Preparation method of carbon fiber reinforced hafnium carbide-based ultrahigh-temperature ceramic composite material

Abstract

The invention provides a preparation method of a carbon fiber reinforced hafnium carbide-based ultrahigh-temperature ceramic composite material, and belongs to the technical field of ceramic composite materials. The preparation method comprises the following steps: treating carbon fibers, preparing a hafnium carbide precursor solution, compounding, mixing, molding and sintering. The step of preparing the hafnium carbide precursor solution comprises the following steps: adding hafnium tetrachloride and citric acid into ethylene glycol monomethyl ether, stirring at 58-63 DEG C for 2.0-2.5 hours, then reducing the temperature to 47-52 DEG C in a nitrogen atmosphere, adding ethylenediamine and triethanolamine, and reacting for 3.7-4.2 hours to obtain the hafnium carbide precursor solution; the product prepared by the method disclosed by the invention is good in strength and toughness, excellent in high-temperature-resistant stability and good in ablation resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of ceramic composite materials, and in particular relates to a method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material. Background Art

[0002] Hafnium carbide is a compound composed of hafnium (Hf) and carbon (C). From the basic properties, hafnium carbide has an extremely high melting point of about 3890°C, making it one of the compounds with the highest known melting points. It also has a high hardness, which gives it good wear resistance and allows it to withstand harsh friction environments. It also has excellent chemical stability and can maintain its structure and stability in a variety of chemical environments. It also has excellent antioxidant properties in high-temperature environments and can effectively resist oxygen erosion. In the field of ceramics, hafnium carbide plays a vital role. Due to its ultra-high melting point and good high-temperature stability, hafnium carbide is often used to prepare ultra-high temperature ceramic materials and is widely used in extreme high-temperature environments such as aerospace and the nuclear industry.

[0003] However, hafnium carbide-based ceramic materials have some inherent defects, such as high brittleness and easy fracture; insufficient ablation resistance and easy fracture when subjected to external impact or thermal stress, which limits their use in complex environments such as high temperature and high speed.

[0004] Carbon fiber has the advantages of high strength, high modulus, low density and good thermal stability. The high strength of carbon fiber makes it difficult to break when subjected to large external forces, and can provide a strong bearing capacity for the hafnium carbide ceramic matrix. Its high modulus makes the carbon fiber less deformed when subjected to force, effectively enhancing the stability of the ceramic material. In addition, the addition of carbon fiber can effectively improve the brittleness of the hafnium carbide ceramic matrix. When the material is impacted by external forces, the carbon fiber will change the expansion direction during the crack expansion process, increase the tortuosity of the crack expansion path, absorb more energy, and thus improve the toughness of the composite material, better play the strengthening and toughening properties of carbon fiber in the hafnium carbide ceramic matrix, and at the same time improve the anti-ablation performance of the composite material. However, the use of carbon fiber as a reinforcement phase in hafnium carbide-based ultra-high temperature ceramic composites has the following problems: First, the interfacial bonding force between the carbon fiber and the hafnium carbide matrix is ​​weak, resulting in low stress transfer efficiency. During the stress process, the carbon fiber is easily pulled out of the hafnium carbide matrix and cannot fully exert its reinforcing effect. Second, the dispersion performance of carbon fiber is poor and the agglomeration is strong, which leads to poor homogeneity of the composite material. Stress concentration points are easily formed at the agglomeration of carbon fiber, which reduces the comprehensive performance of the composite material. Third, the existing preparation process is relatively complicated and costly, making it difficult to achieve large-scale industrial production. Summary of the invention

[0005] In order to solve the technical problems existing in the prior art, the present invention provides a method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material. The composite material has high toughness and mechanical strength, excellent ablation resistance, and good high temperature stability.

