An aerogel modified dipping solution, its preparation method and the obtained modified aerogel

Abstract

The present invention provides an aerogel modified dipping solution, a preparation method thereof, and a prepared modified aerogel, belonging to the technical field of aerogels. A fiber felt coil is placed into a gel tank, and the aerogel modified dipping solution is added. After the liquid delivery of the solution is completed, the solution circulation device and the ultrasonic device are turned on to allow the solution to fully enter the interior of the fiber felt. After 10 - 20 minutes of circulation, the solution circulation device and the ultrasonic device are turned off, and the solution is waited to gel. The remaining solution in the recovery pipeline and the gel tank is recovered; the wet gel is aged at room temperature for 12 - 24 hours and then dried to obtain the modified aerogel. The aerogel modified dipping solution prepared by the present invention is transported to the gel tank containing the fiber felt coil. The prepared modified aerogel has low cost, good mechanical properties, low thermal conductivity, good heat insulation and heat preservation effects, light weight, and high hydrophobicity.

Description

Technical Field

[0001] The present invention relates to the technical field of aerogels, and particularly relates to an aerogel modified dipping solution, a preparation method thereof, and a prepared modified aerogel. Background Art

[0002] During the production process of aerogels, a large amount of glue solution will remain at the bottom of the reaction kettle and in the conveying pipeline, resulting in loss of raw materials. And cost often determines whether an enterprise can gain a foothold in the fierce competition in the aerogel market. Aerogel thermal insulation products can be applied to many industries such as aerospace, new energy vehicles, oil pipelines, and single crystal furnaces due to their excellent performance. From the current market applications, the usage of aerogels in these industries is very small, mainly due to their high prices. In order to enhance the influence of the enterprise in the industry and enable aerogels to be widely used in the industry.

[0003] Currently, during the production process of aerogel products, there are basically two methods for immersing glue into the substrate: natural immersion of sheet materials, and slow penetration of the sol into the substrate, that is, manual dipping, and only a small amount of single sheets can be dipped at a time. For the roll materials, they are immersed in the colloid, and then the colloid is circulated using a traditional circulating pump. These two methods lead to unstable product quality and a low yield rate.

[0004] Ceramic aerogels containing ceramic nanoparticles, nanofibers or nanosheets have become emerging thermal insulation materials due to their low density, ultra-low thermal conductivity, and high temperature resistance / fire resistance. US Patent US9828251B2 describes a sol-gel synthesis method of a high-performance silica aerogel with a thermal conductivity lower than . Chinese Patent Applications CN111848140A and CN112778017A respectively describe various preparation methods of thermal insulation ceramic aerogels using ceramic fibers or nanowires as building blocks. However, their practical applications are severely limited by their relatively poor mechanical properties. Summary of the Invention

[0005] The purpose of the present invention is to provide an aerogel modified dipping solution, a preparation method thereof, and a prepared modified aerogel. The prepared aerogel modified dipping solution is transported to a gel tank containing a fiber felt roll material, and the prepared modified aerogel has low cost, good mechanical properties, low thermal conductivity, good heat insulation and heat preservation effects, light weight, and high hydrophobicity.

[0006] The technical solution of the present invention is realized as follows:

[0007] The present invention provides a preparation method of an aerogel modified dipping solution, comprising the following steps:

[0008] (1)Preparation of LDH / GO composite material: Dissolve ferric nitrate, nickel nitrate, and magnesium nitrate in water to obtain a mixed metal solution; drop an alkali solution into the mixed metal solution, add graphene oxide, heat and stir for reaction, centrifuge, wash, and dry to obtain the LDH / GO composite material;

[0009] (2)Reduction: Reduce the LDH / GO composite material with hydrazine hydrate vapor to obtain the LDH / graphene composite material;

[0010] (3)Intercalation: Add the LDH / graphene composite material to water, add stearic acid and a surfactant, heat and stir for reaction, centrifuge, wash, and dry to obtain the intercalated LDH / graphene composite material;

[0011] (4)Modification: Add the intercalated LDH / graphene composite material to water, add dopamine hydrochloride and a catalyst, heat and stir for reaction, centrifuge, wash, and dry to obtain the modified intercalated LDH / graphene composite material;

[0012] (5)Preparation of the glue solution: Mix tetraethyl orthosilicate, ethanol, and water evenly, stir and react to obtain the glue solution;

[0013] (6)Preparation of the aerogel-modified dipping solution: Add the modified intercalated LDH / graphene composite material to the glue solution, stir and mix evenly, add a catalyst, and stir and mix evenly to obtain the aerogel-modified dipping solution.

