A ceramic nanofiber forming method based on inorganic molecular chain electrospinning and pretreatment-calcination

Abstract

The application relates to a ceramic nanofiber forming method based on inorganic molecular chain electrospinning and pretreatment-calcination, which comprises the following steps: carrying out coordination modification and linear connection on a metal alkoxide monomer, introducing water-containing gel microspheres to trigger hydrolysis-polycondensation reaction and the like to obtain linear inorganic long-chain sol, and electrospinning to form precursor nanofiber. In a ligand treatment device, hydroxyl radicals generated by ultraviolet light excitation are used to remove organic ligands in the fiber, and ligand-free inorganic nanofiber is obtained. In a differential speed transportation-microwave oxygen-poor calcination device, microwave heating is carried out under an oxygen-poor atmosphere, a local electric field generated by an auxiliary roller is used to promote uniform formation of crystal nuclei, the fiber structure is densified through differential speed stretching, and finally, a ceramic nanofiber product with good flexibility and uniform structure is obtained. Compared with the prior art, the application realizes controllable ceramic nanofiber structure, low-temperature and high-efficiency preparation, and excellent product performance.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial preparation technology, and in particular to a method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination. Background Technology

[0002] Ceramic nanofibers, as important one-dimensional nanomaterials, have shown great potential in energy, environment, and biomedicine due to their high aspect ratio, large specific surface area, and excellent physicochemical stability. One method involves preparing spinning solutions using the sol-gel method and combining it with electrospinning technology to obtain ceramic precursor nanofibers with tunable composition and diverse structures. These precursor nanofibers are then transformed into dense ceramic nanofibers after high-temperature calcination. High-temperature calcination is crucial to the bulk structure of ceramic nanofibers, involving complex processes such as organic phase removal, grain nucleation, and grain growth. Traditional high-temperature calcination methods generate a large amount of gas during organic phase removal, leading to numerous pore defects and cracks within the fibers, making it difficult to obtain ceramic nanofibers with excellent mechanical properties.

[0003] To address the aforementioned issues, researchers have optimized the mechanical properties of ceramic fibers through various calcination processes. Patent document ZL202010484946.5 employs a gradient heating method, controlling the gradient heating rate and gradient holding time to ensure uniform grain growth within the fiber, thus forming ceramic fibers with a certain mechanical strength. However, this patent involves calcination in an air atmosphere, resulting in excessively large grain sizes and limitations in the fiber's mechanical properties. Patent document ZL202111391723.5 uses an alternating inert atmosphere for calcination, controlling the oxygen concentration during the calcination process to reduce the oxygen ion exchange rate and inhibit rapid grain growth, thereby forming dense ceramic nanofibers. However, this patent requires a long pre-sintering time, making it difficult to meet the needs of large-scale production. Patent document ZL202411182140.5 uses microwave pretreatment to remove organic components from inorganic fibers in advance, reducing pore defects generated during fiber calcination. However, this method still removes organic components at high temperatures, resulting in large grains in the fiber and limited improvement in mechanical properties. Summary of the Invention

[0004] The purpose of this invention is to overcome the defects of the prior art by providing a ceramic nanofiber forming method based on inorganic molecular chain electrospinning and pretreatment-calcination, which yields ceramic nanofiber products with fine grains, dense structure and excellent flexibility.

[0005] The objective of this invention can be achieved through the following technical solutions: This invention provides a method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination, comprising the following steps: S1. The metal alkoxide monomers are coordinated and linearly linked. Then, hydrolysis-condensation, chain extension and end-capping reactions are triggered by introducing hydrogel microspheres to obtain linear inorganic long-chain sol, which is then electrospun into precursor nanofibers. S2. The precursor nanofibers are placed in a ligand treatment device, oxygen and atomized water are introduced, and ultraviolet light is used to irradiate them in sequence to generate hydroxyl radicals. The hydroxyl radicals are then used to act on the fibers to cleave and remove their organic ligands, resulting in ligand-free inorganic nanofibers. S3. The ligand-free inorganic nanofibers are fed into a differential transport-microwave oxygen-deficient calcination device. In the differential transport-microwave oxygen-deficient calcination device, an oxygen-deficient atmosphere is established by an oxygen-deficient module, and the fibers are heated by a microwave device. At the same time, an auxiliary roller with a high dielectric material lattice structure on its surface generates a local electric field with the fiber under the action of microwaves, which promotes the uniform formation of crystal nuclei. The fiber is then differentially stretched by rollers with a speed difference, and finally, a flexible ceramic nanofiber product is obtained.

[0006] Furthermore, in S1, the specific process of coordinating and linearly linking the metal alkoxide monomers includes: Linear and rigid bidentate linkers are added to metal alkoxide solution to bridge the metal alkoxide monomers as intermediates to form a linear framework. Then, a flexible bidentate stabilizer is added to replace the remaining active groups to form a stable linear pre-coordinated framework. The metal alkoxide is selected from one or more alkoxides of titanium, zirconium, aluminum, tin, and hafnium; The linear, rigid bidental connector is selected from p-phenylenediamine, terephthalic acid, or 1,4-benzenediol; The flexible bidental stabilizer is selected from ethylenediamine, tetramethylethylenediamine, or acetylacetone.

[0007] Furthermore, in S1, the process of triggering the hydrolysis-condensation reaction by introducing hydrogel microspheres includes: Thermosensitive hydrogel microspheres are added and heated and uniformly dispersed by ultrasonic treatment, thereby controllably releasing the contained water molecules, initiating the hydrolysis-condensation of the linear pre-coordinated framework, and forming low-polymerization linear inorganic molecular chains. The temperature-sensitive hydrogel microspheres are selected from one or more combinations of poly(N-isopropylacrylamide) hydrogel microspheres, poly(N-isopropylacrylamide-acrylic acid) hydrogel microspheres, poly(N-isopropylacrylamide-hydroxyethyl methacrylate) hydrogel microspheres, and carboxymethyl chitosan hydrogel microspheres. The amount of temperature-sensitive hydrogel microspheres added is 5% to 20% of the mass of the metal alkoxide monomer. The ultrasonic treatment has a power of 10~100kHz and a temperature of 5~60℃.

[0008] Further, in S1, based on the total mass of the linear pre-coordinated framework solution, the mass fraction of the metal alkoxide is 22wt% to 30wt%, the mass fraction of the linear, rigid bidental connector is 6wt% to 8wt%, the mass fraction of the flexible bidental stabilizer is 4wt% to 10wt%, and the remainder is solvent.

