Carbon aerogel-pyrolytic carbon composite material and preparation method thereof

Abstract

The application discloses a carbon aerogel-pyrolytic carbon composite material and a preparation method thereof. The preparation method comprises the following steps: preparing carbon aerogel; placing the carbon aerogel into a deposition furnace, and introducing carbon source gas and carrier gas to perform chemical vapor deposition to obtain the carbon aerogel-pyrolytic carbon composite material. The carbon aerogel-pyrolytic carbon composite material preparation method provided by the application is stable and efficient, the required raw materials are simple to obtain and various in types, and the method has the advantages of low cost, simple process, high production efficiency, good controllability and cleanness. The prepared carbon aerogel-pyrolytic carbon composite material is a new carbon-carbon composite material, has the characteristics of controllable density, good mechanical property and high conductivity, and has excellent comprehensive performance, and has great application potential in the fields of ablation-resistant materials, thermal field materials and new energy materials.

Description

TECHNICAL FIELD

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

[0002] Carbon materials are considered as ideal high-temperature engineering structural materials due to their wide range of raw materials and high-temperature stability, including carbon / carbon (C / C) composite materials, carbon aerogel materials, pyrolytic carbon, carbon fibers, etc. Among them, carbon aerogel has significant advantages among many new high-efficiency thermal protection material options. Carbon aerogel has low density, high porosity, good electrical conductivity, and other characteristics, and has extremely high temperature resistance. In an oxygen-free environment, even if it is subjected to an ultra-high temperature of 2800℃, it can still maintain its mesoporous structure well, so that its thermal conductivity is still low at high temperatures. However, the carbon aerogel skeleton particle connection strength is low, brittle and easy to break, and has poor toughness, and in an oxygen-containing environment, it is easily oxidized at a temperature higher than 500℃, and is difficult to meet the extreme harsh environment of thermal / power / oxygen coupling in the service environment of hypersonic aircraft.

[0003] In recent years, carbon aerogel has become increasingly important in practical applications, but it is still a great challenge to prepare carbon aerogel-based materials with excellent formability and high mechanical strength. At present, the idea that is concerned is to use other reinforcing materials to improve the mechanical properties. The final form of carbon aerogel composite material can be roughly divided into block and flake, and the reinforcing materials that have been widely studied include graphene, carbon nanotubes, carbon microspheres, and other nanomaterials, as well as carbon foam, metal doping, and the introduction of ceramic phase. In addition, people have been exploring the use of lightweight and low-thermal-conductivity fibers as skeleton materials to prepare carbon aerogel composite materials with better mechanical strength. However, these methods still have problems such as high cost, long preparation period, and harsh experimental conditions, and further research or adjustment of new technical solutions is needed.

[0004] Pyrolytic carbon is a carbon material deposited on the surface of a hot substrate by dehydrogenation of gaseous hydrocarbons, which has high bending strength, low elastic modulus, good wear resistance and chemical inertness, and is particularly suitable for coating materials. Since its successful application in the atomic energy industry, it has been widely used in the fields of aviation, aerospace, medicine, electronics and machinery. Therefore, it is expected to improve the mechanical properties of carbon aerogel by introducing pyrolytic carbon through CVI, and to prepare a new carbon-carbon composite material. SUMMARY

[0005] In view of the poor mechanical properties of the existing carbon aerogel and the problems in the reinforcing method, the purpose of the present application is to provide a carbon aerogel-pyrolytic carbon composite material and a preparation method thereof. The preparation method uses carbon aerogel instead of traditional carbon fiber preform as raw material for chemical vapor infiltration (CVI) treatment.

[0006] To achieve the above object, the present application provides the following technical solutions.

[0007] The carbon aerogel-pyrolytic carbon composite material provided by the present application takes the microparticles in the carbon aerogel as the core, and generates the pyrolytic carbon by in-situ deposition of the carbon source gas and coats the microparticles.