[0014] As a further improvement of the present invention, in step (1), the molar ratio of ferric nitrate, nickel nitrate, and magnesium nitrate is 1:2:1, the alkali solution is a 2 - 3 mol / L NaOH or KOH solution, the alkali solution adjusts the pH value of the solution to 8 - 9, the addition amount of graphene oxide is 0.5 - 1 wt% of the total mass of the system, the temperature of the heating and stirring reaction is 90 - 95 °C, and the time is 4 - 6 h.

[0015] As a further improvement of the present invention, in step (2), the reduction time is 10 - 12 h.

[0016] As a further improvement of the present invention, in step (3), the mass ratio of the LDH / graphene composite material, stearic acid, and the surfactant is 100:3 - 4:1 - 2, the surfactant is selected from at least one of sodium dodecylbenzenesulfonate, sodium dodecyl sulfate, and sodium dodecyl sulfonate, the temperature of the heating and stirring reaction is 40 - 50 °C, and the time is 1 - 2 h.

[0017] As a further improvement of the present invention, the mass ratio of the intercalated LDH / graphene composite material, dopamine hydrochloride and the catalyst in step (4) is 10:1-2:0.1-0.2. The catalyst is a Tris-HCl solution with a pH value of 8.5-9.5. The temperature of the heating and stirring reaction is 45-55°C, and the time is 3-5 h.

[0018] As a further improvement of the present invention, the mass ratio of the alkyl orthosilicate, ethanol and water in step (5) is 1-1.2:3-5:0.4-0.7. The alkyl orthosilicate is methyl orthosilicate or ethyl orthosilicate. The stirring reaction time is 10-20 min.

[0019] As a further improvement of the present invention, the mass ratio of the glue solution, the modified intercalated LDH / graphene composite material and the catalyst in step (6) is 10:1-2:0.1-0.2. The catalyst is a 3-4 mol / L NaOH or KOH solution.

[0020] The present invention further protects an aerogel modified dipping solution prepared by the above preparation method.

[0021] The present invention further protects a preparation method of a modified aerogel, including the following steps:

[0022] Put the fiber felt coil into the gel tank, add the above aerogel modified dipping solution. After the glue solution is delivered, turn on the glue solution circulation device and the ultrasonic device to make the glue solution fully enter the fiber felt. After 10-20 min of circulation, turn off the glue solution circulation device and the ultrasonic device, wait for the glue solution to gel, and recover the remaining glue solution in the pipeline and the gel tank; age the wet gel at room temperature for 12-24 h, and perform a drying treatment to obtain the modified aerogel.

[0023] The present invention further protects a modified aerogel prepared by the above preparation method.

[0024] The present invention has the following beneficial effects:

[0025] The present invention prepares an aerogel modified dipping solution. By preparing the LDH / GO composite material, it has a unique layered structure and various advantageous properties (interlayer anion exchange ability, rich active sites, large surface area, adjustable layer board composition, low cost and simple preparation process). At the same time, the composite structure of LDH and GO greatly reduces the thermal conductivity of the aerogel and has a high-temperature heat insulation effect. At the same time, the graphene obtained after the reduction of graphene oxide further improves the hydrophobic performance and mechanical properties of the aerogel.

[0026] The LDH / graphene composite material after intercalation with stearic acid and surfactant greatly expands the layer spacing, thus improving the heat insulation performance. The two have a synergistic effect, and also improve the compatibility and dispersibility of the product, enhance the mechanical properties, and improve the corrosion resistance of the material.

