A method for enhancing the ablative resistance of carbon / carbon composites

Abstract

This invention provides a method for enhancing the ablation resistance of carbon / carbon composite materials, belonging to the technical field of carbon / carbon composite materials. It includes the following steps: preparing SiBN multiphase ceramic powder, preparing SiBN multiphase ceramic powder slurry, plasma-treating carbon fiber preforms, and impregnation-drying-sintering cycle. The step of preparing the SiBN multiphase ceramic powder slurry involves adding silane-treated SiBN multiphase ceramic powder to a phenolic resin solution, performing ball milling and homogenization, and then adding it to an organic thickening liquid while stirring at 340-370 rpm. Yttrium oxide and acetylated chitosan are added, and stirring continues for 30-40 minutes to obtain the SiBN multiphase ceramic powder slurry. This invention obtains carbon / carbon composite materials by employing the PIP method to introduce SiBN composite ceramic components into the high thermal conductivity carbon / carbon skeleton, thereby improving the ablation resistance of the composite material while enhancing its thermal conductivity.

Description

Technical Field

[0001] This invention belongs to the field of carbon / carbon composite material technology, and specifically relates to a method for enhancing the ablation resistance of carbon / carbon composite materials. Background Technology

[0002] The structural design and material properties of thermal protection systems are the core factors determining the safety and reliability of high-speed aircraft, launch vehicles, and other major aerospace equipment. Their performance directly restricts the improvement of the equipment's flight speed, range, and load-bearing capacity. In the extreme service environments of aerospace equipment, especially core components such as the throat liner and nozzle of aerospace engines, they need to continuously withstand multiple harsh effects such as ultra-high temperatures above 2000°C, severe thermal shock, strong oxidizing atmospheres, and high-speed airflow erosion. This places extremely stringent technical requirements on the high temperature resistance, ablation resistance, and structural stability of thermal protection materials. High-performance thermal protection materials, as key materials to ensure the stable operation of such equipment, need to possess core characteristics such as ultra-high thermal conductivity, ultra-high load-bearing capacity, and high ablation resistance.

[0003] To address the challenges of ultra-high temperature service environments, thermal protection materials are evolving from refractory metals to ultra-high temperature ceramics (UHTC) and their composites. While UHTC ceramics possess high melting points and oxidation resistance, their inherent brittleness drives the development towards fiber-reinforced composites. Although silicon carbide fibers exhibit some oxidation resistance, they decompose thermally above 1600°C, making them unsuitable for ultra-high temperature service requirements. Carbon fiber, on the other hand, is a macroscopic fiber reinforcement that maintains high specific strength, high specific modulus, and low coefficient of thermal expansion above 3000°C. It can be molded into preforms using mature processes such as winding, weaving, and needle punching. Carbon fiber-reinforced ceramic matrix composites are therefore widely recognized as ideal materials for future ultra-high temperature thermal protection.

[0004] Currently, researchers from various countries have developed a variety of carbon fiber ceramic matrix composites, such as carbon / carbon-UHTC and carbon / carbon-UHTC-SiC, and have carried out a great deal of research on the composition design, preparation process and performance characterization of these materials.

[0005] Studies have shown that UHTC-SiC composite ceramics exhibit superior ablation resistance compared to a single UHTC matrix. The core mechanism lies in two aspects: firstly, the Zr / Hf / Ta-Si-O high-temperature glass phase generated during the high-temperature oxidation of UHTC-SiC composite ceramics during ablation can effectively seal cracks and pores in the composite material, forming a continuous and dense oxygen barrier layer that hinders oxygen diffusion into the material; secondly, the refractory metal oxide particles such as zirconium oxide and hafnium oxide generated during oxidation can play a "pinning" role, inhibiting the glass damage of high-velocity gas particles in the molten SiO2 phase, thereby giving the composite material excellent ablation resistance.

[0006] Based on this, high thermal conductivity carbon / carbon composites have become an important research direction for improving thermal protection due to their ability to quickly conduct and diffuse heat and reduce local temperature peaks. The typical modification approach is to directly introduce high-temperature components into the carbon / carbon composite matrix, thereby improving the overall oxidation and ablation resistance of the composite material by changing the matrix composition. The specific mechanism is that the introduced metal or ceramic particles generate corresponding molten oxides during oxidation or ablation, which can seal defects such as pores and cracks on the surface of the composite material, isolate the active sites on the surface of the carbon / carbon composite material, increase the initial oxidation temperature of the material, and the formed molten oxides have a low oxygen permeability, further preventing oxygen diffusion.

[0007] Currently, conventional carbon / carbon-UHTC-SiC composite materials are mainly prepared by chemical vapor infiltration (CVI) and precursor impregnation pyrolysis (PIP). The resulting composite materials exhibit good ablation resistance, but their thermal conductivity is usually ≤15W / m·K. As the ablation temperature increases, the ablation rate of the material increases significantly, making it difficult to meet the long-term service requirements under extreme ultra-high temperature environments.

[0008] Meanwhile, in existing preparation processes, the ceramization temperature of the precursor is usually no more than 1600℃, which is far lower than the local high temperature caused by the high thermal conductivity of the carbon / carbon skeleton. Excessively high heat treatment temperature can easily lead to thermal decomposition of the micro / nano structure ceramic matrix, further restricting the improvement of material performance. Although some researchers have achieved significant improvement in high thermal conductivity carbon / carbon composite materials (thermal conductivity 218W / m·K) compared to conventional carbon / carbon composite materials (36W / m·K) through coating modification, reducing the ablation temperature by 149℃ and the ablation rate from 13.57μm / s to 0.52μm / s under the same ablation environment, the coating has poor adhesion. Once the coating is damaged under the action of thermal shock airflow, the exposed carbon / carbon composite matrix will rapidly undergo oxidation and ablation, making it impossible to achieve long-term effective thermal protection.

