Preparation method of carbon fiber reinforced carbon aerogel heat insulation composite material

Abstract

The invention relates to a preparation method of a carbon fiber reinforced carbon aerogel heat insulation composite material, which comprises the following steps: firstly, pre-oxidizing a commercial polyacrylonitrile (PAN) needled felt reinforcement at 195-255 DEG C to obtain pre-oxidized felt reinforcements with different pre-oxidation degrees; uniformly mixing phenolic resin serving as an organic sol raw material, hexamethylenetetramine serving as a cross-linking curing agent and normal propyl alcohol serving as a solvent according to a proper proportion to form organic sol; secondly, the pre-oxidized felt blank body is placed in a stainless steel mold, organic sol is poured into the stainless steel mold, the pre-oxidized felt is completely immersed in the sol, and the pre-oxidized felt reinforcement is fully soaked in the organic sol under the vacuum negative pressure condition; sealing the stainless steel mold dipped with the pre-oxidized felt, and curing and aging for 40-80 hours at 80 DEG C to obtain pre-oxidized felt reinforced organic wet gel; placing the wet gel at room temperature for 24 hours, and drying the wet gel in an air dry oven at 60 DEG C for 72 hours to obtain pre-oxidized felt reinforced organic aerogel; and finally, carbonizing the pre-oxidized felt reinforced organic aerogel at 850-1100 DEG C for 3 hours by using a vacuum carbonization furnace at a heating rate of 3-5 DEG C / min to obtain the carbon fiber reinforced carbon aerogel composite material.

Description

Technical Field

[0001] The present invention relates to the field of preparation of carbon aerogel thermal insulation composite materials, and specifically to the preparation technology of carbon fiber reinforced carbon aerogel thermal insulation composite materials. Background Art

[0002] Aerogel is a highly dispersed solid material with a nano-porous three-dimensional network structure formed by the aggregation of nano-scale colloidal particles and filled with a gaseous dispersion medium in the pores. In the aerogel system, silica aerogel was first used as a thermal insulation material, but the temperature tolerance of silica aerogel is only 800 °C, and there are problems of shrinkage and cracking at high temperatures. In addition to the excellent properties of general aerogels such as light weight, high porosity, low density, and large specific surface area, carbon aerogel also has the advantages of carbon materials such as excellent electrical conductivity, acid and alkali resistance, etc. Since its birth, it has been favored by researchers and shows good application prospects in the fields of thermotics, acoustics, electricity, catalysis, hydrogen storage, etc. In addition, carbon aerogel has the highest thermal stability and can still maintain its nano-porous structure above 2800 °C in an inert atmosphere. Therefore, it can maintain a low thermal conductivity at high temperatures and has great application potential in the field of ultra-high temperature thermal insulation materials. Generally speaking, the thermal protection system does not need to directly bear loads, but during the flight of a hypersonic aircraft, it may be subjected to aerodynamic loads, vibration loads, and thermal shocks, etc. If the material strength is too low, it will bring many unsafe factors during the flight of the aircraft. As a thermal-load integrated component, carbon fiber reinforced carbon aerogel is expected to achieve breakthroughs in high-end thermal protection application fields such as the power device of hypersonic aircraft.

[0003] Since the volume shrinkage rate of the organic aerogel during the carbonization process far exceeds that of the carbon fiber reinforcement, directly introducing carbon fiber into the organic precursor of the carbon aerogel will result in a large number of defects after carbonization due to shrinkage mismatch during the carbonization process, making it difficult to effectively composite. Using polyacrylonitrile fibers with different degrees of pre-oxidation as the reinforcement can achieve shrinkage matching between the organic aerogel matrix and the polyacrylonitrile fibers during the carbonization process, and obtain a thermal insulation composite material with shrinkage matching between the carbon fiber and the carbon aerogel matrix. At the same time, by appropriately increasing the wet gel pore size and the network skeleton strength, the gel shrinkage rate under atmospheric pressure drying conditions can be greatly reduced, thereby greatly reducing the equipment cost and making the large-scale commercial production of aerogel possible. Summary of the Invention

[0004] The purpose of the present invention is to break through the size limitation of the preparation of carbon aerogel through fiber reinforcement and atmospheric pressure drying, develop a new type of thermal protection material with integrated thermal insulation and load-bearing, and provide a carbon fiber reinforced carbon aerogel thermal insulation composite material.

