A method for preparing carbon nanotube-modified natural graphite

Abstract

The present invention discloses a method for preparing a carbon nanotube-modified natural graphite film, comprising the following steps: modifying carbon nanotubes; adding the modified carbon nanotubes to an ethanol / water mixed solution to obtain a modified carbon nanotube dispersion; adding expanded graphite and a surfactant to the ethanol / water mixed solution to obtain a graphite dispersion; adding the modified carbon nanotube dispersion to the graphite dispersion to obtain a mixed slurry, ultrasonically dispersing and mixing, stirring and evaporating part of the solution to obtain a concentrated slurry; delivering the concentrated slurry to a forming net, vacuum-removing the solution to obtain a carbon nanotube-modified natural graphite preform, drying and compacting the preform to obtain a carbon nanotube-modified natural graphite film. The present invention solves the problems of poor carbon nanotube dispersibility and weak interfacial bonding force by optimizing the carbon nanotube modification process and the preparation process of the composite material, thereby achieving the technical effect of significantly improving thermal conductivity when a low proportion of carbon nanotubes is added to the natural graphite film.

Description

Technical Field

[0001] The present invention relates to the technical field of graphite film materials, and in particular to a method for preparing carbon nanotube-modified natural graphite. Background Art

[0002] As electronic devices move toward miniaturization, integration, and higher performance, the heat generated by chips and other electronic components continues to increase, making thermal management an increasingly prominent issue. The development of efficient heat dissipation materials is crucial for ensuring the stable operation and longevity of electronic devices.

[0003] Natural graphite has excellent thermal conductivity. Its two-dimensional lamellar 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. The thermal conductivity of single-walled carbon nanotubes can reach 3980W / m·K at room temperature, and the thermal conductivity of multi-walled carbon nanotubes is about 2860W / m·K, which is much higher than that of traditional thermal conductive materials. This excellent thermal conductivity makes carbon nanotubes an ideal additive to improve the performance of thermal conductive materials. At present, scholars at home and abroad have conducted extensive research on carbon nanotube-modified thermal conductive materials. However, in the existing technology, the dispersion of carbon nanotubes in the matrix material is poor, and the interface bonding is not tight enough, resulting in the actual thermal conductivity of the composite material often being lower than the theoretical expected value. In order to solve these problems, many researchers have proposed different surface modification methods, including chemical modification, physical modification, etc., aiming to enhance the compatibility and interface bonding between carbon nanotubes and the matrix material, thereby improving the dispersion and thermal conductivity of the composite material. Summary of the Invention

[0005] Based on the problems existing in the background technology, the present invention provides a preparation method of 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 interface bonding force are solved, thereby achieving the technical effect of significantly improving the thermal conductivity coefficient when a low proportion of carbon nanotubes is added to the natural graphite film.

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

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

[0008] S1. Modifying carbon nanotubes by ultrasonically dispersing carbon nanotubes in dimethyl sulfoxide, adding melamine, and continuing ultrasonic dispersion to dissolve the melamine. The temperature is raised to 60-65°C, and a dimethyl sulfoxide solution of o-phthalaldehyde is added dropwise. The reaction is continued. After the reaction is completed, the modified carbon nanotubes are filtered, washed, and dried.

[0009] S2. The modified carbon nanotubes are added to an ethanol / water mixed solution to obtain a modified carbon nanotube dispersion;

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

[0011] S4. The modified carbon nanotube dispersion was added to the graphite dispersion to obtain a mixed slurry, which was mixed using an ultrasonic disperser, and the mixed slurry was heated and stirred to evaporate part of the solution to obtain a concentrated slurry;

[0012] S5. The concentrated slurry is sent to a forming net, and the solution is removed under vacuum to obtain a carbon nanotube-modified natural graphite preform. The carbon nanotube-modified natural graphite preform is dried and compacted to obtain a 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] Furthermore, in step S1, the mass ratio of o-phthalaldehyde to melamine is 1:(1.4-1.7); and the concentration of o-phthalaldehyde is 2-3 wt%.

[0015] Furthermore, in step S1, the dropping speed 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 dodecylbenzene sulfonate, and the amount of the surfactant used is 2-5% of the amount of expanded graphite used.