[0009] As can be seen from the above, the existing thermal protection material system, especially the high thermal conductivity carbon / carbon composite material, still has many problems in terms of high temperature stability, long-term ablation resistance and protection reliability. Developing a carbon / carbon composite material that can significantly improve ablation resistance and service reliability while improving thermal conductivity is of great research significance. Summary of the Invention

[0010] To address the technical problems existing in the prior art, this invention provides a method for enhancing the ablation resistance of carbon / carbon composite materials. The method employs the PIP method to introduce SiBN composite ceramic components into the interior of a high thermal conductivity carbon / carbon skeleton, thereby improving the ablation resistance of the composite material while enhancing its thermal conductivity.

[0011] To address the aforementioned technical problems, the present invention adopts the following technical solution:

[0012] A method for enhancing the ablation resistance of carbon / carbon composite materials includes preparing SiBN multiphase ceramic powder, preparing SiBN multiphase ceramic powder slurry, plasma treating carbon fiber preform, and impregnation-drying-sintering cycle steps, as detailed below:

[0013] 1. Preparation of SiBN multiphase ceramic powder

[0014] (1) Preparation of dry gel

[0015] Tetraethyl orthosilicate and triethyl borate were added to anhydrous ethanol and stirred at 300-320 rpm for 30-40 min. Hydrochloric acid solution was added to adjust the pH to 3-4. Deionized water was added and stirring was continued for 10-15 min. Tween 80 was added and the mixture was kept in a water bath at 35-37℃ and stirred for 1.5-2.0 h. Zirconium source solution was added at a rate of 0.1-0.2 g / min and kept in a water bath at 35-37℃ and stirred for 30-35 min at a stirring speed of 300-330 rpm. The mixture was then transferred to a sealed container and aged at 25-27℃ for 12-13 h. Finally, the mixture was vacuum dried at 40-42℃ for 10-12 h at a vacuum degree of -0.08 to -0.09 MPa to obtain a dry gel.

[0016] The mass ratio of tetraethyl orthosilicate, triethyl borate, anhydrous ethanol, deionized water, Tween 80, and zirconium source solution is 6.0-6.5:2.5-3.0:30:1.0-1.3:0.5-0.7:4.2-4.3.

[0017] The zirconium source solution is prepared by adding 0.2-0.3g of zirconium isopropoxide to 4.0g of anhydrous ethanol and stirring until homogeneous.

[0018] The hydrochloric acid solution has a mass concentration of 5.0-6.0%;

[0019] (2) Sintering

[0020] The dried gel was placed in a tube furnace, and ammonia gas was introduced at a flow rate of 50-55 mL / min. The temperature was increased to 580-600℃ at a rate of 1.5-2.0℃ / min and held for 50-60 min. The ammonia flow rate was then increased to 75-80 mL / min, and the temperature was increased to 1000-1100℃ at a rate of 2.5-3.0℃ / min and held for 3.8-4.2 h. Then, under an argon atmosphere, the temperature was increased to 1480-1520℃ at a flow rate of 100-110 mL / min and held for 2.0-2.3 h. After naturally cooling to room temperature, the powder was pulverized to 50-100 nm to obtain SiBN multiphase ceramic powder.

[0021] 2. Preparation of SiBN multiphase ceramic powder slurry

[0022] SiBN multiphase ceramic powder was added to anhydrous ethanol, the temperature was raised to 36-40℃, and stirred for 20-25 min. KH550 silane coupling agent was added, the temperature was raised to 62-67℃, and stirred for 2.5-3.0 h. After filtration, washing and drying, silane-treated SiBN multiphase ceramic powder was obtained.

[0023] The mass ratio of the SiBN multiphase ceramic powder, anhydrous ethanol, and kH550 silane coupling agent is 10:70-80:1.0-1.3.

[0024] Hydroxypropyl methylcellulose was added to a phenolic resin solution, and the temperature was raised to 48-52℃. The solution was stirred for 50-60 minutes to obtain an organic thickening solution. Silane-treated SiBN multiphase ceramic powder was added to the phenolic resin solution and ball-milled for 2.0-2.5 hours at a ball-to-material ratio of 6-8:1 and a milling speed of 240-250 rpm. After ball milling, homogenization was performed three times at a pressure of 30-40 MPa for 5-6 minutes each time. After homogenization, the powder was added to the organic thickening solution while stirring at 340-370 rpm. Yttrium oxide and acetylated chitosan were added, and stirring was continued for 30-40 minutes to obtain a SiBN multiphase ceramic powder slurry.

[0025] The mass ratio of the hydroxypropyl methylcellulose to the phenolic resin solution is 2-3:30;

[0026] The mass ratio of the silane-treated SiBN multiphase ceramic powder, phenolic resin liquid, organic thickening liquid, yttrium oxide, and acetylated chitosan is 50-53:45:32-33:0.7-0.8:3-4.

[0027] The phenolic resin solution is a mixture of phenolic resin and anhydrous ethanol, wherein the mass ratio of phenolic resin to anhydrous ethanol is 1:2.8-3.2.

[0028] The method for preparing acetylated chitosan is as follows: chitosan is added to a mixed solvent of dimethyl sulfoxide and glacial acetic acid, stirred at 48-52℃ for 2.5-3.0h, triethylamine is added, stirred for 10-15min, acetic anhydride is added, stirred at room temperature for 8-10h, after precipitation and washing, and vacuum dried at 50-53℃ and -0.08~-0.09MPa for 10-12h to obtain acetylated chitosan;

[0029] In the mixed solvent, the volume ratio of glacial acetic acid to dimethyl sulfoxide is 3.5-4.0:1;

[0030] The mass-to-volume ratio of chitosan, mixed solvent, triethylamine, and acetic anhydride is 10-12 g: 150 mL: 2.0-3.0 mL: 10-15 mL.