[0006] A method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material, comprising the steps of carbon fiber processing, preparing a hafnium carbide precursor solution, compounding, mixing, and molding and sintering, as follows: 1. Carbon fiber processing (1) Preprocessing The carbon fiber is mixed evenly with 4-7 times the mass of acetone, and subjected to a water bath reflux reaction at a reaction temperature of 70-75°C and a reaction time of 7.8-8.3h. After the reflux reaction is completed, the carbon fiber is centrifugally washed and dried to obtain a pretreated carbon fiber; The carbon fiber has a length of 1.7-2.2 mm and a diameter of 110-130 nm; (2) Reprocessing The pretreated carbon fiber is put into an ethanol solution, and the temperature is raised to 62-66°C at a rate of 0.7-1.2°C / min, and then the reprocessing liquid is slowly added, and the addition rate is controlled to be 0.42-0.54g / min. Stirring is performed while adding, and the stirring speed is 140-180rpm. After the stirring is completed, the reaction is kept warm for 3.8-4.2h, and the reprocessed carbon fiber is obtained by filtering, washing, and drying; The mass ratio of the pretreated carbon fiber, the ethanol solution, and the reprocessing liquid is 8.2-8.8:85-95:20-25; The mass concentration of the ethanol solution is 40-44%; The preparation method of the reprocessing liquid is as follows: adding pyromellitic anhydride to N,N-dimethylformamide, stirring evenly, adding kH792 and chitosan solution, and performing ultrasonic dispersion, wherein the ultrasonic time is 20-30 minutes, the ultrasonic power is 65-70W, and the ultrasonic frequency is 12-17kHz. After the ultrasonic dispersion is completed, the reprocessing liquid is obtained; The chitosan solution is a mixture of chitosan and 4.8-5.2wt% acetic acid solution, and the mass ratio of the chitosan to the 4.8-5.2wt% acetic acid solution is 1.2-1.4:10.5-11.0; The mass ratio of the N,N-dimethylformamide, pyromellitic anhydride, kH792 and chitosan solution is 46-55:2.4-2.6:1.0-1.3:11.5-12.5.

[0007] 2. Preparation of Hafnium Carbide Precursor Solution Add hafnium tetrachloride and citric acid to ethylene glycol monomethyl ether, heat to 58-63°C at a rate of 1.5-2.5°C / min, keep warm and stir for 2.0-2.5h, then lower the temperature to 47-52°C under nitrogen atmosphere, add ethylenediamine and triethanolamine, and after the addition is complete, keep warm and react at 48-52°C for 3.7-4.2h to obtain a hafnium carbide precursor solution; The volume mass ratio of the ethylene glycol monomethyl ether, hafnium tetrachloride, citric acid, ethylenediamine and triethanolamine is 450-550 mL: 12.0-12.8 g: 13.6-14.5 g: 0.6-1.0 g: 0.6-0.8 g.

[0008] 3. Compound The reprocessed carbon fiber is placed in an ethanol solution, and after being evenly dispersed, a hafnium carbide precursor solution is added for ultrasonic dispersion, the ultrasonic time is 37-42 minutes, the ultrasonic power is 245-255W, and the ultrasonic frequency is 26-33kHz. After the ultrasonic treatment, the temperature is increased to 68-72°C, and the reaction is kept warm for 7.8-8.3 hours under a nitrogen atmosphere to obtain a carbon fiber / hafnium carbide composite; The mass ratio of the reprocessed carbon fiber, ethanol solution, and hafnium carbide precursor solution is 1.0-1.5 g: 36-43 g: 780-820 mL; The mass concentration of the ethanol solution is 48-52%.

[0009] 4. Mixing Dispersing the carbon fiber / hafnium carbide composite, hafnium boride, modified alumina and sodium carboxymethyl cellulose in deionized water, raising the temperature to 50-55° C., stirring at the temperature for 57-65 minutes, filtering, washing and drying to obtain a mixture; The mass ratio of the carbon fiber / hafnium carbide composite, hafnium boride, modified alumina, sodium carboxymethyl cellulose and deionized water is 100:8.0-8.5:1.8-2.2:1.0-1.6:480-520; The preparation method of the modified alumina comprises the following steps: adding polyvinyl butyral to an ethanol solution, raising the temperature to 52-56° C., stirring at 320-340 rpm for 38-43 minutes to obtain an impregnation solution; adding alumina powder to the impregnation solution, keeping the solution warm at 38-42° C. for 1.8-2.2 hours, filtering, washing and drying after the impregnation to obtain the modified alumina; The particle size of the aluminum oxide powder is 110-130 nm; The mass ratio of the ethanol solution to polyvinyl butyral is 100:4.2-4.8; The mass concentration of the ethanol solution is 30-34%; The mass ratio of the alumina powder to the impregnation liquid is 1:6-8.

