A carbon-carbon composite material, its preparation method and use

Abstract

The present application belongs to the technical field of composite materials, and particularly relates to a carbon-carbon composite material and a preparation method and application thereof. The present application sequentially repeats the laying of a net tire and mixed material powder (including graphene powder and pitch powder) to obtain a preform by using the net tire to seal the layer; the preform is sequentially subjected to segmented hot-pressing curing, carbonization treatment, vapor deposition carbon and graphitization treatment to obtain the carbon-carbon composite material. The present application adopts a full net tire preform, and the single preform can reduce the difference in resistivity. The pitch powder and high-conductivity graphene powder are used together to directly perform mold pressing, thereby reducing the resistivity and its dispersion type. Vapor deposition is used to replace pitch impregnation-carbonization densification, thereby reducing the time and raw material cost caused by multiple pitch impregnation-carbonization densification, and overcoming the defects of long densification process period and high cost.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of composite materials, and particularly relates to a carbon-carbon composite material and a preparation method and application thereof. BACKGROUND

[0002] Photovoltaic power generation is a kind of sustainable green energy, and is increasingly valued and developed by countries around the world. Monocrystalline silicon wafer is a core component of a solar cell, and restricts the development of photovoltaic power generation. In a Czochralski monocrystalline silicon furnace, a heater is used to heat polycrystalline silicon to melt it.

[0003] As a heating element of a monocrystalline furnace, the carbon-carbon heater is currently made of a carbon-carbon composite material prepared by a traditional pitch impregnation-carbonization process. However, the carbon-carbon composite material is usually prepared by using different preforms such as carbon cloth, net tire and carbon wire. Since the resistivities of different preforms are different, the resistivity of the carbon-carbon composite heater is high and discrete. In addition, the pitch impregnation-carbonization process has a low pitch carbon content, and requires a large number of impregnation times, resulting in a high production cycle and cost. SUMMARY

[0004] Therefore, the application provides a carbon-carbon composite material, a preparation method and application thereof. The carbon-carbon composite material has excellent mechanical properties, low and stable resistivity, and low cost.

[0005] To achieve the above object, the application provides the following technical scheme.

[0006] The application provides a preparation method of a carbon-carbon composite material, comprising the following steps.

[0007] The net tire and the mixed powder are repeatedly laid in sequence, and the net tire is used for sealing to obtain a preform. The mixed powder comprises graphene powder and pitch powder.

[0008] The preform is sequentially subjected to segmented hot pressing curing, carbonization treatment, gas phase deposition carbon and graphitization treatment to obtain the carbon-carbon composite material.

[0009] Preferably, the mass ratio of the graphene powder to the pitch powder in the mixed powder is (1-5):200.

[0010] Preferably, the number of repeated layings is 15-35 times; the thickness of the powder layer obtained by one laying is 0.5-1 mm; and the mass of the mixed powder used for one laying is 35-45% of the mass of one layer of net tire.

[0011] Preferably, the segmental hot-pressing curing comprises a first stage hot-pressing, a second stage hot-pressing, a third stage hot-pressing and a fourth stage hot-pressing; the first stage hot-pressing has a pressure of 1 MPa and a temperature of 85-90℃, and a holding time of 40-50 min; the second stage hot-pressing has a pressure of 1.5-3 MPa and a temperature of 110-120℃, and a holding time of 30-45 min; the third stage hot-pressing has a pressure of 2-4 MPa and a temperature of 150-170℃, and a holding time of 30-45 min; and the fourth stage hot-pressing has a pressure of 4-5 MPa and a temperature of 165-175℃, and a holding time of 55-65 min.

[0012] Preferably, the temperature rising procedure of the carbonization treatment is as follows: rising from room temperature to 580-620℃ within 300 min, holding for 60-90 min, then rising to 800-900℃ within 60-80 min, and holding for 90-120 min.

[0013] Preferably, the temperature rising procedure of the carbonization treatment is as follows: rising from room temperature to 580-620℃ within 300 min, holding for 60-90 min, then rising to 800-900℃ within 60-80 min, and holding for 90-120 min.

[0014] Preferably, the carbon source used in the vapor deposition is methane; the flow rate of the methane is 110-130 SLM; and the pressure of the vapor deposition is -96 to -98 kPa.