[0009] Further, in S2, the ligand processing device includes a main housing of the ligand processing device and a component disposed within the main housing of the ligand processing device: The first processing area for generating ozone includes a first ultraviolet light source emitting 185nm ultraviolet light and a concave mirror. The concave mirror is located below the first ultraviolet light source. An oxygen inlet is provided on the first processing area. The concave mirror is used to convert the light emitted by the first ultraviolet light source into parallel light. The second processing zone for generating hydroxyl radicals is provided with a second ultraviolet light source that emits ultraviolet light in the 254nm band, and the second processing zone is provided with an atomized water inlet. A gradient outlet for uniformly removing hydroxyl radicals is provided at the bottom of the main housing of the ligand processing device; The first treatment zone and the second treatment zone are separated by a partition, and the second treatment zone is provided with a grooved flow channel to allow ozone and water molecules to fully mix and react.

[0010] Furthermore, the first ultraviolet light source is a low-pressure mercury lamp, an excimer light source, or a laser light source; The second ultraviolet light source is a low-pressure mercury lamp, an ozone-free low-pressure mercury lamp, or an ultraviolet light-emitting diode. The power density of the first and second ultraviolet light sources is 10~100 mW / cm². 2 ; The concave mirror is made of fused silica, calcium fluoride, or zinc selenide. The partition is made of aluminum, stainless steel, fused silica or polytetrafluoroethylene; Ultraviolet light in the 185nm band breaks down oxygen to produce oxygen atoms. The oxygen atoms combine with oxygen to generate ozone. Ultraviolet light in the 254nm band causes ozone to react with atomized water molecules to generate hydroxyl radicals. The hydroxyl radicals are uniformly dispersed into the precursor nanofibers through the gradient outlet. Through their strong oxidizing properties, they break down the carbon-carbon bonds and carbon-hydrogen bonds of the organic ligands in the fibers, achieving a removal rate of not less than 95%, while retaining the metal-oxygen backbone structure.

[0011] Furthermore, in S3, the differential transport-microwave oxygen-deficient calcination device includes a main shell of the calcination device and the following disposed in the main shell of the calcination device: multiple rollers for transporting and stretching fibers, a microwave device for providing microwave heating, an auxiliary roller with a surface coated with a high dielectric constant material, and an oxygen-deficient module for constructing and maintaining an oxygen-deficient atmosphere. The microwave device is located on one side of the roller, the auxiliary roller is located on the other side of the roller, and the ligand-free inorganic nanofibers are placed between the auxiliary roller and the roller.

[0012] Furthermore, the oxygen-deficient module includes an oxygen-deficient pipe and multiple oxygen-deficient gas inlets disposed on the oxygen-deficient pipe, wherein a mixed gas of nitrogen, argon or helium with an oxygen content of not more than 18% is introduced into the oxygen-deficient pipe. The microwave device is a microwave generator with gradient calcination characteristics; The calcination temperature of the microwave device is 250~1500℃, and it is divided into 2~4 temperature gradient ranges.

[0013] Furthermore, the high dielectric constant material on the surface of the auxiliary roller is alumina, silicon nitride, or ferrite. The surface of the auxiliary roller is provided with a micron-scale lattice structure. Under the action of a microwave field, the micron-scale lattice structure can generate a local electric field focusing effect, which accelerates the migration of metal and oxygen ions inside the fiber, thereby promoting the rapid and uniform formation of crystal nuclei and inhibiting grain growth. The size of the lattice unit is 0.5~20μm, and the unit spacing is 0.5~1000μm; The number of rollers is at least two, and the operating speed increases in a gradient, ranging from 0.1 to 100 m / min. The speed difference applies a stretching force to the crystallizing ceramic fibers, causing the internal crystals to be tightly arranged along the fiber axis and releasing residual stress.

[0014] Furthermore, in S3, the prepared ceramic nanofiber product has a grain size of 4~25 nm and a pore volume of no more than 5 mm. 3 / g, with an average fiber diameter of 50~500 nm; When the ceramic nanofiber product is a single fiber, its tensile strength is not less than 0.5 GPa and its elongation at break is not less than 1.5%. When the ceramic nanofiber product is a fiber membrane, its softness is not higher than 300 mN.

[0015] The technical principle of this invention is as follows: The precursor nanofiber material described in this invention patent is a ceramic precursor nanofiber material. Utilizing deep ultraviolet ligand debinding technology, highly reactive oxygen species (hydroxyl radicals) are uniformly diffused into the interior of the ceramic precursor nanofiber material. This decomposes the weak carbon-carbon bonds (332 kJ / mol), carbon-oxygen bonds (326 kJ / mol), and carbon-hydrogen bonds (414 kJ / mol) on the metal-oxygen backbone, while retaining the metal-oxygen skeleton (aluminum-oxygen bond: 511 kJ / mol, titanium-oxygen bond: 672 kJ / mol, zirconium-oxygen bond: 760 kJ / mol, etc.). The electron-withdrawing ability of the hydroxyl radicals (with an oxidation potential reaching 2.8 V – one of the strongest oxidizing agents in nature) is used to gradually degrade the larger molecular weight ligands.

[0016] Microwave calcination can directly penetrate the fiber material, heating the inside and outside of the material almost simultaneously. In addition, the lattice structure on the surface of the auxiliary roller forms a local electric field under the action of microwaves, further accelerating the movement rate of ions in the fiber and enabling the grains to nucleate quickly and uniformly. The differential transport of the roller applies stress in the direction of movement of the fiber material, which helps the crystals to arrange more compactly during the calcination process, releases the residual stress in the nanofibers, and, combined with the oxygen-deficient atmosphere, inhibits the rapid increase in grain size, which is conducive to the formation of fine, uniform and dense ceramic grains.

[0017] Compared with the prior art, the present invention has the following beneficial effects: 1) This invention, through coordination modification in step S1 and the introduction of hydrogel microspheres to trigger a controllable reaction, can synthesize linear inorganic long chains with controllable molecular weight and structure, laying the material foundation for the preparation of uniform and continuous precursor nanofibers. Secondly, step S2 innovatively uses hydroxyl radicals to cleave and remove organic ligands under mild conditions, which can effectively avoid fiber pore defects and cracks caused by traditional high-temperature removal methods, and preserve the intact inorganic framework. Finally, step S3 combines the three factors of oxygen-deficient atmosphere to inhibit grain growth, microwave heating to promote uniform nucleation, and differential stretching to induce close crystal arrangement, ultimately obtaining ceramic nanofiber products with fine grains, dense structure, and excellent flexibility, comprehensively improving their mechanical properties and structural reliability.