[0010] 5. Molding and sintering The mixture is formed into a rough blank, which is placed in an argon atmosphere, heated to 580-620°C at a rate of 5.0-7.0°C / min, kept warm for 18-23 minutes, then heated to 1460-1520°C at a rate of 1.5-2.5°C / min, kept warm for 2.8-3.5 hours, to obtain a carbon fiber reinforced hafnium carbide based ultra-high temperature ceramic composite material.

[0011] Compared with the prior art, the present invention has achieved the following beneficial effects: 1. The present invention adopts carbon fiber as a reinforcing phase and hafnium carbide as a ceramic matrix to prepare an ultra-high temperature ceramic composite material; the carbon fiber is treated twice, firstly, it is pretreated to remove oil impurities and other components on the surface of the carbon fiber; in the re-treatment step, the re-treatment liquid is treated with pyromellitic anhydride to treat kH792 and chitosan, pyromellitic anhydride can react with the amino groups of kH792 and chitosan to undergo an amidation reaction, and an imide ring structure can be formed through a dehydration reaction during the amidation reaction, and chitosan can improve the dispersibility and stability of the carbon fiber; then a hafnium carbide precursor solution containing an amino group is prepared by a specific method; in the composite step, the carbon fiber The imide ring can be combined with the hafnium carbide precursor, so that the carbon fiber and the hafnium carbide are tightly and firmly combined together, the interface compatibility and bonding uniformity are enhanced, the reinforcing performance of the carbon fiber is better exerted, the stress is effectively transmitted, and the strength, toughness and stability of the composite material are improved; in the mixing step, the aluminum oxide is treated with polyvinyl butyral, which can reduce the surface energy of the aluminum oxide particles and reduce the agglomeration between the particles. The modified aluminum oxide obtained after the treatment can be combined with the carbon fiber / hafnium carbide composite, which improves the dispersion uniformity and homogeneity of the mixture, thereby ensuring the strength uniformity and high temperature resistance of the composite material, and improving the comprehensive performance of the composite material; 2. The carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material prepared by the method of the present invention has a flexural strength of 854-875 MPa and a fracture toughness of 11.5-11.8 MPa·m at room temperature. 1 / 2 After standing at 2200℃ for 120h, the flexural strength is 796-834MPa and the fracture toughness is 10.8-11.2MPa·m 1 / 2 ; 3. The carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material prepared by the method of the present invention has a mass ablation rate of -0.09 to -0.05 mg / s when ablated for 5 min at 2500°C in an oxyhydrogen flame. DETAILED DESCRIPTION

[0012] In order to more clearly understand the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described.

[0013] Example 1 1. Carbon fiber processing (1) Preprocessing The carbon fiber was mixed evenly with 4 times the mass of acetone, and subjected to a water bath reflux reaction at a reaction temperature of 70°C and a reaction time of 7.8 hours. After the reflux reaction was completed, the carbon fiber was centrifugally washed and dried to obtain a pretreated carbon fiber; The carbon fiber has a length of 1.7 mm and a diameter of 110 nm; (2) Reprocessing 8.2 g of pretreated carbon fiber was added to 85 g of 40 wt% ethanol solution, and the temperature was raised to 62 ° C at a rate of 0.7 ° C / min, and then 20 g of re-treatment liquid was slowly added, and the addition rate was controlled to be 0.42 g / min. Stirring was performed while adding, and the stirring speed was 140 rpm. After the stirring was completed, the reaction was kept warm for 3.8 hours, and the re-treated carbon fiber was obtained by filtering, washing and drying; The preparation method of the reprocessing liquid is as follows: add 2.4g of pyromellitic anhydride to 46g of N,N-dimethylformamide, stir evenly, add 1.0g of kH792 and 11.5g of chitosan solution, and perform ultrasonic dispersion, wherein the ultrasonic time is 20min, the ultrasonic power is 65W, and the ultrasonic frequency is 12kHz. After the ultrasonic dispersion is completed, the reprocessing liquid is obtained; The chitosan solution is a mixture of chitosan and 4.8 wt % acetic acid solution, and the mass ratio of the chitosan to the 4.8 wt % acetic acid solution is 1.2:10.5.

