CN114716268B - Preparation of Glass-MoSi on surface of carbon/carbon composite material 2 @Y 2 O 3 Method for preparing-SiC oxidation-resistant coating - Google Patents

Abstract

The invention discloses a method for preparing Glass-MoSi on the surface of a carbon/carbon composite material ₂ @Y ₂ O ₃ -a method of oxidation resistant coating of SiC comprising the steps of: step one, moSi preparation ₂ @Y ₂ O ₃ Microcapsules; step two, preparing a carbon/carbon composite material with a SiC inner coating on the surface; step three, preparing MoSi by using self-produced water thermoelectric deposition equipment ₂ @Y ₂ O ₃ An outer coating of core-shell structure; step four, preparing glass powder; step five, mixing the glass powder prepared in the step four with molybdenum disilicide according to the mass ratio of (4-8) to 1, diluting the mixture into slightly flowing slurry by using absolute ethyl alcohol, brushing the slurry on the surface of the sample by using a brush, and then preserving the temperature of the sample for 2-6 min at 1400 ℃ in an argon atmosphere to finally obtain compactThe high-temperature oxidation resistant coating; the method forms compact Glass-MoSi on the surface of the carbon/carbon composite material ₂ @Y ₂ O ₃ -SiC oxidation resistant coating.

Description

Preparation of Glass-MoSi2@Y2O3-SiC anti-oxidation coating on the surface of carbon/carbon composites method

technical field

The invention belongs to the technical field of C/C composite materials, and relates to a method for preparing a high-temperature anti-oxidation coating of a C/C composite material, in particular to a glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating prepared on the surface of a carbon/carbon composite material layer method.

Background technique

C/C composite material is a new ultra-high temperature structural material. It not only has the advantages of low density, high specific strength, low linear expansion coefficient, strong thermal and electrical conductivity, corrosion resistance, and high friction coefficient, but also has a series of excellent high temperature properties. Performance, such as thermal shock resistance, good thermal stability, and ablation resistance. Therefore, it is widely used in aerospace field. However, C/C composites will be severely oxidized in an oxidizing environment exceeding 500 °C, which severely limits its application in high-temperature fields. At present, there are two methods for the oxidation resistance of C/C composites, namely: internal matrix modification technology to improve the oxidation resistance of carbon fiber and matrix carbon by adding modification inhibitors (such as borate, phosphate) and External anti-oxidation coating technology to isolate oxygen-containing gas from contact with the substrate [Yang Xin, Huang Qizhong, Su Zhean, Chang Xin. Research progress in high temperature anti-oxidation protection of C/C composites[J]. Aerospace Materials Technology, 2014, 4( 01): 1-15.]. However, anti-oxidation coating technology has great potential for future applications.

The melting point of MoSi ₂ is as high as 2030 ℃. It has good self-healing ability at high temperature and can be used stably at 1600 ℃. It is a good candidate material for high-temperature protective coatings. However, it has a large brittleness below 1000 ℃ and insufficient high-temperature strength. In particular, the low creep resistance limits its application as a high-temperature structural material. Therefore, we coated the surface of MoSi ₂ with a layer of Y ₂ O ₃ to weaken its brittleness at medium and low temperatures, forming a MoSi ₂ /Y ₂ O ₃ core-shell microcapsule. Chen et al prepared 0.5 wt% Y ₂ O ₃ -MoSi ₂ /SiC composite material by pressureless sintering method. Due to the reduction of sintering activation energy and grain refinement, the composite structure is dense and uniform, and its mechanical properties and 1200 ℃ high temperature resistance Oxidation properties have been improved to varying degrees[F.Chen, JG Xu, JH Yan, SW Tang, Effects of Y ₂ O ₃ on SiC/MoSi ₂ composite by mechanical-assistant combustion synthesis, Int. J. Refract Metal Hard Mater.36 (2013) 143-148.]. Wang et al. prepared MoSi ₂ -Y ₂ O ₃ composite coatings by supersonic atmospheric plasma spraying method, which has a dense microstructure, good adhesion on the SiC transition layer, and no obvious defects at the interface, so that it can be used at 1500 Effectively improve the oxidation resistance of composite coatings at ℃[Wang Chang-Cong, Li Ke-Zhi, He Dan-Yang, et al. Oxidation behavior and mechanism of MoSi ₂ -Y ₂ O ₃ composite coating fabricated by supersonic atmospheric plasma spraying. 2020 , 506(C).]. The direct synthesis of self-healing MoSi ₂ /Y ₂ O ₃ core-shell microcapsules has not been reported yet. The synthesized microcapsules have excellent anti-oxidation properties, so they have broad application prospects.

