CN114853453B - Hydrophobic ceramic aerogel material with micro-nano structure and preparation method thereof - Google Patents

Hydrophobic ceramic aerogel material with micro-nano structure and preparation method thereof Download PDF

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CN114853453B
CN114853453B CN202210590133.3A CN202210590133A CN114853453B CN 114853453 B CN114853453 B CN 114853453B CN 202210590133 A CN202210590133 A CN 202210590133A CN 114853453 B CN114853453 B CN 114853453B
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silane
hydrophobic
aerogel material
hydrolysate
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张恩爽
雷朝帅
李文静
王鹏
徐沛
张昊
刘圆圆
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Aerospace Research Institute of Materials and Processing Technology
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Abstract

The invention relates to a hydrophobic ceramic aerogel material with a micro-nano structure and a preparation method thereof, wherein the method comprises the following steps: uniformly mixing the alumina nano powder and the sulfuric acid solution by using water to obtain a mixed solution, and then putting the mixed solution at the temperature of between 150 and 300 ℃ for hydrothermal reaction for 12 to 18 hours to obtain gel; aging the gel to obtain a gel block; soaking the gel block in hydrophobic treatment liquid for 24-96 h; the preparation of the hydrophobic treatment liquid comprises the following steps: preparing silane into a silane solution by using ethanol, adding acetic acid or oxalic acid into the silane solution to react for 0.5-12 h to obtain a hydrolysate, adding an ammonium fluoride solution or an ammonia water solution into the hydrolysate, and stirring for 1-30 min to obtain a hydrophobic treatment solution; and sequentially carrying out solvent replacement and supercritical drying on the treated gel block to prepare the hydrophobic ceramic aerogel material with the micro-nano structure. The hydrophobic ceramic aerogel material with the super-hydrophobic, high-temperature-resistant and efficient heat insulation micro-nano structure is obtained.

Description

Hydrophobic ceramic aerogel material with micro-nano structure and preparation method thereof
Technical Field
The invention relates to the technical field of aerogel preparation, in particular to a hydrophobic ceramic aerogel material with a micro-nano structure and a preparation method thereof.
Background
The nano porous aerogel material is a gel material with a dispersion medium of gas, is a nano porous solid material with a network structure formed by mutually accumulating colloidal particles or high polymer molecules, and the size of pores in the material is in the order of nanometers. The porosity is as high as 80-99.8%, the typical size of the pores is 1-100 nm, and the ratio of the pore size to the pore size is higher than that of the pore sizeThe surface area is 200-1000 m 2 A density of as low as 3kg/m 3 And the room temperature thermal conductivity can be as low as 0.012W/m.k. Due to the characteristics, the aerogel material has wide application potential in the aspects of thermal, acoustic, optical, microelectronic and particle detection. Currently, the most widespread field of application of aerogels is still the field of thermal insulation, since the unique nanostructure of aerogels can effectively reduce convection conduction, solid phase conduction and thermal radiation.
The aerogel has a structure collapse and pulverization caused by the fine nano network structure when meeting water without hydrophobic treatment, and many characteristics (such as high specific surface area, high porosity or low density) of the aerogel are lost. Thus, having hydrophobic characteristics is an important property of aerogels. At present, for general aerogel materials, conventionally adopted hydrophobic treatment methods include a gas-phase hydrophobic method and a liquid-phase hydrophobic method, the gas-phase hydrophobic method is to place an aerogel sample piece in a vacuum tank, and perform hydrophobic treatment on the surface of the aerogel material by using a silane hydrophobic reagent to evaporate, so as to obtain a hydrophobic aerogel material, and the liquid-phase hydrophobic method is to directly place a wet gel sample piece in the silane hydrophobic reagent to perform soaking treatment, perform hydrophobic treatment on the surface of the wet gel material, and finally perform supercritical drying, so as to obtain the hydrophobic aerogel material. However, most of the hydrophobic treatments of the traditional gas phase hydrophobic method and the liquid phase hydrophobic method rely on the reaction with hydroxyl on the surface of the material to be hydrophobic, so as to improve the hydrophobicity. However, because of the inert surface of alumina, the content of surface hydroxyl groups is low, and the number of active sites is low, the traditional gas phase hydrophobic method and liquid phase hydrophobic method are not suitable for the hydrophobic treatment of alumina aerogel.
In conclusion, it is necessary to solve the problem of hydrophobic inert surface of alumina aerogel, and provide a method for preparing hydrophobic alumina aerogel material with super-hydrophobicity, high temperature resistance and high-efficiency heat insulation.
Disclosure of Invention
In order to solve one or more technical problems in the prior art, the invention provides a hydrophobic ceramic aerogel material with a super-hydrophobic, tough structure, high temperature resistance and high-efficiency heat insulation micro-nano structure and a preparation method thereof.
