Flexible ceramic nanofiber paper based on linear inorganic molecular chain as well as preparation method and application of flexible ceramic nanofiber paper

Abstract

The invention belongs to the technical field of nanofiber materials, and particularly relates to flexible ceramic nanofiber paper based on linear inorganic molecular chains and a preparation method and application thereof.The preparation method comprises the following steps that an alcoholic solution of long inert ligands / short inert ligands is prepared and dropwise added into a metal alkoxide monomer solution; adding a catalyst into the long ligand modified monomer solution, mixing with the short ligand modified monomer solution, and adding deionized water; adding a chain extender and an end-capping reagent to obtain a linear inorganic long chain with long-short side groups; preparing a spinning solution, and performing spinning forming in an auxiliary force field to obtain a precursor; and carrying out infrared radiation treatment, non-adhesion rolling and instantaneous cooling shaping, then carrying out deep ultraviolet radiation, and then calcining. Compared with the prior art, the problems that in the prior art, due to the fact that fiber inner hole defects are likely to be caused, ceramic fiber paper is insufficient in flexibility, poor in uniformity and prone to embrittlement are solved. According to the preparation method of the scheme, preparation of the ceramic nanofiber paper with uniform thickness and gram weight and excellent flexibility can be realized.

Description

Technical Field

[0001] This invention belongs to the field of nanofiber materials technology, specifically relating to a flexible ceramic nanofiber paper based on linear inorganic molecular chains, its preparation method, and its application. Background Technology

[0002] Ceramic fiber paper, with its high-temperature resistance, corrosion resistance, and flame-retardant properties, is widely used in aerospace thermal insulation, flame-retardant noise reduction in transportation equipment, and thermal runaway protection for new energy batteries. Traditional methods for preparing ceramic fiber paper mainly include wet papermaking and dry forming. Wet papermaking typically uses micron-sized ceramic short fibers as raw materials, preparing ceramic fiber paper through dispersion, forming, and dehydration processes. However, because the fibers rely mainly on simple physical bonding, the paper has low strength and is prone to dusting. Furthermore, fibers tend to agglomerate in wet systems, making stable dispersion difficult and resulting in insufficient uniformity in the finished product's basis weight and thickness. Since nanofibers, due to their high specific surface area, are even more prone to agglomeration than micron-sized fibers, this technology is unsuitable for the forming and preparation of high-performance nanofiber paper. Dry forming technology mainly constructs ceramic fibers into sheet structures through airflow web laying, hot pressing, and bonding curing processes. This method often requires the addition of a large amount of organic binder, which affects the temperature resistance and structural stability of the ceramic fiber paper. Meanwhile, dry forming makes it difficult to achieve controllable spreading and uniform regulation of nanofibers, resulting in nanofiber paper with poor uniformity and many internal defects, which cannot meet the application requirements of complex scenarios.

[0003] In recent years, electrospinning has become an important route for preparing ceramic nanofiber paper due to its ability to directly prepare nanoscale continuous fibers. For example, patent CN202411668911.1 mixes PVA solution with oxide substrate sol and uses electrospinning technology to obtain precursor composite nanofiber paper, which is then calcined at high temperature to obtain ceramic nanofiber paper. However, the fibers obtained by this method rely only on simple physical overlap, lacking strong bonding force, resulting in insufficient mechanical properties. Patent ZL202210597804.9 uses electrospinning technology to obtain precursor nanofiber paper, then overlaps at least two sheets of paper at their edges, covers the overlap with a strip-shaped connecting layer, and uses a method of dipping diluted precursor sol to spot-coat and bond the connecting layer, finally obtaining a ceramic nanofiber membrane after calcination. However, the strengthening effect of this technology is mainly concentrated at the splicing interface, making it difficult to achieve overall reinforcement of the fiber paper. Furthermore, thickness fluctuations at the splicing points result in poor uniformity of the fiber paper. Dot-coating bonding relies on manual operation, leading to poor consistency and repeatability in the amount of coating and the degree of wetting, hindering large-scale production. In addition, all these methods require the removal of the polymer template during the ceramicization process. The thermal decomposition of the polymer inevitably causes defects in the fiber's internal pores, resulting in insufficient flexibility and brittleness in the ceramic fiber paper, making it difficult to meet the application requirements of high-precision fields.

[0004] Therefore, there is an urgent need to develop a new method for the large-scale continuous manufacturing of flexible ceramic nanofiber paper to meet its application needs in aerospace, new energy and flexible electronics. Summary of the Invention

[0005] The purpose of this invention is to address at least one of the aforementioned problems by providing a flexible ceramic nanofiber paper based on linear inorganic molecular chains, its preparation method, and its applications. This addresses the issues in existing technologies where the removal of polymer templates easily leads to defects in the fiber's internal pores, resulting in insufficient flexibility, poor uniformity, and brittleness in the ceramic nanofiber paper. The preparation method of this invention can achieve the preparation of ceramic nanofiber paper with uniform thickness and basis weight and excellent flexibility.

[0006] The objective of this invention is achieved through the following technical solution: The first aspect of this invention discloses a method for preparing flexible ceramic nanofiber paper based on linear inorganic molecular chains, comprising the following steps: S1: Prepare alcohol solutions with long inert ligands and short inert ligands respectively, and add them dropwise to metal alkoxide monomer solutions for coordination modification to obtain long-ligand modified monomer solutions and short-ligand modified monomer solutions; add a catalyst to the long-ligand modified monomer solution and mix it with the short-ligand modified monomer solution, then add deionized water to carry out a hydrolysis-condensation reaction to obtain a low-polymerization degree linear inorganic molecular chain with long-short ligands; then add a chain extender to carry out a chain extension reaction, and then add an end-capping agent to terminate the chain extension reaction to obtain a linear inorganic long chain with long-short side groups; S2: The linear inorganic long chain with long-short side groups obtained in step S1 is prepared into a spinning solution and spun in an auxiliary force field to obtain precursor nanofiber paper. S3: The precursor nanofiber paper obtained in step S2 is subjected to infrared radiation treatment, non-adhesive rolling and instantaneous cooling and shaping in sequence, and then the organic ligands are decomposed by deep ultraviolet irradiation, followed by calcination to obtain ceramic nanofiber paper.

[0007] Preferably, in the alcohol solution of the long inert ligand, the long inert ligand and the alcohol solvent are mixed in a molar ratio of 1:5 to 1:10, and in the alcohol solution of the short inert ligand, the short inert ligand and the alcohol solvent are mixed in a molar ratio of 1:5 to 1:10. The long inert ligand is selected from one or more of citric acid, aminotriacetic acid, ethylenediaminetetraacetic acid, ammonium citrate, stearic acid, oleic acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid and lauric acid; The short inert ligand is selected from one or more of acetic acid, oxalic acid, ethylenediamine, acetylacetone, and trifluoroacetylacetone; The alcohol solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, ethylene glycol, butanediol, hexanediol, and glycerol; The metal alkoxide is selected from one or more of the following sources: titanium, zirconium, aluminum, tin, hafnium, gallium, tantalum, and niobium. The titanium source is selected from one or more of the following sources: titanium tetraethanol, titanium tetraethanolamine, titanium n-propoxide, titanium isopropoxide, titanium n-butoxide, titanium isobutoxide, titanium tert-butoxide, titanium tetrapentoxide, and titanium isooctanol. The zirconium source is selected from one or more of the following sources: zirconium tetraethanolamine, zirconium tetraethanolamine, zirconium n-propoxide, zirconium isopropoxide, zirconium n-butoxide, zirconium isobutoxide, zirconium tert-butoxide, and zirconium tetrapentoxide. The aluminum source is selected from the following sources: aluminum trimethoxy, aluminum triethanolamine, aluminum tri-n-propoxy, aluminum isopropoxide, aluminum n-butoxide, and aluminum sec-butoxide. The source is selected from one or more of aluminum tert-butoxide; the tin source is selected from one or more of tetramethyltin, tetraethanoltin, n-propoxidetin, isopropoxidetin, n-butoxidetin, isobutoxidetin, tert-butoxidetin, and tetrapentoxidetin; the hafnium source is selected from one or more of tetramethylhafnium, tetraethanolhafnium, n-propoxidehafnium, isopropoxidehafnium, n-butoxidehafnium, isobutoxidehafnium, tert-butoxidehafnium, and tetrapentoxidehafnium; the gallium source is selected from one or two of gallium isopropoxide and gallium tert-butoxide; the tantalum source is selected from one or two of tantalum isopropoxide and tantalum n-butoxide; the niobium source is selected from one or two of niobium isopropoxide and niobium n-butoxide. The catalyst is selected from one or more of boron trifluoride, aluminum trichloride, boron tribromide, boron triiodide, tin tetrachloride, silicon tetrachloride, titanium tetrachloride, zirconium tetrachloride, hafnium tetrachloride, tetracyanoethylene, and trinitrobenzene; The chain extender is selected from one or more of the following: diisopropoxydiacetylacetonitrile, diisopropyl bis(ethyl acetoacetate)titanate, di(diethylcitrate)zirconium dipropoxide, di(ethyl acetoacetate)diisopropoxyaluminate, titanium dichlorodecene, zirconium dichlorodecene, hafnium dichlorodecene, molybdenum dichlorodecene, vanadium dichlorodecene, and niobium dichlorodecene. The end-capping agent is selected from one or more of common chemical end-capping agents, visible light responsive end-capping agents, and ultraviolet light responsive end-capping agents; the common chemical end-capping agent is selected from one or two of methyl isocyanate and phenyl isocyanate; the visible light end-capping agent is selected from one or more of 2-diazo-1-naphthol-5-sulfonyl chloride, ethyl diazonate, and 4-azido-2,3,5,6-tetrafluorobenzoic acid; the ultraviolet light responsive end-capping agent is selected from one or more of 4-azidobenzoic acid, 3-azidopropyltrimethoxysilane, and 1,3-dioxopentanepropyltrimethoxysilane.

