Preparation method and application of elastic ceramic nanofiber flake product

Abstract

This invention discloses a method for preparing and applying elastic ceramic nanofiber flocs. Precursor coiled nanofibers are dynamically assembled using a periodically arranged spinneret module to form three-dimensional interwoven precursor nanofiber flocs. These flocs are then calcined at high temperature to obtain elastic ceramic nanofiber flocs. The flocs are cut into pre-formed sheets, conveyed by a conveying device, and wound onto the main mold of a self-rotating forming device under the action of auxiliary forming rollers. Adhesive is sprayed from the pre-formed sheets to achieve interlayer bonding, producing preforms. The main mold and preforms are placed into a matching mold to form a forming module. The preforms are then impregnated by an ultrasonic impregnation and homogenization device, followed by low-temperature treatment to form ice crystals in the impregnation solution perpendicular to the fiber direction, achieving inter-sheet stitching. Finally, the preforms are dried and demolded to obtain the finished product. This invention preserves the intrinsic elasticity and three-dimensional network structure of the fibers without damaging their structure and morphology, enabling short-process, high-efficiency, and continuous preparation of floc products.

Description

Technical Field

[0001] This invention relates to the field of nanofiber materials technology, specifically to a method for preparing and applying elastic ceramic nanofiber flocs. Background Technology

[0002] With the rapid development of high-end equipment manufacturing and new energy fields, more stringent performance requirements have been placed on the temperature resistance and reliability of high-temperature working components. For example, the hot-end components of new-generation aircraft need to withstand the impact of high-temperature airflow exceeding 1400℃ for extended periods without cracking; the combustion chamber walls of hypersonic missiles need to continuously withstand temperatures exceeding 1000℃ and also possess excellent thermal shock resistance. Ceramic fiber materials, with their lightweight, low thermal conductivity, good chemical stability, and excellent high-temperature resistance, have become commonly used materials for thermal protection of high-temperature equipment and have been widely applied in fields such as industrial high-temperature insulation and aerospace thermal protection.

[0003] To address the diverse shape and structural requirements of ceramic fibers in various applications, there is an urgent need to develop a universally applicable method for preparing ceramic fiber products. Patent ZL202511586088.4 describes mixing short ceramic fibers with talc, a protective agent, and inorganic insulating powder, followed by mechanical dry pressing to obtain ceramic fiber products. However, the weak bonding between the components in this product results in poor shock resistance and easy powder shedding. Patent CN202011570129.8 further describes preparing a uniform slurry from short ceramic fibers with solvents and additives, injecting it into a mold, and then demolding and drying to obtain ceramic fiber products. This method improves the structural uniformity of the material and reduces powder shedding to some extent, but the short ceramic fibers do not maintain a continuous morphological structure, leading to poor damage resistance and brittleness in actual use. These ceramic fiber preforms fail to meet the demands for high-performance preforms in fields such as industrial high-temperature insulation and aerospace thermal protection. Summary of the Invention

[0004] To address the fact that existing ceramic fiber preforms cannot meet the demands for high-performance preforms in fields such as industrial high-temperature insulation and aerospace thermal protection, this invention provides an elastic ceramic nanofiber floc product that can be directly formed based on the three-dimensional network structure of ceramic fibers, and its continuous preparation method. This method preserves the intrinsic elasticity and three-dimensional network structure of the fiber assembly without damaging the original structure and morphology of the fibers, enabling short-process, high-efficiency, and continuous production from flocs to finished products.

[0005] The objective of this invention can be achieved through the following technical solutions: One objective of this invention is to provide a method for preparing elastic ceramic nanofiber flocculent products, comprising the following steps: S1. The prepared inorganic long-chain spinning solution is loaded onto the spinning nozzle, and an auxiliary force field is applied to stretch the spinning solution to form a whipping jet. At the same time, a multi-point micro-disturbance air intake device is used to deliver airflow, so that the whipping jet is solidified to obtain precursor crimped nanofibers. Then, the precursor crimped nanofibers are dynamically assembled in the air by periodically arranging spinneret modules to obtain precursor nanofiber flakes with a three-dimensional interwoven structure. Finally, the precursor nanofiber flakes are calcined at high temperature to obtain elastic ceramic nanofiber flakes. S2. The elastic ceramic nanofiber flocs prepared in S1 are sequentially cut, shaped, ultrasonically impregnated and homogenized, low-temperature settling and dried to obtain ceramic nanofiber floc products. S21. Cut the elastic ceramic nanofiber flocs obtained in S1 according to the desired product shape to obtain multiple pre-made sheets; S22. The multiple prefabricated sheets obtained in S1 are placed on the conveying device in sequence, and wound around the main mold set on the periphery of the self-rotating forming device under the drive of the auxiliary forming roller. The surface of the prefabricated sheets is sprayed with glue by the glue spraying device, so that the multiple prefabricated sheets are bonded together to form a prefabricated part. S23. Remove the main mold and the preforms on it, and place them in the matching mold to form a molding module; place the molding module in the ultrasonic impregnation and homogenization device, and the impregnation liquid penetrates into the preforms in the molding module; S24. The molding module is placed in a low-temperature environment. The impregnation liquid of the preforms in the molding module crystallizes into ice crystals in a direction perpendicular to the fiber layer. The ice crystals tightly stitch together multiple preforms. S25. After drying the molding module and removing the matching mold, the elastic ceramic nanofiber flocculent product is obtained.

[0006] Furthermore, the preparation method of the elastic ceramic nanofiber flocculent product includes the following steps: S1. The prepared inorganic long-chain spinning solution is loaded onto the spinning nozzle, and then an auxiliary force field is applied to stretch the solution and form a violently whipping jet. At the same time, a slow airflow with specific properties is delivered to the whipping area using a multi-point micro-disturbance air inlet device, so that the whipping jet can be rapidly solidified to obtain precursor crimped nanofibers. Then, the motion parameters of the periodically arranged spinneret module are controlled to allow the precursor crimped nanofibers to be dynamically assembled in the air to obtain precursor nanofiber flakes with a three-dimensional interwoven structure. Finally, the precursor nanofiber flakes are subjected to high-temperature calcination to obtain elastic ceramic nanofiber flakes.

[0007] S2. The elastic ceramic nanofiber flocs prepared in S1 are sequentially cut, preformed, ultrasonically impregnated and homogenized, low-temperature settling, and dried to prepare ceramic nanofiber floc-based preforms. Specifically, the following steps are included: S21. Cut the elastic ceramic nanofiber flocs obtained in S1 according to the required preform shape to fit the mold shape. S22. The cut elastic ceramic nanofiber flakes are placed in the preform forming device and transported to the auxiliary forming roller and the self-rotating forming device by the conveying device. Under the combined rotation of the two, the flakes are wound around the surface of the main mold. At the same time, the real-time glue spraying device sprays glue on the surface of the fiber flakes in real time, so that the flakes are bonded together to form a preform. S23. Remove the main mold and the prepared preform at the same time, and combine them with the matching mold to form a molding module; then, put the molding module into the ultrasonic impregnation and homogenization device, and adjust the ultrasonic frequency and ultrasonic time to make the impregnation liquid enter the preform evenly, while the surface of the preform is finely homogenized and shaped to obtain a preform with a smooth surface. S24. The preform prepared in step 23 is placed in a low-temperature environment. The liquid in the preform forms ice crystals at an angle perpendicular to the fiber layer, which tightly stitches the floc layers together, thereby obtaining a structurally stable preform. S25. The preforms prepared in step 24 are dried to directly obtain planar, cylindrical, conical and funnel-shaped ceramic nanofiber-based preforms. Furthermore, the periodically arranged spinneret module includes alternating first and second spinnerets. The first spinneret has multiple vertical spinning nozzles spaced apart along its length, and the second spinneret has two rows of inclined first and second spinning nozzles arranged along its length. The included angle between the first and second inclined spinning nozzles is an obtuse angle. The operating speed of the first and second spinnerets is 20~100cm / min, and the operating speed of the conveyor belt is 0.2~2.0m / min. The multi-point micro-disturbance air intake device includes air supply units symmetrically arranged on both sides of the periodically arranged spinneret module. Each air supply unit includes a flow stabilizing grid and a multi-jet head array connected to the flow stabilizing grid. The jet heads of the multi-jet head array include coaxially arranged inner and outer tubes. The inner tube cavity forms an inner channel, and the gap between the inner and outer tubes forms an outer channel. The inner channel supplies a temperature-controllable dry airflow, and the outer channel is used to introduce a humidity-controllable humidified airflow. The air supply unit has a nozzle density ≥900 / m³. 2The airflow velocity is 0.5~5m / s, the temperature is 10~50℃, and the humidity is 10~99%. That is, the multi-point micro-disturbance air intake device is symmetrically arranged on both sides of the spinneret, and includes two symmetrically distributed air supply units; each air supply unit includes a flow stabilizing grid and a multi-jet head array connected to the flow stabilizing grid. The air outlets of the multi-jet head array are perpendicular to the jet direction and can deliver gases with different humidity and temperature. The periodically arranged spinneret module consists of a single-row spinneret and a double-row spinneret arranged periodically. The double-row spinneret obliquely sprays curled nanofibers, causing them to interweave horizontally in the air, while the single-row spinneret vertically sprays fibers, which interweave vertically at the horizontal interweaving points, thus forming a three-dimensional interwoven structure.

