CN114870757B - High-temperature-resistant micro-nanofiber composite aerogel material and preparation method thereof - Google Patents
High-temperature-resistant micro-nanofiber composite aerogel material and preparation method thereof Download PDFInfo
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Abstract
The invention relates to a high-temperature-resistant micro-nanofiber composite aerogel material and a preparation method thereof, wherein the method comprises the following steps: preparing nanometer powder dispersion liquid from alumina nanometer powder by using water, adding a sulfuric acid solution and loose fiber cotton into the nanometer powder dispersion liquid, uniformly dispersing to obtain a mixed solution, and then placing the mixed solution at the temperature of 150-300 ℃ for hydrothermal reaction for 12-18 h to obtain gel; aging the gel to obtain an aged gel block; placing the aged gel block in an iron salt solution for soaking for 6-72h, and then sequentially carrying out solvent replacement and supercritical drying to obtain a composite aerogel material; and (3) carrying out heat treatment on the composite aerogel material to obtain the high-temperature-resistant micro-nanofiber composite aerogel material. The high-temperature-resistant micro-nanofiber composite aerogel material with good temperature resistance, high-efficiency heat insulation and strong structure is obtained.
Description
Technical Field
The invention relates to the technical field of aerogel preparation, in particular to a high-temperature-resistant micro-nanofiber composite aerogel material and a preparation method thereof.
Background
The nano porous aerogel material is a gel material with a dispersion medium of gas, is a nano porous solid material with a network structure formed by mutually accumulating colloidal particles or high polymer molecules, and the size of pores in the material is in the order of nanometers. The porosity of the porous material reaches 80-99.8%, the typical size of the pores is 1-100 nm, and the specific surface area is 200-1000 m 2 A density of as low as 3kg/m 3 The thermal conductivity coefficient at room temperature can be as low as 0.012W/(m.K). Due to the characteristics, the aerogel material has wide application potential in the aspects of thermal, acoustic, optical, microelectronic and particle detection. Currently, the widest field of application of aerogels is still the field of thermal insulation, since the unique nanostructure of aerogels can effectively reduce convection conduction, solid phase conduction and thermal radiation.
Most of traditional aerogel materials are pearl necklace-shaped structures formed by accumulating nano particles, the aerogel materials with the structures are brittle, and fiber reinforcement is needed in practical application to achieve structure reinforcement. The structural strength of the aerogel can be effectively improved by adopting a fiber reinforced mode, however, the existing RTM (resin transfer molding) process for injecting glue requires the thickness and the shape of the material, and the material with large size and large thickness often has the problem of internal defects. The nanofiber aerogel is a novel aerogel material, and a three-dimensional network structure with a high specific surface area can be obtained by taking nanofibers as basic units and mutually lapping and winding the nanofibers. Compared with the traditional pearl necklace-shaped aerogel material, the nanofiber aerogel has the advantages that the structural strength is improved, the process complexity is reduced, and the problem of powder falling of the traditional aerogel material can be solved. In addition, the three-dimensional network framework of the material has good toughness, can be machined in various shapes and with high precision, and is not limited by thickness, size and shape in material forming. However, the micron Kong Duowei size overlapped by the nanofibers, such a structure would result in the thermal conductivity of the aerogel being not low enough.
With the development of science and technology, various fields put higher demands on the strength, temperature resistance, light weight, high-efficiency heat insulation, process performance and the like of heat insulation materials. Therefore, it is very necessary to provide a composite aerogel material with good temperature resistance, high thermal insulation efficiency and strong structure and a preparation method thereof.
Disclosure of Invention
In order to solve one or more technical problems in the prior art, the invention provides a high-temperature-resistant micro-nanofiber composite aerogel material and a preparation method thereof.
The invention provides a preparation method of a high-temperature-resistant micro-nanofiber composite aerogel material in a first aspect, which comprises the following steps:
(1) Preparing nanometer powder dispersion liquid from alumina nanometer powder by using water, adding a sulfuric acid solution and loose fiber cotton into the nanometer powder dispersion liquid, uniformly dispersing to obtain a mixed solution, and then placing the mixed solution at a temperature of between 150 and 300 ℃ for hydrothermal reaction for 12 to 18 hours to obtain gel;
(2) Aging the gel to obtain an aged gel block;
(3) Placing the aged gel block obtained in the step (2) into an iron salt solution for soaking for 6-72h, and then sequentially carrying out solvent replacement and supercritical drying to obtain a composite aerogel material;
(4) And (4) carrying out heat treatment on the composite aerogel material obtained in the step (3) to obtain the high-temperature-resistant micro-nanofiber composite aerogel material.
Preferably, the mass fraction of the alumina nano powder contained in the mixed solution is 5 to 20%; and/or the mass fraction of the loose fiber contained in the mixed solution is 1-5%.