[0019] Furthermore, 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, drying is performed by step drying, first pre-drying at 40°C for 40-60 minutes, then heating to 60°C and drying for 30-40 minutes, and finally drying 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 treatment uses a bidirectional press to apply a pressure of 5 MPa at room temperature 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] Beneficial effects of the present invention:

[0024] 1. This invention introduces modified carbon nanotubes (CNTs) into natural graphite. CNTs inherently possess extremely high thermal conductivity. Adding these to a natural graphite film improves the thermal conductivity of the composite material at a macroscopic level. This modification enhances the dispersion and interfacial bonding of the CNTs, creating a more uniform heat conduction path and improving the overall thermal conductivity of the composite material.

[0025] 2. The present invention modifies carbon nanotubes using melamine and o-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 not only forms multiple interactions with the carbon nanotubes and graphite through π-π interactions and hydrogen bonds, but also serves as a rigid skeleton to provide additional heat conduction channels. The coating of the network structure can effectively prevent the agglomeration of carbon nanotubes and improve their dispersibility in the graphite matrix. The planar structure of the triazine rings facilitates the directional arrangement of carbon nanotubes between graphite layers, which helps 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; 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to further explain the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0028] Figure 1 This is a flow chart of the preparation process of the present invention;

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

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

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

[0032] Figure 5 A schematic diagram of the second direction of the hot pressing device used in the flat plate press;

[0033] Figure 6 A schematic diagram of the third direction of the hot pressing device used in the flat plate press;

[0034] Figure 7 A schematic diagram of a conduction slide used in a flatbed press;

[0035] Figure 8 Schematic diagram of the peeling assist device used in the flatbed press. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described in detail below with reference to specific embodiments, but the protection scope 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 comprises the following steps:

[0039] S1. To modify carbon nanotubes, 5 g of carbon nanotubes were ultrasonically dispersed in 500 mL of dimethyl sulfoxide, 2.5 g of melamine was added, and ultrasonic dispersion was continued to dissolve the melamine. The temperature was raised to 60°C, and a dimethyl sulfoxide solution of o-phthalaldehyde (o-phthalaldehyde concentration was 2 wt %, o-phthalaldehyde amount was 4 g) 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. The modified carbon nanotubes prepared in S1 were added to a mixed solution of ethanol / water (volume ratio 4:1) to obtain a modified carbon nanotube dispersion having a solid content of 10%;

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

[0042] S4. The modified carbon nanotube dispersion was added to the graphite dispersion to obtain a mixed slurry, which was mixed using an ultrasonic disperser. The mixed slurry was heated to 60 ° C, the stirring rate was set to 300 rpm, and the solution was evaporated with stirring to obtain a concentrated slurry having a solid content of 30%;

[0043] S5. The concentrated slurry is sent to a forming net, the solution is removed by vacuum, and a carbon nanotube-modified natural graphite preform is obtained. The carbon nanotube-modified natural graphite preform is dried and compacted.

[0044] The drying process was carried out in a step-by-step manner, first pre-drying at 40°C for 40 minutes, then heating to 60°C for 40 minutes, and finally drying at 80°C for 20 minutes. The entire drying process was carried out in a vacuum environment.

[0045] The compaction process uses a two-way press to apply a 5MPa pressure for pre-compaction at room temperature for 2 minutes, then heat up to 60℃ and increase the pressure to 15MPa 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 o-phthalaldehyde were adjusted in the step of modifying the carbon nanotubes. The specific steps are as follows:

[0049] S1. Modifying carbon nanotubes: 5 g of carbon nanotubes were ultrasonically dispersed in 500 mL of dimethyl sulfoxide, 3 g of melamine was added, and ultrasonic dispersion was continued to dissolve the melamine. The temperature was raised to 60°C, and a dimethyl sulfoxide solution of o-phthalaldehyde (o-phthalaldehyde concentration was 2 wt %, o-phthalaldehyde amount was 4.8 g) 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 are not modified. The specific steps are as follows:

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

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

[0055] S3. The carbon nanotube dispersion was added to the graphite dispersion to obtain a mixed slurry, which was mixed using an ultrasonic disperser. The mixed slurry was heated to 60 ° C, the stirring rate was set to 300 rpm, and the solution was evaporated with stirring to obtain a concentrated slurry having a solid content of 30%;

[0056] S4. The concentrated slurry is sent to a forming net, the solution is removed by vacuum, and a carbon nanotube-modified natural graphite preform is obtained. The carbon nanotube-modified natural graphite preform is dried and compacted.