[0008] Preferably, the linear inorganic long chain with long-short side groups is prepared into a spinning solution by negative pressure suction. The conditions for negative pressure suction are: constant temperature heating of 30~150℃ and pressure of 0~-0.1MPa; The external force of the auxiliary force field is selected from one or more of electrostatic force, airflow force, and centrifugal force.

[0009] Preferably, the infrared radiation band of the infrared radiation treatment is 0.75~1000μm; The non-adhesive roller pressing pressure is 0.1~5MPa; The temperature range for the instantaneous cooling and shaping is -5 to 15°C.

[0010] Preferably, the wavelength of the deep ultraviolet irradiation is 180~300nm; The calcination is performed under alternating atmosphere or inert gas. The alternating atmosphere calcination is a periodically switching atmosphere consisting of a mixture of oxygen-containing gas and an inert gas. The oxygen-containing gas is selected from one or two of air and oxygen, and the inert gas is selected from one or more of nitrogen, argon, helium, neon, krypton, xenon, and radon. The switching cycle is 10-600 s / time. The oxygen volume fraction in the inert gas calcination is controlled to be ≤18%. The peak temperature of the calcination is 400-1500℃.

[0011] Preferably, the spinning process is carried out in a uniform liquid-feed spinning system; The uniform liquid supply spinning system includes a spinneret and a main channel, a circulating liquid temperature control layer, a shear screw, and a necked-down fractal liquid supply channel located inside the spinneret. The main flow channel is arranged parallel to the spinneret, and the necked-down fractal liquid supply channel is connected to the side of the main flow channel and communicates with the bottom nozzle of the spinneret. The circulating fluid temperature control layer is arranged around the outside of the main flow channel and the necked fractal fluid supply channel. The shearing screw is located inside the main channel and is parallel to the spinneret.

[0012] Preferably, the uniform liquid supply spinning system further includes a guide cone and a circulating liquid storage tank; The guide cone is disposed at the liquid distribution port of the necked-down fractal liquid supply channel; The inlet and outlet of the circulating liquid temperature control layer are respectively sealed to the circulating liquid storage tank via flange interfaces.

[0013] Preferably, the infrared radiation treatment, the non-adhesive rolling, and the instantaneous cooling and shaping are all performed in an infrared softening and welding-instantaneous cooling and shaping device; The infrared softening welding-instant cooling and shaping device includes an infrared radiation source, a low surface energy roll, a low surface energy transition roll, and a cold shaping roll. The infrared radiation source is located upstream of the low surface energy roll and is used for infrared radiation treatment. The low surface energy roll, low surface energy transition roll, and cold setting roll are arranged in parallel to each other and in sequence, and the axis height of the low surface energy transition roll is lower than the axis height of the low surface energy roll and the cold setting roll. The cold setting roller has a spiral conveying channel inside its body.

[0014] The second aspect of this invention discloses a flexible ceramic nanofiber paper based on linear inorganic molecular chains, which is obtained by any of the preparation methods described above; The ceramic nanofiber paper has a fiber diameter of 50~500nm, a thickness of 20μm~5mm, and a basis weight of 20~200g / m³. 2 Fracture toughness ≥ 0.24 MJ / m 3 Both the basis weight and thickness CV values ​​are ≤5%.

[0015] The third aspect of this invention discloses the application of flexible ceramic nanofiber paper based on linear inorganic molecular chains in battery heat insulation pads, thermal control insulation layers, flexible electrode or separator support layers, fireproof and noise-reducing insulation layers, energy storage and thermal management components, high-temperature resistant filter media, catalyst carriers, flexible electrolyte support frameworks and interface buffer layers, ion conduction support networks, high insulation and high thermal conductivity encapsulation and structural support layers, and sensitive unit carriers and high-temperature resistant stable substrates.

[0016] The working principle of this invention is as follows: (1) This invention utilizes long and short inert ligands to modify metal alkoxide monomers, transforming them into bifunctional alkoxide monomers with two alkoxy groups. Under the action of a catalyst, the electropositivity of the metal center of the long-ligand modified monomer is enhanced, and the metal-oxygen bond is activated, thereby improving the polycondensation activity of the long-ligand modified monomer and enabling it to copolymerize with the short-ligand modified monomer. The polycondensation reaction extends linearly along the one-dimensional direction, forming a linear inorganic long chain with a synergistic distribution of long and short side groups. The long side groups can improve the thermal mobility of the chain segments, while the short ligands reduce the proportion of organic components, allowing the linear inorganic long chain to be formulated into a stable spinning solution and form a thermoplastic precursor nanofiber paper without relying on an organic polymer template.

[0017] (2) This invention utilizes infrared radiation to induce molecular-level thermal excitation in linear inorganic long chains. By controlling the infrared radiation frequency to match the characteristic vibrational frequency of the long side groups in the inorganic long chains, strong resonance absorption is induced in the long side group segments, causing the precursor nanofibers to exhibit significant thermal softening and thermoplastic behavior. During the subsequent hot pressing process, adjacent fibers in the softened state undergo interpenetration and diffusion at the contact interface, thereby achieving in-situ fusion and physical adhesion between fibers, forming a continuously bonded two-dimensional network reinforcement structure.

[0018] Compared with the prior art, the present invention has the following beneficial effects: (1) The ceramic nanofiber paper prepared by the present invention is composed of nanoscale ceramic fibers. It is not easy to produce stripe deposition or band accumulation in the width direction, and has excellent uniformity. It is suitable for continuous application scenarios with high requirements for quality consistency.

[0019] (2) This invention forms a stable fusion bond inside the ceramic nanofiber paper, constructing a continuous and stable two-dimensional fiber connection network, making it less prone to powder shedding and tearing, with a fracture toughness ≥0.24MJ / m. 3 It has excellent flexibility and fracture resistance.

[0020] (3) The ceramic nanofiber paper prepared by this invention has a fiber diameter of 50~500nm, a thickness that can be controlled within the range of 20μm~5mm, and a basis weight of 20~200g / m². 2 With a thickness and weight CV value of ≤5%, it combines the characteristics of being lightweight, high temperature resistant, flame retardant, heat insulation and structural stability. It has good engineering adaptability and application expansion, and can be used in the fields of heat insulation protection of new energy batteries, flame retardant noise reduction of transportation equipment, and thermal management of flexible wearable devices. Attached Figure Description

[0021] Figure 1 A partial cross-sectional view of a uniform liquid supply spinning system.

[0022] Figure 2 This is a side-view cross-sectional structural diagram of the circulating fluid temperature control layer.

[0023] Figure 3 This is a schematic diagram of the necked-down fractal liquid supply channel.

[0024] Figure 4 This is a schematic diagram of the infrared softening welding-instant cooling and shaping device.

[0025] Figure 5 This is a schematic diagram of the structure of the cold setting roller.

[0026] Figure 6 An optical photograph of the ceramic nanofiber paper prepared in Example 1.

[0027] Figure 7 The image shown is a SEM image of the ceramic nanofiber paper fiber fusion structure prepared in Example 1.

