CN104130013B - The preparation method of the crystal whisker toughened mullite compound coating of a kind of carbon/carbon compound material SiC - Google Patents

Abstract

The invention provides a method for preparing a carbon/carbon composite SiC whisker toughened mullite composite coating: disperse mullite powder and SiC whisker in butanol, and stir while heating to obtain a suspension after ultrasonic vibration A2; add carbon iodide to the suspension A2, and stir while heating to obtain the suspension B; pour the suspension B into a hydrothermal kettle with a graphite electrode as the anode and a conductive substrate as the cathode for electromagnetic induction heating double pulse electrophoresis Depositing, drying the sample taken out, the carbon/carbon composite material SiC whisker toughened mullite composite outer coating surface prepared by the present invention has no cracks, and the outer coating and the substrate have high bonding strength; the structure can be obtained at low temperature Controllable and good performance carbon/carbon composite material SiC whisker toughened mullite composite outer coating; the preparation process is simple, the operation is convenient, the raw materials are easy to obtain, the preparation cost is low, and it has broad development prospects.

Description

A preparation method of carbon/carbon composite material SiC whisker toughened mullite composite coating

technical field

The invention relates to a method for preparing a carbon/carbon composite material composite outer coating, in particular to a method for preparing an electromagnetic induction heating-double pulse electrophoresis deposition carbon/carbon composite material SiC whisker toughened mullite composite outer coating .

Background technique

C/C composite material is also called carbon fiber carbon-based composite material. Because it is only composed of a single carbon element, it not only has excellent ablation resistance of carbon and graphite materials, low density, low thermal expansion coefficient, etc. There are also excellent mechanical properties. In particular, its strength does not decrease but increases with the increase of temperature, making it one of the most promising high-tech new materials, and is widely used as ablation materials and thermal structural materials in the field of aviation and aerospace technology. However, C/C composites are rapidly oxidized in an oxidizing atmosphere with a temperature exceeding 500 °C, which greatly limits their applications. Therefore, the oxidation protection of C/C composites has become one of the research hotspots in recent years. At the same time, it is of great significance to protect it from high temperature oxidation resistance for its high temperature application.

Anti-oxidation coating is considered to be an effective method to solve the problem of high-temperature oxidation protection of carbon/carbon composites. SiC coating has good physical and chemical compatibility with C/C composite materials and is generally used as a transition layer, but a single SiC coating cannot provide effective protection for C/C substrates, so the anti-oxidation outer coating has become the current Research hotspots.

So far, there are many kinds of composite coatings prepared, such as SiC whisker toughened MoSi ₂ -SiC-Si coating [FuQian-Gang, LiHe-Jun, LiKe-Zhi, ShiXiao-Hong, HuZhi-Biao, HuangMin, SiCwhisker-toughened MoSi ₂ -SiC-Sicoatingtoprotectcarbon/carboncompositesagainstoxidation, Carbon.2006,44,1866.], MoSi ₂ /SiC coating [HuangJF, WangB, LiHJ, etal.AMoSi ₂ /SiCoxidationprotectivecoatingforcarbon/carboncomposites.Corboncomposites. ):834-839.], SiC-MoSi ₂ -(Ti _0.8 Mo _0.2 )Si ₂ composite coating [JiaoGS, LiHJ, LiKZ, etal.SiC-MoSi ₂ -(Ti _0.8 Mo _0.2 )Si ₂ multi-compositioncoatingforcarbon/ carboncomposites.Surf.Coat.Technol, 2006,201(6):3452-3456.] and so on. The prepared composite coating can effectively protect the C/C composite material. However, in order to make the anti-oxidation coating develop towards the direction of long life, high temperature resistance, and erosion resistance, continuous efforts are still needed. Mullite (thermal expansion coefficient is 5.0×10 ^-6 /℃) ceramic material has high refractoriness, good thermal shock resistance, chemical corrosion resistance, creep resistance, high softening temperature under load, and good volume stability. It is an ideal advanced refractory material. materials are widely used in various fields. SiC whiskers have the characteristics of thermal expansion coefficient close to that of mullite, high temperature resistance, high strength, high elastic modulus, and good chemical stability. It has become an effective way to improve the toughness and reliability of mullite ceramics. Its research as an anti-oxidation coating is rarely reported.

