CN117228677A - Preparation method of double-rare earth enhanced silica block aerogel capable of being stably synthesized - Google Patents

Abstract

The application provides a preparation method of a double-rare earth reinforced silica block aerogel capable of being stably synthesized, which is characterized by comprising the following steps: dissolving rare earth nitrate I and rare earth nitrate II in ethanol respectively, heating at 60 ℃ for reaction for 30min, mixing proportionally to obtain a rare earth mixed solution, slowly dripping an alkaline catalyst into silica sol, uniformly stirring, slowly dripping the obtained rare earth mixed solution into the silica sol, uniformly stirring, standing for aging, and performing supercritical drying to obtain the double rare earth co-doped silica gel. The application improves the use strength and the use temperature of the silicon dioxide aerogel, expands the application of the silicon dioxide aerogel in the high-temperature field, has simple process and high production efficiency, and is beneficial to improving the production efficiency and mass production.

Description

Preparation of a stable synthetic double rare earth reinforced silica bulk aerogel method

Technical field

The invention belongs to the technical field of aerogel preparation, and specifically relates to a preparation method that can stably synthesize dual rare earth reinforced silica bulk aerogels.

Background technique

With the continuous upgrading and development of my country's advanced aircraft and thermal protection systems, more severe challenges have been posed to existing thermal protection and insulation materials. Commonly used thermal insulation materials in the aerospace field are mainly phenolic foam composite materials, ceramic foam composite materials and new aerogel materials.

Aerogel is a material with a nanoscale porous structure formed by the mutual aggregation of nanoparticles. Its high porosity reduces the heat conduction of solid phase materials. The nanoporous structure inhibits the convective heat transfer of the gas in it, and the multiple pore walls reduce the heat transfer. radiation heat transfer. At present, medium and high temperature aerogel materials, such as alumina aerogel and zirconia aerogel, are still in the laboratory stage. The high-temperature stability of the materials is extremely poor and the application effects are not ideal. Among them, silica aerogel is currently the most widely used. widely.

Traditional silica aerogel materials have the excellent characteristics of high specific surface area and low density. However, pure silica aerogel has extremely poor strength, is prone to cracking, and is prone to sintering and structural collapse at high temperatures. Its long-term stable use range It is limited to below 650℃, and the maximum operating temperature does not exceed 900℃, which greatly restricts the application range of silica airgel materials.

Although the temperature resistance of silica aerogels prepared by doping other elements has been improved to a certain extent, its operating temperature is still lower than 1100°C and cannot be used in high temperature environments. Existing rare earth silicate ceramic materials have a temperature resistance of over 1600°C. However, the density of ceramic materials is relatively high, the porosity is low, the pore diameter is relatively large, and the thermal conductivity is relatively high, and the thermal insulation performance decreases as the temperature increases. drop, not suitable for high temperature insulation. Studies have shown that rare earth elements can inhibit the high-temperature sintering of silica to varying degrees, improve the high-temperature resistance of silica, and further maintain the spatial network structure of the aerogel while maintaining its low density. Therefore, rare earth doped Heterosilica aerogels have great application prospects in thermal insulation.

Contents of the invention

In order to solve the problems in the prior art, the present invention provides a preparation method that can stably synthesize dual rare earth-enhanced silica bulk aerogels, and adopts a sol-gel method to obtain dual rare earth co-doped silica gels. It improves the use intensity and temperature of silica aerogel, expands its application in high-temperature fields, has a simple process and high production efficiency, which is conducive to improving production efficiency and large-scale production.

The present invention solves its technical problems by adopting the following technical solutions:

The object of the present invention is to provide a preparation method that can stably synthesize dual rare earth reinforced silica bulk aerogels, which is characterized in that it includes the following steps:

Dissolve rare earth nitrate I and rare earth nitrate II in ethanol, heat and react at 60°C for 30 minutes, and then mix in proportion to obtain a rare earth mixed solution. Take an alkaline catalyst and slowly drip it into the silica sol. Stir evenly and then mix the rare earth mixed solution. The mixed solution is slowly dropped into the silica sol, stirred evenly, and then left to stand at room temperature to obtain a double rare earth co-doped silica gel; the obtained double rare earth co-doped silica gel is left to stand for aging and supercritical drying to obtain Double rare earth co-doped silica airgel block; the molar ratio of the rare earth nitrate I and the rare earth nitrate II is 1:1.