[0028] In the diagram: 1. Uniform liquid supply spinning system; 1-1. Spinneret; 1-2. Main channel; 1-3. Circulating liquid temperature control layer; 1-4. Shear screw; 1-5. Necked-down fractal liquid supply channel; 1-6. Guide cone; 1-7. Liquid inlet; 1-8. Liquid outlet; 1-9. Circulating liquid storage tank; 2. Infrared softening welding-instant cooling and setting device; 2-1. Infrared radiation source; 2-2. Low surface energy roll; 2-3. Low surface energy transition roll; 2-4. Cold setting roll; 2-5. Spiral conveyor channel. Detailed Implementation

[0029] 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.

[0030] In the following embodiments and comparative examples, unless otherwise specified, the raw materials or processing techniques are all conventional commercially available raw materials or conventional processing techniques in the art. Unless otherwise specified, the functional components or structures are all conventional components or conventional structures used in the art to achieve the corresponding functions.

[0031] The linear inorganic molecular chain provided by this invention is a linear inorganic long chain containing both long and short organic side groups, which can be formulated into a spinning solution and formed into a thermoplastic precursor nanofiber paper. The precursor nanofiber paper can enter a softened state under infrared heating conditions, facilitating roll forming of a fiber fusion network and rapid cooling for shaping. After deep ultraviolet pretreatment and controlled calcination in an alternating atmosphere / oxygen-deficient environment, a ceramic nanofiber paper with uniform thickness and basis weight and excellent flexibility can be obtained.

[0032] A method for preparing ceramic nanofiber paper based on linear inorganic molecular chains involves coordinating and modifying metal alkoxide monomers with long / short inert ligands to transform them into bifunctional alkoxide monomers. A catalyst is added to the long-ligand-modified monomer to enable copolymerization with the short-ligand-modified monomer, resulting in low-polymerization-degree linear inorganic molecular chains. A chain extender is added to extend the chain, and the chain extension reaction is terminated using a capping agent, thereby synthesizing a spinning solution of linear inorganic molecular chains with long-short side groups. This solution is spun using a high-speed uniform liquid feeding spinning system to obtain precursor nanofiber paper. Infrared heating and pressure treatment are then applied to form a fusion network between the fibers, followed by flash cooling and shaping. Finally, calcination yields flexible ceramic nanofiber paper.

[0033] Specifically, the following steps are included: S1. Dilute the long and short inert ligands with an alcohol solvent, and add the two mixed solutions dropwise to the metal alkoxide monomer solution. Perform coordination modification by rapid stirring to obtain two bifunctional coordination-modified monomer solutions. Add a catalyst to the long ligand-modified monomer solution to enable copolymerization with the short ligand-modified monomer. Blend the two modified monomer solutions, and then add deionized water to allow the two modified monomers to undergo a hydrolysis-condensation reaction to obtain a low-polymerization-degree linear inorganic molecular chain with long and short ligands. Then add a chain extender to extend the chain, and then add a UV-responsive end-capping agent under visible light conditions. Treat the solution with UV light to terminate the chain extension reaction and obtain a linear inorganic long chain with long and short side groups.

[0034] S2. Under constant temperature conditions, the linear inorganic long-chain solution synthesized in S1 is prepared into a spinning solution by negative pressure suction, and then supplied to a high-speed uniform liquid supply spinning system 1. In an auxiliary force field, a precursor nanofiber paper with uniform basis weight is obtained by spinning. Among them, the uniform liquid supply spinning system 1 with low interference high density nozzle arrangement and uniform pressure and stable flow liquid supply structure suppresses the difference in liquid output from the nozzle and the fluctuation of deposition distribution, so as to realize the continuous forming of thin and uniform precursor nanofiber paper.

[0035] S3. The precursor nanofiber paper prepared in S2 is fed to the infrared softening and welding-instant cooling and setting device 2 to treat the precursor nanofiber paper with infrared radiation to rapidly soften the fibers. Then, the nanofiber paper is fed to the low surface energy roller, and the pressure is adjusted to perform non-adhesive roller pressing on the precursor nanofiber paper to make the fiber contact points weld together. The low surface energy transition roller suppresses local debonding, and the cold setting roller achieves instant cooling and setting to form a continuous and adhesive two-dimensional network structure. The hot-pressed nanofiber paper is further fed to the deep ultraviolet pretreatment device to cause the organic ligands to decompose, and then fed to the microwave-assisted oxygen-deficient calcination device for calcination to finally obtain flexible ceramic nanofiber paper.

[0036] In step S2, the high-speed uniform liquid supply spinning system 1 includes a low-interference, high-density spinneret 1-1, a main channel 1-2 within the spinneret 1-1, a circulating liquid temperature control layer 1-3, a shear screw 1-4, and a necked-down fractal liquid supply channel 1-5, as shown below. Figures 1-3As shown; the main channel 1-2 is located on the upper layer of the spinneret 1-1 and is used to realize the main supply and distribution of the solution; the circulating liquid temperature control layer 1-3 surrounds the outside of the main channel 1-1 and the necked fractal liquid supply channel 1-5 and is used to control the temperature of the channel, eliminate viscosity fluctuations caused by local temperature differences, and ensure that the spinning solution has stable rheological properties. Specifically, the circulating liquid temperature control layer 1-3 is a spiral tube, and its inlet end 1-7 and outlet end 1-8 are respectively sealed to the circulating liquid storage tank 1-9 through flange interfaces; the shear screw 1-4 is located inside the main channel 1-2 and is parallel to the spinneret 1-1. It is used to apply continuous dynamic shear force to the spinning solution, effectively suppress the gelation tendency of the spinning solution during the transportation process and enhance the dispersion uniformity; the necked fractal liquid supply channel 1-5 is located at the lower end of the main channel 1-2 and is connected to the main channel 1-2. It is used to perform step-by-step pressure equalization and diversion of the fluid and suppress the supply pulsation. It is also equipped with a guide cone 1-6 inside. The solution enters the necked-down fractal liquid supply channel 1-5 through the main channel 1-2. Under the action of step-by-step diversion and necked-down section, a controlled pressure drop is formed, which makes the pressure and flow rate between different flow paths tend to be consistent, thereby improving the consistency of liquid output from each nozzle and making the basis weight and thickness of the precursor nanofiber paper more uniform.

[0037] In step S2, the bottom end of the low-interference high-density nozzle arrangement spinneret 1-1 is the spinning nozzle, and the nozzle is connected to the necking and fractal liquid supply channel 1-5 to reduce the mutual interference between the electric field and the flow field at the nozzle and improve the stability of parallel forming.

[0038] In step S2, the circulating liquid temperature control layer 1-3 surrounds the outside of the main flow channel and the fractal flow channel. Its inlet end 1-7 and outlet end 1-8 are sealed to the circulating liquid storage tank 1-9 through flange interfaces to achieve stable control of the temperature of the liquid supply channel.

[0039] In step S2, the necked fractal liquid supply channel 1-5 is located at the lower end of the main channel and communicates with the main channel. The internal liquid distribution port is equipped with a guide cone, which is used to rectify the spinning liquid axially and spread it radially, suppress local vortices and deflection, so that the spinning liquid forms a stable and uniform velocity field and pressure field before entering the nozzle, so as to further improve the distribution uniformity and the consistency of the liquid output from the nozzle.

[0040] In step S3, the infrared softening welding-instant cooling and shaping device 2 includes an infrared radiation source 2-1, a low surface energy roll 2-2, a low surface energy transition roll 2-3, and a cold shaping roll 2-4, as shown below. Figure 4 , 5As shown; during operation, infrared radiation source 2-1 heats the precursor nanofiber paper in a non-contact manner, causing the fiber surface to enter a controllable softening state; low surface energy roller 2-2 is used to perform non-adhesive rolling of the fiber paper under a set pressure, so that the fibers are fused at the overlap point and form a continuous and bonded two-dimensional network structure; low surface energy transition roller 2-3 suppresses local debonding and structural damage by adjusting the height difference and contact path; cold setting roller 2-4 is used to rapidly cool the fused area to achieve instantaneous cold setting, quickly locking the formed fiber connection network, thereby obtaining a continuous and stable two-dimensional fiber network structure.

[0041] In step S3, the infrared radiation source 2-1 is located directly above the starting end of the conveyor belt (used to convey the precursor nanofiber paper for spinning and forming), with its radiation surface facing the conveyor belt; the low surface energy transition roller 2-3 is set between the low surface energy roller 2-2 and the cold setting roller 2-4, and its axis height is lower than that of the rollers on both sides to achieve a stable transition; a spiral conveying channel 2-5 is set in the body of the cold setting roller 2-4 to pass condensate to achieve rapid heat exchange and cooling of the roller body.

