阅读说明：本技术 氧化铝/气凝胶复合多孔材料及其制备方法 (Alumina/aerogel composite porous material and preparation method thereof ) 是由 刘珊 贾慧娇 毛智勇 王达健 于 2020-05-12 设计创作，主要内容包括：本发明公开了一种氧化铝/气凝胶复合多孔材料及其制备方法,氧化铝/气凝胶复合多孔材料的制备方法包括：将拟薄水铝石和氟化铝混合后球磨,烘干,得到混合粉体,将混合粉体与聚乙烯醇水溶液混合,得到造粒粉料,将造粒粉料置于模具中压制成型,脱模后获得坯体,将坯体烧结,再升温至1000～1500℃烧结1～3h,得到基体；对基体采用浸渍步骤操作1～5次,得到氧化铝/气凝胶复合多孔材料,本发明采用压片成型法制备多孔片状互锁结构氧化铝材料并以溶胶浸渍法将铝硅复合气凝胶引入多孔片状互锁结构氧化铝材料中,材料制备过程中,使用设备简单安全,原料成本低廉,制备工艺稳定,操作步骤简单。所获得成品孔隙率最高可达到60～70％,比表面积可达到10～40m～(2)/g。(The invention discloses an alumina/aerogel composite porous material and a preparation method thereof, wherein the preparation method of the alumina/aerogel composite porous material comprises the following steps: mixing pseudo-boehmite and aluminum fluoride, ball-milling, drying to obtain mixed powder, mixing the mixed powder with a polyvinyl alcohol aqueous solution to obtain granulated powder, placing the granulated powder in a mold for press molding, demolding to obtain a blank, sintering the blank, and heating to 1000-1500 ℃ for sintering for 1-3 hours to obtain a matrix; the method comprises the steps of dipping a matrix for 1-5 times to obtain the alumina/aerogel composite porous material, preparing the porous flaky interlocking structure alumina material by a tabletting forming method, and introducing the aluminum-silicon composite aerogel into the porous flaky interlocking structure alumina material by a sol dipping methodIn the porous sheet interlocking structure aluminum oxide material, in the material preparation process, the used equipment is simple and safe, the raw material cost is low, the preparation process is stable, and the operation steps are simple. The porosity of the obtained finished product can reach 60-70% at most, and the specific surface area can reach 10-40 m 2 /g。)

1. An alumina/aerogel composite porous material, comprising: the aerogel material comprises a substrate and a nano-porous aerogel material covering the surface of the substrate, wherein the substrate is formed by interlocking flaky alumina.

2. The alumina/aerogel composite porous material according to claim 1, wherein the aluminum oxide materials interlocked into a sheet shape are inserted into each other, and a plurality of adjacent sheet-shaped aluminum oxide materials enclose a pore structure after the insertion, and the nano-porous aerogel material is filled in the pore structure.

3. The method for preparing the alumina/aerogel composite porous material according to claim 1 or 2, comprising the steps of:

1) mixing pseudo-boehmite and aluminum fluoride, ball-milling, drying to obtain mixed powder, mixing the mixed powder with a polyvinyl alcohol aqueous solution serving as a binder to obtain granulated powder, placing the granulated powder in a mold, performing compression molding, demolding to obtain a blank body, sintering the blank body at 550-650 ℃ for 1-2 h for removing glue, and heating to 1000-1500 ℃ for sintering for 1-3 h to obtain a matrix;

2) and (3) carrying out dipping step operation on the matrix for 1-5 times to obtain the alumina/aerogel composite porous material, wherein the dipping step operation is as follows: immersing the substrate into a mixture of sol and a gel accelerator, wherein the mixture of sol and gel accelerator submerges the substrate, adding absolute ethyl alcohol until the sol forms gel, standing and aging for 24-48 h, removing the absolute ethyl alcohol, adding a mixed solution of n-hexane and hexamethyldisilazane, replacing the mixed solution of n-hexane and hexamethyldisilazane every 10-24 h, drying the substrate in the gel after replacing for 3-5 times, and taking out the substrate, wherein the sol is aluminum sol, silica sol or aluminum-silicon composite sol.

