A method for preparing a helically intertwined high-entropy ceramic nanofiber

Abstract

The application belongs to the field of nanofiber materials, and specifically discloses a preparation method of spiral-interlaced high-entropy ceramic nanofiber. Alcoholate precursors containing four or five metal elements are mixed and reacted with carbonizable organic polymers after being complexed by a complexing agent and hydrolytic copolymerization to obtain a high-entropy carbide ceramic polymer precursor; the precursor is prepared into a spinning solution with a binder, a spinning aid and an organic solvent, electrospun and dynamically received by a rotating metal needle, and a spiral-interlaced structure fiber is obtained by adjusting the rotating speed of the receiving needle; and the ceramic nanofiber is obtained after glue removal and high-temperature carbonization. The application realizes controllable preparation of the spiral-interlaced structure of the high-entropy carbide ceramic nanofiber, and the obtained fiber has excellent mechanical flexibility and high-temperature stability, and is suitable for high-temperature filtration, catalytic carrier and aerospace thermal protection fields.

Description

Technical Field

[0001] This invention belongs to the field of nanofiber materials, and specifically discloses a method for preparing helical interwoven high-entropy ceramic nanofibers. Background Technology

[0002] High-entropy carbide ceramics, due to their ultra-high melting point, excellent thermochemical stability, and good high-temperature mechanical properties, have broad application prospects in ultra-high temperature thermal protection systems, nuclear reactor cladding materials, and hot-end components of aero-engines. However, the inherent high brittleness and low fracture toughness of high-entropy carbide ceramics severely restrict their reliable application under complex stress environments. How to improve their mechanical flexibility has become a key problem that urgently needs to be solved in this field.

[0003] Preparing high-entropy ceramics into nanofiber morphology is one of the effective ways to improve their mechanical flexibility. Currently, the preparation of high-entropy ceramic nanofibers mainly adopts the sol-gel method combined with electrospinning technology, achieving ceramic transformation through blending of metal alkoxide precursors with spinnable polymers, spinning, and high-temperature heat treatment. However, the high-entropy ceramic nanofibers prepared by existing technologies are usually linear or randomly oriented fiber membranes, with fibers mainly bonded by physical stacking, lacking structural synergistic reinforcement effects. The widely existing helical interwoven structure in nature can effectively dissipate strain energy through configuration unfolding during stretching or bending, significantly improving the ductility and fracture resistance of materials, providing important inspiration for the design of high-performance fiber materials. However, most existing helical fiber preparation methods are applicable to polymer systems. For high-entropy ceramics, due to the low ceramic conversion rate of the precursor solution, the easy shrinkage and deformation of fibers during high-temperature heat treatment, and the difficulty in maintaining the helical structure, how to controllably prepare the helical interwoven structure of high-entropy ceramic fibers at the nanoscale still lacks effective technical means.

[0004] Furthermore, existing patents such as CN111303581B disclose methods for preparing high-entropy ceramic fibers, but the resulting fibers are linear and do not involve helical structures. While CN114988881A relates to the preparation of high-entropy ceramic fibers, it does not design helical structures for the macroscopic morphology of the fibers. Therefore, developing a method for controllably preparing high-entropy ceramic nanofibers with helical interwoven structures is of great significance for expanding the application fields of high-entropy ceramic materials. This invention aims to overcome the shortcomings of the prior art by providing a method for preparing helical interwoven high-entropy ceramic nanofibers. Through the synergistic combination of precursor composition optimization and dynamic rotation receiving technology, the controllable preparation of helical interwoven structures of high-entropy carbide ceramic nanofibers is achieved. Summary of the Invention

[0005] The purpose of this invention is to provide a helical winding structure of high-entropy carbide ceramic nanofibers and its preparation method. It aims to overcome the inherent limitations of existing high-entropy ceramic fiber preparation technologies, such as the limited product morphology, lack of three-dimensional helical configuration design, and the difficulty in achieving controllable construction of macroscopic fiber morphology using traditional electrospinning methods. This invention provides a helical ceramic fiber material with excellent structural flexibility, high specific surface area, and good deformation resistance, to meet the urgent need for non-linear ceramic micro / nanofibers in fields such as catalysis, sensing, electromagnetic shielding, and extreme environment thermal protection.

[0006] To achieve the above objectives, the present invention adopts the following technical solution. The specific steps are as follows: (1) Dissolve the high-entropy transition metal alkoxide precursor in an anhydrous organic solvent and stir until completely dissolved; the high-entropy transition metal alkoxide precursor contains at least four or five alkoxides corresponding to metal elements selected from zirconium, titanium, tantalum, chromium, manganese, lanthanum, cobalt, nickel, ytterbium, hafnium, vanadium, niobium, molybdenum or tungsten, wherein the molar ratio of each metal element is 0.15~0.35:0.15~0.35:0.15~0.35:0.15~0.35 (when there are four elements) or 0.10~0.30:0.10~0.30:0.10~0.30:0.10~0.30:0.10~0.30 (when there are five elements), and the sum of the molar ratios of each element is 1; (2) Slowly add the complexing agent to the solution obtained in step (1). The molar ratio of the complexing agent to the total metal alkoxide is 1.2:1 to 1.5:1. After the addition is complete, continue stirring to react and obtain a uniform and transparent metal alkoxide complex solution. (3) Under an inert atmosphere, the solution obtained in step (2) is heated to a certain temperature, and a mixture of deionized water and anhydrous organic solvent is slowly added dropwise. The molar ratio of deionized water to total metal elements is 1.1:1~1.5:1, and the mass ratio of anhydrous organic solvent to deionized water is 5:1~10:1. After the addition is complete, the reaction is refluxed, and part of the solvent is removed by atmospheric distillation to obtain metal alkoxide copolymer. (4) The metal alkoxide copolymer obtained in step (3) is mixed with the carbonizable organic polymer in a certain proportion, heated and reacted under an inert atmosphere, and cooled to room temperature to obtain a high-entropy carbide ceramic polymer precursor. (5) The precursor obtained in step (4) is mixed with binder, spinning aid and organic solvent in proportion, mechanically stirred at room temperature, and allowed to stand to degas, so as to obtain a uniform, transparent and viscous spinning precursor solution. (6) Inject the precursor solution obtained in step (5) into a syringe, fix it on a micro-injection pump, use a stainless steel flat needle as a spinneret, use a vertically installed metal receiving needle as a collecting device, apply a high voltage electric field to perform electrospinning, the fiber is stretched and wound on the rotating receiving needle under the action of the electric field force, and the spiral diameter and winding density of the fiber are controlled by adjusting the rotation speed and receiving distance of the receiving needle to obtain the precursor spiral wound structure fiber; (7) Place the fiber-bearing receiving needle obtained in step (6) in a tube furnace and perform a debinding heat treatment under an inert atmosphere to allow the organic components to be pyrolyzed and discharged. (8) Place the degummed spiral fibers obtained in step (7) into a graphite crucible, put it into a high-temperature sintering furnace, and perform high-temperature carbonization heat treatment under vacuum or inert atmosphere protection to obtain high-entropy carbide spiral wound ceramic nanofibers.

