Preparation method of carbon / carbon composite material containing SiC coating

Abstract

The invention belongs to the technical field of ceramic coatings, and particularly relates to a preparation method of a carbon / carbon composite material containing a SiC coating. The preparation method comprises the following steps: dispersing a SiC coating raw material in a solvent to prepare SiC coating slurry; the preparation method comprises the following steps: activating a carbon / carbon composite base material, dipping the carbon / carbon composite base material in SiC coating slurry, and carrying out primary high-temperature sintering at 1300-1600 DEG C to form a silicon carbide porous layer on the carbon / carbon composite base material; and carrying out secondary high-temperature sintering at 1800-2100 DEG C to form a compact silicon carbide porous layer, thereby obtaining the silicon carbide composite material. According to the preparation method, the mechanical property and the high-temperature resistance of the carbon / carbon composite material can be remarkably improved by selecting the raw materials of the SiC coating, controlling the proportion and optimizing the dipping and sintering process. The preparation method is simple, low in energy consumption, low in cost, short in time consumption, high in yield and easy for mass production, and has a good industrial application prospect.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic coatings, and in particular relates to a method for preparing a carbon / carbon composite material containing a SiC coating. Background Art

[0002] Carbon / carbon composite material is a lightweight thermal structural material due to its low thermal expansion coefficient (1-2×10 -6 / ℃), excellent thermal cycling resistance and high specific strength, and has potential for application in aerospace and re-entry vehicles. However, due to the poor oxidation resistance of carbon / carbon composite substrates in oxygen-containing and water vapor environments, their reusability and long-term thermal applications are limited.

[0003] Silicon-based ceramic coatings can protect carbon / carbon composite substrates from oxidation at high temperatures and in oxygen-containing environments. Among the numerous silicon-based ceramic coatings, SiC protective coatings are widely used due to their excellent physicochemical compatibility with carbon / carbon composite substrates and the formation of SiO2 on the surface when exposed to air at high temperatures. Furthermore, compared with other preparation methods such as chemical vapor reaction (CVR), plasma spraying, and chemical vapor deposition (CVD), the PC method can form a strong interface between the SiC coating and the carbon / carbon composite substrate based on chemical bonding. However, despite the aforementioned unique advantages of the PC method, the substrate material is directly embedded in the mixed powder in the PC method, and the substrate often has surface defects. Therefore, when the mixed powder is directly treated at high temperatures (1900–2100°C) for long periods of time (1–3 hours), the substrate carbon / carbon composite is susceptible to silicification reactions of free Si during the preparation of the SiC coating, resulting in a significant degradation of its mechanical properties and high-temperature resistance.

[0004] Therefore, there is an urgent need to propose a preparation method that can improve the mechanical properties and high temperature resistance of silicon-based ceramic coatings. Summary of the Invention

[0005] The present invention aims to address at least one of the technical problems existing in the aforementioned prior art. To this end, the present invention provides a method for preparing a carbon / carbon composite material containing a SiC coating. The SiC-coated carbon / carbon composite material prepared by the present invention can improve the mechanical properties and high-temperature resistance of the carbon / carbon composite material.

[0006] The invention provides a method for preparing a carbon / carbon composite material containing a SiC coating.

[0007] Specifically, a method for preparing a carbon / carbon composite material containing a SiC coating comprises the following steps:

[0008] The SiC coating raw material is dispersed in a solvent to prepare a SiC coating slurry; after activating a carbon / carbon composite substrate, the substrate is immersed in the SiC coating slurry and then subjected to a high-temperature sintering at 1300-1600°C to form a silicon carbide porous layer on the carbon / carbon composite substrate; after cooling, the substrate is subjected to a secondary high-temperature sintering at 1800-2100°C to form a dense silicon carbide porous layer, thereby preparing a carbon / carbon composite material containing a SiC coating;

[0009] Calculated by mass percentage, the SiC coating raw material includes: 5% to 20% amorphous carbon, 75% to 85% Si and 5% to 20% Al2O3.