The invention provides a preparation method of a hydrophobic ceramic aerogel material with a micro-nano structure in a first aspect, which comprises the following steps:
(1) Uniformly mixing the alumina nano powder and a sulfuric acid solution by using water to obtain a mixed solution, and then placing the mixed solution at the temperature of 150-300 ℃ for hydrothermal reaction for 12-18 h to obtain gel;
(2) Aging the gel to obtain an aged gel block;
(3) Soaking the aged gel block in a hydrophobic treatment solution for 24-96 h; the preparation of the hydrophobic treatment liquid comprises the following steps: preparing silane into silane solution by using ethanol, adding acetic acid or oxalic acid into the silane solution to react for 0.5-12 h to obtain hydrolysate, adding ammonium fluoride solution or ammonia water solution into the hydrolysate, and stirring for 1-30 min to obtain hydrophobic treatment liquid;
(4) And (4) sequentially carrying out solvent replacement and supercritical drying on the aged gel block treated in the step (3) to prepare the hydrophobic ceramic aerogel material with the micro-nano structure.
Preferably, the silane is one or more of methyltrimethoxysilane, methyltriethoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethylmethoxysilane, trimethylmethoxysilane and trimethylethoxysilane; the mass fraction of silane contained in the silane solution is 2-20%; and/or the dosage of the acetic acid and/or the oxalic acid is 0.1 to 5 percent of the mass of the silane solution.
Preferably, the mass ratio of the hydrolysate to the ammonium fluoride solution is 100: (1-20), or the mass ratio of the hydrolysate to the ammonia water solution is 100: (1-20).
Preferably, the concentration of the ammonium fluoride solution or the ammonia water solution is 0.1-4 mol/L.
Preferably, the particle size of the aluminum oxide nano powder is 10-100 nm; and/or the mass fraction of the alumina nano powder contained in the mixed solution is 5-20%.
Preferably, the amount of the sulfuric acid solution is 0.8 to 7% of the total mass of the mixed solution.
Preferably, the concentration of the sulfuric acid solution is 0.1-30 mmol/L.
Preferably, the aging is: aging for 1-6h at 20-90 ℃.
Preferably, the supercritical drying is supercritical carbon dioxide drying, and preferably, the temperature of the supercritical drying is 20-60 ℃ and the pressure is 10-16 MPa.
In a second aspect, the invention provides the hydrophobic ceramic aerogel material with the micro-nano structure prepared by the preparation method in the first aspect.
Compared with the prior art, the invention at least has the following beneficial effects:
(1) Compared with the traditional pearl necklace-shaped aerogel material, the pearl necklace-shaped aerogel material has better mechanical strength, and the microstructure of the pearl necklace-shaped aerogel material is formed by mutually winding nanowires, so that the aerogel has good toughness.
(2) According to the method, silane is used as a precursor, an acid catalytic hydrolysis process is carried out, an ammonium fluoride solution or an ammonia water solution is added to prepare a hydrophobic treatment solution, an aged gel block is placed in the hydrophobic treatment solution to be soaked for 24-96 hours, so that the hydrophobic treatment solution can coat and grow silane particles (hydrophobic particles) on the surface of an inert alumina wet gel, the alumina nanowires are used as a basic unit, and the silane particles (silane nanoparticles) are modified on the surface of the alumina nanowires, so that the hydrophobic ceramic aerogel material with a hierarchical micro-nano structure is obtained; the method is not influenced by the hydroxyl content and activity on the surface of aerogel or the surface of wet gel, effectively solves the technical problem that the inert surface of the alumina is difficult to be subjected to hydrophobic treatment, and has the advantage of simple operation.
(3) According to the invention, in the hydrophobic modification process, hydrophobic nanoparticles (silane nanoparticles) are adopted to perform coating growth on the surface of alumina wet gel, and the alumina nanowire aerogel is physically coated, so that on one hand, the aerogel material prepared by the invention has super-hydrophobic property, on the other hand, the aerogel material disclosed by the invention consists of a micron-scale length alumina nanowire network and nano-scale silane particles (also referred to as silane nanoparticles) distributed in pores of the alumina nanowire network, and has a graded micro-nano structure.
(4) The invention discloses a method for preparing a high-temperature resistant aerogel heat insulation material by doping modification, and provides a method for preparing an aerogel material with a stable structure by a nanowire self-supporting mode for high-temperature resistant high-efficiency heat insulation application.
(5) The gel process in the preparation method of the aerogel is a hydrothermal process, is different from the traditional RTM (resin transfer molding) pressing glue injection process, is not limited by the shape and size of the reinforcement, and can be used for preparing aerogel materials with any shape and thickness.
(6) The invention can adopt water phase as reaction medium, and avoids environmental pollution and waste caused by using organic solvent in the preparation process.
(7) The density of the ceramic aerogel material prepared by the invention can be as low as 0.12g/cm 3 The following, ultra low density aerogel materials have properties of ultra low density compared to other low density aerogel materials of the same strength; the aerogel material prepared by the method of the invention is kept lowOn the premise of thermal conductivity, the heat-insulating material also has excellent high-temperature resistance, and can realize long-term heat insulation application at 1200 ℃.
(8) The porosity of the ceramic aerogel material prepared by the method is more than 95%, the diameter of a nanowire unit of the aerogel material is 20-50 nm, the length of the nanowire unit is 5-30 mu m, the specific surface area is large, and the heat-resistant temperature is more than 1200 ℃.
Drawings
FIG. 1 is a flow chart of the preparation of the present invention.
FIG. 2 is a schematic diagram of structural changes in a preparation process of the hydrophobic ceramic aerogel material with a micro-nano structure in the invention.
