Lanthanum zirconate doped aerogel composite material and preparation method thereof

Abstract

The invention discloses a lanthanum zirconate doped aerogel composite material and a preparation method thereof. The preparation method comprises the following six steps: preparation of zirconium-lanthanum sol, modification of fibers with lanthanum zirconate aerogel, preparation of a porous preform, sol impregnation and aging, supercritical drying and high-temperature sintering. The lanthanum zirconate doped aerogel composite material prepared by the method has the characteristics of high temperature resistance, low thermal conductivity, high toughness, capability of forming large-size complex components and the like, the maximum size can reach 1500mm in length, 800mm in width and 100mm in thickness, and the lanthanum zirconate doped aerogel composite material can be used as a high-temperature thermal insulation material in the fields of aerospace, nuclear power, industrial high-temperature furnaces and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of thermal insulation materials, and specifically relates to a lanthanum zirconate-doped aerogel composite material and a preparation method thereof. Background Art

[0002] Aerogel is an ultra-low thermal conductivity material with a nanoporous structure. Its room temperature thermal conductivity is as low as 0.012 W / (m·K). It has broad application prospects as a thermal insulation material. Among them, oxide aerogels such as silicon oxide and aluminum oxide aerogels have good thermal stability in high temperature environments, so they can be used as new high-temperature thermal insulation materials. Since pure aerogels are brittle and have low mechanical properties, ceramic particles, whiskers or fibers are generally introduced to prepare composite materials to improve their mechanical properties. The silica aerogel composite product with fiber as the reinforcement phase has a room temperature thermal conductivity of less than 0.021 W / (m·K), a thermal conductivity of 0.042 W / (m·K) at 800℃, and a short-term use temperature of 900℃. The thermal insulation performance is significantly better than that of traditional thermal insulation materials. It has been used as a thermal protection system for high-speed aircraft, a thermal insulation layer for petrochemical pipelines, and a fireproof and thermal insulation pad for new energy vehicles. Compared with silica aerogel composites, alumina aerogel composites show better temperature resistance, with a short-term operating temperature of over 1300°C and a typical thermal conductivity of 0.082 W / (m·K) at 1200°C.

[0003] However, with the rapid development of technology in the fields of aerospace, nuclear power, high-temperature industrial furnaces, etc., the requirements for thermal insulation materials are no longer limited to high temperature resistance and low thermal conductivity. They also require thermal insulation materials to have excellent load-bearing properties and be able to form large-scale complex components. Existing silicon oxide and aluminum oxide aerogel composite materials cannot meet the stringent requirements of these fields at the same time.

[0004] Therefore, the preparation of large-scale complex components that have high temperature resistance, low thermal conductivity, and high strength and toughness is a major challenge in the current field of thermal insulation materials. Summary of the invention

[0005] In view of the problem that there is a lack of thermal insulation materials for preparing large-sized complex components with high temperature resistance, low thermal conductivity and high toughness in the prior art, the present invention provides a lanthanum zirconate doped aerogel composite material and a preparation method thereof, and the preparation of the lanthanum zirconate doped aerogel composite material is achieved by adopting zirconium-lanthanum sol preparation, lanthanum zirconate aerogel modified fiber, porous preform preparation, sol impregnation and aging, supercritical drying, and high-temperature sintering processes. The lanthanum zirconate doped aerogel composite material prepared by the present invention has the characteristics of high temperature resistance, low thermal conductivity, high toughness, and can be formed into large-sized complex components. The maximum size can reach 1500mm in length, 800mm in width, and 100mm in thickness, and can be used as a high-temperature thermal insulation material in the fields of aerospace, nuclear power, and industrial high-temperature furnaces.

[0006] The technical solution of the present invention is as follows: The preparation method of a lanthanum zirconate-doped aerogel composite material described in the present invention comprises six steps: preparation of zirconium-lanthanum sol, modification of lanthanum zirconate aerogel fibers, preparation of a porous preform, sol impregnation and aging, supercritical drying, and high-temperature sintering.

