CN113716572B - Preparation method of alumina-silica aerogel composite material - Google Patents
Preparation method of alumina-silica aerogel composite material Download PDFInfo
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B33/00—Silicon; Compounds thereof
- C01B33/113—Silicon oxides; Hydrates thereof
- C01B33/12—Silica; Hydrates thereof, e.g. lepidoic silicic acid
- C01B33/14—Colloidal silica, e.g. dispersions, gels, sols
- C01B33/157—After-treatment of gels
- C01B33/158—Purification; Drying; Dehydrating
- C01B33/1585—Dehydration into aerogels
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- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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- B01J13/00—Colloid chemistry, e.g. the production of colloidal materials or their solutions, not otherwise provided for; Making microcapsules or microballoons
- B01J13/0091—Preparation of aerogels, e.g. xerogels
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- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/02—Aluminium oxide; Aluminium hydroxide; Aluminates
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- C04B30/00—Compositions for artificial stone, not containing binders
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- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
- C01P2004/82—Particles consisting of a mixture of two or more inorganic phases two phases having the same anion, e.g. both oxidic phases
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- C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B14/02—Granular materials, e.g. microballoons
- C04B14/04—Silica-rich materials; Silicates
- C04B14/06—Quartz; Sand
- C04B14/064—Silica aerogel
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- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B14/00—Use of inorganic materials as fillers, e.g. pigments, for mortars, concrete or artificial stone; Treatment of inorganic materials specially adapted to enhance their filling properties in mortars, concrete or artificial stone
- C04B14/02—Granular materials, e.g. microballoons
- C04B14/30—Oxides other than silica
- C04B14/303—Alumina
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- C04B2201/00—Mortars, concrete or artificial stone characterised by specific physical values
- C04B2201/30—Mortars, concrete or artificial stone characterised by specific physical values for heat transfer properties such as thermal insulation values, e.g. R-values
- C04B2201/32—Mortars, concrete or artificial stone characterised by specific physical values for heat transfer properties such as thermal insulation values, e.g. R-values for the thermal conductivity, e.g. K-factors
Abstract
The invention belongs to the field of heat insulation materials, and discloses a preparation method of an alumina-silica aerogel composite material. In addition, the alumina aerogel approximately forms a gradient structure on the outermost layer of the composite gel, a silicon dioxide aerogel network structure can be well protected at high temperature, and the alumina aerogel and the silicon dioxide aerogel are matched with each other to jointly improve the heat insulation and mechanical properties of the composite material.
Description
Technical Field
The invention belongs to the field of heat insulation materials, and particularly relates to a preparation method of an alumina-silica aerogel composite material.
Background
With the flying speed of the aircraft becoming faster and the surface temperature becoming higher and higher, the thermal insulation effect and the mechanical property of the conventional aluminum silicate or mullite fiber cannot meet the thermal protection requirement of the aerospace aircraft at a high temperature section, and the use of the novel nano aerogel thermal insulation composite material becomes the leading direction of high-efficiency thermal insulation.
Aerogel is the most ideal light heat-insulating material at present, is a light, amorphous and porous solid material composed of nano colloidal particles or high polymer molecules, and has extremely low density, high specific surface area and high porosity. The pore size of the aerogel (< 50 nm) is smaller than the mean free path of air molecules (about 70 nm), there is no air convection in the aerogel pores, and thus there is extremely low gaseous heat conduction; meanwhile, the aerogel has extremely high porosity and low volume ratio of solid, so that the solid heat conduction is very low, so that the aerogel has extremely low heat conductivity and is considered as the solid material with the best heat insulation performance found at present.
Currently, aerogel composite materials of silica system are widely researched and applied, but silica aerogel has no shielding capability to infrared rays with the wave band ranging from 2 μm to 8 μm. At high temperatures, the thermal radiation energy in this band will pass almost entirely through the aerogel. While at high temperature, siO 2 The aerogel nanopores easily collapse and the aerogel structure tends to densify, resulting in SiO 2 The temperature of the aerogel can not be higher than 650 ℃ when the aerogel is used for a long time. Therefore, the availability of high temperature resistant aerogel thermal insulation composites that are resistant to infrared radiation would be of great significance to the development of high speed aircraft.
