A method for preparing template-free flexible silica nanofiber yarns using airflow assistance

Abstract

This invention discloses a method for preparing template-free flexible silica nanofiber yarns using airflow-assisted spinning, comprising the following steps: S1, preparing a linear silica sol spinning solution; S2, using an airflow-assisted conjugate electrospinning process to prepare flexible silica nanofiber yarns from the linear silica spinning sol; S3, placing the flexible silica nanofiber yarns in a muffle furnace under air atmosphere for high-temperature calcination to obtain continuous flexible silica nanofiber yarns. This invention utilizes the above-mentioned airflow-assisted method for preparing template-free flexible silica nanofiber yarns, and through airflow-assisted conjugate electrospinning, achieves large-scale preparation of silica nanofiber yarns, and the prepared silica nanofiber yarns exhibit excellent high-temperature resistance and flexibility.

Description

Technical Field

[0001] This invention relates to the field of silica nanofiber yarn preparation, and more particularly to a method for preparing template-free flexible silica nanofiber yarn with airflow assistance. Background Technology

[0002] Silica nanofibers, as an emerging ceramic material, combine the excellent properties of silica ceramics, such as high melting point, high temperature resistance, lightweight, and wear resistance, with the characteristics of nanofibers, such as small size effect, large aspect ratio, high porosity, and large specific surface area. They are widely used in new energy, aerospace, electronic information, and extreme environment fields.

[0003] Currently, methods for preparing silica nanofibers include electrospinning, melt spinning, centrifugal spinning, impregnation, and sol-gel methods. Among these, silica nanofibers prepared by electrospinning can have a larger aspect ratio and can further refine the fiber diameter, thereby improving the flexibility of silica nanofibers.

[0004] Silica nanofiber yarn is a product of secondary processing of nanofibers. By combining the high temperature resistance, lightweight, wear resistance and fire resistance of silica materials, higher value-added textile materials are prepared, thus making the application of silica nanofibers more extensive, especially easier to integrate into the textile market.

[0005] Currently, conjugate electrospinning is a novel process for preparing nanofiber yarns and a novel spinning form within electrospinning technology. The conjugate electrospinning process is simple and stable, and can form continuous nanofiber yarns with uniform twist. It involves two devices with electrodes placed opposite each other, and the nozzles of the two devices have high voltages of opposite polarities. Under the influence of an electric field, a silica spinning solution is ejected from the spinneret onto a collector to form silica nanofibers. At this point, the two bundles of nanofibers carrying different charges attract, collide, and bind together to form a continuous nanofiber bundle. Under the winding action of a traction and twisting device, a highly oriented, continuous, flexible silica nanofiber yarn is finally obtained.

[0006] However, the key to preparing silica nanofibers by electrospinning is the need to obtain a spinnable inorganic silica precursor using a long-chain organic polymer template. Then, under the influence of an electric field, continuous silica hybrid nanofibers are prepared, followed by high-temperature calcination to remove the organic polymer template and obtain pure silica nanofibers. During this process, the thermal decomposition of the organic polymer template introduces numerous porosity defects within the nanofibers, ultimately negatively impacting their mechanical properties and potentially preventing the formation of continuous, flexible silica nanofiber yarns.

[0007] In recent years, there have been reports on the preparation of silica nanofibers using template-free polymer-assisted methods. For example, CN202011435280.0 discloses a one-step template-free method for preparing fluffy and flexible three-dimensional silica nanofibers. However, there has never been a report on the preparation of flexible silica nanofiber yarns using polymer template-free methods.

[0008] Furthermore, in the process of conjugated electrospinning, the spinning precursor solution needs to be injected dropwise to form individual fibers, and then twisted to form a yarn. The injection speed, twisting speed and yarn collection speed need to be matched, which makes it impossible to generate a large number of nanofiber yarns in a short time, limiting the growth of output and resulting in low production efficiency. Summary of the Invention

[0009] To address the aforementioned problems, this invention provides a method for preparing template-free flexible silica nanofiber yarns using airflow-assisted processes. The flexible silica nanofiber yarns prepared using a reliable, continuous filament production process without polymer templates and with airflow assistance exhibit excellent high-temperature resistance and flexibility.

[0010] To achieve the above objectives, the present invention provides a method for preparing template-free flexible silica nanofiber yarns with airflow assistance, comprising the following steps:

[0011] S1. Preparation of linear silica sol spinning solution:

[0012] Weigh out a certain amount of tetraethyl orthosilicate and ethanol, put them into water and stir continuously. Then add dilute hydrochloric acid catalyst and stir again to adjust the hydrolysis and polycondensation conditions of silica precursor to obtain linear silica sol spinning solution.