[0015] Preferably, the procedure of the graphitization treatment comprises:

[0016] First stage: rising from room temperature to 1100-1150℃ within 300 min, and introducing nitrogen gas to maintain a slight positive pressure, with a flow rate of 0.4-0.8 SLM;

[0017] Second stage: switching the nitrogen gas to argon gas to maintain a slight positive pressure, with a flow rate of 0.3-0.5 SLM, and rising the temperature from the temperature of the first stage to 1850-1880℃ within 480 min, and holding for 300 min;

[0018] Third stage: naturally lowering the temperature from the temperature of the second stage to room temperature through first and second temperature lowering; the first temperature lowering naturally lowers the temperature from the temperature of the second stage to 1100℃, and in the process of the first temperature lowering, argon gas is introduced at a flow rate of 0.3-0.5 SLM to maintain a slight positive pressure for temperature lowering;

[0019] The second temperature lowering naturally lowers the temperature from 1100℃ to room temperature, and in the process of the second temperature lowering, the argon gas is switched to nitrogen gas, with a flow rate of 0.3-0.5 SLM to maintain a slight positive pressure for temperature lowering.

[0020] The present invention also provides a carbon-carbon composite material prepared by the preparation method described above, wherein the resistivity of the carbon-carbon composite material is 15-22 μΩ·m.

[0021] The present invention also provides the application of the carbon-carbon composite material described in the above technical solution in the preparation of heaters.

[0022] This invention provides a method for preparing a carbon-carbon composite material, comprising the following steps: repeatedly laying a mesh and a mixture powder in sequence, sealing the mesh with the mesh to obtain a preform, wherein the mixture powder includes graphene powder and asphalt powder; subjecting the preform to segmented hot pressing curing, carbonization treatment, vapor deposition carbon, and graphitization treatment in sequence to obtain a carbon-carbon composite material. This invention employs a fully mesh-based precast body. The single precast body reduces resistivity differences. Hot pressing is performed directly using a combination of asphalt powder and highly conductive graphene powder. The addition of asphalt powder increases the proportion of asphalt carbon in the matrix composition, resulting in higher graphitization of the asphalt carbon and enhancing the electrical properties of the carbon-carbon composite material, thus reducing resistivity. The addition of highly conductive graphene further strengthens the electrical properties of the carbon-carbon composite material, reducing resistivity. The fully mesh-based precast body has a simple structure, and compared to traditional precast bodies using multiple materials such as carbon cloth, carbon fiber, and mesh, its isotropic electrical properties are more pronounced, thereby reducing the resistivity dispersion of the carbon-carbon composite material and enhancing its resistivity stability. Furthermore, vapor deposition replaces asphalt impregnation-carbonization densification, reducing the time and raw material costs associated with multiple asphalt impregnation-carbonization densification processes. This overcomes the disadvantages of long densification process cycles and high costs, enabling industrial-scale production. Attached Figure Description

[0023] Figure 1 This is a schematic diagram of the mold used in an embodiment of the present invention;

[0024] Figure 2 This is a flowchart illustrating a method for preparing a heater for a hydrogenation furnace according to an embodiment of the present invention. Detailed Implementation

[0025] This invention provides a method for preparing carbon-carbon composite materials, comprising the following steps:

[0026] The mesh and the mixture powder are repeatedly laid in sequence, and then sealed with the mesh to obtain a preform. The mixture powder includes graphene powder and asphalt powder.

[0027] The preform is subjected to segmented hot pressing curing, carbonization, vapor deposition of carbon, and graphitization in sequence to obtain a carbon-carbon composite material.

[0028] Unless otherwise specified, the present invention does not have special requirements on the source of raw materials used, and commercially available products well known to those skilled in the art can be used.

[0029] The present application repeatedly lays the web tire and the mixed material powder in sequence, seals with the web tire, and obtains the preform.

[0030] In the present application, the grammage of the web tire is preferably 250-350 g / m 2 , more preferably 250 g / m 2 ; the material of the web tire is preferably carbon fiber; the length of the web tire is preferably 935-960 mm, more preferably 935 mm, and the width is preferably 560-600 mm, more preferably 560 mm.