Preferably, the diameter of the loose fiber is 6-8 μm, and the length is 3-5 mm; and/or the fiber loose cotton is one or more of mullite fiber loose cotton, basalt fiber loose cotton, glass fiber loose cotton and rock wool fiber loose cotton.
Preferably, the iron salt contained in the iron salt solution is a soluble iron salt, and preferably, the iron salt is ferric trichloride; and/or in step (3), the impregnation is carried out under closed conditions.
Preferably, the mass fraction of iron ions contained in the iron salt solution is 0.1-5%; and/or the volume usage of the ferric salt solution is 1-10 times of the volume of the aged gel block.
Preferably, the particle size of the aluminum oxide nano powder is 10-100 nm; and/or in the step (1), the uniform dispersion mode is to disperse for 5-120min in a high-speed dispersion machine at the rotating speed of 1000-8000 r/min.
Preferably, the dosage of the sulfuric acid solution accounts for 0.8 to 7 percent of the total mass of the mixed solution; and/or the concentration of the sulfuric acid solution is 0.1-30 mmol/L.
Preferably, the aging is: aging for 1-6h at 20-90 ℃; ethanol is used as a solvent for solvent replacement; and/or the supercritical drying is supercritical carbon dioxide drying, preferably, the temperature of the supercritical drying is 20-60 ℃, and the pressure is 10-16 MPa.
Preferably, the temperature of the heat treatment is 1000-1200 ℃, and the time of the heat treatment is 0.5-2 h; and/or the heat treatment is carried out in an air atmosphere.
The invention provides a high-temperature-resistant micro-nanofiber composite aerogel material prepared by the preparation method of the first aspect of the invention.
Compared with the prior art, the invention at least has the following beneficial effects:
(1) Compared with the traditional pearl necklace-shaped aerogel material, the high-temperature-resistant micro-nano fiber composite aerogel material has better mechanical strength, and the microstructure of the high-temperature-resistant micro-nano fiber composite aerogel material is composed of a network structure formed by mutually winding aluminum oxide nanowires (nano fibers) and loose fiber cotton (micro fibers) and iron oxide nanoparticles doped in the network structure in situ; the invention designs the microfiber-doped nanofiber toughening and reinforcing aerogel, which has a hierarchical structure of microfiber and nanofiber, and iron oxide nanoparticles formed in situ can form an effective infrared radiation effect, so that the heat insulation performance of the material is improved.
(2) According to the invention, the gel is soaked in the ferric salt solution after being aged, so that sulfuric acid and iron ions contained in the gel nanowire can directly generate ferric sulfate precipitate, the ferric sulfate precipitate is separated out in situ in a network structure of the gel formed by winding the nanowire and the micro-fiber, and the high-temperature-resistant micro-nanofiber composite aerogel material containing iron oxide particles can be obtained through heat treatment (calcination), so that the gel has an excellent infrared radiation resistance effect; according to the method, the doped iron oxide nanoparticles can be generated in situ in the aerogel in a manner of doping the iron oxide nanoparticles in the aerogel material, and compared with the method of directly doping the iron oxide nanoparticles, the problems of agglomeration, sedimentation, uneven dispersion and the like caused by doping physical particles are avoided; in addition, the invention discovers that for the alumina nanowire aerogel generated by the reaction of the alumina nano powder and the sulfuric acid, if the iron oxide nano particles are directly added during the preparation of the gel, the sulfuric acid in the solution can react with the iron oxide to generate ferric sulfate, the content of the sulfuric acid in the solution is reduced, the parameters of the reaction system are unbalanced, the alumina nano powder cannot be effectively catalyzed to generate the nanowires, the hydrothermal process is influenced, the gel cannot be obtained, the subsequent operation cannot be carried out, and further the aerogel material cannot be prepared.
(3) The gel process in the preparation method of the aerogel is a hydrothermal process, is different from the traditional RTM (resin transfer molding) pressing glue injection process, is not limited by the shape and size of the reinforcement, and can be used for preparing aerogel materials with any shape and thickness.
(4) The aerogel material with a stable structure is prepared in a nanowire self-supporting mode, the micron-sized fiber reinforcement is added, the supporting effect can be realized at high temperature, the temperature resistance of the material can be effectively improved, and the aerogel material is very suitable for high-temperature-resistant high-efficiency heat insulation application.
(5) The invention can adopt water phase as reaction medium, and avoids environmental pollution and waste caused by using organic solvent in the preparation process.
