Gradient structure ultra-light ablation-resistant composite material and preparation method thereof

Abstract

The invention discloses a preparation method of an ultra-light ablation-resistant composite material with a gradient structure, and belongs to the technical field of composite material preparation. In order to solve the technical problem that a traditional material is difficult to consider low density, heat insulation property and ablation resistance at the same time, vermiculite nanosheets and water-soluble phenolic resin are compounded in a solution state, a three-dimensional porous matrix is constructed by adopting directional freeze drying, the surface of the matrix is coated with a ceramic precursor, and then high-temperature cracking is performed to form a compact ceramic layer; and gradient transition from the internal porous structure to the outer ceramic layer is realized. The ablation-resistant composite material with the gradient structure, which is low in density, excellent in heat insulation performance, enhanced in ablation resistance and high in interface bonding strength, can be obtained.

Description

Technical Field

[0001] This invention provides a gradient structure ultralight ablation-resistant composite material and its preparation method, belonging to the field of composite material preparation technology. Background Technology

[0002] Single thermal insulation materials or ablation-resistant coatings are no longer sufficient to meet increasingly stringent thermal protection requirements. Traditional materials generally suffer from high density, difficulty in simultaneously achieving thermal insulation and ablation resistance, and weak adhesion between the coating and the substrate. While existing technologies have proposed solutions such as carbon-ceramic composites or ceramic coatings, achieving lightweight materials and integrated functionality remains a critical technical challenge in this field. Summary of the Invention

[0003] The purpose of this invention is to propose a gradient structure ultralightweight ablation-resistant composite material and its preparation method, so as to solve the technical problems of existing thermal protection materials such as high density, difficulty in achieving both thermal insulation and ablation resistance, weak bonding between coating and matrix, and easy peeling of structure. The invention achieves the technical effects of material lightweighting, simultaneous improvement of thermal insulation and ablation resistance, high interlayer bonding strength, and a combination of thermal stability and mechanical properties.

[0004] To achieve the above-mentioned technical objectives, the present invention adopts the following technical solution.

[0005] A method for preparing a gradient-structured, ultralight, ablation-resistant composite material includes the following steps: 1) Disperse sodium vermiculite in deionized water, add quaternary ammonium salt, ball mill at room temperature, centrifuge, wash with water, dry and grind, and then dissolve in deionized water to obtain vermiculite nanosheet dispersion. 2) The vermiculite nanosheet dispersion was uniformly mixed with the water-soluble phenolic resin solution, injected into a mold, and subjected to directional rapid freezing treatment with liquid nitrogen. Then, it was freeze-dried to remove the solvent, forming a phenolic resin / vermiculite composite material with a three-dimensional nanoporous structure. Then, it was heated to the curing temperature by programmed temperature rise to fully crosslink the phenolic resin and obtain the cured composite matrix. 3) The ceramic precursor solution is uniformly coated onto the surface of the cured composite matrix by brushing. The ceramic precursor is then subjected to high-temperature pyrolysis under an inert atmosphere to generate a dense ceramic layer in situ on the surface of the composite matrix. By controlling the number of brushings and the concentration of the ceramic precursor solution, a gradient structure ultra-lightweight ablation-resistant composite material is finally obtained.

[0006] Further, in step 1), the mass ratio of sodium vermiculite, quaternary ammonium salt, and deionized water is 1:(1~4):(4:10).

[0007] Further, in step 1), the quaternary ammonium salt is one of hexadecyltrimethylammonium bromide or hexadecyltrimethylammonium chloride.

[0008] Further, in step 1), the centrifugation rate is 7000~9000 r / min, the product is washed with water 4~5 times, dried in an oven at 40~60℃, and the grinding time is 0.25~4h.

[0009] Furthermore, in step 2), the mass ratio of solute in the vermiculite nanosheet dispersion to the water-soluble phenolic resin solution is 1:(1:5); the solid content of the water-soluble phenolic resin solution is 40%~90%.

[0010] Furthermore, in step 2), the freeze-drying temperature is -40℃ to -196℃, and the drying time is 24~48h; the programmed temperature rise curing conditions are 120℃ for 12h and 140℃ for 12h.

