A multi-element oxide high-temperature resistant aerogel composite material and preparation method thereof

Abstract

The present invention relates to a multi-element oxide high-temperature resistant aerogel composite material and a preparation method thereof. The method comprises: using water to uniformly disperse an aluminum source and a magnesium source to obtain a dispersion, then adding a structure modifier and a mineralizer to the dispersion and performing a hydrothermal reaction to obtain a composite precursor sol; the aluminum source is aluminum oxide nanowires and / or aluminum oxide nanobelts; the magnesium source is magnesium oxide nanopowder; mullite nanofibers, silicon carbide nanopowder, and an inorganic gelling agent are added to the composite precursor sol and mixed uniformly, and after the system is gelled, it is aged to obtain a wet gel; the inorganic gelling agent is calcium aluminosilicate cement and / or calcium ion-doped zirconium oxide sol; the wet gel is sequentially subjected to solvent replacement and supercritical drying to obtain a multi-element oxide high-temperature resistant aerogel composite material. The present invention improves the temperature resistance of the material, effectively controls the particle size and structure of the material, and can effectively improve the mechanical and thermal properties and high-temperature sintering performance of the aerogel thermal insulation material.

Description

Technical Field

[0001] The present invention belongs to the technical field of high-temperature resistant heat-insulating materials, and in particular relates to a multi-component oxide high-temperature resistant aerogel composite material and a preparation method thereof. Background Art

[0002] As aircraft advance toward higher Mach numbers, the ambient temperature outside the aircraft increases significantly. Traditional silica aerogels are struggling to meet the demands for heat resistance and thermal insulation. Alumina aerogels, with their high melting point, are ideal for ultra-high-temperature insulation. However, alumina's high-temperature crystal structure easily undergoes structural changes, causing the material to collapse, limiting its application in heat-resistant and thermal insulation applications.

[0003] Multi-component doping can achieve control over the high-temperature crystal structure of alumina materials, thereby improving the temperature resistance of alumina aerogels. At present, alumina aerogels mainly improve the temperature resistance of materials by doping with silicon or magnesium elements to form mullite or aluminum-magnesium spinel crystal structures. Multi-component aerogel materials based on silicon and magnesium doping are generally synthesized and prepared by the sol-gel method. The hydrolysis and polycondensation reactions of multi-component metal precursors are difficult to control, resulting in a large amount of alumina boehmite crystal structures in the material, which limits the improvement of the material's temperature resistance. At the same time, these aerogel materials are assembled in a nanoparticle chain bead structure. The point-to-point contact of the nanoparticles makes the sintering activation energy of the material low, resulting in limited improvement in the temperature resistance of the aerogel material. There is an urgent need to prepare multi-component oxide aerogels with a high sintering energy characteristic crystal structure to further improve the temperature resistance and thermal insulation properties of the aerogel.

[0004] In summary, it is very necessary to provide a multi-element oxide high-temperature resistant aerogel composite material and a preparation method thereof. Summary of the Invention

[0005] In order to solve one or more technical problems existing in the prior art, the present invention provides a multi-element oxide high-temperature resistant aerogel composite material and a preparation method thereof.

[0006] In a first aspect, the present invention provides a method for preparing a multi-element oxide high-temperature resistant aerogel composite material, the method comprising the following steps:

[0007] (1) uniformly dispersing an aluminum source and a magnesium source with water to obtain a dispersion, then adding a structure modifier and a mineralizer to the dispersion and performing a hydrothermal reaction to obtain a composite precursor sol; the aluminum source is aluminum oxide nanowires and / or aluminum oxide nanobelts; and the magnesium source is magnesium oxide nanopowder;

[0008] (2) adding mullite nanofibers, silicon carbide nanopowder and an inorganic gelling agent to the composite precursor sol and mixing them uniformly to obtain a reaction system, and aging the reaction system after it is gelled to obtain a wet gel; the inorganic gelling agent is calcium aluminosilicate cement and / or calcium ion-doped zirconia sol;

[0009] (3) The wet gel is subjected to solvent replacement and supercritical drying in sequence to obtain a multi-element oxide high-temperature resistant aerogel composite material.

[0010] Preferably, the molar ratio of the aluminum contained in the aluminum source to the magnesium contained in the magnesium source is (0.95-10):1.

[0011] Preferably, the sum of the mass percentages of the aluminum source and the magnesium source in the dispersion is 5-15%.

[0012] Preferably, the structure modifier is an organic weak acid; preferably, the organic weak acid is acetic acid solution, oxalic acid solution, oxalic acid solution and citric acid solution; preferably, the concentration of the organic weak acid is 0.1 to 5 mol / L.

[0013] Preferably, the mineralizer is one or more of ammonium fluoride powder, aluminum fluoride powder, and lithium fluoride powder.

[0014] Preferably, the mass amount of the structure modifier is 3-5% of the sum of the mass amounts of the aluminum source and the magnesium source; and / or the mass amount of the mineralizer is 1-2% of the sum of the mass amounts of the aluminum source and the magnesium source.