(6) The density of the aerogel material prepared by the invention can be as low as 0.13g/cm 3 Compared with other low-density aerogel materials with the same strength, the aerogel material has the characteristic of ultralow density; the aerogel material prepared by the method has excellent high temperature resistance on the premise of keeping low room temperature thermal conductivity (which can be as low as about 0.023W/(m.K)), and can realize long-term heat insulation application at 1200 ℃.
(7) The porosity of the high-temperature-resistant micro-nanofiber composite aerogel material prepared by the method can reach more than 96 percent, the diameter of an alumina nanowire (alumina nanofiber) unit contained in the aerogel can be 20-50 nm, the length of the alumina nanowire unit can be 5-30 mu m, and the specific surface area is large (can reach 130 m) 2 (more than g), the heat-resistant temperature is more than 1200 ℃.
Drawings
FIG. 1 is a flow chart of the preparation of the present invention.
FIG. 2 is a schematic diagram of the structural change of the doped iron oxide nanoparticles in the aerogel material according to the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. It is to be understood that the embodiments described are only a few embodiments of the present invention, and not all embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
The invention provides a preparation method of a high-temperature-resistant micro-nanofiber composite aerogel material in a first aspect, which comprises the following steps:
(1) Preparing nanometer powder dispersion liquid from alumina nanometer powder by using water, adding a sulfuric acid solution and loose fiber cotton (micrometer fiber reinforcement) into the nanometer powder dispersion liquid, uniformly dispersing to obtain a mixed solution, and performing hydrothermal reaction on the mixed solution at the temperature of 150-300 ℃ for 12-18 h (such as 12, 13, 14, 15, 16, 17 or 18 h) to obtain gel; in the present invention, the gel is a semi-solid gel; the invention has no special limit to the sources of the alumina nano powder and the fiber loose cotton, and can be directly purchased in the market; the preparation of the nano powder dispersion liquid is not particularly limited, the alumina nano powder is added into the water, for example, the alumina nano powder is uniformly mixed in a stirring and/or ultrasonic mode, and the conditions of stirring and ultrasonic are not particularly required, so that the alumina nano powder is uniformly mixed in the water; specifically, for example, after magnetic stirring for 1 to 24 hours, ultrasound for 1 to 4 hours, and in the ultrasound process, for example, stopping for 5 minutes every 10 minutes of ultrasound, and then continuing ultrasound; in some specific embodiments, for example, magnetic stirring is performed for 1h, followed by sonication for 1h; in the invention, the dispersion mode after adding the sulfuric acid solution and the fiber loose cotton into the nano powder dispersion liquid can be, for example, dispersion for 5-120min in a high-speed dispersion machine at the rotating speed of 1000-8000 r/min; in the invention, the mixed solution is put into a closed container to carry out hydrothermal reaction for 12 to 18 hours at a temperature of between 150 and 300 ℃ to obtain semi-solid gel; in the present invention, the hydrothermal reaction is required to be carried out under a closed condition, and the material of the closed container is required to be a material which does not react with the system.
(2) Aging the gel to obtain an aged gel block; for example, the gel is aged for 1 to 6 hours in the air at the temperature of between 20 and 90 ℃, specifically, the gel is placed in a container and aged in the air in a non-sealed environment, the aging temperature is between 20 and 90 ℃, and the aging time is 1 to 6 hours, so that the gel block can slightly and slowly shrink in the air atmosphere, the strength of the gel block can be improved, and the demolding is facilitated.
(3) Soaking (soaking) the aged gel block obtained in the step (2) in an iron salt solution (also referred to as an iron ion-containing solution) for 6-72h (for example, 6, 10, 12, 15, 18, 24, 40, 48, 60 or 72 h), preferably for 18-30 h, and then sequentially performing solvent replacement and supercritical drying to obtain a composite aerogel material; in the invention, the iron salt contained in the iron salt solution is soluble iron salt, and the iron salt solution is preferably iron salt aqueous solution; in the present invention, during the immersion, the liquid surface of the iron salt solution may be allowed to pass through the aged gel block, and preferably, the volume of the iron salt solution is 1 to 10 times of the volume of the aged gel block; in the invention, the time for carrying out the impregnation is 6-72h, if the impregnation time is too short, the reaction between the ferric salt solution and the sulfuric acid is incomplete, so that not enough ferric oxide nano-particles are generated, and the improvement of the heat insulation performance of the material is not facilitated.
(4) Carrying out heat treatment on the composite aerogel material obtained in the step (3) to prepare a high-temperature-resistant micro-nanofiber composite aerogel material; in the present invention, it is preferable that the heat treatment temperature is 1000 to 1200 ℃ and the heat treatment time is 0.5 to 2 hours.
