CN117228677A - Preparation method of double-rare earth enhanced silica block aerogel capable of being stably synthesized - Google Patents
Preparation method of double-rare earth enhanced silica block aerogel capable of being stably synthesized Download PDFInfo
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- CN117228677A CN117228677A CN202311141992.5A CN202311141992A CN117228677A CN 117228677 A CN117228677 A CN 117228677A CN 202311141992 A CN202311141992 A CN 202311141992A CN 117228677 A CN117228677 A CN 117228677A
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- 229910052761 rare earth metal Inorganic materials 0.000 title claims abstract description 140
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 title claims abstract description 130
- 239000004964 aerogel Substances 0.000 title claims abstract description 45
- 239000000377 silicon dioxide Substances 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims abstract description 25
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 146
- 150000002910 rare earth metals Chemical class 0.000 claims abstract description 74
- 238000003756 stirring Methods 0.000 claims abstract description 50
- RMAQACBXLXPBSY-UHFFFAOYSA-N silicic acid Chemical compound O[Si](O)(O)O RMAQACBXLXPBSY-UHFFFAOYSA-N 0.000 claims abstract description 36
- 239000000741 silica gel Substances 0.000 claims abstract description 32
- 229910002027 silica gel Inorganic materials 0.000 claims abstract description 32
- -1 rare earth nitrate Chemical class 0.000 claims abstract description 29
- 229910002651 NO3 Inorganic materials 0.000 claims abstract description 28
- 238000000352 supercritical drying Methods 0.000 claims abstract description 25
- 238000000034 method Methods 0.000 claims abstract description 23
- 239000003054 catalyst Substances 0.000 claims abstract description 22
- 238000006243 chemical reaction Methods 0.000 claims abstract description 19
- 238000002156 mixing Methods 0.000 claims abstract description 15
- 239000011259 mixed solution Substances 0.000 claims abstract description 14
- 238000010438 heat treatment Methods 0.000 claims abstract description 8
- 239000004965 Silica aerogel Substances 0.000 claims description 38
- 239000000243 solution Substances 0.000 claims description 37
- BOTDANWDWHJENH-UHFFFAOYSA-N Tetraethyl orthosilicate Chemical compound CCO[Si](OCC)(OCC)OCC BOTDANWDWHJENH-UHFFFAOYSA-N 0.000 claims description 32
- 239000000499 gel Substances 0.000 claims description 17
- 230000009977 dual effect Effects 0.000 claims description 13
- 230000032683 aging Effects 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 239000000843 powder Substances 0.000 claims description 11
- 238000007789 sealing Methods 0.000 claims description 10
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical group Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 claims description 8
- NGDQQLAVJWUYSF-UHFFFAOYSA-N 4-methyl-2-phenyl-1,3-thiazole-5-sulfonyl chloride Chemical compound S1C(S(Cl)(=O)=O)=C(C)N=C1C1=CC=CC=C1 NGDQQLAVJWUYSF-UHFFFAOYSA-N 0.000 claims description 4
- 239000003377 acid catalyst Substances 0.000 claims description 4
- HSJPMRKMPBAUAU-UHFFFAOYSA-N cerium(3+);trinitrate Chemical compound [Ce+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O HSJPMRKMPBAUAU-UHFFFAOYSA-N 0.000 claims description 4
- 230000003301 hydrolyzing effect Effects 0.000 claims description 4
- KUBYTSCYMRPPAG-UHFFFAOYSA-N ytterbium(3+);trinitrate Chemical compound [Yb+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O KUBYTSCYMRPPAG-UHFFFAOYSA-N 0.000 claims description 4
- 238000001035 drying Methods 0.000 claims description 3
- 230000002378 acidificating effect Effects 0.000 claims description 2
- 238000001816 cooling Methods 0.000 claims description 2
- FYDKNKUEBJQCCN-UHFFFAOYSA-N lanthanum(3+);trinitrate Chemical compound [La+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O FYDKNKUEBJQCCN-UHFFFAOYSA-N 0.000 claims description 2
- DFCYEXJMCFQPPA-UHFFFAOYSA-N scandium(3+);trinitrate Chemical compound [Sc+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O DFCYEXJMCFQPPA-UHFFFAOYSA-N 0.000 claims description 2
- 230000002194 synthesizing effect Effects 0.000 claims description 2
- 235000012239 silicon dioxide Nutrition 0.000 abstract description 8
- 238000004519 manufacturing process Methods 0.000 abstract description 7
- 230000009286 beneficial effect Effects 0.000 abstract description 4
- 230000002431 foraging effect Effects 0.000 abstract 1
- 235000019441 ethanol Nutrition 0.000 description 42
- 239000000463 material Substances 0.000 description 22
- 230000000052 comparative effect Effects 0.000 description 19
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical group [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 14
- 235000011114 ammonium hydroxide Nutrition 0.000 description 14
- 239000002131 composite material Substances 0.000 description 14
- 239000003085 diluting agent Substances 0.000 description 12
- 229910052769 Ytterbium Inorganic materials 0.000 description 10
