A method for preparing a high carbon yield carbon / carbon composite brake disc

Abstract

The application discloses a preparation method of a high-carbon-yield carbon / carbon composite brake disc. A plurality of porous carbon materials in a circular ring shape are stacked to form a column and are arranged in the middle of a gas limiting cylinder, and then are arranged in a chemical vapor deposition furnace, and then the porous carbon materials are subjected to chemical vapor deposition densification to obtain a carbon / carbon composite material blank, and the carbon / carbon composite material blank is subjected to heat treatment and machining to obtain the carbon / carbon composite brake disc. The porous carbon materials are selected from carbon fiber preforms or carbon / carbon porous bodies. A gas limiting plate is arranged every 200-400 mm along the height direction of the column, and a gasket is arranged between any two adjacent porous carbon materials. The preparation method of the high-carbon-yield carbon / carbon composite brake disc provided by the application rationally arranges the gas limiting cylinder, the gasket, the inner ring gas limiting plate and the outer ring gas limiting plate, so that the gas flow channel is lengthened when chemical vapor deposition is performed, the carbon source gas is fully utilized, and the carbon yield of the carbon source gas is greatly improved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of carbon / carbon composite material preparation, and particularly relates to a preparation method of carbon / carbon composite material with high carbon yield. BACKGROUND

[0002] Carbon / carbon composite material has the characteristics of low density, high specific strength, excellent high-temperature mechanical properties, thermal properties (ablation resistance, thermal shock resistance), and excellent friction and wear properties, and has been widely used in aerospace, chemical industry, energy and biomedical fields as thermal protection, structural parts and brakes.

[0003] Carbon / carbon composite material is a composite material with carbon fiber fabric as reinforcing material and carbon as matrix. The carbon matrix is mainly obtained by densifying the carbon fiber fabric through chemical vapor deposition process (CVD). At present, the carbon source gas used in the chemical vapor deposition process is usually one or several of propylene, propane or natural gas. The carbon source gas is cracked into carbon under high temperature conditions, and fills the pores of the carbon fiber fabric to continuously densify the carbon fiber fabric to obtain carbon / carbon composite material. The densification rate of carbon / carbon composite material is closely related to the rate of carbon deposition by pyrolysis of carbon source gas, which is measured by the carbon yield index of carbon source gas.

[0004] The ratio of the mass of carbon deposited in the carbon fiber fabric to the total mass of carbon in the carbon source gas is the carbon yield. The carbon yield of the current carbon source gas is usually low: for example, the carbon yield of carbon source gas propylene is usually less than 40% (the carbon yield is different according to the density of the carbon fiber fabric before deposition); for example, the carbon yield of carbon source gas natural gas is usually less than 30% (the carbon yield is different according to the density of the carbon fiber fabric before deposition).

[0005] Low carbon yield restricts the potential of low-cost development of carbon / carbon composite material on the one hand; on the other hand, the residual carbon source gas in the carbon source gas that cannot be utilized is also high, that is, the carbon content in the tail gas is high, which will exacerbate the adverse effects on the environment (waste gas or carbon dioxide produced after incineration). Therefore, how to improve the carbon yield of carbon source gas in the preparation process of carbon / carbon composite material and ensure the quality of the product is a technical difficulty that needs to be broken through in the industry, and is also a key point for the low-cost development of carbon / carbon composite material. SUMMARY

[0006] In view of the low carbon yield of carbon source gas in the preparation process of carbon / carbon composite material, which leads to the difficulty in reducing the preparation cost of carbon / carbon composite material, and the excessive carbon content in the tail gas leading to environmental pollution, the purpose of the present application is to provide a preparation method of carbon / carbon composite material brake disc with high carbon yield. The process technology used in the method greatly improves the carbon yield of carbon source gas, the density of the prepared carbon / carbon composite material brake disc meets the requirements, the total chemical vapor deposition time is short, and the preparation cost of carbon / carbon composite material brake disc is low.

[0007] In order to achieve the above object, the present application adopts the following technical scheme:

[0008] The present application discloses a preparation method of a high-carbon-yield carbon / carbon composite brake disc. A plurality of porous carbon materials in the shape of a ring are stacked to form a column and are placed in the middle of a gas-limiting cylinder, and then are placed in a chemical vapor deposition furnace. The porous carbon materials are then subjected to chemical vapor deposition densification to obtain a carbon / carbon composite material blank. The carbon / carbon composite material blank is subjected to heat treatment and machining to obtain the carbon / carbon composite brake disc. The porous carbon materials are selected from carbon fiber preforms or carbon / carbon porous bodies.