[0014] 2. Preparation of Hafnium Carbide Precursor Solution To 450 mL of ethylene glycol monomethyl ether, add 12.0 g of hafnium tetrachloride and 13.6 g of citric acid, heat to 58 ° C at a rate of 1.5 ° C / min, keep stirring for 2.0 hours, then lower the temperature to 47 ° C under a nitrogen atmosphere, add 0.6 g of ethylenediamine and 0.6 g of triethanolamine, and after the addition is complete, keep reacting at 48 ° C for 4.2 hours to obtain a hafnium carbide precursor solution.

[0015] 3. Compound 1.0 g of reprocessed carbon fiber was placed in 36 g of 48 wt% ethanol solution. After uniform dispersion, 780 mL of hafnium carbide precursor solution was added for ultrasonic dispersion. The ultrasonic time was 37 min, the ultrasonic power was 245 W, and the ultrasonic frequency was 26 kHz. After the ultrasonic treatment, the temperature was raised to 68 ° C and kept warm for 7.8 h under a nitrogen atmosphere to obtain a carbon fiber / hafnium carbide composite.

[0016] 4. Mixing Disperse 100 g of carbon fiber / hafnium carbide composite, 8.0 g of hafnium boride, 1.8 g of modified alumina, and 1.0 g of sodium carboxymethyl cellulose in 480 g of deionized water, raise the temperature to 50° C., keep stirring for 65 minutes, filter, wash, and dry to obtain a mixture; The preparation method of the modified alumina is as follows: add 4.2g of polyvinyl butyral to 100g of 30wt% ethanol solution, raise the temperature to 52°C, stir at 320rpm for 38min to obtain an impregnation solution; put the alumina powder into the impregnation solution of 6 times the mass, keep warm and immerse at 38°C for 1.8h, and after the impregnation is completed, filter, wash and dry to obtain the modified alumina; The particle size of the aluminum oxide powder is 110 nm.

[0017] 5. Molding and sintering The mixture is formed into a rough blank, and the rough blank is placed in an argon atmosphere, heated to 580°C at a rate of 5.0°C / min, kept warm for 18 minutes, and then heated to 1460°C at a rate of 1.5°C / min, kept warm for 3.5 hours, to obtain a carbon fiber reinforced hafnium carbide based ultra-high temperature ceramic composite material.

[0018] Example 2 1. Carbon fiber processing (1) Preprocessing The carbon fiber was mixed evenly with 7 times the mass of acetone, and subjected to a water bath reflux reaction at a temperature of 75°C and a reaction time of 8.3 h. After the reflux reaction was completed, the carbon fiber was centrifugally washed and dried to obtain a pretreated carbon fiber. The carbon fiber has a length of 2.2 mm and a diameter of 130 nm; (2) Reprocessing 8.8 g of pretreated carbon fiber was added to 95 g of 44 wt% ethanol solution, and the temperature was raised to 66 ° C at a rate of 1.2 ° C / min, and then 25 g of re-treatment liquid was slowly added, and the addition rate was controlled to be 0.54 g / min. Stirring was performed while adding, and the stirring speed was 180 rpm. After the stirring was completed, the reaction was kept warm for 4.2 hours, and the re-treated carbon fiber was obtained by filtering, washing and drying; The preparation method of the reprocessing liquid is as follows: add 2.6g of pyromellitic anhydride to 55g of N,N-dimethylformamide, stir evenly, add 1.3g of kH792 and 12.5g of chitosan solution, and perform ultrasonic dispersion, wherein the ultrasonic time is 30min, the ultrasonic power is 70W, and the ultrasonic frequency is 17kHz. After the ultrasonic dispersion is completed, the reprocessing liquid is obtained; The chitosan solution is a mixture of chitosan and 5.2 wt % acetic acid solution, and the mass ratio of the chitosan to the 5.2 wt % acetic acid solution is 1.4:11.0.