[0007] Preferably, the high-entropy transition metal alkoxide precursor in step (1) is a combination of alkoxides corresponding to at least four or five metal elements. The metal elements are selected from any four or five of zirconium, titanium, tantalum, chromium, manganese, lanthanum, cobalt, nickel, ytterbium, hafnium, vanadium, niobium, molybdenum, or tungsten, and the metal elements include at least one rare earth metal element or at least one of chromium, manganese, cobalt, or nickel. The alkoxide is selected from any one or more combinations of zirconium propoxide, zirconium isopropoxide, zirconium butoxide, titanium isopropoxide, titanium butoxide, tantalum ethoxide, tantalum isopropoxide, chromium isopropoxide, chromium isopropoxide, manganese isopropoxide, lanthanum ethoxide, cobalt isopropoxide, nickel ethoxide, ytterbium isopropoxide, hafnium ethoxide, vanadium isopropoxide, niobium ethoxide, molybdenum ethoxide, or tungsten ethoxide. When the metal element is titanium, zirconium, or hafnium, its isopropoxide or n-propoxide salt is preferred; when the metal element is tantalum or niobium... When the metal element is chromium, manganese, cobalt, or nickel, its isopropoxide or ethanolate is preferred; when the metal element is lanthanum or ytterbium, its isopropoxide is preferred; when the metal element is lanthanum or ytterbium, its isopropoxide is preferred; when the four elements are combined, the molar ratio of each metal element is 0.10~0.40:0.10~0.40:0.10~0.40; when the five elements are combined, the molar ratio of each metal element is 0.08~0.32:0.08~0.32:0.08~0.32:0.08~0.32:0.08~0.32; and the sum of the molar ratios of each element is 1; the anhydrous organic solvent is selected from any one of n-propanol, isopropanol, n-butanol, ethanol, methanol, isobutanol, ethylene glycol methyl ether, or ethylene glycol ethyl ether; the solid content of the high-entropy transition metal alkoxide precursor in the organic solvent is 5~35 wt%.

[0008] Preferably, the metal element combination of the high-entropy transition metal alkoxide precursor in step (1) is any one of the following quaternary combinations: Zr-Ti-Ta-Cr, Zr-Ti-Ta-Mn, Zr-Ti-Ta-La, Zr-Ti-Cr-Mn, Zr-Ta-Cr-Mn, Ti-Ta-Cr-Mn, Zr-Ti-Ta-Co, Zr-Ti-Ta-Ni, Zr-Ti-Ta-Yb, Zr-Ti-Cr-Co, Zr-Ti-Cr-Ni, Hf-Ti-Ta-Cr, Zr-Hf-Ta-Cr, Zr-T i-Nb-Cr, Zr-Ti-Ta-V, Zr-Ti-Ta-Mo or Zr-Ti-Ta-W; or any of the following five-component combinations: Zr-Ti-Ta-Cr-Mn, Zr-Ti-Ta-Cr-La, Zr-Ti-Ta-Cr-Co, Zr- Ti-Ta-Cr-Ni, Zr-Ti-Ta-Cr-Yb, Zr-Ti-Ta-Mn-Co, Zr-Ti-Cr-Mn-Co, Hf-Ti-Ta-Cr-Mn, Zr-Ti-Nb-Ta-Cr or Zr-Ti-Ta-Cr-V.

[0009] Preferably, the complexing agent in step (2) is selected from any one or more combinations of benzoylacetone, dibenzoylmethane, triethanolamine or ethylene glycol; the molar ratio of the complexing agent to the total metal alkoxide is 1.0:1 to 2.0:1; the dropping rate is 0.5 to 3 mL / min; after the dropping is completed, stirring is continued at 15 to 45 °C for 1 to 6 h.

[0010] Preferably, the inert atmosphere in step (3) is selected from any one of nitrogen, argon or helium; the heating temperature is 40~90 °C; in the mixed solution of deionized water and anhydrous organic solvent, the molar ratio of deionized water to total metal elements is 0.6:1~1.8:1, the mass ratio of anhydrous organic solvent to deionized water is 2:1~12:1, the dropping rate is 0.2~1.5 mL / min; the reflux reaction time after dropping is 0.5~4 h; the amount of solvent removed by atmospheric distillation is 15%~50% of the original solution volume.

[0011] Preferably, the carbonizable organic polymer in step (4) is selected from any one of allyl-functionalized phenolic resin, phenolic resin, furfuryl alcohol resin, urea-formaldehyde resin or polycarbosilane; the mass ratio of the total number of moles of metal elements in the metal alkoxide copolymer to the carbonizable organic polymer is 1 mol: 5~50 g; the reaction temperature is 50~110 °C, and the reaction time is 0.5~5 h; the carbonizable organic polymer and the metal alkoxide copolymer are mixed by mechanical stirring or ultrasonic dispersion.

[0012] Preferably, the binder in step (5) is selected from any one of polyvinyl butyral, polyacrylate, or polyvinyl acetate; the spinning aid is selected from any one of polyvinylpyrrolidone, polyethylene oxide, or polyacrylonitrile; the organic solvent is selected from any one of n-propanol, isopropanol, ethanol, acetone, or dimethylformamide; the mass ratio of the precursor to the binder, spinning aid, and organic solvent is 30:5~18:3~8:150~350; the mechanical stirring time is 3~15 h, the stirring rate is 150~600 r / min; and the standing degassing time is 1~6 h.

[0013] Preferably, in step (6), the inner diameter of the spinneret is 0.2~1.0 mm, the spinneret is connected to a positive high voltage of 10~30 kV; the receiving needle is a vertically installed metal needle with a diameter of 0.3~3.0 mm, the receiving needle is connected to a negative high voltage of -6~-1 kV; the receiving needle is driven to rotate by a stepper motor with a rotation speed of 300~3500 r / min; the vertical distance between the spinneret and the receiving needle is 8~50 cm; the feeding speed is 5~40 mL / h; the ambient temperature is 20~30 °C, and the ambient relative humidity is below 60%.

[0014] Preferably, in step (6), a loose spiral structure fiber is obtained when the receiving needle rotation speed is 300~1200 r / min, and a tightly twisted spiral structure fiber is obtained when the receiving needle rotation speed is 1800~3500 r / min; the shorter the receiving distance, the smaller the spiral diameter and pitch.

[0015] Preferably, the inert atmosphere in step (7) is selected from either nitrogen or argon, with a gas flow rate of 300~1200 sccm and a purging time of 15~60 min; during the heat treatment of adhesive removal, the gas flow rate is adjusted to 50~300 sccm, and the temperature is raised from room temperature to 400~900 °C at a heating rate of 0.3~3 °C / min, held for 1~4 h, and then naturally cooled to room temperature.

[0016] Preferably, the high-temperature sintering furnace mentioned in step (8) is a vacuum sintering furnace or an atmosphere sintering furnace; the vacuum degree is 10. -5 ~10 -1 Pa; the inert atmosphere is selected from either argon or helium, and the gas flow rate is 50~500 sccm; the high-temperature carbonization heat treatment is a staged heating: the temperature is raised to 1200~1600 °C at a heating rate of 2~15 °C / min and held for 0.5~2 h; then the temperature is raised to 1500~1900 °C at a heating rate of 2~15 °C / min and held for 1~4 h; then the furnace is cooled to room temperature.

