An oxidation-resistant carbon aerogel material and preparation method thereof

Abstract

The present invention discloses an antioxidant carbon aerogel material and a preparation method thereof. The method comprises the following steps: sequentially adding a solvent, a boron-containing modifier, and a silicon-containing modifier to a phenolic resin to carry out an esterification reaction; sequentially curing, drying, and carbonizing to obtain a borosilicate-modified carbon aerogel; depositing a SiC inner coating on the borosilicate-modified carbon aerogel with the assistance of supercritical CO2; and sequentially preparing a Zr-Si ceramic oxygen barrier layer and a SiO2 sealing layer by a sol-gel method to obtain a carbon aerogel material having a SiC-Zr / Si-SiO2 composite coating. The present invention also provides an aerogel material prepared by the method, wherein the antioxidant performance of the aerogel material is significantly improved and the aerogel material can be used to prepare heat-insulating materials for application in high-temperature thermal protection.

Description

Technical Field

[0001] The present invention belongs to the field of carbon aerogel materials, and in particular relates to an oxidation-resistant carbon aerogel material and a preparation method thereof. Background Art

[0002] Carbon materials boast high specific strength, excellent high-temperature mechanical properties, high thermal conductivity, low thermal expansion coefficient, and excellent thermal shock resistance, making them widely used in high-temperature insulation, industrial, and civilian applications. Porous carbon materials, such as carbon aerogels, offer significant advantages such as high specific surface area, low thermal conductivity, and ultra-high temperature resistance (maintaining a good pore structure above 2000°C in an inert atmosphere), making them an ideal thermal insulation material system for high-temperature thermal protection.

[0003] However, carbon materials begin to oxidize at 450°C in air, and the oxidation rate increases with increasing temperature. Carbon aerogels, in particular, are susceptible to high-temperature oxidation in aerobic environments due to their nanoporous structure, high porosity, and high specific surface area, significantly limiting their engineering applications. Therefore, ensuring the stable and long-lasting oxidation resistance of carbon aerogels is a prerequisite for fully utilizing their properties.

[0004] Currently, there are two main approaches to improving the high-temperature oxidation resistance of carbon aerogel materials: first, modifying the material matrix to resist oxidation; second, protecting it with antioxidant coating technology. Matrix antioxidant modification technology involves internally modifying the material's composition to passivate the matrix itself. Coating antioxidant modification technology involves applying an antioxidant coating to the surface of the carbon aerogel, isolating the material from direct contact with the oxidizing atmosphere. This improves the carbon aerogel's oxidation resistance at higher temperatures, allowing it to maintain its excellent performance even in high-temperature oxidizing atmospheres and expanding its scope of application.

[0005] CN105646007A discloses a method for preparing a medium- and low-temperature, long-term, anti-oxidation coating on the surface of a carbon / carbon composite material. A SiC / B4C-B2O3-SiO2-Al2O3 medium- and low-temperature, long-term, anti-oxidation coating is prepared on the surface of a carbon / carbon composite material using a chemical vapor deposition process combined with a coating-sintering process. The prepared coating provides long-term anti-oxidation protection for the carbon / carbon composite material at temperatures between 600 and 1000°C. CN116375504A discloses a dense, high-temperature, anti-oxidation coating on the surface of a carbon-based or ceramic-based composite material and a method for preparing the same. By introducing a certain amount of kyanite into the coating slurry, the kyanite undergoes a phase transformation to form mullite during high-temperature sintering. The volume expansion associated with the kyanite phase transformation effectively heals pores and microcracks in the coating, increasing the coating's density and providing excellent oxidation protection for the substrate material at temperatures above 1200°C. CN116082065A discloses a method for increasing the sintered density of an anti-oxidation coating on the surface of a carbon-based or ceramic-based composite material, and a composite anti-oxidation coating. By adding HfSi2 and ZrSi2 to the coating slurry and introducing a small amount of oxygen during the coating sintering process, HfSi2 and / or ZrSi2 are oxidized in situ to produce SiO2 self-healing phase and volume expansion to fill the pores and cracks in the coating, thereby significantly improving the problems of loose structure, poor bonding between particles, and low interface bonding strength of ceramic coatings prepared by traditional slurry-sintering process.

