CN108689679B - Preparation method of high-temperature-resistant gradient fiber composite aerogel thermal insulation material - Google Patents
Preparation method of high-temperature-resistant gradient fiber composite aerogel thermal insulation material Download PDFInfo
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Abstract
The invention relates to a preparation method of a high-temperature-resistant gradient fiber composite aerogel heat insulation material, which comprises the steps of taking cheap silica sol and alumina sol as a silicon source and an aluminum source, taking inorganic glass fiber, alumina silicate fiber, alumina fiber and the like as aerogel structure reinforcements, taking absolute ethyl alcohol and deionized water as solvents, combining an acid catalyst, mixing according to a certain proportion, preparing gradient fiber composite alcogel by sol-gel, aging, solvent replacement and other methods, and drying a sample by a simple and low-cost vacuum drying method to finally obtain the gradient fiber composite aerogel.
Description
Technical Field
The invention belongs to the technical field of preparation of inorganic nano materials with high-efficiency gradient heat insulation and high temperature resistance, and particularly relates to a preparation method of a high temperature resistant gradient fiber composite aerogel heat insulation material.
Background
The aerogel is a three-dimensional nano-network structure formed by mutually coalescing colloidal particles or high polymer molecules, and is a novel nano-porous material. The nano-silica gel has the characteristics of high specific surface area, high porosity, low refractive index, ultralow density, super-strong adsorbability and the like, so that the nano-silica gel has wide application prospects in the aspects of thermal, optical, electrical, acoustic and the like. In the aspect of thermal, the nano porous network structure of the aerogel can effectively inhibit solid phase heat conduction and gas phase heat conduction, has excellent heat insulation characteristics, is a solid material with the lowest heat conductivity in the world at present, and has wide application prospects in the fields of space flight and aviation, chemical metallurgy, energy-saving buildings and the like.
According to the current reports at home and abroad, the traditional SiO of single system2The aerogel thermal insulation material has a plurality of excellent characteristics, but the long-term stable use temperature is only limited below 650 ℃, so that the SiO is greatly restricted2The application range of aerogel materials. The study shows that Al2O3The aerogel has stable forming, high structural strength and temperature resistance of over 1000 ℃, but has better heat insulation effect than SiO2The aerogel materials are less desirable. It is known that the strength of pure silica-based, aluminum-based and other oxide aerogels is very low, large samples cannot be prepared, and machining and molding are difficult, so that large-scale application is difficult to realize. Therefore, pure nano-aerogels must be structurally reinforced with reinforcing materials such as fibers. Therefore, Al is reinforced with alumina fibers2O3Aerogel used as high-temperature resistant layer for resisting high-temperature heat source, and glass fiber reinforced SiO2Aerogel is used as an efficient heat insulation layer, and in order to better solve the problem of interface combination, an interface self-healing transition layer, namely aluminum silicate fiber reinforced SiO, is inserted between the aerogel and the aerogel2/Al2O3The composite aerogel forms a complete and integrated gradient fiber composite aerogel heat insulation material, and the composite material can resist high temperature, can achieve the optimal heat insulation effect, and has great scientific research value and wide practical application prospect.
Disclosure of Invention
The invention aims to design a fiber composite aerogel system, which utilizes alumina fibers to reinforce Al2O3Aerogel used as high-temperature resistant layer for resisting high-temperature heat source, and glass fiber reinforced SiO2Aerogel is used as an efficient heat insulation layer, and an interface self-healing transition layer aluminum silicate fiber reinforced SiO is adopted in the middle2/Al2O3Composite aerogel solution to interface bonding problemsThe problem is to provide a preparation method of a high temperature resistant gradient fiber composite aerogel heat insulation material with high temperature resistance, easy forming and processing and high-efficiency heat insulation effect.