[0008] In other words, the air supply units of the multi-point micro-disturbance air intake device are symmetrically arranged on both sides of the spinneret, generating slow airflows in opposite directions. By controlling the temperature and humidity parameters of the airflow, the evaporation of the solvent in the jet is accelerated, allowing the jet curl structure to solidify and set rapidly. The entire device is made of one of polytetrafluoroethylene, polypropylene, polyetheretherketone, and polyvinyl chloride. The air supply unit has a nozzle density ≥900 nozzles / m³. 2 The airflow velocity is 0.5~5m / s, and the supplied airflow is one of the following: high temperature drying, high temperature and high humidity, normal temperature drying, and normal temperature and high humidity. Its temperature is 10~50℃ and its humidity is 10~99%.

[0009] In the periodically arranged spinneret module, the double-row spinnerets are symmetrically designed, with the two side nozzles tilted at an angle of 0~90°. The double-row symmetrical tilted nozzles spray horizontally interwoven crimped nanofibers in the air. The single-row spinneret has vertically positioned nozzles that vertically spray crimped nanofibers at the horizontal interweaving points, thus forming a three-dimensional interwoven structure in the air. By further controlling the running speed of the spinnerets and the conveyor belt, multiple crimped nanofibers can be dynamically assembled in the air to obtain precursor nanofiber flakes with a three-dimensional interwoven structure in one step. The running speed of the spinnerets is 20~100cm / min, and the running speed of the conveyor belt is 0.2~2.0m / min. The high-temperature calcination temperature is set to 200~1500℃. The thickness of the elastic ceramic nanofiber flakes is 0.2~10cm.

[0010] Furthermore, the product forming device includes a self-rotating forming device, a pair of feeding components arranged on both sides of the self-rotating forming device, the feeding components including a pair of auxiliary forming rollers arranged sequentially from the inside to the outside of the self-rotating forming device, a conveying device, a main mold arranged around the self-rotating forming device, and a glue spraying device arranged above or below the self-rotating forming device. The conveying device includes a conveyor belt and a rotating roller disposed below the conveyor belt, which can convey the cut fiber flakes to the auxiliary forming pressure roller. The linear speed of the conveyor belt is 0.1~0.5m / min. The pair of auxiliary forming rollers are a pair of circular rollers spaced apart vertically, which can apply a pressure of 0.1~10MPa to the flakes and transport the flakes to the self-rotating forming device; The rotational speed of the self-rotating forming device is 0.5~5 rpm; The spray nozzle of the adhesive spraying device is a wide-angle atomizing nozzle designed to prevent clogging. The adhesive spraying rate is 0.05~0.5 g / min, and the atomizing pressure is 0.05~0.2 MPa. The adhesive used for spraying is selected from one or more combinations of water glass, silica sol, tetraethyl orthosilicate solution, aluminum alkoxide solution, zirconium propoxide solution, tetraisopropyl titanate solution, and gallium ethoxide solution, and the sol concentration is 0.1~5 wt%. In other words, the molding device consists of a conveying device, an auxiliary molding roller, a self-rotating molding device, a main mold, and a real-time adhesive spraying device. The conveying device is located at the feed end of the device and is used to transport the cut elastic ceramic fiber flakes; the auxiliary forming roller is located downstream of the conveying device and presses the flakes transported to this position to adjust their thickness; the self-rotating forming device is connected to the main mold and is located after the auxiliary forming roller. The self-rotating forming device is used to receive the pressed flakes and directly wind them onto the surface of the main mold for forming; the real-time adhesive spraying device is located at the upper left and lower right positions of the main mold winding and sprays adhesive into the interlayer of flakes during the winding process.

[0011] Furthermore, the conveying device in the forming apparatus consists of a rotating roller and a conveyor belt, which can convey the cut fiber flakes to the auxiliary forming pressure roller. The conveyor belt has a linear speed of 0.1~0.5m / min. The auxiliary forming pressure roller consists of two circular pressure rollers, which can apply a pressure of 0.1~10MPa to the flakes and convey them to the self-rotating forming device. The self-rotating forming device can fix the main mold and assemble the cut flakes into preforms of the required structure by rotation. Its rotation speed is 0.5~5rpm. The nozzle of the real-time adhesive spraying device adopts an anti-clogging wide-angle atomizing nozzle, with an adhesive spraying amount of 0.05~0.5g / min and an atomizing air pressure of 0.05~0.2MPa. The sprayed adhesive is selected from one or more combinations of water glass, silica sol, tetraethyl orthosilicate solution, aluminum alkoxide solution, zirconium propoxide solution, tetraisopropyl titanate solution, and gallium ethoxide solution, and the sol concentration is 0.1~5wt%.

[0012] Furthermore, the molding module includes a main mold and a matching mold sleeved around the main mold; The matching mold is provided with an upper fixing port and a lower fixing port at the top and bottom, respectively; The main mold and the matching mold can be any one of the following shapes: cylindrical, conical, funnel-shaped, or planar. The main mold and the matching mold are made of one of the following materials: stainless steel, alloy steel, polyetheretherketone, polyurethane, epoxy resin, liquid silicone, polytetrafluoroethylene, and polyethylene.

[0013] Furthermore, the molding module includes a main mold as the inner core and a matching mold as the outer cover. The matching mold is coaxially arranged with the main mold, and the inner diameter of the matching mold is larger than the outer diameter of the main mold. The annular cavity formed between the two can be used to place the preform. The molding module is provided with an upper fixing port and a lower fixing port, respectively, for fixing it in the preform molding device and the ultrasonic impregnation and homogenization device. The mold can be customized into a cylindrical, conical, funnel-shaped, or planar shape; the material of the mold is selected from stainless steel, alloy steel, polyetheretherketone, polyurethane, epoxy resin, liquid silicone, polytetrafluoroethylene, and polyethylene.

[0014] Furthermore, the ultrasonic impregnation and homogenization device includes a housing, a sealing cap on top of the housing, and inside the housing: a fixing member, a mold fixing rod above the fixing member, and an ultrasonic generator beside the fixing member; a water exchange port is also provided at the bottom of the housing, and the housing contains impregnation liquid. In other words, the ultrasonic impregnation and homogenization device consists of an ultrasonic generator, a mold fixing rod, a water exchange port, impregnation liquid, a sealing cap, and a fixing member. The sealing cap covers the top of the ultrasonic impregnation and homogenization device to seal the ultrasonic environment; the impregnation liquid is injected into the molding module from the top of the ultrasonic impregnation and homogenization device; the mold fixing rod is located above the molding module and fixed through an upper fixing port, and the fixing member is located below the molding module and connected through a lower fixing port, together fixing the molding module in the ultrasonic impregnation and homogenization device; the ultrasonic generator is distributed around the molding module, and the ultrasonic vibrations it generates are evenly transmitted to the surface and interior of the preform through the impregnation liquid, achieving sufficient and uniform impregnation and structural homogenization of the preform. Furthermore, the ultrasonic impregnation and leveling device can impregnate and finely level the preform; the ultrasonic generator operates at a frequency of 10~100kHz; the temperature of the impregnation solution is maintained at 20~40℃, and the height of the impregnation solution must completely submerge the preform and be above its top; the impregnation solution is selected from one or more of water, ethylene glycol, propylene glycol, and acetone; the gap width between the main mold and the matching mold is 5~10cm.

[0015] Furthermore, in S1, the calcination temperature of the precursor nanofiber flocs is set to 200~1500℃; the thickness of the elastic ceramic nanofiber flocs is 0.2~10cm; The external force in the auxiliary force field is selected from one or a combination of electrostatic force, airflow force, and centrifugal force.

[0016] Furthermore, in S23, the gap width between the main mold and the matching mold is 5~10cm.