[0042] In some specific embodiments, in step S1, dilution involves diluting the inert ligand with the alcohol solvent at a molar ratio of 1:5 to 1:10, with a dropwise addition rate of 0.01 to 0.2 wt% / s of the metal alkoxide monomer mass; rapid stirring is performed at 300 to 1000 r / min; the metal alkoxide is selected from one or more combinations of titanium, zirconium, aluminum, tin, hafnium, gallium, tantalum, and niobium sources; the titanium source is selected from one or more combinations of titanium tetraethanol, titanium tetraethanolamine, titanium n-propoxide, titanium isopropoxide, titanium n-butoxide, titanium isobutoxide, titanium tert-butoxide, titanium tetrapentoxide, and titanium isooctoxide; the zirconium source is selected from zirconium tetraethanolamine, zirconium tetraethanolamine, zirconium n-propoxide, zirconium isopropoxide, zirconium n-butoxide, zirconium isobutoxide, and zirconium tert-butoxide. The aluminum source is selected from one or more combinations of zirconium tetrapentoxide; the aluminum source is selected from one or more combinations of aluminum trimethoxy, aluminum triethanoloxide, aluminum tri-n-propoxy, aluminum isopropoxide, aluminum n-butoxide, aluminum sec-butoxide, and aluminum tert-butoxide; the tin source is selected from one or more combinations of tin tetramethanol, tin tetraethanoloxide, tin n-propoxide, tin isopropoxide, tin n-butoxide, tin isobutoxide, tin tert-butoxide, and tin tetrapentoxide; the hafnium source is selected from one or more combinations of hafnium tetramethanol, hafnium tetraethanoloxide, hafnium n-propoxide, hafnium isopropoxide, hafnium n-butoxide, hafnium isobutoxide, hafnium tert-butoxide, and hafnium tetrapentoxide; the gallium source is selected from one or more combinations of gallium isopropoxide and gallium tert-butoxide; the tantalum source is selected from one or more combinations of tantalum isopropoxide and tantalum n-butoxide; the niobium source is selected from niobium isopropoxide and niobium n-butoxide. One or two combinations of the following: the long inert ligand is selected from one or more of citric acid, aminotriacetic acid, ethylenediaminetetraacetic acid, ammonium citrate, stearic acid, oleic acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid, and lauric acid; the short inert ligand is selected from one or more of acetic acid, oxalic acid, ethylenediamine, acetylacetone, and trifluoroacetylacetone; the catalyst is selected from one or more of boron trifluoride, aluminum trichloride, boron tribromide, boron triiodide, tin tetrachloride, silicon tetrachloride, titanium tetrachloride, zirconium tetrachloride, hafnium tetrachloride, tetracyanoethylene, and trinitrobenzene; the chain extender is titanium dichlorophenocene, zirconium dichlorophenocene, hafnium dichlorophenocene, molybdenum dichlorophenocene, vanadium dichlorophenocene, niobium dichlorophenocene, titanium-bis(benzotriazole) complex, titanium-bis(benzotriazole) complex, etc. One or more of (2-mercaptoquinazolin-4-one) complexes and zirconium-bis(benzotriazole) complexes; the end-capping agent is selected from one or more of common chemical end-capping agents, visible light responsive end-capping agents, and ultraviolet light responsive end-capping agents; the common chemical end-capping agent is selected from one or a combination of two of methyl isocyanate and phenyl isocyanate; the visible light end-capping agent is selected from one or a combination of several of 2-diazo-1-naphthol-5-sulfonyl chloride, ethyl diazonate, and 4-azido-2,3,5,6-tetrafluorobenzoic acid; the ultraviolet light responsive end-capping agent is selected from one or a combination of two of 4-azidobenzoic acid, 3-azidopropyltrimethoxysilane, and 1,3-dioxopentanepropyltrimethoxysilane.

[0043] In some specific embodiments, in step S2, the negative pressure suction conditions are constant temperature heating of 30~150℃ and pressure of 0~-0.1MPa. The external force in the auxiliary force field is selected from one or more combinations of electrostatic force, airflow force, and centrifugal force. The shear screws 1-4 are one or more combinations of polytetrafluoroethylene, polyoxymethylene, polyetheretherketone, polyphenylene sulfide, alumina ceramic, zirconium oxide ceramic, and silicon nitride ceramic materials, and their rotation speed is 100~2000 r / min. The circulating fluid passing through the circulating fluid temperature control layer 1-3 is selected from one or more combinations of perfluoropolyether oil, silicone oil, triaryl phosphate, trialkyl phosphate, and alkyl-aryl phosphate, and the temperature control range is -5~100℃. The necked-down fractal liquid supply channel 1-5 adopts a multi-stage flow channel structure consisting of 3 to 10 main flow channels (arranged in parallel) and connecting the main flow channels. The length of each stage flow channel is 10 to 25 mm, and the diameter is 2.4 to 6 mm. The throat diameter of the necked-down fractal liquid supply channel 1-5 is 30% to 75% of the main pipe diameter. The guide cone 1-6 is an elliptical cone with a bottom diameter of 2.20 to 5.90 mm, a top diameter of 0.70 to 3.30 mm, and an axial height of 2.0 to 8.0 mm. The cone is selected from one or more of stainless steel, titanium alloy, aluminum alloy, nickel-based alloy, and copper alloy.

[0044] In some specific embodiments, in step S3, the infrared radiation treatment (infrared radiation source 2-1) has a wavelength range of 0.75~1000μm; the core material of the rolls (low surface energy rolls 2-2 and low surface energy transition rolls 2-3) is selected from one or more of medium carbon steel, alloy steel and stainless steel, and a low surface energy roll sleeve is provided on its outer surface. The roll sleeve material is selected from one or more of polytetrafluoroethylene, perfluoroalkoxy resin, fluorinated ethylene propylene copolymer, silicone rubber and fluororubber, and the roll pressure is 0.1~5MPa; the condensate passing through the spiral conveying channel 2-5 inside the cold setting roll 2-4 is one or more combinations of ethylene glycol solution, propylene glycol solution, methyl silicone oil, phenylmethyl silicone oil, fluorosilicone oil, alkylated aromatic hydrocarbons, diesters and polyol esters, and the temperature control range is -5~15℃. The deep ultraviolet light source of the deep ultraviolet pretreatment device emits wavelengths of 180~300nm, causing pre-decomposition of organic side groups and reducing the risk of transient exothermic reactions during subsequent calcination. The calcination method is alternating atmosphere calcination or oxygen-deficient calcination. Alternating atmosphere calcination uses a mixture of oxygen-containing gas and inert gas, which is periodically switched. The oxygen-containing gas is selected from one or two of air and oxygen, and the inert gas is selected from one or more of nitrogen, argon, helium, neon, krypton, xenon, and radon. The switching cycle is 10~600s / time. In oxygen-deficient calcination, the oxygen volume fraction is controlled to be ≤18%. The peak calcination temperature is 400~1500℃, and a continuous heating-holding-cooling thermal process or a segmented thermal process is adopted. The controlled thermal process inhibits excessive grain growth, and finally, ceramic nanofiber paper with uniform thickness and basis weight and excellent flexibility is obtained.

[0045] The prepared ceramic nanofiber paper has a fiber diameter of 50-500 nm, a thickness of 20 μm-5 mm, and a basis weight of 20-200 g / m². 2 Fracture toughness ≥ 0.24 MJ / m 3 Both the basis weight and thickness CV values ​​are ≤5%.

[0046] The prepared ceramic nanofiber paper can be used in battery heat insulation pads for new energy vehicles, thermal control insulation layers for electronic devices, flexible electrode and separator support layers for solid-state lithium batteries, fireproof and noise-reducing insulation layers for drones, energy storage and thermal management components for flexible wearable devices, high-temperature resistant filter media for gas filtration and separation devices, catalyst carriers for high-efficiency catalytic reactors, flexible electrolyte support frameworks and interface buffer layers in flexible solid-state batteries, ion conduction support networks in solid-state electrolyte systems, high-insulation and high-thermal-conductivity encapsulation and structural support layers in semiconductor devices, and sensitive unit carriers and high-temperature resistant stable substrates in sensors.

