High-strength ablation-resistant nanoporous organic silicon aerogel composite material, preparation method and application thereof

Abstract

This invention relates to a high-strength, ablation-resistant nanoporous silicone aerogel composite material, its preparation method, and its applications. The composite material uses silicone aerogel as the matrix and a fiber preform as the reinforcement; the raw materials for the silicone aerogel include silane monomers and hydroxyl silicone oil. The preparation method is an RTM molding process, in which the fiber preform is pre-placed in a mold, then the precursor solution is injected into the mold, followed by mold closing and curing. This composite material is applied in the field of high-temperature thermal insulation. Compared with existing technologies, this invention does not require solvent washing or secondary modification; it can be obtained simply by drying at room temperature and pressure. The prepared composite material is lightweight, has low thermal conductivity, is hydrophobic, and does not shed powder. Its excellent mechanical strength and high-temperature oxidation resistance make the widespread application of silicone aerogel in the field of high-temperature thermal insulation possible.

Description

Technical Field

[0001] This invention relates to the field of heat insulation materials, specifically to a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material, its preparation method, and its application. Background Technology

[0002] With the rapid development of aerospace vehicles, the flight airspace and speed range of new aircraft are constantly expanding. Traditional thermal insulation materials are increasingly unable to meet the thermal protection requirements of aircraft under different flight conditions. There is a huge potential demand for new thermal insulation materials that combine lightweight, high efficiency, high temperature resistance, oxidation resistance, and wave transmission properties. Silica itself, as an inorganic material with low dielectric constant, low thermal conductivity, high temperature resistance, and oxidation resistance, can be used to prepare silica aerogel composite materials with a three-dimensional nanoporous structure, achieving both lightweight and high-efficiency thermal insulation. It shows great potential in replacing traditional thermal insulation materials. However, its complicated preparation process, high production cost, low strength, fragility, easy powdering, and hygroscopicity are also factors that hinder its widespread application.

[0003] For example, Chinese patent CN 109607551B discloses a method for preparing silica aerogel composite materials by impregnating radiation-resistant fibers with silica sol. The prepared material has a wave transmittance of ≥90% and can withstand high temperatures up to 1100℃. However, due to the low strength and hygroscopic nature of silica aerogel, solvent replacement is required before drying, relying on costly supercritical drying. In addition, hydrophobic modification treatment is also necessary. Similarly, Chinese patents CN 113563049B, CN 113336482B, CN112592149B, and CN 110787745B also have similar problems. After preparing the wet gel, solvent replacement is required first, followed by hydrophobic modification or reinforcement using various silanes or silicone oils. This preparation method not only increases costs and prolongs the preparation cycle, but also easily pollutes the environment due to the large amount of solvent removed, and it does not fundamentally solve the problem of low strength of silica aerogel.

[0004] In addition, some researchers have attempted to use organosilanes to prepare flexible organosilicon aerogel composites to circumvent the problems of low strength, easy powdering, and easy moisture absorption of silica aerogel composites. For example, Chinese patent CN 112876205B discloses an ablation-resistant and powder-resistant aerogel-based composite material and its preparation method. This method directly uses a gel formed by the hydrolysis and polymerization of organic silanes as the matrix and flexible fiber felt as the reinforcement to prepare a flexible organosilicon aerogel composite material. Then, a ceramicizable precursor layer is added to the surface of the composite material through secondary impregnation to achieve the purpose of ablation resistance. Since water is used as a solvent and urea as a catalyst in the gel preparation, the wet gel still needs to be washed and replaced with organic solvent before drying. In addition, the pore size of the obtained aerogel is relatively large, which will reduce its thermal insulation performance. Summary of the Invention

[0005] The purpose of this invention is to overcome at least one of the defects of the prior art by providing a high-strength, ablation-resistant nanoporous organosilicone aerogel composite material, its preparation method, and its applications, which can be obtained simply by drying at room temperature and pressure without solvent washing or secondary modification. The prepared composite material is lightweight, has low thermal conductivity, is hydrophobic, and does not shed powder. Its excellent mechanical strength and high-temperature oxidation resistance make the widespread application of silica aerogel in high-temperature thermal insulation fields possible.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material is provided, wherein the composite material uses organosilicon aerogel as the matrix and fiber preform as the reinforcement; the raw materials of organosilicon aerogel include silane monomers and hydroxyl silicone oil.