[0017] The purpose of this invention is to provide a method for preparing helically intertwined high-entropy ceramic nanofibers. By combining a polymer precursor method with rotating receiving needle electrospinning technology, using metal alkoxides (zirconium n-propoxide, titanium isopropoxide, tantalum ethoxide, chromium isopropoxide) as the metal source and allyl-functionalized phenolic resin as the carbon source and polymer framework, continuous helical winding (twisted) high-entropy carbide ceramic nanofibers were successfully prepared through sol-gel reaction, electrospinning, desizing pyrolysis, and high-temperature carbothermal reduction treatment. This helical winding structure endows the material with excellent flexibility, high specific surface area, and good structural deformation resistance, while the high-entropy component design ensures excellent thermal stability and oxidation resistance. This invention overcomes the inherent limitations of existing high-entropy ceramic fiber preparation technologies, such as the single product morphology and lack of three-dimensional helical configuration design, and solves the problem of controlling the macroscopic morphology of fibers using traditional electrospinning methods. It provides a non-linear ceramic micro / nanofiber material that can be used in fields such as catalyst supports, high-temperature filtration, electromagnetic shielding, flexible electronic devices, and extreme environment thermal protection. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0019] Figure 1 Here is a SEM image of the helical interwoven high-entropy ceramic nanofibers obtained in Example 1; Figure 2 Here is a SEM image of the helical interwoven high-entropy ceramic nanofibers obtained in Example 2; Figure 3 This is a SEM image of the helical interwoven high-entropy ceramic nanofibers obtained in Example 3. Detailed Implementation

[0020] This invention provides a method for preparing helical interwoven high-entropy ceramic nanofibers. The technical solution provided by this invention will be described in detail below with reference to the embodiments, but these should not be construed as limiting the scope of protection of this invention. Example 1

[0021] Step 1: Weigh 10.74 g of zirconium n-propoxide, 6.67 g of titanium isopropoxide, 9.51 g of tantalum ethoxide, and 10.72 g of chromium isopropoxide in a molar ratio of Zr:Ti:Ta:Cr = 0.20:0.20:0.20:0.40. Dissolve them in 250 mL of anhydrous n-propanol and stir at 300 r / min for 30 min until completely dissolved.

[0022] Step 2: Add 15.0 mL of acetylacetone dropwise to the solution obtained in Step 1 at a rate of 2 mL / min. After the addition is complete, continue stirring at 300 r / min for 3 h to obtain a uniform and transparent metal alkoxide complex solution.

[0023] Step 3: Under nitrogen protection, the solution obtained in Step 2 was heated to 70 °C, and a mixed solution of 3.6 g of deionized water and 28.8 g of anhydrous n-propanol was added dropwise at a rate of 0.6 mL / min. After the addition was completed, the mixture was refluxed at 70 °C for 1 h, and then 80 mL of solvent was removed by distillation at 90 °C under normal pressure to obtain the metal alkoxide copolymer.

[0024] Step 4: Add 6.5 g of allyl-functionalized phenolic resin to the metal alkoxide copolymer obtained in Step 3, heat to 80 °C for 1.5 h under nitrogen protection, and cool naturally to room temperature to obtain a high-entropy carbide ceramic polymer precursor.

[0025] Step 5: Take 30.0 g of the precursor obtained in Step 4, add 10.0 g of polyvinyl butyral, 5.0 g of polyvinylpyrrolidone and 250 g of anhydrous n-propanol, stir at 400 r / min at room temperature for 8 h, and let stand to degas for 3 h to obtain the spinning precursor solution.

[0026] Step 6: Inject the precursor solution obtained in Step 5 into a 0.5 mm inner diameter spinneret at a rate of 20 mL / h. Connect the spinneret to a positive high voltage of 20 kV. Connect the vertically installed 1.0 mm diameter stainless steel receiving needle to a negative high voltage of -3 kV. Control the receiving needle rotation speed at 2000 r / min. The vertical distance between the spinneret and the receiving needle is 20 cm. The ambient temperature is 25±2 °C and the relative humidity is <45%. Perform electrospinning for 15 min to obtain precursor spiral fibers wound on the receiving needle.

[0027] Step 7: Place the fiber-bearing receiving needle obtained in Step 6 into a tube furnace, purge with high-purity nitrogen at 500 sccm for 30 min, adjust to 150 sccm, heat to 600 °C at 0.8 °C / min and hold for 2 h, then allow to cool naturally to room temperature to complete the glue removal process.

[0028] Step 8: Remove the spiral fiber from the receiving needle after debinding in Step 7, place it in a graphite crucible, and put it into a vacuum sintering furnace to a vacuum level of 10. -3 Pa was heated to 1400 °C at a rate of 5 °C / min and held for 30 min, then heated to 1750 °C at a rate of 5 °C / min and held for 2 h. The mixture was then cooled to room temperature in the furnace to obtain (Zr). 0.2 Ti 0.2 Ta 0.2 Cr 0.4C-helical winding structure high-entropy carbide ceramic nanofibers.

[0029] The SEM image of the helical interwoven high-entropy ceramic nanofibers prepared in this embodiment is as follows: Figure 1 As shown. Example 2

[0030] Step 1: Weigh zirconium n-propoxide, titanium isopropoxide, tantalum ethoxide, and manganese isopropoxide in a molar ratio of Zr:Ti:Ta:Mn = 0.25:0.25:0.25:0.25, dissolve them in anhydrous ethanol, with a solid content of 10 wt%, and stir at 350 r / min for 40 min until completely dissolved.

[0031] Step 2: Add benzoylacetone (molar ratio of 1.5:1 to total metal alkoxide) dropwise to the solution obtained in Step 1 at a rate of 1.5 mL / min. After the addition is complete, continue stirring at 350 r / min for 4 h to obtain a uniform and transparent metal alkoxide complex solution.

[0032] Step 3: Under argon protection, heat the solution obtained in Step 2 to 60 °C, and add a mixed solution of deionized water and anhydrous ethanol dropwise at a rate of 0.8 mL / min (molar ratio of deionized water to total metal elements is 1.5:1, and mass ratio of anhydrous ethanol to deionized water is 6:1). After the addition is complete, reflux at 60 °C for 2 h, and then distill at 85 °C under normal pressure to remove 25% of the original solution volume of solvent, to obtain the metal alkoxide copolymer.

[0033] Step 4: Add phenolic resin (total metal element moles to resin mass ratio of 1 mol: 15 g) to the metal alkoxide copolymer obtained in Step 3, heat to 90 °C for 1 h under argon protection, and allow to cool naturally to room temperature to obtain the high-entropy carbide ceramic polymer precursor.

[0034] Step 5: Take 30.0 g of the precursor obtained in Step 4, add 8.0 g of polyacrylate, 6.0 g of polyethylene oxide and 200 g of anhydrous isopropanol, stir at 500 r / min at room temperature for 6 h, and let stand to degas for 4 h to obtain the spinning precursor solution.

[0035] Step 6: Inject the precursor solution obtained in Step 5 into a 0.3 mm inner diameter spinneret at a rate of 15 mL / h. Connect the spinneret to a positive high voltage of 15 kV and connect the vertically installed 0.5 mm diameter stainless steel receiving needle to a negative high voltage of -2 kV. Control the rotation speed of the receiving needle to 600 r / min, the vertical distance between the spinneret and the receiving needle to 15 cm, the ambient temperature to 22±2 °C, and the relative humidity to <50%. Perform electrospinning for 20 min to obtain a loose spiral structure precursor fiber wound on the receiving needle.

[0036] Step 7: Place the fiber-receiving needle obtained in Step 6 into a tube furnace, purge with high-purity argon gas at 800 sccm for 20 min, adjust to 200 sccm, heat to 500 °C at 1.0 °C / min and hold for 3 h, then allow to cool naturally to room temperature to complete the glue removal process.

[0037] Step 8: Remove the spiral fiber from the receiving needle after debinding in Step 7, place it in a graphite crucible, and put it into a vacuum sintering furnace to a vacuum level of 10. -2 Pa was heated to 1300 °C at 8 °C / min and held for 1 h, then heated to 1650 °C at 8 °C / min and held for 3 h, and then cooled to room temperature in the furnace to obtain (Zr). 0.25 Ti 0.25 Ta 0.25 Mn 0.25 C-helical winding structure high-entropy carbide ceramic nanofibers.

