High-strength environment-friendly metal oxide aerogel and preparation method thereof

Abstract

The invention discloses a high-strength environment-friendly metal oxide aerogel and a preparation method thereof, and the preparation process comprises the following steps: hydrolyzing a precursor of a metal oxide in an ethanol aqueous solution to prepare a metal oxide sol; adding phenolic resin and a curing agent into the sol, and stirring until the phenolic resin and the curing agent are dissolved and uniformly mixed to obtain hybrid sol; adding a coagulant, uniformly stirring, transferring into a reaction kettle, and forming gel at a set temperature; sealing and aging the gel in a reaction kettle at a set temperature, and curing according to a set program; and drying the cured hybrid gel at normal pressure according to a set program, thereby obtaining the high-strength environment-friendly phenolic hybrid metal oxide aerogel. The invention further discloses the prepared metal oxide aerogel. The environment-friendly metal oxide aerogel has the performance characteristics of high strength and toughness, low heat conductivity and drying shrinkage rate, excellent heat insulation performance, high-temperature structural stability and the like.

Description

Technical Field

[0001] This invention belongs to the field of metal oxide aerogel materials, and particularly relates to a high-strength environmentally friendly metal oxide aerogel and its preparation method. Background Technology

[0002] Metal oxide aerogels possess excellent properties such as high specific surface area and porosity, extremely low density and thermal conductivity, and outstanding thermal and chemical stability, including Al₂O₃, ZrO₂, TiO₂, Y₂O₃ aerogels and their composite aerogels. Based on these performance advantages, metal oxide aerogels have enormous application prospects in fields such as construction, new energy, catalysis, and aerospace. In particular, compared with organic aerogels, carbon aerogels, and carbide aerogels, metal oxide aerogels have significant advantages in thermal conductivity (<0.05 W / m·K), thermal stability (>800℃), and chemical stability. Therefore, metal oxide aerogels are considered ideal candidate materials for high-temperature insulation and heat protection. However, the extremely high porosity and weak "pearl chain" structure lead to extremely low strength (<0.5 MPa) and high structural brittleness (<10%) in metal oxide aerogels.

[0003] Secondly, during solvent removal, the capillary tension between the solvent and the aerogel structure leads to significant shrinkage and structural damage. Atmospheric pressure drying cannot produce intact bulk aerogel materials; therefore, conventional aerogels must employ supercritical drying. However, supercritical drying equipment is expensive, complex to operate, hazardous, and space-constrained, limiting the large-scale and rapid preparation of oxide aerogels. Furthermore, metal oxide aerogels are difficult to use long-term at temperatures exceeding 800°C. At temperatures above 800°C, metal oxide aerogels undergo rapid sintering, resulting in a sharp decrease in porosity, volume shrinkage, and eventual structural collapse. Finally, metal oxide aerogels require extensive and prolonged dissolution exchange before drying, significantly extending the preparation cycle; moreover, the solvent poses an environmental threat. Therefore, extremely low strength, dependence on supercritical drying, high-temperature structural stability, and solvent exchange are key factors limiting the development and widespread application of oxide aerogel technology.

[0004] Phenolic resins are a class of high-performance thermosetting resins, including high thermal stability, flame retardancy, and insulation. In particular, the high thermal stability and low carbon residue of phenolic resins have made them one of the most important thermal protection materials in the aerospace field. Phenolic resins contain a large number of hydroxyl groups, which can form structural bonds with oxide aerogels. Furthermore, the hydrogen bonds and interpenetrating networks formed between phenolic resins and oxide aerogels greatly improve the interfacial bonding and overall structural strength of the oxide aerogel particles. Thus, the structural strength of the oxide aerogel is fundamentally and significantly enhanced. Simultaneously, the high structural strength can resist capillary tension during atmospheric pressure drying, thereby achieving atmospheric pressure drying and low shrinkage, and suppressing phase transformation and sintering of metal oxide aerogels at high temperatures. Summary of the Invention

[0005] To address the problems of low strength, dependence on supercritical drying, poor high-temperature structural stability, and environmental pollution caused by large amounts of solvents in existing metal oxide aerogels, this invention provides a high-strength, environmentally friendly metal oxide aerogel and its preparation method.

