Carbon / carbon composite aerogel based on congruent resin coating and preparation method

Abstract

The invention provides a carbon / carbon composite aerogel based on congruent resin coating and a preparation method thereof, and the carbon / carbon composite aerogel is obtained by coating organic aerogel with congruent organic resin and sequentially carrying out dipping, drying and in-situ carbonization. The preparation method comprises the following steps: preparing organic aerogel; preparing organic resin sol with the same components as the organic aerogel; when the organic resin sol is in a prepolymerization state, carrying out confinement impregnation on the organic aerogel to force the organic resin sol to form a film on the surface of the organic aerogel; carrying out gradient drying and curing to obtain an aerogel composite material with a compact shell layer on the surface; and finally, carrying out in-situ carbonization on the aerogel composite material to form the carbon / carbon composite aerogel. Compared with traditional carbon aerogel, the prepared carbon / carbon composite aerogel has better mechanical strength, and the compressive strength is improved by 2-7 times; the specific surface area is reduced by not more than 10%; the high-temperature stability is obviously improved, and great benefits are achieved for practical application.

Description

Technical Field

[0001] The invention relates to the technical field of nanoporous materials, and specifically relates to a carbon / carbon composite aerogel coated with a resin having the same composition and a preparation method thereof. Background Art

[0002] Carbon aerogel is a three-dimensional, porous, lightweight material primarily composed of carbon. It exhibits high specific surface area, low density, high electrical conductivity, excellent chemical stability, and a tunable pore structure. However, its practical application still faces a series of technical bottlenecks, including the poor mechanical properties of conventional carbon aerogels (compressive strength <1 MPa) and insufficient high-temperature stability (easily collapsing at temperatures above 800°C). Heterogeneous composites (such as SiO2 / RF and CNT / RF) are prone to structural cracking due to mismatched interfacial expansion coefficients. During the sol-gel coating process, the sol easily penetrates into the aerogel pores (penetration depth >50 μm), leading to pore blockage and a decrease in specific surface area.

[0003] The invention patent application with publication number CN119350701A discloses a hybrid skeleton absorbing aerogel wrapped with multi-walled carbon nanotubes and a preparation method thereof. This method uses titanium carbide / aramid nanofiber aerogel to impregnate a carbon nanotube dispersion to prepare a carbon nanotube-wrapped aerogel. However, since the impregnation range is uncontrollable, the carbon nanotubes penetrate into the pores of the aerogel to form microporous aerogel, which reduces the specific surface area and the thermal insulation effect.

[0004] Another invention patent application with publication number CN119528599A discloses a method for preparing multi-scale reinforced carbon aerogel composite materials by using expandable graphite to assist in reducing carbonization shrinkage. This method uses expandable graphene-enhanced phenolic sol to impregnate PAN-based pre-oxidized fiber felt to prepare carbon aerogel, which effectively enhances the mechanical strength and high-temperature thermal insulation properties. However, this method still has the problem of easy interface peeling at high temperatures. Summary of the Invention

[0005] To solve the above problems, the purpose of the present invention is to provide a carbon / carbon composite aerogel based on homologous resin coating and a preparation method. The method achieves seamless interface bonding through homologous organic resin coating to avoid heterogeneous defects; combines sol viscosity control with confined impregnation process to inhibit sol penetration into pores (penetration depth <5μm); in-situ carbonization forms a continuous carbon / carbon network, improves mechanical strength (compressive strength increased by 2-7 times), significantly improves high-temperature stability, and reduces specific surface area by no more than 10%.

[0006] The purpose of the present invention is achieved through the following technical solutions: A carbon / carbon composite aerogel coated with a resin of the same composition is obtained by coating an organic resin of the same composition on an organic aerogel and sequentially performing the steps of impregnation, drying and in-situ carbonization.