[0031] In the present application, the mixed material powder comprises graphene powder and asphalt powder; the particle size of the graphene powder is preferably 10-90 μm, more preferably 20-50 μm; the particle size of the asphalt powder is preferably 50-250 μm, more preferably 50-80 μm; the asphalt powder is preferably coal tar pitch; the mass ratio of the graphene powder to the asphalt powder in the mixed material powder is preferably (1-5):200, more preferably (1-3):200; the preparation method of the mixed material powder is preferably stirring the graphene powder and the asphalt powder in a stirrer; the stirring temperature is preferably room temperature; the stirring rate is preferably 200-300 rpm, more preferably 250 rpm; and the stirring time is preferably 30-90 min, more preferably 60 min.

[0032] In the present application, the number of repeated layings is preferably 15-35 times, more preferably 15-25 times; the thickness of the powder layer obtained by one laying is preferably 0.5-1 mm, more preferably 0.5-0.8 mm; and the mass of the mixed material powder used for one laying is preferably 35-45% of the mass of one web tire, more preferably 40%.

[0033] In the present application, the preform is subjected to segmented hot-pressing curing in a mold; the mold is composed of an upper mold, a lower mold and clamps, and the upper mold and the lower mold are connected by the clamps. Figure 1 The structure of the mold used in the embodiments of the present application is shown in the figure, in which 1 is the upper mold, 2 is the lower mold, and 3-6 are the clamps connecting the upper mold and the lower mold.

[0034] After obtaining the preform, the preform is subjected to segmented hot-pressing curing in the present application, and a cured material is obtained.

[0035] In the present application, the segmental autoclave curing preferably comprises a first stage autoclave, a second stage autoclave, a third stage autoclave and a fourth stage autoclave; the pressure of the first stage autoclave is preferably 1 MPa, the temperature is preferably 85-90℃, more preferably 88℃, the holding time is preferably 40-50 min, more preferably 45 min, the heating rate from room temperature to the temperature of the first stage autoclave is preferably 2-5℃ / min, more preferably 3℃ / min; the pressure of the second stage autoclave is preferably 1.5-3 MPa, more preferably 2 MPa, the temperature is preferably 110-120℃, more preferably 120℃, the holding time is preferably 30-45 min, more preferably 30-35 min, the heating rate from the temperature of the first stage autoclave to the temperature of the second stage autoclave is preferably 1.5-2.5℃ / min, more preferably 2℃ / min; the pressure of the third stage autoclave is preferably 2-4 MPa, more preferably 3 MPa, the temperature is preferably 150-170℃, more preferably 160℃, the holding time is preferably 30-45 min, more preferably 30-35 min, the heating rate from the temperature of the second stage autoclave to the temperature of the third stage autoclave is preferably 1-2℃ / min, more preferably 1℃ / min; the pressure of the fourth stage autoclave is preferably 4-5 MPa, more preferably 5 MPa, the temperature is preferably 165-175℃, more preferably 170℃, the holding time is preferably 55-65 min, more preferably 60 min, the heating rate from the temperature of the third stage autoclave to the temperature of the fourth stage autoclave is preferably 1-2℃ / min, more preferably 1℃ / min.

[0036] In the segmental autoclave curing process, when the temperature approaches the softening point, the asphalt will start to soften from solid state to form a flow state, bonding the upper and lower tire nets; when the temperature is higher, the asphalt will decompose, and the small molecules of polycyclic aromatic hydrocarbons will volatilize; after cooling, the flow state asphalt will form solid asphalt, bonding the tire nets. The present application makes the overall curing material more uniform and the mechanical properties more excellent through segmental autoclave curing.

[0037] After obtaining the curing material, the present application performs carbonization treatment on the curing material to obtain a carbonized material.

[0038] In the present application, the equipment used for the carbonization treatment is preferably a carbonization furnace; the heating program of the carbonization treatment is preferably: heating from room temperature to 580-620℃ within 300 min, holding for 60-90 min, then heating to 800-900℃ within 60-80 min, holding for 90-120 min, more preferably: heating from room temperature to 600℃ within 300 min, holding for 60 min, then heating to 850℃ within 60 min, holding for 120 min.

[0039] The solidified asphalt is continuously decomposed at different temperature stages, and finally forms asphalt carbon.

[0040] After obtaining the carbonized material, the carbonized material is subjected to gas phase deposition carbon to obtain a carbon deposition carbonized material.

