A method of supercritical fluid assisted deposition of modified carbon aerogel materials and materials produced by the method

Abstract

The application discloses a method for modifying carbon aerogel material by supercritical fluid assisted deposition and a material prepared by the method. The method comprises the following steps: preparing a ceramic precursor solution; loading the ceramic precursor solution and the carbon aerogel material into a reaction kettle and sealing the kettle; filling the reaction kettle with carbon dioxide and then heating the reaction kettle so that the carbon dioxide in the reaction kettle reaches a supercritical state; after the ceramic precursor in the reaction kettle is completely dissolved and adsorption equilibrium is reached, rapidly depressurizing the reaction kettle to atmospheric pressure to obtain the carbon aerogel material on which the ceramic precursor is deposited; and solidifying and pyrolyzing the carbon aerogel material to prepare the modified carbon aerogel material. The application also relates to the modified carbon aerogel material prepared by the method. The method can realize large-scale preparation of the modified carbon aerogel material, and the prepared material not only has low density and excellent heat insulation performance, but also has obviously improved temperature resistance in an oxygen environment.

Description

Technical Field

[0001] This invention belongs to the field of antioxidant modification of carbon aerogel materials, specifically relating to a supercritical assisted deposition modified carbon aerogel material and its preparation method. Background Technology

[0002] Carbon aerogel materials are materials with a three-dimensional continuous network structure composed of nano-carbon particles. They have advantages such as high specific surface area, low thermal conductivity, and resistance to ultra-high temperature, and have great potential as a new generation of ultra-high temperature resistant thermal insulation materials.

[0003] However, in an oxygen-rich environment exceeding 400°C, carbon aerogel materials begin to oxidize, leading to a significant decline in their thermal insulation performance and other physicochemical properties. Therefore, stable and durable antioxidant protection has become a key factor restricting the widespread application of carbon aerogel materials in high-temperature insulation.

[0004] The main approaches to oxidation resistance in carbon aerogel materials include matrix anti-oxidation technology and external coating anti-oxidation technology. Matrix anti-oxidation technology improves the material's antioxidant properties by adding modified inhibitors during the carbon aerogel material preparation process. External coating anti-oxidation technology creates a shell on the material surface to isolate oxygen-containing gases from the matrix, preventing contact and thus achieving an antioxidant effect. While matrix anti-oxidation technology can effectively protect carbon aerogel materials from low-temperature oxidation to a certain extent, the added modified inhibitors (such as borates and phosphates) can adversely affect the material's high-temperature mechanical properties. Furthermore, with prolonged anti-oxidation time and increased temperature, borate-based glasses exhibit high vapor pressure and oxygen diffusion permeability, thus limiting their effectiveness to below 1000℃. Compared to matrix anti-oxidation technology, external coating anti-oxidation technology effectively isolates the carbon material from the external oxygen atmosphere, preventing the oxygen atmosphere from diffusing into the matrix material, thereby achieving oxidation protection for longer periods and at higher temperatures. It is currently the most widely used oxidation protection technology.

[0005] External coating anti-oxidation technologies mainly include embedding, slurry sintering, chemical vapor deposition, reactive melting, thermal spraying, and precursor impregnation pyrolysis. However, these methods all form a hard shell of a certain thickness on the surface of carbon aerogel materials, preventing the antioxidant components from penetrating into the material's interior, and also suffer from poor uniformity in the anti-oxidation coating thickness. Especially for the precursor impregnation pyrolysis method, media migration occurs during precursor curing or drying, easily leading to uneven distribution of antioxidant components and making effective anti-oxidation difficult. Particularly for carbon aerogel materials with nanoporous structures, the pore structure collapses during drying due to solvent capillary action, not only failing to provide anti-oxidation but also affecting the material's density, uniformity, strength, and thermal insulation properties. To address the issue of antioxidant component uniformity, CN104446656B discloses a solvent-assisted deposition method introduced after the impregnation step in the precursor impregnation method, preparing a uniform anti-oxidation layer in porous carbon materials while simultaneously improving the antioxidant performance of the porous carbon materials. However, the antioxidant layer prepared by this method only coats the surface of the material and can hardly penetrate into the interior of the material, so it cannot achieve overall coating of the porous material skeleton and its antioxidant effect is very limited.