[0006] This invention discloses a method for preparing a high-strength, environmentally friendly metal oxide aerogel. First, a phenolic resin network is formed and aged at low temperature. Then, a phenolic resin network is formed at high temperature, forming an interpenetrating network, an organic-inorganic hybrid bond, and hydrogen bonds with the already formed metal oxide aerogel network. Furthermore, the phenolic resin network reduces the capillary tension between the aerogel and the solvent, thereby achieving solvent-free, atmospheric pressure drying and improved strength and toughness. Specifically, the method includes the following steps:

[0007] Step 1: Prepare metal oxide sol by hydrolyzing the precursor of the metal oxide in an aqueous ethanol solution.

[0008] Step 2: Add phenolic resin and curing agent to the above sol, and stir until the phenolic resin and curing agent are dissolved and uniformly mixed to obtain a hybrid sol.

[0009] Step 3: Add the coagulant, stir well, and transfer to the reactor to form a gel at the set temperature.

[0010] Step 4: The gel is sealed and aged in the reactor at a set temperature and then cured according to the set procedure.

[0011] Step 5: Dry the cured hybrid gel at normal pressure according to the set program to obtain a high-strength, environmentally friendly phenolic hybrid metal oxide aerogel.

[0012] Furthermore, in step 1, the metal oxide is any one or more of Al2O3, ZrO2, TiO2, Y2O3, and La2O3 in any proportion.

[0013] Furthermore, in step 1, the precursors of Al2O3 include aluminum trichloride hexahydrate, aluminum nitrate nonahydrate, aluminum isopropoxide, and aluminum sec-butoxide; the precursors of ZrO2 include zirconium oxychloride octahydrate and zirconium oxynitrate dihydrate; the precursors of TiO2 include titanium tetrachloride, tetrabutyl titanate, and tetraethyl titanate; the precursor of Y2O3 is yttrium trichloride hexahydrate; and the precursor of La2O3 is lanthanum trichloride hexahydrate.

[0014] Furthermore, in step 1, the molar ratio of the metal oxide precursor to ethanol to water is 1:(4-16):(8-24); the hydrolysis temperature is 40-75℃, and the hydrolysis time is 2-8 hours.

[0015] Furthermore, in step 2, the phenolic resin refers to one of thermoplastic phenolic resin, thermosetting phenolic resin, boron-modified phenolic resin, zirconium-modified phenolic resin, and silicon-modified phenolic resin; the phenolic resin is in the form of powder or ethanol solution (45-75%); the curing agent is hexamethylenetetramine; the amount of phenolic resin added is 10% to 30% of the total mass of the sol, the amount of curing agent added is 10% to 30% of the mass of the phenolic resin, and the amount of curing agent added is 5-20% of the mass of the phenolic resin.

[0016] Furthermore, in step 3, the coagulant is 1,2-epoxypropane, and its molar ratio with the metal oxide is (1-8):1, and the gelation temperature is 15-40℃.

[0017] Furthermore, in step 4, the aging temperature is 40-90℃, the aging time is 12-24 hours, and the curing process is 2-6 hours at 120-150℃ and 2-6 hours at 160-200℃.

[0018] Furthermore, in step 5, the equipment used for atmospheric pressure drying is a conventional oven, and the drying program is 12 hours at 40-60℃, 4-8 hours at 80-100℃, and 4-8 hours at 100-120℃.

[0019] The present invention provides a high-strength environmentally friendly metal oxide aerogel, which is prepared by the above-described method for preparing high-strength environmentally friendly metal oxide aerogel.

[0020] The beneficial technical effects of this invention are as follows:

[0021] 1. The metal oxide aerogel of the present invention fundamentally strengthens the overall structure of the metal oxide aerogel by forming an interpenetrating network, an organic-inorganic hybrid structure and hydrogen bonding between the phenolic resin and the metal oxide aerogel, and reduces the capillary tension between the aerogel and the solvent, thereby achieving preparation by atmospheric pressure drying, avoiding the use of expensive and dangerous supercritical drying, and reducing the preparation cost.

[0022] 2. The metal oxide aerogel prepared by this invention does not require solvent exchange, which greatly shortens the preparation cycle, reduces the preparation cost, and avoids environmental pollution caused by solvents.

[0023] 3. The metal oxide aerogel prepared by this invention has low drying shrinkage, intact macroscopic structure, no cracks, high compressive strength, and high toughness.

[0024] 4. The metal oxide aerogel prepared by this invention has good thermal insulation properties at both low and high temperatures and low thermal conductivity.

[0025] 5. The metal oxide aerogel prepared by this invention has self-flame retardancy, can withstand the impact of high-temperature flames, maintains structural integrity in flames, and does not drip or peel off.