Compared with the traditional pearl necklace-shaped aerogel material, the high-temperature-resistant micro-nanofiber composite aerogel material has better mechanical strength, and the microstructure of the high-temperature-resistant micro-nanofiber composite aerogel material is composed of a network structure formed by mutually winding aluminum oxide nanowires (nanofibers) and loose fiber cotton (microfibers) and iron oxide nanoparticles doped in the network structure in situ; the invention designs the microfiber-doped nanofiber toughening and reinforcing aerogel which has a hierarchical structure of microfiber and nanofiber, and iron oxide nanoparticles formed in situ can form an effective infrared radiation effect, so that the heat insulation performance of the material is improved; according to the invention, the gel is soaked in the ferric salt solution after being aged, so that sulfuric acid and iron ions contained in the gel nanowire can directly generate ferric sulfate precipitate, the ferric sulfate precipitate is in-situ separated out in a network structure of the gel formed by winding the nanowire and the micron fiber, an iron-based anti-radiation agent precursor is in-situ modified, and the high-temperature-resistant micro-nano fiber composite aerogel material containing ferric oxide can be obtained through heat treatment (calcination), so that the gel has an excellent infrared radiation resistant effect; according to the method, the doped iron oxide nanoparticles can be generated in situ in the aerogel in a manner of doping the iron oxide nanoparticles in the aerogel material, and compared with the method of directly doping the iron oxide nanoparticles, the problems of agglomeration, sedimentation and uneven dispersion caused by doping physical particles are solved; the aerogel material with a stable structure is prepared in a nanowire self-supporting mode, the micron-sized fiber reinforcement is added, the supporting effect can be realized at high temperature, the temperature resistance of the material can be effectively improved, and the aerogel material is very suitable for high-temperature-resistant high-efficiency heat insulation application.
According to some preferred embodiments, the mixed solution contains 5 to 20% by mass (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20%) of alumina nano-powder, more preferably 8 to 20%; and/or the mass fraction of loose fiber contained in the mixed solution is 1 to 5% (e.g., 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%); in the present invention, it is preferable that the mass fraction of the loose fiber contained in the mixed solution is 1 to 5%; the invention finds that the fiber loose cotton is beneficial to increasing the toughness of the aerogel, the strength of the aerogel is slightly improved if the doping amount is too small, and the thermal conductivity is increased more if the doping amount is too large.
According to some preferred embodiments, the loose fiber has a diameter of 6 to 8 μm and a length of 3 to 5mm; and/or the fiber loose cotton is one or more of mullite fiber loose cotton, aluminum silicate fiber loose cotton, basalt fiber loose cotton, glass fiber loose cotton and rock wool fiber loose cotton.
According to some preferred embodiments, the iron salt contained in the iron salt solution is a soluble iron salt, preferably, the iron salt is ferric chloride; and/or in step (3), the impregnation is carried out under closed conditions.
According to some preferred embodiments, the mass fraction of iron ions contained in the iron salt solution is 0.1 to 5% (e.g., 0.1%, 0.5%, 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, or 5%); in the present invention, it is preferable that the mass fraction of the iron ions contained in the iron salt solution is 0.1 to 5%, more preferably 1 to 5%, and still more preferably 2 to 5%, and if the concentration of the iron salt solution is too small, the radiation-resistant effect of the material is not significant; the invention discovers that if the concentration of the ferric salt solution is too high, part of ferric trichloride can not react with sulfuric acid due to the limited amount of sulfuric acid in the nano wire, and ferric trichloride crystals can exist in the aerogel material after subsequent drying and heat treatment, so that the problems of unobvious improvement on heat insulation performance, density increase and loss of ultra-light weight property exist.
According to some preferred embodiments, the volume of the iron salt solution is used in an amount of 1 to 10 times (e.g., 1, 2, 3, 4, 5, 6, 7, 8, 9, or 10 times) the volume of the aged gel mass.
According to some preferred embodiments, the alumina nano powder has a particle size of 10 to 100nm; and/or in step (1), the dispersing is carried out uniformly in a manner of dispersing for 5-120min (for example, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115 or 120 min) in a high-speed disperser at a rotating speed of 1000-8000r/min (for example, 1000, 1500, 2000, 2500, 3000, 3500, 4000, 4500, 5000, 5500, 6000, 6500, 7000, 7500 or 8000 r/min).
According to some preferred embodiments, the sulfuric acid solution is used in an amount of 0.8 to 7% (e.g., 0.8%, 1%, 1.5%, 2%, 2.5%, 3%, 3.5%, 4%, 4.5%, 5%, 5.5%, 6%, 6.5%, or 7%) of the total mass of the mixed solution; in the present invention, it is preferable that the amount of the sulfuric acid solution is 0.8 to 7% of the total mass of the mixed solution, and if the amount of the sulfuric acid solution is too large, the alumina nanowires become short and thick, which is not favorable for the assembly process, may cause severe pulverization and shrinkage of the material, and may also cause weak strength of the material and increase of the thermal conductivity.