[0007] Furthermore, the organic resin and organic aerogel of the same composition include any one of the following combinations: phenolic aerogel and phenolic resin, polyimide aerogel and polyimide resin, polyurethane aerogel and polyurethane resin, cellulose aerogel and cellulose-based resin, and epoxy aerogel and epoxy resin. In each of the above combinations, the phenolic aerogel and phenolic resin use the same phenolic and aldehyde compounds, the polyimide aerogel and polyimide resin use the same dianhydride and diamine, the polyurethane aerogel and polyurethane resin use the same polyol and isocyanate, the cellulose aerogel and cellulose-based resin use the same modified cellulose, and the epoxy aerogel and epoxy resin use the same epoxy polymer.

[0008] A method for preparing a carbon / carbon composite aerogel coated with a resin of the same composition comprises the following steps: (1) Preparation of organic aerogel.

[0009] (2) Prepare an organic resin sol with the same composition as the organic aerogel.

[0010] (3) When the organic resin sol is in a prepolymerized state, the organic aerogel is impregnated in a limited area to force the organic resin sol to form a thin film on the surface of the organic aerogel.

[0011] (4) Gradient drying and curing are then performed to obtain an aerogel composite material with a dense shell layer on the surface.

[0012] (5) Finally, the aerogel composite material is in situ carbonized (so that the organic resin sol coating layer and the organic aerogel are simultaneously converted into a carbon skeleton) to form a carbon / carbon composite aerogel.

[0013] Furthermore, before the confined impregnation, the prepared organic aerogel or the formulated organic resin sol is surface modified.

[0014] Furthermore, the surface modification of the organic aerogel or the surface modification of the organic resin sol is achieved by directly adding a modifier and stirring; the modifier includes one or two of coupling agent-modified KH550, KH560, and APTES.

[0015] Furthermore, the solid content of the organic resin sol is 5%-20%, and the viscosity of the organic resin sol in the prepolymerized state is 150-200 mPa•s. Viscosity regulation can prevent the viscosity from being too low to penetrate into the aerogel material.

[0016] Furthermore, the confined impregnation step is: evacuating to 0.05-0.01 MPa and maintaining for 8-12 minutes, injecting prepolymer resin sol, and rapidly pressurizing to 0.5-1.5 MPa and maintaining for 5-10 minutes, so that the organic aerogel is immersed in the organic resin sol by pressurized infiltration under vacuum conditions.

[0017] Furthermore, the gradient drying step comprises: first drying at room temperature for 10-30 minutes, then drying by any of supercritical drying, room temperature drying, or freeze drying until solidified. Preferably, supercritical drying is performed after room temperature drying. The supercritical drying parameters are: supercritical drying kettle temperature of 35-45°C, pressure of 6-10 MPa, CO2 flow rate of 600-1500 kg / h, and drying time of 8-14 hours.

[0018] Furthermore, the thickness of the dense shell is 50-200 nm.

[0019] Furthermore, the in-situ carbonization step is: carbonizing the dried and solidified aerogel composite material with argon or nitrogen at a flow rate of 50-100 ml / min as a protective gas at a temperature of 600-1500°C for 1-3 hours, and heating the temperature to the carbonization temperature at a rate of 1-3°C / min.

[0020] The beneficial effects of the present invention are: (1) Using the same composition interface design: the chemical composition of the coating layer is consistent with that of the substrate, and a seamless carbon / carbon interface is formed after carbonization, which greatly improves the interface strength.

[0021] (2) Adopting sol penetration inhibition technology: by increasing the viscosity of the sol (prepolymerizing the sol to the critical gel point) and co-impregnating it with vacuum-pressure, surface confinement can be achieved, thus reducing the pore blockage rate (pore blockage rate <5%).

[0022] (3) In-situ carbonization synergistic shrinkage: The coating and the substrate are pyrolyzed basically simultaneously, inhibiting carbonization cracking (shrinkage rate is reduced by more than 30%).

