A method for preparing a C / C composite ZrB2-SiC(Al) oxidation-resistant coating by hot-pressing rapid sintering

Abstract

The application relates to a method for preparing a ZrB2-SiC (Al) oxidation-resistant coating of C / C composite material through hot-pressing rapid sintering, and belongs to the technical field of design and preparation of oxidation-resistant coatings of C / C composite material. The method solves the problems of the prior art, such as complex preparation process, long cycle, difficulty in scale implementation, insufficient oxidation resistance of the ZrB2-SiC coating, poor uniformity of each phase of the ceramic, and low coating density. The method uses superfine powder and a wet ball milling process to improve the uniformity of each phase of the coating and reduce powder agglomeration. The method uses rapid sintering through discharge plasma and stepwise heating to promote rapid and sufficient sintering of the powder, so that the oxidation-resistant coating with high density and strong bonding force with the matrix is obtained. A small amount of Al2O3 is added to promote the sintering of the powder, and the outermost SiO2-rich glass layer generated after oxidation is modified to form Si-O-Al bonds, enhance the stability of the SiO2-rich glass film, and further improve the oxidation resistance of the ZrB2-SiC coating. The method is simple in process, short in preparation cycle, and easy to implement on a large scale.

Description

Technical Field

[0001] This invention relates to the field of design and preparation technology of antioxidant coatings for C / C composite materials, and specifically to a method for preparing a ZrB2-SiC(Al) antioxidant coating for C / C composite materials by hot pressing and rapid sintering. Background Technology

[0002] C / C composites possess high specific strength and excellent high-temperature mechanical properties, making them highly promising high-temperature structural materials for aerospace applications. However, their susceptibility to oxidation in oxygen-rich environments (around 400°C) severely limits their reliable application. Anti-oxidation coatings are an effective way to address this issue. ZrB2-SiC ceramics exhibit good oxidation resistance over a wide temperature range, making them one of the most promising anti-oxidation coating systems for C / C composites.

[0003] However, under higher temperatures and prolonged oxidation conditions, the volatilization of the SiO2-rich glass film on the surface of ZrB2-SiC ceramics intensifies, leading to a decrease in oxidation resistance. Existing methods for preparing ZrB2-SiC anti-oxidation coatings typically involve complex processes, long preparation cycles, and high costs, making them difficult to scale up. Furthermore, the high-temperature oxidation resistance of coatings prepared using existing methods is not significantly improved, and the uniformity of phase distribution and coating density in the multiphase ceramic are not high.

[0004] In summary, existing technologies suffer from problems such as complex ZrB2-SiC coating preparation processes, long preparation cycles, high costs, difficulty in large-scale implementation, insufficient high-temperature oxidation resistance of the prepared ZrB2-SiC coatings, uneven distribution of phases in multiphase ceramics, and low coating density. Summary of the Invention

[0005] In view of the above problems, the present invention provides a method for preparing C / C composite material ZrB2-SiC(Al) anti-oxidation coating by hot pressing and rapid sintering, which solves the problems of complex preparation process, long preparation cycle, high cost, difficulty in large-scale implementation, insufficient high-temperature anti-oxidation performance of ZrB2-SiC coating, uniform distribution of phases in multiphase ceramic and low coating density in the prior art.

[0006] This invention provides a method for preparing a ZrB2-SiC(Al) anti-oxidation coating of C / C composite material by hot pressing and rapid sintering. ZrB2 ultrafine powder and α-SiC ultrafine powder are measured and mixed according to a preset ratio. A small amount of Al2O3 ultrafine powder is added. After wet ball milling, a uniformly composite ZrB2-SiC(Al) composite powder is obtained. The pretreated C / C composite matrix is ​​fully embedded in the ZrB2-SiC(Al) composite powder and placed in a graphite mold for spark plasma sintering. After stepped heating sintering and rapid cooling, a ZrB2-SiC(Al) anti-oxidation coating is obtained on the surface of the C / C composite matrix. The method maintains that the mass fraction of α-SiC ultrafine powder in the ZrB2 and SiC mixed powder is 10 wt.% to 40 wt.%, and the Al / Si molar ratio in the ZrB2-SiC(Al) composite powder is maintained in the range of 0 to 0.1.