[0005] The present invention is a preparation method of a carbon fiber reinforced carbon aerogel thermal insulation composite material, and its steps are as follows: S1. Pre-oxidize the commodity polyacrylonitrile (PAN) needle-punched felt reinforcement at 195 - 255 °C to obtain pre-oxidized felt reinforcements with different degrees of pre-oxidation; S2. Use phenolic resin (P) as the raw material for the organic sol, hexamethylenetetramine (H) as the cross-linking curing agent, and n-propanol as the solvent (S). After mixing evenly, form an organic sol; S3. Place the pre-oxidized felt blank in a stainless-steel mold, then pour in the organic sol to completely submerge the pre-oxidized felt. Under vacuum negative pressure conditions, allow the organic sol to fully penetrate the pre-oxidized felt reinforcement; S4. Seal the stainless-steel mold impregnated with the pre-oxidized felt and cure and age it at 80 °C for 40 - 80 h to obtain an organic wet gel reinforced with the pre-oxidized felt; S5. Place the wet gel at room temperature for 24 h, then dry it in a forced-air drying oven at 60 °C for 72 h to obtain an organic aerogel reinforced with the pre-oxidized felt; S6. Carbonize the organic aerogel reinforced with the pre-oxidized felt in a vacuum carbonization furnace at 850 - 1100 °C for 3 h, with a heating rate of 3 - 5 °C / min, to obtain a carbon fiber-reinforced carbon aerogel composite material.

[0006] The present invention has the following beneficial effects: The strength of carbon aerogel is very low. Usually, supercritical drying technology is required to prepare the organic aerogel precursor, so it is difficult to fabricate large-size carbon aerogel components. Using inexpensive industrial phenolic resin as the raw material and n-propanol with a relatively high boiling point as the solvent, the curing and aging temperatures in the sol-gel process can be carried out at a relatively high temperature (lower than the boiling point of the solvent), obtaining an organic gel with a stable skeleton, intact micro-pore structure, and suitable for preparation by atmospheric pressure drying method.

[0007] In addition, using carbon fiber reinforcement is an effective method to improve the strength of aerogel. However, the linear shrinkage rate is large during the pyrolysis process of the organic aerogel precursor. Directly compounding carbon fiber with the organic precursor of carbon aerogel, there is a problem that the shrinkage of the reinforcement fiber and the aerogel matrix is not easy to match during the carbonization process. Using polyacrylonitrile fibers with different degrees of pre-oxidation as the reinforcement to achieve the shrinkage matching between the organic aerogel matrix and the polyacrylonitrile fiber during the carbonization process, and obtain a heat-insulating composite material with shrinkage matching between the carbon fiber and the carbon aerogel matrix. Through fiber reinforcement and atmospheric pressure drying, it helps to break through the size limitation in the preparation of carbon aerogel, develop a new type of thermal protection material integrating heat insulation and load-bearing, promote the upgrading of thermal protection materials, and make large-scale commercial production of aerogel possible. Description of the Drawings

[0008] Figure 1 is the macroscopic morphology of the pre-oxidized felt and organic aerogel composite material, Figure 2 is the macroscopic morphology of the carbon fiber / carbon aerogel thermal insulation composite material formed after carbonization, Figure 3The microscopic morphology of the carbon fiber / carbon aerogel composite material prepared by the method described in Example 1, Figure 4 The microscopic morphology of the carbon fiber / carbon aerogel composite material prepared by the method described in Example 2, Figure 5 The microscopic morphology of the carbon fiber / carbon aerogel composite material prepared by the method described in Example 2, Figure 6 The microscopic morphology of the aerogel matrix in the carbon fiber / carbon aerogel, Figure 7 The thermal conductivity of the aerogel described in the example. Detailed implementation manners

[0009] In order to make the objectives and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. Embodiment