The technical scheme of the invention is as follows: a preparation method of a high-temperature-resistant gradient fiber composite aerogel thermal insulation material comprises the following specific steps: a preparation method of a high-temperature-resistant gradient fiber composite aerogel thermal insulation material comprises the following specific steps:
(1) mixing silica sol, absolute ethyl alcohol and deionized water according to a volume ratio of 1: (0.5-2.0): (0.1-1.0) are uniformly mixed to prepare a solution, and the solution is mixed and stirred for 30-60 min at the temperature of 45-50 ℃ to obtain clear SiO2Continuously adding an acid catalyst into the sol solution, adjusting the pH value of the solution to 4-6, then soaking the sol solution into glass fibers in a mold, sealing the film, and placing the glass fibers in a vacuum drying oven at 50-60 ℃ for 3-6 hours to obtain glass fiber composite SiO2Taking out the fiber composite wet gel A together with the die, and placing aluminum silicate fibers on the upper surface of the fiber composite wet gel A;
(2) mixing silica sol, alumina sol, absolute ethyl alcohol and deionized water according to a volume ratio of 1: (0.2-5): (0.5-3.0): (0.2-2.0) are uniformly mixed to prepare a solution, the solution is mixed and stirred for 30-60 min at the temperature of 45-50 ℃, the acid catalyst is continuously added, the pH value of the solution is adjusted to 4-6, and the clear SiO is obtained2-Al2O3Sol solution of the SiO2-Al2O3Slowly dipping the sol solution into the aluminum silicate fibers in the mold in the step (1), sealing the film, placing the film in a vacuum drying oven at 50-60 ℃ for 2-5 hours to obtain and mark fiber composite wet gel A-B, taking the fiber composite wet gel A-B together with the mold out, and placing alumina fibers on the upper surface of the fiber composite wet gel A-B;
(3) mixing alumina sol, absolute ethyl alcohol and deionized water according to a volume ratio of 1: (0.1-1.0): (0.2-2.0) are uniformly mixed to prepare a solution, the solution is mixed and stirred for 30-60 min at the temperature of 45-50 ℃, the acid catalyst is continuously added, the pH value of the solution is adjusted to 4-6, and the clear Al is obtained2O3Sol solution of the Al2O3Slowly dipping the sol solution in the step (2) mold for oxidationSealing the film in the aluminum fiber, placing the aluminum fiber in a vacuum drying oven at the temperature of 60-65 ℃ for 1-3 hours to obtain and mark as fiber composite wet gel A-B-C, taking out the fiber composite wet gel A-B-C together with a mold, placing the fiber composite wet gel A-B-C at normal temperature, adding an aging solution, and performing aging treatment on the composite wet gel to obtain an aged gradient fiber composite wet gel;
(4) adding an organic solvent into the mold in the step (3) to carry out solvent replacement on the gradient fiber composite wet gel to obtain gradient fiber composite alcogel;
(5) drying the gradient fiber composite alcogel displaced in the step (4) to obtain gradient fiber composite aerogel;
(6) and (5) carrying out high-temperature heat treatment on the gradient fiber composite aerogel in the step (5) to obtain the high-temperature-resistant gradient fiber composite aerogel heat-insulating material.
Preferably, the silica sol in the steps (1) and (2) has the particle size of 10-20 nm and SiO2The mass content of (A) is 20-45%.
Preferably, the alumina sol in the steps (2) and (3) is a colloidal solution with positive charges and feather-like nano alumina colloidal particles dispersed in water; particle size of 10-20 nm, large specific surface area, Al2O3The mass content of (A) is 20-30%.
Preferably, the acidic catalyst in steps (1), (2) and (3) is one of hydrochloric acid, nitric acid or perchloric acid.
Preferably, the aging solution in the step (3) is a mixed solution of one or two or more of tetraethyl orthosilicate, tetramethyl orthosilicate, aluminum sec-butoxide and aluminum isopropoxide.
Preferably, the organic solvent in step (4) is one of ethanol, methanol or acetone.
Preferably, the solvent in the step (4) is replaced by replacing the organic solvent once every 12-24 h for 3-5 times.
Preferably, the drying process in the step (5) is as follows: vacuum drying, wherein the drying temperature is a gradient control heating method, the temperature is 45-55 ℃, and the drying time is 3-8 h; drying for 5-15 h at 60-70 ℃; drying for 2-5 h at 100-120 ℃.
Preferably, the high-temperature heat treatment process in the step (6) comprises: under the aerobic condition, the heat treatment temperature is 300-500 ℃, and the heat treatment time is 1-3 h.