[0007] Furthermore, the method for preparing the C / C composite material ZrB2-SiC(Al) antioxidant coating by hot pressing and rapid sintering includes the following steps:

[0008] Step S1. Process the C / C composite matrix, grind its surface, clean it and dry it to obtain a pretreated C / C composite matrix;

[0009] Step S2. Weigh a certain mass of ZrB2 ultrafine powder, α-SiC ultrafine powder, and Al2O3 ultrafine powder respectively. Mix the two powders thoroughly according to the preset mass ratio of ZrB2 ultrafine powder and α-SiC ultrafine powder, and add a small amount of Al2O3 ultrafine powder as a dopant to obtain a composite powder to be ball-milled. Perform ball milling on the composite powder using a wet ball milling process. Dry the ball-milled powder and grind and break up any agglomerated powder to obtain a uniformly composite ZrB2-SiC(Al) composite powder.

[0010] Step S3. Place the pretreated C / C composite matrix into the pretreated graphite mold, and then pour the uniformly composite ZrB2-SiC(Al) composite powder into the pretreated graphite mold in three batches to fully embed the C / C composite matrix and spread it evenly, thus completing the assembly of the graphite mold.

[0011] Step S4. Place the assembled graphite mold into a spark plasma sintering furnace for sintering. Set the sintering temperature to 1600-1900℃, adopt a stepped heating process, with a heating rate of 50-100℃ / min, a sintering pressure of 30-50MPa, and a holding time of 5-30min. After sintering, wait for the furnace temperature to cool to below 40℃ before removing the mold. A ZrB2-SiC(Al) anti-oxidation coating is obtained on the surface of the pretreated C / C composite matrix.

[0012] Furthermore, the ZrB2 ultrafine powder has a particle size of no more than 2 μm and a purity of no less than 99%; the α-SiC ultrafine powder has a particle size of no more than 100 nm and a purity of no less than 99%; and the Al2O3 ultrafine powder has a particle size of no more than 10 nm and a purity of no less than 99.99%.

[0013] Furthermore, the preset mass ratio of ZrB2 ultrafine powder to α-SiC ultrafine powder in step S2 is 4:1.

[0014] Furthermore, the wet ball milling process in step S2 involves placing the composite powder to be milled into a ball mill jar, adding a certain mass of anhydrous ethanol and grinding balls, and using an omnidirectional planetary ball mill to fully mix the composite powder. The mass ratio of the composite powder to anhydrous ethanol is between 1:4.4 and 1:5, and the mass ratio of the composite powder to the grinding balls is 1:3. The ball mill speed is set to 130–150 rpm, and a forward and reverse ball milling process is employed. Based on a preset milling time, the composite powder is thoroughly dispersed and mixed evenly. After milling, the anhydrous ethanol and grinding balls are removed, and the composite powder is dried. Finally, an agate mortar is used to break up any agglomerated powder.

[0015] Furthermore, the preset ball milling time refers to 30 minutes of clockwise rotation, 30 minutes of counterclockwise rotation, 10 minutes of intermittent rotation, and a total of 300 minutes of ball milling.

[0016] Furthermore, the pre-processed graphite mold in step S3 refers to fully wrapping the inner wall of the graphite mold with graphite paper, and pressing it so that the pressure head fits tightly with the inner wall of the graphite mold to obtain the graphite mold.

[0017] Furthermore, surface smoothing in step S1 refers to smoothing the surface with sandpaper of different grits; cleaning in step S1 refers to ultrasonic cleaning with deionized water and anhydrous ethanol.

[0018] Furthermore, the sintering pressure in step S4 is 40 MPa; the stepped heating process specifically refers to a heating rate of 100 °C / min from room temperature to 800 °C, followed by holding at 800 °C for 1 min; a heating rate of 100 °C / min from 800 °C to 1400 °C, followed by holding at 1400 °C for 1 min; and a heating rate of 50 °C / min from 1400 °C to 1850 °C, followed by holding at 1850 °C for 5 min.

