A method for preparing a stable synthetic dual-rare-earth-enhanced silicon dioxide bulk aerogel

Abstract

The application provides a preparation method of a stable synthetic double-rare earth reinforced silicon dioxide bulk aerogel, and is characterized in that the method comprises the following steps: rare earth nitrate I and rare earth nitrate II are respectively dissolved in ethanol, heated at 60 DEG C for 30 min, and then mixed in proportion to obtain a rare earth mixed solution; an alkaline catalyst is slowly dropped into a silica sol, and the obtained rare earth mixed solution is slowly dropped into the silica sol after uniform stirring; and after uniform stirring, the obtained double-rare earth co-doped silica gel is obtained through aging and supercritical drying. The application improves the use strength and temperature of the silica aerogel, expands the application of the silica aerogel in the high-temperature field, and is simple in process, high in production efficiency, and beneficial to improving the production efficiency and large-scale production.

Description

Technical Field

[0001] This invention belongs to the field of aerogel preparation technology, specifically relating to a method for preparing a stable synthesis of dual rare earth-reinforced silica bulk aerogel. Background Technology

[0002] 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. The thermal insulation materials commonly used in the aerospace field are mainly phenolic foam composites, ceramic foam composites, and novel aerogel materials.

[0003] Aerogels are materials with nanoscale porous structures formed by the aggregation of nanoparticles. Their high porosity reduces the thermal conductivity of solid materials, the nanoporous structure inhibits convective heat transfer of gases within them, and the multiple pore walls reduce irradiation heat transfer. Currently, medium- and high-temperature aerogel materials, such as alumina aerogels and zirconia aerogels, are still in the laboratory stage. These materials have extremely poor high-temperature stability, resulting in unsatisfactory application effects. Among them, silica aerogels are currently the most widely used.

[0004] Traditional silica aerogel materials have excellent properties such as high specific surface area and low density. However, pure silica aerogel has extremely poor strength, is prone to cracking, and is easily sintered and collapses at high temperatures. Its long-term stable use range is limited to below 650℃, and the maximum use temperature does not exceed 900℃, which greatly restricts the application range of silica aerogel materials.

[0005] While silica aerogels prepared by doping with other elements show some improvement in temperature resistance, their operating temperature remains below 1100℃, making them unsuitable for high-temperature environments. Existing rare-earth silicate ceramic materials can withstand temperatures above 1600℃, but these materials have high density, low porosity, large pore size, and relatively high thermal conductivity, and their insulation performance decreases with increasing temperature, making them unsuitable for high-temperature insulation. Research indicates that rare-earth elements can inhibit high-temperature sintering of silica to varying degrees, improving its high-temperature resistance. Furthermore, while maintaining its low density, they can further preserve the spatial network structure of the aerogel. Therefore, rare-earth-doped silica aerogels have significant application potential in thermal insulation. Summary of the Invention

[0006] To address the problems in the prior art, this invention provides a method for the stable synthesis of dual rare earth-reinforced silica bulk aerogels. The method uses a sol-gel method to obtain dual rare earth co-doped silica gels, which improves the strength and temperature of silica aerogels, expands their application in high-temperature fields, and features a simple process with high production efficiency, which is conducive to improving production efficiency and large-scale production.

[0007] The technical problem solved by this invention is achieved by the following technical solution:

[0008] The present invention aims to provide a method for preparing a stable synthetic dual-rare-earth-enhanced silica bulk aerogel, characterized by comprising the following steps:

[0009] Rare earth nitrate I and rare earth nitrate II were dissolved separately in ethanol and reacted at 60°C for 30 min. Then they were mixed in a certain proportion to obtain a rare earth mixed solution. An alkaline catalyst was slowly added dropwise to a silica sol and stirred evenly. The resulting rare earth mixed solution was then slowly added dropwise to the silica sol and stirred evenly. After standing at room temperature, a double rare earth co-doped silica gel was obtained. The obtained double rare earth co-doped silica gel was aged and supercritically dried to obtain a double rare earth co-doped silica aerogel block. The molar ratio of rare earth nitrate I to rare earth nitrate II was 1:1.

[0010] Furthermore, the rare earth nitrate I / rare earth nitrate II is selected from ytterbium nitrate, yttrium nitrate, cerium nitrate, lanthanum nitrate, or scandium nitrate.

