at room temperature with a pressure of 5 MPa for 2 minutes, followed by heating to 60°C, increasing the pressure to 15 MPa, and maintaining this pressure for 10 minutes.

[0059] A carbon nanotube-modified natural graphite film with a thickness of 0.25 mm was obtained.

[0060] Comparative Example 2

[0061] The difference between this comparative example and Example 1 is that the amount of melamine and phthalaldehyde used in the carbon nanotube modification step was increased. The specific steps are as follows:

[0062] S1. To modify carbon nanotubes, 5g of carbon nanotubes were ultrasonically dispersed in 500mL of dimethyl sulfoxide, 5g of melamine was added, and ultrasonic dispersion was continued until the melamine dissolved. The temperature was raised to 60℃, and a dimethyl sulfoxide solution of phthalaldehyde (phthalaldehyde concentration of 2wt% and phthalaldehyde amount of 8g) was added dropwise. The reaction was continued. After the reaction was completed, the mixture was filtered, washed, and dried to obtain modified carbon nanotubes.

[0063] The remaining steps are the same as in Example 1.

[0064] Comparative Example 3

[0065] The difference between this comparative example and Example 1 is that in step S5, direct drying was used instead of step drying. That is, the carbon nanotube modified natural graphite preform was dried and compacted. The drying temperature was 80°C and the drying time was 60 min.

[0066] Comparative Example 4

[0067] This comparative example is a natural graphite film.

[0068] Test case

[0069] The performance of the natural graphite composite films prepared in Examples 1-2 and Comparative Examples 1-2, and the natural graphite film in Comparative Example 3 were tested.

[0070] Thermal diffusivity test: The thermal diffusivity of the natural graphite composite film was tested using Netzsch LFA467. The test temperature was set at room temperature (25℃), the voltage was 260V, the sampling time was 30ms, the detection area was 14mm, and the test sample size was a circular piece with a diameter of 2.54cm.

[0071] Density test: calculated using the weight and size method;

[0072] Thermal conductivity: calculated based on thermal diffusivity, density, and specific heat capacity (0.85 J / g*K);

[0073] The test results are shown in Table 1.

[0074] Table 1

[0075] As shown in Table 1, the thermal conductivity of the composite film material is significantly improved in Examples 1 and 2 of this invention by modifying carbon nanotubes before adding them to the natural graphite film, compared to the direct addition in Comparative Example 1. In this invention, nitrogen-containing functional groups are introduced onto the surface of carbon nanotubes through the Schiff base reaction of melamine and phthalaldehyde, forming a network structure with triazine rings as the core, which significantly improves the surface activity and dispersibility of the carbon nanotubes. The modified carbon nanotubes have better interfacial compatibility with the graphite matrix, and the enhanced surface activity of the modified carbon nanotubes facilitates uniform dispersion, achieving a more uniform heat conduction path and improving the overall thermal conductivity of the composite film material. In Comparative Example 2, the amount of melamine and phthalaldehyde was increased. Excessive melamine and phthalaldehyde tend to coat the carbon nanotube surface too thickly, increasing thermal resistance. Excess melamine may also self-aggregate to form agglomerates, which is detrimental to the overall improvement of the thermal conductivity of the composite film. In Comparative Example 3, the composite film was dried directly during the molding stage without a stepped drying process, which easily led to cracking of the composite film and a reduction in its thermal conductivity.

[0076] Example 3

[0077] In the preparation method of carbon nanotube modified natural graphite film of the present invention, the compaction process of S5 adopts a bidirectional pressure plate press. In order to further improve the quality of the processed carbon nanotube modified natural graphite film and reduce the damage to the carbon nanotube modified natural graphite film during demolding after compaction, the plate press adopts a plate press structure specially made for the present invention.

[0078] Please refer to Figures 2-8. The flatbed press includes: an operating platform 1, on which a vertical guide rail 2 is mounted. The vertical guide rail 2 is slidably connected to two opposing hot pressing devices 3. The two hot pressing devices 3 are connected to two drive components 4 installed on the side of the vertical guide rail 2, so that the two drive components 4 can control the two hot pressing devices 3 to perform bidirectional pressure compaction on the carbon nanotube modified natural graphite preform placed between the two hot pressing devices 3.