[0006] Therefore, there is a great need for a technology that can solve the aforementioned technical problems in existing antioxidant technologies for carbon aerogel materials, such as matrix antioxidant technology and external coating antioxidant technology. Summary of the Invention

[0007] To address one or more of the aforementioned technical problems in the existing technology, this invention provides a method for modifying carbon aerogel materials using supercritical assisted deposition. The modified carbon aerogel material prepared by this method has the characteristics of low density, good thermal insulation performance, high temperature resistance, and large-scale production capability.

[0008] In a first aspect, the present invention provides a method for supercritical assisted deposition of modified carbon aerogel materials, the method comprising the following steps:

[0009] (1) A ceramic precursor solution is provided, the ceramic precursor solution comprising 95% to 100% by mass of a ceramic precursor and 0% to 5% by mass of a curing agent;

[0010] (2) The ceramic precursor solution and carbon aerogel material are loaded into the reactor and the reactor body is sealed.

[0011] (3) Carbon dioxide is introduced into the reactor, and then the ceramic precursor solution in the reactor is stirred and heated while stirring, so that the carbon dioxide in the reactor reaches a supercritical state.

[0012] (4) After the ceramic precursor in the reactor is completely dissolved and adsorption equilibrium is reached, the reactor is depressurized to atmospheric pressure to obtain a carbon aerogel material with the ceramic precursor deposited.

[0013] (5) The carbon aerogel material with the ceramic precursor deposited is cured and pyrolyzed to obtain the modified carbon aerogel material.

[0014] The present invention provides, in a second aspect, a modified 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) This invention achieves overall oxidation resistance and excellent thermal insulation performance of the material. It utilizes the excellent fluidity of supercritical carbon dioxide to dissolve ceramic precursors and migrate them into the material's interior, rather than simply depositing them on the surface to form an oxidation-resistant hard shell. Simultaneously, by screening the structure of the ceramic precursors, the invention makes them more likely to deposit on the carbon nanoframework rather than remaining within the nanopores of the carbon aerogel. Furthermore, by employing rapid depressurization, the supercritical carbon dioxide quickly loses its dissolving ability for the ceramic precursors, causing them to precipitate on the nanopore walls of the carbon aerogel material. This achieves deposition on the nanoframework without blocking the nanopores of the aerogel, thus achieving overall oxidation resistance, improving the material's high-temperature reliability, and simultaneously maintaining its thermal insulation performance.

[0017] (2) The antioxidant effect is controllable. Since carbon aerogel materials have a continuous porous structure and supercritical carbon dioxide has excellent solubility, ceramic precursors can diffuse to the nanopore walls with the flow of supercritical carbon dioxide. By controlling the process parameters (pressure and temperature) of supercritical deposition, uniform deposition on the surface of the three-dimensional network skeleton of carbon aerogel materials can be achieved. Moreover, by controlling the loading of ceramic precursors in supercritical carbon dioxide, controllable deposition of ceramic precursors on carbon aerogel skeletons can be achieved.

[0018] (3) The material modified by the method of this invention exhibits excellent high-temperature resistance and oxidation resistance. This invention features a specially designed precursor structure, selecting a ceramic precursor with relatively weak polarity and containing both silicon-hydrogen bonds and carbon-carbon double bonds. During deposition, it tends to deposit on the carbon nanoframework rather than remaining within the nanopores of the carbon aerogel. Furthermore, the selected ceramic precursor can be pyrolyzed and ceramicized at high temperatures, and the ceramicized product exhibits excellent high-temperature resistance. The resulting modified carbon aerogel material possesses excellent high-temperature resistance and oxidation resistance.

[0019] (4) The material prepared by the method of the present invention has advantages such as low density, good temperature resistance in aerobic environments, and excellent thermal insulation performance. In the present invention, the ceramic precursor is dissolved in supercritical carbon dioxide, and supercritical assisted deposition technology is used to diffuse the ceramic precursor into the interior of the nanostructure of carbon aerogel material. After reaching adsorption equilibrium, the supercritical carbon dioxide is rapidly depressurized, causing it to lose its ability to dissolve the modified material. The modified material will precipitate on the nanopore walls of the aerogel material, achieving uniform deposition on the surface of the carbon aerogel material. The resulting material not only has low density and excellent thermal insulation performance, but also significantly improved temperature resistance in aerobic environments.