Among the numerous aerogels, al 2 O 3 Aerogel has low thermal conductivity and good high-temperature (such as the temperature higher than 1050 ℃ under the condition of long-term use) stability, and is an ideal material for preparing high-temperature-resistant heat-insulating materials. However, alumina aerogel has a disadvantage that it undergoes crystal transition at high temperature to cause structural collapse and tends to shrink at high temperature.
The method of mixing silica and alumina sol is a common method for improving the temperature resistance of silica aerogel at present. However, the low strength, brittleness, poor infrared radiation blocking capability, and difficulty in forming inherent in alumina-silica aerogel materials limit the industrial applicability of alumina-silica aerogels. Therefore, the preparation of the alumina-silica aerogel composite material with the use temperature of more than 1200 ℃ and better heat insulation performance and mechanical property has very important practical significance.
Disclosure of Invention
The invention aims to provide a preparation method of an alumina-silica aerogel composite material.
In order to realize the purpose, the technical scheme adopted by the invention is as follows:
the preparation method of the alumina-silica aerogel composite material is characterized by comprising the following steps:
(1) And preparing a silica gel: uniformly mixing a silicon source, ethanol and water to obtain silicon dioxide sol, sequentially adding a gel catalyst, uniformly stirring, adjusting pH to promote gel polycondensation, and standing at room temperature to form silicon dioxide gel;
(2) Preparing aluminum sol: preparing an aluminum source, a chelating agent, a solvent for the aluminum sol, water and a catalyst for the aluminum sol to obtain the aluminum sol, wherein the molar ratio of the aluminum source to the chelating agent to the solvent for the aluminum sol to the water to the catalyst for the aluminum sol is 1 (0.001 to 0.06): (4 to 32): (0.6 to 4): (0.0001. About.1);
(3) And dipping: soaking the silicon dioxide gel in the step (1) in the aluminum sol for 8 to 48h, and taking out;
(4) And (3) gelling: standing the silica gel obtained in the step (3) for a gelling reaction to obtain alumina-silica composite wet gel;
(5) And (3) drying: and (4) drying the alumina-silica composite wet gel material obtained in the step (4) to obtain the alumina-silica aerogel composite material.
Preferably, in the step (1), the silica sol is obtained by mixing a silicon source, ethanol, water = 1: 2 to 60: 1 to 30 in a molar ratio; the silicon source is one or more than two of ethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate or alkyl alkoxy silane; the alkyl alkoxy silane comprises one or more than two of methyl trimethoxy silane, dimethyl dimethoxy silane, methyl triethoxy silane, dimethyl diethoxy silane, vinyl triethoxy silane, propyl trimethoxy silane or propyl triethoxy silane.
Preferably, in step (1), the gelling catalyst is one or a combination of two of basic catalysts such as sodium hydroxide, potassium hydroxide, ammonia water and ammonium fluoride aqueous solution; the pH of the silica sol is adjusted to 6~8 by the gelling catalyst; the gelling catalyst is an acidic catalyst, the pH of the solution is regulated to 2~6, and the acidic catalyst is one or the combination of more than two of sulfuric acid, hydrochloric acid, hydrofluoric acid, oxalic acid, acetic acid or benzenesulfonic acid.
Preferably, in the step (2), the aluminum source is one or a combination of two or more of aluminum isopropoxide, aluminum sec-butoxide and aluminum nitrate; the chelating agent is one of acetylacetone and ethyl acetoacetate; the solvent for the aluminum sol is one or a combination of more than two of ethanol, isopropanol and n-butanol; the catalyst for the aluminum sol is one or a combination of more than two of the group consisting of sodium hydroxide, potassium hydroxide, ammonia water and ammonium fluoride.