[0079] The working principle and technical effects of the above technical solution are as follows:

[0080] The flat platen press used in this invention, during the compaction process, places the carbon nanotube-modified natural graphite preform on the lower hot pressing device 3, and simultaneously activates two driving components 4. The two driving components 4 control the two hot pressing devices 3 to slide towards each other on the vertical guide rail 2, bringing the two hot pressing devices 3 closer to each other, thereby performing bidirectional pressure compaction on the carbon nanotube-modified natural graphite preform placed between the two hot pressing devices 3. The hot pressing plate 307 is provided with a medium flow channel, so that the temperature of the hot pressing plate 307 can be changed by injecting hot or cold fluid into the medium flow channel, so as to reach the preset hot pressing temperature and ensure the compaction effect of the carbon nanotube-modified natural graphite film. The driving component 4 includes: two driving cylinders fixed on the side of the vertical guide rail 2, the output ends of the two driving cylinders are connected to the driving slides slidable on the vertical guide rail 2, and the driving slides are connected to the hot pressing devices slidable on the vertical guide rail 2. After the drive cylinder is started, it can drive the drive slide to slide on the vertical guide rail 2, thereby driving the hot pressing device 3 to move through the drive slide, and the movement stability is good.

[0081] In this invention, the use of a specially designed flatbed press for bidirectional compaction of carbon nanotube-modified natural graphite preforms has the following advantages: The opposing movement of two hot-pressing devices 3 applies uniform bidirectional pressure to the carbon nanotube-modified natural graphite preforms, helping to eliminate internal pores and resulting in a denser graphite film, significantly improving its density. Bidirectional compaction also contributes to the homogenization of the internal structure of the graphite film; by applying uniform pressure, the distribution of carbon nanotubes and natural graphite within the graphite film is ensured to be more uniform, thereby improving its overall performance.

[0082] The hot pressing device 3 includes: a conductive slide 301, which is connected to a drive slide. The rear side of the conductive slide 301 is slidably mounted in the T-shaped slide of the vertical guide rail 2 via two or more T-shaped sliders 302. A transverse support plate 303 is fixedly connected to the front side of the conductive slide 301. A longitudinal slide shaft 304 is slidably connected in the longitudinal slide hole in the middle of the transverse support plate 303. An axial groove on the side of the longitudinal slide shaft 304 is in sliding contact with an axial protrusion in the longitudinal slide hole. A transverse hanger 305 with a transverse slide is fixedly connected to the bottom of the longitudinal slide shaft 304. A transverse shaft 304 is slidably connected in the transverse slide of the transverse hanger 305. 06, the horizontal shaft 306 is fixedly connected to the hot press plate 307 via the base; the horizontal frame plate 303 has two side sliding holes 308 at both ends, which are sleeved on the outside of the two side sliding shafts 309, and the bottoms of the two longitudinal sliding shafts 304 are fixedly connected to the two ends of the hot press plate 307; the diameter of the side sliding shaft 309 is smaller than the diameter of the side sliding hole 308, and there is a gap between the side sliding shaft 309 and the side sliding hole 308 for the side sliding shaft 309 to tilt; the two ends of the tension spring 310 sleeved on the side sliding shaft 309 are fixedly connected to the horizontal frame plate 303 and the hot press plate 307 respectively; the hot press device 3 also includes: slidingly mounted on The two transverse guide holes of the transverse support plate 303 contain correction rods 311. The outer ends of the two correction rods 311 can be inserted into the axial grooves 312 of the two side sliding shafts 309, and the correction rods 311 and the axial grooves 312 are in sliding fit. The two inner ends are fixedly connected to two correction slides 313 that slide in the sliding grooves on the transverse support plate 303. The two correction slides 313 are rotatably connected to one end of the two correction connecting rods 314. The other ends of the two correction connecting rods 314 are rotatably connected to the two ends of the front and rear slides 315. The lower surface of the front and rear slides 315 slides on the transverse support plate 303. On the upper surface, the front and rear slides 315 are slidably mounted on the transverse guide shaft 316 on the front side of the transmission slide 301 through the central transverse hole; two horizontal racks 317 are fixedly connected to the front side of the front and rear slides 315, and two force transmission gears 318 are meshed above the two horizontal racks 317. The two force transmission gears 318 are fixedly connected to the two ends of the force transmission shaft 319, and the force transmission shaft 319 is rotatably connected to the bracket above the transverse frame plate 303. The force transmission worm gear 320 is fixedly connected to the middle of the force transmission shaft 319; the longitudinal slide shaft 304 is a worm structure, and the worm structure of the longitudinal slide shaft 304 meshes with the force transmission worm gear 320.

[0083] The working principle and technical effects of the above technical solution are as follows:

[0084] In the flatbed press used in this invention, the structural design of the hot pressing device 3 allows it to better contact carbon nanotube-modified natural graphite preforms of different shapes, ensuring contact area and improving compaction uniformity. During use, the conductive slide 301 moves vertically under the drive of the driving slide. The rear side of the conductive slide 301 is slidably mounted in the T-shaped slide of the vertical guide rail 2 via two or more T-shaped sliders 302, ensuring the vertical stability of the conductive slide 301. During compaction, when the two hot pressing devices 3 approach each other, the conductive slide 301 drives the transverse support plate 303 to move. The transverse support plate 303, through the tension spring 310, drives the hot pressing plate 307 to move. The hot pressing plates 307 of the two hot pressing devices 3 are respectively pressed onto the carbon nanotube-modified natural graphite preforms. On both sides of the nanotube-modified natural graphite preform, after the hot press plate 307 contacts the carbon nanotube-modified natural graphite preform, as the pressure gradually increases, the transverse support plate 303 and the hot press plate 307 move closer to each other. The transverse support plate 303 slides on the longitudinal sliding shaft 304. The axial groove on the side of the longitudinal sliding shaft 304 slides in contact with the axial protrusion in the longitudinal sliding hole to prevent the longitudinal sliding shaft 304 from rotating. The two side sliding shafts 309 move within the two side sliding holes 308, changing their relative positions. Since the diameter of the side sliding shaft 309 is smaller than the diameter of the side sliding hole 308, a gap is provided between the side sliding shaft 309 and the side sliding hole 308 to allow the side sliding shaft 309 to tilt, so that the hot press plate 307 can tilt within a certain range according to the shape of the carbon nanotube-modified natural graphite preform. This improves the contact effect with the carbon nanotube-modified natural graphite preform. As the pressure continues to increase, the length of the longitudinal sliding shaft 304 extending above the transverse support plate 303 gradually increases. At this time, the longitudinal sliding shaft 304 meshes with the force transmission worm gear 320 and rotates. When the force transmission worm gear 320 rotates, it drives the two force transmission gears 318 to rotate through the force transmission shaft 319. When the two force transmission gears 318 rotate, they mesh and drive the two horizontal racks 317 to move forward. The horizontal racks 317 slide in the rectangular sleeve on the upper surface of the transverse support plate 303, improving their stability during movement. When the horizontal racks 317 move forward, they can drive the front and rear slides 315 to move forward on the transverse guide shaft 316. The front and rear slides 315 drive the rear ends of the two straightening connecting rods 314 to move forward. The front end of rod 314 drives two straightening slide blocks 313 to move away from each other in the grooves on the transverse frame plate 303, thereby pushing two straightening rods 311 away from each other. This controls the two straightening rods 311 to gradually insert into the axial grooves 312 of the two side sliding shafts 309. At this time, the two side sliding shafts 309 can be pressed and fixed, and gradually made to be perpendicular to the transverse frame plate 303, and to be collinear with the axis of the side sliding hole 308. The bottom of the two side sliding shafts 309 gradually straightens the hot press plate 307, making the hot press plate 307 parallel to the transverse frame plate 303. With continuous pressure, the hot press plate 307 first applies lateral or oblique pressure to the carbon nanotube modified natural graphite preform in contact with it.To improve the uniformity of initial pressure applied to the carbon nanotube-modified natural graphite preform, when the preset pressure is reached, the hot press plate 307 is controlled to apply pressure vertically, effectively compacting the carbon nanotube-modified natural graphite preform and ensuring uniformity and thickness of compaction at each location, thus improving the film-forming effect. After compaction, the two conductive slides 301 move away from each other under the action of the two drive slides. At this time, the transverse support plate 303 first moves away from the hot press plate 307, releasing the elastic force of the tension spring 310, and causing the straightening connecting rod 314 to disengage from the axial groove 312 of the side slide shaft 309, gradually reducing the pressure on the processed carbon nanotube-modified natural graphite film, rather than directly detaching from the carbon nanotube-modified natural graphite film. This prevents sudden pressure release from potentially deforming or cracking the graphite film. After pressure release, it is necessary to wait for the temperature of the hot press plate 307 to drop to room temperature or near room temperature, as the graphite film may be more flexible at high temperatures and easier to handle after cooling.

[0085] A peeling auxiliary device is installed on the hot press plate 307. The peeling auxiliary device includes a peeling cylinder 321 fixed to the upper surface of the hot press plate 307. The cylinder shaft of the peeling cylinder 321 is connected to one end of a transverse force transmission frame 322 that slides in a guide sleeve on the upper surface of the hot press plate 307. The other end of the transverse force transmission frame 322 is slidably mounted on the middle of two columns 323. The two columns 323 are located on the side of the hot press plate 307. The bottom of the two columns 323 is fixed to the peeling top plate 324. The peeling top plate 324 and the transverse force transmission frame 322 are connected by multiple tension springs 325. One end of the peeling top plate 324 near the side of the hot press plate 307 is provided with an inclined surface, which slides in cooperation with an inclined surface two below the side of the hot press plate 307.

