A flexible ceramic ultrafine fiber material based on air stream blowing and a preparation method thereof

Abstract

The present application belongs to the technical field of ceramic ultra-fine fiber material, and relates to a flexible ceramic ultra-fine fiber material based on airflow blowing and a preparation method thereof. First, a polar solvent is mixed with a metal alkoxide and stirred to obtain a low-activity functional modified metal alkoxide through an association reaction; then, deionized water and a non-ionic surfactant are added and ultrasonically dispersed to obtain an ultra-fine colloidal particle stable sol after concentration; subsequently, a cyclone auxiliary environment atmosphere control and a heat auxiliary fiber receiving technology are combined to perform airflow blowing through a 'V-shaped' spinneret, and a multi-morphology ceramic precursor fiber material is obtained after drying; then, after being ceramized through an array type laser spot welding technology, the flexible ceramic ultra-fine fiber material is obtained through a flash crystal technology 'ultra-high speed heating-rapid cooling' treatment. The flexible ceramic ultra-fine fiber material has an average fiber diameter of 10-800 nm, a grain size of 2-30 nm, and a bending stiffness of 30-100 mN.

Description

Technical Field

[0001] This invention belongs to the field of ceramic microfiber material technology, and relates to a flexible ceramic microfiber material based on airflow blowing and its preparation method. Background Technology

[0002] Ceramic ultrafine fiber materials combine the advantages of ceramic materials, such as high temperature resistance, corrosion resistance, and oxidation resistance, with the characteristics of ultrafine fibers, such as high porosity, large specific surface area, light weight, and small size effect, occupying an irreplaceable position in key fields such as aerospace, energy and chemical industry, and electronic information. Currently, ceramic ultrafine fibers can be obtained by spinning inorganic sol-gel spinning solutions using air-blowing technology. Among these steps, the properties of the inorganic sol and the ceramization step of the precursor fibers are the key steps in the preparation of ceramic ultrafine fibers by the sol-gel method.

[0003] However, during sol-gel formation, excessively rapid hydrolysis of metal alkoxide monomers can induce cross-linking reactions, forming branched gel networks. Conversely, excessively slow monomer condensation rates hinder further chain extension of oligomers, resulting in low molecular chain entanglement and difficulty in obtaining spinnable inorganic sols. Currently, to increase the viscosity of inorganic sols, spinning aids such as polymers are added, followed by high-temperature calcination to remove them, yielding ceramic fibers. However, the thermal decomposition of spinning aids during calcination generates numerous pore defects within the single fiber. Furthermore, the high-temperature conditions of traditional calcination processes tend to lead to larger grain sizes within the single fiber, making these ceramic ultrafine fibers highly susceptible to stress concentration and brittle fracture or even pulverization under external forces, failing to meet practical application requirements.

[0004] To overcome the above shortcomings, some researchers have explored various approaches. For example, patent ZL202111391693.8 utilizes monodentate and bridging ligands to conduct multiple coordination reactions with alkoxides. After controlling the number of functional groups of the alkoxide monomer to approximately two, the alkoxide undergoes a controlled hydrolysis-condensation reaction along a linear direction, followed by vacuum distillation to obtain a linear inorganic sol without the addition of a polymer template. However, this method may result in particle agglomeration during concentration, forming secondary particles or larger aggregates, making it difficult to achieve a high degree of matching between the gelation rate and the fiber-forming process, thus preventing further drawing and refining during spinning. Patent CN202311309911.8 spins spinnable alumina gel and then microwaves it under air atmosphere and normal pressure at a heating rate of 50~100℃ / min to obtain dense alumina ceramic fibers with a diameter of 10~20μm and an average grain size of 110nm. However, the ceramic fibers produced by this method have a relatively coarse diameter and large grain size, which cannot further improve the flexibility of the ceramic fibers. Patent CN202410747348.0 improves the crystallinity and density of boron nitride ceramic fibers through yttrium aluminum synergistic doping to enhance the mechanical properties of boron nitride fibers. However, this method introduces heteroatoms, making it impossible to obtain pure ceramic ultrafine fibers.

[0005] Therefore, there is an urgent need to develop a method for obtaining flexible ceramic ultrafine fiber materials with small and uniform inorganic sol particles that can be spun directly without relying on spinning aids, while suppressing fiber grain coarsening during the ceramization stage. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of the prior art and provide a flexible ceramic microfiber material based on airflow blowing and its preparation method.