[0010] In some embodiments of the present invention, the SiC coating raw material comprises, by mass percentage, 5% to 15% amorphous carbon, 75% to 85% Si, and 10% to 20% Al2O3; preferably, by mass percentage, the SiC coating raw material comprises, by mass percentage, 8% to 12% amorphous carbon, 78% to 82% Si, and 10% to 14% Al2O3.

[0011] In some embodiments of the present invention, the amorphous carbon includes any one of charcoal, activated carbon, carbon black, and coke; preferably, the amorphous carbon is activated carbon.

[0012] In some embodiments of the present invention, the solvent is ethanol and / or acetone; preferably ethanol.

[0013] In some embodiments of the present invention, the mass ratio of the SiC coating raw material to the solvent is 1:0.5-5; preferably, the mass ratio of the SiC coating raw material to the solvent is 1:1-3, such as 1:2.

[0014] In some embodiments of the present invention, the activation process is: activation at 100°C to 200°C for 5 to 15 hours, or activation at 700°C to 1000°C for 0.5 to 2 hours; preferably, the activation process is: activation at 120°C to 200°C for 8 to 12 hours, or activation at 800°C to 1000°C for 0.5 to 1.5 hours. Activation at 100°C to 200°C for 5 to 10 hours is mainly for surface modification and activation, which can effectively improve the wettability of the carbon / carbon composite substrate surface and enhance the adhesion (adhesion) between the carbon / carbon composite substrate and the SiC coating slurry. Activation at 700°C to 1000°C for 0.5 to 2 hours can significantly increase the specific surface area and porosity of the carbon / carbon composite substrate, increase its surface active sites, and improve the adsorption performance of the carbon / carbon composite substrate to the SiC coating slurry.

[0015] In some embodiments of the present invention, the carbon / carbon composite substrate is washed and dried before the activation step. Specifically, the washing step is performed using ethanol for 1 to 3 times, and the drying step is performed under vacuum at 50°C to 80°C for 8 to 12 hours.

[0016] In some embodiments of the present invention, the carbon / carbon composite substrate comprises at least one of a carbon material, a carbide material, and a chopped fiber reinforcement as its primary component; preferably, the carbon / carbon composite substrate comprises at least one of the following: a carbon material, a carbide material, and a chopped fiber reinforcement. The carbon material comprises carbon fiber and / or graphite; preferably, carbon fiber. The carbide material comprises pyrolyzed resin and / or semi-coke; preferably, pyrolyzed resin. The short fiber reinforcement comprises carbon fiber short fibers and / or silicon carbide particles; preferably, carbon fiber short fibers.

[0017] In some embodiments of the present invention, the impregnation process is: impregnating the carbon / carbon composite substrate under vacuum conditions for 0.5 to 2 hours.

[0018] In some embodiments of the present invention, the high-temperature sintering process is carried out under a protective atmosphere for 1 to 3 hours. Preferably, the protective atmosphere is N2 and / or Ar.

[0019] In some embodiments of the present invention, the secondary high-temperature sintering process is carried out under a protective atmosphere, and the time of the primary high-temperature sintering is 0.5 to 2 hours. Preferably, the protective atmosphere is N2 and / or Ar.

[0020] The present invention uses amorphous carbon, Si, and Al2O3 as raw materials for the SiC coating to produce a SiC coating slurry. The SiC coating is then prepared on the surface of a carbon / carbon composite substrate through two high-temperature sintering steps using a slurry impregnation reaction sintering method. In this preparation process, the carbon / carbon composite substrate and the SiC coating slurry undergo a first high-temperature sintering reaction at a relatively low temperature (1300-1600°C), preforming a nanostructured porous silicon carbide layer on the substrate surface. This porous silicon carbide layer can fill irregular, large cracks and pores in the C / C substrate, delaying further penetration of free silicon and protecting the C / C substrate from severe silicification. A second high-temperature sintering step is then performed at a high temperature (1900-2100°C). The nanostructured porous silicon carbide layer improves crystal nucleation efficiency, produces a grain refinement effect, and forms a dense silicon carbide coating.