- 239000008367 deionised water Substances 0.000 description 6
- 229910021641 deionized water Inorganic materials 0.000 description 6
- DZGCGKFAPXFTNM-UHFFFAOYSA-N ethanol;hydron;chloride Chemical compound Cl.CCO DZGCGKFAPXFTNM-UHFFFAOYSA-N 0.000 description 6
- 239000000203 mixture Substances 0.000 description 6
- 238000009413 insulation Methods 0.000 description 5
- 239000011148 porous material Substances 0.000 description 5
- 229910052727 yttrium Inorganic materials 0.000 description 5
- 239000012774 insulation material Substances 0.000 description 3
- MCMNRKCIXSYSNV-UHFFFAOYSA-N Zirconium dioxide Chemical compound O=[Zr]=O MCMNRKCIXSYSNV-UHFFFAOYSA-N 0.000 description 2
- 229910010293 ceramic material Inorganic materials 0.000 description 2
- 238000005336 cracking Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 239000006260 foam Substances 0.000 description 2
- 238000001879 gelation Methods 0.000 description 2
- 238000005191 phase separation Methods 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 238000003980 solgel method Methods 0.000 description 2
- 239000002904 solvent Substances 0.000 description 2
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 239000002253 acid Substances 0.000 description 1
- 230000004931 aggregating effect Effects 0.000 description 1
- 239000003513 alkali Substances 0.000 description 1
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 1
- 230000003321 amplification Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000013329 compounding Methods 0.000 description 1
- 230000018109 developmental process Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 230000007774 longterm Effects 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 238000003199 nucleic acid amplification method Methods 0.000 description 1
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 1
- 229910052710 silicon Inorganic materials 0.000 description 1
- 239000010703 silicon Substances 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
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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
Technical Field
The application belongs to the technical field of aerogel preparation, and particularly relates to a preparation method of a double-rare earth reinforced silica block aerogel capable of being stably synthesized.
Background
With the continuous upgrading and development of advanced aircrafts and heat protection systems in China, more serious challenges are presented to the existing heat protection and insulation materials. The heat insulation materials commonly used in the aerospace field are mainly phenolic foam composite materials, ceramic foam composite materials and novel aerogel materials.
Aerogel is a material with nano-scale porous structure formed by mutually aggregating nano-particles, the high porosity of the material reduces the heat conduction of solid phase material, the nano-porous structure inhibits the convection heat transfer of gas in the material, and the multiple pore walls reduce the irradiation heat transfer. At present, middle and high temperature aerogel materials, such as alumina aerogel and zirconia aerogel, still stay in a laboratory stage, the high temperature stability of the materials is extremely poor, the application effect is not ideal, and the silica aerogel is most widely used at present.
The traditional silica aerogel material has the excellent characteristics of high specific surface area and low density, but the pure silica aerogel has extremely poor strength and is easy to crack, and the structure collapse is easy to sinter at high temperature, so that the long-term stable use range is only limited to below 650 ℃, and the maximum use temperature is not more than 900 ℃, thereby greatly restricting the application range of the silica aerogel material.
Although the temperature resistance of the silica aerogel prepared by the method of compounding doped other elements is improved to a certain extent, the use temperature of the silica aerogel is still lower than 1100 ℃, and the silica aerogel cannot be used in a high-temperature environment. The existing rare earth silicate ceramic material has the temperature resistance reaching more than 1600 ℃, but the ceramic material has the disadvantages of higher density, lower porosity, larger pore diameter and relatively higher heat conductivity, and the heat insulation performance can be reduced along with the temperature rise, thus being not suitable for high-temperature heat insulation. Research shows that the rare earth elements can inhibit high-temperature sintering of silicon dioxide to different degrees, improve high-temperature resistance of the silicon dioxide, and further maintain the spatial network structure of the aerogel under the condition of maintaining the low density of the silicon dioxide, so that the rare earth doped silicon dioxide aerogel has a very wide application prospect in the aspect of heat preservation and heat insulation.