[0007] The purpose of the present invention is achieved through the following technical solutions: A method for preparing a lanthanum zirconate-doped aerogel composite material comprises the following steps: S1. Preparation of zirconium-lanthanum sol: S1-1, adding a zirconium source precursor to a solvent, stirring evenly, heating to 50°C to 85°C for reaction for 0.5h to 10h, and cooling to room temperature to obtain a zirconium source precursor solution; The zirconium source precursor is basic zirconium carbonate or zirconium acetate; When basic zirconium carbonate is used as a zirconium source precursor, the corresponding solvent is an ethanol solution of an organic acid, wherein the mass fraction of the organic acid is 30% to 80%; the organic acid is any one of oxalic acid, citric acid, tartaric acid, acetic acid, and malic acid; the molar ratio of basic zirconium carbonate to the organic acid is 1:(4 to 8); When zirconium acetate is used as a zirconium source precursor, the corresponding solvent is one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, and tert-butanol; the molar ratio of zirconium acetate to the solvent is 1:(3-10); S1-2, adding the lanthanum source precursor to the solvent, rapidly stirring and heating to 40°C to 75°C for 0.5h to 4h, and cooling to room temperature to obtain a lanthanum source precursor solution; The lanthanum source precursor is one of lanthanum chloride trihydrate, lanthanum chloride hexahydrate, and lanthanum nitrate hexahydrate; The solvent is one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol and tert-butanol; The molar ratio of the lanthanum source precursor to the solvent is 1:(3-30); S1-3, under stirring, adding the zirconium source precursor solution obtained in S1-1 to the lanthanum source precursor solution obtained in S1-2, stirring evenly to obtain a precursor mixture; When basic zirconium carbonate is used as the zirconium source precursor, the molar ratio of the zirconium source precursor to the lanthanum source precursor is 1:2; When zirconium acetate is used as the zirconium source precursor, the molar ratio of the zirconium source precursor to the lanthanum source precursor is 1:1; S1-4, slowly adding propylene oxide to the precursor mixture obtained in the above step at -10°C to 20°C for 15 min to 60 min to obtain a zirconium-lanthanum sol; When basic zirconium carbonate is used as a zirconium source precursor, the molar ratio of the zirconium source precursor to propylene oxide is 1:(10-20); When zirconium acetate is used as a zirconium source precursor, the molar ratio of the zirconium source precursor to propylene oxide is 1:(3.5-10); S2, lanthanum zirconate aerogel modified fiber: Under a pressure of -0.1 MPa to 0 MPa, the obtained zirconium-lanthanum sol is slowly impregnated into the ceramic long fiber felt for 0.5 h to 4 h to obtain a sol-fiber mixture, and the sol-fiber mixture is maintained at 50° C. to 90° C. for 8 h to 30 h to form a gel-fiber composite; The gel-fiber composite is placed in an autoclave, and after adding alcohol, it is kept sealed, heated to above the critical point of the alcohol and kept for 1 hour to 10 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, thereby obtaining a zirconium-lanthanum aerogel modified ceramic fiber felt; The ceramic long fiber felt is one of quartz fiber, aluminum silicate fiber, aluminum oxide fiber, mullite fiber and zirconium oxide fiber; the aspect ratio of the fiber is 20000-80000; The alcohol is one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol and tert-butanol; the volume ratio of the alcohol to the gel-fiber complex is 1:(0.4-1.8); S3. Preparation of porous preform: The obtained zirconium-lanthanum aerogel modified ceramic fiber felt is pressed into a designed shape by using a high-temperature alloy mold and fixed, and the temperature is raised to 900°C to 1200°C at a rate of 2°C / min to 10°C / min, maintained for 1h to 6h, and naturally cooled to obtain a porous preform; S4. Sol impregnation and aging: Under a pressure condition of -0.1 MPa to 0 MPa, the sol is impregnated into the obtained porous preform for 1 h to 5 h to obtain a sol-preform mixture, and the sol-preform mixture is maintained at 40° C. to 85° C. for 8 h to 30 h to form a gel-preform composite; The sol is one of silicon oxide, aluminum oxide, and zirconium oxide sols or a mixture of any two of them in any proportion; The solid content of the sol is 6% to 25%, and the solvent used is one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, and tert-butanol; S5, Supercritical Drying: The obtained gel-preform composite is placed in an autoclave, and after adding alcohol, it is kept sealed, heated to above the critical point of alcohol and kept for 4 hours to 12 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, thereby obtaining an aerogel composite material blank; The alcohol is one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol and tert-butanol; the volume ratio of the alcohol to the gel-preform complex is 1:(0.4-5.4); S6, high temperature sintering: The obtained aerogel composite material blank is placed in a high temperature furnace, and the temperature is increased from room temperature to 650°C to 1200°C at a heating rate of 1.0°C / min to 6.0°C / min, and maintained for 1.5h to 10h, and naturally cooled to obtain a lanthanum zirconate doped aerogel composite material. The typical properties of the prepared lanthanum zirconate doped aerogel composite material are: The maximum size reaches 1500mm in length, 800mm in width and 100mm in thickness; Density: 0.40g / cm 3 -0.48g / cm 3 ; After heat treatment at 1300℃ for 2h, the thickness shrinkage is 0.1%-0.8%; Thermal conductivity at room temperature is 0.029W / (m·K)-0.037W / (m·K), thermal conductivity at 1200℃ is 0.042W / (m·K)-0.054W / (m·K); The compressive strength at 3% deformation is 0.51MPa-0.64MPa, and the flexural strength is 2.3MPa-3.4MPa.

[0008] Furthermore, the zirconium source precursor described in S1 is basic zirconium carbonate.

[0009] Furthermore, the ceramic long fiber felt described in S2 is quartz fiber; and the alcohol described is ethanol.

[0010] Furthermore, the sol described in S4 is alumina sol.

[0011] The present invention also relates to a lanthanum zirconate-doped aerogel composite material, which is obtained by using the above-mentioned method for preparing a lanthanum zirconate-doped aerogel composite material. The typical properties of the prepared lanthanum zirconate-doped aerogel composite material are: The maximum size reaches 1500mm in length, 800mm in width and 100mm in thickness; Density: 0.40g / cm 3 -0.48g / cm 3 ; After heat treatment at 1300℃ for 2h, the thickness shrinkage is 0.1%-0.8%; Thermal conductivity at room temperature is 0.029W / (m·K)-0.037W / (m·K), thermal conductivity at 1200℃ is 0.042W / (m·K)-0.054W / (m·K); The compressive strength at 3% deformation is 0.51MPa-0.64MPa, and the flexural strength is 2.3MPa-3.4MPa.

[0012] Compared with the prior art, the present invention has the following beneficial effects: 1. At present, adding sunscreen particles to the sol to introduce sunscreen components into the aerogel insulation material is a common means to improve the thermal insulation performance. However, the sunscreen particles added to the sol are easy to settle, and it is difficult to ensure their mixing uniformity, especially when introducing sunscreens into large-sized complex components. There is currently no effective means. The preparation method of a lanthanum zirconate doped aerogel composite material described in the present invention adopts an in-situ modification method to prepare a uniform and stable zirconium-lanthanum sol with a zirconium source precursor and a lanthanum source precursor as raw materials, and then obtains a fiber uniformly modified with lanthanum zirconate through impregnation, gel aging, supercritical drying process, and high-temperature sintering process. Lanthanum zirconate has extremely low intrinsic thermal conductivity (1.55W / (m·K)) and excellent infrared light-shielding performance, and its uniform introduction can effectively reduce the high-temperature thermal conductivity of the fiber. At the same time, the lanthanum zirconate aerogel has a nanoscale structure, and its solid-state thermal conductivity is relatively low. Therefore, the lanthanum zirconate doped aerogel composite material prepared by the present invention has a very low comprehensive thermal conductivity.