So far, the preparation methods of the outer coating are various, mainly as follows: supercritical fluid technology, chemical vapor deposition, embedding method, in-situ forming, sol-gel method, magma coating reaction, explosion Spraying and ultrasonic spraying, etc. The use of supercritical fluid technology to prepare C/C composite coatings requires high temperature and high pressure for the preparation process, which requires high equipment requirements, and the formed outer coating must be heat treated in an inert atmosphere. The preparation cycle It is relatively long [BemeburgPL, KrukonisVJ.Processingofcarbon/carboncompositesusingsupercriticalfluidtechnology[P].UnitedStatesPatentUS5035921,1991], the coating prepared by the in-situ forming method needs to be treated at 1500°C at high temperature, and cannot be prepared at one time [HuangJian-Feng, LiHe-Jun, ZengXie-Rong, LiKe-Zhi.Surf.coat.Technol.2006,200,5379.], the surface of the outer coating prepared by sol-gel method is easy to crack and the coating thickness is insufficient [HuangJian-Feng, ZengXie-Rong, LiHe-Jun, XiongXin-Bo, SunGuo-ling.Surf.coat.Technol.2005,190,255.], and although adopting detonation spraying and ultrasonic spraying method to prepare part alloy coating, still, this technology still has many imperfections Where, the high-temperature anti-oxidation performance of the prepared coating still needs to be further improved [TerentievaVS, BogachkovaOP, GoriatchevaEV. However, the method of preparing SiC whisker toughened mullite composite outer coating by electromagnetic induction heating-double pulse electrophoretic deposition method has not been reported yet.

Contents of the invention

The purpose of the present invention is to provide a method for preparing a carbon/carbon composite material SiC whisker toughened mullite composite coating, which can be used to prepare a carbon/carbon composite material SiC with uniform thickness, no penetrating cracks and micropores The whisker-toughened mullite composite outer coating has simple process equipment, short reaction cycle and low cost.

To achieve the above object, the present invention adopts the following technical solutions:

1) First, disperse the mixed powder composed of mullite powder and SiC whiskers in 50-80mL butanol to prepare suspension A1 with a mixed powder concentration of 30-45g/L, and the SiC whiskers in the mixed powder The mass fraction of mullite is 20-40%, and the mass fraction of mullite powder is 60-80%. The suspension A1 is ultrasonically oscillated for 5-10 minutes, and then stirred on a magnetic stirrer for 1-2 hours while heating to obtain a suspension A2, the heating temperature is controlled at 60-80°C;

2) Add carbon iodide to the suspension A2 to obtain a mixture, the concentration of carbon iodide in the mixture is 0.5-1.0 g/L, stir the mixture on a magnetic stirrer for 1-2 hours, heat while stirring, and control the heating temperature at 60～80℃, to obtain suspension B;

3) Pour the suspension B into a hydrothermal kettle with the graphite electrode as the anode and the conductive substrate as the cathode, clamp the C/C composite material sample with SiC coating on the cathode, and then seal the hydrothermal kettle Then put it into the electromagnetic induction heater, then connect the negative and positive poles of the water heating kettle to the pulse power supply and perform electromagnetic induction heating double pulse electrophoretic deposition. During the deposition process, the heating current of the electromagnetic induction heater is controlled at 200-300A, and the electromagnetic induction heating The heat preservation power current of the device is controlled at 200-300A (to control the hydrothermal reaction temperature at 180-250°C), the pulse power supply voltage is 220V, the pulse power supply cycle is controlled at 1000-3000ms, the pulse power supply peak current is controlled at 40-60A, and the pulse power supply The working time of the forward pulse of the power supply is controlled at 400-800ms, the working time of the reverse pulse of the pulse power supply is controlled at 100-300ms, the forward and reverse pulse width of the pulse power supply is controlled at 100-300μs, the working time of the pulse power supply group is controlled at 8-12min, the pulse power supply The total working time is controlled within 10-25 minutes, and naturally cooled to room temperature after deposition;

4) After step 3), open the hydrothermal kettle and take out the sample, and then dry the taken out sample in an electric blast drying oven at 40-80° C. for 2-6 hours.

The aspect ratio of the SiC whiskers is 50-100, the average particle size of the mullite powder is controlled at 50-100 nm, the purity of carbon iodide is ≥99.7%, and the purity of butanol is ≥99.8%.

The ultrasonic power of the ultrasonic vibration is 500-1000W.

The filling degree of the hydrothermal kettle is controlled at 50-80%.

