Porous nanofiber-based ceramic paper based on linear inorganic molecular chains and methods of making

Abstract

The present application relates to a kind of porous nanofiber-based ceramic paper based on linear inorganic molecular chain and preparation method, to several metal alkoxide monomer is added phosphonic acid-based multi-dentate phosphoracyl ligand is preliminary coordinated, join several electronegativity gradient inert ligand is modified, chain after reaction, end-capping, join binder to form spherical micelle, obtain high degree of polymerization linear inorganic long chain solution;To metal alkoxide monomer is added inert long chain ligand, reaction, obtain low degree of polymerization linear inorganic chain solution;Mix high degree of polymerization linear inorganic long chain solution and low degree of polymerization linear inorganic chain solution, spinning, multiple softening-pressurization and gradient pressure treatment realize fiber welding, shaping, remove molecular chain ligand and micelle form porous structure, calcination, obtain porous nanofiber-based ceramic paper based on linear inorganic molecular chain.Compared with prior art, the present application shows excellent flexibility and damage resistance.

Description

Technical Field

[0001] This invention belongs to the field of ceramic nanofiber paper preparation technology, and relates to a porous nanofiber-based ceramic paper based on linear inorganic molecular chains and its preparation method. Background Technology

[0002] Ceramic fiber paper, due to its high temperature resistance, corrosion resistance, and excellent insulation properties, is widely used in aerospace thermal insulation, thermal runaway protection of new energy batteries, and thermal management of high-end electronic devices. As these applications evolve towards lightweight and high-performance, existing ceramic fiber paper is gradually revealing two key technological requirements in practical applications: firstly, it needs to further improve material performance by constructing micro-nano porous structures within the fibers to meet the comprehensive performance requirements under extreme conditions; secondly, it needs to further enhance the mechanical strength of ceramic fiber paper to meet the reliable service performance requirements under complex load conditions in engineering applications.

[0003] However, existing preparation techniques still have significant limitations. For example, patent CN103011778A uses an electrospinning combined with a sol-gel route, introducing block polymers as pore-forming agents into the aluminum sol spinning solution, and adding polyethylene oxide and polyvinylpyrrolidone as spinning aids. After forming aluminum oxide gel fibers through electrospinning, the organic components are removed by calcination, thereby obtaining a porous alumina nanofiber membrane. However, the thermal decomposition process of the organic pore-forming agents and spinning aids in this patent is prone to introducing shrinkage and defects, resulting in a brittle porous nanofiber film structure that lacks the overall flexibility and maneuverability required for paper-like materials, making it difficult to apply to the practical application scenarios of ceramic fiber paper. Patent CN104532661A uses aluminosilicate ceramic short fibers as raw materials. After pulping and dispersion, a fiber paper blank is formed using a wet papermaking process. During the forming process, an organic emulsion binder and a hydrophilic surfactant are introduced for surface sizing and reinforcement. Finally, ceramic fiber paper is obtained through vacuum dehydration and drying. However, this patent mainly uses micron-sized short chopped ceramic fibers as the skeleton, and the reinforcement mechanism relies on the physical bonding of the fiber network by an external organic binder, resulting in insufficient overall mechanical strength. At the same time, the resulting material has a high bulk density and a pore structure dominated by random pores. Therefore, the resulting ceramic fiber paper is difficult to meet the requirements of engineering applications for lightweight, high temperature resistance, long-term service stability, and structural reliability. Patent CN114524680A introduces silica sol into the interior of an electrospun ceramic nanofiber scaffold, followed by drying and calcination. This allows the sol to spread within the fiber scaffold and form a silica nanofilm, thereby separating the original interconnected channels. A certain degree of bonding structure can be formed between the fiber scaffold and the two-dimensional nanofilm. However, the enhancement mechanism of this patent essentially relies on the film overlap phase formed by the added sol. The resulting bonding points are prone to shrinkage and cracking during drying and heat treatment, resulting in insufficient interface stability. Furthermore, the mesoporous structure of this patent consists of inter-fiber pores spontaneously formed by sol penetration and film formation. The pore size and spatial distribution are difficult to control precisely, resulting in a narrow overall process control window and limited repeatability and scalability, which cannot meet the needs of engineering applications.

[0004] Therefore, there is an urgent need to develop a new method for the large-scale continuous manufacturing of porous nanofiber-based flexible ceramic paper to break through the bottleneck of its large-scale application in high-end fields such as aerospace, new energy and flexible electronics. Summary of the Invention

[0005] The purpose of this invention is to overcome at least one of the defects of the prior art and provide a porous nanofiber-based ceramic paper based on linear inorganic molecular chains and its preparation method. This invention exhibits excellent flexibility and damage resistance.

[0006] The objective of this invention can be achieved through the following technical solutions: One of the technical solutions of this invention is to provide a porous nanofiber-based ceramic paper based on linear inorganic molecular chains. The process involves adding phosphonic acid-based multidentate phosphoryl ligands to several metal alkoxide monomers for initial coordination. The phosphonic acid-based multidentate phosphoryl ligands are ligands with one phosphonic acid group at one end and a multidentate phosphoryl group at the other end. Several inert ligands with varying electronegativity are added for coordination modification. After reaction, the chains are extended and capped. A binder is added to form spherical micelles, resulting in a high-polymerization-degree linear inorganic long-chain solution. Inert long-chain ligands are added to the metal alkoxide monomers, and the reaction is carried out to obtain a low-polymerization-degree linear inorganic chain solution. The high-polymerization-degree linear inorganic long-chain solution and the low-polymerization-degree linear inorganic chain solution are mixed, spun, and subjected to multiple softening-pressurization and gradient pressure treatments to achieve fiber welding. The fibers are then shaped, the molecular chain ligands and micelles are removed to form a porous structure, and calcined to obtain the porous nanofiber-based ceramic paper based on linear inorganic molecular chains.

[0007] One of the technical solutions of the present invention is to provide a method for preparing porous nanofiber-based ceramic paper based on linear inorganic molecular chains, the method comprising the following steps: S1. Phosphonic acid-based multidentate phosphoryl ligands are added to several metal alkoxide monomers for initial coordination, several inert ligands with electronegativity gradients are added for coordination modification, an acid catalyst and water are added for hydrolysis-condensation reaction, a metal-centered bifunctional chain extender is added for chain extension, a photoresponsive end-capping agent is added for end-capping, an alcohol solvent and a binder are added, and the interaction between the phosphonic acid-based multidentate phosphoryl ligands and the binder is utilized to make the binder uniformly distributed near the phosphonic acid-based multidentate phosphoryl ligands to form spherical micelles, thus obtaining a high degree of polymerization linear inorganic long-chain solution containing micelles; Inert long-chain ligands and alcohol solvents are added to metal alkoxide monomers for coordination, and water is added to carry out hydrolysis-condensation reaction to obtain a low degree of polymerization linear inorganic chain solution. A high / low molecular weight linear inorganic chain spinning solution is obtained by mixing a high degree of polymerization linear inorganic long chain solution and a low degree of polymerization linear inorganic chain solution. S2. Spinning of high / low molecular weight linear inorganic molecular chain spinning solution to obtain precursor nanofiber paper; S3. The precursor nanofiber paper is softened by thermal excitation and then pressure-fused. Through multiple softening-pressurization and gradient pressure treatments, stable fiber fusion is achieved, forming a two-dimensional network structure. Precursor nanofiber paper was irradiated to remove molecular chain ligands and micelles to form a porous structure, and then calcined to obtain porous nanofiber-based ceramic paper based on linear inorganic molecular chains.