[0019] Furthermore, according to the method for preparing the ZrB2-SiC(Al) anti-oxidation coating of C / C composite material by hot pressing and rapid sintering, the prepared ZrB2-SiC(Al) anti-oxidation coating has a uniform thickness, ranging from 700 to 800 μm, and a crack width of 4 μm.

[0020] Compared with the prior art, the present invention has at least the following beneficial effects:

[0021] (1) The method of preparing C / C composite material ZrB2-SiC(Al) antioxidant coating by hot pressing and rapid sintering of the present invention uses ultrafine powder and combines it with an all-round wet ball milling process to pretreat the composite powder, so that the composite powder is fully dispersed and mixed evenly, thereby improving the uniformity of the distribution of each phase in the ceramic coating and reducing powder agglomeration.

[0022] (2) The method for preparing C / C composite material ZrB2-SiC(Al) anti-oxidation coating by hot pressing rapid sintering of the present invention adopts spark plasma rapid sintering technology, combined with a unique stepped heating process, and holds the temperature at 800℃ and 1400℃ respectively, and reasonably adjusts the heating rate in the high temperature zone to promote rapid and full sintering of ceramic powder, so as to prepare an anti-oxidation coating with high density and strong bonding force with C / C matrix.

[0023] (3) The method of preparing C / C composite material ZrB2-SiC(Al) anti-oxidation coating by hot pressing and rapid sintering of the present invention uses the addition of trace amounts of Al2O3 to promote the sintering of composite powder, and at the same time, it can modify the outermost SiO2-rich glass layer generated after oxidation to form Si-O-Al bonds, which enhances the stability of the SiO2-rich glass film on the surface of the coating after oxidation, and further improves the oxidation protection capability of ZrB2-SiC coating.

[0024] (4) The method of preparing C / C composite material ZrB2-SiC(Al) antioxidant coating by hot pressing rapid sintering of the present invention is simple, has a short preparation cycle, and is easy to implement on a large scale. Attached Figure Description

[0025] The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0026] Figure 1 This is the XRD energy spectrum of the ZrB2-SiC antioxidant coating prepared in Example 2 of this invention;

[0027] Figure 2a This is a cross-sectional SEM image of the ZrB2-SiC antioxidant coating prepared in Example 2 of this invention;

[0028] Figure 2b This is a SEM image of the ZrB2-SiC antioxidant coating surface prepared in Example 2 of the present invention;

[0029] Figure 2c This is a cross-sectional SEM image of the ZrB2-SiC(Al) antioxidant coating prepared in Example 3 of this invention;

[0030] Figure 2dThis is a SEM image of the ZrB2-SiC(Al) antioxidant coating surface prepared in Example 3 of the present invention;

[0031] Figure 3 The oxidation weight gain curves of the ZrB2-SiC(Al) antioxidant coating prepared in Example 3 of the present invention and the ZrB2-SiC antioxidant coating prepared in Example 2 of the present invention at 1400℃ are shown.

[0032] Figure 4a The image shows the surface morphology of the ZrB2-SiC antioxidant coating prepared in Example 2 of this invention.

[0033] Figure 4b This is a magnified view of a portion of the surface of the ZrB2-SiC antioxidant coating prepared in Example 2 of the present invention;

[0034] Figure 4c The image shows the surface morphology of the ZrB2-SiC(Al) antioxidant coating prepared in Example 3 of this invention.

[0035] Figure 4d This is a magnified view of a portion of the surface of the ZrB2-SiC(Al) antioxidant coating prepared in Example 3 of the present invention. Detailed Implementation

[0036] To better understand the above-described objectives, features, and advantages of the present invention, the invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be noted that, unless otherwise specified, the embodiments of the present invention and the features thereof can be combined with each other. Furthermore, the present invention can be implemented in other ways different from those described herein; therefore, the scope of protection of the present invention is not limited to the specific embodiments disclosed below.