The beneficial effects of the present invention are reflected in:

1) The carbon/carbon composite material SiC whisker toughened mullite composite outer coating surface prepared by the present invention has no cracks, and the outer coating is closely combined with the SiC inner coating;

2) The present invention can obtain a carbon/carbon composite SiC whisker toughened mullite composite outer coating with controllable structure and good performance at low temperature;

3) The preparation process of the present invention is simple, the operation is convenient, the raw materials are easy to obtain, the preparation cost is low, and it has broad development prospects.

Description of drawings

Fig. 1 is the surface SEM photo of the carbon/carbon composite material SiC whisker toughened mullite composite outer coating prepared by embodiment 5;

Fig. 2 is the XRD spectrum of the SiC whisker toughened mullite composite outer coating of the carbon/carbon composite material prepared in Example 5.

detailed description

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Example 1:

1) Select commercially available SiC whiskers (the aspect ratio is 50-100), mullite powder (the commercially available mullite powder has been dry-milled for about 45 hours, and the average particle size is controlled at about 100nm), carbon iodide (purity ≥ 99.7%), and butanol (purity ≥ 99.8%) as raw materials;

2) First, disperse the mixed powder composed of mullite powder and SiC whiskers in 50mL butanol, and prepare a suspension A1 with a mixed powder concentration of 30g/L, and the mass fraction of SiC whiskers in the mixed powder 20%, the mass fraction of mullite powder is 80%, the suspension A1 is ultrasonically oscillated for 10min, the ultrasonic power is 500W, and then placed on a magnetic stirrer to stir for 1h, while heating while stirring, the heating temperature is controlled at 60°C , to obtain suspension A2;

3) Add carbon iodide to the suspension A2 to obtain a mixture, the concentration of carbon iodide in the mixture is 0.5g/L, put the mixture on a magnetic stirrer and stir for 1h, heat while stirring, the heating temperature is controlled at 60°C, Obtain suspension B;

4) Pour the suspension B into a hydrothermal kettle with the graphite electrode as the anode and the conductive substrate as the cathode, the filling degree is 50%, and the C/C composite material sample with SiC coating is sandwiched in the hydrothermal On the cathode in the kettle (the sample is submerged into the suspension B), then seal the hydrothermal kettle and put it into the electromagnetic induction heater, and then connect the positive and negative poles of the hydrothermal kettle with the SMD-P intelligent multi-pulse electroplating power supply (Handan Dashun Electroplating Equipment Co., Ltd.) Connect the corresponding two poles and perform electromagnetic induction heating double pulse electrophoretic deposition: the heating current of the electromagnetic induction heater is controlled at 200A, the heat preservation power current is controlled at 200A, and the water heating temperature is controlled at 180°C. The pulse power supply voltage is 220V, the period is controlled at 1000ms, the peak current is controlled at 40A, the forward pulse working time is controlled at 400ms, the reverse pulse working time is controlled at 100ms, the positive and negative pulse width is controlled at 100μs, and the group working time is controlled at 9min. The total working time is controlled at 20min, and naturally cooled to room temperature after deposition;

5) After step 4), open the above-mentioned hydrothermal kettle, take out the sample, and then dry the taken out sample in an electric blast drying oven at 40°C for 6 hours to obtain the carbon/carbon composite SiC whisker toughened Mullite composite outer coating.

Example 2:

1) Select commercially available SiC whiskers (the aspect ratio is 50-100), mullite powder (the commercially available mullite powder has been dry-milled for about 45 hours, and the average particle size is controlled at about 100nm), carbon iodide (purity ≥ 99.7%), and butanol (purity ≥ 99.8%) as raw materials;

2) First, disperse the mixed powder composed of mullite powder and SiC whiskers in 50mL butanol, and prepare a suspension A1 with a mixed powder concentration of 30g/L, and the mass fraction of SiC whiskers in the mixed powder The mass fraction of mullite powder is 30%, the mass fraction of mullite powder is 70%, the suspension A1 is ultrasonically oscillated for 8min, the ultrasonic power is 600W, and then placed on a magnetic stirrer to stir for 1h, heating while stirring, and the heating temperature is controlled at 60°C , to obtain suspension A2;

3) Add carbon iodide to the suspension A2 to obtain a mixture, the concentration of carbon iodide in the mixture is 0.5g/L, put the mixture on a magnetic stirrer and stir for 1h, heat while stirring, the heating temperature is controlled at 60°C, Obtain suspension B;