Contents of the invention

In view of the deficiencies in the existing technology, the purpose of the present invention is to provide a method for preparing Glass-MoSi2@Y2O3-SiC anti-oxidation coating on the surface of carbon/carbon composite material, which can form a dense coating on the surface of C/C composite material , and can self-repair and self-heal anti-oxidation coating and thermal shock resistance in high temperature environment.

In order to achieve the above object, the present invention adopts the following technical solutions to achieve:

A method for preparing a Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating on the surface of a carbon/carbon composite material, comprising the following steps:

Step 1. Preparation of MoSi ₂ @Y ₂ O ₃ core-shell microcapsules:

1) Add MoSi ₂ powder into the Erlenmeyer flask, then mix isopropanol and absolute ethanol into the Erlenmeyer flask for ultrasonic vibration to obtain a suspension A with a MoSi ₂ mass concentration of 10-20g/L;

The volume ratio of isopropanol to absolute ethanol is (0~4):1;

2) Add yttrium nitrate, urea and polyethylene glycol 4000 to suspension A, stir to disperse evenly, and obtain suspension B;

Wherein the molar ratio of yttrium nitrate to urea is 1: (1~8); the mass concentration of yttrium nitrate is 20~40g/L; the mass concentration of polyethylene glycol 4000 is 0.01~0.04g/mL;

3) Put the obtained suspension B into a hydrothermal kettle, heat and stir at 80~150°C for 2~5h, then centrifuge and wash the obtained product to obtain product C;

4) After drying the product C separated in step 3), put it into a tube furnace and keep it warm at 500-800°C for 2-3 hours under an argon atmosphere to obtain the final product D, which is MoSi ₂ @Y ₂ O ₃ microcapsules;

Step 2, preparing the SiC inner coating of the carbon/carbon composite material sample:

Embedding the carbon/carbon composite material in the mixed powder in the graphite crucible, so that the mixed powder completely covers the carbon/carbon composite material;

The batching of described mixed powder comprises the silicon powder of 40～60 parts, the graphite powder of 20～40 parts and the aluminum oxide powder of 5～20 parts in parts by mass;

Put the graphite crucible into the reaction furnace, vacuum the reaction furnace and then pass in argon gas, so that the reaction furnace is heated from room temperature to 1900~2200 °C at a rate of 5~20 °C/min under the protection of argon gas and kept for 1 ~4 hours, then turn off the power supply, and the reaction furnace is naturally cooled to room temperature to obtain a carbon/carbon composite material with a SiC inner coating on the surface;

Step 3. Prepare the intermediate coating of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules of carbon/carbon composites using self-made hydrothermal electrodeposition equipment:

MoSi ₂ @Y ₂ O ₃ suspension configuration: Add self-made MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsule powder into isopropanol solution to make the mass concentration: 10~40g/L, magnetically stir 12h;

Then add iodine so that the mass concentration of iodine is 0~3g/L, magnetically stir for 30min, then ultrasonically shake for 30min, and finally magnetically stir for 24h to obtain MoSi ₂ @Y ₂ O ₃ suspension;

The MoSi ₂ @Y ₂ O ₃ suspension was placed in the self-made hydrothermal electrodeposition equipment, and the carbon/carbon composite material containing the SiC inner coating prepared in step 2 was used as the negative electrode. The deposition voltage was 10~30V, and the hydrothermal temperature was 80 Under the condition of ~160℃, hydrothermal electrodeposition was carried out for 20~60min; the deposition was repeated 3-5 times to realize the uniform deposition of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules on the surface of carbon/carbon composite material containing SiC inner coating;

Step 4. Preparation of glass powder:

Mix 50-75% of silicon dioxide, 15-30% of boron oxide and 5-20% of alumina powder according to the mass percentage, ball mill and sieve, and then calcined at 1000-1500°C for 2-5 hours, and then Glass powder is obtained after ball milling and sieving;

Step 5, preparing the glass outer coating of the carbon/carbon composite material sample:

Mix the glass powder prepared in step 4 with molybdenum disilicide powder in a mass ratio of (4~8): 1, then dilute it with absolute ethanol to form a slightly flowing slurry, and then use a brush to paint it in step 3. MoSi ₂ @Y ₂ O ₃ -SiC-carbon/carbon composite material surface, and then keep it at 1400℃ for 2~6min under argon atmosphere, and finally get dense Glass-MoSi ₂ @Y ₂ O ₃ -SiC C/C High temperature oxidation resistant coating for composite materials.

Preferably, the ultrasonic oscillation in the step 1 is to place the suspension in a 200-300W ultrasonic generator and vibrate for 30-60 minutes.

Preferably, the stirring in the step 1 is stirring with a magnetic stirrer for 1~3h.