[0015] Preferably, the temperature of the hydrothermal reaction is 180-290° C., and the time of the hydrothermal reaction is 6 h to 24 h.

[0016] Preferably, the mass amount of the mullite nanofiber is 20-60% of the sum of the mass amounts of the aluminum source and the magnesium source; and / or the mass amount of the silicon carbide nanopowder is 4-8% of the sum of the mass amounts of the aluminum source and the magnesium source.

[0017] Preferably, the mass amount of the inorganic gelling agent is 10-30% of the sum of the mass amounts of the aluminum source and the magnesium source.

[0018] In a second aspect, the present invention provides a multi-component oxide high-temperature resistant aerogel composite material prepared by the preparation method described in the first aspect of the present invention.

[0019] Compared with the prior art, the present invention has at least the following beneficial effects:

[0020] The present invention uses high-temperature-resistant alumina nanowires and / or alumina nanobelts as precursors and, through magnesium doping, controls the alumina crystal structure, thereby improving the material's temperature resistance. A composite precursor sol is synthesized using a hydrothermal reaction, resulting in mild reaction conditions and a controllable reaction process. The introduction of a mineralizer and a structure modifier during the reaction effectively controls the material's particle size and structure, avoiding the uncontrollable hydrolysis and polycondensation of metal salts. The present method uses an inorganic gelling agent as a gelling agent, enabling the preparation of bulk wet gels under mild conditions while avoiding the energy-intensive freeze-drying and high-temperature sintering process, resulting in a simple and effective preparation method. The present invention proposes a novel method for preparing a multi-component oxide aerogel composite material based on an alumina-magnesium spinel crystal structure. By using one- or two-dimensional structural components, the method overcomes the shortcomings of conventional chain-beaded aerogels, such as insufficient mechanical strength and low sintering energy, and improves the mechanical and thermal properties of the aerogel material. Furthermore, the method employs calcium aluminosilicate cement and / or calcium ion-doped zirconia sol as gelling aids for the first time, simplifying the high-temperature heat treatment process and achieving low carbonization in the preparation process. DETAILED DESCRIPTION

[0021] To make the objectives, technical solutions, and advantages of the present invention more clear, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0022] In a first aspect, the present invention provides a method for preparing a multi-element oxide high-temperature resistant aerogel composite material, the method comprising the following steps:

[0023] (1) using water to uniformly disperse an aluminum source and a magnesium source to obtain a dispersion, and then adding a structure modifier and a mineralizer to the dispersion and performing a hydrothermal reaction to obtain a composite precursor sol; the aluminum source is aluminum oxide nanowires and / or aluminum oxide nanobelts; the magnesium source is magnesium oxide nanopowder; in the present invention, specifically, for example, high-temperature resistant aluminum oxide nanowires and / or aluminum oxide nanobelts are used as precursors, nano magnesium oxide (magnesium oxide nanopowder) is used as a magnesium source, and are added to water according to a certain magnesium-aluminum ratio, and then an organic weak acid is introduced as a structure modifier, and a mineralizer is added at the same time, and a high-temperature hydrothermal reaction is performed to prepare a composite precursor sol; the present invention does not specifically limit the sources of aluminum oxide nanowires, aluminum oxide nanobelts and magnesium oxide nanopowder, and can use products that can be directly purchased or products synthesized by existing methods;

[0024] (2) adding mullite nanofibers, silicon carbide nanopowder (nano-silicon carbide) and an inorganic gelling agent to the composite precursor sol and mixing them uniformly to obtain a reaction system, and aging the reaction system after the reaction system is gelled to obtain a wet gel; the inorganic gelling agent is calcium aluminosilicate cement and / or calcium ion-doped zirconia sol; in the present invention, calcium aluminosilicate cement refers to a silicate cement with calcium aluminosilicate as the main component; in the present invention, the calcium ion-doped zirconia sol is obtained by adding calcium ion inorganic salt to the zirconia sol, and the solid content of the zirconia sol is, for example, 20 to 25 wt%, and the mass percentage of the calcium ion inorganic salt in the calcium ion-doped zirconia sol is, for example, 5 to 10 wt%. t%, the calcium ion inorganic salt can be, for example, calcium chloride; in the present invention, for example, an appropriate amount of mullite nanofibers, silicon carbide nanopowder and inorganic gelling agent are added to the composite precursor sol system obtained in step (1) and mixed evenly, and after the system forms a solid gel, it is aged to obtain a skeleton-reinforced wet gel (abbreviated as wet gel); in the present invention, system gel (gelation) refers to the system forming a solid gel; in the present invention, the aging is, for example, aging at room temperature of 15 to 35° C. for 24 to 48 hours; the present invention does not specifically limit the sources of mullite nanofibers, silicon carbide nanopowder, calcium aluminosilicate cement, etc., and products that can be directly purchased or synthesized by existing methods can be used;

[0025] (3) The wet gel is subjected to solvent replacement and supercritical drying in sequence to obtain a multi-element oxide high-temperature resistant aerogel composite material; in the present invention, supercritical drying is carried out in a supercritical drying kettle, for example, supercritical carbon dioxide drying. The present invention does not specifically limit the conditions of supercritical drying, which is a conventional technology in the field; the multi-element oxide high-temperature resistant aerogel composite material (also referred to as a high-temperature resistant aerogel insulation composite material) obtained by the present invention can withstand a high temperature of 1400°C.