[0007] The objective of this invention can be achieved through the following technical solutions: A method for preparing flexible ceramic microfiber materials based on air-blown spinning includes the following steps: S1: A polar solvent is mixed with a metal alkoxide and stirred to carry out an association reaction, resulting in a low-activity functional modified metal alkoxide. S2: Deionized water is added to the functional modified metal alkoxide obtained in step S1 to carry out hydrolysis-condensation reaction. At the same time, a nonionic surfactant is added and ultrasonically dispersed. After concentration, a spinnable ultrafine colloid stabilized sol is obtained. S3: The ultrafine sol obtained in step S2 is extruded from the spinneret and blown by airflow. The blown spinning is aided by vortex airflow pressurization to refine the fiber. After drying, a multi-morphological ceramic precursor fiber material is obtained. S4: Pre-ceramicize the ceramic precursor fiber material obtained in step S3 using array laser spot welding technology to obtain laser-anchored shrinkage-controlled ceramic fiber material. S5: The laser-anchored shrinkage-controlled ceramic fiber material obtained in step S4 is ceramicized using scintillation technology to obtain a flexible ceramic ultrafine fiber material.

[0008] Further, in step S1, the polar solvent is selected from one or more of triethylamine, acetone, dimethyl sulfoxide, methanol, ethanol, isopropanol, n-butanol, isobutanol, tert-butanol, tert-amyl alcohol, ethylene glycol, benzyl alcohol, formic acid, acetic acid, acetoacetic acid, acetylacetone, N-methylpyrrolidone, N,N-dimethylformamide, or N,N-dimethylacetamide; The metal alkoxide is selected from one or more of silicon source, aluminum source, zirconium source or titanium source; The mass ratio of the metal alkoxide to the polar solvent is 1:0.1~2; The stirring rate is 100~1000 r / min; The association reaction is carried out at a temperature of 40~100℃ for a time of 1~48h.

[0009] Furthermore, the silicon source is selected from one or more of tetraethyl orthosilicate, tetra-n-butoxysilane, tetra-n-propoxysilane, trimethylsilyl acetate, or vinyltriethoxysilane; The aluminum source is selected from one or more of aluminum n-propoxide, aluminum isopropoxide, aluminum sec-butoxide, aluminum n-butoxide, aluminum tert-butoxide, aluminum isobutoxide, aluminum neopentyl alcohol, aluminum n-octanol, or aluminum ethoxide; The zirconium source is selected from one or more of zirconium tetraethanolamine, zirconium isopropoxide, zirconium n-butoxide, zirconium isobutoxide, zirconium tert-butoxide, or zirconium tetrapentoxide. The titanium source is selected from one or more of titanium tetramethanol, titanium n-propoxide, titanium isopropoxide, titanium n-butoxide, titanium tert-butoxide, titanium tetrapentoxide, or titanium isooctoxide.

[0010] Further, in step S2, the mass fraction of the functionally modified metal alkoxide in the ultrafine colloidal stabilized sol is 20-50 wt%, and the amount of nonionic surfactant added is 0.1-10 wt% of the functionally modified metal alkoxide. The nonionic surfactant is selected from one or more of polyethylene glycol, poly(N,N-diethylacrylamide), polyoxyethylene alkyl ether, glyceryl monostearate, polyether-modified siloxane, or 4-diethoxymethylsilylbutylamine. The hydrolysis-condensation reaction is carried out at a temperature of 30~100℃ and a reaction time of 1~18h; the hydrolysis-condensation reaction is carried out under constant temperature conditions.

[0011] The average particle size of the spinnable ultrafine sol is 1~10 nm.

[0012] Furthermore, in step S3, the vortex airflow pressurized assisted blow spinning process utilizes the pressurization effect generated by the rapid flow of airflow between narrow spinnerets to form a vortex airflow, so as to promote the ultrafine sol particles to undergo tensile deformation due to the full stretching force of the airflow. The spinneret is a "V-shaped" spinneret, wherein the inner diameter of the spinning solution outlet is 0.075~0.15mm and the wall thickness is 0.1~0.2mm, the inner diameter of the airflow outlet is 1.25~6.5mm and the wall thickness is 0.1~0.2mm, and the included angle of the V-groove is 60~120°. The extrusion rate of the spinneret is 0.1~100mL / h; The velocity of the vortex airflow is 1~50m / s; The spinning region of the airflow blowing process exhibits a temperature and humidity gradient distribution.

[0013] The temperature and humidity gradient distribution is achieved through a cyclone-assisted environmental atmosphere control module, which includes an arc-shaped guide plate and a hot and humid air jet unit. Specifically, an arc-shaped guide plate is installed in the spinning area, and a hot and humid air jet device is installed on the guide plate. By controlling the temperature and humidity gradient distribution in each area of ​​the spinning environment, and utilizing the difference in the curing and shaping rate of inorganic sol under different temperatures and humidity, precise control of continuous inorganic precursor ultrafine fibers is achieved under the coupling effect of temperature and humidity. The drying process is carried out using a perforated heating receiving plate at a temperature of 40-80°C. The perforated heating receiving plate consists of a heating rod attached below it. This heat-assisted fiber receiving technology promotes the rapid evaporation of residual solvents in the fiber material.