Preferably, the washing in step 1 is to wash with distilled water and absolute ethanol for 2 to 5 times respectively.

Preferably, the drying in step 1 is drying in an oven at 60-80°C for 1-3 hours.

Compared with the prior art, the present invention has the following technical effects:

The present invention synthesizes and prepares MoSi ₂ @Y ₂ O ₃ microcapsules through the solvothermal method-solid-state sintering method, which is applied on the surface of C/C composite materials, has good compatibility with the matrix, and is used to relieve ceramic coatings. The problem of easy cracking caused by thermal mismatch can improve the oxidation resistance of carbon/carbon composite materials; MoSi ₂ is oxidized to SiO ₂ at high temperature, and SiO ₂ reacts with Y ₂ O ₃ to form yttrium silicate whiskers. The toughening of the whiskers can prevent further cracking of the coating; at the same time, it also increases the viscosity of SiO ₂ glass, thereby reducing the diffusion rate of oxygen and playing a self-healing effect. Glass-MoSi ₂ @Y ₂ prepared by this method The O ₃ -SiC composite coating has a dense surface, no cracks, and no holes, which can effectively prevent oxygen from penetrating into the carbon oxide/carbon matrix; it can form a dense coating on the surface of the C/C composite material. Capable of self-repair and self-healing, with strong anti-oxidation and thermal shock resistance;

The preparation process of the invention is simple, the conditions are easy to control, the production cost is low, and the industrial production is easy.

Description of drawings

Fig. 1 is the surface XRD spectrum of the Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating prepared by the method of the present invention;

Fig. 2 is the SEM picture of MoSi ₂ @Y ₂ O ₃ microcapsules prepared by the method of the present invention;

Figure 3 is a SEM image of the surface morphology of the Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating prepared by the method of the present invention;

Figure 4 is the static oxidation curve of the Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating sample prepared by the method of the present invention in air at 1773 K;

Detailed ways

The specific content of the present invention will be further explained in detail below in conjunction with the examples.

Example 1:

Step 1. Preparation of MoSi ₂ @Y ₂ O ₃ core-shell microcapsules:

1) Add 1 g of MoSi ₂ powder into the conical flask, then mix 50mL of isopropanol and absolute ethanol into the conical flask, put the suspension into a 300W ultrasonic generator and shake for 30min to obtain the mass concentration of MoSi ₂ Suspension A of 20g/L;

The volume ratio of isopropanol and absolute ethanol is 4:1;

2) Add 1.375g of yttrium nitrate, 2.4g of urea and polyethylene glycol 4000 to the suspension A, stir with a magnetic stirrer for 2 hours to make it evenly dispersed, and obtain the suspension B;

Wherein the yttrium nitrate and urea molar ratio is 1:8; The mass concentration of yttrium nitrate is 27.5g/L; The mass concentration of polyethylene glycol 4000 is 0.025g/mL;

3) Put the obtained suspension B into a hydrothermal kettle, heat and stir at 120°C for 3 hours, then centrifuge the obtained product and wash it with distilled water and absolute ethanol for 5 times respectively to obtain product C;

4) Dry the product C separated in step 3) in an oven at 60°C for 3 hours, and then put it into a tube furnace at 800°C for 2 hours under an argon atmosphere to obtain the final product D, which is MoSi ₂ @Y ₂ O ₃ microcapsules ;

Step 2, preparing the SiC inner coating of the carbon/carbon composite material sample:

Embedding the carbon/carbon composite material in the mixed powder in the graphite crucible, so that the mixed powder completely covers the carbon/carbon composite material;

The batching of described mixed powder comprises the silicon powder of 60 parts, the graphite powder of 30 parts and the aluminum oxide powder of 10 parts in parts by mass;

Put the graphite crucible into the reaction furnace, vacuum the reaction furnace and then pass in argon gas, so that the reaction furnace is heated from room temperature to 2200 °C at a rate of 10 °C/min under the protection of argon gas and kept for 2 hours, and then closed Power supply, the reaction furnace is naturally cooled to room temperature, and a carbon/carbon composite material with a SiC inner coating on the surface is obtained;

Step 3. Prepare the intermediate coating of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules of carbon/carbon composites using self-made hydrothermal electrodeposition equipment:

MoSi ₂ @Y ₂ O ₃ suspension configuration: add self-made MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsule powder into isopropanol solution to make the mass concentration: 30g/L, magnetically stir for 12h;

Then add iodine to make the mass concentration 2g/L, magnetically stir for 30min, then ultrasonically oscillate for 30min, and finally magnetically stir for 24h to obtain MoSi ₂ @Y ₂ O ₃ suspension;

