A multifunctional sintering furnace for the production of graphene thermal conductive films

Abstract

The present invention discloses a multifunctional sintering furnace for the production of graphene heat-conducting films, which comprises a vacuum furnace shell provided with a furnace door. The inner cavity of the vacuum furnace shell is communicated with a vacuum generating device. A heating and heat preservation device, a first heating electrode device, a second heating electrode and a pressurizing device are arranged in the vacuum furnace shell. The heating and heat preservation device includes a stainless steel outer cylinder and a graphite inner cylinder arranged inside the stainless steel outer cylinder. A graphite heater is arranged on the outer side of the graphite inner cylinder. A graphite heat preservation layer is arranged between the graphite heating cylinder and the stainless steel outer cylinder. The stainless steel outer cylinder is fixedly connected with the vacuum furnace shell, and a heat insulation space is arranged between the stainless steel outer cylinder and the inner wall of the vacuum furnace shell. The present invention provides an equipment platform for combining the carbonization, graphitization and flat pressing processes to be completed together, that is, while heating at a high temperature, the pressurizing process is completed. In terms of time, the two sequential processes of carbonization and graphitization are combined and completed in one piece of equipment, reducing one cycle of heating-cooling.

Description

Technical Field

[0001] The present invention relates to the technical field of graphene heat conduction film production, and specifically to a multifunctional sintering furnace for graphene heat conduction film production. Background Art

[0002] The preparation process of graphene heat conduction film generally includes four processes: pulping, coating, sintering, and calendering. Among them, the sintering process includes two process steps: carbonization and graphitization. The carbonization process is generally carried out in a temperature range of dozens to 1200 °C, and its main functions are to remove water, oxygen, and inorganic salts and other impurities; the graphitization process is generally carried out in a temperature range of 2600 - 3100 °C, and its main function is to form an ordered structure and improve the heat conduction performance of the graphene film.

[0003] The existing sintering process separates the carbonization process and the graphitization process and carries them out in different sintering furnaces, which has the following several defects:

[0004] 1. Long sintering process time: In the existing sintering process, carbonization and graphitization are realized in different vacuum sintering equipment, and two heating and cooling operations are required, resulting in a very long sintering process time, low equipment utilization rate, and small production capacity.

[0005] 2. High energy consumption of the sintering process: (1) Separating the carbonization process and the graphitization process and realizing them in different vacuum equipment requires two heating and cooling operations, and the cooling process is a process of wasting energy and increasing energy consumption. (2) In order to improve the degree of graphitization and enhance the performance of the graphene heat conduction film, the existing process is achieved by increasing the graphitization temperature. However, the higher the temperature, the greater the energy consumption. Under the same conditions, the energy consumption of the graphitization process at 3000 °C is more than twice that of the graphitization process at 2600 °C.

[0006] 3. Low process yield: The material after the carbonization process is very brittle, and product loss is extremely likely to occur during the transportation process, reducing the yield. Summary of the Invention

[0007] The purpose of the present invention is to provide a multifunctional sintering furnace for graphene heat conduction film production, which combines the carbonization, graphitization, and flat pressing processes in one device, that is, while heating at a high temperature, the pressurization process is completed. In terms of time, the carbonization and graphitization processes, which are two consecutive processes, are combined in one device, reducing one heating-cooling cycle, and can solve the problems of long process time and high energy consumption mentioned in the above background art.

[0008] To achieve the above purpose, the present invention provides the following technical solutions:

[0009] A multifunctional sintering furnace for producing graphene thermal conductive films, comprising a vacuum furnace shell provided with a furnace door, and the inner cavity of the vacuum furnace shell is connected to a vacuum generating device. A heating and heat preservation device, a first heating electrode device, a second heating electrode and a pressurizing device are arranged in the vacuum furnace shell; the heating and heat preservation device includes a stainless steel outer cylinder and a graphite inner cylinder arranged inside the stainless steel outer cylinder. A graphite heater is arranged on the outer side of the graphite inner cylinder, and a graphite heat preservation layer is arranged between the graphite heater and the stainless steel outer cylinder. The stainless steel outer cylinder is fixedly connected to the vacuum furnace shell, and a heat insulation space is arranged between the stainless steel outer cylinder and the inner wall of the vacuum furnace shell; the first heating electrode device is provided with two groups of electrodes, and the graphite heater is provided with graphite electrodes. The electrodes are connected to the graphite electrodes of the graphite heater to form a first heating circuit, and the first heating circuit forms a heating environment not lower than 1500 °C in the graphite inner cylinder; the second heating electrode and the pressurizing device include an upper electrode device and a lifting lower electrode device. The upper electrode device is arranged at the top of the vacuum furnace shell. The upper electrode device is provided with an upper electrode rod that passes through the vacuum furnace shell, the stainless steel outer cylinder, and the graphite heat preservation layer and extends into the graphite inner cylinder. The upper electrode rod includes an upper conductive rod and an upper graphite pressing head connected to the upper conductive rod; the lifting lower electrode device is arranged at the bottom of the vacuum furnace shell. The lifting lower electrode device includes a lifting device and a lower electrode rod connected to the lifting device. The lower electrode rod includes a lower conductive rod and a lower graphite pressing head connected to the lower conductive rod. The lower graphite pressing head can be lifted and lowered through the vacuum furnace shell, the stainless steel outer cylinder, and the graphite heat preservation layer; a material placement area for placing the crude graphene thermal conductive film can be formed between the upper graphite pressing head and the lower graphite pressing head; the upper electrode rod and the lower electrode rod are short-circuited and connected in the graphite inner cylinder to form a second heating circuit, and the second heating circuit forms a heating environment not lower than 2600 °C in the graphite inner cylinder; the upper graphite pressing head of the upper electrode device serves as a fixed end, and the lower graphite pressing head and the lifting device serve as a moving pressurizing end. A pressure not less than 1600 Kg is generated by pressurizing the fixed end and the moving pressurizing end.