[0011] Furthermore, the rare earth nitrate I is yttrium nitrate, and the rare earth nitrate II is ytterbium nitrate.

[0012] Furthermore, the mass ratio of rare earth nitrate I / rare earth nitrate II to ethanol is 1:9-10.

[0013] Furthermore, the alkaline catalyst is ammonia.

[0014] Furthermore, the static aging process involves stirring the mixture evenly at room temperature or 50–60°C and then allowing it to stand at room temperature for 24–48 hours.

[0015] Furthermore, the preparation method of the silica sol is as follows: tetraethyl orthosilicate, ethanol and water are mixed sequentially in a molar ratio, an acidic catalyst is added, the mixture is mechanically stirred for 60-120 minutes, sealed and allowed to stand, and the silica sol is obtained after complete hydrolysis reaction.

[0016] Furthermore, the molar ratio of the tetraethyl orthosilicate, ethanol and water can be 1:(10-20):(4-5).

[0017] Furthermore, the acidic catalyst is selected from hydrochloric acid with a mass fraction of 0.05 wt%, and the molar ratio of tetraethyl orthosilicate to hydrochloric acid is 1:10. -4 .

[0018] Furthermore, during the preparation of silica sol, it is sealed and left to stand at room temperature for 24–48 hours.

[0019] Furthermore, the molar ratio of the tetraethyl orthosilicate to rare earth nitrate I / rare earth nitrate II is 1:0.05 to 0.5.

[0020] Furthermore, the molar ratio of the tetraethyl orthosilicate to the alkaline catalyst is 1:0.05 to 0.25, and the alkaline catalyst is ammonia.

[0021] Furthermore, the supercritical drying medium is ethanol, the drying temperature is 260-270°C, the holding time is 2-4 hours, and the supercritical pressure is 8-12 MPa.

[0022] Furthermore, a method for preparing a stable synthetic dual-rare-earth-reinforced silica bulk aerogel includes the following steps:

[0023] Preparation of silica sol: Tetraethyl orthosilicate, ethanol and water are mixed sequentially in molar ratio, an acidic catalyst is added, and the mixture is mechanically stirred for 60-120 min. After being sealed and allowed to stand, silica sol is obtained after complete hydrolysis reaction.

[0024] Preparation of rare earth solutions: Rare earth nitrate I and rare earth nitrate II powders were dissolved in ethanol, heated at 60°C for 30 min to react fully, and then cooled to room temperature to obtain rare earth solution I and rare earth solution II.

[0025] Preparation of gel: The alkaline catalyst was slowly added dropwise to the obtained silica sol and stirred for 1 min. A certain amount of rare earth solution I and rare earth solution II were mixed to obtain a rare earth mixed solution. After stirring evenly, the mixed solution was slowly added dropwise to the silica sol containing the alkaline catalyst. After stirring evenly at room temperature or 50-60℃, the mixture was allowed to stand at room temperature to obtain a double rare earth co-doped silica gel.

[0026] Drying: After the dual rare earth co-doped silica gel is allowed to stand for aging, it is subjected to supercritical drying to obtain dual rare earth co-doped silica aerogel blocks.

[0027] This invention uses tetraethyl orthosilicate as the silicon source, rare earth nitrates as co-doping materials, ethanol as a universal solvent, and acids and bases as catalysts to obtain dual rare earth co-doped silica gel via a sol-gel method. After static aging, dual rare earth co-doped silica aerogel blocks are obtained through supercritical drying using ethanol as the medium. This invention, by incorporating dual rare earth elements into the silica aerogel, helps to increase the high-temperature stability of the silica aerogel, improving not only its strength and temperature performance but also resulting in aerogels with low density and large specific surface area. The method is simple, has high production efficiency, and low equipment requirements, facilitating large-scale production. It holds promise as a thermal insulation material with extremely low thermal conductivity that can be applied in high-temperature fields.

