Preparation method of carbon nanotube modified natural graphite

Abstract

The invention discloses a preparation method of a carbon nanotube modified natural graphite film. The preparation method comprises the following steps: modifying a carbon nanotube; adding the modified carbon nanotubes into an ethanol / water mixed solution to obtain a modified carbon nanotube dispersion liquid; adding expanded graphite and a surfactant into the ethanol / water mixed solution to obtain a graphite dispersion liquid; adding the modified carbon nanotube dispersion liquid into the graphite dispersion liquid to obtain mixed slurry, performing ultrasonic dispersion and mixing, and stirring to evaporate part of the solution to obtain concentrated slurry; and feeding the concentrated slurry to a forming net, removing the solution in vacuum to obtain a carbon nanotube modified natural graphite preform, and drying and compacting the preform to obtain the carbon nanotube modified natural graphite film. By optimizing the modification process of the carbon nanotubes and the preparation process of the composite material, the problems of poor dispersity, weak interface bonding force and the like of the carbon nanotubes are solved, so that the technical effect of remarkably improving the heat conductivity coefficient when the low-proportion carbon nanotubes are added into the natural graphite film is realized.

Description

Technical Field

[0001] The 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 develop towards miniaturization, integration and high performance, the heat generated by chips and other electronic components continues to increase, and thermal management issues are becoming increasingly prominent. The development of efficient heat dissipation materials is of great significance to ensure the stable operation and service life of electronic devices.

[0003] Natural graphite has excellent thermal conductivity. Its two-dimensional layer structure makes it show a thermal conductivity of about 700W / m·K in the in-plane direction. It has been widely used in the heat dissipation of electronic products. However, with the improvement of the integration of electronic devices and the increase of power density, the thermal conductivity of a single natural graphite material can no longer 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 prior art, 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 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 interface bonding force 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] The present invention is implemented by 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, continuing ultrasonic dispersion to dissolve melamine, raising the temperature to 60-65° C., dropping a dimethyl sulfoxide solution of o-phthalaldehyde, and continuing the reaction. After the reaction is completed, filtering, washing, and drying to obtain modified carbon nanotubes;

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

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

[0011] S4. The modified carbon nanotube dispersion is added to the graphite dispersion to obtain a mixed slurry, mixed using an ultrasonic disperser, the mixed slurry is heated, stirred and evaporated to obtain a concentrated slurry;

[0012] S5. Send the concentrated slurry to a forming net, remove the solution in vacuum, obtain a carbon nanotube-modified natural graphite preform, dry and compact the carbon nanotube-modified natural graphite preform, and 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 2-3wt%.

[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] Further, 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, drying for 30-40 minutes, and finally drying at 80°C for 20-30 minutes. The entire drying process is performed in a vacuum environment.

[0022] Furthermore, in step S5, the compaction treatment uses a bidirectional press to apply a 5 MPa pressure 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. In the present invention, modified carbon nanotubes are introduced into natural graphite. The carbon nanotubes themselves have extremely high thermal conductivity. By adding them into the natural graphite film, the thermal conductivity of the composite material is improved at the macro level. The present invention enhances the dispersibility and interface bonding force of the carbon nanotubes by modifying them, realizes a more uniform heat conduction path, and improves the overall thermal conductivity of the composite material.

[0025] 2. In the present invention, carbon nanotubes are modified by melamine and o-phthalaldehyde. These two substances form a network structure with triazine rings as the core on the surface of carbon nanotubes through Schiff base reaction. The triazine ring network structure can not only form multiple interactions with carbon nanotubes and graphite through π-π effects and hydrogen bonds, but also provide additional heat conduction channels as a rigid skeleton; the coating of the network structure can effectively prevent carbon nanotubes from agglomerating 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 an efficient heat conduction channel.