[0011] Furthermore, in step 3), the ceramic precursor solution is selected from one of the following: polycarbosilane precursor, polysilazane precursor, polysiloxane precursor, or polyboronsilazane precursor solution.

[0012] Furthermore, in step 3), the concentration of the ceramic precursor solution is 1% to 40%.

[0013] Furthermore, in step 3), the high-temperature pyrolysis heating rate is 1~5℃ / min, and the high-temperature pyrolysis temperature is 1200~1600℃.

[0014] A gradient-structured, ultralight, ablation-resistant composite material was prepared by the above-described method.

[0015] The present invention has achieved the following beneficial effects.

[0016] 1. This invention combines water-soluble phenolic resin with water-soluble vermiculite nanosheets in a solution state and constructs a three-dimensional porous network structure by freeze-drying, resulting in a matrix material with ultra-lightweight and good thermal insulation properties.

[0017] 2. The present invention involves brushing a ceramic precursor onto the surface of a porous composite matrix and then subjecting it to high-temperature pyrolysis to generate a dense ceramic layer in situ on the surface of the material, thereby significantly improving the material's resistance to airflow erosion and oxidation under high-temperature conditions.

[0018] 3. This invention achieves a continuous gradient change in composition and performance by gradually transitioning from an internal porous structure to a dense ceramic layer on the surface. The interlayer interface has high bonding strength, which helps to reduce the risk of structural delamination caused by thermal stress mismatch.

[0019] 4. This invention utilizes the ceramicization properties of vermiculite under high temperature conditions to create a synergistic effect between it and the carbon skeleton formed after the carbonization of phenolic resin, thereby further enhancing the thermal stability and mechanical properties of the matrix material. Attached Figure Description

[0020] Figure 1 This is a flowchart of the method for preparing the gradient structure ultralightweight ablation-resistant composite material of the present invention. Detailed Implementation

[0021] To make the various technical features, advantages, or effects of the present invention more apparent and understandable, detailed descriptions are provided below through embodiments.

[0022] Example 1.

[0023] 1) Disperse 5g of sodium vermiculite in deionized water, add 15g of quaternary ammonium salt, ball mill at room temperature, centrifuge at 8000r / min, wash with water 4 times, dry at 50℃ and grind for 3h, and then dissolve in 40g of deionized water to obtain vermiculite nanosheet dispersion.

[0024] 2) The vermiculite nanosheet dispersion was uniformly mixed with the water-soluble phenolic resin solution. The mass ratio of vermiculite to phenolic resin solute was 1:3, and the solid content of the water-soluble phenolic resin solution was 60%. The mixed solution was injected into a mold, and liquid nitrogen was poured into the bottom for directional rapid freezing treatment. Then, it was freeze-dried at -80℃ for 36 hours to remove the solvent, forming a phenolic resin / vermiculite composite material with a three-dimensional nanoporous structure. Then, it was heated to the curing temperature at 120℃ for 12 hours and at 140℃ for 12 hours to fully crosslink the phenolic resin, and the cured porous composite matrix was obtained.

[0025] 3) A 5% polycarbosilane precursor solution is uniformly coated multiple times onto the surface of the cured composite matrix until a film is formed on the surface. The ceramic precursor is then subjected to high-temperature pyrolysis under an inert atmosphere and heat-treated at 3℃ / min to 1500℃. A dense ceramic layer is generated in situ on the surface of the composite matrix to obtain a gradient structure ultra-lightweight ablation-resistant composite material.

[0026] Example 2.

[0027] 1) Disperse 5g of sodium vermiculite in deionized water, add 5g of quaternary ammonium salt, ball mill at room temperature, centrifuge at 7000r / min, wash with water 4 times, dry at 40℃ and grind for 0.25h, and then dissolve in 20g of deionized water to obtain vermiculite nanosheet dispersion.