[0008] Furthermore, the silane monomer is selected from at least one of difunctional and trifunctional silanes; the molecular weight of the hydroxyl silicone oil is between 1,000 and 15,000, its main chain is a straight-chain Si-O-Si structure, the side groups are hydrophobic methyl, vinyl, phenyl or active group Si-OH, and the hydroxyl content is 3-25%.

[0009] Furthermore, the difunctional silanes include dimethyldimethoxysilane, diphenyldimethoxysilane, methylphenyldimethoxysilane, methylvinyldimethoxysilane; dimethyldiethoxysilane, diphenyldiethoxysilane, methylphenyldiethoxysilane, methylvinyldiethoxysilane;

[0010] The trifunctional silanes include methyltrimethoxysilane, vinyltrimethoxysilane, or phenyltrimethoxysilane; methyltrimethethoxysilane, vinyltriethoxysilane, or phenyltriethoxysilane.

[0011] Furthermore, the fiber preform is woven from one or more of organic or inorganic fibers, with a density of 0.1-0.5 g / cm³. 3 Organic fibers include polyacrylonitrile pre-oxidized fibers, viscose-based fibers, biomass fibers, or phenolic fibers; inorganic fibers include quartz fibers, glass fibers, or alumina fibers.

[0012] A method for preparing a high-strength, ablation-resistant nanoporous silicone aerogel composite material as described above, wherein the method is an RTM molding process, in which a fiber preform is placed in a mold, a precursor solution is injected into the mold, and then the mold is closed and cured.

[0013] Furthermore, the method includes the following steps:

[0014] Preparation of organosilicon sol: Dissolve silane monomer and acetic acid solution in alcohol solvent, stir until silane is completely hydrolyzed, add hydroxyl silicone oil and continue stirring, then add alkaline catalyst and mix and stir to obtain organosilicon sol;

[0015] Injection: Place the fiber preform in the mold and apply silicone sol. After the sol has completely impregnated the fiber reinforcement, seal the mold.

[0016] Gel-aging: After the mold is transferred to a heated environment for gel aging, a wet gel composite material is obtained;

[0017] Drying: After drying the wet gel composite material, a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material is obtained.

[0018] The prepared composite material has a density of 0.3-0.8 g / cm³. 3 The average pore size is 40-200 nm, the tensile strength is 5-25 MPa, the compressive strength is 60-200 MPa, and the thermal conductivity is 0.03-0.06 W / m·K.

[0019] The drying process can be carried out by naturally drying the wet gel composite material at room temperature for 1-7 days, or by rapidly gradient drying in a 50-120℃ forced-air drying oven. That is, room temperature and normal pressure drying is preferred in the initial stage of drying, and the temperature of 90-120℃ can be used to enhance drying in the later stage.

[0020] During injection, the liquid is injected into the mold by means of gravity, vacuuming or pressurization. Depending on the density of the fiber reinforcement and the viscosity of the organosilicon sol, the negative pressure of vacuum-assisted injection is 0-1 bar, and the pressure of pressurized injection is 1-3 bar.

[0021] Furthermore, in the organosilicon sol, the mass ratio of silane monomer to hydroxyl silicone oil is (15-50):(50-85), preferably (1-4):18.5, and the mass fraction of solute is 20-60%, preferably 30-50%.

[0022] The molar amount of water in the acetic acid solution is 0.8-1.5 times the molar amount of alkoxy groups in the silane monomer, and the amount of alkaline catalyst is 0.001-0.03 times the total mass of the organosilicon sol, preferably 0.01-0.02 times.

[0023] Furthermore, the alcohol solvent is selected from at least one of methanol, ethanol, ethylene glycol, isopropanol, or benzyl alcohol; the alkaline catalyst is tetramethylammonium hydroxide or ammonia.