[0010] The multifunctional sintering furnace for producing graphene thermal conductive films in this solution can well complete the three processes of carbonization, graphitization, and rolling in the production of graphene thermal conductive films. After obtaining the crude graphene thermal conductive film through the previous pulping and coating production equipment, the lower graphite pressing head of the multifunctional sintering furnace in this solution descends to the outside of the bottom of the vacuum furnace shell through the lifting device, places the crude graphene thermal conductive film on the lower graphite pressing head, and then sends the crude graphene thermal conductive film into the graphite inner cylinder through the lifting device. After the three processes of carbonization, graphitization, and rolling are carried out, the lifting device lowers the lower graphite pressing head to the outside of the furnace shell bottom again, and the staff can take out the finished graphene thermal conductive film;

[0011] During the production process, graphite heating is used for the first stage of heating. The electrodes on both sides of the vacuum furnace shell are in contact with the graphite electrodes of the graphite heater. When the electrodes are energized, the graphite heater generates heat to heat the crude graphene thermal conductive film in the graphite inner tube. Non-contact thermocouples can be used to monitor temperature changes in real time. After carbonization is completed, the electrodes are powered off. The second stage of heating uses large current short-circuit heating, that is, the lower graphite pressure head in the multifunctional sintering furnace moves up, carrying the crude graphene thermal conductive film to press against the upper graphite pressure head. After the short circuit is energized, a large amount of heat is generated to increase the temperature. At the same time, the lifting device continuously increases the pressure upward through the lower electrode, and the pressure is monitored by a pressure sensor to obtain the required pressure. While heating for the second time, the crude graphene thermal conductive film is subjected to a calendering process to obtain a finished graphene thermal conductive film. In the above process, the vacuum generating device evacuates the vacuum furnace shell as required.

[0012] As a preferred solution of the present invention, the left electrode, the right electrode, and the thermocouple are respectively arranged on both sides of the vacuum furnace shell, and one end of the left electrode, the right electrode, and the thermocouple are arranged outside the vacuum furnace shell, and the other end of the left electrode and the right electrode are in contact with the graphite electrode of the graphite heater. In this solution, the two groups of electrodes are divided into the left electrode and the right electrode, and the thermocouple is added to complete the heating and temperature measurement work of the first stage heating process, and there is no direct contact with the heating device during the second stage heating.

[0013] As a preferred solution of the present invention, the left electrode and the right electrode are respectively provided with an electrode tube, an electrode water pipe is provided in the electrode tube, an electrode water cooling joint is provided at the rear end of the electrode tube and is connected to the electrode water pipe and the external circulating cooling water circuit, the electrode tube passes through the vacuum furnace shell and an electrode temperature-resistant insulating sleeve is provided between the electrode tube and the vacuum furnace shell, one end of the graphite electrode passes through the stainless steel outer cylinder and the graphite insulation layer and is connected and fixed to the graphite heater, the other end of the graphite electrode is arranged on the outside of the stainless steel outer cylinder and an insulating sleeve is provided between the stainless steel outer cylinder, and the electrode tube contacts the graphite electrode to form a first heating circuit.

[0014] In this scheme, the left electrode and the right electrode include an electrode tube and a graphite electrode. During the first stage heating process, the electrode tube is connected to the graphite electrode to supply power to the graphite heater for heating. During the heating process, a circulating cooling water circuit is used to inject cooling water into the electrode water tube through the electrode water cooling joint to remove heat and cool the electrode tube. After the heating is completed, the electrode tube does not directly contact the second stage high temperature heating device. The thermocouple does not directly contact the graphite heater when detecting the temperature during the first stage heating process, and stays away from the second stage high temperature heating device during the second stage high temperature heating process.