[0047] Example 1 This embodiment provides a ceramic nanofiber paper based on linear inorganic molecular chains and its preparation method, the specific steps of which are as follows: (1) Octanoic acid and isopropanol were uniformly mixed at a molar ratio of 1:10, and acetylacetone and isopropanol were uniformly mixed at a molar ratio of 1:10. These mixtures were then added dropwise to titanium isopropoxide, with the molar ratios of titanium isopropoxide to octanoic acid and acetylacetone being 1:2 and 1:2, respectively. The mixture was stirred at 40°C for 2.5 h at a stirring speed of 500 r / min to allow some alkoxy groups to be replaced by inert ligands, thereby obtaining a bifunctional coordination-modified monomer solution retaining only two reactive sites. Subsequently, titanium tetrachloride was added as a catalyst to the long inert ligand-modified monomer solution, with a molar ratio of 0.03:1 to titanium isopropoxide, allowing the long ligand-modified monomer to copolymerize with the short ligand-modified monomer. The long ligand-modified monomer solution and the short ligand-modified monomer solution were mixed, with a molar ratio of 1:3 between the long and short ligands. Deionized water was added dropwise at 80°C, and the mixture was stirred for 4 h to obtain a low-polymerization-degree linear inorganic molecular chain. Titanium dichlorophenocene was added to the reaction system as a chain extender, and the reaction was carried out for 5 hours to extend the low degree of polymerization linear inorganic molecular chains. Then, 4-azidobenzoic acid was added as a UV-responsive end-capping agent, and the reaction system was irradiated with UV light for 40 minutes to terminate the chain extension reaction, and finally a linear inorganic long-chain solution with Ti-O as the repeating unit and long and short side group structure was obtained.

[0048] (2) The above linear inorganic long-chain solution was subjected to negative pressure suction at 80℃ and -0.01MPa for 2 hours to obtain a stable spinning solution with a viscosity of 200mPa•s and a solid content of 20wt%. The spinning solution was continuously supplied to a high-speed uniform liquid supply spinning system. The system includes a main channel, a shear screw, a circulating liquid temperature control layer, and a necked-down fractal liquid supply channel structure. The necked-down fractal liquid supply channel adopts a structure of 5 main channels and multi-stage branch channels. Each branch channel is 15mm long and 6.0mm in diameter. The branch channels are connected step by step in a symmetrical distribution manner. The throat diameter of the necked-down fractal liquid supply channel is set to 50% of the corresponding main channel diameter. A stable pressure drop is generated through multi-stage necking to achieve balanced flow of each nozzle. At the end of the necked fractal liquid supply channel, the guide cone at the distribution port is an elliptical cone structure with a bottom diameter of 4.5 mm, a top diameter of 1.5 mm, and an axial height of 5.0 mm. Made of stainless steel, it is used for axial rectification and radial spreading of the fluid. Before entering the nozzle, the spinning solution is continuously sheared and homogenized by a shearing screw made of polytetrafluoroethylene (PTFE) at a speed of 800 r / min. Perfluoropolyether oil is circulated in the circulating fluid temperature control layer to maintain the channel temperature at 40°C. After the above treatment, a precursor nanofiber paper with uniform basis weight is obtained through parallel electrospinning using multiple nozzles.

[0049] (3) The precursor nanofiber paper is continuously fed to the infrared softening and welding-instant cooling and setting device. The radiation band is selected as 5.8~5.9μm to allow the linear inorganic molecular chains on the fiber surface to quickly enter the thermoplastic softening state. Subsequently, the precursor nanofiber paper enters the low surface energy roll area. The core material of the roll is alloy steel, and its outer surface is covered with polytetrafluoroethylene roll sleeve. The roll pressure is set to 1.0MPa to allow the fiber overlap points to weld without sticking to the roll. A low surface energy transition roll is set between the low surface energy roll and the cold setting roll. Its axis height is lower than that of the roll axis height on both sides to suppress local debonding. Subsequently, the fiber paper enters the cold setting roll area. The cold setting roll is equipped with a spiral condensate conveying channel. The condensate is an ethylene glycol aqueous solution. The roll surface temperature is controlled at -5℃ to lock the two-dimensional network structure after welding through instant cooling.

[0050] (4) The precursor nanofiber paper after hot pressing and shaping is transported to a deep ultraviolet pretreatment device and irradiated with deep ultraviolet light with wavelengths of 185nm and 254nm to cause the organic ligands to break; then it is transported to a microwave-assisted oxygen-deficient calcination device and calcined under the condition of oxygen volume fraction of 18%, with a calcination peak temperature of 600℃ and a holding time of 2h, and then naturally cooled to room temperature to obtain flexible ceramic nanofiber paper.

[0051] (5) The obtained ceramic nanofiber paper has a fiber diameter of 200 nm, a thickness of 120 μm, and a basis weight of 45 g / m. 2Fracture toughness 0.31 MJ / m 3 The thickness and basis weight CV values ​​are both less than 5%. Fiber diameter was measured using a scanning electron microscope at 5000-20000x magnification. Image processing software was used to randomly select 100 fibers to measure their diameter and average the result. The thickness of the ceramic nanofiber paper was measured according to "GB-T 451.2-2023 Determination of Thickness of Paper and Paperboard," using a high-precision digital thickness gauge. Ten points were evenly selected at different locations on the sample, and the average value was taken. The basis weight of the ceramic nanofiber paper was measured according to "GB-T451.2-2023 Determination of Basis Weight of Paper, Paperboard and Paper Products." The sample was cut to a fixed size and weighed using a 0.01% precision electronic balance, and the weight was converted to mass per square meter. The fracture toughness was determined by tensile testing according to "GB-T 12914-2018 Determination of Tensile Strength of Paper and Paperboard." The fracture toughness value was calculated by integrating the area under the tensile stress-strain curve. The CV value of thickness and basis weight was calculated using the formula CV = ( σ / μ The result is calculated as () × 100%, where σ The standard deviation of the test sample. μ This is the sample average. Figure 6 Further optical photographs of the ceramic nanofiber paper are shown, as well as... Figure 7 Further, SEM images of the ceramic nanofiber paper fiber fusion structure are shown. The SEM images clearly show that a good in-situ fusion and physical adhesion structure is formed between the fibers. This structure effectively enhances the mechanical properties of the ceramic nanofiber paper, making it exhibit excellent flexibility and able to remain intact without cracking after multiple folds.

[0052] Example 2 This embodiment provides a ceramic nanofiber paper based on linear inorganic molecular chains and its preparation method, the specific steps of which are as follows: (1) Oleic acid and isopropanol were uniformly mixed at a molar ratio of 1:9, and trifluoroacetylacetone and isopropanol were uniformly mixed at a molar ratio of 1:9. These mixtures were then added dropwise to zirconium isopropoxide, with the molar ratios of zirconium isopropoxide to oleic acid and trifluoroacetylacetone being 1:2 and 1:2, respectively. The mixture was stirred at 35°C for 2 hours at a stirring speed of 600 r / min to allow some alkoxy groups to be replaced by inert ligands, thereby obtaining a bifunctional coordination-modified monomer solution with only two reactive sites. Subsequently, zirconium tetrachloride was added as a catalyst to the long inert ligand-modified monomer solution, with a molar ratio of 0.028:1 to zirconium isopropoxide, allowing the long ligand-modified monomer to copolymerize with the short ligand-modified monomer. The long ligand-modified monomer solution and the short ligand-modified monomer solution were mixed, with a molar ratio of 1:3 between the long and short ligands. Deionized water was added dropwise at 80°C, and the mixture was stirred for 4 hours to obtain a low-polymerization-degree linear inorganic molecular chain. Zirconium dichlorocerocene was added to the reaction system as a chain extender, and the reaction was carried out for 4 hours to extend the low degree of polymerization linear inorganic molecular chains. Then, 3-azidopropyltrimethoxysilane was added as a UV-responsive end-capping agent, and the reaction system was irradiated with UV light for 30 minutes to terminate the chain extension reaction, finally obtaining a linear inorganic long-chain solution with Zr-O as the repeating unit and having both long and short side group structures.

[0053] (2) The above linear inorganic long-chain solution was subjected to negative pressure suction at 80℃ and -0.1MPa for 1 hour to obtain a stable spinning solution with a viscosity of 180mPa•s and a solid content of 25wt%. The spinning solution was continuously supplied to a high-speed uniform liquid supply spinning system. The necked fractal liquid supply channel adopts a structure of 10 main channels and multi-stage branch channels. Each branch channel is 10mm long and 2.4mm in diameter, and the branch channels are symmetrically distributed. The throat diameter of the necked fractal liquid supply channel is 30% of the corresponding main channel diameter, and the flow rate is balanced through multi-stage pressure drop. The guide cone at the end of the necked fractal liquid supply channel is an elliptical cone structure with a bottom diameter of 2.2mm, a top diameter of 0.7mm, and an axial height of 2mm. It is made of titanium alloy and is used for fluid rectification and radial spreading. Before entering the spinning head, the spinning solution is sheared and homogenized by a shearing screw made of polyetheretherketone (PEEK) with a rotation speed set at 1200 r / min. Silicone oil is circulated in the circulating fluid temperature control layer to stabilize the flow channel temperature at 45°C. Parallel electrospinning through multiple nozzles yields a precursor nanofiber paper with uniform basis weight.