[0021] The reaction principle is as follows:

[0022] In the initial stages of the reaction, Al2O3(s) + 3C(s) = 3CO(g) + 2Al(g) and Al2O3(s) + 3Si(s) = 3SiO(g) + 2Al(g), Al2O3 can be reduced by carbon and silicon to form gaseous CO and SiO. Then, according to the reaction equations SiO(s) + 2C(s) = SiC(s) + CO(g), CO(g) + 2Si(l) = SiC(s) + SiO(g), SiO(g) + 3CO(g) = SiC(s) + 2CO2(g), and Si(l) + C(s) = SiC(s), the resulting gaseous SiO reacts with carbon and CO to form SiC particles. As the temperature gradually increases, the SiC grains continue to grow in specific directions, forming a nanoporous layer. Finally, after a second high-temperature sintering step, the SiC porous layer's grains are refined, forming a dense SiC coating.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The present invention uses a slurry impregnation reaction sintering method to prepare a SiC coating on the surface of a carbon / carbon composite substrate. The carbon / carbon composite substrate is impregnated with a slurry of carbon, Si, and Al2O3. During a high-temperature sintering process, the carbon and Si react with Al2O3 to generate CO and SiO gases, respectively. The CO and SiO gases then react with the unreacted Si and C to in-situ generate SiC, thereby producing a SiC porous layer. A secondary high-temperature sintering process refines the grains of the SiC porous layer, forming a dense SiC porous layer. The present invention significantly improves the mechanical properties and high-temperature resistance of the carbon / carbon composite material by selecting the raw materials for the SiC coating, controlling the ratio, and optimizing the impregnation and sintering process.

[0025] (2) The preparation method provided by the present invention has a simple process, low energy consumption, low cost, short time consumption, high output, good economic benefits, easy mass production, and good industrial application prospects.

[0026] (3) The carbon / carbon composite material containing SiC coating prepared by the present invention has the characteristics of high yield, high oxidation resistance, high temperature resistance, etc., and can be widely used in the fields of radio frequency electrodes, brake pads and nuclear fission. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the XRD pattern of the SiC coating of the carbon / carbon composite material prepared in Example 4;

[0028] Figure 2 This is the FTIR graph of the SiC coating of the carbon / carbon composite material prepared in Example 4. DETAILED DESCRIPTION

[0029] In order to make the technical solution of the present invention more clearly understood by those skilled in the art, the following examples are given for illustration. It should be noted that the following examples do not limit the scope of protection claimed by the present invention.

[0030] Unless otherwise specified, the raw materials, reagents or devices used in the following examples and comparative examples can be obtained from conventional commercial sources or by existing known methods.

[0031] Example 1

[0032] A method for preparing a carbon / carbon composite material containing a SiC coating comprises the following steps:

[0033] S1: The carbon / carbon composite substrate was ultrasonically cleaned with ethanol three times, and dried in a drying oven at 80° C. for 12 h for later use.

[0034] S2: The cleaned and dried carbon / carbon composite substrate is placed in a box furnace and kept at 150° C. for 8 hours to activate it.

[0035] S3: Mix activated carbon powder, Si powder and Al2O3 powder in a mass percentage of 5wt%:75wt%:20wt%, add ethanol (the mass ratio of mixed powder to ethanol is 1:2) to the mixed powder (SiC coating raw material) to make it disperse evenly to form a SiC coating slurry.

[0036] S4: Place the activated carbon / carbon composite substrate in the SiC coating slurry and immerse it under vacuum for 1 hour.

[0037] S5: Coat an appropriate amount of mixed powder on the surface of the carbon / carbon composite substrate, place the sample in a graphite furnace, and under Ar gas protection, heat it up (heating rate of 5°C / min, the same below) to 1300°C, keep it warm for 1.5 hours, and wait for the graphite furnace to cool down (cooling rate of 5°C / min, the same below) to room temperature and take out the sample.

