Preparation method of flexible hierarchical pore inorganic nanofiber aerogel for heat management

Abstract

The invention relates to a preparation method of flexible hierarchical pore inorganic nanofiber aerogel for heat management. The method comprises the following steps: preparing a polyacetylacetone zirconium-aluminum precursor, preparing a spinning solution, carrying out airflow spinning and carrying out heat treatment, namely preparing the polyacetylacetone zirconium-aluminum precursor by taking zirconium oxychloride, aluminum chloride, acetylacetone and triethylamine as raw materials, dissolving the precursor, a spinning aid, a softening agent and a pore forming agent in methanol according to a ratio, and stirring to obtain the spinning solution; the spinning solution is subjected to airflow spinning to obtain flexible ceramic nanofibers; and placing the flexible fiber in a muffle furnace, carrying out medium-high temperature heat treatment, and sintering to obtain the flexible hierarchical pore inorganic nanofiber aerogel for heat management, which is used as an ultra-high temperature resistant heat insulation material.

Description

Technical Field

[0001] The present invention relates to the field of nanofiber materials, and in particular to a method for preparing a flexible multi-level porous inorganic nanofiber aerogel for heat management. Background Art

[0002] In recent years, aerogel has attracted widespread attention as a new type of thermal insulation material. Aerogel is considered to be an ideal lightweight and efficient thermal insulation material due to its special microporous structure, extremely low density and ultra-high thermal insulation performance. It has broad application prospects in the field of national defense, aerospace and aviation, which is developing towards lightweight. At present, aerogels that have attracted much attention in this field include SiO 2 、Al 2 O 3 、ZrO 2 , single or multi-composite ceramic aerogels such as SiC, organic aerogels such as polyimide, and carbon aerogels, etc.

[0003] Ceramic aerogel has become a new hot spot in thermal protection materials in recent years due to its unique advantages such as strong oxidation resistance and excellent high temperature resistance. 2 Aerogel is the most mature and widely used type of high-performance aerogel thermal insulation material. 2 The short-term use temperature of aerogel does not exceed 700-800℃. This is because at high temperature, SiO 2 The particles are prone to sintering, the microscopic pore structure is destroyed, and the macroscopic size is severely shrunk, resulting in reduced thermal insulation performance. Although the temperature resistance of SiO2 can be further improved to 1200℃ by adjusting the nanostructure and post-processing modification, it is difficult to further improve the temperature resistance of SiO2 due to its temperature resistance limitation. 2 The aerogel has a high tolerance to temperature. 2 O 3 Aerogels have high thermal and chemical stability at high temperatures due to their good crystallization properties and unique fiber network structure. However, due to the natural brittle nature of ceramic materials, there is a bottleneck problem of mechanical and thermal exclusivity that has plagued them for nearly a hundred years. Ceramic aerogels usually suffer from severe strength degradation and structural damage under large mechanical stress or thermal shock, which seriously damages their thermal insulation performance. Research on ceramic aerogels with low thermal conductivity, high temperature resistance, good thermal oxidation resistance, high mechanical strength, and light weight for use in hypersonic aircraft has become an urgent problem to be solved in materials research. Summary of the invention

[0004] In view of the deficiencies in the prior art, the present invention provides a method for preparing a flexible multi-level porous inorganic nanofiber aerogel for heat management in airflow spinning. The present invention also provides a method for preparing nano-ceramic fibers using a polyacetylacetonate zirconium aluminum precursor sol spinning solution.