Further, the rare earth nitrate I/rare earth nitrate II is selected from the group consisting of ytterbium nitrate, yttrium nitrate, cerium nitrate, lanthanum nitrate or scandium nitrate.

Further, the rare earth nitrate I is yttrium nitrate, and the rare earth nitrate II is ytterbium nitrate.

Further, the mass ratio of the rare earth nitrate I/rare earth nitrate II to ethanol is 1:9-10.

Further, the alkaline catalyst is ammonia water.

Further, the static aging is to stir evenly at room temperature or 50-60°C and then allow to stand and age at room temperature for 24-48 hours.

Further, the preparation method of the silica sol is: sequentially mix ethyl orthosilicate, ethanol and water in molar ratios, add an acidic catalyst, mechanically stir for 60 to 120 minutes, seal and let stand, and obtain after full hydrolysis reaction Silica sol.

Further, the molar ratio of ethyl orthosilicate, ethanol and water may be 1: (10-20): (4-5).

Further, the acidic catalyst uses hydrochloric acid with a mass fraction of 0.05 wt%, and the molar ratio of the ethyl orthosilicate to hydrochloric acid is 1:10 ^-4 .

Further, during the preparation process of the silica sol, it is sealed and left to stand at room temperature for 24 to 48 hours.

Further, the molar ratio of ethyl orthosilicate to rare earth nitrate I/rare earth nitrate II is 1:0.05-0.5.

Further, the molar ratio of the ethyl orthosilicate to the alkaline catalyst is 1:0.05-0.25, and the alkaline catalyst is ammonia water.

Further, the supercritical drying medium is ethanol, the drying temperature is 260-270°C, the holding time is 2-4h, and the supercritical pressure is 8-12MPa.

Further, a preparation method for stably synthesizing dual rare earth reinforced silica bulk aerogels includes the following steps:

Preparation of silica sol: Mix ethyl orthosilicate, ethanol and water in molar ratio in sequence, add acidic catalyst, mechanically stir for 60 to 120 minutes, seal and let stand, and obtain silica sol after full hydrolysis reaction;

Preparation of rare earth solution: Dissolve rare earth nitrate I and rare earth nitrate II powders in ethanol respectively, heat at 60°C for 30 minutes to fully react, then cool to room temperature to obtain rare earth solution I and rare earth solution II;

Preparation of gel: Slowly drop the alkaline catalyst into the obtained silica sol, stir for 1 minute, mix a certain amount of rare earth solution I and rare earth solution II to obtain a rare earth mixed solution, stir evenly, and slowly drop the mixed solution. Add the alkaline catalyst to the silica sol, stir evenly at room temperature or 50-60°C, and then let it stand at room temperature to obtain double rare earth co-doped silica gel;

Drying: The double rare earth co-doped silica gel is allowed to stand for aging and then supercritically dried to obtain a double rare earth co-doped silica airgel block.

The present invention uses ethyl orthosilicate as the silicon source, rare earth nitrate as the co-doping raw material, ethanol as the general solvent, acid and alkali as the catalyst, and adopts the sol-gel method to obtain double rare earth co-doped silica gel; After standing and aging, using ethanol as the medium and supercritical drying, the double rare earth co-doped silica airgel block was obtained. By incorporating double rare earth elements into the silica aerogel, the present invention helps to increase the high-temperature stability of the silica aerogel, which not only improves the use strength and temperature, but also results in a low density and large specific surface area of the aerogel. ; The method has simple process, high production efficiency, low equipment requirements, and is conducive to large-scale production. It is expected to become a thermal insulation material that can be applied to high-temperature fields and has extremely low thermal conductivity.

Compared with the existing technology, the beneficial technical effects of the present invention are:

Through physical stirring and heating treatment, the present invention ensures the uniform dispersion of rare earth elements, ensures the uniformity of the product, and avoids the problem of uneven distribution of rare earth elements in the silica matrix due to phase separation. By ensuring the uniformity of the solvent and adjusting the proportion and priority of the alkaline catalyst, the gelation time can be controlled and the time required for gelation can be greatly shortened. By controlling and adjusting the proportion of rare earth elements and the molding process, the density and microstructure of the airgel can be controlled, thereby controlling the thermal conductivity of the airgel. The process of the present invention is simple, the cost is low, and the reaction conditions are controllable. By controlling the ratio of ethanol and rare earth elements, the dual rare earth co-doped silica airgel bulk material prepared has a complete bulk structure and can be adapted to mold preparation. Requirements, by controlling the appropriate enlargement of the mold, the availability of special-shaped products in the field of heat insulation can be fully met.