According to some preferred embodiments, the concentration of the sulfuric acid solution is 0.1 to 30mmol/L (e.g., 0.1, 0.5, 1, 3, 5, 8, 10, 15, 20, 25, or 30 mmol/L); in the invention, the concentration of the sulfuric acid solution is preferably 0.1-30 mmol/L, and the discovery of the invention shows that by adopting the sulfuric acid solution with the preferred concentration, compared with the sulfuric acid solution with high concentration, the alumina nanowire with longer length-diameter ratio can be ensured to be obtained, the formation of a gel block with stronger strength is facilitated, and the aerogel can be tougher after drying.
According to some preferred embodiments, the aging is: aging for 1-6h at 20-90 ℃.
According to some preferred embodiments, the solvent displacement uses ethanol as a solvent; and/or the supercritical drying is supercritical carbon dioxide drying, preferably, the temperature of the supercritical drying is 20-60 ℃, and the pressure is 10-16 MPa; in the present invention, the time for each solvent substitution and the time for supercritical drying are not particularly required, and conventional time parameters may be used, for example, the number of solvent substitutions may be 2 to 4, the time for each solvent substitution may be 1 to 4 days, and the time for supercritical drying may be 18 to 36 hours.
According to some preferred embodiments, the temperature of the heat treatment is 1000 to 1200 ℃ (e.g., 1000 ℃, 1050 ℃, 1100 ℃, 1150 ℃ or 1200 ℃), and the time of the heat treatment is 0.5 to 2 hours (e.g., 0.5, 1, 1.5 or 2 hours); and/or the heat treatment is carried out in an air atmosphere; the heat treatment temperature of the invention is only 1000-1200 ℃, grading heat treatment is not needed, and sintering heat treatment process is not needed at relatively high temperature, so that the prepared high-temperature-resistant micro-nanofiber composite aerogel material has higher strength and long-term heat-resistant temperature of more than 1200 ℃.
According to some specific embodiments, the preparation of the high-temperature-resistant micro-nanofiber composite aerogel material comprises the following steps:
(1) uniformly mixing aluminum oxide nano powder with the particle size range of 10-100nm by deionized water through stirring and ultrasonic to obtain nano powder dispersion liquid, then adding sulfuric acid solution with the concentration of 0.1-30 mmol/L and loose fiber cotton with the diameter of 6-8 mu m and the length of 3-5mm into the nano powder dispersion liquid, and uniformly dispersing the mixture in a high-speed dispersion machine at the rotating speed of 1000-8000r/min for 5-120min to obtain mixed liquid; in the mixed solution, the mass percent of the aluminum oxide nano powder is 5-20%, the mass percent of the fiber loose cotton is 1-5%, and the dosage of the sulfuric acid solution accounts for 1% of the total weight of the mixed solution.
(2) Putting the mixed solution into a closed container, and carrying out hydrothermal reaction for 12-18 h at 150-300 ℃ to obtain semisolid gel; the reaction needs to be carried out under fully closed conditions, and the material of the container needs to be a polymer material which does not react with the system.
(3) And (3) aging the gel block body in the air at the temperature of 20-90 ℃ for 1-6h to obtain an aged gel block.
(4) Soaking the aged gel block in iron salt solution under sealed condition for 6-72h; the ferric salt solution is a ferric salt aqueous solution, the ferric salt contained in the ferric salt solution is soluble ferric salt, preferably ferric trichloride, and the mass fraction of ferric ions contained in the ferric salt solution is 0.1-5%; the dosage of the ferric salt solution is 1 to 10 times, preferably 3 times of the volume of the aged gel block.
(5) Sequentially carrying out a solvent replacement process and a supercritical drying step on the gel block soaked in the step (4) to prepare a composite aerogel material; the method comprises the following specific steps: the solvent replacement adopts ethanol as a solvent, and after 3 times of replacement is carried out according to 10 times of the volume of the gel block, the time of solvent replacement for each time is 1 to 4 days; then carrying out supercritical carbon dioxide drying process, wherein the temperature of supercritical drying is 20-60 ℃, the pressure is 10-16MPa, and the time is 18-36 h.
(6) And (3) carrying out heat treatment on the composite aerogel material in an air atmosphere, wherein the heat treatment temperature is 1000-1200 ℃, and the heat treatment time is 0.5-2h, so as to obtain the high-temperature-resistant micro-nano fiber composite aerogel material.
The invention provides a high-temperature-resistant micro-nanofiber composite aerogel material prepared by the preparation method of the first aspect of the invention.
The invention will be further described by way of example only, without the scope of protection of the invention being limited to these examples.