[0020] (5) The method of the present invention has a wide range of applications. The modification effect of the method of the present invention is not limited by the shape and size of the material. Large-sized, thick, and irregularly shaped parts can also achieve the same performance effect as small samples. Therefore, the method of the present invention can realize the large-scale preparation of modified carbon aerogels. Attached Figure Description

[0021] Figure 1 A schematic diagram of the equipment used in the method of the present invention is shown. Wherein: 1. Carbon dioxide sampling bomb; 2. Pressure gauge; 3. Reactor; 4. Magnetic stirrer; 5. Heating and cooling circulator; 6. Carbon aerogel material; 7. Precursor solution; 8. Support. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be fully described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0023] As described above, the present invention provides a method for supercritical assisted deposition of modified carbon aerogel materials in a first aspect, the method comprising the following steps:

[0024] (1) A ceramic precursor solution is provided, the ceramic precursor solution comprising 95% to 100% by mass of a ceramic precursor and 0% to 5% by mass of a curing agent;

[0025] (2) The ceramic precursor solution and carbon aerogel material are loaded into the reactor and the reactor body is sealed.

[0026] (3) Carbon dioxide is introduced into the reactor, and then the ceramic precursor solution in the reactor is stirred and heated while stirring, so that the carbon dioxide in the reactor reaches a supercritical state.

[0027] (4) After the ceramic precursor in the reactor is completely dissolved and adsorption equilibrium is reached, the reactor is depressurized to atmospheric pressure to obtain a carbon aerogel material with the ceramic precursor deposited.

[0028] (5) The carbon aerogel material with the ceramic precursor deposited is cured and pyrolyzed to obtain the modified carbon aerogel material.

[0029] Supercritical fluids are fluids existing between the gas and liquid phases at temperatures and pressures above their critical state, possessing many of the superior physical properties of both phases. Supercritical carbon dioxide is characterized by its small molecular weight, low density, and rapid diffusion, thus exhibiting better permeation, transport, and dissolution properties than other solvents. Furthermore, supercritical carbon dioxide fluid technology offers advantages such as chemical inertness, simple processing, and the reusability of solvents and fluid media.

[0030] This invention involves dissolving a modified material (i.e., a ceramic precursor) of a carbon aerogel in supercritical carbon dioxide. Utilizing the excellent permeability and diffusion capacity of supercritical carbon dioxide, the modified material migrates into the nanostructure of the carbon aerogel. After adsorption equilibrium is reached, the supercritical carbon dioxide is rapidly depressurized, causing it to lose its ability to dissolve the modified material. The modified material then precipitates on the nanopore walls of the carbon aerogel, thereby achieving uniform deposition on the surface of the carbon aerogel and its composite materials.

[0031] In this invention, the pressure relief is preferably performed rapidly. More preferably, the pressure relief time is 50-80 seconds, that is, the pressure inside the reactor is reduced from the current high pressure to atmospheric pressure within 50-80 seconds. If the pressure relief time is too long, the nanopores of the resulting aerogel may be blocked; if the pressure relief time is too short, the nanostructure of the aerogel material may be damaged.

[0032] In this invention, the curing agent may or may not be added as needed. Without adding a curing agent, the content of the curing agent in the ceramic precursor solution is zero. With the addition of a curing agent, the concentration of the curing agent in the ceramic precursor solution can be no more than 5% by mass, for example, 1, 2, 3, 4, or 5% by mass or a subrange thereof, such as 0.001% by mass to 5% by mass. Accordingly, the concentration of the ceramic precursor in the ceramic precursor solution can be 95, 96, 97, 98, 99, or 100% by mass.

[0033] In some preferred embodiments, the ceramic precursor can be selected from any one of polysiloxane, polycarbosilane, polysilazane, and polyborosilicate, and the structure of the ceramic precursor contains both silicon-hydrogen bonds and carbon-carbon double bonds. This invention selects ceramic precursors with relatively weak polarity that simultaneously contain silicon-hydrogen bonds and carbon-carbon double bonds by screening the structure of the ceramic precursor. More preferably, the ratio of silicon-hydrogen bonds to carbon-carbon double bonds in the structure of the ceramic precursor is 10:3 to 10:10, for example, 10:4, 10:5, 10:6, 10:7, 10:8, 10:9, or 10:10. The inventors have discovered that such ceramic precursors can achieve maximum solubility in supercritical carbon dioxide by adjusting the supercritical deposition temperature and deposition pressure. Moreover, the ceramic precursors can be pyrolyzed and ceramicized at high temperatures, and the ceramicized products have excellent high-temperature resistance. The resulting modified carbon aerogel materials have excellent high-temperature resistance and oxidation resistance. Furthermore, by appropriately controlling the depressurization rate during the deposition process, these ceramic precursors can be deposited on the carbon nanoframework instead of remaining in the nanopores of the carbon aerogel.