The MoSi ₂ @Y ₂ O ₃ suspension was placed in the preparation of self-made hydrothermal electrodeposition equipment, and the carbon/carbon composite material containing the SiC inner coating prepared in step 2 was used as the negative electrode. The deposition voltage was 25V and the hydrothermal temperature was 100°C. 40min under hydrothermal electrodeposition; repeat the deposition 3 times to realize the uniform deposition of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules on the surface of carbon/carbon composite material with SiC inner coating;

Step 4. Preparation of glass powder:

Mix 65% silicon dioxide, 20% boron oxide and 15% alumina powder by mass percentage, ball mill and sieve, then calcinate at 1300°C for 3 hours, and then ball mill and sieve to obtain glass powder;

Step 5, preparing the glass outer coating of the carbon/carbon composite material sample:

Mix the glass powder prepared in step 4 with molybdenum disilicide powder at a mass ratio of 4:1, then dilute with absolute ethanol to form a slightly flowing slurry, and then use a brush to paint the MoSi ₂ @ prepared in step 3 The surface of the Y ₂ O ₃ -SiC-carbon/carbon composite material, and then kept at 1400°C for 4 minutes under an argon atmosphere, and finally a dense Glass-MoSi ₂ @Y ₂ O ₃ -SiC C/C composite high-temperature anti-oxidation coating was obtained. Floor.

Example 2:

Step 1. Preparation of MoSi ₂ @Y ₂ O ₃ core-shell microcapsules:

1) Add 0.5g of MoSi ₂ powder into the conical flask, then mix 50mL of isopropanol and absolute ethanol into the conical flask, put the suspension in a 200W ultrasonic generator and shake for 60min, and get the mass concentration of MoSi ₂ as Suspension A of 10g/L;

The volume ratio of isopropanol and absolute ethanol is 2:1;

2) Add yttrium nitrate, urea and polyethylene glycol 4000 to the suspension A, stir with a magnetic stirrer for 3 hours to disperse evenly, and obtain the suspension B;

Wherein the yttrium nitrate and urea molar ratio is 1:6; The mass concentration of yttrium nitrate is 20g/L; The mass concentration of polyethylene glycol 4000 is 0.01g/mL;

3) Put the obtained suspension B into a hydrothermal kettle, heat and stir at 80°C for 5 hours, then centrifuge the obtained product and wash with distilled water and absolute ethanol three times respectively to obtain product C;

4) Dry the product C separated in step 3) in an oven at 80°C for 1h, then put it into a tube furnace and keep it warm at 600°C for 2.5h under an argon atmosphere to obtain the final product D, which is MoSi ₂ @Y ₂ O ₃ microcapsules ;

Step 2, preparing the SiC inner coating of the carbon/carbon composite material sample:

Embedding the carbon/carbon composite material in the mixed powder in the graphite crucible, so that the mixed powder completely covers the carbon/carbon composite material;

The batching of described mixed powder comprises the silicon powder of 40 parts, the graphite powder of 20 parts and the aluminum oxide powder of 5 parts in parts by mass;

Put the graphite crucible into the reaction furnace, vacuum the reaction furnace and then pass in argon gas, so that the reaction furnace is heated from room temperature to 1900 °C at a rate of 20 °C/min under the protection of argon gas and kept for 4 hours, and then closed Power supply, the reaction furnace is naturally cooled to room temperature, and a carbon/carbon composite material with a SiC inner coating on the surface is obtained;

Step 3. Prepare the intermediate coating of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules of carbon/carbon composites using self-made hydrothermal electrodeposition equipment:

MoSi ₂ @Y ₂ O ₃ suspension configuration: add self-made MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsule powder into isopropanol solution to make the mass concentration: 10g/L, magnetically stir for 12h;

Then add iodine to make the mass concentration 3g/L, magnetically stir for 30min, then ultrasonically oscillate for 30min, and finally magnetically stir for 24h to obtain MoSi ₂ @Y ₂ O ₃ suspension;

Put the MoSi ₂ @Y ₂ O ₃ suspension in the preparation of self-made hydrothermal electrodeposition equipment, and use the carbon/carbon composite material containing SiC inner coating prepared in step 2 as the negative electrode, under the conditions of deposition voltage 30V and hydrothermal temperature 80°C The hydrothermal electrodeposition was carried out for 60 minutes; the deposition was repeated 5 times to realize the uniform deposition of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules on the surface of the carbon/carbon composite material containing the SiC inner coating;

Step 4. Preparation of glass powder:

Mix 75% silicon dioxide, 15% boron oxide and 10% alumina powder by mass percentage, ball mill and sieve, then calcinate at 1000°C for 5 hours, and then ball mill and sieve to obtain glass powder;

Step 5, preparing the glass outer coating of the carbon/carbon composite material sample:

Mix the glass powder prepared in step 4 with molybdenum disilicide powder at a mass ratio of 8:1, then dilute it with absolute ethanol to form a slightly flowing slurry, and then use a brush to paint the MoSi ₂ @ prepared in step 3 The surface of the Y ₂ O ₃ -SiC-carbon/carbon composite material, and then kept at 1400°C for 2 minutes under an argon atmosphere, and finally a dense Glass-MoSi ₂ @Y ₂ O ₃ -SiC C/C composite high-temperature anti-oxidation coating was obtained. Floor.