[0026] 6. The phenolic resin in the metal oxide aerogel prepared by this invention inhibits the phase transformation and sintering of metal oxides at high temperatures, ensuring the structural stability of the metal oxide aerogel at high temperatures.

[0027] 7. The phenolic resin in the metal oxide aerogel prepared by this invention is carbonized at high temperature. The cracked carbon reduces the infrared transmittance of the metal oxide aerogel, thereby reducing its thermal conductivity at high temperature and ensuring its heat insulation effect at high temperature. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the preparation process of a high-strength, environmentally friendly metal oxide aerogel according to the present invention.

[0029] Figure 2 This is a schematic diagram of the chemical structure and reaction process of a high-strength, environmentally friendly metal oxide aerogel according to the present invention.

[0030] Figure 3 This is a macroscopic comparison diagram of samples from Examples 1 and 2.

[0031] Figure 4 This is a scanning electron microscope image of Example 2.

[0032] Figure 5 This is a pressure photograph of Example 4.

[0033] Figure 6 This is a stress-strain curve diagram of the compression test in Example 4.

[0034] Figure 7 This is a temperature curve of Example 5 on a 210°C hot plate.

[0035] Figure 8 This is a temperature curve of Example 6 under butane flame impact at 1350°C. Detailed Implementation

[0036] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0037] The preparation process of a high-strength, environmentally friendly metal oxide aerogel according to the present invention is as follows: Figure 1 As shown, the specific steps include:

[0038] Step 1: Prepare metal oxide sol by hydrolyzing the precursor of the metal oxide in an aqueous ethanol solution.

[0039] The metal oxides are any one or more of Al2O3, ZrO2, TiO2, Y2O3, and La2O3 in any proportion. The precursors of Al2O3 include aluminum trichloride hexahydrate, aluminum nitrate nonahydrate, aluminum isopropoxide, and aluminum sec-butoxide; the precursors of ZrO2 include zirconium oxychloride octahydrate and zirconium oxynitrate dihydrate; the precursors of TiO2 include titanium tetrachloride, tetrabutyl titanate, and tetraethyl titanate; the precursor of Y2O3 is yttrium trichloride hexahydrate; and the precursor of La2O3 is lanthanum trichloride hexahydrate.

[0040] The precursor of the metal oxide: the molar ratio of ethanol:water is 1:(4~16):(8~24); the hydrolysis temperature is 40~75℃, and the hydrolysis time is 2-8 hours.

[0041] Step 2: Add phenolic resin and curing agent to the above sol, and stir until the phenolic resin and curing agent are dissolved and uniformly mixed to obtain a hybrid sol.

[0042] Phenolic resin refers to one of the following: thermoplastic phenolic resin, thermosetting phenolic resin, boron-modified phenolic resin, zirconium-modified phenolic resin, and silicon-modified phenolic resin; the state of phenolic resin is powder or ethanol solution (45-75%); the curing agent is hexamethylenetetramine; the amount of phenolic resin added is 10% to 30% of the total mass of the sol, the amount of curing agent added is 10% to 30% of the mass of the phenolic resin, and the amount of curing agent added is 5-20% of the mass of the phenolic resin.

[0043] Step 3: Add the coagulant, stir well, and transfer to the reactor to form a gel at the set temperature.

[0044] The coagulant is 1,2-epoxypropane, and its molar ratio with the metal oxide is (1-8):1. The gelation temperature is 15-40℃.

[0045] Step 4: The gel is sealed and aged in the reactor at a set temperature and then cured according to the set procedure.

[0046] The aging temperature is 40-90℃, and the aging time is 12-24 hours; the curing process is 2-6 hours at 120-150℃ and 2-6 hours at 160-200℃.

[0047] Step 5: Dry the cured hybrid gel at normal pressure according to the set program to obtain a high-strength, environmentally friendly phenolic hybrid metal oxide aerogel.

[0048] The equipment used for atmospheric pressure drying is a conventional drying oven. The drying program is 12 hours at 40-60℃, 4-8 hours at 80-100℃, and 4-8 hours at 100-120℃.

[0049] The chemical structure and reaction process of a high-strength, environmentally friendly metal oxide aerogel of the present invention are as follows: Figure 2 As shown, the process first involves forming and aging at low temperatures, followed by the formation of a phenolic resin network at high temperatures. This network then forms an interpenetrating network, an organic-inorganic hybrid bond, and hydrogen bonds with the already formed metal oxide aerogel network. Furthermore, the phenolic resin network reduces the capillary tension between the aerogel and the solvent, thereby achieving solvent-free, atmospheric pressure drying and improved strength and toughness.