[0017] Further, in S24, the low-temperature shaping treatment refers to placing the preform in a low-temperature environment to create a temperature gradient difference, driving the liquid in the preform to crystallize from the external environment towards the main mold to form ice crystals, thereby making adjacent flocculent layers tightly adhered; the temperature of the low-temperature environment is -100~-5℃, and the temperature of the preform is 15~30℃. Even further, the low-temperature environment is achieved at -100~-5℃ by adding liquid nitrogen; the main mold has an annular flow channel inside, and a circulating medium with a set temperature is continuously introduced into this channel to exchange heat with the preform, dynamically maintaining the preform temperature at 15~30℃; the circulating medium is a synthetic heat-conducting oil or an ethylene glycol solution with a volume concentration of not less than 50%, wherein the synthetic heat-conducting oil is selected from alkylbenzene type, polyol ester type, or methyl silicone oil type; Furthermore, in S25, the drying process refers to placing the flakes into a drying device to allow the ice crystals to sublimate directly without damaging the interlayer structure of the preform; the drying is selected from one or more of vacuum drying, supercritical drying, and atmospheric pressure drying.

[0018] The second objective of this invention is to provide an application of the elastic ceramic nanofiber flocs prepared by the method described above, in flame-retardant materials, heat-insulating materials, thermal insulation materials, and sound-absorbing and noise-reducing materials. For example, it can be used in high-temperature heat shields for high-speed aircraft; the planar ceramic nanofiber flocs can be used in battery heat insulation pads and fire blankets for new energy vehicles, the core functional layer of fire-fighting heat-insulating clothing, portable fire-resistant cloaks for fire escape, fire-resistant and noise-reducing layers for exterior walls of high-rise buildings, flame-retardant and heat-insulating layers for biopharmaceutical storage and cold chain transportation, flame-retardant and noise-reducing heat-insulating materials for large aircraft, ships, submarines, subways, and high-speed rail, heat-insulating and protective layers for robots, flame-retardant and heat-insulating layers for oil depots, fire-resistant and noise-reducing heat-insulating layers for drones, and sound-absorbing and noise-reducing functional layers for high-voltage substations and communication base stations; the cylindrical ceramic nanofiber flocs are suitable for fire-resistant and heat-insulating coverings for ultra-high-voltage cables and pipeline cabins; the funnel-shaped ceramic nanofiber flocs are used as fire-resistant and heat-insulating layers for special pipeline connections and equipment diameter-changing interfaces.

[0019] Compared with the prior art, the present invention has the following advantages: (1) This invention proposes a continuous preparation process for elastic ceramic nanofiber flocs, realizing the continuous production of irregular ceramic fiber flocs throughout the entire process; (2) The present invention designs an elastic ceramic nanofiber floc base preform forming device and an ultrasonic impregnation and homogenization device. The preform is automatically formed by self-rotation winding and real-time glue spraying. Combined with ultrasonic impregnation and homogenization, a preform with a smooth surface and uniform structure is obtained, which solves the problems of weak bonding force and uneven structure of dry pressing method and destruction of fiber continuous morphology and high product brittleness of slurry method. (3) The ceramic nanofiber flocs produced by this invention have excellent heat insulation and noise reduction properties. They can be customized into various irregular structures such as conical, cylindrical, planar, and funnel shapes according to actual needs, which can directly meet the application needs of aerospace, energy infrastructure, safety protection, transportation and other fields. Attached Figure Description

[0020] Figure 1 Schematic diagram of a multi-point micro-disturbance air intake device; Figure 2 A schematic diagram of a periodically arranged spinneret module; Figure 3 Schematic diagram of preform forming device; Figure 4 This is a schematic diagram of the molding module; Figure 5 This is a schematic diagram of an ultrasonic impregnation and homogenization device. Figure 6 This is a schematic diagram of the shape of the prefabricated component.

[0021] In the diagram: 1 is a multi-point micro-disturbance air intake device; 1-1 is a flow stabilizer grille; 1-2 is an air blowing port; 2 is a periodically arranged spinneret module; 2-1 is a single-row spinneret; 2-2 is a double-row spinneret; 3 is a preform forming device; 3-1 is a conveying device; 3-2 is an auxiliary forming roller; 3-3 is a self-rotating forming device; 3-4 is the main mold; 3-5 is a real-time glue spraying device; 4 is a forming module; 4-1 is a preform; 4-2 is a matching mold; 4-3 is the upper fixing port; 4-4 is the lower fixing port; 5 is an ultrasonic impregnation and leveling device; 5-1 is an ultrasonic generator; 5-2 is a mold fixing rod; 5-3 is a water exchange port; 5-4 is an impregnation liquid; 5-5 is a sealing cap; 5-6 is a fixing component. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0023] Example 1: This embodiment provides an elastic ceramic nanofiber flocculent product and its preparation method, the specific steps of which are as follows: (1) Terephthalic acid, the first bidentate linker, was added to toluene (mass ratio of 1:5). This diluted solution was then added to aluminum triethanolamine, where the aluminum salt monomers were linked by the linker as intermediates. A hydrophobic second bidentate linker, acetylacetone, was then added to the system to replace the remaining active monomers of the aluminum salt, forming a linear pre-coordinated framework. The linker content was 10 wt%, the aluminum salt content was 30 wt%, the second bidentate linker content was 10 wt%, and the terephthalic acid content was 50 wt%. Hydrochloric acid was then added to adjust the pH of the reaction system to 3, and a total amount of [missing information] was then introduced into the solution. Aluminum salt monomers are mixed with 15 wt% water, and the linear pre-coordinated framework is condensed into low-polymerization linear inorganic molecular chains under isothermal heating and negative pressure suction. Then, after the chain extension reaction is completed, phenyl isocyanate end-capping agent is added to the system to obtain a spinnable linear inorganic long-chain solution with Al-O as the repeating unit. Finally, the inorganic long-chain solution is added to a solvent (specifically, 80 wt% ethanol, 15 wt% diethyl ether, and 5 wt% N,N-dimethylacetamide) to obtain a spinning solution with a solid content of 20 wt%.

[0024] The spinning solution is loaded into the periodically arranged spinneret module 2. The periodically arranged spinneret module 2 includes alternating first spinnerets 2-1 and second spinnerets 2-2, as well as an electric field control device and a high-voltage electrostatic generator connected to the first spinnerets 2-1 and second spinnerets 2-2. The first spinnerets 2-1 are provided with a plurality of vertical spinning nozzles at intervals along their length, and the second spinnerets 2-2 are provided with two rows of inclined first and second spinning nozzles along their length. That is, the positive electrode of the high-voltage electrostatic generator is connected to each spinning nozzle of the first spinnerets 2-1 and the second spinnerets 2-2, and the negative electrode is connected to the conveyor belt or grounded, thereby forming a high-voltage electrostatic field between the nozzles and the conveyor belt. An airflow field is formed by connecting the air source to the airflow nozzles corresponding to each spinning nozzle. The generation of the high-voltage electrostatic field and the airflow field in this embodiment is consistent with that provided by the prior art, so it will not be elaborated on in this embodiment. The multi-point micro-disturbance air intake device 1 includes a pair of air supply elements disposed on both sides of the periodically arranged spinneret module 2. The air supply elements include a multi-jet head array and a flow stabilizing grid 1-1 disposed on the front side of the multi-jet head array. The axis of the air outlet 1-2 of the jet head in the multi-jet head array is perpendicular to its jet direction. The spinning solution is loaded into the first spinneret 2-1 and the second spinneret 2-2, and an electrostatic field and an airflow field are applied. The solution is subjected to force to form an unstable whip jet, and it is rapidly separated and solidified under the ambient temperature and high humidity (temperature 25℃, relative humidity 50%) environment applied by the multi-point micro-disturbance air intake device 1 to form highly curled precursor nanofibers. (2) The angle between the first inclined spinning nozzle and the second inclined spinning nozzle and the horizontal plane is set to 45° respectively. The running speed of the first spinneret 2-1 and the second spinneret 2-2 is 20cm / min. The running speed of the conveyor belt set below the periodically arranged spinneret module 2 is 2.0m / min. By coordinating the setting of the speed of the first spinneret 2-1 and the second spinneret 2-2 and the conveyor belt, the curled nanofibers are dynamically interwoven in the air and assembled on the conveyor belt into a precursor curled nanofiber floc with a three-dimensional interwoven structure and a thickness of 5cm. Then, it is rapidly calcined at 1000℃ to obtain an elastic ceramic curled nanofiber floc. (3) According to the target cylinder size (inner diameter 40cm, height 60cm), the elastic ceramic nanofiber flocs are cut into rectangular sheets with a width of 60cm and a length slightly larger than the circumference of the target cylinder; (4) Place the cut flakes on the conveyor belt of the conveyor device, set the conveyor belt speed to 0.3m / min, adjust the pressure applied to the flakes by the auxiliary pressure roller to 2.0MPa, and transport the flakes to the self-rotating forming device. While rotating with the cylindrical main mold and winding layer by layer, atomize the surface of the fiber layer with a concentration of 1.5wt% at a rate of 0.5g / min using atomized air pressure of 0.2MPa. (5) After winding and spraying, the main mold covering the preform is removed from the self-rotating molding device and used as the inner core to combine with a cylindrical polytetrafluoroethylene matching mold with an inner diameter of 50cm to form a molding module. The module is fixed as a whole through the upper and lower fixing ports of the module.