[0028] Compared with the prior art, the beneficial technical effects of the present invention are as follows:

[0029] This invention ensures uniform dispersion of rare earth elements through physical stirring and heating, guaranteeing product uniformity and avoiding uneven distribution of rare earth elements in the silica matrix due to phase separation. By ensuring solvent uniformity and adjusting the proportion and priority of alkaline catalysts, the gelation time can be controlled, significantly shortening the required gelation time. By controlling and adjusting the proportion of rare earth elements and the molding process, the density and microstructure of the aerogel can be controlled, thereby controlling the thermal conductivity of the aerogel. This invention features a simple process, low cost, and controllable reaction conditions. By controlling the ratio of ethanol and rare earth elements, the prepared dual rare earth co-doped silica aerogel bulk material has a complete bulk structure, which can meet the requirements of mold preparation. By controlling the appropriate scale-up of the mold, it can fully meet the usability requirements of irregularly shaped products in the field of thermal insulation.

[0030] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, and in order to make the above contents, objectives, features and advantages of the present invention more obvious and understandable, specific embodiments of the present invention are described below. Attached Figure Description

[0031] Figure 1 This is a macroscopic image of the dual rare earth co-doped silica gel obtained in Example 1 of the preparation method of a stable synthesis method for dual rare earth reinforced silica bulk aerogel of the present invention.

[0032] Figure 2 This is a macroscopic view of the dual rare earth co-doped silica aerogel obtained in Example 1 of the preparation method of a stable synthesis method for dual rare earth reinforced silica bulk aerogel of the present invention.

[0033] Figure 3 This is a microscopic morphology image of the dual rare earth co-doped silica aerogel obtained in Example 1 of the preparation method for a stable synthesis of dual rare earth reinforced silica bulk aerogel of the present invention.

[0034] Figure 4 This is a comparison image of the silica aerogels obtained in Example 4 and Comparative Example 1 after heat insulation at room temperature and 1000℃ for 5 minutes, respectively, in the preparation method of a stable synthesis of dual rare earth reinforced silica bulk aerogel of the present invention.

[0035] Figure 5 This is a macroscopic view of the silica aerogels obtained in Comparative Examples 2, 3, and 4 in the preparation method of a stable synthesis of dual rare earth reinforced silica bulk aerogels of the present invention. Detailed Implementation

[0036] 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 embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0037] In addition, unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be obtained by purchasing them from the market or prepared by existing methods.

[0038] Example 1:

[0039] A method for preparing a stable synthetic dual-rare-earth-reinforced silica bulk aerogel includes the following steps:

[0040] (1) Tetraethyl orthosilicate, anhydrous ethanol and deionized water were mixed evenly at room temperature for 15 min. Then, 0.05 wt% hydrochloric acid ethanol dilution was added dropwise through a constant pressure funnel at a rate of 6 s / drop. After stirring for 120 min, the mixture was sealed and allowed to stand at room temperature for 24 h to obtain silica sol.

[0041] (2) Yttrium nitrate (Y(NO3)3·4H2O) and ytterbium nitrate (Yb(NO3)3·5H2O) powders were dissolved in ethanol at a mass ratio of 1:9. After the reaction was fully carried out at 60°C for 30 min, the mixture was cooled to room temperature to obtain light white Y(NO3)3 and milky white Yb(NO3)3 rare earth solutions.

[0042] (3) Add ammonia-ethanol dilution (molar ratio of tetraethyl orthosilicate to ammonia is 1:0.05) to the silica sol obtained in step (1) and stir for 1 min to obtain the material after adding alkaline catalyst.

[0043] (4) According to the molar ratio of tetraethyl orthosilicate to Y or Yb, 1:0.05, add the Y(NO3)3 solution and Yb(NO3)3 solution obtained in step (2) to the material obtained in step (3) respectively, stir for 1 min, slowly drop the rare earth mixed solution into the silica sol, stir for 5 min, and after stirring evenly at room temperature, a composite sol solution is obtained. Pour the obtained composite sol solution into a mold and let it stand at 25℃ for 2 h to obtain the double rare earth co-doped silica gel. The macroscopic image of the double rare earth co-doped silica gel is attached. Figure 1 As shown.

[0044] (5) The above-mentioned dual rare earth co-doped silica gel was placed in a high-pressure reactor for supercritical drying after being aged at 25°C for 24 hours. Ethanol was used as the supercritical drying medium, with the ethanol pressure controlled at 8-10 MPa, the temperature controlled at 270°C, and the supercritical drying time being 2 hours, to obtain blocky dual rare earth co-doped silica aerogel.