[0050] Example 1

[0051] Example 1 is a blank control example, showing the preparation of pure Al2O3 aerogel:

[0052] S1. Mix 14.4g aluminum trichloride hexahydrate, 13g deionized water and 33g ethanol evenly, and hydrolyze in a water bath at 60℃ for 4 hours to prepare Al2O3 sol.

[0053] S2, Blank control: No phenolic resin was added.

[0054] S3. Add 12g of 1,2-epoxypropane as a coagulant, stir well, and transfer to a reaction vessel. Gel at 25°C for 20 minutes.

[0055] S4. The gel is sealed and aged in a reactor at 60°C for 16 hours, then cured in an oven according to the procedure, kept at 150°C for 3 hours, kept at 180°C for 3 hours, and then cooled.

[0056] S5. Dry the gel at 60℃ for 12 hours, at 80℃ for 8 hours, and at 100℃ for 8 hours to obtain pure Al2O3 aerogel.

[0057] Example 2

[0058] Example 2 illustrates the preparation of phenolic resin-reinforced Al2O3 aerogel:

[0059] S1. Mix 14.4g aluminum trichloride hexahydrate, 13g deionized water and 33g ethanol evenly, and hydrolyze in a water bath at 60℃ for 4 hours to prepare Al2O3 sol.

[0060] S2. Dissolve 2g of hexamethylenetetramine in Al2O3 sol, then add 40g of 50% boron phenolic resin solution and stir until homogeneous to obtain a hybrid sol.

[0061] S3. Add 12g of 1,2-epoxypropane as a coagulant, stir well, and transfer to a reaction vessel. Gel at 25°C for 20 minutes.

[0062] S4. The gel is sealed and aged in a reactor at 60°C for 16 hours, then cured in an oven according to the procedure, kept at 150°C for 3 hours, kept at 180°C for 3 hours, and then cooled.

[0063] S5. Dry the gel at 60℃ for 12 hours, at 80℃ for 8 hours, and at 100℃ for 8 hours to obtain phenolic hybrid Al2O3 aerogel.

[0064] The prepared phenolic hybrid Al2O3 aerogel has a complete structure, no cracks, and high strength. Its appearance is similar to that of pure Al2O3 aerogel. Figure 3 As shown. Density is 0.25 g / cm³. 3 The thermal conductivity is 0.04 W / m·K, and the compressive strength is 7.8 MPa. Example 2: Scanning electron microscopy image of the phenolic hybrid Al₂O₃ aerogel structure is shown below. Figure 4 As shown, the phenolic hybrid Al2O3 aerogel contains a large number of macropores and mesopores, and has a cluster structure composed of lamellae and particles. Such a structure is crucial for improving the structural strength.

[0065] Example 3

[0066] Example 3 describes the preparation of phenolic resin-reinforced ZrO2 aerogel:

[0067] S1. Mix 19.3g zirconium oxychloride octahydrate, 10.8g deionized water and 33g ethanol evenly, and hydrolyze in a water bath at 60℃ for 4 hours to prepare ZrO2 sol.

[0068] S2. Add 1.5g of hexamethylenetetramine to the Al2O3 sol, dissolve it, then add 30g of 50% boron phenolic resin solution, stir evenly, and obtain the hybrid sol.

[0069] S3. Add 12g of 1,2-epoxypropane as a coagulant, stir well, and transfer to a reaction vessel. Gel at 20°C for 12 minutes.

[0070] S4. The gel was sealed and aged in a reactor at 65°C for 12 hours, and then cured in an oven at 140°C for 5 hours and 190°C for 2 hours according to the procedure, and then cooled.

[0071] S5. Dry the gel at 60℃ for 12 hours, 80℃ for 8 hours, and 100℃ for 8 hours to obtain phenolic hybrid ZrO2 aerogel.

[0072] The prepared phenolic hybrid ZrO2 aerogel has a complete structure, is free of cracks, has high strength, and a density of 0.30 g / cm³. 3 It has a thermal conductivity of 0.045 W / m·K and a compressive strength of 6.53 MPa.

[0073] Example 4

[0074] Example 4 illustrates the preparation of phenolic resin-reinforced Y2O3 aerogel:

[0075] S1. Mix 18.2g of yttrium trichloride hexahydrate, 15.1g of deionized water and 38.64g of ethanol evenly, and hydrolyze in a water bath at 65°C for 3 hours to prepare Y2O3 sol.