Preferably, in the step (2), the preparation of the aluminum sol is carried out in the following way: firstly, uniformly mixing an aluminum source and the chelating agent, then adding the solvent for the aluminum sol and uniformly mixing, then adding the water and the catalyst for the aluminum sol and uniformly mixing to obtain the aluminum sol.
Preferably, the aging process is further included after the gelling in the step (4), and specifically, the alumina-silica composite wet gel is aged for 8 to 24h at room temperature or at the temperature of 30 to 60 ℃ by heating.
Preferably, the method further comprises a solvent replacement process after the aging treatment, specifically, the alumina-silica composite wet gel is placed in absolute ethyl alcohol for solvent replacement, the number of times of replacement is 1~4, and the time of replacement is 2 to 12h each time.
Preferably, in the step (5), the drying treatment is one of supercritical drying, freeze drying and atmospheric drying.
A preparation method for preparing an alumina-silica aerogel felt composite material is characterized by comprising the following steps:
(a) Preparing a silicon dioxide gel felt: dipping the fibrofelt into the silica sol catalyzed by the gelling catalyst before gelling to prepare the silica gel felt or dipping the fibrofelt into the silica sol and then catalyzing and gelling by the gelling catalyst to prepare the silica gel felt;
(b) Preparing aluminum sol: preparing an aluminum source, a chelating agent, a solvent for the aluminum sol, water and a catalyst for the aluminum sol to obtain the aluminum sol, wherein the molar ratio of the aluminum source to the chelating agent to the solvent for the aluminum sol to the water to the catalyst for the aluminum sol is 1 (0.001 to 0.06): (4 to 32): (0.6 to 4): (0.0001. About.1);
(c) And dipping: dipping the silica gel felt in the step (1) in the aluminum sol and then taking out;
(d) And (3) gelling: standing the silica gel obtained in the step (3) for a gelling reaction to obtain an alumina-silica composite wet gel felt;
(e) And drying: and (4) drying the alumina-silica wet gel material obtained in the step (4) to obtain the alumina-silica aerogel felt composite material.
Wherein the silica sol in the step (a) is obtained by mixing a silicon source, ethanol and water in a molar ratio of (2) - (60) to (1) - (30); the silicon source is one or more than two of ethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate or alkyl alkoxy silane; the alkyl alkoxy silane comprises one or more than two of methyl trimethoxy silane, dimethyl dimethoxy silane, methyl triethoxy silane, dimethyl diethoxy silane, vinyl triethoxy silane, propyl trimethoxy silane or propyl triethoxy silane.
The gelling catalyst is one or a combination of two of alkaline catalysts such as sodium hydroxide, potassium hydroxide, ammonia water and ammonium fluoride aqueous solution; the pH of the silica sol is adjusted to 6~8 by the gelling catalyst; the gelling catalyst is an acidic catalyst, the pH of the solution is regulated to 2~6, and the acidic catalyst is one or the combination of more than two of sulfuric acid, hydrochloric acid, hydrofluoric acid, oxalic acid, acetic acid or benzenesulfonic acid.
Preferably, in the step (a), the fiber mat is one of a glass fiber mat, an aluminum silicate fiber mat, a quartz fiber mat, a high silica fiber mat, a carbon fiber mat, a pre-oxidized fiber mat, a mullite fiber mat, a basalt fiber mat, a silicon carbide fiber mat, an alumina fiber mat and a boron nitride fiber mat.
Preferably, in the step (b), the aluminum source is one or a combination of two or more of aluminum isopropoxide, aluminum sec-butoxide and aluminum nitrate; the chelating agent is one of acetylacetone and ethyl acetoacetate; the solvent for the aluminum sol is one or a combination of more than two of ethanol, isopropanol and n-butanol; the catalyst for the aluminum sol is one or a combination of more than two of the group consisting of sodium hydroxide, potassium hydroxide, ammonia water and ammonium fluoride.
Preferably, in step (b), the preparation of the aluminum sol is carried out as follows: firstly, uniformly mixing an aluminum source and the chelating agent, then adding the solvent for the aluminum sol and uniformly mixing, then adding the water and the catalyst for the aluminum sol and uniformly mixing to obtain the aluminum sol.