[0008] Furthermore, in step S1, the metal alkoxide monomer corresponding to the high-polymerization-degree linear inorganic long chain is selected from zirconium tetraethanolamine, zirconium tetramethanol, zirconium isopropoxide, zirconium n-propoxide, zirconium isobutoxide, zirconium tert-butoxide, zirconium n-butoxide, zirconium tetrapentoxide, titanium tetraethanolamine, titanium isobutoxide, titanium n-propoxide, titanium n-butoxide, titanium tetraethanolamine, titanium tert-butoxide, titanium isooctanol, titanium tetrapentoxide, titanium isopropoxide, tin n-propoxide, tin n-butoxide, tin tetraethanolamine, tin tert-butoxide, tin tetraethanolamine, tin isobutoxide, and isopropanol. Tin, tin tetrapentoxide, aluminum n-butoxide, aluminum trimethoxy, aluminum tri-n-propoxy, aluminum isopropoxide, aluminum sec-butoxide, aluminum triethanolamine, aluminum tert-butoxide, indium isopropoxide, indium triethoxy, indium tert-butoxide, gallium isopropoxide, gallium triethoxy, gallium n-butoxide, gallium tert-butoxide, hafnium tetramethanol, hafnium tetraethanol, hafnium n-propoxide, hafnium isopropoxide, hafnium n-butoxide, hafnium isobutoxide, hafnium tert-butoxide, hafnium tetrapentoxide, tantalum isopropoxide, tantalum n-butoxide, niobium isopropoxide, niobium n-butoxide (two or more of these), Phosphono-based multidentate phosphoryl ligands are selected from 11-phosphono-1,1,1-tris(dimethoxyphosphonomethyl)undecane, 11-(bis(2-(dimethoxyphosphonooxy)ethyl)amino)-undecylphosphonic acid, 1,1-bis(dimethoxyphosphonomethyl)-1-(8-phosphonooctyl)propane, bis(dimethoxyphosphonomethyl)-(8-phosphonooctyl)phosphine oxide, N,N One or more of bis(2-(dimethoxyphosphoryl)ethyl)-11-phosphonoundecaneamide, The molar ratio of the total metal alkoxide monomers to the phosphonate polydentate phosphoryl ligands is (1~2):(1~4); The initial coordination temperature is 20~160 ℃, and the time is 2~6 h.

[0009] Further, in step S1, the inert ligands corresponding to the high-polymerization-degree linear inorganic long chain with electronegativity gradient are divided into three categories: weakly inert ligands, moderately inert ligands, and strongly inert ligands. The weakly inert ligands are selected from one or more of diethyl ether, acetone, 1,4-dioxane, tetrahydrofuran, and butanone. The moderately inert ligands are selected from one or more of formic acid, acetic acid, propionic acid, isobutyric acid, butyric acid, butyl acetate, ethyl acetate, methyl methacrylate, methylamine, cyclohexanone, ethylamine, isopropylamine, n-propylamine, and methylcyclohexanone. The strongly inert ligands are selected from one or more of acetylacetone, hexafluoroacetylacetone, benzoylacetone, trifluoroacetylacetone, methyl acetoacetate, diethanolamine, tert-butyl acetoacetate, ethyl acetoacetate, and triethanolamine. The molar ratio of the weakly inert ligands, moderately inert ligands, and strongly inert ligands is (1~8):(1~8):(1~8). The molar ratio of the total metal alkoxide monomers to the total inert ligands of the electronegativity gradient is (1~2):(3~7); The temperature for coordination modification is 20~160 ℃, and the time is 2~6 h.

[0010] Furthermore, in step S1, the acid catalyst corresponding to the highly polymerized linear inorganic long chain is selected from one or more of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, phosphoric acid, and formic acid. The metal-centered bifunctional chain extender is selected from one or more of the following: diisopropyl bis(ethyl acetoacetate)titanate, diisopropoxydiacetylacetonate, (ethyl acetoacetate)diisopropoxyaluminate, di(diethylcitrate)dipropoxide zirconium, zirconium dichlorodecane, titanium dichlorodecane, molybdenum dichlorodecane, vanadium dichlorodecane, and hafnium dichlorodecane. The photoresponsive end-capping agent is selected from one or more of 2-diazo-1-naphthol-5-sulfonyl chloride, ethyl diazonyl chloride, and 4-azido-2,3,5,6-tetrafluorobenzoic acid. The alcohol solvent is selected from one or more of methanol, n-propanol, glycerol, n-pentanol, tert-butanol, isopropanol, sec-butanol, n-butanol, butanediol, hexanediol, ethylene glycol, and ethanol. The binder is selected from one or more of the following: n-octyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, didodecyldimethylammonium bromide, decaalkyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, eicosyltrimethylammonium bromide, octadecyltrimethylammonium bromide, docosyltrimethylammonium bromide, (2-hydroxyethyl)hexadecyldimethylammonium bromide, cocamidopropyl betaine, and 1-hexadecyl-3-methylimidazolium bromide. The molar ratio of the total metal alkoxide monomers to hydrogen ions in the acid catalyst is (1~2):(1~4), and the molar ratio of the total metal alkoxide monomers to water, metal-centered bifunctional chain extender, photoresponsive end-capping agent, alcohol solvent and binder is (1~2):(1~5):(1~2):(1~4):(1~10):(0.1~1). The hydrolysis-condensation reaction takes place at a temperature of 20–160 °C for 2–6 h. The chain extension temperature is 20~160 ℃, and the time is 2~6 h. The sealing temperature is 20~160 ℃, the light emission wavelength is 200~800 nm, and the time is 0.4~1.2 h. The temperature for forming spherical micelles is 20~160 ℃, and the time is 1~3 h; The degree of polymerization of highly polymerizable linear inorganic long chains is 2000~5000.

[0011] As a preferred technical solution, the degree of polymerization of the high-polymerization-degree linear inorganic long chain before chain extension in step S1 is 20~1000.

[0012] Furthermore, in step S1, the metal alkoxide monomer corresponding to the low degree of polymerization linear inorganic chain is selected from zirconium tetraethanolamine, zirconium tetramethanol, zirconium isopropoxide, zirconium n-propoxide, zirconium isobutoxide, zirconium tert-butoxide, zirconium n-butoxide, zirconium tetrapentoxide, titanium tetraethanolamine, titanium isobutoxide, titanium n-propoxide, titanium n-butoxide, titanium tetraethanolamine, titanium tert-butoxide, titanium isooctanol, titanium tetrapentoxide, titanium isopropoxide, tin n-propoxide, tin n-butoxide, tin tetraethanolamine, tin tert-butoxide, tin tetraethanolamine, tin isobutoxide, and isopropanol. Tin, tin tetrapentoxide, aluminum n-butoxide, aluminum trimethoxy, aluminum tri-n-propoxy, aluminum isopropoxide, aluminum sec-butoxide, aluminum triethanolamine, aluminum tert-butoxide, indium isopropoxide, indium triethoxy, indium tert-butoxide, gallium isopropoxide, gallium triethoxy, gallium n-butoxide, gallium tert-butoxide, hafnium tetramethanol, hafnium tetraethanol, hafnium n-propoxide, hafnium isopropoxide, hafnium n-butoxide, hafnium isobutoxide, hafnium tert-butoxide, hafnium tetrapentoxide, tantalum isopropoxide, tantalum n-butoxide, niobium isopropoxide, niobium n-butoxide, one or more of the following: The inert long-chain 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 alcohol solvent is selected from one or more of methanol, n-propanol, glycerol, n-pentanol, tert-butanol, isopropanol, sec-butanol, n-butanol, butanediol, hexanediol, ethylene glycol, and ethanol. The molar ratio of metal alkoxide monomer to inert long-chain ligand, alcohol solvent and water is (1~2):(1~4):(2~20):(1~5); The coordination temperature is 20–160 °C, and the time is 2–6 h. The hydrolysis-condensation reaction is carried out at a temperature of 20~160 ℃ for 2~6 h. The degree of polymerization of low-polymerization linear inorganic chains ranges from 20 to 1000.

[0013] Furthermore, in step S1, the molar ratio of the metal alkoxide monomers corresponding to the high-polymerization-degree linear inorganic long chain and the low-polymerization-degree linear inorganic chain is 1:(0.5~2); The viscosity of the high / low molecular weight linear inorganic molecular chain spinning solution is 20~12000 mPa·s, the electrical conductivity is 0.5~2000 μS / cm, and the surface tension is 30~60 mN / m.