The above description is only an overview of the technical solution of the present invention. In order to have a clearer understanding of the technical means of the present invention, it can be implemented according to the content of the description, and in order to make the above content of the present invention and its purpose, features and advantages more obvious and easy to understand. It should be understood that the specific embodiments of the present invention are listed below.

Description of drawings

Figure 1 is a macroscopic view of the dual rare earth co-doped silica gel obtained in Example 1 of a method for stably synthesizing dual rare earth enhanced silica bulk aerogels according to the present invention.

Figure 2 is a macroscopic view of the double rare earth co-doped silica aerogel obtained in Example 1 of the preparation method of the present invention that can stably synthesize double rare earth enhanced silica bulk aerogel.

Figure 3 is a microscopic morphology diagram of the dual rare earth co-doped silica aerogel obtained in Example 1 of a method for stably synthesizing dual rare earth reinforced silica bulk aerogels according to the present invention.

Figure 4 shows the silica aerogel obtained in Example 4 and Comparative Example 1 in a preparation method of the present invention that can stably synthesize dual rare earth reinforced silica bulk aerogels and is insulated for 5 minutes at normal temperature and 1000°C. Comparison picture after.

Figure 5 is a macroscopic view of the silica aerogels obtained in Comparative Example 2, Comparative Example 3, and Comparative Example 4 in a method for stably synthesizing dual rare earth reinforced silica bulk aerogels according to the present invention.

Detailed ways

The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the following examples are only illustrative and explain the present invention and should not be construed as limiting the scope of the present invention. All technologies implemented based on the above contents of the present invention are covered by the scope of protection intended by the present invention.

In addition, unless otherwise specified, various raw materials, reagents, instruments and equipment used in the present invention can be purchased from the market or prepared by existing methods.

Example 1:

A preparation method for stably synthesizing dual rare earth reinforced silica bulk aerogels, including the following steps:

(1) Mix tetraethyl orthosilicate, absolute ethanol, and deionized water at a molar ratio of 1:10:4 at room temperature and stir evenly for 15 minutes, then add mass dropwise through a constant pressure funnel at a rate of 6 s/drop. Dilute hydrochloric acid ethanol with a fraction of 0.05wt%, stir for 120 minutes, seal and let stand at room temperature for 24 hours, to obtain silica sol.

(2) Dissolve yttrium nitrate (Y(NO ₃ ) ₃ ·4H ₂ O) and ytterbium nitrate (Yb(NO ₃ ) ₃ ·5H ₂ O) powder into ethanol in a mass ratio of 1:9, 60 After heating at ℃ for 30 minutes to fully react, and then cooling to room temperature, light white Y(NO ₃ ) ₃ and milky white Yb(NO ₃ ) ₃ rare earth solutions were obtained.

(3) Drop ammonia ethanol dilution into the silica sol obtained in step (1) (the molar ratio of ethyl orthosilicate to ammonia is 1:0.05) and stir for 1 minute to obtain the material after adding the alkaline catalyst.

(4) According to the molar ratio of tetraethyl orthosilicate to Y or Yb being 1:0.05, add the Y(NO ₃ ) ₃ solution and Yb(NO ₃ ) ₃ solution obtained in step (2) to the obtained solution in step (3) respectively. Materials, stir for 1 minute, slowly drop the rare earth mixed solution into the silica sol, stir for 5 minutes, and stir evenly at room temperature to obtain a composite sol solution. Pour the obtained composite sol solution into a mold and let it stand at 25°C for 2 hours to obtain Double rare earth co-doped silica gel, the macroscopic picture of double rare earth co-doped silica gel is shown in Figure 1.

(5) Put the above double rare earth co-doped silica gel at 25°C, let it stand for aging for 24 hours, and then put it into a high-pressure reactor for supercritical drying. Use ethanol as the medium for supercritical drying, and the ethanol pressure is controlled at 8～10MPa, control the temperature at 270℃, and the supercritical drying time is 2h, to obtain a massive double rare earth co-doped silica aerogel.

The basic properties of the double rare earth co-doped silica aerogel obtained in this example are shown in Table 1.