[0013] 2. The oxide aerogel itself has significant brittleness and low mechanical properties. Even if it is reinforced with fibers, its mechanical strength still cannot meet the application scenarios with high requirements. The preparation method of a lanthanum zirconate-doped aerogel composite material described in the present invention is to mold and high-temperature sinter the zirconium-lanthanum aerogel modified fiber to convert the zirconium-lanthanum aerogel into lanthanum zirconate aerogel to obtain a lanthanum zirconate-fiber porous preform. The molding method is used to increase the contact area and bonding force between the zirconium-lanthanum aerogel and the fiber. It is in-situ converted into lanthanum zirconate aerogel on the fiber surface and sintered to strengthen. The lanthanum zirconate aerogel and the fiber form a good surface bonding force, thereby obtaining a high-strength porous preform and a lanthanum zirconate-doped aerogel composite material.

[0014] 3. The preparation method of a lanthanum zirconate-doped aerogel composite material described in the present invention uses a high aspect ratio ceramic fiber felt as a reinforcing phase, which has good flexibility and can be prepared into a large-sized complex-shaped preform by molding, and then strengthened by sintering the lanthanum zirconate aerogel and compounded with an oxide aerogel, and finally a high-strength and tough lanthanum zirconate-doped aerogel composite material and its components can be obtained. When high aspect ratio fibers are used to prepare aerogel composite materials, the entanglement and overlap forces between the fibers are strong. When the composite material is subjected to tensile or bending loads, the extraction of the high aspect ratio fibers requires more energy, so the composite material has better toughness. The ceramic fiber felt has a longitudinal needle-punched structure, and its interlayer bonding force and integrity are strong. Therefore, the lanthanum zirconate-doped aerogel composite material of the present invention can be formed into large-sized complex-shaped components, with a maximum size of 1500 mm in length, 800 mm in width, and 100 mm in thickness. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] The accompanying drawings are used to provide further understanding of the present invention and constitute a part of the specification. They are used to explain the present invention together with the embodiments of the present invention and do not constitute a limitation of the present invention.

[0016] Figure 1 This is a physical picture of the lanthanum zirconate aerogel prepared in Example 1 of the present invention after drying and before heat treatment; Figure 2 This is a physical picture of the lanthanum zirconate aerogel prepared in Example 1 of the present invention after heat treatment at 1200°C; Figure 3 This is a scanning electron microscope image of the lanthanum zirconate aerogel prepared in Example 1 of the present invention; Figure 4 This is the energy spectrum of the lanthanum zirconate aerogel prepared in Example 1 of the present invention; Figure 5 This is a pore size distribution curve of the lanthanum zirconate aerogel prepared in Example 1 of the present invention; Figure 6 This is a physical picture of the lanthanum zirconate-doped aerogel composite material prepared in Example 1 of the present invention; Figure 7 This is a physical picture of the lanthanum zirconate-doped aerogel composite material prepared in Example 1 of the present invention before heat treatment; Figure 8 This is a physical picture of the lanthanum zirconate-doped aerogel composite material prepared in Example 1 of the present invention after heat treatment at 1300°C. DETAILED DESCRIPTION

[0017] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0018] Embodiment 1: A method for preparing a lanthanum zirconate-doped aerogel composite material comprises the following steps: S1. Preparation of zirconium-lanthanum sol: S1-1, adding basic zirconium carbonate to an ethanol solution of oxalic acid (mass fraction of 55%) and stirring evenly, heating to 65°C for reaction for 3h, and cooling to room temperature to obtain a zirconium source precursor solution; The molar ratio of basic zirconium carbonate to oxalic acid is 1:6; S1-2, adding lanthanum chloride trihydrate to ethanol, rapidly stirring and heating to 60° C. for 2 h, and cooling to room temperature to obtain a lanthanum source precursor solution; The molar ratio of lanthanum chloride trihydrate to ethanol is 1:20; S1-3, under stirring, adding the zirconium source precursor solution to the lanthanum source precursor solution and stirring evenly to obtain a precursor mixed solution; the molar ratio of zirconium basic carbonate to lanthanum chloride trihydrate is 1:2; S1-4, slowly adding propylene oxide to the precursor mixture at 10°C for 35 minutes to obtain a zirconium-lanthanum sol; the molar ratio of basic zirconium carbonate to propylene oxide is 1:16; S2, lanthanum zirconate aerogel modified fiber: Under a pressure of -0.05 MPa, the zirconium-lanthanum sol is slowly impregnated into the mullite fiber felt and maintained for 2 hours to obtain a sol-fiber mixture; the sol-fiber mixture is maintained at 75° C. for 24 hours to form a gel-fiber composite; The gel-fiber composite is placed in an autoclave, a certain amount of ethanol is added and kept sealed, and the autoclave is heated to above the critical point of ethanol and kept for 6 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, thereby obtaining zirconium-lanthanum aerogel modified mullite fiber felt; The aspect ratio of mullite fiber is 55000; The volume ratio of ethanol to gel-fiber complex was 1:0.9; S3. Preparation of porous preform: A high-temperature alloy mold is used to press the zirconium-lanthanum aerogel-modified mullite fiber felt into a designed shape and fix it, and the temperature is raised to 1100°C at a rate of 5°C / min and maintained for 4 hours, and then naturally cooled to obtain a porous preform; S4. Sol impregnation and aging: Under a pressure condition of -0.05 MPa, the alumina sol is impregnated into the porous preform and maintained for 2 hours to obtain a sol-preform mixture; the sol-preform mixture is maintained at 65° C. for 24 hours to form a gel-preform composite; The solid content of the alumina sol is 12%, and the solvent used is ethanol; S5, Supercritical Drying: The gel-preform composite is placed in an autoclave, a certain amount of ethanol is added and kept sealed, and the autoclave is heated to above the critical point of ethanol and kept for 8 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, to obtain an aerogel composite material blank; the volume ratio of ethanol to the gel-preform composite is 1:2.4; S6, high temperature sintering: The aerogel composite material blank was placed in a high-temperature furnace, heated from room temperature to 1100°C at a heating rate of 5°C / min, maintained for 4 hours, and naturally cooled to obtain a lanthanum zirconate-doped alumina aerogel composite material.

[0019] The prepared lanthanum zirconate-doped alumina aerogel composite material has a maximum size of 1500 mm in length, 800 mm in width, and 100 mm in thickness; its density is 0.45 g / cm 3 ; After heat treatment at 1300℃ for 2h, the thickness shrinkage is 0.1%; the thermal conductivity at room temperature and 1200℃ are 0.035W / (m·K) and 0.049W / (m·K) respectively; the compressive strength at 3% deformation is 0.59MPa, and the bending strength is 2.8MPa.