[0025] (6) Immerse the fixed molding module into the impregnation tank of the ultrasonic impregnation and leveling device, inject impregnation liquid at a temperature of 25°C into the tank. The impregnation liquid is an ethylene glycol solution. Continue until the liquid surface completely submerges the preform. Start the ultrasonic generator, set the working frequency to 40kHz, and ultrasonically treat for 15 minutes. During this process, the ultrasonic waves promote the uniform penetration of the impregnation liquid into the preform. After the treatment is completed, drain the impregnation liquid through the water exchange port.

[0026] (7) The entire molding module after ultrasonic impregnation is transferred to a cryogenic equipment and kept in a low-temperature environment of -60°C for 4 hours. During this process, the impregnation liquid inside the preform crystallizes in a direction perpendicular to the fiber layer, and the formed ice crystals stitch the layers of the flocs together more tightly.

[0027] (8) Place the low-temperature shaped module in a vacuum drying oven at 50°C for 12 hours to allow the internal ice crystals to sublimate. After drying, first remove the matching mold, and then remove the fully shaped and structurally stable cylindrical elastic ceramic nanofiber preform from the main mold.

[0028] (9) Through the above steps, a cylindrical elastic ceramic nanofiber preform with an inner diameter of 40cm and a height of 60cm was successfully prepared. This preform is suitable for fireproof and heat-insulating coating of ultra-high voltage cables and pipeline cabins.

[0029] Example 2: This embodiment provides an elastic ceramic nanofiber flocculent product and its preparation method, the specific steps of which are as follows: (1) The first bidentate linker, 1,4-naphthyldiamine, was added to a mixed solvent of toluene and petroleum ether (mass ratio of the two was 4:1, and the ratio of linker to solvent was 1:5). Then, the diluted solution was added to aluminum isopropoxide. The aluminum salt monomers were linked by the linker as intermediates. Then, hydrophobic second bidentate dibenzoylmethane was added to the system to replace the remaining active monomers of the aluminum salt, forming a linear pre-coordinated framework. The content of the linker was 12 wt%, the content of the aluminum salt was 26 wt%, the content of the second bidentate was 5 wt%, and the content of the mixed solvent was 57 wt%. Then, acetic acid was added. The pH of the reaction system was adjusted to 4 with acid, and then water of 8 wt% of the mass of the aluminum salt monomer was introduced into the solution. Under constant temperature heating at 45°C and negative pressure suction, the linear pre-coordinated framework was condensed into low-polymerization linear inorganic molecular chains. Then, after the chain extension reaction was completed, isocyanate end-capping agent was added to the system to obtain a spinnable linear inorganic long-chain solution with Al-O as the repeating unit. Finally, the inorganic long-chain solution was added to a solvent (specifically, 65 wt% ethanol, 25 wt% acetone, and 10 wt% N,N-dimethylformamide) to obtain a spinning solution with a solid content of 25 wt%.

[0030] Consistent with the steps in Example 1, the spinning solution is loaded into a dual force field of electrostatics and airflow. The solution is subjected to force to form an unstable whipping jet, and rapidly separates and solidifies under the ambient temperature and high humidity (temperature 25°C, relative humidity 80%) environment applied by the multi-point micro-disturbance air intake device to form highly curled precursor nanofibers. (2) The angle between the first inclined spinning nozzle and the second inclined spinning nozzle and the horizontal plane is set to 55°, the running speed of the first spinneret 2-1 and the second spinneret 2-2 is 30 cm / min, and the running speed of the conveyor belt set below the periodically arranged spinneret module 2 is 0.2 m / min. By coordinating the setting of the speed of the first spinneret 2-1 and the second spinneret 2-2 and the conveyor belt, the coiled nanofibers are dynamically interwoven in the air and assembled on the conveyor belt into a precursor coiled nanofiber floc with a three-dimensional interwoven structure and a thickness of 3 cm. Then, it is rapidly calcined at 1000℃ to obtain an elastic ceramic coiled nanofiber floc. (3) According to the target cone size (inner diameter 50cm, height 60cm), the elastic ceramic nanofiber flocs are cut into trapezoidal sheets that fit the cone surface unfolding shape; (4) Place the cut flakes on the conveyor belt of the conveyor device, set the conveyor belt speed to 0.2m / min, adjust the pressure applied to the flakes by the auxiliary pressure roller to 2.0MPa, and transport the flakes to the self-rotating forming device. While rotating with the conical main mold and winding layer by layer, spray a 5wt% zirconium propoxide solution evenly on the surface of the fiber layer at a rate of 0.15g / min with an atomizing air pressure of 0.2MPa. (5) After the winding and spraying are completed, the main mold covering the conical preform is removed from the self-rotating molding device and used as the inner core to combine with a conical polyurethane matching mold to form a conical cavity molding module. The gap between the matching mold and the main mold is 6cm, and the whole module is locked and fixed through the upper and lower fixing ports of the module.

[0031] (6) Immerse the fixed molding module into the impregnation tank of the ultrasonic impregnation and leveling device, inject impregnation liquid at a temperature of 30°C into the tank. The impregnation liquid is an ethylene glycol solution. Continue until the liquid surface completely submerges the preform. Start the ultrasonic generator, set the working frequency to 50kHz, and ultrasonically treat for 15 minutes. During this process, the ultrasonic waves promote the uniform penetration of the impregnation liquid into the preform. After the treatment is completed, drain the impregnation liquid through the water exchange port.

[0032] (7) The entire molding module after ultrasonic impregnation is transferred to a cryogenic equipment and kept in a low-temperature environment of -10℃ for 12 hours. During this process, the impregnation liquid inside the preform crystallizes in a direction perpendicular to the fiber layer, and the formed ice crystals stitch the layers of the flocs together more tightly.

[0033] (8) Place the low-temperature shaped module in a vacuum drying oven at 60°C for 10 hours to allow the internal ice crystals to sublimate. After drying, first remove the conical matching mold, and then remove the shaped and stable conical elastic ceramic nanofiber preform from the main mold.

[0034] (9) Through the above steps, a conical elastic ceramic nanofiber preform with an inner diameter of 50 cm and a height of 60 cm was successfully prepared. This preform is suitable for high-temperature heat shields for high-speed aircraft.

[0035] Example 3: This embodiment provides an elastic ceramic nanofiber flocculent product and its preparation method, the specific steps of which are as follows: (1) The first bidentate linker, 2,6-diaminoanthraquinone, was added to a mixed solvent of xylene and n-hexane (mass ratio of xylene to hexane was 3:1, and mass ratio of linker to solvent was 1:8). The solution was stirred continuously until completely dissolved. Then, the diluted solution was added to aluminum sec-butoxide. The aluminum salt monomers were linked by the linker as an intermediate. Then, hydrophobic second bidentate acetylacetone was added to the system to replace the remaining active monomers of the aluminum salt, forming a linear pre-coordinated framework. The content of the linker was 8 wt%, the content of the aluminum salt was 32 wt%, the content of the second bidentate was 12 wt%, and the content of the mixed solvent was 48 wt%. Then, the following was added: The pH of the reaction system was adjusted to 3.5 by adding methanesulfonic acid. Then, water with a total mass of 10 wt% of the aluminum salt monomer was introduced into the solution. Under constant temperature heating at 55°C and negative pressure suction, the linear pre-coordinated framework was condensed into low-polymerization linear inorganic molecular chains. After the chain extension reaction was completed, isophorone diisocyanate (IPDI) end-capping agent was added to the system to obtain a spinnable linear inorganic long-chain solution with Al-O as the repeating unit. Finally, the inorganic long-chain solution was added to a solvent (specifically, isopropanol 70 wt%, butanone 20 wt%, and dimethyl sulfoxide 10 wt%) to obtain a spinning solution with a solid content of 18 wt%.