[0014] Furthermore, the spinning region is divided into three areas, from top to bottom: spinning area 1, spinning area 2, and spinning area 3. The length ratio of spinning area 1, spinning area 2, and spinning area 3 is 2:1.5:1. The spinning region exhibits a temperature and humidity gradient distribution, with the temperature and humidity gradually increasing. The temperature satisfies the formula T. n =T0+5(n-1), humidity satisfies formula H n =H0+10(n-1), where n=1, 2, 3, T0 is the gradient starting temperature 20~60℃, T1 is the temperature of spinning zone 1, T2 is the temperature of spinning zone 2, T3 is the temperature of spinning zone 3; H0 is the gradient starting humidity 10~50%, H1 is the humidity of spinning zone 1, H2 is the humidity of spinning zone 2, H3 is the humidity of spinning zone 3; Furthermore, in step S4, the conditions for the array-type laser spot welding technology are: a spot density of 3~10 spots / cm². 2The laser wavelength is 350~380nm, the laser power is 30~100W, the spot diameter is 20~100µm, the welding speed is 10~40mm / s, and the pressure is 0.05~0.2MPa.

[0015] The array-type laser spot welding technology involves using a laser array to ceramicize the ceramic precursor fiber material at multiple points before calcination, forming "fixed anchor points". During the subsequent calcination process, the shrinkage direction of the surrounding fibers is constrained (diffused outward from the anchor points), improving shrinkage uniformity and enhancing mechanical properties and structural stability.

[0016] Further, in step S5, the scintillation technique is as follows: the laser-anchored shrinkage-controlled ceramic fiber material obtained in step S4 is placed in a vacuum or inert atmosphere, heated to a calcination temperature of 800-1400℃ within 5-500s, held at that temperature for 10-120s, and then cooled to the target temperature within 5-500s.

[0017] The inert atmosphere is selected from nitrogen or argon.

[0018] The scintillation technology uses "ultra-high-speed heating-rapid cooling" as its core process. This process suppresses grain coarsening while densifying the material, ultimately resulting in flexible ceramic ultrafine fiber materials.

[0019] The present invention also provides a flexible ceramic microfiber material based on airflow blowing, which is prepared by the method described in any of the preceding claims, wherein the average fiber diameter of the flexible ceramic microfiber material is 10~800nm, the grain size is 2~30nm, and the bending stiffness is 30~100mN.

[0020] The mechanism of this invention is as follows: Metal alkoxides possess multiple reactive alkoxy groups. They undergo hydrolysis and condensation via nucleophilic reactions, eventually forming inorganic sols. This invention utilizes the synergistic regulation of steric hindrance and electronic effects to induce association reactions between metal alkoxide molecules and polar molecules, forming stable oligomeric structures. This structure significantly reduces the reactivity of the metal center while shielding hydrolysis sites, achieving controllable passivation of the hydrolysis-condensation kinetics. Furthermore, nonionic surfactants can inhibit particle aggregation, with the core mechanism being steric stabilization. The hydrophilic end of the nonionic surfactant adsorbs onto the particle surface via hydrogen bonds, forming a directional anchoring layer; the hydrophobic end extends outward, constructing a physical barrier with a thickness δ of approximately 5–50 nm. When the interparticle spacing is <2δ, the compression of the adsorption layer leads to a sharp decrease in the conformational entropy of the molecular chain and triggers a local increase in osmotic pressure, generating a strong entropic repulsion. This effect effectively counteracts the van der Waals forces between particles, ultimately resulting in a stable sol with uniformly dispersed ultrafine particles.

[0021] In the method for preparing flexible ultrafine ceramic fibers based on the stabilized sol of the aforementioned ultrafine particles provided by this invention, the inorganic sol is extruded from a "V-shaped" spinneret and stretched into a spinning jet by airflow. The rapid flow of airflow between the narrow "V-shaped" nozzles generates a pressurization effect, thereby forming a vortex airflow. This causes the inorganic sol to undergo stretching deformation due to the full stretching force of the airflow, achieving further refinement of the ceramic precursor fibers. The temperature and humidity gradient distribution is achieved through a cyclone-assisted environmental atmosphere control module. Specifically, this is achieved by adding an arc-shaped guide plate to the spinning area and installing a hot and humid airflow jet device on the guide plate to control the temperature and humidity gradient distribution in each area of ​​the spinning environment. Utilizing the difference in the solidification and shaping rate of the spinning jet under different temperatures and humidity levels, the morphology of the ceramic precursor ultrafine fibers is controlled under the coupled effect of temperature and humidity. The use of a heated mesh receiving plate, a heat-assisted fiber receiving technology, can promote the rapid evaporation of residual solvents in the fibers.

