A carbon-carbon heater and its manufacturing process

Abstract

This invention discloses a carbon-carbon heater and its manufacturing process, belonging to the technical field of carbon-carbon heaters. The process includes nine steps: preform manufacturing, curing process, chemical vapor infiltration treatment, CVI-asphalt carbon interface layer formation, impregnation, carbonization, repeated impregnation and carbonization, precision machining, and coating treatment. Through innovative process design, this invention increases the density of the carbon-carbon heater to 1.5-1.8 g / cm³ with uniform distribution (deviation <3%), achieves a resistance consistency of ≤±2.3%, and extends its high-temperature oxidation resistance life to over 5000 hours, fully meeting the requirements of advanced crystal pulling processes.

Description

Technical Field

[0001] This invention belongs to the field of carbon-carbon heater technology, specifically a carbon-carbon heater and its manufacturing process. Background Technology

[0002] Carbon-carbon composite materials are widely used in high-temperature applications such as heaters for semiconductor single-crystal silicon crystal pulling furnaces due to their high strength, excellent high-temperature stability, and high designability. However, existing carbon-carbon heater manufacturing processes still face many technical bottlenecks, which restrict their performance improvement and large-scale application.

[0003] Current state of technology:

[0004] 1. Precast structure defects: Traditional precast structures often use carbon cloth laminates combined with short-cut fiber needle punching process, but the interlayer bonding force of the fibers is insufficient, resulting in low Z-direction strength (usually <20MPa). In addition, during the chemical vapor infiltration (CVI) process, uneven pore distribution can easily form a "shell-core" structure with a significant density gradient (surface >1.5g / cm³, core <0.6g / cm³).

[0005] 2. Limitations of CVI process: Conventional CVI uses a single methane gas source for high-concentration (>50%) deposition, which rapidly forms a dense layer on the surface, hindering gas diffusion into the interior. The final product has a closed-cell rate of up to 30%-40%, and the thermal conductivity fluctuates by more than ±15%.

[0006] 3. Low impregnation-carbonation efficiency: Existing technologies mostly use ordinary asphalt for direct impregnation, with a carbonation yield of >40%, which leads to premature closure of pores. It is necessary to repeat the impregnation 6-8 times to achieve a density of 1.7g / cm³, which takes more than 500 hours.

[0007] 4. Weak interfacial bonding: Due to the difference in thermal expansion coefficients between CVI carbon and pitch carbon (CVI carbon: 3.5×10-6 / ℃; pitch carbon: 5.8×10-6 / ℃), microcracks are easily generated at high temperatures, resulting in poor resistance uniformity (deviation > 10%), which affects the temperature field control accuracy of the crystal pulling furnace (above ±3℃).

[0008] 5. Insufficient machining accuracy: When machining carbon materials on traditional lathes, improper cutting parameters (such as feed rate > 0.1 mm / rev) can lead to edge chipping, dimensional tolerances of critical parts > ±0.05 mm, and surface roughness Ra > 3.2 μm, making it difficult to meet the requirements of modular assembly.

[0009] The aforementioned problems result in existing carbon-carbon heaters having defects such as uneven density (1.3-1.6 g / cm³), discrete resistance distribution (±12%), short thermal shock life at high temperatures (<1000 cycles, ΔT=1500℃), and poor temperature field uniformity after assembly (>±2.5℃), making it difficult to meet the stringent requirements of third-generation semiconductor single-crystal silicon growth for heater thermal field accuracy (±1℃) and service life (>3000h). Summary of the Invention

[0010] To address the above problems, this invention provides a carbon-carbon heater and its manufacturing process. Through innovative process design, the density of the carbon-carbon heater is increased to 1.5-1.8 g / cm³ with uniform distribution (deviation <3%), the resistance consistency reaches ≤±2.3%, and the high-temperature oxidation resistance life is extended to more than 5000 hours, fully adapting to the requirements of advanced crystal pulling processes.

[0011] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0012] A manufacturing process for a carbon-carbon heater includes the following steps:

[0013] S1, Preform Manufacturing: The preform is woven using carbon cloth, mesh and carbon rope. During the preform forming process, each layer is coated with resin and graphitized coconut powder. After weaving, the preform is needle-punched to obtain the preform.

[0014] S2, Curing process: The preform undergoes a three-stage curing process;

[0015] S3, Chemical Vapor Infiltration Treatment: The cured preform is placed in a CVI furnace, using natural gas and nitrogen as gas sources. The furnace temperature is controlled at 800-1200℃, the furnace pressure at 1000-3000Pa, and the reaction time at 50-300h. After the reaction is completed, the preform is taken out, and its density is 0.7-1.2g / cm3.