[0005] The technical solution of the present invention is as follows:

[0006] A method for preparing a flexible multi-level porous inorganic nanofiber aerogel for heat management, the preparation method comprising the following steps:

[0007] Step 1: Preparation of poly(zirconium aluminum acetylacetonate) precursor

[0008] Dissolve a zirconium oxychloride raw material and an aluminum chloride raw material in anhydrous methanol, add acetylacetone and stir; then add a triethylamine-methanol mixed solution, stir and react to obtain a solution containing polyacetylacetonate zirconium aluminum, concentrate the solution containing polyacetylacetonate zirconium aluminum under reduced pressure to remove the solvent methanol to obtain a powder, add acetone to dissolve the soluble matter, remove the insoluble matter by suction filtration, and recover the acetone by concentrating the obtained filtrate under reduced pressure until a dry powder is obtained to obtain a polyacetylacetonate zirconium aluminum precursor;

[0009] Step 2: Preparation of the precursor spinning solution

[0010] The poly(zirconium aluminum acetylacetonate) precursor is dissolved in anhydrous methanol, a silane coupling agent and a pore-forming agent are added, and the solution is formed by stirring to obtain a precursor spinning solution;

[0011] Step 3: Preparation of flexible zirconia alumina nanofibers

[0012] The precursor spinning solution is transferred into a syringe in a spinning device, and the spinning solution is pressurized by an air compressor and ejected from a spinning needle under the conditions of a temperature of 10°C to 40°C and a relative humidity of 20% to 40%. After multi-stage drawing and collection, flexible zirconium oxide alumina nanofibers with a diameter of 10 μm to 40 μm are obtained in a receiver;

[0013] Step 4: Preparation of flexible hierarchical porous inorganic nanofiber aerogel for thermal management

[0014] The flexible zirconia alumina nanofibers obtained in step 3 are placed in a high-temperature furnace for heat treatment, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconia alumina fibers; sintering is performed to obtain a flexible multi-level porous inorganic nanofiber aerogel for heat management with a diameter of 100nm to 600nm.

[0015] The present application also provides a flexible multi-level porous inorganic nanofiber aerogel for heat management prepared according to the preparation method.

[0016] Beneficial effects:

[0017] Compared with the prior art, the present invention has the following significant advantages:

[0018] The preparation of the precursor spinning solution in the method of the present invention is simpler. The preparation of the spinning solution in the prior art needs to be obtained through reduced pressure concentration, while the spinning solution of the present invention can be obtained by directly dissolving the precursor poly(zirconium aluminum acetylacetonate), the softener KH-550, the pore-forming agent CTAB and the auxiliary agent in a solvent. Secondly, the present invention chooses to add a very small amount of water-soluble high molecular polymer as an auxiliary agent, which unexpectedly improves the spinnability of the spinning solution for air-spinning, increases the solid content of the precursor spinning solution, and is conducive to air-spinning to obtain uniform ultrafine precursor fibers.

[0019] The fiber diameter obtained by the air-spinning method of the present invention is 100nm-600nm, and it is continuous and flexible. Under the premise of ensuring the quality of zirconia alumina fiber, the diameter of zirconia alumina ultrafine fiber is reduced, and its ultra-high temperature thermal insulation and mechanical properties can be improved at the same time. The thermal conductivity of the obtained aerogel is only 18-23mW / (mK). By burning with a butane spray gun at 1300℃ and observing the temperature of the back of the aerogel with an infrared thermal imager, it can be seen that the thermal insulation performance of the three-component nanofiber aerogel used in the method of the present invention is better than that of other two-component aerogels.

[0020] The present invention further simplifies the process flow, optimizes the fiber quality, and improves environmental protection on the basis of maintaining the advantages of the prior art, which are beneficial to large-scale industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a photo of the flexible multi-level porous inorganic nanofiber aerogel fiber for heat management prepared in Example 1;

[0022] Figure 2 is a scanning electron microscope photograph of the flexible multi-level porous inorganic nanofiber aerogel for heat management prepared in Example 1;

[0023] Figure 3 is a photo of the flexible multi-level porous inorganic nanofiber aerogel fiber for heat management prepared in Example 2;

[0024] Figure 4 is a photo of the flexible multi-level porous inorganic nanofiber aerogel fiber for heat management prepared in Example 3;

[0025] Figure 5 Use an infrared thermal imager to compare the temperature change curve of the back side of the aerogel under the flame of a butane spray gun;

[0026] Figure 6 This is a photo of the multi-needle spinning device of Example 8;