Preferably, in the step (c), the immersion time is 8 to 48h.
Preferably, the aging process is further included after the gelling in the step (d), and specifically, the alumina-silica composite wet gel mat is aged for 8 to 24h at room temperature or under the condition of heating at 30 to 60 ℃.
Preferably, the method further comprises a solvent replacement process after the aging treatment, specifically, the alumina-silica composite wet gel mat is placed in absolute ethyl alcohol for solvent replacement, the number of times of replacement is 1~4, and the time of replacement is 2 to 12h each time.
The alumina-silica aerogel composite material is prepared by the method.
Preferably, the thermal conductivity coefficient of the alumina-silica aerogel felt prepared by the invention is 0.021 to 0.025w/(m.DEG C).
Has the advantages that:
the invention provides a preparation method of an alumina-silica aerogel composite material, after silica gel is prepared, an alumina sol mixed solution is continuously soaked on the surface of the silica gel, the silica gel is compounded by using an alumina aerogel coating method, si-OH and Si-OR bonds (wherein R is alkyl) on the surface of the silica gel can react with-Al-O-bonds to form a silicon-alumina aerogel composite network structure, the silica aerogel network framework can play a role in supporting the alumina aerogel framework, the occurrence of collapse of the alumina aerogel structure at high temperature at present is reduced, and meanwhile, the mechanical property enhancement of the silica aerogel is improved by the alumina aerogel framework. In addition, the alumina aerogel approximately forms a gradient structure on the outermost layer of the composite gel, a silicon dioxide aerogel network structure can be well protected at high temperature, and the alumina aerogel and the silicon dioxide aerogel are matched with each other to jointly improve the heat insulation and mechanical properties of the composite material.
The traditional silica aerogel has better heat preservation performance at the medium-low temperature of below 600 ℃, but the internal structure of the traditional silica aerogel is damaged after the traditional silica aerogel is used for a long time in a high-temperature environment with the temperature of over 600 ℃, so that the heat insulation effect of the material is greatly reduced, and the application of the material in the high-temperature environment is limited.
The preparation method for the alumina and silica aerogel composite material provided by the invention has the advantages of simple preparation process and simplicity and convenience in operation, and the application range of the aerogel composite material in the high-temperature field is expanded.
Detailed Description
The present invention will be further described with reference to the following specific examples. It should be understood that the following examples are illustrative only and are not intended to limit the scope of the present invention.
Example 1:
a preparation method of an alumina-silica aerogel composite material comprises the following steps:
(1) And preparing a silica gel: uniformly mixing a silicon source, ethanol and water to obtain silicon dioxide sol, sequentially adding a gel catalyst, uniformly stirring, adjusting pH to promote gel polycondensation, and standing at room temperature to form silicon dioxide gel;
(2) Preparing aluminum sol: preparing an aluminum sol from an aluminum source, a chelating agent, a solvent for the aluminum sol, water and a catalyst for the aluminum sol, wherein the molar ratio of the aluminum source to the chelating agent to the solvent for the aluminum sol to the water to the catalyst for the aluminum sol is 1:4:0.6:0.0001;
(3) And dipping: dipping the silica gel obtained in the step (1) in the aluminum sol for 12 hours and then taking out;
(4) And (3) gelling: standing the silica gel obtained in the step (3) for a gelling reaction to obtain alumina-silica composite wet gel;
(5) Aging treatment of the composite gel: carrying out aging treatment on the alumina-silica composite wet gel in the step (4) for 24 hours at room temperature;
(6) Solvent replacement of complex gel: placing the aged alumina-silica composite wet gel obtained in the step (5) in absolute ethyl alcohol for solvent replacement, wherein the number of times of replacement is 2, and the time of replacement is 12 hours each time;
(7) And (3) drying: and (4) carrying out supercritical drying treatment on the alumina-silica composite wet gel obtained in the step (6) to obtain the alumina-silica aerogel composite material.