[0006] All of the above-mentioned methods utilize chemical vapor deposition (CVD) and coating-sintering processes to enhance the oxidation resistance of carbon materials. However, these traditional CVD and coating-sintering processes, when used to enhance the oxidation resistance of carbon aerogels, suffer from the problem that the coating material cannot evenly penetrate the porous structure of the carbon aerogel, preventing effective oxidation resistance. Another approach involves liquid-phase impregnation, where porous carbon materials are modified with silicone oil and then pyrolyzed at high temperatures to produce a SiC coating. However, during the drying process, the coating precursor experiences dielectric migration, resulting in an uneven coating. Currently, the preparation of oxidation-resistant coatings for highly porous carbon materials faces challenges in achieving uniformity. Therefore, there is an urgent need to develop nanoporous carbon aerogel oxidation-resistant coating technology that can meet the requirements of applications in aerobic environments up to 1800°C. Therefore, there is an urgent need to improve existing oxidation-resistant coating processes to enhance the oxidation resistance of carbon aerogel materials, thereby producing a high-temperature-resistant, oxidation-resistant carbon aerogel material and providing a new approach for the development of high-temperature thermal protection materials. Summary of the Invention

[0007] In order to solve one or more technical problems existing in the prior art, the present invention provides a method for preparing an oxidation-resistant carbon aerogel material in a first aspect, the preparation method comprising the following steps:

[0008] (1) Preparation of boron-silicon-modified phenolic resin: a solvent, a boron-containing modifier, and a silicon-containing modifier are sequentially added to a phenolic resin to carry out an esterification reaction, and the boron-silicon-modified phenolic resin is obtained after removing the solvent;

[0009] (2) Preparation of borosilicate modified phenolic aerogel: adding a solvent and a curing agent to the borosilicate modified phenolic resin in sequence to carry out a curing reaction, and then drying to obtain a borosilicate modified phenolic aerogel;

[0010] (3) Preparation of borosilicate modified carbon aerogel: carbonizing the borosilicate modified phenolic aerogel in an inert atmosphere to obtain borosilicate modified carbon aerogel;

[0011] (4) Preparation of SiC inner coating: placing the borosilicate modified carbon aerogel and SiC ceramic precursor solution in a reaction vessel, and depositing the SiC inner coating on the borosilicate modified carbon aerogel with the assistance of supercritical CO2 to obtain a borosilicate modified carbon aerogel containing the SiC inner coating;

[0012] (5) Preparation of ceramic oxygen barrier layer: preparing a Zr-Si ceramic oxygen barrier layer on the borosilicate modified carbon aerogel containing a SiC inner coating by a sol-gel method to obtain a double-coated borosilicate modified carbon aerogel having a SiC inner coating and a Zr-Si ceramic oxygen barrier layer;

[0013] (6) Preparation of SiO2 sealing layer: A SiO2 sealing layer was prepared on the surface of the double-coated boron silicon modified carbon aerogel by a sol-gel method, thereby preparing a carbon aerogel material with a SiC-Zr / Si-SiO2 composite coating.

[0014] In a second aspect, the present invention provides an oxidation-resistant carbon aerogel material prepared by the method described in the first aspect of the present invention.

[0015] Compared with the prior art, the present invention has at least the following beneficial effects:

[0016] (1) For the first time, the technology of matrix modification combined with skeleton modification was used to improve the antioxidant performance of porous carbon aerogel materials. By designing and synthesizing boron silicon and other heteroatom-doped modified phenolic resin as the organic precursor resin for preparing carbon aerogel, the bulk antioxidant of carbon aerogel was achieved. Then, supercritical deposition technology was combined with sol-gel technology to prepare SiC-Zr / Si-SiO2 composite coating on the three-dimensional nano-skeleton of carbon aerogel to achieve the skeleton antioxidant of carbon aerogel, and finally achieve the effect of double protection, significantly improving the antioxidant performance of carbon aerogel materials. The boron silicon heteroatom doping combined with SiC-Zr / Si-SiO2 composite coating system can achieve effective protection of carbon aerogel materials at a temperature resistance level of 2200℃.

[0017] (2) A ceramic inner coating-ceramic oxygen barrier-oxide sealing layer, namely a SiC-Zr / Si-SiO2 composite coating system, was designed to make the carbon aerogel material suitable for different service environments. Below 800°C, the silicon-boron modified carbon aerogel inside the carbon aerogel material is distributed more continuously, which can protect the fiber and matrix. In the low temperature range of 800-1000℃, the oxidation products of Zr are B2O3 and ZrO2, which play a dual role of filling cracks and pores and blocking airflow erosion; at 1000-1400℃, the surface SiO2 and SiO2 generated by the oxidation of SiC can, on the one hand, flow to form a glass film to fill defects such as cracks and nanopores, and on the other hand, SiO2 can also act as a sealing glass phase to effectively prevent and slow down the diffusion and penetration of oxygen; at 1400-1800℃, a borosilicate glass self-healing phase is formed in the coating, which effectively seals and heals cracks and pores, slows down the diffusion and penetration of oxygen, and thus improves the oxidation resistance of the material; at 1800-2200℃, a large amount of SiO2 glass phase evaporates, and the precipitated ZrO2 gradually sinters densely, which can effectively protect the substrate.