[0026] The present invention uses high-temperature resistant aluminum oxide nanowires and / or aluminum oxide nanobelts as precursors, and at the same time controls the aluminum oxide crystal structure by doping with magnesium elements, thereby improving the temperature resistance of the material and further improving the ablation resistance of the material, so that it can still maintain good structural integrity and performance stability under extremely high temperature conditions. The present invention uses aluminum oxide nanowires or nanobelts with better high-temperature resistance as sol precursors. Nanowires and nanobelts are different from traditional nanoparticles. The nanowire / belt contact area is small and the high-temperature stability is excellent. Highly active nano-magnesium oxide is used as the magnesium source. Nano-magnesium oxide has high activity and can perform interface or structural modification on one-dimensional aluminum oxide nanowires or two-dimensional aluminum oxide nanobelts. In the present invention, it can The present invention forms a partial aluminum-magnesium spinel crystal form by using a temperature-resistant phase aluminum oxide nanowire and / or aluminum oxide nanobelt. The temperature resistance of this structure is better than that of nano-alumina sol, and it has the characteristics of high sintering activation energy, which is manifested by its own high temperature resistance. When the material is used at high temperature, the aluminum and magnesium on the surface of the nanowire or nanobelt will be in situ produced and developed into an aluminum-magnesium spinel structure, and the surface of the nanowire or nanobelt is modified to further improve its temperature resistance. The present invention synthesizes a composite precursor sol by hydrothermal reaction, the reaction conditions are mild and the reaction process is controllable, and at the same time, a mineralizer and a structure modifier are introduced into the reaction process to effectively control the particle size and structure of the material, thereby avoiding the uncontrollable nature of the hydrolysis and polycondensation of the metal salt. The present invention finds that the mineralizer can reduce The activation energy of the hydrothermal reaction of magnesium and aluminum can promote the growth and development of crystals, thereby controlling the particle size and structure of the material. The structure modifier can promote the ripening and rearrangement of particles under the conditions of the hydrothermal reaction, and can adjust the morphology and structure of the material. The present invention improves the mechanical properties, thermal insulation properties and ablation resistance of the aerogel composite material by optimizing the particle size and structure of the material, thereby making it have better performance in a high-temperature environment; the method of the present invention adopts an inorganic gelling agent as a gelling factor, which can realize the preparation of bulk wet gel under mild conditions, while avoiding the high energy consumption process of freeze drying + high temperature sintering. The preparation method is simple and effective. In addition, the present invention finds that calcium aluminosilicate cement and / or calcium ion doped zirconia sol as It is an inorganic gelling agent that not only plays a gelling role but also can form a stable ceramic structure at high temperature, which helps to improve the thermal insulation effect of the material. In contrast, traditional high-temperature adhesives such as silica sol and aluminum dihydrogen phosphate have weak hydration resistance and are generally subjected to high-temperature treatment to solidify and enhance material properties, which increases production costs and process complexity. In addition, silica sol has limited temperature resistance, and aluminum dihydrogen phosphate easily expands during high-temperature curing to produce an uneven macroporous structure, which will reduce the overall mechanical and thermal properties of the material. In the present invention, the addition of mullite nanofibers and silicon carbide nanopowders further enhances the mechanical properties and high-temperature radiation resistance of the material, so that it has better compressive and tensile strength and thermal insulation properties at high temperatures.The present invention proposes a new method for preparing a multi-component oxide aerogel composite material based on an aluminum-magnesium spinel crystal structure. By adopting one- and two-dimensional structural components, the shortcomings of insufficient mechanical strength and low sintering energy of traditional chain-beaded structure aerogels are overcome, and the mechanical and thermal properties of the aerogel material are improved. At the same time, calcium aluminosilicate cement and / or calcium ion-doped zirconia sol are used as gelling agents for the first time. These gelling agents have the characteristics of high temperature resistance and high strength, and can be directly aged and dried subsequently without the need for high-temperature treatment of organic matter, thus achieving low carbonization of the preparation process.

[0027] According to some preferred embodiments, the molar ratio of the aluminum contained in the aluminum source to the magnesium contained in the magnesium source is (0.95-10):1, preferably (1-10):1 (for example, 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1 or 10:1). In the present invention, this preferred magnesium-aluminum ratio can enable the composite precursor sol (also referred to as aluminum-magnesium precursor sol) to appear in a surface-modified state and a mixed state of aluminum-magnesium spinel, further improving the high-temperature stability of alumina.