[0031] 3. Plasma-treated carbon fiber preforms

[0032] The carbon fiber preform is placed in a plasma treatment device, and a vacuum of 5-8 Pa is drawn. Argon gas is introduced, and the argon gas flow rate is controlled at 30-35 mL / min, the treatment power is 100-110 W, and the treatment time is 10-15 min. The vacuum is maintained at 5-8 Pa. The process is then switched to a mixed gas, with a flow rate of 30-35 mL / min, a power of 80-90 W, and a treatment time of 5-6 min. After the treatment is completed, the preform is allowed to cool naturally to room temperature to obtain the plasma-treated carbon fiber preform.

[0033] The areal density of the carbon fiber preform is 320-350 g / m³. 2 The thickness is 3-5mm, and the carbon fiber is T700 grade;

[0034] The mixed gas is a mixture of argon and ammonia, with a volume ratio of argon to ammonia of 8-9:1.

[0035] 4. Impregnation-drying-sintering cycle

[0036] Plasma-treated carbon fiber preforms are placed in an impregnation apparatus, and a vacuum of 1-2 Pa is applied. Six to eight times their mass of SiBN multiphase ceramic powder slurry is injected, and the mixture is impregnated for 50-60 min. Then, the pressure is increased to 0.30-0.32 MPa at a rate of 0.04-0.05 MPa / min, and the impregnation is maintained at this temperature for 25-30 min. Next, the pressure is increased to 0.40-0.43 MPa at a rate of 0.01-0.02 MPa / min, and the impregnation is maintained at this temperature for 2.0-2.3 h. After impregnation, the preforms are dried at 58-62℃ for 7.5-8.0 h, at 95-100℃ for 5.6-6.0 h, and at 150-153℃. After 3.8-4.2 hours, place the sample into a tube furnace, introduce argon gas at a flow rate of 65-70 mL / min, increase the temperature to 490-500℃ at a rate of 2.0-2.5℃ / min, hold for 2.0-2.2 hours, increase the temperature to 900-910℃ at a rate of 3.0-3.5℃ / min, hold for 2.8-3.2 hours, increase the temperature to 1450-1550℃ at a rate of 1.0-1.5℃ / min, hold for 4.0-4.5 hours, and cool to room temperature with the furnace to obtain a carbon / carbon composite material blank. The above operation is a dipping-drying-sintering process, and the above process is repeated 3 times to obtain the carbon / carbon composite material.

[0037] In the preparation of carbon / carbon composite materials, this invention introduces SiBN multiphase ceramic powder. The SiBN ceramic forms a continuous glassy protective film at high temperature, which hinders oxygen diffusion into the interior, prevents carbon fiber oxidation, and further improves ablation resistance and stability. The introduction of zirconium can increase the viscosity and high-temperature stability of the glassy phase, prevent the protective film from being lost at high temperature, enhance bending resistance, and further improve the density of the material. The multiphase ceramic powder can also form a continuous thermally conductive network with carbon fibers, improving thermal conductivity.

[0038] Specifically, tetraethyl orthosilicate is used as the silicon source, and triethyl borate as the boron source. A sol is formed through hydrolysis and condensation catalyzed by hydrochloric acid. Tween 80 is used as a dispersant to inhibit the aggregation of gel particles. The introduction of a zirconium source can regulate the crystal structure of the ceramic through zirconium ions, improving the thermal conductivity and ablation resistance of the subsequent multiphase ceramic. In the sintering step, an ammonia atmosphere is used to introduce nitrogen, and high-temperature sintering promotes ceramic grain densification, which is beneficial for the dispersion and impregnation filling of the pores in the carbon fiber preform. During slurry preparation, the multiphase ceramic powder is first treated with a silane coupling agent to improve the compatibility between the ceramic powder and phenolic resin, enhance its dispersion performance in the phenolic resin, and improve interfacial bonding. The phenolic resin liquid serves as a carbon source precursor and binder, and hydroxypropyl methylcellulose acts as a thickener to prevent sedimentation of the slurry during impregnation. Acetylated chitosan, as a biopolymer modifier, mainly functions as an auxiliary binder and dispersant. Acetylation of chitosan improves its solubility, and the acetyl groups enhance its compatibility with phenolic resins. The amino groups of chitosan can bond with the multiphase ceramic powders via hydrogen bonds, further improving the dispersion stability of the slurry. Before impregnation, the carbon fiber preform undergoes plasma treatment to increase the surface roughness and specific surface area of ​​the carbon fibers. Based on physical etching, nitrogen-containing functional groups are introduced onto the carbon fiber surface, making the hydrophobic carbon fibers easier to wet with the slurry and strengthening their bonding with the resin, coupling agent, and other components in the slurry, thereby enhancing the mechanical properties of the composite material. Multiple cycles of impregnation, drying, and sintering ensure that the slurry fully penetrates into the preform, resulting in a high-density, high-thermal-conductivity, and ablation-resistant carbon / carbon composite material.

[0039] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0040] 1. The carbon / carbon composite material obtained by this invention has a mass ablation rate of 0.00010-0.00017 g / s and a linear ablation rate of 0.21-0.25 μm / s at 1700℃;

[0041] 2. The carbon / carbon composite material obtained by this invention has a flexural strength of 391-398 MPa, a flexural modulus of 60-68 GPa, and a thermal conductivity of 358.5-364.2 W / m·K;

[0042] 3. The carbon / carbon composite material obtained in this invention was heated to 1000℃ at a rate of 20℃ / min and held for 72h, and then heated to 1600℃ at a rate of 10℃ / min and held for 96h. The flexural strength was measured again to be 372-385MPa and the flexural modulus to be 57-66Gpa. Detailed Implementation

[0043] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention are now described.