[0020] Figure 1 This is a physical picture of the lanthanum zirconate aerogel prepared in Example 1 after drying and before heat treatment. Figure 2 This is a physical picture of the lanthanum zirconate aerogel prepared in Example 1 after heat treatment at 1200° C. From the figure, it can be seen that the size of the lanthanum zirconate aerogel does not change significantly after the heat treatment, showing good thermal stability.

[0021] Figure 3 The scanning electron microscope image of the lanthanum zirconate aerogel prepared in Example 1, Figure 4 The energy spectrum of the lanthanum zirconate aerogel prepared in Example 1, Figure 5 This is the pore size distribution curve of the lanthanum zirconate aerogel prepared in Example 1. From the figure, it can be seen that the lanthanum zirconate aerogel exhibits a typical nanoparticle skeleton and nanopore structure, and the zirconium, lanthanum and oxygen elements are evenly distributed.

[0022] Figure 6 This is a physical picture of the lanthanum zirconate-doped aerogel composite material prepared in Example 1. It can be seen from the figure that it exhibits good blockiness and dimensional stability.

[0023] Figure 7 This is a physical picture of the lanthanum zirconate-doped aerogel composite material prepared in Example 1 before heat treatment. Figure 8 This is a physical picture of the lanthanum zirconate-doped aerogel composite material prepared in Example 1 after heat treatment at 1300° C. From the figure, it can be seen that the composite material does not undergo obvious changes in appearance and size after the heat treatment and has good temperature resistance.

[0024] Embodiment 2: A method for preparing a lanthanum zirconate-doped aerogel composite material comprises the following steps: S1. Preparation of zirconium-lanthanum sol: S1-1, adding zirconium acetate to isopropanol and stirring evenly, heating to 50°C for reaction for 8h, and cooling to room temperature to obtain a zirconium source precursor solution; The molar ratio of zirconium acetate to isopropanol is 1:5.5; S1-2, adding lanthanum nitrate hexahydrate to isopropanol, stirring rapidly and heating to 40° C. for 4 hours, and cooling to room temperature to obtain a lanthanum source precursor solution; The molar ratio of lanthanum nitrate hexahydrate to isopropanol is 1:30; S1-3, under stirring, adding the zirconium source precursor solution to the lanthanum source precursor solution and stirring evenly to obtain a precursor mixed solution; the molar ratio of zirconium acetate to lanthanum nitrate hexahydrate is 1:1; S1-4, slowly adding propylene oxide to the precursor mixture at -10°C for 15 minutes to obtain a zirconium-lanthanum sol; the molar ratio of zirconium acetate to propylene oxide is 1:6; S2, lanthanum zirconate aerogel modified fiber: Under a pressure of 0 MPa, the zirconium-lanthanum sol is slowly impregnated into the mullite fiber felt and maintained for 4 hours to obtain a sol-fiber mixture; the sol-fiber mixture is maintained at 90° C. for 8 hours to form a gel-fiber composite; The gel-fiber composite is placed in an autoclave, a certain amount of isopropanol is added and kept sealed, heated to above the critical point of isopropanol and kept for 10 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, thereby obtaining zirconium-lanthanum aerogel modified mullite fiber felt; The aspect ratio of mullite fiber is 80,000; The volume ratio of isopropyl alcohol to gel-fiber complex was 1:1.8; S3. Preparation of porous preform: The zirconium-lanthanum aerogel modified mullite fiber felt was pressed into a designed shape and fixed by using a high-temperature alloy mold, and the temperature was raised to 1200°C at a rate of 10°C / min and maintained for 1h, and then naturally cooled to obtain a porous preform; S4. Sol impregnation and aging: Under a pressure of 0 MPa, the alumina sol is impregnated into the porous preform and maintained for 5 hours to obtain a sol-preform mixture; the sol-preform mixture is maintained at 85° C. for 8 hours to form a gel-preform composite; The solid content of the alumina sol is 6%, and the solvent used is isopropanol; S5, Supercritical Drying: The gel-preform composite is placed in an autoclave, a certain amount of isopropanol is added and kept sealed, heated to above the critical point of isopropanol for 12 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, to obtain an aerogel composite material blank; the volume ratio of isopropanol to the gel-preform composite is 1:3; S6, high temperature sintering: The aerogel composite material blank was placed in a high temperature furnace, heated from room temperature to 1200°C at a heating rate of 6°C / min, maintained for 1.5 hours, and naturally cooled to obtain a lanthanum zirconate-doped alumina aerogel composite material; The prepared lanthanum zirconate-doped alumina aerogel composite material has a maximum size of 1500 mm in length, 800 mm in width, and 100 mm in thickness; its density is 0.40 g / cm 3 ; After heat treatment at 1300℃ for 2h, the thickness shrinkage is 0.5%; the thermal conductivity at room temperature and 1200℃ are 0.032W / (m·K) and 0.052W / (m·K) respectively; the compressive strength at 3% deformation is 0.51MPa, and the bending strength is 2.6MPa.