Table 1 Basic properties of aerogels

density 0.19g/cm ³ Specific surface area 875.84m ² /g average pore size 12.93nm

Example 2:

A preparation method for stably synthesizing dual rare earth reinforced silica bulk aerogels, including the following steps:

(1) Mix tetraethyl orthosilicate, absolute ethanol, and deionized water at a molar ratio of 1:20:5 at room temperature and stir evenly for 15 minutes, then add mass dropwise through a constant pressure funnel at a rate of 6 s/drop. Dilute hydrochloric acid ethanol with a fraction of 0.05wt%, stir for 120 minutes, seal and let stand at room temperature for 24 hours, to obtain silica sol.

(2) Dissolve Y(NO ₃ ) ₃ ·4H ₂ O and Yb(NO ₃ ) ₃ ·5H ₂ O powders in ethanol at a mass ratio of 1:9, heat at 60°C for 30 minutes to fully react, and then cool After reaching room temperature, light white Y(NO ₃ ) ₃ and milky white Yb(NO ₃ ) ₃ rare earth solutions were obtained.

(3) Drop ammonia ethanol dilution into the silica sol obtained in step (1) (the molar ratio of ethyl orthosilicate to ammonia is 1:0.25) and stir for 1 minute to obtain the material after adding the alkaline catalyst.

(4) According to the molar ratio of tetraethyl orthosilicate to Y or Yb being 1:0.125, add the Y(NO ₃ ) ₃ solution and Yb(NO ₃ ) ₃ solution obtained in step (2) to the obtained solution in step (3) respectively. Materials, stir for 1 minute, slowly drop the mixed solution into the silica sol, stir for 5 minutes, stir evenly at room temperature to obtain a composite sol solution, pour the obtained composite sol solution into a mold and let it stand at 25°C for 4 hours to obtain a double Rare earth co-doped silica gel.

(5) Put the above double rare earth co-doped silica gel at 25°C, let it stand for aging for 24 hours, and then put it into a high-pressure reactor for supercritical drying. Use ethanol as the medium for supercritical drying, and the ethanol pressure is controlled at 8~10MPa, control the temperature at 270°C, and supercritical drying time at 2h to obtain massive dual rare earth co-doped silica aerogels.

The basic properties of the double rare earth co-doped silica aerogel obtained in this example are shown in Table 2.

Table 2 Basic properties of aerogels

density 0.09g/cm ³ Specific surface area 521.30m ² /g average pore size 13.35nm

Example 3:

A preparation method for stably synthesizing dual rare earth reinforced silica bulk aerogels, including the following steps:

(1) Mix tetraethyl orthosilicate, absolute ethanol, and deionized water at a molar ratio of 1:20:5 at room temperature and stir evenly for 15 minutes, then add mass dropwise through a constant pressure funnel at a rate of 6 s/drop. Dilute hydrochloric acid ethanol with a fraction of 0.05wt%, stir for 120 minutes, seal and let stand at room temperature for 24 hours, to obtain silica sol.

(2) Dissolve Y(NO ₃ ) ₃ ·4H ₂ O and Yb(NO ₃ ) ₃ ·5H ₂ O powders in ethanol at a mass ratio of 1:9, heat at 60°C for 30 minutes to fully react, and then cool After reaching room temperature, light white Y(NO ₃ ) ₃ and milky white Yb(NO ₃ ) ₃ rare earth solutions were obtained.

(3) Drop ammonia ethanol dilution into the silica sol obtained in step (1) (the molar ratio of ethyl orthosilicate to ammonia is 1:0.25) and stir for 1 minute to obtain the material after adding the alkaline catalyst.

(4) According to the molar ratio of tetraethyl orthosilicate to Y or Yb being 1:0.25, add the Y(NO ₃ ) ₃ solution and Yb(NO ₃ ) ₃ solution obtained in step (2) to the obtained solution in step (3) respectively. Materials, stir for 1 minute, slowly drop the mixed solution into the silica sol, stir for 5 minutes, stir evenly at room temperature to obtain a composite sol solution, pour the obtained composite sol solution into a mold and let it stand at 25°C for 8 hours to obtain a double Rare earth co-doped silica gel.

(5) Put the above double rare earth co-doped silica gel at 25°C, let it stand for aging for 24 hours, and then put it into a high-pressure reactor for supercritical drying. Use ethanol as the medium for supercritical drying, and the ethanol pressure is controlled at 8~10MPa, control the temperature at 270°C, and supercritical drying time at 2h to obtain massive dual rare earth co-doped silica aerogels.