[0027] Figure 7 This is a photo of the flexible multi-level porous inorganic nanofiber aerogel for heat management prepared with high efficiency in Example 9; DETAILED DESCRIPTION

[0028] The preferred embodiments of the present invention will be described in detail below in conjunction with examples. It should be understood that the following examples are provided only for the purpose of illustration and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0029] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0030] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0031] An embodiment of the present application provides a method for preparing a flexible multi-level porous inorganic nanofiber aerogel for heat management. The preparation method comprises the following steps:

[0032] Step 1: Preparation of poly(zirconium aluminum acetylacetonate) precursor

[0033] Dissolve a zirconium oxychloride raw material and an aluminum chloride raw material in anhydrous methanol, add acetylacetone and stir; then add a triethylamine-methanol mixed solution, stir and react to obtain a solution containing polyacetylacetonate zirconium aluminum, concentrate the solution containing polyacetylacetonate zirconium aluminum under reduced pressure to remove the solvent methanol to obtain a powder, add acetone to dissolve the soluble matter, remove the insoluble matter by suction filtration, and recover the acetone by concentrating the obtained filtrate under reduced pressure until a dry powder is obtained to obtain a polyacetylacetonate zirconium aluminum precursor;

[0034] Step 2: Preparation of the precursor spinning solution

[0035] The poly(zirconium aluminum acetylacetonate) precursor is dissolved in anhydrous methanol, a silane coupling agent and a pore-forming agent are added, and the solution is formed by stirring to obtain a precursor spinning solution;

[0036] Step 3: Preparation of flexible zirconia alumina nanofibers

[0037] The precursor spinning solution is transferred into a syringe in a spinning device, and the spinning solution is pressurized by an air compressor and ejected from a spinning needle under the conditions of a temperature of 10°C to 40°C and a relative humidity of 20% to 40%. After multi-stage drawing and collection, flexible zirconium oxide alumina nanofibers with a diameter of 10 μm to 40 μm are obtained in a receiver;

[0038] Step 4: Preparation of flexible hierarchical porous inorganic nanofiber aerogel for thermal management

[0039] The flexible zirconia alumina nanofibers obtained in step 3 are placed in a high-temperature furnace for heat treatment, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconia alumina fibers; sintering is performed to obtain a flexible multi-level porous inorganic nanofiber aerogel for heat management with a diameter of 100nm to 600nm.

[0040] In one embodiment, the zirconium oxychloride raw material in step 1 is zirconium oxychloride octahydrate, and the aluminum chloride raw material is aluminum chloride hexahydrate.

[0041] In one embodiment, in step 1, the mass molar ratio of zirconium oxychloride raw material: aluminum chloride raw material: acetylacetone: triethylamine is 1:1:(3.6-4.0):(3.8-5), and the volume ratio of triethylamine: methanol in the triethylamine-methanol mixed solution is (35-45):100.

[0042] In one embodiment, the acetone is added in step 1 in a ratio of zirconium oxychloride raw material: acetone = 50 g: (300-800) mL.

[0043] In one embodiment, in step 2, a silane coupling agent and a pore-forming agent are added, wherein the silane coupling agent is added at a ratio of 3%-4% of the total material mass, and the pore-forming agent is added at a ratio of 5%-6% of the total material mass.

[0044] In one embodiment, in step 3, the spinning solution is pressurized by an air compressor and ejected from the spinning needle. The spinning solution is pressurized by an air compressor to a gas pressure of 0.2 to 0.3 MPa and ejected from the spinning needle with an aperture of 0.03 to 0.20 mm.

[0045] In one embodiment, the size of the spinning needle in step 3 is 21G-25G, the volume of the syringe is 5mL-50mL, and the receiver is an open box, a mesh basket, a gauze, or a combination of the two.

[0046] In one embodiment, the output pressure of the air compressor in step 3 is 0.1 MPa to 0.8 MPa, the spinning environment temperature is 10° C. to 40° C., and the ambient humidity is 10% to 70%.