[0009] A gas-limiting plate is arranged every 200-400 mm along the height direction of the column. M gas-limiting plates divide the column into M sub-columns. A gasket is arranged between any two adjacent porous carbon materials or between any two adjacent gas-limiting plates and porous carbon materials. The gas-limiting plates are divided into inner ring gas-limiting plates and outer ring gas-limiting plates. In the entire column, the inner ring gas-limiting plates and the outer ring gas-limiting plates are arranged alternately. When the gas inlet is located at the inner diameter of the column, the first gas-limiting plate at the bottom of the column is an inner ring gas-limiting plate. When the gas inlet is located at the outer diameter of the column, the first gas-limiting plate at the bottom of the column is an outer ring gas-limiting plate. The inner ring gas-limiting plate is in the shape of a circular plate and has a diameter consistent with the outer diameter of the porous carbon material. The outer ring gas-limiting plate is in the shape of a ring, has an inner diameter consistent with the inner diameter of the porous carbon material, and has an outer diameter consistent with the inner diameter of the gas-limiting cylinder. The bottom end of the gas-limiting cylinder is provided with a gas inlet, and the top is open. When the gas inlet is located at the inner diameter of the column, the carbon source gas flows from the inner diameter of the first sub-column to the outer diameter during chemical vapor deposition, then flows from the outer diameter of the second sub-column to the inner diameter, and then flows from the inner diameter of the third sub-column to the outer diameter, and so on, until finally flowing to the exhaust pipeline and being discharged. When the gas inlet is located at the outer diameter of the column, the carbon source gas flows from the outer diameter of the first sub-column to the inner diameter during chemical vapor deposition, then flows from the inner diameter of the second sub-column to the outer diameter, and then flows from the outer diameter of the third sub-column to the inner diameter, and so on, until finally flowing to the exhaust pipeline and being discharged.

[0010] The preparation method of the high-carbon-yield carbon / carbon composite brake disc provided by the present application uses the following tooling: a gas-limiting cylinder, a gasket, an inner ring gas-limiting plate, and an outer ring gas-limiting plate. The tooling is reasonably arranged to make the gas flow path longer during chemical vapor deposition, so that the carbon source gas is fully utilized, and the carbon yield of the carbon source gas is greatly improved.

[0011] In a preferred embodiment, the density of the carbon fiber preform is 0.4-0.8 g / cm 3 .

[0012] Preferably, the carbon fiber preform is first heat treated at a temperature of 1600-2000℃ for 1-3 hours under a pressure of less than 5000 Pa, and then subjected to chemical vapor deposition densification.

[0013] Preferably, the gas limiting cylinder, the gasket and the gas limiting plate are made of graphite or carbon / carbon composite material.

[0014] Preferably, the inner diameter of the gas limiting cylinder is 60-160 mm larger than the outer diameter of the carbon fiber preform. The inventors have found that, when the inner diameter of the gas limiting cylinder is controlled within the above range, the final carbon yield is the highest. If the inner diameter of the gas limiting cylinder is too small, the gas residence time is too small, which is not conducive to improving the carbon yield of the carbon source gas and is not conducive to the convenience of furnace loading operation. If the inner diameter of the gas limiting cylinder is too large, the residence time is too long, and carbon black may be produced after the carbon source gas is thermally cracked, which is not conducive to improving the carbon yield and the quality of the product.

[0015] Preferably, the thickness of the gas limiting plate is 4-8 mm.

[0016] Preferably, the thickness of the gasket is 2-4 mm. In the present application, a gasket is arranged between any two adjacent porous carbon materials in the column or between any two adjacent gas limiting plates and porous carbon materials to form a channel for the carbon source gas.

[0017] Preferably, the carbon source gas used in the chemical vapor deposition is at least one selected from propylene, propane and natural gas, preferably selected from propylene or a mixed gas of propane and natural gas.

[0018] In actual operation, if the carbon source gas used in the chemical vapor deposition is propylene, a carrier gas is further included, and the carrier gas is nitrogen.

[0019] Preferably, the temperature at the top of the column is 20-40℃ lower than the temperature at the bottom of the column during the chemical vapor deposition.

[0020] In actual operation, two temperature measuring thermocouples are arranged in the material column: one temperature measuring thermocouple is placed on the surface of the carbon fiber porous body at the bottom of the material column, and the other thermocouple is placed on the surface of the carbon fiber porous body at the top of the material column; the inventor finds that by setting the temperature difference, the temperature of the gas inlet in the furnace is high, and the temperature of the gas outlet is low. The relatively high temperature of the gas inlet in the furnace and the relatively low temperature of the gas outlet are conducive to the carbon source gas reaching the pyrolysis temperature as soon as it enters the furnace, and part of the pyrolyzed gas flows in the channel formed by the material column and deposits in the carbon fiber porous body. The carbon source gas that has not been pyrolyzed continues to flow along the channel formed by the tool design, and at the same time, it is pyrolyzed and deposited in the carbon fiber porous body through which it flows. The design of the temperature of the material column (high at the bottom and low at the top) can avoid excessive pyrolysis of the gas in the flow, which consumes the carbon source gas and leads to the inability to immediately deposit as densified carbon, thereby improving the carbon yield of the carbon source gas. In this way, high carbon yield and efficient deposition of the carbon source gas are achieved.

[0021] However, the temperature difference needs to be effectively controlled, and too small or too large temperature difference is not conducive to achieving high carbon yield deposition of the carbon source gas. Too small temperature difference or even negative temperature difference will lead to insufficient pyrolysis of the carbon source gas entering the furnace, resulting in low carbon yield; too large temperature difference will lead to excessive pyrolysis of the carbon source gas entering the furnace, which may react to form other organic matter, thereby adversely affecting the improvement of carbon yield.