4) Pour the suspension B into a hydrothermal kettle with the graphite electrode as the anode and the conductive substrate as the cathode, the filling degree is 50%, and the C/C composite material sample with SiC coating is sandwiched in the hydrothermal On the cathode in the kettle (the sample is submerged into the suspension B), then seal the hydrothermal kettle and put it into the electromagnetic induction heater, and then connect the positive and negative poles of the hydrothermal kettle with the SMD-P intelligent multi-pulse electroplating power supply Corresponding two poles are connected and double-pulse electrophoretic deposition is carried out by electromagnetic induction heating: the heating current of the electromagnetic induction heater is controlled at 220A, the heat preservation power current is controlled at 220A, and the water heating temperature is controlled at 190°C. The pulse power supply voltage is 220V, the period is controlled at 1500ms, the peak current is controlled at 45A, the forward pulse working time is controlled at 400ms, the reverse pulse working time is controlled at 100ms, the positive and negative pulse width is controlled at 100μs, and the group working time is controlled at 11min. The total working time is controlled at 25 minutes, and naturally cooled to room temperature after deposition;

5) After step 4), open the above-mentioned hydrothermal kettle, take out the sample, and then dry the taken out sample in an electric blast drying oven at 50°C for 5 hours to obtain a carbon/carbon composite SiC whisker toughened Mullite composite outer coating.

Example 3:

1) Select commercially available SiC whiskers (the aspect ratio is 50-100), mullite powder (the commercially available mullite powder has been dry-milled for about 45 hours, and the average particle size is controlled at about 100nm), carbon iodide (purity ≥ 99.7%), and butanol (purity ≥ 99.8%) as raw materials;

2) First, disperse the mixed powder composed of mullite powder and SiC whiskers in 60mL butanol, and prepare suspension A1 with a mixed powder concentration of 45g/L, and the mass fraction of SiC whiskers in the mixed powder 35%, the mass fraction of mullite powder is 65%, the suspension A1 is ultrasonically oscillated for 6min, the ultrasonic power is 800W, then placed on a magnetic stirrer and stirred for 2h, while heating while stirring, the heating temperature is controlled at 60°C , to obtain suspension A2;

3) Add carbon iodide to the suspension A2 to obtain a mixture, the concentration of carbon iodide in the mixture is 0.5g/L, put the mixture on a magnetic stirrer and stir for 2h, heat while stirring, the heating temperature is controlled at 60°C, Obtain suspension B;

4) Pour the suspension B into a hydrothermal kettle with the graphite electrode as the anode and the conductive substrate as the cathode, the filling degree is 60%, and the C/C composite material sample with SiC coating is clamped in the hydrothermal On the cathode in the kettle (the sample is submerged into the suspension B), then seal the hydrothermal kettle and put it into the electromagnetic induction heater, and then connect the positive and negative poles of the hydrothermal kettle with the SMD-P intelligent multi-pulse electroplating power supply Corresponding two poles are connected and electromagnetic induction heating double pulse electrophoretic deposition is carried out: the heating current of the electromagnetic induction heater is controlled at 240A, the heat preservation power current is controlled at 240A, and the water heating temperature is controlled at 200°C. The pulse power supply voltage is 220V, the cycle is controlled at 1500ms, the peak current is controlled at 50A, the forward pulse working time is controlled at 400ms, the reverse pulse working time is controlled at 200ms, the positive and negative pulse width is controlled at 200μs, and the group working time is controlled at 10min. The total working time is controlled at 12 minutes, and naturally cooled to room temperature after deposition;

5) After step 4), open the above-mentioned hydrothermal kettle, take out the sample, and then dry the taken out sample in an electric blast drying oven at 60°C for 4 hours to obtain the carbon/carbon composite SiC whisker toughened Mullite composite outer coating.

Example 4:

1) Select commercially available SiC whiskers (the aspect ratio is 50-100), mullite powder (the commercially available mullite powder has been dry-milled for about 45 hours, and the average particle size is controlled at about 100nm), carbon iodide (purity ≥ 99.7%), and butanol (purity ≥ 99.8%) as raw materials;

2) First, disperse the mixed powder composed of mullite powder and SiC whiskers in 70mL butanol, and prepare suspension A1 with a mixed powder concentration of 35g/L, and the mass fraction of SiC whiskers in the mixed powder 40%, the mass fraction of mullite powder is 60%, the suspension A1 is ultrasonically oscillated for 6min, the ultrasonic power is 800W, and then placed on a magnetic stirrer to stir for 2h, while heating while stirring, the heating temperature is controlled at 60°C , to obtain suspension A2;

3) Add carbon iodide to the suspension A2 to obtain a mixture, the concentration of carbon iodide in the mixture is 1.0 g/L, put the mixture on a magnetic stirrer and stir for 2 hours, heat while stirring, and control the heating temperature at 60°C, Obtain suspension B;