[0038] S6: Place the sample in a graphite furnace, and under Ar gas protection, heat it up (heating rate of 5°C / min, the same below) to 1800°C, keep it warm for 1 hour, wait for the graphite furnace to cool down (cooling rate of 5°C / min, the same below) to room temperature, and take out the sample to obtain a carbon / carbon composite material containing SiC coating.

[0039] Example 2

[0040] A method for preparing a carbon / carbon composite material containing a SiC coating comprises the following steps:

[0041] S1: The carbon / carbon composite substrate was ultrasonically cleaned with ethanol three times, and dried in a drying oven at 80° C. for 12 h for later use.

[0042] S2: The cleaned and dried carbon / carbon composite substrate is placed in a box furnace and kept at 900° C. for 1 hour to activate it.

[0043] S3: Mix activated carbon powder, Si powder and Al2O3 powder in a mass percentage of 10wt%:75wt%:15wt%, add ethanol (the mass ratio of mixed powder to ethanol is 1:2) to the mixed powder (SiC coating raw material) to make it disperse evenly to form a SiC coating slurry.

[0044] S4: Place the activated carbon / carbon composite substrate in the SiC coating slurry and immerse it under vacuum conditions for 1 hour.

[0045] S5: After coating an appropriate amount of mixed powder on the surface of the carbon / carbon composite substrate, the sample was placed in a graphite furnace. Under Ar gas protection, the temperature was raised to 1400°C and kept at this temperature for 1.5 hours. The sample was taken out after the graphite furnace cooled to room temperature.

[0046] S6: The sample is placed in a graphite furnace, and under Ar gas protection, the temperature is raised to 1900°C and kept at this temperature for 1 hour. After the graphite furnace is cooled to room temperature, the sample is taken out to obtain a carbon / carbon composite material containing a SiC coating.

[0047] Example 3

[0048] A method for preparing a carbon / carbon composite material containing a SiC coating comprises the following steps:

[0049] S1: The carbon / carbon composite substrate was ultrasonically cleaned with ethanol three times, and dried in a drying oven at 80° C. for 12 h for later use.

[0050] S2: The cleaned and dried carbon / carbon composite substrate is placed in a box furnace and kept at 150° C. for 12 hours to activate it.

[0051] S3: Mix activated carbon powder, Si powder and Al2O3 powder in a mass percentage of 15wt%:75wt%:10wt%, add ethanol (the mass ratio of mixed powder to ethanol is 1:2) to the mixed powder (SiC coating raw material) to make it disperse evenly to form a SiC coating slurry.

[0052] S4: Place the activated carbon / carbon composite substrate in the SiC coating slurry and immerse it under vacuum conditions for 1 hour.

[0053] S5: Coat an appropriate amount of mixed powder on the surface of the carbon / carbon composite substrate, place the sample in a graphite furnace, and heat it to 1500°C under Ar gas protection. Keep it warm for 1 hour, and take out the sample after the graphite furnace cools to room temperature.

[0054] S6: The sample is placed in a graphite furnace, and under Ar gas protection, the temperature is raised to 2100°C and kept at this temperature for 0.5 h. After the graphite furnace is cooled to room temperature, the sample is taken out to obtain a carbon / carbon composite material containing a SiC coating.

[0055] Example 4

[0056] A method for preparing a carbon / carbon composite material containing a SiC coating comprises the following steps:

[0057] S1: The carbon / carbon composite substrate was ultrasonically cleaned with ethanol three times, and dried in a drying oven at 80° C. for 12 h for later use.

[0058] S2: The cleaned and dried carbon / carbon composite substrate is placed in a box furnace and kept at 150° C. for 12 hours to activate it.

[0059] S3: Mix activated carbon powder, Si powder and Al2O3 powder in a mass ratio of 10wt%:80wt%:10wt%, add ethanol (the mass ratio of mixed powder to ethanol is 1:2) to the mixed powder (SiC coating raw material) to make it disperse evenly to form a SiC coating slurry.