FIG. 3 is an optical photograph of the hydrophobic ceramic aerogel material with a micro-nano structure prepared by the invention contacting with water. In the figure: 1: a hydrophobic ceramic aerogel material with a micro-nano structure; 2: and (3) water.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It should be apparent that the described embodiments are only some of the embodiments of the present invention, and not all of them. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention provides a preparation method of a hydrophobic ceramic aerogel material with a micro-nano structure in a first aspect, which comprises the following steps:
(1) Uniformly mixing the alumina nano powder and a sulfuric acid solution by using water to obtain a mixed solution, and then carrying out hydrothermal reaction on the mixed solution at the temperature of between 150 and 300 ℃ for 12 to 18 hours (for example, 12, 13, 14, 15, 16, 17 or 18 hours) to obtain gel; in the present invention, the gel is a semi-solid gel; the source of the alumina nano powder is not particularly limited, and the product which can be directly purchased in the market is adopted; in the invention, for example, the alumina nano powder and the sulfuric acid solution are uniformly mixed by water in a stirring (such as magnetic stirring) and/or ultrasonic mode, the invention has no special requirement on the stirring and ultrasonic conditions, and the alumina nano powder and the sulfuric acid solution can be uniformly mixed in the water; specifically, for example, after magnetic stirring for 1 to 24 hours, ultrasound for 1 to 4 hours, and in the ultrasound process, for example, stopping for 5 minutes every 10 minutes of ultrasound, and then continuing ultrasound; in some specific embodiments, for example, magnetic stirring is performed for 1h, followed by sonication for 1h; in the invention, the mixed solution is put into a closed container to carry out hydrothermal reaction for 12 to 18 hours at a temperature of between 150 and 300 ℃ to obtain semi-solid gel; in the present invention, the hydrothermal reaction is performed under a sealed condition, and the material of the sealed container is required to be a material that does not react with the system.
(2) Aging the gel to obtain an aged gel block; for example, the gel is aged for 1 to 6 hours in air at the temperature of between 20 and 90 ℃, specifically, the gel is placed in a container and aged in the air in a non-sealed environment, the aging temperature is between 20 and 90 ℃, and the aging time is 1 to 6 hours, so that a gel block can slightly and slowly shrink in the air atmosphere, the strength of the gel block can be improved, and demolding is facilitated.
(3) Soaking the aged gel block in a hydrophobic treatment solution for 24-96 h (for example, 24, 28, 30, 36, 40, 45, 50, 60, 72, 80, 85, 90 or 96 h); the hydrophobic treatment liquid is prepared by the following steps: preparing silane into a silane solution by using ethanol, adding acetic acid or oxalic acid into the silane solution to react for 0.5-12 h (such as 0.5, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 or 12 h) to obtain a hydrolysate, adding an ammonium fluoride solution or an ammonia water solution into the hydrolysate, and stirring for 1-30 min (such as 1, 5, 10, 15, 20, 25 or 30 min), preferably for 5-15 min to obtain a hydrophobic treatment solution; in the preparation process of the hydrolysate, silane is hydrolyzed and condensed under the catalysis of acid, but the hydrolysis speed is far higher than the condensation speed; in the invention, preferably, the gel is aged to improve the strength of the gel block and then is placed in the hydrophobic treatment liquid for soaking for 24-96 hours; in the present invention, when the soaking is performed, the liquid surface of the hydrophobic treatment liquid is allowed to completely submerge the aged gel block, and preferably, the volume of the hydrophobic treatment liquid is 4 to 6 times of the volume of the aged gel block; in the invention, the soaking, namely the in-situ gel hydrophobic reaction is preferably carried out for 24-96 hours, and if the soaking time is too short, the generation of enough silane nano-particles on the surface of the inert alumina wet gel block is not facilitated, so that the hydrophobic property is incomplete.
(4) Sequentially carrying out solvent replacement and supercritical drying on the aged gel block treated in the step (3) to prepare a hydrophobic ceramic aerogel material with a micro-nano structure; in the present invention, the solvent substitution may be performed using, for example, ethanol as a solvent, and the supercritical drying may be, for example, supercritical carbon dioxide drying.
According to the method, silane is used as a precursor, an acid catalysis hydrolysis process is carried out to obtain a hydrolysate, an ammonium fluoride solution or an ammonia water solution is added to obtain a hydrophobic treatment liquid, and an aged gel block is placed in the hydrophobic treatment liquid to be soaked for 24-96 hours, so that the hydrophobic treatment liquid can coat and grow silane particles (hydrophobic particles) on the surface of an inert alumina wet gel; the method is not influenced by the hydroxyl content and activity on the surface of aerogel or the surface of wet gel, effectively solves the technical problem that the inert surface of the alumina is difficult to be subjected to hydrophobic treatment, and has the advantage of simple operation. According to the invention, in the hydrophobic modification process, hydrophobic nano particles (silane nano particles) are adopted to perform coating growth on the surface of alumina wet gel and physically coat the alumina nano wire aerogel, and the silane particle coating can make the aerogel material prepared by the invention have super-hydrophobic property on one hand, and on the other hand, the aerogel material in the invention consists of a micron-scale length alumina nano wire network and nano-scale silane particles (also called as silane nano particles) distributed in pores of the alumina nano wire network, and has a hierarchical micro-nano structure.