[0018] 2) The ligand removal device used in this invention allows oxygen and atomized water to mix and collide sequentially. After sufficient contact, highly oxidizing hydroxyl radicals are generated and diffused into the ceramic precursor nanofibers, which can effectively remove inert organic ligands in the fibers, with a ligand removal rate of ≥95%.

[0019] 3) The differential transport-microwave oxygen-deficient calcination device used in this invention can form a local electric field inside the fiber under the action of microwaves, which accelerates the movement rate of ions in the fiber and enables the grains to nucleate quickly and uniformly. The residual stress in the nanofiber is released by the oxygen-deficient atmosphere and differential transport, which inhibits the rapid increase of grain size. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the ligand processing device in this invention; Figure 2 This is a schematic diagram of the differential transport-microwave oxygen-deficient calcination device in this invention.

[0021] In the diagram: 1-Ligand processing device; 2-Differential transport-microwave oxygen-deficient calcination device; 101-185nm ultraviolet lamp; 102-Concave mirror; 103-Oxygen inlet; 104-Separator; 105-Atomized water inlet; 106-254nm ultraviolet lamp; 107-Gradient active free radical outlet; 208-Oxygen-deficient module; 2081-Oxygen pipeline; 2082-Oxygen-deficient gas inlet; 209-Microwave irradiation device; 210-Roller; 211-Auxiliary roller. Detailed Implementation

[0022] S1. A linear, rigid bidentate linker is diluted with a non-polar solvent. Then, under an inert atmosphere, low temperature, and high-speed stirring, the diluted solution is slowly added dropwise to a metal alkoxide solution. The linker acts as an intermediate to intersect the metal alkoxide monomers, forming a linear linkage structure. A flexible, bidentate stabilizer is then added to replace the remaining active groups on the metal alkoxide monomers, forming a stable linear pre-coordinated framework. Temperature-sensitive hydrogel microspheres are further added, and the solution is ultrasonically treated to uniformly heat and disperse the microspheres, releasing water molecules uniformly into the solution. This causes the linear pre-ligand to undergo hydrolysis-condensation to obtain low-polymerization linear inorganic molecular chains. A chain extender is then added to allow the low-polymerization linear inorganic molecular chains to complete the chain extension reaction. A capping agent is added to terminate the chain extension reaction, thereby obtaining linear inorganic long chains with controllable molecular weight. The solution is further concentrated using negative pressure suction to produce a high-concentration linear inorganic long-chain sol, and precursor nanofiber materials are prepared using electrospinning technology.

[0023] S2. The precursor nanofiber material is placed under the ligand treatment device 1; oxygen and atomized water are introduced into the ligand treatment device 1, and hydroxyl radicals are formed under 185nm and 254nm ultraviolet light irradiation in sequence; then the hydroxyl radicals are dispersed into the fiber material, causing the ligands in the fiber to be cleaved and thus removing the ligands, to obtain the ligand-free inorganic nanofiber material.

[0024] S3. The ligand-free inorganic nanofiber material is transported to a differential transport-microwave oxygen-deficient calcination device. The inorganic nanofiber material is calcined by controlling the microwave power. At the same time, the auxiliary roller is attached to the surface of the fiber material. Through the polarization effect of microwave, a local electric field is generated between the high dielectric material on the surface of the auxiliary roller and the fiber, so that crystal nuclei are uniformly formed inside the fiber. In addition, the calcination environment is controlled to be an oxygen-deficient atmosphere to inhibit the rapid growth of grains. At the same time, the speed difference between the transport rollers is controlled to perform differential stretching on the crystallized ceramic fiber, so that the crystal structure in the fiber is tightly arranged, thereby obtaining nano-ceramic fibers with fine grains, dense structure and flexibility.

[0025] The ligand processing device 1 includes a 185nm ultraviolet lamp 101 at the top, a concave mirror 102 below the 185nm ultraviolet lamp 101, a partition 104 directly below the concave mirror 102, an oxygen inlet 103 between the concave mirror 102 and the partition, a 254nm ultraviolet lamp 106 directly below the partition 104, an atomized water inlet 105 between the 254nm ultraviolet lamp 106 and the partition 104, and a gradient outlet 107 at the bottom of the device; 185nm ultraviolet... Lamp 101, oxygen inlet 103, and concave mirror 102 are located above partition 104 to generate ozone; 254nm ultraviolet lamp 106 and atomized water inlet 105 are located below partition 104 to generate high-energy oxygen atoms and hydroxyl radicals; the space between partition 104 and 254nm ultraviolet lamp 106 is designed with a grooved flow channel to allow water molecules and ozone to react fully and obtain a high concentration of hydroxyl radicals; the hydroxyl radicals flow out from gradient outlet 107 and disperse in the fiber material, causing the ligands on the fiber to break down.

[0026] In one embodiment of the present invention, the differential transport-microwave oxygen-deficient calcination device 2 mainly includes a roller 210, a microwave device 209, an auxiliary roller 211, and an oxygen-deficient module 208. The oxygen-deficient module 208 includes an oxygen-deficient pipe 2081 and an oxygen-deficient air inlet 2082. The auxiliary roller 211 is a roller with a surface coated with a high dielectric constant material. During operation, the roller 210 applies a stretching force to the fiber material. Below the roller 210 is the microwave device 209, which is used to calcine the fiber material. Above the roller 210 is the auxiliary roller 211, and above the auxiliary roller 211 is the oxygen-deficient module 208. The oxygen-deficient module 208 is used to construct the oxygen-deficient environment in the differential transport-microwave oxygen-deficient calcination device 2.