[0028] According to some preferred embodiments, the sum of the mass percentages of the aluminum source and the magnesium source in the dispersion is 5-15% (e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14% or 15%).

[0029] According to some preferred embodiments, the structure modifier is an organic weak acid; preferably, the organic weak acid is acetic acid solution (acetic acid aqueous solution), oxalic acid solution (oxalic acid aqueous solution), and citric acid solution (citric acid aqueous solution). These organic weak acids can promote the ripening and rearrangement of particles under hydrothermal reaction conditions, and can adjust the morphology and structure of the material; preferably, the concentration of the organic weak acid is 0.1 to 5 mol / L (for example, 0.1, 0.5, 0.8, 1, 1.5, 2, 2.5, 3, 3.5, 4, 4.5 or 5 mol / L).

[0030] According to some preferred embodiments, the mineralizer is one or more of ammonium fluoride powder, aluminum fluoride powder, and lithium fluoride powder. In the present invention, unlike the use of a catalyst such as ammonium fluoride solution to promote the gel reaction, the present invention uses solid ammonium fluoride powder, aluminum fluoride powder, lithium fluoride powder, etc. as a mineralizer. The present invention finds that the mineralizer can provide a stable and continuous mineralization effect during the hydrothermal reaction, helps to control the particle size and structure of the material, ensures the uniformity of the material structure, and the uniform pore structure enables the aerogel material to have better thermal insulation effect and structural stability at high temperatures.

[0031] According to some preferred embodiments, the mass amount of the structure modifier is 3-5% (e.g., 3%, 3.5%, 4%, 4.5% or 5%) of the sum of the mass amounts of the aluminum source and the magnesium source; and / or the mass amount of the mineralizer is 1-2% (e.g., 1%, 1.5% or 2%) of the sum of the mass amounts of the aluminum source and the magnesium source. In the present invention, by strictly controlling the amount of structure modifier and mineralizer within an appropriate range, key parameters such as the microstructure, particle size, porosity, etc. of the material can be effectively regulated, thereby obtaining a multi-oxide high-temperature resistant aerogel composite material with excellent performance; the present invention finds that the structure modifier can regulate the crystal morphology and microstructure of the material during the hydrothermal reaction process, ensuring that the material has uniform nano-scale dispersion and pore structure, and an appropriate amount of structure modifier can enhance the mechanical properties of the material, so that it maintains good strength and toughness in a high-temperature environment. By regulating the porosity and pore size distribution, the structure modifier can improve the thermal insulation performance of the aerogel and reduce heat conduction. If the amount of structure modifier is too small, it may make it difficult to optimize the pore structure of the material, reduce the thermal insulation performance and mechanical properties, and lead to Materials are prone to structural instability or failure in high-temperature environments. If the amount of structure modifier used is too high, it may lead to excessive modulation, resulting in uneven phase separation or the introduction of excessive defects, thereby affecting the overall performance of the material. The present invention has found that mineralizers promote the uniform growth and arrangement of nanocrystals during the hydrothermal reaction, ensuring the uniformity and stability of the material structure. An appropriate amount of mineralizer helps control the particle size and morphology of the material, preventing the particles from being too large or uneven, thereby improving the mechanical properties and thermal insulation properties of the material. If the amount of mineralizer used is too small, it may not be sufficient to effectively promote crystal growth and particle size control. If the amount of mineralizer used is too large, it may lead to excessive mineralization, excessive or uneven crystal growth, the formation of coarse grains or uneven phase distribution, and reduced material performance.

[0032] According to some preferred embodiments, the temperature of the hydrothermal reaction is 180-290°C (180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C, 250°C, 260°C, 270°C, 280°C or 290°C), and the time of the hydrothermal reaction is 6h-24h (for example, 6, 8, 10, 12, 14, 16, 18, 20, 22 or 24h); in the present invention, preferably, the temperature of the hydrothermal reaction is 180-290°C. If the temperature is too low, a good mineralization reaction will not occur. If the temperature is too high, the reaction conditions are harsh and it is difficult to control the morphology and structure.