[0054] (3) The precursor nanofiber paper is fed to the infrared softening and welding-instant cooling and setting device. The infrared radiation band is selected as 3.32~3.33μm to make the fiber enter the thermoplastic softening state. Then, it is rolled at the low surface energy roller covered with perfluoroalkoxy resin sleeve. The rolling pressure is set to 1.5MPa to promote the welding of fiber overlap points. After the low surface energy transition roller suppresses local debonding, it enters the cold setting roller area. Methyl silicone oil is introduced into the cold setting roller as a condensate. The roller surface temperature is controlled at 5℃ to achieve instant cooling and setting.

[0055] (4) The precursor nanofiber paper after hot pressing and shaping is transported to a deep ultraviolet pretreatment device and irradiated with deep ultraviolet light with wavelengths of 185nm and 254nm to cause the organic ligands to break; then it is transported to a microwave-assisted oxygen-deficient calcination device and calcined under the condition of oxygen volume fraction of 16%, with a calcination peak temperature of 1000℃ and a holding time of 2h, and then naturally cooled to room temperature to obtain flexible ceramic nanofiber paper.

[0056] (5) The obtained ceramic nanofiber paper has a fiber diameter of 300 nm, a thickness of 200 μm, and a basis weight of 80 g / m. 2 Fracture toughness 0.35 MJ / m 3 The thickness and basis weight CV values ​​are both ≤5%.

[0057] Example 3 This embodiment provides a ceramic nanofiber paper based on linear inorganic molecular chains and its preparation method, the specific steps of which are as follows: (1) Lauric acid and sec-butanol were uniformly mixed at a molar ratio of 1:8, and acetic acid and sec-butanol were uniformly mixed at a molar ratio of 1:8. These mixtures were then added dropwise to aluminum sec-butoxide, with the molar ratios of aluminum sec-butoxide to lauric acid and acetic acid being 1:1 and 1:1, respectively. The mixture was stirred at 38°C for 2 hours at a stirring speed of 700 r / min to allow some alkoxy groups to be replaced by inert ligands, thereby obtaining a bifunctional coordination-modified monomer solution retaining only two reactive sites. Subsequently, aluminum trichloride was added as a catalyst to the long inert ligand-modified monomer solution, with a molar ratio of 0.025:1 to aluminum sec-butoxide, to allow the long ligand-modified monomer to copolymerize with the short ligand-modified monomer. The long ligand-modified monomer solution and the short ligand-modified monomer solution were mixed, with the molar ratio of long ligand to short ligand being 1:3. Deionized water was added dropwise at 70°C, and the mixture was stirred for 4 hours to obtain a low-polymerization-degree linear inorganic molecular chain. (Ethyl acetoacetate) diisopropoxyaluminate was added to the reaction system as a chain extender and reacted for 4 h. Then, 3-azidopropyltrimethoxysilane was added as a UV-responsive end-capping agent, and the reaction system was irradiated with UV light for 30 min to terminate the chain extension reaction, finally obtaining a linear inorganic long-chain solution with Al-O as the repeating unit and having long and short side group structures.

[0058] (2) The above linear inorganic long-chain solution was subjected to negative pressure suction at 70℃ and -0.05MPa for 1 hour to obtain a stable spinning solution with a viscosity of 260mPa•s and a solid content of 22wt%. The spinning solution was continuously supplied to a high-speed uniform liquid supply spinning system. The high-speed uniform liquid supply spinning system includes a main channel, a shear screw, a circulating liquid temperature control layer, and a necked-down fractal liquid supply channel structure. The necked-down fractal liquid supply channel adopts a three-main-channel structure, with each level of the branch channel having a length of 25mm, a diameter of 6mm, and a throat diameter set to 75% of the corresponding main channel diameter. A stable pressure drop is formed through the multi-stage necked-down structure to achieve uniform distribution of the flow rate of each nozzle. The guide cone at the end of the necked-down fractal liquid supply channel is an elliptical cone structure with a bottom diameter of 5.9mm, a top diameter of 3.3mm, and an axial height of 8mm. It is made of aluminum alloy and is used to rectify the spinning solution axially and spread it radially, suppressing local deviation and vortices. Before entering the spinning nozzle, the spinning solution is continuously sheared and homogenized by a shear screw with a rotation speed set at 600 r / min. Triaryl phosphate is introduced into the circulating liquid temperature control layer to maintain the flow channel temperature at 35°C, thereby achieving stable liquid supply under low shear and low disturbance conditions. After the above treatment, a precursor nanofiber paper with uniform basis weight is obtained by parallel electrospinning with multiple nozzles.

[0059] (3) The obtained precursor nanofiber paper is continuously fed to an infrared softening and welding-instant cooling and setting device. The infrared radiation band is selected as 5.8~5.9μm to rapidly induce the linear inorganic molecular chains on the fiber surface into a thermoplastic softening state. Subsequently, the precursor nanofiber paper enters the low surface energy roll area. The core material of the roll is alloy steel, and its outer surface is covered with a low surface energy roll sleeve. The fiber paper is subjected to non-adhesive rolling under a rolling pressure of 0.8MPa to fuse the fiber overlap points. A low surface energy transition roll is set between the low surface energy roll and the cold setting roll to suppress local debonding and stress concentration. Subsequently, the fiber paper enters the cold setting roll area. A spiral condensate conveying channel is set inside the cold setting roll. The condensate is a propylene glycol aqueous solution, and the roll surface temperature is controlled at -10℃. The two-dimensional network structure after welding is locked by the instant cooling effect.

[0060] (4) The precursor nanofiber paper after hot pressing and shaping is transported to a deep ultraviolet pretreatment device and irradiated with deep ultraviolet light with wavelengths of 185nm and 254nm to cause the organic ligands to break; then it is transported to a microwave-assisted oxygen-deficient calcination device and calcined under the condition of oxygen volume fraction of 17%, with a calcination peak temperature of 800℃ and a holding time of 2h, and then naturally cooled to room temperature to obtain flexible ceramic nanofiber paper.

[0061] (5) The obtained ceramic nanofiber paper has a fiber diameter of 250 nm and a basis weight of approximately 30 g / m. 2The fracture toughness is 0.28 MJ / m. 3 The material maintains good flexibility and structural integrity even under low weight conditions.

[0062] Example 4 As a specific example of the present invention, linear inorganic molecular chains can also be synthesized after protonation of the silicon source (the silicon source is selected from one or more combinations of tetraethyl orthosilicate, tetra-n-butoxysilane, tetra-n-propoxysilane, trimethylsilyl acetate, or vinyltriethoxysilane). The specific steps are as follows: (1) Prepare a silanol salt solution with pH=1 and tetraethyl orthosilicate content of 80wt% by mixing hydrochloric acid, anhydrous ethanol and tetraethyl orthosilicate.

[0063] (2) Oleic acid and ethanol were uniformly mixed at a molar ratio of 1:5, and acetic acid and sec-butanol were uniformly mixed at a molar ratio of 1:5. These mixtures were then added dropwise to a silanol salt solution. The molar ratios of tetraethyl orthosilicate to oleic acid and acetic acid were 1:2 and 1:2, respectively. The mixture was stirred at 35°C for 2 hours at a stirring speed of 750 r / min to allow some alkoxy groups to be replaced by inert ligands, thus obtaining a bifunctional coordination-modified monomer solution retaining only two reactive sites. Subsequently, silicon tetrachloride was added as a catalyst to the long inert ligand-modified monomer solution at a molar ratio of 0.026:1 to tetraethyl orthosilicate, enabling the long ligand-modified monomer to copolymerize with the short ligand-modified monomer. The long ligand-modified monomer solution and the short ligand-modified monomer solution were mixed at a molar ratio of 1:3. Deionized water was added dropwise at 65°C, and the mixture was stirred for 4 hours to obtain a low-polymerization-degree linear inorganic molecular chain. A chain extension reaction was carried out on a low-polymerization-degree linear inorganic molecular chain for 4 hours. Then, 3-azidopropyltrimethoxysilane was added as a UV-responsive end-capping agent, and the reaction system was irradiated with UV light for 35 minutes to terminate the chain extension reaction. Finally, a linear inorganic long-chain solution with Si-O as the repeating unit and long and short side group structure was obtained.