[0027] In one embodiment of the present invention, in step S1, the metal alkoxide monomer comprises three or more hydrolyzable coordinating groups; the metal alkoxide is selected from one or more combinations of titanium, tantalum, tin, niobium, gallium, hafnium, zirconium, or aluminum sources; the linear, rigid bidentate linker has a conjugated aromatic ring or a rigid heterocyclic skeleton, with its two coordinating atoms located at para or linearly symmetrical sites, capable of coordinating with different metal alkoxide monomers respectively, thereby achieving linear connection of the metal alkoxide monomers; the linear, rigid bidentate linker is selected from one or more of p-phenylenediamine, 1,4-naphthylenediamine, terephthalic acid, or 1,4-diphenylacetic acid; the flexible, bidentate stabilizer forms a high-energy coordination bond with the metal center of the metal alkoxide monomer. The kinetic dissociation is difficult, and the ligand itself does not contain a conjugated aromatic ring or a rigid heterocyclic skeleton, exhibiting excellent chemical stability and forming a stable chemical structure with the metal alkoxide. The flexible, bidentate stabilizer is selected from one or more of ethylenediamine, tetramethylethylenediamine, and acetylacetone. The thermosensitive hydrogel microspheres are selected from one or more combinations of poly(N-isopropylacrylamide) hydrogel microspheres, poly(N-isopropylacrylamide-acrylic acid) hydrogel microspheres, poly(N-isopropylacrylamide-hydroxyethyl methacrylate) hydrogel microspheres, and carboxymethyl chitosan hydrogel microspheres, with the total water content of the thermosensitive hydrogel microspheres being 5-20 wt% of the metal alkoxide monomer mass. The ultrasonic treatment power is 10-100 kHz, and the temperature is 5-60 °C.

[0028] In one embodiment of the present invention, the precursor ceramic nanofibers mentioned in step S2 are fiber materials containing a metal-oxygen backbone and ligands, wherein the metal-oxygen backbone is one or more of zirconium-oxygen, aluminum-oxygen, tin-oxygen, hafnium-oxygen, titanium-oxygen, and inorganic elements, and the molecular weight is 1,000 to 1,000,000.

[0029] In one embodiment of the present invention, the process parameters for electrospinning are: the injection speed of a single needle is 0.5~10ml / h, the voltage is 10~50kV, and the receiving distance is 5~40cm.

[0030] In one embodiment of the present invention, in step S2, the preparation process of the hydroxyl radical is as follows: First, oxygen molecules in the air are cracked using parallel ultraviolet light in the 185nm band to obtain ground-state oxygen atoms, which then react with oxygen to generate oxygen species such as ozone. Next, ultraviolet light in the 254nm band causes these oxygen species to further combine with water molecules in the air to generate hydroxyl radicals with higher cracking ability. The hydroxyl radicals are then transported into the fiber material to cause the ligands to crack and thus remove the ligands, obtaining the ligand-free inorganic nanofiber material with a ligand removal rate ≥95%.

[0031] In one embodiment of the present invention, the ligand removal device described in step S2 is designed with a 185nm ultraviolet light source that is a combination of one or more of the following: a low-pressure mercury lamp, an excimer light source, a synchrotron radiation light source, and a laser light source; and a 254nm ultraviolet light source that is a combination of one or more of the following: a low-pressure mercury lamp, an ozone-free low-pressure mercury lamp, and an ultraviolet light-emitting diode, with the power of the ultraviolet lamp being 10~100mW / cm². 2 The concave mirror is made of fused silica, fused silicon, calcium fluoride, magnesium fluoride, zinc selenide, zinc sulfide, and molded glass aspherical composite material, with a refraction angle of 10~360°; the partition is made of aluminum, copper, stainless steel, soda-lime glass, fused silica, polymethyl methacrylate, polycarbonate, polyethylene, polypropylene, and polytetrafluoroethylene; the atomized water inlet refers to the inlet through which deionized water is introduced after ultrasonic atomization; the gradient active free radical outlet is a channel with progressively increasing width, allowing hydroxyl free radicals to adhere uniformly within the fiber material.

[0032] In one embodiment of the present invention, the roller device 210 mentioned in step S3 is composed of several identical rollers, with the running speed gradient between each roller increasing progressively, ranging from 0.1 to 100 m / min; the roller 210 is made of one or more combinations of alumina, mullite, and zirconium oxide; the microwave device 209 has gradient calcination characteristics, divided into 2 to 4 temperature ranges, ranging from 250 to 1500°C; the high dielectric constant material on the surface of the auxiliary roller 211 is one or more combinations of oxide ceramics, non-oxide ceramics, and ferrite, and is attached to the fiber surface to synchronously follow the movement speed of the fiber material. The surface structure of the high-dielectric material is composed of lattice units at the micrometer scale, which can generate extremely strong local electric field focusing and directional polarization effects, enabling rapid migration of metal ions and oxygen ions in the fiber, accelerating the instantaneous heating rate inside the fiber material, and inhibiting grain growth. The size of the lattice units is 0.5~20μm, the distance between them is 0.5~1000μm, and the structure is any one or a combination of rod-shaped, spherical, cubic, and grooved. The oxygen-deficient system consists of several nozzles that control the oxygen content. The gas in the oxygen-deficient pipeline includes oxygen, nitrogen, argon, helium, neon, krypton, xenon, and radon, with an oxygen content ≤18%.

[0033] In one embodiment of the present invention, the ceramic nanofiber material morphology in step S3 specifically includes single fibers, fiber membranes, and bulk materials.

[0034] In one embodiment of the present invention, the flexible nanoceramic fibers described in step S3 possess excellent flexibility properties, with a softness ≤300mN, a grain size of 4~25nm, and a pore volume ≤5mm. 3 / g, with an average fiber diameter of 50~500nm, the tensile strength of the flexible single fiber is ≥0.5GPa and the elongation at break is ≥1.5%. The fiber softness is tested according to the standard "GB / T8942-2016 Determination of Softness of Paper Towels". The grain size is calculated by X-ray diffraction data according to the Scherrer formula D=Kλ / (βcosθ), where K is a constant, λ is the X-ray wavelength, β is the half-width at half-maximum of the diffraction peak, and θ is the diffraction angle. In the above formula, the value of the constant K is related to the definition of β. When β is the half-width at half-maximum, K is 0.89; when β is the integral width, K is 1.0.

[0035] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. In the following embodiments and comparative examples, unless otherwise specified, the raw materials or processing techniques are conventional commercially available raw materials or conventional processing techniques in the art. Unless otherwise specified, the functional components or structures are conventional components or structures used in the art to achieve the corresponding functions.