Disclosure of Invention
In order to solve the problems in the prior art, the application provides the preparation method for stably synthesizing the double-rare-earth reinforced silica block aerogel, which adopts a sol-gel method to obtain double-rare-earth co-doped silica gel, improves the use strength and temperature of the silica aerogel, expands the application of the silica aerogel in the high-temperature field, has simple process and high production efficiency, and is beneficial to improving the production efficiency and mass production.
The application solves the technical problems by adopting the following technical scheme:
the application aims to provide 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:
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.
further, the rare earth nitrate I/II is selected from 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/the rare earth nitrate II to the ethanol is 1:9-10.
Further, the alkaline catalyst is ammonia water.
Further, standing and aging are carried out for 24-48 hours after stirring uniformly at normal temperature or 50-60 ℃.
Further, the preparation method of the silica sol comprises the following steps: 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.
Further, the molar ratio of the ethyl orthosilicate, the ethanol and the water can be 1: (10-20): (4-5).
Further, hydrochloric acid with the mass fraction of 0.05wt% is selected as the acidic catalyst, and the mol ratio of the tetraethoxysilane to the hydrochloric acid is 1:10 -4 。
Further, in the preparation process of the silica sol, the silica sol is sealed and kept stand for 24 to 48 hours at room temperature.
Further, the mol ratio of the tetraethoxysilane to the rare earth nitrate I/the rare earth nitrate II is 1:0.05-0.5.
Further, the mol ratio of the tetraethoxysilane 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 ℃, the heat preservation time is 2-4 h, and the supercritical pressure is 8-12 MPa.
Further, the preparation method of the double-rare earth reinforced silica block aerogel capable of being stably synthesized comprises 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.
According to the application, tetraethoxysilane is used as a silicon source, rare earth nitrate is used as a co-doping raw material, ethanol is used as a general solvent, acid and alkali are used as catalysts, and a sol-gel method is adopted to obtain double rare earth co-doping silica gel; and standing and aging, taking ethanol as a medium, and performing supercritical drying to obtain the double-rare earth co-doped silica aerogel block. According to the application, the double rare earth elements are doped in the silica aerogel, so that the high-temperature stability of the silica aerogel is improved, the use strength and the temperature are improved, and the obtained aerogel has low density and large specific surface area; the method has simple process, high production efficiency and lower equipment requirement, is beneficial to large-scale production, and is expected to become a heat insulation material which can be applied to the high-temperature field and has extremely low heat conductivity coefficient.
Compared with the prior art, the application has the beneficial technical effects that:
the application ensures uniform dispersion of rare earth elements and uniformity of products through physical stirring and heating treatment, and avoids the problem of uneven distribution of rare earth elements in a silicon dioxide matrix due to phase separation. The proportion and the priority order of the alkaline catalyst are adjusted by ensuring the uniformity of the solvent, so that the controllability of the gel time is realized, and the time required by the gel is greatly shortened. The density and microstructure of the aerogel can be controlled by controlling and adjusting the proportion of rare earth elements, the forming process and the like, so that the heat conductivity of the aerogel is controlled. The preparation method has the advantages of simple process, lower cost and controllable reaction conditions, and the prepared double-rare earth co-doped silica aerogel block material has a complete block structure by controlling the proportion of ethanol and rare earth elements, can meet the preparation requirements of a mold, and can completely meet the usability of a special-shaped piece product in the heat insulation field by controlling the proper amplification of the mold.
The foregoing description is only an overview of the present application, and is intended to be implemented in accordance with the teachings of the present application in order that the technical means thereof may be more clearly understood, and in order that the present application may be more readily understood, its objects, features and advantages be more particularly described below.
Drawings
FIG. 1 is a macroscopic view of a dual rare earth co-doped silica gel obtained in example 1 in a method for preparing a dual rare earth reinforced silica block aerogel capable of being stably synthesized according to the present application.