[0010] The preparation method of the carbon fiber-reinforced carbon aerogel thermal insulation composite material of the present invention specifically comprises the following steps: S1. Using an electric resistance furnace or a blast drying oven, pre-oxidize a commercial polyacrylonitrile needle-punched felt reinforcement at 235°C for 10 h with a heating rate of 1°C / min to obtain a pre-oxidized felt reinforcement; S2. Using phenolic resin (P) as the raw material of the organic sol, hexamethylenetetramine (H) as the cross-linking curing agent, and n-propanol as the solvent (S), mix them evenly to form an organic sol. Among them, the weight ratio of phenolic resin to hexamethylenetetramine is P:H = 3:1, and the weight ratio of phenolic resin to n-propanol is P:S = 1:9; S3. Place the pre-oxidized fiber felt blank in a stainless steel mold, then pour in the organic sol to make the sol completely cover the pre-oxidized felt, and under the condition of vacuum negative pressure, make the organic sol fully penetrate the pre-oxidized felt reinforcement; S4. Seal the stainless steel mold impregnated with the pre-oxidized felt, and carry out curing and aging at 80°C for 80 h to obtain a pre-oxidized felt-reinforced organic wet gel; S5. Place the wet gel at room temperature for 24 h, and then dry it in a blast drying oven at 60°C for 72 h to obtain a pre-oxidized felt-reinforced organic aerogel; S6. Use a vacuum carbonization furnace to carbonize the pre-oxidized felt-reinforced organic aerogel at 1000°C for 3 h with a heating rate of 5°C / min to obtain a carbon fiber-reinforced carbon aerogel composite material. Embodiment

[0011] The preparation method of the carbon fiber-reinforced carbon aerogel thermal insulation composite material of the present invention specifically comprises the following steps: S1. Using an electric resistance furnace or a blast drying oven, pre-oxidize a commercial polyacrylonitrile needle-punched felt reinforcement at 215°C for 10 h with a heating rate of 1°C / min to obtain a pre-oxidized felt reinforcement; S2. Using phenolic resin (P) as the raw material of the organic sol, hexamethylenetetramine (H) as the crosslinking curing agent, and n-propanol as the solvent (S), mix them evenly to form an organic sol. Among them, the weight ratio of phenolic resin to hexamethylenetetramine is P∶H = 4∶1, and the weight ratio of phenolic resin to n-propanol is P∶S = 1∶8; S3. Place the pre-oxidized fiber felt blank in a stainless steel mold, then pour in the organic sol to completely submerge the pre-oxidized felt, and under the condition of vacuum negative pressure, make the organic sol fully penetrate the pre-oxidized felt reinforcement; S4. Seal the stainless steel mold impregnated with the pre-oxidized felt, and carry out curing and aging at 80 °C for 80 h to obtain an organic wet gel reinforced with the pre-oxidized felt; S5. Place the wet gel at room temperature for 24 h, and then dry it in a forced-air drying oven at 60 °C for 72 h to obtain an organic aerogel reinforced with the pre-oxidized felt; S6. Carbonize the organic aerogel reinforced with the pre-oxidized felt in a vacuum carbonization furnace at 1000 °C for 3 h, and the heating rate is 5 °C / min to obtain a carbon fiber reinforced carbon aerogel composite material. Example

[0012] The preparation method of the carbon fiber reinforced carbon aerogel thermal insulation composite material of the present invention specifically comprises the following steps: S1. Use an electric resistance furnace or a forced-air drying oven to pre-oxidize a commercial polyacrylonitrile needle-punched felt reinforcement at 195 °C for 10 h, and the heating rate is 1 °C / min to obtain a pre-oxidized felt reinforcement; S2. Using phenolic resin (P) as the raw material of the organic sol, hexamethylenetetramine (H) as the crosslinking curing agent, and n-propanol as the solvent (S), mix them evenly to form an organic sol. Among them, the weight ratio of phenolic resin to hexamethylenetetramine is P∶H = 5∶1, and the weight ratio of phenolic resin to n-propanol is P∶S = 1∶7; S3. Place the pre-oxidized fiber felt blank in a stainless steel mold, then pour in the organic sol to completely submerge the pre-oxidized felt, and under the condition of vacuum negative pressure, make the organic sol fully penetrate the pre-oxidized felt reinforcement; S4. Seal the stainless steel mold impregnated with the pre-oxidized felt, and carry out curing and aging at 80 °C for 80 h to obtain an organic wet gel reinforced with the pre-oxidized felt; S5. Place the wet gel at room temperature for 24 h, and then dry it in a forced-air drying oven at 60 °C for 72 h to obtain an organic aerogel reinforced with the pre-oxidized felt; S6. Carbonize the organic aerogel reinforced with the pre-oxidized felt in a vacuum carbonization furnace at 1000 °C for 3 h, and the heating rate is 5 °C / min to obtain a carbon fiber reinforced carbon aerogel composite material.