[0028] 2) The vermiculite nanosheet dispersion and the water-soluble phenolic resin solution were uniformly mixed. The mass ratio of vermiculite to phenolic resin solute was 1:1, and the solid content of the water-soluble phenolic resin solution was 40%. The mixed solution was injected into a mold, and liquid nitrogen was poured into the bottom for directional rapid freezing treatment. Then, it was freeze-dried at -40℃ for 48 hours to remove the solvent, forming a phenolic resin / vermiculite composite material with a three-dimensional nanoporous structure. Then, it was heated to the curing temperature at 120℃ for 12 hours and at 140℃ for 12 hours to fully crosslink the phenolic resin, and the cured porous composite matrix was obtained.

[0029] 3) A 1% polycarbosilane precursor solution is uniformly coated multiple times onto the surface of the cured composite matrix until a film is formed on the surface. The ceramic precursor is then subjected to high-temperature pyrolysis under an inert atmosphere and heat-treated at 1℃ / min to 1200℃. A dense ceramic layer is generated in situ on the surface of the composite matrix to obtain a gradient structure ultra-lightweight ablation-resistant composite material.

[0030] Example 3.

[0031] 1) Disperse 5g of sodium vermiculite in deionized water, add 20g of quaternary ammonium salt, ball mill at room temperature, centrifuge at 9000r / min, wash with water 5 times, dry at 60℃ and grind for 4h, and then dissolve in 50g of deionized water to obtain vermiculite nanosheet dispersion.

[0032] 2) The vermiculite nanosheet dispersion and the water-soluble phenolic resin solution were uniformly mixed. The mass ratio of vermiculite to phenolic resin solute was 1:5, and the solid content of the water-soluble phenolic resin solution was 90%. The mixed solution was injected into a mold, and liquid nitrogen was poured into the bottom for directional rapid freezing treatment. Then, it was freeze-dried at -196℃ for 24 hours to remove the solvent, forming a phenolic resin / vermiculite composite material with a three-dimensional nanoporous structure. Then, it was heated to the curing temperature at 120℃ for 12 hours and at 140℃ for 12 hours to fully crosslink the phenolic resin, and the cured porous composite matrix was obtained.

[0033] 3) A 40% polycarbosilane precursor solution is uniformly coated multiple times onto the surface of the cured composite matrix until a film is formed on the surface. The ceramic precursor is then subjected to high-temperature pyrolysis under an inert atmosphere and heat-treated at 1600℃ with a temperature increase of 5℃ / min. A dense ceramic layer is generated in situ on the surface of the composite matrix to obtain a gradient structure ultra-lightweight ablation-resistant composite material.

[0034] Comparative Example 1.

[0035] 1) Pour the water-soluble phenolic resin solution into the mold, pour liquid nitrogen into the bottom for directional rapid freezing treatment, and then freeze-dry at -80℃ for 24h to remove the solvent, resulting in a porous phenolic resin material; then heat it at 120℃ for 12h and 140℃ for 12h to the curing temperature to fully crosslink the phenolic resin, thus obtaining a cured porous composite matrix.

[0036] 2) A 5% polycarbosilane precursor solution is uniformly coated multiple times onto the surface of the cured composite matrix until a film is formed on the surface. The ceramic precursor is then subjected to high-temperature pyrolysis under an inert atmosphere and heat-treated at 1500℃ with a temperature increase of 5℃ / min. A dense ceramic layer is generated in situ on the surface of the composite matrix to obtain a gradient structure ultra-lightweight ablation-resistant composite material.

[0037] The room temperature thermal conductivity of the composite material was tested according to GB / T 10295-2008 "Determination of Steady-State Thermal Resistance and Related Properties of Thermal Insulation Materials", and the ablation resistance of the composite material was tested according to GJB 323B-2018 "Test Method for Ablation of Ablation Materials". The test results of the products prepared in the examples and comparative examples are shown in Table 1.