Pure SiO reported in the literature2The maximum service temperature of the aerogel material is only 650 ℃, and SiO at the temperature2The three-dimensional network structure of the aerogel has almost collapsed and the specific surface area is as low as 50m2Below/g, the porosity is extremely low, and the heat insulation effect of the aerogel material is lost. The gradient fiber composite aerogel heat-insulating material is tested by a cold surface temperature instrument under the aerobic condition, and a heat source at 1200 ℃ is directly contacted with the alumina fiber reinforced Al2O3Aerogel, test time 5h, found: the gradient fiber composite aerogel material keeps the structure intact and has good high temperature resistance and heat insulation effect. Wherein the thermal conductivity is less than 0.05W/mK at 25 ℃, the thermal conductivity is less than 0.1W/mK at 800 ℃ of the hot face, the thermal conductivity is 0.2W/mK at 1000 ℃ of the hot face, and the thermal conductivity is less than 0.3W/mK at 1200 ℃ of the hot face.
Has the advantages that:
1. the gradient fiber composite aerogel thermal insulation material is prepared by adopting a vacuum drying technology. Firstly, preparing fiber composite wet gel by a simple sol-gel method, and then preparing the gradient fiber composite aerogel heat insulation material which is high temperature resistant and easy to mold and process by utilizing technologies such as low-cost vacuum drying, high-temperature heat treatment and the like.
2. The silica-based aerogel is more applied in the field of heat insulation and has the best heat insulation effect, the heat conductivity can be as low as 0.016W/m.K, the long-term use temperature is not more than 650 ℃, and the aluminum-based aerogel and other aerogels have the high temperature resistance of 1000-1200 ℃, but the heat insulation effect is not as good as that of the silica-based aerogel. Therefore, the invention uses alumina fiber to reinforce Al2O3The aerogel is used as the high-temperature resistant surface of the heat insulation material to improve the temperature resistance of the composite aerogel, and the aluminum silicate fiber is used for reinforcing SiO2/Al2O3The composite aerogel is used as an interface self-healing transition layer, not only solves the problem of interface combination, but also plays a role of a heat transfer transition layer of the composite aerogel, and further enables the glass fiber to reinforce SiO2Aerogel hairPlays a role of a high-efficiency heat insulation layer. Therefore, the invention has great research value and application prospect in the aspects of improving the use temperature and the heat insulation effect of the fiber composite aerogel.
Drawings
Fig. 1 is an SEM photograph of the gradient fiber composite aerogel prepared in example 1.
Detailed Description
Example 1
Mixing silica Sol (SiO)2The particle size is 10nm, the content is 20wt percent), absolute ethyl alcohol and deionized water are uniformly mixed according to the volume ratio of 1:0.5:0.1 to prepare a solution, and the solution is mixed and stirred for 30min at the temperature of 45 ℃ to obtain clear SiO2Adding hydrochloric acid into the sol solution, adjusting the pH value of the solution to 4, soaking the sol solution into a glass fiber felt in a mold, sealing the film, and placing the film in a vacuum drying oven at 50 ℃ for 3 hours to obtain glass fiber composite SiO2Wet gel, marked as fiber composite wet gel A, taking out the mold, and placing aluminum silicate fiber on the upper surface of the mold; continuing to mix silica Sol (SiO)2Particle size of 10nm, content of 20 wt%), alumina sol (Al)2O3Particle size of 10nm, content of 20 wt%), anhydrous ethanol, deionized water at volume ratio of 1:0.2:0.5:0.2, mixing at 45 deg.C for 30min, adding hydrochloric acid, adjusting pH to 4, and mixing with the SiO solid2/Al2O3Slowly soaking the sol solution in the aluminum silicate fiber felt in the mold, sealing the film, placing in a vacuum drying oven at 50 ℃ for 2h to obtain and mark as fiber composite wet gel A-B, taking out the mold, and placing alumina fiber on the upper surface of the mold; then adding alumina sol (Al)2O3Particle size of 10nm, content of 20 wt%), anhydrous ethanol, and deionized water at volume ratio of 1:0.1:0.2, mixing at 45 deg.C for 30min, adding hydrochloric acid, adjusting pH to 4, and mixing the Al with the mixture2O3Slowly soaking the sol solution in the alumina fiber felt in the mold, sealing the film, placing in a vacuum drying oven at 60 deg.C for 1h to obtain gradient fiber composite wet gel A-B-C, standing at room temperature, and adding tetraethoxysilaneAnd the ethyl ester is aging liquid, and the composite wet gel is aged, and is replaced once every 24 hours for 3 times to obtain the aged gradient fiber composite wet gel. And adding an ethanol solvent into the sample in the mold, and replacing the solvent for 3 times, wherein each time lasts for 24 hours, so as to finally obtain the gradient fiber composite alcohol gel. And then putting the gradient fiber composite alcogel into a vacuum drying oven for gradient temperature rise drying, drying for 3h at 45 ℃, drying for 10h at 60 ℃ and drying for 5h at 100 ℃ to prepare the gradient fiber composite aerogel, and performing heat treatment for 1h at high temperature of 500 ℃ to finally obtain the gradient fiber composite aerogel heat insulation material. The SEM photograph of the prepared gradient fiber composite aerogel is shown in fig. 1. According to the characterization, the thermal conductivity of the composite aerogel at 25 ℃ is 0.043W/m.K, the thermal conductivity at 800 ℃ of the thermal surface is 0.086W/m.K, the thermal conductivity at 1000 ℃ of the thermal surface is 0.164W/m.K, and the thermal conductivity at 1200 ℃ of the thermal surface is 0.273W/m.K.