[0033] According to some preferred embodiments, the mass dosage of the mullite nanofiber is 20-60% (for example, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55% or 60%) of the sum of the mass dosages of the aluminum source and the magnesium source; and / or the mass dosage of the silicon carbide nanopowder is 4-8% (for example, 4%, 5%, 6%, 7% or 8%) of the sum of the mass dosages of the aluminum source and the magnesium source; in the present invention, by controlling the dosage of mullite nanofiber and silicon carbide nanopowder within an appropriate range, the mechanical properties, thermal insulation properties and high temperature resistance of the multi-oxide high temperature resistant aerogel composite material can be effectively improved. The present invention finds that mullite nanofiber has excellent high temperature strength and toughness, and its addition to the material can effectively improve the mechanical properties of the composite material. Performance, mullite nanofiber has low thermal conductivity, which can effectively prevent heat conduction and improve the thermal insulation effect of the composite material, and mullite nanofiber has excellent thermal stability, which can maintain structural stability at high temperatures, thereby improving the overall thermal stability of the composite material, and an appropriate amount of mullite nanofiber helps to form a uniform nanoscale pore structure, improving the thermal insulation and mechanical properties of the aerogel; silicon carbide nanopowder has excellent high-temperature radiation resistance, and its addition can effectively reduce the high-temperature thermal conductivity of the composite material, ensuring that the material has good thermal insulation effect at high temperatures. If the silicon carbide nanopowder content is insufficient, it is difficult to effectively play an anti-radiation effect and cannot effectively improve the high-temperature thermal insulation performance of the material. If the silicon carbide nanopowder content is too high, it may cause the solid-phase thermal conductivity of the material to increase, reducing its thermal insulation performance at low temperatures.

[0034] According to some preferred embodiments, the mass amount of the inorganic gelling agent is 10 to 30% (for example, 10%, 15%, 20%, 25% or 30%) of the sum of the mass amounts of the aluminum source and the magnesium source; in the present invention, a suitable amount of inorganic gelling agent ensures the uniformity and formability of the wet gel structure, improves the overall performance of the material, and an appropriate amount of inorganic gelling agent can optimize the pore size distribution of the material, enhance the thermal insulation performance of the aerogel, and effectively prevent heat conduction. The present invention finds that if the content of the inorganic gelling agent is insufficient, it may lead to unstable wet gel structure, poor molding effect, insufficient uniformity of the material, and the possible reduction of mechanical properties and thermal stability of the material. If the content of the inorganic gelling agent is too high, it will affect its thermal insulation effect and reduce the optimization effect of the porosity and pore size distribution of the material.

[0035] According to some preferred embodiments, the solvent replacement uses ethanol (anhydrous ethanol) as the solvent, the time for each solvent replacement is 18 to 30 hours, and the number of solvent replacements is 3 to 5 times; and / or the time for supercritical drying is 48 to 96 hours.

[0036] In a second aspect, the present invention provides a multi-component oxide high-temperature resistant aerogel composite material prepared by the preparation method described in the first aspect of the present invention.

[0037] The present invention will be further described below by way of examples, but the protection scope of the present invention is not limited to these examples.

[0038] Example 1

[0039] (1) Weighing 5 g of aluminum oxide nanowires and 4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 1:1), adding them to water and dispersing them uniformly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 5%; then adding 0.5 mol / L acetic acid aqueous solution as a structure modifier and adding mineralizer ammonium fluoride powder to the dispersion liquid and hydrothermally reacting them at a high temperature of 180°C for 24 hours to prepare a composite precursor sol; the mass amount of the acetic acid aqueous solution is 4% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0040] (2) Add 5.4 g of mullite nanofiber, 0.45 g of silicon carbide nanopowder and 0.9 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, age it at room temperature at 25°C for 48 h to obtain a wet gel.

[0041] (3) The wet gel obtained in step (2) is placed in an ethanol solvent for solvent replacement, the solvent replacement is performed 3 times, and the time for each solvent replacement is 24 hours. Then, it is sent to a supercritical drying kettle for supercritical carbon dioxide drying for 72 hours to obtain a multi-element oxide high-temperature resistant aerogel composite material.

[0042] Example 2

[0043] (1) Weighing 5 g of aluminum oxide nanowires and 1 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 4:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 5%; then adding acetic acid aqueous solution with a concentration of 5 mol / L as a structure modifier and adding aluminum fluoride powder as a mineralizer to the dispersion liquid and hydrothermally reacting them at a high temperature of 240°C for 6 h to prepare a composite precursor sol; the mass amount of the acetic acid aqueous solution is 3% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the aluminum fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0044] (2) Add 3 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 1.2 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, age it at room temperature at 25°C for 48 h to obtain a wet gel.

[0045] (3) The wet gel obtained in step (2) is placed in an ethanol solvent for solvent replacement, the solvent replacement is performed 3 times, and the time for each solvent replacement is 24 hours. Then, the wet gel is sent to a supercritical drying kettle for supercritical carbon dioxide drying for 72 hours to obtain a multi-element oxide high-temperature resistant aerogel composite material.

[0046] Example 3

[0047] (1) Weighing 5 g of aluminum oxide nanowires and 1 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 4:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 10%; then adding acetic acid aqueous solution with a concentration of 5 mol / L as a structure modifier and adding lithium fluoride powder as a mineralizer to the dispersion liquid and hydrothermally reacting them at a high temperature of 290°C for 12 hours to prepare a composite precursor sol; the mass amount of the acetic acid aqueous solution is 3% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the lithium fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0048] (2) Add 1.2 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 1.8 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, age it at room temperature at 25°C for 48 h to obtain a wet gel.