FIG. 2 is a macroscopic view of a dual rare earth co-doped silica aerogel obtained in example 1 in a method for preparing a dual rare earth reinforced silica aerogel capable of being stably synthesized according to the present application.
FIG. 3 is a microscopic morphology of the dual rare earth co-doped silica aerogel obtained in example 1 in a method for preparing a dual rare earth reinforced silica aerogel capable of being stably synthesized according to the present application.
FIG. 4 is a comparative graph of silica aerogel obtained in example 4 and comparative example 1 after heat insulation at room temperature and 1000℃for 5min in a preparation method of a stably synthesized dual rare earth reinforced silica aerogel according to the present application.
FIG. 5 is a macroscopic view of silica aerogel obtained in comparative examples 2, 3 and 4 in the preparation method of the stable synthesis dual rare earth reinforced silica aerogel according to the present application.
Detailed Description
The technical scheme of the application is further described in detail below with reference to the attached drawings and specific embodiments. It is to be understood that the following examples are illustrative only and are not to be construed as limiting the scope of the application. All techniques implemented based on the above description of the application are intended to be included within the scope of the application.
In addition, unless otherwise specifically indicated, the various raw materials, reagents, instruments and equipment used in the present application may be obtained commercially or prepared by existing methods.
Example 1:
a preparation method of a double-rare earth reinforced silica block aerogel capable of being stably synthesized comprises the following steps:
(1) Tetraethyl orthosilicate, absolute ethyl alcohol and deionized water are mixed according to the mole ratio of 1:10:4, uniformly mixing and stirring for 15min at normal temperature, dropwise adding ethanol hydrochloride diluent with the mass fraction of 0.05wt% into the mixture at the speed of 6 s/drop through a constant pressure funnel, stirring for 120min, and then sealing and standing for 24h at room temperature to obtain the silica sol.
(2) Yttrium nitrate (Y (NO) 3 ) 3 ·4H 2 O) and ytterbium nitrate (Yb (NO) 3 ) 3 ·5H 2 The mass ratio of O) powder to ethanol is 1:9 is dissolved in ethanol, heated at 60 ℃ for 30min for full reaction, cooled to room temperature to obtain light white Y (NO) 3 ) 3 And milky Yb (NO) 3 ) 3 Rare earth solution.
(3) And (3) dropwise adding ammonia water and ethanol diluent (the molar ratio of tetraethoxysilane to ammonia water is 1:0.05) into the silica sol obtained in the step (1), and stirring for 1min to obtain a material added with the alkaline catalyst.
(4) The mol ratio of tetraethyl orthosilicate to Y or Yb is 1:0.05, and Y (NO) obtained in the step (2) 3 ) 3 Solution and Yb (NO) 3 ) 3 And (3) respectively adding the materials obtained in the step (3) into the solution, stirring for 1min, slowly dripping the rare earth mixed solution into the silica sol, stirring for 5min, stirring uniformly at normal temperature to obtain a composite sol solution, pouring the obtained composite sol solution into a mold, and standing at 25 ℃ for 2h to obtain the double rare earth co-doped silica gel, wherein the macroscopic diagram of the double rare earth co-doped silica gel is shown in the attached figure 1.
(5) Placing the double rare earth co-doped silica gel at 25 ℃, standing and aging for 24 hours, then placing the double rare earth co-doped silica gel into a high-pressure reaction kettle for supercritical drying, and taking ethanol as a supercritical drying medium, wherein the ethanol pressure is controlled at 8-10 MPa, the temperature is controlled at 270 ℃, and the supercritical drying time is 2 hours, thus obtaining the massive double rare earth co-doped silica aerogel.
The basic properties of the dual rare earth co-doped silica aerogel obtained in this example are shown in table 1.
TABLE 1 basic Properties of aerogels
| Density of | 0.19g/cm 3 |
| Specific surface area | 875.84m 2 /g |
| Average pore diameter | 12.93nm |
Example 2:
a preparation method of a double-rare earth reinforced silica block aerogel capable of being stably synthesized comprises the following steps:
(1) Tetraethyl orthosilicate, absolute ethyl alcohol and deionized water are mixed according to the mole ratio of 1:20:5, uniformly mixing and stirring for 15min at normal temperature, dropwise adding ethanol hydrochloride diluent with the mass fraction of 0.05wt% into the mixture at the speed of 6 s/drop through a constant pressure funnel, stirring for 120min, and then sealing and standing for 24h at room temperature to obtain the silica sol.