[0047] In one embodiment, in step 4, the fiber obtained in step 3 is placed in a high temperature furnace for heat treatment, and the temperature is increased to 200°C at a heating rate of 0.5°C / min to 1°C / min, and the sintering is performed by heating the temperature to 800°C to 1000°C at a heating rate of 1°C / min to 2°C / min, and the temperature is kept for 1h to 3h for sintering.

[0048] In one embodiment, the silane coupling agent is KH-550: γ-aminopropyltriethoxysilane.

[0049] In one embodiment, the pore former is CTAB: hexadecyltrimethylammonium bromide.

[0050] One embodiment of the present application provides a flexible multi-level porous inorganic nanofiber aerogel for heat management prepared according to the preparation method.

[0051] Embodiment 1:

[0052] (1) Preparation of poly(zirconium aluminum acetylacetonate) precursor sol spinning solution:

[0053] 300g of poly(zirconium aluminum acetylacetonate), 60g of KH-550 (γ-aminopropyltriethoxysilane coupling agent), 90g of CTAB (hexadecyltrimethylammonium bromide), and 72g of polyvinylpyrrolidone were weighed and dissolved in 1080g of anhydrous methanol under stirring. When the solid was completely dissolved and the reaction solution turned into a transparent solution, the poly(zirconium aluminum acetylacetonate) precursor sol spinning solution was obtained.

[0054] (2) Air-jet spinning

[0055] The spinning solution was added to a glass syringe with a 21G needle, and the spinning solution was slowly pushed out by gravity, and the fibers were collected by covering the gauze in a carton. At a temperature of 25°C, a humidity of 50%, an air pressure of 0.3MPa, a propulsion speed of 10mL / h, and a receiving distance of 25cm, the spinning solution was sprayed out from the stainless steel needle to obtain poly(zirconium aluminum acetylacetonate) precursor fibers.

[0056] (3) Medium and high temperature heat treatment

[0057] The fiber obtained in step (3) is placed in a high temperature furnace for heat treatment, and the temperature is raised to 200°C at a heating rate of 0.5-1°C / min, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconium oxide alumina fiber; the temperature is raised to 800-1000°C at a heating rate of 1-2°C / min, and the temperature is kept for 1-3 hours for sintering to obtain a flexible multi-level porous inorganic nanofiber aerogel for heat management. The fiber photo is as shown in Figure 1 As shown, the diameter of 100 to 300 nm scanning electron microscopy results are as follows Figure 2 As shown, it can be used for a long time at a temperature of 1300°C.

[0058] Embodiment 2:

[0059] (1) Preparation of poly(zirconium aluminum acetylacetonate) precursor sol spinning solution:

[0060] 300g of poly(zirconium aluminum acetylacetonate), 42.6g of KH-550 (γ-aminopropyltriethoxysilane coupling agent), 78.6g of CTAB (hexadecyltrimethylammonium bromide), and 72g of polyvinylpyrrolidone were weighed and dissolved in 1080g of anhydrous methanol under stirring. When the solid was completely dissolved and the reaction solution turned into a transparent solution, the poly(zirconium aluminum acetylacetonate) precursor sol spinning solution was obtained.

[0061] (2) Air-jet spinning

[0062] The spinning solution was added to a glass syringe with a 21G needle, and the spinning solution was slowly pushed out by gravity, and the fibers were collected by covering the gauze in a carton. At a temperature of 25°C, a humidity of 50%, an air pressure of 0.3MPa, a propulsion speed of 10mL / h, and a receiving distance of 25cm, the spinning solution was sprayed out from the stainless steel needle to obtain poly(zirconium aluminum acetylacetonate) precursor fibers.

[0063] (3) Medium and high temperature heat treatment

[0064] The fiber obtained in step (3) is placed in a high temperature furnace for heat treatment, and the temperature is raised to 200°C at a heating rate of 0.5-1°C / min, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconium oxide alumina fiber; the temperature is raised to 800-1000°C at a heating rate of 1-2°C / min, and the temperature is kept for 1-3 hours for sintering to obtain a flexible multi-level porous inorganic nanofiber aerogel for heat management. The fiber photo is as shown in Figure 3 As shown, it can be used for a long time at a temperature of 1300°C.