[0016] S4, CVI-asphalt carbon interface layer formation: The preform treated in step S3 is impregnated with low carbon yield asphalt, and then carbonized. During the carbonization process, natural gas is continuously introduced at a flow rate of 1-100 L / min for 2-100 h at a temperature of 800-1200 ℃. At 800-1200 ℃, a small amount of natural gas and nitrogen are introduced for 1-50 h to form the CVI-asphalt carbon interface layer.

[0017] S5, Impregnation: Place the asphalt into a cylinder, heat it to 120-200℃, add foaming agent, continue to heat to 150-300℃, stir for 1-8 hours to obtain foamed asphalt, and then immerse the precast body treated in step S4 into the foamed asphalt, fill with nitrogen and keep it under pressure of 2-10MPa for 5-10 hours.

[0018] S6, Carbonization: The preform treated in step S5 is kept at 800-1200℃ for 2-10 hours;

[0019] S7, Repeated impregnation and carbonization: Repeat step S5 impregnation and S6 carbonization 2-5 times, with one high-temperature treatment in between, at a temperature of 1800-3000℃ for 5-80 hours, and the final product density is 1.5-1.8 g / cm³.

[0020] S8, Finish turning: The finished product is finished using a high-precision CNC lathe with a cutting speed of 180-200m / min, a feed rate of 0.05-0.08mm / rev, a depth of cut of 0.1-0.2mm, to complete the final dimension machining, ensuring that the tolerance of key parts is ±0.02mm and the surface roughness Ra≤1.6μm;

[0021] S9, Coating treatment: The finished product after step S8 is coated with a plasma spraying technology. The spraying solvent is resin and graphitized coconut powder. After spraying, it is treated at a high temperature of 1500-2500℃ for 5-80 hours to obtain the carbon-carbon heater product.

[0022] In the above technical solution, carbon cloth, mesh, and carbon rope weaving provide the basic skeleton, needle punching enhances the interlayer bonding, and resin and graphitized coconut powder coating improve the initial density; staged temperature curing of resin avoids thermal stress cracking and forms a stable matrix; natural gas is cracked at high temperature and low pressure to generate pyrolytic carbon, which gradually fills the pores of the preform and increases the density to 0.7-1.2 g / cm³; low-carbon yield asphalt is impregnated and then carbonized, combined with secondary deposition of natural gas, to form a gradient carbon structure and alleviate thermal expansion differences; foaming agent causes asphalt to expand and then penetrate under pressure to fill the micropores; multiple impregnation-carbonization cycles (interspersed with high-temperature graphitization) further increase the density to 1.5-1.8 g / cm³; high-parameter CNC machining ensures dimensional accuracy (±0.02 mm) and low roughness (Ra≤1.6 μm) and optimizes electrical contact performance; plasma spraying of resin-graphitized coconut powder composite layer, after high-temperature treatment, forms an antioxidant protective layer and extends service life.

[0023] In a preferred implementation, the mesh tire accounts for more than 30% of the total tire weight.

[0024] In a preferred embodiment, the resin in steps S1 and S9 is one or more of phenolic resin, furfuryl ketone resin, and epoxy resin. The high carbon residue of the phenolic resin used in this technical solution is suitable for step S1, forming a glassy carbon-reinforced matrix after carbonization. The high-temperature resistance of the furfuryl ketone resin is used for the coating in S9, and during high-temperature treatment, it is co-carbonized with graphitized coconut powder to form a dense protective layer. The epoxy resin in S1 acts as a low-temperature curing binder, improving the initial strength of the preform and reducing needle-puncture damage.

[0025] In a preferred embodiment, the preparation process of graphitized coconut powder in steps S1 and S9 is as follows: coconut powder is obtained by crushing, calcining, grinding, high temperature treatment, screening, and mixing, with a particle size distribution of 100 mesh 10%-40%, 200 mesh 20%-40%, and 500 mesh 20%-50%. The calcination is carried out at 200-400℃ for 2-5 hours and at 500-800℃ for 5-10 hours. The high temperature treatment is carried out at 1800-2400℃ for 5-30 hours. The mass percentage of graphitized coconut powder is 30%-60%.