[0038] The SEM image of the helical interwoven high-entropy ceramic nanofibers prepared in this embodiment is as follows: Figure 2 As shown. Example 3

[0039] Step 1: Weigh zirconium isopropoxide, titanium n-butoxide, tantalum isopropoxide, and lanthanum isopropoxide in a molar ratio of Zr:Ti:Ta:La = 0.30:0.25:0.25:0.20, dissolve them in isopropanol, with a solid content of 20 wt%, and stir at 400 r / min for 25 min until completely dissolved. Step 2: Add dibenzoylmethane (molar ratio of 1.2:1 to total metal alkoxide) dropwise to the solution obtained in Step 1 at a rate of 1.0 mL / min. After the addition is complete, continue stirring at 400 r / min for 5 h to obtain a uniform and transparent metal alkoxide complex solution.

[0040] Step 3: Under helium protection, heat the solution obtained in Step 2 to 80 °C, and add a mixed solution of deionized water and isopropanol at a rate of 0.4 mL / min (molar ratio of deionized water to total metal elements is 0.8:1, and mass ratio of isopropanol to deionized water is 10:1). After the addition is complete, reflux at 80 °C for 0.5 h, and then remove 20% of the original solution volume of solvent by distillation at 80 °C under normal pressure to obtain the metal alkoxide copolymer.

[0041] Step 4: Add furfuryl alcohol resin (total metal element moles to resin mass ratio of 1 mol: 40 g) to the metal alkoxide copolymer obtained in Step 3, heat to 70 °C for 3 h under helium protection, and allow to cool naturally to room temperature to obtain the high-entropy carbide ceramic polymer precursor.

[0042] Step 5: Take 30.0 g of the precursor obtained in Step 4, add 15.0 g of polyvinyl acetate, 3.0 g of polyacrylonitrile and 300 g of anhydrous acetone, stir at 250 r / min at room temperature for 12 h, let stand to degas for 5 h, and obtain the spinning precursor solution.

[0043] Step 6: Inject the precursor solution obtained in Step 5 into a 0.8 mm inner diameter spinneret at a rate of 10 mL / h. Connect the spinneret to a positive high voltage of 25 kV and connect the vertically installed 2.0 mm diameter stainless steel receiving needle to a negative high voltage of -5 kV. Control the receiving needle rotation speed at 3000 r / min, the vertical distance between the spinneret and the receiving needle at 40 cm, the ambient temperature at 28±2 °C and the relative humidity at <40%, and perform electrospinning for 10 min to obtain a tightly twisted spiral precursor fiber wound on the receiving needle.

[0044] Step 7: Place the fiber-bearing receiving needle obtained in Step 6 into a tube furnace, purge with high-purity nitrogen at 400 sccm for 50 min, adjust to 80 sccm, heat to 800 °C at 2.0 °C / min and hold for 1.5 h, then allow to cool naturally to room temperature to complete the glue removal process.

[0045] Step 8: Remove the spiral fiber from the receiving needle after debinding in Step 7, place it in a graphite crucible, and put it into an atmosphere sintering furnace. High-purity argon gas is introduced at 200 sccm, and the temperature is increased to 1500 °C at 10 °C / min and held for 0.5 h. Then, the temperature is increased to 1850 °C at 10 °C / min and held for 1.5 h. The furnace is then cooled to room temperature to obtain (Zr... 0.3 Ti 0.25 Ta 0.25 La 0.2 C-helical winding structure high-entropy carbide ceramic nanofibers.

[0046] The SEM image of the helical interwoven high-entropy ceramic nanofibers prepared in this embodiment is as follows: Figure 3 As shown. Example 4

[0047] Step 1: Weigh out hafnium ethanol, titanium isopropoxide, tantalum ethanol, chromium isopropoxide, and manganese isopropoxide in a molar ratio of Hf:Ti:Ta:Cr:Mn = 0.20:0.20:0.20:0.20, dissolve them in n-butanol, with a solid content of 15 wt%, and stir at 300 r / min for 35 min until completely dissolved.

[0048] Step 2: Add triethanolamine (molar ratio of 1.8:1 to the total metal alkoxide) dropwise to the solution obtained in Step 1 at a rate of 2.5 mL / min. After the addition is complete, continue stirring at 300 r / min for 2 h to obtain a uniform and transparent metal alkoxide complex solution.

[0049] Step 3: Under nitrogen protection, heat the solution obtained in Step 2 to 50 °C, and add a mixed solution of deionized water and n-butanol at a rate of 1.2 mL / min (molar ratio of deionized water to total metal elements is 1.1:1, and mass ratio of n-butanol to deionized water is 5:1). After the addition is complete, reflux at 50 °C for 3 h, and then distill at 95 °C under normal pressure to remove 35% of the original solution volume of solvent to obtain the metal alkoxide copolymer.

[0050] Step 4: Add urea-formaldehyde resin (total metal element moles to resin mass ratio of 1 mol: 10 g) to the metal alkoxide copolymer obtained in Step 3, heat to 100 °C for 0.5 h under nitrogen protection, and cool naturally to room temperature to obtain the high-entropy carbide ceramic polymer precursor.

[0051] Step 5: Take 30.0 g of the precursor obtained in Step 4, add 6.0 g of polyvinyl butyral, 8.0 g of polyvinylpyrrolidone and 180 g of anhydrous dimethylformamide, stir at 600 r / min at room temperature for 5 h, and let stand to degas for 2 h to obtain the spinning precursor solution.

[0052] Step 6: Inject the precursor solution obtained in Step 5 into a 0.6 mm inner diameter spinneret at a rate of 30 mL / h. Connect the spinneret to a positive high voltage of 18 kV and connect the vertically installed 1.5 mm diameter stainless steel receiving needle to a negative high voltage of -4 kV. Control the receiving needle rotation speed at 1500 r / min, the vertical distance between the spinneret and the receiving needle at 25 cm, the ambient temperature at 25±2 °C and the relative humidity at <55%, and perform electrospinning for 25 min to obtain precursor spiral fibers wound on the receiving needle.

[0053] Step 7: Place the fiber-receiving needle obtained in Step 6 into a tube furnace, purge with high-purity nitrogen at 600 sccm for 40 min, adjust to 120 sccm, heat to 700 °C at 0.5 °C / min and hold for 2.5 h, then allow to cool naturally to room temperature to complete the glue removal process.

[0054] Step 8: Remove the spiral fiber from the receiving needle after debinding in Step 7, place it in a graphite crucible, and put it into a vacuum sintering furnace to a vacuum level of 10. -4 Pa was heated to 1350 °C at a rate of 3 °C / min and held for 1.5 h, then heated to 1800 °C at a rate of 3 °C / min and held for 1 h. The mixture was then cooled to room temperature in the furnace to obtain (Hf). 0.2 Ti 0.2 Ta 0.2 Cr 0.2 Mn 0.2 C-helical winding structure high-entropy carbide ceramic nanofibers. Example 5

[0055] Step 1: Weigh zirconium n-propoxide, titanium isopropoxide, niobium ethoxide, tantalum ethoxide, and chromium isopropoxide in a molar ratio of Zr:Ti:Nb:Ta:Cr = 0.18:0.22:0.20:0.20. Dissolve them in ethylene glycol methyl ether to a solid content of 25 wt%. Stir at 450 r / min for 20 min until completely dissolved.