[0065] Embodiment 3:

[0066] (1) Preparation of poly(zirconium aluminum acetylacetonate) precursor sol spinning solution:

[0067] 300g of poly(zirconium aluminum acetylacetonate), 64.5g of KH-550 (γ-aminopropyltriethoxysilane coupling agent), 96.8g of CTAB (hexadecyltrimethylammonium bromide), and 72g of polyvinylpyrrolidone were weighed and dissolved in 1080g of anhydrous methanol under stirring. When the solid was completely dissolved and the reaction solution turned into a transparent solution, the poly(zirconium aluminum acetylacetonate) precursor sol spinning solution was obtained.

[0068] (2) Air-jet spinning

[0069] The spinning solution was added to a glass syringe with a 21G needle, and the spinning solution was slowly pushed out by gravity, and the fibers were collected by covering the gauze in a carton. At a temperature of 25°C, a humidity of 50%, an air pressure of 0.3MPa, a propulsion speed of 10mL / h, and a receiving distance of 25cm, the spinning solution was sprayed out from the stainless steel needle to obtain poly(zirconium aluminum acetylacetonate) precursor fibers.

[0070] (3) Medium and high temperature heat treatment

[0071] The fiber obtained in step (3) is placed in a high temperature furnace for heat treatment, and the temperature is raised to 200°C at a heating rate of 0.5-1°C / min, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconium oxide alumina fiber; the temperature is raised to 800-1000°C at a heating rate of 1-2°C / min, and the temperature is kept for 1-3 hours for sintering to obtain a flexible multi-level porous inorganic nanofiber aerogel for heat management. The fiber photo is as shown in Figure 4As shown, it can be used for a long time at a temperature of 1300°C.

[0072] Embodiment 4:

[0073] (1) Preparation of poly(zirconium aluminum acetylacetonate) precursor sol spinning solution:

[0074] 300 g of poly(zirconium aluminum acetylacetonate), 90 g of CTAB, and 72 g of polyvinyl pyrrolidone were weighed and dissolved in 1080 g of anhydrous methanol under stirring. When the solid was completely dissolved and the reaction liquid turned into a transparent solution, the poly(zirconium aluminum acetylacetonate) precursor sol spinning solution was obtained.

[0075] (2) Air-jet spinning

[0076] The spinning solution was added to a glass syringe with a 21G needle, and the spinning solution was slowly pushed out by gravity, and the fibers were collected by covering the gauze in a carton. At a temperature of 25°C, a humidity of 50%, an air pressure of 0.3MPa, a propulsion speed of 10mL / h, and a receiving distance of 25cm, the spinning solution was sprayed out from the stainless steel needle to obtain poly(zirconium aluminum acetylacetonate) precursor fibers.

[0077] (3) Medium and high temperature heat treatment

[0078] The fiber obtained in step (3) is placed in a high temperature furnace for heat treatment, and the temperature is raised to 200°C at a heating rate of 0.5-1°C / min, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconium oxide alumina fiber; the temperature is raised to 800-1000°C at a heating rate of 1-2°C / min, and the temperature is kept for 1-3 hours for sintering to obtain ZrO 2 Al 2 O 3 Flexible multi-level porous inorganic nanofiber aerogel for heat management. The obtained flexible multi-level porous inorganic nanofiber aerogel for heat management has a diameter of 100 to 300 nm and can be used for a long time at a temperature of 1300°C.

[0079] Embodiment 5:

[0080] (1) Preparation of poly(zirconium acetylacetonate) precursor sol spinning solution:

[0081] 300 g of zirconium polyacetylacetonate, 60 g of KH-550, 90 g of CTAB, and 72 g of polyvinyl pyrrolidone were weighed and dissolved in 1080 g of anhydrous methanol under stirring. When the solid was completely dissolved and the reaction liquid turned into a transparent solution, the zirconium polyacetylacetonate aluminum precursor sol spinning solution was obtained.