[0023] The carbon / carbon composite aerogel prepared by the present invention has better mechanical strength than traditional carbon aerogels, with compressive strength increased by 2-7 times; the specific surface area is reduced by no more than 10%; and the high-temperature stability is significantly improved, which has great benefits for practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a process roadmap for preparing the carbon / carbon composite aerogel of the present invention. DETAILED DESCRIPTION

[0025] The following specific embodiments illustrate the embodiments of the present invention. Those skilled in the art can easily understand the other advantages and effects of the present invention from the contents disclosed in this specification. The described embodiments are only some embodiments of the present invention, not all 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. Example 1

[0026] This embodiment provides a method for preparing a carbon / carbon composite aerogel coated with a resin of the same composition, comprising the following steps: (1) Preparation of RF aerogel: Resorcinol (R) and formaldehyde (F) were mixed in a molar ratio of 1:2, deionized water was added to adjust the solid content to 10%, and sodium carbonate (R / C molar ratio was 200) was added as a catalyst. The mixture was stirred magnetically for 30 min until it was completely dissolved. The sol was poured into a mold and gelled at a constant temperature of 60 °C for 48 h. After gelling, the mixture was immersed in methanol for aging for 48 h (methanol was replaced every 8 h), and then solvent replacement was performed for 72 h (methanol was replaced every 24 h). Finally, the RF aerogel was dried for 12 h under supercritical conditions (40 °C, 10 MPa) with a CO2 flow rate of 1000 kg / h.

[0027] (2) Preparation of RF resin sol with the same composition: The RF resin sol was prepared with the same R / F molar ratio (1:2) as that of the RF aerogel, and its solid content was 20%. It was prepolymerized at 50 °C for 1-2 h. When the sol approached the gel point (the sol viscosity was 150-200 mPa·s, in the prepolymerized state), it was prepared for the next step.

[0028] (3) Surface modification of RF aerogel: carried out simultaneously with step (2), KH550 was mixed with methanol / water (volume ratio of KH550: ethanol: water = 1:4:0.5) to prepare KH550 hydrolyzate, and magnetically stirred at 55 °C for 2 h; RF aerogel was immersed in KH550 hydrolyzate, vacuum immersed for 20 min (vacuum degree 40 MPa), and then taken out and dried at 60 °C for 2 h.

[0029] (4) Vacuum-pressure synergistic impregnation: The modified RF aerogel obtained in step (3) is placed in a vacuum impregnation tank, evacuated to 40 kPa and maintained for 10 min, and then the RF resin sol in the pre-polymerized state is injected and quickly pressurized to about 1 MPa and maintained for 10 min, so that the RF aerogel is immersed in the RF resin sol by pressure infiltration under vacuum conditions.

[0030] (5) Gradient drying and curing: The material obtained in step (4) was allowed to stand at room temperature for 30 minutes, and then dried using CO 2 Supercritical drying (40°C, 10 MPa, 800 kg / h) for 12 h.

[0031] (6) The material obtained in step (5) was placed in a graphite boat, which was placed in a carbonization furnace. High-purity argon gas with a flow rate of 100 mL / min was used as a protective gas. The temperature was raised from room temperature to 1050°C at a rate of 2°C / min, and the temperature was kept at this temperature for 3 h. The carbon / carbon composite aerogel was then naturally cooled to room temperature.

[0032] Preparation of control group 1: The RF aerogel prepared in step (1) was directly carbonized according to the method of step (6) to obtain carbon aerogel.

[0033] The performance of the carbon / carbon composite aerogel (Example 1) was compared with that of the carbon aerogel (Control Group 1). The specific data are shown in Table 1.

[0034] Table 1 Comparison of properties between carbon / carbon composite aerogel and carbon aerogel

[0035] Through appearance observation, the carbon / carbon composite aerogel prepared in Example 1 has no carbonization cracking problem; as shown in Table 1 and through BET test, the specific surface area of the carbon / carbon composite aerogel prepared in Example 1 is 611m 2 / g, compared with the carbon aerogel prepared in control group 1 (677m 2 / g) decreased by 9.7%, and the pore size distribution curve showed that the volume retention rate of mesopores (2-50nm) was 96%, proving that the sol coating layer did not significantly block the internal pores of the aerogel; in addition, the density and residual carbon retention (the carbon / carbon composite aerogel increased by 23.3% and 7.6% respectively compared with the carbon aerogel) tests also indirectly proved this point; at the same time, the compressive strength of the carbon / carbon composite aerogel of Example 1 was greatly improved compared with the carbon aerogel of Control Group 1, with an improvement of 5 times. Example 2

