Preparation method of tough high-temperature-resistant medium-entropy ceramic nano aerogel

Abstract

The invention relates to a preparation method of tough high-temperature-resistant medium-entropy ceramic nano aerogel, and belongs to the technical field of aerogel materials. The method comprises the following steps: adding metal oxide nanoparticles into deionized water according to an equal molar ratio, uniformly stirring and mixing at room temperature to obtain a metal oxide nanoparticle dispersion liquid with an equal molar ratio, carrying out a high-temperature and high-pressure hydrothermal reaction on the dispersion liquid to prepare a metal hydroxide dispersion liquid with an equal molar ratio, then adding a certain amount of organic acid, and carrying out hydrothermal reaction to obtain the metal oxide nanoparticles with an equal molar ratio. Uniformly stirring, pouring into a mold, adding a certain amount of epoxypropane, and thermally curing to obtain nano wet gel; placing the nano wet gel in a low-surface-tension mixed solvent for solvent replacement to obtain low-surface-energy solvent system nano wet gel, and performing drying and high-temperature quenching treatment to obtain the tough high-temperature-resistant medium-entropy ceramic nano aerogel. The preparation process is simple, green, environment-friendly and low in cost, the high-temperature mechanical property of the medium-entropy ceramic nano aerogel can be effectively improved, and the heat insulation performance is excellent.

Description

Technical Field

[0001] The invention relates to a method for preparing strong, tough, high-temperature-resistant medium-entropy ceramic nano aerogel, and belongs to the technical field of aerogel materials. Background Art

[0002] Medium-entropy ceramics generally refer to solid solutions composed of three or more ceramic components, in which the content of metal elements is in an equimolar ratio or close to an equimolar ratio. It is a new type of ceramic material with great development potential. As an entropy-stabilized oxide material, compared with single-component ceramic materials, medium-entropy ceramic materials have excellent thermal stability, corrosion resistance, oxidation resistance, high wear resistance, etc. These outstanding performance advantages make it a hot spot and frontier in current research.

[0003] Aerogel is a bulk material with a three-dimensional network self-supporting structure. Its internal interconnected open channels are filled with a large amount of air medium (generally greater than 90%). It has low volume density, high porosity, large specific surface area, low thermal conductivity, etc., and has nano effect on the macro scale. It shows great application prospects in the fields of thermal, optics, electricity, acoustics, catalysis, etc. However, at present, there are very few reports at home and abroad on the preparation method of medium-entropy ceramic nanoaerogel materials and related research and applications in the field of high-temperature thermal insulation. Patent CN202210948172.6 discloses a method for preparing medium-entropy ceramic nanofiber aerogel. A medium-entropy ceramic nanofiber aerogel material with a fluffy three-dimensional structure is prepared by electrospinning, which has the advantages of high flexibility, excellent high-temperature thermal insulation performance, and strong ability to reflect thermal radiation. However, the mechanical strength of the nanofiber aerogel prepared by the above method is poor (less than 1MPa); and the basic unit of the above aerogel is nanofiber, whose diameter is 200-1500nm, so it is difficult to form nanopores, resulting in a significant increase in the gas phase heat transfer and thermal convection of the material; in addition, the preparation method of the above material involves high voltage operation and the use of a large amount of organic solvents such as methanol, ethanol or acetic acid, which brings safety risks such as easy ignition and volatilization of toxic gases.

[0004] At present, the existing medium-entropy ceramic aerogel systems are relatively simple, mostly based on medium-entropy alloy aerogels, so there is an urgent need to expand the types of medium-entropy ceramic nanoaerogel materials. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a method for preparing a strong, high-temperature resistant medium-entropy ceramic nanoaerogel, the method comprising the following steps:

[0006] (1) adding metal oxide nanoparticles in an equal molar ratio into deionized water, stirring and mixing at room temperature to obtain a dispersion of metal oxide nanoparticles in an equal molar ratio;

[0007] (2) subjecting the equimolar ratio metal oxide nanoparticle dispersion to a high temperature and high pressure hydrothermal reaction to prepare an equimolar ratio metal hydroxide dispersion;

[0008] (3) adding a certain amount of organic acid to the metal hydroxide dispersion, stirring evenly and pouring into a mold, adding a certain amount of propylene oxide, and thermally curing at an appropriate temperature to obtain a nano wet gel;

[0009] (4) after taking the nano wet gel out of the mold, placing it in a mixed solvent with low surface tension for solvent replacement to obtain a low surface energy solvent nano wet gel;

[0010] (5) The low surface energy solvent-based nano-wet gel is dried to obtain a nano-aerogel, which is then subjected to a high temperature quenching treatment to obtain a strong, tough, high temperature resistant medium entropy ceramic nano-aerogel.