[0014] Further, in step S2, the high / low molecular weight linear inorganic molecular chain spinning solution is supplied to a multi-stage equal flow supply spinning device for spinning. The multi-stage equal flow supply spinning device includes a shell, a shearing screw, and several equal flow tubes and nozzles. The shearing screw is horizontally arranged at the axis inside the innermost equal flow tube. Several equal flow tubes are coaxially arranged inside the shell along the axial direction of the multi-stage equal flow supply spinning device. Several equal flow holes are opened on the wall of several equal flow tubes. Several equal flow tubes are connected to each other through equal flow holes. Several equal flow tubes form independent annular chambers. A liquid collection chamber is formed between the outermost equal flow tube and the shell. Several nozzles are arranged on the shell. The diameter of the flow equalization holes in several flow equalization tubes decreases sequentially from the inside to the outside, while the number of holes increases sequentially. They are arranged in a staggered pattern along the axial direction of the multi-stage flow equalization liquid supply spinneret. The rotational speed of the shear screw is 100~2000 r / min. Several flow equalization tubes are divided into three layers from the inside out: a primary flow equalization tube, a secondary flow equalization tube, and a tertiary flow equalization tube. The diameter of the primary flow equalization tube is 16–20 mm, the secondary flow equalization tube is 10–14 mm, and the tertiary flow equalization tube is 4–8 mm. The primary flow equalization tube contains 5–10 flow equalization orifices with a diameter of 2–4 mm; the secondary flow equalization tube contains 10–20 flow equalization orifices with a diameter of 0.5–2 mm; and the tertiary flow equalization tube contains 20–40 flow equalization orifices with a diameter of 0.1–0.5 mm. The spinning voltage is -120~120 kV, the airflow velocity is 0~60 m / s, the spinning solution supply rate is 1~300 mL / h, the distance between the nozzle and the receiving device is 20~70 cm, the ambient temperature is 15~40 ℃, and the relative humidity is 20~95%.

[0015] In step S2, the spinning solution is sheared and homogenized by the shear screw, which is used to apply continuous shearing and disturbance to the spinning solution entering the multi-stage uniform flow supply spinneret, so as to ensure the uniformity and stability of the spinning solution during the transportation process, thereby suppressing local gelation and improving the uniformity of the system. The spinning solution enters the multi-stage flow equalization tube in sequence. Through the step-by-step diffusion of the multi-stage flow distribution structure and the distributed pressure drop effect generated by the annular pressure equalization chamber, the momentum of the spinning solution is redistributed in the radial and circumferential directions, thereby forming a more stable velocity field and pressure field. The spinning solution permeates from the inside out through the orderly diameter and number of equalization holes on each level of the equalization pipe and collects in the outermost flow channel. This allows the spinning solution to form a controlled pressure drop distribution during the step-by-step permeation process, thereby suppressing the flow deviation phenomenon. The staggered equalization holes can avoid the flow superposition interference between multiple flow channels, further improving the overall uniformity of liquid supply. By combining a shear screw and a multi-stage flow equalization tube, the spinning solution is continuously sheared and dispersed, and subjected to multi-stage pressure equalization and flow division treatment. This improves the uniformity of pressure and flow rate of the spinning solution at the nozzle inlet, reduces inlet flow fluctuations, and continuously delivers it to the whip-driven airflow spinning nozzle through the outermost flow channel. This achieves synchronous and uniform liquid supply by distributing the inlet pressure and flow rate of multiple nozzles, and synchronous and stable spinning by ensuring jet consistency under the condition of multiple nozzles in parallel, thus obtaining precursor nanofiber paper with uniform basis weight.

[0016] As a preferred technical solution, the shearing screw is made of one or more of the following materials: alumina ceramic, zirconium oxide ceramic, silicon nitride ceramic, polyphenylene sulfide, polytetrafluoroethylene, polyoxymethylene, and polyetheretherketone. The material of the flow equalization tube is selected from one or more of the following: polyetheretherketone, polyphenylene sulfide, polyimide, perfluoroalkoxy, alumina ceramic, silicon nitride ceramic, silicon carbide ceramic, mullite ceramic, and zirconium oxide ceramic. The shape of the flow equalization orifice is selected from one or more of the following: circular, elliptical, rhomboid, polygonal, and slit, to adapt to spinning solutions with different rheological properties.

[0017] Further, in step S3, the precursor nanofiber paper is fed to an infrared softening-gradient pressure setting device for thermal excitation softening, pressure welding, and fiber stabilization welding through multiple softening-pressurization and gradient pressure treatments, forming a two-dimensional network structure. The infrared softening-gradient pressure setting device includes a pressure regulating device, a conveyor belt, a cooling air device, several rollers, and an infrared radiation source. The pressure regulating device is horizontally suspended above the infrared softening-gradient pressure setting device. The lower end of the pressure regulating device is connected to several rollers arranged along the conveying direction of the conveyor belt. Several infrared radiation sources are inclinedly arranged above the front side of each roller, with the radiation end of the infrared radiation source pointing towards the contact area between the roller and the conveyor belt. The cooling air device is located behind the pressure regulating device and arranged above the end of the conveyor belt. The infrared light emission wavelength is 0.75~500 μm, and the power is 0.1~200 kW. The angle between the radiation axis of the infrared radiation source and the horizontal plane is... θ The angle is 30~60°. The pressure regulating device is set with progressively increasing gradient pressure, and the roller pressing pressure is 0.1~5 MPa. The softening-pressurization process is repeated 3 to 10 times. The temperature of the cold air supply is 5~20℃.

[0018] As a preferred technical solution, the material of the roll is selected from one or more of medium carbon steel, alloy steel, and stainless steel.

[0019] In step S3, the precursor nanofiber paper is thermally excited under infrared radiation, which makes the fibers soften rapidly. Non-contact heating causes the low-polymerization degree inorganic molecular chain long chain ligand to undergo molecular-level thermal excitation and enter a controllable softening state, thereby achieving in-situ fusion and physical adhesion between fibers under the action of roller pressing. Then, pressure is immediately applied to the precursor nanofiber paper to cause the fiber contact points to fuse. By applying controllable pressure to each roller, the precursor nanofiber paper is kept in a stable pressurized state during the conveying process, thereby promoting the full adhesion of adjacent fibers at the contact interface. Stable fiber fusion was achieved by subjecting the precursor nanofiber paper to multiple softening-pressurization and gradient pressure treatments. Finally, the precursor nanofiber paper is cold-air shaped to form a continuous and bonded two-dimensional network structure. The precursor ceramic nanofiber paper, after infrared softening and rolling treatment, is rapidly cooled and shaped to achieve rapid cooling of the formed fiber bonded structure. Through the synergistic effect of pressure loading, infrared non-contact heating, and rapid cooling, the precursor ceramic nanofiber paper is softened by heat, the interface is fused, and it is cooled and shaped, thereby constructing a continuous and stable two-dimensional fiber network structure.

[0020] Furthermore, in step S3, the precursor nanofiber paper is transported to a deep ultraviolet radiation device for irradiation pretreatment to remove molecular chain ligands and micelles to form a porous structure. The deep ultraviolet light emission wavelength is 185~254 nm. In step S3, the precursor nanofiber paper is fed into a pulsed microwave calcination device for oxygen-deficient calcination. The pulse power is 10~500 kW, the pulse width is 0.1~5 s, and the pulse interval is 0.1~0.5 Hz. The oxygen-containing gas for oxygen-deficient calcination is selected from one or more of air and oxygen, and the inert gas is selected from one or more of nitrogen, argon, helium, neon, krypton, xenon, and radon. The oxygen volume fraction is controlled to be ≤18%, the peak temperature of calcination is 400~1600 ℃, and the holding time is 0.5~3 h.