[0036] This embodiment provides a method for preparing a carbon / carbon composite aerogel coated with a resin of the same composition, comprising the following steps: (1) Preparation of RF aerogel: Resorcinol (R) and formaldehyde (F) were mixed in a molar ratio of 1:2, deionized water was added to adjust the solid content to 10%, sodium carbonate catalyst (R / C molar ratio was 200) was added, and magnetic stirring was performed for 30 min until it was completely dissolved. The sol was introduced into the mold and gelled at a constant temperature of 60 °C for 48 h. After gelling, it was immersed in methanol for aging for 48 h (methanol was replaced every 8 h), and then solvent replacement was performed for 72 h (methanol was replaced every 24 h), and finally in CO 2 RF aerogel was obtained by drying under supercritical conditions (40 °C, 10 MPa) at a flow rate of 1000 kg / h for 12 h.

[0037] (2) Preparation of RF resin sol with the same composition: The RF resin sol was prepared with the same R / F molar ratio (1:2) as that of the RF aerogel, and its solid content was 15%. The RF resin sol was prepolymerized at 50 °C for 1-2 h until the RF resin sol approached the gel point (at this time, the viscosity of the RF resin sol was 150-200 mPa·s, and it was in a prepolymerized state).

[0038] (3) Surface modification of RF resin sol: KH550 was mixed with methanol / water (volume ratio of KH550: ethanol: water = 1:4:0.5) to prepare KH550 hydrolyzate, and magnetically stirred at 55 °C for 2 h; 1 wt% (based on the solid content of RF resin) of KH550 hydrolyzate was added to the prepolymerized RF resin sol, stirred and allowed to stand until the sol viscosity was 150-200 mPa•s, and then prepared for the next step.

[0039] (4) Vacuum-pressure synergistic impregnation: Place the RF aerogel in a vacuum impregnation tank, evacuate to 40 kPa and maintain for 10 min, then inject the pre-polymerized RF resin sol modified by step (3), quickly pressurize to about 1 MPa and maintain for 10 min, so that the RF aerogel is immersed in the RF resin sol by pressure infiltration under vacuum conditions.

[0040] (5) Gradient drying and curing: The material obtained in step (4) was allowed to stand at room temperature for 30 minutes, and then dried using CO 2 Supercritical drying (40°C, 10 MPa, 800 kg / h) for 12 h.

[0041] (6) The material obtained in step (5) was placed in a graphite boat, which was placed in a carbonization furnace. High-purity argon gas with a flow rate of 100 mL / min was used as a protective gas. The temperature was raised from room temperature to 1200°C at a rate of 3°C / min, and the temperature was kept for 2 h. The carbon boat was then naturally cooled to room temperature, thereby obtaining a carbon / carbon composite aerogel.

[0042] Preparation of control group 2: The RF aerogel was carbonized according to step (6) to obtain carbon aerogel.

[0043] The performance of the carbon / carbon composite aerogel (Example 2) was compared with that of the carbon aerogel (Control Group 2). The specific data are shown in Table 2.

[0044] Table 2 Comparison of performance between carbon / carbon composite aerogel and carbon aerogel

[0045] Through appearance observation, the carbon / carbon composite aerogel prepared in Example 2 has no carbonization cracking problem; as shown in Table 1 and through BET test, the specific surface area of the carbon / carbon composite aerogel prepared in Example 2 is 598m 2 / g, compared with the carbon aerogel prepared in control group 2 (645 m 2The carbon / carbon composite aerogel of Example 2 exhibited a 7.3% decrease in carbon content ( / g), and the pore size distribution curve showed a 95% volume retention of mesopores (2-50 nm), demonstrating that the sol coating did not significantly block the aerogel's internal pores. This was also indirectly supported by density and residual carbon content (the carbon / carbon composite aerogel increased by 22.9% and 7.2%, respectively, compared to the carbon aerogel in Control 2). Furthermore, the compressive strength of the carbon / carbon composite aerogel of Example 2 was significantly improved, by a factor of 6, compared to the carbon aerogel in Control 2. Example 3