(2) Will Y (NO) 3 ) 3 ·4H 2 O and Yb (NO) 3 ) 3 ·5H 2 The mass ratio of the O powder to the ethanol is 1:9 is dissolved in ethanol, heated at 60 ℃ for 30min for full reaction, cooled to room temperature to obtain light white Y (NO) 3 ) 3 And milky Yb (NO) 3 ) 3 Rare earth solution.
(3) And (3) dropwise adding ammonia water and ethanol diluent (the molar ratio of tetraethoxysilane to ammonia water is 1:0.25) into the silica sol obtained in the step (1), and stirring for 1min to obtain a material added with the alkaline catalyst.
(4) The mol ratio of tetraethyl orthosilicate to Y or Yb is 1:0.125, and the Y (NO) obtained in the step (2) 3 ) 3 Solution and Yb (NO) 3 ) 3 And (3) respectively adding the materials obtained in the step (3) into the solution, stirring for 1min, slowly dripping the mixed solution into the silica sol, stirring for 5min, uniformly stirring at normal temperature to obtain a composite sol solution, pouring the obtained composite sol solution into a mould, and standing at 25 ℃ for 4h to obtain the double rare earth co-doped silica gel.
(5) Placing the double rare earth co-doped silica gel at 25 ℃, standing and aging for 24 hours, then placing the double rare earth co-doped silica gel into a high-pressure reaction kettle for supercritical drying, and taking ethanol as a supercritical drying medium, wherein the ethanol pressure is controlled at 8-10 MPa, the temperature is controlled at 270 ℃, and the supercritical drying time is 2 hours, thus obtaining the massive double rare earth co-doped silica aerogel.
The basic properties of the dual rare earth co-doped silica aerogel obtained in this example are shown in table 2.
TABLE 2 basic Properties of aerogels
| Density of | 0.09g/cm 3 |
| Specific surface area | 521.30m 2 /g |
| Average pore diameter | 13.35nm |
Example 3:
a preparation method of a double-rare earth reinforced silica block aerogel capable of being stably synthesized comprises the following steps:
(1) Tetraethyl orthosilicate, absolute ethyl alcohol and deionized water are mixed according to the mole ratio of 1:20:5, uniformly mixing and stirring for 15min at normal temperature, dropwise adding ethanol hydrochloride diluent with the mass fraction of 0.05wt% into the mixture at the speed of 6 s/drop through a constant pressure funnel, stirring for 120min, and then sealing and standing for 24h at room temperature to obtain the silica sol.
(2) Will Y (NO) 3 ) 3 ·4H 2 O and Yb (NO) 3 ) 3 ·5H 2 The mass ratio of the O powder to the ethanol is 1:9 is dissolved in ethanol, heated at 60 ℃ for 30min for full reaction, cooled to room temperature to obtain light white Y (NO) 3 ) 3 And milky Yb (NO) 3 ) 3 Rare earth solution.
(3) And (3) dropwise adding ammonia water and ethanol diluent (the molar ratio of tetraethoxysilane to ammonia water is 1:0.25) into the silica sol obtained in the step (1), and stirring for 1min to obtain a material added with the alkaline catalyst.
(4) The mol ratio of tetraethyl orthosilicate to Y or Yb is 1:0.25, and Y (NO) obtained in the step (2) 3 ) 3 Solution and Yb (NO) 3 ) 3 And (3) respectively adding the materials obtained in the step (3) into the solution, stirring for 1min, slowly dripping the mixed solution into the silica sol, stirring for 5min, uniformly stirring at normal temperature to obtain a composite sol solution, pouring the obtained composite sol solution into a mould, and standing at 25 ℃ for 8h to obtain the double rare earth co-doped silica gel.
(5) Placing the double rare earth co-doped silica gel at 25 ℃, standing and aging for 24 hours, then placing the double rare earth co-doped silica gel into a high-pressure reaction kettle for supercritical drying, and taking ethanol as a supercritical drying medium, wherein the ethanol pressure is controlled at 8-10 MPa, the temperature is controlled at 270 ℃, and the supercritical drying time is 2 hours, thus obtaining the massive double rare earth co-doped silica aerogel.