[0060] S4: Place the activated carbon / carbon composite substrate in the SiC coating slurry and immerse it under vacuum conditions for 1 hour.

[0061] S5: Coat an appropriate amount of mixed powder on the surface of the carbon / carbon composite substrate, place the sample in a graphite furnace, and heat it to 1500°C under Ar gas protection. Keep it warm for 1 hour, and take out the sample after the graphite furnace cools to room temperature.

[0062] S6: The sample is placed in a graphite furnace, and under Ar gas protection, the temperature is raised to 1900°C and kept at this temperature for 1 hour. After the graphite furnace is cooled to room temperature, the sample is taken out to obtain a carbon / carbon composite material containing a SiC coating.

[0063] Figure 1 and Figure 2 The XRD patterns and FTIR patterns of the SiC coating of the carbon / carbon composite material prepared in Example 4 are shown respectively. Figure 1 and Figure 2 It can be seen that the XRD pattern shows obvious β-phase SiC and a clear C peak at the position of 2θ of 26.05, indicating that β-phase SiC is generated on the surface of the carbon / carbon composite substrate. The FTIR image shows that the β-phase SiC is generated at 522-980 cm -1 There is a strong Si-C tensile peak between them, which further indicates the formation of surface SiC.

[0064] Comparative Example 1

[0065] A method for preparing a carbon / carbon composite material containing a SiC coating comprises the following steps:

[0066] S1: The carbon / carbon composite substrate was ultrasonically cleaned with ethanol three times, and dried in a drying oven at 80° C. for 12 h for later use.

[0067] S2: The cleaned and dried carbon / carbon composite substrate is placed in a box furnace and kept at 150° C. for 12 hours to activate it.

[0068] S3: Mix activated carbon powder, Si powder and Al2O3 powder in a mass percentage of 25wt%:65wt%:15wt%, add ethanol (the mass ratio of mixed powder to ethanol is 1:2) to the mixed powder (SiC coating raw material) to make it disperse evenly to form a SiC coating slurry.

[0069] S4: Place the activated carbon / carbon composite substrate in the SiC coating slurry and immerse it under vacuum conditions for 1 hour.

[0070] S5: Coat an appropriate amount of mixed powder on the surface of the carbon / carbon composite substrate, place the sample in a graphite furnace, and heat it to 1500°C under Ar gas protection. Keep it warm for 1 hour, and take out the sample after the graphite furnace cools to room temperature.

[0071] S6: The sample is placed in a graphite furnace, and under Ar gas protection, the temperature is raised to 1900°C and kept at this temperature for 1 hour. After the graphite furnace is cooled to room temperature, the sample is taken out to obtain a carbon / carbon composite material containing a SiC coating.

[0072] Performance tests were performed on the samples prepared in Examples 1-4 and Comparative Example 1, and the test items included bulk density (tested with reference to GB / T 39862-2021), high temperature resistance and mechanical properties.

[0073] Among them, the high temperature resistance performance includes: (1) 1500℃, 50h, dry air mass loss (%): under dry air conditions, the sample is placed in a tube furnace, the temperature is set to 1500℃, dry air is introduced, and the mass loss of the sample is tested after treatment for 50h; (2) 1500℃, 10h, wet oxygen condition mass loss (%): under wet oxygen conditions, the sample is placed in a tube furnace, the temperature is set to 1500℃, and wet oxygen air is generated using a humidity generator, the flow rate is adjusted to 5L / min, the humidity is 20%, and the mass loss of the sample is tested after treatment for 10h.

[0074] The mechanical properties include hardness (GPa) and elastic modulus (GPa). The samples were subjected to three-point bending tests using an American CMT5304-30KN electronic universal testing machine.

[0075] The test results are shown in Table 1.