[0044] Example 1

[0045] 1. Preparation of SiBN multiphase ceramic powder

[0046] (1) Preparation of dry gel

[0047] 6.5 g of tetraethyl orthosilicate and 3.0 g of triethyl borate were added to 30 g of anhydrous ethanol and stirred at 320 rpm for 40 min. 6.0 wt% hydrochloric acid solution was added to adjust the pH to 4. 1.3 g of deionized water was added and stirring was continued for 15 min. 0.7 g of Tween 80 was added, and the mixture was kept in a water bath at 37 °C and stirred for 2.0 h. 4.3 g of zirconium source solution was added at a rate of 0.2 g / min, and the mixture was kept in a water bath at 37 °C and stirred for 35 min at a stirring speed of 330 rpm. The mixture was then transferred to a sealed container and allowed to stand at 27 °C for 12 h. Finally, it was vacuum dried at 42 °C for 10 h at a vacuum degree of -0.09 MPa to obtain a dry gel.

[0048] The zirconium source solution is prepared by adding 0.3g of zirconium isopropoxide to 4.0g of anhydrous ethanol and stirring until homogeneous.

[0049] (2) Sintering

[0050] The dried gel was placed in a tube furnace, and ammonia gas was introduced at a flow rate of 55 mL / min. The temperature was increased to 600℃ at a rate of 2.0℃ / min and held for 60 min. The ammonia flow rate was increased to 80 mL / min, and the temperature was increased to 1100℃ at a rate of 3.0℃ / min and held for 4.2 h. Then, under an argon atmosphere, the temperature was increased to 1520℃ at a flow rate of 100 mL / min and held for 2.3 h. After naturally cooling to room temperature, the gel was pulverized to 100 nm to obtain SiBN multiphase ceramic powder.

[0051] 2. Preparation of SiBN multiphase ceramic powder slurry

[0052] 10g of SiBN multiphase ceramic powder was added to 80g of anhydrous ethanol, the temperature was raised to 40℃, and stirred for 25min. Then, 1.3g of kH550 silane coupling agent was added, the temperature was raised to 67℃, and stirred for 3.0h. After filtration, washing and drying, silane-treated SiBN multiphase ceramic powder was obtained.

[0053] 3g of hydroxypropyl methylcellulose was added to 30g of phenolic resin solution, the temperature was raised to 52℃, and the mixture was stirred for 60min to obtain an organic thickening solution. 53g of silane-treated SiBN multiphase ceramic powder was added to 45g of phenolic resin solution and ball-milled for 2.5h at a ball-to-material ratio of 8:1 at a speed of 250rpm. After ball milling, homogenization was performed three times at a pressure of 40MPa for 5min each time. After homogenization, the powder was added to 33g of organic thickening solution while stirring at 370rpm. 0.8g of yttrium oxide and 4g of acetylated chitosan were added, and stirring was continued for 40min to obtain a SiBN multiphase ceramic powder slurry.

[0054] The phenolic resin solution is a mixture of phenolic resin and anhydrous ethanol, wherein the mass ratio of phenolic resin to anhydrous ethanol is 1:3.2.

[0055] The method for preparing acetylated chitosan is as follows: 12g of chitosan is added to a mixed solvent of 150mL dimethyl sulfoxide and glacial acetic acid, stirred at 52℃ for 3.0h, 3.0mL of triethylamine is added, stirred for 15min, 15mL of acetic anhydride is added, stirred at room temperature for 10h, washed after precipitation, and vacuum dried at 53℃ and -0.09MPa for 10h to obtain acetylated chitosan;

[0056] In the mixed solvent, the volume ratio of glacial acetic acid to dimethyl sulfoxide is 4.0:1.

[0057] 3. Plasma-treated carbon fiber preforms

[0058] The carbon fiber preform was placed in a plasma treatment device, and the vacuum was evacuated to a vacuum degree of 8 Pa. Argon gas was introduced, and the argon gas flow rate was controlled at 35 mL / min, the treatment power was 110 W, and the treatment time was 15 min. The vacuum degree was maintained at 8 Pa. The device was then switched to a mixed gas, with a mixed gas flow rate of 35 mL / min, a control power of 90 W, and a treatment time of 5 min. After the treatment was completed, the preform was allowed to cool naturally to room temperature to obtain the plasma-treated carbon fiber preform.

[0059] The areal density of the carbon fiber preform is 350 g / m³. 2 The thickness is 5mm, and the carbon fiber is T700 grade;

[0060] The mixed gas is a mixture of argon and ammonia, with a volume ratio of argon to ammonia of 9:1.

[0061] 4. Impregnation-drying-sintering cycle

[0062] The plasma-treated carbon fiber preform was placed in an impregnation apparatus, and a vacuum of 1 Pa was applied. Eight times its mass of SiBN multiphase ceramic powder slurry was injected and impregnated for 60 min. Then, the pressure was increased to 0.32 MPa at a rate of 0.04 MPa / min and held for 30 min. Next, the pressure was increased to 0.43 MPa at a rate of 0.01 MPa / min and held for 2.3 h. After impregnation, the preform was dried at 62℃ for 8.0 h, at 100℃ for 6.0 h, and at 153℃ for 4.2 h. The sample was placed in a tube furnace, and argon gas was introduced at a flow rate of 70 mL / min. The temperature was increased to 500℃ at a rate of 2.5℃ / min and held for 2.2 h. The temperature was then increased to 910℃ at a rate of 3.5℃ / min and held for 3.2 h. Finally, the temperature was increased to 1550℃ at a rate of 1.5℃ / min and held for 4.5 h. The sample was then cooled to room temperature in the furnace to obtain a carbon / carbon composite material blank. The above operation was performed as an impregnation-drying-sintering process. The above process was repeated 3 times to obtain the carbon / carbon composite material.