4. The preparation method according to claim 3, wherein in the step 1), the ratio of the pseudoboehmite to the aluminum fluoride is (10-20) in parts by mass: 1;

in the step 1), the drying temperature is 50-80 ℃, and the drying time is 12-36 h;

in the step 1), the dried powder is sieved, and the mesh number of a sieve used for sieving is 40-50 meshes.

5. The production method according to claim 3, wherein in the step 1), the concentration of polyvinyl alcohol in the aqueous polyvinyl alcohol solution is 5 wt%;

in the step 1), the ratio of the mixed powder to the polyvinyl alcohol aqueous solution is (10-15) by mass: 1;

in the step 1), the pressure of the compression molding in the mold is 4-10 Mpa;

in the step 1), the ball milling uses absolute ethyl alcohol as a wet ball milling solvent, the rotation speed of the ball milling is 100-400 r/min, and the ball milling time is 1-6 h.

6. The preparation method according to claim 3, wherein in the step 2), the ratio of the sol to the gel accelerator is (2-13) in parts by mass: 1, the gel accelerator is propylene oxide;

in the step 2), the time for forming gel by the sol is 10-60 min;

in the step 2), the ratio of the normal hexane to the hexamethyldisilazane is (6-10) to (1-4) in parts by volume.

7. The method according to claim 3, wherein in the step 2), the method for replacing the mixed solution of n-hexane and hexamethyldisilazane at a time is as follows: removing the original mixed solution of the normal hexane and the hexamethyldisilazane, and adding a new mixed solution of the normal hexane and the hexamethyldisilazane.

8. The method according to claim 3, wherein in the step 2), the drying is: drying at room temperature of 20-25 ℃ for 12-48 h, and then drying at 40-70 ℃ for 24-72 h.

9. The preparation method according to claim 3, wherein in the step 2), the gel accelerator is added and then stirred for 1-2 min;

in the step 2), the substrate is immersed into the mixture of the sol and the gel accelerator under a vacuum environment.

10. The method according to claim 3, wherein the aluminum-silicon composite sol is prepared in step 2) by: uniformly mixing aluminum sol and silica sol to obtain the aluminum-silicon composite sol;

according to the weight parts of the materials, the ratio of aluminum to silicon in the aluminum-silicon composite sol is 1 (0.1-10), and the aluminum sol and the silicon sol are mixed and stirred for 10-24 hours until the mixture is uniform;

in the step 2), the method for preparing the aluminum sol comprises the following steps: uniformly mixing an aluminum source, first ethanol and first deionized water to obtain an aluminum sol, wherein the ratio of the aluminum source to the first ethanol to the first deionized water is (15-17) to (9-11) in parts by mass;

the stirring speed for uniformly mixing the aluminum source, the first ethanol and the first deionized water is 300-500 r/min, and the stirring time is 2-4 h;

in the step 2), the method for preparing the silica sol comprises: mixing a silicon source, second ethanol and second deionized water, adjusting the pH to 3-4, and uniformly stirring to obtain silica sol, wherein the ratio of the silicon source to the second ethanol to the second deionized water is (2-8) to (10-16) in parts by weight;

after the pH is adjusted to 3-4, stirring is uniformly carried out at a rotating speed of 200-600 r/min for 1-3 h, and nitric acid is used for adjusting the pH.

Technical Field

The invention belongs to the technical field of porous ceramic materials, and particularly relates to an alumina/aerogel composite porous material and a preparation method thereof.

Background

The alumina material is a common ceramic material and has good chemical stability, high temperature resistance, corrosion resistance and stable mechanical properties. The porous alumina ceramic material mostly uses isotropic alumina grains as a structural unit, but in recent years, porous alumina ceramic materials formed by using alumina wafers as the structural unit and mutually crossing the wafers appear, and the alumina ceramic material has the excellent performance of common alumina materials, and also has a special sheet-shaped two-dimensional structure which has strong adhesive force, moderate surface activity and excellent light reflection capability and shielding capability, so the sheet-shaped porous alumina material has potential application in heat insulation materials, high-temperature catalyst carrier materials, refractory materials and the like.