Example 1
(1) Uniformly mixing aluminum oxide nano powder with the particle size range of 10-15nm with deionized water by stirring and ultrasound (firstly, magnetically stirring for 1 hour, and then, ultrasonically stirring for 1 hour) to obtain nano powder dispersion liquid; then adding sulfuric acid solution with the concentration of 10mmol/L and mullite fiber loose cotton with the average diameter of 7 mu m and the length range of 3-5mm into the nano powder dispersion liquid, and dispersing for 30min in a high-speed dispersion machine at the rotating speed of 5000r/min to uniformly disperse to obtain mixed liquid; in the mixed solution, the mass percent of the aluminum oxide nano powder is 8%, the mass percent of the fiber loose cotton is 4%, and the dosage of the sulfuric acid solution accounts for 1% of the total weight of the mixed solution.
(2) The mixed solution is put into a closed container to carry out hydrothermal reaction for 12 hours at 240 ℃ to obtain semisolid gel.
(3) And (3) aging the gel for 2h in an air non-sealed environment at 60 ℃ to obtain an aged gel block.
(4) Soaking the aged gel block in ferric trichloride aqueous solution under sealed condition for 12h; the mass fraction of iron ions contained in the ferric trichloride aqueous solution is 2%; the amount of the ferric salt solution used was 3 times the volume of the aged gel pieces.
(5) Sequentially carrying out a solvent replacement process and a supercritical drying step on the gel block soaked in the step (4) to prepare a composite aerogel material; the method comprises the following specific steps: the solvent replacement adopts ethanol as a solvent, and after 3 times of replacement is carried out according to 10 times of the volume of the gel block, the time of solvent replacement is 3 days each time; then, a supercritical carbon dioxide drying process is carried out, wherein the temperature of the supercritical drying is 50 ℃, the pressure is 14MPa, and the time is 24h.
(6) And (3) carrying out heat treatment on the composite aerogel material in an air atmosphere, wherein the heat treatment temperature is 1150 ℃ and the heat treatment time is 0.5h, so as to obtain the high-temperature-resistant micro-nano fiber composite aerogel material.
The high-temperature-resistant micro-nanofiber composite aerogel material prepared by the embodiment has good structural strength, and when a heat insulation performance test is carried out, the surface of the high-temperature-resistant micro-nanofiber composite aerogel material is found to have no light loss, no color change and no shedding.
The heat-resistant temperature of the high-temperature-resistant micro-nanofiber composite aerogel material prepared by the embodiment is 1200 ℃; wherein the heat-resistant temperature test is as follows: carrying out heat treatment (air atmosphere) on the aerogel material finally prepared in each embodiment at a certain high temperature for 30min, wherein the linear shrinkage rate of the aerogel material is not more than 5%, and the aerogel material can tolerate the high temperature; for the embodiment, the high-temperature-resistant micro-nanofiber composite aerogel material prepared by the embodiment is subjected to heat treatment (air atmosphere) at 1200 ℃ for 30min, the linear shrinkage rate of the aerogel material is not more than 5%, and the heat-resistant temperature is 1200 ℃.
The compressive strength of the high-temperature-resistant micro-nanofiber composite aerogel material prepared in the embodiment under 10% of compression is 0.7MPa, and the test standard adopted in the compressive strength test is GB/T13480 2014 'determination of compressive performance of heat-insulating products for buildings'.
Example 2
Example 2 is essentially the same as example 1, except that:
in the step (1), in the mixed solution, the mass percentage of the alumina nano powder is 6%, the mass percentage of the fiber loose cotton is 2%, and the dosage of the sulfuric acid solution accounts for 0.8% of the total weight of the mixed solution.
In the step (4), the aged gel block is placed in a ferric trichloride aqueous solution to be soaked for 48 hours under a closed condition; the mass fraction of iron ions contained in the ferric trichloride aqueous solution is 1%; the amount of the ferric salt solution used was 3 times the volume of the aged gel pieces.
Example 3
Example 3 is essentially the same as example 1, except that:
in the step (1), in the mixed solution, the mass percentage of the alumina nano powder is 20%, the mass percentage of the fiber loose cotton is 5%, and the use amount of the sulfuric acid solution accounts for 7% of the total weight of the mixed solution.
In the step (4), the aged gel block is placed in an aqueous solution of ferric trichloride and is soaked for 6 hours under a closed condition; the mass fraction of iron ions contained in the ferric trichloride aqueous solution is 5%; the amount of the iron salt solution was 3 times the volume of the aged gel pieces.
Example 4
Example 4 is essentially the same as example 1, except that:
in the step (1), in the mixed solution, the mass percentage of the alumina nano powder is 8%, the mass percentage of the fiber loose cotton is 16%, and the dosage of the sulfuric acid solution accounts for 1% of the total weight of the mixed solution.