[0013] S2. Flexible silica nanofiber yarns are prepared from linear silica spinning sol using an airflow-assisted conjugate electrospinning process.

[0014] S3. The flexible silica nanofiber yarn is placed in a muffle furnace with an air atmosphere and calcined at high temperature to obtain a continuous flexible silica nanofiber yarn.

[0015] Preferably, in step S1, the molar ratio of tetraethyl orthosilicate: ethanol: water: hydrochloric acid is 1:1 to 3:1 to 3:0.005 to 0.01.

[0016] Preferably, the hydrolysis process in step S1 is as follows: stirring at 300-800 r / min for 6-72 h at room temperature.

[0017] Preferably, the polycondensation process described in step S1 is as follows: polycondensation is carried out in a vacuum oven at a temperature of 40 to 150°C and a pressure of 5 to 80 kPa until the sol viscosity is 50 to 350 mPa·s.

[0018] Preferably, the linear silica sol spinning solution prepared in step S1 has a degree of polymerization greater than 3000 and a degree of branching ≤ 0.2.

[0019] Preferably, in step S2, an airflow nozzle is installed over the electrospinning nozzle, with an airflow-assisted air pressure of 50-500 kPa and an air hole size of 16-26 G.

[0020] Preferably, the electrospinning nozzle size in step S2 is 18-28G, the liquid supply rate is 0.1-10ml / h, the metal funnel rotation speed is 50-300r / min, and the winding speed is 0.5-5r / min;

[0021] The spinning voltage of the conjugate spinning nozzle is 5–30 kV, and the spinning angle is 15°–75°.

[0022] The spinning voltage of the conjugate spinning negative nozzle is 5–30 kV, and the spinning angle is 15°–75°.

[0023] The spinning temperature is room temperature and the humidity is 20-60%. The linear silica sol spinning solution is extruded from an airflow-assisted electrostatic spinning nozzle. The silica precursor forms flexible silica nanofiber yarn under the combined action of airflow and electric field.

[0024] Preferably, the calcination process in step S3 is as follows: the flexible silica nanofiber yarn is heated from room temperature to 250-400°C at a rate of 5°C / min, and then kept at that temperature for 60-120min.

[0025] The present invention has the following beneficial effects:

[0026] 1. Using tetraethyl orthosilicate as the silicon source, ethanol as the solvent, water as the hydrolysis reactant and hydrochloric acid as the catalyst, an electrospinning gel solution was prepared. Flexible silica nanofiber yarns were prepared using airflow-assisted conjugate electrospinning technology, which can replace the hybrid silica nanofibers currently prepared using polymer templates. This can effectively avoid the phenomenon of reduced mechanical properties caused by pore defects due to polymer decomposition during high-temperature calcination.

[0027] 2. Large-scale preparation of silica nanofiber yarns was achieved by using airflow-assisted conjugate electrospinning.

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0029] Figure 1 This is a flowchart of the method for preparing template-free flexible silica nanofiber yarn with airflow assistance according to the present invention;

[0030] Figure 2 SEM image of flexible silica nanofiber yarn prepared by the airflow-assisted preparation method of template-free flexible silica nanofiber yarn described in this invention. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages disclosed in the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are merely illustrative of the embodiments of the present invention and are not intended to limit the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments in this application without creative effort are within the scope of protection of this application. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout.

[0032] It should be noted that the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product, or server that includes a series of steps or units is not necessarily limited to those steps or units that are explicitly listed, but may include other steps or units that are not explicitly listed or that are inherent to such process, method, product, or device.

[0033] Similar labels and letters in the following figures indicate similar items; therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0034] like Figure 1 and Figure 2 As shown, the method for preparing template-free flexible silica nanofiber yarn with airflow assistance includes the following steps:

[0035] S1. Preparation of linear silica sol spinning solution:

[0036] Weigh out a certain amount of tetraethyl orthosilicate and ethanol, put them into water and stir continuously. Then add dilute hydrochloric acid catalyst and stir again to adjust the hydrolysis and polycondensation conditions of silica precursor, and obtain a clear and transparent linear silica sol spinning solution with high degree of polymerization and low degree of branching.

[0037] The hydrolysis-condensation reaction mechanism using tetraethyl orthosilicate as the silicon source, ethanol as the solvent, water as the hydrolysis reactant, and hydrochloric acid as the catalyst is as follows:

[0038] The hydrolysis reaction produces hydroxyl compounds and ethanol, with the final hydroxyl compound being silicic acid. Since the hydrolysis and condensation processes are dynamic, the condensation reaction is a condensation polymerization reaction between hydroxyl compounds to form a sol mixture.