A macroscopic view of the bulk dual-rare earth co-doped silica aerogel obtained in example 3 is shown in fig. 2, and a microscopic structure view is shown in fig. 3. It can be seen that the double rare earth reinforced silica block aerogel with low density and large specific surface area is obtained by double rare earth co-doping.
The basic properties of the dual 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 of a double-rare earth reinforced silica block aerogel capable of being stably synthesized comprises the following steps:
(1) Tetraethyl orthosilicate, absolute ethyl alcohol and deionized water are mixed according to the mole ratio of 1:15:4, uniformly mixing and stirring for 15min at normal temperature, dropwise adding ethanol hydrochloride diluent with the mass fraction of 0.05wt% into the mixture at the speed of 6 s/drop through a constant pressure funnel, stirring for 120min, and then sealing and standing for 24h at room temperature to obtain the silica sol.
(2) Will Y (NO) 3 ) 3 ·4H 2 O and Yb (NO) 3 ) 3 ·5H 2 The mass ratio of the O powder to the ethanol is 1:9 is dissolved in ethanol, heated at 60 ℃ for 30min for full reaction, cooled to room temperature to obtain light white Y (NO) 3 ) 3 And milky Yb (NO) 3 ) 3 Rare earth solution.
(3) And (3) dropwise adding ammonia water and ethanol diluent (the molar ratio of tetraethoxysilane to ammonia water is 1:0.25) into the silica sol obtained in the step (1), and stirring for 1min to obtain a material added with the alkaline catalyst.
(4) The mol ratio of tetraethyl orthosilicate to Y or Yb is 1:0.05, and Y (NO) obtained in the step (2) 3 ) 3 Solution and Yb (NO) 3 ) 3 Adding the materials obtained in the step (3) into the solution respectively, stirring for 1min, slowly dripping the mixed solution into the silica sol, stirring for 5min, stirring uniformly at normal temperature to obtain a composite sol solution, pouring the obtained composite sol solution into a mold, and standing at 25 ℃ for 1h to obtain the double rare earthCo-doped silica gel.
(5) Placing the double rare earth co-doped silica gel at 25 ℃, standing and aging for 24 hours, then placing the double rare earth co-doped silica gel into a high-pressure reaction kettle for supercritical drying, and taking ethanol as a supercritical drying medium, wherein the ethanol pressure is controlled at 8-10 MPa, the temperature is controlled at 270 ℃, and the supercritical drying time is 2 hours, thus obtaining the massive double rare earth co-doped silica aerogel.
Comparative example 1:
the preparation method of the silica block aerogel comprises the following steps:
(1) Tetraethyl orthosilicate, absolute ethyl alcohol and deionized water are mixed according to the mole ratio of 1:20:5, uniformly mixing and stirring for 15min at normal temperature, dropwise adding ethanol hydrochloride diluent with the mass fraction of 0.05wt% into the mixture at the speed of 6 s/drop through a constant pressure funnel, stirring for 120min, and then sealing and standing for 24h at room temperature to obtain the silica sol.
(2) Dropwise adding ammonia water and ethanol diluent (tetraethoxysilane: ammonia water=1:0.25) into the silica sol obtained in the step (1), stirring for 1min to obtain a material added with an alkaline catalyst, pouring into a mould, and standing at 25 ℃ for 12h to obtain the silica gel.
(3) And standing and aging the silica gel at 25 ℃ for 24 hours, then placing the silica gel into a high-pressure reaction kettle for supercritical drying, and taking ethanol as a supercritical drying medium, wherein the ethanol pressure is controlled at 8-10 MPa, the temperature is controlled at 270 ℃, and the supercritical drying time is 2 hours, thus obtaining the silica aerogel.
The aerogels obtained in example 4 and comparative example 1 were each observed by heating at 1000℃for 5min, see FIG. 4. It can be seen that the aerogel without rare earth doping has poor stability and is easy to crush at high temperature, the heating surface is basically flat without cracking after the double rare earth doping, the stability of the silica gel is obviously increased, the service temperature of the material is improved, and the structural collapse at high temperature is prevented.
Comparative example 2:
the preparation method of the silica block aerogel comprises the following steps:
(1) Tetraethyl orthosilicate, absolute ethyl alcohol and deionized water are mixed according to the mole ratio of 1:15:4, uniformly mixing and stirring for 15min at normal temperature, dropwise adding ethanol hydrochloride diluent with the mass fraction of 0.05wt% into the mixture at the speed of 6 s/drop through a constant pressure funnel, stirring for 120min, and then sealing and standing for 24h at room temperature to obtain the silica sol.