[0037] Example 1

[0038] A specific embodiment of the present invention discloses a method for preparing a ZrB2-SiC(Al) anti-oxidation coating of C / C composite material by hot pressing and rapid sintering. ZrB2 ultrafine powder and α-SiC ultrafine powder are measured and mixed according to a preset ratio. A small amount of Al2O3 ultrafine powder is added. The mixture is then wet-milled using an omnidirectional planetary ball mill to obtain a uniformly composite ZrB2-SiC(Al) powder. The pretreated C / C composite matrix is ​​fully embedded in the ZrB2-SiC(Al) composite powder and placed in a graphite mold for spark plasma sintering. After stepped heating sintering and rapid cooling, a ZrB2-SiC(Al) anti-oxidation coating is obtained on the surface of the C / C composite matrix. The method maintains that the mass fraction of SiC ultrafine powder in the ZrB2 and SiC mixed powder is 10 wt.% to 40 wt.%, and the Al / Si molar ratio in the ZrB2-SiC(Al) composite powder is maintained in the range of 0 to 0.1.

[0039] The method for preparing C / C composite material ZrB2-SiC(Al) antioxidant coating by hot pressing and rapid sintering according to the embodiments of the present invention includes the following specific steps:

[0040] Step S1. Process the C / C composite matrix and smooth its surface with sandpaper of different grits; ultrasonically clean the smoothed C / C composite matrix with deionized water and anhydrous ethanol; after cleaning, put it in a drying oven to dry, and obtain the pretreated C / C composite matrix after drying.

[0041] Preferably, the drying temperature is 70℃ and the drying time is 5 hours.

[0042] Step S2. Weigh a certain mass of ZrB2 ultrafine powder, α-SiC ultrafine powder, and Al2O3 ultrafine powder respectively. Mix the two powders thoroughly according to a preset mass ratio of ZrB2 ultrafine powder to α-SiC ultrafine powder, and add a small amount of Al2O3 ultrafine powder as a dopant to obtain a composite powder to be ball-milled. Use a wet ball milling process to wet ball mill the powder to be ball-milled using an omnidirectional planetary ball mill. Then, dry and grind the powder to obtain a uniform composite ZrB2-SiC(Al) powder. The preset mass ratio of ZrB2 ultrafine powder to α-SiC ultrafine powder is 4:1. Preferably, the drying temperature is 70℃ and the drying time is 12h.

[0043] It is worth noting that the particle size of ZrB2 ultrafine powder does not exceed 2μm and the purity is not less than 99%; the particle size of α-SiC ultrafine powder does not exceed 100nm and the purity is not less than 99%; and the particle size of Al2O3 ultrafine powder does not exceed 10nm and the purity is not less than 99.99%.

[0044] Specifically, the wet ball milling process involves placing the composite powder to be milled into a ball mill jar, adding a certain mass of anhydrous ethanol and grinding balls, and then using an omnidirectional planetary ball mill to thoroughly mix the composite powder. The mass ratio of the composite powder to anhydrous ethanol is between 1:4.4 and 1:5, and the mass ratio of the composite powder to the grinding balls is 1:3. The ball mill speed is set to 130–150 rpm, and a forward and reverse ball milling process is employed. Based on a preset milling time, the mill rotates forward for 30 minutes, then reverses for 30 minutes, with a 10-minute interval, for a total of 300 minutes, to thoroughly disperse and mix the composite powder. After milling, the anhydrous ethanol and grinding balls are removed, and the composite powder is dried. Finally, an agate mortar is used to break up any agglomerated powder.

[0045] Step S3. Place the pretreated C / C composite matrix into the pretreated graphite mold, and then pour the uniformly composited ZrB2-SiC(Al) composite powder into the pretreated graphite mold in three batches to fully embed the pretreated C / C composite matrix and spread it evenly, so that the ceramic coating thickness on the surface of the ZrB2-SiC sample after sintering is uniform. The upper and lower pressure heads compact the uniformly composited ZrB2-SiC(Al) composite powder, keeping the pressure heads and the inner wall of the graphite mold tightly fitted and not loose, thus completing the assembly of the graphite mold.

[0046] Specifically, the pretreatment of graphite molds refers to fully wrapping the inner wall of the graphite mold with graphite paper, so that the press head fits tightly with the inner wall of the graphite mold when pressed.