[0034] In some preferred embodiments, the curing agent may be selected from any one of platinum catalyst, dicumyl peroxide, azobisisobutyronitrile, and benzoyl peroxide.

[0035] In some preferred embodiments, the carbon aerogel material can be pure carbon aerogel or carbon fiber reinforced carbon aerogel composite material.

[0036] In step (2), the mass ratio of the ceramic precursor solution to the carbon aerogel material can preferably be (1-10):(90-99), for example (1, 2, 3, 4, 5, 6, 7, 8, 9 or 10):(90, 91, 92, 93, 94, 95, 96, 97, 98 or 99), for example 1:99, 5:95 or 10:90.

[0037] In some preferred embodiments, the reactor is equipped with a support for loading the carbon aerogel material. Thus, in step (2), the ceramic precursor solution can be first loaded into the bottom of the reactor, and then the carbon aerogel material can be loaded onto the support inside the reactor, thereby preventing the carbon aerogel material from immersing in the ceramic precursor solution.

[0038] Preferably, in step (3), while the ceramic precursor is stirred at a speed of 300 to 800 rpm (e.g., 400, 500, 600 or 700 rpm), carbon dioxide is introduced into the reactor at a pressurization rate of 100 to 500 kPa / min (e.g., 200, 300 or 400 kPa / min) until the pressure inside the reactor reaches 35,000 to 55,000 kPa (e.g., 40,000, 45,000 or 50,000 kPa). Then, the temperature inside the reactor is raised to 31 to 38°C (e.g., 32, 33, 34, 35, 36 or 37°C) at a rate of 2 to 5°C / min (e.g., 3 or 4 min), thereby causing the carbon dioxide inside the reactor to reach a supercritical state.

[0039] Preferably, in step (4), the time to reach the adsorption equilibrium is 0.5 to 5 hours (e.g., 1, 2, 3 or 4 hours).

[0040] Preferably, in step (5), the curing temperature can be 80 to 300°C (e.g., 100, 150, 200 or 250°C).

[0041] Preferably, in step (5), the rate of heating to the curing temperature can be 1-10 °C / min (e.g., 2, 3, 4, 5, 6, 7, 8 or 9 °C / min).

[0042] Preferably, in step (5), the curing time can be 6 to 24 hours (e.g., 12 or 18 hours); the curing atmosphere is nitrogen or argon.

[0043] Preferably, in step (5), the pyrolysis temperature is 800-1600℃, for example, 900, 1000, 1100, 1200, 1300, 1400 or 1500℃.

[0044] Preferably, in step (5), the rate of heating to the pyrolysis temperature is 1 to 5 °C / min, for example 2, 3 or 4 °C / min.

[0045] Preferably, in step (5), the pyrolysis time is 0.5 to 5 hours, for example, 1, 2, 3 or 4 hours.

[0046] Preferably, in step (5), the atmosphere for pyrolysis is nitrogen or argon.

[0047] The method of this invention can be referred to Figure 1The schematic diagram is shown below. As shown, the precursor solution 7 is loaded into the reaction vessel 3, the carbon aerogel material (i.e., carbon aerogel or carbon aerogel composite material) is placed on the support 8, the reaction vessel 3 is tightened, and carbon dioxide is introduced into the reaction vessel 3 through the carbon dioxide sampling bomb 1. After observing that the pressure on the pressure gauge 2 reaches the experimental pressure, the valve of the carbon dioxide sampling bomb 1 is closed, and then the magnetic stirrer 4 is turned on for stirring. At the same time, the heating and cooling cycler 5 is turned on for heating. After adsorption equilibrium is reached, the heating and cooling cycler 5 and the magnetic stirrer 4 are turned off, and the pressure in the reaction vessel 3 is depressurized. After the pressure gauge 2 shows that the pressure has reached atmospheric pressure, the reaction vessel 3 is opened and the modified sample is taken out.

[0048] The present invention provides, in a second aspect, a modified carbon aerogel material prepared by the method described in the first aspect of the present invention.

[0049] Example

[0050] The present invention will be further described below with reference to embodiments. These embodiments are not intended to limit the scope of protection of the present invention, and any improvements made based on the present invention that do not depart from its spirit are within the scope of protection of the present invention.

[0051] The carbon aerogels used in all embodiments and comparative examples were from the same batch. The carbon aerogel composite materials used in all embodiments and comparative examples were also from the same batch.