[0076] S2. Dissolve 2g of hexamethylenetetramine in Y2O3 sol, then add 150g of powdered linear phenolic resin and stir until homogeneous to obtain a hybrid sol.

[0077] S3. Add 14g of 1,2-epoxypropane as a coagulant, stir well, and transfer to a reaction vessel. Gel at 25°C for 20 minutes.

[0078] S4. The gel is sealed and aged in a reactor at 60°C for 16 hours, then cured in an oven at 160°C for 3 hours and 180°C for 3 hours, and then cooled.

[0079] S5. The gel is dried at 50°C for 12 hours, 70°C for 8 hours, and 120°C for 6 hours to obtain phenolic hybrid Y2O3 aerogel.

[0080] The prepared phenolic hybrid Y₂O₃ aerogel has a complete structure, is free of cracks, has high strength, and a density of 0.28 g / cm³. 3 It has a thermal conductivity of 0.05 W / m·K and a compressive strength of 5.52 MPa.

[0081] Pressure test of phenolic hybrid Y2O3 aerogel in Example 4 (equipment as follows) Figure 5 As shown), the stress-strain results of the compression test are as follows: Figure 6 As shown, the phenolic hybrid Y2O3 aerogel has extremely high pressure resistance, capable of withstanding pressures at least 3500 times its own weight.

[0082] Example 5

[0083] Example 5 illustrates the preparation of phenolic resin-reinforced Al2O3-Y2O3 aerogel:

[0084] S1. Mix 7.2g aluminum trichloride hexahydrate, 6.1g yttrium chloride hexahydrate, 13g deionized water and 33g ethanol evenly, and hydrolyze in a water bath at 60°C for 4 hours to prepare Al2O3 sol.

[0085] S2. Dissolve 2g of hexamethylenetetramine in Al2O3-Y2O3 colloid, then add 30g of 50% boron phenolic resin solution and stir until homogeneous to obtain a hybrid sol.

[0086] S3. Add 14g of 1,2-epoxypropane as a coagulant, stir well, and transfer to a reaction vessel. Gel at 25°C for 15 minutes.

[0087] S4. The gel is sealed and aged in a reactor at 60°C for 16 hours, then cured in an oven at 150°C for 3 hours and 180°C for 3 hours, and then cooled.

[0088] S5. The gel is dried at 60℃ for 12 hours, 80℃ for 8 hours, and 100℃ for 8 hours to obtain phenolic hybrid Al2O3-Y2O3 aerogel.

[0089] The prepared phenolic hybrid Al₂O₃-Y₂O₃ aerogel exhibited a complete structure, no cracks, and high strength. Its density was 0.32 g / cm³. 3 It has a thermal conductivity of 0.039 W / m·K and a compressive strength of 8.25 MPa.

[0090] The temperature curve of the phenolic hybrid Al2O3-Y2O3 aerogel in Example 5 on a 210℃ hot stage is shown below. Figure 7 As shown, the phenolic hybrid Al2O3-Y2O3 aerogel has excellent thermal insulation properties.

[0091] Example 6

[0092] Example 6 illustrates the preparation of phenolic resin-reinforced Al2O3-Y2O3-ZrO2 aerogel:

[0093] S1. Mix 4.8g aluminum trichloride hexahydrate, 6.1g yttrium chloride hexahydrate, 6.4g zirconium oxychloride octahydrate, 12g deionized water, and 28g ethanol evenly, and hydrolyze in a water bath at 65°C for 3 hours to prepare Al2O3-Y2O3-ZrO2 sol.

[0094] S2. Dissolve 2g of hexamethylenetetramine in Al2O3-Y2O3-ZrO2 sol, then add 25g of powdered boron phenolic resin and stir until homogeneous to obtain a hybrid sol.

[0095] S3. Add 12g of 1,2-epoxypropane as a coagulant, stir well, and transfer to a reaction vessel. Gel at 25°C for 15 minutes.

[0096] S4. The gel is sealed and aged in a reactor at 65°C for 12 hours, then cured in an oven at 160°C for 3 hours and 190°C for 3 hours, and then cooled.

[0097] S5. The gel is dried at 60℃ for 12 hours, 80℃ for 8 hours, and 100℃ for 8 hours to obtain phenolic hybrid Al2O3-Y2O3-ZrO2 aerogel.

[0098] The prepared phenolic hybrid Al₂O₃-Y₂O₃-ZrO₂ aerogel had a complete structure without cracks. Its density was 0.29 g / cm³. 3 It has a thermal conductivity of 0.042 W / m·K and a compressive strength of 8.12 MPa. It can insulate against the impact of a butane flame at 1350℃. The temperature curve is shown below. Figure 8 As shown.