[0049] (3) The wet gel obtained in step (2) is placed in an ethanol solvent for solvent replacement, the solvent replacement is performed 3 times, and the time for each solvent replacement is 24 hours. Then, the wet gel is sent to a supercritical drying kettle for supercritical carbon dioxide drying for 72 hours to obtain a multi-element oxide high-temperature resistant aerogel composite material.

[0050] Example 4

[0051] (1) Weighing 5 g of aluminum oxide nanowires and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 10%; then adding a 1 mol / L aqueous solution of oxalic acid as a structure modifier and a mineralizer ammonium fluoride powder to the dispersion liquid and hydrothermally reacting them at a high temperature of 240°C for 24 hours to prepare a composite precursor sol; the mass amount of the aqueous solution of oxalic acid is 5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0052] (2) Add 2 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 1 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, it is aged at room temperature of 25°C for 48 h to obtain a wet gel.

[0053] (3) The wet gel obtained in step (2) is placed in an ethanol solvent for solvent replacement, the solvent replacement is performed 3 times, and the time for each solvent replacement is 24 hours. Then, the wet gel is sent to a supercritical drying kettle for supercritical carbon dioxide drying for 72 hours to obtain a multi-element oxide high-temperature resistant aerogel composite material.

[0054] Example 5

[0055] (1) Weighing 5 g of aluminum oxide nanowires and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 5%; then adding a 1 mol / L citric acid aqueous solution as a structure modifier and a mineralizer ammonium fluoride powder to the dispersion liquid and hydrothermally reacting them at a high temperature of 240°C for 10 h to prepare a composite precursor sol; the mass amount of the citric acid aqueous solution is 4% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0056] (2) Add 2 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 1 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, it is aged at room temperature of 25°C for 48 h to obtain a wet gel.

[0057] (3) The wet gel obtained in step (2) is placed in an ethanol solvent for solvent replacement, the solvent replacement is performed 3 times, and the time for each solvent replacement is 24 hours. Then, the wet gel is sent to a supercritical drying kettle for supercritical carbon dioxide drying for 72 hours to obtain a multi-element oxide high-temperature resistant aerogel composite material.

[0058] Example 6

[0059] (1) Weighing 5 g of aluminum oxide nanowires and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 5%; then adding 1 mol / L acetic acid aqueous solution as a structure modifier and adding mineralizer ammonium fluoride powder to the dispersion liquid and hydrothermally reacting them at a high temperature of 180°C for 24 hours to prepare a composite precursor sol; the mass amount of the acetic acid aqueous solution is 4% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0060] (2) Add 3.24 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 0.9 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, age it at room temperature at 25°C for 48 h to obtain a wet gel.

[0061] (3) The wet gel obtained in step (2) is placed in an ethanol solvent for solvent replacement, the solvent replacement is performed 3 times, and the time for each solvent replacement is 24 hours. Then, the wet gel is sent to a supercritical drying kettle for supercritical carbon dioxide drying for 72 hours to obtain a multi-element oxide high-temperature resistant aerogel composite material.

[0062] Example 7

[0063] (1) Weighing 5 g of aluminum oxide nanowires and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 5%; then adding 1 mol / L oxalic acid aqueous solution as a structure modifier and adding mineralizer ammonium fluoride powder to the dispersion liquid and hydrothermally reacting them at a high temperature of 180°C for 24 hours to prepare a composite precursor sol; the mass amount of the oxalic acid aqueous solution is 4% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0064] (2) Add 3.24 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 0.9 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, age it at room temperature at 25°C for 48 h to obtain a wet gel.

[0065] (3) The wet gel obtained in step (2) is placed in an ethanol solvent for solvent replacement, the solvent replacement is performed 3 times, and the time for each solvent replacement is 24 hours. Then, the wet gel is sent to a supercritical drying kettle for supercritical carbon dioxide drying for 72 hours to obtain a multi-element oxide high-temperature resistant aerogel composite material.

[0066] Example 8

[0067] Example 8 is basically the same as Example 7, except that:

[0068] (1) Weighing 5 g of aluminum oxide nanowires and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 5%; then adding 1 mol / L oxalic acid aqueous solution as a structure modifier and adding mineralizer ammonium fluoride powder to the dispersion liquid and hydrothermally reacting them at a high temperature of 180°C for 24 hours to prepare a composite precursor sol; the mass amount of the oxalic acid aqueous solution is 2% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 0.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0069] Example 9

[0070] Example 9 is basically the same as Example 7, except that:

[0071] (1) Weighing 5 g of aluminum oxide nanowires and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 5%; then adding 1 mol / L oxalic acid aqueous solution as a structure modifier and adding mineralizer ammonium fluoride powder to the dispersion liquid and hydrothermally reacting them at a high temperature of 180°C for 24 hours to prepare a composite precursor sol; the mass amount of the oxalic acid aqueous solution is 8% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 4% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0072] Example 10

[0073] Example 10 is substantially the same as Example 7, except that:

[0074] (2) Add 3.24 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 2.16 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, age it at room temperature at 25°C for 48 h to obtain a wet gel.