[0018] (3) The introduction of SiC has two effects: First, since the thermal expansion coefficient of SiC is very close to that of carbon materials, designing it as an inner coating can solve the problem of thermal stress matching between the carbon aerogel matrix and the Zr / Si coating and reduce the generation of cracks. In particular, the use of supercritical assisted deposition technology to achieve uniform deposition of SiC on the three-dimensional skeleton of the carbon aerogel solves the problem that the coating material cannot evenly penetrate into the pore structure when preparing coatings by traditional processes such as chemical vapor deposition. Second, the introduction of a second phase SiC in the ceramic oxygen barrier layer can improve the mismatch between the thermal expansion coefficient of the ceramic oxygen barrier layer and the matrix. When oxidized at high temperature, boron-silicon glass with a higher melting point, greater viscosity, lower oxygen diffusion rate and lower vapor pressure is formed on the surface of the material, thereby obtaining an ideal glassy oxygen barrier layer, so that the carbon-based composite material has both good mechanical properties and anti-oxidation and ablation properties. In particular, the use of sol-gel technology to prepare the ceramic oxygen barrier layer solves the problem of uneven coating caused by the migration of the coating precursor medium when preparing the coating by the liquid phase impregnation method. The present invention cleverly uses SiC as the second phase of the inner coating and the ceramic oxygen barrier layer, and adopts supercritical deposition technology combined with sol-gel technology to prepare the SiC inner coating and the ceramic oxygen barrier layer, thereby achieving effective anti-oxidation of the porous carbon aerogel material. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be fully described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] As described above, the present invention provides a method for preparing an oxidation-resistant carbon aerogel material in a first aspect, the preparation method comprising the following steps:

[0021] (1) Preparation of boron-silicon-modified phenolic resin: a solvent, a boron-containing modifier, and a silicon-containing modifier are sequentially added to a phenolic resin to carry out an esterification reaction, and the boron-silicon-modified phenolic resin is obtained after removing the solvent;

[0022] (2) Preparation of borosilicate modified phenolic aerogel: adding a solvent and a curing agent to the borosilicate modified phenolic resin in sequence to carry out a curing reaction, and then drying to obtain a borosilicate modified phenolic aerogel;

[0023] (3) Preparation of borosilicate modified carbon aerogel: carbonizing the borosilicate modified phenolic aerogel in an inert atmosphere to obtain borosilicate modified carbon aerogel;

[0024] (4) Preparation of SiC inner coating: placing the borosilicate modified carbon aerogel and SiC ceramic precursor solution in a reaction vessel, and depositing the SiC inner coating on the borosilicate modified carbon aerogel with the assistance of supercritical CO2 to obtain a borosilicate modified carbon aerogel containing the SiC inner coating;

[0025] (5) Preparation of ceramic oxygen barrier layer: preparing a Zr-Si ceramic oxygen barrier layer on the borosilicate modified carbon aerogel containing a SiC inner coating by a sol-gel method to obtain a double-coated borosilicate modified carbon aerogel having a SiC inner coating and a Zr-Si ceramic oxygen barrier layer;

[0026] (6) Preparation of SiO2 sealing layer: A SiO2 sealing layer was prepared on the surface of the double-coated boron silicon modified carbon aerogel by a sol-gel method, thereby preparing a carbon aerogel material with a SiC-Zr / Si-SiO2 composite coating.

[0027] The preferred embodiments of the present invention will be further described below in steps.

[0028] Step (1): Preparation of borosilicate modified phenolic resin

[0029] In this step, a solvent, a boron-containing modifier and a silicon-containing modifier are sequentially added to the phenolic resin to carry out an esterification reaction, and the boron-silicon-modified phenolic resin is obtained after removing the solvent.

[0030] In some preferred embodiments, the boron-containing modifier is any one of boric acid, phenylboric acid and p-hydroxyphenylboric acid.

[0031] In other preferred embodiments, the silicon-containing modifier is any one of methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane and ethyl orthosilicate.

[0032] In other preferred embodiments, the solvent is any one of ethanol, ethylene glycol, n-propanol, isopropanol, n-pentanol and butanone.