[0015] As a preferred solution of the present invention, the upper electrode device is insulated and fixed to the vacuum furnace shell through a flange connection, the front end of the upper conductive rod is connected to the upper graphite pressure head, a graphite block is provided at the front end of the upper graphite pressure head, an electrode water pipe is provided in the upper conductive rod, an electrode water cooling joint connected to the electrode water pipe is provided at the rear end of the upper conductive rod, the electrode water cooling joint is connected to an external circulating cooling water circuit, the upper conductive rod is provided with an electrode connecting plate, and the bottom position of the upper graphite pressure head is located in the graphite inner cylinder.

[0016] As a preferred solution of the present invention, one end of the lower conductive rod is connected to the lower graphite pressure head, a plurality of graphite blocks are provided at the front end of the lower graphite pressure head, an electrode water pipe is provided inside the lower conductive rod, an electrode water cooling joint connected to the electrode water pipe is provided at the other end of the lower conductive rod, the electrode water cooling joint is connected to the external circulating cooling water circuit, the electrode water cooling joint is connected to the bakelite board, the bakelite board is connected to the sensor pressure head by bolts, the sensor pressure head is connected to the lifting device, the highest position of the top of the lower graphite pressure head is located inside the graphite inner cylinder, and the lowest position of the top of the lower graphite pressure head is located outside the stainless steel outer cylinder.

[0017] In this scheme, the second stage of heating adopts large current short-circuit heating. The lower graphite pressure head in the multifunctional sintering furnace moves up, carrying the crude graphene thermal conductive film to press against the upper graphite pressure head. After the power is turned on and the short circuit is applied, a large amount of heat is generated to increase the temperature. At this time, the temperature can be monitored in real time by an infrared temperature measuring device. At the same time, the lifting device continuously increases the pressure upward through the lower electrode, and the pressure is monitored by a pressure sensor (sensor pressure head) to obtain the required pressure. While heating for the second time, the crude graphene thermal conductive film is rolled to obtain the finished graphene thermal conductive film. Since the heating temperature in the graphite inner cylinder in the second stage has to reach 2600℃, the conductive rod will be melted. During the heating process, cooling water is injected into the electrode water pipe through the electrode water cooling joint by a circulating cooling water circuit to take away the heat, and the upper and lower conductive poles are cooled.

[0018] As a preferred solution of the present invention, the sensor pressure head is provided with a guide device, and the guide device includes guide plates extending to both sides of the sensor pressure head and vertical guide rods movably connected to the guide plates.

[0019] As a preferred solution of the present invention, the stainless steel outer cylinder includes a cylinder body, an upper cover, and a lower cover, and the bottom of the lower cover is provided with three sets of fixing columns fixedly connected to the vacuum furnace shell. In this solution, the stainless steel outer cylinder and the vacuum furnace shell have no other large contact surfaces except the three sets of fixing columns, and there is mainly an air gap between the two, which can reduce the outflow speed of heat in the stainless steel outer cylinder.

[0020] As a preferred embodiment of the present invention, the graphite insulation layer includes a graphite hard felt inner cylinder and a graphite soft felt outer cylinder. The graphite soft felt outer cylinder wraps the graphite hard felt inner cylinder on the inner side, and the outer side of the graphite soft felt outer cylinder is in close contact with the stainless steel outer cylinder. A graphite inner cylinder and a graphite heater are arranged inside the graphite hard felt inner cylinder. Both ends of the graphite inner cylinder are in close contact with the graphite hard felt inner cylinder respectively. The graphite heater is arranged in the gap between the graphite inner cylinder and the graphite hard felt inner cylinder, and graphite electrodes are arranged on both sides of the graphite heater.

[0021] As a preferred embodiment of the present invention, the graphite inner cylinder, the graphite insulation layer, and the stainless steel outer cylinder are provided with communication vent holes, and the vent holes are communicated with a vacuum generating device.

[0022] As a preferred embodiment of the present invention, it includes a frame. The frame includes an upper accommodation cavity and a lower accommodation cavity. The vacuum furnace shell is arranged in the upper accommodation cavity. The lifting device includes an electric screw jack, a vertical guide rod, and a guide plate. The electric screw jack and the vertical guide rod are arranged in the lower accommodation cavity. The lower electrode rod is connected to the guide plate, and the guide plate is movably connected to the guide rod.