[0011] Preferably, the metal oxide described in step (1) is a mixture of three or more, or five or less, of Al2O3, Y2O3, Gd2O3, Er2O3, Yb2O3, Lu2O3, La2O3, CeO2, Sm2O3, Eu2O3, Nd2O3, TiO2, HfO2, ZrO2, Ta2O5, MgO, CoO, NiO, CuO, ZnO, B2O3, SiO2, and SnO2; the average particle size of the metal oxide nanoparticles is 5-50 nm; and the solid content of the equimolar ratio metal oxide nanoparticle dispersion is 10-40%.

[0012] Preferably, the metal oxide nanoparticle dispersion described in step (2) is placed in a hydrothermal kettle for high-temperature and high-pressure hydrothermal reaction, the reaction temperature of the hydrothermal reaction is 180-250° C., the reaction time is 2-10 h, and the reaction pressure is 1.0-4.0 MPa.

[0013] Preferably, the organic acid in step (3) is any one of citric acid, malic acid, tartaric acid, acetic acid, succinic acid and oxalic acid; the mass ratio of the metal hydroxide dispersion: organic acid: propylene oxide is 100:(5-18):(8-30); the thermal curing temperature is 60-150°C; the nano wet gel has a three-dimensional network structure, a pore size of 10-50nm, and its basic component unit is one of nanowires, nanorods or nanosheets.

[0014] Preferably, the low surface tension mixed solvent described in step (4) is a combination of two or more of n-hexane, aliphatic hydrocarbon naphtha, n-octane, naphtha, methanol, methyl isobutyl ketone, petroleum solvent oil, n-butanol, butyl acetate, cyclohexane, toluene, and o-xylene, which are mixed in any mass ratio, but the surface tension of the mixed solvent is less than 28 mN / m; the number of solvent replacements is 2-4 times.

[0015] Preferably, in step (5), the low surface energy solvent-based nano-wet gel is placed in a fume hood for drying, and the drying method is drying at room temperature and pressure for 6-12 hours; the conditions for the high-temperature quenching treatment are: heating to 400-600°C at a heating rate of 0.5-2°C / min, then heating to 1000-1200°C at a heating rate of 1-3°C / min and keeping warm for 30-60 minutes, then heating to 1600-1800°C at a heating rate of 5-10°C / min and keeping warm for 0.5-2 hours, and finally using any one of high-pressure nitrogen, high-pressure air, high-purity helium, and high-purity argon to perform rapid air cooling quenching treatment on the aerogel.

[0016] Preferably, the tough high temperature resistant medium entropy ceramic nano aerogel is prepared by the above preparation method, and the density of the tough high temperature resistant medium entropy ceramic nano aerogel is 0.10-0.30 g / cm 3 , temperature resistance is 1400-1800℃, tensile strength is greater than 5MPa, Young's modulus is greater than 10MPa, room temperature thermal conductivity is less than 0.02W / (m·K), 1500℃ thermal conductivity is less than 0.12W / (m·K), and the crystal structure is one of rock salt structure, fluorite structure, perovskite structure, spinel structure, pyrochlore structure and olivine structure.

[0017] The present invention prepares a strong, high-temperature resistant medium-entropy ceramic nano-aerogel through the above steps. Compared with the prior art, the present invention has the following beneficial effects:

[0018] (1) The preparation process of the present invention is simple, environmentally friendly and low in cost. Metal oxide nanoparticles and deionized water are used as the main raw materials, a hydrothermal synthesis method is used to form an entropy-increasing hydroxide solid solution, an organic acid is used as a catalyst, and propylene oxide is used as a cross-linking agent, so that the attraction between propylene oxide molecules is enhanced at high temperature to form a nano wet gel with a stable three-dimensional network structure; after the wet gel is dried and subjected to high-temperature quenching treatment, the multi-element ceramic grains will be oriented, and its slow grain growth rate will produce more grain boundaries and higher grain boundary strength, which can effectively improve the high-temperature mechanical properties of the medium-entropy ceramic nano aerogel.