Wherein, in the step (1), the silica sol is obtained by mixing a silicon source, ethanol and water according to a molar ratio of 1: 6: 2; the silicon source is tetraethoxysilane; the gelling catalyst is an aqueous ammonium fluoride solution and the pH of the silica sol is adjusted to 7 by the gelling catalyst.
In the step (2), the specific preparation steps of the aluminum sol are as follows: firstly, uniformly mixing aluminum source sec-butyl alcohol and the chelating agent ethyl acetoacetate, then adding the aluminum sol, using solvent ethanol, uniformly mixing, then adding water and catalyst acetic acid for the aluminum sol, and uniformly mixing to obtain the aluminum sol.
A preparation method for preparing an alumina-silica aerogel felt composite material is characterized by comprising the following steps:
(a) Preparing a silicon dioxide gel felt: uniformly mixing a silicon source, ethanol and water, sequentially adding a gelling catalyst ammonium fluoride to enable the pH of the solution to be 7, uniformly stirring to obtain catalyzed silica sol, and soaking a glass fiber mat and gelling the glass fiber mat in the catalyzed silica sol to obtain a silica gel mat;
(b) Preparing aluminum sol: preparing an aluminum sol from an aluminum source, a chelating agent, a solvent for the aluminum sol, water and a catalyst for the aluminum sol, wherein the molar ratio of the aluminum source to the chelating agent to the solvent for the aluminum sol to the water to the catalyst for the aluminum sol is 1:4:0.6:0.0001;
(c) And dipping: dipping the silica gel felt in the step (1) in the aluminum sol for 12 hours and then taking out;
(d) And (3) gelling: standing the silica gel obtained in the step (3) for a gelling reaction to obtain an alumina-silica composite wet gel felt;
(e) Aging treatment of the composite gel: carrying out aging treatment on the alumina-silica composite wet gel in the step (4) for 24 hours at room temperature;
(f) Solvent replacement of complex gel: placing the aged alumina-silica composite wet gel obtained in the step (5) in absolute ethyl alcohol for solvent replacement, wherein the number of times of replacement is 2, and the time of replacement for each time is 12h;
(g) And (3) drying: and (4) carrying out supercritical drying treatment on the alumina-silica wet gel material obtained in the step (4) to obtain the alumina-silica aerogel felt composite material.
Wherein, in the step (a), the silica sol is obtained by mixing a silicon source, ethanol and water according to a molar ratio of 1: 6: 2; the silicon source is tetraethoxysilane.
In the step (b), the specific preparation steps of the aluminum sol are as follows: uniformly mixing aluminum source sec-butyl alcohol aluminum with the chelating agent ethyl acetoacetate, adding the aluminum sol, using a solvent ethanol, uniformly mixing, adding water and a catalyst acetic acid for the aluminum sol, and uniformly mixing to obtain the aluminum sol.
The alumina-silica aerogel composite material is prepared by the method.
The thermal conductivity coefficient of the alumina-silica aerogel composite felt obtained in the embodiment is 0.025 w/(m.cndot.), and the dimensional shrinkage rate of the alumina-silica aerogel composite felt after being treated at 1000 ℃ for 30min is 12.9%.
Example 2:
a preparation method of an alumina-silica aerogel composite material comprises the following steps:
(1) And preparing the silica gel: uniformly mixing a silicon source, ethanol and water to obtain silicon dioxide sol, sequentially adding a gel catalyst, uniformly stirring, adjusting pH to promote gel polycondensation, and standing at room temperature to form silicon dioxide gel;
(2) Preparing aluminum sol: preparing an aluminum source, a chelating agent, a solvent for the aluminum sol, water and a catalyst for the aluminum sol to obtain the aluminum sol, wherein the molar ratio of the aluminum source to the chelating agent to the solvent for the aluminum sol to the water to the catalyst for the aluminum sol is 1: 0.06:32:4:1;
(3) And dipping: soaking the silica gel obtained in the step (1) in the aluminum sol for 24 hours, and then taking out;
(4) And (3) gelling: standing the silica gel obtained in the step (3) for a gelling reaction to obtain alumina-silica composite wet gel;
(5) Aging treatment of the composite gel: aging the alumina-silica composite wet gel in the step (4) for 12 hours under the condition of heating to 50 ℃;
(6) And (3) drying: and (5) drying the alumina-silica composite wet gel obtained in the step (5) at normal pressure to obtain the alumina-silica aerogel composite material.