[0036] Consistent with the steps of Example 1, the spinning solution is loaded into a dual force field of electrostatics and airflow. The solution is subjected to force to form an unstable whipping jet, and rapidly separates and solidifies under the ambient temperature and high humidity (temperature 40°C, relative humidity 80%) environment applied by the multi-point micro-disturbance air intake device to form highly curled precursor nanofibers. (2) The angle of the symmetrical tilted nozzle is set to 60°, the running speed of the spinneret is 60cm / min, and the running speed of the conveyor belt is 0.2m / min. By coordinating the speed of the spinneret and the conveyor belt, the coiled nanofibers are dynamically interwoven in the air and assembled into a precursor coiled nanofiber floc with a three-dimensional interwoven structure and a thickness of 3cm. Then, it is rapidly calcined at 1000℃ to obtain an elastic ceramic coiled nanofiber floc. (3) According to the target funnel shape dimensions (upper inner diameter 30cm, lower inner diameter 50cm, vertical height 70cm), the elastic ceramic nanofiber flocs are cut into fan-shaped sheets that fit the curved surface of the funnel. (4) Place the cut flakes on the conveyor belt of the conveyor device, set the conveyor belt speed to 0.2m / min, adjust the pressure applied to the flakes by the auxiliary pressure roller to 1.8MPa, and convey the flakes to the self-rotating forming device. While rotating with the funnel-shaped main mold and winding layer by layer, spray a 0.1wt% tetraethyl orthosilicate solution at a rate of 0.12g / min onto the surface of the fiber layer with an atomizing air pressure of 0.18MPa. (5) After winding and spraying, the main mold covering the funnel-shaped preform is removed from the self-rotating molding device and used as the inner core to combine with a funnel-shaped epoxy resin matching mold to form a funnel forming module. The gap between the matching mold and the main mold is 10cm, and the whole module is locked and fixed through the upper and lower fixing ports of the module.

[0037] (6) Immerse the fixed molding module into the impregnation tank of the ultrasonic impregnation and leveling device, inject impregnation liquid at a temperature of 28°C into the tank, the impregnation liquid is acetone solution, until the liquid surface completely submerges the preform, start the ultrasonic generator, set the working frequency to 45kHz, and ultrasonically treat for 18 minutes. During this process, the ultrasonic waves promote the uniform penetration of the impregnation liquid into the preform. After the treatment is completed, drain the impregnation liquid through the water exchange port.

[0038] (7) The entire molding module after ultrasonic impregnation is transferred to a cryogenic equipment and kept in a low-temperature environment of -100℃ for 12 hours. During this process, the impregnation liquid inside the preform crystallizes in a direction perpendicular to the fiber layer, and the formed ice crystals stitch the layers of the flocs together more tightly.

[0039] (8) Transfer the low-temperature sizing module to the high-pressure autoclave of the supercritical drying device and dry it at 45°C for 10 hours to dry the inside. After drying, first remove the funnel-shaped matching mold, and then remove the sizing funnel-shaped elastic ceramic nanofiber preform from the main mold.

[0040] (9) Through the above steps, a funnel-shaped elastic ceramic nanofiber preform with an upper inner diameter of 30cm, a lower inner diameter of 50cm, and a height of 70cm was successfully prepared. This preform is suitable for fireproof and heat-insulating layers for special pipe connections and equipment diameter-changing interfaces.

[0041] Example 4: This embodiment provides an elastic ceramic nanofiber flocculent product and its preparation method, the specific steps of which are as follows: (1) Tetraethyl orthosilicate was added to anhydrous ethanol (mass ratio of 1:3) to prepare a homogeneous diluted silicon source solution. Then, under stirring, the diluted solution was slowly added to a mixed solvent of deionized water and ethanol (mass ratio of water to ethanol 1:2), and hydrochloric acid was added as a hydrolysis catalyst to adjust the pH of the reaction system to 2-3 to control the hydrolysis rate of silane. The tetraethyl orthosilicate content was 40wt%, the water content was 20wt%, the ethanol content was 35wt%, and the hydrochloric acid content was about 5wt%. The hydrolysis reaction was carried out under constant temperature heating (40℃) to gradually hydrolyze tetraethyl orthosilicate into active silanol monomers containing silanol groups. Then, the system was heated to 6℃ under stirring. At 0℃, and maintaining a slightly negative pressure environment (-0.02 to -0.04 MPa), a dehydration condensation reaction is induced between silanol monomers. By controlling the degree of condensation, a low-polymerization-degree linear inorganic molecular chain with Si-O-Si as the repeating unit is obtained. To prevent excessive cross-linking of the molecular chain, after the condensation reaction reaches the target viscosity, a small amount of trimethylchlorosilane is added to the system as an end-capping agent to react with the active silanol groups at the chain ends, thereby obtaining a spinnable linear inorganic molecular chain solution with passivated end groups and a stable structure. Finally, the inorganic molecular chain solution is concentrated or diluted to adjust the solvent composition by adding appropriate amounts of N,N-dimethylacetamide and acetone, thereby obtaining a silicon-based precursor spinning solution with a solid content of 25 wt% and suitable viscosity and volatility for spinning. The spinning solution is loaded into a dual force field of electrostatics and airflow. The solution is subjected to force to form an unstable whipping jet, and it rapidly separates and solidifies under the ambient temperature and high humidity (temperature 30℃, relative humidity 70%) environment applied by the multi-point micro-disturbance air intake device to form highly curled precursor nanofibers. (2) The angle between the first inclined spinning nozzle and the second inclined spinning nozzle and the horizontal plane is set to 55°, the running speed of the first spinneret 2-1 and the second spinneret 2-2 is 70 cm / min, and the running speed of the conveyor belt set below the periodically arranged spinneret module 2 is 1.0 m / min. By coordinating the setting of the speed of the first spinneret 2-1 and the second spinneret 2-2 and the conveyor belt, the coiled nanofibers are dynamically interwoven in the air and assembled on the conveyor belt into a precursor coiled nanofiber floc with a three-dimensional interwoven structure and a thickness of 5 cm. Then, it is rapidly calcined at 1000℃ to obtain an elastic ceramic coiled nanofiber floc. (3) According to the target cylinder size (inner diameter 30cm, height 60cm), the elastic ceramic nanofiber flocs are cut into rectangular sheets with a width of 60cm and a length slightly larger than the circumference of the target cylinder; (4) Place the cut flakes on the conveyor belt of the conveyor device, set the conveyor belt speed to 0.2m / min, adjust the pressure applied to the flakes by the auxiliary pressure roller to 5.0MPa, and transport the flakes to the self-rotating forming device. While rotating with the cylindrical main mold and winding layer by layer, use 0.2MPa atomized air pressure to uniformly spray 1.5wt% aluminum alkoxide sol at a rate of 0.5g / min onto the surface of the fiber layer. (5) After winding and spraying, the main mold covering the preform is removed from the self-rotating molding device and used as the inner core to combine with a cylindrical polyether ether ketone matching mold with an inner diameter of 40cm to form a molding module. The module is fixed as a whole through the upper and lower fixing ports of the module.

[0042] (6) Immerse the fixed molding module into the impregnation tank of the ultrasonic impregnation and leveling device, inject impregnation liquid at a temperature of 25°C into the tank, the impregnation liquid is propylene glycol solution, until the liquid surface completely submerges the preform, start the ultrasonic generator, set the working frequency to 40kHz, and ultrasonically treat for 15 minutes. During this process, the ultrasonic waves promote the uniform penetration of the impregnation liquid into the preform. After the treatment is completed, drain the impregnation liquid through the water exchange port.

[0043] (7) The entire molding module after ultrasonic impregnation is transferred to a cryogenic equipment and kept in a low-temperature environment of -70°C for 5 hours. During this process, the impregnation liquid inside the preform crystallizes in a direction perpendicular to the fiber layer, and the formed ice crystals stitch the layers of the flocs together more tightly.

[0044] (8) Place the low-temperature shaped module in a vacuum drying oven at 60°C for 10 hours to allow the ice crystals to sublimate. After drying, first remove the matching mold, and then remove the fully shaped and structurally stable cylindrical elastic ceramic nanofiber preform from the main mold.

[0045] (9) Through the above steps, a cylindrical elastic ceramic nanofiber preform with an inner diameter of 30cm and a height of 60cm was successfully prepared. This preform is suitable for fireproof and heat-insulating coating of ultra-high voltage cables and pipeline cabins.

[0046] Example 5: This embodiment provides an elastic ceramic nanofiber flocculent product and its preparation method, the specific steps of which are as follows: (1) The first bidentate linker, 1,4-naphthyldiamine, was added to toluene (mass ratio of 1:10). Then, the diluted solution was added to titanium isopropoxide alkoxide. The linker served as an intermediate to intermittently link the titanium metal salt monomers. Then, the hydrophobic second bidentate linker, trifluoroacetylacetone, was added to replace the remaining active groups of the titanium metal salt, forming a pre-coordinated framework with a linear structure. The content of the linker was 8 wt%, the content of the alkoxide was 30 wt%, the content of the second bidentate linker was 2 wt%, and the content of toluene was 60 wt%. Then, hydrochloric acid was added to adjust the pH of the reaction system. For step 3, water of 10 wt% of the metal alkoxide monomer mass is introduced into the solution, and the linear pre-coordinated framework is condensed into low-polymerization linear inorganic molecular chains under constant temperature heating and negative pressure suction. Then, after the chain extension reaction is completed, methyl isocyanate end-capping agent is added to the system to obtain a spinnable linear inorganic long-chain solution with Ti-O as the repeating unit. Finally, the inorganic long-chain solution is added to a solvent (specifically, 70 wt% ethanol, 20 wt% diethyl ether, and 10 wt% N,N-dimethylacetamide) to obtain a spinning solution with a solid content of 10 wt%.