[0019] (2) The medium-entropy ceramic nano-aerogel of the present invention has a nanowire, nanorod or nanosheet crystal morphology; compared with the nanofiber aerogel prepared by the electrospinning method, its pore structure is smaller, which can effectively inhibit gas phase heat conduction and heat convection at high temperatures, and thus has lower room temperature and high temperature thermal conductivity. In addition, the medium-entropy ceramic nano-aerogel of the present invention is a rigid skeleton, which is thicker than the flexible skeleton of nanofibers. After calcination at a temperature below the melting point of the material, sintering and fusion will not occur between the nano-units, which can effectively avoid the problems of collapse of the aerogel nano-skeleton, volume shrinkage, and thermal insulation failure.

[0020] (3) The present invention adopts a normal pressure drying method to prepare the medium entropy ceramic nano aerogel, which does not require the cumbersome process of supercritical drying and freeze drying methods. The process is simple and easy to achieve large-scale industrial production. The present invention uses a low surface energy solvent to replace the solvent of the nano wet gel, eliminating the capillary tension difference between the inner and outer interfaces of the wet gel during the drying process at room temperature and pressure, effectively ensuring the nanoporous structure of the medium entropy ceramic nano aerogel, and greatly reducing the preparation cycle and production cost of the material.

[0021] (4) The present invention adopts high-temperature calcination and rapid air-cooling quenching process to obtain medium-entropy ceramic nanoaerogel. Its entropy-increasing effect can effectively inhibit the agglomeration and sintering of the basic structural units of the nanoaerogel during high-temperature heat treatment. The resulting large lattice distortion and smaller grain size can enhance the carrier transport barrier, making the thermal insulation performance of the medium-entropy ceramic nanoaerogel more excellent. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0023] Figure 1 The tough and high temperature resistant (La 0.25 Ce 0.25 Sm 0.25 Eu 0.25 )SEM image of 3O4 medium entropy ceramic nanoaerogel;

[0024] Figure 2 The tough and high temperature resistant (Hf 0.25 Zr 0.25 Er 0.25 Y 0.25 )TEM image of the basic structural unit of 3O4 mesoentropic ceramic nanoaerogel;

[0025] Figure 3 The tough and high temperature resistant (Mg 0.25 Co 0.25 Cu 0.25 Zn 0.25 )TEM image of the basic structural unit of 3O4 mesoentropic ceramic nanoaerogel. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the preferred embodiments of the present invention, rather than all the embodiments; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0027] Example 1

[0028] A strong and high temperature resistant (La 0.25 Ce 0.25 Sm 0.25 Eu 0.25 )3O4 medium entropy ceramic nano aerogel preparation method, comprising the following steps:

[0029] (1) adding 100 g of La2O3, CeO2, Sm2O3, and Eu2O3 nanoparticles (average particle size 10 nm) in equal molar ratio into 900 g of deionized water, stirring and mixing at room temperature to obtain an equal molar ratio metal oxide nanoparticle dispersion with a solid content of 10%;

[0030] (2) placing the metal oxide nanoparticle dispersion prepared in step (1) in a hydrothermal reactor, and subjecting the dispersion to a high temperature and high pressure hydrothermal reaction to obtain a metal hydroxide dispersion having an equimolar ratio, wherein the reaction temperature of the hydrothermal reaction is 250° C., the reaction time is 2 h, and the reaction pressure is 4.0 MPa;

[0031] (3) adding 50 g of citric acid to the metal hydroxide dispersion prepared in step (2), stirring evenly and pouring into a mold, adding 80 g of propylene oxide, and thermally curing at 60° C. to obtain a nano wet gel having a three-dimensional network structure, wherein the pore size is 50 nm and the basic component unit is a nanowire structure;

[0032] (4) after taking out the nano wet gel prepared in step (3) from the mold, placing it in a mixed solvent of n-hexane / o-xylene with a mass ratio of 1:1 and performing solvent exchange 4 times to obtain a nano wet gel in a n-hexane / o-xylene solvent system;

[0033] (5) placing the n-hexane / o-xylene solvent nano-wet gel obtained in step (4) in a fume hood and drying at room temperature and pressure for 6 hours; performing high-temperature heat treatment on the dried aerogel using a tubular furnace: heating the temperature to 400°C at a heating rate of 0.5°C / min, then heating the temperature to 1000°C at a heating rate of 1°C / min and keeping the temperature for 30 minutes, and finally heating the temperature to 1600°C at a heating rate of 5°C / min and keeping the temperature for 1 hour; then performing air cooling quenching treatment on the aerogel using high-pressure nitrogen to obtain a tough and high-temperature resistant (La 0.25 Ce0.25 Sm 0.25 Eu 0.25 )3O4 medium-entropy ceramic nanoaerogel.