[0039] The process of hydrolysis reaction:

[0040]

[0041] The process of polycondensation reaction:

[0042]

[0043] After hydrolysis and condensation reactions occur, colloidal particles appear in the reaction system, and they gradually grow larger as the reaction proceeds. The gelation process is a spatial framework structure formed by sol particles linked together by van der Waals forces, hydrogen bonds, or chemical bonds.

[0044] Preferably, in step S1, the molar ratio of tetraethyl orthosilicate:ethanol:water:hydrochloric acid is 1:1-3:1-3:0.005-0.01. The hydrolysis process in step S1 is as follows: stirring at 300-800 r / min for 6-72 h at room temperature. The polycondensation process in step S1 is as follows: polycondensation is carried out in a vacuum oven at a temperature of 40-150℃ and a pressure of 5-80 kPa until the sol viscosity reaches 50-350 mPa·s. The linear silica sol spinning solution prepared in step S1 has a degree of polymerization greater than 3000 and a degree of branching ≤0.2.

[0045] S2. Flexible silica nanofiber yarns are prepared from linear silica spinning sol using an airflow-assisted conjugate electrospinning process.

[0046] Preferably, in step S2, an airflow nozzle is fitted over the electrospinning nozzle, with an airflow-assisted pressure of 50–500 kPa and an orifice size of 16–26 G. The electrospinning nozzle in step S2 has a size of 18–28 G, a liquid supply rate of 0.1–10 ml / h, a metal funnel rotation speed of 50–300 r / min, and a winding speed of 0.5–5 r / min. The spinning voltage of the conjugate spinning positive nozzle is 5–30 kV, and the spinning angle is 15°–75°. The spinning voltage of the conjugate spinning negative nozzle is 5–30 kV, and the spinning angle is 15°–75°. The spinning temperature is room temperature, and the humidity is 20–60%. The linear silica sol spinning solution is extruded from the airflow-assisted electrospinning nozzle, and the silica precursor forms flexible silica nanofiber yarns under the combined action of airflow and electric field.

[0047] Under the synergistic effect of an electric field and airflow, the charged sol spinning solution is ejected from the electrospinning nozzle, forming a fine jet. After stretching, solvent evaporation, and solidification, it forms silica nanofibers, which are then deposited on a metal funnel and twisted into yarn. In other words, yarn materials can be rapidly prepared by adding an additional airflow-assisted nozzle.

[0048] S3. The flexible silica nanofiber yarn is placed in a muffle furnace with an air atmosphere and calcined at high temperature to obtain a continuous flexible silica nanofiber yarn.

[0049] Preferably, the calcination process in step S3 is as follows: the flexible silica nanofiber yarn is heated from room temperature to 250-400°C at a rate of 5°C / min, and then kept at that temperature for 60-120min.

[0050] To further illustrate this invention, the following embodiments, comparative examples, and test examples are disclosed:

[0051] The method for preparing template-free flexible silica nanofiber yarn with airflow assistance as described in Example 1 includes the following steps:

[0052] Step 1: Preparation of linear silica sol spinning solution: First, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid are mixed in a molar ratio of 1:1:1:0.005; then, hydrolysis is carried out at room temperature with a stirring speed of 500 r / min for 48 h; finally, the spinning solution is placed in a vacuum oven at 100℃ and 70 kPa to condense until the sol viscosity reaches 200 mPa·s.

[0053] Step 2: Preparation of flexible silica nanofiber yarn: First, based on conjugate electrospinning technology, the following parameters were set: air pressure was set to 200 kPa, pore size was 18 G; electrospinning nozzle size was 20 G, liquid supply rate was 5 ml / h, metal funnel rotation speed was 100 r / min, and winding speed was 1 r / min; the spinning voltage of the conjugate spinning positive nozzle was 20 kV and the spinning angle was 45°; the spinning voltage of the conjugate spinning negative nozzle was 20 kV and the spinning angle was 45°; the spinning temperature was room temperature and the humidity was 30%.

[0054] The linear silica sol spinning solution is then extruded from the nozzle of an airflow-assisted electrospinning nozzle, and the silica precursor forms flexible silica nanofiber yarns under the combined action of airflow and electric field.

[0055] The method for preparing template-free flexible silica nanofiber yarn with airflow assistance as described in Example 2 includes the following steps:

[0056] Step 1: Preparation of linear silica sol spinning solution: First, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid are mixed in a molar ratio of 1:3:1:0.005; then, hydrolysis is carried out at room temperature with a stirring speed of 500 r / min for 48 h; finally, the spinning solution is placed in a vacuum oven at 90℃ and 60 kPa to condense until the sol viscosity reaches 180 mPa·s.