[0023] During the production process of the existing graphene thermal conductive film,

[0024] The carbonization process is as follows: it is heated from room temperature to 80 °C in 10 min and kept warm for 300 min; then it is heated to 90 °C in 10 min and kept warm for 600 min; it is heated to 100 °C in 10 min and kept warm for 600 min; it is heated to 110 °C in 10 min and kept warm for 300 min; it is heated to 120 °C in 20 min and kept warm for 240 min; it is heated to 140 °C in 30 min and kept warm for 90 min; it is heated to 165 °C in 30 min and kept warm for 60 min; it is heated to 200 °C in 30 min and kept warm for 60 min; it is heated to 250 °C in 30 min and kept warm for 60 min; it is heated to 300 °C in 30 min and kept warm for 60 min; it is heated to 400 °C in 60 min and kept warm for 60 min; it is heated to 1000 °C in 120 min and kept warm for 60 min; it is heated to 1600 °C in 120 min and then cooled naturally. The cooling process takes about 12 hours, and the entire process cycle takes about 62 hours, with low efficiency.

[0025] The graphitization process is to raise the temperature from room temperature to 1000 °C in 150 min, hold for 2 hours; then raise the temperature to 1300 °C at a rate of 2 °C / min, hold for 2 hours; then raise the temperature to 2850 °C at a rate of 2 °C / min and then naturally cool to 2700 °C, hold for 2 hours; then raise the temperature to 2800 °C at a rate of 5 °C / min and hold for 4 hours; then raise the temperature to 3000 °C at a rate of 2 °C / min, hold for half an hour, and then naturally cool. The pure heating process takes nearly 32 hours, and the natural cooling process takes about 40 hours. One process cycle takes three days, and the energy consumption is 2500 kWh, with huge energy consumption and time consumption.

[0026] The flat pressing (calendering) process is 50 - 70 MPa, hold the pressure for 10 - 30 min; then increase the pressure to 80 - 100 MPa, hold the pressure for 10 - 30 min; then raise the pressure to 200 - 300 MPa, hold the pressure for 10 - 30 min, and then release the pressure to the normal state.

[0027] After the above three-step process, the thermal diffusion coefficient of the obtained film is about 670 mm² / s. With the process of this solution, the carbonization, graphitization, and flat pressing (calendering) processes are completed in one step. First, a pre-reduction process below 400 °C is carried out using graphite heating, that is, raise the temperature to 80 °C in 10 min and hold for 60 min; then raise the temperature to 400 °C at a rate of 2 °C / min and hold for 60 min. Then, start short-circuit heating and apply pressure simultaneously. The temperature rises from 400 °C to 2600 °C within 2 hours, and the pressure gradually increases from 100 kg to 1400 - 1600 kg (the pressure is about 3 MPa, varying depending on the area). After this process, the thermal diffusion coefficient of the obtained film can reach 900 mm² / s, and the thermal diffusion coefficient is significantly improved. The entire process cycle of this solution is about 20 hours, which is greatly shortened compared to the step-by-step process. The energy consumption for a single experiment is about 1300 kWh, which is significantly reduced compared to the step-by-step method.

[0028] Compared with the prior art, the beneficial effects of the present invention are:

[0029] In the present invention, an equipment platform is provided for combining the carbonization, graphitization, and flat pressing processes to be completed together, that is, while heating at high temperature, the pressurization process is completed. In terms of time, the carbonization and graphitization processes, which are sequential processes, are combined and completed in one device, reducing one heating-cooling cycle. Specifically,

[0030] 1. Shorten the time of the sintering process: Compared with the existing carbonization process and graphitization process, the process time is shortened by 45%.

[0031] 2. Reduce the energy consumption of the sintering process: Compared with the existing carbonization process and graphitization process, the energy consumption is reduced by 55%.

[0032] 3. Improved the yield of graphene thermal conductive film: Compared with the existing carbonization process and graphitization process, the yield has increased by 5%. Description of the Drawings

[0033] Figure 1 It is a structural schematic diagram of the present invention.

[0034] Figure 2 It is a structural schematic diagram of the vacuum furnace shell of the present invention.

[0035] Figure 3 It is an external structural schematic diagram of the heating and heat preservation device of the present invention.

[0036] Figure 4 It is an internal structural schematic diagram of the heating and heat preservation device of the present invention.

[0037] Figure 5 It is a structural schematic diagram of the telescopic electrode of the present invention.

[0038] Figure 6 It is a structural schematic diagram of the upper electrode rod of the present invention.

[0039] Figure 7 It is a structural schematic diagram of the lower electrode rod of the present invention.

[0040] Figure 8 It is a structural schematic diagram of the lifting device of the present invention.

[0041] Figure 9 It is a schematic diagram of the frame structure of the present invention.