[0056] Step 2: Add acetylacetone (molar ratio of acetylacetone to total metal alkoxide of 1.3:1) dropwise to the solution obtained in Step 1 at a rate of 0.8 mL / min. After the addition is complete, continue stirring at 450 r / min for 3.5 h to obtain a uniform and transparent metal alkoxide complex solution.

[0057] Step 3: Under argon protection, heat the solution obtained in Step 2 to 75 °C, and add a mixed solution of deionized water and ethylene glycol methyl ether at a rate of 1.0 mL / min (molar ratio of deionized water to total metal elements is 1.4:1, and mass ratio of ethylene glycol methyl ether to deionized water is 9:1). After the addition is complete, reflux at 75 °C for 1.5 h, and then remove 40% of the original solution volume of solvent by distillation at 100 °C under normal pressure to obtain the metal alkoxide copolymer.

[0058] Step 4: Add polycarbosilane (total metal element moles to polycarbosilane mass ratio of 1 mol: 30 g) to the metal alkoxide copolymer obtained in Step 3, heat to 85 °C for 2 h under argon protection, and allow to cool naturally to room temperature to obtain the high-entropy carbide ceramic polymer precursor.

[0059] Step 5: Take 30.0 g of the precursor obtained in Step 4, add 12.0 g of polyvinyl butyral, 4.0 g of polyvinylpyrrolidone and 220 g of anhydrous ethylene glycol ethyl ether, stir at 350 r / min at room temperature for 10 h, and let stand to degas for 1.5 h to obtain the spinning precursor solution.

[0060] Step 6: Inject the precursor solution obtained in Step 5 into a 0.4 mm inner diameter spinneret at a rate of 25 mL / h. Connect the spinneret to a positive high voltage of 22 kV. Connect the vertically installed 0.8 mm diameter stainless steel receiving needle to a negative high voltage of -3 kV. Control the receiving needle rotation speed to 800 r / min. The vertical distance between the spinneret and the receiving needle is 12 cm. The ambient temperature is 23±2 °C and the relative humidity is <48%. Perform electrospinning for 12 min to obtain a loose spiral structure precursor fiber wound on the receiving needle.

[0061] Step 7: Place the fiber-receiving needle obtained in Step 6 into a tube furnace, purge with high-purity argon gas at 700 sccm for 25 min, adjust to 100 sccm, heat to 550 °C at 1.5 °C / min and hold for 3.5 h, then allow to cool naturally to room temperature to complete the glue removal process.

[0062] Step 8: Remove the spiral fiber from the receiving needle after debinding in Step 7, place it in a graphite crucible, and put it into a vacuum sintering furnace to a vacuum level of 10. -5 Pa was heated to 1450 °C at a rate of 12 °C / min and held for 1 h, then heated to 1700 °C at a rate of 12 °C / min and held for 2.5 h, and then cooled to room temperature in the furnace to obtain (Zr). 0.18 Ti 0.22 Nb 0.2 Ta 0.2 Cr 0.2 C-helical winding structure high-entropy carbide ceramic nanofibers. Example 6

[0063] Step 1: Weigh zirconium n-butoxide, titanium n-butoxide, tantalum isopropoxide, and vanadium ethanol in a molar ratio of Zr:Ti:Ta:V = 0.35:0.25:0.20:0.20, dissolve them in methanol, with a solid content of 8 wt%, and stir at 500 r / min for 15 min until completely dissolved.

[0064] Step 2: Add ethylene glycol (molar ratio of ethylene glycol to total metal alkoxides of 2.0:1) dropwise to the solution obtained in Step 1 at a rate of 3.0 mL / min. After the addition is complete, continue stirring at 500 r / min for 1.5 h to obtain a uniform and transparent metal alkoxide complex solution.

[0065] Step 3: Under nitrogen protection, heat the solution obtained in Step 2 to 40 °C, and add a mixed solution of deionized water and methanol at a rate of 1.5 mL / min (molar ratio of deionized water to total metal elements is 1.6:1, and mass ratio of methanol to deionized water is 3:1). After the addition is complete, reflux at 40 °C for 3.5 h, and then remove 45% of the original solution volume of solvent by distillation at 65 °C under normal pressure to obtain the metal alkoxide copolymer.

[0066] Step 4: Add allyl-functionalized phenolic resin (total metal element moles to resin mass ratio of 1 mol: 45 g) to the metal alkoxide copolymer obtained in Step 3, heat to 60 °C for 4 h under nitrogen protection, and allow to cool naturally to room temperature to obtain a high-entropy carbide ceramic polymer precursor.

[0067] Step 5: Take 30.0 g of the precursor obtained in Step 4, add 14.0 g of polyacrylate, 3.5 g of polyacrylonitrile and 280 g of anhydrous isobutanol, stir at 180 r / min at room temperature for 14 h, and let stand to degas for 6 h to obtain the spinning precursor solution.

[0068] Step 6: Inject the precursor solution obtained in Step 5 into a 1.0 mm inner diameter spinneret at a rate of 8 mL / h. Connect the spinneret to a positive high voltage of 28 kV and connect the vertically installed 2.5 mm diameter stainless steel receiving needle to a negative high voltage of -6 kV. Control the receiving needle rotation speed at 3200 r / min, the vertical distance between the spinneret and the receiving needle at 45 cm, the ambient temperature at 28±2 °C and the relative humidity at <35%, and perform electrospinning for 8 min to obtain a tightly twisted spiral precursor fiber wound on the receiving needle.

[0069] Step 7: Place the fiber-receiving needle obtained in Step 6 into a tube furnace, purge with high-purity argon gas at 900 sccm for 15 min, adjust to 50 sccm, heat to 850 °C at 2.5 °C / min and hold for 1 h, then allow to cool naturally to room temperature to complete the glue removal process.

[0070] Step 8: Remove the spiral fiber from the receiving needle after debinding in Step 7, place it in a graphite crucible, and put it into an atmosphere sintering furnace. High-purity argon gas is introduced at 100 sccm, and the temperature is increased to 1550 °C at 4 °C / min and held for 0.5 h. Then, the temperature is increased to 1900 °C at 4 °C / min and held for 1 h. The furnace is then cooled to room temperature to obtain (Zr... 0.35 Ti 0.25 Ta 0.2 V 0.2 C-helical winding structure high-entropy carbide ceramic nanofibers. Example 7

[0071] Step 1: Weigh zirconium n-propoxide, titanium isopropoxide, chromium ethanol, and cobalt isopropoxide in a molar ratio of Zr:Ti:Cr:Co = 0.25:0.30:0.25:0.20, dissolve them in isobutanol, with a solid content of 30 wt%, and stir at 250 r / min for 50 min until completely dissolved.

[0072] Step 2: Add benzoylacetone (molar ratio of 1.0:1 to the total metal alkoxide) dropwise to the solution obtained in Step 1 at a rate of 0.5 mL / min. After the addition is complete, continue stirring at 250 r / min for 6 h to obtain a uniform and transparent metal alkoxide complex solution.

[0073] Step 3: Under helium protection, heat the solution obtained in Step 2 to 90 °C, and add a mixed solution of deionized water and isobutanol at a rate of 0.2 mL / min (molar ratio of deionized water to total metal elements is 0.6:1, and mass ratio of isobutanol to deionized water is 12:1). After the addition is complete, reflux at 90 °C for 0.5 h, and then distill at 95 °C under normal pressure to remove 15% of the original solution volume of solvent, to obtain the metal alkoxide copolymer.