[0045] The basic properties of the dual rare earth co-doped silica aerogel obtained in this embodiment are shown in Table 1.

[0046] Table 1. Basic properties of aerogels

[0047] density <![CDATA[0.19g / cm 3 ]]> Specific surface area <![CDATA[875.84m 2 / g]]> Average aperture 12.93nm

[0048] Example 2:

[0049] A method for preparing a stable synthetic dual-rare-earth-reinforced silica bulk aerogel includes the following steps:

[0050] (1) Tetraethyl orthosilicate, anhydrous ethanol and deionized water were mixed evenly at room temperature for 15 min. Then, 0.05 wt% hydrochloric acid ethanol dilution was added dropwise through a constant pressure funnel at a rate of 6 s / drop. After stirring for 120 min, the mixture was sealed and allowed to stand at room temperature for 24 h to obtain silica sol.

[0051] (2) Dissolve Y(NO3)3·4H2O and Yb(NO3)3·5H2O powders in ethanol at a mass ratio of 1:9. After heating at 60°C for 30 min to react fully, cool to room temperature to obtain light white Y(NO3)3 and milky white Yb(NO3)3 rare earth solutions.

[0052] (3) Add ammonia-ethanol dilution (molar ratio of tetraethyl orthosilicate to ammonia is 1:0.25) to the silica sol obtained in step (1) and stir for 1 min to obtain the material after adding alkaline catalyst.

[0053] (4) Add the Y(NO3)3 solution and Yb(NO3)3 solution obtained in step (2) to the material obtained in step (3) according to the molar ratio of tetraethyl orthosilicate to Y or Yb of 1:0.125. Stir for 1 min, slowly drop the mixed solution into the silica sol, stir for 5 min, 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 4 h to obtain a double rare earth co-doped silica gel.

[0054] (5) The above-mentioned dual rare earth co-doped silica gel was placed in a high-pressure reactor for supercritical drying after being aged at 25°C for 24 hours. Ethanol was used as the supercritical drying medium, with the ethanol pressure controlled at 8-10 MPa, the temperature controlled at 270°C, and the supercritical drying time being 2 hours, to obtain blocky dual rare earth co-doped silica aerogel.

[0055] The basic properties of the dual rare earth co-doped silica aerogel obtained in this embodiment are shown in Table 2.

[0056] Table 2. Basic properties of aerogels

[0057] density <![CDATA[0.09g / cm 3 ]]> Specific surface area <![CDATA[521.30m 2 / g]]> Average aperture 13.35nm

[0058] Example 3:

[0059] A method for preparing a stable synthetic dual-rare-earth-reinforced silica bulk aerogel includes the following steps:

[0060] (1) Tetraethyl orthosilicate, anhydrous ethanol and deionized water were mixed evenly at room temperature for 15 min. Then, 0.05 wt% hydrochloric acid ethanol dilution was added dropwise through a constant pressure funnel at a rate of 6 s / drop. After stirring for 120 min, the mixture was sealed and allowed to stand at room temperature for 24 h to obtain silica sol.

[0061] (2) Dissolve Y(NO3)3·4H2O and Yb(NO3)3·5H2O powders in ethanol at a mass ratio of 1:9. After heating at 60°C for 30 min to react fully, cool to room temperature to obtain light white Y(NO3)3 and milky white Yb(NO3)3 rare earth solutions.

[0062] (3) Add ammonia-ethanol dilution (molar ratio of tetraethyl orthosilicate to ammonia is 1:0.25) to the silica sol obtained in step (1) and stir for 1 min to obtain the material after adding alkaline catalyst.

[0063] (4) According to the molar ratio of tetraethyl orthosilicate to Y or Yb, the Y(NO3)3 solution and Yb(NO3)3 solution obtained in step (2) are added to the material obtained in step (3) respectively, stirred for 1 min, and the mixed solution is slowly dripped into the silica sol. After stirring for 5 min, the composite sol solution is obtained after stirring evenly at room temperature. The obtained composite sol solution is poured into a mold and left to stand at 25℃ for 8 h to obtain the double rare earth co-doped silica gel.