[0024] The acetic acid solution is an aqueous solution of acetic acid with a molar concentration of 1-10 mmol / L, and the alkaline catalyst is tetramethylammonium hydroxide with a mass fraction of 25%.

[0025] Furthermore, the stirring time for complete hydrolysis of the silane is 30-60 minutes, and the stirring time can be adjusted according to the amount of acetic acid solution added. Stirring continues for 5-10 minutes, and the mixing time is also 5-10 minutes. The heating temperature is 60-100℃, and the aging time is 6-72 hours. The gelation temperature and aging time can slightly adjust the microstructure and overall mechanical strength of the aerogel.

[0026] An application of a high-strength, ablation-resistant nanoporous silicone aerogel composite material as described above, which is used in the field of high-temperature thermal insulation.

[0027] Compared with the prior art, the present invention has the following advantages:

[0028] (1) In the preparation of aerogels, this invention uses alcohols with low boiling points and low surface tension as solvents, which reduces the capillary effect of the solvent in the pores of the wet gel during the drying stage. The aerogel composite can be dried directly at room temperature and pressure and still maintain good morphology. This effectively avoids the complex methods required for the preparation of traditional silica aerogels, such as solvent replacement or even supercritical drying.

[0029] (2) This invention introduces two active materials, small-molecule silane and long-chain macromolecular silicone oil, as silicon sources into the aerogel matrix. By controlling the phase separation mode of the sol-gel process, it promotes the formation of a stronger nanoscale three-dimensional network microstructure, rather than the particle stacking structure of traditional silicone aerogels. The prepared aerogel has strength and rigidity that traditional silicone aerogels do not possess, changing the current situation of low strength, easy powdering, and poor molding of silicone aerogels. With the reinforcement of the fiber preform, the mechanical strength and molding effect of the aerogel composite material are further improved, and its practical performance far exceeds that of traditional silicone aerogel composite materials.

[0030] (3) Since the silicon source used in this invention has hydrophobic groups, no additional modification is required to achieve the hydrophobic purpose, reducing process cost and complexity. This invention can control the microstructure and high-temperature oxidation-decomposition characteristics of aerogel composite materials by changing the ratio of the two silicon sources and the type of organic groups, thereby obtaining the thermal protection scheme that best suits specific working conditions. Attached Figure Description

[0031] Figure 1 The tensile strength (left) and compressive strength (right) curves of the sample in Example 14 are shown.

[0032] Figure 2 The back temperature rise curve of the sample in Example 9 after heating with an 800°C quartz lamp for 800 seconds.

[0033] Figure 3 This is a scanning electron microscope image of the sample from Example 9.

[0034] Figure 4 This is a photograph of the water contact angle of the sample in Example 9. Detailed Implementation

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0036] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material, its preparation method at room temperature and pressure, and its application are disclosed. This composite material uses organosilicon aerogel as the matrix and a fiber preform as the reinforcement. It is prepared via an RTM molding process, in which the fiber preform is pre-placed into a designed mold, and then the matrix is ​​injected into the mold using gravity, vacuum, or pressurization. The molding process involves mold closing and curing. The specific steps include:

[0037] (1) Preparation of organosilicon sol: First, mix silane monomer and acetic acid solution in alcohol solvent, mix and stir at room temperature for 30-60 min, add hydroxyl silicone oil after the silane is completely hydrolyzed and continue stirring for 5-10 min, and finally add alkaline catalyst and mix and stir for 5-10 min to obtain organosilicon sol.