[0074] Step 4: Add phenolic resin (total metal element moles to resin mass ratio of 1 mol: 8 g) to the metal alkoxide copolymer obtained in Step 3, heat to 105 °C for 0.5 h under helium protection, and allow to cool naturally to room temperature to obtain the high-entropy carbide ceramic polymer precursor.

[0075] Step 5: Take 30.0 g of the precursor obtained in Step 4, add 5.0 g of polyvinyl acetate, 7.0 g of polyvinylpyrrolidone and 350 g of anhydrous n-propanol, stir at 550 r / min at room temperature for 4 h, and let stand for degassing for 2.5 h to obtain the spinning precursor solution.

[0076] Step 6: Inject the precursor solution obtained in Step 5 into a 0.7 mm inner diameter spinneret at a rate of 35 mL / h. Connect the spinneret to a positive high voltage of 12 kV and connect the vertically installed 0.3 mm diameter stainless steel receiving needle to a negative high voltage of -1 kV. Control the receiving needle rotation speed at 500 r / min, the vertical distance between the spinneret and the receiving needle at 50 cm, the ambient temperature at 20±2 °C and the relative humidity at <58%, and perform electrospinning for 30 min to obtain a loose spiral structure precursor fiber wound on the receiving needle.

[0077] Step 7: Place the fiber-bearing receiving needle obtained in Step 6 into a tube furnace, purge with high-purity nitrogen at 300 sccm for 60 min, adjust to 250 sccm, heat to 400 °C at 3.0 °C / min and hold for 4 h, then allow to cool naturally to room temperature to complete the glue removal process.

[0078] Step 8: Remove the spiral fiber from the receiving needle after debinding in Step 7, place it in a graphite crucible, and put it into a vacuum sintering furnace to a vacuum level of 10. -1 Pa was heated to 1200 °C at a rate of 15 °C / min and held for 2 h, then heated to 1500 °C at a rate of 15 °C / min and held for 4 h, and then cooled to room temperature in the furnace to obtain (Zr). 0.25 Ti 0.3 Cr 0.25 Co 0.2 C-helical winding structure high-entropy carbide ceramic nanofibers. Example 8

[0079] Step 1: Weigh zirconium isopropoxide, titanium n-butoxide, tantalum ethoxide, and nickel ethoxide in a molar ratio of Zr:Ti:Ta:Ni = 0.15:0.25:0.35:0.25, dissolve them in ethylene glycol ethyl ether, with a solid content of 12 wt%, and stir at 320 r / min for 45 min until completely dissolved.

[0080] Step 2: Add dibenzoylmethane (molar ratio of 1.6:1 to total metal alkoxide) dropwise to the solution obtained in Step 1 at a rate of 2.2 mL / min. After the addition is complete, continue stirring at 320 r / min for 2.5 h to obtain a uniform and transparent metal alkoxide complex solution.

[0081] Step 3: Under argon protection, heat the solution obtained in Step 2 to 55 °C, and add a mixed solution of deionized water and ethylene glycol ethyl ether at a rate of 0.7 mL / min (molar ratio of deionized water to total metal elements is 1.2:1, and mass ratio of ethylene glycol ethyl ether to deionized water is 7:1). After the addition is complete, reflux at 55 °C for 2.5 h, and then remove 30% of the original solution volume of solvent by distillation at 105 °C under normal pressure to obtain the metal alkoxide copolymer.

[0082] Step 4: Add furfuryl alcohol resin (total metal element moles to resin mass ratio of 1 mol: 35 g) to the metal alkoxide copolymer obtained in Step 3, heat to 75 °C for 2.5 h under argon protection, and allow to cool naturally to room temperature to obtain the high-entropy carbide ceramic polymer precursor.

[0083] Step 5: Take 30.0 g of the precursor obtained in Step 4, add 9.0 g of polyvinyl butyral, 5.0 g of polyethylene oxide and 240 g of anhydrous isopropanol, stir at 420 r / min at room temperature for 9 h, and let stand to degas for 3.5 h to obtain the spinning precursor solution.

[0084] Step 6: Inject the precursor solution obtained in Step 5 into a 0.5 mm inner diameter spinneret at a rate of 18 mL / h. Connect the spinneret to a positive high voltage of 20 kV and connect the vertically installed 1.8 mm diameter stainless steel receiving needle to a negative high voltage of -2.5 kV. Control the receiving needle rotation speed at 2500 r / min, the vertical distance between the spinneret and the receiving needle at 30 cm, the ambient temperature at 24±2 °C and the relative humidity at <42%, and perform electrospinning for 18 min to obtain a tightly twisted spiral precursor fiber wound on the receiving needle.

[0085] Step 7: Place the fiber-receiving needle obtained in Step 6 into a tube furnace, purge with high-purity nitrogen at 550 sccm for 35 min, adjust to 180 sccm, heat to 650 °C at 0.6 °C / min and hold for 2 h, then allow to cool naturally to room temperature to complete the glue removal process.

[0086] Step 8: Remove the spiral fiber from the receiving needle after debinding in Step 7, place it in a graphite crucible, and put it into a vacuum sintering furnace to a vacuum level of 10. -3 Pa was heated to 1400 °C at a rate of 6 °C / min and held for 0.8 h, then heated to 1780 °C at a rate of 6 °C / min and held for 1.8 h, and then cooled to room temperature in the furnace to obtain (Zr). 0.15 Ti 0.25 Ta 0.35 Ni 0.25 C-helical winding structure high-entropy carbide ceramic nanofibers. Example 9

[0087] Step 1: Weigh zirconium n-propoxide, titanium isopropoxide, tantalum ethoxide, chromium isopropoxide, and ytterbium isopropoxide in a molar ratio of Zr:Ti:Ta:Cr:Yb = 0.22:0.18:0.20:0.22:0.18. Dissolve them in a mixed solvent of n-propanol and ethanol in a volume ratio of 1:1, with a solid content of 18 wt%. Stir at 380 r / min for 30 min until completely dissolved.

[0088] Step 2: Add triethanolamine (molar ratio of 1.1:1 to the total metal alkoxide) dropwise to the solution obtained in Step 1 at a rate of 1.8 mL / min. After the addition is complete, continue stirring at 380 r / min for 3 h to obtain a uniform and transparent metal alkoxide complex solution.

[0089] Step 3: Under nitrogen protection, heat the solution obtained in Step 2 to 65 °C, and add a mixed solution of deionized water and n-propanol at a rate of 0.9 mL / min (molar ratio of deionized water to total metal elements is 1.0:1, and mass ratio of n-propanol to deionized water is 4:1). After the addition is complete, reflux at 65 °C for 2 h, and then distill at 90 °C under normal pressure to remove 28% of the original solution volume of solvent, to obtain the metal alkoxide copolymer.

[0090] Step 4: Add urea-formaldehyde resin (total metal element moles to resin mass ratio of 1 mol: 20 g) to the metal alkoxide copolymer obtained in Step 3, heat to 85 °C for 1.5 h under nitrogen protection, and cool naturally to room temperature to obtain the high-entropy carbide ceramic polymer precursor.

[0091] Step 5: Take 30.0 g of the precursor obtained in Step 4, add 11.0 g of polyvinyl butyral, 4.5 g of polyvinylpyrrolidone and 260 g of anhydrous ethanol, stir at 480 r / min at room temperature for 7 h, let stand to degas for 2 h, and obtain the spinning precursor solution.