[0064] (5) The above-mentioned dual rare earth co-doped silica gel was placed in a high-pressure reactor for supercritical drying after being aged at 25°C for 24 hours. Ethanol was used as the supercritical drying medium, with the ethanol pressure controlled at 8-10 MPa, the temperature controlled at 270°C, and the supercritical drying time being 2 hours, to obtain blocky dual rare earth co-doped silica aerogel.

[0065] Macroscopic images of the bulk dual rare-earth co-doped silica aerogel obtained in Example 3 are attached. Figure 2 As shown in the attached diagram, the microstructure is as follows. Figure 3 As shown, it can be seen that dual rare earth co-doping yields dual rare earth reinforced silica bulk aerogels with low density and large specific surface area.

[0066] The basic properties of the dual rare earth co-doped silica aerogel obtained in this embodiment are shown in Table 3.

[0067] Table 3. Basic properties of aerogels

[0068]

[0069]

[0070] Example 4:

[0071] A method for preparing a stable synthetic dual-rare-earth-reinforced silica bulk aerogel includes the following steps:

[0072] (1) Tetraethyl orthosilicate, anhydrous ethanol and deionized water were mixed evenly at room temperature for 15 min. Then, 0.05 wt% hydrochloric acid ethanol dilution was added dropwise through a constant pressure funnel at a rate of 6 s / drop. After stirring for 120 min, the mixture was sealed and allowed to stand at room temperature for 24 h to obtain silica sol.

[0073] (2) Dissolve Y(NO3)3·4H2O and Yb(NO3)3·5H2O powders in ethanol at a mass ratio of 1:9. After heating at 60°C for 30 min to react fully, cool to room temperature to obtain light white Y(NO3)3 and milky white Yb(NO3)3 rare earth solutions.

[0074] (3) Add ammonia-ethanol dilution (molar ratio of tetraethyl orthosilicate to ammonia is 1:0.25) to the silica sol obtained in step (1) and stir for 1 min to obtain the material after adding alkaline catalyst.

[0075] (4) According to the molar ratio of tetraethyl orthosilicate to Y or Yb, the Y(NO3)3 solution and Yb(NO3)3 solution obtained in step (2) are added to the material obtained in step (3) respectively, stirred for 1 min, and the mixed solution is slowly dripped into the silica sol. After stirring for 5 min, the composite sol solution is obtained after stirring evenly at room temperature. The obtained composite sol solution is poured into a mold and left to stand at 25℃ for 1 h to obtain the double rare earth co-doped silica gel.

[0076] (5) The above-mentioned dual rare earth co-doped silica gel was placed in a high-pressure reactor for supercritical drying after being aged at 25°C for 24 hours. Ethanol was used as the supercritical drying medium, with the ethanol pressure controlled at 8-10 MPa, the temperature controlled at 270°C, and the supercritical drying time being 2 hours, to obtain blocky dual rare earth co-doped silica aerogel.

[0077] Comparative Example 1:

[0078] A method for preparing a silica bulk aerogel includes the following steps:

[0079] (1) Tetraethyl orthosilicate, anhydrous ethanol and deionized water were mixed evenly at room temperature for 15 min. Then, 0.05 wt% hydrochloric acid ethanol dilution was added dropwise through a constant pressure funnel at a rate of 6 s / drop. After stirring for 120 min, the mixture was sealed and allowed to stand at room temperature for 24 h to obtain silica sol.

[0080] (2) Add ammonia-ethanol dilution (tetraethyl orthosilicate: ammonia = 1: 0.25) to the silica sol obtained in step (1) and stir for 1 min to obtain the material after adding alkaline catalyst. Pour it into a mold and let it stand at 25°C for 12 h to obtain silica gel.

[0081] (3) The silica gel was placed in a high-pressure reactor for supercritical drying after being aged at 25°C for 24 hours. Ethanol was used as the supercritical drying medium, with the ethanol pressure controlled at 8-10 MPa, the temperature controlled at 270°C, and the supercritical drying time being 2 hours to obtain silica aerogel.

[0082] The aerogels obtained in Example 4 and Comparative Example 1 were heated at 1000°C for 5 minutes and observed, respectively. (See Appendix) Figure 4 It can be seen that the aerogel without rare earth doping has poor stability and is easily crushed at high temperatures. After double rare earth doping in this application, the heating surface is basically flat and no cracks are generated. The stability of the silica gel is significantly increased, which improves the service temperature of the material and prevents structural collapse at high temperatures.