[0036] Example 1 This embodiment provides a method for pretreatment and calcination of ceramic nanofibers based on electrospinning of titanium-oxygen molecular chains.

[0037] Terephthalic acid was diluted with toluene at a ratio of 1:10. Then, under argon atmosphere, at -5°C, and with a stirring speed of 500 rpm / min, the diluted solution was added dropwise to tetrabutyl titanate. Terephthalate groups were used as intermediates to link the titanium alkoxide monomers. Then, ethylenediamine was added to replace the remaining active groups of the titanium alkoxide, forming a linear pre-coordinated framework for the titanium alkoxide. The linear pre-coordinated framework solution contained 30 wt% tetrabutyl titanate, 4 wt% ethylenediamine, 6 wt% terephthalic acid, and 60 wt% toluene. Further water was added to the poly(N-isopropylacrylamide) hydrogel microspheres, with a total amount of 10 wt% of the metal alkoxide monomer. The solution was then subjected to ultrasonic treatment for 15 min at a power of 50 kHz and a temperature of 30 °C. This process ensured uniform heating and dispersion of the microspheres, releasing water molecules uniformly into the solution. This caused the linear preligand to undergo hydrolysis-condensation polymerization to obtain low-polymerization linear inorganic molecular chains. In this embodiment, the poly(N-isopropylacrylamide) hydrogel microspheres were prepared using 3.8 g of N-isopropylacrylamide and 0.066 g of N,N-methylenebisacrylamide. Amine and 0.15g sodium dodecyl sulfate were dissolved in 240ml of water and stirred continuously for 1 hour. The reaction solution was then purified by blowing with N2 for 40 minutes to remove oxygen. The purified reaction solution was then placed in a 70°C water bath. 0.166g ammonium persulfate was dissolved in 10ml of water and added to the above solution to initiate an emulsification polymerization reaction for 4 hours. After the reaction, the solution was cooled to room temperature. Purification was then performed by dialysis using distilled water and electric field dialysis, respectively. The prepared microspheres had a particle size of 5μm, a water content of up to 90%, and a response temperature of 32°C. Further addition of 5 wt% of dichlorodicyclopentadiene titanium by the metal alkoxide monomer allows the low-polymerization-degree linear inorganic molecular chain to complete the chain extension reaction. Then, 5 wt% of 4-azidobenzoic acid by the metal alkoxide monomer is added to terminate the chain extension reaction, thereby obtaining a linear inorganic long chain with controllable molecular weight. The solution was further concentrated by negative pressure suction to produce a high-concentration linear inorganic long-chain sol, and precursor nanofiber materials were prepared by electrospinning technology. Electrospinning process parameters: injection speed of a single needle is 2.5 ml / h, voltage is 30 kV, and receiving distance is 25 cm.

[0038] Oxygen and atomized water are introduced into the ligand processing device 1, with flow rates of 9 L / h and 9 L / h, respectively. In specific implementation, the ligand processing device 1 includes a main housing of the ligand processing device and the following disposed in the main housing: a first processing zone for generating ozone, a second processing zone for generating hydroxyl radicals, and a gradient outlet 107 for uniformly exporting hydroxyl radicals; The first processing area for generating ozone includes a first ultraviolet light source 101 that emits ultraviolet light in the 185nm band and a concave mirror 102. The concave mirror 102 is located below the first ultraviolet light source 101. An oxygen inlet 103 is provided on the first processing area. The concave mirror 102 is used to convert the light emitted by the first ultraviolet light source 101 into parallel light. The second processing zone for generating hydroxyl radicals is provided with a second ultraviolet light source 106 that emits ultraviolet light in the 254nm band, and the second processing zone is provided with an atomized water inlet 105. A gradient outlet 107 for uniformly exporting hydroxyl radicals is provided at the bottom of the main housing of the ligand processing device; The first treatment zone and the second treatment zone are separated by a partition 104, and the second treatment zone is provided with a grooved flow channel to allow ozone and water molecules to fully mix and react.

[0039] Hydroxyl radicals are formed sequentially under 185nm and 254nm ultraviolet light irradiation. The 185nm ultraviolet light source is an excimer light source, and the 254nm ultraviolet light source is a low-pressure mercury lamp. The power of the ultraviolet lamp is 50mW / cm². 2 ; Subsequently, hydroxyl radicals are dispersed into the fiber material through outlets with progressively increasing widths of 3 cm, causing the ligands in the fiber to cleave and thus removing the ligands, resulting in ligand-free inorganic nanofiber material.

[0040] The ligand-free inorganic nanofiber material is transported to a differential transport-microwave oxygen-deficient calcination device 2, and the microwave power is controlled at 1.8 GHz to make the amorphous inorganic nanofibers nucleate uniformly, and the grain growth is inhibited under a 10% oxygen-deficient atmosphere. In specific implementation, the differential transport-microwave oxygen-deficient calcination device 2 includes a main shell of the calcination device and the following disposed in the main shell of the calcination device: multiple rollers 210 for transporting and stretching fibers, a microwave device 209 for providing microwave heating, an auxiliary roller 211 with a surface coated with a high dielectric constant material, and an oxygen-deficient module 208 for constructing and maintaining an oxygen-deficient atmosphere. A microwave device 209 is located on one side of the roller 210, and an auxiliary roller 211 is located on the other side of the roller 210. Ligand-free inorganic nanofibers are placed between the auxiliary roller 211 and the roller 210. The oxygen-deficient module 208 includes an oxygen-deficient pipe 2081 and multiple oxygen-deficient gas inlets 2082 located on the oxygen-deficient pipe 2081. A mixed gas of nitrogen, argon, or helium with an oxygen content not exceeding 18% is introduced into the oxygen-deficient pipe 2081. The microwave device 209 is a microwave generator with gradient calcination characteristics. The calcination temperature of the microwave device 209 is 250~1500℃, divided into three temperature gradient ranges.

[0041] The auxiliary roller 211 has a micron-scale lattice structure on its surface. Under the action of a microwave field, the micron-scale lattice structure can generate a local electric field focusing effect, which accelerates the migration of metal and oxygen ions inside the fiber, thereby promoting the rapid and uniform formation of crystal nuclei and inhibiting grain growth. The length and width of the lattice unit are 0.5~20μm, the height is 10~300μm, and the horizontal and vertical spacing of each unit is 0.5~1000μm. The number of rollers 210 is at least 2, and the running speed increases in a gradient, with a speed range of 0.1~100 m / min. The speed difference applies a stretching force to the crystallizing ceramic fiber, causing the internal crystals to be tightly arranged along the fiber axis and releasing residual stress.