[0027] After the prepared intercalated LDH / graphene composite material is further modified by polydopamine, it can react better with silica sol, so as to be stably fixed and adsorbed on the sol. And its basic property can further synergistically catalyze the reaction of silica sol in situ on the basis of alkali catalysts (NaOH or KOH), so as to better prepare an aerogel with uniform pore distribution, good mechanical properties, good hydrophobicity and better heat insulation and heat preservation effects.

[0028] In the preparation process of the modified aerogel of the present invention, ultrasonic-assisted dipping is adopted, which has the following advantages:

[0029] ① There is no need to distinguish between sheet materials and coil materials. The base material and the sol are mixed in the same container. Adding ultrasonic assistance can complete the impregnation in a short time, without restrictions on quantity, thickness, etc., and the quality is uniform; ② On the other hand, ultrasonic-assisted dipping catalyzes and accelerates the reaction rate from sol to gel, improving the overall production efficiency; ③ The ultrasonic-assisted device can be synchronously added to the modification equipment to catalyze the modification reaction.

[0030] The modified aerogel dipping solution prepared in the present invention is transported to a gel tank containing fiber felt coils. The prepared modified aerogel has low cost, good mechanical properties, low thermal conductivity, good heat insulation and heat preservation effects, light weight and high hydrophobicity. Specific Embodiments

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0032] Graphene oxide, with a content > 99%, 1 - 2 μm, a thickness of 1 - 1.5 nm, and 3 - 5 layers, was purchased from Zhongke Leiming (Beijing) Technology Co., Ltd. Example 1

[0033] This example provides a method for preparing a modified aerogel dipping solution, including the following steps:

[0034] (1)Preparation of LDH / GO composite material: 0.01 mol of iron nitrate, 0.02 mol of nickel nitrate, and 0.01 mol of magnesium nitrate were dissolved in 100 mL of water to obtain a mixed metal solution; 2 mol / L of NaOH solution was added dropwise to the mixed metal solution to adjust the pH value of the solution to 8, graphene oxide was added, and the addition amount was 0.5 wt% of the total mass of the system. The mixture was heated to 90 °C, stirred and reacted for 4 h, centrifuged, washed, and dried to obtain the LDH / GO composite material;

[0035] (2)Reduction: The LDH / GO composite material was reduced by hydrazine hydrate vapor for 10 h to obtain the LDH / graphene composite material;

[0036] (3)Intercalation: 10 g of the LDH / graphene composite material was added to 200 mL of water, 0.3 g of stearic acid and 0.1 g of sodium dodecylbenzenesulfonate were added, the mixture was heated to 40 °C, stirred and reacted for 1 h, centrifuged, washed, and dried to obtain the intercalated LDH / graphene composite material;

[0037] (4)Modification: 10 g of the intercalated LDH / graphene composite material was added to 200 mL of water, 1 g of dopamine hydrochloride and 0.1 g of catalyst were added, the mixture was heated to 45 °C, stirred and reacted for 3 h, centrifuged, washed, and dried to obtain the modified intercalated LDH / graphene composite material;

[0038] The catalyst was a Tris-HCl solution with a pH value of 8.5;

[0039] (5)Preparation of the glue solution: 10 g of methyl orthosilicate, 30 g of ethanol, and 4 g of water were mixed evenly and stirred and reacted for 10 min to obtain the glue solution;

[0040] (6)Preparation of the aerogel-modified dipping solution: 1 g of the modified intercalated LDH / graphene composite material was added to 10 g of the glue solution, stirred and mixed for 10 min, 0.1 g of catalyst was added, and stirred and mixed for 15 min to obtain the aerogel-modified dipping solution;

[0041] The catalyst was 3 mol / L of NaOH solution. Example 2

[0042] This example provides a method for preparing an aerogel-modified dipping solution, including the following steps:

[0043] (1)Preparation of LDH / GO composite material: 0.01 mol of iron nitrate, 0.02 mol of nickel nitrate, and 0.01 mol of magnesium nitrate were dissolved in 100 mL of water to obtain a mixed metal solution; 3 mol / L KOH solution was added dropwise to the mixed metal solution to adjust the pH value of the solution to 9, graphene oxide was added, and the addition amount was 1 wt% of the total mass of the system. The mixture was heated to 95 °C, stirred and reacted for 6 h, centrifuged, washed, and dried to obtain the LDH / GO composite material;