The macroscopic picture of the bulk double rare earth co-doped silica aerogel obtained in Example 3 is shown in Figure 2, and the microstructure picture is shown in Figure 3. It can be seen that dual rare earth enhanced silica bulk aerogels with low density and large specific surface area are obtained through dual rare earth co-doping.

The basic properties of the double rare earth co-doped silica aerogel obtained in this example are shown in Table 3.

Table 3 Basic properties of aerogels

Example 4:

A preparation method for stably synthesizing dual rare earth reinforced silica bulk aerogels, including the following steps:

(1) Mix tetraethyl orthosilicate, anhydrous ethanol, and deionized water at a molar ratio of 1:15:4 at room temperature and stir evenly for 15 minutes. Add mass into them through a constant pressure funnel at a rate of 6 s/drop. Dilute hydrochloric acid ethanol with a fraction of 0.05wt%, stir for 120 minutes, seal and let stand at room temperature for 24 hours, to obtain silica sol.

(2) Dissolve Y(NO ₃ ) ₃ ·4H ₂ O and Yb(NO ₃ ) ₃ ·5H ₂ O powders in ethanol at a mass ratio of 1:9, heat at 60°C for 30 minutes to fully react, and then cool After reaching room temperature, light white Y(NO ₃ ) ₃ and milky white Yb(NO ₃ ) ₃ rare earth solutions were obtained.

(3) Drop ammonia ethanol dilution into the silica sol obtained in step (1) (the molar ratio of ethyl orthosilicate to ammonia is 1:0.25) and stir for 1 minute to obtain the material after adding the alkaline catalyst.

(4) According to the molar ratio of tetraethyl orthosilicate to Y or Yb being 1:0.05, add the Y(NO ₃ ) ₃ solution and Yb(NO ₃ ) ₃ solution obtained in step (2) to the obtained solution in step (3) respectively. Materials, stir for 1 minute, slowly drop the mixed solution into the silica sol, stir for 5 minutes, stir evenly at room temperature to obtain a composite sol solution, pour the obtained composite sol solution into a mold and let it stand at 25°C for 1 hour to obtain a double Rare earth co-doped silica gel.

(5) Put the above double rare earth co-doped silica gel at 25°C, let it stand for aging for 24 hours, and then put it into a high-pressure reactor for supercritical drying. Use ethanol as the medium for supercritical drying, and the ethanol pressure is controlled at 8~10MPa, control the temperature at 270°C, and supercritical drying time at 2h to obtain massive dual rare earth co-doped silica aerogels.

Comparative example 1:

A preparation method of silica bulk aerogel, including the following steps:

(1) Mix tetraethyl orthosilicate, absolute ethanol, and deionized water at a molar ratio of 1:20:5 at room temperature and stir evenly for 15 minutes, then add mass dropwise through a constant pressure funnel at a rate of 6 s/drop. Dilute hydrochloric acid ethanol with a fraction of 0.05wt%, stir for 120 minutes, seal and let stand at room temperature for 24 hours, to obtain silica sol.

(2) Add ammonia ethanol dilution (ethyl orthosilicate: ammonia = 1:0.25) dropwise into the silica sol obtained in step (1) and stir for 1 minute to obtain the material after adding the alkaline catalyst. Pour into the mold. Let it stand for 12 hours at 25°C to obtain silica gel.

(3) Aging the above silica gel at 25°C for 24 hours and then placing it into a high-pressure reactor for supercritical drying. Use ethanol as the medium for supercritical drying. The ethanol pressure is controlled at 8 to 10 MPa. The temperature is 270°C and the supercritical drying time is 2 hours to obtain silica aerogel.

The aerogels obtained in Example 4 and Comparative Example 1 were heated at 1000°C for 5 minutes respectively for observation, see Figure 4. It can be seen that the aerogel without rare earth doping has poor stability and is easily pulverized at high temperatures. After double rare earth doping in this application, the heating surface is basically flat without cracking, and the stability of the silica gel is significantly increased, improving Increase the service temperature of the material and prevent structural collapse at high temperatures.

Comparative example 2:

A preparation method of silica bulk aerogel, including the following steps:

(1) Mix tetraethyl orthosilicate, anhydrous ethanol, and deionized water at a molar ratio of 1:15:4 at room temperature and stir evenly for 15 minutes. Add mass into them through a constant pressure funnel at a rate of 6 s/drop. Dilute hydrochloric acid ethanol with a fraction of 0.05wt%, stir for 120 minutes, seal and let stand at room temperature for 24 hours, to obtain silica sol.