[0057] The drying process was carried out in a step-by-step manner, first pre-drying at 40°C for 40 minutes, then heating to 60°C for 40 minutes, and finally drying at 80°C for 20 minutes. The entire drying process was carried out in a vacuum environment.

[0058] The compaction process uses a two-way press to apply a 5MPa pressure for pre-compaction at room temperature for 2 minutes, then heat up to 60℃ and increase the pressure to 15MPa 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 o-phthalaldehyde is increased in the step of modifying the carbon nanotubes. The specific steps are as follows:

[0062] S1. Modifying carbon nanotubes: ultrasonically disperse 5 g of carbon nanotubes in 500 mL of dimethyl sulfoxide, add 5 g of melamine, continue ultrasonic dispersion to dissolve the melamine, raise the temperature to 60°C, dropwise add a dimethyl sulfoxide solution of o-phthalaldehyde (o-phthalaldehyde concentration is 2 wt %, o-phthalaldehyde amount is 8 g), continue the reaction, and after completion of the reaction, filter, wash, and dry 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 is performed without stepwise drying, that is, the carbon nanotube-modified natural graphite preform is dried and compacted, wherein the drying temperature is 80° C. and the drying time is 60 min.

[0066] Comparative Example 4

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

[0068] Test example

[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 was tested.

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

[0071] Density test: calculated by 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]

[0076] As can be seen from the results in Table 1, the thermal conductivity of the composite film material is significantly improved after the carbon nanotubes are modified and added to the natural graphite film in Examples 1 and 2 of the present invention compared to the direct addition in Comparative Example 1. In the present invention, nitrogen-containing functional groups are introduced on the surface of carbon nanotubes by the Schiff base reaction of melamine and o-phthalaldehyde, and a network structure with a triazine ring as the core is formed, which significantly improves the surface activity and dispersibility of the carbon nanotubes; the interface compatibility between the modified carbon nanotubes and the graphite matrix is ​​better, and the surface activity of the modified carbon nanotubes is enhanced, which is conducive to 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 o-phthalaldehyde is increased, and excess melamine and o-phthalaldehyde are easily coated too thickly on the surface of the carbon nanotubes, increasing thermal resistance. Excess melamine may also self-polymerize to form agglomerates, which is not conducive to the improvement of the thermal conductivity of the overall composite film. In Comparative Example 3, direct drying is performed in the forming stage without adopting a step-by-step drying process, which easily leads to cracking of the composite film, thereby reducing the thermal conductivity of the composite film.

[0077] Example 3

[0078] In the method for preparing a carbon nanotube-modified natural graphite film described in the present invention, the compaction treatment in S5 uses a bidirectionally pressurized flat plate press. In order to further improve the quality of the processed carbon nanotube-modified natural graphite film and reduce damage to the carbon nanotube-modified natural graphite film during demolding after compaction, the flat plate press adopts a flat plate press structure specially designed for the present invention.

[0079] See also Figure 2-Figure 8The flatbed press comprises: an operating platform 1, on which a vertical guide rail 2 is mounted, the vertical guide rail 2 being slidably connected to two upper and lower oppositely arranged hot pressing devices 3, the two hot pressing devices 3 being connected to two driving components 4 installed on the sides of the vertical guide rail 2, so that the two hot pressing devices 3 are controlled by the two driving components 4 to perform bidirectional pressure compaction treatment on the carbon nanotube-modified natural graphite preform placed between the two hot pressing devices 3.

[0080] The working principle and technical effects of the above technical solution are as follows:

[0081] The flat plate press used in the present invention places the carbon nanotube-modified natural graphite preform on the hot pressing device 3 below during compaction treatment, and starts two driving components 4 synchronously. The two driving components 4 control the two hot pressing devices 3 to slide toward each other on the vertical guide rail 2, and the two hot pressing devices 3 approach each other, thereby performing bidirectional pressurization and compaction treatment on the carbon nanotube-modified natural graphite preform placed between the two hot pressing devices 3. A medium circulation channel is provided in the hot pressing plate 307 to change the temperature of the hot pressing plate 307 by injecting hot fluid or cold fluid into the medium circulation channel, so as to achieve 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 slide slidably mounted on the vertical guide rail 2, and the driving slide is connected to the hot pressing device 3 slidably mounted on the vertical guide rail 2. After the driving cylinder is started, it can drive the driving slide to slide on the vertical guide rail 2, thereby driving the hot pressing device 3 to move through the driving slide, and the movement stability is good.