[0034] The tough and high temperature resistant (La 0.25 Ce 0.25 Sm 0.25 Eu 0.25 )3O4 medium entropy ceramic nanoaerogel has a density of 0.10 g / cm 3 , temperature resistance is 1400℃, tensile strength is 5.5MPa, Young's modulus is 11MPa, room temperature thermal conductivity is 0.015W / (m·K), 1500℃ thermal conductivity is 0.11W / (m·K), and the crystal structure is rock salt structure.

[0035] Figure 1 The tough and high temperature resistant (La 0.25 Ce 0.25 Sm 0.25 Eu 0.25 )3O4 medium entropy ceramic nanoaerogel SEM image, it can be seen that the basic structural unit of the aerogel is a nanowire morphology.

[0036] Example 2

[0037] A tough and high temperature resistant (Hf 0.25 Zr 0.25 Er 0.25 Y 0.25 )3O4 medium entropy ceramic nano aerogel preparation method, comprising the following steps:

[0038] (1) adding 40 g of HfO2, ZrO2, Er2O3, and Y2O3 nanoparticles (average particle size 5 nm) in equal molar ratio into 60 g of deionized water, stirring and mixing at room temperature to obtain an equal molar ratio metal oxide nanoparticle dispersion with a solid content of 40%;

[0039] (2) placing the metal oxide nanoparticle dispersion prepared in step (1) in a hydrothermal reactor, and subjecting the dispersion to a high-temperature and high-pressure hydrothermal reaction to obtain a metal hydroxide dispersion having an equimolar ratio, wherein the reaction temperature of the hydrothermal reaction is 180° C., the reaction time is 10 h, and the reaction pressure is 1.0 MPa;

[0040] (3) adding 18 g of oxalic acid to the metal hydroxide dispersion prepared in step (2), stirring evenly and pouring into a mold, adding 30 g of propylene oxide, and thermally curing at 150° C. to obtain a nano wet gel having a three-dimensional network structure, wherein the pore size is 10 nm and the basic component unit is a nanorod structure;

[0041] (4) after taking out the nano wet gel prepared in step (3) from the mold, placing it in a mixed solvent of aliphatic hydrocarbon naphtha / cyclohexane with a mass ratio of 2:1 and performing two solvent exchanges to obtain aliphatic hydrocarbon naphtha / cyclohexane solvent system nano wet gel;

[0042] (5) placing the aliphatic hydrocarbon naphtha / cyclohexane solvent nano-wet gel obtained in step (4) in a fume hood and drying at room temperature and pressure for 12 h; performing high-temperature heat treatment on the dried aerogel using a muffle furnace: heating the temperature to 600° C. at a heating rate of 2° C. / min, then heating the temperature to 1200° C. at a heating rate of 3° C. / min and keeping the temperature for 60 min, and finally heating the temperature to 1800° C. at a heating rate of 10° C. / min and keeping the temperature for 2 h; and then performing air cooling quenching treatment on the aerogel using high-pressure air to obtain a tough and high-temperature resistant (Hf 0.25 Zr 0.25 Er 0.25 Y 0.25 )3O4 medium-entropy ceramic nanoaerogel.

[0043] The tough and high temperature resistant (Hf 0.25 Zr 0.25 Er 0.25 Y 0.25 )3O4 medium entropy ceramic nanoaerogel has a density of 0.30 g / cm 3 , temperature resistance is 1800℃, tensile strength is 8MPa, Young's modulus is 20MPa, room temperature thermal conductivity is 0.012W / (m·K), 1500℃ thermal conductivity is 0.10W / (m·K), and the crystal structure is fluorite structure.

[0044] Figure 2 The tough and high temperature resistant (Hf 0.25 Zr 0.25 Er 0.25 Y 0.25 )3O4 medium entropy ceramic nanoaerogel TEM image, it can be seen that the basic structural unit of the aerogel is a nanorod morphology.