[0063] Example 2

[0064] 1. Preparation of SiBN multiphase ceramic powder

[0065] (1) Preparation of dry gel

[0066] 6.3 g of tetraethyl orthosilicate and 2.6 g of triethyl borate were added to 30 g of anhydrous ethanol and stirred at 310 rpm for 35 min. 5.5 wt% hydrochloric acid solution was added to adjust the pH to 3.6. 1.2 g of deionized water was added and stirring was continued for 13 min. 0.6 g of Tween 80 was added and the mixture was kept in a water bath at 36 ℃ and stirred for 1.8 h. 4.3 g of zirconium source solution was added at a rate of 0.1 g / min and the mixture was kept in a water bath at 36 ℃ and stirred for 32 min at a stirring speed of 320 rpm. The mixture was then transferred to a sealed container and allowed to stand at 26 ℃ for 13 h. Finally, it was vacuum dried at 42 ℃ for 10 h at a vacuum degree of -0.09 MPa to obtain a dry gel.

[0067] The zirconium source solution is prepared by adding 0.3g of zirconium isopropoxide to 4.0g of anhydrous ethanol and stirring until homogeneous.

[0068] (2) Sintering

[0069] The dried gel was placed in a tube furnace, and ammonia gas was introduced at a flow rate of 53 mL / min. The temperature was increased to 590 °C at a rate of 1.8 °C / min and held for 55 min. The ammonia flow rate was then increased to 77 mL / min, and the temperature was increased to 1050 °C at a rate of 2.8 °C / min and held for 4.0 h. Then, under an argon atmosphere, the temperature was increased to 1500 °C at a flow rate of 105 mL / min and held for 2.2 h. After naturally cooling to room temperature, the gel was pulverized to 70 nm to obtain SiBN multiphase ceramic powder.

[0070] 2. Preparation of SiBN multiphase ceramic powder slurry

[0071] 10g of SiBN multiphase ceramic powder was added to 75g of anhydrous ethanol, the temperature was raised to 38℃, and stirred for 23min. Then, 1.2g of kH550 silane coupling agent was added, the temperature was raised to 66℃, and stirred for 2.8h. After filtration, washing and drying, silane-treated SiBN multiphase ceramic powder was obtained.

[0072] 3g of hydroxypropyl methylcellulose was added to 30g of phenolic resin solution, the temperature was raised to 50℃, and the mixture was stirred for 55min to obtain an organic thickening solution. 52g of silane-treated SiBN multiphase ceramic powder was added to 45g of phenolic resin solution and ball-milled for 2.3h at a ball-to-material ratio of 7:1 at a speed of 245rpm. After ball milling, homogenization was performed three times at a pressure of 35MPa for 6min each time. After homogenization, the mixture was added to 33g of organic thickening solution while stirring at 360rpm. 0.8g of yttrium oxide and 4g of acetylated chitosan were added, and stirring was continued for 35min to obtain a SiBN multiphase ceramic powder slurry.

[0073] The phenolic resin solution is a mixture of phenolic resin and anhydrous ethanol, wherein the mass ratio of phenolic resin to anhydrous ethanol is 1:3.0.

[0074] The preparation method of the acetylated chitosan is as follows: 10g of chitosan is added to a mixed solvent of 150mL dimethyl sulfoxide and glacial acetic acid, stirred at 50℃ for 2.8h, 2.5mL of triethylamine is added, stirred for 13min, 12mL of acetic anhydride is added, stirred at room temperature for 9h, washed after precipitation, and vacuum dried at 52℃ and -0.09MPa for 10h to obtain acetylated chitosan;

[0075] In the mixed solvent, the volume ratio of glacial acetic acid to dimethyl sulfoxide is 3.8:1.

[0076] 3. Plasma-treated carbon fiber preforms

[0077] The carbon fiber preform was placed in a plasma treatment device, and the vacuum was evacuated to a vacuum degree of 6 Pa. Argon gas was introduced, and the argon gas flow rate was controlled at 32 mL / min, the treatment power was 105 W, and the treatment time was 13 min. The vacuum degree was maintained at 7 Pa. The device was then switched to a mixed gas, with a mixed gas flow rate of 32 mL / min, a control power of 85 W, and a treatment time of 6 min. After the treatment was completed, the preform was allowed to cool naturally to room temperature to obtain the plasma-treated carbon fiber preform.

[0078] The areal density of the carbon fiber preform is 330 g / m³. 2 The thickness is 4mm, and the carbon fiber is T700 grade;

[0079] The mixed gas is a mixture of argon and ammonia, with a volume ratio of argon to ammonia of 9:1.

[0080] 4. Impregnation-drying-sintering cycle

[0081] The plasma-treated carbon fiber preform was placed in an impregnation apparatus, and a vacuum of 1 Pa was applied. Seven times its mass of SiBN multiphase ceramic powder slurry was injected and impregnated for 55 min. Then, the pressure was increased to 0.32 MPa at a rate of 0.04 MPa / min and held for 28 min. Next, the pressure was increased to 0.42 MPa at a rate of 0.01 MPa / min and held for 2.2 h. After impregnation, the preform was dried at 60℃ for 7.8 h, at 97℃ for 5.8 h, and at 152℃ for 4.0 h. The sample was placed in a tube furnace, and argon gas was introduced at a flow rate of 68 mL / min. The temperature was increased to 495°C at a rate of 2.2°C / min and held for 2.2 h. The temperature was then increased to 905°C at a rate of 3.3°C / min and held for 3.0 h. Finally, the temperature was increased to 1500°C at a rate of 1.2°C / min and held for 4.3 h. The sample was then cooled to room temperature in the furnace to obtain a carbon / carbon composite material blank. The above operation was performed as an impregnation-drying-sintering process. The above process was repeated 3 times to obtain the carbon / carbon composite material.