[0019] 2. Preparation of Hafnium Carbide Precursor Solution To 550 mL of ethylene glycol monomethyl ether, add 12.8 g of hafnium tetrachloride and 14.5 g of citric acid, heat to 63 ° C at a rate of 2.5 ° C / min, keep stirring for 2.5 hours, then lower the temperature to 52 ° C under a nitrogen atmosphere, add 1.0 g of ethylenediamine and 0.8 g of triethanolamine, and after the addition is complete, keep reacting at 52 ° C for 3.7 hours to obtain a hafnium carbide precursor solution.

[0020] 3. Compound 1.5 g of reprocessed carbon fiber was placed in 43 g of 52 wt% ethanol solution. After uniform dispersion, 820 mL of hafnium carbide precursor solution was added for ultrasonic dispersion. The ultrasonic time was 42 min, the ultrasonic power was 255 W, and the ultrasonic frequency was 33 kHz. After the ultrasonic treatment, the temperature was raised to 72 ° C and the reaction was kept warm for 8.3 h under a nitrogen atmosphere to obtain a carbon fiber / hafnium carbide composite.

[0021] 4. Mixing Disperse 100 g of carbon fiber / hafnium carbide composite, 8.5 g of hafnium boride, 2.2 g of modified alumina, and 1.6 g of sodium carboxymethyl cellulose in 520 g of deionized water, raise the temperature to 55° C., keep stirring for 57 minutes, filter, wash, and dry to obtain a mixture; The preparation method of the modified alumina is as follows: add 4.8g of polyvinyl butyral to 100g of 34wt% ethanol solution, raise the temperature to 56°C, stir at 340rpm for 43min to obtain an impregnation solution; put the alumina powder into the impregnation solution of 8 times the mass, keep warm and immerse at 42°C for 2.2h, filter, wash and dry after the impregnation to obtain the modified alumina; The particle size of the aluminum oxide powder is 130 nm.

[0022] 5. Molding and sintering The mixture is formed into a rough blank, and the rough blank is placed in an argon atmosphere, heated to 620°C at a rate of 7.0°C / min, kept warm for 23 minutes, and then heated to 1520°C at a rate of 2.5°C / min, kept warm for 2.8 hours, to obtain a carbon fiber reinforced hafnium carbide based ultra-high temperature ceramic composite material.

[0023] Example 3 1. Carbon fiber processing (1) Preprocessing The carbon fiber was mixed evenly with acetone of 5 times its mass, and subjected to a water bath reflux reaction at a reaction temperature of 73°C and a reaction time of 8.0 h. After the reflux reaction was completed, the carbon fiber was washed and dried by centrifugation to obtain a pretreated carbon fiber; The carbon fiber has a length of 2.0 mm and a diameter of 120 nm; (2) Reprocessing 8.5 g of pretreated carbon fiber was added to 90 g of 42 wt% ethanol solution, and the temperature was raised to 64 ° C at a rate of 1.0 ° C / min, and then 23 g of re-treatment liquid was slowly added, and the addition rate was controlled to be 0.50 g / min. Stirring was performed while adding, and the stirring speed was 160 rpm. After the stirring was completed, the reaction was kept warm for 4.0 hours, and the re-treated carbon fiber was obtained by filtering, washing and drying; The preparation method of the reprocessing liquid is as follows: add 2.5g of pyromellitic anhydride to 50g of N,N-dimethylformamide, stir evenly, add 1.2g of kH792 and 12.0g of chitosan solution, and perform ultrasonic dispersion, wherein the ultrasonic time is 25min, the ultrasonic power is 68W, and the ultrasonic frequency is 15kHz. After the ultrasonic dispersion is completed, the reprocessing liquid is obtained; The chitosan solution is a mixture of chitosan and 5.0 wt % acetic acid solution, and the mass ratio of the chitosan to the 5.0 wt % acetic acid solution is 1.3:10.7.