[0026] In a preferred embodiment, the three-stage curing process in step S2 is as follows: heating from room temperature to 60℃±20℃ and holding for 2-5 hours; heating from 60℃ to 100℃±20℃ at a rate of 20℃±5℃ / h; holding at 100℃±10℃ for 1±0.5 hours; heating from 100℃ to 180℃±10℃ at a rate of 12℃±5℃ / h, taking 4-12 hours, with a maximum pressure Pmax≤1.0MPa; and finally holding at 180℃±10℃ for 4±1 hours. This technical solution utilizes a first stage of slow preheating to allow the resin to initially crosslink, volatilize, and dissipate; a second stage of rapid heating to trigger the main curing reaction; and a third stage of slow heating to the final curing temperature, combined with a pressure ≤1.0MPa to compact the interlayer and eliminate microcracks.

[0027] In a preferred embodiment, the proportion of natural gas in the total gas volume in step S3 is less than 20%.

[0028] In a preferred embodiment, the yield of low-carbon yield asphalt in step S4 is less than 30%, the impregnation pressure is 1-10 MPa, and the holding time is 2-50 h. This technical solution uses low-carbon yield asphalt, which, after carbonization, generates an open porous structure (pore size 0.1-1 μm), becoming a permeation channel for CVI deposition. The impregnation pressure of 1-10 MPa forces the low-viscosity asphalt into the submicron-sized pores, and the holding time of 2-50 h ensures sufficient wetting and avoids backflow.

[0029] A carbon-carbon heater is manufactured using the above-mentioned production process.

[0030] In a preferred embodiment, the heater has uniform resistance and heating properties, making it suitable for crystal pulling processes.

[0031] Compared with the prior art, the beneficial effects of the present invention are: (1) The present invention achieves high density, high strength and uniform performance of carbon-carbon heater through multi-step composite process, optimizes heat conduction and resistance stability, and the final product is highly accurate and durable;

[0032] (2) The present invention enhances the uniformity of the preform structure by increasing the proportion of mesh to >30%, reducing anisotropy, and improving the mechanical strength and thermal stability of the final product; wherein the mesh, as a thin layer material with disordered distribution of short-cut carbon fibers, enhances the mechanical strength when it is laminated and woven with carbon cloth: the high proportion of mesh (>30%) forms a three-dimensional mesh support between layers, improves the Z-direction fiber bonding force, and more effectively hooks the fibers during needle punching; pore control: the mesh fibers are randomly distributed to fill the gaps in the carbon cloth, reducing the proportion of large-sized pores, making the subsequent CVI and impregnation more uniform; thermal performance optimization: the disordered fiber network disperses thermal stress and reduces the risk of local overheating caused by whisker orientation;

[0033] (3) By selecting a specific resin type, the present invention balances processability and final performance (such as temperature resistance and residual carbon rate) to ensure the bonding strength between the preform and the coating; by multi-stage calcination and particle size distribution design, the graphitized coconut powder has both high conductivity and pore filling ability, thus optimizing the resistance uniformity of the heater; by precisely controlling the heating rate and heat preservation stage, the invention avoids bubbles and delamination defects caused by concentrated release of volatiles during resin curing; by using low-yield asphalt (<30%) to form a porous carbon structure, it provides channels for subsequent CVI secondary deposition and strengthens the interface bonding; the resulting carbon-carbon heater product is adapted to the ±1℃ temperature field accuracy requirements of the single crystal silicon crystal pulling process by controlling the resistance uniformity (<3% deviation) and the high emissivity coating (ε>0.9 after plasma spraying). Detailed Implementation

[0034] To enable those skilled in the art to better understand the technical solution, the present invention will be described in detail below with reference to embodiments. The description in this part is only exemplary and explanatory, and should not be used to limit the scope of protection of the present invention in any way.

[0035] The preparation process of graphitized coconut powder in the following embodiments is as follows: coconut powder is obtained by crushing, calcining, grinding, high temperature, screening and mixing. The calcination is carried out at 400℃ for 3 hours and 500℃ for 10 hours. The high temperature is carried out at 2400℃ for 10 hours.

[0036] Example 1:

[0037] A manufacturing process for a carbon-carbon heater includes the following steps:

[0038] S1, Precast body: carbon cloth (T700 grade) + mesh (35% by weight) + carbon rope woven precast body, each layer is coated with phenolic resin and graphitized coconut powder (mass ratio 1:1, particle size distribution 100 mesh 30%, 200 mesh 30%, 500 mesh 40%), needle punching density 20 needles / cm².

[0039] S2, Curing: Three-stage curing (60℃×3h→100℃×1h→180℃×4h, maximum pressure 0.8MPa).