[0008] Preferably, the density of the carbon aerogel-pyrolytic carbon composite material is 0.2 g / cm 3 ~ 1.8 g / cm 3 .

[0009] Preferably, the bending strength of the carbon aerogel-pyrolytic carbon composite material is 0.5 ~ 80 MPa, and the compressive strength is 0.3 ~ 136 MPa.

[0010] Preferably, the carbon aerogel is at least one of carbon black aerogel, resorcinol-formaldehyde-based carbon aerogel, phenol-furfural-based carbon aerogel, and cellulose-based aerogel; the density of the carbon aerogel is 0.01 g / cm 3 ~ 0.40 g / cm 3 .

[0011] Preferably, the carbon source gas is at least one of natural gas, propylene and propane.

[0012] The present application also provides a preparation method of the carbon aerogel-pyrolytic carbon composite material, comprising the following steps:

[0013] S1. Preparing a carbon aerogel;

[0014] S2. Placing the carbon aerogel obtained in S1 in a chemical vapor deposition furnace, introducing a carbon source gas and a carrier gas, and performing CVI treatment to obtain a carbon aerogel-pyrolytic carbon composite material.

[0015] Preferably, in step S1, the shape and size of the carbon aerogel can be processed according to different use requirements.

[0016] Specifically, in step S1, the shape of the carbon aerogel is at least one of circular, square, circular ring and irregular shape, and the size thereof meets the volume requirement of the deposition furnace.

[0017] Preferably, in step S2, the carrier gas is at least one of nitrogen and argon.

[0018] Preferably, in step S2, the process conditions of the CVI treatment are specifically as follows: the temperature is 950 ~ 1180℃, the pressure is 0.1 ~ 30 kPa, the volume ratio of the carbon source gas to the carrier gas is (1 ~ 3) : (1 ~ 2), and the treatment time is not less than 2 h.

[0019] Specifically, in step S2, the chemical vapor deposition furnace comprises a furnace body 2, a furnace cover 4, a gas inlet pipe 1, a heating body 3, a thermocouple 5, a tail gas flange 6, a carrier plate 8, a graphite cylinder 9, and a support plate 10; the support plate 10 is arranged at the bottom of the furnace body 2, the graphite cylinder 9 is arranged on the support plate 10, the carrier plate 8 is arranged on the graphite cylinder 9, the carrier plate 8 is provided with a gas passage hole, and a sample is arranged on the carrier plate 8; the gas inlet pipe 1 is located at the bottom of the furnace body 2 and penetrates through the support plate 10, and the tail gas flange 6 is located at the middle position of the furnace cover 4; the thermocouple 5 penetrates through the furnace cover 4, the temperature measuring end of the thermocouple 5 is located between the heating body 3 and the sample, the distance between the temperature measuring end of the thermocouple 5 and the sample is 0.1-3 cm, and the thermocouple 5 is used for monitoring the temperature of the reaction zone; the heating body 3 is used for regulating the temperature of the reaction zone; when the CVI treatment is performed, the carbon source gas and the carrier gas enter the region enclosed by the carrier plate 8, the graphite cylinder 9 and the support plate 10 through the gas inlet pipe 1, are fully mixed and cracked, then flow out from the gas passage hole to the vicinity of the sample, and penetrate into the interior of the carbon aerogel to continue the reaction to form the carbon aerogel-pyrolytic carbon composite material.

[0020] Principle of the present application:

[0021] The present application can improve the mechanical properties of the material without damaging the substrate. The method fills the internal voids of the material with pyrolytic carbon and improves the carbon aerogel skeleton structure, thereby densifying the carbon aerogel material while maintaining the original shape of the material. In addition, by adjusting the CVI process parameters to control the quality of the deposited pyrolytic carbon, the mechanical properties, electrical conductivity and thermal conductivity of the composite material can be balanced, and a new type of carbon-carbon composite material can be obtained.