According to some preferred embodiments, the silane is one or more of methyltrimethoxysilane, methyltriethoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethylmethoxysilane, trimethylmethoxysilane, trimethylethoxysilane; a mass fraction of silane contained in the silane solution is 2 to 20% (e.g., 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%); and/or the acetic acid and/or the oxalic acid is used in an amount of 0.1 to 5% (e.g., 0.1%, 0.5%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%) by mass of the silane solution. In the invention, the mass fraction of the silane contained in the silane solution is preferably 2-20%, and the dosage of the acetic acid and/or the oxalic acid is preferably 0.1-5% of the mass of the silane solution, so that the micro-nano structure hydrophobic ceramic aerogel material with ultrahigh hydrophobicity and more excellent heat insulation performance can be ensured. The invention discovers that if the concentration of silane contained in the silane solution is too high, the viscosity of the formed hydrolysate is too high, so that the hydrophobic treatment solution is not favorably fed into the interior of a gel block to be subjected to hydrophobic treatment, the hydrophobic treatment cannot be well carried out, and silane particles are accumulated on the surface of an aerogel material to influence the heat-resistant temperature; if the dosage or concentration of the acetic acid and/or the oxalic acid is too large, the condensation is influenced while the silane hydrolysis rate is influenced, the condensation is relatively favorable for growing into aggregates of small particles to a certain extent, the monodisperse small particles are relatively unfavorable for obtaining, and the heat insulation performance of the material is influenced while the hydrophobic performance is influenced; if the silane solution contains too small a concentration of silane, or the amount or concentration of acetic acid and/or oxalic acid is too small, the hydrolysis rate tends to be slow, and the time is prolonged, which may result in a prolonged production cycle.
According to some preferred embodiments, the mass ratio of the hydrolysate to the ammonium fluoride solution is 100: (1-20) (e.g., 100: (1-20) (e.g., 100. In the present invention, it is preferable that the mass ratio of the hydrolysate to the ammonium fluoride solution is 100: (1-20) or the mass ratio of the hydrolysate to the ammonia water solution is 100: (1-20), so that the micro-nano structure hydrophobic ceramic aerogel material with ultrahigh hydrophobicity and more excellent heat insulation performance can be obtained; the invention discovers that the reaction speed is influenced by the dosage of the ammonium fluoride solution or the ammonia water solution, and the proper dosage is selected under the requirement of a certain preparation period, so that a uniform hydrophobic structure can be obtained; if the amount of the silane-modified aerogel is large, the reaction is fast, and the gel reaction can occur when the hydrophobic treatment liquid does not completely and uniformly penetrate into the gel, so that the hydrophobic property is not uniform, the hydrophobic effect is influenced, and silane particles are easy to accumulate on the surface of the aerogel to influence the heat-resistant temperature; if the dosage of the ammonium fluoride solution or the ammonia water solution is too small, the gel is incomplete and the hydrophobic effect is poor under the same preparation period.
According to some preferred embodiments, the concentration of the ammonium fluoride solution or the aqueous ammonia solution is 0.1 to 4mol/L, preferably 0.1 to 2mol/L.
According to some preferred embodiments, the alumina nano powder has a particle size of 10 to 100nm; and/or the mass fraction of the alumina nano powder contained in the mixed solution is 5 to 20% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%).
According to some preferred embodiments, the sulfuric acid solution is used in an amount of 0.8 to 7% (e.g., 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or 7%) of the total mass of the mixed solution; in the present invention, it is preferable that the amount of the sulfuric acid solution is 0.8 to 7% of the total mass of the mixed solution, and if the amount of the sulfuric acid solution is too large, the nanowires become short and thick, which is not favorable for the assembly process, may cause severe pulverization and shrinkage of the material, and may also cause weak strength of the material and increase the thermal conductivity.
According to some preferred embodiments, the concentration of the sulfuric acid solution is 0.1 to 30mmol/L (e.g., 0.1, 0.5, 1, 3, 5, 8, 10, 15, 20, 25, or 30 mmol/L); in the invention, the concentration of the sulfuric acid solution is preferably 0.1-30 mmol/L, and the invention finds that by adopting the sulfuric acid solution with the preferred concentration, compared with the sulfuric acid solution with high concentration, the nanowire with longer length-diameter ratio can be ensured, the formation of a gel block with stronger strength is facilitated, and the aerogel can be stronger after being dried.
According to some preferred embodiments, the aging is: aging for 1-6h at 20-90 ℃; and/or the supercritical drying is supercritical carbon dioxide drying, preferably, the temperature of the supercritical drying is 20-60 ℃, and the pressure is 10-16 MPa.
According to some specific embodiments, the preparation of the hydrophobic ceramic aerogel material with a micro-nano structure comprises the following steps:
(1) mixing the alumina nano powder with the particle size range of 10-100nm and a sulfuric acid solution with the concentration of 0.1-30 mmol/L into deionized water, and uniformly mixing in a stirring and ultrasonic mode to obtain a mixed solution; in the mixed solution, the mass percentage of the aluminum oxide nano powder is 5-20%, and the dosage of the sulfuric acid solution accounts for 1% of the total weight of the mixed solution.