[0042] In the figure: 1. Vacuum furnace shell; 2. Furnace door; 3. Stainless steel outer cylinder; 4. Graphite inner cylinder

[0043] 5. Graphite heater; 6. Graphite heat preservation layer; 7. Electrode

[0044] 8. Graphite electrode; 9. Upper electrode device; 10. Lower electrode device

[0045] 11. Upper conductive rod; 12. Upper graphite pressing head; 13. Lifting device

[0046] 14. Lower conductive rod; 15. Lower graphite pressing head; 16. Material placement area

[0047] 17. Thermocouple; 18. Electrode tube; 19. Electrode water cooling joint

[0048] 20. Heat-resistant insulating sleeve; 21. Insulating sleeve; 22. Graphite block

[0049] 23. Electrode connecting plate; 24. Electrical insulating board; 25. Bolt

[0050] 26. Sensor indenter 27. Guide plate 28. Vertical guide rod

[0051] 29. Cylinder body 30. Upper cover 31. Lower cover 32. Fixed column

[0052] 33. Graphite hard felt inner cylinder 34. Graphite soft felt outer cylinder 35. Vent hole

[0053] 36. Frame 37. Upper accommodation cavity 38. Lower accommodation cavity

[0054] 39. Electric screw jack. Detailed implementation mode

[0055] Next, in combination with the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0056] For the convenience of understanding the present invention, the present invention will be described more comprehensively with reference to the relevant drawings. Several embodiments of the present invention are given. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0057] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be a middle element. When an element is considered to be "connected" to another element, it can be directly connected to the other element or there may be a middle element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration.

[0058] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs. The terms used in the description of the present invention herein are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0059] As Figures 1 - 9 , the present invention provides a technical solution:

[0060] A multifunctional sintering furnace for producing graphene thermal conductive films, comprising a vacuum furnace shell 1, the vacuum furnace shell is provided with a furnace door 2, the inner cavity of the vacuum furnace shell 1 is connected to a vacuum generating device (not shown in the figure), and a heating and heat preservation device, a first heating electrode device, a second heating electrode and a pressurizing device are arranged in the vacuum furnace shell 1; the heating and heat preservation device includes a stainless steel outer cylinder 3 and a graphite inner cylinder 4 arranged inside the stainless steel outer cylinder 3, a graphite heater 5 is arranged on the outer side of the graphite inner cylinder 4, a graphite heat preservation layer 6 is arranged between the graphite heater 5 and the stainless steel outer cylinder 3, the stainless steel outer cylinder 3 is fixedly connected to the vacuum furnace shell 1, and a heat insulation space is arranged between the stainless steel outer cylinder 3 and the inner wall of the vacuum furnace shell 1; the first heating electrode device is provided with two groups of electrodes 7, the graphite heater 5 is provided with graphite electrodes 8, the electrodes 7 are connected to the graphite electrodes 8 of the graphite heater 5 to form a first heating circuit, and the first heating circuit forms a heating environment not lower than 1500 °C in the graphite inner cylinder 4; the second heating electrode and pressurizing device includes an upper electrode device 9 and a lifting type lower electrode device 10, the upper electrode device 9 is arranged at the top of the vacuum furnace shell 1, the upper electrode device 9 is provided with an upper electrode rod passing through the vacuum furnace shell 1, the stainless steel outer cylinder 3 and the graphite heat preservation layer 6 and extending into the graphite inner cylinder 4, and the upper electrode rod includes an upper conductive rod 11 and an upper graphite pressing head 12 connected to the upper conductive rod 11; the lifting type lower electrode device 10 is arranged at the bottom of the vacuum furnace shell 1, the lifting type lower electrode device 10 includes a lifting device 13 and a lower electrode rod connected to the lifting device 13, the lower electrode rod includes a lower conductive rod 14 and a lower graphite pressing head 15 connected to the lower conductive rod 14, and the lower graphite pressing head 15 can be lifted through the vacuum furnace shell 1, the stainless steel outer cylinder 3 and the graphite heat preservation layer 6; a material placement area 16 for placing the crude graphene thermal conductive film can be formed between the upper graphite pressing head 12 and the lower graphite pressing head 15; the upper electrode rod and the lower electrode rod are short-circuited and connected in the graphite inner cylinder 4 to form a second heating circuit, and the second heating circuit forms a heating environment not lower than 2600 °C in the graphite inner cylinder 4; the upper graphite pressing head 12 of the upper electrode device 9 is used as a fixed end, and the lower graphite pressing head 15 and the lifting device 13 are used as a moving pressurizing end, and the fixed end and the moving pressurizing end apply a pressure not less than 1600 Kg to the crude graphene thermal conductive film.