[0092] Step 6: Inject the precursor solution obtained in Step 5 into a 0.6 mm inner diameter spinneret at a rate of 22 mL / h. Connect the spinneret to a positive high voltage of 23 kV. Connect the vertically installed 1.2 mm diameter stainless steel receiving needle to a negative high voltage of -3.5 kV. Control the receiving needle rotation speed at 2200 r / min. The vertical distance between the spinneret and the receiving needle is 18 cm. The ambient temperature is 25±2 °C and the relative humidity is <45%. Perform electrospinning for 14 min to obtain a tightly twisted spiral precursor fiber wound on the receiving needle.

[0093] Step 7: Place the fiber-receiving needle obtained in Step 6 into a tube furnace, purge with high-purity argon gas at 650 sccm for 30 min, adjust to 130 sccm, heat to 620 °C at 0.8 °C / min and hold for 2 h, then allow to cool naturally to room temperature to complete the glue removal process.

[0094] Step 8: Remove the spiral fiber from the receiving needle after debinding in Step 7, place it in a graphite crucible, and put it into an atmosphere sintering furnace. High-purity argon gas is introduced at 300 sccm, and the temperature is increased to 1380 °C at 5 °C / min and held for 0.5 h. Then, the temperature is increased to 1730 °C at 5 °C / min and held for 2 h. The furnace is then cooled to room temperature to obtain (Zr... 0.22 Ti 0.18 Ta 0.2 Cr 0.22 Yb 0.18 C-helical winding structure high-entropy carbide ceramic nanofibers. Example 10

[0095] Step 1: Weigh zirconium n-propoxide, titanium isopropoxide, tantalum ethoxide, chromium isopropoxide, and molybdenum ethoxide in a molar ratio of Zr:Ti:Ta:Cr:Mo = 0.28:0.18:0.18:0.18:0.18. Dissolve them in a mixed solvent of n-propanol and acetone in a volume ratio of 2:1, with a solid content of 22 wt%. Stir at 280 r / min for 55 min until completely dissolved.

[0096] Step 2: Add acetylacetone (molar ratio of acetylacetone to total metal alkoxide of 1.7:1) dropwise to the solution obtained in Step 1 at a rate of 2.8 mL / min. After the addition is complete, continue stirring at 280 r / min for 2 h to obtain a uniform and transparent metal alkoxide complex solution.

[0097] Step 3: Under argon protection, heat the solution obtained in Step 2 to 85 °C, and add a mixed solution of deionized water and n-propanol dropwise at a rate of 1.3 mL / min (molar ratio of deionized water to total metal elements is 1.7:1, and mass ratio of n-propanol to deionized water is 2:1). After the addition is complete, reflux at 85 °C for 1 h, and then remove 50% of the original solution volume of solvent by distillation at 85 °C under normal pressure to obtain the metal alkoxide copolymer.

[0098] Step 4: Add allyl-functionalized phenolic resin (total metal element moles to resin mass ratio of 1 mol: 50 g) to the metal alkoxide copolymer obtained in Step 3, heat to 110 °C for 0.5 h under argon protection, and allow to cool naturally to room temperature to obtain a high-entropy carbide ceramic polymer precursor.

[0099] Step 5: Take 30.0 g of the precursor obtained in Step 4, add 16.0 g of polyacrylate, 7.0 g of polyethylene oxide and 320 g of anhydrous dimethylformamide, stir at 200 r / min at room temperature for 15 h, and let stand to degas for 1 h to obtain the spinning precursor solution.

[0100] Step 6: Inject the precursor solution obtained in Step 5 into a 0.9 mm inner diameter spinneret at a rate of 40 mL / h. Connect the spinneret to a positive high voltage of 30 kV. Connect the vertically installed 3.0 mm diameter stainless steel receiving needle to a negative high voltage of -5.5 kV. Control the receiving needle rotation speed at 1200 r / min. The vertical distance between the spinneret and the receiving needle is 35 cm. The ambient temperature is 30±2 °C and the relative humidity is <50%. Perform electrospinning for 6 min to obtain precursor spiral fibers wound on the receiving needle.

[0101] Step 7: Place the fiber-receiving needle obtained in Step 6 into a tube furnace, purge with high-purity nitrogen at 1000 sccm for 15 min, adjust to 300 sccm, heat to 900 °C at 1.2 °C / min and hold for 1 h, then allow to cool naturally to room temperature to complete the glue removal process.

[0102] Step 8: Remove the spiral fiber from the receiving needle after debinding in Step 7, place it in a graphite crucible, and put it into a vacuum sintering furnace to a vacuum level of 10. -3 Pa was heated to 1600 °C at a rate of 2 °C / min and held for 0.5 h, then heated to 1650 °C at a rate of 2 °C / min and held for 3.5 h. The mixture was then cooled to room temperature in the furnace to obtain (Zr). 0.28 Ti 0.18 Ta 0.18 Cr 0.18 Mo 0.18 C-helical winding structure high-entropy carbide ceramic nanofibers.

[0103] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing helical interwoven high-entropy ceramic nanofibers, characterized in that, Includes the following steps: (1) Dissolve the high-entropy transition metal alkoxide precursor in an anhydrous organic solvent and stir until completely dissolved; the high-entropy transition metal alkoxide precursor contains at least four or five alkoxides corresponding to metal elements selected from zirconium, titanium, tantalum, chromium, manganese, lanthanum, cobalt, nickel, ytterbium, hafnium, vanadium, niobium, molybdenum or tungsten, wherein the molar ratio of each metal element is 0.15~0.35:0.15~0.35:0.15~0.35:0.15~0.35 (when there are four elements) or 0.10~0.30:0.10~0.30:0.10~0.30:0.10~0.30:0.10~0.30 (when there are five elements), and the sum of the molar ratios of each element is 1; (2) Slowly add the complexing agent to the solution obtained in step (1). The molar ratio of the complexing agent to the total metal alkoxide is 1.2:1 to 1.5:

1. After the addition is complete, continue stirring to react and obtain a uniform and transparent metal alkoxide complex solution. (3) Under an inert atmosphere, the solution obtained in step (2) is heated to a certain temperature, and a mixture of deionized water and anhydrous organic solvent is slowly added dropwise. The molar ratio of deionized water to total metal elements is 1.1:1~1.5:1, and the mass ratio of anhydrous organic solvent to deionized water is 5:1~10:

1. After the addition is complete, the reaction is refluxed, and part of the solvent is removed by atmospheric distillation to obtain metal alkoxide copolymer. (4) The metal alkoxide copolymer obtained in step (3) is mixed with the carbonizable organic polymer in a certain proportion, heated and reacted under an inert atmosphere, and cooled to room temperature to obtain a high-entropy carbide ceramic polymer precursor. (5) The precursor obtained in step (4) is mixed with binder, spinning aid and organic solvent in proportion, mechanically stirred at room temperature, and allowed to stand to degas, so as to obtain a uniform, transparent and viscous spinning precursor solution. (6) Inject the precursor solution obtained in step (5) into a syringe, fix it on a micro-injection pump, use a stainless steel flat needle as a spinneret, use a vertically installed metal receiving needle as a collecting device, apply a high voltage electric field to perform electrospinning, the fiber is stretched and wound on the rotating receiving needle under the action of the electric field force, and the spiral diameter and winding density of the fiber are controlled by adjusting the rotation speed and receiving distance of the receiving needle to obtain the precursor spiral wound structure fiber; (7) Place the fiber-bearing receiving needle obtained in step (6) in a tube furnace and perform a debinding heat treatment under an inert atmosphere to allow the organic components to be pyrolyzed and discharged. (8) Place the degummed spiral fibers obtained in step (7) into a graphite crucible, put it into a high-temperature sintering furnace, and perform high-temperature carbonization heat treatment under vacuum or inert atmosphere protection to obtain high-entropy carbide spiral wound ceramic nanofibers.