[0021] The porous nanofibers in the ceramic paper have a grain size of 5–35 nm, a pore size of 0.5–80 nm, and a total pore volume of 0.1–1 cm³. 3 / g, specific surface area of ​​100~1500 m² 2 / g, with a diameter of 50~800 nm. The basis weight of the ceramic paper is 20~220 g / m³. 2 The thickness ranges from 20 μm to 5 mm, with both basis weight and thickness coefficient of variation (CV) ≤ 5%, tensile strength from 0.1 to 10 MPa, and fracture toughness ≥ 0.24 MJ / m. 3 .

[0022] One of the technical solutions of this invention is to provide an application of the porous nanofiber-based ceramic paper based on linear inorganic molecular chains. The ceramic paper is used as a flexible electrode and separator support substrate for solid-state lithium batteries, an energy storage and thermal management unit for flexible wearable devices, a thermal insulation layer for new energy vehicle battery systems, a thermal management layer for electronic devices, flame-retardant, noise-reducing, and heat-insulating components for drones, an ion-conducting electrolyte support carrier for solid-state batteries, a conductive support framework for the positive electrode of high-energy batteries, and an electrochemically active material carrier system. Alternatively, it can be used as a high-temperature resistant adsorption material in gas adsorption and separation systems, a catalyst carrier in industrial chemical reactors, an adsorption material in industrial sugar decolorization units, a purification layer in crude oil refining equipment, and a highly sensitive gas response element in gas monitoring systems.

[0023] The technical principle of this invention is as follows: (1) This invention addresses the imbalance in hydrolysis rate and tendency for bulk gelation of multifunctional metal alkoxide monomers in mixed systems due to differences in electronegativity. By introducing inert ligands with electronegativity gradients, the activity of metal centers can be controlled and adjusted. By utilizing the competitive coordination principle of preferential chelation between strongly electropositive metal centers and strongly electronegative inert ligands, the simultaneous hydrolysis and controlled polycondensation of multi-component systems are ensured, and the hydrolysis-polycondensation process is transformed from a three-dimensional network configuration to a one-dimensional linear molecular chain. Linear inorganic chains with different degrees of polymerization were obtained by controlling the end-capping with or without chain extension and light irradiation. These chains were then mixed to obtain high / low molecular weight linear inorganic molecular chain spinning solutions. The low degree of polymerization linear inorganic chains served as molecular-scale lubricating phases, exhibiting reversible softening and chain segment rearrangement capabilities under thermal excitation conditions, thereby endowing the precursor nanofiber paper with thermoplasticity. (2) This invention utilizes the coordination ability of phosphonic acid groups to metal centers and the large steric hindrance effect of multidentate phosphoryl groups to stably occupy coordination sites that are originally prone to hydrolysis, thereby ensuring the effective retention of multidentate phosphoryl groups in linear inorganic molecular chains. By introducing a binder into a linear inorganic long-chain system, relying on the multidentate phosphoryl P=O group and the binder HN + Hydrogen bonding between molecules, ion pair bridging between binder anions and cations, and hydrophobic interactions between binder molecules constrain the originally dispersed molecular assembly into a stable spherical micelle structure, realizing a self-assembly regulation process with multidentate phosphoryl groups as anchors and binder aggregation nuclei as the center. This micelle structure remains stable under the synergistic constraint of hydrogen bond network and ion pair bridging during subsequent spinning and infrared hot pressing processes. After ultraviolet treatment and calcination, it is transformed into a porous structure, thereby enabling the controllable preparation of porous ceramic nanofibers with uniform pore size and large specific surface area. (3) In this invention, infrared radiation is used to induce inert long-chain ligands on low-polymerization linear inorganic chains to generate molecular-level thermal excitation. By controlling the infrared radiation frequency to match the characteristic vibration frequency of the inert long-chain ligands on the low-polymerization linear inorganic chains, the long-chain ligands generate strong resonance absorption and soften. Subsequently, taking advantage of the low molecular weight and high chain segment flexibility of the low-polymerization linear inorganic chains, the inert long-chain ligands in the infrared-excited softened state can promote the low-polymerization linear inorganic chains to flow along the fiber surface. Under the action of external pressure, molecular-level migration and redistribution occur in the fiber overlap area, and a continuous transition layer is formed between adjacent fibers at the overlap point as a molecular-level binder. This makes the precursor nanofibers exhibit significant thermal softening and interfacial weldability characteristics. Under subsequent hot pressing, the softened low-polymerization linear inorganic chains penetrate into the fiber skeleton composed of high-polymerization linear inorganic long chains, forming an interpenetrating chain segment structure. On the other hand, they generate diffusion connections at the fiber-fiber contact interface, thereby achieving in-situ fusion and physical adhesion between fibers, ultimately constructing a continuous two-dimensional fiber connection reinforcement network structure.

[0024] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention utilizes the inert long-chain ligands on low-polymerization linear inorganic molecular chains to undergo molecular-level thermal excitation under infrared radiation conditions, which softens them by heat and promotes the low-polymerization linear inorganic molecular chains to lubricate along the fiber surface, forming a strong in-situ fusion structure at the overlap point of ceramic nanofibers, thereby establishing a stable connection interface between adjacent fibers, and constructing a continuous two-dimensional fiber support network structure inside the material, making the material less prone to brittle fracture under tension or bending conditions, and exhibiting excellent flexibility and damage resistance. (2) The present invention utilizes a multi-stage uniform flow supply spinneret to continuously shear and disperse the spinning solution and perform step-by-step pressure equalization and diversion treatment through the coaxial combination structure of the shear screw and the multi-stage uniform flow tube, thereby reducing the fluctuation of the inlet flow rate and suppressing the flow deviation phenomenon. At the same time, the diameter of the uniform flow holes decreases and the number increases at each stage to form a controlled pressure drop distribution, so that the spinning solution before entering the nozzle obtains a stable and consistent pressure field and velocity field, thereby ensuring the consistency of the jet and the uniformity of the paper under the condition of parallel spinning of multiple nozzles. (3) The flexible porous ceramic nanofiber paper prepared by the present invention has the characteristics of being lightweight, thin, heat resistant, flame retardant, heat insulation and structural stability. It can also be used as a white activated carbon material. The adsorbed substances are desorbed by high temperature calcination, so that the material can be repeatedly recycled. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the structure of the multi-stage flow equalization liquid supply spinneret in an embodiment of the present invention; Figure 2 This is a schematic diagram of the infrared softening-gradient pressure shaping device in an embodiment of the present invention.

[0026] Explanation of markings in the diagram: 1—Multi-stage flow equalization liquid supply spinneret equipment; 1-1—Shearing screw; 1-2—First-stage flow equalization pipe; 1-3—Second-stage flow equalization pipe; 1-4—Third-stage flow equalization pipe; 1-5—Flow equalization orifice; 2—Infrared softening-gradient pressure shaping equipment, 2-1—Pressure regulating device, 2-2—Infrared radiation source, 2-3—Cold air device. Detailed Implementation

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

[0028] In the description of this invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention. Furthermore, the terms "first," "second," "third," etc., used to describe a common object only indicate different instances of the same object, and do not imply that the objects described in this way must be in a given order, whether temporally, spatially, sequentially, or in any other way.

[0029] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0030] Unless otherwise specified, the equipment used in the following embodiments is conventional equipment in the art; unless otherwise specified, the reagents used are commercially available products or prepared by conventional methods in the art. In the following embodiments, unless otherwise described in detail, conventional experimental methods in the art can be used.

[0031] Unless otherwise specified, the following procedures are generally performed at room temperature and atmospheric pressure.

[0032] The multi-stage flow equalization spinneret 1 used in the following embodiments, such as Figure 1 As shown, the device includes a housing, a shearing screw 1-1, and several flow equalization tubes and nozzles. The shearing screw 1-1 is horizontally positioned at the axis of the innermost flow equalization tube, i.e., the first-stage flow equalization tube 1-2. Several flow equalization tubes, i.e., the first-stage flow equalization tube 1-2, the second-stage flow equalization tube 1-3, and the third-stage flow equalization tube 1-4, are coaxially arranged inside the housing from the inside out along the axial direction of the multi-stage flow equalization liquid supply spinneret 1. Several flow equalization holes 1-5 are opened on the wall of the flow equalization tubes. The flow equalization tubes are connected to each other through the flow equalization holes 1-5, and the flow equalization tubes form independent annular chambers. The outermost flow equalization tube, i.e., the third-stage flow equalization tube 1-4, forms a liquid collection chamber with the housing. Several nozzles are installed on the housing. The diameter of the flow equalization holes in several flow equalization tubes decreases sequentially from the inside to the outside, while the number of holes increases sequentially. They are arranged in a staggered pattern along the axial direction of the multi-stage flow equalization liquid supply spinneret 1.