[0038] The alcohol solvent is selected from at least one of methanol, ethanol, or isopropanol. The mass fraction of the solute in the organosilicon sol is 30-50%, and the solute includes the following mass components: 15-50 parts of silane monomer and 50-85 parts of hydroxyl silicone oil. The silane monomer is selected from at least one of difunctional and trifunctional silanes; difunctional silanes include dimethyldimeth(eth)oxysilane, diphenyldimeth(eth)oxysilane, methylphenyldimeth(eth)oxysilane, and methylvinyldimeth(eth)oxysilane; trifunctional silanes include methyltrimeth(eth)oxysilane, vinyltrimeth(eth)oxysilane, or phenyltrimeth(eth)oxysilane. The hydroxyl silicone oil has a molecular weight between 1000 and 15000, its main chain is a straight-chain Si-O-Si structure, and its side groups are hydrophobic methyl, vinyl, phenyl, and active Si-OH groups, with a hydroxyl content of 3-25%. The acetic acid solution is an aqueous solution of acetic acid with a molar concentration of 1-10 mmol / L. The molar amount of water in the acetic acid solution is 0.8-1.5 times the molar amount of meth(eth)oxy groups in the silane monomer. The alkaline catalyst is 25% tetramethylammonium hydroxide, and the amount of alkaline catalyst is 0.01-0.02 times the total mass of the organosilicon sol. The stirring time for silane hydrolysis can be adjusted according to the amount of acetic acid solution added.

[0039] (2) Injection: Place the fiber preform in a mold and inject the prepared silicone sol from step (1). After the sol completely impregnates the fiber reinforcement, seal the mold. The fiber preform is made of one or more of organic or inorganic fibers. Organic fibers include polyacrylonitrile pre-oxidized fibers, viscose-based fibers, biomass fibers, and phenolic fibers. Inorganic fibers include quartz fibers, glass fibers, and alumina fibers. The fiber density is 0.1-0.5 g / cm³. 3 Depending on the density of the fiber reinforcement and the viscosity of the silicone sol, the vacuum-assisted injection pressure is 0-1 bar, and the pressure-assisted injection pressure is 1-3 bar.

[0040] (3) Gel-aging: The mold is transferred to an environment of 60-100℃ for gel aging for 6-72 hours to obtain a wet gel composite material. The gel temperature and gel aging time can slightly adjust the microstructure and overall mechanical strength of the aerogel.

[0041] (4) Drying: The wet gel composite material obtained in step (3) is naturally dried at room temperature for 1-7 days to obtain a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material; it can also be rapidly gradient dried in a 50-120℃ forced-air drying oven. Room temperature and normal pressure drying is preferred in the initial stage, while 90-120℃ can be used to enhance drying in the later stage. The density of the prepared composite material is 0.3-0.8 g / cm³. 3 The average pore size is 40-200 nm, the tensile strength is 5-25 MPa, the compressive strength is 60-200 MPa, and the thermal conductivity is 0.03-0.06 W / m·K.

[0042] Example 1

[0043] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0044] (1) Preparation of organosilicon sol: First, dimethyldimethoxysilane and 5 mmol / L acetic acid solution are mixed in isopropanol solvent and stirred at room temperature for 40 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for another 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for another 10 min to obtain organosilicon sol. The mass ratio of dimethyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 2:0.6:18.5:8:0.36.

[0045] (2) Injection of adhesive: The adhesive with a density of 0.16 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0046] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0047] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0048] The density of the obtained organosilicon aerogel composite material is 0.43 g / cm³. 3 It has an average pore size of 41 nm, a tensile strength of 5.8 MPa, a compressive strength of 73 MPa, and a thermal conductivity of 0.035 W / m·K.

[0049] Example 2

[0050] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0051] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 2:0.4:18.5:8:0.36.

[0052] (2) Injection of adhesive: The adhesive with a density of 0.16 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0053] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0054] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0055] The density of the obtained organosilicon aerogel composite material is 0.44 g / cm³. 3 It has an average pore size of 45 nm, a tensile strength of 5.9 MPa, a compressive strength of 77 MPa, and a thermal conductivity of 0.036 W / m·K.

[0056] Example 3

[0057] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0058] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 3:0.6:18.5:7:0.36.

[0059] (2) Injection of adhesive: The adhesive with a density of 0.16 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0060] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0061] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0062] The density of the obtained organosilicon aerogel composite material is 0.44 g / cm³. 3 It has an average pore size of 67 nm, a tensile strength of 5.7 MPa, a compressive strength of 82 MPa, and a thermal conductivity of 0.038 W / m·K.

[0063] Example 4

[0064] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0065] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 4:0.8:18.5:6:0.36.