[0024] 2. Preparation of Hafnium Carbide Precursor Solution To 500 mL of ethylene glycol monomethyl ether, add 12.4 g of hafnium tetrachloride and 14.1 g of citric acid, heat to 60 ° C at a rate of 2.0 ° C / min, keep stirring for 2.3 hours, then lower the temperature to 50 ° C under a nitrogen atmosphere, add 0.8 g of ethylenediamine and 0.7 g of triethanolamine, and after the addition is complete, keep reacting at 50 ° C for 4.0 hours to obtain a hafnium carbide precursor solution.

[0025] 3. Compound 1.2 g of reprocessed carbon fiber was placed in 40 g of 50 wt% ethanol solution. After uniform dispersion, 800 mL of hafnium carbide precursor solution was added for ultrasonic dispersion. The ultrasonic time was 40 min, the ultrasonic power was 250 W, and the ultrasonic frequency was 30 kHz. After the ultrasonic treatment, the temperature was raised to 70 ° C. Under a nitrogen atmosphere, the reaction was kept warm for 8.0 h to obtain a carbon fiber / hafnium carbide composite.

[0026] 4. Mixing Disperse 100 g of carbon fiber / hafnium carbide composite, 8.3 g of hafnium boride, 2.0 g of modified alumina, and 1.3 g of sodium carboxymethyl cellulose in 500 g of deionized water, raise the temperature to 52° C., keep stirring for 60 min, filter, wash, and dry to obtain a mixture; The preparation method of the modified alumina is as follows: add 4.5g of polyvinyl butyral to 100g of 32wt% ethanol solution, raise the temperature to 54°C, stir at 330rpm for 40min to obtain an impregnation solution; put the alumina powder into the impregnation solution of 7 times the mass, keep warm and immerse at 40°C for 2.0h, filter, wash and dry after the impregnation to obtain the modified alumina; The particle size of the aluminum oxide powder is 120 nm.

[0027] 5. Molding and sintering The mixture is formed into a rough blank, and the rough blank is placed in an argon atmosphere, heated to 600°C at a rate of 6.0°C / min, kept warm for 20 minutes, and then heated to 1500°C at a rate of 2.0°C / min, kept warm for 3.0 hours, to obtain a carbon fiber reinforced hafnium carbide based ultra-high temperature ceramic composite material.

[0028] Comparative Example 1 Based on Example 3, the following changes are made: In the reprocessing step of the carbon fiber treatment, the preparation method of the reprocessing liquid is as follows: 1.2g of kH792 is added to 50g of N,N-dimethylformamide, and ultrasonic dispersion is performed. The ultrasonic time is 25min, the ultrasonic power is 68W, and the ultrasonic frequency is 15kHz. After the ultrasonic dispersion is completed, the reprocessing liquid is obtained; The pretreatment steps of carbon fiber treatment, the steps of preparing the hafnium carbide precursor solution, the compounding, mixing, and molding and sintering steps are exactly the same as those in Example 3.

[0029] Comparative Example 2 Based on Example 3, the following changes are made: The step of preparing the hafnium carbide precursor solution is to place 12.4 g of hafnium carbide powder in 40 g of 50 wt% ethanol solution and stir evenly to obtain the hafnium carbide precursor solution; the particle size of the hafnium carbide powder is 150 nm; In the mixing step, the modified alumina is replaced by an untreated alumina powder in equal amounts, wherein the alumina powder has a particle size of 120 nm; The carbon fiber processing, compounding, and molding and sintering steps are exactly the same as those in Example 3.

[0030] Performance Testing The comprehensive performance of the products obtained from test examples 1-3 and comparative examples 1-2 is as follows:

[0031] Among them, the high and low temperature cycle resistance test method is to heat the product to 2500℃ at a rate of 50℃ / min, keep it warm for 12.0h, and then reduce it to room temperature at a rate of 60℃ / min; the above operation is one cycle. After 10 cycles, the fracture toughness and flexural strength are tested again.