(2) Dissolve Y(NO ₃ ) ₃ ·4H ₂ O and Yb(NO ₃ ) ₃ ·5H ₂ O powders in ethanol at a mass ratio of 1:9, heat at 60°C for 30 minutes to fully react, and then cool After reaching room temperature, light white Y(NO ₃ ) ₃ and milky white Yb(NO ₃ ) ₃ rare earth solutions were obtained.

(3) According to the molar ratio of tetraethyl orthosilicate to Y or Yb being 1:0.05, add the Y(NO ₃ ) ₃ solution and Yb(NO ₃ ) ₃ solution obtained in step (2) to the obtained solution in step (1) respectively. In the silica sol, a mixed material was obtained.

(4) Drop ammonia ethanol dilution into the material obtained in step (3) (the molar ratio of ethyl orthosilicate to ammonia is 1:0.25), stir for 5 minutes, and stir evenly at room temperature to obtain a composite sol solution. The composite sol solution was poured into the mold and left to stand at 25°C for about 48 hours to obtain double rare earth co-doped silica gel.

(5) Put the above double rare earth co-doped silica gel at 25°C, let it stand for aging for 24 hours, and then put it into a high-pressure reactor for supercritical drying. Use ethanol as the medium for supercritical drying, and the ethanol pressure is controlled at 8~10MPa, control the temperature at 270°C, and supercritical drying time at 2h to obtain massive dual rare earth co-doped silica aerogels.

Comparative example 3:

The difference from Comparative Example 2 is that only single rare earth Y is doped, Y(NO ₃ ) ₃ ·5H ₂ O powder is selected in step (2), and Y(NO ₃ ) ₃ ·5H ₂ O powder is mixed with ethanol. The mass ratio is 1:9. Dissolve in ethanol, heat at 60°C for 30 minutes to fully react, and then cool to room temperature to obtain a light white Y(NO ₃ ) ₃ rare earth solution. The molar ratio of tetraethyl orthosilicate to Y in step (3) The ratio is 1:0.5, and the composite sol solution is left to stand for about 72 hours.

Comparative example 4:

The difference from Comparative Example 3 is that the only doped single rare earth is Yb, and in step (2) it is Yb(NO ₃ ) ₃ ·5H ₂ O powder. Yb(NO ₃ ) ₃ ·5H ₂ O powder is mixed with Dissolve ethanol in ethanol at a mass ratio of 1:9, heat at 60°C for 30 minutes to fully react, and then cool to room temperature to obtain a milky white Yb( _NO3 ) ₃ rare earth solution. The mole of tetraethyl orthosilicate and Yb in step (3) The ratio is 1:0.5, and the composite sol solution is allowed to stand for about 50 hours.

The basic properties of the doped silica aerogels obtained in Comparative Examples 2, 3, and 4 are shown in Table 4.

Table 4 Basic properties of doped silica aerogels

nature Comparative example 2 Comparative example 3 Comparative example 4 density 0.10g/cm ³ 0.16g/cm ³ 0.19g/cm ³ Specific surface area 559.82m ² /g 516.88m ² /g 444.50m ² /g Aperture 12.93nm 13.71nm 13.66nm Gel time ~48h ~72h ~50h

Referring to Table 4 and Figure 5, compared with the dual rare earth co-doped aerogels of Examples 1 to 4, when the order of adding the alkaline catalyst is changed, Comparative Examples 2, 3, and 4 require longer gelation time and gelation time. The glue time is uncontrollable. Compared with the double rare earth co-doped aerogel of Comparative Example 2, Comparative Examples 3 and 4 are only doped with one kind of rare earth nitrate, and the resulting gel has a higher density, and it takes a long time to fully gel. Referring to Figure 5, Comparative Example 3 is only doped with Y, a rare earth element, and the gel is incomplete. Complete gelation requires a long gel time (~72h), which greatly extends the gel time; Comparative Example 4 is only doped with Y, a rare earth element. Yb is a rare earth element. During the gelation process, it is easy to form floc phase separation and cause gel cracking. Complete gelation also requires a longer gelation time (~50h). In each embodiment of the present invention, the order of adding the alkaline catalyst is optimized, and when two rare earths with the same proportion are used for co-doping, it has a suitable gel time and can form a complete block, and the air condensation obtained The glue has good uniformity.

The above serial numbers of the embodiments of the present invention are only for description and do not represent the advantages and disadvantages of the embodiments.