[0025] Embodiment 3: A method for preparing a lanthanum zirconate-doped aerogel composite material comprises the following steps: S1. Preparation of zirconium-lanthanum sol: S1-1, adding basic zirconium carbonate to an ethanol solution of acetic acid (mass fraction of 30%) and stirring evenly, heating to 50° C. to react for 10 h, and cooling to room temperature to obtain a zirconium source precursor solution; The molar ratio of basic zirconium carbonate to acetic acid is 1:4; S1-2, adding lanthanum chloride hexahydrate to sec-butyl alcohol, stirring rapidly and heating to 75° C. for 0.5 h, and cooling to room temperature to obtain a lanthanum source precursor solution; The molar ratio of lanthanum chloride hexahydrate to sec-butyl alcohol is 1:3; S1-3, under stirring, adding the zirconium source precursor solution to the lanthanum source precursor solution and stirring evenly to obtain a precursor mixed solution; the molar ratio of basic zirconium carbonate to lanthanum chloride hexahydrate is 1:2; S1-4, slowly adding propylene oxide to the precursor mixture at 20°C for 60 minutes to obtain a zirconium-lanthanum sol; the molar ratio of basic zirconium carbonate to propylene oxide is 1:20; S2, lanthanum zirconate aerogel modified fiber: Under a pressure of -0.1 MPa, the zirconium-lanthanum sol was slowly impregnated into the quartz fiber felt and kept for 0.5 h to obtain a sol-fiber mixture; the sol-fiber mixture was kept at 90° C. for 8 h to form a gel-fiber composite; The gel-fiber composite is placed in an autoclave, a certain amount of sec-butyl alcohol is added and kept sealed, heated to above the critical point of sec-butyl alcohol for 10 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, thereby obtaining zirconium-lanthanum aerogel modified quartz fiber felt; The aspect ratio of quartz fiber is 70,000; The volume ratio of sec-butyl alcohol to gel-fiber complex was 1:0.4; S3. Preparation of porous preform: Using a high-temperature alloy mold, the zirconium-lanthanum aerogel-modified quartz fiber felt was pressed into a designed shape and fixed, and the temperature was raised to 900°C at a rate of 2°C / min and maintained for 6 hours, and then naturally cooled to obtain a porous preform; S4. Sol impregnation and aging: Under a pressure condition of -0.1 MPa, the silica sol is impregnated into the porous preform and maintained for 1 hour to obtain a sol-preform mixture; the sol-preform mixture is maintained at 40° C. for 30 hours to form a gel-preform composite; The solid content of the silica sol is 25%, and the solvent used is sec-butyl alcohol; S5, supercritical drying; The gel-preform composite is placed in an autoclave, a certain amount of sec-butanol is added and kept sealed, heated to above the critical point of sec-butanol for 4 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, to obtain an aerogel composite material blank; the volume ratio of sec-butanol to the gel-preform composite is 1:5.4; S6, high temperature sintering: The aerogel composite material blank was placed in a high-temperature furnace, heated from room temperature to 650°C at a heating rate of 1.0°C / min, maintained for 10 hours, and naturally cooled to obtain a lanthanum zirconate-doped silica aerogel composite material.

[0026] The prepared lanthanum zirconate-doped silica aerogel composite material has a maximum size of 1500 mm in length, 800 mm in width, and 100 mm in thickness; its density is 0.48 g / cm 3 ; After heat treatment at 800℃ for 2h, the thickness shrinkage rate is 0.6%; the thermal conductivity at room temperature and 800℃ are 0.029W / (m·K) and 0.044W / (m·K) respectively; the compressive strength at 3% deformation is 0.64MPa, and the bending strength is 3.4MPa.

[0027] Embodiment 4: A method for preparing a lanthanum zirconate-doped aerogel composite material comprises the following steps: S1. Preparation of zirconium-lanthanum sol: S1-1, adding basic zirconium carbonate to an ethanol solution of citric acid (mass fraction of 50%) and stirring evenly, heating to 65°C for reaction for 3.5h, and cooling to room temperature to obtain a zirconium source precursor solution; The molar ratio of basic zirconium carbonate to citric acid is 1:8; S1-2, adding lanthanum chloride trihydrate to tert-butyl alcohol, stirring rapidly and heating to 45° C. for 2 h, and cooling to room temperature to obtain a lanthanum source precursor solution; The molar ratio of lanthanum chloride trihydrate to tert-butyl alcohol is 1:30; S1-3, under stirring, adding the zirconium source precursor solution to the lanthanum source precursor solution and stirring evenly to obtain a precursor mixed solution; the molar ratio of zirconium basic carbonate to lanthanum chloride trihydrate is 1:2; S1-4, slowly adding propylene oxide to the precursor mixture at 10°C for 35 minutes to obtain a zirconium-lanthanum sol; the molar ratio of basic zirconium carbonate to propylene oxide is 1:16; S2, lanthanum zirconate aerogel modified fiber: Under a pressure of -0.05 MPa, the zirconium-lanthanum sol is slowly impregnated into the zirconium oxide fiber felt for 2 hours to obtain a sol-fiber mixture; the sol-fiber mixture is maintained at 75° C. for 24 hours to form a gel-fiber composite; The gel-fiber composite is placed in an autoclave, a certain amount of tert-butanol is added and kept sealed, heated to above the critical point of tert-butanol for 6 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, thereby obtaining zirconium-lanthanum aerogel modified zirconia fiber felt; The aspect ratio of zirconia fiber is 40,000; The volume ratio of tert-butyl alcohol to gel-fiber complex was 1:0.9; S3. Preparation of porous preform: Using a high-temperature alloy mold, the zirconium-lanthanum aerogel modified zirconia fiber felt was pressed into a designed shape and fixed, and the temperature was raised to 1050°C at a rate of 5°C / min and maintained for 4 hours, and then naturally cooled to obtain a porous preform; S4. Sol impregnation and aging: Under a pressure condition of -0.06 MPa, the zirconium oxide sol is impregnated into the porous preform and maintained for 2 hours to obtain a sol-preform mixture; the sol-preform mixture is maintained at 85° C. for 8 hours to form a gel-preform composite; The solid content of the zirconium oxide sol is 9.5%, and the solvent used is tert-butyl alcohol; S5, Supercritical Drying: The gel-preform composite is placed in an autoclave, a certain amount of tert-butanol is added and kept sealed, and the autoclave is heated to above the critical point of tert-butanol and kept for 8 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, to obtain an aerogel composite material blank; the volume ratio of tert-butanol to the gel-preform composite is 1:0.4; S6, high temperature sintering: The aerogel composite material blank was placed in a high-temperature furnace, heated from room temperature to 1000°C at a heating rate of 5°C / min, maintained for 4 hours, and naturally cooled to obtain a lanthanum zirconate-doped zirconia aerogel composite material.