[0040] S3, Chemical Vapor Infiltration Treatment: The cured preform is placed in a CVI furnace with a natural gas content of 15%, a furnace temperature of 1000℃ for 150 hours, a furnace pressure of 2000Pa, and the preform density reaches 1.0g / cm³.

[0041] S4, Interface layer formation: Impregnate mesophase bitumen (yield 25%, pressure 5MPa×10h), introduce natural gas during carbonization (50L / min×50h, 1000℃), then introduce a small amount of natural gas and nitrogen for 30h to form CVI-bitumen carbon interface layer.

[0042] S5, Impregnation: Asphalt is placed in a cylinder and heated to 150°C. Azodicarbonamide, a foaming agent, is added and the temperature is raised to 300°C. The mixture is stirred for 5 hours to obtain foamed asphalt. The precast body is then immersed in the foamed asphalt, filled with nitrogen, and held under pressure of 5 MPa for 8 hours.

[0043] S6, Carbonization: The preform treated in step S5 is kept at 1200℃ for 3 hours;

[0044] S7, Repeated impregnation and carbonization: Repeat steps S5 (impregnation) and S6 (carbonization) three times, with a high-temperature treatment interspersed in between. The temperature is 3000℃ and the time is 5h. The final product density is 1.8g / cm³.

[0045] S8, Finishing: The finished product is precision machined using a high-precision CNC lathe with a cutting speed of 190m / min, a feed rate of 0.06mm / rev, a depth of cut of 0.15mm, and a surface Ra=1.2μm.

[0046] S9, Coating: Plasma spraying of phenolic resin + 50% graphitized coconut powder, followed by treatment at 2500℃ for 10 hours; to obtain carbon-carbon heater product.

[0047] Example 2:

[0048] A manufacturing process for a carbon-carbon heater includes the following steps:

[0049] S1, Precast body: carbon cloth (T700 grade) + mesh (45% by weight) + carbon rope woven precast body, each layer is coated with furfuryl ketone resin and graphitized coconut powder (mass ratio 3:2, particle size distribution 100 mesh 10%, 200 mesh 40%, 500 mesh 50%), needle punching density 20 needles / cm².

[0050] S2, Curing: Three-stage curing (80℃×2h→120℃×0.5h→170℃×10h, maximum pressure 0.9MPa);

[0051] S3, Chemical Vapor Infiltration Treatment: The cured preform is placed in a CVI furnace with a natural gas content of 18%, a furnace temperature of 1200℃ for 80 hours, a furnace pressure of 1000Pa, and the preform density reaches 0.9g / cm³.

[0052] S4, Interface layer formation: Impregnate mesophase bitumen (yield 28%, pressure 8MPa×36h), introduce natural gas during carbonization (20L / min×100h, 800℃), then introduce a small amount of natural gas and nitrogen for 40h to form CVI-bitumen carbon interface layer.

[0053] S5, Impregnation: Asphalt is placed in a cylinder and heated to 120°C. Azodicarbonamide, a foaming agent, is added and the temperature is raised to 200°C. The mixture is stirred for 3 hours to obtain foamed asphalt. The precast body is then immersed in the foamed asphalt, filled with nitrogen, and held under pressure of 3 MPa for 10 hours.

[0054] S6, Carbonization: The preform treated in step S5 is kept at 1000℃ for 8 hours;

[0055] S7, Repeated impregnation and carbonization: Repeat steps S5 (impregnation) and S6 (carbonization) 4 times, with one high-temperature treatment in between, at a temperature of 2000℃ for 20 hours, and the final product density is 1.6 g / cm³.

[0056] S8, Finishing: The finished product is precision machined using a high-precision CNC lathe with a cutting speed of 200m / min, a feed rate of 0.08mm / rev, a depth of cut of 0.2mm, and a surface Ra=1.4μm.

[0057] S9, Coating: Plasma spraying of phenolic resin + 40% graphitized coconut powder, followed by treatment at 2000℃ for 35 hours; to obtain carbon-carbon heater product.

[0058] Example 3:

[0059] A manufacturing process for a carbon-carbon heater includes the following steps:

[0060] S1, Precast body: carbon cloth (T700 grade) + mesh (40% by weight) + carbon rope woven precast body, each layer is coated with epoxy resin and graphitized coconut powder (mass ratio 2:3, particle size distribution 100 mesh 25%, 200 mesh 40%, 500 mesh 35%), needle punching density 20 needles / cm².