The embodiments of the present invention have been described above in conjunction with the accompanying drawings. However, the present invention is not limited to the above-mentioned specific implementations. The above-mentioned specific implementations are only illustrative and not restrictive. Those of ordinary skill in the art will Under the inspiration of the present invention, many forms can be made without departing from the spirit of the present invention and the scope protected by the claims, and these all fall within the protection of the present invention.

Claims (10)

1. The preparation method of the double-rare earth reinforced silica block aerogel capable of being stably synthesized is characterized by comprising the following steps of: respectively dissolving rare earth nitrate I and rare earth nitrate II in ethanol, heating at 60 ℃ for reaction for 30min, mixing proportionally to obtain a rare earth mixed solution, slowly dripping an alkaline catalyst into silica sol, uniformly stirring, slowly dripping the obtained rare earth mixed solution into the silica sol, uniformly stirring, and standing at normal temperature to obtain double rare earth co-doped silica gel; standing, aging and supercritical drying the obtained double-rare earth co-doped silica gel to obtain a double-rare earth co-doped silica aerogel block; the molar ratio of the rare earth nitrate I to the rare earth nitrate II is 1:1.

2. the method for preparing the stable synthetic dual-rare earth reinforced silica block aerogel according to claim 1, which is characterized by comprising the following steps: the rare earth nitrate I/II is selected from ytterbium nitrate, yttrium nitrate, cerium nitrate, lanthanum nitrate or scandium nitrate.

3. The method for preparing the double rare earth reinforced silica block aerogel capable of being stably synthesized according to claim 2, which is characterized in that: the mass ratio of the rare earth nitrate I/the rare earth nitrate II to the ethanol is 1:9-10.

4. The method for preparing the silica block aerogel capable of stably synthesizing the double rare earth enhancement type according to claim 1, wherein the method for preparing the silica sol is as follows: sequentially mixing ethyl orthosilicate, ethanol and water according to a molar ratio, adding an acid catalyst, mechanically stirring for 60-120 min, sealing and standing, and fully hydrolyzing to obtain the silica sol.

5. The method for preparing the stable synthetic dual-rare earth reinforced silica block aerogel according to claim 4, which is characterized in that: the molar ratio of the ethyl orthosilicate, the ethanol and the water can be 1: (10-20): (4-5).

6. The method for preparing the stable synthetic dual-rare earth reinforced silica block aerogel according to claim 4, which is characterized in that: the acidic catalyst is hydrochloric acid with the mass fraction of 0.05wt%, and the mol ratio of the ethyl orthosilicate to the hydrochloric acid is 1:10 ^-4 。

7. The method for preparing the stable synthetic dual-rare earth reinforced silica block aerogel according to claim 4, which is characterized in that: the mol ratio of the tetraethoxysilane to the rare earth nitrate I/the rare earth nitrate II is 1:0.05-0.5.

8. The method for preparing the stable synthetic dual-rare earth reinforced silica block aerogel according to claim 4, which is characterized in that: the mol ratio of the tetraethoxysilane to the alkaline catalyst is 1:0.05-0.25.

9. The method for preparing the stable synthetic dual rare earth reinforced silica block aerogel according to claim 4, comprising the following steps:

preparation of silica sol: sequentially mixing ethyl orthosilicate, ethanol and water according to a molar ratio, adding an acid catalyst, mechanically stirring for 60-120 min, sealing and standing, and fully hydrolyzing to obtain silica sol;

preparing a rare earth solution: dissolving rare earth nitrate I and rare earth nitrate II powder in ethanol respectively, heating at 60 ℃ for 30min for full reaction, and cooling to room temperature to obtain a rare earth solution I and a rare earth solution II;

preparation of the gel: slowly dripping an alkaline catalyst into the obtained silica sol, stirring for 1min, mixing a certain amount of rare earth solution I and rare earth solution II to obtain a rare earth mixed solution, uniformly stirring, slowly dripping the mixed solution into the silica sol added with the alkaline catalyst, uniformly stirring at normal temperature or 50-60 ℃, and standing at normal temperature to obtain double rare earth co-doped silica gel;

and (3) drying: and standing and aging the double-rare earth co-doped silica gel, and then performing supercritical drying to obtain the double-rare earth co-doped silica aerogel block.

10. The dual rare earth reinforced silica aerogel monolith obtainable by the method of any one of claims 1 to 9.