[0022] Preferably, the temperature of the chemical vapor deposition is 950-1200℃, the pressure of the chemical vapor deposition is 800-5000Pa, the flow rate of the carbon source gas per kilogram of porous carbon material is 0.1-0.6 SL / Min, and the deposition time is 330-560h.

[0023] Further preferably, the chemical vapor deposition is divided into four stages: when the density of the porous carbon material is ≤0.8g / cm 3 , it is the first stage; in the first stage, based on the total weight of the porous carbon material to be loaded into the furnace, 0.46-0.60 SL / Min of carbon source gas is introduced per kilogram of porous carbon material, and the deposition time is 100-160h; when the density of the porous carbon material is >0.8g / cm 3 and ≤1.3g / cm 3 , it is the second stage; in the second stage, based on the total weight of the porous carbon material to be loaded into the furnace, 0.31-0.45 SL / Min of carbon source gas is introduced per kilogram of porous carbon material, and the deposition time is 90-150h; when the density of the porous carbon material is >1.3g / cm 3 and ≤1.65g / cm 3When it is the third stage, based on the total weight of the porous carbon material to be loaded into the furnace, 0.21-0.30 SL / Min of carbon source gas is introduced per kilogram of the porous carbon material, and the deposition time is 80-140 h, and when the density of the porous carbon material is >1.65 g / cm 3 When it is the fourth stage, based on the total weight of the porous carbon material to be loaded into the furnace, 0.10-0.20 SL / Min of carbon source gas is introduced per kilogram of the porous carbon material, and the deposition time is 60-110 h.

[0024] In actual operation, surface machining of the carbon fiber porous body is further included between the chemical vapor deposition stages, which is a technology well known in the industry and is used for the purpose of increasing the opening rate of the surface of the carbon / carbon porous body and is beneficial to the next deposition densification.

[0025] Further preferably, the position of any sub-column in the column is different in different chemical vapor deposition stages.

[0026] The inventor has found that the position of the sub-column in the column is different in different CVD deposition stages, which is beneficial to the consistency of the quality of the product. For example, CVD1 (the first stage) is located at the bottom of the sub-column, CVD2 is located at the lower position in the column, CVD3 is located at the upper position in the column, and CVD4 is located at the top position in the column.

[0027] Preferably, the temperature of the heat treatment of the carbon / carbon composite material is 1800-2200 ℃, and the time of the heat treatment is 1-3 h; during the heat treatment, the heating rate is controlled to be ≤200 ℃ / h, and the pressure in the furnace is controlled to be <1500 Pa.

[0028] After the final heat treatment, the carbon / carbon composite material is machined according to the drawing requirements to obtain a carbon / carbon composite material brake disc.

[0029] Beneficial effects

[0030] The present application makes the gas flow through the channel longer through the design of the tooling, which is beneficial to the full utilization of the carbon source gas and improves the carbon yield of the carbon source gas.

[0031] The present application controls the temperature difference between the upper and lower columns to make the carbon source gas fully pyrolyze, which is beneficial to improving the carbon yield of the carbon source gas, reducing the carbon content in the tail gas, and thus reducing the impact on the environment.

[0032] The present application designs different flow rates according to different densities of the carbon fiber porous body, which is beneficial to preparing high-density carbon / carbon composite materials.

[0033] The method for preparing the carbon / carbon composite material has high carbon yield, short cycle, and low cost. BRIEF DESCRIPTION OF DRAWINGS

[0034] Figure 1 Schematic diagram of loading of porous carbon material into a furnace.

[0035] Figure 2 Schematic diagram of outer ring gas limiting plate.

[0036] Figure 3 Schematic diagram of inner ring gas limiting plate. DETAILED DESCRIPTION

[0037] Example 1

[0038] The size of the carbon fiber preform used in this example is: an outer diameter of 400 mm, an inner diameter of 220 mm, a thickness of 28 mm, a quantity of 60, and a density of the carbon fiber preform of 0.55 g / cm 3 The carbon fiber preform is first subjected to heat treatment, the temperature of the heat treatment is 1800℃, the time of the heat treatment is 2h, and the pressure control of the whole process of the heat treatment is less than 3000Pa.

[0039] The tooling used includes a gas limiting cylinder, a gasket, and a gas limiting plate (outer ring gas limiting plate and inner ring gas limiting plate), and the material of the tooling is graphite, wherein the thickness of the gasket is 3mm; the bottom center of the gas limiting cylinder is provided with a gas inlet, the top is open, the inner diameter of the gas limiting cylinder is 500mm, the inner ring gas limiting plate is a circular plate, and the diameter is consistent with the outer diameter of the carbon fiber preform, the thickness of the inner ring gas limiting plate is 6mm, the outer ring gas limiting plate is a circular ring, the inner diameter is consistent with the inner diameter of the porous carbon material, the outer diameter is consistent with the inner diameter of the gas limiting cylinder, and the thickness of the outer ring gas limiting plate is 6mm.