[0083] Comparative Example 2:

[0084] A method for preparing a silica bulk aerogel includes the following steps:

[0085] (1) Tetraethyl orthosilicate, anhydrous ethanol and deionized water were mixed evenly at room temperature for 15 min. Then, 0.05 wt% hydrochloric acid ethanol dilution was added dropwise through a constant pressure funnel at a rate of 6 s / drop. After stirring for 120 min, the mixture was sealed and allowed to stand at room temperature for 24 h to obtain silica sol.

[0086] (2) Dissolve Y(NO3)3·4H2O and Yb(NO3)3·5H2O powders in ethanol at a mass ratio of 1:9. After heating at 60°C for 30 min to react fully, cool to room temperature to obtain light white Y(NO3)3 and milky white Yb(NO3)3 rare earth solutions.

[0087] (3) Add the Y(NO3)3 solution and Yb(NO3)3 solution obtained in step (2) to the silica sol obtained in step (1) at a molar ratio of tetraethyl orthosilicate to Y or Yb of 1:0.05 to obtain a mixture.

[0088] (4) Add ammonia-ethanol dilution (molar ratio of tetraethyl orthosilicate to ammonia is 1:0.25) to the material obtained in step (3), stir for 5 minutes, and stir evenly at room temperature to obtain composite sol solution. Pour the obtained composite sol solution into a mold and let it stand at 25°C for about 48 hours to obtain double rare earth co-doped silica gel.

[0089] (5) The above-mentioned dual rare earth co-doped silica gel was placed in a high-pressure reactor for supercritical drying after being aged at 25°C for 24 hours. Ethanol was used as the supercritical drying medium, with the ethanol pressure controlled at 8-10 MPa, the temperature controlled at 270°C, and the supercritical drying time being 2 hours, to obtain blocky dual rare earth co-doped silica aerogel.

[0090] Comparative Example 3:

[0091] The difference from Comparative Example 2 is that only single rare earth Y is doped. In step (2), Y(NO3)3·5H2O powder is selected. Y(NO3)3·5H2O powder and ethanol are dissolved in ethanol at a mass ratio of 1:9. After heating at 60°C for 30 min to fully react, the solution is cooled to room temperature to obtain a light white Y(NO3)3 rare earth solution. In step (3), the molar ratio of tetraethyl orthosilicate to Y is 1:0.5. The composite sol solution is left to stand for about 72 h.

[0092] Comparative Example 4:

[0093] The difference from Comparative Example 3 is that the only doped rare earth element is Yb, and in step (2) it is Yb(NO3)3·5H2O powder. Yb(NO3)3·5H2O powder and ethanol are dissolved in ethanol at a mass ratio of 1:9. After heating at 60°C for 30 min to fully react, the mixture is cooled to room temperature to obtain a milky white Yb(NO3)3 rare earth solution. In step (3), the molar ratio of tetraethyl orthosilicate to Yb is 1:0.5. The composite sol solution is left to stand for about 50 h.

[0094] The basic properties of the doped silica aerogels obtained in Comparative Examples 2, 3, and 4 are shown in Table 4.

[0095] Table 4. Basic properties of doped silica aerogels

[0096] nature Comparative Example 2 Comparative Example 3 Comparative Example 4 density <![CDATA[0.10g / cm 3 ]]> <![CDATA[0.16g / cm 3 ]]> <![CDATA[0.19g / cm 3 ]]> Specific surface area <![CDATA[559.82m 2 / g]]> <![CDATA[516.88m 2 / g]]> <![CDATA[444.50m 2 / g]]> aperture 12.93nm 13.71nm 13.66nm gel time ～48h ～72h ～50h

[0097] See Table 4 and Appendix Figure 5 Compared to the dual rare-earth co-doped aerogels of Examples 1-4, Comparative Examples 2, 3, and 4 required longer gelation times and the gelation time was uncontrollable after changing the order of alkaline catalyst addition. Compared to the dual rare-earth co-doped aerogel of Comparative Example 2, Comparative Examples 3 and 4, which were doped with only one rare-earth nitrate, resulted in gels with higher densities and longer complete gelation times. See Appendix. Figure 5 Comparative Example 3, doped with only Y, resulted in incomplete gelation, requiring a long gelation time (~72h) for complete gelation, significantly extending the gelation period. Comparative Example 4, doped with only Yb, was prone to flocculent phase separation during gelation, leading to gel cracking; complete gelation also required an even longer gelation time (~50h). In the embodiments of this invention, the order of adding the alkaline catalyst was optimized. Furthermore, when two rare earth elements in the same proportion were co-doped, a suitable gelation time was achieved, resulting in the formation of a complete blocky body and good aerogel uniformity.