Example 2
Mixing silica Sol (SiO)2The particle size is 20nm, the content is 45wt percent), absolute ethyl alcohol and deionized water are uniformly mixed according to the volume ratio of 1:2:1 to prepare a solution, and the solution is mixed and stirred for 60min at the temperature of 50 ℃ to obtain clear SiO2Adding hydrochloric acid into the sol solution, adjusting the pH value of the solution to 6, soaking the sol solution into a glass fiber felt in a mold, sealing the film, and placing the glass fiber felt in a vacuum drying oven at 60 ℃ for 6 hours to obtain glass fiber composite SiO2Wet gel, marked as fiber composite wet gel A, taking out the mold, and placing aluminum silicate fiber on the upper surface of the mold; continuing to mix silica Sol (SiO)2Particle size of 20nm, content of 45 wt%), alumina sol (Al)2O3Particle size of 20nm, content of 30 wt%), anhydrous ethanol, deionized water at volume ratio of 1:5:3:2, mixing at 50 deg.C for 60min, adding hydrochloric acid, adjusting pH to 6, and mixing with the above solution2/Al2O3Slowly soaking the sol solution in the aluminum silicate fiber felt in the mold, sealing the film, placing in a vacuum drying oven at 60 ℃ for 5 hours to obtain and mark fiber composite wet gel A-B, taking out the mold, and placing alumina fiber on the upper surface of the mold; then adding alumina sol (Al)2O3Particle size of 20nm, the content of which is 30wt percent), absolute ethyl alcohol and deionized water are uniformly mixed according to the volume ratio of 1:1:2 to prepare a solution, the solution is mixed and stirred for 60min at the temperature of 50 ℃, hydrochloric acid is continuously added, the pH value of the solution is adjusted to be 6, and the Al is added2O3Slowly soaking the sol solution in the alumina fiber felt in the mold, sealing the film, placing the film in a 65 ℃ vacuum drying oven for 3 hours to obtain gradient fiber composite wet gel A-B-C, placing the gradient fiber composite wet gel at normal temperature, taking a mixed solution of tetraethyl orthosilicate and aluminum sec-butoxide as an aging solution, carrying out aging treatment on the composite wet gel, replacing the gel once every 12 hours for 5 times, and obtaining the aged gradient fiber composite wet gel. And adding an ethanol solvent into the sample in the mold, and replacing the solvent for 5 times, wherein each time is 12 hours, so as to finally obtain the gradient fiber composite alcohol gel. And then putting the gradient fiber composite alcogel into a vacuum drying oven for gradient temperature rise drying, drying for 8 hours at 55 ℃, 5 hours at 70 ℃ and 2 hours at 120 ℃ to prepare the gradient fiber composite aerogel, and performing heat treatment for 3 hours at 300 ℃ to finally obtain the gradient fiber composite aerogel heat insulation material. According to the characterization, the thermal conductivity of the composite aerogel at 25 ℃ is 0.046W/m.K, the thermal conductivity at 800 ℃ of the thermal surface is 0.091W/m.K, the thermal conductivity at 1000 ℃ of the thermal surface is 0.169W/m.K, and the thermal conductivity at 1200 ℃ of the thermal surface is 0.282W/m.K.