(2) Placing the above mixed solution in a sealed container, and performing hydrothermal reaction at 150-300 deg.C for 12-18 to obtain semisolid gel block; the method comprises the following specific steps: the reaction needs to be carried out under fully closed conditions, and the material of the container needs to be a polymer material which does not react with the system.
(3) And (3) aging the gel block in the air at the temperature of 20-90 ℃ for 1-6h to obtain an aged gel block.
(4) Placing the aged gel block in a hydrophobic treatment solution to be soaked for 24-96 h, and then carrying out in-situ gel hydrophobic reaction for 24-96 h; the hydrophobic treatment liquid is prepared by the following steps: preparing silane into silane solution by using ethanol, wherein the mass fraction of the silane contained in the silane solution is 2-20%; then adding acetic acid or oxalic acid into the silane solution to carry out hydrolysis reaction for 0.5 to 12 hours at room temperature (for example, 20 to 35 ℃) under the stirring condition to obtain hydrolysate; then adding an ammonium fluoride solution or an ammonia water solution into the hydrolysate and stirring for 1-30 min to obtain a hydrophobic treatment solution; the mass ratio of the consumption of the hydrolysate to the consumption of the ammonium fluoride solution or the ammonia water solution is 100: (1-20); the dosage of the acetic acid or the oxalic acid is 0.1 to 5 percent of the mass of the silane solution; the volume consumption of the hydrophobic treatment liquid is 4-6 times of the volume of the aged gel block; in the present invention, the stirring method and conditions are not particularly limited, and for example, a magnetic stirring method can be used.
(5) Carrying out a solvent replacement process and a supercritical drying step on the treated aged gel block obtained in the step (4) to prepare a hydrophobic ceramic aerogel material with a micro-nano structure (also called as a hydrophobic nanowire aerogel material); the method comprises the following specific steps: and the solvent replacement adopts ethanol as a solvent, and after 3 times of replacement is carried out according to 10 times of the volume of the gel block, the supercritical drying process of carbon dioxide is carried out. The supercritical drying temperature is 20-60 deg.C, and the pressure is 10-16MPa; in the present invention, there is no particular requirement on the time for each solvent substitution and the time for supercritical drying, and conventional time parameters are adopted, for example, the time for each solvent substitution may be 1 to 4 days, and the time for supercritical drying may be 18 to 36 hours, for example.
In a second aspect, the invention provides the hydrophobic ceramic aerogel material with the micro-nano structure prepared by the preparation method in the first aspect.
The invention will be further illustrated by way of example, but the scope of protection is not limited to these examples.
Example 1
(1) Mixing the alumina nano powder with the particle size range of 10-15nm and a sulfuric acid solution with the concentration of 10mmol/L into deionized water, and uniformly mixing in a stirring and ultrasonic mode to obtain a mixed solution; in the mixed solution, the mass percentage of the aluminum oxide nano powder is 8%, and the dosage of the sulfuric acid solution accounts for 1% of the total weight of the mixed solution.
(2) The mixture was put in a closed vessel and subjected to hydrothermal reaction at 240 ℃ for 12 hours to obtain a semisolid gel block (gel).
(3) And (3) aging the gel block body for 2h in an air non-sealed environment at the temperature of 60 ℃ to obtain an aged gel block.
(4) Soaking the aged gel block in a hydrophobic treatment solution for 24 hours; the hydrophobic treatment liquid is prepared by the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane in the silane solution is 5%; then adding acetic acid into the silane solution, carrying out hydrolysis reaction for 1h at room temperature under the condition of stirring to obtain a hydrolysate, then adding an ammonium fluoride solution into the hydrolysate, and stirring for 10min at room temperature to obtain a hydrophobic treatment solution; the concentration of the ammonium fluoride solution is 0.3mol/L; the mass ratio of the hydrolysate to the ammonium fluoride solution is 100:10; the using amount of the acetic acid is 2% of the mass of the silane solution; the volume of the hydrophobic treatment liquid is 5 times of the volume of the aged gel block.
(5) Carrying out a solvent replacement process and a supercritical drying step on the treated aged gel block obtained in the step (4) to prepare a hydrophobic ceramic aerogel material (also called as a hydrophobic nanowire aerogel material) with a micro-nano structure; the method comprises the following specific steps: and the solvent replacement adopts ethanol as a solvent, the ethanol is replaced for 3 times according to 10 times of the volume of the gel block, each time of replacement is 3 days, and finally the supercritical carbon dioxide drying process is carried out, wherein the temperature of the supercritical drying is 50 ℃, the pressure is 14MPa, and the time is 24h.
The hydrophobic ceramic aerogel material with the micro-nano structure prepared by the embodiment has good structural strength, and no light loss, no color change and no shedding on the surface of the aerogel material are found during heat insulation performance test.