Wherein, in the step (1), the silica sol is obtained by mixing a silicon source, ethanol and water according to a molar ratio of 1: 40: 15; the silicon source is methyl trimethoxy silane; the gelling catalyst is an ammonia solution, and the pH of the silica sol is adjusted to 6 by the gelling catalyst.
In the step (2), the specific preparation steps of the aluminum sol are as follows: firstly, uniformly mixing aluminum isopropoxide serving as an aluminum source and ethyl acetoacetate serving as a chelating agent, then adding n-butyl alcohol serving as a solvent for the aluminum sol, uniformly mixing, then adding water and formic acid serving as a catalyst for the aluminum sol, and uniformly mixing to obtain the aluminum sol.
A preparation method for preparing an alumina-silica aerogel felt composite material is characterized by comprising the following steps:
(a) Preparing a silicon dioxide gel felt: uniformly mixing a silicon source, ethanol and water to obtain silica sol, uniformly stirring to obtain silica sol, soaking a fiber material into the silica sol, and then adding a gelling catalyst to obtain a silica gel felt;
(b) And preparing the aluminum sol: preparing an aluminum source, a chelating agent, a solvent for the aluminum sol, water and a catalyst for the aluminum sol to obtain the aluminum sol, wherein the molar ratio of the aluminum source to the chelating agent to the solvent for the aluminum sol to the water to the catalyst for the aluminum sol is 1: 0.06:32:4:1;
(c) And dipping: dipping the silicon dioxide gel felt in the step (1) in the aluminum sol for 24 hours and then taking out;
(d) And (3) gelling: standing the silicon dioxide gel obtained in the step (3) for a gelling reaction to obtain an alumina-silica composite wet gel felt;
(e) Aging treatment of the composite gel: aging the alumina-silica composite wet gel in the step (4) for 12 hours under the condition of heating to 50 ℃;
(f) And (3) drying: and (4) drying the alumina-silica wet gel material obtained in the step (4) at normal pressure to obtain the alumina-silica aerogel felt composite material.
Wherein, in the step (a), the silica sol is obtained by mixing a silicon source, ethanol and water according to a molar ratio of 1: 40: 15; the silicon source is methyl trimethoxy silane; the gelling catalyst is an ammonia solution, and the pH of the silica sol is adjusted to 6 by the gelling catalyst.
In the step (b), the specific preparation steps of the aluminum sol are as follows: firstly, uniformly mixing aluminum isopropoxide serving as an aluminum source and ethyl acetoacetate serving as a chelating agent, then adding n-butyl alcohol serving as a solvent for the aluminum sol, uniformly mixing, then adding water and formic acid serving as a catalyst for the aluminum sol, and uniformly mixing to obtain the aluminum sol.
The alumina-silica aerogel composite material is prepared by the method.
The thermal conductivity coefficient of the alumina-silica aerogel composite felt obtained in the embodiment is 0.021 w/(m.cndot.), and the dimensional shrinkage rate of the alumina-silica aerogel composite felt after being treated at 1000 ℃ for 30min is 13.6%.
Example 3:
a preparation method of an alumina-silica aerogel composite material comprises the following steps:
(1) And preparing the silica gel: uniformly mixing a silicon source, ethanol and water to obtain silicon dioxide sol, sequentially adding a gel catalyst, uniformly stirring, adjusting pH to promote gel polycondensation, and standing at room temperature to form silicon dioxide gel;
(2) And preparing the aluminum sol: preparing an aluminum source, a chelating agent, a solvent for the aluminum sol, water and a catalyst for the aluminum sol to obtain the aluminum sol, wherein the molar ratio of the aluminum source to the chelating agent to the solvent for the aluminum sol to the water to the catalyst for the aluminum sol is 1: 0.03:18:2.3:0.005;
(3) And dipping: soaking the silica gel obtained in the step (1) in the aluminum sol for 18 hours and then taking out;
(4) And (3) gelling: standing the silica gel obtained in the step (3) for a gelling reaction to obtain alumina-silica composite wet gel;
(5) And (3) drying: and (5) performing supercritical drying treatment on the alumina-silica composite wet gel obtained in the step (4) to obtain the alumina-silica aerogel composite material.