[0047] Step S4. Place the assembled graphite mold into a spark plasma sintering furnace for sintering. Set the sintering temperature to 1600-1900℃, adopt a stepped heating process, with a heating rate of 50-100℃ / min, a sintering pressure of 30-50MPa, and a holding time of 5-30min. After sintering, wait for the furnace temperature to cool to below 40℃ before removing the mold. A ZrB2-SiC(Al) anti-oxidation coating is obtained on the surface of the pretreated C / C composite matrix.

[0048] Specifically, the sintering pressure in step S4 is 40 MPa; the stepped heating process specifically refers to the heating rate from room temperature to 800℃ being 100℃ / min, and holding at 800℃ for 1 min; the heating rate from 800℃ to 1400℃ being 100℃ / min, and holding at 1400℃ for 1 min; and the heating rate from 1400℃ to 1850℃ being 50℃ / min, and holding at 1850℃ for 5 min.

[0049] Compared with existing technologies, the method for preparing C / C composite material ZrB2-SiC(Al) anti-oxidation coating by hot pressing rapid sintering proposed in this invention uses ultrafine powder and combines it with an all-round wet ball milling process to pre-treat the composite powder, so that the composite powder is fully dispersed and uniformly mixed, thereby improving the uniformity of phase distribution in the ceramic coating and reducing powder agglomeration. It employs spark plasma rapid sintering technology, combined with a unique stepped heating process, and controls the temperature at 800℃ and 1400℃ respectively, while reasonably regulating the heating rate in the high-temperature zone to promote rapid and complete sintering of the ceramic powder, resulting in an anti-oxidation coating with high density and strong adhesion to the C / C matrix. The addition of trace amounts of Al2O3 promotes the sintering of the composite powder and modifies the outermost SiO2-rich glass layer formed after oxidation, forming Si-O-Al bonds, enhancing the stability of the SiO2-rich glass film on the surface of the oxidized coating, and further improving the oxidation protection capability of the ZrB2-SiC coating. The process is simple, has a short preparation cycle, and is easy to scale up.

[0050] Example 2

[0051] Based on Example 1, this invention proposes a method for preparing a C / C composite material ZrB2-SiC antioxidant coating by hot pressing and rapid sintering, without adding Al2O3 in step A2 corresponding to step S2 in Example 1, while keeping other steps unchanged and further refined. The method includes the following specific steps:

[0052] Step A1. Process the C / C composite material to obtain a cylindrical C / C composite material matrix with a diameter of 12 mm and a height of 2 mm. Polish the surface of the cylindrical C / C composite material matrix with 800 grit and 2000 grit sandpaper respectively, then perform ultrasonic cleaning with deionized water and anhydrous ethanol. After cleaning, place it in a drying oven at 70℃ for 5 hours and take out the pre-treated cylindrical C / C composite material matrix for later use.

[0053] Step A2. Weigh 24g of ZrB2 ultrafine powder with a particle size not exceeding 2μm and 6g of α-SiC ultrafine powder with a particle size not exceeding 100nm respectively, and mix them thoroughly to obtain the composite powder to be ball-milled. Using an omnidirectional planetary ball mill, employ the wet ball milling method, place the composite powder to be ball-milled into a polytetrafluoroethylene ball milling jar, and pour anhydrous ethanol into the ball milling jar. The ball milling jar has a volume of 500ml, and the volume of anhydrous ethanol poured into the ball milling jar is about 170ml, which covers the surface of the composite powder to be ball-milled in the ball milling jar. The total volume of the composite powder to be ball-milled and the anhydrous ethanol after pouring in is about half of the volume of the ball milling jar, and does not exceed 2 / 3 of the volume of the ball milling jar.

[0054] Take 90g of agate grinding balls, set the ball mill speed to 130 rpm, rotate clockwise for 30 minutes, rotate counterclockwise for 30 minutes, and pause for 10 minutes, for a total of 300 minutes of ball milling. After ball milling, pour out the anhydrous ethanol and grinding balls, place the composite powder in a 70℃ drying oven and dry for 12 hours. Grind and crush the dried powder agglomerates using an agate mortar and pestle to obtain a uniformly composite ZrB2-SiC composite powder.