[0045] Example 3

[0046] A strong and high temperature resistant (Mg 0.25 Co 0.25 Cu 0.25 Zn 0.25 )3O4 medium entropy ceramic nano aerogel preparation method, comprising the following steps:

[0047] (1) adding 60 g of MgO, CoO, CuO, and ZnO nanoparticles (average particle size 50 nm) in equal molar ratio into 140 g of deionized water, stirring and mixing at room temperature to obtain an equal molar ratio metal oxide nanoparticle dispersion with a solid content of 30%;

[0048] (2) placing the metal oxide nanoparticle dispersion prepared in step (1) in a hydrothermal reactor, and subjecting the dispersion to a high-temperature and high-pressure hydrothermal reaction to obtain a metal hydroxide dispersion having an equimolar ratio, wherein the reaction temperature of the hydrothermal reaction is 200° C., the reaction time is 6 h, and the reaction pressure is 1.8 MPa;

[0049] (3) adding 20 g of acetic acid to the metal hydroxide dispersion prepared in step (2), stirring evenly and pouring into a mold, adding 40 g of propylene oxide, and thermally curing at 120° C. to obtain a nano wet gel having a three-dimensional network structure, wherein the pore size is 20 nm, and the basic component unit is a nano sheet structure;

[0050] (4) after taking out the nano wet gel prepared in step (3) from the mold, placing it in a mixed solvent of n-octane / butyl acetate with a mass ratio of 3:2 and performing solvent exchange three times to obtain a nano wet gel in a n-octane / butyl acetate solvent system;

[0051] (5) placing the n-octane / butyl acetate solvent system nano wet gel obtained in step (4) in a fume hood and drying at room temperature and pressure for 10 h; performing high temperature heat treatment on the dried aerogel using a tubular furnace: heating the temperature to 550° C. at a heating rate of 1.5° C. / min, then heating the temperature to 1050° C. at a heating rate of 1.5° C. / min and keeping the temperature for 40 min, and finally heating the temperature to 1650° C. at a heating rate of 6° C. / min and keeping the temperature for 0.5 h; then performing air cooling quenching treatment on the aerogel using high pressure helium to obtain a tough and high temperature resistant (Mg 0.25 Co 0.25 Cu 0.25 Zn 0.25 )3O4 medium-entropy ceramic nanoaerogel.

[0052] The tough and high temperature resistant (Mg 0.25 Co 0.25 Cu 0.25 Zn 0.25 )3O4 medium entropy ceramic nanoaerogel has a density of 0.20 g / cm 3 , temperature resistance is 1500℃, tensile strength is 6MPa, Young's modulus is 15MPa, room temperature thermal conductivity is 0.017W / (m·K), 1500℃ thermal conductivity is 0.095W / (m·K), and the crystal structure is spinel structure.

[0053] Figure 3 The tough and high temperature resistant (Mg 0.25 Co 0.25 Cu 0.25 Zn 0.25)3O4 medium-entropy ceramic nanoaerogel TEM image, it can be seen that the basic structural unit of the aerogel is a nanosheet morphology.

[0054] Example 4

[0055] A strong and high temperature resistant (Ti 0.2 G 0.2 Lu 0.2 Ta 0.2 Sn 0.2 )3O4 medium entropy ceramic nano aerogel preparation method, comprising the following steps:

[0056] (1) adding 30 g of TiO2, Gd2O3, Lu2O3, Ta2O5, and SnO2 nanoparticles (average particle size 30 nm) in equal molar ratio into 120 g of deionized water, stirring and mixing at room temperature to obtain an equal molar ratio metal oxide nanoparticle dispersion with a solid content of 20%;

[0057] (2) placing the metal oxide nanoparticle dispersion prepared in step (1) in a hydrothermal reactor, and subjecting the dispersion to a high temperature and high pressure hydrothermal reaction to obtain a metal hydroxide dispersion having an equimolar ratio, wherein the reaction temperature of the hydrothermal reaction is 220° C., the reaction time is 5 h, and the reaction pressure is 2.9 MPa;

[0058] (3) adding 18 g of tartaric acid to the metal hydroxide dispersion prepared in step (2), stirring evenly and pouring into a mold, adding 35 g of propylene oxide, and thermally curing at 80° C. to obtain a nano wet gel having a three-dimensional network structure, wherein the pore size is 40 nm, and the basic component unit is a nanowire structure;

[0059] (4) after taking out the nano wet gel prepared in step (3) from the mold, placing it in a mixed solvent of naphtha / methyl isobutyl ketone with a mass ratio of 2:3 and performing solvent exchange four times to obtain a nano wet gel in a naphtha / methyl isobutyl ketone solvent system;