[0052] Example 1

[0053] 10g of polycarbosilane was mixed with 0.01g of platinum catalyst to obtain a polycarbosilane solution. 1g of the polycarbosilane solution was weighed and added to the reactor. Then, 99g of carbon aerogel was placed on the reactor support, and the reactor was tightened. Carbon dioxide was introduced into the reactor at a rate of 100kPa / min, and the ceramic precursor solution in the reactor was stirred (500rpm). Simultaneously, heating was started, and the temperature was raised to 33℃ at a rate of 2℃ / min (hereinafter referred to as the first heating rate) to bring the carbon dioxide in the reactor to a supercritical state. After the ceramic precursor in the reactor was completely dissolved, adsorption equilibrium was reached after 5 hours. At this time, the pressure inside the reactor was 40000kPa and the temperature was 33℃. Heating was stopped, and the reactor was quickly depressurized to atmospheric pressure to obtain carbon aerogel with polycarbosilane deposited. The carbon aerogel was placed in a nitrogen atmosphere furnace and cured at 300℃ for 6 hours at a rate of 2℃ / min (referred to as the second heating rate). After curing, it was pyrolyzed at 800℃ for 1 hour at a rate of 1℃ / min (referred to as the third heating rate) to obtain SiC modified carbon aerogel.

[0054] Example 2

[0055] 10g of polysiloxane and 0.02g of dicumyl peroxide were mixed and stirred to obtain a polysiloxane solution. 3g of the polysiloxane solution was weighed and added to a reaction vessel. Then, 97g of carbon aerogel composite material was placed on the support of the reaction vessel, and the reaction vessel was tightened. Carbon dioxide was introduced into the reaction vessel at a rate of 200kPa / min to stir the ceramic precursor solution in the reaction vessel. At the same time, heating was started, and the temperature was increased to 31℃ at a rate of 3℃ / min to make the carbon dioxide in the reaction vessel reach a supercritical state. After the ceramic precursor in the reaction vessel was completely dissolved, adsorption equilibrium was reached after 1 hour. At this time, the pressure in the vessel was 35000kPa and the temperature was 31℃. Heating was stopped, and the pressure in the reaction vessel was quickly released to atmospheric pressure to obtain a carbon aerogel composite material with polysiloxane deposited. The carbon aerogel composite material was placed in an argon atmosphere furnace and cured at 80°C for 10 h at a rate of 1°C / min. After curing, it was pyrolyzed at 1000°C for 0.5 h at a rate of 2°C / min to obtain the SiOC modified carbon aerogel composite material.

[0056] Example 3

[0057] 10g of polysilazane and 0.006g of azobisisobutyronitrile were mixed and stirred to obtain a polysilazane solution. 5g of the polysilazane solution was weighed and added to the reactor. Then, 95g of carbon aerogel was placed on the reactor support, and the reactor was tightened. Carbon dioxide was introduced into the reactor at a rate of 300kPa / min, and the ceramic precursor solution in the reactor was stirred. At the same time, heating was started, and the temperature was increased to 32℃ at a rate of 5℃ / min, so that the carbon dioxide in the reactor reached the supercritical state. After the ceramic precursor in the reactor was completely dissolved, adsorption equilibrium was reached after 2 hours. At this time, the pressure in the reactor was 50000kPa and the temperature was 32℃. Heating was stopped, and the reactor was quickly depressurized to atmospheric pressure to obtain carbon aerogel with polysilazane deposited. The carbon aerogel was placed in an argon atmosphere furnace and cured at 100°C for 12 hours at a rate of 3°C / min. After curing, it was pyrolyzed at 1600°C for 2 hours at a rate of 3°C / min to obtain SiCN-modified carbon aerogel.

[0058] Example 4

[0059] 10g of polyborosilazane and 0.5g of benzoyl peroxide were mixed and stirred to obtain a polyborosilazane solution. 7g of the polyborosilazane solution was weighed and added to a reaction vessel. Then, 93g of the carbon aerogel composite material was placed on the support of the reaction vessel, and the reaction vessel was tightened. Carbon dioxide was introduced into the reaction vessel at a rate of 400kPa / min to stir the ceramic precursor solution in the reaction vessel. At the same time, heating was started, and the temperature was increased to 35℃ at a rate of 4℃ / min to make the carbon dioxide in the reaction vessel reach a supercritical state. After the ceramic precursor in the reaction vessel was completely dissolved, adsorption equilibrium was reached after 3 hours. At this time, the pressure in the vessel was 55000kPa and the temperature was 35℃. Heating was stopped, and the pressure in the reaction vessel was quickly released to atmospheric pressure to obtain a carbon aerogel composite material with polyborosilazane deposited. The carbon aerogel composite material was placed in an argon atmosphere furnace and cured at 200℃ for 18h at a rate of 3℃ / min. After curing, it was pyrolyzed at 1200℃ for 0.5h at a rate of 4℃ / min to obtain the SiBCN modified carbon aerogel composite material.