[0028] The prepared lanthanum zirconate-doped zirconia aerogel composite material has a maximum size of 1500 mm in length, 800 mm in width, and 100 mm in thickness; its density is 0.42 g / cm 3 ; After heat treatment at 1000℃ for 2h, the thickness shrinkage is 0.3%; the thermal conductivity at room temperature and 1200℃ are 0.031W / (m·K) and 0.042W / (m·K) respectively; the compressive strength at 3% deformation is 0.52MPa, and the bending strength is 2.3MPa.

[0029] Embodiment 5: A method for preparing a lanthanum zirconate-doped aerogel composite material comprises the following steps: S1. Preparation of zirconium-lanthanum sol: S1-1, adding basic zirconium carbonate to an ethanol solution of tartaric acid (mass fraction of 55%) and stirring evenly, heating to 65°C for reaction for 3h, and cooling to room temperature to obtain a zirconium source precursor solution; The molar ratio of basic zirconium carbonate to tartaric acid is 1:6.5; S1-2, adding lanthanum chloride trihydrate to ethanol, rapidly stirring and heating to 60° C. for 2 h, and cooling to room temperature to obtain a lanthanum source precursor solution; The molar ratio of lanthanum chloride trihydrate to ethanol is 1:20; S1-3, under stirring, adding the zirconium source precursor solution to the lanthanum source precursor solution and stirring evenly to obtain a precursor mixed solution; the molar ratio of zirconium basic carbonate to lanthanum chloride trihydrate is 1:2; S1-4, slowly adding propylene oxide to the precursor mixture at 10°C for 35 minutes to obtain a zirconium-lanthanum sol; the molar ratio of basic zirconium carbonate to propylene oxide is 1:16; S2, lanthanum zirconate aerogel modified fiber: Under a pressure of -0.05 MPa, the zirconium-lanthanum sol was slowly impregnated into the alumina fiber felt and maintained for 2 hours to obtain a sol-fiber mixture; the sol-fiber mixture was maintained at 75° C. for 24 hours to form a gel-fiber composite; The gel-fiber composite is placed in an autoclave, a certain amount of ethanol is added and kept sealed, and the autoclave is heated to above the critical point of ethanol and kept for 6 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, thereby obtaining a zirconium-lanthanum aerogel modified alumina fiber felt; The aspect ratio of alumina fiber is 40,000; The volume ratio of ethanol to gel-fiber complex was 1:0.9; S3. Preparation of porous preform: A high-temperature alloy mold was used to press the zirconium-lanthanum aerogel-modified alumina fiber felt into a designed shape and fixed it, and the temperature was raised to 1100°C at a rate of 5°C / min and maintained for 4 hours, and then naturally cooled to obtain a porous preform; S4. Sol impregnation and aging: Under a pressure condition of -0.05 MPa, the alumina sol is impregnated into the porous preform and maintained for 2 hours to obtain a sol-preform mixture; the sol-preform mixture is maintained at 65° C. for 24 hours to form a gel-preform composite; The solid content of the alumina sol is 13%, and the solvent used is ethanol; S5, Supercritical Drying: The gel-preform composite is placed in an autoclave, a certain amount of ethanol is added and kept sealed, and the autoclave is heated to above the critical point of ethanol and kept for 8 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, to obtain an aerogel composite material blank; the volume ratio of ethanol to the gel-preform composite is 1:2.4; S6, high temperature sintering: The aerogel composite material blank was placed in a high-temperature furnace, heated from room temperature to 1100°C at a heating rate of 5°C / min, maintained for 4 hours, and naturally cooled to obtain a lanthanum zirconate-doped alumina aerogel composite material.

[0030] The prepared lanthanum zirconate-doped alumina aerogel composite material has a maximum size of 1500 mm in length, 800 mm in width, and 100 mm in thickness; its density is 0.46 g / cm 3 ; After heat treatment at 1300℃ for 2h, the thickness shrinkage is 0.2%; the thermal conductivity at room temperature and 1200℃ are 0.037W / (m·K) and 0.051W / (m·K) respectively; the compressive strength at 3% deformation is 0.62MPa, and the bending strength is 2.5MPa.

[0031] Embodiment 6: A method for preparing a lanthanum zirconate-doped aerogel composite material comprises the following steps: S1. Preparation of zirconium-lanthanum sol: S1-1, adding basic zirconium carbonate to an ethanol solution of malic acid (mass fraction of 30%) and stirring evenly, heating to 50°C for reaction for 10 hours, and cooling to room temperature to obtain a zirconium source precursor solution; The molar ratio of basic zirconium carbonate to malic acid is 1:5; S1-2, adding lanthanum chloride hexahydrate to n-propanol, stirring rapidly and heating to 75° C. for 0.5 h, and cooling to room temperature to obtain a lanthanum source precursor solution; The molar ratio of lanthanum chloride hexahydrate to n-propanol is 1:10; S1-3, under stirring, adding the zirconium source precursor solution to the lanthanum source precursor solution and stirring evenly to obtain a precursor mixed solution; the molar ratio of basic zirconium carbonate to lanthanum chloride hexahydrate is 1:2; S1-4, slowly adding propylene oxide to the precursor mixture at 20°C for 45 minutes to obtain a zirconium-lanthanum sol; the molar ratio of basic zirconium carbonate to propylene oxide is 1:20; S2, lanthanum zirconate aerogel modified fiber: Under a pressure of -0.1 MPa, the zirconium-lanthanum sol was slowly impregnated into the aluminum silicate fiber felt and maintained for 0.5 h to obtain a sol-fiber mixture; the sol-fiber mixture was maintained at 90° C. for 8 h to form a gel-fiber composite; The gel-fiber composite is placed in an autoclave, a certain amount of n-propanol is added and the autoclave is kept airtight, the autoclave is heated to above the critical point of n-propanol and kept for 10 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, thereby obtaining zirconium-lanthanum aerogel modified aluminum silicate fiber felt; The aspect ratio of aluminum silicate fiber is 45000; The volume ratio of n-propanol to gel-fiber complex was 1:1; S3. Preparation of porous preform: A high-temperature alloy mold was used to press the zirconium-lanthanum aerogel-modified aluminum silicate fiber felt into a designed shape and fixed it, and the temperature was raised to 950°C at a rate of 4°C / min and maintained for 5 hours, and then naturally cooled to obtain a porous preform. S4. Sol impregnation and aging: Under a pressure condition of -0.1 MPa, the silica sol is impregnated into the porous preform and maintained for 1.5 hours to obtain a sol-preform mixture; the sol-preform mixture is maintained at 40° C. for 30 hours to form a gel-preform composite; The solid content of the silica sol is 15%, and the solvent used is ethanol; S5, Supercritical Drying: The gel-preform composite is placed in an autoclave, a certain amount of n-propanol is added and kept sealed, and the autoclave is heated to above the critical point of n-propanol and kept for 9 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, to obtain an aerogel composite material blank; the volume ratio of n-propanol to the gel-preform composite is 1:4; S6, high temperature sintering: The aerogel composite material blank was placed in a high-temperature furnace, heated from room temperature to 700°C at a heating rate of 2.5°C / min, maintained for 6 hours, and naturally cooled to obtain a lanthanum zirconate-doped silica aerogel composite material.