[0055] Step A3. Fully wrap the inner wall of the graphite mold with graphite paper, and press it so that the pressure head fits tightly with the inner wall of the graphite mold.

[0056] A pretreated cylindrical C / C composite matrix is ​​placed in a pretreated graphite mold. Then, uniformly compounded ZrB2-SiC composite powder is spread evenly around the pretreated cylindrical C / C composite matrix in three layers (0.8g, 0.4g, and 0.7g) to fully embed it. This even spreading ensures a uniform thickness of the ZrB2-SiC composite powder. Upper and lower pressure heads are used to compact the uniformly compounded ZrB2-SiC powder, ensuring a tight fit between the pressure heads and the inner wall of the graphite mold, thus completing the assembly of the graphite mold. The uniform thickness of the ZrB2-SiC composite powder after spreading is 1mm to 1.5mm.

[0057] Step A4. Place the assembled graphite mold into a spark plasma sintering furnace for sintering, setting the sintering pressure to 40 MPa. Design a unique stepped heating process: the heating rate from room temperature to 800℃ is 100℃ / min, holding at 800℃ for 1 min; the heating rate from 800℃ to 1400℃ is 100℃ / min, holding at 1400℃ for 1 min; the heating rate from 1400℃ to 1850℃ is 50℃ / min, holding at 1850℃ for 5 min. After sintering, remove the mold after the furnace temperature drops below 40℃, obtaining a ZrB2-SiC anti-oxidation coating on the surface of the pretreated cylindrical C / C composite matrix.

[0058] Figure 1 Figure 2(a) shows the surface XRD pattern of the ZrB2-SiC anti-oxidation coating prepared in Example 2 of this invention. The phase composition of this coating is mainly SiC and ZrB2. Figure 2(a) is a cross-sectional SEM image of the ZrB2-SiC anti-oxidation coating prepared in Example 2 of this invention. As can be seen from the figure, the ceramic coating is well bonded to the substrate, with no obvious cracks or fissures. Figure 2(b) is a surface SEM image of the ZrB2-SiC anti-oxidation coating prepared in Example 2 of this invention. The figure shows that the phases of the coating are dispersed, tightly bonded, and have a dense surface without obvious pores or cracks.

[0059] Example 3

[0060] Based on Example 2, a small amount of Al2O3 is added to step B2, which corresponds to step A2 in Example 2. This invention proposes a method for preparing a C / C composite material ZrB2-SiC(Al) antioxidant coating by hot pressing and rapid sintering, including the following specific steps:

[0061] Step B1. Process the C / C composite material to obtain a cylindrical C / C composite matrix with a diameter of 12.5 mm and a height of 2.5 mm. Polish the surface of the cylindrical C / C composite matrix with 400-grit, 1200-grit, and 2000-grit sandpaper respectively, then ultrasonically clean it with deionized water and anhydrous ethanol. After cleaning, dry it in a 70℃ drying oven for 5 hours, and then take out the pre-treated cylindrical C / C composite matrix for later use.

[0062] Step B2. Weigh 23.8782g of ZrB2 ultrafine powder with a particle size not exceeding 2μm and 5.9696g of α-SiC ultrafine powder with a particle size not exceeding 100nm, mix them thoroughly, and add 0.1522g of Al2O3 ultrafine powder with a particle size not exceeding 10nm as a dopant to obtain the composite powder to be ball-milled. Using an omnidirectional planetary ball mill, employ the wet ball milling method, place the composite powder to be ball-milled into a polytetrafluoroethylene ball milling jar, and pour anhydrous ethanol into the ball milling jar. The ball milling jar has a volume of 500ml, and the volume of anhydrous ethanol poured into the ball milling jar is about 170ml, which covers the surface of the powder to be ball-milled in the ball milling jar. The total volume of the composite powder to be ball-milled and the anhydrous ethanol after pouring in is about half of the volume of the ball milling jar, not exceeding 2 / 3 of the volume of the ball milling jar.