[0046] This embodiment provides a method for preparing a carbon / carbon composite aerogel coated with a resin of the same composition, comprising the following steps: (1) Preparation of polyimide aerogel: pyromellitic dianhydride and 4,4'-diamino-2, 2'-dimethyl-1,1'-biphenyl were mixed in a molar ratio of 1:0.97, dissolved in NMP solution and adjusted to a solid content of 10%, and 2 wt% acetic anhydride and 1 wt% triethylamine were added. The mixture was stirred magnetically for 30 min until homogeneous. The sol was poured into a mold and gelled in a water bath at a constant temperature of 60 °C for 12 h. After gelation, the mixture was immersed in methanol for replacement for 48 h (methanol was replaced every 8 h). Finally, the polyimide aerogel was obtained by drying under supercritical conditions (40 °C, 10 MPa) with a CO2 flow rate of 1000 kg / h for 12 h.

[0047] (2) Preparation of polyimide resin sol with the same composition: The polyimide resin sol was prepared by using the same molar ratio of pyromellitic dianhydride and 4,4'-diamino-2, 2'-dimethyl-1,1'-biphenyl (1:0.97) as that of the polyimide aerogel, and its solid content was 5%.

[0048] (3) Surface modification of polyimide resin sol: KH550 was mixed with methanol / water (volume ratio of KH550: ethanol: water = 1:4:0.5) to prepare KH550 hydrolyzate, and magnetically stirred at 55 °C for 2 h; 1 wt% of KH550 hydrolyzate was added to the polyimide resin sol prepared in step (2), stirred and allowed to stand until the viscosity of the polyimide resin sol was 150-200 mPa·s (the polyimide resin sol was in a prepolymerized state at this time), and then prepared for the next step.

[0049] (4) Vacuum-pressure synergistic impregnation: Place the polyimide aerogel in a vacuum impregnation tank, evacuate to 0.01 MPa, and then inject the pre-polymerized polyimide resin sol. Maintain for 30 minutes to ensure penetration, so that the polyimide aerogel is immersed in the polyimide resin sol by pressure penetration under vacuum conditions.

[0050] (5) Gradient drying and curing: The material obtained in step (4) was allowed to stand at room temperature for 30 min, then heated to 250 °C (Ar protection) at a rate of 2 °C / min and kept at this temperature for one hour.

[0051] (6) The material obtained in step (5) was placed in a graphite boat, which was then placed in a carbonization furnace. High-purity argon gas with a flow rate of 100 mL / min was used as a protective gas. The temperature was raised from room temperature to 300°C at a rate of 2°C / min and kept at that temperature for 1 h. The temperature was then raised from 300°C to 800°C and kept at that temperature for 2 h. The carbon / carbon composite aerogel was then naturally cooled to room temperature to obtain a carbon / carbon composite aerogel.

[0052] Preparation of control group 3: The polyimide aerogel was carbonized according to step (6) to obtain carbon aerogel.

[0053] The performance of carbon / carbon composite aerogel is compared with that of carbon aerogel. The specific data are shown in Table 3.

[0054] Table 3 Comparison of performance between carbon / carbon composite aerogel and carbon aerogel

[0055] Through appearance observation, the carbon / carbon composite aerogel prepared in Example 3 has no carbonization cracking problem; According to Table 3 and the BET test, the specific surface area of the carbon / carbon composite aerogel in Example 3 is 521m 2 / g, compared with the carbon aerogel prepared in control group 3 (575 m 2 The carbon / carbon composite aerogel showed a 9.4% decrease in carbon content ( / g), demonstrating that the sol coating did not significantly block the aerogel's internal pores. Density testing also indirectly supports this finding (the carbon / carbon composite aerogel increased by 12.5% compared to carbon aerogel). Furthermore, the carbon / carbon composite aerogel exhibited significant improvements in stability and compressive strength compared to carbon aerogel, with stability increasing by 190°C and compressive strength increasing by twofold.