The porous skeleton structure of the alumina flake-like interlocking structure has good high-temperature resistance and mechanical strength, but the specific surface area is expected to be increased.

Disclosure of Invention

In view of the shortcomings of the prior art, the present invention aims to provide an alumina/aerogel composite porous material.

The invention also aims to provide the preparation method of the alumina/aerogel composite porous material, the preparation method adopts a tabletting forming method to prepare the matrix, and adopts a sol dipping method to introduce the nano porous aerogel material into the matrix, so that the used raw materials are low in cost, the instruments and equipment are simple and safe, the preparation process is stable and controllable, and the operation process is simpler and more convenient.

The purpose of the invention is realized by the following technical scheme.

An alumina/aerogel composite porous material, comprising: the aerogel material comprises a substrate and a nano-porous aerogel material covering the surface of the substrate, wherein the substrate is formed by interlocking flaky alumina.

In the technical scheme, the sheet-shaped aluminum oxide materials which are interlocked with each other are mutually inserted and connected, a pore structure is defined by a plurality of adjacent sheet-shaped aluminum oxide materials after the sheet-shaped aluminum oxide materials are inserted and connected, and the nano-porous aerogel material is filled in the pore structure.

A preparation method of an alumina/aerogel composite porous material comprises the following steps:

1) mixing pseudo-boehmite and aluminum fluoride, ball-milling, drying to obtain mixed powder, mixing the mixed powder with a polyvinyl alcohol aqueous solution serving as a binder to obtain granulated powder, placing the granulated powder in a mold, performing compression molding, demolding to obtain a blank body, sintering the blank body at 550-650 ℃ for 1-2 h for removing glue, and heating to 1000-1500 ℃ for sintering for 1-3 h to obtain a matrix;

in the step 1), the ball milling uses absolute ethyl alcohol as a wet ball milling solvent, the rotation speed of the ball milling is 100-400 r/min, and the ball milling time is 1-6 h.

In the step 1), the ratio of the pseudoboehmite to the aluminum fluoride is (10-20) in parts by mass: 1.

in the step 1), the drying temperature is 50-80 ℃, and the drying time is 12-36 h.

In the step 1), the dried powder is sieved, and the mesh number of a sieve used for sieving is 40-50 meshes.

In the step 1), the concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 5 wt%.

In the step 1), the ratio of the mixed powder to the polyvinyl alcohol aqueous solution is (10-15) by mass: 1.

in the step 1), the pressure of the compression molding in the mold is 4-10 Mpa.

2) And (3) carrying out dipping step operation on the matrix for 1-5 times to obtain the alumina/aerogel composite porous material, wherein the dipping step operation is as follows: immersing the substrate into a mixture of sol and a gel accelerator, wherein the mixture of sol and gel accelerator submerges the substrate, adding absolute ethyl alcohol until the sol forms gel, standing and aging for 24-48 h, removing the absolute ethyl alcohol, adding a mixed solution of n-hexane and hexamethyldisilazane, replacing the mixed solution of n-hexane and hexamethyldisilazane every 10-24 h, drying the substrate in the gel after replacing for 3-5 times, and taking out the substrate, wherein the sol is aluminum sol, silica sol or aluminum-silicon composite sol.

In the step 2), the matrix is subjected to the dipping step for 1-3 times.

In the step 2), the method for preparing the aluminum-silicon composite sol comprises the following steps: and uniformly mixing the aluminum sol and the silica sol to obtain the aluminum-silicon composite sol.

In the technical scheme, the ratio of aluminum to silicon in the aluminum-silicon composite sol is 1 (0.1-10) by weight, and the aluminum sol and the silicon sol are mixed and stirred for 10-24 hours until the mixture is uniform.

In the step 2), the ratio of the sol to the gel accelerator is (2-13) by mass: 1, the gel accelerator is propylene oxide.

In the step 2), the time for forming the sol into gel is 10-60 min.

In the step 2), the ratio of the normal hexane to the hexamethyldisilazane is (6-10) to (1-4) in parts by volume.

In the step 2), the method for replacing the mixed solution of n-hexane and hexamethyldisilazane at each time comprises the following steps: removing the original mixed solution of the normal hexane and the hexamethyldisilazane, and adding a new mixed solution of the normal hexane and the hexamethyldisilazane.