[0032] The invention adopts carbon fiber as a reinforcing phase and hafnium carbide as a ceramic matrix to prepare an ultra-high temperature ceramic composite material; the carbon fiber is treated twice, firstly, the carbon fiber is pretreated to remove components such as oil, dirt and impurities on the surface of the carbon fiber; in the re-treatment step, the re-treatment liquid is treated with pyromellitic anhydride to treat kH792 and chitosan, and pyromellitic anhydride can react with the amino groups of kH792 and chitosan to form an imide ring structure through a dehydration reaction during the amidation reaction, and chitosan can improve the dispersibility and stability of the carbon fiber; then, a hafnium carbide precursor solution containing an amino group is prepared by a specific method; in the composite step, the imine ring structure of the carbon fiber is The amine ring can be combined with the hafnium carbide precursor, so that the carbon fiber and the hafnium carbide are tightly and firmly combined together, the interface compatibility and bonding uniformity are enhanced, the reinforcing performance of the carbon fiber is better exerted, the stress is effectively transmitted, and the strength, toughness and stability of the composite material are improved; in the mixing step, the aluminum oxide is treated with polyvinyl butyral, which can reduce the surface energy of the aluminum oxide particles and reduce the agglomeration between the particles. The modified aluminum oxide obtained after the treatment can be combined with the carbon fiber / hafnium carbide composite, which improves the dispersion uniformity and homogeneity of the mixture, thereby ensuring the strength uniformity and high temperature resistance of the composite material, and improving the comprehensive performance of the composite material.

[0033] Comparative Example 1 only uses kH792 to reprocess the carbon fiber. Although it can modify the carbon fiber, its function is relatively simple. The cross-linking effect of isophthalic acid dianhydride and the protective effect of chitosan are omitted, which will not only reduce the stability of the carbon fiber, but also weaken the interface bonding with hafnium carbide, and ultimately reduce the strength and toughness of the product, and also weaken the high temperature resistance to a certain extent; Comparative Example 2 directly uses hafnium carbide powder to mix with the reprocessed fiber, which has poor interface compatibility with carbon fiber and weak bonding force, and in the mixing step, the aluminum oxide is not modified, so that the homogeneity of the mixture is poor, which ultimately leads to poor structure and uniformity of the composite material, making the material prone to cracks and damage when subjected to external forces, high temperatures and other conditions, reducing the strength, toughness, high temperature resistance and ablation resistance of the material.

[0034] Unless otherwise specified, all percentages used in the present invention are by mass.

[0035] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions described in the aforementioned embodiments or replace some of the technical features therein by equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material, characterized in that: It includes carbon fiber processing, preparation of hafnium carbide precursor solution, compounding, mixing, and molding and sintering steps; The carbon fiber treatment includes pretreatment and retreatment steps; The reprocessing step comprises: putting the pretreated carbon fiber into an ethanol solution, heating it to 62-66° C., adding a reprocessing solution, and keeping the temperature for reaction for 3.8-4.2 hours to obtain a reprocessed carbon fiber; The preparation method of the reprocessing liquid is as follows: adding pyromellitic anhydride to N,N-dimethylformamide, stirring evenly, adding KH792 and chitosan solution, and performing ultrasonic dispersion to obtain the reprocessing liquid; The steps of preparing the hafnium carbide precursor solution are: adding hafnium tetrachloride and citric acid to ethylene glycol monomethyl ether, stirring at 58-63° C. for 2.0-2.5 hours, then lowering the temperature to 47-52° C. under a nitrogen atmosphere, adding ethylenediamine and triethanolamine, and reacting for 3.7-4.2 hours to obtain the hafnium carbide precursor solution.

2. The method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material according to claim 1, characterized in that: In the carbon fiber processing step, the pretreatment step is to mix the carbon fiber and 4-7 times the mass of acetone uniformly, and perform a water bath reflux reaction at a reaction temperature of 70-75° C. for a reaction time of 7.8-8.3 h. After the reflux reaction is completed, the carbon fiber is centrifugally washed and dried to obtain a pretreated carbon fiber; The carbon fiber has a length of 1.7-2.2 mm and a diameter of 110-130 nm.