[0082] In the present invention, the use of the specially designed flat plate press of the present invention to perform bidirectional compaction treatment on the carbon nanotube-modified natural graphite preform has the following advantages: through the relative movement of the two hot pressing devices 3, the carbon nanotube-modified natural graphite preform is uniformly pressurized in both directions, which helps to eliminate the internal pores of the carbon nanotube-modified natural graphite preform, makes the processed graphite film more dense, and significantly improves the density of the carbon nanotube-modified natural graphite film; bidirectional compaction also helps to homogenize the internal structure of the graphite film. By uniformly applying pressure, it can be ensured that the carbon nanotubes and natural graphite inside the graphite film are more evenly distributed, thereby improving its overall performance.

[0083] The hot pressing device 3 includes: a conducting slide 301, the conducting slide 301 is connected to the driving slide, the rear side of the conducting slide 301 is slidably arranged in the T-shaped slideway of the vertical guide rail 2 through two or more T-shaped sliders 302; the front side of the conducting slide 301 is fixedly connected with a horizontal frame 303, the longitudinal sliding hole in the middle of the horizontal frame 303 is slidably connected to the longitudinal sliding shaft 304, the axial groove on the side of the longitudinal sliding shaft 304 is in sliding contact with the axial protrusion in the longitudinal sliding hole, the bottom of the longitudinal sliding shaft 304 is fixedly connected to a horizontal hanger 305 with a horizontal slideway, and the horizontal hanger 305 is slidably connected to the horizontal shaft 3 in the horizontal slideway 06, the horizontal axis 306 is fixed to the hot pressing plate 307 through the base; two side sliding holes 308 are provided at both ends of the horizontal frame 303 and are sleeved on the outside of the two side sliding shafts 309, and the bottoms of the two longitudinal sliding shafts 304 are relatively fixed to the two ends of the hot pressing plate 307; the diameter of the side sliding shaft 309 is smaller than the diameter of the side sliding hole 308, and a gap is provided 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 tensioning spring 310 sleeved on the side sliding shaft 309 are fixedly connected to the horizontal frame 303 and the hot pressing plate 307 respectively; the hot pressing device 3 also includes: a sliding spring 310 provided on the horizontal frame 303 and the hot pressing plate 307 The correction plug rods 311 in the two horizontal guide holes of the horizontal frame plate 303, the outer ends of the two correction plug rods 311 can be inserted into the axial grooves 312 of the two side sliding shafts 309, and the correction plug rods 311 slide in cooperation with the axial grooves 312; the two inner ends are fixedly connected to the two correction slides 313 slidably arranged in the upper slide grooves of the horizontal frame plate 303, the two correction slides 313 are rotatably connected to one end of the two correction connecting rods 314, and the other ends of the two correction connecting rods 314 are relatively rotatably connected to the two ends of the front and rear slides 315, the lower surfaces of the front and rear slides 315 are slidably arranged on the horizontal frame plate 303 On the upper surface, the front and rear slides 315 are slid onto the horizontal guide shaft 316 on the front side of the conduction slide 301 through the middle horizontal hole; two horizontal racks 317 are fixed on the front side of the front and rear slides 315, and the two horizontal racks 317 are meshed with two power transmission gears 318 above. The two power transmission gears 318 are relatively fixed to the two ends of the power transmission shaft 319, and the power transmission shaft 319 is rotatably connected to the bracket above the horizontal frame plate 303. The middle part of the power transmission shaft 319 is fixed to the power transmission worm gear 320; the longitudinal sliding shaft 304 is a worm structure, and the worm structure of the longitudinal sliding shaft 304 is meshed with the power transmission worm gear 320.