[0056] Other aspects of the present invention that are not described in detail are all conventional techniques known to those skilled in the art.

[0057] It should be noted that the terms "comprises," "includes," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a series of elements includes not only those elements, but also other elements not explicitly listed, or elements that are inherent to such process, method, article, or apparatus.

[0058] The protection scope of the present invention is not limited to the technical solutions disclosed in the specific implementation methods. Any modifications, equivalent replacements, improvements, etc. made to the above embodiments based on the technical essence of the present invention fall within the protection scope of the present invention.

Claims

1. A carbon / carbon composite aerogel coated with a resin of the same composition, characterized in that: It is obtained by coating an organic resin with the same composition on an organic aerogel, and then sequentially undergoing impregnation, drying and in-situ carbonization.

2. The carbon / carbon composite aerogel coated with a resin of the same composition according to claim 1, characterized in that: The organic resin and organic aerogel of the same composition include any one of the following combinations: phenolic aerogel and phenolic resin, polyimide aerogel and polyimide resin, polyurethane aerogel and polyurethane resin, cellulose aerogel and cellulose-based resin, epoxy aerogel and epoxy resin.

3. The method for preparing carbon / carbon composite aerogel coated with resin of the same composition according to claim 1, characterized in that: The following steps are involved: Preparation of organic aerogels; preparing an organic resin sol having the same composition as that of the organic aerogel; When the organic resin sol is in a pre-polymerized state, the organic aerogel is impregnated in a limited area to force the organic resin sol to form a thin film on the surface of the organic aerogel; Then, gradient drying and curing are performed to obtain an aerogel composite material with a dense shell layer on the surface; Finally, the aerogel composite material is in-situ carbonized to form a carbon / carbon composite aerogel.

4. The method for preparing carbon / carbon composite aerogel coated with resin of the same composition according to claim 1, characterized in that: Before the confined impregnation, the prepared organic aerogel or the configured organic resin sol is surface modified.

5. The method for preparing carbon / carbon composite aerogel coated with resin of the same composition according to claim 4, characterized in that: The surface modification of the organic aerogel or the organic resin sol is achieved by directly adding a modifier and stirring; the modifier includes one or two of coupling agent-modified KH550, KH560, and APTES.

6. The method for preparing carbon / carbon composite aerogel coated with resin of the same composition according to claim 1, characterized in that: The solid content of the organic resin sol is 5%-20%, and the viscosity of the organic resin sol in the prepolymerized state is 150-200 mPa•s.

7. The method for preparing carbon / carbon composite aerogel coated with resin of the same composition according to claim 1, characterized in that: The confined impregnation step is: evacuating to 0.05-0.01 MPa and maintaining it for 8-12 minutes, injecting the prepolymer resin sol, and rapidly pressurizing to 0.5-1.5 MPa and maintaining it for 5-10 minutes.

8. The method for preparing carbon / carbon composite aerogel coated with resin of the same composition according to claim 1, characterized in that: The gradient drying step comprises: first drying at room temperature for 10-30 minutes, and then drying to solidification by any drying method selected from supercritical drying, room temperature drying or freeze drying.

9. The method for preparing carbon / carbon composite aerogel coated with resin of the same composition according to claim 1, characterized in that: The thickness of the dense shell is 50-200 nm.

10. The method for preparing carbon / carbon composite aerogel coated with resin of the same composition according to claim 1, characterized in that: The in-situ carbonization step comprises: carbonizing the dried and solidified aerogel composite material at 600-1500° C. for 1-3 hours using argon or nitrogen at a flow rate of 50-100 ml / min as a protective gas, and heating the temperature to the carbonization temperature at a rate of 1-3° C. / min.

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