3. The method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material according to claim 1, characterized in that: In the carbon fiber processing step, the reprocessing step is to put the pretreated carbon fiber into an ethanol solution, heat it to 62-66°C at a rate of 0.7-1.2°C / min, and then slowly add the reprocessing liquid, control the addition rate to 0.42-0.54g / min, stir while adding, and the stirring speed is 140-180rpm. After the stirring is completed, keep the temperature for reaction for 3.8-4.2h, filter, wash and dry to obtain the reprocessed carbon fiber; The mass ratio of the pretreated carbon fiber, the ethanol solution, and the reprocessing liquid is 8.2-8.8:85-95:20-25; The mass concentration of the ethanol solution is 40-44%.

4. The method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material according to claim 1, characterized in that: In the preparation method of the reprocessing liquid, the ultrasonic dispersion has an ultrasonic time of 20-30 min, an ultrasonic power of 65-70 W, and an ultrasonic frequency of 12-17 kHz; The chitosan solution is a mixture of chitosan and 4.8-5.2wt% acetic acid solution, and the mass ratio of the chitosan to the 4.8-5.2wt% acetic acid solution is 1.2-1.4:10.5-11.0; The mass ratio of the N,N-dimethylformamide, pyromellitic anhydride, kH792 and chitosan solution is 46-55:2.4-2.6:1.0-1.3:11.5-12.

5.

5. The method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material according to claim 1, characterized in that: In the step of preparing the hafnium carbide precursor solution, the volume mass ratio of ethylene glycol monomethyl ether, hafnium tetrachloride, citric acid, ethylenediamine and triethanolamine is 450-550 mL: 12.0-12.8 g: 13.6-14.5 g: 0.6-1.0 g: 0.6-0.8 g.

6. The method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material according to claim 1, characterized in that: The composite step comprises placing the reprocessed carbon fiber in an ethanol solution, and after uniform dispersion, adding a hafnium carbide precursor solution, and performing ultrasonic dispersion, wherein the ultrasonic time is 37-42 minutes, the ultrasonic power is 245-255W, and the ultrasonic frequency is 26-33kHz. After the ultrasonic treatment, the temperature is increased to 68-72°C, and the reaction is kept warm for 7.8-8.3 hours under a nitrogen atmosphere to obtain a carbon fiber / hafnium carbide composite. The mass ratio of the reprocessed carbon fiber, ethanol solution, and hafnium carbide precursor solution is 1.0-1.5 g: 36-43 g: 780-820 mL; The mass concentration of the ethanol solution is 48-52%.

7. The method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material according to claim 1, characterized in that: The mixing step comprises dispersing the carbon fiber / hafnium carbide composite, hafnium boride, modified alumina and sodium carboxymethyl cellulose in deionized water, raising the temperature to 50-55° C., stirring at the temperature for 57-65 minutes, filtering, washing and drying to obtain a mixture; The mass ratio of the carbon fiber / hafnium carbide composite, hafnium boride, modified aluminum oxide, sodium carboxymethyl cellulose and deionized water is 100:8.0-8.5:1.8-2.2:1.0-1.6:480-520.

8. The method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material according to claim 7, characterized in that: The preparation method of the modified alumina comprises the following steps: adding polyvinyl butyral to an ethanol solution, raising the temperature to 52-56° C., stirring at 320-340 rpm for 38-43 minutes to obtain an impregnation solution; adding alumina powder to the impregnation solution, keeping the solution warm at 38-42° C. for 1.8-2.2 hours, filtering, washing and drying after the impregnation to obtain the modified alumina; The particle size of the aluminum oxide powder is 110-130 nm; The mass ratio of the ethanol solution to polyvinyl butyral is 100:4.2-4.8; The mass concentration of the ethanol solution is 30-34%; The mass ratio of the alumina powder to the impregnation liquid is 1:6-8.

9. The method for preparing a carbon fiber reinforced hafnium carbide-based ultra-high temperature ceramic composite material according to claim 1, characterized in that: The molding and sintering steps are as follows: molding the mixed material to obtain a rough blank, placing the rough blank in an argon atmosphere, heating it to 580-620°C at a rate of 5.0-7.0°C / min, keeping it warm for 18-23 minutes, then heating it to 1460-1520°C at a rate of 1.5-2.5°C / min, keeping it warm for 2.8-3.5 hours, and obtaining a carbon fiber reinforced hafnium carbide based ultra-high temperature ceramic composite material.

Images