Example 3
Mixing silica Sol (SiO)2The particle size is 15nm, the content is 30wt percent), absolute ethyl alcohol and deionized water are uniformly mixed according to the volume ratio of 1:1:0.5 to prepare a solution, and the solution is mixed and stirred for 50min at the temperature of 45 ℃ to obtain clear SiO2Adding nitric acid into the sol solution continuously, adjusting the pH value of the solution to 5, soaking the sol solution into a glass fiber felt in a mold, sealing a film, and placing the film in a vacuum drying oven at 55 ℃ for 4 hours to obtain glass fiber composite SiO2Wet gel, marked as fiber composite wet gel A, taking out the mold, and placing aluminum silicate fiber on the upper surface of the mold; then adding silica Sol (SiO)2Particle size of 15nm, content of 30 wt%), alumina sol (Al)2O3Particle size of 15nm, content of 25 wt%), anhydrous ethanol, and deionized water at volume ratio of 1:1:1:1, mixing at 50 deg.C for 60min, and adding nitrateAcid, adjusting the pH value of the solution to 5, and adding the SiO2/Al2O3Slowly soaking the sol solution in the aluminum silicate fiber felt in the mold, sealing the film, placing in a vacuum drying oven at 50 ℃ for 3h to obtain and mark as fiber composite wet gel A-B, taking out the mold, and placing alumina fiber on the upper surface of the mold; then adding alumina sol (Al)2O3Particle size of 15nm, content of 25 wt%), anhydrous ethanol, and deionized water at volume ratio of 1:0.5:1, mixing at 50 deg.C for 45min, adding nitric acid, adjusting pH to 5, and mixing the Al with the mixture2O3Slowly soaking the sol solution in the alumina fiber felt in the mold, sealing the film, placing the film in a vacuum drying oven at 60 ℃ for 2h to obtain the gradient fiber composite wet gel A-B-C, placing the gradient fiber composite wet gel at normal temperature, taking the mixed solution of tetramethyl orthosilicate and aluminum isopropoxide as an aging solution, carrying out aging treatment on the composite wet gel, replacing the gel once every 18h for 4 times, and obtaining the aged gradient fiber composite wet gel. And adding a methanol solvent into the sample in the mold, and replacing the solvent for 4 times, wherein each time is 18 hours, so as to finally obtain the gradient fiber composite alcohol gel. And then putting the gradient fiber composite alcogel into a vacuum drying oven for gradient temperature rise drying, drying for 5h at 50 ℃, drying for 15h at 65 ℃ and drying for 3h at 110 ℃ to prepare the gradient fiber composite aerogel, and performing heat treatment for 2h at the high temperature of 400 ℃ to finally obtain the gradient fiber composite aerogel heat insulation material. According to the characterization, the thermal conductivity of the composite aerogel at 25 ℃ is 0.044W/m.K, the thermal conductivity at 800 ℃ of the hot face is 0.085W/m.K, the thermal conductivity at 1000 ℃ of the hot face is 0.175W/m.K, and the thermal conductivity at 1200 ℃ of the hot face is 0.277W/m.K.