[0040] Taking the gas inlet as the center, the carbon fiber preforms are first stacked one by one, and the gasket is placed between the carbon fiber preforms and the gas limiting plate and the carbon fiber preform to form a channel for the carbon source gas during the stacking process. During the loading process, a gas limiting plate is provided every about 300mm (specifically, every 10 preforms) along the height direction of the material column, a total of 6 gas limiting plates, because the gas inlet is located in the center of the material column, the first gas limiting plate is an inner ring gas limiting plate, the second gas limiting plate is an outer ring gas limiting plate, the third gas limiting plate is an inner ring gas limiting plate, and so on, the inner ring gas limiting plate and the outer ring gas limiting plate are alternately arranged until the preform is installed. Then the gas limiting cylinder is sleeved outside the material column and is concentric with the material column.

[0041] After the loading is completed, the material column is finally placed in a chemical vapor deposition furnace for chemical vapor deposition densification. During the chemical vapor deposition process, natural gas and propylene are used as carbon source gas, the carbon source gas is introduced into the furnace from the gas inlet in the center of the material column, flows from the inner diameter to the outer diameter of the first sub-material column, then flows from the outer diameter to the inner diameter of the second sub-material column, and then flows from the inner diameter to the outer diameter of the third sub-material column, and so on, and finally flows to the tail gas pipeline and is discharged.

[0042] In the chemical vapor deposition, the temperature of the column is controlled to be 1100-1130℃, i.e. the temperature of the top of the column is 30℃ lower than that of the bottom of the column. The chemical vapor deposition is divided into four stages. The flow rate of propylene in each stage is designed as follows: the flow rate of natural gas is 0.52 SL / Min, 0.38 SL / Min, 0.25 SL / Min and 0.15 SL / Min per kilogram of the preform or the carbon / carbon porous body, respectively. The volume ratio of the natural gas to the propylene is 9:1. The deposition pressure is about 3000 Pa. The time of the four stages is 150 h, 130 h, 110 h and 100 h, respectively. The loading position of each sub-column is different in the four chemical vapor deposition stages. The chemical vapor deposition stages and the stages in between also include surface machining, i.e. obtaining the carbon / carbon composite material blank. Finally, the carbon / carbon composite material blank is subjected to heat treatment. The temperature of the heat treatment is controlled to be 1900℃, and the time of the heat treatment is 2 h. In the heat treatment, the heating rate is controlled to be 150℃ / h, and the pressure in the furnace is controlled to be less than 1000 Pa.

[0043] The carbon / carbon composite material after the heat treatment is machined according to the drawing to obtain the carbon / carbon composite brake disc.

[0044] The carbon yield of the carbon source gas in the first stage of the chemical vapor deposition is calculated because the density of the preform is basically the same in the first stage. The density of the obtained carbon / carbon composite brake disc is tested disc by disc, and the average density is calculated. The microstructure of the deposited carbon is observed under a polarizing microscope, and the proportion of the smooth layer and the rough layer is calculated for each of the upper, middle and lower parts of the first stage of the chemical vapor deposition column. The test data are shown in Table 1.

[0045] Example 2

[0046] The preform (size, density and quantity), the tooling and the loading method are the same as in Example 1. The difference is the chemical vapor deposition process. The specific chemical vapor deposition process is as follows:

[0047] After the loading is completed, the column is finally placed in the chemical vapor deposition furnace for chemical vapor deposition densification. In the chemical vapor deposition process, propylene is used as the carbon source gas, and nitrogen is used as the carrier gas. The carbon source gas and the carrier gas are introduced into the furnace from the gas inlet at the center of the column, flow from the inner diameter to the outer diameter of the first sub-column, then flow from the outer diameter to the inner diameter of the second sub-column, and then flow from the inner diameter to the outer diameter of the third sub-column, and so on, and finally flow to the exhaust pipeline and be discharged.

[0048] Chemical vapor deposition, control the deposition temperature is 960 ~ 990 ℃, namely the temperature of the top of the column, the bottom of the column than the temperature of 30 ℃, chemical vapor deposition into four stages, each stage of propylene flow design: with each kilogram of preform or carbon / carbon porous body as a basis, the flow of carbon source gas is 0.52 SL / Min, 0.38 SL / Min, 0.24 SL / Min, 0.14 SL / Min, the volume ratio of propylene gas and the carrier gas is 1:1, the deposition pressure is about 1300 Pa, four stage time is 110 h, 100 h, 90 h, 70 h, and through the furnace control to make each sub column in the 4 chemical vapor deposition stage position is different, chemical vapor deposition stage and stage also includes surface machining, namely obtain carbon / carbon composite material blank, finally the carbon / carbon composite material blank is heat treated, control the heat treatment temperature is 2000 ℃, heat treatment time is 3 h; heat treatment, control the heating rate is 100 ℃ / h, control the furnace pressure is less than 1200 Pa.

[0049] The carbon / carbon composite material after heat treatment is processed according to the drawing, and a carbon / carbon composite brake disc is obtained.

[0050] The carbon yield is calculated by the same method as in Example 1, the density of the final carbon / carbon composite brake disc and the structure of the deposited carbon are tested, and the data results are shown in Table 1.

[0051] Example 3

[0052] The same size and density of the preform as in Example 1 is used, and the number of preforms is 63. The carbon fiber preform is first heat treated, the heat treatment temperature is 1650 ℃, and the heat treatment time is 1 h, and the whole process pressure control is less than 2000 Pa.