[0060] (5) placing the naphtha / methyl isobutyl ketone solvent system nano wet gel obtained in step (4) in a fume hood and drying at room temperature and pressure for 7 hours; performing high temperature heat treatment on the dried aerogel using a muffle furnace: heating the temperature to 530°C at a heating rate of 0.8°C / min, then heating the temperature to 1030°C at a heating rate of 1.2°C / min and keeping the temperature for 45 minutes, and finally heating the temperature to 1730°C at a heating rate of 7°C / min and keeping the temperature for 0.8 hours; then performing air cooling quenching treatment on the aerogel using high pressure air to obtain a strong and high temperature resistant (Ti 0.2 G 0.2 Lu 0.2 Ta 0.2 Sn 0.2 )3O4 medium-entropy ceramic nanoaerogel.

[0061] The tough and high temperature resistant (Ti 0.2 G 0.2 Lu 0.2 Ta 0.2 Sn 0.2 )3O4 medium entropy ceramic nanoaerogel has a density of 0.25 g / cm 3 , temperature resistance is 1650℃, tensile strength is 9MPa, Young's modulus is 19MPa, room temperature thermal conductivity is 0.019W / (m·K), 1500℃ thermal conductivity is 0.106W / (m·K), and the crystal structure is perovskite structure.

[0062] Example 5

[0063] A tough and high temperature resistant (Al 0.2 Si 0.2 B 0.2 Yb 0.2 Ni 0.2 )3O4 medium entropy ceramic nano aerogel preparation method, comprising the following steps:

[0064] (1) adding 15 g of Al2O3, SiO2, B2O3, Yb2O3, and NiO nanoparticles (average particle size 25 nm) in equal molar ratios to 85 g of deionized water, and stirring and mixing at room temperature to obtain an equal molar ratio metal oxide nanoparticle dispersion with a solid content of 15%;

[0065] (2) placing the metal oxide nanoparticle dispersion prepared in step (1) in a hydrothermal reactor, and subjecting the dispersion to a high temperature and high pressure hydrothermal reaction to obtain a metal hydroxide dispersion having an equimolar ratio, wherein the reaction temperature of the hydrothermal reaction is 240° C., the reaction time is 7 h, and the reaction pressure is 3.4 MPa;

[0066] (3) adding 8 g of malic acid to the metal hydroxide dispersion prepared in step (2), stirring evenly and pouring into a mold, adding 14 g of propylene oxide, and thermally curing at 130° C. to obtain a nano wet gel having a three-dimensional network structure, wherein the pore size is 35 nm, and the basic component unit is a nano sheet structure;

[0067] (4) after taking out the nano wet gel prepared in step (3) from the mold, placing it in a methanol / toluene solvent with a mass ratio of 1:2 for two solvent exchanges to obtain a methanol / toluene solvent nano wet gel;

[0068] (5) placing the methanol / toluene solvent nano-wet gel obtained in step (4) in a fume hood and drying at room temperature and pressure for 11 hours; performing high-temperature heat treatment on the dried aerogel using a tubular furnace: heating the temperature to 580°C at a heating rate of 0.8°C / min, then heating the temperature to 1180°C at a heating rate of 2.5°C / min and keeping the temperature for 45 minutes, and finally heating the temperature to 1800°C at a heating rate of 10°C / min and keeping the temperature for 1.5 hours; then performing air cooling quenching treatment on the aerogel using high-pressure argon gas to obtain a tough and high-temperature resistant (Al 0.2 Si 0.2 B 0.2 Yb 0.2 Ni 0.2 )3O4 medium-entropy ceramic nanoaerogel.

[0069] The tough and high temperature resistant (Al 0.2 Si 0.2 B 0.2 Yb 0.2 Ni 0.2 )3O4 medium entropy ceramic nanoaerogel has a density of 0.22 g / cm 3 , temperature resistance is 1700℃, tensile strength is 5.8MPa, Young's modulus is 13.5MPa, room temperature thermal conductivity is 0.016W / (m·K), 1500℃ thermal conductivity is 0.089W / (m·K), and the crystal structure is olivine structure.

[0070] The specific embodiments of the present invention disclosed above are intended to help understand the content of the present invention and implement it accordingly. It can be understood by those skilled in the art that various replacements, changes and modifications are possible without departing from the spirit and scope of the present invention. The present invention should not be limited to the contents disclosed in the embodiments of this specification, and the scope of protection of the present invention shall be subject to the scope defined in the claims.