[0075] Comparative Example 1

[0076] (1) Weighing 5 g of aluminum oxide nanowires and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 5%; then adding 1 mol / L oxalic acid aqueous solution as a structure modifier and adding mineralizer ammonium fluoride powder to the dispersion liquid and hydrothermally reacting them at a high temperature of 100°C for 24 hours to prepare a composite precursor sol; the mass amount of the oxalic acid aqueous solution is 4% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0077] (2) Add 3.24 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 0.9 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, age it at room temperature at 25°C for 48 h to obtain a wet gel.

[0078] (3) The wet gel obtained in step (2) is placed in an ethanol solvent for solvent replacement, the solvent replacement is performed 3 times, and the time for each solvent replacement is 24 hours. Then, the wet gel is sent to a supercritical drying kettle for supercritical carbon dioxide drying for 72 hours to obtain a multi-element oxide high-temperature resistant aerogel composite material.

[0079] Comparative Example 2

[0080] (1) Weighing 5 g of aluminum oxide nanowires and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 5%; then adding 1 mol / L oxalic acid aqueous solution as a structure modifier and adding mineralizer ammonium fluoride powder to the dispersion liquid and hydrothermally reacting them at a high temperature of 180°C for 24 hours to prepare a composite precursor sol; the mass amount of the oxalic acid aqueous solution is 4% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0081] (2) Add 3.24 g of mullite nanofibers and 0.3 g of silicon carbide nanopowder to the composite precursor sol system obtained above.

[0082] In this comparative example, no inorganic gelling agent, calcium aluminosilicate cement, was added to the composite precursor sol system. As a result, the system could not gel and no wet gel could be obtained, resulting in the failure of the experiment.

[0083] Comparative Example 3

[0084] (1) Weighing 5 g of aluminum oxide nanowires and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1), adding them to water and dispersing them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanowires and magnesium oxide nanopowder in the dispersion liquid is 5%; then adding 1 mol / L oxalic acid aqueous solution as a structure modifier and adding mineralizer ammonium fluoride powder to the dispersion liquid and hydrothermally reacting them at a high temperature of 180°C for 24 hours to prepare a composite precursor sol; the mass amount of the oxalic acid aqueous solution is 4% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0085] (2) Add 0.54 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 0.9 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, age it at room temperature at 25°C for 48 h to obtain a wet gel.

[0086] (3) The wet gel obtained in step (2) is placed in an ethanol solvent for solvent replacement, the solvent replacement is performed 3 times, and the time for each solvent replacement is 24 hours. Then, the wet gel is sent to a supercritical drying kettle for supercritical carbon dioxide drying for 72 hours to obtain an aerogel thermal insulation composite material.

[0087] Comparative Example 4

[0088] Comparative Example 4 is substantially the same as Comparative Example 3, except that:

[0089] (2) Add 4.32 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 0.9 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, age it at room temperature at 25°C for 48 h to obtain a wet gel.

[0090] Comparative Example 5

[0091] Comparative Example 5 is substantially the same as Example 7, except that:

[0092] (2) Add 0.9 g of inorganic gelling agent calcium aluminosilicate cement to the composite precursor sol system obtained above and mix them evenly to obtain a reaction system. After the reaction system is gelled, age it at room temperature of 25° C. for 48 h to obtain a wet gel.

[0093] Comparative Example 6

[0094] Comparative Example 6 is substantially the same as Example 7, except that:

[0095] (1) Weighing 5 g of aluminum oxide nanowires and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1) and adding them to water for uniform dispersion to obtain a dispersion, wherein the total mass percentage of the aluminum oxide nanowires and the magnesium oxide nanopowder in the dispersion is 5%; then adding a 1 mol / L oxalic acid aqueous solution as a structure modifier to the dispersion and hydrothermally reacting at a high temperature of 180°C for 24 h to prepare a composite precursor sol; the mass amount of the oxalic acid aqueous solution is 4% of the total mass amount of the aluminum oxide nanowires and the magnesium oxide nanopowder.

[0096] Comparative Example 7

[0097] Comparative Example 7 is substantially the same as Example 7, except that:

[0098] (2) 3.24 g of mullite nanofiber, 0.3 g of silicon carbide nanopowder and 0.9 g of silica sol (solid content of silica sol is 30 wt%) were added to the composite precursor sol system obtained above and mixed evenly to obtain a reaction system. After the reaction system was gelled, it was aged at 80°C for 24 h and then aged at 180°C for 24 h to obtain a wet gel.