2. The method according to claim 1, characterized in that, The high-entropy transition metal alkoxide precursor in step (1) is a combination of alkoxides corresponding to at least four or five metal elements. The metal elements are selected from any four or five of zirconium, titanium, tantalum, chromium, manganese, lanthanum, cobalt, nickel, ytterbium, hafnium, vanadium, niobium, molybdenum, or tungsten, and the metal elements include at least one rare earth metal element or at least one of chromium, manganese, cobalt, or nickel. The alkoxide is selected from any one or more combinations of zirconium isopropoxide, zirconium isopropoxide, zirconium butoxide, titanium isopropoxide, titanium butoxide, tantalum ethoxide, tantalum isopropoxide, chromium isopropoxide, chromium isopropoxide, manganese isopropoxide, lanthanum ethoxide, cobalt isopropoxide, nickel ethoxide, ytterbium isopropoxide, hafnium ethoxide, vanadium isopropoxide, niobium ethoxide, molybdenum ethoxide, or tungsten ethoxide. When the metal element is titanium, zirconium, or hafnium, its isopropoxide or n-propoxide salt is preferred; when the metal element is tantalum or niobium, ... The preferred metal is its ethanolate; when the metal element is chromium, manganese, cobalt, or nickel, its isopropoxide or ethanolate is preferred; when the metal element is lanthanum or ytterbium, its isopropoxide is preferred; the molar ratio of each metal element in the four-element combination is 0.10~0.40:0.10~0.40:0.10~0.40; the molar ratio of each metal element in the five-element combination is 0.08~0.32:0.08~0.32:0.08~0.32:0.08~0.32:0.08~0.32; and the sum of the molar ratios of each element is 1; the anhydrous organic solvent is selected from any one of n-propanol, isopropanol, n-butanol, ethanol, methanol, isobutanol, ethylene glycol methyl ether, or ethylene glycol ethyl ether; the solid content of the high-entropy transition metal alkoxide precursor in the organic solvent is 5~35 wt%.

3. The method according to claim 1, characterized in that, The metal element combination of the high-entropy transition metal alkoxide precursor mentioned in step (1) is any one of the following quaternary combinations: Zr-Ti-Ta-Cr, Zr-Ti-Ta-Mn, Zr-Ti-Ta-La, Zr-Ti-Cr-Mn, Zr-Ta-Cr-Mn, Ti-Ta-Cr-Mn, Zr-Ti-Ta-Co, Zr-Ti-Ta-Ni, Zr-Ti-Ta-Yb, Zr-Ti-Cr-Co, Zr-Ti-Cr-Ni, Hf-Ti-Ta-Cr, Zr-Hf-Ta-Cr, Zr-Ti- Nb-Cr, Zr-Ti-Ta-V, Zr-Ti-Ta-Mo or Zr-Ti-Ta-W; or any of the following five-component combinations: Zr-Ti-Ta-Cr-Mn, Zr-Ti-Ta-Cr-La, Zr-Ti-Ta-Cr-Co, Zr-T i-Ta-Cr-Ni, Zr-Ti-Ta-Cr-Yb, Zr-Ti-Ta-Mn-Co, Zr-Ti-Cr-Mn-Co, Hf-Ti-Ta-Cr-Mn, Zr-Ti-Nb-Ta-Cr or Zr-Ti-Ta-Cr-V.

4. The method according to claim 1, characterized in that, The complexing agent mentioned in step (2) is selected from any one or more combinations of benzoyl acetone, dibenzoylmethane, triethanolamine or ethylene glycol; the molar ratio of the complexing agent to the total metal alkoxide is 1.0:1 to 2.0:1; the dropping rate is 0.5 to 3 mL / min; after the dropping is completed, continue stirring at 15 to 45 °C for 1 to 6 h.

5. The method according to claim 1, characterized in that, The inert atmosphere mentioned in step (3) is selected from any one of nitrogen, argon or helium; the heating temperature is 40~90 °C; in the mixed solution of deionized water and anhydrous organic solvent, the molar ratio of deionized water to total metal elements is 0.6:1~1.8:1, the mass ratio of anhydrous organic solvent to deionized water is 2:1~12:1, the dropping rate is 0.2~1.5 mL / min; the reflux reaction time after dropping is 0.5~4 h; the amount of solvent removed by atmospheric distillation is 15%~50% of the original solution volume.

6. The method according to claim 1, characterized in that, The carbonizable organic polymer mentioned in step (4) is selected from any one of allyl-functionalized phenolic resin, phenolic resin, furfuryl alcohol resin, urea-formaldehyde resin or polycarbosilane; the mass ratio of the total number of moles of metal elements in the metal alkoxide copolymer to the carbonizable organic polymer is 1 mol: 5~50 g; the reaction temperature is 50~110 °C and the reaction time is 0.5~5 h; the carbonizable organic polymer and the metal alkoxide copolymer are mixed by mechanical stirring or ultrasonic dispersion.

7. The method according to claim 1, characterized in that, The binder in step (5) is selected from any one of polyvinyl butyral, polyacrylate, or polyvinyl acetate; the spinning aid is selected from any one of polyvinylpyrrolidone, polyethylene oxide, or polyacrylonitrile; the organic solvent is selected from any one of n-propanol, isopropanol, ethanol, acetone, or dimethylformamide; the mass ratio of the precursor to the binder, spinning aid, and organic solvent is 30:5~18:3~8:150~350; the mechanical stirring time is 3~15 h, the stirring rate is 150~600 r / min; and the standing degassing time is 1~6 h.

8. The method according to claim 1, characterized in that, In step (6), the inner diameter of the spinneret is 0.2~1.0mm, and the spinneret is connected to a positive high voltage of 10~30 kV; the receiving needle is a vertically installed metal needle with a diameter of 0.3~3.0mm, and the receiving needle is connected to a negative high voltage of -6~-1 kV; the receiving needle is driven to rotate by a stepper motor with a rotation speed of 300~3500 r / min; the vertical distance between the spinneret and the receiving needle is 8~50 cm; the feeding speed is 5~40 mL / h; the ambient temperature is 20~30 °C, and the ambient relative humidity is below 60%.

9. The method according to claim 1, characterized in that, In step (6), a loose spiral structure fiber is obtained when the receiving needle rotates at 300~1200 r / min, and a tightly twisted spiral structure fiber is obtained when the receiving needle rotates at 1800~3500 r / min; the shorter the receiving distance, the smaller the spiral diameter and pitch.

10. The method according to claim 1, characterized in that, The inert atmosphere mentioned in step (7) is selected from either nitrogen or argon, with a gas flow rate of 300~1200 sccm and a purging time of 15~60 min; during the heat treatment of glue removal, the gas flow rate is adjusted to 50~300 sccm, and the temperature is raised from room temperature to 400~900 °C at a heating rate of 0.3~3 °C / min, held for 1~4 h, and then naturally cooled to room temperature.

11. The method according to claim 1, characterized in that, The high-temperature sintering furnace mentioned in step (8) is a vacuum sintering furnace or an atmosphere sintering furnace; the vacuum degree is 10. -5 ~10 -1 Pa; the inert atmosphere is selected from either argon or helium, and the gas flow rate is 50~500 sccm; the high-temperature carbonization heat treatment is a staged heating: the temperature is raised to 1200~1600 °C at a heating rate of 2~15 °C / min and held for 0.5~2 h; then the temperature is raised to 1500~1900 °C at a heating rate of 2~15 °C / min and held for 1~4 h; then the furnace is cooled to room temperature.

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