[0057] Step 2: Preparation of flexible silica nanofiber yarn: First, based on conjugate electrospinning technology, the following parameters were set: air pressure was set to 200 kPa, pore size was 18 G; electrospinning nozzle size was 20 G, liquid supply rate was 4 ml / h; metal funnel rotation speed was 150 r / min, winding speed was 1 r / min; the spinning voltage of the conjugate spinning positive nozzle was 20 kV, and the spinning angle was 45°; the spinning voltage of the conjugate spinning negative nozzle was 20 kV, and the spinning angle was 45°; the spinning temperature was room temperature, and the humidity was 40%.

[0058] The linear silica sol spinning solution is then extruded from the nozzle of an airflow-assisted electrospinning nozzle, and the silica precursor forms flexible silica nanofiber yarns under the combined action of airflow and electric field.

[0059] The method for preparing template-free flexible silica nanofiber yarn with airflow assistance as described in Example 3 includes the following steps:

[0060] Step 1: Preparation of linear silica sol spinning solution: First, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid are mixed in a molar ratio of 1:3:3:0.005; then, hydrolysis is carried out at room temperature with a stirring speed of 500 r / min for 48 h; finally, the spinning solution is placed in a vacuum oven at 50℃ and 10 kPa to condense until the sol viscosity reaches 200 mPa·s.

[0061] Step 2: Preparation of flexible silica nanofiber yarn: First, based on conjugate electrospinning technology, the following parameters were set: air pressure was set to 400 kPa, pore size was 20 G; electrospinning nozzle size was 22 G, liquid supply rate was 3 ml / h; metal funnel rotation speed was 200 r / min, winding speed was 2 r / min; the spinning voltage of the conjugate spinning positive nozzle was 20 kV, and the spinning angle was 45°; the spinning voltage of the conjugate spinning negative nozzle was 20 kV, and the spinning angle was 45°; the spinning temperature was room temperature, and the humidity was 30%.

[0062] The linear silica sol spinning solution is then extruded from the nozzle of an airflow-assisted electrospinning nozzle, and the silica precursor forms flexible silica nanofiber yarns under the combined action of airflow and electric field.

[0063] The method for preparing template-free flexible silica nanofiber yarn with airflow assistance as described in Example 4 includes the following steps:

[0064] Step 1: Preparation of linear silica sol spinning solution: First, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid are mixed in a molar ratio of 1:1:3:0.005; then, hydrolysis is carried out at room temperature with a stirring speed of 500 r / min for 48 h; finally, the spinning solution is placed in a vacuum oven at 70℃ and 70 kPa to condense until the sol viscosity reaches 150 mPa·s.

[0065] Step 1: Preparation of linear silica sol spinning solution: Gas pressure set at 200 kPa, pore size at 18 G; electrospinning nozzle size at 20 G, liquid supply rate at 3 ml / h; metal funnel rotation speed at 200 r / min, winding speed at 3 r / min; spinning voltage of conjugate spinning positive nozzle at 20 kV, spinning angle at 45°; spinning voltage of conjugate spinning negative nozzle at 20 kV, spinning angle at 45°; spinning temperature at room temperature, humidity at 30%.

[0066] The linear silica sol spinning solution is then extruded from the nozzle of an airflow-assisted electrospinning nozzle, and the silica precursor forms silica nanofiber yarn under the combined action of airflow and electric field.

[0067] The method for preparing template-free flexible silica nanofiber yarn with airflow assistance as described in Example 5 includes the following steps:

[0068] Step 1: Preparation of linear silica sol spinning solution: First, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid are mixed in a molar ratio of 1:1:1:0.01; then, hydrolysis is carried out at room temperature with a stirring speed of 500 r / min for 48 h; finally, the spinning solution is placed in a vacuum oven at 40℃ and 20 kPa to condense until the sol viscosity reaches 300 mPa·s.

[0069] Step 2: Preparation of flexible silica nanofiber yarn: First, based on conjugate electrospinning technology, the following parameters were set: air pressure was set to 200 kPa, pore size was 18 G; electrospinning nozzle size was 20 G, liquid supply rate was 2 ml / h; metal funnel rotation speed was 50 r / min, winding speed was 0.5 r / min; the spinning voltage of the conjugate spinning positive nozzle was 20 kV, and the spinning angle was 45°; the spinning voltage of the conjugate spinning negative nozzle was 20 kV, and the spinning angle was 45°; the spinning temperature was room temperature, and the humidity was 30%.