[0063] Take 90g of agate grinding balls, set the ball mill speed to 130 rpm, rotate clockwise for 30 minutes, rotate counterclockwise for 30 minutes, and pause for 10 minutes, for a total of 300 minutes of ball milling. After ball milling, pour out the anhydrous ethanol and grinding balls, place the composite powder in a 70℃ drying oven and dry for 12 hours. Grind and crush the powder agglomerates obtained after drying using an agate mortar and pestle to obtain a uniformly composite ZrB2-SiC(Al) composite powder.

[0064] Step B3. Fully wrap the inner wall of the graphite mold with graphite paper, and press it so that the pressure head fits tightly with the inner wall of the graphite mold.

[0065] A pretreated cylindrical C / C composite matrix is ​​placed in a pretreated graphite mold. Then, uniformly compounded ZrB2-SiC(Al) powder is spread evenly around the pretreated cylindrical C / C composite matrix in three layers (0.8g, 0.4g, and 0.7g) to fully embed it. This even spreading ensures a uniform thickness of the ZrB2-SiC(Al) composite powder. Upper and lower pressure heads compact the uniformly compounded ZrB2-SiC(Al) composite powder, ensuring a tight fit between the pressure heads and the inner wall of the graphite mold, thus completing the assembly of the graphite mold. The uniform thickness of the ZrB2-SiC(Al) composite powder after spreading is 1mm to 1.5mm.

[0066] Step B4. Place the assembled graphite mold into a spark plasma sintering furnace for sintering, setting the sintering pressure to 40 MPa. Design a unique stepped heating process: the heating rate from room temperature to 800℃ is 100℃ / min, with a holding time of 1 min at 800℃; the heating rate from 800℃ to 1400℃ is 100℃ / min, with a holding time of 1 min at 1400℃; the heating rate from 1400℃ to 1850℃ is 50℃ / min, with a holding time of 5 min at 1850℃. After sintering, remove the mold after the furnace temperature drops below 40℃, obtaining a ZrB2-SiC(Al) anti-oxidation coating on the surface of the pretreated cylindrical C / C composite matrix.

[0067] Figure 2c and 2d The figures show the cross-section and surface morphology of the ZrB2-SiC(Al) coating. As can be seen from the figures, the prepared ZrB2-SiC(Al) coating has no obvious pores or microcracks on its surface, exhibits higher densification, and shows uniform distribution of each phase. The coating is tightly bonded to the substrate without cracking.

[0068] Figure 3 This is a comparison of the oxidation weight gain of the ZrB2-SiC(Al) antioxidant coating prepared in Example 3 of the present invention and the ZrB2-SiC antioxidant coating prepared in Example 2 of the present invention after oxidation at 1400℃ for 20h. As can be seen from the figure, the oxidation weight gain of the ZrB2-SiC(Al) coating sample is significantly smaller than that of the ZrB2-SiC coating sample, and the antioxidant performance is significantly improved. Figure 4a and Figure 4b The image shows the surface morphology of the ZrB2-SiC antioxidant coating and a magnified view of a portion thereof. Figure 4c and Figure 4dThe figures show the surface morphology of the ZrB2-SiC(Al) anti-oxidation coating and its magnified partial view. As can be seen from the figures, compared to the ZrB2-SiC anti-oxidation coating, the surface crack width of the ZrB2-SiC(Al) anti-oxidation coating is significantly reduced after oxidation, the number of island-like ZrO2 agglomerates is decreased, and a small amount of Al doping can improve the stability of the glass film, reduce volatilization, and reduce the crack width from 7 μm to 4 μm.