Example 3:

Step 1. Preparation of MoSi ₂ @Y ₂ O ₃ core-shell microcapsules:

1) Add 0.75g of MoSi ₂ powder into the conical flask, then mix 50mL of absolute ethanol and pour it into the conical flask, put the suspension in a 250W ultrasonic generator and shake for 50min to obtain a MoSi ₂ mass concentration of 15g/L Suspension A;

2) Add yttrium nitrate, urea and polyethylene glycol 4000 to the suspension A, stir with a magnetic stirrer for 1 hour to disperse evenly, and obtain the suspension B;

Wherein the yttrium nitrate and urea molar ratio is 1:4:1; The mass concentration of yttrium nitrate is 40g/L; The mass concentration of polyethylene glycol 4000 is 0.04g/mL;

3) Put the obtained suspension B into a hydrothermal kettle, heat and stir at 150°C for 2 hours, then centrifuge the obtained product and wash it 4 times with distilled water and absolute ethanol respectively to obtain product C;

4) The product C separated in step 3) was dried in an oven at 70°C for 2 hours, then put into a tube furnace and kept at 500°C for 3 hours under an argon atmosphere to obtain the final product D, which was MoSi ₂ @Y ₂ O ₃ microcapsules;

Step 2, preparing the SiC inner coating of the carbon/carbon composite material sample:

Embedding the carbon/carbon composite material in the mixed powder in the graphite crucible, so that the mixed powder completely covers the carbon/carbon composite material;

The batching of described mixed powder comprises the silicon powder of 50 parts, the graphite powder of 40 parts and the aluminum oxide powder of 20 parts in parts by mass;

Put the graphite crucible into the reaction furnace, vacuum the reaction furnace and then pass in argon gas, so that the reaction furnace is heated from room temperature to 2000 °C at a rate of 5 °C/min under the protection of argon and kept for 1 hour, and then closed Power supply, the reaction furnace is naturally cooled to room temperature, and a carbon/carbon composite material with a SiC inner coating on the surface is obtained;

Step 3. Prepare the intermediate coating of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules of carbon/carbon composites using self-made hydrothermal electrodeposition equipment:

MoSi ₂ @Y ₂ O ₃ suspension configuration: Add self-made MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsule powder into isopropanol solution to make the mass concentration: 40g/L, magnetically stir for 12h;

Then add iodine to make the mass concentration 1g/L, magnetically stir for 30min, then ultrasonically shake for 30min, and finally magnetically stir for 24h to obtain MoSi ₂ @Y ₂ O ₃ suspension;

Put the MoSi ₂ @Y ₂ O ₃ suspension in the preparation of self-made hydrothermal electrodeposition equipment, and use the carbon/carbon composite material containing SiC inner coating prepared in step 2 as the negative electrode, under the conditions of deposition voltage 10V and hydrothermal temperature 160°C 20 min under hydrothermal electrodeposition; repeat the deposition 4 times to realize the uniform deposition of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules on the surface of the carbon/carbon composite material with SiC inner coating;

Step 4. Preparation of glass powder:

Mix 50% silicon dioxide, 30% boron oxide and 20% alumina powder by mass percentage, ball mill and sieve, then calcinate at 1500°C for 2 hours, and then ball mill and sieve to obtain glass powder;

Step 5, preparing the glass outer coating of the carbon/carbon composite material sample:

Mix the glass powder prepared in step 4 with molybdenum disilicide powder at a mass ratio of 6:1, then dilute with absolute ethanol to form a slightly flowing slurry, and then use a brush to paint the MoSi ₂ @ prepared in step 3 The surface of the Y ₂ O ₃ -SiC-carbon/carbon composite material, and then held at 1400°C for 6 minutes under an argon atmosphere, and finally a dense Glass-MoSi ₂ @Y ₂ O ₃ -SiC C/C composite high-temperature anti-oxidation coating Floor.