In the step 2), the drying is: drying at room temperature of 20-25 ℃ for 12-48 h, and then drying at 40-70 ℃ for 24-72 h.

In the step 2), the gel accelerator is added and then stirred for 1-2 min.

In the step 2), the substrate is immersed into the mixture of the sol and the gel accelerator under a vacuum environment.

In the step 2), the method for preparing the aluminum sol comprises the following steps: uniformly mixing an aluminum source, first ethanol and first deionized water to obtain aluminum sol, wherein the mass fraction of the aluminum source, the first ethanol and the first deionized water is 1 (15-17) to (9-11).

In the technical scheme, the stirring speed for uniformly mixing the aluminum source, the first ethanol and the first deionized water is 300-500 r/min, and the stirring time is 2-4 h.

In the step 2), the method for preparing the silica sol comprises: and mixing a silicon source, second ethanol and second deionized water, adjusting the pH to 3-4, and uniformly stirring to obtain silica sol, wherein the ratio of the silicon source to the second ethanol to the second deionized water is (2-8) to (10-16) in parts by mass.

In the technical scheme, after the pH is adjusted to 3-4, the stirring speed for uniformly stirring is 200-600 r/min, the stirring time is 1-3 h, and nitric acid is used for adjusting the pH.

The invention has the beneficial effects that: the porous flaky interlocking structure aluminum oxide material is prepared by a tabletting forming method, and the aluminum-silicon composite aerogel is introduced into the porous flaky interlocking structure aluminum oxide material by a sol-gel impregnation method. The porosity of the obtained finished product can reach 60-70% at most, and the specific surface area can reach 10-40 m²/g。

Drawings

FIG. 1 is an X-ray diffraction pattern of the substrate prepared in example 1;

FIG. 2 is a scanning electron microscope micrograph of a substrate prepared according to example 1;

FIG. 3 is a microscopic morphology image of a scanning electron microscope of the alumina/aerogel composite porous material prepared in example 1;

FIG. 4 is a scanning electron microscope microscopic morphology of the alumina/aerogel composite porous material prepared in example 2.

Detailed Description

The technical scheme of the invention is further explained by combining specific examples.

Pseudoboehmite was purchased from catatonia, middle alumen, Shandong aluminum industries, aluminum fluoride, polyvinyl alcohol, anhydrous aluminum chloride, ethyl orthosilicate, propylene oxide, n-hexane, and hexamethyldisilazane were all purchased from Aladdin.

The model of the XRD testing instrument is as follows: ARL Equinox 3000, France

The model of the SEM test instrument is as follows: FEI Verios 460L, Germany

The model of the BET test instrument is: BELSORP-max, Japan

The method for replacing the mixed solution of n-hexane and hexamethyldisilazane in each time in the following examples was: removing the original mixed solution of the normal hexane and the hexamethyldisilazane, and adding a new mixed solution of the normal hexane and the hexamethyldisilazane.

Example 1

A preparation method of an alumina/aerogel composite porous material comprises the following steps:

1) mixing pseudo-boehmite and aluminum fluoride, performing wet ball milling in a ball mill, and taking absolute ethyl alcohol as a wet ball milling solvent (ball milling by using alumina balls), wherein the ratio of the pseudo-boehmite to the aluminum fluoride is 10: 1, the rotation speed of ball milling is 250r/min, the ball milling time is 3h, the ball milled powder is dried in an oven at 60 ℃ for 24h, a screen with 40 meshes is adopted for sieving to obtain mixed powder, the mixed powder is mixed with a polyvinyl alcohol aqueous solution serving as a binder to obtain granulated powder, and the concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 5 wt%. Placing the granulated powder into a mould, performing compression molding under the pressure of 6Mpa, demolding to obtain a blank, sintering the blank in a muffle furnace at the temperature of 600 ℃ for 1h for removing glue, and then heating to 1500 ℃ for sintering for 2h to obtain a matrix, wherein the ratio of the mixed powder to the polyvinyl alcohol aqueous solution is 12.5: 1.