[0047] The spinning solution is loaded into a dual force field of electrostatics and airflow. The solution is subjected to force to form an unstable whipping jet, and it rapidly separates and solidifies under the ambient temperature and high humidity (temperature 20℃, relative humidity 80%) environment applied by the multi-point micro-disturbance air intake device to form highly curled precursor nanofibers. (2) The angle between the first inclined spinning nozzle and the second inclined spinning nozzle and the horizontal plane is set to 65°, the running speed of the first spinneret 2-1 and the second spinneret 2-2 is 70 cm / min, and the running speed of the conveyor belt set below the periodically arranged spinneret module 2 is 1.5 m / min. By coordinating the setting of the speed of the first spinneret 2-1 and the second spinneret 2-2 and the conveyor belt, the curled nanofibers are dynamically interwoven in the air and assembled on the conveyor belt into a precursor curled nanofiber floc with a three-dimensional interwoven structure and a thickness of 3 cm. Then, it is rapidly calcined at 900°C to obtain an elastic ceramic curled nanofiber floc. (3) According to the target cone size (inner diameter 40cm, height 60cm), the elastic ceramic nanofiber flocs are cut into trapezoidal sheets that fit the cone surface unfolding shape; (4) Place the cut flakes on the conveyor belt of the conveyor device, set the conveyor belt speed to 0.2m / min, adjust the pressure applied to the flakes by the auxiliary pressure roller to 2.0MPa, and transport the flakes to the self-rotating forming device. While rotating with the conical main mold and winding layer by layer, spray water glass with a concentration of 5wt% at a rate of 0.15g / min at an atomizing air pressure of 0.2MPa. (5) After the winding and spraying are completed, the main mold covering the conical preform is removed from the self-rotating molding device and used as the inner core to combine with a conical polyurethane matching mold to form a conical cavity molding module. The gap between the matching mold and the main mold is 10cm, and the whole module is locked and fixed through the upper and lower fixing ports of the module.

[0048] (6) Immerse the fixed molding module into the impregnation tank of the ultrasonic impregnation and leveling device, inject impregnation liquid at a temperature of 30°C into the tank. The impregnation liquid is composed of acetone. Continue until the liquid surface completely submerges the preform. Start the ultrasonic generator, set the working frequency to 50kHz, and perform ultrasonic treatment for 30 minutes. During this process, the ultrasonic waves promote the uniform penetration of the impregnation liquid into the preform. After the treatment is completed, drain the impregnation liquid through the water exchange port.

[0049] (7) The entire molding module after ultrasonic impregnation is transferred to a cryogenic equipment and kept in a low-temperature environment of -100℃ for 12 hours. During this process, the impregnation liquid inside the preform crystallizes in a direction perpendicular to the fiber layer, and the formed ice crystals stitch the layers of the flocs together more tightly.

[0050] (8) Transfer the low-temperature sizing module to the high-pressure vessel of the supercritical drying device and dry it at 50°C for 10 hours. After drying, first remove the conical matching mold, and then remove the sizing and structurally stable conical elastic ceramic nanofiber preform from the main mold.

[0051] (9) Through the above steps, a conical elastic ceramic nanofiber preform with an inner diameter of 40 cm and a height of 60 cm was successfully prepared. This preform is suitable for high-temperature heat shields for high-speed aircraft.

[0052] Example 6: This embodiment provides an elastic ceramic nanofiber flocculent product and its preparation method, the specific steps of which are as follows: (1) Tetraethyl orthosilicate was added to anhydrous ethanol (mass ratio of 1:3) to prepare a silicon source dilution solution. Then, under stirring, deionized water and hydrochloric acid were added to the dilution solution to adjust the pH to 2-3. The solution was hydrolyzed at a constant temperature of 40°C for 1 hour to obtain a pre-hydrolyzed silica sol containing silanol active sites. The tetraethyl orthosilicate content was 40wt%, the water content was 20wt%, the ethanol content was 35wt%, and the hydrochloric acid content was 5wt%. The solution was set aside. At the same time, terephthalic acid linker was added to toluene (compared to 1:5) and stirred. After dissolution, the diluted solution is added to aluminum triethanolamine. A linker acts as an intermediate to interlock the aluminum salt monomers. Then, a hydrophobic second bidentate linker, acetylacetone, is added to the system to replace the remaining active monomers of the aluminum salt, forming a linear aluminum-based pre-coordinated framework. The aluminum-based pre-coordinated framework contains 10 wt% terephthalic acid, 30 wt% aluminum triethanolamine, 10 wt% acetylacetone, and 50 wt% toluene. The pre-hydrolyzed silica sol and the aluminum-based pre-coordinated framework solution are mixed at a mass ratio of 1:2 under stirring. The mixing rate was controlled by slow dropwise addition. After the addition was complete, the temperature was raised to 50°C and reacted at a constant temperature for 1 hour to allow the active segments containing silanol groups to undergo a co-condensation reaction with the aluminum-based pre-coordinated framework, forming an aluminum-silicon composite prepolymer containing Si-O-Al heterobonding. Then, hydrochloric acid was added to adjust the pH of the reaction system to 3-4. Subsequently, water with a total volume of 15wt% of the mass of aluminum triethanolamine in the aluminum-based pre-coordinated framework was introduced into the solution, and the aluminum-silicon composite prepolymer was further condensed into low-polymerization linear inorganic molecular chains under constant temperature heating at 60°C and negative pressure suction of -0.06MPa. After the initial reaction is completed and the viscosity of the system reaches the spinnable value, a phenyl isocyanate end-capping agent is added to the system. The amount of end-capping agent added is 10 wt% of the mass of aluminum triethanolamine in the aluminum-based pre-coordinated framework. It reacts with the active hydroxyl groups at the chain ends to obtain a spinnable linear inorganic long-chain solution with Si-O-Al as the repeating unit and a stable structure. Finally, the inorganic long-chain solution is added to a mixed solvent (specifically, 80 wt% ethanol, 15 wt% diethyl ether, and 5 wt% N,N-dimethylacetamide) and the solid content is adjusted to 20 wt% to obtain a uniform and transparent aluminum-silicon composite spinning solution.

[0053] Consistent with the steps in Example 1, the aluminum-silicon composite spinning solution is loaded into a dual force field of electrostatics and airflow. The solution is subjected to force to form an unstable whipping jet, and rapidly separates and solidifies under the ambient temperature and high humidity (temperature 25°C, relative humidity 80%) environment applied by the multi-point micro-disturbance air intake device to form highly curled precursor nanofibers. (2) The angle between the first inclined spinning nozzle and the second inclined spinning nozzle and the horizontal plane is set to 80°, the running speed of the first spinneret 2-1 and the second spinneret 2-2 is 100cm / min, and the running speed of the conveyor belt set below the periodically arranged spinneret module 2 is 1.7m / min. By coordinating the setting of the speed of the first spinneret 2-1 and the second spinneret 2-2 and the conveyor belt, the curled nanofibers are dynamically interwoven in the air and assembled on the conveyor belt into a precursor curled nanofiber floc with a three-dimensional interwoven structure and a thickness of 3cm. Then, it is rapidly calcined at 1000℃ to obtain an elastic ceramic curled nanofiber floc. (3) According to the target funnel shape dimensions (upper inner diameter 60cm, lower inner diameter 30cm, vertical height 60cm), the elastic ceramic nanofiber flocs are cut into fan-shaped sheets that fit the curved surface of the funnel. (4) Place the cut wadding on the conveyor belt of the conveyor device, set the conveyor belt speed to 0.3 m / min, adjust the pressure applied to the wadding by the auxiliary pressure roller to 1.5 MPa, and convey the wadding to the self-rotating forming device. While rotating with the funnel-shaped main mold and winding layer by layer, spray a 0.1 wt% tetraethyl orthosilicate solution at a rate of 0.12 g / min with an atomizing air pressure of 0.15 MPa. (5) After winding and spraying, the main mold covering the funnel-shaped preform is removed from the self-rotating molding device and used as the inner core to combine with a funnel-shaped epoxy resin matching mold to form a funnel forming module. The gap between the matching mold and the main mold is 10cm, and the whole module is locked and fixed through the upper and lower fixing ports of the module.