[0076] Table 1

[0077]

[0078]

[0079] By analyzing the data in Table 1 and comparing Examples 1, 3, and 4 with Comparative Example 1, it can be found that the performance of the prepared carbon / carbon composite material samples is related to the raw material ratio, temperature, and time. When the slurry composition increases with the increase of C and Si content, and the appropriate Al2O3 ratio, the hardness tester elastic modulus of the sample increases, and it can be seen that the increase in SiC conversion rate improves the mechanical properties of the material. As the sintering temperature increases, the mechanical properties of the sample increase accordingly. It can be seen that suitable high temperatures promote particle diffusion and densification, and improve density and mechanical properties. Too low a temperature will lead to insufficient densification, while too high a temperature may cause excessive grain growth. In addition, a suitable holding time helps the SiC layer to fully densify. Too short a time may lead to insufficient densification, while too long a time may cause excessive grain growth.

[0080] Analysis of Examples 1 and 2 shows that the activation method of the carbon / carbon composite substrate will also affect the performance of the carbon / carbon composite material containing the SiC coating. The carbon / carbon composite material prepared by activating the carbon / carbon composite substrate at 150°C for 8 hours in Example 1 has significantly better performance than the carbon / carbon composite material prepared by activating the carbon / carbon composite substrate at 900°C for 1 hour in Example 2. The carbon / carbon composite material prepared in Example 1 has a higher density, better high-temperature resistance and mechanical properties at high temperatures, indicating that the carbon / carbon composite material prepared by long-term activation at low temperature has lower mass loss, smaller porosity, smaller substrate defects, and stronger bonding ability between the SiC coating and the substrate.

[0081] The above-described embodiments merely illustrate several implementations of the present invention, and while their descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, all of which fall within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be determined by the appended claims.

Claims

1. A method for preparing a carbon / carbon composite material containing a SiC coating, characterized in that: The following steps are involved: The SiC coating raw material is dispersed in a solvent to prepare a SiC coating slurry; After activating the carbon / carbon composite substrate, the substrate is immersed in the SiC coating slurry, and then sintered at a high temperature of 1300-1600° C. to form a porous silicon carbide layer on the carbon / carbon composite substrate; After cooling, a secondary high-temperature sintering is performed at 1800-2100°C to form a dense silicon carbide porous layer, thereby obtaining a carbon / carbon composite material containing a SiC coating; Calculated by mass percentage, the SiC coating raw material includes: 5% to 20% amorphous carbon, 75% to 85% Si and 5% to 20% Al2O3.

2. The preparation method according to claim 1, characterized in that Calculated by mass percentage, the SiC coating raw material includes: 5% to 15% amorphous carbon, 75% to 85% Si and 10% to 20% Al2O3; preferably, calculated by mass percentage, the SiC coating raw material includes: 8% to 12% amorphous carbon, 78% to 82% Si and 10% to 14% Al2O3.

3. The preparation method according to claim 1 or 2, characterized in that The amorphous carbon includes any one of charcoal, activated carbon, carbon black, and coke.

4. The preparation method according to claim 1 or 2, characterized in that The solvent is ethanol and / or acetone.

5. The preparation method according to claim 4, characterized in that The mass ratio of the SiC coating raw material to the solvent is 1:0.5-5.

6. The preparation method according to claim 1 or 2, characterized in that The activation process is: activating at 100° C. to 200° C. for 5 to 15 hours.

7. The preparation method according to claim 1 or 2, characterized in that The activation process is: activating at 700° C. to 1000° C. for 0.5 to 2 hours.

8. The preparation method according to claim 1 or 2, characterized in that The main components of the carbon / carbon composite substrate include at least one of a carbon material, a carbide material, and a chopped fiber reinforcement.

9. The preparation method according to claim 1 or 2, characterized in that: The impregnation process is: impregnating the carbon / carbon composite substrate under vacuum conditions for 0.5 to 2 hours.

10. The preparation method according to claim 9, characterized in that The first high-temperature sintering process is carried out under a protective atmosphere, and the time of the first high-temperature sintering is 1 to 3 hours; the second high-temperature sintering process is carried out under a protective atmosphere, and the time of the first high-temperature sintering is 0.5 to 2 hours.

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