[0061] On both sides of the vacuum furnace shell 1, a left electrode, a right electrode and a thermocouple 17 are respectively arranged, one ends of the left electrode, the right electrode and the thermocouple 17 are arranged outside the vacuum furnace shell 1, and the other ends of the left electrode and the right electrode are in contact with the graphite electrodes 8 of the graphite heater 5.

[0062] The left electrode and the right electrode are respectively provided with electrode tubes 18. An electrode water pipe is arranged inside the electrode tube 18. An electrode water-cooling joint 19 is arranged at the rear end of the electrode tube 18 and is communicated with the electrode water pipe and the external circulating cooling water path. The electrode tube 18 passes through the vacuum furnace shell 1, and a heat-resistant insulating sleeve 20 is arranged between the electrode tube 18 and the vacuum furnace shell 1. One end of the graphite electrode 8 passes through the stainless steel outer cylinder 3, the graphite heat-insulating layer 6 and is fixedly connected with the graphite heater 5. The other end of the graphite electrode 8 is arranged outside the stainless steel outer cylinder 3, and an insulating sleeve 21 is arranged between the graphite electrode 8 and the stainless steel outer cylinder 3. The electrode tube 18 contacts with the graphite electrode 8 to form a first heating circuit.

[0063] The upper electrode device 9 and the vacuum furnace shell 1 are connected and insulated and fixed by a flange. The front end of the upper conductive rod 11 is connected with the upper graphite pressure head 12. A graphite block 22 is arranged at the front end of the upper graphite pressure head 12. An electrode water pipe is arranged inside the upper conductive rod 11. An electrode water-cooling joint 19 communicated with the electrode water pipe is arranged at the rear end of the upper conductive rod 11. The electrode water-cooling joint 19 is communicated with the external circulating cooling water path. An electrode connecting plate 23 is arranged on the upper conductive rod 11. The bottom position of the upper graphite pressure head 12 is located inside the graphite inner cylinder 4.

[0064] One end of the lower conductive rod 14 is connected with the lower graphite pressure head 15. A plurality of graphite blocks 22 are arranged at the front end of the lower graphite pressure head 15. An electrode water pipe is arranged inside the lower conductive rod 14. An electrode water-cooling joint 19 communicated with the electrode water pipe is arranged at the other end of the lower conductive rod 14. The electrode water-cooling joint 19 is communicated with the external circulating cooling water path. The electrode water-cooling joint 19 is connected with the bakelite board 24. The bakelite board 24 is connected with the sensor pressure head 26 through bolts 25. The sensor pressure head 26 is connected with the lifting device 13. The highest position of the top of the lower graphite pressure head 15 is located inside the graphite inner cylinder 4, and the lowest position of the top of the lower graphite pressure head 15 is located outside the stainless steel outer cylinder 3.

[0065] The sensor pressure head 26 is provided with a guiding device. The guiding device includes guiding plates 27 extending towards both sides of the sensor pressure head and vertical guiding rods 28 movably connected with the guiding plates 27.

[0066] The stainless steel outer cylinder 3 includes a cylinder body 29, an upper cover 30 and a lower cover 31. Three groups of fixing columns 32 are arranged at the bottom of the lower cover 31 and are fixedly connected with the vacuum furnace shell 1.

[0067] The graphite heat-insulating layer 6 includes a graphite hard felt inner cylinder 33 and a graphite soft felt outer cylinder 34. The graphite soft felt outer cylinder 34 wraps the graphite hard felt inner cylinder 33 on the inner side. The outer side of the graphite soft felt outer cylinder 34 is closely attached to the stainless steel outer cylinder 3. The graphite inner cylinder 4 and the graphite heater 5 are arranged inside the graphite hard felt inner cylinder 33. Both ends of the graphite inner cylinder 4 are respectively closely attached to the graphite hard felt inner cylinder 33. The graphite heater 5 is arranged in the gap between the graphite inner cylinder 4 and the graphite hard felt inner cylinder 33. Graphite electrodes 8 are respectively arranged on both sides of the graphite heating cylinder 5.

[0068] The graphite inner cylinder 4, the graphite thermal insulation layer 6, and the stainless steel outer cylinder 3 are provided with communication holes 35 that are interconnected, and the communication holes 35 are connected to a vacuum generating device.

[0069] It includes a frame 36. The frame 36 includes an upper accommodation cavity 37 and a lower accommodation cavity 38. The vacuum furnace shell 1 is arranged in the upper accommodation cavity 37. The lifting device 13 includes an electric screw jack 39, a vertical guide rod 28, and a guide plate 27. The electric screw jack 39 and the vertical guide rod 28 are arranged in the lower accommodation cavity 38. The lower electrode rod is connected to the guide plate 27, and the guide plate 27 is movably connected to the vertical guide rod 28.