[0026] 3. In the composite film forming process, the present invention adopts a step-by-step drying process, which effectively prevents the film material from cracking and improves the product qualification rate; adopts a two-way pressurization compaction process to ensure the product density and mechanical strength; the overall process route is simple and controllable, and it is easy to realize industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The accompanying drawings are used to provide further explanation of 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 The present invention is a process flow chart for preparing the same;

[0029] Figure 2 A schematic diagram of a first direction of a 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 a hot pressing device used in a flat plate press in a second direction;

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

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

[0035] Figure 8 Schematic diagram of the peeling auxiliary device used in the flat plate press. DETAILED DESCRIPTION

[0036] The technical solution of the present invention is further described in detail below in conjunction with 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. Modify the carbon nanotubes by ultrasonically dispersing 5 g of carbon nanotubes in 500 mL of dimethyl sulfoxide, adding 2.5 g of melamine, continuing ultrasonic dispersion to dissolve the melamine, raising the temperature to 60° C., dropping a dimethyl sulfoxide solution of o-phthalaldehyde (the concentration of o-phthalaldehyde is 2 wt %, and the amount of o-phthalaldehyde is 4 g), and continuing the reaction. After the reaction is completed, filter, wash, and dry to obtain modified carbon nanotubes;

[0040] S2. The modified carbon nanotubes prepared in S1 are added to a mixed solution of ethanol / water (volume ratio 4:1) to obtain a modified carbon nanotube dispersion, wherein the solid content of the modified carbon nanotube dispersion is 10%;

[0041] S3. 95 g of expanded graphite and 3.8 g of a surfactant were added to a mixed solution of ethanol / water (volume ratio 4:1) 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, and the mixed slurry was heated to 60 ° C, the stirring rate was set to 300 rpm, and part of the solution was evaporated by stirring to obtain a concentrated slurry, the solid content of the concentrated slurry was 30%;

[0043] S5. The concentrated slurry is sent to a forming net, and the solution is removed by vacuum to obtain a carbon nanotube-modified natural graphite preform, and 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°C and increase the pressure to 15MPa for 10 minutes.

[0046] The 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 in the step of modifying the carbon nanotubes, the amounts of melamine and o-phthalaldehyde are adjusted. The specific steps are as follows:

[0049] S1. Modify the carbon nanotubes by ultrasonically dispersing 5 g of carbon nanotubes in 500 mL of dimethyl sulfoxide, adding 3 g of melamine, continuing ultrasonic dispersion to dissolve the melamine, heating to 60° C., dropping a dimethyl sulfoxide solution of o-phthalaldehyde (the concentration of o-phthalaldehyde is 2 wt %, and the amount of o-phthalaldehyde is 4.8 g), and continuing the reaction. After the reaction is completed, filter, wash, and dry 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:

[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 a mixed solution of ethanol / water (volume ratio 4:1) 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, and the mixed slurry was heated to 60 ° C, the stirring rate was set to 300 rpm, and part of the solution was evaporated by stirring to obtain a concentrated slurry, the solid content of the concentrated slurry was 30%;

[0056] S4. sending the concentrated slurry to a forming net, removing the solution by vacuum, obtaining a carbon nanotube-modified natural graphite preform, drying and compacting the carbon nanotube-modified natural graphite preform,

[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°C and increase the pressure to 15MPa for 10 minutes.

[0059] The 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 in the step of modifying the carbon nanotubes, the dosage of melamine and o-phthalaldehyde is increased. The specific steps are as follows:

[0062] S1. Modify the carbon nanotubes by ultrasonically dispersing 5 g of carbon nanotubes in 500 mL of dimethyl sulfoxide, adding 5 g of melamine, continuing ultrasonic dispersion to dissolve the melamine, heating to 60° C., dropping a dimethyl sulfoxide solution of o-phthalaldehyde (the concentration of o-phthalaldehyde is 2 wt %, and the amount of o-phthalaldehyde is 8 g), continuing the reaction, and after the reaction is completed, filtering, washing, and drying 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 step-by-step 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 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 disc with a diameter of 2.54cm.