Wherein, in the step (1), the silica sol is obtained by mixing a silicon source, ethanol and water according to a molar ratio of 1: 30: 8; the silicon source is methyl orthosilicate; the gelling catalyst is an ammonia solution, and the pH of the silica sol is adjusted to 8 by the gelling catalyst.
In the step (2), the specific preparation steps of the aluminum sol are as follows: firstly, uniformly mixing aluminum nitrate serving as an aluminum source and acetylacetone serving as a chelating agent, then adding ethanol serving as a solvent for the aluminum sol, uniformly mixing, then adding water and oxalic acid serving as a catalyst for the aluminum sol, and uniformly mixing to obtain the aluminum sol.
A preparation method for preparing an alumina-silica aerogel felt composite material is characterized by comprising the following steps:
(a) Preparing a silicon dioxide gel felt: uniformly mixing a silicon source, ethanol and water to obtain silica sol, uniformly stirring to obtain silica sol, soaking a fiber material into the silica sol, and then adding a gelling catalyst to obtain a silica gel felt;
(b) Preparing aluminum sol: preparing an aluminum source, a chelating agent, a solvent for the aluminum sol, water and a catalyst for the aluminum sol to obtain the aluminum sol, wherein the molar ratio of the aluminum source, the chelating agent, the solvent for the aluminum sol, the water and the catalyst for the aluminum sol is 1: 0.03:18:2.3:0.005;
(c) And dipping: dipping the silica gel felt in the step (1) in the aluminum sol for 24 hours and then taking out;
(d) And (3) gelling: standing the silicon dioxide gel obtained in the step (3) for a gelling reaction to obtain an alumina-silica composite wet gel felt;
(e) And (3) drying: and (4) carrying out supercritical drying treatment on the alumina-silica wet gel material obtained in the step (4) to obtain the alumina-silica aerogel felt composite material.
Wherein, in the step (a), the silica sol is obtained by mixing a silicon source, ethanol and water according to a molar ratio of 1: 30: 8; the silicon source is methyl orthosilicate; the gelling catalyst ammonia adjusted the pH of the silica sol to 8.
In the step (b), the specific preparation steps of the aluminum sol are as follows: firstly, uniformly mixing aluminum nitrate serving as an aluminum source and acetylacetone serving as a chelating agent, then adding ethanol serving as a solvent for the aluminum sol, uniformly mixing, then adding water and oxalic acid serving as a catalyst for the aluminum sol, and uniformly mixing to obtain the aluminum sol.
The alumina-silica aerogel composite material is prepared by the method.
The thermal conductivity coefficient of the alumina-silica aerogel composite felt obtained in the embodiment is 0.023 w/(m DEG C), and the dimensional shrinkage rate of the alumina-silica aerogel composite felt processed at 1000 ℃ for 30min is 15%.
Example 4:
during the preparation process, the gel aging process in the step (5) is not included.
In the step (1), the silica sol is obtained by mixing silicon source, ethanol and water according to the molar ratio of 1: 20: 6; the silicon source is methyltrimethoxysilane and dimethyldimethoxysilane; the gel catalyst is acid catalyst hydrochloric acid, and the pH value of the solution is adjusted to be 4.
The other steps are the same as in example 1.
The alumina-silica aerogel composite material is prepared by the method.
The thermal conductivity coefficient of the alumina-silica aerogel composite felt obtained in the embodiment is 0.022 w/(m.cndot.), and the dimensional shrinkage rate of the alumina-silica aerogel composite felt after being treated at 1000 ℃ for 30min is 13.9%.