[0082] Example 3

[0083] 1. Preparation of SiBN multiphase ceramic powder

[0084] (1) Preparation of dry gel

[0085] 6.0 g of tetraethyl orthosilicate and 2.3 g of triethyl borate were added to 30 g of anhydrous ethanol and stirred at 300 rpm for 30 min. 5.0 wt% hydrochloric acid solution was added to adjust the pH to 3. 1.0 g of deionized water was added and stirring was continued for 10 min. 0.5 g of Tween 80 was added, and the mixture was kept in a water bath at 35 °C and stirred for 1.5 h. 4.2 g of zirconium source solution was added at a rate of 0.1 g / min, and the mixture was kept in a water bath at 35 °C and stirred for 30 min at 300 rpm. The mixture was then transferred to a sealed container and aged at 25 °C for 13 h. Finally, it was vacuum dried at 40 °C for 12 h at a vacuum degree of -0.08 MPa to obtain a dry gel.

[0086] The zirconium source solution is prepared by adding 0.2g of zirconium isopropoxide to 4.0g of anhydrous ethanol and stirring until homogeneous.

[0087] (2) Sintering

[0088] The dried gel was placed in a tube furnace, and ammonia gas was introduced at a flow rate of 50 mL / min. The temperature was increased to 580 °C at a rate of 1.5 °C / min and held for 50 min. The ammonia flow rate was increased to 75 mL / min, and the temperature was increased to 1000 °C at a rate of 2.5 °C / min and held for 3.8 h. Then, under an argon atmosphere, the temperature was increased to 1480 °C at a flow rate of 100 mL / min and held for 2.0 h. After naturally cooling to room temperature, the gel was pulverized to 50 nm to obtain SiBN multiphase ceramic powder.

[0089] 2. Preparation of SiBN multiphase ceramic powder slurry

[0090] 10g of SiBN multiphase ceramic powder was added to 70g of anhydrous ethanol, the temperature was raised to 36℃, and stirred for 20min. Then, 1.0g of kH550 silane coupling agent was added, the temperature was raised to 62℃, and stirred for 2.5h. After filtration, washing and drying, silane-treated SiBN multiphase ceramic powder was obtained.

[0091] 2g of hydroxypropyl methylcellulose was added to 30g of phenolic resin solution, the temperature was raised to 48℃, and the mixture was stirred for 50min to obtain an organic thickening solution. 50g of silane-treated SiBN multiphase ceramic powder was added to 45g of phenolic resin solution and ball-milled for 2.0h at a ball-to-material ratio of 6:1 at a speed of 240rpm. After ball milling, homogenization was performed three times at a pressure of 30MPa for 6min each time. After homogenization, the mixture was added to 32g of organic thickening solution while stirring at 340rpm. 0.7g of yttrium oxide and 3g of acetylated chitosan were added, and stirring was continued for 30min to obtain a SiBN multiphase ceramic powder slurry.

[0092] The phenolic resin solution is a mixture of phenolic resin and anhydrous ethanol, wherein the mass ratio of phenolic resin to anhydrous ethanol is 1:2.8.

[0093] The method for preparing acetylated chitosan is as follows: 10g of chitosan is added to a mixed solvent of 150mL dimethyl sulfoxide and glacial acetic acid, stirred at 48℃ for 2.5h, 2.0mL of triethylamine is added, stirred for 10min, 10mL of acetic anhydride is added, stirred at room temperature for 8h, washed after precipitation, and vacuum dried at 50℃ and -0.08MPa for 12h to obtain acetylated chitosan;

[0094] In the mixed solvent, the volume ratio of glacial acetic acid to dimethyl sulfoxide is 3.5:1.

[0095] 3. Plasma-treated carbon fiber preforms

[0096] The carbon fiber preform was placed in a plasma treatment device, and the vacuum was evacuated to a vacuum degree of 5 Pa. Argon gas was introduced, and the argon gas flow rate was controlled at 30 mL / min, the treatment power was 100 W, and the treatment time was 10 min. The vacuum degree was maintained at 5 Pa. The device was then switched to a mixed gas, with a mixed gas flow rate of 30 mL / min, a control power of 80 W, and a treatment time of 5 min. After the treatment was completed, the preform was allowed to cool naturally to room temperature to obtain the plasma-treated carbon fiber preform.

[0097] The areal density of the carbon fiber preform is 320 g / m³. 2 The thickness is 3mm, and the carbon fiber is T700 grade;

[0098] The mixed gas is a mixture of argon and ammonia, with a volume ratio of argon to ammonia of 8:1.