Example 5
Example 5 is essentially the same as example 1, except that:
in the step (1), the concentration of the sulfuric acid solution used is 2mol/L.
Example 6
Example 6 is essentially the same as example 1, except that:
the step (1) is as follows: uniformly mixing aluminum oxide nano powder with the particle size range of 10-15nm and a sulfuric acid solution with the concentration of 10mmol/L by using deionized water through stirring and ultrasound (firstly, magnetic stirring is carried out for 1 hour, and then, ultrasound is carried out for 1 hour) to obtain a mixed solution; in the mixed solution, the mass percentage of the aluminum oxide nano powder is 8%, and the dosage of the sulfuric acid solution accounts for 1% of the total weight of the mixed solution.
The aerogel material prepared in the embodiment has better strength, and forms a complete block.
Example 7
Example 7 is essentially the same as example 1, except that:
in the step (1), the amount of the sulfuric acid solution is 0.5% of the total weight of the mixed solution.
The aerogel material that this embodiment made is relatively weak in strength, has the pulverization phenomenon.
Example 8
Example 8 is essentially the same as example 1, except that:
in the step (1), the amount of the sulfuric acid solution is 20% of the total weight of the mixed solution.
The aerogel material that this embodiment made is relatively weak in strength, has the pulverization phenomenon.
Example 9
Example 9 is essentially the same as example 1, except that:
in the step (4), the aged gel block is placed in an aqueous solution of ferric trichloride and is soaked for 12 hours under a closed condition; the mass fraction of iron ions contained in the ferric trichloride aqueous solution is 11%; the amount of the ferric salt solution used was 3 times the volume of the aged gel pieces.
Example 10
Example 10 is essentially the same as example 1, except that:
in the step (4), the aged gel block is placed in an aqueous solution of ferric trichloride and is soaked for 12 hours under a closed condition; the mass fraction of iron ions contained in the ferric trichloride aqueous solution is 0.1%; the amount of the ferric salt solution used was 3 times the volume of the aged gel pieces.
Example 11
(1) Uniformly mixing aluminum oxide nano powder with the particle size range of 10-15nm with deionized water by stirring and ultrasound (firstly, magnetically stirring for 1 hour, and then, ultrasonically stirring for 1 hour) to obtain nano powder dispersion liquid; then adding sulfuric acid solution with the concentration of 10mmol/L and aluminum silicate fiber loose cotton with the average diameter of 7 mu m and the length range of 3-5mm into the nano powder dispersion liquid, and dispersing uniformly in a high-speed dispersion machine at the rotating speed of 5000r/min for 30min to obtain a mixed liquid; in the mixed solution, the mass percent of the aluminum oxide nano powder is 8%, the mass percent of the fiber loose cotton is 4%, and the dosage of the sulfuric acid solution accounts for 1% of the total weight of the mixed solution.
(2) The mixed solution is put into a closed container to carry out hydrothermal reaction for 12 hours at 240 ℃ to obtain semisolid gel.
(3) And (3) aging the gel for 2h in an air non-sealed environment at 60 ℃ to obtain an aged gel block.
(4) Sequentially carrying out a solvent replacement process and a supercritical drying step on the aged gel block to prepare an aerogel material; the method comprises the following specific steps: the solvent replacement adopts ethanol as a solvent, and after 3 times of replacement is carried out according to 10 times of the volume of the gel block, the time of solvent replacement is 3 days each time; then, a supercritical carbon dioxide drying process is carried out, wherein the temperature of the supercritical drying is 50 ℃, the pressure is 14MPa, and the time is 24h.
(5) And (3) carrying out heat treatment on the aerogel material under the air atmosphere, wherein the heat treatment temperature is 1150 ℃ and the heat treatment time is 0.5h, so as to obtain the composite aerogel material.
Example 12
Example 12 is essentially the same as example 1, except that:
(5) directly performing supercritical carbon dioxide drying on the gel block soaked in the step (4) without solvent replacement to prepare a composite aerogel material; the supercritical carbon dioxide drying temperature is 50 deg.C, pressure is 14MPa, and time is 24h.
The aerogel material prepared in the example has serious pulverization and is difficult to form.
Example 13
Example 13 is essentially the same as example 1, except that:
in the step (5), normal pressure drying is adopted to replace the supercritical carbon dioxide drying process.
The aerogel material prepared by the embodiment has larger shrinkage and larger density.
Example 14
Example 14 is essentially the same as example 1, except that:
the heat treatment process of step (6) is not included.