4) Pour the suspension B into a hydrothermal kettle with the graphite electrode as the anode and the conductive substrate as the cathode, the filling degree is 70%, and the C/C composite material sample with SiC coating is clamped in the hydrothermal On the cathode in the kettle (the sample is submerged into the suspension B), then seal the hydrothermal kettle and put it into the electromagnetic induction heater, and then connect the positive and negative poles of the hydrothermal kettle with the SMD-P intelligent multi-pulse electroplating power supply Corresponding two poles are connected and double-pulse electrophoretic deposition is carried out by electromagnetic induction heating: the heating current of the electromagnetic induction heater is controlled at 260A, the heat preservation power current is controlled at 260A, and the water heating temperature is controlled at 210°C. The pulse power supply voltage is 220V, the cycle is controlled at 2000ms, the peak current is controlled at 55A, the forward pulse working time is controlled at 600ms, the reverse pulse working time is controlled at 200ms, the positive and negative pulse width is controlled at 200μs, and the group working time is controlled at 8min. The total working time is controlled at 25 minutes, and naturally cooled to room temperature after deposition;

5) After step 4), open the above-mentioned hydrothermal kettle, take out the sample, and then dry the taken out sample in an electric blast drying oven at 60°C for 4 hours to obtain the carbon/carbon composite SiC whisker toughened Mullite composite outer coating.

Example 5:

1) Select commercially available SiC whiskers (the aspect ratio is 50-100), mullite powder (the commercially available mullite powder has been dry-milled for about 45 hours, and the average particle size is controlled at about 100nm), carbon iodide (purity ≥ 99.7%), and butanol (purity ≥ 99.8%) as raw materials;

2) First, disperse the mixed powder composed of mullite powder and SiC whiskers in 80mL butanol, and prepare suspension A1 with a mixed powder concentration of 40g/L, and the mass fraction of SiC whiskers in the mixed powder 25%, the mass fraction of mullite powder is 75%, the suspension A1 is ultrasonically oscillated for 5min, the ultrasonic power is 1000W, and then placed on a magnetic stirrer to stir for 2h, while heating while stirring, the heating temperature is controlled at 80°C , to obtain suspension A2;

3) Add carbon iodide to the suspension A2 to obtain a mixture, the concentration of carbon iodide in the mixture is 1.0 g/L, put the mixture on a magnetic stirrer and stir for 2 hours, heat while stirring, the heating temperature is controlled at 80 °C, Obtain suspension B;

4) Pour the suspension B into a hydrothermal kettle with the graphite electrode as the anode and the conductive substrate as the cathode. On the cathode in the kettle (the sample is submerged into the suspension B), then seal the hydrothermal kettle and put it into the electromagnetic induction heater, and then connect the positive and negative poles of the hydrothermal kettle with the SMD-P intelligent multi-pulse electroplating power supply Corresponding two poles are connected and electromagnetic induction heating double-pulse electrophoretic deposition is carried out: the heating current of the electromagnetic induction heater is controlled at 300A, the heat preservation power current is controlled at 300A, and the water heating temperature is controlled at 250°C. The pulse power supply voltage is 220V, the cycle is controlled at 3000ms, the peak current is controlled at 60A, the forward pulse working time is controlled at 800ms, the reverse pulse working time is controlled at 300ms, the positive and negative pulse width is controlled at 300μs, and the group working time is controlled at 12min. The total working time is controlled at 25 minutes, and naturally cooled to room temperature after deposition;

5) After step 4), open the above-mentioned hydrothermal kettle, take out the sample, and then dry the taken out sample in an electric blast drying oven at 80°C for 2 hours to obtain the carbon/carbon composite SiC whisker toughened Mullite composite outer coating.

It can be seen from Fig. 1 and Fig. 2 that the outer coating prepared by the present invention is composed of mullite (3Al ₂ O ₃ ·SiO ₂ ) and SiC, and the surface is flat and uniform, relatively dense, and without cracks on the surface.