[0082] (2) Air-jet spinning

[0083] The spinning solution was added to a glass syringe with a 21G needle, and the spinning solution was slowly pushed out by gravity, and the fibers were collected by covering the gauze in a carton. At a temperature of 25°C, a humidity of 50%, an air pressure of 0.3MPa, a propulsion speed of 10mL / h, and a receiving distance of 25cm, the spinning solution was sprayed out from the stainless steel needle to obtain poly(zirconium aluminum acetylacetonate) precursor fibers.

[0084] (3) Medium and high temperature heat treatment

[0085] The fiber obtained in step (3) is placed in a high temperature furnace for heat treatment, and the temperature is raised to 200°C at a heating rate of 0.5-1°C / min, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconium oxide fiber; the temperature is raised to 800-1000°C at a heating rate of 1-2°C / min, and the temperature is kept for 1-3 hours for sintering to obtain ZrO 2 SiO 2 Flexible multi-level porous inorganic nanofiber aerogel for heat management. Flexible multi-level porous inorganic nanofiber aerogel for heat management (diameter 100-300nm, can be used for a long time at 1300℃) is obtained.

[0086] Embodiment 6:

[0087] (1) Preparation of spinning solution:

[0088] 300 g of aluminum acetylacetonate, 60 g of KH-550, 90 g of CTAB, and 72 g of polyvinyl pyrrolidone were weighed and dissolved in 1080 g of anhydrous methanol under stirring. When the solid was completely dissolved and the reaction liquid turned into a transparent solution, the aluminum acetylacetonate sol spinning solution was obtained.

[0089] (2) Air-jet spinning

[0090] The spinning solution was added to a glass syringe with a 21G needle, and the spinning solution was slowly flowed out by gravity, and the fibers were collected by covering the gauze in a carton. At a temperature of 25°C, a humidity of 50%, an air pressure of 0.3MPa, a propulsion speed of 10mL / h, and a receiving distance of 25cm, the spinning solution was sprayed out from the stainless steel needle to obtain aluminum acetylacetonate precursor fibers.

[0091] (3) Medium and high temperature heat treatment

[0092] The fiber obtained in step (3) is placed in a high temperature furnace for heat treatment, and the temperature is raised to 200°C at a heating rate of 0.5-1°C / min, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconium oxide alumina fiber; the temperature is raised to 800-1000°C at a heating rate of 1-2°C / min, and the temperature is kept for 1-3 hours for sintering to obtain Al 2 O 3 SiO 2Flexible multi-level porous inorganic nanofiber aerogel for heat management. The obtained flexible multi-level porous inorganic nanofiber aerogel for heat management has a diameter of 100 to 300 nm and can be used for a long time at a temperature of 1300°C.

[0093] Example 7

[0094] Ultra-high temperature flame test:

[0095] (1) The samples obtained in Examples 1-6 were burned with a butane torch at 1300°C.

[0096] (2) Use an infrared thermal imager to observe the temperature on the back of the aerogel and record and plot it. Figure 5 As shown, by comparison, examples 1-3 have the best thermal insulation performance, and the thermal insulation temperature is kept below 50° C. Flexible multi-level porous inorganic nanofiber aerogel for thermal management.

[0097] Embodiment 8:

[0098] (1) Preparation of poly(zirconium aluminum acetylacetonate) precursor sol spinning solution:

[0099] 300 g of poly(zirconium aluminum acetylacetonate), 60 g of KH-550, 90 g of CTAB, and 72 g of polyvinyl pyrrolidone were weighed and dissolved in 1080 g of anhydrous methanol under stirring. When the solid was completely dissolved and the reaction liquid turned into a transparent solution, the poly(zirconium aluminum acetylacetonate) precursor sol spinning solution was obtained.