[0053] The tooling used includes a gas limiting cylinder, a gasket, a gas limiting plate (an outer ring gas limiting plate and an inner ring gas limiting plate), and the material of the tooling is graphite, wherein the thickness of the gasket is 2 mm; the bottom center of the gas limiting cylinder is provided with a gas inlet, and the top is open, the inner diameter of the gas limiting cylinder is 465 mm, the inner ring gas limiting plate is a circular plate, and the diameter is consistent with the outer diameter of the carbon fiber preform, the thickness of the inner ring gas limiting plate is 4 mm, the outer ring gas limiting plate is a circular ring, the inner diameter is consistent with the inner diameter of the porous carbon material, and the outer diameter is consistent with the inner diameter of the gas limiting cylinder, the thickness of the outer ring gas limiting plate is 4 mm.

[0054] With the gas inlet as the center, the carbon fiber preform is stacked layer by layer first, and the gasket is placed between the carbon fiber preforms during the stacking process, and the gas limiting plate is placed between the carbon fiber preforms to form the channel of the carbon source gas. During the furnace loading process, a gas limiting plate is arranged every about 210 mm (specifically, every 7 preforms) along the height direction of the material column, a total of 9 gas limiting plates. Since the gas inlet is located in the center of the material column, the first gas limiting plate is an inner ring gas limiting plate, the second gas limiting plate is an outer ring gas limiting plate, and the third gas limiting plate is an inner ring gas limiting plate. The inner ring gas limiting plate and the outer ring gas limiting plate are alternately arranged until the preform is installed. Then the gas limiting cylinder is sleeved outside the material column and is concentric with the material column.

[0055] After the completion of the furnace loading, the material column is finally placed in the chemical vapor deposition furnace for chemical vapor deposition densification. During the chemical vapor deposition process, natural gas and propylene are used as carbon source gas, which is introduced into the furnace from the gas inlet in the center of the material column, flows from the inner diameter to the outer diameter of the first sub-material column, then from the outer diameter to the inner diameter of the second sub-material column, and then from the inner diameter to the outer diameter of the third sub-material column, and so on, and finally flows to the tail gas pipeline and is discharged.

[0056] During the chemical vapor deposition, the deposition temperature is controlled to be 1020-1040°C, that is, the temperature at the top of the material column is 20°C lower than the temperature at the bottom of the material column. The chemical vapor deposition is divided into four stages, and the flow rate of propylene in each stage is designed as follows: based on per kilogram of preform or carbon / carbon porous body, the flow rate of natural gas introduced is 0.46 SL / Min, 0.31 SL / Min, 0.21 SL / Min and 0.10 SL / Min respectively, the volume ratio of natural gas introduced to propylene introduced is 9:1, the deposition pressure is about 2500 Pa, the time of the four stages is 160 h, 150 h, 130 h and 100 h respectively, and the furnace loading position of each sub-material column is different in the four chemical vapor deposition stages through furnace loading control. The chemical vapor deposition stage and the stage also include surface machining, that is, the carbon / carbon composite material blank is obtained, and finally the carbon / carbon composite material blank is heat treated, the heat treatment temperature is controlled to be 2150°C, and the heat treatment time is 1 h; during the heat treatment, the heating rate is controlled to be 190°C / h, and the furnace pressure is controlled to be less than 1400 Pa.

[0057] Then the heat-treated carbon / carbon composite material is processed according to the drawing to obtain the carbon / carbon composite material brake disc.

[0058] The carbon yield is calculated by the same method as in Example 1, and the density of the final carbon / carbon composite material brake disc and the structure test of the deposited carbon are tested, and the data results are shown in Table 1.

[0059] Example 4

[0060] The same size, density, and number of preforms as in Example 1 were used. The carbon fiber preforms were first heat treated at a temperature of 2000℃ for 3h, and the pressure was controlled to be less than 5000Pa throughout the heat treatment process.

[0061] The tooling used included a gas limiting cylinder, a gasket, and a gas limiting plate (an outer ring gas limiting plate and an inner ring gas limiting plate), and the material of the tooling was carbon / carbon composite material. The thickness of the gasket was 4mm. The bottom end of the gas limiting cylinder was provided with a gas inlet, and the top was open. The inner diameter of the gas limiting cylinder was 555mm. The inner ring gas limiting plate was a circular plate, and the diameter was consistent with the outer diameter of the carbon fiber preform. The thickness of the inner ring gas limiting plate was 8mm. The outer ring gas limiting plate was a circular ring, and the inner diameter was consistent with the inner diameter of the porous carbon material, and the outer diameter was consistent with the inner diameter of the gas limiting cylinder. The thickness of the outer ring gas limiting plate was 8mm.

[0062] The carbon fiber preforms were stacked one by one with the gas inlet as the center. During the stacking process, the gasket was placed between the carbon fiber preforms, and the gas limiting plate was placed between the carbon fiber preforms to form a channel for the carbon source gas. During the loading process, a gas limiting plate was provided every about 385mm (specifically, every 12 preforms) along the height direction of the material column, and a total of 5 gas limiting plates were provided. Since the gas inlet was located at the center of the material column, the first gas limiting plate was an inner ring gas limiting plate, the second gas limiting plate was an outer ring gas limiting plate, and the third gas limiting plate was an inner ring gas limiting plate. The inner ring gas limiting plate and the outer ring gas limiting plate were alternately arranged until the preforms were installed. Then, the gas limiting cylinder was sleeved outside the material column and was concentric with the material column.