[0042] The speed difference of the rollers was further adjusted to 0.2 m / min to perform differential stretching on the ceramic fibers after initial nucleation; at the same time, the high dielectric constant of alumina was used to generate a locally amplified electric field on the fiber surface, so that the crystal structure in the fiber was compactly arranged. A grain size of 10 nm and a pore volume of 3 mm were obtained. 3 Flexible titanium dioxide nano-ceramic fibers with an average fiber diameter of 300 nm, tensile strength of 0.6 GPa, elongation at break of 1.6%, and softness of 285 mN.

[0043] Example 2 This embodiment provides a method for pretreatment and calcination of ceramic nanofibers based on zirconium-oxygen molecular chain electrospinning. p-Phenylenediamine was diluted with dichloromethane at a ratio of 1:8. Then, under argon atmosphere, at -10°C, and with a stirring speed of 600 rpm / min, the diluted p-Phenylenediamine was added dropwise to zirconium butoxide. The zirconium alkoxide monomers were linked intermittently using the p-Phenylenediamine group as an intermediate. Then, acetylacetone was added to replace the remaining active groups of the zirconium alkoxide, forming a linear pre-coordinated structure of the zirconium alkoxide. The linear pre-coordinated framework solution contained 22 wt% zirconium butoxide, 6 wt% acetylacetone, 8 wt% p-Phenylenediamine, and 64 wt% dichloromethane. Further, 10 wt% of poly(N-isopropylacrylamide) hydrogel microspheres (prepared by the same method as in Example 1) were added to the solution. The solution was subjected to ultrasonic treatment for 16 min at an ultrasonic power of 45 kHz and a temperature of 40 °C to uniformly heat and disperse the microspheres, uniformly release water molecules into the solution, and allow the linear preligand to undergo hydrolysis-condensation to obtain low-polymerization linear inorganic molecular chains. Further addition of 4.5 wt% zirconium dichloroethylene metal alkoxide monomers to complete the chain extension reaction of the low-polymerization degree linear inorganic molecular chain, followed by the addition of 4.5 wt% 1,3-dioxopentanepropyltrimethoxysilane to terminate the chain extension reaction, thereby obtaining a linear inorganic long chain with controllable molecular weight. The solution was further concentrated by negative pressure suction to produce a high-concentration linear inorganic long-chain sol, and precursor nanofiber materials were prepared by electrospinning technology. Electrospinning process parameters: injection speed of a single needle is 1.5 ml / h, voltage is 28 kV, and receiving distance is 30 cm.

[0044] Oxygen and atomized water are introduced into the ligand processing device 1, with flow rates of 10 L / h and 12 L / h, respectively. Hydroxyl radicals are formed sequentially under 185nm and 254nm ultraviolet light irradiation. The 185nm ultraviolet light source is a laser source, and the 254nm ultraviolet light source is an ultraviolet light-emitting diode. The power of the ultraviolet lamp is 60mW / cm². 2 ; Subsequently, hydroxyl radicals are dispersed into the fiber material through outlets with progressively increasing widths of 2.5 cm, causing the ligands in the fiber to cleave and thus removing the ligands, resulting in ligand-free inorganic nanofiber material.

[0045] The ligand-free inorganic nanofiber material is transported to a differential transport-microwave oxygen-deficient calcination device 2, and the microwave power is controlled at 2.3 GHz to make the amorphous inorganic nanofibers nucleate uniformly, and the grain growth is inhibited under an oxygen-deficient atmosphere of 8.5%. The speed difference of the rollers was further adjusted to 0.25 m / min to perform differential stretching on the ceramic fibers after initial nucleation; at the same time, the high dielectric constant of alumina was used to generate a locally amplified electric field on the fiber surface, so that the crystal structure in the fiber was compactly arranged. A grain size of 15 nm and a pore volume of 2.8 mm were obtained. 3 Flexible zirconia nano-ceramic fibers with an average fiber diameter of 250 nm, tensile strength of 0.65 GPa, elongation at break of 2.2%, and softness of 278 mN.

[0046] Example 3 This embodiment provides a method for pretreatment and calcination of ceramic nanofibers based on electrospinning of aluminum-oxygen molecular chains.

[0047] Terephthalic acid was diluted with toluene at a ratio of 1:5. Then, under argon atmosphere, at -10°C, and with a stirring speed of 700 rpm / min, the diluted terephthalic acid was added dropwise to aluminum sec-butoxide. The terephthalate group was used as an intermediate to link the aluminum alkoxide monomers. Then, acetylacetone was added to replace the remaining active groups of the aluminum alkoxide, forming a linear pre-coordinated framework of the aluminum alkoxide. The linear pre-coordinated framework solution contained 30 wt% aluminum sec-butoxide, 10 wt% acetylacetone, 10 wt% terephthalic acid, and 50 wt% toluene. Further, 10 wt% of poly(N-isopropylacrylamide) hydrogel microspheres were added (the specific preparation method is the same as in Example 1), and the solution was subjected to ultrasonic treatment for 20 min at an ultrasonic power of 60 kHz and a temperature of 35 °C to uniformly heat and disperse the microspheres, uniformly release water molecules into the solution, and cause the linear preligand to undergo hydrolysis-condensation to obtain low-polymerization linear inorganic molecular chains. Further addition of 5 wt% hafnium dichlorodecane, a metal alkoxide monomer, allows the low-polymerization-degree linear inorganic molecular chain to complete the chain extension reaction. Then, 4.5 wt% 3-azidopropyltrimethoxysilane, a metal alkoxide monomer, is added to terminate the chain extension reaction, thereby obtaining a linear inorganic long chain with controllable molecular weight. The solution was further concentrated by negative pressure suction to produce a high-concentration linear inorganic long-chain sol, and precursor nanofiber materials were prepared by electrospinning technology. Electrospinning process parameters: injection speed of a single needle is 3ml / h, voltage is 24kV, and receiving distance is 32cm.