[0033] In other preferred embodiments, the mass ratio of the phenolic resin, the silicon-containing modifier, the boron-containing modifier and the solvent is 10:(1-4):(0.5-3):(15-100), for example, 10:(1, 2, 3 or 4):(0.5, 1, 1.5, 2, 2.5 or 3):(15, 20, 30, 40, 50, 60, 70, 80, 90 or 100).

[0034] In other preferred embodiments, the esterification reaction is carried out by heating. More preferably, the esterification reaction temperature is 50-150° C. (e.g., 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, or 150° C.), and the reaction time is 5-20 h (e.g., 5, 10, 15, or 20 h).

[0035] Preferably, the solvent removal can be carried out by vacuum distillation. More preferably, the vacuum distillation is carried out at a distillation temperature of 40-180° C. (e.g., 40, 50, 80, 100, 120, 150, or 180° C.), a distillation pressure of 100-1000 Pa (e.g., 200, 300, 400, 500, 600, 700, 800, 900, or 1000 Pa), and a distillation time of 0.5-3 h (e.g., 0.5, 1, 2, or 3 h).

[0036] Step (2): Preparation of borosilicate modified phenolic aerogel

[0037] In this step, a solvent and a curing agent are sequentially added to the borosilicate modified phenolic resin to carry out a curing reaction, and then dried to obtain a borosilicate modified phenolic aerogel.

[0038] Preferably, the curing agent is hexamethylenetetramine.

[0039] Preferably, the solvent is any one of ethanol, ethylene glycol, n-propanol, isopropanol, n-pentanol and butanone.

[0040] Preferably, the mass ratio of the curing agent, borosilicate modified phenolic resin and solvent is (2-5):20:(30-180), for example, (2, 3, 4, 5):20:(30, 50, 80, 100, 150 / 180).

[0041] Preferably, the curing reaction temperature is 70-140° C. (e.g., 80, 90, 100, 110, 120, 130, or 140° C.) More preferably, the curing reaction time is 12-90 h (e.g., 12, 24, 36, 48, 60, 72, 84, or 90 h).

[0042] In this step, the drying method is atmospheric pressure drying or supercritical drying.

[0043] Step (3): Preparation of borosilicate modified carbon aerogel

[0044] In this step, the borosilicate modified phenolic aerogel is carbonized in an inert atmosphere to obtain borosilicate modified carbon aerogel.

[0045] Preferably, the carbonization is carried out in an inert atmosphere, more preferably, the inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

[0046] Preferably, the carbonization temperature may be 800-1400° C. (eg, 800, 900, 1000, 1100, 1200, 1300, or 1400° C.), and the carbonization time may be 0.5-3 h (eg, 0.5, 1, 2, or 3 h).

[0047] Step (4): Preparation of SiC inner coating

[0048] In this step, the borosilicate modified carbon aerogel and SiC ceramic precursor solution are placed in a reaction container, and a SiC inner coating is deposited on the borosilicate modified carbon aerogel with the assistance of supercritical CO2 to obtain a borosilicate modified carbon aerogel containing a SiC inner coating.

[0049] Preferably, the SiC ceramic precursor is polycarbosilane.

[0050] Preferably, the SiC ceramic precursor solution is a mixture of polycarbosilane and a catalyst. More preferably, the catalyst is any one of a platinum catalyst, dicumyl peroxide, azobisisobutyronitrile, and dibenzoyl peroxide.

[0051] Preferably, the mass ratio of the polycarbosilane to the catalyst is 100:(0-5), for example, 100:(0, 1, 2, 3, 4 or 5).

[0052] Preferably, the mass ratio of the SiC ceramic precursor solution to the borosilicate modified carbon aerogel is (1-10):100, for example, (1, 2, 3, 4, 5, 6, 7, 8, 9 or 10):100.