[0044] (2)Reduction: The LDH / GO composite material was reduced by hydrazine hydrate vapor for 12 h to obtain the LDH / graphene composite material;

[0045] (3)Intercalation: 10 g of the LDH / graphene composite material was added to 200 mL of water, 0.4 g of stearic acid and 0.2 g of sodium dodecyl sulfate were added, the mixture was heated to 50 °C, stirred and reacted for 2 h, centrifuged, washed, and dried to obtain the intercalated LDH / graphene composite material;

[0046] (4)Modification: 10 g of the intercalated LDH / graphene composite material was added to 200 mL of water, 2 g of dopamine hydrochloride and 0.2 g of catalyst were added, the mixture was heated to 55 °C, stirred and reacted for 5 h, centrifuged, washed, and dried to obtain the modified intercalated LDH / graphene composite material;

[0047] The catalyst was a Tris-HCl solution with a pH value of 9.5;

[0048] (5)Preparation of the glue solution: 12 g of tetraethyl orthosilicate, 50 g of ethanol, and 7 g of water were mixed evenly and stirred and reacted for 20 min to obtain the glue solution;

[0049] (6)Preparation of the aerogel-modified dipping solution: 2 g of the modified intercalated LDH / graphene composite material was added to 10 g of the glue solution, stirred and mixed for 10 min, 0.2 g of catalyst was added, and stirred and mixed for 15 min to obtain the aerogel-modified dipping solution;

[0050] The catalyst was a 4 mol / L NaOH or KOH solution. Example 3

[0051] This example provides a method for preparing an aerogel-modified dipping solution, including the following steps:

[0052] (1)Preparation of LDH / GO composite material: Dissolve 0.01 mol of iron nitrate, 0.02 mol of nickel nitrate, and 0.01 mol of magnesium nitrate in 100 mL of water to obtain a mixed metal solution; Drop 2.5 mol / L NaOH solution into the mixed metal solution, adjust the pH value of the solution to 8.5, add graphene oxide, and the addition amount is 0.7 wt% of the total mass of the system. Heat to 92 °C, stir and react for 5 h, centrifuge, wash, and dry to obtain the LDH / GO composite material;

[0053] (2)Reduction: Reduce the LDH / GO composite material with hydrazine hydrate vapor for 11 h to obtain the LDH / graphene composite material;

[0054] (3)Intercalation: Add 10 g of the LDH / graphene composite material to 200 mL of water, add 0.35 g of stearic acid and 0.15 g of sodium dodecyl sulfate, heat to 45 °C, stir and react for 1.5 h, centrifuge, wash, and dry to obtain the intercalated LDH / graphene composite material;

[0055] (4)Modification: Add 10 g of the intercalated LDH / graphene composite material to 200 mL of water, add 1.5 g of dopamine hydrochloride and 0.15 g of catalyst, heat to 50 °C, stir and react for 4 h, centrifuge, wash, and dry to obtain the modified intercalated LDH / graphene composite material;

[0056] The catalyst is a Tris-HCl solution with a pH value of 9;

[0057] (5)Preparation of the glue solution: Mix 11 g of tetraethyl orthosilicate, 40 g of ethanol, and 5 g of water evenly, stir and react for 15 min to obtain the glue solution;

[0058] (6)Preparation of the aerogel-modified dipping solution: Add 1.5 g of the modified intercalated LDH / graphene composite material to 10 g of the glue solution, stir and mix for 10 min, add 0.15 g of catalyst, and stir and mix for 15 min to obtain the aerogel-modified dipping solution;

[0059] The catalyst is a 3.5 mol / L KOH solution.

[0060] Comparative Example 1

[0061] Compared with Example 3, the difference is that graphene oxide was not added in step (1).

[0062] Specifically as follows:

[0063] (1)Preparation of LDH composite material: 0.01 mol of iron nitrate, 0.02 mol of nickel nitrate, and 0.01 mol of magnesium nitrate were dissolved in 100 mL of water to obtain a mixed metal solution; 2.5 mol / L of NaOH solution was added dropwise to the mixed metal solution, the pH value of the solution was adjusted to 8.5, heated to 92 °C, stirred and reacted for 5 h, centrifuged, washed, and dried to obtain the LDH composite material.