[0032] The prepared lanthanum zirconate-doped silica aerogel composite material has a maximum size of 1500 mm in length, 800 mm in width, and 100 mm in thickness; its density is 0.46 g / cm 3 ; After heat treatment at 800℃ for 2h, the thickness shrinkage rate is 0.8%; the thermal conductivity at room temperature and 800℃ are 0.034W / (m·K) and 0.054W / (m·K) respectively; the compressive strength at 3% deformation is 0.55MPa, and the bending strength is 2.4MPa.

[0033] Comparative Example 1: The difference between Comparative Example 1 and Example 1 is that in S1, the molar ratio of zirconium basic carbonate to lanthanum chloride trihydrate is 1:1.2, and the rest is the same as Example 1.

[0034] The prepared lanthanum zirconate-doped alumina aerogel composite material has a thermal conductivity of 0.058 W / (m·K) at 1200℃. When the molar ratio of zirconium basic carbonate to lanthanum chloride trihydrate is 1:1.2, the molar ratio of zirconium to lanthanum is 1:0.6, and the zirconium basic carbonate cannot be completely converted into lanthanum zirconate, the shading effect decreases, and the high-temperature thermal conductivity increases significantly.

[0035] Comparative Example 2: The difference between Comparative Example 2 and Example 1 is that in S1, the molar ratio of basic zirconium carbonate to propylene oxide is 1:6, and the rest is the same as Example 1.

[0036] The prepared lanthanum zirconate-doped alumina aerogel composite material has a compressive strength of 0.45 MPa at 3% deformation and a flexural strength of 1.9 MPa, indicating that when the proportion of propylene oxide is low, the zirconium-lanthanum sol reaction is not sufficient and the gel network structure strength is low, resulting in low mechanical properties of the composite material.

[0037] Comparative Example 3: The difference between Comparative Example 3 and Example 1 is that in S2, the gel-fiber composite is dried by normal pressure drying, and the rest is the same as Example 1.

[0038] The thermal conductivity of the prepared lanthanum zirconate doped alumina aerogel composite material was 0.041 and 0.060 W / (m·K) at room temperature and 1200°C, respectively. During the atmospheric pressure drying process, due to the excessive surface tension of the solvent, it was impossible to obtain a lanthanum zirconate aerogel with a nanoporous structure and high dispersion, and thus the thermal conductivity of the prepared lanthanum zirconate doped alumina aerogel composite material was relatively high.

[0039] Comparative Example 4: The difference between Comparative Example 4 and Example 1 is that in S2, the aspect ratio of the mullite fiber is 10000, and the rest is the same as Example 1.

[0040] The prepared lanthanum zirconate doped alumina aerogel composite material has a flexural strength of 1.7 MPa. When the fiber aspect ratio is small, the pull-out effect between the aerogel and the fiber is weakened, so that the flexural strength decreases significantly.

[0041] Comparative Example 5: The difference between Comparative Example 5 and Example 1 is that in S3, the preparation temperature of the porous preform is 650° C., and the rest is the same as Example 1.

[0042] The prepared lanthanum zirconate-doped alumina aerogel composite material has a thermal conductivity of 0.065 W / (m·K) at 1200℃. The temperature for the zirconium and lanthanum components to be converted into lanthanum zirconate needs to reach above 800℃. When the preparation temperature is too low, the zirconium and lanthanum components are not fully converted into lanthanum zirconate, which significantly reduces the shading effect of lanthanum zirconate and makes the solid-state heat transfer more significant, resulting in a high high-temperature thermal conductivity.

[0043] Comparative Example 6: The difference between Comparative Example 6 and Example 1 is that in S6, the sintering temperature is 600°C, and the rest is the same as Example 1.

[0044] The prepared lanthanum zirconate-doped alumina aerogel composite material has a compressive strength of 0.49 MPa at 3% deformation and a flexural strength of 2.1 MPa, indicating that when the sintering temperature is low, the interface bonding strength between the three phases of alumina aerogel, lanthanum zirconate and fiber decreases, resulting in a decrease in the comprehensive mechanical properties of the composite material.

[0045] In addition, it should be understood that although the present specification is described according to implementation modes, not every implementation mode contains only one independent technical solution. This description of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation modes that can be understood by those skilled in the art.