[0060] Example 5

[0061] 9g of polycarbosilane and 0.02g of platinum catalyst were weighed and mixed to obtain a polycarbosilane solution. 3g of the polycarbosilane solution was added to a reactor, and then 91g of carbon aerogel was placed on the reactor support and the reactor was tightened. Carbon dioxide was introduced into the reactor at a rate of 500kPa / min, and the ceramic precursor solution in the reactor was stirred. Simultaneously, heating was started, and the temperature was increased to 34℃ at a rate of 3℃ / min to bring the carbon dioxide in the reactor to a supercritical state. After the ceramic precursor in the reactor was completely dissolved, adsorption equilibrium was reached after 4 hours. At this time, the pressure inside the reactor was 3700kPa and the temperature was 34℃. Heating was stopped, and the reactor was quickly depressurized to atmospheric pressure to obtain carbon aerogel with polycarbosilane deposited. The carbon aerogel was placed in a nitrogen atmosphere furnace and cured at a rate of 8℃ / min to 160℃ for 20 hours. After curing, it was pyrolyzed at a rate of 5℃ / min to 1300℃ for 4 hours to obtain SiC modified carbon aerogel.

[0062] Example 6

[0063] 10g of polysilazane and 0.25g of dicumyl peroxide were mixed and stirred to obtain a polysilazane solution. 10g of the polysilazane solution was weighed and added to a reaction vessel. Then, 90g of the carbon aerogel composite material was placed on the support of the reaction vessel, and the reaction vessel was tightened. Carbon dioxide was introduced into the reaction vessel at a rate of 270kPa / min to stir the ceramic precursor solution in the reaction vessel, while simultaneously starting heating and raising the temperature to 36℃ at a rate of 5℃ / min, so that the carbon dioxide in the reaction vessel reached a supercritical state. After the ceramic precursor in the reaction vessel was completely dissolved, adsorption equilibrium was reached after 0.5h. At this time, the pressure inside the vessel was 48000kPa and the temperature was 36℃. Heating was stopped, and the pressure in the reaction vessel was rapidly released to atmospheric pressure, yielding a carbon aerogel composite material with polysilazane deposited. The carbon aerogel composite material was placed in an argon atmosphere furnace and cured at 240℃ for 24 hours at a rate of 10℃ / min. After curing, it was pyrolyzed at 1400℃ for 5 hours at a rate of 2℃ / min to obtain the SiCN-modified carbon aerogel composite material.

[0064] Example 7

[0065] 10g of polyborosilazane was mixed with 0.05g of platinum catalyst to obtain a polyborosilazane solution. 8g of the polyborosilazane solution was weighed and added to a reactor. Then, 92g of carbon aerogel was placed on the reactor's support, and the reactor was tightened. Carbon dioxide was introduced into the reactor at a rate of 150kPa / min, and the ceramic precursor solution in the reactor was stirred. Simultaneously, heating was started, and the temperature was increased to 38℃ at a rate of 4℃ / min, so that the carbon dioxide in the reactor reached a supercritical state. After the ceramic precursor in the reactor was completely dissolved, adsorption equilibrium was reached after 3.5h. At this time, the pressure inside the reactor was 12000kPa and the temperature was 38℃. Heating was stopped, and the reactor was quickly depressurized to atmospheric pressure, resulting in carbon aerogel with polyborosilazane deposited. The carbon aerogel was placed in a nitrogen atmosphere furnace and cured at 270°C for 15 h at a rate of 5°C / min. After curing, it was pyrolyzed at 1500°C for 3.5 h at a rate of 3°C / min to obtain SiBCN modified carbon aerogel.