[0098] The sequence numbers of the above embodiments of the present invention are for descriptive purposes only and do not represent the superiority or inferiority of the embodiments.

[0099] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A method for the preparation of a stable synthetic dual rare earth enhanced silica monolith aerogel, characterized by, The preparation method comprises the following steps: The rare earth nitrate I and the rare earth nitrate II are respectively dissolved in ethanol, and then mixed in a certain proportion after being heated at 60℃ for 30 min to obtain a rare earth mixed solution; the alkaline catalyst is slowly dropped into the silica sol, and then the obtained rare earth mixed solution is slowly dropped into the silica sol, and the obtained double-rare earth co-doped silica gel is obtained after being stirred and uniformly placed at room temperature; the obtained double-rare earth co-doped silica gel is aged and supercritically dried 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; the rare earth nitrate I / rare earth nitrate II is selected from ytterbium nitrate, yttrium nitrate, cerium nitrate, lanthanum nitrate or scandium nitrate; The silica sol is prepared by mixing tetraethyl orthosilicate, ethanol and water in a certain molar ratio, adding an acidic catalyst, mechanically stirring for 60-120 min, sealing and placing, and fully hydrolyzing to obtain the silica sol; the molar ratio of the tetraethyl orthosilicate to the rare earth nitrate I / rare earth nitrate II is 1:0.05-0.5, and the molar ratio of the tetraethyl orthosilicate to the alkaline catalyst is 1:0.05-0.25; the supercritical drying medium is ethanol, the drying temperature is 260-270℃, the holding time is 2-4 h, and the supercritical pressure is 8-12 MPa.

2. A process for the stable synthesis of dual rare earth enhanced silica monolith aerogels as claimed in claim 1, wherein: The mass ratio of the rare earth nitrate I / rare earth nitrate II to ethanol is 1:9-10.

3. A process for the stable synthesis of dual rare earth enhanced silica monolith aerogels as claimed in claim 1, wherein: The molar ratio of the tetraethyl orthosilicate, ethanol and water can be 1:(10-20):(4-5).

4. A process for the stable synthesis of dual rare earth enhanced silica aerogel monoliths as claimed in claim 1, wherein: The acid catalyst is selected from hydrochloric acid with a mass fraction of 0.05 wt%, and the molar ratio of tetraethyl orthosilicate to hydrochloric acid is 1:10 -4 .

5. A process for the stable synthesis of dual rare earth enhanced silica aerogel monoliths as claimed in claim 1, wherein, The preparation method comprises the following steps: The silica sol is prepared by mixing tetraethyl orthosilicate, ethanol and water in a certain molar ratio, adding an acidic catalyst, mechanically stirring for 60-120 min, sealing and placing, and fully hydrolyzing to obtain the silica sol; The rare earth solution is prepared by dissolving the rare earth nitrate I and the rare earth nitrate II powders in ethanol respectively, fully reacting at 60℃ for 30 min, and cooling to room temperature to obtain the rare earth solution I and the rare earth solution II; The gel is prepared by slowly dropping the alkaline catalyst into the obtained silica sol, stirring for 1 min, mixing a certain amount of the rare earth solution I and the rare earth solution II to obtain a rare earth mixed solution, slowly dropping the mixed solution into the silica sol to which the alkaline catalyst is added, and uniformly stirring at room temperature or 50-60℃, and then uniformly placing at room temperature to obtain a double-rare earth co-doped silica gel; The double-rare earth co-doped silica gel is aged and then supercritically dried to obtain a double-rare earth co-doped silica aerogel block.

6. The double-rare earth enhanced silica block aerogel obtained by the preparation method in any one of claims 1-5.

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