[0048] Oxygen and atomized water are introduced into the ligand processing device 1, with flow rates of 9 L / h and 10 L / h, respectively. Hydroxyl radicals are formed sequentially under 185nm and 254nm ultraviolet light irradiation. The 185nm ultraviolet light source is a laser source, and the 254nm ultraviolet light source is an ultraviolet light-emitting diode. The power of the ultraviolet lamp is 55mW / cm². 2 ; Subsequently, hydroxyl radicals are dispersed into the fiber material through outlets with progressively increasing widths of 2.1 cm, causing the ligands in the fibers to cleave and thus removing the ligands, resulting in ligand-free inorganic nanofiber material.

[0049] The ligand-free inorganic nanofiber material is transported to a differential transport-microwave oxygen-deficient calcination device 2, and the microwave power is controlled at 2.3 GHz to make the amorphous inorganic nanofibers nucleate uniformly, and the grain growth is inhibited under a 5% oxygen-deficient atmosphere. The speed difference of the rollers was further adjusted to 0.24 m / min to perform differential stretching on the ceramic fibers after initial nucleation; at the same time, the high dielectric constant of alumina was used to generate a locally amplified electric field on the fiber surface, so that the crystal structure in the fiber was compactly arranged. A grain size of 5 nm and a pore volume of 5 mm were obtained. 3 Flexible alumina nano-ceramic fibers with an average fiber diameter of 70 nm, tensile strength of 0.68 GPa, elongation at break of 2.4%, and softness of 295 mN.

[0050] Example 4 This embodiment provides a method for pretreatment and calcination of ceramic nanofibers based on silicon-oxygen molecular chain electrospinning.

[0051] A silanol salt solution with pH=1 and a tetraethyl orthosilicate content of 80wt% was prepared by mixing hydrochloric acid, anhydrous ethanol and tetraethyl orthosilicate. Terephthalic acid was diluted with dichloromethane at a ratio of 1:10. Then, under argon atmosphere, at -10°C, and with a stirring speed of 700 rpm / min, the diluted terephthalic acid was added dropwise to a silanolate solution. The silanolate monomers were linked intermittently using terephthalate groups as intermediates. Then, ethylenediamine was added to replace the remaining active groups of the silanolate, forming a linear pre-coordinated framework of the silanolate. The linear pre-coordinated framework solution contained 30 wt% tetraethyl orthosilicate, 4 wt% ethylenediamine, 6 wt% terephthalic acid, and 60 wt% dichloromethane. Further, 16 wt% of poly(N-isopropylacrylamide) hydrogel microspheres (prepared by the same method as in Example 1) were added to the solution. The solution was subjected to ultrasonic treatment for 22 min at an ultrasonic power of 58 kHz and a temperature of 42 °C to uniformly heat and disperse the microspheres, uniformly release water molecules into the solution, and allow the linear preligand to undergo hydrolysis-condensation to obtain low-polymerization linear inorganic molecular chains. Further addition of 5 wt% vanadium dichloroethylene metal alkoxide monomer to complete the chain extension reaction of the low-polymerization degree linear inorganic molecular chain, and then adding 4.2 wt% 3-azidopropyltrimethoxysilane to terminate the chain extension reaction, thereby obtaining a linear inorganic long chain with controllable molecular weight. The solution was further concentrated by negative pressure suction to produce a high-concentration linear inorganic long-chain sol, and precursor nanofiber materials were prepared by electrospinning technology. Electrospinning process parameters: injection rate of a single needle is 3.3 ml / h, voltage is 18 kV, and receiving distance is 17 cm.

[0052] Atomized water is introduced into the ligand processing device 1 at a flow rate of 5 L / h. Further irradiation with a single-band ultraviolet light source, specifically a 160-200nm xenon excimer ultraviolet lamp, generates hydroxyl radicals, emitting photons with energies of 5.6-9.8 eV and a power of 48 mW / cm². 2 ; Subsequently, hydroxyl radicals are dispersed into the fiber material through outlets with progressively increasing widths of 2.7 cm, causing the ligands in the fiber to cleave and thus removing the ligands, resulting in ligand-free inorganic nanofiber material.

[0053] The ligand-free inorganic nanofiber material was transported to a differential transport-microwave oxygen-deficient calcination device (2), and the microwave power was controlled at 2.7 GHz to make the amorphous inorganic nanofibers nucleate uniformly and inhibit grain growth in a 7% oxygen-deficient atmosphere. The speed difference of the rollers was further adjusted to 0.19 m / min to perform differential stretching on the ceramic fibers after initial nucleation; at the same time, the high dielectric constant of alumina was used to generate a locally amplified electric field on the fiber surface, so that the crystal structure in the fiber was compactly arranged. A grain size of 25 nm and a pore volume of 2 mm were obtained. 3 Flexible silica nano-ceramic fibers with an average fiber diameter of 450 nm, tensile strength of 0.8 GPa, elongation at break of 3%, and softness of 298 mN.

[0054] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination, characterized in that, Includes the following steps: S1. The metal alkoxide monomers are coordinated and linearly linked. Then, hydrolysis-condensation, chain extension and end-capping reactions are triggered by introducing hydrogel microspheres to obtain linear inorganic long-chain sol, which is then electrospun into precursor nanofibers. S2. The precursor nanofibers are placed in the ligand treatment device (1), oxygen and atomized water are introduced, and ultraviolet light is used to irradiate them in sequence to generate hydroxyl radicals. The hydroxyl radicals are then used to act on the fibers to cleave and remove their organic ligands, resulting in ligand-free inorganic nanofibers. S3. The ligand-free inorganic nanofibers are fed into the differential transport-microwave oxygen-deficient calcination device (2). In the differential transport-microwave oxygen-deficient calcination device (2), an oxygen-deficient atmosphere is established by the oxygen-deficient module (208), and the fibers are heated by the microwave device (209). At the same time, the auxiliary roller (211) with a high dielectric material lattice structure on its surface generates a local electric field with the fiber under the action of microwave, which promotes the uniform formation of crystal nuclei. The fiber is then stretched at a differential speed by the roller (210) with a speed difference, and finally a flexible ceramic nanofiber product is obtained.

2. The method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination according to claim 1, characterized in that, In S1, the specific process of coordinating and linearly linking the metal alkoxide monomers includes: Linear and rigid bidentate linkers are added to metal alkoxide solution to bridge the metal alkoxide monomers as intermediates to form a linear framework. Then, a flexible bidentate stabilizer is added to replace the remaining active groups to form a stable linear pre-coordinated framework. The metal alkoxide is selected from one or more alkoxides of titanium, zirconium, aluminum, tin, and hafnium; The linear, rigid bidental connector is selected from p-phenylenediamine, terephthalic acid, or 1,4-benzenediol; The flexible bidental stabilizer is selected from ethylenediamine, tetramethylethylenediamine, or acetylacetone.