Example 4
Mixing silica Sol (SiO)2Particle size of 12nm, content of 25 wt%), absolute ethyl alcohol and deionized water according to volume ratio of 1:1.5:0.8 to prepare solution, mixing and stirring at 45 ℃ for 40min to obtain clear SiO2Adding nitric acid into the sol solution continuously, adjusting the pH value of the solution to 6, soaking the sol solution into a glass fiber felt in a mold, sealing a film, and placing the film in a vacuum drying oven at 55 ℃ for 5 hours to obtain glass fiber composite SiO2The gel is a wet gel and the gel is a dry gel,marking as fiber composite wet gel A, taking out the mold, and placing aluminum silicate fibers on the upper surface of the mold; then adding silica Sol (SiO)2Particle size of 12nm, content of 25 wt%), alumina sol (Al)2O3Particle size of 12nm and content of 23 wt%), anhydrous ethanol and deionized water in a volume ratio of 1:2:1.5:1.5 to prepare a solution, mixing and stirring at 50 ℃ for 50min, continuously adding nitric acid, adjusting pH value of the solution to 6, and adding the SiO2/Al2O3Slowly soaking the sol solution in the aluminum silicate fiber felt in the mold, sealing the film, placing the film in a vacuum drying oven at 50 ℃ for 4 hours to obtain and mark fiber composite wet gel A-B, taking out the mold, and placing alumina fibers on the upper surface of the mold; then adding alumina sol (Al)2O3Particle size of 12nm, content of 23 wt%), anhydrous ethanol, deionized water at volume ratio of 1:0.8:0.6, mixing at 45 deg.C for 60min, adding nitric acid, adjusting pH to 6, and mixing with Al2O3Slowly soaking the sol solution in the alumina fiber felt in the mold, sealing the film, placing in a 65 ℃ vacuum drying oven for 1.5 hours to obtain the gradient fiber composite wet gel A-B-C, placing at normal temperature, taking secondary butanol aluminum as an aging solution, aging the composite wet gel, and replacing for 4 times every 20 hours to obtain the aged gradient fiber composite wet gel. And adding a methanol solvent into the sample in the mold, and replacing the solvent for 3 times, wherein each time is 24 hours, so as to finally obtain the gradient fiber composite alcohol gel. And then putting the gradient fiber composite alcogel into a vacuum drying oven for gradient temperature rise drying, drying for 6 hours at 48 ℃, drying for 12 hours at 60 ℃ and drying for 4 hours at 120 ℃ to prepare the gradient fiber composite aerogel, and performing heat treatment for 3 hours at 350 ℃ to finally obtain the gradient fiber composite aerogel heat insulation material. According to the characterization, the thermal conductivity of the composite aerogel at 25 ℃ is 0.048W/m.K, the thermal conductivity at 800 ℃ of the thermal surface is 0.097W/m.K, the thermal conductivity at 1000 ℃ of the thermal surface is 0.178W/m.K, and the thermal conductivity at 1200 ℃ of the thermal surface is 0.285W/m.K.
Example 5
Mixing silica Sol (SiO)2Particle size of 18nm, content of 40 wt.%), and absolute ethyl alcoholUniformly mixing deionized water according to the volume ratio of 1:0.9:0.6 to prepare a solution, and mixing and stirring at 45 ℃ for 30min to obtain clear SiO2Adding perchloric acid into the sol solution continuously, adjusting the pH value of the solution to be 4, soaking the sol solution into a glass fiber felt in a mould, sealing a film, and placing the glass fiber felt in a vacuum drying oven at 55 ℃ for 3 hours to obtain glass fiber composite SiO2Wet gel, marked as fiber composite wet gel A, taking out the mold, and placing aluminum silicate fiber on the upper surface of the mold; then adding silica Sol (SiO)2Particle size of 18nm, content of 40 wt%), alumina sol (Al)2O3Particle size of 18nm, content of 28 wt%), anhydrous ethanol, deionized water at volume ratio of 1:4:2.5:1.6, mixing at 50 deg.C for 40min, adding perchloric acid, adjusting pH to 5, and mixing with SiO2/Al2O3Slowly soaking the sol solution in the aluminum silicate fiber felt in the mold, sealing the film, placing in a vacuum drying oven at 55 ℃ for 3h to obtain and mark as fiber composite wet gel A-B, taking out the mold, and placing alumina fiber on the upper surface of the mold; then adding alumina sol (Al)2O3Particle size of 18nm, content of 28 wt%), anhydrous ethanol, and deionized water at volume ratio of 1:0.4:1.2, mixing at 45 deg.C for 60min, adding perchloric acid, adjusting pH to 5, and mixing with Al2O3Slowly soaking the sol solution in the alumina fiber felt in the mold, sealing the film, placing the film in a 65 ℃ vacuum drying oven for 1.5 hours to obtain gradient fiber composite wet gel A-B-C, placing the gradient fiber composite wet gel at normal temperature, taking a mixed solution of tetraethyl orthosilicate and aluminum isopropoxide as an aging solution, carrying out aging treatment on the composite wet gel, replacing the gel once every 15 hours for 5 times to obtain gradient fiber composite wet gel, adding an acetone solvent into a sample in the mold, and replacing the solvent for 4 times, wherein each time is 20 hours to finally obtain the gradient fiber composite alcohol gel. Then the gradient fiber composite aerogel is put into a vacuum drying oven for gradient temperature rise drying, drying is carried out for 7 hours at 50 ℃, 7 hours at 70 ℃ and 4 hours at 100 ℃ to prepare the gradient fiber composite aerogel, and the gradient fiber composite aerogel is subjected to heat treatment for 2 hours at the high temperature of 450 ℃ to finally obtain the gradient fiber composite aerogelGlue heat insulating material. According to the characterization, the thermal conductivity of the composite aerogel at 25 ℃ is 0.046W/m.K, the thermal conductivity at 800 ℃ of the thermal surface is 0.091W/m.K, the thermal conductivity at 1000 ℃ of the thermal surface is 0.181W/m.K, and the thermal conductivity at 1200 ℃ of the thermal surface is 0.295W/m.K.