[0099] 4. Impregnation-drying-sintering cycle

[0100] The plasma-treated carbon fiber preform was placed in an impregnation apparatus, and a vacuum of 2 Pa was applied. Six times its mass of SiBN multiphase ceramic powder slurry was injected and impregnated for 50 min. Then, the pressure was increased to 0.30 MPa at a rate of 0.05 MPa / min and held for 25 min. Next, the pressure was increased to 0.40 MPa at a rate of 0.02 MPa / min and held for 2.0 h. After impregnation, the preform was dried at 58℃ for 7.5 h, at 95℃ for 5.6 h, and at 150℃ for 3.8 h. The material was placed in a tube furnace, and argon gas was introduced at a flow rate of 65 mL / min. The temperature was increased to 490℃ at a rate of 2.0℃ / min and held for 2.0 h. The temperature was then increased to 900℃ at a rate of 3.0℃ / min and held for 2.8 h. Finally, the temperature was increased to 1450℃ at a rate of 1.0℃ / min and held for 4.0 h. The material was then cooled to room temperature in the furnace to obtain a carbon / carbon composite material blank. The above operation was performed as an impregnation-drying-sintering process. The above process was repeated 3 times to obtain the carbon / carbon composite material.

[0101] Comparative Example 2.1

[0102] The changes made in Example 2 are as follows:

[0103] In the step of preparing SiBN multiphase ceramic powder, in the step of preparing dry gel, the operation of "adding 4.3g of zirconium source solution, controlling the addition rate at 0.1g / min, maintaining the water bath temperature at 36℃ and stirring for 32min at a stirring speed of 320rpm" is omitted.

[0104] In the step of preparing SiBN multiphase ceramic powder slurry, the silanization treatment step of SiBN multiphase ceramic powder is omitted; the silane-treated SiBN multiphase ceramic powder is replaced with an equal amount of SiBN multiphase ceramic powder.

[0105] The rest of the operations are exactly the same.

[0106] Comparative Example 2.2

[0107] The changes made in Example 2 are as follows:

[0108] In the step of preparing SiBN multiphase ceramic powder, in the step of preparing dry gel, triethyl borate is replaced with tetraethyl orthosilicate in equal amounts;

[0109] The acetylated chitosan component is omitted, and the acetylated chitosan component is replaced in equal amounts with silane-treated SiBN multiphase ceramic powder;

[0110] The rest of the operations are exactly the same.

[0111] Performance testing

[0112] The thermal conductivity, ablation performance, and mechanical properties of the carbon / carbon composite materials prepared in Examples 1-3, Comparative Example 2.1, and Comparative Example 2.2 were tested, and the results are as follows:

[0113]

[0114] The ablation rate was tested by placing the carbon / carbon composite materials prepared in Examples 1-3, Comparative Examples 2.1 and 2.2 on a plasma torch ablation tester. The test conditions were: arc voltage 70V, arc current 450A, heater power 35kW, argon pressure 43MPa, argon flow rate 600mL / min, nozzle diameter 8mm, ablation temperature 1700℃, and after 780s of ablation, the mass ablation rate and linear ablation rate were tested.

[0115] Furthermore, the carbon / carbon composite materials obtained in Examples 1-3, Comparative Examples 2.1, and Comparative Examples 2.2 were subjected to temperature increases to 1000°C at a rate of 20°C / min and held at that temperature for 72 hours in air, followed by temperature increases to 1600°C at a rate of 10°C / min and held at that temperature for 96 hours. The flexural strength and flexural modulus were then tested again, and the results are as follows:

[0116]

[0117] Comparative Example 2.1 omitted the zirconium source component, making the SiBN ceramic grains prone to agglomeration. Furthermore, the omission of silanization treatment for the ceramic powder resulted in poor bonding with the resin interface. The absence of zirconium doping led to coarse grains, decreased mechanical properties, increased porosity and cracks after sintering, decreased flexural strength, and reduced thermal conductivity. Moreover, a stable protective layer could not be formed during ablation, causing rapid oxidation of the carbon fibers and a decline in ablation performance. Comparative Example 2.2 omitted the boron phase, preventing the formation of an effective SiBN ceramic phase. This resulted in a matrix dominated by SiO2 and Si3N4, significantly reducing its ablation resistance and flexural strength. The omission of acetylated chitosan further resulted in poor slurry dispersion, leading to a decrease in thermal conductivity, mechanical properties, and stability.

[0118] Unless otherwise specified, all proportions mentioned in this invention are mass proportions, and all percentages are mass percentages.

[0119] 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 foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for enhancing the ablation resistance of carbon / carbon composite materials, characterized in that, This includes the following steps: preparation of SiBN multiphase ceramic powder, preparation of SiBN multiphase ceramic powder slurry, plasma treatment of carbon fiber preform, and impregnation-drying-sintering cycle. The preparation of SiBN multiphase ceramic powder includes the steps of preparing dry gel and sintering. The steps for preparing the dry gel are as follows: tetraethyl orthosilicate and triethyl borate are added to anhydrous ethanol and stirred; hydrochloric acid solution is added to adjust the pH to 3-4; deionized water and Tween 80 are added; the mixture is kept in a water bath at 35-37℃ and stirred for 1.5-2.0 h; zirconium source solution is added at a rate of 0.1-0.2 g / min; the mixture is kept in a water bath and stirred for 30-35 min; and the dry gel is obtained after aging and drying. The mass ratio of tetraethyl orthosilicate, triethyl borate, anhydrous ethanol, deionized water, Tween 80, and zirconium source solution is 6.0-6.5:2.5-3.0:30:1.0-1.3:0.5-0.7:4.2-4.