[0054] (6) Immerse the fixed molding module into the impregnation tank of the ultrasonic impregnation and leveling device, inject impregnation liquid at a temperature of 28°C into the tank. The impregnation liquid is an ethylene glycol solution. Continue until the liquid surface completely submerges the preform. Start the ultrasonic generator, set the working frequency to 45kHz, and ultrasonically treat for 20 minutes. During this process, the ultrasonic waves promote the uniform penetration of the impregnation liquid into the preform. After the treatment is completed, drain the impregnation liquid through the water exchange port.

[0055] (7) The entire molding module after ultrasonic impregnation is transferred to a cryogenic equipment and kept in a low-temperature environment of -70°C for 12 hours. During this process, the impregnation liquid inside the preform crystallizes in a direction perpendicular to the fiber layer, and the formed ice crystals stitch the layers of the flocs together more tightly.

[0056] (8) Transfer the low-temperature sizing module to the high-pressure autoclave of the supercritical drying device and dry it at 60°C for 10 hours to dry the inside. After drying, first remove the funnel-shaped matching mold, and then remove the sizing funnel-shaped elastic ceramic nanofiber preform from the main mold.

[0057] (9) Through the above steps, a funnel-shaped elastic ceramic nanofiber preform with an upper inner diameter of 60cm, a lower inner diameter of 30cm, and a height of 60cm was successfully prepared. This preform is suitable for fireproof and heat-insulating layers for special pipe connections and equipment diameter-changing interfaces.

[0058] Example 7: Example 7, as a special case of application for planar products, differs from the layer-by-layer winding of the above examples. This example achieves layer-by-layer bonding through a liftable platform and real-time adhesive spraying. The specific process is as follows: (1) The first bidentate linker, 5-hydroxyisophthalic acid, was added to a mixed solvent of xylene and n-butyl ether (mass ratio of xylene to n-butyl ether: 3:2, mass ratio of linker to solvent: 1:6). The diluted solution was then slowly added dropwise to aluminum trisec-butoxide. The aluminum salt monomers were interleaved by the linker, which served as an intermediate. Then, the hydrophobic second bidentate linker, benzoyltrifluoroacetone, was added to the system to replace the remaining active monomers of the aluminum salt, forming a linear pre-coordinated framework. The content of the linker was 7 wt%, the content of the aluminum salt was 33 wt%, the content of the second bidentate linker was 9 wt%, and the content of the mixed solvent was 51 wt%. Then, the following was added: Citric acid was added to adjust the pH of the reaction system to 5. Then, water, with a total volume of 6 wt% of the aluminum salt monomer, was introduced into the solution. Under constant temperature heating at 55°C and negative pressure suction, the linear pre-coordinated framework was condensed into low-polymerization linear inorganic molecular chains. After the chain extension reaction was completed, p-toluenesulfonyl isocyanate end-capping agent was added to the system to obtain a spinnable linear inorganic long-chain solution with Al-O as the repeating unit. Finally, the inorganic long-chain solution was added to a solvent (specifically, methanol 60 wt%, tetrahydrofuran 30 wt%, and N-methylpyrrolidone 10 wt%) to obtain a spinning solution with a solid content of 16 wt%.

[0059] Consistent with the steps in Example 1, the spinning solution is loaded into a dual force field of electrostatics and airflow. The solution is subjected to force to form an unstable whipping jet, and rapidly separates and solidifies under the ambient temperature and high humidity (temperature 30°C, relative humidity 80%) environment applied by the multi-point micro-disturbance air intake device to form highly curled precursor nanofibers. (2) The angle between the first inclined spinning nozzle and the second inclined spinning nozzle and the horizontal plane is set to 60°, the running speed of the first spinneret 2-1 and the second spinneret 2-2 is 50cm / min, and the running speed of the conveyor belt set below the periodically arranged spinneret module 2 is 0.1m / min. By coordinating the setting of the first spinneret 2-1 and the second spinneret 2-2 and the speed of the conveyor belt, the coiled nanofibers are dynamically interwoven in the air and assembled on the conveyor belt into a precursor coiled nanofiber floc with a three-dimensional interwoven structure and a thickness of 6cm. The floc is then pressed by a pressure roller to obtain a thin and dense ceramic nanofiber floc with a thickness of 3cm. Then, it is rapidly calcined at 1200℃ to obtain an elastic ceramic coiled nanofiber floc. (3) According to the planar dimensions of the target planar product (40cm×60cm), the elastic ceramic nanofiber flocs are cut into rectangular sheets of the corresponding size; (4) Place the cut flakes on the conveyor belt of the conveyor device, set the conveyor belt speed to 0.4 m / min, adjust the auxiliary pressure roller to apply a pressure of 2.0 MPa to the flakes, and after the flakes are pressed by the pressure roller, they are continued to be conveyed to the flat forming platform. The platform is composed of a liftable support structure, and the real-time glue spraying device above it operates synchronously. With an atomizing air pressure of 0.05 MPa, the silica sol with a concentration of 1.5 wt% is uniformly sprayed on the surface of the continuously fed flakes at a rate of 0.05 g / min to achieve interlayer bonding and preliminary shaping.

[0060] (5) After the adhesive is applied, the pre-formed flat part is removed from the flat forming platform and used as the inner core. It is then aligned with a flat polyethylene matching mold with dimensions of 45cm×65cm×25cm to form a closed flat forming module. The inner core and the matching mold are fixed together through the pre-set upper and lower fixing ports on the module.

[0061] (6) Immerse the fixed molding module into the impregnation tank of the ultrasonic impregnation and leveling device, inject impregnation liquid at a temperature of 30°C into the tank. The impregnation liquid is an ethylene glycol solution. Continue until the liquid surface completely submerges the preform. Start the ultrasonic generator, set the working frequency to 50kHz, and ultrasonically treat for 15 minutes. During this process, the ultrasonic waves promote the uniform penetration of the impregnation liquid into the preform. After the treatment is completed, drain the impregnation liquid through the water exchange port.

[0062] (7) The entire molding module after ultrasonic impregnation is transferred to a cryogenic equipment and kept in a low-temperature environment of -70°C for 4 hours. During this process, the impregnation liquid inside the preform crystallizes in a direction perpendicular to the fiber layer, and the formed ice crystals stitch the layers of the flocs together more tightly.

[0063] (8) Place the low-temperature shaped module in a vacuum drying oven at 60°C for 12 hours to completely remove the internal ice crystals. After drying, first remove the matching mold, and then remove the fully shaped and structurally stable planar elastic ceramic nanofiber preform from the main mold.

[0064] (9) Through the above steps, a planar elastic ceramic nanofiber preform of 40cm×60cm×20cm was successfully prepared. This preform is suitable for battery heat insulation pads and fireproof blankets for new energy vehicles, fireproof insulation and noise reduction layers for the exterior walls of high-rise buildings, flame-retardant insulation layers for biomedical storage and cold chain transportation, flame-retardant and noise-reducing insulation materials for large aircraft, ships, submarines, subways and high-speed railways, heat insulation and protection layers for robots, flame-retardant insulation layers for oil depots, fireproof and noise-reducing insulation layers for drones, and sound-absorbing and noise-reducing functional layers for high-voltage substations and communication base stations.

[0065] Example 8: Example 8, as a special case of planar component application, differs from the layer-by-layer winding and flat stacking of the above examples. In this example, no further processing is performed on the calcined flakes; they are applied directly after calcination. The specific process is as follows: (1) First-didentate phenylenediamine was added to p-xylene (mass ratio of the two was 1:8), and then the diluted solution was added to zirconium isopropoxide. A linker was used as an intermediate to link the metal alkoxide monomers intermittently. Then, a hydrophobic second-didentate linker, hexafluoroacetylacetone, was added to replace the remaining active groups of the metal alkoxide, forming a linear pre-coordinated framework. The content of the linker was 8 wt%, the content of the alkoxide was 22 wt%, the content of the second-didentate linker was 6 wt%, and the content of xylene was 64 wt%. Then, hydrochloric acid was added to adjust the pH of the reaction system to 3.5. Then, water of 12 wt% of the total mass of the metal alkoxide monomer is introduced into the solution, and the linear pre-coordinated framework is condensed into low-polymerization linear inorganic molecular chains under constant temperature heating and negative pressure suction. Then, after the chain extension reaction is completed, phenyl isocyanate end-capping agent is added to the system to obtain a spinnable linear inorganic long-chain solution with Zr-O as the repeating unit. Finally, the inorganic long-chain solution is added to a solvent (specifically, 80 wt% ethanol, 15 wt% diethyl ether, and 5 wt% N,N-dimethylacetamide) to obtain a spinning solution with a solid content of 15 wt%.