[0100] (2) Air-jet spinning

[0101] Add the spinning solution into two glass syringes with 21G needles, push the spinning solution out slowly by gravity, and collect the fibers by covering the gauze in the carton. At a temperature of 25°C, a humidity of 50%, an air pressure of 0.3MPa, a propulsion speed of 10mL / h, and a receiving distance of 15cm, spray the spinning solution from the two stainless steel needles for reference. Figure 6 As shown, poly(zirconium aluminum acetylacetonate) precursor fibers were obtained in a shorter time.

[0102] (3) Medium and high temperature heat treatment

[0103] The fiber obtained in step (3) is placed in a high-temperature furnace for heat treatment, and the temperature is raised to 200°C at a heating rate of 0.5-1°C / min, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconium oxide alumina fiber; the temperature is raised to 800-1000°C at a heating rate of 1-2°C / min, and the temperature is kept for 1-3 hours for sintering to obtain a large-volume flexible multi-level porous inorganic nanofiber aerogel for heat management, such as Figure 7 As shown, it can be used for a long time at a temperature of 1300°C.

[0104] Embodiment 9:

[0105] (1) Preparation of poly(zirconium aluminum acetylacetonate) precursor sol spinning solution:

[0106] 300 g of poly(zirconium aluminum acetylacetonate), 60 g of KH-550, 90 g of CTAB, and 72 g of polyvinyl pyrrolidone were weighed and dissolved in 1080 g of anhydrous methanol under stirring. When the solid was completely dissolved and the reaction liquid turned into a transparent solution, the poly(zirconium aluminum acetylacetonate) precursor sol spinning solution was obtained.

[0107] (2) Air-jet spinning

[0108] The spinning solution was added into three glass syringes with 21G needles, and the spinning solution was slowly flowed out by gravity, and the fibers were collected by covering the gauze in the carton. At a temperature of 25°C, a humidity of 50%, an air pressure of 0.3MPa, a propulsion speed of 10mL / h, and a receiving distance of 15cm, the spinning solution was ejected from three stainless steel needles to obtain polyacetylacetonate zirconium aluminum precursor fibers.

[0109] (3) Medium and high temperature heat treatment

[0110] The fiber obtained in step (3) is placed in a high-temperature furnace for heat treatment, and the temperature is increased to 200°C at a heating rate of 0.5-1°C / min, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconium oxide alumina fiber; the temperature is increased to 800-1000°C at a heating rate of 1-2°C / min, and the temperature is kept for 1-3 hours for sintering to obtain ultra-low thermal conductivity flexible ceramic fiber aerogel with a diameter of 100-300nm, which can be used for a long time at a temperature of 1300°C.

[0111] The difference between Example 1 to Example 3 lies in the ratio of KH-550 and CTAB. According to the usage results, it can be proved that in the present invention, KH-550 and CTAB can be used to prepare flexible multi-level porous inorganic nanofiber aerogel at 3-4% and 5-6% of the total material mass, respectively, and the prepared flexible multi-level porous inorganic nanofiber aerogel has good thermal insulation performance.

[0112] Examples 4-6 prepared two-component nanofiber aerogels and compared their performance with the three-component ceramic nanofiber aerogels of Example 1. The results of the ultra-high temperature flame of Example 7 show that the results can be seen in Figure 5 The three-component flexible ceramic nanofiber aerogel in Example 1 has the lowest thermal conductivity and the best thermal insulation performance.

[0113] Compared with Example 1, Example 8-Example 9 converts the multi-channel airflow joint, increases the number of air pipes, syringes, spinning needles and air spray joints, improves the spinning efficiency, and can quickly prepare three-dimensional nanofiber aerogel.

[0114] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the protection scope of the present invention.