[0061] S2, Curing: Three-stage curing (40℃×5h→80℃×1.5h→190℃×12h, maximum pressure 0.7MPa);

[0062] S3, Chemical Vapor Infiltration Treatment: The cured preform is placed in a CVI furnace with a natural gas content of 16%, a furnace temperature of 800℃ for 150 hours, a furnace pressure of 2000Pa, and the preform density reaches 1.0g / cm³.

[0063] S4, Interface layer formation: Impregnate mesophase bitumen (yield 25%, pressure 5MPa×10h), introduce natural gas during carbonization (50L / min×50h, 1000℃), then introduce a small amount of natural gas and nitrogen for 15h to form CVI-bitumen carbon interface layer.

[0064] S5, Impregnation: Asphalt is placed in a cylinder and heated to 200°C. Azodicarbonamide, a foaming agent, is added and the temperature is raised to 250°C. The mixture is stirred for 8 hours to obtain foamed asphalt. The precast body is then immersed in the foamed asphalt, filled with nitrogen, and held under pressure of 10 MPa for 6 hours.

[0065] S6, Carbonization: The preform treated in step S5 is kept at 800℃ for 10 hours;

[0066] S7, Repeated impregnation and carbonization: Repeat steps S5 (impregnation) and S6 (carbonization) 5 times, with one high-temperature treatment in between, at a temperature of 1800℃ for 60 hours, and the final product density is 1.5 g / cm³.

[0067] S8, Finishing: The finished product is precision machined using a high-precision CNC lathe with a cutting speed of 180m / min, a feed rate of 0.05mm / rev, a depth of cut of 0.1mm, and a surface Ra=1.6μm.

[0068] S9, Coating: Plasma spraying of phenolic resin + 60% graphitized coconut powder, followed by treatment at 1800℃ for 65 hours; to obtain carbon-carbon heater product.

[0069] Comparative Example 1:

[0070] The difference between this comparative example and Example 1 is that the preform is made of carbon cloth and carbon rope laminated together, without a mesh (the mesh accounts for 0%), and the rest is the same as Example 1.

[0071] Comparative Example 2:

[0072] The difference between this comparative example and Example 1 is that the foaming agent is omitted in step S5, and ordinary asphalt is directly impregnated (yield 45%) without high-pressure impregnation. The rest is the same as in Example 1.

[0073] Comparative Example 3:

[0074] The difference between this comparative example and Example 1 is that step S4 is omitted, and the S5 impregnation process is performed directly. The rest is the same as in Example 1.

[0075] A series of quality tests were conducted on the carbon-carbon heater products obtained in Examples 1-3 and Comparative Examples 1-3, including: density uniformity test: the overall density was determined using the water displacement method, and samples were taken along the preform cross-section for the surface layer (0-2mm), transition layer (2-5mm), and core layer (>5mm), and the density gradient deviation was calculated (Δρ= (ρmax-ρmin) / ρavg×100%); resistance uniformity test: 20 measurement points were selected at equal intervals on the heater surface, and the resistance value was measured using the four-probe method to calculate the resistance fluctuation rate; high-temperature oxidation resistance life test: the sample was placed in an air atmosphere at 1600℃, and a protective gas (nitrogen:argon=1:3) was introduced, and the time required for the oxidation weight loss rate to be >5% was recorded; thermal shock life test: the sample was heated from room temperature to 1500℃ (heating rate 200℃ / min), held for 5 minutes, and then water-quenched and cooled, and the cycle was repeated until visible cracks appeared; processing accuracy verification: the key dimension tolerances were checked using a coordinate measuring machine, and the Ra value was measured using a surface roughness meter. The test results are shown in the table below.

[0076] Table 1

[0077] It should be noted that, in this document, the terms "comprising," "including," and any other variations are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Specific examples have been used in this document to illustrate the principles and implementation methods of the present invention. These examples are merely for the purpose of helping to understand the method and core ideas of the present invention. The above descriptions are only preferred embodiments of the present invention. It should be pointed out that, due to the limitations of written expression and the objective existence of infinite specific structures, those skilled in the art can make several improvements, modifications, or variations without departing from the principles of the present invention, and can also combine the above technical features in an appropriate manner. These improvements, modifications, variations, or combinations, or the direct application of the concept and technical solution of the present invention to other situations without modification, should all be considered within the scope of protection of the present invention.