3. The method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination according to claim 2, characterized in that, In S1, the process of triggering a hydrolysis-condensation reaction by introducing hydrogel microspheres includes: Thermosensitive hydrogel microspheres are added and heated and uniformly dispersed by ultrasonic treatment, thereby controllably releasing the contained water molecules, initiating the hydrolysis-condensation of the linear pre-coordinated framework, and forming low-polymerization linear inorganic molecular chains. The temperature-sensitive hydrogel microspheres are selected from one or more combinations of poly(N-isopropylacrylamide) hydrogel microspheres, poly(N-isopropylacrylamide-acrylic acid) hydrogel microspheres, poly(N-isopropylacrylamide-hydroxyethyl methacrylate) hydrogel microspheres, and carboxymethyl chitosan hydrogel microspheres. The amount of temperature-sensitive hydrogel microspheres added is 5% to 20% of the mass of the metal alkoxide monomer. The ultrasonic treatment has a power of 10~100kHz and a temperature of 5~60℃.

4. The method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination according to claim 3, characterized in that, Based on the total mass of the linear pre-coordinated framework solution, the mass fraction of the metal alkoxide is 22wt% to 30wt%, the mass fraction of the linear, rigid bidental connector is 6wt% to 8wt%, the mass fraction of the flexible bidental stabilizer is 4wt% to 10wt%, and the balance is solvent.

5. The method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination according to claim 1, characterized in that, In S2, the ligand processing device (1) includes a main housing of the ligand processing device and a component disposed within the main housing of the ligand processing device: The first processing area for generating ozone is provided with a first ultraviolet light source (101) that emits ultraviolet light in the 185nm band and a concave mirror (102). The concave mirror (102) is located below the first ultraviolet light source (101). The first processing area is provided with an oxygen inlet (103). The concave mirror (102) is used to convert the light emitted by the first ultraviolet light source (101) into parallel light. The second processing zone for generating hydroxyl radicals is provided with a second ultraviolet light source (106) that emits ultraviolet light in the 254nm band, and the second processing zone is provided with an atomized water inlet (105). A gradient outlet (107) for uniformly exporting hydroxyl radicals is provided at the bottom of the main housing of the ligand processing device; The first treatment zone and the second treatment zone are separated by a partition (104), and the second treatment zone is provided with a grooved flow channel to allow ozone and water molecules to fully mix and react.

6. The method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination according to claim 5, characterized in that, The first ultraviolet light source (101) is a low-pressure mercury lamp, an excimer light source, or a laser light source; The second ultraviolet light source (106) is a low-pressure mercury lamp, an ozone-free low-pressure mercury lamp, or an ultraviolet light-emitting diode. The power density of the first ultraviolet light source (101) and the second ultraviolet light source (106) is 10~100 mW / cm². 2 ; The concave mirror (102) is made of fused silica, calcium fluoride or zinc selenide; The partition (104) is made of aluminum, stainless steel, fused silica or polytetrafluoroethylene; Ultraviolet light in the 185nm band breaks down oxygen to produce oxygen atoms. The oxygen atoms combine with oxygen to generate ozone. Ultraviolet light in the 254nm band causes ozone to react with atomized water molecules to generate hydroxyl radicals. The hydroxyl radicals are uniformly dispersed into the precursor nanofibers through the gradient outlet (107). Through their strong oxidizing properties, they break down the carbon-carbon bonds and carbon-hydrogen bonds of the organic ligands in the fibers, achieving a removal rate of not less than 95%, while retaining the metal-oxygen backbone structure.

7. The method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination according to claim 1, characterized in that, In S3, the differential transport-microwave oxygen-deficient calcination device (2) includes a main shell of the calcination device and the following disposed in the main shell of the calcination device: multiple rollers (210) for transporting and stretching fibers, a microwave device (209) for providing microwave heating, an auxiliary roller (211) with a surface coated with a high dielectric constant material, and an oxygen-deficient module (208) for constructing and maintaining an oxygen-deficient atmosphere. The microwave device (209) is located on one side of the roller (210), the auxiliary roller (211) is located on the other side of the roller (210), and the ligand-free inorganic nanofibers are placed between the auxiliary roller (211) and the roller (210).

8. The method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination according to claim 7, characterized in that, The oxygen-deficient module (208) includes an oxygen-deficient pipe (2081) and a plurality of oxygen-deficient gas inlets (2082) provided on the oxygen-deficient pipe (2081). A mixture of nitrogen, argon or helium with an oxygen content of not more than 18% is introduced into the oxygen-deficient pipe (2081). The microwave device (209) is a microwave generator with gradient calcination characteristics; The calcination temperature of the microwave device (209) is 250~1500℃, and it is divided into 2~4 temperature gradient ranges.

9. The method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination according to claim 7, characterized in that, The high dielectric constant material on the surface of the auxiliary roller (211) is alumina, silicon nitride or ferrite. The surface of the auxiliary roller (211) is provided with a micron-scale lattice structure. The micron-scale lattice structure can generate a local electric field focusing effect under the action of microwave field, which accelerates the migration of metal and oxygen ions inside the fiber, thereby promoting the rapid and uniform formation of crystal nuclei and inhibiting grain growth. The size of the lattice unit is 0.5~20μm, and the unit spacing is 0.5~1000μm; The number of rollers (210) is at least two, and the operating speed increases in a gradient, with a speed range of 0.1~100 m / min. The speed difference applies a stretching force to the crystallizing ceramic fiber, causing the internal crystals to be tightly arranged along the fiber axis and releasing residual stress.

10. The method for forming ceramic nanofibers based on inorganic molecular chain electrospinning and pretreatment-calcination according to claim 1, characterized in that, In step S3, the prepared ceramic nanofiber product has a grain size of 4-25 nm and a pore volume of no more than 5 mm. 3 / g, with an average fiber diameter of 50~500 nm; When the ceramic nanofiber product is a single fiber, its tensile strength is not less than 0.5 GPa and its elongation at break is not less than 1.5%. When the ceramic nanofiber product is a fiber membrane, its softness is not higher than 300 mN.

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