[0022] In traditional processes, ceramic precursor fiber materials require high-temperature calcination to achieve ceramization, a process that compromises the flexibility of the ceramic fibers. This invention first employs array-type laser spot welding technology to pre-ceramize the ceramic precursor fiber material at multiple points, forming "fixed anchor points" to improve the uniformity of shrinkage during subsequent calcination. Then, using scintillation technology and a controlled "ultra-high-speed heating-rapid cooling" process, it overcomes the limitations of traditional calcination processes, rapidly passing through the surface diffusion temperature range of the material, avoiding grain coarsening, and achieving densification through rapid material migration at high temperatures.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention first mixes a polar solvent with a metal alkoxide to induce an association reaction, yielding a low-activity functional modified metal alkoxide. Then, deionized water is added to initiate a slow hydrolysis-rapid polycondensation reaction. Simultaneously, a nonionic surfactant is added to increase the steric hindrance between the particles, and ultrasonic dispersion is employed. After concentration, a stable ultrafine inorganic sol is obtained. Next, a vortex-assisted airflow pressurized blowing process is used to extrude the inorganic sol from a "V-shaped" nozzle from top to bottom. Combined with cyclone-assisted environmental atmosphere control technology (temperature and humidity gradient distribution in the spinning area) and heat-assisted fiber receiving technology (heating a perforated receiving plate), multi-morphological (e.g., fiber membrane or fiber flake) ceramic precursor fiber materials are obtained. Then, array-type laser spot welding technology is used to pre-ceramize the ceramic precursor fiber material at multiple points, forming "fixed anchor points." Finally, scintillation technology is used to control the material through an "ultra-high-speed heating-rapid cooling" process, suppressing grain coarsening while achieving material densification, resulting in a flexible ceramic ultrafine fiber material.

[0024] 2) The inorganic sol particles prepared by this invention are uniformly dispersed, small in size, and not prone to agglomeration. They can be directly air-blown without relying on spinning aids. Under the conditions of coupled temperature and humidity control, various forms of ceramic precursor fiber materials such as fiber membranes and fiber flakes can be flexibly produced. The ceramicization stage adopts a two-step synergistic process. First, a laser array is used to pre-ceramize multiple points to generate "fixed anchor points". Then, through the "ultra-high speed heating-rapid cooling" process, densification occurs while suppressing grain coarsening. Finally, ceramic ultrafine fiber materials with enhanced mechanical properties, stable structure, and good flexibility are generated.

[0025] 3) The flexible ultrafine ceramic fiber prepared by the present invention has an average diameter of 10~800nm, a grain size of 2~30nm, and a bending stiffness of 30~100mN. Attached Figure Description

[0026] Figure 1 This is a process flow diagram of the preparation method of flexible ultrafine ceramic fiber material based on airflow blowing according to various embodiments of the present invention; Figure 2 This is a schematic diagram of the spinning region in this invention; Figure 3 This is a schematic diagram of the cross-sectional structure of the "V-shaped" spinneret in this invention, wherein the included angle of the V-shaped groove α=β=60~120°; Figure 4 This is a schematic diagram of the outlet end face of the "V-shaped" spinneret in this invention; Among them, 1-"V-shaped" spinneret, 101-spinning solution channel, 102-airflow channel, 103-spinning solution outlet, 104-airflow outlet, 2-cyclone-assisted environmental atmosphere control module, 201-arc-shaped guide plate, 202-hot and humid airflow jet unit, 3-mesh-type heating receiver plate, 301-mesh-type receiver plate, 302-heating rod; Figure 5 This is a particle size distribution diagram of the ultrafine inorganic aluminum sol in Example 1 of the present invention; Figure 6 This is a scanning electron microscope image of the flexible alumina ultrafine fiber membrane in Example 1 of the present invention; Figure 7 This is a particle size distribution diagram of the ultrafine inorganic aluminum sol in Example 2 of the present invention; Figure 8 This is a scanning electron microscope image of the flexible alumina ultrafine fiber flocs in Example 2 of the present invention; Figure 9 This is a particle size distribution diagram of the ultrafine inorganic titanium sol in Example 3 of the present invention; Figure 10 This is a scanning electron microscope image of the flexible titanium dioxide ultrafine fiber membrane in Example 3 of the present invention; Figure 11 This is a particle size distribution diagram of the ultrafine inorganic titanium sol in Example 4 of the present invention; Figure 12 This is a scanning electron microscope image of the flexible titanium dioxide ultrafine fiber flocs in Example 4 of the present invention. Detailed Implementation