Example 6
Mixing silica Sol (SiO)2Particle size of 16nm and content of 28 wt%), absolute ethyl alcohol and deionized water according to volume ratio of 1:1.4:0.7, mixing and stirring at 45 deg.C for 60min to obtain clear SiO2Adding perchloric acid into the sol solution continuously, adjusting the pH value of the solution to 5, soaking the sol solution into a glass fiber felt in a mold, sealing a film, and placing the glass fiber felt in a vacuum drying oven at 55 ℃ for 4 hours to obtain glass fiber composite SiO2Wet gel, marked as fiber composite wet gel A, taking out the mold, and placing aluminum silicate fiber on the upper surface of the mold; then adding silica Sol (SiO)2Particle size of 16nm, content of 28 wt%), alumina sol (Al)2O3Particle size of 16nm and content of 22 wt%), anhydrous ethanol and deionized water in a volume ratio of 1:3.5:2.5:1.8 to prepare a solution, mixing and stirring at 50 ℃ for 30min, continuously adding perchloric acid, adjusting pH value of the solution to 5, and mixing the SiO powder with the solution2/Al2O3Slowly soaking the sol solution in the aluminum silicate fiber felt in the mold, sealing the film, placing the film in a vacuum drying oven at 60 ℃ for 4.5 hours to obtain and mark a fiber composite wet gel A-B, taking out the mold, and placing alumina fibers on the upper surface of the mold; then adding alumina sol (Al)2O3Particle size of 16nm, content of 22 wt%), anhydrous ethanol, and deionized water at volume ratio of 1:0.3:1.2, mixing at 50 deg.C for 50min, adding perchloric acid, adjusting pH to 4, and mixing with Al2O3Slowly soaking the sol solution in the alumina fiber felt in the mold, sealing the film, placing in a vacuum drying oven at 50 deg.C for 2h to obtain gradient fiber composite wet gel A-B-C, placing at normal temperature, aging the composite wet gel with mixed solution of tetramethyl orthosilicate and aluminum sec-butoxide as aging solution, changing every 20h for 3 times to obtain aged gelThe gradient fiber of (3) is compounded with the wet gel. And adding an acetone solvent into the sample in the mold, and replacing the solvent for 5 times, wherein each time is 15 hours, so as to finally obtain the gradient fiber composite alcohol gel. And then putting the gradient fiber composite alcogel into a vacuum drying oven for gradient temperature rise drying, drying for 4 hours at 55 ℃, drying for 12 hours at 65 ℃ and drying for 2 hours at 120 ℃ to prepare the gradient fiber composite aerogel, and performing heat treatment for 2.5 hours at 380 ℃ to finally obtain the gradient fiber composite aerogel heat insulation material. According to the characterization, the thermal conductivity of the composite aerogel at 25 ℃ is 0.047W/m.K, the thermal conductivity at 800 ℃ of the thermal surface is 0.088W/m.K, the thermal conductivity at 1000 ℃ of the thermal surface is 0.176W/m.K, and the thermal conductivity at 1200 ℃ of the thermal surface is 0.289W/m.K.