[0064] Comparative Example 2

[0065] Compared with Example 3, the difference is that step (3) was not carried out.

[0066] Specifically as follows:

[0067] (1)Preparation of LDH / GO composite material: 0.01 mol of iron nitrate, 0.02 mol of nickel nitrate, and 0.01 mol of magnesium nitrate were dissolved in 100 mL of water to obtain a mixed metal solution; 2.5 mol / L of NaOH solution was added dropwise to the mixed metal solution, the pH value of the solution was adjusted to 8.5, graphene oxide was added, and the addition amount was 0.7 wt% of the total mass of the system, heated to 92 °C, stirred and reacted for 5 h, centrifuged, washed, and dried to obtain the LDH / GO composite material;

[0068] (2)Reduction: The LDH / GO composite material was reduced by hydrazine hydrate vapor for 11 h to obtain the LDH / graphene composite material;

[0069] (3)Modification: 10 g of the LDH / graphene composite material was added to 200 mL of water, 1.5 g of dopamine hydrochloride and 0.15 g of catalyst were added, heated to 50 °C, stirred and reacted for 4 h, centrifuged, washed, and dried to obtain the modified LDH / graphene composite material;

[0070] The catalyst was a Tris-HCl solution with a pH value of 9;

[0071] (4)Preparation of glue solution: 11 g of tetraethyl orthosilicate, 40 g of ethanol, and 5 g of water were mixed evenly and stirred and reacted for 15 min to obtain the glue solution;

[0072] (5)Preparation of aerogel modified dipping solution: 1.5 g of the modified LDH / graphene composite material was added to 10 g of the glue solution, stirred and mixed for 10 min, 0.15 g of catalyst was added, and stirred and mixed for 15 min to obtain the aerogel modified dipping solution;

[0073] The catalyst was a 3.5 mol / L KOH solution.

[0074] Comparative Example 3

[0075] Compared with Example 3, the difference is that step (4) was not carried out.

[0076] The details are as follows:

[0077] (1) Preparation of LDH / GO composite material: Dissolve 0.01 mol of iron nitrate, 0.02 mol of nickel nitrate, and 0.01 mol of magnesium nitrate in 100 mL of water to obtain a mixed metal solution; Drop 2.5 mol / L of NaOH solution into the mixed metal solution, adjust the pH value of the solution to 8.5, add graphene oxide, and the addition amount is 0.7 wt% of the total mass of the system. Heat to 92 °C, stir and react for 5 h, centrifuge, wash, and dry to obtain the LDH / GO composite material;

[0078] (2) Reduction: Reduce the LDH / GO composite material with hydrazine hydrate vapor for 11 h to obtain the LDH / graphene composite material;

[0079] (3) Intercalation: Add 10 g of the LDH / graphene composite material to 200 mL of water, add 0.35 g of stearic acid and 0.15 g of sodium dodecyl sulfate, heat to 45 °C, stir and react for 1.5 h, centrifuge, wash, and dry to obtain the intercalated LDH / graphene composite material;

[0080] (4) Preparation of the glue solution: Mix 11 g of tetraethyl orthosilicate, 40 g of ethanol, and 5 g of water evenly, stir and react for 15 min to obtain the glue solution;

[0081] (5) Preparation of the aerogel-modified dipping solution: Add 1.5 g of the intercalated LDH / graphene composite material to 10 g of the glue solution, stir and mix for 10 min, add 0.15 g of the catalyst, and stir and mix for 15 min to obtain the aerogel-modified dipping solution;

[0082] The catalyst is 3.5 mol / L of KOH solution.

[0083] Comparative Example 4

[0084] Compared with Example 3, the difference is that the modified intercalated LDH / graphene composite material is not added in step (6).