[0066] Example 8

[0067] 10g of polycarbosilane was mixed with 0.01g of platinum catalyst to obtain a polycarbosilane solution. 1g of the polycarbosilane solution was weighed and added to the reactor. Then, 99g of carbon aerogel was placed on the reactor support, and the reactor was tightened. Carbon dioxide was introduced into the reactor at a rate of 100kPa / min, and the ceramic precursor solution in the reactor was stirred (500rpm). Simultaneously, heating was started, and the temperature was raised to 33℃ at a rate of 2℃ / min (hereinafter referred to as the first heating rate) to bring the carbon dioxide in the reactor to a supercritical state. After the ceramic precursor in the reactor was completely dissolved, adsorption equilibrium was reached after 5 hours. At this time, the pressure inside the reactor was 40000kPa and the temperature was 33℃. Heating was stopped, and the reactor was quickly depressurized to atmospheric pressure to obtain carbon aerogel with polycarbosilane deposited. The carbon aerogel was placed in a nitrogen atmosphere furnace and cured at 300℃ for 6 hours at a rate of 2℃ / min (referred to as the second heating rate). After curing, it was pyrolyzed at 800℃ for 1 hour at a rate of 1℃ / min (referred to as the third heating rate) to obtain SiC modified carbon aerogel.

[0068] Example 9

[0069] 10g of polycarbosilane was mixed with 0.01g of platinum catalyst to obtain a polycarbosilane solution. 1g of the polycarbosilane solution was weighed and added to the reactor. Then, 99g of carbon aerogel was placed on the reactor support, and the reactor was tightened. Carbon dioxide was introduced into the reactor at a rate of 100kPa / min, and the ceramic precursor solution in the reactor was stirred (500rpm). Simultaneously, heating was started, and the temperature was raised to 33℃ at a rate of 2℃ / min (hereinafter referred to as the first heating rate) to bring the carbon dioxide in the reactor to a supercritical state. After the ceramic precursor in the reactor was completely dissolved, adsorption equilibrium was reached after 5 hours. At this time, the pressure inside the reactor was 40000kPa and the temperature was 33℃. Heating was stopped, and the reactor was quickly depressurized to atmospheric pressure to obtain carbon aerogel with polycarbosilane deposited. The carbon aerogel was placed in a nitrogen atmosphere furnace and cured at 300℃ for 6 hours at a rate of 2℃ / min (referred to as the second heating rate). After curing, it was pyrolyzed at 800℃ for 1 hour at a rate of 1℃ / min (referred to as the third heating rate) to obtain SiC modified carbon aerogel.

[0070] Comparative Example 1

[0071] The procedure was carried out in essentially the same manner as in Example 1, except that the reactor was rapidly depressurized to atmospheric pressure over a period of 40 seconds.

[0072] Comparative Example 2

[0073] The procedure was carried out in essentially the same manner as in Example 1, except that the reactor was rapidly depressurized to atmospheric pressure over a period of 90 seconds.

[0074] Comparative Example 3

[0075] The procedure was carried out in essentially the same manner as in Example 1, except that a ceramic precursor with a silicon-hydrogen bond to carbon-carbon double bond ratio of 10:1 was used.

[0076] Comparative Example 4

[0077] The procedure was carried out in essentially the same manner as in Example 1, except that a ceramic precursor with a ratio of 10:12 of silicon-hydrogen bonds to carbon-carbon double bonds was used.

[0078] Comparative Example 5

[0079] The same procedure as in Example 1 was followed, except that the deposition temperature was 25°C.

[0080] Comparative Example 6

[0081] The same procedure as in Example 1 was followed, except that the deposition temperature was 40°C.

[0082] Comparative Example 7

[0083] The same procedure as in Example 1 was followed, except that the deposition pressure was 30,000 kPa.

[0084] Comparative Example 8

[0085] 99g of carbon aerogel was placed in an argon atmosphere furnace and heated to 300℃ at a rate of 2℃ / min for 6 hours, and then heated to 800℃ at a rate of 1℃ / min for 1 hour.

[0086] Comparative Example 9

[0087] 97g of carbon aerogel composite material was placed in an argon atmosphere furnace and heated to 80℃ at a rate of 1℃ / min for 10h, and then heated to 1000℃ at a rate of 2℃ / min for 0.5h.

[0088] The inventors also measured the density, room temperature thermal conductivity, residual weight in air at 1500°C, and residual weight in a furnace at 1400°C for 30 minutes for the materials prepared in each embodiment and comparative example. The results are shown in Table 4.