[0033] The infrared softening-gradient pressure setting device 2 used in the following embodiments, such as Figure 2 As shown, the device includes a pressure regulating device 2-1, a conveyor belt, a cooling air device 2-3, several rollers, and an infrared radiation source 2-2. The pressure regulating device 2-1 is horizontally suspended above the infrared softening-gradient pressurization and shaping equipment 2. The lower end of the pressure regulating device 2-1 is connected to several rollers arranged along the conveying direction of the conveyor belt. Several infrared radiation sources 2-2 are inclinedly arranged above the front side of each roller, and the radiation end of the infrared radiation source 2-2 points to the contact area between the roller and the conveyor belt. The cooling air device 2-3 is located behind the pressure regulating device 2-1 and is arranged above the end section of the conveyor belt.

[0034] Example 1: A porous nanofiber-based ceramic paper based on linear inorganic molecular chains and its preparation method are described below: S1. 11-phosphono-1,1,1-tris(dimethoxyphosphorylmethyl)undecane was added to a 1:1 molar ratio of titanium n-butoxide and aluminum sec-butoxide. The molar ratio of the total amount of titanium n-butoxide and aluminum sec-butoxide to 11-phosphono-1,1,1-tris(dimethoxyphosphorylmethyl)undecane was 1:2. The mixture was stirred at 25 °C for 2 h to allow preliminary coordination of the metal centers, yielding titanium alkoxide and aluminum alkoxide precursors with a multidentate phosphoryl group at one end and a phosphonic acid group at the other. A gradient inert ligand solution was prepared by mixing diethyl ether, acetic acid, and acetylacetone in a molar ratio of 2:4:4. Titanium alkoxide and aluminum alkoxide precursors were then added. The molar ratio of the total amount of titanium n-butoxide and aluminum sec-butoxide to the total amount of diethyl ether, acetic acid, and acetylacetone was 1:3. The mixture was stirred at 25 °C for 2 h to allow for sufficient coordination modification of the metal centers, yielding modified titanium alkoxide and aluminum alkoxide monomers. Hydrochloric acid was added to the modified titanium alkoxide monomer and aluminum alkoxide monomer, with a molar ratio of the total n-butoxide titanium and sec-butoxide aluminum to the hydrogen ions in the hydrochloric acid of 1:2. Deionized water was then added, with a molar ratio of the total n-butoxide titanium and sec-butoxide aluminum to water of 1:1. The mixture was stirred at 25 °C for 2 h, allowing the modified titanium alkoxide monomer and aluminum alkoxide monomer to undergo a stepwise hydrolysis-condensation reaction, forming a linear inorganic chain with titanium and aluminum as metal nodes, with a degree of polymerization of 50. Titanium diisopropoxybisacetylacetone, titanium n-butoxide, and aluminum sec-butoxide were added to the system in a molar ratio of 1:1 to titanium diisopropoxybisacetylacetone. The mixture was stirred at 80 °C for 2 h to extend the chain. Then, ethyl diazonium was added in a molar ratio of 1:2 to ethyl diazonium. The mixture was stirred at 25 °C under 254 nm light irradiation for 0.5 h to cap the chain, forming a highly polymerized linear inorganic long chain with a degree of polymerization of 2000. Ethanol was added to the system, with the total molar ratio of titanium n-butoxide and aluminum sec-butoxide to ethanol being 1:1. Subsequently, hexadecyltrimethylammonium bromide was added, with the total molar ratio of titanium n-butoxide and aluminum sec-butoxide to hexadecyltrimethylammonium bromide being 1:0.15. The reaction was stirred at 25 °C for 1 h. Utilizing the interaction between 11-phosphono-1,1,1-tris(dimethoxyphosphorylmethyl)undecane and hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium bromide was uniformly distributed near 11-phosphono-1,1,1-tris(dimethoxyphosphorylmethyl)undecane, forming spherical micelles, thus obtaining a high-polymerization-degree linear inorganic long-chain solution containing micelles. Octanoic acid and isopropanol were mixed at a molar ratio of 1:10 and added to a titanium butoxide system. The molar ratio of titanium butoxide to octanoic acid was 1:2. The mixture was stirred at 40 °C for 2.5 h to allow coordination of the metal centers. Deionized water was added to the system at 80 °C. The molar ratio of titanium n-butoxide to water was 1:1. The reaction was carried out by stirring at 80 °C for 4 hours, which caused the titanium alkoxide monomer to undergo hydrolysis-condensation reaction, forming a low degree of polymerization linear inorganic chain with titanium as the metal node and obtaining its solution with a degree of polymerization of 60. A high / low molecular weight linear inorganic chain spinning solution was obtained by mixing a high degree of polymerization linear inorganic long chain solution and a low degree of polymerization linear inorganic chain solution at a molar ratio of 1:1. The solution had a viscosity of 200 mPa·s, an electrical conductivity of 35 μS / cm, and a surface tension of 45 mN / m. S2. The high / low molecular weight linear inorganic molecular chain spinning solution is supplied to the multi-stage uniform flow supply spinneret 1 for spinning. The rotation speed of the shear screw 1-1 is 800 r / min, and the material is polytetrafluoroethylene. The diameter of the first-stage uniform flow tube is 16 mm, the diameter of the second-stage uniform flow tube is 10 mm, and the diameter of the third-stage uniform flow tube is 4 mm. The number of uniform flow holes in the first-stage uniform flow tube is 5 with a diameter of 2 mm, the number of uniform flow holes in the second-stage uniform flow tube is 10 with a diameter of 0.5 mm, and the number of uniform flow holes in the third-stage uniform flow tube is 20 with a diameter of 0.1 mm. The material of the uniform flow tube is polyetheretherketone, and the orifice shape of the uniform flow holes is circular. The spinning voltage is 55 kV, the airflow velocity is 30 m / s, the spinning solution supply rate is 100 mL / h, the distance between the nozzle and the receiving device is 30 cm, the ambient temperature is 30 ℃, and the relative humidity is 40%. The precursor nanofiber paper is obtained. S3. The precursor nanofiber paper is fed into the infrared softening-gradient pressure setting equipment 2 for thermal excitation softening, pressure welding, and multiple softening-pressurization and gradient pressure treatments to achieve stable fiber welding and settling to form a two-dimensional network structure. The infrared light emission wavelength is 5.8 μm, the power is 1 kW, and the angle between the radiation axis of the infrared radiation source 2-2 and the horizontal plane is... θ The pressure is set at 30°, and the pressure regulating device 2-1 is set with progressively increasing gradient pressure. The roller pressing pressure is 0.5 MPa, 1 MPa, 2 MPa and 3 MPa, and the number of softening-pressurization cycles is 4. The roller material is stainless steel, and the cold air supply temperature is 5 ℃. The precursor nanofiber paper was pretreated by irradiation in a deep ultraviolet radiation device to remove molecular chain ligands and micelles, forming a porous structure. The deep ultraviolet light emission wavelength was 254 nm. Then, it was transported to a pulsed microwave calcination device for oxygen-deficient calcination. The pulse power was 100 kW, the pulse width was 0.1 s, and the pulse interval was 0.2 Hz. Oxygen-deficient calcination was carried out in a mixed gas of oxygen and nitrogen with an oxygen volume fraction of 18%. The peak temperature of calcination was 600 ℃, and the holding time was 2 h. Then, it was naturally cooled to room temperature to obtain porous nanofiber-based ceramic paper based on linear inorganic molecular chains.