Claims

1. A method for preparing a lanthanum zirconate-doped aerogel composite material, characterized in that: The following steps are involved: S1. Preparation of zirconium-lanthanum sol: S1-1, adding a zirconium source precursor to a solvent, stirring evenly, heating to 50°C to 85°C for reaction for 0.5h to 10h, and cooling to room temperature to obtain a zirconium source precursor solution; The zirconium source precursor is basic zirconium carbonate or zirconium acetate; When basic zirconium carbonate is used as a zirconium source precursor, the corresponding solvent is an ethanol solution of an organic acid, wherein the mass fraction of the organic acid is 30% to 80%; the organic acid is any one of oxalic acid, citric acid, tartaric acid, acetic acid, and malic acid; the molar ratio of basic zirconium carbonate to the organic acid is 1:(4 to 8); When zirconium acetate is used as a zirconium source precursor, the corresponding solvent is one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, and tert-butanol; the molar ratio of zirconium acetate to the solvent is 1:(3-10); S1-2, adding the lanthanum source precursor to the solvent, rapidly stirring and heating to 40°C to 75°C for 0.5h to 4h, and cooling to room temperature to obtain a lanthanum source precursor solution; The lanthanum source precursor is one of lanthanum chloride trihydrate, lanthanum chloride hexahydrate, and lanthanum nitrate hexahydrate; The solvent is one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol and tert-butanol; The molar ratio of the lanthanum source precursor to the solvent is 1:(3-30); S1-3, under stirring, adding the zirconium source precursor solution obtained in S1-1 to the lanthanum source precursor solution obtained in S1-2, stirring evenly to obtain a precursor mixture; When basic zirconium carbonate is used as the zirconium source precursor, the molar ratio of the zirconium source precursor to the lanthanum source precursor is 1:2; When zirconium acetate is used as the zirconium source precursor, the molar ratio of the zirconium source precursor to the lanthanum source precursor is 1:1; S1-4, slowly adding propylene oxide to the precursor mixture obtained in the above step at -10°C to 20°C for 15 min to 60 min to obtain a zirconium-lanthanum sol; When basic zirconium carbonate is used as a zirconium source precursor, the molar ratio of the zirconium source precursor to propylene oxide is 1:(10-20); When zirconium acetate is used as a zirconium source precursor, the molar ratio of the zirconium source precursor to propylene oxide is 1:(3.5-10); S2, lanthanum zirconate aerogel modified fiber: Under a pressure of -0.1 MPa to 0 MPa, the obtained zirconium-lanthanum sol is slowly impregnated into the ceramic long fiber felt for 0.5 h to 4 h to obtain a sol-fiber mixture, and the sol-fiber mixture is maintained at 50° C. to 90° C. for 8 h to 30 h to form a gel-fiber composite; The gel-fiber composite is placed in an autoclave, and after adding alcohol, it is kept sealed, heated to above the critical point of the alcohol and kept for 1 hour to 10 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, thereby obtaining a zirconium-lanthanum aerogel modified ceramic fiber felt; The ceramic long fiber felt is one of quartz fiber, aluminum silicate fiber, aluminum oxide fiber, mullite fiber and zirconium oxide fiber; the aspect ratio of the fiber is 20000-80000; The alcohol is one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol and tert-butanol; the volume ratio of the alcohol to the gel-fiber complex is 1:(0.4-1.8); S3. Preparation of porous preform: The obtained zirconium-lanthanum aerogel modified ceramic fiber felt is pressed into a designed shape by using a high-temperature alloy mold and fixed, and the temperature is raised to 900°C to 1200°C at a rate of 2°C / min to 10°C / min, maintained for 1h to 6h, and naturally cooled to obtain a porous preform; S4. Sol impregnation and aging: Under a pressure condition of -0.1 MPa to 0 MPa, the sol is impregnated into the obtained porous preform for 1 h to 5 h to obtain a sol-preform mixture, and the sol-preform mixture is maintained at 40° C. to 85° C. for 8 h to 30 h to form a gel-preform composite; The sol is one of silicon oxide, aluminum oxide, and zirconium oxide sols or a mixture of any two of them in any proportion; The solid content of the sol is 6% to 25%, and the solvent used is one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol, and tert-butanol; S5, Supercritical Drying: The obtained gel-preform composite is placed in an autoclave, and after adding alcohol, it is kept sealed, heated to above the critical point of alcohol and kept for 4 hours to 12 hours, and the gas in the autoclave is slowly discharged until the pressure is 0, thereby obtaining an aerogel composite material blank; The alcohol is one of ethanol, isopropanol, n-propanol, n-butanol, sec-butanol and tert-butanol; the volume ratio of the alcohol to the gel-preform complex is 1:(0.4-5.4); S6, high temperature sintering: The obtained aerogel composite material blank is placed in a high temperature furnace, and the temperature is increased from room temperature to 650°C to 1200°C at a heating rate of 1.0°C / min to 6.0°C / min, and maintained for 1.5h to 10h, and naturally cooled to obtain a lanthanum zirconate doped aerogel composite material. The typical properties of the prepared lanthanum zirconate doped aerogel composite material are: The maximum size reaches 1500mm in length, 800mm in width and 100mm in thickness; Density: 0.40g / cm 3 -0.48g / cm 3 ; After heat treatment at 1300℃ for 2h, the thickness shrinkage is 0.1%-0.8%; Thermal conductivity at room temperature is 0.029W / (m·K)-0.037W / (m·K), thermal conductivity at 1200℃ is 0.042W / (m·K)-0.054W / (m·K); The compressive strength at 3% deformation is 0.51MPa-0.64MPa, and the flexural strength is 2.3MPa-3.4MPa.

2. The method for preparing a lanthanum zirconate-doped aerogel composite material according to claim 1, characterized in that: The zirconium source precursor described in S1 is basic zirconium carbonate.

3. The method for preparing a lanthanum zirconate-doped aerogel composite material according to claim 1, characterized in that: The ceramic long fiber felt described in S2 is quartz fiber; the alcohol described is ethanol.

4. The method for preparing a lanthanum zirconate-doped aerogel composite material according to claim 1, characterized in that: The sol described in S4 is an alumina sol.

5. A lanthanum zirconate-doped aerogel composite material, characterized in that: According to the preparation method of a lanthanum zirconate-doped aerogel composite material according to any one of claims 1 to 4, the typical properties of the prepared lanthanum zirconate-doped aerogel composite material are: The maximum size reaches 1500mm in length, 800mm in width and 100mm in thickness; Density: 0.40g / cm 3 -0.48g / cm 3 ; After heat treatment at 1300℃ for 2h, the thickness shrinkage is 0.1%-0.8%; Thermal conductivity at room temperature is 0.029W / (m·K)-0.037W / (m·K), thermal conductivity at 1200℃ is 0.042W / (m·K)-0.054W / (m·K); The compressive strength at 3% deformation is 0.51MPa-0.64MPa, and the flexural strength is 2.3MPa-3.4MPa.

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