[0063] After the loading was completed, the material column was finally placed in a chemical vapor deposition furnace for chemical vapor deposition densification. During the chemical vapor deposition process, natural gas and propylene were used as the carbon source gas, which was introduced into the furnace from the gas inlet at the center of the material column, flowed from the inner diameter to the outer diameter of the first sub-material column, then flowed from the outer diameter to the inner diameter of the second sub-material column, and then flowed from the inner diameter to the outer diameter of the third sub-material column, and so on, and finally flowed to the tail gas pipeline and was discharged.

[0064] The chemical vapor deposition is divided into four stages, and the flow rate of propylene in each stage is designed as follows: the flow rate of natural gas is 0.57 SL / Min, 0.42 SL / Min, 0.28 SL / Min and 0.18 SL / Min per kilogram of the preform or the carbon / carbon porous body, respectively, the volume ratio of the natural gas to the propylene is 9:1, the deposition pressure is about 4500 Pa, the time of the four stages is 150 h, 140 h, 120 h and 80 h, respectively, and the loading position of each sub-column is different in the four chemical vapor deposition stages through the loading control, the chemical vapor deposition stages and the stages therebetween further include surface machining, i.e., the carbon / carbon composite material blank is obtained, and finally the carbon / carbon composite material blank is subjected to heat treatment, the temperature of the heat treatment is controlled to be 1800℃, and the time of the heat treatment is controlled to be 3 h; during the heat treatment, the temperature rising rate is controlled to be 100℃ / h, and the pressure in the furnace is controlled to be less than 1500 Pa.

[0065] The carbon / carbon composite material after the heat treatment is further machined according to the drawing to obtain the carbon / carbon composite material brake disc.

[0066] The carbon yield, the density of the final carbon / carbon composite material brake disc and the structure of the deposited carbon are calculated by the same method as in Example 1, and the data results are shown in Table 1.

[0067] Example 5

[0068] The size of the carbon fiber preform used in this example is: the outer diameter is 400 mm, the inner diameter is 220 mm, the thickness is 28 mm, the number is 64 discs, and the density of the carbon fiber preform is 0.45 g / cm 3 The carbon fiber preform is first subjected to heat treatment, the temperature of the heat treatment is 1950℃, the time of the heat treatment is 2 h, and the pressure during the whole heat treatment process is controlled to be less than 4000 Pa.

[0069] The tooling used includes a gas limiting cylinder, a gasket, a gas limiting plate (an outer ring gas limiting plate and an inner ring gas limiting plate), and the material of the tooling is graphite, wherein the thickness of the gasket is 3 mm; the bottom center of the gas limiting cylinder is provided with a gas inlet, and the top is open, the inner diameter of the gas limiting cylinder is 490 mm, the inner ring gas limiting plate is a circular plate, and the diameter is consistent with the outer diameter of the carbon fiber preform, the thickness of the inner ring gas limiting plate is 4 mm, the outer ring gas limiting plate is a circular ring, the inner diameter is consistent with the inner diameter of the porous carbon material, the outer diameter is consistent with the inner diameter of the gas limiting cylinder, and the thickness of the outer ring gas limiting plate is 8 mm.

[0070] With the gas inlet as the center, the carbon fiber preform is stacked layer by layer first, and the gasket is placed between the carbon fiber preforms during the stacking process, and the gas limiting plate is placed between the carbon fiber preforms to form the channel of the carbon source gas. During the furnace loading process, a gas limiting plate is arranged every 240 mm (specifically, every 8 preforms) along the height direction of the material column, a total of 8 gas limiting plates. Because the gas inlet is located in the center of the material column, the first gas limiting plate is an inner ring gas limiting plate, the second gas limiting plate is an outer ring gas limiting plate, and the third gas limiting plate is an inner ring gas limiting plate. The inner ring gas limiting plate and the outer ring gas limiting plate are alternately arranged until the preform is installed. Then the gas limiting cylinder is sleeved outside the material column and is concentric with the material column.

[0071] After the furnace loading is completed, the material column is finally placed in the chemical vapor deposition furnace for chemical vapor deposition densification. During the chemical vapor deposition process, natural gas and propylene are used as carbon source gas, the carbon source gas is introduced into the furnace from the gas inlet in the center of the material column, flows from the inner diameter to the outer diameter of the first sub-material column, then from the outer diameter to the inner diameter of the second sub-material column, and then from the inner diameter to the outer diameter of the third sub-material column, and so on, and finally flows to the tail gas pipeline and is discharged.