[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] From the results in Table 1, it can be seen that the thermal conductivity of the composite film material is significantly improved by adding the modified carbon nanotubes to the natural graphite film in Examples 1 and 2 of the present invention compared with the direct addition in Comparative Example 1. In the present invention, nitrogen-containing functional groups are introduced on the surface of carbon nanotubes through the Schiff base reaction of melamine and o-phthalaldehyde, and a network structure with triazine ring as the core is formed, which significantly improves the surface activity and dispersibility of 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 the excess melamine and o-phthalaldehyde are easy to coat the surface of the carbon nanotubes too thickly, increasing thermal resistance, and the excess melamine may also self-polymerize to form agglomerates, which is not conducive to the improvement of the overall thermal conductivity of the 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 adopts a bidirectional 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 flat press adopts a flat press structure specially made for the present invention;

[0079] See also Figure 2-Figure 8The flat plate press comprises: an operating platform 1, a vertical guide rail 2 is mounted on the operating platform 1, the vertical guide rail 2 is slidably connected to two upper and lower oppositely arranged hot pressing devices 3, the two hot pressing devices 3 are 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 flow 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 flow channel, so as to achieve a 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 fixedly arranged on the side of the vertical guide rail 2, the output ends of the two driving cylinders are connected to the driving slide seat slidably arranged on the vertical guide rail 2, and the driving slide seat is connected to the hot pressing device 3 slidably arranged 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 made 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 compact, 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 comprises: 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 more than two T-shaped sliding blocks 302; a transverse frame 303 is fixedly connected to the front side of the conducting slide 301, a longitudinal sliding shaft 304 is slidably connected in the longitudinal sliding hole in the middle of the transverse frame 303, an axial groove on the side of the longitudinal sliding shaft 304 is in sliding contact with the axial protrusion in the longitudinal sliding hole, a transverse hanger 305 with a transverse slideway is fixedly connected to the bottom of the longitudinal sliding shaft 304, and the transverse slideway of the transverse hanger 305 is slidably connected to the transverse shaft 304 06, the horizontal axis 306 is fixedly connected to the hot pressing plate 307 through the base; two side sliding holes 308 are provided at both ends of the horizontal frame plate 303 and are sleeved on the outside of the two side sliding axes 309, and the bottoms of the two longitudinal sliding axes 304 are relatively fixedly connected to the two ends of the hot pressing plate 307; the diameter of the side sliding axis 309 is smaller than the diameter of the side sliding hole 308, and a gap is provided between the side sliding axis 309 and the side sliding hole 308 for the side sliding axis 309 to tilt; the two ends of the tensioning spring 310 sleeved on the side sliding axis 309 are fixedly connected to the horizontal frame plate 303 and the hot pressing plate 307 respectively; the hot pressing device 3 also includes: a side sliding hole 308 provided on the side sliding hole 308, and a side sliding hole 308 provided on the side sliding axis 309. The correction plug rods 311 in the two transverse guide holes of the transverse 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 and the axial grooves 312 are slidably matched; the two inner ends are fixedly connected to the two correction slide seats 313 slidably arranged in the slide grooves on the transverse frame plate 303, the two correction slide seats 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 slide tables 315, and the lower surfaces of the front and rear slide tables 315 are slidably arranged on the transverse frame plate 303. On the upper surface, the front and rear slides 315 are slidably mounted on the horizontal guide shaft 316 on the front side of the conduction slide 301 through the middle horizontal hole; two horizontal racks 317 are fixedly connected to 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, and the two power transmission gears 318 are relatively fixedly connected 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, and the middle part of the power transmission shaft 319 is fixedly connected 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 the 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 performed, when the two hot pressing devices 3 are close to 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 on the carbon nanotubes. 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 transverse frame plate 303 and the hot pressing plate 307 approach each other, and the transverse 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, the contact effect with the carbon nanotube-modified natural graphite preform is improved. 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 with the power transmission worm gear 320 to rotate. When the power transmission worm gear 320 rotates, it drives the two power transmission gears 318 to rotate through the power transmission shaft 319. When the two power transmission gears 318 rotate, the meshing transmission drives the two horizontal racks 317 to move forward. 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. 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. The front and rear slides 315 drive the rear ends of the two correction connecting rods 314 to move forward. The two correction connecting rods 314 are connected to the horizontal guide shaft 316. The front end of the rod 314 drives the two correction slides 313 to move away from each other in the slide groove on the horizontal frame plate 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 plate 303, and make the side sliding shafts 309 and the axis of the side sliding hole 308 colinear, 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 plate 303. With continuous pressure, 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 move away from each other under the drive of the two driving slides. At this time, the transverse frame plate 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 separate from the axial groove 312 of the side sliding shaft 309, gradually reducing the pressure on the processed carbon nanotube-modified natural graphite film, rather than 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 the pressure relief, it is necessary to wait for the temperature of the hot press plate 307 to drop to room temperature or close to room temperature. The graphite film at high temperature may be softer and easier to handle after cooling down.