[0022] Advantages of the present application:

[0023] 1. The carbon aerogel-pyrolytic carbon composite material disclosed by the present application is a new type of carbon-carbon composite material. By adjusting the chemical vapor infiltration process parameters to control the quality of the deposited pyrolytic carbon, the mechanical properties and other properties of the composite material can be balanced, and the material has good electrical conductivity and mechanical properties. It has great application potential in the fields of ablation-resistant materials, thermal field materials, and new energy materials.

[0024] 2. The preparation method of the carbon aerogel-pyrolytic carbon composite material provided by the present application is stable and efficient, the required raw materials are simple and diverse to obtain, and has the advantages of low cost, simple process, high production efficiency, good controllability, etc.

[0025] 3. The present application realizes in-situ deposition of pyrolytic carbon by chemical vapor infiltration of carbon source gas through the pores in the aerogel, improves the carbon aerogel skeleton structure, maintains the original shape of the material, and realizes near-net-shape forming.

[0026] 4、The application can process carbon aerogel materials of any shape and size according to the furnace space, and the preparation process is clean and pollution-free. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 The structure diagram of the chemical vapor deposition furnace in the application is shown in the figure, wherein 1 is an air inlet pipe, 2 is a furnace body, 3 is a heating body, 4 is a furnace cover, 5 is a thermocouple, 6 is a tail gas flange, 7 is a sample, 8 is a carrier plate, 9 is a graphite cylinder, and 10 is a support plate.

[0028] Figure 2 The flowchart of preparing the carbon aerogel-pyrolytic carbon composite material is shown in the figure.

[0029] Figure 3 The scanning electron microscope (SEM) image of the microstructure morphology of the carbon black aerogel in Example 1 is shown in the figure.

[0030] Figure 4 The SEM images of the carbon aerogel-pyrolytic carbon composite material with a density of 0.65 g / cm 3 prepared in Example 1 under different magnifications are shown in the figures.

[0031] Figure 5 The effect display figures of the carbon aerogel-pyrolytic carbon composite material with specific shapes (circular and square rings) in (a) Example 1 and (b) Example 4 are shown in the figures.

[0032] Figure 6 The curve figures of the bending mechanical property and the compression mechanical property test of the carbon aerogel-pyrolytic carbon composite material with different densities in Example 1 are shown in the figures. DETAILED DESCRIPTION

[0033] In order for those skilled in the art to better understand the technical solutions of the application, and to make the purpose, features and advantages of the application more clear, the application will be further described below in combination with specific examples.

[0034] The structure diagram of the chemical vapor deposition furnace used in the examples of the application is shown in the figure. Figure 1

[0035] The carbon black aerogels in Examples 1-3 are all prepared according to the preparation method disclosed in the patent CN115466528B, the resorcinol-formaldehyde-based carbon aerogel in Example 4 and the phenol-furfural-based carbon aerogel in Example 5 are both prepared by the existing atmospheric drying method, and the cellulose-based aerogel in Example 6 is prepared according to the existing conventional preparation method.

[0036] Example 1

[0037] First, a carbon black aerogel with a density of 0.15 g / cm 3 is prepared by a chemical vapor deposition method, and then it is processed into​ The circular blocks were placed on the carrier plate of the chemical vapor deposition furnace. The furnace temperature was set to rise to 980°C at a rate of <10°C / min and then held. At this time, a mixture of propylene (99.9% purity) and argon (99.9% purity) was introduced through the inlet pipe, with a volume ratio of propylene to argon of 2:1 and a total flow rate of 6 L / min. The chemical vapor infiltration process was carried out at a temperature of 980°C and a pressure of 2 kPa. After 2-15 hours of treatment, the furnace was shut down for cooling, and carbon aerogel-pyrolytic carbon composite materials of different densities were obtained. The heating and cooling processes in the furnace were carried out under an argon atmosphere, and the propylene charging time was the same as the CVI treatment time.