Claims

1. A method for preparing a flexible multi-level porous inorganic nanofiber aerogel for heat management, characterized in that: The preparation method comprises the following steps: Step 1: Preparation of poly(zirconium aluminum acetylacetonate) precursor Dissolve a zirconium oxychloride raw material and an aluminum chloride raw material in anhydrous methanol, add acetylacetone and stir; then add a triethylamine-methanol mixed solution, stir and react to obtain a solution containing polyacetylacetonate zirconium aluminum, concentrate the solution containing polyacetylacetonate zirconium aluminum under reduced pressure to remove the solvent methanol to obtain a powder, add acetone to dissolve the soluble matter, remove the insoluble matter by suction filtration, and recover the acetone by concentrating the obtained filtrate under reduced pressure until a dry powder is obtained to obtain a polyacetylacetonate zirconium aluminum precursor; Step 2: Preparation of the precursor spinning solution The poly(zirconium aluminum acetylacetonate) precursor is dissolved in anhydrous methanol, a silane coupling agent and a pore-forming agent are added, and the solution is formed by stirring to obtain a precursor spinning solution; Step 3: Preparation of flexible zirconia alumina nanofibers The precursor spinning solution is transferred into a syringe in a spinning device, and the spinning solution is pressurized by an air compressor and ejected from a spinning needle under the conditions of a temperature of 10°C to 40°C and a relative humidity of 20% to 40%. After multi-stage drawing and collection, flexible zirconium oxide alumina nanofibers with a diameter of 10 μm to 40 μm are obtained in a receiver; Step 4: Preparation of flexible hierarchical porous inorganic nanofiber aerogel for thermal management The flexible zirconia alumina nanofibers obtained in step 3 are placed in a high-temperature furnace for heat treatment, so that the polyacetylacetonate zirconium aluminum precursor is fully decomposed and crystallized to be converted into zirconia alumina fibers; sintering is performed to obtain a flexible multi-level porous inorganic nanofiber aerogel for heat management with a diameter of 100nm to 600nm.

2. The preparation method according to claim 1, characterized in that: The zirconium oxychloride raw material in step 1 is zirconium oxychloride octahydrate, and the aluminum chloride raw material is aluminum chloride hexahydrate.

3. The preparation method according to claim 1, characterized in that: In the step 1, the mass molar ratio of zirconium oxychloride raw material: aluminum chloride raw material: acetylacetone: triethylamine is 1:1:(3.6-4.0):3.8-5, and the volume ratio of triethylamine: methanol in the triethylamine-methanol mixed solution is (35-45):

100.

4. The preparation method according to claim 1, characterized in that: In the step 1, acetone is added in a ratio of zirconium oxychloride raw material: acetone = 50 g: (300-800) mL.

5. The preparation method according to claim 1, characterized in that: In the step 2, a silane coupling agent and a pore-forming agent are added, wherein the silane coupling agent is added at a ratio of 3%-4% of the total material mass, and the pore-forming agent is added at a ratio of 5%-6% of the total material mass.

6. The preparation method according to claim 1, characterized in that: In step 3, the spinning solution is pressurized by an air compressor and ejected from the spinning needle. The spinning solution is pressurized by an air compressor to a gas pressure of 0.2-0.3 MPa and ejected from the spinning needle with an aperture of 0.03-0.20 mm.

7. The preparation method according to claim 1, characterized in that: The size of the spinning needle in step 3 is 21G to 25G, the volume of the syringe is 5mL to 50mL, and the receiver is an open box, a mesh basket, a gauze, or a combination of the two.

8. The preparation method according to claim 1, characterized in that: In step 3, the output pressure of the air compressor is 0.1MPa-0.8MPa, the spinning environment temperature is 10°C-40°C, and the ambient humidity is 10%-70%.

9. The preparation method according to claim 1, characterized in that: In step 4, the fiber obtained in step 3 is placed in a high-temperature furnace for heat treatment, and the temperature is increased to 200°C at a heating rate of 0.5°C / min to 1°C / min. The sintering is performed by heating the temperature to 800°C to 1000°C at a heating rate of 1°C / min to 2°C / min, and the temperature is kept for 1h to 3h for sintering.

10. The flexible multi-level porous inorganic nanofiber aerogel for heat management prepared by the preparation method according to any one of claims 1 to 9.

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