The diameter of a nanowire unit contained in the finally prepared hydrophobic ceramic aerogel material with the micro-nano structure is 20-50 nm, and the length of the nanowire unit is 5-30 microns; the heat-resistant temperature of the hydrophobic ceramic aerogel material with the micro-nano structure prepared by the embodiment is 1200 ℃; wherein the test of the heat-resisting temperature is as follows: carrying out heat treatment (air atmosphere) on the ceramic aerogel material finally prepared in each embodiment at a certain high temperature for 30min, wherein the linear shrinkage rate of the aerogel material is not more than 5%, which indicates that the aerogel material can endure the high temperature; for the present embodiment, the hydrophobic ceramic aerogel material with a micro-nano structure prepared in the present embodiment is heat-treated (in an air atmosphere) at 1200 ℃ for 30min, the linear shrinkage rate of the aerogel material is not greater than 5%, and the heat-resistant temperature is 1200 ℃.
The compression strength of the hydrophobic ceramic aerogel material with the micro-nano structure prepared in the embodiment is 0.74MPa under 10% of compression, and the test standard adopted by the compression strength test is GB/T13480 2014 'determination of compression performance of heat insulation products for buildings'.
Example 2
Example 2 is essentially the same as example 1, except that:
(4) soaking the aged gel block in a hydrophobic treatment solution for 96 hours; the preparation of the hydrophobic treatment liquid comprises the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane in the silane solution is 2%; then adding acetic acid into the silane solution, stirring, and carrying out hydrolysis reaction for 12 hours at room temperature to obtain a hydrolysate, and then adding an ammonium fluoride solution into the hydrolysate, and stirring for 10 minutes at room temperature to obtain a hydrophobic treatment solution; the concentration of the ammonium fluoride solution is 0.1mol/L; the mass ratio of the hydrolysate to the ammonium fluoride solution is 100:1; the using amount of the acetic acid is 0.1 percent of the mass of the silane solution; the volume of the hydrophobic treatment liquid is 4 times of the volume of the aged gel block.
Example 3
Example 3 is essentially the same as example 1, except that:
(4) soaking the aged gel block in a hydrophobic treatment solution for 24 hours; the hydrophobic treatment liquid is prepared by the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane in the silane solution is 20%; then adding acetic acid into the silane solution, stirring, and carrying out hydrolysis reaction for 0.5h at room temperature to obtain a hydrolysate, and then adding an ammonium fluoride solution into the hydrolysate, stirring for 10min at room temperature to obtain a hydrophobic treatment solution; the concentration of the ammonium fluoride solution is 2mol/L; the mass ratio of the hydrolysate to the ammonium fluoride solution is 100:20; the using amount of the acetic acid is 5% of the mass of the silane solution; the volume of the hydrophobic treatment liquid is 6 times of the volume of the aged gel block.
Example 4
Example 4 is essentially the same as example 1, except that:
(4) soaking the aged gel block in a hydrophobic treatment solution for 24 hours; the hydrophobic treatment liquid is prepared by the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane in the silane solution is 5%; then adding acetic acid into the silane solution, carrying out hydrolysis reaction for 1h at room temperature under the condition of stirring to obtain a hydrolysate, then adding an ammonium fluoride solution into the hydrolysate, and stirring for 10min at room temperature to obtain a hydrophobic treatment solution; the concentration of the ammonium fluoride solution is 0.3mol/L; the mass ratio of the hydrolysate to the ammonium fluoride solution is 100:0.5; the using amount of the acetic acid is 2% of the mass of the silane solution; the volume of the hydrophobic treatment liquid is 5 times of the volume of the aged gel block.
Example 5
(4) Placing the aged gel block in a hydrophobic treatment solution for soaking for 24 hours; the hydrophobic treatment liquid is prepared by the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane contained in the silane solution is 5%; then adding acetic acid into the silane solution, carrying out hydrolysis reaction for 1h at room temperature under the condition of stirring to obtain a hydrolysate, then adding an ammonium fluoride solution into the hydrolysate, and stirring for 10min at room temperature to obtain a hydrophobic treatment solution; the concentration of the ammonium fluoride solution is 0.3mol/L; the mass ratio of the hydrolysate to the ammonium fluoride solution is 100:25; the using amount of the acetic acid is 2% of the mass of the silane solution; the volume of the hydrophobic treatment liquid is 5 times of the volume of the aged gel block.
Example 6
Example 6 is essentially the same as example 1, except that:
(4) soaking the aged gel block in a hydrophobic treatment solution for 24 hours; the hydrophobic treatment liquid is prepared by the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane in the silane solution is 5%; then adding acetic acid into the silane solution, carrying out hydrolysis reaction for 1h at room temperature under the condition of stirring to obtain a hydrolysate, then adding an ammonium fluoride solution into the hydrolysate, and stirring for 10min at room temperature to obtain a hydrophobic treatment solution; the concentration of the ammonium fluoride solution is 0.3mol/L; the mass ratio of the hydrolysate to the ammonium fluoride solution is 100:10; the using amount of the acetic acid is 6% of the mass of the silane solution; the volume of the hydrophobic treatment liquid is 5 times of the volume of the aged gel block.
Example 7
Example 7 is essentially the same as example 1, except that:
(4) soaking the aged gel block in a hydrophobic treatment solution for 24 hours; the hydrophobic treatment liquid is prepared by the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane in the silane solution is 25%; then adding acetic acid into the silane solution, carrying out hydrolysis reaction for 1h at room temperature under the condition of stirring to obtain a hydrolysate, then adding an ammonium fluoride solution into the hydrolysate, and stirring for 10min at room temperature to obtain a hydrophobic treatment solution; the concentration of the ammonium fluoride solution is 0.3mol/L; the mass ratio of the hydrolysate to the ammonium fluoride solution is 100:10; the using amount of the acetic acid is 2% of the mass of the silane solution; the volume of the hydrophobic treatment liquid is 5 times of the volume of the aged gel block.