Example 4:

Step 1. Preparation of MoSi ₂ @Y ₂ O ₃ core-shell microcapsules:

1) Add MoSi ₂ powder into the conical flask, then mix isopropanol and absolute ethanol into the conical flask, put the suspension in a 250W ultrasonic generator and shake for 50min to obtain MoSi ₂ with a mass concentration of 18g/ Suspension A of L;

The volume ratio of isopropanol and absolute ethanol is 3:1;

2) Add yttrium nitrate, urea and polyethylene glycol 4000 to the suspension A, stir with a magnetic stirrer for 3 hours to disperse evenly, and obtain the suspension B;

Wherein the molar ratio of yttrium nitrate to urea is 1:2; the mass concentration of yttrium nitrate is 25g/L; the mass concentration of polyethylene glycol 4000 is 0.03g/mL;

3) Put the obtained suspension B into a hydrothermal kettle, heat and stir at 100°C for 3 hours, then centrifuge the obtained product and wash it with distilled water and absolute ethanol for 5 times respectively to obtain product C;

4) Dry the product C separated in step 3) in an oven at 70°C for 2 hours, then put it into a tube furnace and keep it at 700°C for 2.5 hours under an argon atmosphere to obtain the final product D, which is MoSi ₂ @Y ₂ O ₃ microcapsules ;

Step 2, preparing the SiC inner coating of the carbon/carbon composite material sample:

Embedding the carbon/carbon composite material in the mixed powder in the graphite crucible, so that the mixed powder completely covers the carbon/carbon composite material;

The batching of described mixed powder comprises the silicon powder of 55 parts, the graphite powder of 30 parts and the aluminum oxide powder of 15 parts in parts by mass;

Put the graphite crucible into the reaction furnace, vacuum the reaction furnace and then pass in argon gas, so that the reaction furnace is heated from room temperature to 2000 °C at a rate of 15 °C/min under the protection of argon gas and kept for 3 hours, and then closed Power supply, the reaction furnace is naturally cooled to room temperature, and a carbon/carbon composite material with a SiC inner coating on the surface is obtained;

Step 3. Prepare the intermediate coating of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules of carbon/carbon composites using self-made hydrothermal electrodeposition equipment:

MoSi ₂ @Y ₂ O ₃ suspension configuration: Add self-made MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsule powder into isopropanol solution to make the mass concentration: 25g/L, magnetically stir for 12h, Then ultrasonically oscillate for 30 minutes, and finally magnetically stir for 24 hours to obtain the MoSi ₂ @Y ₂ O ₃ suspension;

The MoSi ₂ @Y ₂ O ₃ suspension was placed in the preparation of self-made hydrothermal electrodeposition equipment, and the carbon/carbon composite material containing the SiC inner coating prepared in step 2 was used as the negative electrode. The deposition voltage was 30V and the hydrothermal temperature was 800°C. The hydrothermal electrodeposition was carried out for 50 minutes; the deposition was repeated 3 times to realize the uniform deposition of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules on the surface of the carbon/carbon composite material containing the SiC inner coating;

Step 4. Preparation of glass powder:

Mix 70% silica, 20% boria and 10% alumina powder by mass percentage, ball mill and sieve, then calcinate at 1300°C for 2.5h, and then ball mill and sieve to obtain glass powder ;

Step 5, preparing the glass outer coating of the carbon/carbon composite material sample:

Mix the glass powder prepared in step 4 with molybdenum disilicide powder at a mass ratio of 5:1, then dilute it with absolute ethanol to form a slightly flowing slurry, and then use a brush to paint the MoSi ₂ @Y prepared in step 3 ₂ O ₃ -SiC-carbon/carbon composite surface, and then hold it at 1400°C for 4 minutes under an argon atmosphere, and finally obtain a dense Glass-MoSi ₂ @Y ₂ O ₃ -SiC C/C composite high-temperature anti-oxidation coating .

Example 5:

1) Add 0.75g of MoSi ₂ powder into the conical flask, then mix 50mL of absolute ethanol and pour it into the conical flask, put the suspension in a 250W ultrasonic generator and shake for 50min to obtain a MoSi ₂ mass concentration of 15g/L Suspension A;

The volume ratio of isopropanol and absolute ethanol is 2:1;

2) Add yttrium nitrate, urea and polyethylene glycol 4000 to the suspension A, stir with a magnetic stirrer for 1 hour to disperse evenly, and obtain the suspension B;

Wherein the yttrium nitrate and urea molar ratio is 1:1; The mass concentration of yttrium nitrate is 30g/L; The mass concentration of polyethylene glycol 4000 is 0.015g/mL;

3) Put the obtained suspension B into a hydrothermal kettle, heat and stir at 120°C for 3 hours, then centrifuge the obtained product and wash twice with distilled water and absolute ethanol respectively to obtain product C;