[0064] (3) The above linear inorganic long-chain solution was subjected to negative pressure suction at 80℃ and -0.03MPa for 1 hour to obtain a stable spinning solution with a viscosity of 120mPa•s and a solid content of 23wt%. The spinning solution was continuously supplied to a high-speed uniform liquid supply spinning system. The system includes a main channel, a shear screw, a circulating liquid temperature control layer, and a necked-down fractal liquid supply channel structure. The necked-down fractal liquid supply channel adopts a structure of 5 main channels and multi-stage branch channels. Each branch channel is 18mm long and 3.5mm in diameter. The branch channels are connected step by step in a symmetrical distribution manner. The throat diameter of the necked-down fractal liquid supply channel is set to 60% of the corresponding main channel diameter. A stable pressure drop is generated through multi-stage necking to achieve balanced flow of each nozzle. At the end of the necked fractal liquid supply channel, the guide cone at the distribution port is an elliptical cone structure with a bottom diameter of 3.8 mm, a top diameter of 1.6 mm, and an axial height of 4.0 mm. Made of stainless steel, it is used for axial rectification and radial spreading of the fluid. Before entering the nozzle, the spinning solution is continuously sheared and homogenized by a shearing screw made of polytetrafluoroethylene (PTFE) at a speed of 1200 r / min. Perfluoropolyether oil is circulated in the circulating fluid temperature control layer to maintain the channel temperature at 40°C. After the above treatment, a precursor nanofiber paper with uniform basis weight is obtained through parallel electrospinning using multiple nozzles.

[0065] (4) The precursor nanofiber paper is continuously fed to the infrared softening and welding-instant cooling and setting device. The infrared radiation band is selected as 3.32~3.33μm to allow the linear inorganic molecular chains on the fiber surface to quickly enter the thermoplastic softening state. Subsequently, the precursor nanofiber paper enters the low surface energy roll area. The core material of the roll is alloy steel, and its outer surface is covered with polytetrafluoroethylene roll sleeve. The roll pressure is set to 0.6MPa to allow the fiber overlap points to weld without sticking to the roll. A low surface energy transition roll is set between the low surface energy roll and the cold setting roll. Its axis height is lower than that of the roll axis height on both sides to suppress local debonding. Subsequently, the fiber paper enters the cold setting roll area. The cold setting roll is equipped with a spiral condensate conveying channel. The condensate is an ethylene glycol aqueous solution. The roll surface temperature is controlled at 15℃ to lock the two-dimensional network structure after welding through instant cooling.

[0066] (5) The precursor nanofiber paper after hot pressing and shaping is transported to a deep ultraviolet pretreatment device and irradiated with deep ultraviolet light with wavelengths of 185nm and 254nm to cause the organic ligands to break; then it is transported to a microwave-assisted oxygen-deficient calcination device and calcined under the condition of oxygen volume fraction of 15%, with a calcination peak temperature of 1000℃ and a holding time of 2h, and then naturally cooled to room temperature to obtain flexible ceramic nanofiber paper.

[0067] (6) The obtained ceramic nanofiber paper has a fiber diameter of 150 nm, a thickness of 100 μm, and a basis weight of 38 g / m. 2Fracture toughness 0.29 MJ / m 3 The thickness and weight CV values ​​are both less than 5%.

[0068] Comparative Example 1 This comparative example is basically the same as Example 1, except that in step (1), instead of modifying and copolymerizing with long and short inert ligands respectively, only the short inert ligand acetylacetone is used for single coordination modification of titanium isopropoxide, and no octanoic acid is added; the remaining catalytic, hydrolysis-condensation, chain extension, end-capping, spinning, infrared treatment, rolling, cold setting, and calcination conditions are the same as in Example 1. The resulting precursor fibers showed decreased stability and poor fiber continuity during spinning, and the degree of interfiber fusion was limited after infrared softening. The final ceramic nanofiber paper fibers had a diameter of 220 nm, a thickness of 130 μm, and a basis weight of 47 g / m². 2 The fracture toughness is 0.21 MJ / m. 3 The thickness CV value is 7.8%, and the basis weight CV value is 8.4%.

[0069] Comparative Example 2 This comparative example is basically the same as Example 1, except that: infrared radiation treatment is not performed in step (3), and the precursor nanofiber paper is directly rolled in the low surface energy roll area after spinning and forming, followed by cold setting, deep ultraviolet irradiation and calcination; the other conditions are the same as in Example 1. Since the precursor nanofibers are not fully softened before rolling, effective chain segment interpenetration and interfacial diffusion are difficult to occur at the fiber overlap points, and the fibers in the obtained ceramic nanofiber paper are mainly physically overlapped. The final obtained ceramic nanofiber paper has a fiber diameter of 205nm, a thickness of 125μm, and a basis weight of 46g / m³. 2 The fracture toughness is 0.18 MJ / m. 3 The thickness CV value is 6.5%, and the basis weight CV value is 6.9%.

[0070] Comparative Example 3 This comparative example is basically the same as Example 1, except that the cold setting step is omitted in step (3). After infrared radiation treatment and non-adhesive rolling, the precursor nanofiber paper is directly cooled naturally, and then subjected to deep ultraviolet irradiation and calcination. The other conditions are the same as in Example 1. Due to the lack of a rapid cooling and setting process, the local connection structure formed by the fibers after hot pressing cannot be locked in time, and it is easy to loosen or locally de-adhede during subsequent transportation and cooling. The final ceramic nanofiber paper has a fiber diameter of 200nm, a thickness of 128μm, and a basis weight of 45g / m³. 2 The fracture toughness is 0.23 MJ / m. 3 The thickness CV value is 6.7%, and the basis weight CV value is 6.4%.

[0071] Comparative Example 4 This comparative example is basically the same as Example 1, except that in step (3), the infrared radiation band was adjusted from 5.8–5.9 μm to 2.0–2.1 μm, while the other processing conditions remained unchanged. Because the selected infrared radiation band did not match the characteristic vibrational frequency of the organic side groups in the linear inorganic long chain sufficiently, the thermal softening effect of the precursor nanofiber paper was weakened, and the degree of fusion at the fiber contact points decreased. The final ceramic nanofiber paper had a fiber diameter of 210 nm, a thickness of 122 μm, and a basis weight of 45 g / m². 2 The fracture toughness is 0.24 MJ / m. 3 The thickness CV value is 5.9%, and the basis weight CV value is 6.1%.

[0072] Therefore, this invention utilizes long and short inert ligands to modify metal alkoxide monomers, transforming them into bifunctional alkoxide monomers with two alkoxy groups. Under the action of a catalyst, the electropositivity of the metal center of the long-ligand modified monomer is enhanced, and the metal-oxygen bond is activated, thereby improving the polycondensation activity of the long-ligand modified monomer and enabling it to copolymerize with the short-ligand modified monomer. The polycondensation reaction extends linearly along one dimension, forming a linear inorganic long chain with a synergistic distribution of long and short side groups. The long side groups can improve the thermal mobility of the chain segments, while the short ligands reduce the proportion of organic components, allowing this linear inorganic long chain to be formulated into a stable spinning solution and form a thermoplastic precursor nanofiber paper without relying on an organic polymer template.

[0073] Simultaneously, this invention utilizes infrared radiation to induce molecular-level thermal excitation in linear inorganic long chains. By controlling the infrared radiation frequency to match the characteristic vibrational frequency of the long side groups in the inorganic long chains, strong resonant absorption is induced in the long side group segments, causing the precursor nanofibers to exhibit significant thermal softening and thermoplastic behavior. During subsequent hot pressing, adjacent fibers in the softened state undergo interpenetration and diffusion at the contact interface, thereby achieving in-situ fusion and physical adhesion between fibers, forming a continuously bonded two-dimensional network reinforcement structure.

[0074] 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 preparing flexible ceramic nanofiber paper based on linear inorganic molecular chains, characterized in that, Includes the following steps: S1: Prepare alcohol solutions of long inert ligands and short inert ligands respectively, and add them dropwise to the metal alkoxide monomer solution for coordination modification to obtain long ligand modified monomer solution and short ligand modified monomer solution; A catalyst was added to a long-ligand modified monomer solution and mixed with a short-ligand modified monomer solution. Then, deionized water was added to carry out a hydrolysis-condensation reaction to obtain a low-polymerization degree linear inorganic molecular chain with long and short ligands. A chain extender was then added to carry out a chain extension reaction, and then a capping agent was added to terminate the chain extension reaction to obtain a linear inorganic long chain with long and short side groups. S2: The linear inorganic long chain with long-short side groups obtained in step S1 is formulated into a spinning solution and spun in an auxiliary force field to obtain precursor nanofiber paper. S3: The precursor nanofiber paper obtained in step S2 is subjected to infrared radiation treatment, non-adhesive rolling and instantaneous cooling and shaping in sequence, and then the organic ligands are decomposed by deep ultraviolet irradiation, followed by calcination to obtain ceramic nanofiber paper.