[0066] The spinning solution is loaded into a dual force field of electrostatics and airflow. The solution is subjected to force to form an unstable whipping jet, and it rapidly separates and solidifies under the ambient temperature and high humidity (temperature 20℃, relative humidity 90%) environment applied by the multi-point micro-disturbance air intake device to form highly curled precursor nanofibers. (2) The angle between the first inclined spinning nozzle and the second inclined spinning nozzle and the horizontal plane is set to 40°, the running speed of the first spinneret 2-1 and the second spinneret 2-2 is 100cm / min, and the running speed of the conveyor belt set below the periodically arranged spinneret module 2 is 2.0m / min. By coordinating the setting of the speed of the first spinneret 2-1 and the second spinneret 2-2 and the conveyor belt, the curled nanofibers are dynamically interwoven in the air and assembled on the conveyor belt into a precursor curled nanofiber floc with a three-dimensional interwoven structure and a thickness of 6cm. Then, it is rapidly calcined at 900℃ to obtain an elastic ceramic curled nanofiber floc. (3) According to the planar dimensions of the target planar product (30cm×60cm), the elastic ceramic nanofiber flocs are cut into rectangular sheets of the corresponding size; (4) Through the above steps, a planar elastic ceramic nanofiber preform of 30cm×60cm×6cm was successfully prepared. This planar preform is suitable for the core functional layer of battery heat insulation pads and fire blankets and fire-fighting heat insulation clothing for new energy vehicles.

[0067] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for preparing an elastic ceramic nanofiber flocculent product, characterized in that, Includes the following steps: S1. The prepared inorganic long-chain spinning solution is loaded onto the spinning nozzle, and an auxiliary force field is applied to stretch the spinning solution to form a whip jet. At the same time, the airflow is delivered by the multi-point micro-disturbance air intake device (1) to solidify the whip jet and obtain the precursor coiled nanofiber. Then, the precursor coiled nanofiber is dynamically assembled in the air by periodically arranging the spinneret module (2) to obtain the precursor nanofiber flake with a three-dimensional interwoven structure. Finally, the precursor nanofiber flocs were calcined at high temperature to obtain elastic ceramic nanofiber flocs. S2. The elastic ceramic nanofiber flocs prepared in S1 are sequentially cut, shaped, ultrasonically impregnated and homogenized, low-temperature settling and dried to obtain ceramic nanofiber floc products. S21. Cut the elastic ceramic nanofiber flocs obtained in S1 according to the desired product shape to obtain multiple pre-made sheets; S22. The multiple prefabricated sheets obtained in S1 are placed sequentially on the conveying device (3-1), and wound around the main mold (3-4) set around the self-rotating forming device (3-3) under the drive of the auxiliary forming roller (3-2). The surface of the prefabricated sheets is sprayed with glue by the glue spraying device (3-5) so that the multiple prefabricated sheets are bonded together to form a prefabricated part. S23. Remove the main mold (3-4) and the preforms on it and place them in the matching mold (4-2) to form a molding module (4); place the molding module (4) into the ultrasonic impregnation and leveling device (5) and the impregnation liquid penetrates into the preforms in the molding module (4); S24. The molding module (4) is placed in a low-temperature environment. The impregnation liquid of the preform in the molding module (4) forms ice crystals in a direction perpendicular to the fiber layer. The ice crystals tightly stitch the multiple preform sheets together. S25. After drying the molding module (4) and removing the matching mold (4-2), the elastic ceramic nanofiber flocculent product is obtained.

2. The method for preparing an elastic ceramic nanofiber flocculent product according to claim 1, characterized in that, The periodically arranged spinneret module (2) includes alternating first spinnerets (2-1) and second spinnerets (2-2). The first spinneret (2-1) has multiple vertical spinning nozzles spaced apart along its length. The second spinneret (2-2) has two rows of staggered first and second inclined spinning nozzles along its length. The first spinneret (2-1) and the second spinneret (2-2) operate at a speed of 20~100cm / min, and the conveyor belt operates at a speed of 0.2~2.0m / min. The multi-point micro-disturbance air intake device (1) includes air supply units symmetrically arranged on both sides of the periodically arranged spinneret module (2). Each air supply unit includes a flow stabilizing grid (1-1) and a multi-jet head array connected to the flow stabilizing grid. The jet heads of the multi-jet head array include coaxially arranged inner and outer tubes. The inner tube cavity forms an inner channel, and the gap between the inner and outer tubes forms an outer channel. The inner channel supplies temperature-controlled dry airflow, and the outer channel is used to introduce humidity-controlled humid airflow. The air supply unit has a nozzle density ≥900 / m³. 2 The airflow velocity is 0.5~5m / s, the temperature is 10~50℃, and the humidity is 10~99%.

3. The method for preparing an elastic ceramic nanofiber flocculent product according to claim 1, characterized in that, The product forming device (3) includes a self-rotating forming device (3-3), a pair of feeding components arranged on both sides of the self-rotating forming device (3-3), the feeding components including a pair of auxiliary forming rollers (3-2) arranged sequentially from the inside to the outside of the self-rotating forming device (3-3), and a conveying device (3-1). A main mold (3-4) is arranged around the self-rotating forming device (3-3), and a glue spraying device (3-5) is arranged above or below the self-rotating forming device (3-3). The conveying device (3-1) includes a conveyor belt and a rotating roller arranged below the conveyor belt, which can convey the cut fiber flakes to the auxiliary forming pressure roller (3-2). The linear speed of the conveyor belt is 0.1~0.5m / min. The pair of auxiliary forming rollers (3-2) are a pair of circular rollers spaced apart vertically, which can apply a pressure of 0.1~10MPa to the flakes and transport the flakes to the self-rotating forming device (3-3). The rotational speed of the self-rotating forming device (3-3) is 0.5~5 rpm; The nozzle of the adhesive spraying device (3-5) is a wide-angle atomizing nozzle designed to prevent clogging. The amount of adhesive sprayed is 0.05~0.5g / min, and the atomizing pressure is 0.05~0.2MPa. The adhesive used for spraying is selected from one or more of the following: water glass, silica sol, tetraethyl orthosilicate solution, aluminum alkoxide solution, zirconium propoxide solution, tetraisopropyl titanate solution, and gallium ethoxide solution, and the sol concentration is 0.1~5wt%.

4. The method for preparing an elastic ceramic nanofiber flocculent product according to claim 1, characterized in that, The molding module (4) includes a main mold (3-4) and a matching mold (4-2) fitted around the main mold (3-4). The matching mold (4-2) is provided with an upper fixing port (4-3) and a lower fixing port (4-4) at the top and bottom respectively. The main mold (3-4) and the matching mold (4-2) can be any one of the following shapes: cylindrical, conical, funnel-shaped, or planar. The main mold (3-4) and the matching mold (4-2) are made of one of the following materials: stainless steel, alloy steel, polyether ether ketone, polyurethane, epoxy resin, liquid silicone, polytetrafluoroethylene, and polyethylene.

5. The method for preparing an elastic ceramic nanofiber flocculent product according to claim 1, characterized in that, The ultrasonic impregnation and homogenization device (5) includes a housing, a sealing cover (5-5) on the top of the housing, and a fixing member (5-6) inside the housing, a mold fixing rod (5-2) above the fixing member (5-6), and an ultrasonic generator (5-1) on the side of the fixing member (5-6); a water exchange port (5-3) is also provided at the bottom of the housing, and the impregnation liquid (5-4) is contained inside the housing.

6. The method for preparing an elastic ceramic nanofiber flocculent product according to claim 1, characterized in that, In S1, the calcination temperature of the precursor nanofiber flocs is set to 200~1500℃; the thickness of the elastic ceramic nanofiber flocs is 0.2~10cm. The external force in the auxiliary force field is selected from one or a combination of electrostatic force, airflow force, and centrifugal force.

7. The method for preparing an elastic ceramic nanofiber flocculent product according to claim 1, characterized in that, In S23, the gap width between the main mold (3-4) and the matching mold (4-2) is 5~10cm.

8. The method for preparing an elastic ceramic nanofiber flocculent product according to claim 1, characterized in that, In S24, the temperature of the low-temperature environment is -100~-5℃, and the temperature of the preform is 15~30℃.

9. The method for preparing an elastic ceramic nanofiber flocculent product according to claim 1, characterized in that, In S25, the drying process is selected from one or more of vacuum drying, supercritical drying, and atmospheric pressure drying.

10. An application of the elastic ceramic nanofiber flocs prepared by the preparation method according to any one of claims 1-9, characterized in that, It is used in flame-retardant materials, heat-insulating materials, thermal insulation materials, and sound-absorbing and noise-reducing materials.

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