[0053] In some particularly preferred embodiments, the deposition is carried out as follows: CO2 is charged into the reactor at a pressure increase rate of 100 to 500 kPa / min (for example, 100, 200, 300, 400 or 500 kPa / min), and the SiC ceramic precursor solution in the reactor is stirred at a speed of 300 to 800 rpm (for example, 300, 400, 500, 600, 700 or 800 rpm), and then the temperature in the reactor is raised to 28 to 40°C (for example, 28, 30, 35 or 40°C) at a rate of 2 to 5°C / min (for example, 2, 3, 4 or 5°C / min), so that the CO2 in the reactor reaches a supercritical state, and the SiC ceramic precursor in the reactor is completely dissolved and adsorption is achieved after 0.5 to 5 h (for example, 0.5, 1, 2, 3, 4 or 5 h). After equilibration, the reactor is depressurized to atmospheric pressure for 50 to 80 seconds (e.g., 50, 60, 70, or 80 seconds) to obtain a carbon aerogel material on which a SiC ceramic precursor is deposited; the carbon aerogel material on which a SiC ceramic precursor is deposited is then cured in a nitrogen or argon atmosphere at 80 to 300° C. (e.g., 80, 100, 150, 200, 250, or 300° C.) for 6 to 24 hours (e.g., 6, 12, 18, or 24 hours). 4h), then the temperature is increased to 800-1600°C (for example, 800, 900, 1000, 1100, 1200, 1300, 1400, 1500 or 1600°C) at a heating rate of 1-5°C / min (for example, 1, 2, 3, 4 or 5°C / min) and cracked for 0.5 to 5h (for example, 0.5, 1, 2, 3, 4 or 5h) to obtain a borosilicate modified carbon aerogel with a SiC inner coating deposited thereon.

[0054] Step (5): Preparation of ceramic oxygen barrier layer

[0055] In this step, a Zr-Si ceramic oxygen barrier layer is prepared on the borosilicate modified carbon aerogel containing the SiC inner coating by a sol-gel method to obtain a double-coated borosilicate modified carbon aerogel having a SiC inner coating and a Zr-Si ceramic oxygen barrier layer.

[0056] In some particularly preferred embodiments, the Zr-Si ceramic oxygen barrier layer is prepared by immersing the borosilicate modified carbon aerogel containing the SiC inner coating in a mixed solution containing a Zr precursor and a Si precursor, then in situ curing, taking out and drying, and then performing high-temperature cracking to obtain a carbon aerogel containing a SiC-Zr / Si coating.

[0057] Preferably, the Zr precursor is a ZrC ceramic precursor or a ZrB2 ceramic precursor.

[0058] In addition, preferably, the Si precursor is a SiC ceramic precursor.

[0059] Further preferably, the mixed solution of the Zr precursor and the Si precursor is prepared by dissolving the Zr precursor and the Si precursor in a solvent. Preferably, the solvent is any one of cyclohexane, tetrahydrofuran, butyl ether, cyclopentyl methyl ether, methyl acetate, ethyl acetate, and butyl acetate.

[0060] More preferably, the mass ratio of the Zr precursor, the Si precursor, the solvent and the borosilicate modified carbon aerogel containing the SiC inner coating is (2-20):(1-10):(30-50):10, for example, (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19 or 20):(1, 2, 3, 4, 5, 6, 7, 8, 9 or 10):(30, 40, 50):10.

[0061] Preferably, the in-situ curing has a curing pressure of 0.5 to 5 MPa (e.g., 0.5, 1, 2, 3, 4 or 5 MPa), a curing temperature of 80 to 130° C. (e.g., 80, 90, 100, 110, 120 or 130° C.), and a curing time of 8 to 24 h (e.g., 8, 12, 18 or 24 h).

[0062] Preferably, the drying temperature is 50-150° C. (eg, 50, 100, or 150° C.), and the drying time is 10-30 h (eg, 10, 20, or 30 h).

[0063] Preferably, the pyrolysis temperature of the high-temperature pyrolysis is 1400-1600°C (for example, 1400, 1500 or 1600°C), the heating rate is 1-5°C / min (for example, 1, 2, 3, 4 or 5°C / min), the pyrolysis time is 1-5h (for example, 1, 2, 3, 4 or 5h), and the pyrolysis atmosphere is argon.

[0064] Step (6): Preparation of SiO2 sealing layer

[0065] In this step, a SiO2 sealing layer is prepared on the surface of the double-coated boron-silicon modified carbon aerogel by a sol-gel method, thereby preparing a carbon aerogel material resin having a SiC-Zr / Si-SiO2 composite coating.

[0066] More preferably, the SiO2 sealing layer is prepared by immersing the double-coated boron silicon modified carbon aerogel in a SiO2 precursor solution, then curing it in situ, taking it out and drying it to obtain a carbon aerogel material with a SiC-Zr / Si-SiO2 composite coating.

[0067] Preferably, the solid content of the SiO2 precursor solution is 5-25% (eg, 5, 10, 15, 20 or 25%).

[0068] Preferably, the mass ratio of the SiO2 precursor solution to the double-coated boron silicon modified carbon aerogel is (10-30):100, for example, (10, 20 or 30):100.

[0069] Preferably, the in-situ curing has a curing pressure of 0.5 to 5 MPa (e.g., 0.5, 1, 2, 3, 4 or 5 MPa), a curing temperature of 50 to 100° C. (e.g., 50, 60, 70, 80, 90 or 100° C.), and a curing time of 8 to 24 h (e.g., 8, 12, 18 or 24 h).