[0066] (2) Injection of adhesive: The adhesive with a density of 0.16 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0067] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0068] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0069] The density of the obtained organosilicon aerogel composite material is 0.44 g / cm³. 3 It has an average pore size of 96 nm, a tensile strength of 5.6 MPa, a compressive strength of 89 MPa, and a thermal conductivity of 0.039 W / m·K.

[0070] Example 5

[0071] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0072] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 5:0.9:18.5:5:0.36.

[0073] (2) Injection of adhesive: The adhesive with a density of 0.16 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0074] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0075] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0076] The density of the obtained organosilicon aerogel composite material is 0.45 g / cm³. 3 It has an average pore size of 191 nm, a tensile strength of 5.2 MPa, a compressive strength of 74 MPa, and a thermal conductivity of 0.048 W / m·K.

[0077] Example 6

[0078] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0079] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 4:0.8:18.5:6:0.18.

[0080] (2) Injection of adhesive: The adhesive with a density of 0.16 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0081] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0082] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0083] The density of the obtained organosilicon aerogel composite material is 0.44 g / cm³. 3 It has an average pore size of 122 nm, a tensile strength of 5.2 MPa, a compressive strength of 94 MPa, and a thermal conductivity of 0.046 W / m·K.

[0084] Example 7

[0085] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0086] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 4:0.8:18.5:6:0.5.

[0087] (2) Injection of adhesive: The adhesive with a density of 0.16 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0088] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0089] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0090] The density of the obtained organosilicon aerogel composite material is 0.44 g / cm³. 3 It has an average pore size of 57 nm, a tensile strength of 7.6 MPa, a compressive strength of 110 MPa, and a thermal conductivity of 0.037 W / m·K.

[0091] Example 8

[0092] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0093] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 4:0.8:18.5:6:0.5.

[0094] (2) Injection of adhesive: The adhesive with a density of 0.22 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0095] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0096] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0097] The density of the obtained organosilicon aerogel composite material is 0.50 g / cm³. 3 It has an average pore size of 63 nm, a tensile strength of 10.1 MPa, a compressive strength of 134 MPa, and a thermal conductivity of 0.041 W / m·K.

[0098] Example 9

[0099] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0100] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 4:0.8:18.5:6:0.5.

[0101] (2) Injection of adhesive: The adhesive with a density of 0.27 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0102] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0103] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0104] The density of the obtained organosilicon aerogel composite material is 0.53 g / cm³. 3 It has an average pore size of 61 nm, a tensile strength of 11.3 MPa, a compressive strength of 155 MPa, and a thermal conductivity of 0.044 W / m·K.

[0105] Figure 2 The back temperature rise curve of a 100mm×100mm×20mm sample heated by an 800℃ quartz lamp for 800s is shown. After 800s of quartz lamp heating, the back temperature of the sample does not exceed 100℃, and the overall weight loss is only 3.1%, demonstrating good thermal insulation and ablation resistance.

[0106] Figure 3 These are scanning electron microscope (SEM) images of the samples. The left image shows good compatibility between the matrix and reinforcement of the composite material, while the right image, enlarged, shows that the aerogel matrix has a uniform nanoporous structure.

[0107] Figure 4 The image shows the water contact angle of the sample, which is 129°.

[0108] Example 10

[0109] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0110] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 4:0.8:18.5:6:0.5.

[0111] (2) Injection of adhesive: The adhesive with a density of 0.40 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0112] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0113] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0114] The density of the obtained organosilicon aerogel composite material is 0.63 g / cm³. 3 It has an average pore size of 64 nm, a tensile strength of 17.6 MPa, a compressive strength of 182 MPa, and a thermal conductivity of 0.046 W / m·K.

[0115] Example 11

[0116] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0117] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 4:0.8:23.0:6:0.57.

[0118] (2) Injection of adhesive: The adhesive with a density of 0.16 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0119] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0120] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0121] The density of the obtained organosilicon aerogel composite material was 0.41 g / cm³. 3 It has an average pore size of 72 nm, a tensile strength of 6.1 MPa, a compressive strength of 127 MPa, and a thermal conductivity of 0.035 W / m·K.