[0041] In the present application, the temperature rising procedure of the gas phase deposition is preferably that the temperature is raised from room temperature to 1100-1140℃ within 300min, and after preheating for 120-150min, the gas phase deposition is started, and more preferably that the temperature is raised from room temperature to 1120℃ within 300min, and after preheating for 120min, the gas phase deposition is started; the temperature of the gas phase deposition is preferably 1120℃, and the time is preferably 80h; the carbon source used in the gas phase deposition is preferably methane; the flow rate of the methane is preferably 110-130SLM, and more preferably 120SLM; the pressure of the gas phase deposition is preferably -96--98kPa, and more preferably -96--97kPa; the gas phase deposition carbon is preferably to the density of the obtained carbon deposition carbonized material being 1.65-1.75g / cm 3 , and more preferably 1.75g / cm 3 .

[0042] The present application deposits carbon in the surface and pores of the carbonized material obtained by the above carbonization treatment through gas phase deposition.

[0043] After obtaining the carbon deposition carbonized material, the carbon deposition carbonized material is subjected to graphitization treatment to obtain a carbon-carbon composite material.

[0044] In the present application, the procedure of the graphitization treatment preferably comprises:

[0045] First stage: the temperature is raised from room temperature to 1100-1150℃ within 300min, and nitrogen gas is introduced to keep a slight positive pressure, and the flow rate of the nitrogen gas is 0.4-0.8SLM;

[0046] Second stage: the nitrogen gas is switched to argon gas, and a slight positive pressure is kept, the flow rate of the argon gas is 0.3-0.5SLM, and the temperature is raised from the temperature of the first stage to 1850-1880℃ within 480min, and the temperature is kept for 300min;

[0047] Third stage: the temperature is naturally lowered from the temperature of the second stage to room temperature through first and second temperature lowering; the first temperature lowering is to naturally lower the temperature from the temperature of the second stage to 1100℃, and in the process of the first temperature lowering, 0.3-0.5SLM flow rate of argon gas is introduced, and the lowering is kept under a slight positive pressure;

[0048] The second temperature reduction is from 1100 DEG C to room temperature naturally, and in the process of the second temperature reduction, the argon is switched to nitrogen, the flow rate of the nitrogen is 0.3-0.5 SLM, and the temperature reduction is carried out under the condition of micro-positive pressure.

[0049] In the embodiment of the present application, the specific procedure of the graphitization treatment is as follows: the first stage is to increase the temperature from room temperature to 1100 DEG C within 300 min, nitrogen is introduced to keep micro-positive pressure, and the flow rate of the nitrogen is 0.5 SLM; the second stage is to switch the nitrogen to argon to keep micro-positive pressure, the flow rate of the argon is 0.5 SLM, and the temperature is increased from the temperature of the first stage to 1850 DEG C within 480 min, and the temperature is kept for 300 min; the third stage is to naturally reduce the temperature from the temperature of the second stage to room temperature through the first temperature reduction and the second temperature reduction; the first temperature reduction is to naturally reduce the temperature from the temperature of the second stage to 1100 DEG C, 0.5 SLM argon is introduced in the process of the first temperature reduction, and the temperature reduction is carried out under the condition of micro-positive pressure; the second temperature reduction is to naturally reduce the temperature from 1100 DEG C to room temperature, and in the process of the second temperature reduction, the argon is switched to nitrogen, the flow rate of the nitrogen is 0.5 SLM, and the temperature reduction is carried out under the condition of micro-positive pressure.

[0050] The present application converts carbon to graphite through graphitization treatment, reduces the resistivity, and improves the electrical performance.

[0051] The present application also provides the carbon-carbon composite material prepared by the preparation method.

[0052] In the present application, the resistivity of the carbon-carbon composite material is 15-22 mu omega.m.

[0053] The present application also provides the application of the carbon-carbon composite material in preparing a heater.

[0054] In the present application, the heater is preferably a heater for hydrogenation furnace.

[0055] The present application is not specially limited to the preparation method of the heater, and the heater can be machined and spliced according to the actual drawing of the required heater.