Example 8
Example 8 is essentially the same as example 1, except that:
in the step (1), the concentration of the sulfuric acid solution used is 2mol/L.
Example 9
Example 9 is essentially the same as example 1, except that:
in the step (1), the amount of the sulfuric acid solution is 0.5% of the total weight of the mixed solution.
The ceramic aerogel material prepared by the embodiment has weak strength and has a pulverization phenomenon.
Example 10
Example 10 is essentially the same as example 1, except that:
in the step (1), the amount of the sulfuric acid solution is 20% of the total weight of the mixed solution.
The ceramic aerogel material prepared by the embodiment has weak strength and has a pulverization phenomenon.
Example 11
Example 11 is essentially the same as example 1, except that:
directly carrying out a solvent replacement process and a supercritical drying process on the aged gel block obtained in the step (3) without carrying out the hydrophobization process in the step (4) to obtain a ceramic aerogel material; the method comprises the following specific steps: and (3) replacing the solvent by using ethanol as a solvent according to 10 times of the volume of the gel block for 3 times, wherein each time is 3 days, and finally performing a supercritical carbon dioxide drying process, wherein the temperature of supercritical drying is 50 ℃, the pressure is 14MPa, and the time is 24h.
Example 12
Example 12 is essentially the same as example 1, except that:
(4) placing the aged gel block in a hydrophobic treatment solution for soaking for 24 hours; the preparation of the hydrophobic treatment liquid comprises the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane contained in the silane solution is 5%; then adding an ammonium fluoride solution into the silane solution, and stirring at room temperature for 10min to obtain a hydrophobic treatment solution; the concentration of the ammonium fluoride solution is 0.3mol/L; the mass ratio of the silane solution to the ammonium fluoride solution is 100:10; the volume of the hydrophobic treatment liquid is 5 times of the volume of the aged gel block.
The ceramic aerogel material prepared by the embodiment can keep the structural integrity, and other performance indexes are shown in table 1.
Example 13
Example 13 is essentially the same as example 1, except that:
(4) placing the aged gel block in a hydrophobic treatment solution for soaking for 24 hours; the preparation of the hydrophobic treatment liquid comprises the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane contained in the silane solution is 5%; then adding acetic acid into the silane solution, and carrying out hydrolysis reaction for 1h at room temperature under the stirring condition to obtain a hydrolysate, namely the hydrophobic treatment solution; the using amount of the acetic acid is 2% of the mass of the silane solution; the volume of the hydrophobic treatment liquid is 5 times of the volume of the aged gel block.
The ceramic aerogel material prepared by the embodiment can keep the structural integrity, and other performance indexes are shown in table 1.
Example 14
Example 14 is essentially the same as example 1, except that:
(4) soaking the aged gel block in a hydrophobic treatment solution for 12 hours; the preparation of the hydrophobic treatment liquid comprises the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane contained in the silane solution is 5%; then adding acetic acid into the silane solution, carrying out hydrolysis reaction for 1h at room temperature under the condition of stirring to obtain a hydrolysate, then adding an ammonium fluoride solution into the hydrolysate, and stirring for 10min at room temperature to obtain a hydrophobic treatment solution; the concentration of the ammonium fluoride solution is 0.3mol/L; the mass ratio of the hydrolysate to the ammonium fluoride solution is 100:10; the using amount of the acetic acid is 2% of the mass of the silane solution; the volume of the hydrophobic treatment liquid is 5 times of the volume of the aged gel block.
The ceramic aerogel material prepared in the example has no chalking, no shrinkage and good formability, and other performance indexes are shown in table 1.
Example 15
(1) Mixing the alumina nano powder with the particle size range of 10-15nm and a sulfuric acid solution with the concentration of 10mmol/L into deionized water, and uniformly mixing in a stirring and ultrasonic mode to obtain a mixed solution; in the mixed solution, the mass percentage of the aluminum oxide nano powder is 8%, and the dosage of the sulfuric acid solution accounts for 1% of the total weight of the mixed solution.
(2) The mixture was subjected to hydrothermal reaction at 240 ℃ for 12 hours in a closed vessel to obtain a semisolid gel mass (gel).
(3) And (3) aging the gel block in an air-tight environment for 2 hours at the temperature of 60 ℃ to obtain an aged gel block.
(4) Carrying out a solvent replacement process and a supercritical drying step on the aged gel block obtained in the step (3) to prepare an aerogel material; the method comprises the following specific steps: the solvent replacement adopts ethanol as a solvent, the replacement is carried out for 3 times according to 10 times of the volume of the gel block, each time for 3 days, and then the supercritical carbon dioxide drying process is carried out, wherein the temperature of the supercritical drying is 50 ℃, the pressure is 14MPa, and the time is 24h.