Claims (6)
1. A preparation method of an alumina-silica aerogel felt composite material is characterized in that,
the method comprises the following steps:
(a) Preparing a silicon dioxide gel felt: uniformly mixing a silicon source, ethanol and water to obtain silicon dioxide sol, sequentially adding a gelling catalyst, uniformly stirring, and impregnating the fiber felt with the silicon dioxide sol catalyzed by the gelling catalyst before gelling to prepare a silicon gel felt or impregnating the fiber felt with the silicon dioxide sol and catalyzing gelling by the gelling catalyst to prepare the silicon dioxide gel felt;
(b) Preparing aluminum sol: preparing an aluminum source, a chelating agent, a solvent for the aluminum sol, water and a catalyst for the aluminum sol to obtain the aluminum sol, wherein the molar ratio of the aluminum source to the chelating agent to the solvent for the aluminum sol to the water to the catalyst for the aluminum sol is 1: (0.001 to 0.06): (4 to 32): (0.6 to 4): (0.0001. About.1);
(c) And dipping: dipping the silica gel felt in the step (a) in the aluminum sol and then taking out;
(d) And (3) gelling: standing the silica gel obtained in the step (c) for a gelling reaction to obtain an alumina-silica composite wet gel felt;
(e) And (3) drying: drying the alumina-silica wet gel material obtained in the step (d) to obtain an alumina-silica aerogel felt composite material;
wherein the silica sol in the step (a) is prepared by mixing a silicon source, ethanol, water = 1: 2 to 60: 1 to 30 in a molar ratio; the silicon source is one or more than two of ethyl orthosilicate, methyl orthosilicate, butyl orthosilicate, isopropyl orthosilicate or alkyl alkoxy silane; the alkyl alkoxy silane comprises one or more than two of methyl trimethoxy silane, dimethyl dimethoxy silane, methyl triethoxy silane, dimethyl diethoxy silane, vinyl triethoxy silane, propyl trimethoxy silane or propyl triethoxy silane; the aluminum source is one or the combination of more than two of aluminum isopropoxide, aluminum sec-butoxide and aluminum nitrate;
the gelling catalyst is one or a combination of two of alkaline catalysts such as sodium hydroxide, potassium hydroxide, ammonia water and ammonium fluoride aqueous solution; the pH of the silica sol is adjusted to 6~8 by the gelling catalyst; or the gelling catalyst is an acidic catalyst, the pH of the solution is regulated to 2~6, and the acidic catalyst is one or the combination of more than two of sulfuric acid, hydrochloric acid, hydrofluoric acid, oxalic acid, acetic acid or benzenesulfonic acid.
2. The method of preparing an alumina-silica aerogel blanket composite of claim 1, wherein:
the chelating agent is one of acetylacetone and ethyl acetoacetate; the solvent for the aluminum sol is one or a combination of more than two of ethanol, isopropanol and n-butanol; the catalyst for the aluminum sol is one or a combination of more than two of the group consisting of sodium hydroxide, potassium hydroxide, ammonia water and ammonium fluoride.
3. The method of preparing an alumina-silica aerogel blanket composite of claim 1, wherein:
the preparation of the aluminum sol is carried out by adopting the following method: firstly, uniformly mixing an aluminum source and the chelating agent, then adding the solvent for the aluminum sol and uniformly mixing, then adding the water and the catalyst for the aluminum sol and uniformly mixing to obtain the aluminum sol.
4. The method of preparing an alumina-silica aerogel blanket composite of claim 1, wherein:
the soaking time in the step (c) is 8 to 48h.
5. The method of preparing an alumina-silica aerogel blanket composite of claim 1, wherein:
and (d) after the gelation, further comprising an aging process, specifically, carrying out aging treatment on the alumina-silica composite wet gel for 8 to 24h at room temperature or at the temperature of 30 to 60 ℃ by heating.
6. An alumina-silica aerogel blanket composite obtained by the production method according to any one of claims 1 to 5.
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