[0035] In Example 1, the porous nanofibers in the ceramic paper had a grain size of 6 nm, a pore size of 15 nm, and a total pore volume of 0.6 cm³. 3 / g, specific surface area is 900 m² 2 / g, with a diameter of 200 nm The basis weight of the ceramic paper is 45 g / m². 2 The thickness is 120 μm, the coefficient of variation (CV) for basis weight is 4.7%, the coefficient of variation for thickness is 4.3%, both the coefficients of variation for basis weight and thickness are <5%, the tensile strength is 9 MPa, and the fracture toughness is 0.31 MJ / m.3 .

[0036] Example 2: A porous nanofiber-based ceramic paper based on linear inorganic molecular chains and its preparation method are described below: S1. 1,1-bis(dimethoxyphosphorylmethyl)-1-(8-phosphonooctyl)propane was added to a 1:1 molar ratio system of titanium n-butoxide and zirconium n-butoxide. The molar ratio of the total amount of titanium n-butoxide and zirconium n-butoxide to 1,1-bis(dimethoxyphosphorylmethyl)-1-(8-phosphonooctyl)propane was 1:2. The mixture was stirred at 25 °C for 2 h to allow preliminary coordination of the metal centers, yielding titanium alkoxide and zirconium alkoxide precursors with ligands having a multidentate phosphoryl group at one end and a phosphonate group at the other end. A gradient inert ligand solution was prepared by mixing acetone, propionic acid, and trifluoroacetylacetone in a molar ratio of 4:2:4. Titanium alkoxide and zirconium alkoxide precursors were then added. The molar ratio of the total of titanium n-butoxide and zirconium n-butoxide to the total of acetone, propionic acid, and trifluoroacetylacetone was 1:3. The mixture was stirred at 25 °C for 2 h to allow for sufficient coordination modification of the metal centers, yielding modified titanium alkoxide and zirconium alkoxide monomers. Hydrochloric acid was added to the modified titanium alkoxide monomer and zirconium alkoxide monomer, with a molar ratio of the total n-butoxide titanium and n-butoxide zirconium to hydrogen ions in the hydrochloric acid of 1:2. Deionized water was then added, with a molar ratio of the total n-butoxide titanium and n-butoxide zirconium to water of 1:2. The mixture was stirred at 25 °C for 2 h, allowing the modified titanium alkoxide monomer and zirconium alkoxide monomer to undergo a stepwise hydrolysis-condensation reaction, forming linear inorganic chains with titanium and zirconium as metal centers, with a degree of polymerization of 60. Zirconium bis(diethylcitrate)dipropoxide, titanium n-butoxide, and zirconium n-butoxide were added to the system in a molar ratio of 1:1 to zirconium bis(diethylcitrate)dipropoxide. The mixture was stirred at 90 °C for 3 h to extend the chain. Then, ethyl diazonium was added, and the molar ratio of the total of titanium n-butoxide and zirconium n-butoxide to ethyl diazonium was 1:2. The mixture was stirred at 25 °C under 254 nm light irradiation for 0.5 h to end-cap the chain, forming a high-polymerization-degree linear inorganic long chain with a degree of polymerization of 2200. n-Propanol was added to the system, and the molar ratio of the total of n-butoxide titanium and n-butoxide zirconium to n-propanol was 1:1. Then, dodecyltrimethylammonium bromide was added, and the molar ratio of the total of n-butoxide titanium and n-butoxide zirconium to dodecyltrimethylammonium bromide was 1:0.2. The reaction was stirred at 25 °C for 1 h. Utilizing the interaction between 1,1-bis(dimethoxyphosphorylmethyl)-1-(8-phosphonooctyl)propane and dodecyltrimethylammonium bromide, dodecyltrimethylammonium bromide was uniformly distributed near 1,1-bis(dimethoxyphosphorylmethyl)-1-(8-phosphonooctyl)propane, forming spherical micelles, thus obtaining a high-polymerization-degree linear inorganic long-chain solution containing micelles. Oleic acid and isopropanol were mixed in a molar ratio of 1:9 and added to a titanium butoxide system. The molar ratio of titanium butoxide to oleic acid was 1:2. The mixture was stirred at 40 °C for 2 h to allow coordination of the metal centers. Deionized water was added to the system at 80 °C. The molar ratio of titanium n-butoxide to water was 1:1. The mixture was kept at the temperature and stirred for 4 h to allow the titanium alkoxide monomer to undergo hydrolysis-condensation reaction, forming a low-polymerization degree linear inorganic chain with titanium as the metal node and obtaining its solution with a polymerization degree of 80. A high / low molecular weight linear inorganic chain spinning solution was obtained by mixing a high degree of polymerization linear inorganic long chain solution and a low degree of polymerization linear inorganic chain solution at a molar ratio of 1:1. The solution had a viscosity of 180 mPa·s, an electrical conductivity of 40 μS / cm, and a surface tension of 50 mN / m. S2. The high / low molecular weight linear inorganic molecular chain spinning solution is supplied to the multi-stage uniform flow supply spinneret 1 for spinning. The rotation speed of the shear screw 1-1 is 800 r / min, and the material is polytetrafluoroethylene. The diameter of the first-stage uniform flow tube is 20 mm, the diameter of the second-stage uniform flow tube is 14 mm, and the diameter of the third-stage uniform flow tube is 8 mm. The number of uniform flow holes in the first-stage uniform flow tube is 10 with a diameter of 4 mm, the number of uniform flow holes in the second-stage uniform flow tube is 20 with a diameter of 2 mm, and the number of uniform flow holes in the third-stage uniform flow tube is 40 with a diameter of 0.5 mm. The material of the uniform flow tube is alumina ceramic, and the orifice shape of the uniform flow holes is circular. The spinning voltage is 50 kV, the airflow velocity is 35 m / s, the spinning solution supply rate is 80 mL / h, the distance between the nozzle and the receiving device is 35 cm, the ambient temperature is 28 ℃, and the relative humidity is 45%. The precursor nanofiber paper is obtained. S3. The precursor nanofiber paper is fed into the infrared softening-gradient pressure setting equipment 2 for thermal excitation softening, pressure welding, and multiple softening-pressurization and gradient pressure treatments to achieve stable fiber welding and settling to form a two-dimensional network structure. The infrared light emission wavelength is 3.32 μm, the power is 1 kW, and the angle between the radiation axis of the infrared radiation source 2-2 and the horizontal plane is... θ The pressure is set at 60°, and the pressure regulating device 2-1 is set with progressively increasing gradient pressure. The roller pressing pressure is 2 MPa, 3 MPa, 4 MPa and 5 MPa. The number of softening-pressurization cycles is 4. The roller material is stainless steel, and the cold air supply temperature is 20 ℃. The precursor nanofiber paper was pretreated by irradiation in a deep ultraviolet radiation device to remove molecular chain ligands and micelles, forming a porous structure. The deep ultraviolet light emission wavelength was 254 nm. Then, it was transported to a pulsed microwave calcination device for oxygen-deficient calcination with a pulse power of 150 kW, a pulse width of 1 s, and a pulse interval of 0.3 Hz. Oxygen-deficient calcination was carried out in a mixture of oxygen and nitrogen with an oxygen volume fraction of 16%, with a peak calcination temperature of 1000 ℃ and a holding time of 2 h. Subsequently, it was naturally cooled to room temperature to obtain porous nanofiber-based ceramic paper based on linear inorganic molecular chains.

[0037] In Example 2, the porous nanofibers in the ceramic paper had a grain size of 8 nm, a pore size of 20 nm, and a total pore volume of 0.5 cm³. 3 / g, specific surface area is 1000 m² 2 / g, with a diameter of 300 nm. The basis weight of the ceramic paper is 80 g / m². 2 The thickness is 200 μm, the coefficient of variation for basis weight is 4.6%, the coefficient of variation for thickness is 4.2%, both the coefficients of variation for basis weight and thickness are <5%, the tensile strength is 8 MPa, and the fracture toughness is 0.35 MJ / m. 3 .