Claims (9)
1. A preparation method of a high-temperature-resistant gradient fiber composite aerogel thermal insulation material comprises the following specific steps:
(1) mixing silica sol, absolute ethyl alcohol and deionized water according to a volume ratio of 1: (0.5-2.0): (0.1-1.0) are uniformly mixed to prepare a solution, and the solution is mixed and stirred for 30-60 min at the temperature of 45-50 ℃ to obtain clear SiO2Continuously adding an acid catalyst into the sol solution, adjusting the pH value of the solution to 4-6, then soaking the sol solution into glass fibers in a mold, sealing the film, and placing the glass fibers in a vacuum drying oven at 50-60 ℃ for 3-6 hours to obtain glass fiber composite SiO2Taking out the fiber composite wet gel A together with the die, and placing aluminum silicate fibers on the upper surface of the fiber composite wet gel A;
(2) mixing silica sol, alumina sol, absolute ethyl alcohol and deionized water according to a volume ratio of 1: (0.2-5): (0.5-3.0): (0.2-2.0) are uniformly mixed to prepare a solution, the solution is mixed and stirred for 30-60 min at the temperature of 45-50 ℃, the acid catalyst is continuously added, the pH value of the solution is adjusted to 4-6, and the clear SiO is obtained2-Al2O3Sol solution of the SiO2-Al2O3Dipping the sol solution into the aluminum silicate fibers in the mold in the step (1), sealing, placing in a vacuum drying oven at 50-60 ℃ for 2-5 hours to obtain and mark fiber composite wet gel A-B, taking out the fiber composite wet gel A-B together with the mold, and placing alumina fibers on the upper surface of the fiber composite wet gel A-B;
(3) mixing alumina sol, absolute ethyl alcohol and deionized water according to a volume ratio of 1: (0.1-1.0): (0.2-2.0) are uniformly mixed to prepare a solution, the solution is mixed and stirred for 30-60 min at the temperature of 45-50 ℃, the acid catalyst is continuously added, the pH value of the solution is adjusted to 4-6, and the clear Al is obtained2O3Sol solution of the Al2O3Slowly dipping the sol solution into the alumina fiber in the mold in the step (2), sealing the film, placing the film in a vacuum drying oven at the temperature of 60-65 ℃ for 1-3 hours to obtain and record fiber composite wet gel A-B-C, taking out the fiber composite wet gel A-B-C together with the mold, placing the fiber composite wet gel A-B-C, adding an aging liquid, and performing aging treatment on the composite wet gel to obtain an aged gradient fiber composite wet gel;
(4) adding an organic solvent into the mold in the step (3) to carry out solvent replacement on the gradient fiber composite wet gel to obtain gradient fiber composite alcogel;
(5) drying the gradient fiber composite alcogel displaced in the step (4) to obtain gradient fiber composite aerogel;
(6) and (5) carrying out high-temperature heat treatment on the gradient fiber composite aerogel in the step (5) to obtain the high-temperature-resistant gradient fiber composite aerogel heat-insulating material.
2. The method according to claim 1, wherein the silica sol in the steps (1) and (2) has a silica particle size of 10 to 20nm and SiO2The mass content of (A) is 20-45%.
3. The method according to claim 1, wherein the alumina sol in steps (2) and (3) is a colloidal solution of positively charged feathered nano alumina colloidal particles dispersed in water; particle size of 10-20 nm, large specific surface area, Al2O3The mass content of (A) is 20-30%.
4. The method according to claim 1, wherein the acidic catalyst used in the steps (1), (2) and (3) is one of hydrochloric acid, nitric acid and perchloric acid.
5. The method according to claim 1, wherein the aging solution in the step (3) is one or a mixture of two or more of tetraethyl orthosilicate, tetramethyl orthosilicate, aluminum sec-butoxide and aluminum isopropoxide.
6. The method according to claim 1, wherein the organic solvent in the step (4) is one of ethanol, methanol and acetone.
7. The method according to claim 1, wherein the solvent in the step (4) is replaced with the organic solvent every 12 to 24 hours for 3 to 5 times.
8. The method according to claim 1, wherein the drying process in the step (5) is: vacuum drying, wherein the drying temperature is a gradient control heating method, the temperature is 45-55 ℃, and the drying time is 3-8 h; drying for 5-15 h at 60-70 ℃; drying for 2-5 h at 100-120 ℃.
9. The method according to claim 1, wherein the high temperature heat treatment process in the step (6) is: the heat treatment temperature is 300-500 ℃, and the heat treatment time is 1-3 h.
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