4) The product C separated in step 3) was dried in an oven at 70°C for 2 hours, then put into a tube furnace and kept at 600°C for 3 hours under an argon atmosphere to obtain the final product D, which was MoSi ₂ @Y ₂ O ₃ microcapsules;

Step 2, preparing the SiC inner coating of the carbon/carbon composite material sample:

Embedding the carbon/carbon composite material in the mixed powder in the graphite crucible, so that the mixed powder completely covers the carbon/carbon composite material;

The batching of described mixed powder comprises the silicon powder of 60 parts, the graphite powder of 2～40 parts and the aluminum oxide powder of 10 parts in mass parts;

Put the graphite crucible into the reaction furnace, vacuum the reaction furnace and then pass in argon gas, so that the reaction furnace is heated from room temperature to 2200 °C at a rate of 5 °C/min under the protection of argon gas and kept for 4 hours, and then closed Power supply, the reaction furnace is naturally cooled to room temperature, and a carbon/carbon composite material with a SiC inner coating on the surface is obtained;

Step 3. Prepare the intermediate coating of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules of carbon/carbon composites using self-made hydrothermal electrodeposition equipment:

MoSi ₂ @Y ₂ O ₃ suspension configuration: add self-made MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsule powder into isopropanol solution to make the mass concentration: 30g/L, magnetically stir for 12h;

Then add iodine to make the mass concentration 2g/L, magnetically stir for 30min, then ultrasonically oscillate for 30min, and finally magnetically stir for 24h to obtain MoSi ₂ @Y ₂ O ₃ suspension;

Put the MoSi ₂ @Y ₂ O ₃ suspension in the preparation of self-made hydrothermal electrodeposition equipment, and use the carbon/carbon composite material containing SiC inner coating prepared in step 2 as the negative electrode, under the conditions of deposition voltage 30V and hydrothermal temperature 140°C 30min under hydrothermal electrodeposition; repeat the deposition 4 times to realize the uniform deposition of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules on the surface of carbon/carbon composite material with SiC inner coating;

Step 4. Preparation of glass powder:

Mix 60% silicon dioxide, 30% boron oxide and 10% alumina powder by mass percentage, ball mill and sieve, then calcinate at 1200°C for 4 hours, and then ball mill and sieve to obtain glass powder;

Step 5, preparing the glass outer coating of the carbon/carbon composite material sample:

Mix the glass powder prepared in step 4 with molybdenum disilicide powder at a mass ratio of 5:1, then dilute with absolute ethanol to form a slightly flowing slurry, and then use a brush to paint the MoSi ₂ @ prepared in step 3 Y ₂ O ₃ -SiC-carbon/carbon composite surface, and then hold it at 1400°C for 3 minutes under an argon atmosphere, and finally obtain a dense Glass-MoSi ₂ @Y ₂ O ₃ -SiC C/C composite high-temperature anti-oxidation coating Floor.

Fig. 1 is the surface XRD pattern of the Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating prepared in Example 1 of the present invention. As can be seen from Fig. 1, the surface coating is composed of MoSi ₂ phase and SiO ₂ glass phase;

Fig. 2 is a SEM image of MoSi ₂ @Y ₂ O ₃ microcapsules prepared by the method of the present invention. It can be seen from Figure 2 that the sheet-like Y ₂ O ₃ covers the MoSi ₂ particles, forming a core-shell structure.

Fig. 3 is a SEM image of the surface morphology of the Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating prepared in Example 1 of the present invention. It can be seen from Figure 3 that the surface of the prepared composite coating is dense and free of holes and cracks.

Fig. 4 is the static oxidation curve of the Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating sample prepared in Example 1 of the present invention at 1773 K in air. It can be seen from Figure 4 that the weight loss rate of the sample increased rapidly in the first 30 hours, which may be due to the large loss of the outermost glass sealing layer caused by high temperature; the weight loss rate of the sample after 30 hours is relatively stable, which may be due to the MoSi ₂ @ Y ₂ O ₃ microcapsules play a role, the crack propagation of the coating is hindered by the formation of yttrium silicate whiskers, which makes it difficult to form penetrating cracks, and also increases the viscosity of SiO ₂ glass, thereby reducing the diffusion rate of oxygen; After 182 hours of oxidation at 1773k air atmosphere, the weight loss rate was only 2.02%, and the carbon/carbon matrix was not oxidized, so it can be explained that the prepared Glass-MoSi ₂ @Y ₂ O ₃ -SiC composite coating has Good antioxidant properties.