[0122] Example 12

[0123] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0124] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 4:0.8:15.0:6:0.44.

[0125] (2) Injection of adhesive: The adhesive with a density of 0.16 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0126] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0127] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0128] The density of the obtained organosilicon aerogel composite material was 0.48 g / cm³. 3 It has an average pore size of 54 nm, a tensile strength of 11.7 MPa, a compressive strength of 102 MPa, and a thermal conductivity of 0.051 W / m·K.

[0129] Example 13

[0130] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0131] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 4:0.8:12.2:6:0.39.

[0132] (2) Injection of adhesive: The adhesive with a density of 0.16 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0133] (3) Gel-aging: The mold was transferred to an environment of 80°C and gel aged for 24 hours to obtain a wet gel composite material.

[0134] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0135] The density of the obtained organosilicon aerogel composite material is 0.54 g / cm³. 3 It has an average pore size of 48 nm, a tensile strength of 14.2 MPa, a compressive strength of 114 MPa, and a thermal conductivity of 0.052 W / m·K.

[0136] Example 14

[0137] A high-strength, ablation-resistant nanoporous organosilicon aerogel composite material and its preparation method are detailed below:

[0138] (1) Preparation of organosilicon sol: First, methylphenyldimethoxysilane and 5 mmol / L acetic acid solution are mixed and stirred in isopropanol solvent at room temperature for 50 min. After the silane is completely hydrolyzed, hydroxyl silicone oil is added and stirred for 10 min. Finally, 25% tetramethylammonium hydroxide solution is added and stirred for 10 min to obtain organosilicon sol. The mass ratio of methylphenyldimethoxysilane, acetic acid solution, isopropanol, hydroxyl silicone oil and tetramethylammonium hydroxide solution is 4:0.8:15:6:0.44.

[0139] (2) Injection of adhesive: The adhesive with a density of 0.4 g / cm³ is then injected. 3 The quartz fiber preform is placed in the mold and the silicone sol prepared in step (1) is injected. After the sol completely impregnates the fiber reinforcement, the mold is sealed.

[0140] (3) Gel-aging: The mold was transferred to an environment of 70°C and gel aged for 24 hours to obtain a wet gel composite material.

[0141] (4) Drying: The wet gel composite material obtained in step (3) is first dried naturally at room temperature for 3 days, and then placed in a 100℃ forced-air drying oven for enhanced drying for 5 hours.

[0142] The density of the obtained organosilicon aerogel composite material is 0.67 g / cm³. 3 The average pore size is 61 nm, the tensile strength is 21.8 MPa, and the compressive strength is 170 MPa. Figure 1 Thermal conductivity 0.054 W / m·K.

[0143] The basic physical parameters of the samples obtained from each embodiment are summarized in Table 1 below.

[0144] Table 1

[0145]

[0146]

[0147] The main difference between Examples 1 and 2 is that the silane monomer used in Example 1 is dimethyldimethoxysilane, while that used in Example 2 is methylphenyldimethoxysilane. The basic physical properties of the composite materials prepared by the two are not much different, but their high-temperature oxidation-cracking characteristics are different.

[0148] The main difference between Examples 2-5 lies in the different ratios of silane monomers and hydroxyl silicone oils, which leads to different nucleation-growth mechanisms during the gelation stage. With increasing silane ratio, the aerogel pore structure becomes larger, and the material's compressive strength increases. However, when the ratio of silane monomers to hydroxyl silicone oils reaches the level of Example 5, the mechanical properties of the aerogel rapidly decline, while the thermal conductivity increases dramatically.

[0149] The main difference between Examples 6 and 7 is that the amount of catalyst was adjusted based on Example 2. The amount of catalyst was used to control the gelation rate, which ultimately led to differences in gel structure and mechanical strength.

[0150] Between Examples 8 and 10, the main change is that the density of the fiber reinforcement was adjusted based on Example 7. As the density of the fiber reinforcement increases, the density, mechanical strength, and thermal conductivity of the composite all increase, but the back temperature of the quartz lamp heating material decreases.