[0027] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are based on the technical solution of the present invention and provide detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0028] Unless otherwise specified, all raw materials used in the embodiments of this invention are commercially available products, and all equipment used is commercially available equipment unless otherwise specified. The following improvements have been made to the equipment: Figure 2 As shown: (1) The spinneret adopts a “V-shaped” spinneret 1, which includes a spinning liquid channel 101 and an airflow channel 102. The inner diameter of the spinning liquid outlet 103 is 0.1 mm and the wall thickness is 0.15 mm. The inner diameter of the airflow outlet 104 is 3 mm and the wall thickness is 0.15 mm. The included angle of the V-shaped groove is α=β=60°. (2) A cyclone-assisted environmental atmosphere control module 2 is installed in the spinning area. The cyclone-assisted environmental atmosphere control module 2 includes an arc-shaped guide plate 201 and a hot and humid air jet unit 202 installed on the arc-shaped guide plate 201. The arc-shaped guide plate 201 is located in the middle position on both sides of each spinning area to guide the airflow to form a stable spinning environment atmosphere. (3) A heated mesh receiving plate 3 is used to receive airflow blown fibers. The heated mesh receiving plate 3 is composed of a mesh receiving plate 301 and a heating rod 302, wherein the heating rod 302 is located below the mesh receiving plate 301.

[0029] Example 1 A flexible alumina ultrafine fiber membrane is prepared by the following steps: S1. Mix 20g aluminum isopropoxide with 20g isopropanol and stir at 500r / min for 30min at 60℃. Then slowly add 2g N,N-dimethylformamide, heat to 80℃ and carry out association reaction for 4h to obtain functional modified aluminum isopropoxide.

[0030] S2. Cool the functional modified aluminum isopropoxide obtained in step S1 to 40°C, add 100g of deionized water and 3g of polyethylene glycol dropwise, and stir at 400r / min to allow the hydrolysis-condensation reaction to occur for 12h. Then concentrate to obtain stable and spinnable ultrafine inorganic aluminum sol particles.

[0031] Dynamic light scattering (DLS) was used to determine the particle size distribution and average particle size of the obtained ultrafine colloidal inorganic aluminum sol. This method detects the dynamic scattered light signal generated after laser irradiation of the colloidal particles, analyzes the Brownian motion rate (i.e., diffusion coefficient) of the colloidal particles, and then calculates the hydrodynamic diameter of the colloidal particles by combining the Stokes-Einstein equation. This diameter reflects the effective size of the colloidal particles in the actual dispersion state, including the solvation layer on their surface.

[0032] The particle size distribution of this ultrafine inorganic aluminum sol was determined as follows: Figure 5 As shown, the average particle size is 1 nm.

[0033] S3. The inorganic aluminum sol obtained in step S2 is extruded from a "V-shaped" spinneret at an extrusion rate of 1 mL / h and stretched to form a spinning jet under an airflow velocity of 10 m / s. Subsequently, the spinning jet passes through three spinning zones with temperature and humidity gradients. The temperatures of spinning zone 1, spinning zone 2, and spinning zone 3 are 40℃, 45℃, and 50℃, respectively, and the humidity is 10%, 20%, and 30%, respectively. The spinning distance is 45 cm, 20 cm in spinning zone 1, 15 cm in spinning zone 2, and 10 cm in spinning zone 3. The spun inorganic aluminum ceramic precursor fibers are deposited on a mesh receiving plate heated to 50℃ to obtain an inorganic aluminum ceramic precursor fiber membrane.

[0034] S4. The inorganic aluminum-ceramic precursor fiber membrane obtained in step S3 is pre-ceramized using array-type laser spot welding technology, wherein the lattice density is 3 dots / cm². 2 The laser wavelength was 355nm, the laser power was 40W, the spot diameter was 30µm, the welding speed was 20mm / s, and the pressure was 0.1MPa, resulting in a laser-anchored shrinkage-controlled inorganic aluminum ceramic precursor fiber membrane.

[0035] S5. The laser-anchored shrinkage-controlled inorganic aluminum ceramic precursor fiber membrane obtained in step S4 is ceramicized using scintillation technology. In a nitrogen atmosphere, the temperature is raised to 1000℃ in 10s, held for 30s, and then lowered to room temperature in 15s to obtain a flexible alumina ultrafine fiber membrane.

[0036] The flexible alumina ultrafine fiber membrane prepared in this embodiment has an average fiber diameter of 10 nm (e.g., Figure 6 As shown in the figure, the grain size is 2 nm and the bending stiffness is 34 mN.

[0037] The following methods were used to test each performance metric: The average fiber diameter was measured using scanning electron microscopy (SEM). First, a clear microscopic image of the fiber was obtained using SEM. Then, the diameter of each of the 100 fibers was measured using the image analysis software ImageJ. Finally, the average value was taken as the average fiber diameter.

[0038] The grain size was calculated based on X-ray diffraction (XRD) data according to the Scherrer formula D = Kλ / (βcosθ), where λ is the X-ray wavelength, β is the full width at half maximum (FWHM) of the diffraction peak, θ is the diffraction angle, and the constant K is 0.89.

[0039] Bending stiffness was determined using a dynamic mechanical analyzer (DMA) and a three-point bending test method.