[0038] Figure 3 This is a structural morphology diagram of the carbon black aerogel used in Example 1. Figure 4 Images (a), (b), and (c) show the product obtained in Example 1 after CVI treatment for 5 hours, with a density of 0.65 g / cm³. 3 Scanning electron microscope images of carbon aerogel-pyrolytic carbon composites at different magnifications; Figure 5 In Example 1, (a) shows a sample with a density of 1.26 g / cm³ obtained after CVI treatment for 15 hours. 3 Morphological illustration of carbon aerogel-pyrolytic carbon composite material; Figure 6 In Example 1, (a) shows a sample with a density of 0.74 g / cm³ obtained after CVI treatment for 6 hours. 3 The bending mechanical properties of the carbon aerogel-pyrolytic carbon composite material are shown in Figure (b). Figure (c) shows the carbon aerogel-pyrolytic carbon composite material with a density of 0.85 g / cm³ obtained by CVI treatment for 8 hours in Example 1. 3 Figure showing the compressive mechanical properties of carbon aerogel-pyrolytic carbon composite material.

[0039] The obtained carbon aerogel-pyrolytic carbon composite material has a density of 0.21 g / cm³. 3 (Obtained from CVI treatment for 2 hours) ~1.26 g / cm³ 3 (Results obtained after 15 hours of CVI treatment) All products retain their overall shape. It is in the form of round lumps; its density was measured to be 0.74 g / cm³. 3 The flexural strength of the carbon aerogel-pyrolytic carbon composite material is approximately 4.1 MPa; the measured density is 0.85 g / cm³. 3 The compressive strength of the carbon aerogel-pyrolytic carbon composite material is approximately 7.4 MPa, its electrical conductivity at room temperature is approximately 3100 S / m, and its thermal conductivity is 1.85 W / (m·K).

[0040] Example 2

[0041] First, a sample with a density of 0.10 g / cm³ was prepared using chemical vapor deposition. 3Carbon black aerogel was processed into 80mm×80mm×10mm cubes and placed on a carrier plate in a chemical vapor deposition (CVI) furnace. The furnace temperature was raised to 1030℃ at a rate of <15℃ / min and then held. A mixture of propane (99.6% purity) and nitrogen (99.9% purity) was introduced through the inlet pipe at a volume ratio of 1:1 and a total flow rate of 4L / min. The CVI process was carried out at 1030℃ and 1.5kPa. After 20 hours of treatment, the furnace was shut down for cooling, yielding a carbon aerogel-pyrolytic carbon composite material. Both heating and cooling processes were conducted under a nitrogen atmosphere, and the propane charging time was the same as the CVI treatment time.

[0042] The obtained carbon aerogel-pyrolytic carbon composite material has a density of 1.55 g / cm³. 3 The overall shape remains a cube of 80mm×80mm×10mm; the flexural strength of the carbon aerogel-pyrolytic carbon composite material was measured to be approximately 54.1MPa, the compressive strength to be approximately 76MPa, the electrical conductivity at room temperature to be approximately 5300S / m, and the thermal conductivity to be 15.33W / (m·k).

[0043] Example 3

[0044] First, a sample with a density of 0.32 g / cm³ was prepared using chemical vapor deposition. 3 Carbon black aerogel was processed into cuboids of 150mm × 100mm × 10mm and placed on a carrier plate in a chemical vapor deposition (CVD) furnace. The furnace temperature was raised to 1180℃ at a rate of <10℃ / min and then held. A mixture of natural gas and argon (99.9% purity) was introduced through the inlet pipe at a volume ratio of 3:1 and a total flow rate of 8L / min. The CVD process was carried out at 1180℃ and 10kPa. After 100 hours of treatment, the furnace was shut down for cooling, yielding a carbon aerogel-pyrolytic carbon composite material. Both heating and cooling processes were conducted under an argon atmosphere, and the natural gas charging time was the same as the CVI treatment time.

[0045] The obtained carbon aerogel-pyrolytic carbon composite material has a density of 1.8 g / cm³. 3 The overall shape remains a cuboid with an outer contour of 150mm×100mm×10mm; the flexural strength of the carbon aerogel-pyrolytic carbon composite material was measured to be approximately 81MPa, the compressive strength to be approximately 136MPa, the electrical conductivity at room temperature to be approximately 6100S / m, and the thermal conductivity to be 19.15W / (m·k).