[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 slidably 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 a stripping top plate 324, the stripping top plate 324 and the transverse force frame 322 are connected by a plurality of tension springs 325; an inclined surface 1 is provided at one end of the stripping top plate 324 close to the side of the hot press plate 307, and the inclined surface 1 is slidably matched with the inclined surface 2 at the lower side of the hot press plate 307.

[0087] After the temperature of the hot press plate 307 drops to room temperature or close to room temperature, the stripping auxiliary device on the hot press 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 axis 304. The transverse force 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 stripping top plate 324 to move in the direction of the hot press 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 press plate 307, and when sliding to the lower side of the inclined surface 2 at the side of the hot press plate 307, one end of the two hot press plates 307 is separated from each other. When one end of the two hot pressing plates 307 is slowly separated, the other end of the two hot pressing plates 307 is still 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 deviation in the two side sliding holes 308, and the horizontal axis 306 slides in the horizontal slideway 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 been 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 has been separated, gradually control the separation of the two hot pressing plates 307, and then use your fingers or tools to gently peel the graphite film from the flat plate from the edge. Pay attention to the uniform force to avoid excessive local force causing the film material to tear, and ensure the compaction processing effect.

[0088] Finally, it should be noted that the above-mentioned embodiments only express several implementation methods of the present invention and are not intended to limit the invention. For those skilled in the art, any modification, equivalent replacement, improvement, etc. made without departing from the concept of the present invention should be included in the protection scope of the invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached 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, continuing ultrasonic dispersion to dissolve melamine, raising the temperature to 60-65° C., dropping a dimethyl sulfoxide solution of o-phthalaldehyde, and continuing the reaction. After the reaction is completed, filtering, washing, and drying to obtain modified carbon nanotubes; S2. adding the modified carbon nanotubes to an ethanol / water mixed solution to obtain a modified carbon nanotube dispersion; S3. The expanded graphite and the surfactant are added to an ethanol / water mixed solution to obtain a graphite dispersion; S4. The modified carbon nanotube dispersion is added to the graphite dispersion to obtain a mixed slurry, mixed using an ultrasonic disperser, the mixed slurry is heated, stirred and evaporated to obtain a concentrated slurry; S5. Send the concentrated slurry to a forming net, remove the solution in vacuum, obtain a carbon nanotube-modified natural graphite preform, dry and compact the carbon nanotube-modified natural graphite preform, and obtain a carbon nanotube-modified natural graphite film.

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

4. The method for preparing a 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 a carbon nanotube-modified natural graphite film according to claim 1, characterized in that: 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, characterized in that: 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, 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 a 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° C., the stirring rate 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, characterized in that: In step S5, drying is performed by step drying, first pre-drying at 40°C for 40-60 minutes, then heating to 60°C, drying for 30-40 minutes, and finally drying at 80°C for 20-30 minutes. 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, characterized in that: In step S5, the compaction treatment uses a bidirectional press to apply a 5 MPa pressure 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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