2. The method for preparing flexible ceramic nanofiber paper based on linear inorganic molecular chains according to claim 1, characterized in that, In the alcohol solution of the long inert ligand, the long inert ligand and the alcohol solvent are mixed in a molar ratio of 1:5 to 1:10; in the alcohol solution of the short inert ligand, the short inert ligand and the alcohol solvent are mixed in a molar ratio of 1:5 to 1:

10. The long inert ligand is selected from one or more of citric acid, aminotriacetic acid, ethylenediaminetetraacetic acid, ammonium citrate, stearic acid, oleic acid, hexanoic acid, heptanoic acid, octanoic acid, decanoic acid and lauric acid; The short inert ligand is selected from one or more of acetic acid, oxalic acid, ethylenediamine, acetylacetone, and trifluoroacetylacetone; The alcohol solvent is selected from one or more of methanol, ethanol, n-propanol, isopropanol, n-butanol, sec-butanol, tert-butanol, n-pentanol, ethylene glycol, butanediol, hexanediol, and glycerol; The metal alkoxide is selected from one or more of the following sources: titanium, zirconium, aluminum, tin, hafnium, gallium, tantalum, and niobium. The titanium source is selected from one or more of the following sources: titanium tetraethanol, titanium tetraethanolamine, titanium n-propoxide, titanium isopropoxide, titanium n-butoxide, titanium isobutoxide, titanium tert-butoxide, titanium tetrapentoxide, and titanium isooctanol. The zirconium source is selected from one or more of the following sources: zirconium tetraethanolamine, zirconium tetraethanolamine, zirconium n-propoxide, zirconium isopropoxide, zirconium n-butoxide, zirconium isobutoxide, zirconium tert-butoxide, and zirconium tetrapentoxide. The aluminum source is selected from the following sources: aluminum trimethoxy, aluminum triethanolamine, aluminum tri-n-propoxy, aluminum isopropoxide, aluminum n-butoxide, and aluminum sec-butoxide. The source is selected from one or more of aluminum tert-butoxide; the tin source is selected from one or more of tetramethyltin, tetraethanoltin, n-propoxidetin, isopropoxidetin, n-butoxidetin, isobutoxidetin, tert-butoxidetin, and tetrapentoxidetin; the hafnium source is selected from one or more of tetramethylhafnium, tetraethanolhafnium, n-propoxidehafnium, isopropoxidehafnium, n-butoxidehafnium, isobutoxidehafnium, tert-butoxidehafnium, and tetrapentoxidehafnium; the gallium source is selected from one or two of gallium isopropoxide and gallium tert-butoxide; the tantalum source is selected from one or two of tantalum isopropoxide and tantalum n-butoxide; the niobium source is selected from one or two of niobium isopropoxide and niobium n-butoxide. The catalyst is selected from one or more of boron trifluoride, aluminum trichloride, boron tribromide, boron triiodide, tin tetrachloride, silicon tetrachloride, titanium tetrachloride, zirconium tetrachloride, hafnium tetrachloride, tetracyanoethylene, and trinitrobenzene; The chain extender is selected from one or more of the following: diisopropoxydiacetylacetonitrile, diisopropyl bis(ethyl acetoacetate)titanate, di(diethylcitrate)zirconium dipropoxide, di(ethyl acetoacetate)diisopropoxyaluminate, titanium dichlorodecene, zirconium dichlorodecene, hafnium dichlorodecene, molybdenum dichlorodecene, vanadium dichlorodecene, and niobium dichlorodecene. The end-capping agent is selected from one or more of common chemical end-capping agents, visible light responsive end-capping agents, and ultraviolet light responsive end-capping agents; the common chemical end-capping agent is selected from one or two of methyl isocyanate and phenyl isocyanate; the visible light end-capping agent is selected from one or more of 2-diazo-1-naphthol-5-sulfonyl chloride, ethyl diazonate, and 4-azido-2,3,5,6-tetrafluorobenzoic acid; the ultraviolet light responsive end-capping agent is selected from one or more of 4-azidobenzoic acid, 3-azidopropyltrimethoxysilane, and 1,3-dioxopentanepropyltrimethoxysilane.

3. The method for preparing flexible ceramic nanofiber paper based on linear inorganic molecular chains according to claim 1, characterized in that, The linear inorganic long chain with long-short side groups is formulated into a spinning solution by negative pressure suction. The conditions for negative pressure suction are: constant temperature heating of 30~150℃ and pressure of 0~-0.1MPa; The external force of the auxiliary force field is selected from one or more of electrostatic force, airflow force, and centrifugal force.

4. The method for preparing flexible ceramic nanofiber paper based on linear inorganic molecular chains according to claim 1, characterized in that, The infrared radiation band of the infrared radiation treatment is 0.75~1000μm; The non-adhesive roller pressing pressure is 0.1~5MPa; The temperature range for the instantaneous cooling and shaping is -5 to 15°C.

5. The method for preparing flexible ceramic nanofiber paper based on linear inorganic molecular chains according to claim 1, characterized in that, The wavelength of the deep ultraviolet irradiation is 180~300nm; The calcination is performed under alternating atmosphere or inert gas. The alternating atmosphere calcination is a periodically switching atmosphere consisting of a mixture of oxygen-containing gas and an inert gas. The oxygen-containing gas is selected from one or two of air and oxygen, and the inert gas is selected from one or more of nitrogen, argon, helium, neon, krypton, xenon, and radon. The switching cycle is 10-600 s / time. The oxygen volume fraction in the inert gas calcination is controlled to be ≤18%. The peak temperature of the calcination is 400-1500℃.

6. The method for preparing flexible ceramic nanofiber paper based on linear inorganic molecular chains according to claim 1, characterized in that, The spinning process is carried out in a uniform liquid supply spinning system (1); The uniform liquid supply spinning system (1) includes a spinneret (1-1) and a main channel (1-2), a circulating liquid temperature control layer (1-3), a shear screw (1-4), and a necked fractal liquid supply channel (1-5) located inside the spinneret (1-1). The main channel (1-2) is arranged parallel to the spinneret (1-1), and the necked fractal liquid supply channel (1-5) is connected to the side of the main channel (1-2) and communicates with the bottom nozzle of the spinneret (1-1). The circulating liquid temperature control layer (1-3) is arranged around the outside of the main flow channel (1-2) and the necked fractal liquid supply channel (1-5); The shearing screw (1-4) is located inside the main channel (1-2) and is parallel to the spinneret (1-1).

7. The method for preparing flexible ceramic nanofiber paper based on linear inorganic molecular chains according to claim 6, characterized in that, The uniform liquid supply spinning system (1) also includes a guide cone (1-6) and a circulating liquid storage tank (1-9). The guide cone (1-6) is disposed at the liquid outlet of the necked fractal liquid supply channel (1-5); The inlet (1-7) and outlet (1-8) of the circulating liquid temperature control layer (1-3) are respectively sealed to the circulating liquid storage tank (1-9) through flange interfaces.

8. The method for preparing flexible ceramic nanofiber paper based on linear inorganic molecular chains according to claim 1, characterized in that, The infrared radiation treatment, the non-adhesive rolling and the instant cooling and shaping are all carried out in the infrared softening and welding-instant cooling and shaping device (2); The infrared softening welding-instant cooling and shaping device (2) includes an infrared radiation source (2-1), a low surface energy roll (2-2), a low surface energy transition roll (2-3), and a cold shaping roll (2-4). The infrared radiation source (2-1) is located upstream of the low surface energy roll (2-2) and is used for infrared radiation treatment; The low surface energy roll (2-2), low surface energy transition roll (2-3), and cold setting roll (2-4) are arranged in parallel and sequentially, and the axial height of the low surface energy transition roll (2-3) is lower than the axial height of the low surface energy roll (2-2) and the cold setting roll (2-4). The cold setting roller (2-4) has a spiral conveying channel (2-5) inside its roller body.

9. A flexible ceramic nanofiber paper based on linear inorganic molecular chains, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 8; The ceramic nanofiber paper has a fiber diameter of 50~500nm, a thickness of 20μm~5mm, and a basis weight of 20~200g / m³. 2 Fracture toughness ≥ 0.24 MJ / m 3 Both the basis weight and thickness CV values ​​are ≤5%.

10. The application of a flexible ceramic nanofiber paper based on linear inorganic molecular chains in battery heat insulation pads, thermal control insulation layers, flexible electrode or separator support layers, fireproof and noise-reducing insulation layers, energy storage and thermal management components, high-temperature resistant filter media, catalyst carriers, flexible electrolyte support frameworks and interface buffer layers, ion conduction support networks, high insulation and high thermal conductivity encapsulation and structural support layers, and sensitive unit carriers and high-temperature resistant stable substrates.

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