[0040] Example 2 The specific preparation steps of a flexible alumina ultrafine fiber flocculant are as follows: S1. Mix 20g aluminum isopropoxide with 30g isopropanol and stir at 500r / min for 30min at 60℃. Then slowly add 10g N,N-dimethylformamide, heat to 80℃ and carry out association reaction for 8h to obtain functional modified aluminum isopropoxide.

[0041] S2. Cool the functional modified aluminum isopropoxide obtained in step S1 to 40°C, add 180g of deionized water and 4g of polyethylene glycol dropwise, stir at 400r / min, and allow the hydrolysis-condensation reaction to occur for 15h. Then concentrate to obtain stable and spinnable ultrafine inorganic aluminum sol particles.

[0042] DLS analysis revealed the following particle size distribution of the ultrafine inorganic aluminum sol: Figure 7 As shown, the average particle size is 7 nm.

[0043] S3. The inorganic aluminum sol obtained in step S2 is extruded from a "V-shaped" spinneret at an extrusion rate of 5 mL / h and stretched to form a spinning jet under an airflow velocity of 20 m / s. Subsequently, the spinning jet passes through three spinning zones with temperature and humidity gradients. The temperatures of spinning zone 1, spinning zone 2, and spinning zone 3 are 30℃, 35℃, and 40℃, respectively, and the humidity is 20%, 30%, and 40%, respectively. The spinning distance is 90 cm, 40 cm in spinning zone 1, 30 cm in spinning zone 2, and 20 cm in spinning zone 3. The spun inorganic aluminum ceramic precursor fibers are deposited on a mesh receiving plate heated to 60℃ to obtain inorganic aluminum ceramic precursor fiber flakes.

[0044] S4. The inorganic aluminum ceramic precursor fiber flocs obtained in step S3 are pretreated using array laser spot welding technology, wherein the lattice density is 8 dots / cm². 2 Laser wavelength 355nm, laser power 50W, spot diameter 50µm, welding speed 40mm / s, pressure 0.2MPa, laser-anchored shrinkage-controlled inorganic aluminum ceramic precursor fiber flocs were obtained.

[0045] S5. The laser-anchored shrinkage-controlled inorganic aluminum ceramic precursor fiber flocs obtained in step S4 are ceramicized using scintillation technology. In a nitrogen atmosphere, the temperature is raised to 1000℃ in 20s, held for 40s, and then lowered to room temperature in 30s to obtain flexible alumina ultrafine fiber flocs.

[0046] The flexible alumina ultrafine fiber flocs prepared in this embodiment have an average fiber diameter of 586 nm (e.g., Figure 8 As shown in the figure, the grain size is 21 nm and the bending stiffness is 45 mN.

[0047] Example 3 A flexible titanium dioxide ultrafine fiber membrane is prepared by the following steps: S1. Mix 50g of titanium isopropoxide with 60g of isopropanol and stir at 600 r / min at 50℃ for 45min. Then slowly add 5g of dimethyl sulfoxide and let the association reaction proceed for 12h to obtain functionalized titanium isopropoxide.

[0048] S2. Cool the functional modified isopropoxide titanium obtained in step S1 to 40°C, add 150g of deionized water and 0.5g of glycerol monostearate dropwise, stir at 500r / min, and allow the hydrolysis-condensation reaction to occur for 16h. Then concentrate to obtain stable and spinnable ultrafine inorganic titanium sol particles.

[0049] DLS analysis revealed the following particle size distribution of the ultrafine inorganic titanium sol: Figure 9 As shown, the average particle size is 4.8 nm.

[0050] S3. The inorganic titanium sol obtained in step S2 is extruded from a "V-shaped" spinneret at an extrusion rate of 30 mL / h and stretched to form a spinning jet under an airflow velocity of 50 m / s. Subsequently, the spinning jet passes through three spinning zones with temperature and humidity gradients. The temperatures of spinning zone 1, spinning zone 2, and spinning zone 3 are 35℃, 40℃, and 45℃, respectively, and the humidity is 15%, 25%, and 35%, respectively. The spinning distance is 45 cm, 20 cm in spinning zone 1, 15 cm in spinning zone 2, and 10 cm in spinning zone 3. The spun inorganic titanium ceramic precursor fibers are deposited on a mesh receiving plate heated to 60℃ to obtain an inorganic titanium ceramic precursor fiber membrane.

[0051] S4. The inorganic titanium-ceramic precursor fiber membrane obtained in step S3 is pre-ceramized using array-type laser spot welding technology, wherein the lattice density is 5 dots / cm². 2 The laser wavelength was 360nm, the laser power was 60W, the spot diameter was 30µm, the welding speed was 15mm / s, and the pressure was 0.1MPa, resulting in a laser-anchored shrinkage-controlled inorganic titanium ceramic precursor fiber membrane.