2) the matrix is subjected to one-time operation of dipping steps to obtain the alumina/aerogel composite porous material, wherein the operation of each dipping step is as follows: preparing propylene oxide as gel promoter, mixing the sol and gel promoter, stirring for 2min to uniformity, and immersing the substrate in the mixture of sol and gel promoter (mixture volume: 27.69 cm) in a vacuum tank under vacuum³) And the mixture of sol and gel promoter is submerged in the matrix for 50min until the sol forms gel, and thenAdding 25ml of absolute ethanol until the absolute ethanol is not gelled, standing and aging for 24h, pouring out to remove the absolute ethanol, adding 20ml of mixed solution of n-hexane and hexamethyldisilazane, replacing the mixed solution of n-hexane and hexamethyldisilazane every 12h, drying the matrix in the gel at room temperature of 20-25 ℃ for 24h after replacing for 3 times, drying the matrix at 60 ℃ for 48h, and taking out the matrix, wherein the sol is an aluminum-silicon composite sol, the volume part ratio of the n-hexane to the hexamethyldisilazane is 7:3, and the mass part ratio of the sol to the gel accelerator is 10: 1.

in the step 2), the method for preparing the aluminum-silicon composite sol comprises the following steps: adding the aluminum sol into the silica sol under the stirring condition, and stirring for 10 hours until the mixture is uniform to obtain the aluminum-silicon composite sol, wherein the ratio of aluminum to silicon in the aluminum-silicon composite sol is 2:3 according to the parts by weight of the materials.

The method for preparing the aluminum sol comprises the following steps: mixing anhydrous aluminum chloride, first ethanol and first deionized water, and stirring for 4 hours at 480r/min until the mixture is uniform to obtain the aluminum sol, wherein the mass portion ratio of the anhydrous aluminum chloride to the first ethanol to the first deionized water is 1:16: 10.

The method for preparing the silica sol comprises the following steps: and mixing tetraethoxysilane, second ethanol and second deionized water, stirring uniformly, adjusting the pH to 3.4 by using nitric acid with the concentration of 69 wt%, and stirring uniformly for 3 hours at the speed of 400r/min (the nitric acid is used as a catalyst) to obtain the silica sol, wherein the ratio of the tetraethoxysilane to the second ethanol to the second deionized water is 1:4:12 in parts by weight.

The X-ray diffraction pattern of the matrix obtained in step 1) of example 1 is shown in FIG. 1, and it can be seen that the main crystal phases in the matrix are alumina (corundum type) phases.

Fig. 2 shows the microscopic morphology of the substrate obtained in step 1) in example 1 under a scanning electron microscope, and it can be seen that the substrate is formed by interlocking flaky alumina materials, and the flaky alumina materials interlocked with each other are inserted into each other and a plurality of adjacent flaky alumina materials enclose a pore structure after insertion.

Fig. 3 is a microscopic morphology diagram of a scanning electron microscope of the alumina/aerogel composite porous material prepared by the present embodiment, after the alumina-silica mixed sol is impregnated, the matrix surface is covered and the porous structure is filled with the nano-porous aerogel material.

Example 1 the specific surface area of the prepared alumina/aerogel composite porous material reaches 10.561m²G, bulk density 1.48g/cm³The porosity is 68.3 percent, the porosity is reduced by 3 to 4 percent compared with the matrix prepared in the step 1), and the bulk density is increased by 0.06g/cm³Specific surface area is 2.238m²Increase of/g to 10.561m²(ii) in terms of/g. Therefore, the aerogel is attached to the flaky structure of the alumina, and the flaky structure of the alumina provides a carrier for the application of the performance of the aerogel with high specific surface area in the fields of optics, catalysts and the like.