[0056] Figure 2 The method flow chart for preparing the heater for hydrogenation furnace is shown in the figure. Figure 2 As shown in the figure, the present application obtains the carbon-carbon composite material through the preparation of the preform, hot pressing, carbonization, vapor deposition and graphitization, and then obtains the carbon-carbon composite material heater through the machining of the spliced carbon-carbon composite material.

[0057] The technical solutions in the present application will be clearly and completely described in combination with the embodiments in the present application, but they should not be understood as limitations to the protection scope of the present application.

[0058] Example 1

[0059] The weight is 250g / m 2 Carbon fiber mesh is cut into small pieces with dimensions of 935mm x 560mm. Graphene powder (50μm particle size) and asphalt powder (coal tar pitch) with a particle size of 50-80μm are mixed in a mixer at a mass ratio of 1:200 at 250rpm for 60 minutes to obtain a mixed powder. The cut mesh is laid at the bottom of the lower mold, and the mixed powder is evenly spread on the mesh to a thickness of 0.5mm. The mass of the mixed powder used for each layer is 40% of the mass of one layer of mesh. The layers are repeated 15 times, and then sealed with mesh to form a 16-layer mesh preform. The upper mold is then placed on top, and the upper and lower molds are connected with clamps. The mold containing the preform is then placed in a flatbed hot press for segmented hot pressing and curing. The process is as follows: a) The hot press is subjected to a constant pressure of 1MPa, and the temperature is increased from room temperature at a rate of 3℃ / min. a) Pre-curing: Increase the temperature at a rate of 2℃ / min to 88℃ and hold for 45 minutes. b) Increase the pressure to 2MPa and raise the temperature to 120℃ at a rate of 2℃ / min, holding for 30 minutes. c) Increase the pressure to 3MPa and raise the temperature to 160℃ at a rate of 1℃ / min, holding for 30 minutes. d) Continue to raise the temperature to 170℃ at a rate of 1℃ / min and hold for 60 minutes under a constant pressure of 5MPa. e) Turn off the machine and allow it to cool naturally to room temperature. Place the cured material in a carbonization furnace and raise the temperature from room temperature to 600℃ within 300 minutes, hold for 60 minutes, then raise the temperature to 850℃ within 60 minutes and hold for 120 minutes for carbonization. Place the carbonized material in a deposition furnace for carbon deposition to increase its density to 1.75 g / cm³. 3 The specific parameters are as follows: The temperature is raised from room temperature to 1120℃ within 300 minutes, held for 120 minutes for preheating, then methane is introduced at a flow rate of 120 SLM, and carbon is deposited in the vapor phase at -96 kPa for 80 hours. The resulting carbon-deposited material is then placed in a graphitization furnace for graphitization treatment. The specific procedure is as follows: First stage: The temperature is raised from room temperature to 1100℃ within 300 minutes, and nitrogen is introduced to maintain a slight positive pressure at a flow rate of 0.5 SLM; Second stage: The nitrogen is switched to argon, maintaining a slight positive pressure at a flow rate of 0.5 SLM, and the process is carried out at 480 min... The internal temperature is raised to 1850℃ in the first stage and held for 300 minutes. In the third stage, the temperature is naturally cooled from the second stage temperature to room temperature through the first and second cooling processes. The first cooling process involves naturally cooling from the second stage temperature to 1100℃, during which argon gas is introduced at a flow rate of 0.5 SLM and the cooling is carried out under a slightly positive pressure. The second cooling process involves naturally cooling from 1100℃ to room temperature, during which the argon gas is switched to nitrogen gas at a flow rate of 0.5 SLM and the cooling is carried out under a slightly positive pressure, resulting in a carbon-carbon composite material.

[0060] Example 2

[0061] The difference from Example 1 is that the mass ratio of graphene powder to asphalt powder is 3:200, while the rest is the same as Example 1.

[0062] Example 3

[0063] The difference from Example 1 is that the mass ratio of graphene powder to asphalt powder is 5:200, while the rest is the same as Example 1.

[0064] Comparative Example 1

[0065] The difference from Example 3 is that the mixed powder composed of graphene powder and asphalt powder is replaced with asphalt powder, while the rest is the same as Example 3.

[0066] Application Examples 1-3

[0067] The carbon-carbon composite materials prepared in Examples 1-3 were machined according to the drawings of the heater for the hydrogenation furnace, and then the machined parts were spliced ​​together to obtain the heater for the hydrogenation furnace.