[0038] 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 porous nanofiber-based ceramic paper based on linear inorganic molecular chains, characterized in that, Phosphonate-based multidentate phosphoryl ligands are added to several metal alkoxide monomers for initial coordination. The phosphonate-based multidentate phosphoryl ligands are ligands with a phosphonate group at one end and a multidentate phosphoryl group at the other end. Several inert ligands with electronegativity gradients are added for coordination modification. After reaction, chain extension and end capping are performed, and a binder is added to form spherical micelles to obtain a high degree of polymerization linear inorganic long-chain solution. Inert long-chain ligands are added to metal alkoxide monomers and reacted to obtain a low degree of polymerization linear inorganic chain solution. A high-polymerization-degree linear inorganic long-chain solution and a low-polymerization-degree linear inorganic chain solution are mixed, spun, and subjected to multiple softening-pressurization and gradient pressure treatments to achieve fiber fusion, shaping, removal of molecular chain ligands and micelles to form a porous structure, and calcination to obtain porous nanofiber-based ceramic paper based on linear inorganic molecular chains.

2. A method for preparing porous nanofiber-based ceramic paper based on linear inorganic molecular chains as described in claim 1, characterized in that, The method includes the following steps: S1. Phosphonic acid-based multidentate phosphoryl ligands are added to several metal alkoxide monomers for initial coordination, several inert ligands with electronegativity gradients are added for coordination modification, an acid catalyst and water are added for hydrolysis-condensation reaction, a metal-centered bifunctional chain extender is added for chain extension, a photoresponsive end-capping agent is added for end-capping, an alcohol solvent and a binder are added so that the binder is distributed near the phosphonic acid-based multidentate phosphoryl ligands to form spherical micelles, and a high degree of polymerization linear inorganic long-chain solution containing micelles is obtained. Inert long-chain ligands and alcohol solvents are added to metal alkoxide monomers for coordination, and water is added to carry out hydrolysis-condensation reaction to obtain a low degree of polymerization linear inorganic chain solution. A high / low molecular weight linear inorganic chain spinning solution is obtained by mixing a high degree of polymerization linear inorganic long chain solution and a low degree of polymerization linear inorganic chain solution. S2. Spinning of high / low molecular weight linear inorganic molecular chain spinning solution to obtain precursor nanofiber paper; S3. The precursor nanofiber paper is softened by thermal excitation and then pressure-fused. Through multiple softening-pressurization and gradient pressure treatments, stable fiber fusion is achieved, forming a two-dimensional network structure. Precursor nanofiber paper was irradiated to remove molecular chain ligands and micelles to form a porous structure, and then calcined to obtain porous nanofiber-based ceramic paper based on linear inorganic molecular chains.

3. The method for preparing porous nanofiber-based ceramic paper based on linear inorganic molecular chains according to claim 2, characterized in that, In step S1, the metal alkoxide monomers corresponding to the high degree of polymerization linear inorganic long chains are selected from zirconium tetraethanolamine, zirconium tetramethanol, zirconium isopropoxide, zirconium n-propoxide, zirconium isobutoxide, zirconium tert-butoxide, zirconium n-butoxide, zirconium tetrapentoxide, titanium tetraethanolamine, titanium isobutoxide, titanium n-propoxide, titanium n-butoxide, titanium tetraethanolamine, titanium tert-butoxide, titanium isooctanol, titanium tetrapentoxide, titanium isopropoxide, tin n-propoxide, tin n-butoxide, tin tetraethanolamine, tin tert-butoxide, tin tetraethanolamine, tin isobutoxide, and tin isopropoxide. Two or more of the following: tin tetrapentoxide, aluminum n-butoxide, aluminum trimethoxy, aluminum tri-n-propoxy, aluminum isopropoxide, aluminum sec-butoxide, aluminum triethanolamine, aluminum tert-butoxide, indium isopropoxide, indium triethoxy, indium tert-butoxide, gallium isopropoxide, gallium triethoxy, gallium n-butoxide, gallium tert-butoxide, hafnium tetramethanol, hafnium tetraethanol, hafnium n-propoxide, hafnium isopropoxide, hafnium n-butoxide, hafnium isobutoxide, hafnium tert-butoxide, hafnium tetrapentoxide, tantalum isopropoxide, tantalum n-butoxide, niobium isopropoxide, and niobium n-butoxide. Phosphono-based multidentate phosphoryl ligands are selected from 11-phosphono-1,1,1-tris(dimethoxyphosphonomethyl)undecane, 11-(bis(2-(dimethoxyphosphonooxy)ethyl)amino)-undecylphosphonic acid, 1,1-bis(dimethoxyphosphonomethyl)-1-(8-phosphonooctyl)propane, bis(dimethoxyphosphonomethyl)-(8-phosphonooctyl)phosphine oxide, N,N One or more of bis(2-(dimethoxyphosphoryl)ethyl)-11-phosphonoundecaneamide, The molar ratio of the total metal alkoxide monomers to the phosphonate polydentate phosphoryl ligands is (1~2):(1~4); The initial coordination temperature is 20~160 ℃, and the time is 2~6 h.

4. The method for preparing porous nanofiber-based ceramic paper based on linear inorganic molecular chains according to claim 2, characterized in that, In step S1, the inert ligands corresponding to the high-polymerization-degree linear inorganic long chain with electronegativity gradient are divided into three categories: weakly inert ligands, moderately inert ligands, and strongly inert ligands. Weakly inert ligands are selected from one or more of diethyl ether, acetone, 1,4-dioxane, tetrahydrofuran, and butanone. Moderately inert ligands are selected from one or more of formic acid, acetic acid, propionic acid, isobutyric acid, butyric acid, butyl acetate, ethyl acetate, methyl methacrylate, methylamine, cyclohexanone, ethylamine, isopropylamine, n-propylamine, and methylcyclohexanone. Strongly inert ligands are selected from one or more of acetylacetone, hexafluoroacetylacetone, benzoylacetone, trifluoroacetylacetone, methyl acetoacetate, diethanolamine, tert-butyl acetoacetate, ethyl acetoacetate, and triethanolamine. The molar ratio of weakly inert ligands, moderately inert ligands, and strongly inert ligands is (1~8):(1~8):(1~8). The molar ratio of the total metal alkoxide monomers to the total inert ligands of the electronegativity gradient is (1~2):(3~7); The temperature for coordination modification is 20~160 ℃, and the time is 2~6 h.

5. The method for preparing porous nanofiber-based ceramic paper based on linear inorganic molecular chains according to claim 2, characterized in that, In step S1, the acid catalyst corresponding to the highly polymerized linear inorganic long chain is selected from one or more of hydrochloric acid, nitric acid, sulfuric acid, acetic acid, phosphoric acid, and formic acid. The metal-centered bifunctional chain extender is selected from one or more of the following: diisopropyl bis(ethyl acetoacetate)titanate, diisopropoxydiacetylacetonate, (ethyl acetoacetate)diisopropoxyaluminate, di(diethylcitrate)dipropoxide zirconium, zirconium dichlorodecane, titanium dichlorodecane, molybdenum dichlorodecane, vanadium dichlorodecane, and hafnium dichlorodecane. The photoresponsive end-capping agent is selected from one or more of 2-diazo-1-naphthol-5-sulfonyl chloride, ethyl diazonyl chloride, and 4-azido-2,3,5,6-tetrafluorobenzoic acid. The alcohol solvent is selected from one or more of methanol, n-propanol, glycerol, n-pentanol, tert-butanol, isopropanol, sec-butanol, n-butanol, butanediol, hexanediol, ethylene glycol, and ethanol. The binder is selected from one or more of the following: n-octyltrimethylammonium bromide, dodecyltrimethylammonium bromide, tetradecyltrimethylammonium bromide, didodecyldimethylammonium bromide, decaalkyltrimethylammonium bromide, hexadecyltrimethylammonium bromide, hexadecyltrimethylammonium chloride, eicosyltrimethylammonium bromide, octadecyltrimethylammonium bromide, docosyltrimethylammonium bromide, (2-hydroxyethyl)hexadecyldimethylammonium bromide, cocamidopropyl betaine, and 1-hexadecyl-3-methylimidazolium bromide. The molar ratio of the total metal alkoxide monomers to hydrogen ions in the acid catalyst is (1~2):(1~4), and the molar ratio of the total metal alkoxide monomers to water, metal-centered bifunctional chain extender, photoresponsive end-capping agent, alcohol solvent and binder is (1~2):(1~5):(1~2):(1~4):(1~10):(0.1~1). The hydrolysis-condensation reaction takes place at a temperature of 20–160 °C for 2–6 h. The chain extension temperature is 20~160 ℃, and the time is 2~6 h. The sealing temperature is 20~160 ℃, the light emission wavelength is 200~800 nm, and the time is 0.4~1.2 h. The temperature for forming spherical micelles is 20~160 ℃, and the time is 1~3 h; The degree of polymerization of highly polymerizable linear inorganic long chains is 2000~5000.