[0070] In a second aspect, the present invention provides an oxidation-resistant carbon aerogel material produced by the preparation method described in the first aspect of the present invention. The oxidation-resistant carbon aerogel material produced by the method of the present invention has significantly improved antioxidant properties and can be used to prepare thermal insulation materials for high-temperature thermal protection applications.

[0071] Example

[0072] The present invention is further described below with reference to the following examples. The following examples are not intended to limit the scope of protection of the present invention, and any improvements made on the basis of the present invention that do not violate the spirit of the present invention are within the scope of protection of the present invention.

[0073] Example 1

[0074] (1) Add 100g of phenolic resin and 900g of anhydrous ethanol to a 1L three-necked flask in sequence and stir to dissolve the phenolic resin. Add 5g of boric acid to the flask, start stirring and heating at the same time, and react at 50°C for 5h. Then add 10g of methyltrimethoxysilane to the flask and heat to react for 5h. After the product cools, transfer it to the rotary flask of a rotary evaporator and remove the solvent by reduced pressure distillation. Set the distillation temperature to 40°C, the distillation time to 0.5h, and the system pressure to 100Pa to obtain borosilicate-modified phenolic resin.

[0075] (2) Weigh 100 g of the borosilicate-modified phenolic resin obtained in step (1), 2 g of hexamethylenetetramine, and 600 g of ethanol, stir and mix at room temperature, transfer to a hydrothermal kettle, and cure at 70° C. for 12 h. After curing, remove the borosilicate-modified phenolic wet gel from the hydrothermal kettle and dry it at normal pressure to obtain a borosilicate-modified phenolic aerogel.

[0076] (3) The borosilicate modified phenolic aerogel obtained in step (2) was transferred to an atmosphere furnace and carbonized at 800°C for 0.5h under a nitrogen atmosphere to obtain a borosilicate modified carbon aerogel.

[0077] (4) 1g of polycarbosilane and 0.005g of platinum catalyst were mixed and stirred to obtain a polycarbosilane solution, which was added to the reactor. Then 99g of carbon aerogel was placed in the reactor and the reactor was tightened. Carbon dioxide was filled into the reactor at a rate of 100kPa / min, and the ceramic precursor solution in the reactor was stirred (300rpm). At the same time, heating was turned on and the temperature was raised to 28°C at a rate of 2°C / min (hereinafter referred to as the first heating rate) to make the carbon dioxide in the reactor reach a supercritical state. After the polycarbosilane in the reactor was completely dissolved and the adsorption equilibrium was reached after 0.5h, the heating was stopped and the reactor was quickly depressurized to atmospheric pressure within 50s to obtain a carbon aerogel with polycarbosilane deposited. The carbon aerogel was placed in an atmosphere furnace with a nitrogen atmosphere and heated to 80°C at a rate of 1°C / min (hereinafter referred to as the second heating rate) for curing for 6h. After the curing was completed, the temperature was raised to 800°C for pyrolysis for 0.5h to obtain a boron silicon modified carbon aerogel containing a SiC inner coating.

[0078] (5) Weigh 20g of ZrC ceramic precursor, 10g of SiC ceramic precursor and 300g of cyclohexane and mix them evenly. Place 100g of carbon aerogel with SiC inner coating deposited in a mold and seal it. Inject the mixed solution of ceramic precursors into the mold, apply a pressure of 0.5MPa to the mold, and cure it at 100℃ for 8h. After the mold cools down, take out the carbon aerogel and let it air at room temperature, and then dry it at 100℃ for 10h. Then, pyrolyze the carbon aerogel at 1400℃ in a nitrogen atmosphere for 1h to obtain a carbon aerogel containing SiC-ZrC / SiC coating.

[0079] (6) The carbon aerogel with the deposited SiC-ZrC / SiC coating obtained in step (5) is placed in a mold and sealed. 10 g of a SiO2 precursor solution with a solid content of 5% is injected into the mold, a pressure of 0.2 MPa is applied to the mold, and the mold is cured at 50°C for 5 h. The carbon aerogel is removed and air-dried at room temperature to obtain a carbon aerogel with a SiC-ZrC / SiC-SiO2 coating.