Example 2

A preparation method of an alumina/aerogel composite porous material comprises the following steps:

1) mixing pseudo-boehmite and aluminum fluoride, performing wet ball milling in a ball mill, and taking absolute ethyl alcohol as a wet ball milling solvent (ball milling by using alumina balls), wherein the ratio of the pseudo-boehmite to the aluminum fluoride is 10: 1, ball milling at the rotation speed of 200r/min for 4h, drying in an oven at 60 ℃ for 24h after ball milling, sieving by using a sieve with the mesh number of 40 to obtain mixed powder, and mixing the mixed powder with a polyvinyl alcohol aqueous solution serving as a binder to obtain granulated powder, wherein the concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 5 wt%. Placing the granulated powder into a mould, performing compression molding under the pressure of 6Mpa, demolding to obtain a blank, sintering the blank in a muffle furnace at the temperature of 600 ℃ for 1h for removing glue, and then heating to 1500 ℃ for sintering for 2h to obtain a matrix, wherein the ratio of the mixed powder to the polyvinyl alcohol aqueous solution is 12.5: 1.

2) the matrix is subjected to 2 times of dipping steps to obtain the alumina/aerogel composite porous material, wherein each dipping step comprises the following operations: preparing propylene oxide as gel promoter, mixing the sol and gel promoter, stirring for 3min to uniformity, and immersing the substrate in the mixture of sol and gel promoter (mixture volume: 27.69 cm) in a vacuum tank under vacuum condition³) And the mixture of sol and gel promoter is submerged in the matrix for 45min to form solForming gel, adding 25ml of absolute ethanol until the gel is submerged in a matrix, standing and aging for 24h, pouring out to remove the absolute ethanol, adding 20ml of mixed solution of n-hexane and hexamethyldisilazane, replacing the mixed solution of n-hexane and hexamethyldisilazane every 12h, drying the matrix in the gel at room temperature of 20-25 ℃ for 24h after 3 times of replacement, drying at 60 ℃ for 48h, and taking out the matrix, wherein the sol is aluminum-silicon composite sol, the ratio of the n-hexane to the hexamethyldisilazane is 7:3 in parts by volume, and the ratio of the sol to the gel accelerator is 10 in parts by mass: 1.

in the step 2), the method for preparing the aluminum-silicon composite sol comprises the following steps: adding the aluminum sol into the silica sol under the stirring condition, and stirring for 10 hours until the mixture is uniform to obtain the aluminum-silicon composite sol, wherein the ratio of aluminum to silicon in the aluminum-silicon composite sol is 2:3 according to the parts by weight of the materials.

The method for preparing the aluminum sol comprises the following steps: mixing anhydrous aluminum chloride, first ethanol and first deionized water, and stirring for 4 hours at 500r/min until the mixture is uniform to obtain the aluminum sol, wherein the mass portion ratio of the anhydrous aluminum chloride to the first ethanol to the first deionized water is 1:16: 10.

The method for preparing the silica sol comprises the following steps: and mixing tetraethoxysilane, second ethanol and second deionized water, stirring uniformly, adjusting the pH to 3.4 by using nitric acid with the concentration of 69 wt%, and stirring uniformly for 3 hours at the speed of 400r/min (the nitric acid is used as a catalyst) to obtain the silica sol, wherein the ratio of the tetraethoxysilane to the second ethanol to the second deionized water is 1:4:12 in parts by weight.

Example 2 the specific surface area of the prepared alumina/aerogel composite porous material reaches 22.902m²G, bulk density 1.54g/cm³The porosity is 65.3%, and the filling degree of the nano-porous aerogel material in the pore structure is improved due to the secondary impregnation treatment, so that compared with the embodiment 1, the porosity of the material is reduced, the specific surface area is increased, and the use requirements such as catalytic load are met.

Fig. 4 is a scanning electron microscope microscopic morphology image of the alumina/aerogel composite porous material prepared by the present embodiment, and it can be seen that the alumina flake structure after 2 times of impregnation and compounding is further filled, and the aluminum-silicon aerogel attached on the alumina flake structure is relatively uniform. This confirms that such compounding is feasible and that compounding conditions and times can be adjusted according to material requirements.