Claims

1. A method for preparing a strong, high-temperature resistant medium-entropy ceramic nanoaerogel, characterized in that: The following steps are involved: Adding metal oxide nanoparticles into deionized water in an equal molar ratio, stirring and mixing at room temperature to obtain a metal oxide nanoparticle dispersion in an equal molar ratio; The equimolar ratio metal oxide nanoparticle dispersion is subjected to a high temperature and high pressure hydrothermal reaction to prepare an equimolar ratio metal hydroxide dispersion; A certain amount of organic acid is added to the metal hydroxide dispersion, and the mixture is poured into a mold after being stirred evenly, and a certain amount of propylene oxide is added, and the mixture is thermally cured at an appropriate temperature to obtain a nano wet gel; After taking the nano wet gel out of the mold, placing it in a mixed solvent with low surface tension for solvent replacement to obtain a low surface energy solvent nano wet gel; The low surface energy solvent-based nano-wet gel is dried to obtain a nano-aerogel, which is then subjected to a high-temperature quenching treatment to obtain a strong, tough, high-temperature resistant medium-entropy ceramic nano-aerogel.

2. The method according to claim 1, characterized in that: The metal oxide is a mixture of three or more, or five or less, of Al2O3, Y2O3, Gd2O3, Er2O3, Yb2O3, Lu2O3, La2O3, CeO2, Sm2O3, Eu2O3, Nd2O3, TiO2, HfO2, ZrO2, Ta2O5, MgO, CoO, NiO, CuO, ZnO, B2O3, SiO2, and SnO2; the average particle size of the metal oxide nanoparticles is 5-50 nm; and the solid content of the equimolar ratio metal oxide nanoparticle dispersion is 10-40%.

3. The method according to claim 1, characterized in that The metal oxide nanoparticle dispersion with an equal molar ratio is placed in a hydrothermal kettle for high-temperature and high-pressure hydrothermal reaction. The reaction temperature of the hydrothermal reaction is 180-250° C., the reaction time is 2-10 hours, and the reaction pressure is 1.0-4.0 MPa.

4. The method according to claim 1, characterized in that The organic acid is any one of citric acid, malic acid, tartaric acid, acetic acid, succinic acid and oxalic acid; the mass ratio of the metal hydroxide dispersion: organic acid: propylene oxide is 100: (5-18): (8-30); the thermal curing temperature is 60-150°C; the nano wet gel has a three-dimensional network structure, the pore size is 10-50nm, and the basic component unit is one of nanowires, nanorods or nanosheets.

5. The method according to claim 1, characterized in that The low surface tension mixed solvent is a combination of two or more of n-hexane, aliphatic hydrocarbon naphtha, n-octane, naphtha, methanol, methyl isobutyl ketone, white spirit, n-butanol, butyl acetate, cyclohexane, toluene, and o-xylene, and the surface tension of the mixed solvent is less than 28 mN / m.

6. The method according to claim 1, characterized in that The number of solvent replacement is 2-4 times.

7. The method according to claim 1, characterized in that The low surface energy solvent-based nano wet gel is placed in a fume hood for drying at room temperature and pressure for 6-12 hours.

8. The method according to claim 1, characterized in that: The conditions of the high temperature quenching treatment are: heating to 400-600°C at a heating rate of 0.5-2°C / min, then heating to 1000-1200°C at a heating rate of 1-3°C / min and keeping warm for 30-60min, then heating to 1600-1800°C at a heating rate of 5-10°C / min and keeping warm for 0.5-2h, and finally using any one of high-pressure nitrogen, high-pressure air, high-purity helium, and high-purity argon to perform rapid air cooling quenching treatment on the aerogel.

9. A strong, tough, high temperature resistant medium entropy ceramic nanoaerogel prepared by the method according to any one of claims 1 to 8.

10. The strong, tough, high temperature resistant medium entropy ceramic nano aerogel according to claim 9, characterized in that: The density of the tough, high temperature resistant medium entropy ceramic nano aerogel is 0.10-0.30 g / cm 3 , temperature resistance is 1400-1800℃, tensile strength is greater than 5MPa, Young's modulus is greater than 10MPa, room temperature thermal conductivity is less than 0.02W / (m·K), 1500℃ thermal conductivity is less than 0.12W / (m·K), and the crystal structure is one of rock salt structure, fluorite structure, perovskite structure, spinel structure, pyrochlore structure and olivine structure.

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