[0080] (7) Material performance test: The above materials were subjected to an isothermal static firing experiment at 1600℃ in a muffle furnace, and the appearance, size and weight before and after static firing were recorded. After the material was isothermal static fired at 1600℃ for 2h, the appearance was intact and crack-free, the shrinkage rate in the thickness direction was 3%, and the residual weight was 95%. The above materials were subjected to oxyacetylene test at 1800℃ and 2200℃ (test time was 1500s), and the appearance, linear ablation rate and mass ablation rate before and after the test were recorded. After the above materials were subjected to oxyacetylene test at 1800℃, the surface layer partially turned white, and the linear ablation rate was 5.34×10 -5 mm / s, and the mass ablation rate is 8.68×10 -6 After the above material was tested with oxyacetylene at 2200℃, the surface of the material turned partially white, and the linear ablation rate was 9.41×10 -4 mm / s, and the mass ablation rate is 8.02×10 -5 g / s.

[0081] Examples 2 to 6

[0082] The preparation was carried out in substantially the same manner as in Example 1, with the differences shown in Tables 1 to 5.

[0083] Comparative Example 1

[0084] This comparative example provides a method for preparing a conventional carbon aerogel, and the specific steps are as follows:

[0085] (1) Weigh 100 g of phenolic resin, 2 g of hexamethylenetetramine, and 600 g of ethanol, stir and mix at room temperature, transfer to a hydrothermal autoclave, and cure at 70°C for 12 h. After curing, remove the wet phenolic gel from the hydrothermal autoclave and dry it at normal pressure to obtain a phenolic aerogel.

[0086] (2) The phenolic aerogel prepared in step (1) was transferred to an atmosphere furnace and carbonized at 800° C. for 0.5 h under a nitrogen atmosphere to obtain a carbon aerogel.

[0087] Comparative Example 2

[0088] The method is basically the same as that of Example 1, except that step (4), step (5) and step (6) in Example 1 are not performed.

[0089] Comparative Example 3

[0090] The method is basically the same as that of Example 1, except that step (5) and step (6) in Example 1 are not performed.

[0091] Comparative Example 4

[0092] The method is basically the same as that of Example 1, except that step (4) in Example 1 is not performed.

[0093] Comparative Example 5

[0094] The method is basically the same as that of Example 1, except that step (5) in Example 1 is not performed.

[0095] Comparative Example 6

[0096] The method is basically the same as that of Example 1, except that step (6) in Example 1 is not performed.

[0097]

[0098]

[0099]

[0100] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing an oxidation-resistant carbon aerogel material, characterized in that: The preparation method comprises the following steps: (1) Preparation of boron-silicon modified phenolic resin: Solvent, boron-containing modifier and silicon-containing modifier are sequentially added to phenolic resin to carry out esterification reaction, and boron-silicon modified phenolic resin is obtained after removing the solvent; (2) Preparation of borosilicate modified phenolic aerogel: adding a solvent and a curing agent to the borosilicate modified phenolic resin in sequence to carry out a curing reaction, and then drying to obtain a borosilicate modified phenolic aerogel; (3) Preparation of borosilicate modified carbon aerogel: carbonizing the borosilicate modified phenolic aerogel in an inert atmosphere to obtain borosilicate modified carbon aerogel; (4) Preparation of SiC inner coating: the borosilicate modified carbon aerogel and SiC ceramic precursor solution are placed in a reaction vessel, and the SiC inner coating is deposited on the borosilicate modified carbon aerogel with the assistance of supercritical CO2 to obtain a borosilicate modified carbon aerogel containing a SiC inner coating, wherein the SiC ceramic precursor in the reaction vessel is completely dissolved, and after 0.5 to 5 hours to reach adsorption equilibrium, the reactor is depressurized to atmospheric pressure for 50 to 80 seconds to obtain a carbon aerogel material with SiC ceramic precursor deposited thereon; and then the carbon aerogel material with SiC ceramic precursor deposited thereon is heated at 80 to 300°C in a nitrogen or argon atmosphere. o C for 6~24h, then raise the temperature to 800-1600 at a heating rate of 1~5℃ / min. o C was pyrolyzed for 0.5 to 5 h to obtain borosilicate-modified carbon aerogel with a SiC inner coating deposited; (5) Preparation of ceramic oxygen barrier layer: The borosilicate modified carbon aerogel containing SiC inner coating is immersed in a mixed solution containing Zr precursor and Si precursor, then in situ cured, taken out and dried, and then subjected to high-temperature cracking to obtain a double-coated borosilicate modified carbon aerogel having SiC inner coating and Zr-Si ceramic oxygen barrier layer, wherein the curing pressure of the in situ curing is 0.5~5MPa, the curing temperature is 80~130℃, and the curing time is 8~24h; (6) Preparation of SiO2 sealing layer: The double-coated boron silicon modified carbon aerogel is immersed in a SiO2 precursor solution, then in-situ cured, taken out and dried to obtain a carbon aerogel material with a SiC-Zr / Si-SiO2 composite coating. The in-situ curing has a curing pressure of 0.5-5 MPa, a curing temperature of 50-100°C, and a curing time of 8-24 h.