6. The method for preparing porous nanofiber-based ceramic paper based on linear inorganic molecular chains according to claim 2, characterized in that, In step S1, the corresponding low-polymerization-degree linear inorganic chain uses metal alkoxide monomers selected from zirconium tetraethanolamine, zirconium tetramethanol, zirconium isopropoxide, zirconium n-propoxide, zirconium isobutoxide, zirconium tert-butoxide, zirconium n-butoxide, zirconium tetrapentoxide, titanium tetraethanolamine, titanium isobutoxide, titanium n-propoxide, titanium n-butoxide, titanium tetraethanolamine, titanium tert-butoxide, titanium isooctanol, titanium tetrapentoxide, titanium isopropoxide, tin n-propoxide, tin n-butoxide, tin tetraethanolamine, tin tert-butoxide, tin tetraethanolamine, tin isobutoxide, tin isoprop ... One or more of the following: tin pentanol, aluminum n-butoxide, aluminum trimethoxy, aluminum tri-n-propoxy, aluminum isopropoxide, aluminum sec-butoxide, aluminum triethanolamine, aluminum tert-butoxide, indium isopropoxide, indium triethoxy, indium tert-butoxide, gallium isopropoxide, gallium triethoxy, gallium n-butoxide, gallium tert-butoxide, hafnium tetramethanol, hafnium tetraethanol, hafnium n-propoxide, hafnium isopropoxide, hafnium n-butoxide, hafnium isobutoxide, hafnium tert-butoxide, hafnium tetrapentanol, tantalum isopropoxide, tantalum n-butoxide, niobium isopropoxide, and niobium n-butoxide. The inert long-chain 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 alcohol solvent is selected from one or more of methanol, n-propanol, glycerol, n-pentanol, tert-butanol, isopropanol, sec-butanol, n-butanol, butanediol, hexanediol, ethylene glycol, and ethanol. The molar ratio of metal alkoxide monomer to inert long-chain ligand, alcohol solvent and water is (1~2):(1~4):(2~20):(1~5); The coordination temperature is 20–160 °C, and the time is 2–6 h. The hydrolysis-condensation reaction is carried out at a temperature of 20~160 ℃ for 2~6 h. The degree of polymerization of low-polymerization linear inorganic chains ranges from 20 to 1000.

7. The method for preparing porous nanofiber-based ceramic paper based on linear inorganic molecular chains according to claim 2, characterized in that, In step S1, the molar ratio of the metal alkoxide monomers corresponding to the high-polymerization-degree linear inorganic long chain and the low-polymerization-degree linear inorganic chain is 1:(0.5~2); The viscosity of the high / low molecular weight linear inorganic molecular chain spinning solution is 20~12000 mPa·s, the electrical conductivity is 0.5~2000 μS / cm, and the surface tension is 30~60 mN / m.

8. The method for preparing porous nanofiber-based ceramic paper based on linear inorganic molecular chains according to claim 2, characterized in that, In step S2, the high / low molecular weight linear inorganic molecular chain spinning solution is supplied to a multi-stage uniform flow supply spinning device for spinning. The multi-stage uniform flow supply spinning device includes a shell, a shearing screw, and several flow equalization tubes and nozzles. The shearing screw is horizontally arranged at the axis of the innermost flow equalization tube. Several flow equalization tubes are coaxially arranged in the shell along the axial direction of the multi-stage uniform flow supply spinning device. Several flow equalization holes are opened on the wall of the several flow equalization tubes. The several flow equalization tubes are interconnected through the flow equalization holes and form independent annular chambers between the several flow equalization tubes. A liquid collection chamber is formed between the outermost flow equalization tube and the shell. Several nozzles are arranged on the shell. The diameter of the flow equalization holes in several flow equalization tubes decreases sequentially from the inside to the outside, while the number of holes increases sequentially. They are arranged in a staggered pattern along the axial direction of the multi-stage flow equalization liquid supply spinneret. The rotational speed of the shear screw is 100~2000 r / min. Several flow equalization tubes are divided into three layers from the inside out: a primary flow equalization tube, a secondary flow equalization tube, and a tertiary flow equalization tube. The diameter of the primary flow equalization tube is 16–20 mm, the secondary flow equalization tube is 10–14 mm, and the tertiary flow equalization tube is 4–8 mm. The primary flow equalization tube contains 5–10 flow equalization orifices with a diameter of 2–4 mm; the secondary flow equalization tube contains 10–20 flow equalization orifices with a diameter of 0.5–2 mm; and the tertiary flow equalization tube contains 20–40 flow equalization orifices with a diameter of 0.1–0.5 mm. The spinning voltage is -120~120 kV, the airflow velocity is 0~60 m / s, the spinning solution supply rate is 1~300 mL / h, the distance between the nozzle and the receiving device is 20~70 cm, the ambient temperature is 15~40 ℃, and the relative humidity is 20~95%.

9. The method for preparing porous nanofiber-based ceramic paper based on linear inorganic molecular chains according to claim 2, characterized in that, In step S3, the precursor nanofiber paper is fed to an infrared softening-gradient pressure setting device for thermal excitation softening and pressure welding. Through multiple softening-pressing and gradient pressure treatments, the fibers are stably welded and shaped into a two-dimensional network structure. The infrared softening-gradient pressure setting device includes a pressure regulating device, a conveyor belt, a cooling air device, several rollers, and infrared radiation sources. The pressure regulating device is horizontally suspended above the infrared softening-gradient pressure setting device. The lower end of the pressure regulating device is connected to several rollers arranged along the conveying direction of the conveyor belt. Several infrared radiation sources are inclinedly arranged above the front side of each roller. The radiation end of the infrared radiation source points to the contact area between the roller and the conveyor belt. The cooling air device is located behind the pressure regulating device and arranged above the end of the conveyor belt. The infrared light emission wavelength is 0.75~500 μm, and the power is 0.1~200 kW. The angle between the radiation axis of the infrared radiation source and the horizontal plane is... θ The angle is 30~60°. The pressure regulating device is set with progressively increasing gradient pressure, and the roller pressing pressure is 0.1~5 MPa. The softening-pressurization process is repeated 3 to 10 times. The temperature of the cold air supply is 5~20℃.

10. The method for preparing porous nanofiber-based ceramic paper based on linear inorganic molecular chains according to claim 2, characterized in that, In step S3, the precursor nanofiber paper is transported to a deep ultraviolet radiation device for irradiation pretreatment to remove molecular chain ligands and micelles to form a porous structure. The deep ultraviolet light emission wavelength is 185~254 nm. In step S3, the precursor nanofiber paper is fed into a pulsed microwave calcination device for oxygen-deficient calcination. The pulse power is 10~500 kW, the pulse width is 0.1~5 s, and the pulse interval is 0.1~0.5 Hz. The oxygen-containing gas for oxygen-deficient calcination is selected from one or more of air and oxygen, and the inert gas is selected from one or more of nitrogen, argon, helium, neon, krypton, xenon, and radon. The oxygen volume fraction is controlled to be ≤18%, the peak temperature of calcination is 400~1600 ℃, and the holding time is 0.5~3 h.

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