Example 15
(1) Uniformly mixing aluminum oxide nano powder with the particle size range of 10-15nm and iron oxide nano particles with the particle size range of 20-40 nm by using deionized water through stirring and ultrasound (firstly, magnetically stirring for 1 hour, and then, ultrasonically stirring for 1 hour) to obtain nano powder dispersion liquid; then adding sulfuric acid solution with the concentration of 10mmol/L and mullite fiber loose cotton with the average diameter of 7 mu m and the length range of 3-5mm into the nano powder dispersion liquid, and dispersing uniformly in a high-speed dispersion machine at the rotating speed of 5000r/min for 30min to obtain a mixed liquid; in the mixed solution, the mass percent of the aluminum oxide nano powder is 8%, the mass percent of the iron oxide nano particles is 2%, the mass percent of the fiber loose cotton is 4%, and the dosage of the sulfuric acid solution accounts for 1% of the total weight of the mixed solution.
(2) The mixed solution is put into a closed container to carry out hydrothermal reaction for 12 hours at 240 ℃.
In the embodiment, the ferric oxide nanoparticles are directly added in the step (1), sulfuric acid in the solution reacts with ferric oxide to generate ferric sulfate, the content of sulfuric acid in the solution is reduced, parameters of a reaction system are unbalanced, the aluminum oxide nano powder cannot be effectively catalyzed to generate nanowires, a hydrothermal process is affected, gel cannot be obtained, subsequent operation cannot be performed, and further the gas outlet gel material cannot be prepared.
In Table 1, the symbol "-" indicates that the performance index was not tested.
The invention has not been described in detail and is in part known to those of skill in the art.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (12)
1. A preparation method of a high-temperature-resistant micro-nanofiber composite aerogel material is characterized by comprising the following steps of:
(1) Preparing aluminum oxide nano powder into nano powder dispersion liquid by using water, adding a sulfuric acid solution and fiber loose cotton into the nano powder dispersion liquid, uniformly dispersing to obtain a mixed liquid, and then carrying out hydrothermal reaction on the mixed liquid at the temperature of 150-300 ℃ for 12-18h to obtain gel;
(2) Aging the gel to obtain an aged gel block;
(3) Placing the aged gel block obtained in the step (2) into an iron salt solution for soaking for 6-72h, and then sequentially carrying out solvent replacement and supercritical drying to obtain a composite aerogel material;
(4) And (4) carrying out heat treatment on the composite aerogel material obtained in the step (3) to obtain the high-temperature-resistant micro-nanofiber composite aerogel material.
2. The method of claim 1, wherein:
the mass fraction of the alumina nano powder contained in the mixed solution is 5 to 20 percent; and/or
The mass fraction of the loose fiber cotton contained in the mixed solution is 1~5%.
3. The method of claim 1, wherein:
the diameter of the fiber loose cotton is 6~8 mu m, and the length of the fiber loose cotton is 3-5mm; and/or
The fiber loose cotton is one or more of mullite fiber loose cotton, basalt fiber loose cotton, glass fiber loose cotton and rock wool fiber loose cotton.
4. The method of claim 1, wherein:
the ferric salt contained in the ferric salt solution is soluble ferric salt; and/or
In the step (3), the impregnation is performed under a closed condition.
5. The method of claim 4, wherein:
the ferric salt contained in the ferric salt solution is ferric trichloride.
6. The production method according to claim 1, characterized in that:
the mass fraction of iron ions contained in the iron salt solution is 0.1-5%; and/or
The volume usage of the ferric salt solution is 1 to 10 times of the volume of the aged gel block.
7. The production method according to any one of claims 1 to 6, characterized in that:
the particle size of the alumina nano powder is 10 to 100nm; and/or
In the step (1), the dispersion is carried out uniformly in a high-speed dispersion machine at the rotating speed of 1000-8000r/min for 5-120min.
8. The production method according to any one of claims 1 to 6, characterized in that:
the dosage of the sulfuric acid solution accounts for 0.8 to 7 percent of the total mass of the mixed solution; and/or
The concentration of the sulfuric acid solution is 0.1 to 30mmol/L.
9. The production method according to any one of claims 1 to 6, characterized in that:
the aging is as follows: aging at 20 to 90 ℃ for 1 to 6h;
ethanol is used as a solvent for solvent replacement; and/or
The supercritical drying is supercritical carbon dioxide drying.
10. The method of claim 9, wherein:
the temperature of the supercritical drying is 20 to 60 ℃, and the pressure is 10 to 169Pc.
11. The production method according to any one of claims 1 to 6, characterized in that:
the temperature of the heat treatment is 1000 to 1200 ℃, and the time of the heat treatment is 0.5 to 2h; and/or
The heat treatment is performed in an air atmosphere.
12. The high-temperature-resistant micro-nanofiber composite aerogel material prepared by the preparation method of any one of claims 1 to 11.
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