Claims

1. A manufacturing process for a carbon-carbon heater, characterized in that, Includes the following steps: S1, Preform Manufacturing: The preform is woven using carbon cloth, mesh and carbon rope. During the preform forming process, each layer is coated with resin and graphitized coconut powder. After weaving, the preform is needle-punched to obtain the preform. S2, Curing process: The preform undergoes a three-stage curing process; S3, Chemical Vapor Infiltration (CVI) Treatment: The cured preform is placed in a CVI furnace using natural gas and nitrogen as gas sources. The furnace temperature is controlled at 800-1200℃, the furnace pressure at 1000-3000Pa, and the reaction time at 50-300 hours. After the reaction is complete, the preform is removed, and its density is 0.7-1.2 g / cm³. 3 ; S4, CVI-asphalt carbon interface layer formation: The preform treated in step S3 is impregnated with low carbon yield asphalt, and then carbonized. During the carbonization process, natural gas is continuously introduced at a flow rate of 1-100 L / min for 2-100 h at a temperature of 800-1200 ℃. At 800-1200 ℃, a small amount of natural gas and nitrogen are introduced for 1-50 h to form the CVI-asphalt carbon interface layer. S5, Impregnation: Place the asphalt into a cylinder, heat it to 120-200℃, add foaming agent, continue to heat to 150-300℃, stir for 1-8 hours to obtain foamed asphalt, and then immerse the precast body treated in step S4 into the foamed asphalt, fill with nitrogen and keep it under pressure of 2-10MPa for 5-10 hours. S6, Carbonization: The preform treated in step S5 is kept at 800-1200℃ for 2-10 hours; S7, Repeated Impregnation and Carbonization: Repeat step S5 (impregnation) and S6 (carbonization) 2-5 times, interspersed with a high-temperature treatment at 1800-3000℃ for 5-80 hours. The final product density is 1.5-1.8 g / cm³. 3 ; S8, Finish turning: The finished product is finished using a high-precision CNC lathe with a cutting speed of 180-200m / min, a feed rate of 0.05-0.08mm / rev, a depth of cut of 0.1-0.2mm, to complete the final dimension machining, ensuring that the tolerance of key parts is ±0.02mm and the surface roughness Ra≤1.6μm; S9, Coating treatment: The finished product after step S8 is coated with a plasma spraying technology. The spraying solvent is resin and graphitized coconut powder. After spraying, it is treated at a high temperature of 1500-2500℃ for 5-80 hours to obtain the carbon-carbon heater product.

2. The manufacturing process of a carbon-carbon heater according to claim 1, characterized in that, The mesh tire accounts for more than 30% of the total weight.

3. The manufacturing process of a carbon-carbon heater according to claim 1, characterized in that, In steps S1 and S9, the resin is one or more of phenolic resin, furfuryl ketone resin, and epoxy resin.

4. The manufacturing process of a carbon-carbon heater according to claim 1, characterized in that, The preparation process of graphitized coconut powder in steps S1 and S9 is as follows: coconut powder is obtained by crushing, calcining, grinding, high temperature treatment, screening and mixing, with a particle size distribution of 100 mesh 10%-40%, 200 mesh 20%-40%, and 500 mesh 20%-50%. The calcination is carried out at 200-400℃ for 2-5 hours and at 500-800℃ for 5-10 hours. The high temperature treatment is carried out at 1800-2400℃ for 5-30 hours. The mass percentage of graphitized coconut powder is 30%-60%.

5. The manufacturing process of a carbon-carbon heater according to claim 1, characterized in that, The three-stage curing process in step S2 is as follows: heating from room temperature to 60°C and holding for 2-5 hours; heating from 60°C to 100°C at a rate of 20±5°C / hour; holding at 100°C for 1±0.5 hours; heating from 100°C to 180°C at a rate of 12±5°C / hour, taking 4-12 hours, with a maximum pressure Pmax≤1.0MPa; and finally holding at 180°C for 4±1 hours.

6. The manufacturing process of a carbon-carbon heater according to claim 1, characterized in that, In step S3, natural gas accounts for less than 20% of the total gas volume.

7. The manufacturing process of a carbon-carbon heater according to claim 1, characterized in that, In step S4, the yield of low-carbon asphalt is less than 30%, the impregnation pressure is 1-10 MPa, and the holding time is 2-50 h.

8. A carbon-carbon heater, characterized in that, It is prepared using the production process described in any one of claims 1-7.

9. The carbon-carbon heater according to claim 8, characterized in that, The heater has uniform resistance and heating properties, making it suitable for crystal pulling processes.

Images