[0084] The working principle and technical effects of the above technical solution are as follows:

[0085] In the flat plate press used in the present invention, the structural design of the hot pressing device 3 enables it to better contact with carbon nanotube-modified natural graphite preforms of different shapes, ensure the contact area, and improve the compaction uniformity. When in use, the conductive slide 301 moves up and down under the drive of the driving slide. The rear side of the conductive slide 301 is slid in the T-shaped slide of the vertical guide rail 2 through more than two T-shaped sliders 302 to ensure the stability of the conductive slide 301 in the up and down directions. When the compaction process is carried out, when the two hot pressing devices 3 approach each other, the conductive slide 301 drives the horizontal frame 303 to move, and the horizontal frame 303 drives the hot pressing plate 307 to move through the tensioning spring 310. The hot pressing plates 307 of the two hot pressing devices 3 are pressed respectively on the carbon nanotube-modified natural graphite preforms. On the upper and lower sides of the carbon nanotube modified natural graphite preform, after the hot pressing plate 307 contacts the carbon nanotube modified natural graphite preform, as the pressure gradually increases, the horizontal frame plate 303 and the hot pressing plate 307 approach each other, and the horizontal frame 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 in the two side sliding holes 308 to change 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 for the side sliding shaft 309 to tilt, so that the hot pressing plate 307 can be tilted within a certain range according to the shape of the carbon nanotube modified natural graphite preform. Thereby improving 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 horizontal frame plate 303 gradually increases, at this time the longitudinal sliding shaft 304 engages the power transmission worm gear 320 to rotate, and when the power transmission worm gear 320 rotates, it drives the two power transmission gears 318 to rotate through the power transmission shaft 319, and when the two power transmission gears 318 rotate, the meshing transmission drives the two horizontal racks 317 to move forward, and the horizontal racks 317 are slidably arranged in the rectangular sliding sleeve on the upper surface of the horizontal frame plate 303 to improve its stability during movement, and when the horizontal racks 317 move forward, they can drive the front and rear slides 315 to move forward on the horizontal guide shaft 316, and the front and rear slides 315 drive the rear ends of the two correction links 314 to move forward, and the two correction links The front end of the rod 314 drives the two correction slides 313 to move away from each other in the sliding groove on the horizontal frame 303, thereby pushing the two correction plug rods 311 away from each other, and controlling the two correction plug rods 311 to gradually insert into the axial groove 2 312 of the two side sliding shafts 309. At this time, the two side sliding shafts 309 can be pressed and fixed, and gradually make the two side sliding shafts 309 perpendicular to the horizontal frame 303, and make the side sliding shafts 309 and the axis of the side sliding hole 308 collinear, and gradually correct the hot pressing plate 307 through the bottom of the two side sliding shafts 309 so that the hot pressing plate 307 is parallel to the horizontal frame 303. As the pressure is continuously applied, in this process, the hot pressing plate 307 first performs side pressure or oblique pressure on the carbon nanotube-modified natural graphite preform in contact with it,Improve the uniformity of the initial pressure applied to the carbon nanotube-modified natural graphite preform. When the preset pressure is reached, control the hot press plate 307 to apply pressure in the vertical direction, so that the carbon nanotube-modified natural graphite preform is effectively compacted, and ensure the uniformity and thickness of the compaction at each position, thereby improving the film-making effect. After the compaction process, the two conductive slides 301 are driven away from each other by the two driving slides. At this time, the transverse frame 303 first moves away from the hot press plate 307, releasing the elastic force of the tensioning spring 310, and allowing the correction link 314 to disengage from the axial groove 312 of the side sliding shaft 309, gradually reducing the pressure on the processed carbon nanotube-modified natural graphite film instead of directly separating from the carbon nanotube-modified natural graphite film, to prevent sudden pressure relief from causing deformation or rupture of the graphite film. After pressure relief, it is necessary to wait for the temperature of the hot press plate 307 to drop to room temperature or near room temperature. The graphite film at high temperature may be relatively soft and easier to handle after cooling.

[0086] The hot press plate 307 is provided with a stripping auxiliary device, which includes a stripping cylinder 321 fixedly connected to the upper surface of the hot press plate 307. The cylinder shaft of the stripping cylinder 321 is connected to one end of a transverse force frame 322 slidingly arranged in a guide sleeve on the upper surface of the hot press plate 307. The other end of the transverse force frame 322 is slidably arranged in the middle of two columns 323. The two columns 323 are located on the side of the hot press plate 307. The bottoms of the two columns 323 are fixedly connected to the stripping top plate 324. The stripping top plate 324 and the transverse force frame 322 are connected by a plurality of tension springs 325. The stripping top plate 324 is provided with an inclined surface 1 at one end close to the side of the hot press plate 307, and the inclined surface 1 slides with the inclined surface 2 at the lower side of the hot press plate 307.