[0013] Figure 1Figure 0 shows the macroscopic morphology of the pre-oxidized felt and organic aerogel composite material. There are no macroscopic defects in the sample after atmospheric drying. Figure 2 Figure 2 shows the macroscopic morphology of the carbon fiber / carbon aerogel thermal insulation composite material formed after carbonization. After carbonization, the fibers and the matrix shrink and match, and there are no defects such as macroscopic cracks. Figure 3 Figure 4 shows the microscopic morphology of the carbon fiber / carbon aerogel composite material prepared by the method described in Example 1. The shrinkage of the carbon fiber felt is less than that of the aerogel matrix, and there are some pores in the matrix. Figure 4 Figure 6 shows the microscopic morphology of the carbon fiber / carbon aerogel composite material prepared by the method described in Example 2. The shrinkage of the carbon fiber felt and the aerogel matrix is basically the same. Figure 5 Figure 8 shows the microscopic morphology of the carbon fiber / carbon aerogel composite material prepared by the method described in Example 2. The shrinkage of the carbon fiber felt and the aerogel matrix matches well. Figure 6 Figure 10 shows the microscopic morphology of the aerogel matrix in the carbon fiber / carbon aerogel. The pore diameter of the carbon aerogel gel network is 100 - 300 nm. Figure 7 Figure 12 shows the thermal conductivity of the aerogel described in the examples. The thermal conductivities of Example 1, Example 2, and Example 3 are 0.119, 0.102, and 0.093 W / mK, respectively.

[0014] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a carbon fiber reinforced carbon aerogel thermal insulation composite material, characterized in that, The steps are as follows: Step (1): Pre-oxidize the commercial polyacrylonitrile (PAN) needle-punched felt reinforcement at 195 - 255 °C to obtain pre-oxidized felt reinforcements with different degrees of pre-oxidation; Step (2): Use phenolic resin (P) as the raw material of the organic sol, hexamethylenetetramine (H) as the crosslinking curing agent, and n-propanol as the solvent (S). After mixing evenly, form an organic sol; Step (3): Place the pre-oxidized felt blank in a stainless-steel mold, then pour in the organic sol to completely submerge the pre-oxidized felt. Under the condition of vacuum negative pressure, make the organic sol fully penetrate the pre-oxidized felt reinforcement; Step (4): Seal the stainless-steel mold impregnated with the pre-oxidized felt, and carry out curing and aging at 80 °C for 40 - 80 h to obtain a pre-oxidized felt-reinforced organic wet gel; Step (5): Place the wet gel at room temperature for 24 h, and then dry it in a forced-air drying oven at 60 °C for 72 h to obtain a pre-oxidized felt-reinforced organic aerogel; Step (6): Carbonize the pre-oxidized felt-reinforced organic aerogel in a vacuum carbonization furnace at 850 - 1100 °C for 3 h, and the heating rate is 3 - 5 °C / min to obtain a carbon fiber-reinforced carbon aerogel composite material.

2. The preparation method of the carbon fiber reinforced carbon aerogel thermal insulation composite material according to claim 1, characterized in that, The pre-oxidation heating rate of the polyacrylonitrile needle-punched felt is 1 °C / min, the pre-oxidation temperature is 195 - 255 °C, and the pre-oxidation holding time is 10 h.

3. The preparation method of the carbon fiber reinforced carbon aerogel thermal insulation composite material according to claim 1, characterized in that, In the said step (2), the ratio range of P∶H is 3∶1 - 5∶1, and the ratio range of P∶S is 1∶5 - 1∶9.

4. The preparation method of the carbon fiber reinforced carbon aerogel thermal insulation composite material according to claim 1, characterized in that In the said step (4), the curing temperature of the phenolic resin sol is lower than the boiling point of the used solvent n-propanol to prevent excessive pressure in the stainless-steel sealed container.

5. The preparation method of the carbon fiber reinforced carbon aerogel thermal insulation composite material according to claim 1, characterized in that, In the said step (5), the wet gel is placed at room temperature for 24 h to prevent the gel from cracking; drying at 60 °C in a forced-air drying oven for 72 h is carried out under normal pressure.

6. The preparation method of the carbon fiber reinforced carbon aerogel thermal insulation composite material according to claim 1, characterized in that, In the said step (6), the carbonization heating rate is 3 - 5 °C / min, the carbonization temperature is 850 - 1100 °C, and the carbonization time is 3 h.

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