[0099] Comparative Example 8

[0100] Comparative Example 8 is substantially the same as Example 7, except that:

[0101] (1) Weigh 5 g of aluminum oxide nanopowder and 0.4 g of magnesium oxide nanopowder (aluminum-magnesium molar ratio of 10:1), add them to water and disperse them evenly to obtain a dispersion liquid, wherein the total mass percentage of the aluminum oxide nanopowder and the magnesium oxide nanopowder in the dispersion liquid is 5%; then, add 1 mol / L oxalic acid aqueous solution as a structure modifier and ammonium fluoride powder as a mineralizer to the dispersion liquid, and hydrothermally react at a high temperature of 180°C for 24 hours to prepare a composite precursor sol; the mass amount of the oxalic acid aqueous solution is 4% of the total mass amount of the aluminum oxide nanopowder and the magnesium oxide nanopowder; the mass amount of the ammonium fluoride powder is 1.5% of the total mass amount of the aluminum oxide nanopowder and the magnesium oxide nanopowder.

[0102] Comparative Example 9

[0103] Comparative Example 9 is substantially the same as Example 7, except that:

[0104] (1) Weighing 5 g of alumina nanowires and 0.4 g of silica nanopowder, adding them to water and dispersing them evenly to obtain a dispersion, wherein the total mass percentage of the alumina nanowires and silica nanopowder in the dispersion is 5%; then adding 1 mol / L oxalic acid aqueous solution as a structure modifier and ammonium fluoride powder as a mineralizer to the dispersion, and hydrothermally reacting them at a high temperature of 180°C for 24 hours to prepare a composite precursor sol; the mass amount of the oxalic acid aqueous solution is 4% of the total mass amount of the alumina nanowires and the silica nanopowder; the mass amount of the ammonium fluoride powder is 1.5% of the total mass amount of the alumina nanowires and the silica nanopowder.

[0105] The materials prepared in each embodiment of the present invention and each comparative example were tested for thermal conductivity at 1400°C, single-sided shrinkage at 1400°C (volume shrinkage after single-sided radiation heating at 1400°C for 2 hours), and compressive strength at a deformation of 10%. The results are shown in Table 1. As can be seen from Table 1, the materials prepared in each embodiment of the present invention have low thermal conductivity at high temperatures, low single-sided shrinkage at 1400°C, good temperature resistance, and high mechanical strength.

[0106] Table 1

[0107]

[0108]

[0109] In Table 1, the symbol “-” indicates that the performance indicator does not exist.

[0110] Parts of the present invention that are not described in detail are well known to those skilled in the art.

[0111] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A method for preparing a multi-element oxide high temperature resistant aerogel composite material, characterized in that: The method comprises the following steps: (1) uniformly dispersing an aluminum source and a magnesium source with water to obtain a dispersion, then adding a structure modifier and a mineralizer to the dispersion and performing a hydrothermal reaction to obtain a composite precursor sol; the aluminum source is aluminum oxide nanowires and / or aluminum oxide nanobelts; and the magnesium source is magnesium oxide nanopowder; (2) adding mullite nanofibers, silicon carbide nanopowder and an inorganic gelling agent to the composite precursor sol and mixing them uniformly to obtain a reaction system, and aging the reaction system after gelation to obtain a wet gel; the inorganic gelling agent is calcium aluminosilicate cement and / or calcium ion-doped zirconia sol; (3) The wet gel is subjected to solvent replacement and supercritical drying in sequence to obtain a multi-element oxide high-temperature resistant aerogel composite material.

2. The preparation method according to claim 1, wherein: The molar ratio of the aluminum contained in the aluminum source to the magnesium contained in the magnesium source is (0.95-10):

1.

3. The preparation method according to claim 1, wherein: The sum of the mass percentages of the aluminum source and the magnesium source in the dispersion is 5-15%.

4. The preparation method according to claim 1, wherein: The structure modifier is an organic weak acid.

5. The preparation method according to claim 4, characterized in that: The organic weak acid is acetic acid solution, oxalic acid solution, oxalic acid solution and citric acid solution.

6. The preparation method according to claim 4, wherein: The concentration of the organic weak acid is 0.1-5 mol / L.

7. The preparation method according to claim 1, wherein: The mineralizer is one or more of ammonium fluoride powder, aluminum fluoride powder, and lithium fluoride powder.

8. The preparation method according to claim 1, wherein: The mass amount of the structure modifier is 3-5% of the sum of the mass amounts of the aluminum source and the magnesium source; and / or The mass dosage of the mineralizer is 1-2% of the sum of the mass dosages of the aluminum source and the magnesium source.

9. The preparation method according to claim 1, wherein: The temperature of the hydrothermal reaction is 180-290° C., and the time of the hydrothermal reaction is 6 h to 24 h.

10. The preparation method according to claim 1, characterized in that: The mass amount of the mullite nanofiber is 20-60% of the sum of the mass amounts of the aluminum source and the magnesium source; and / or The mass amount of the silicon carbide nanopowder is 4-8% of the sum of the mass amounts of the aluminum source and the magnesium source.

11. The preparation method according to claim 1, characterized in that: The mass amount of the inorganic gelling agent is 10-30% of the sum of the mass amounts of the aluminum source and the magnesium source.

12. A multi-element oxide high temperature resistant aerogel composite material prepared by the preparation method according to any one of claims 1 to 11.

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