Claims (5)

1. A method for preparing Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating on the surface of a carbon/carbon composite material, characterized in that it comprises the following steps: Step 1. Preparation of MoSi ₂ @Y ₂ O ₃ core-shell microcapsules: 1) Add MoSi ₂ powder into the Erlenmeyer flask, then mix isopropanol and absolute ethanol into the Erlenmeyer flask for ultrasonic vibration to obtain a suspension A with a MoSi ₂ mass concentration of 10-20g/L; The volume ratio of isopropanol to absolute ethanol is (0~4):1; 2) Add yttrium nitrate, urea and polyethylene glycol 4000 to suspension A, stir to disperse evenly, and obtain suspension B; Wherein the molar ratio of yttrium nitrate to urea is 1: (1~8); the mass concentration of yttrium nitrate is 20~40g/L; the mass concentration of polyethylene glycol 4000 is 0.01~0.04g/mL; 3) Put the obtained suspension B into a hydrothermal kettle, heat and stir at 80~150°C for 2~5h, then centrifuge and wash the obtained product to obtain product C; 4) After drying the product C separated in step 3), put it into a tube furnace and keep it warm at 500-800°C for 2-3 hours under an argon atmosphere to obtain the final product D, which is MoSi ₂ @Y ₂ O ₃ microcapsules; Step 2, preparing the SiC inner coating of the carbon/carbon composite material sample: Embedding the carbon/carbon composite material in the mixed powder in the graphite crucible, so that the mixed powder completely covers the carbon/carbon composite material; The batching of described mixed powder comprises the silicon powder of 40～60 parts, the graphite powder of 20～40 parts and the aluminum oxide powder of 5～20 parts in parts by mass; Put the graphite crucible into the reaction furnace, vacuum the reaction furnace and then pass in argon gas, so that the reaction furnace is heated from room temperature to 1900~2200 °C at a rate of 5~20 °C/min under the protection of argon gas and kept for 1 ~4 hours, then turn off the power supply, and the reaction furnace is naturally cooled to room temperature to obtain a carbon/carbon composite material with a SiC inner coating on the surface; Step 3. Prepare the intermediate coating of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules of carbon/carbon composites using self-made hydrothermal electrodeposition equipment: MoSi ₂ @Y ₂ O ₃ suspension configuration: Add self-made MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsule powder into isopropanol solution to make the mass concentration: 10~40g/L, magnetically stir 12h; Then add iodine so that the mass concentration of iodine is 0~3g/L, magnetically stir for 30min, then ultrasonically shake for 30min, and finally magnetically stir for 24h to obtain MoSi ₂ @Y ₂ O ₃ suspension; The MoSi ₂ @Y ₂ O ₃ suspension was placed in the self-made hydrothermal electrodeposition equipment, and the carbon/carbon composite material containing the SiC inner coating prepared in step 2 was used as the negative electrode. The deposition voltage was 10~30V, and the hydrothermal temperature was 80 Under the condition of ~160℃, hydrothermal electrodeposition was carried out for 20~60min; the deposition was repeated 3-5 times to realize the uniform deposition of MoSi ₂ @Y ₂ O ₃ core-shell structure microcapsules on the surface of carbon/carbon composite material containing SiC inner coating; Step 4. Preparation of glass powder: Mix 50-75% of silicon dioxide, 15-30% of boron oxide and 5-20% of alumina powder according to the mass percentage, ball mill and sieve, and then calcined at 1000-1500°C for 2-5 hours, and then Glass powder is obtained after ball milling and sieving; Step 5, preparing the glass outer coating of the carbon/carbon composite material sample: Mix the glass powder prepared in step 4 with molybdenum disilicide powder in a mass ratio of (4~8): 1, then dilute it with absolute ethanol to form a slightly flowing slurry, and then use a brush to paint it in step 3. MoSi ₂ @Y ₂ O ₃ -SiC-carbon/carbon composite material surface, and then keep it at 1400℃ for 2~6min under argon atmosphere, and finally get dense Glass-MoSi ₂ @Y ₂ O ₃ -SiC C/C High temperature oxidation resistant coating for composite materials. 2. The method for preparing Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating on the surface of carbon/carbon composite material as claimed in claim 1, characterized in that, in the step 1, the ultrasonic vibration is to make the suspension Put it into a 200~300W ultrasonic generator and vibrate for 30~60min. 3. The method for preparing Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating on the surface of carbon/carbon composite material as claimed in claim 1, characterized in that the stirring in the step 1 is to use a magnetic stirrer Stir for 1~3h. 4. The method for preparing Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating on the surface of carbon/carbon composite material as claimed in claim 1, characterized in that, the washing in the step 1 is to use distilled water and Wash with absolute ethanol 2-5 times. 5. The method for preparing Glass-MoSi ₂ @Y ₂ O ₃ -SiC anti-oxidation coating on the surface of carbon/carbon composite material as claimed in claim 1, characterized in that, in the step 1, drying is at 60~80 Dry in an oven at ℃ for 1~3h.

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