3. The zirconium source solution is prepared by adding 0.2-0.3g of zirconium isopropoxide to 4.0g of anhydrous ethanol and stirring until homogeneous. The sintering step is as follows: the dry gel is placed in a tube furnace, ammonia gas is introduced at a flow rate of 50-55 mL / min, the temperature is increased to 580-600℃ at a rate of 1.5-2.0℃ / min, and held for 50-60 min. The ammonia gas flow rate is increased to 75-80 mL / min, and the temperature is increased to 1000-1100℃ at a rate of 2.5-3.0℃ / min, and held for 3.8-4.2 h. Then, under an argon atmosphere, the argon gas flow rate is 100-110 mL / min, the temperature is increased to 1480-1520℃ at a rate of 4.0-5.0℃ / min, and held for 2.0-2.3 h. After naturally cooling to room temperature, the powder is pulverized to 50-100 nm to obtain SiBN multiphase ceramic powder. The steps for preparing SiBN multiphase ceramic powder slurry are as follows: SiBN multiphase ceramic powder treated with silane is added to phenolic resin liquid, ball milled and homogenized, and then added to organic thickening liquid. At the same time as adding, the stirring speed is 340-370 rpm. Yttrium oxide and acetylated chitosan are added, and stirring is continued for 30-40 min to obtain SiBN multiphase ceramic powder slurry. The organic thickening liquid is a mixture of hydroxypropyl methylcellulose and phenolic resin liquid.

2. The method for enhancing the ablation resistance of carbon / carbon composite materials according to claim 1, characterized in that, In the step of preparing SiBN multiphase ceramic powder slurry, the method for preparing silane-treated SiBN multiphase ceramic powder is as follows: SiBN multiphase ceramic powder is added to anhydrous ethanol, the temperature is raised to 36-40℃, and stirred for 20-25 minutes. Then, kH550 silane coupling agent is added, the temperature is raised to 62-67℃, and stirred for 2.5-3.0 hours. After filtration, washing, and drying, silane-treated SiBN multiphase ceramic powder is obtained. The mass ratio of the SiBN multiphase ceramic powder, anhydrous ethanol, and kH550 silane coupling agent is 10:70-80:1.0-1.

3.

3. The method for enhancing the ablation resistance of carbon / carbon composite materials according to claim 1, characterized in that, In the step of preparing SiBN multiphase ceramic powder slurry, the mass ratio of silane-treated SiBN multiphase ceramic powder, phenolic resin liquid, organic thickening liquid, yttrium oxide, and acetylated chitosan is 50-53:45:32-33:0.7-0.8:3-4. In the organic thickening liquid, the mass ratio of hydroxypropyl methylcellulose to phenolic resin liquid is 2-3:30; The phenolic resin solution is a mixture of phenolic resin and anhydrous ethanol, and the mass ratio of the phenolic resin to anhydrous ethanol is 1:2.8-3.

2.

4. The method for enhancing the ablation resistance of carbon / carbon composite materials according to claim 1, characterized in that, In the step of preparing SiBN multiphase ceramic powder slurry, the method for preparing acetylated chitosan is as follows: chitosan is added to a mixed solvent of dimethyl sulfoxide and glacial acetic acid, stirred at 48-52℃ for 2.5-3.0h, triethylamine is added, stirred for 10-15min, acetic anhydride is added, stirred at room temperature for 8-10h, washed after precipitation, and vacuum dried at 50-53℃ and -0.08~-0.09MPa for 10-12h to obtain acetylated chitosan; In the mixed solvent, the volume ratio of glacial acetic acid to dimethyl sulfoxide is 3.5-4.0:1; The mass-to-volume ratio of chitosan, mixed solvent, triethylamine, and acetic anhydride is 10-12 g: 150 mL: 2.0-3.0 mL: 10-15 mL.

5. The method for enhancing the ablation resistance of carbon / carbon composite materials according to claim 1, characterized in that, The plasma-treated carbon fiber preform is prepared by placing the carbon fiber preform into a plasma treatment device, evacuating it to a vacuum level of 5-8 Pa, introducing argon gas, controlling the argon gas flow rate at 30-35 mL / min, the treatment power at 100-110 W, and the treatment time at 10-15 min, maintaining a vacuum level of 5-8 Pa, switching to a mixed gas, controlling the mixed gas flow rate at 30-35 mL / min, controlling the power at 80-90 W, and the treatment time at 5-6 min, and after the treatment is completed, allowing it to cool naturally to room temperature to obtain the plasma-treated carbon fiber preform. The areal density of the carbon fiber preform is 320-350 g / m³. 2 The thickness is 3-5mm, and the carbon fiber is T700 grade; The mixed gas is a mixture of argon and ammonia, with a volume ratio of argon to ammonia of 8-9:

1.

6. The method for enhancing the ablation resistance of carbon / carbon composite materials according to claim 1, characterized in that, The impregnation-drying-sintering cycle is as follows: the plasma-treated carbon fiber preform is placed in an impregnation device, a vacuum of 1-2 Pa is applied, 6-8 times its mass of SiBN multiphase ceramic powder slurry is injected, and impregnation is carried out for 50-60 min. Then, the pressure is increased to 0.30-0.32 MPa at a rate of 0.04-0.05 MPa / min, and impregnation is maintained at this temperature for 25-30 min. Next, the pressure is increased to 0.40-0.43 MPa at a rate of 0.01-0.02 MPa / min, and impregnation is maintained at this temperature for 2.0-2.3 h. After impregnation, the preform is dried at 58-62℃ for 7.5-8.0 h, then dried at 95-100℃ for 5.6-6.0 h, and finally dried at 150℃. Dry at -153℃ for 3.8-4.2h, place in a tube furnace, introduce argon gas at a flow rate of 65-70mL / min, increase the temperature to 490-500℃ at a rate of 2.0-2.5℃ / min, hold for 2.0-2.2h, increase the temperature to 900-910℃ at a rate of 3.0-3.5℃ / min, hold for 2.8-3.2h, increase the temperature to 1450-1550℃ at a rate of 1.0-1.5℃ / min, hold for 4.0-4.5h, and cool to room temperature in the furnace to obtain a carbon / carbon composite material blank. The above operation is a dipping-drying-sintering process, and the above process is repeated 3 times to obtain the carbon / carbon composite material.

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