[0070] The working process of the present invention: After obtaining the crude graphene thermal conductive film through the production equipment of pulping and coating, the lower graphite pressing head 15 of the multifunctional sintering furnace for producing the graphene thermal conductive film in this solution descends to the bottom of the vacuum furnace shell 1 and is exposed through the lifting device 13. The crude graphene thermal conductive film can be placed on the lower graphite pressing head 15, and then the crude graphene thermal conductive film is sent into the graphite inner cylinder 4 through the lifting device 13. The equipment is closed, and the vacuum generating device continuously evacuates the inside of the equipment.

[0071] For the first-stage heating, graphite heating is adopted. The left electrode and the right electrode are connected to the first heating circuit, and the graphite heater 5 starts to be energized for heating. The pre-reduction process below 1500 °C is completed in the first-stage heating. Using the thermocouple 17 to measure the temperature, first it rises to 80 °C in 10 minutes and is kept warm for 60 minutes; then it rises to 400 °C at a rate of 2 °C / min and is kept warm for 60 minutes; then the left electrode and the right electrode are powered off to end the heating and start the next heating step.

[0072] For the second-stage heating, large-current short-circuit heating is adopted. The lower graphite pressing head 15 moves towards the upper graphite pressing head 12 and is short-circuited and connected after being tightly pressed against each other. The second-stage heating is carried out and at the same time pressure is applied to the crude graphene thermal conductive film. Using the infrared temperature measuring device to measure the temperature, the temperature inside the graphite inner cylinder 4 rises from 400 °C to 2600 °C within 2 hours, and the pressure gradually increases from the initial 100 kg to 1400 - 1600 kg. The pressure borne by the crude graphene thermal conductive film is 2.9 MPa - 3.1 MPa.

[0073] After completing the processes of carbonization, graphitization, and calendering combination and naturally cooling to room temperature, the lifting device 13 lowers the lower graphite pressing head 15 to the bottom of the vacuum furnace shell 1 and exposes it again, and the staff can take out the finished graphene thermal conductive film.

[0074] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirits of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A multifunctional sintering furnace for producing graphene thermal conductive films, comprising a vacuum furnace shell provided with a furnace door, and the inner cavity of the vacuum furnace shell is connected to a vacuum generating device, characterized in that: A heating and heat preservation device, a first heating electrode device, a second heating electrode and a pressurizing device are arranged inside the vacuum furnace shell; The heating and heat preservation device includes a stainless-steel outer cylinder and a graphite inner cylinder arranged inside the stainless-steel outer cylinder. A graphite heater is arranged on the outer side of the graphite inner cylinder. A graphite heat preservation layer is arranged between the graphite heater and the stainless-steel outer cylinder. The stainless-steel outer cylinder is fixedly connected to the vacuum furnace shell. An insulating space is arranged between the stainless-steel outer cylinder and the inner wall of the vacuum furnace shell; The first heating electrode device is provided with two groups of electrodes. The graphite heater is provided with graphite electrodes. The electrodes are connected to the graphite electrodes of the graphite heater to form a first heating circuit. The first heating circuit forms a heating environment not lower than 1500 °C inside the graphite inner cylinder; The second heating electrode and pressurizing device includes an upper electrode device and a lifting lower electrode device. The upper electrode device is arranged on the top of the vacuum furnace shell. The upper electrode device is provided with an upper electrode rod that passes through the vacuum furnace shell, the stainless-steel outer cylinder, and the graphite heat preservation layer and extends into the graphite inner cylinder. The upper electrode rod includes an upper conducting rod and an upper graphite pressing head connected to the upper conducting rod; The lifting lower electrode device is arranged at the bottom of the vacuum furnace shell. The lifting lower electrode device includes a lifting device and a lower electrode rod connected to the lifting device. The lower electrode rod includes a lower conducting rod and a lower graphite pressing head connected to the lower conducting rod. The lower graphite pressing head can be lifted and lowered through the vacuum furnace shell, the stainless-steel outer cylinder, and the graphite heat preservation layer; A material placement area for placing the crude graphene thermal conductive film can be formed between the upper graphite pressing head and the lower graphite pressing head; The upper electrode rod and the lower electrode rod are short-circuited and connected inside the graphite inner cylinder to form a second heating circuit. The second heating circuit forms a heating environment not lower than 2600 °C inside the graphite inner cylinder; The upper graphite pressing head of the upper electrode device serves as a fixed end, and the lower graphite pressing head and the lifting device serve as a movable pressurizing end. A pressure not less than 1600 Kg is generated by pressurizing between the fixed end and the movable pressurizing end.

2. The multifunctional sintering furnace for producing graphene thermal conductive films according to claim 1, wherein: A left electrode, a right electrode, and a thermocouple are respectively arranged on both sides of the vacuum furnace shell. One ends of the left electrode, the right electrode, and the thermocouple are arranged outside the vacuum furnace shell. The other ends of the left electrode and the right electrode are in contact with the graphite electrodes of the graphite heater.