The characteristics of the electromagnetic induction heating-double pulse electrophoretic deposition method are firstly to accelerate the deposition rate of suspended particles in a hydrothermal supercritical environment, so that the suspended particles can quickly react on the surface of the substrate. Electromagnetic induction heating technology is a new type of heating technology. According to the principle of electromagnetic induction, it uses the heat generated by the eddy current in the heated body to heat. Compared with the traditional heating method, it has high heating efficiency, fast speed and reliability. High performance, easy to achieve high temperature and local heating, and has been widely used in the field of industrial heating. At the same time, electromagnetic induction heating can quickly generate local high temperature and high pressure in the reaction system, effectively reducing the reaction activation energy of SiC whiskers and mullite composite suspended particles, making it more complete and sufficient in the hydrothermoelectrophoretic deposition process, thereby A densely structured coating is obtained. Secondly, under the positive and negative pulse power supply, the positive and negative poles are intermittently discharged, so that the suspended particles are deposited on the surface of the substrate, which avoids the uneven coating caused by the traditional continuous arc discharge, and thus obtains a dense coating. This method can avoid the phase transition and embrittlement caused by traditional high-temperature coating, and solve the thermal damage to the substrate during the coating preparation process to a certain extent; at the same time, because the deposition process is a non-linear process, it can be used in complex shapes or porous surfaces. A uniform deposition layer is formed on the surface of the substrate, and the composition, thickness and porosity of the coating can be precisely controlled, making it possible to prepare multi-phase composite coatings and gradient ceramic coatings simply and efficiently; moreover, electrophoretic deposition is the directional movement of charged particles , will not affect the bonding force between the coating and the substrate due to the large amount of gas generated during the electrolysis of water solvent. In addition, the forward pulse controls the grain size and impurity amount of the coating, and the reverse pulse controls the deposition rate and thickness distribution, achieving dense SiC whisker growth with microcracks and different thicknesses under controllable conditions. Tough mullite coating. Electromagnetic induction heating-double pulse electrophoretic deposition also has the characteristics of simple and convenient operation, low cost, and easy control of the deposition process.

Claims (4)

1. a preparation method of carbon/carbon composite material SiC whisker toughened mullite composite coating, it is characterized in that: comprise the following steps: 1) First, disperse the mixed powder composed of mullite powder and SiC whiskers in butanol to prepare a suspension A1 with a mixed powder concentration of 30-45g/L, and the mass fraction of SiC whiskers in the mixed powder 20-40%, the mass fraction of mullite powder is 60-80%, the suspension A1 is ultrasonically oscillated for 5-10 minutes, and then stirred on a magnetic stirrer while heating for 1-2 hours to obtain the suspension A2, heated The temperature is controlled at 60-80°C; 2) Add carbon iodide to the suspension A2 to obtain a mixture, the concentration of carbon iodide in the mixture is 0.5-1.0 g/L, stir the mixture on a magnetic stirrer for 1-2 hours, heat while stirring, and control the heating temperature at 60～80℃, to obtain suspension B; 3) Pour the suspension B into a hydrothermal kettle with the graphite electrode as the anode and the conductive substrate as the cathode, clamp the C/C composite material sample with SiC coating on the cathode, and then seal the hydrothermal kettle Then put it into the electromagnetic induction heater, then connect the negative and positive poles of the water heating kettle to the pulse power supply and perform electromagnetic induction heating double pulse electrophoretic deposition. During the deposition process, the heating current of the electromagnetic induction heater is controlled at 200-300A, and the electromagnetic induction heating The heat preservation power current of the device is controlled at 200-300A, the pulse power supply voltage is 220V, the pulse power cycle is controlled at 1000-3000ms, the pulse power peak current is controlled at 40-60A, the pulse power forward pulse working time is controlled at 400-800ms, the pulse The working time of the reverse pulse of the power supply is controlled at 100-300ms, the forward and reverse pulse width of the pulse power supply is controlled at 100-300μs, the working time of the pulse power supply group is controlled at 8-12min, and the total working time of the pulse power supply is controlled at 10-25min. cool to room temperature; 4) After step 3), open the hydrothermal kettle and take out the sample, and then dry the taken out sample in an electric blast drying oven at 40-80° C. for 2-6 hours. 2. A method for preparing a carbon/carbon composite SiC whisker toughened mullite composite coating according to claim 1, characterized in that: the SiC whisker has an aspect ratio of 50 to 100, and the mullite The average particle size of the stone powder is controlled at 50-100nm, the purity of carbon iodide is ≥99.7%, and the purity of butanol is ≥99.8%. 3. The method for preparing a SiC whisker-toughened mullite composite coating of carbon/carbon composite material according to claim 1, characterized in that: the ultrasonic power of the ultrasonic oscillation is 500-1000W. 4. The method for preparing a SiC whisker-toughened mullite composite coating of carbon/carbon composite material according to claim 1, characterized in that: the filling degree of the hydrothermal kettle is controlled at 50-80%.