[0046] Example 4

[0047] First, a material with a density of 0.06 g / cm³ was prepared by atmospheric pressure drying. 3 Resorcinol-formaldehyde-based carbon aerogel was processed into a square ring with an outer contour of 60mm × 50mm × 15mm and an inner diameter of 30mm × 30mm × 15mm, and placed on a carrier plate in a chemical vapor deposition (CVD) furnace. The furnace temperature was raised to 1100℃ at a rate of <10℃ / min and then held. At this point, a mixture of propylene (99.9% purity) and nitrogen (99.9% purity) was introduced through the inlet pipe at a volume ratio of 2:3 and a total flow rate of 5L / min. The CVD process was carried out at 1100℃ and 1kPa. After 30 hours of treatment, the furnace was shut down for cooling, yielding a carbon aerogel-pyrolytic carbon composite material. Both the heating and cooling processes were conducted under a nitrogen atmosphere, and the propylene charging time was the same as the CVI treatment time.

[0048] Figure 5 (b) is a morphological illustration of the carbon aerogel-pyrolytic carbon composite material prepared in Example 4.

[0049] The obtained carbon aerogel-pyrolytic carbon composite material has a density of 1.35 g / cm³. 3 The overall shape remains a square ring with an outer contour of 60mm×50mm×15mm and an inner hole of 30mm×30mm×15mm. The flexural strength of this carbon aerogel-pyrolytic carbon composite material was measured to be approximately 40.9MPa, the compressive strength to be approximately 63MPa, the electrical conductivity at room temperature to be approximately 4000S / m, and the thermal conductivity to be approximately 13.0W / (m·k).

[0050] Example 5

[0051] First, a material with a density of 0.05 g / cm³ was prepared by atmospheric pressure drying. 3 The phenol-furfural-based carbon aerogel is then processed into... The circular blocks were placed on the carrier plate of the chemical vapor deposition furnace. The furnace temperature was set to rise to 950°C at a rate of <10°C / min and then held. At this time, a mixture of propylene (99.9% purity) and argon (99.9% purity) was introduced through the inlet pipe, with a volume ratio of propylene to argon of 1:1 and a total flow rate of 6 L / min. The chemical vapor infiltration process was carried out at a temperature of 950°C and a pressure of 5 kPa. After 80 hours of treatment, the furnace was shut down for cooling, yielding a carbon aerogel-pyrolytic carbon composite material. Both the heating and cooling processes in the furnace were carried out under an argon atmosphere, and the propylene charging time was the same as the CVI treatment time.

[0052] The obtained carbon aerogel-pyrolytic carbon composite material has a density of 1.41 g / cm³. 3 The overall shape remains unchanged. The carbon aerogel-pyrolytic carbon composite material is shaped like a round block. The measured flexural strength is about 65 MPa, the compressive strength is about 72 MPa, the electrical conductivity at room temperature is about 4800 S / m, and the thermal conductivity is 14.7 W / (m·K).

[0053] Example 6

[0054] First, a material with a density of 0.09 g / cm³ was prepared. 3 Cellulose-based aerogels were processed into 50mm×50mm×20mm cubes and placed on a carrier plate in a chemical vapor deposition (CVI) furnace. The furnace temperature was raised to 1150℃ at a rate of <15℃ / min and then held. A mixture of propylene (99.6% purity) and nitrogen (99.9% purity) was introduced through the inlet pipe at a volume ratio of 1:2 and a total flow rate of 5.4 L / min. The CVI process was carried out at 1150℃ and 10 kPa. After 50 hours of treatment, the furnace was shut down for cooling, yielding a carbon aerogel-pyrolytic carbon composite material. Both heating and cooling processes were conducted under a nitrogen atmosphere, and the propylene charging time was the same as the CVI treatment time.