(5) Carrying out hydrophobic treatment on the aerogel material obtained in the step (4) by a gas phase hydrophobic method to obtain a ceramic aerogel material; the method specifically comprises the following steps: placing the silane solution and the ceramic aerogel material obtained in the step (4) in a vacuum tank, sealing, heating to 120 ℃, and performing hydrophobic treatment on the ceramic aerogel material by using silane solution steam for 12 hours; the preparation of the silane solution is as follows: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane in the silane solution is 10%.
The ceramic aerogel material finally prepared in the embodiment has no chalking, no shrinkage and good formability, but does not have super-hydrophobic property.
Example 16
(1) Mixing the alumina nano powder with the particle size range of 10-15nm and a sulfuric acid solution with the concentration of 10mmol/L into deionized water, and uniformly mixing in a stirring and ultrasonic mode to obtain a mixed solution; in the mixed solution, the mass percentage of the aluminum oxide nano powder is 8%, and the dosage of the sulfuric acid solution accounts for 1% of the total weight of the mixed solution.
(2) The mixture was put in a closed vessel and subjected to hydrothermal reaction at 240 ℃ for 12 hours to obtain a semisolid gel block (gel).
(3) And (3) aging the gel block for 2h in an air-tight environment at 60 ℃.
(4) Carrying out hydrophobic treatment on the gel block aged in the step (3) by a liquid-phase hydrophobic method, which specifically comprises the following steps: soaking the gel block treated in the step (3) in a silane solution for 12 hours; the preparation of the silane solution comprises the following steps: preparing methyl trimethoxy silane into a silane solution by using ethanol, wherein the mass fraction of the methyl trimethoxy silane in the silane solution is 10%.
(5) Carrying out solvent replacement and supercritical drying on the gel block treated in the step (4) to prepare a ceramic aerogel material; the method comprises the following specific steps: the solvent replacement adopts ethanol as solvent, and is carried out for 3 times according to 10 times of the volume of the gel block, each time for 3 days, and then a supercritical carbon dioxide drying process is carried out, wherein the temperature of the supercritical drying is 50 ℃, the pressure is 14MPa, and the time is 24h.
The ceramic aerogel material prepared in the example has no chalking, no shrinkage and good formability, but does not have super-hydrophobic property.
The ceramic aerogel materials finally prepared in the embodiments are subjected to performance tests, and the performance indexes are shown in table 1.
Figure BDA0003667050810000181
Figure BDA0003667050810000191
In Table 1, the symbol "-" indicates that the performance index was not tested.
The invention has not been described in detail and is not limited thereto.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (10)

1. A preparation method of a hydrophobic ceramic aerogel material with a micro-nano structure is characterized by comprising the following steps:
(1) Uniformly mixing the alumina nano powder and a sulfuric acid solution by using water to obtain a mixed solution, and then carrying out hydrothermal reaction on the mixed solution at the temperature of 150 to 300 ℃ for 12 to 18h to obtain gel;
(2) Aging the gel to obtain an aged gel block;
(3) Soaking the aged gel block in a hydrophobic treatment solution for 24 to 96h; the preparation of the hydrophobic treatment liquid comprises the following steps: preparing silane into a silane solution by using ethanol, adding acetic acid or oxalic acid into the silane solution to react for 0.5 to 12h to obtain a hydrolysate, adding an ammonium fluoride solution or an ammonia water solution into the hydrolysate, and stirring for 1 to 30min to obtain a hydrophobic treatment solution; the mass ratio of the hydrolysate to the ammonium fluoride solution is 100: (1 to 20), or the mass ratio of the hydrolysate to the ammonia water solution is 100: (1 to 20);
(4) And (4) sequentially carrying out solvent replacement and supercritical drying on the aged gel block treated in the step (3) to prepare the hydrophobic ceramic aerogel material with the micro-nano structure.
2. The method of claim 1, wherein:
the silane is one or more of methyltrimethoxysilane, methyltriethoxysilane, dimethylethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, dimethylmethoxysilane, trimethylmethoxysilane and trimethylethoxysilane;
the mass fraction of silane contained in the silane solution is 2-20%; and/or
The dosage of the acetic acid and/or the oxalic acid is 0.1 to 5 percent of the mass of the silane solution.
3. The method of claim 1, wherein:
the concentration of the ammonium fluoride solution or the ammonia water solution is 0.1 to 4mol/L.
4. The production method according to any one of claims 1 to 3, characterized in that:
the grain diameter of the alumina nano powder is 10 to 100nm; and/or
The mass fraction of the alumina nano powder contained in the mixed liquid is 5 to 20 percent.
5. The production method according to any one of claims 1 to 3, characterized in that:
the dosage of the sulfuric acid solution accounts for 0.8 to 7 percent of the total mass of the mixed solution.
6. The production method according to any one of claims 1 to 3, characterized in that:
the concentration of the sulfuric acid solution is 0.1 to 30mmol/L.
7. The production method according to any one of claims 1 to 3, characterized in that:
the aging is as follows: aging at 20 to 90 ℃ for 1 to 6h.
8. The production method according to any one of claims 1 to 3, characterized in that:
the supercritical drying is supercritical carbon dioxide drying.
9. The method of claim 8, wherein:
the temperature of the supercritical drying is 20 to 60 ℃, and the pressure is 10 to 169MPa.
10. The hydrophobic ceramic aerogel material with the micro-nano structure prepared by the preparation method of any one of claims 1 to 9.
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