(2) Will Y (NO) 3 ) 3 ·4H 2 O and Yb (NO) 3 ) 3 ·5H 2 The mass ratio of the O powder to the ethanol is 1:9 is dissolved in ethanol, heated at 60 ℃ for 30min for full reaction, cooled to room temperature to obtain light white Y (NO) 3 ) 3 And milky Yb (NO) 3 ) 3 Rare earth solution.
(3) The mol ratio of tetraethyl orthosilicate to Y or Yb is 1:0.05, and Y (NO) obtained in the step (2) 3 ) 3 Solution and Yb (NO) 3 ) 3 And (3) adding the solutions into the silica sol obtained in the step (1) respectively to obtain a mixed material.
(4) And (3) dropwise adding ammonia water and ethanol diluent (the molar ratio of tetraethoxysilane to ammonia water is 1:0.25) into the material obtained in the step (3), stirring and stirring for 5min, uniformly stirring at normal temperature to obtain a composite sol solution, pouring the obtained composite sol solution into a mould, and standing at 25 ℃ for about 48h to obtain the double rare earth co-doped silica gel.
(5) Placing the double rare earth co-doped silica gel at 25 ℃, standing and aging for 24 hours, then placing the double rare earth co-doped silica gel into a high-pressure reaction kettle for supercritical drying, and taking ethanol as a supercritical drying medium, wherein the ethanol pressure is controlled at 8-10 MPa, the temperature is controlled at 270 ℃, and the supercritical drying time is 2 hours, thus obtaining the massive double rare earth co-doped silica aerogel.
Comparative example 3:
the difference from comparative example 2 is that only single rare earth Y is doped, Y (NO) is selected in step (2) 3 ) 3 ·5H 2 O powder, Y (NO) 3 ) 3 ·5H 2 The mass ratio of the O powder to the ethanol is 1:9 is dissolved in ethanol, heated at 60 ℃ for 30min for full reaction, cooled to room temperature to obtain light white Y (NO) 3 ) 3 The molar ratio of the tetraethyl orthosilicate to the Y in the step (3) is 1:0.5,the composite sol solution was allowed to stand for about 72 hours.
Comparative example 4:
the difference from comparative example 3 is that only single rare earth doped is Yb, yb (NO 3 ) 3 ·5H 2 O powder, yb (NO) 3 ) 3 ·5H 2 The mass ratio of the O powder to the ethanol is 1:9 is dissolved in ethanol, heated at 60 ℃ for 30min for full reaction, cooled to room temperature to obtain milky Yb (NO) 3 ) 3 The molar ratio of tetraethyl orthosilicate to Yb in the step (3) is 1:0.5, the composite sol solution is left 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
| Properties of (C) | Comparative example 2 | Comparative example 3 | Comparative example 4 |
| Density of | 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 |
| Pore diameter | 12.93nm | 13.71nm | 13.66nm |
| Gel time | ～48h | ～72h | ～50h |
Referring to table 4 and fig. 5, comparative examples 2, 3, and 4 require longer gel time and uncontrollable gel time after changing the addition sequence of the basic catalyst, compared to the double rare earth co-doped aerogels of examples 1 to 4. Compared with the double rare earth co-doped aerogel of comparative example 2, comparative examples 3 and 4 are doped with only one rare earth nitrate, the obtained gel has a higher density and takes a long time to complete the gel. Referring to FIG. 5, comparative example 3 doped with only Y one rare earth element, the gel was incomplete, and long gel time (72 hours) was required for complete gel, greatly prolonging the gel time; comparative example 4 was doped with Yb, a rare earth element alone, and in the course of gelation, flocculent phase separation was easily generated to cause gel cracking, and longer gel time (-50 h) was required for complete gelation. According to the method, the addition sequence of the optimized alkaline catalyst is optimized in each embodiment, and when two rare earths with the same proportion are selected for co-doping, the gel has proper gel time and can form a complete block body, and the obtained aerogel has good uniformity.
The foregoing embodiment numbers of the present application are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments.
The embodiments of the present application have been described above with reference to the accompanying drawings, but the present application is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present application and the scope of the claims, which are to be protected by the present application.
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.
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