[0055] The obtained carbon aerogel-pyrolytic carbon composite material has a density of 1.26 g / cm³. 3 The overall shape remains a 50mm×50mm×20mm cube; the flexural strength of this carbon aerogel-pyrolytic carbon composite material is measured to be approximately 59MPa, the compressive strength is approximately 64MPa, the electrical conductivity at room temperature is approximately 4300S / m, and the thermal conductivity is approximately 13.9W / (m·k).

[0056] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. It should be noted that, for those skilled in the art, any modifications, improvements, substitutions, and variations made to these embodiments without departing from the concept and principle of the present invention still fall within the protection scope of the present invention.

Claims

1. A carbon aerogel-pyrolytic carbon composite material, characterized in that, The composite material is formed by using microparticles in carbon aerogel as the core, generating pyrolytic carbon through in-situ deposition of carbon source gas, and then coating the microparticles. The density of the composite material is 0.2 g / cm³. 3 ~1.8 g / cm 3 The flexural strength is 0.5~80 MPa, and the compressive strength is 0.3~136 MPa; The carbon aerogel is at least one of carbon black aerogel, resorcinol-formaldehyde-based carbon aerogel, phenol-furfural-based carbon aerogel, and cellulose-based aerogel; the density of the carbon aerogel is 0.01 g / cm³. 3 ~0.40 g / cm 3 ; The carbon aerogel-pyrolytic carbon composite material is prepared by a method comprising the following steps: S1. Preparation of carbon aerogel; S2. The carbon aerogel obtained in S1 is placed in a chemical vapor deposition furnace, and carbon source gas and carrier gas are introduced to perform CVI treatment to obtain a carbon aerogel-pyrolytic carbon composite material. The specific process conditions for CVI treatment are as follows: temperature is 950~1180 ℃, pressure is 0.1~30 kPa, volume ratio of carbon source gas to carrier gas is (1~3):(1~2), and treatment time is not less than 2 h.

2. The carbon aerogel-pyrolytic carbon composite material according to claim 1, characterized in that, The carbon source gas is at least one of natural gas, propylene, and propane.

3. The carbon aerogel-pyrolytic carbon composite material according to claim 1, characterized in that, In step S2, the carbon aerogel is in the shape of at least one of circular, square, annular, and irregular shapes, and its size is sufficient to meet the volume requirements of the deposition furnace.

4. The carbon aerogel-pyrolytic carbon composite material according to claim 1, characterized in that, In step S2, the carrier gas is at least one of nitrogen and argon.

5. The carbon aerogel-pyrolytic carbon composite material according to claim 1, characterized in that, In step S2, the chemical vapor deposition furnace includes a furnace body (2), a furnace cover (4), an inlet pipe (1), a heating element (3), a thermocouple (5), an exhaust flange (6), a carrier plate (8), a graphite cylinder (9), and a support plate (10); wherein, the support plate (10) is located at the bottom of the furnace body (2), the graphite cylinder (9) is placed on the support plate (10), the carrier plate (8) is placed on the graphite cylinder (9), and the carrier plate (8) is provided with ventilation holes; the sample is placed on the carrier plate (8); the inlet pipe (1) is located at the bottom of the furnace body (2) and passes through the support plate (10), and the exhaust flange (6) is located at the furnace cover (4). The thermocouple (5) passes through the furnace cover (4). The temperature measuring end of the thermocouple (5) is located between the heating element (3) and the sample. The distance between the temperature measuring end of the thermocouple (5) and the sample is 0.1~3cm, which is used to monitor the temperature of the reaction zone. The heating element (3) is used to regulate the temperature of the reaction zone. When performing CVI treatment, the carbon source gas and the carrier gas enter the area formed by the carrier plate (8), graphite cylinder (9), and support plate (10) through the air inlet pipe (1) and mix and decompose. Then, they flow out from the vent hole to the vicinity of the sample and penetrate into the carbon aerogel to continue the reaction and form a carbon aerogel-pyrolytic carbon composite material.

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