[0085] The details are as follows:

[0086] (6) Preparation of the aerogel-modified dipping solution: Add 0.15 g of the catalyst to 10 g of the glue solution, stir and mix for 15 min to obtain the aerogel-modified dipping solution;

[0087] The catalyst is 3.5 mol / L of KOH solution. Example 4

[0088] This example provides a preparation method of a modified aerogel, including the following steps:

[0089] Put the fiber felt coil into the gel tank, add the aerogel-modified dipping solution prepared in Example 1. After the delivery of the dipping solution is completed, turn on the dipping solution circulation device and the ultrasonic device with an ultrasonic power of 1000 W to allow the dipping solution to fully enter the interior of the fiber felt. After 10 minutes of circulation, turn off the dipping solution circulation device and the ultrasonic device, wait for the dipping solution to gel, and recover the remaining dipping solution in the recovery pipeline and the gel tank; age the wet gel at room temperature for 12 h and perform a drying treatment to obtain the modified aerogel. Example 5

[0090] This example provides a preparation method for a modified aerogel, including the following steps:

[0091] Put the fiber felt coil into the gel tank, add the aerogel-modified dipping solution prepared in Example 2. After the delivery of the dipping solution is completed, turn on the dipping solution circulation device and the ultrasonic device with an ultrasonic power of 1000 W to allow the dipping solution to fully enter the interior of the fiber felt. After 20 minutes of circulation, turn off the dipping solution circulation device and the ultrasonic device, wait for the dipping solution to gel, and recover the remaining dipping solution in the recovery pipeline and the gel tank; age the wet gel at room temperature for 24 h and perform a drying treatment to obtain the modified aerogel. Example 6

[0092] This example provides a preparation method for a modified aerogel, including the following steps:

[0093] Put the fiber felt coil into the gel tank, add the aerogel-modified dipping solution prepared in Example 3. After the delivery of the dipping solution is completed, turn on the dipping solution circulation device and the ultrasonic device with an ultrasonic power of 1000 W to allow the dipping solution to fully enter the interior of the fiber felt. After 15 minutes of circulation, turn off the dipping solution circulation device and the ultrasonic device, wait for the dipping solution to gel, and recover the remaining dipping solution in the recovery pipeline and the gel tank; age the wet gel at room temperature for 18 h and perform a drying treatment to obtain the modified aerogel.

[0094] Comparative Example 5

[0095] Compared with Example 3, the difference is that the aerogel-modified dipping solution is prepared from Comparative Example 1.

[0096] Comparative Example 6

[0097] Compared with Example 3, the difference is that the aerogel-modified dipping solution is prepared from Comparative Example 2.

[0098] Comparative Example 7

[0099] Compared with Example 3, the difference is that the aerogel-modified dipping solution is prepared from Comparative Example 3.

[0100] Comparative Example 8

[0101] Compared with Example 3, the difference lies in that the aerogel-modified sizing solution is prepared from Comparative Example 4.

[0102] Comparative Example 9

[0103] Compared with Example 3, the difference lies in that ultrasonic treatment is not carried out.

[0104] Specifically, it includes the following steps:

[0105] Put the fiber felt coil into the gel tank, add the aerogel-modified sizing solution prepared in Example 3. After the sizing solution is delivered, turn on the sizing solution circulation device to make the sizing solution fully enter the fiber felt. After 15 minutes of circulation, turn off the sizing solution circulation device and wait for the sizing solution to gel. Recover the remaining sizing solution in the pipeline and the gel tank; age the wet gel at room temperature for 18 hours and perform drying treatment to obtain the modified aerogel.

[0106] Test Example 1

[0107] Perform performance tests on the modified aerogels prepared in Examples 4-6 and Comparative Examples 5-9 of the present invention, and the results are shown in Table 1.

[0108] Calculate the density of the aerogel by measuring the volume and mass of the obtained aerogel.

[0109] Use a NOVA4200e type pore size distribution tester in the BET method with N2 as the carrier gas to test the specific surface area.

[0110] Observe the hydrophobic angle of the aerogel by measuring the contact angle of the water droplet dropped on the surface of the aerogel with a hydrophobic angle measuring instrument.

[0111] Detect the thermal conductivity according to the plate method in ASTM C518.

[0112] Use an Instron 5982 universal material testing machine to test the compressive strength of the sample.