[0151] Between Examples 11-13, the main change is that the solid content of the sol was adjusted based on Example 7. The increase in solid content helps to improve the tensile strength of the composite, but its thermal conductivity and the back temperature of the quartz lamp heating both increase. From the perspective of thermal insulation performance, the solid content should not be too high.

[0152] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material, characterized in that, The composite material uses silicone aerogel as the matrix and fiber preform as the reinforcement; the raw materials of silicone aerogel include silane monomers and hydroxyl silicone oil. The silane monomer is selected from at least one of difunctional and trifunctional silanes; the molecular weight of the hydroxyl silicone oil is between 1,000 and 15,000, its main chain is a straight-chain Si-O-Si structure, the side groups are hydrophobic methyl, vinyl, phenyl or active group Si-OH, and the hydroxyl content is 3-25%. The high-strength, ablation-resistant nanoporous organosilicon aerogel composite material is prepared by an RTM molding process, which involves pre-placing the fiber preform into a mold, injecting the precursor solution into the mold, and then closing the mold for curing. The method includes the following steps: Preparation of organosilicon sol: Dissolve silane monomer and acetic acid solution in alcohol solvent, stir until silane is completely hydrolyzed, add hydroxyl silicone oil and continue stirring, then add alkaline catalyst and mix and stir to obtain organosilicon sol; Injection: Place the fiber preform in the mold and apply silicone sol. After the sol has completely impregnated the fiber reinforcement, seal the mold. Gel-aging: After the mold is transferred to a heated environment for gel aging, a wet gel composite material is obtained; Drying: After drying the wet gel composite material, a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material is obtained. The drying process involves placing the wet gel composite material at room temperature for natural drying for 1-7 days. The alcohol solvent is selected from at least one of methanol, ethanol, ethylene glycol, isopropanol or benzyl alcohol; the alkaline catalyst is tetramethylammonium hydroxide or ammonia.

2. The method for preparing a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material according to claim 1, characterized in that, The difunctional silanes include dimethyldimethoxysilane, diphenyldimethoxysilane, methylphenyldimethoxysilane, methylvinyldimethoxysilane; dimethyldiethoxysilane, diphenyldiethoxysilane, methylphenyldiethoxysilane, methylvinyldiethoxysilane; The trifunctional silanes include methyltrimethoxysilane, vinyltrimethoxysilane, or phenyltrimethoxysilane; methyltrimethethoxysilane, vinyltriethoxysilane, or phenyltriethoxysilane.

3. The method for preparing a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material according to claim 1, characterized in that, The fiber preform is woven from one or more of organic or inorganic fibers, with a density of 0.1-0.5 g / cm³. 3 Organic fibers include polyacrylonitrile pre-oxidized fibers, viscose-based fibers, biomass fibers, or phenolic fibers; inorganic fibers include quartz fibers, glass fibers, or alumina fibers.

4. The method for preparing a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material according to claim 1, characterized in that, In organosilicon sol, the mass ratio of silane monomer to hydroxyl silicone oil is (15-50):(50-85), and the mass fraction of solute is 20-60%. The molar amount of water in the acetic acid solution is 0.8-1.5 times the molar amount of alkoxy groups in the silane monomer, and the amount of alkaline catalyst is 0.001-0.03 times the total mass of the organosilicon sol.

5. The method for preparing a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material according to claim 4, characterized in that, In organosilicon sol, the mass fraction of the solute is 30-50%.

6. The method for preparing a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material according to claim 4, characterized in that, The amount of alkaline catalyst used is 0.01-0.02 times the total mass of the organosilicon sol.

7. The method for preparing a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material according to claim 1, characterized in that, The stirring time for complete hydrolysis of silane is 30-60 min, the stirring time is 5-10 min, and the mixing time is 5-10 min; the heating temperature is 60-100℃, and the aging time is 6-72 h.

8. The application of a high-strength, ablation-resistant nanoporous organosilicon aerogel composite material prepared by the preparation method according to any one of claims 1-3, characterized in that, This composite material is used in high-temperature heat insulation applications.

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