[0072] During the chemical vapor deposition, the deposition temperature of the material column is controlled to be 1040-1075°C, that is, the temperature of the top of the material column is 35°C lower than the temperature of the bottom of the material column. The chemical vapor deposition is divided into four stages, and the flow rate of propylene in each stage is designed as follows: based on per kilogram of preform or carbon / carbon porous body, the flow rate of natural gas introduced is 0.49 SL / Min, 0.42 SL / Min, 0.23 SL / Min and 0.17 SL / Min respectively, the volume ratio of natural gas introduced to propylene introduced is 9:1, the deposition pressure is about 2000 Pa, the time of the four stages is 155 h, 100 h, 120 h and 70 h respectively, and the furnace loading position of each sub-material column is different in the four chemical vapor deposition stages through furnace loading control. The chemical vapor deposition stage and the stage also include surface machining, that is, a carbon / carbon composite material blank is obtained, and finally the carbon / carbon composite material blank is heat treated, the heat treatment temperature is controlled to be 1850°C, and the heat treatment time is 1 h. During the heat treatment, the temperature rising rate is controlled to be 180°C / h, and the furnace pressure is controlled to be less than 1200 Pa.

[0073] Then the heat-treated carbon / carbon composite material is processed according to the drawing to obtain a carbon / carbon composite material brake disc.

[0074] The same method as in Example 1 is used to calculate the statistical carbon yield, the density of the final carbon / carbon composite material brake disc, and the structure detection of the deposited carbon, and the data results are shown in Table 1.

[0075] Example 6

[0076] Other conditions are the same as example 1, except that: carbon fiber preform or carbon / carbon porous body is not adjusted with chemical vapor deposition of different stages of location, that is, carbon fiber preform or carbon / carbon porous body in the four stages of chemical vapor deposition, its position in the column fixed.

[0077] The carbon / carbon composite brake disc obtained is tested in the same way as example 1, and the data results are shown in table 1.

[0078] Comparative example 1

[0079] Other conditions are the same as example 1, except that: the gas flow path is extended without using the tooling (inner ring gas limiting plate, outer ring gas limiting plate) of the application. The test data of the carbon / carbon composite brake disc obtained are shown in table 1.

[0080] Comparative example 2

[0081] Other conditions are the same as example 2, except that: the gas flow path is extended without using the tooling (inner ring gas limiting plate, outer ring gas limiting plate) of the application. The test data of the carbon / carbon composite brake disc obtained are shown in table 1.

[0082] From table 1, it can be seen that, as propylene is used as carbon source gas for chemical vapor deposition (comparative example 2), the tooling of the application can improve the carbon yield of propylene, and is also beneficial to the consistency of the carbon / carbon composite structure. At the same time, it can be seen that: the carbon yield of propylene gas is significantly higher than that of natural gas system (the feature of propylene as gas source for chemical vapor deposition).

[0083] Comparative example 3

[0084] Other conditions are the same as example 1, except that: the temperature at the top of the column is 10℃ lower than the temperature at the lowest end of the column. The test data of the carbon / carbon composite brake disc obtained are shown in table 1.

[0085] Comparative example 4

[0086] Other conditions are the same as example 1, except that: the inner diameter of the gas limiting cylinder used is 600mm, which is 200mm larger than the outer diameter of the preform, exceeding the upper limit requirement of 160mm of the application. The test data of the carbon / carbon composite brake disc obtained are shown in table 1.

[0087] Comparative example 5

[0088] Other conditions are the same as example 1, except that: the flow rate in the four stages of chemical vapor deposition exceeds the required range, which is 0.65SL / Min, 0.50SL / Min, 0.15SL / Min, 0.08SL / Min respectively. The test data of the carbon / carbon composite brake disc obtained are shown in table 1.

[0089] From the data in Table 1, it can be seen that the flow rate is designed to be too large, even if the flow rate is reduced in the subsequent two stages, the carbon / carbon composite material obtained cannot achieve a high density.

[0090] Comparative Example 6

[0091] The other conditions are the same as in Example 1, except that the deposition time in the first stage of chemical vapor deposition is 80 h, the density of the porous carbon fiber body is less than 0.8 g / cm 3 and enters the second stage of chemical vapor deposition, and the second stage of chemical vapor deposition process parameters are used. The test data of the carbon / carbon composite brake disc obtained are shown in Table 1.

[0092] From the data in Table 1, it can be seen that although the carbon yield of the carbon source gas in the first stage is high, the final density of the carbon / carbon composite material obtained is low.

[0093] The carbon yield in the first stage of chemical vapor deposition in the above examples and comparative examples, the density data of the carbon / carbon composite brake disc obtained, and the test data of the deposition carbon microstructure are shown in Table 1 below.

[0094] Table 1 Test data of carbon / carbon composite brake disc

[0095]

[0096] The above is only a preferred embodiment of the present application, and does not limit the application in any way. Any modification, change, and equivalent structural transformation of the above embodiment according to the technical essence of the present application are still within the protection scope of the technical solution of the present application.