Example 3

A preparation method of an alumina/aerogel composite porous material comprises the following steps:

1) mixing pseudo-boehmite and aluminum fluoride, performing wet ball milling in a ball mill, and taking absolute ethyl alcohol as a wet ball milling solvent (ball milling by using alumina balls), wherein the ratio of the pseudo-boehmite to the aluminum fluoride is 10: 1, ball milling at the rotation speed of 200r/min for 4h, drying in an oven at 60 ℃ for 24h after ball milling, sieving by using a sieve with 40 meshes to obtain mixed powder, and mixing the mixed powder with a polyvinyl alcohol aqueous solution serving as a binder to obtain granulated powder, wherein the concentration of polyvinyl alcohol in the polyvinyl alcohol aqueous solution is 5%. Placing the granulated powder into a mould, performing compression molding under the pressure of 6Mpa, demolding to obtain a blank, sintering the blank in a muffle furnace at the temperature of 600 ℃ for 1h for removing glue, and then heating to 1500 ℃ for sintering for 2h to obtain a matrix, wherein the ratio of the mixed powder to the polyvinyl alcohol aqueous solution is 12.5: 1.

2) the matrix is subjected to three times of dipping steps to obtain the alumina/aerogel composite porous material, wherein each dipping step comprises the following operations: preparing propylene oxide as gel promoter, mixing the sol and gel promoter, stirring for 3min to uniformity, and immersing the substrate in the mixture of sol and gel promoter (mixture volume: 27.69 cm) in a vacuum tank under vacuum condition³) And allowing a mixture of the sol and the gel accelerator to submerge a substrate, allowing the sol to form a gel within 45min, adding 25ml of absolute ethyl alcohol until the sol is submerged, standing and aging for 24h, pouring out to remove the absolute ethyl alcohol, adding 20ml of a mixed solution of n-hexane and hexamethyldisilazane, replacing the mixed solution of n-hexane and hexamethyldisilazane every 12h, drying the substrate in the gel at room temperature of 20-25 ℃ for 24h after 3 times of replacement, drying at 60 ℃ for 48h, and taking out the substrate, wherein the sol is an aluminum-silicon composite sol, and the n-hexane and hexamethyldisilazane are counted in parts by volumeThe ratio of (A) to (B) is 7:3, and the ratio of the sol to the gel promoter is 10: 1.

in the step 2), the method for preparing the aluminum-silicon composite sol comprises the following steps: adding the aluminum sol into the silica sol under the stirring condition, and stirring for 10 hours until the mixture is uniform to obtain the aluminum-silicon composite sol, wherein the ratio of aluminum to silicon in the aluminum-silicon composite sol is 2:3 according to the parts by weight of the materials.

The method for preparing the aluminum sol comprises the following steps: mixing anhydrous aluminum chloride, first ethanol and first deionized water, and stirring for 3 hours at 500r/min until the mixture is uniform to obtain the aluminum sol, wherein the mass portion ratio of the anhydrous aluminum chloride to the first ethanol to the first deionized water is 1:16: 10.

The method for preparing the silica sol comprises the following steps: and mixing tetraethoxysilane, second ethanol and second deionized water, stirring uniformly, adjusting the pH to 3.4 by using nitric acid with the concentration of 69 wt%, and stirring uniformly for 3 hours at a speed of 420r/min (the nitric acid is used as a catalyst) to obtain silica sol, wherein the ratio of tetraethoxysilane to second ethanol to second deionized water is 1:4:12 in parts by weight.

Example 3 the specific surface area of the prepared alumina/aerogel composite porous material reaches 37.711m²(g) bulk density of 1.61g/cm³The porosity is 63.1%, and we see that the specific surface area is obviously increased along with the increase of the impregnation times from the group of data, the increase of the specific surface area is the result of continuous impregnation compounding of the aluminum-silicon aerogel, and the aluminum oxide sheet-shaped structure cross interlocking cavities are filled with the aluminum-silicon aerogel, so that the bulk density of the material is obviously increased, and the porosity is reduced therewith. The porosity of the composite decreased from 68.3% to 63.1%, while the bulk density increased to 1.61g/cm with increasing number of impregnations³The compounding of the two materials is further proved to be effective in improving the density of the materials.

According to the invention, the nano-porous aerogel material is filled in the flaky porous alumina matrix, so that the specific surface area of the material can be increased on the premise of ensuring that the porosity is basically unchanged and meeting the application requirements.

The invention has been described in an illustrative manner, and it is to be understood that any simple variations, modifications or other equivalent changes which can be made by one skilled in the art without departing from the spirit of the invention fall within the scope of the invention.