[0068] Performance testing

[0069] The resistivity of the carbon-carbon composite materials obtained in Examples 1-3 and Comparative Example 1 was tested, and the results are shown in Table 1.

[0070] Table 1. Resistivity of carbon-carbon composite materials obtained in Examples 1-3 and Comparative Example 1

[0071] Serial number Resistivity (μΩ.m) Example 1 18.3±0.42 Example 2 15.1±0.36 Example 3 21.6±0.35 Comparative Example 1 Comparative Example 2 23.4±0.70

[0072] As shown in Table 1, compared with Comparative Example 1, the resistivity of Example 3 decreased after the addition of graphene powder, and the fluctuation of resistivity was smaller. Therefore, graphene powder has a significant effect on improving resistivity and its stability.

[0073] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention and not all embodiments. People can obtain other embodiments based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for producing a carbon-carbon composite material, characterized by comprising the steps of: The method comprises the following steps: ​ repeatedly laying a web and a mixture powder in sequence, and using the web to seal a layer to obtain a preform, wherein the mixture powder comprises graphene powder and asphalt powder; a mass ratio of the graphene powder to the asphalt powder in the mixture powder is 5:200; the number of repeated layings is 15-35 times; a thickness of a powder layer obtained by one laying is 0.5-1 mm; and a mass of the mixture powder used for one laying is 35-45% of a mass of one web; the preform is subjected to segmented hot-pressing curing, carbonization treatment, vapor deposition carbon and graphitization treatment in sequence to obtain a carbon-carbon composite material; the segmented hot-pressing curing comprises first-stage hot pressing, second-stage hot pressing, third-stage hot pressing and fourth-stage hot pressing; the first-stage hot pressing is performed at a pressure of 1 MPa and a temperature of 85-90 DEG C for 40-50 min; the second-stage hot pressing is performed at a pressure of 1.5-3 MPa and a temperature of 110-120 DEG C for 30-45 min; the third-stage hot pressing is performed at a pressure of 2-4 MPa and a temperature of 150-170 DEG C for 30-45 min; and the fourth-stage hot pressing is performed at a pressure of 4-5 MPa and a temperature of 165-175 DEG C for 55-65 min; a carbon source used for the vapor deposition is methane; a flow rate of the methane is 110-130 SLM; and a pressure of the vapor deposition is -96 to -98 kPa.

2. The production method according to claim 1, characterized by, a temperature rising procedure of the carbonization treatment is as follows: rising from room temperature to 580-620 DEG C within 300 min, keeping the temperature for 60-90 min, then rising to 800-900 DEG C within 60-80 min, and keeping the temperature for 90-120 min.

3. The preparation method according to claim 1, characterized in that, a temperature rising procedure of the vapor deposition is as follows: rising from room temperature to 1100-1140 DEG C within 300 min, keeping the temperature for 120-150 min for preheating, and then starting the vapor deposition.

4. The method of claim 1, wherein, a procedure of the graphitization treatment comprises: a first stage: rising from room temperature to 1100-1150 DEG C within 300 min, keeping a slight positive pressure by introducing nitrogen gas at a flow rate of 0.4-0.8 SLM; a second stage: switching the nitrogen gas to argon gas, keeping a slight positive pressure, rising the temperature from the temperature of the first stage to 1850-1880 DEG C within 480 min, and keeping the temperature for 300 min; a third stage: naturally lowering the temperature from the temperature of the second stage to room temperature by first lowering and second lowering; the first lowering is naturally lowering the temperature from the temperature of the second stage to 1100 DEG C, and the argon gas is introduced at a flow rate of 0.3-0.5 SLM during the first lowering to keep a slight positive pressure for lowering the temperature; the second lowering is naturally lowering the temperature from 1100 DEG C to room temperature, and the argon gas is switched to nitrogen gas during the second lowering at a flow rate of 0.3-0.5 SLM to keep a slight positive pressure for lowering the temperature.

5. The carbon-carbon composite material produced by the production method according to any one of claims 1 to 4, characterized by a resistivity of the carbon-carbon composite material is 15-22 mu Omega.m.

6. Use of the carbon-carbon composite material of claim 5 in preparing a heater.

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