[0086] After the temperature of the hot press plate 307 drops to or near room temperature, the peeling auxiliary device on the hot press plate 307 can be activated, controlling the peeling cylinder 321 to start. After the peeling cylinder 321 starts, it drives the horizontal transmission frame 322 to move towards the longitudinal sliding shaft 304. The horizontal transmission frame 322 slides in the guide sleeve on the upper surface of the hot press plate 307, and drives the two columns 323 to approach the hot press plate 307. The two columns 323 drive the peeling top plate 324 to move towards the hot press plate 307. At this time, the inclined surface one of the peeling top plate 324 slides relative to the inclined surface two on the lower side of the hot press plate 307. When it slides to the lower side of the inclined surface two of the hot press plate 307, one end of the two hot press plates 307 separates from each other. As one end of the two hot press plates 307 slowly separates, the other ends of the two hot press plates 307 remain in contact under the elastic force of the tension spring 310. At this time, the two side sliding shafts 309 produce a certain degree of tilting offset within the two side sliding holes 308, and the horizontal shaft 306 slides within the transverse slide of the horizontal hanger 305, without hindering the separation. During the initial separation, first observe whether the edge of the graphite film has separated from the plate. If it has not completely separated, you can gently pry the edge with a thin and sharp tool (such as a plastic sheet or a thin metal sheet). If it has separated, gradually control the separation of the two hot press plates 307, and then gently peel the graphite film off the plate with your fingers or a tool starting from the edge. Note that the force should be even to avoid excessive force in some areas causing the film to tear, and ensure the compaction processing effect.

[0087] Finally, it should be noted that the above embodiments are merely illustrative of several implementations of the present invention and are not intended to limit the scope of the invention. For those skilled in the art, any modifications, equivalent substitutions, or improvements made without departing from the concept of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for preparing a carbon nanotube-modified natural graphite film, characterized in that, Includes the following steps: S1. To modify carbon nanotubes, carbon nanotubes are ultrasonically dispersed in dimethyl sulfoxide, melamine is added, and ultrasonic dispersion is continued until the melamine dissolves. The temperature is raised to 60-65℃, and a dimethyl sulfoxide solution of o-phthalaldehyde is added dropwise. The reaction continues. After the reaction is completed, the mixture is filtered, washed, and dried to obtain modified carbon nanotubes. S2. Add the modified carbon nanotubes to the ethanol / water mixed solution to obtain a modified carbon nanotube dispersion; S3. Add expanded graphite and surfactant to an ethanol / water mixed solution to obtain a graphite dispersion; S4. Add the modified carbon nanotube dispersion to the graphite dispersion to obtain a mixed slurry. Mix the slurry using an ultrasonic disperser, heat the mixed slurry, and stir to evaporate part of the solution to obtain a concentrated slurry. S5. The concentrated slurry is fed to the forming screen, and the solution is removed by vacuum to obtain carbon nanotube modified natural graphite preform. The carbon nanotube modified natural graphite preform is dried and compacted to obtain carbon nanotube modified natural graphite film.

2. The method for preparing carbon nanotube-modified natural graphite film according to claim 1, characterized in that, In step S1, the mass ratio of carbon nanotubes to melamine is 1:(0.4-0.65).

3. The method for preparing carbon nanotube-modified natural graphite film according to claim 1, characterized in that, In step S1, the mass ratio of phthalaldehyde to melamine is 1:(1.4-1.7); the concentration of phthalaldehyde is 2-3 wt%.

4. The method for preparing carbon nanotube-modified natural graphite film according to claim 1, characterized in that, In step S2, the solid content of the modified carbon nanotube dispersion is 5-10%.

5. The method for preparing carbon nanotube-modified natural graphite film according to claim 1, characterized in that, In step S3, the solid content of expanded graphite is 8-12%.

6. The method for preparing carbon nanotube-modified natural graphite film according to claim 1, characterized in that, In step S3, the surfactant is sodium dodecylbenzenesulfonate, and the amount of surfactant used is 2-5% of the amount of expanded graphite.

7. The method for preparing carbon nanotube-modified natural graphite film according to claim 1, characterized in that, In step S4, the mass ratio of modified carbon nanotubes to graphite in the mixed slurry is (3-6):(94-97).

8. The method for preparing carbon nanotube-modified natural graphite film according to claim 1, characterized in that, In step S4, the heating temperature of the mixed slurry is 60℃, the stirring rate is 300-400rpm, and the solid content of the concentrated slurry is 20-40%.

9. The method for preparing carbon nanotube-modified natural graphite film according to claim 1, characterized in that, In step S5, the drying adopts a step-by-step drying method. First, it is pre-dried at 40℃ for 40-60 minutes, then the temperature is raised to 60℃ and dried for 30-40 minutes, and finally dried at 80℃ for 20-30 minutes. The entire drying process is carried out in a vacuum environment.

10. The method for preparing carbon nanotube-modified natural graphite film according to claim 1, characterized in that, In step S5, the compaction process uses a flat platen press with bidirectional pressure. At room temperature, a pressure of 5 MPa is applied for pre-compaction for 2-3 minutes, then the temperature is raised to 60°C, the pressure is increased to 15 MPa, and maintained for 8-12 minutes.

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