[0052] S5. The laser-anchored shrinkage-controlled inorganic titanium ceramic precursor fiber membrane obtained in step S4 is ceramicized using scintillation technology. In a nitrogen atmosphere, the temperature is raised to 1200℃ in 20s, held for 60s, and then lowered to room temperature in 20s to obtain a flexible titanium oxide ultrafine fiber membrane.

[0053] The flexible titanium dioxide ultrafine fiber membrane prepared in this embodiment has an average fiber diameter of 425 nm (e.g., Figure 10 As shown in the figure, the grain size is 12nm and the bending stiffness is 52mN.

[0054] Example 4 The specific preparation steps of a flexible titanium dioxide ultrafine fiber sheet are as follows: S1. Mix 50g of titanium isopropoxide with 80g of isopropanol and stir at 600r / min at 50℃ for 45min. Then slowly add 10g of dimethyl sulfoxide and let the association reaction proceed for 12h to obtain functionalized titanium isopropoxide.

[0055] S2. Cool the functional modified isopropoxide titanium obtained in step S1 to 40°C, add 200g of deionized water and 5g of glycerol monostearate dropwise, stir at 500r / min to allow the hydrolysis-condensation reaction to occur for 18h, and then concentrate to obtain stable and spinnable ultrafine inorganic titanium sol particles.

[0056] DLS analysis revealed the following particle size distribution of the ultrafine inorganic titanium sol: Figure 11 As shown, the average particle size is 10 nm.

[0057] S3. The inorganic titanium sol obtained in step S2 is extruded from a "V-shaped" spinneret at an extrusion rate of 50 mL / h and stretched to form a spinning jet under an airflow velocity of 50 m / s. Subsequently, the spinning jet passes through three spinning zones with temperature and humidity gradients. The temperatures of spinning zone 1, spinning zone 2, and spinning zone 3 are 60℃, 65℃, and 70℃, respectively, and the humidity is 40%, 50%, and 60%, respectively. The spinning distance is 135 cm, 60 cm in spinning zone 1, 45 cm in spinning zone 2, and 30 cm in spinning zone 3. The spun inorganic titanium ceramic precursor fibers are deposited on a mesh receiving plate heated to 80℃ to obtain inorganic titanium ceramic precursor fiber flakes.

[0058] S4. The inorganic titanium ceramic precursor fiber flocs obtained in step S3 are pre-ceramized using array-type laser spot welding technology, wherein the lattice density is 8 dots / cm². 2 Laser-anchored shrinkage-controlled inorganic titanium ceramic precursor fiber flocs were obtained by using a laser wavelength of 360nm, a laser power of 80W, a spot diameter of 40µm, a welding speed of 30mm / s, and a pressure of 0.2MPa.

[0059] S5. The laser-anchored shrinkage-controlled inorganic titanium ceramic precursor fiber flocs obtained in step S4 are ceramicized using scintillation technology. In a nitrogen atmosphere, the temperature is raised to 1200℃ in 60s, held for 90s, and then lowered to room temperature in 45s to obtain flexible titanium oxide ultrafine fiber flocs.

[0060] The flexible titanium dioxide ultrafine fiber flocs prepared in this embodiment have an average fiber diameter of 758 nm (e.g., Figure 12 As shown, the grain size is 30 nm and the bending stiffness is 100 mN.

[0061] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for preparing flexible ceramic ultrafine fiber materials based on air-blown spinning, characterized in that, Includes the following steps: S1. A polar solvent is mixed with a metal alkoxide and stirred to carry out an association reaction, resulting in a low-activity functional modified metal alkoxide. S2. Deionized water is added to the functional modified metal alkoxide obtained in step S1 to carry out hydrolysis-condensation reaction. At the same time, a nonionic surfactant is added and ultrasonically dispersed. After concentration, a spinnable ultrafine colloid stabilized sol is obtained. S3. The ultrafine sol obtained in step S2 is extruded from the spinneret and blown by airflow. The blown spinning is aided by vortex airflow pressurization to refine the sol and then dried to obtain ceramic precursor fiber material. S4. Pre-ceramicize the ceramic precursor fiber material obtained in step S3 using array laser spot welding technology to obtain laser-anchored shrinkage-controlled ceramic fiber material. S5. The laser-anchored shrinkage-controlled ceramic fiber material obtained in step S4 is ceramicized using scintillation technology to obtain a flexible ceramic ultrafine fiber material.