[0113]

[0114] It can be seen from the above table that the modified aerogels prepared in Examples 1-3 of the present invention have good comprehensive properties.

[0115] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing an aerogel-modified dipping solution, characterized in that: The following steps are involved: (1) Preparation of LDH / GO composite material: dissolving iron nitrate, nickel nitrate and magnesium nitrate in water to obtain a mixed metal solution; adding alkaline solution dropwise into the mixed metal solution, adding graphene oxide, heating and stirring to react, centrifuging, washing and drying to obtain an LDH / GO composite material, wherein the molar ratio of iron nitrate, nickel nitrate and magnesium nitrate is 1:2:1; (2) Reduction: The LDH / GO composite material is reduced by hydrazine hydrate vapor to obtain the LDH / graphene composite material; (3) intercalation: adding LDH / graphene composite material to water, adding stearic acid and surfactant, heating and stirring to react, centrifuging, washing, and drying to obtain intercalated LDH / graphene composite material, wherein the mass ratio of LDH / graphene composite material, stearic acid and surfactant is 100:3-4:1-2; (4) Modification: adding the intercalated LDH / graphene composite material to water, adding dopamine hydrochloride and a catalyst, heating and stirring to react, centrifuging, washing, and drying to obtain a modified intercalated LDH / graphene composite material, wherein the mass ratio of the intercalated LDH / graphene composite material, dopamine hydrochloride, and the catalyst is 10:1-2:0.1-0.2; (5) Preparation of glue solution: uniformly mix alkyl orthosilicate, ethanol and water, and stir to react to obtain glue solution, wherein the mass ratio of alkyl orthosilicate, ethanol and water is 1-1.2:3-5:0.4-0.7; (6) Preparation of aerogel modified dipping solution: add the modified intercalated LDH / graphene composite material to the glue solution, stir and mix evenly, add the catalyst, stir and mix evenly to obtain the aerogel modified dipping solution, wherein the mass ratio of the glue solution, the modified intercalated LDH / graphene composite material, and the catalyst is 10:1-2:0.1-0.2; the catalyst is a 3-4 mol / L NaOH or KOH solution.

2. The preparation method according to claim 1, characterized in that: The alkali solution in step (1) is a 2-3 mol / L NaOH or KOH solution, the alkali solution is used to adjust the pH value of the solution to 8-9, the amount of graphene oxide added is 0.5-1 wt% of the total mass of the system, the temperature of the heating and stirring reaction is 90-95° C., and the time is 4-6 h.

3. The preparation method according to claim 1, characterized in that: The reduction time in step (2) is 10-12 hours.

4. The preparation method according to claim 1, characterized in that: In step (3), the surfactant is selected from at least one of sodium dodecylbenzene sulfonate, sodium dodecyl sulfate and sodium dodecyl sulfonate, and the temperature of the heating and stirring reaction is 40-50° C. and the time is 1-2 hours.

5. The preparation method according to claim 1, characterized in that: The catalyst in step (4) is a Tris-HCl solution with a pH value of 8.5-9.5, and the temperature of the heating and stirring reaction is 45-55° C. and the time is 3-5 hours.

6. The preparation method according to claim 1, characterized in that: In step (5), the alkyl orthosilicate is methyl orthosilicate or ethyl orthosilicate, and the stirring reaction time is 10-20 minutes.

7. An aerogel modified impregnation solution obtained by the preparation method according to any one of claims 1 to 6.

8. A method for preparing a modified aerogel, characterized in that: The following steps are involved: The fiber felt coil is placed in a gel tank, and the aerogel modified impregnation solution described in claim 7 is added. After the glue solution is transported, the glue solution circulation device and the ultrasonic device are turned on to allow the glue solution to fully enter the interior of the fiber felt. After the circulation is completed for 10-20 minutes, the glue solution circulation device and the ultrasonic device are turned off, and the glue solution is waited for gelation, and the remaining glue solution in the pipeline and the gel tank is recovered; the wet gel is aged at room temperature for 12-24 hours, and dried to obtain a modified aerogel.

9. A modified aerogel obtained by the preparation method as claimed in claim 8.

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