[0038] Table 1 Performance test data of gradient structure ultralightweight ablation resistant composite material The data in Table 1 show that the gradient-structured ultralightweight ablation-resistant composite material prepared in the embodiments of the present invention is significantly superior to the comparative material in terms of density, thermal conductivity, and linear ablation rate. This is because, firstly, the thermal conductivity of the embodiments is all below 0.06 W / (m·K), significantly lower than that of ordinary carbonized or ceramic materials, indicating that the three-dimensional porous structure effectively reduces heat conduction; the thermal conductivity of the comparative material is slightly lower, but the overall structure lacks reinforcing components, resulting in an imbalance in performance. Secondly, the linear ablation rate of the embodiments is significantly lower than that of the comparative material, indicating that the material maintains a lower ablation rate under strong thermal flow erosion. This is because: the outer dense ceramic layer provides an effective anti-oxidation and anti-erosion barrier; the ceramicization ability of the internal vermiculite and the phenolic resin carbon skeleton form a synergistic structure, improving high-temperature stability; and the gradient structure alleviates thermal stress concentration, reducing peeling and structural damage. Finally, the comparative example only consisted of a porous phenolic resin material with a surface ceramic layer, lacking a gradient structure and vermiculite reinforcement, resulting in poor overall performance; while the example achieved a continuous gradient structure of "porous matrix - transition layer - dense ceramic layer", thereby achieving synergistic enhancement in terms of lightweighting, heat insulation, and ablation resistance.

[0039] Although the present invention has been disclosed above with reference to embodiments, it is not intended to limit the present invention. Appropriate modifications or equivalent substitutions made by those skilled in the art to the technical solutions of the present invention should be covered within the protection scope of the present invention, which is defined by the claims.

Claims

1. A method for preparing a gradient-structured ultra-lightweight ablation-resistant composite material, characterized in that, The method comprises the following steps: 1) dispersing sodium vermiculite in deionized water, adding a quaternary ammonium salt, performing normal-temperature ball milling, and then performing centrifugation, water washing, drying, and grinding to obtain a vermiculite nanosheet dispersion liquid dissolved in deionized water; 2) uniformly mixing the vermiculite nanosheet dispersion liquid and a water-soluble phenolic resin solution, injecting into a mold, performing directional rapid freezing treatment using liquid nitrogen, and then performing freeze drying to remove the solvent to form a phenolic resin / vermiculite composite material with a three-dimensional nano-porous structure; and heating to a curing temperature in a programmed heating manner to make the phenolic resin fully crosslink to obtain a cured composite matrix; 3) uniformly coating a ceramic precursor solution on the surface of the cured composite matrix by brushing, performing high-temperature pyrolysis of the ceramic precursor in an inert atmosphere to generate a dense ceramic layer in situ on the surface of the composite matrix; and finally obtaining a gradient-structure super-lightweight ablation-resistant composite material by controlling the number of brushing times and the concentration of the ceramic precursor solution.

2. The method of claim 1, wherein, In step 1), the mass ratio of sodium vermiculite, quaternary ammonium salt, and deionized water is 1:(1-4):(4-10).

3. The method of claim 1 or 2, wherein, In step 1), the quaternary ammonium salt is one of cetyltrimethylammonium bromide and cetyltrimethylammonium chloride.

4. The method of claim 1, wherein, In step 1), the centrifugal rate is 7000-9000 r / min, the water washing is performed 4-5 times, the drying is performed in a 40-60℃ oven, and the grinding time is 0.25-4 h.

5. The method of claim 1, wherein, In step 2), the solute mass ratio of the vermiculite nanosheet dispersion liquid and the water-soluble phenolic resin solution is 1:(1:5), and the solid content of the water-soluble phenolic resin solution is 40%-90%.

6. The method of claim 1, wherein, In step 2), the freeze drying temperature is-40℃ to-196℃, and the drying time is 24-48 h; and the programmed heating curing conditions are 120℃ for 12 h and 140℃ for 12 h.

7. The method of claim 1, wherein, In step 3), the ceramic precursor solution is one of polycarbosilane precursor solution, polysilazane precursor solution, polysiloxane precursor solution, and polyborosilazane precursor solution.

8. The method of claim 1 or 7, wherein, In step 3), the concentration of the ceramic precursor solution is 1%-40%.

9. The method of claim 1, wherein, In step 3), the high-temperature pyrolysis heating rate is 1-5℃ / min, and the high-temperature pyrolysis temperature is 1200-1600℃.

10. A gradient structured ultra-lightweight ablative-resistant composite material, characterized in that, Prepared by the preparation method in any one of claims 1-9.

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