[0087] After the temperature of the hot pressing plate 307 drops to room temperature or close to room temperature, the stripping auxiliary device on the hot pressing plate 307 can be controlled to start, and the stripping cylinder 321 can be controlled to start. After the stripping cylinder 321 is started, it drives the transverse force frame 322 to move in the direction of the longitudinal sliding shaft 304. The transverse force frame 322 slides in the guide sleeve on the upper surface of the hot pressing plate 307 and drives the two columns 323 to approach the hot pressing plate 307. The two columns 323 drive the stripping top plate 324 to move toward the hot pressing plate 307. At this time, the inclined surface 1 of the stripping top plate 324 slides relative to the inclined surface 2 at the lower side of the hot pressing plate 307, and when it slides to the lower side of the inclined surface 2 of the hot pressing plate 307, one end of the two hot pressing plates 307 is separated from each other. When 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 tilt offset in the two side sliding holes 308, and the horizontal shaft 306 slides in the horizontal slide of the horizontal hanger 305, which will not hinder the separation. During the initial separation, first observe whether the edge of the graphite film has separated from the flat plate. If it is not completely separated, you can use a thin and sharp tool (such as a plastic sheet or a thin metal sheet) to gently pry the edge. If it is separated, gradually control the separation of the two hot press plates 307, and then start from the edge with your fingers or a tool to gently peel the graphite film from the flat plate. Pay attention to the uniform force to avoid excessive local force that may cause the film material to tear, and ensure the compaction processing effect.

[0088] Finally, it should be noted that the above-described embodiments merely represent several implementation methods of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made by a person skilled in the art without departing from the spirit of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the patent for this invention should be based on the appended claims.

Claims

1. A method for preparing a carbon nanotube-modified natural graphite film, characterized in that: The following steps are involved: S1. Modifying carbon nanotubes by ultrasonically dispersing carbon nanotubes in dimethyl sulfoxide, adding melamine, and continuing ultrasonic dispersion to dissolve the melamine. The temperature is raised to 60-65°C, and a dimethyl sulfoxide solution of o-phthalaldehyde is added dropwise. The reaction is continued. After the reaction is completed, the modified carbon nanotubes are filtered, washed, and dried. S2. The modified carbon nanotubes are added to an ethanol / water mixed solution to obtain a modified carbon nanotube dispersion; S3. The expanded graphite and a surfactant were added to an ethanol / water mixed solution to obtain a graphite dispersion; S4. The modified carbon nanotube dispersion was added to the graphite dispersion to obtain a mixed slurry, which was mixed using an ultrasonic disperser, and the mixed slurry was heated and stirred to evaporate part of the solution to obtain a concentrated slurry; S5. The concentrated slurry is sent to a forming net, and the solution is removed under vacuum to obtain a carbon nanotube-modified natural graphite preform. The carbon nanotube-modified natural graphite preform is dried and compacted to obtain a carbon nanotube-modified natural graphite film.

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

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

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

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

6. The method for preparing a carbon nanotube-modified natural graphite film according to claim 1, wherein: In step S3, the surfactant is sodium dodecylbenzene sulfonate, and the amount of the surfactant used is 2-5% of the amount of expanded graphite used.

7. The method for preparing a carbon nanotube-modified natural graphite film according to claim 1, wherein: 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 a carbon nanotube-modified natural graphite film according to claim 1, wherein: In step S4, the heating temperature of the mixed slurry is 60° C., the stirring speed is 300-400 rpm, and the solid content of the concentrated slurry is 20-40%.

9. The method for preparing a carbon nanotube-modified natural graphite film according to claim 1, wherein: In step S5, drying is performed in a stepwise manner, first pre-drying at 40°C for 40-60 min, then heating to 60°C and drying for 30-40 min, and finally drying at 80°C for 20-30 min. The entire drying process is performed in a vacuum environment.

10. The method for preparing a carbon nanotube-modified natural graphite film according to claim 1, wherein: In step S5, the compaction treatment uses a bidirectional press to apply a pressure of 5 MPa at room temperature 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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