Claims

1. A method for preparing a high-carbon-yield carbon / carbon composite brake disc, characterized in that: A column of porous carbon material in the shape of a ring is stacked and placed in the middle of a gas-limiting cylinder. Then it is placed in a chemical vapor deposition furnace. The porous carbon material is then densified by chemical vapor deposition to obtain a carbon / carbon composite material blank. The carbon / carbon composite material blank is then heat-treated and machined to obtain a carbon / carbon composite material brake disc. The porous carbon material is selected from carbon fiber preforms or carbon / carbon porous bodies. A gas-limiting plate is installed every 200-400mm along the height of the material column, and M gas-limiting plates divide the material column into M sub-material columns. A gasket is installed between any two adjacent porous carbon materials in each material column, or between any two adjacent gas-limiting plates and porous carbon materials. The gas-limiting plates are divided into inner ring gas-limiting plates and outer ring gas-limiting plates, which are alternately installed throughout the material column. When the air inlet is located on the inner diameter of the material column, the first gas-limiting plate at the bottom of the material column is the inner ring gas-limiting plate; if the air inlet is located on the outer diameter of the material column, the first gas-limiting plate is the outer ring gas-limiting plate. The inner ring gas-limiting plate is circular, and its diameter is the same as the outer diameter of the porous carbon material. The outer ring gas-limiting plate is annular, and its inner diameter is the same as the outer diameter of the porous carbon material. The material has a uniform inner diameter and an outer diameter that matches the inner diameter of the gas limiting cylinder. The gas limiting cylinder has an air inlet at its bottom and an open top. When the air inlet is located within the inner diameter of the material column, during chemical vapor deposition, the carbon source gas enters through the air inlet and flows from the inner diameter of the first sub-column to the outer diameter, then from the outer diameter of the second sub-column to the inner diameter, and then from the inner diameter of the third sub-column to the outer diameter, repeating this cycle until it finally flows into the exhaust pipe and is discharged. When the air inlet is located within the outer diameter of the material column, during chemical vapor deposition, the carbon source gas enters through the air inlet and flows from the outer diameter of the first sub-column to the inner diameter, then from the inner diameter of the second sub-column to the outer diameter, and then from the outer diameter of the third sub-column to the inner diameter, repeating this cycle until it finally flows into the exhaust pipe and is discharged. During the chemical vapor deposition process, the carbon source gas is selected from at least one of propylene, propane, and natural gas. During the chemical vapor deposition process, the temperature at the top of the column is 20-40°C lower than the temperature at the bottom.

2. The method for preparing a high-carbon-yield carbon / carbon composite brake disc according to claim 1, characterized in that: The density of the carbon fiber preform is 0.4~0.8 g / cm³. 3 .

3. The method for preparing a high-carbon-yield carbon / carbon composite brake disc according to claim 1, characterized in that: The carbon fiber preform is first heat-treated and then densified by chemical vapor deposition. The heat treatment temperature is 1600~2000℃, the heat treatment time is 1~3 hours, and the heat treatment pressure is controlled <5000Pa.

4. The method for preparing a high-carbon-yield carbon / carbon composite brake disc according to claim 1, characterized in that: The gas-limiting cylinder, gasket, and gas-limiting plate are all made of graphite or carbon / carbon composite materials.

5. The method for preparing a high-carbon-yield carbon / carbon composite brake disc according to claim 1, characterized in that: The inner diameter of the air-limiting cylinder is 60-160 mm larger than the outer diameter of the carbon fiber preform. The thickness of the gas limiting plate is 4~8mm; The thickness of the gasket is 2~4mm.

6. The method for preparing a high-carbon-yield carbon / carbon composite brake disc according to claim 1, characterized in that: The chemical vapor deposition temperature is 950~1200℃, the chemical vapor deposition pressure is 800~5000Pa, the flow rate of carbon source gas introduced per kilogram of porous carbon material is 0.1~0.6SL / Min, and the chemical vapor deposition time is 330~560h.

7. The method for preparing a high-carbon-yield carbon / carbon composite brake disc according to claim 6, characterized in that: The chemical vapor deposition is divided into four stages, when the density of the porous carbon material is ≤0.8 g / cm³. 3 This is the first stage. In the first stage, based on the total weight of the porous carbon material to be loaded into the furnace, the carbon source gas is introduced at a rate of 0.46~0.60 SL / Min per kilogram of porous carbon material, and the deposition time is 100~160 hours. When the density of the porous carbon material is >0.8 g / cm³, 3 And ≤1.3g / cm 3 In the second stage, based on the total weight of the porous carbon material to be loaded into the furnace, carbon source gas is introduced at a rate of 0.31~0.45 SL / Min per kilogram of porous carbon material, with a deposition time of 90~150 hours. When the density of the porous carbon material is >1.3 g / cm³... 3 And ≤1.65 g / cm 3 In the third stage, based on the total weight of the porous carbon material to be loaded into the furnace, the carbon source gas is introduced at a rate of 0.21~0.30 SL / Min per kilogram of porous carbon material, with a deposition time of 80~140 hours. When the density of the porous carbon material is >1.65 g / cm³... 3 In the fourth stage, based on the total weight of the porous carbon material to be installed in the furnace, carbon source gas is introduced at a rate of 0.10~0.20 SL / Min per kilogram of porous carbon material, and the deposition time is 60~110h.

8. The method for preparing a high-carbon-yield carbon / carbon composite brake disc according to claim 7, characterized in that: The position of any sub-particle in the column varies at different stages of chemical vapor deposition.

9. The method for preparing a high-carbon-yield carbon / carbon composite brake disc according to claim 1, characterized in that: The heat treatment temperature for carbon / carbon composite billets is 1800~2200℃, and the heat treatment time is 1~3h. During heat treatment, the heating rate is controlled to be ≤200℃ / h, and the furnace pressure is controlled to be <1500Pa.

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