2. The preparation method according to claim 1, characterized in that In step (1): The boron-containing modifier is any one of boric acid, phenylboric acid and p-hydroxyphenylboric acid; The silicon-containing modifier is any one of methyltrimethoxysilane, methyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane and ethyl orthosilicate; The solvent is any one of ethanol, ethylene glycol, n-propanol, isopropanol, n-pentanol and butanone; and / or The mass ratio of the phenolic resin, the silicon-containing modifier, the boron-containing modifier and the solvent is 10:(1-4):(0.5-3):(15-100).

3. The preparation method according to claim 1, characterized in that In step (1), the esterification reaction is carried out by heating.

4. The preparation method according to claim 3, characterized in that In step (1), the temperature of the esterification reaction is 50-150° C., and the reaction time is 5-20 h.

5. The preparation method according to claim 3, characterized in that In step (1), the solvent is removed by distillation under reduced pressure.

6. The preparation method according to claim 5, characterized in that In step (1), the distillation temperature of the reduced pressure distillation is 40-180° C., the distillation pressure is 100-1000 Pa, and the distillation time is 0.5-3 h.

7. The preparation method according to any one of claims 1 to 6, characterized in that In step (2): The curing agent is hexamethylenetetramine; The solvent is any one of ethanol, ethylene glycol, n-propanol, isopropanol, n-pentanol and butanone; The mass ratio of the curing agent, borosilicate modified phenolic resin and solvent is (2-5):20:(30-180); The reaction temperature of the curing reaction is 70~140℃; The curing reaction time is 12 to 90 hours; and / or The drying method is atmospheric pressure drying or supercritical drying.

8. The preparation method according to any one of claims 1 to 6, characterized in that In step (3): The carbonization is carried out in an inert atmosphere; The carbonization temperature is 800-1400° C., and the carbonization time is 0.5-3 hours.

9. The preparation method according to claim 8, characterized in that The inert atmosphere is a nitrogen atmosphere or an argon atmosphere.

10. The preparation method according to any one of claims 1 to 6, characterized in that In step (4): The SiC ceramic precursor is polycarbosilane; The SiC ceramic precursor solution is a mixture of polycarbosilane and a catalyst, and the catalyst is any one of a platinum catalyst, dicumyl peroxide, azobisisobutyronitrile and dibenzoyl peroxide; The mass ratio of the polycarbosilane to the catalyst is 100:(0-5); and / or The mass ratio of the SiC ceramic precursor solution to the borosilicate modified carbon aerogel is (1-10):

100.

11. The preparation method according to any one of claims 1 to 6, characterized in that In step (4): The supercritical CO2 is achieved by filling the reactor with CO2 at a pressure increase rate of 100~500kPa / min, stirring the SiC ceramic precursor solution in the reactor at a speed of 300~800rpm, and then raising the temperature in the reactor to 28~40℃ at a rate of 2~5℃ / min, so that the CO2 in the reactor reaches a supercritical state.

12. The preparation method according to any one of claims 1 to 6, characterized in that In step (5): The Zr precursor is a ZrC ceramic precursor or a ZrB2 ceramic precursor, and the Si precursor is a SiC ceramic precursor; The mixed solution of the Zr precursor and the Si precursor is prepared by dissolving the Zr precursor and the Si precursor in a solvent, wherein the solvent is any one of cyclohexane, tetrahydrofuran, butyl ether, cyclopentyl methyl ether, methyl acetate, ethyl acetate and butyl acetate; The mass ratio of the Zr precursor, the Si precursor, the solvent and the borosilicate-modified carbon aerogel containing the SiC inner coating is (2-20):(1-10):(30-50):10; The drying temperature is 50-150°C and the drying time is 10-30h; The pyrolysis temperature of the high temperature pyrolysis is 1400-1600°C, the heating rate is 1-5°C / min, and the pyrolysis time is 1-5h; The cracking atmosphere was argon.

13. The preparation method according to any one of claims 1 to 6, characterized in that In step (6): The solid content of the SiO2 precursor solution is 5-25%; and / or The mass ratio of the SiO2 precursor solution to the double-coated boron silicon modified carbon aerogel is (10-30):

100.

14. An oxidation-resistant carbon aerogel material prepared by the preparation method according to any one of claims 1 to 13.

Images