[0099] In summary, the environmentally friendly metal oxide aerogel of this invention possesses high strength and toughness, low thermal conductivity and drying shrinkage, excellent thermal insulation properties, and high-temperature structural stability. This invention simultaneously solves the problems of strength, long preparation cycle, and high-temperature structural stability in metal oxide aerogels, playing a significant role in promoting the application and development of metal oxide aerogels in new energy, construction, and aerospace fields.

Claims

1. A method for preparing a high-strength, environmentally friendly metal oxide aerogel, characterized in that, First, the aerogel is formed and aged at low temperature. Then, a phenolic resin network is formed at high temperature, creating an interpenetrating network, organic-inorganic hybrid bonding, and hydrogen bonds with the existing metal oxide aerogel network. Furthermore, the phenolic resin network reduces the capillary tension between the aerogel and the solvent, thereby achieving solvent-free, atmospheric pressure drying and improved strength and toughness. Specifically, the process includes the following steps: Step 1: Prepare metal oxide sol by hydrolyzing the precursor of the metal oxide in an aqueous ethanol solution; Step 2: Add phenolic resin and curing agent to the above sol, and stir until the phenolic resin and curing agent are dissolved and uniformly mixed to obtain a hybrid sol; Step 3: Add the coagulant, stir well, and transfer to the reactor to form a gel at the set temperature; Step 4: The gel is sealed and aged in the reactor at a set temperature, and then cured according to the set procedure; Step 5: Dry the cured hybrid gel at normal pressure according to the set program to obtain a high-strength, environmentally friendly phenolic hybrid metal oxide aerogel.

2. The method for preparing a high-strength, environmentally friendly metal oxide aerogel according to claim 1, characterized in that, In step 1, the metal oxide is any one or more of Al2O3, ZrO2, TiO2, Y2O3, and La2O3 in any proportion.

3. The method for preparing a high-strength, environmentally friendly metal oxide aerogel according to claim 2, characterized in that, In step 1, the precursors of Al2O3 include aluminum trichloride hexahydrate, aluminum nitrate nonahydrate, aluminum isopropoxide, and aluminum sec-butoxide; the precursors of ZrO2 include zirconium oxychloride octahydrate and zirconium oxynitrate dihydrate; the precursors of TiO2 include titanium tetrachloride, tetrabutyl titanate, and tetraethyl titanate; the precursor of Y2O3 is yttrium trichloride hexahydrate; and the precursor of La2O3 is lanthanum trichloride hexahydrate.

4. The method for preparing a high-strength, environmentally friendly metal oxide aerogel according to claim 1, characterized in that, In step 1, the molar ratio of the metal oxide precursor to ethanol to water is 1:(4-16):(8-24); the hydrolysis temperature is 40-75℃, and the hydrolysis time is 2-8 hours.

5. The method for preparing a high-strength, environmentally friendly metal oxide aerogel according to claim 1, characterized in that, In step 2, the phenolic resin refers to one of thermoplastic phenolic resin, thermosetting phenolic resin, boron-modified phenolic resin, zirconium-modified phenolic resin, and silicon-modified phenolic resin; the phenolic resin is in the form of powder or ethanol solution; the curing agent is hexamethylenetetramine; the amount of phenolic resin added is 10% to 30% of the total mass of the sol, and the amount of curing agent added is 5% to 20% of the mass of the phenolic resin.

6. The method for preparing a high-strength, environmentally friendly metal oxide aerogel according to claim 1, characterized in that, In step 3, the coagulant is 1,2-epoxypropane, and its molar ratio with the metal oxide is (1-8):1, and the gelation temperature is 15-40℃.

7. The method for preparing a high-strength, environmentally friendly metal oxide aerogel according to claim 1, characterized in that, In step 4, the aging temperature is 40-90℃ and the aging time is 12-24 hours; the curing process is 2-6 hours at 120-150℃ and 2-6 hours at 160-200℃.

8. The method for preparing a high-strength, environmentally friendly metal oxide aerogel according to claim 1, characterized in that, In step 5, the equipment used for atmospheric pressure drying is a conventional drying oven, and the drying program is 12 hours at 40-60℃, 4-8 hours at 80-100℃, and 4-8 hours at 100-120℃.

9. A high-strength, environmentally friendly metal oxide aerogel, characterized in that, It is prepared by the preparation method of the high-strength environmentally friendly metal oxide aerogel according to any one of claims 1-8.

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