[0069] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing a C / C composite material ZrB2-SiC(Al) antioxidant coating by hot pressing and rapid sintering, characterized in that, ZrB2 ultrafine powder and α-SiC ultrafine powder were measured and mixed according to a preset ratio. A small amount of Al2O3 ultrafine powder was added. After wet ball milling, a uniformly composite ZrB2-SiC(Al) composite powder was obtained. The pretreated C / C composite matrix was fully embedded in the ZrB2-SiC(Al) composite powder and placed in a graphite mold for spark plasma sintering. After stepped heating sintering and rapid cooling, a ZrB2-SiC(Al) anti-oxidation coating was obtained on the surface of the C / C composite matrix. The Al / Si molar ratio in the ZrB2-SiC(Al) composite powder was maintained in the range of 0~0.1, and the mass of Al2O3 ultrafine powder was not zero. Includes the following steps: Step S1. Process the C / C composite matrix, grind its surface, clean it and dry it to obtain a pretreated C / C composite matrix; Step S2. Weigh a certain mass of ZrB2 ultrafine powder, α-SiC ultrafine powder, and Al2O3 ultrafine powder respectively. Mix the two powders thoroughly according to the preset mass ratio of ZrB2 ultrafine powder and α-SiC ultrafine powder, and add a small amount of Al2O3 ultrafine powder as a dopant to obtain a composite powder to be ball-milled. Perform ball milling on the composite powder using a wet ball milling process. Dry the ball-milled powder and grind and break up any agglomerated powder to obtain a uniformly composite ZrB2-SiC(Al) composite powder. Step S3. Place the pretreated C / C composite matrix into the pretreated graphite mold, and then pour the uniformly composite ZrB2-SiC(Al) composite powder into the pretreated graphite mold in three batches to fully embed the C / C composite matrix and spread it evenly, thus completing the assembly of the graphite mold. Step S4. Place the assembled graphite mold into a spark plasma sintering furnace for sintering. After sintering, wait for the temperature inside the furnace to cool to below 40°C before taking it out. A ZrB2-SiC(Al) anti-oxidation coating is obtained on the surface of the pretreated C / C composite matrix. The ZrB2 ultrafine powder has a particle size not exceeding 2 μm and a purity not less than 99%; the α-SiC ultrafine powder has a particle size not exceeding 100 nm and a purity not less than 99%; the Al2O3 ultrafine powder has a particle size not exceeding 10 nm and a purity not less than 99.99%. The sintering pressure in step S4 is 40 MPa; the stepped heating process specifically refers to the heating rate from room temperature to 800°C being 100°C / min, holding at 800°C for 1 min; the heating rate from 800°C to 1400°C being 100°C / min, holding at 1400°C for 1 min; and the heating rate from 1400°C to 1850°C being 50°C / min, holding at 1850°C for 5 min. The prepared ZrB2-SiC(Al) antioxidant coating has a uniform thickness, ranging from 700 to 800 μm, and a crack width of 4 μm. The preset mass ratio of ZrB2 ultrafine powder to α-SiC ultrafine powder in step S2 is 4:1; The wet ball milling process in step S2 involves placing the composite powder to be milled into a ball mill jar, adding a certain mass of anhydrous ethanol and grinding balls, and using an omnidirectional planetary ball mill to fully mix the composite powder. The mass ratio of the composite powder to be milled to anhydrous ethanol is in the range of 1:4.4 to 1:5, and the mass ratio of the composite powder to the grinding balls is 1:

3. The ball mill speed is set to 130 to 150 rpm, and combined with forward and reverse ball milling, based on the preset ball milling time, the composite powder is fully dispersed and mixed evenly. After ball milling, the anhydrous ethanol and grinding balls are removed, and the composite powder is dried. The agglomerated powder is then broken up using an agate mortar.

2. The method for preparing a C / C composite material ZrB2-SiC(Al) antioxidant coating by hot pressing and rapid sintering according to claim 1, characterized in that, The preset ball milling time refers to 30 minutes of clockwise rotation, 30 minutes of counterclockwise rotation, and a 10-minute interval, for a total of 300 minutes of ball milling.

3. The method for preparing a C / C composite material ZrB2-SiC(Al) antioxidant coating by hot pressing and rapid sintering according to claim 2, characterized in that, The pre-processed graphite mold in step S3 refers to the graphite mold whose inner wall is fully wrapped with graphite paper, and the pressure head is pressed tightly against the inner wall of the graphite mold to obtain the graphite mold.

4. The method for preparing a C / C composite material ZrB2-SiC(Al) antioxidant coating by hot pressing and rapid sintering according to claim 3, characterized in that, The surface grinding in step S1 refers to grinding the surface with sandpaper of different grits; the cleaning in step S1 refers to ultrasonic cleaning with deionized water and anhydrous ethanol.

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