2. The method of claim 1, wherein the ceramic ultrafine fiber material is prepared by air-laying. In step S1, the polar solvent is selected from one or more of triethylamine, acetone, dimethyl sulfoxide, methanol, ethanol, isopropanol, n-butanol, isobutanol, tert-butanol, tert-amyl alcohol, ethylene glycol, benzyl alcohol, formic acid, acetic acid, acetoacetic acid, acetylacetone, N-methylpyrrolidone, N,N-dimethylformamide, or N,N-dimethylacetamide. The metal alkoxide is selected from one or more of silicon source, aluminum source, zirconium source or titanium source; The mass ratio of the metal alkoxide to the polar solvent is 1:0.1~2; The association reaction is carried out at a temperature of 40~100℃ for a time of 1~48h.

3. The method of claim 2, wherein the ceramic ultrafine fiber material is prepared by air-laying. The silicon source is selected from one or more of tetraethyl orthosilicate, tetra-n-butoxysilane, tetra-n-propoxysilane, trimethylsilyl acetate, or vinyltriethoxysilane; The aluminum source is selected from one or more of aluminum n-propoxide, aluminum isopropoxide, aluminum sec-butoxide, aluminum n-butoxide, aluminum tert-butoxide, aluminum isobutoxide, aluminum neopentyl alcohol, aluminum n-octanol, or aluminum ethoxide; The zirconium source is selected from one or more of zirconium tetraethanolamine, zirconium isopropoxide, zirconium n-butoxide, zirconium isobutoxide, zirconium tert-butoxide, or zirconium tetrapentoxide. The titanium source is selected from one or more of titanium tetramethanol, titanium n-propoxide, titanium isopropoxide, titanium n-butoxide, titanium tert-butoxide, titanium tetrapentoxide, or titanium isooctoxide.

4. The method of claim 1, wherein the ceramic ultrafine fiber material is prepared by air-laying. In step S2, the mass fraction of the functionally modified metal alkoxide in the ultrafine colloidal stabilized sol is 20-50 wt%, and the amount of nonionic surfactant added is 0.1-10 wt% of the functionally modified metal alkoxide. The nonionic surfactant is selected from one or more of polyethylene glycol, poly(N,N-diethylacrylamide), polyoxyethylene alkyl ether, glyceryl monostearate, polyether-modified siloxane, or 4-diethoxymethylsilylbutylamine. The hydrolysis-condensation reaction is carried out at a temperature of 30~100℃ for 1~18h. The average particle size of the ultrafine colloidal stabilized sol is 1~10 nm.

5. The method for preparing a flexible ceramic ultrafine fiber material based on air-blown spinning according to claim 1, characterized in that, In step S3, the vortex airflow pressurization-assisted blow spinning is: using the pressurization effect generated by the rapid flow of airflow between narrow spinnerets to form a vortex airflow, so as to promote the ultrafine sol particles to undergo stretching deformation due to the full stretching force of the airflow. The velocity of the vortex airflow is 1~50m / s.

6. The method of claim 1, wherein the ceramic ultrafine fiber material is prepared by air-laying. The spinning region of the airflow blowing spinneret exhibits a temperature and humidity gradient distribution. The drying process is carried out using a perforated heating receiving plate at a temperature of 40-80°C.

7. The method of claim 6, wherein the ceramic ultrafine fiber material is prepared by air-laying. The spinning region is divided into three areas, from top to bottom: spinning zone 1, spinning zone 2, and spinning zone 3. The spinning region exhibits a temperature and humidity gradient distribution, with the temperature and humidity gradually increasing. The temperature satisfies the formula T. n =T0+5(n-1), humidity satisfies formula H n =H0+10(n-1), where n=1, 2, 3, T0 is the gradient starting temperature 20~60℃, T1 is the temperature of spinning zone 1, T2 is the temperature of spinning zone 2, T3 is the temperature of spinning zone 3; H0 is the gradient starting humidity 10~50%, H1 is the humidity of spinning zone 1, H2 is the humidity of spinning zone 2, H3 is the humidity of spinning zone 3.

8. The method of claim 1, wherein the ceramic ultrafine fiber material is prepared by air-laying. In step S4, the conditions for the array-type laser spot welding technology are: a spot density of 3~10 spots / cm². 2 The laser wavelength is 350~380nm, the laser power is 30~100W, the spot diameter is 20~100μm, the welding speed is 10~40mm / s, and the pressure is 0.05~0.2MPa.

9. The method for preparing a flexible ceramic ultrafine fiber material based on air-blown spinning according to claim 1, characterized in that, In step S5, the scintillation technique is as follows: the laser-anchored shrinkage-controlled ceramic fiber material obtained in step S4 is placed in a vacuum or inert atmosphere, heated to a calcination temperature of 800-1400℃ within 5-500s, held at that temperature for 10-120s, and then cooled to the target temperature within 5-500s.

10. A flexible ceramic microfiber material based on airflow blowing, characterized in that, The flexible ceramic microfiber material is prepared by the method described in any one of claims 1 to 9, wherein the average fiber diameter of the flexible ceramic microfiber material is 10~800nm, the grain size is 2~30nm, and the bending stiffness is 30~100mN.

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