3. The multifunctional sintering furnace for producing graphene thermal conductive films according to claim 2, wherein: The left electrode and the right electrode are respectively provided with electrode tubes. Electrode water pipes are arranged inside the electrode tubes. Electrode water-cooling joints are arranged at the rear ends of the electrode tubes and are communicated with the electrode water pipes and an external circulating cooling water path. The electrode tubes pass through the vacuum furnace shell and there is an electrode temperature-resistant insulating sleeve between the electrode tubes and the vacuum furnace shell. One end of the graphite electrode passes through the stainless-steel outer cylinder and the graphite heat preservation layer and is fixedly connected to the graphite heater. The other end of the graphite electrode is arranged outside the stainless-steel outer cylinder and there is an insulating sleeve between the graphite electrode and the stainless-steel outer cylinder. The electrode tubes are in contact with the graphite electrodes to form a first heating circuit.

4. A multifunctional sintering furnace for producing graphene thermal conductive films according to claim 1, characterized in that: The upper electrode device is connected, insulated and fixed to the vacuum furnace shell through a flange. The front end of the upper conducting rod is connected to an upper graphite pressing head. A graphite block is provided at the front end of the upper graphite pressing head. An electrode water pipe is provided inside the upper conducting rod. An electrode water-cooling joint communicating with the electrode water pipe is provided at the rear end of the upper conducting rod. The electrode water-cooling joint is communicated with an external circulating cooling water circuit. An electrode connecting plate is provided on the upper conducting rod. The bottom position of the upper graphite pressing head is located inside the graphite inner cylinder.

5. A multifunctional sintering furnace for producing graphene thermal conductive films according to claim 1, characterized in that: One end of the lower conducting rod is connected to a lower graphite pressing head. A plurality of graphite blocks are provided at the front end of the lower graphite pressing head. An electrode water pipe is provided inside the lower conducting rod. An electrode water-cooling joint communicating with the electrode water pipe is provided at the other end of the lower conducting rod. The electrode water-cooling joint is communicated with an external circulating cooling water circuit. The electrode water-cooling joint is connected to a bakelite board. The bakelite board is connected to a sensor pressing head through bolts. The sensor pressing head is connected to a lifting device. The highest position of the top of the lower graphite pressing head is located inside the graphite inner cylinder. The lowest position of the top of the lower graphite pressing head is located outside the stainless steel outer cylinder.

6. A multifunctional sintering furnace for producing graphene thermal conductive films according to claim 5, characterized in that: The sensor pressing head is provided with a guiding device. The guiding device includes guiding plates extending towards both sides of the sensor pressing head and vertical guiding rods movably connected to the guiding plates.

7. A multifunctional sintering furnace for producing graphene thermal conductive films according to claim 1, characterized in that: The stainless steel outer cylinder includes a cylinder body, an upper cover and a lower cover. Three groups of fixing columns are provided at the bottom of the lower cover and fixedly connected to the vacuum furnace shell.

8. A multifunctional sintering furnace for producing graphene thermal conductive films according to claim 1, characterized in that: The graphite heat-insulating layer includes a graphite hard felt inner cylinder and a graphite soft felt outer cylinder. The graphite soft felt outer cylinder wraps the graphite hard felt inner cylinder on the inner side. The outer side of the graphite soft felt outer cylinder is in close contact with the stainless steel outer cylinder. A graphite inner cylinder and a graphite heating cylinder are arranged inside the graphite hard felt inner cylinder. Both ends of the graphite inner cylinder are respectively in close contact with the graphite hard felt inner cylinder. The graphite heating cylinder is arranged in the gap between the graphite inner cylinder and the graphite hard felt inner cylinder. Graphite electrodes are respectively arranged on both sides of the graphite heating cylinder.

9. A multifunctional sintering furnace for producing graphene thermal conductive films according to claim 1 or 8, characterized in that: The graphite inner cylinder, the graphite heat-insulating layer and the stainless steel outer cylinder are provided with vent holes communicating with each other. The vent holes are communicated with a vacuum generating device.

10. A multifunctional sintering furnace for producing graphene thermal conductive films according to claim 1, characterized in that: It includes a frame. The frame includes an upper accommodation cavity and a lower accommodation cavity. The vacuum furnace shell is arranged in the upper accommodation cavity. The lifting device includes an electric screw jack, a vertical guiding rod and a guiding plate. The electric screw jack and the vertical guiding rod are arranged in the lower accommodation cavity. The lower electrode rod is connected to the guiding plate. The guiding plate is movably connected to the vertical guiding rod.

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