[0089] Table 1. Raw materials and their proportions used in each embodiment and comparative example

[0090]

[0091]

[0092]

[0093]

[0094] Table 3. Properties of the modified carbon aerogel / carbon aerogel composites prepared in each example

[0095] Example <![CDATA[Density (g / cm 3 )]]> Thermal conductivity at room temperature (W / (m·K)) TG residual weight (%) Muffle furnace residual weight (%) Example 1 0.17 0.050 35 40 Example 2 0.28 0.055 33 42 Example 3 0.19 0.051 35 43 Example 4 0.30 0.056 34 45 Example 5 0.22 0.052 37 47 Example 6 0.35 0.055 36 47 Example 7 0.21 0.050 36 45 Example 8 0.17 0.050 34 38 Example 9 0.19 0.051 35 39 Comparative Example 1 0.18 0.068 30 35 Comparative Example 2 0.27 0.065 35 32 Comparative Example 3 0.16 0.052 2 5 Comparative Example 4 0.17 0.055 5 8 Comparative Example 5 0.15 0.049 0 0 Comparative Example 6 0.16 0.050 3 4 Comparative Example 7 0.17 0.059 7 10 Comparative Example 8 0.15 0.049 0 0 Comparative Example 9 0.21 0.050 0 0

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for modifying carbon aerogel materials using supercritical assisted deposition, characterized in that, The method includes the following steps: (1) Provide a ceramic precursor solution, the ceramic precursor solution comprising 95% to 100% by mass of a ceramic precursor and 0% to 5% by mass of a curing agent, wherein the ceramic precursor is selected from one or more of polysiloxane, polycarbosilane, polysilazane, and polyboronsilazane, and the structure of the ceramic precursor contains both silicon-hydrogen bonds and carbon-carbon double bonds. (2) The ceramic precursor solution and carbon aerogel material are loaded into a reaction vessel and the vessel body is sealed, wherein the mass ratio of the ceramic precursor solution to the carbon aerogel material is (1~10):(90~99). (3) Carbon dioxide is introduced into the reactor, and then the ceramic precursor solution in the reactor is stirred and heated while stirring, so that the carbon dioxide in the reactor reaches a supercritical state. (4) After the ceramic precursor in the reactor is completely dissolved and adsorption equilibrium is reached, the reactor is depressurized to atmospheric pressure to obtain a carbon aerogel material with the ceramic precursor deposited. (5) The carbon aerogel material with the ceramic precursor deposited is cured and pyrolyzed to obtain the modified carbon aerogel material.

2. The method according to claim 1, characterized in that: The ratio of silicon-hydrogen bonds to carbon-carbon double bonds in the structure of the ceramic precursor is 10:3 to 10:

10. The curing agent is selected from any one of platinum catalyst, dicumyl peroxide, azobisisobutyronitrile, and benzoyl peroxide; and / or The carbon aerogel material is either pure carbon aerogel or carbon fiber reinforced carbon aerogel composite material.

3. The method according to claim 1, characterized in that: In step (2), the reactor is equipped with a support for loading the carbon aerogel material.

4. The method according to claim 2, characterized in that: In step (2), the reactor is equipped with a support for loading the carbon aerogel material.

5. The method according to any one of claims 1 to 4, characterized in that: In step (2), the ceramic precursor solution is first loaded into the bottom of the reactor, and then the carbon aerogel material is loaded onto the support inside the reactor, thereby preventing the carbon aerogel material from immersing in the ceramic precursor solution.

6. The method according to any one of claims 1 to 4, characterized in that, In step (3): While the ceramic precursor is stirred at a speed of 300-800 rpm, carbon dioxide is introduced into the reactor at a pressurization rate of 100-500 kPa / min until the pressure inside the reactor reaches 35000-55000 kPa. Then, the temperature inside the reactor is raised to 31-38°C at a rate of 2-5°C / min, thereby causing the carbon dioxide inside the reactor to reach a supercritical state.

7. The method according to any one of claims 1 to 4, characterized in that: In step (4), the time to reach the adsorption equilibrium is 0.5 to 5 hours, and the time to release pressure is 50 to 80 seconds.

8. The method according to any one of claims 1 to 4, characterized in that, In step (5): The curing temperature is 80~300℃. o C; The rate of heating to the curing temperature is 1-10℃ / min; The curing time is 6~24 h; The curing atmosphere is nitrogen or argon.

9. The method according to any one of claims 1 to 4, characterized in that, In step (5): The pyrolysis temperature is 800-1600℃. o C; The rate of heating to the pyrolysis temperature is 1 to 5 °C / min; The pyrolysis time is 0.5 to 5 hours; The atmosphere for pyrolysis is nitrogen or argon.

10. A modified carbon aerogel material prepared by any one of claims 1 to 9.

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