[0070] The linear silica sol spinning solution is then extruded from the nozzle of an airflow-assisted electrospinning nozzle, and the silica precursor forms silica nanofiber yarn under the combined action of airflow and electric field.

[0071] The method for preparing template-free flexible silica nanofiber yarn with airflow assistance as described in Example 6 includes the following steps:

[0072] Step 1: Preparation of linear silica sol spinning solution: First, tetraethyl orthosilicate, ethanol, water, and hydrochloric acid are mixed in a molar ratio of 1:3:3:0.01; then, hydrolysis is carried out at room temperature with a stirring speed of 500 r / min for 48 h; finally, the spinning solution is placed in a vacuum oven at 90℃ and 90 kPa to condense until the sol viscosity reaches 250 mPa·s.

[0073] Step 2: Preparation of flexible silica nanofiber yarn: First, based on conjugate electrospinning technology, the following parameters were set: air pressure was set to 200 kPa, pore size was 18 G; electrospinning nozzle size was 20 G, liquid supply rate was 8 ml / h; metal funnel rotation speed was 200 r / min, winding speed was 3 r / min; the spinning voltage of the conjugate spinning positive nozzle was 20 kV, and the spinning angle was 45°; the spinning voltage of the conjugate spinning negative nozzle was 20 kV, and the spinning angle was 45°; the spinning temperature was room temperature, and the humidity was 30%.

[0074] The linear silica sol spinning solution is then extruded from the nozzle of an airflow-assisted electrospinning nozzle, and the silica precursor forms silica nanofiber yarn under the combined action of airflow and electric field.

[0075] Comparative Example 1

[0076] The preparation method of Comparative Example 1 is the same as that of Example 1, except that the preparation method of the sol-spinning solution in Comparative Example 1 is as follows:

[0077] Tetraethyl orthosilicate was selected as the silicon source, water as the solvent, and hydrochloric acid as the catalyst. The materials were added to the reaction flask in sequence, then sealed and stirred rapidly at room temperature for 8 hours to generate oligomers, which were further polycondensed to form a uniform silica sol spinning solution A. The mass ratio of tetraethyl orthosilicate:water:hydrochloric acid was 1:1:0.01.

[0078] Choose to prepare a 10wt% polyethylene oxide aqueous solution (B). (Taking a 100g polyethylene oxide solution as an example: Weigh 90g of deionized water and add it to a ground glass bottle, then slowly add 10g of polyethylene oxide. After sealing the bottle, heat in a water bath at 80℃ and stir for 4-6 hours to complete the preparation.)

[0079] Mix solutions A and B in a 1:1 ratio and stir for 4-6 hours to prepare the sol-spinning solution.

[0080] Comparative Example 2

[0081] The preparation method of Comparative Example 2 is the same as that of Example 1, except that airflow-assisted conjugate electrospinning is not used in Comparative Example 2 to prepare template-free flexible silica nanofiber yarn.

[0082] Test case

[0083] First, it should be noted that in the test examples, the yield of silica nanofiber yarn is based on the yarn length produced per minute. The method used for testing the breaking strength of silica nanofiber yarn is GB / T 1040.5-2008.

[0084] The results are shown in Table 1.

[0085] Table 1 shows the performance test results of the silica nanofiber yarns obtained in Examples 1-6 and Comparative Examples 1-2.

[0086]

[0087]

[0088] The above data fully demonstrates that the yield of flexible silica nanofiber yarn produced by airflow-assisted fabrication is higher, and the flexible silica nanofiber yarn without the addition of polymer templates has stronger mechanical properties.

[0089] Therefore, the present invention employs the above-mentioned airflow-assisted method for preparing template-free flexible silica nanofiber yarns. This method, which avoids introducing heteroatoms, uses a polymer template-free approach to prepare a continuous long-chain spinnable silica precursor, which can be directly used for conjugated electrospinning to obtain nanofiber yarn materials. This avoids the negative impact of organic matter removal on the fiber yarn structure during high-temperature processes, reducing process complexity and production energy consumption. Furthermore, airflow-assisted conjugated electrospinning can generate propulsion force at the spinneret, allowing for a greater solution injection volume per unit time, thereby significantly improving the production efficiency of nanofiber yarns and facilitating large-scale mass production.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for preparing template-free flexible silica nanofiber yarns with airflow assistance, characterized in that: Includes the following steps: S1. Preparation of linear silica sol spinning solution: Weigh out a certain amount of tetraethyl orthosilicate and ethanol, put them into water and stir continuously. Then add dilute hydrochloric acid catalyst and stir again to adjust the hydrolysis and polycondensation conditions of silica precursor to obtain linear silica sol spinning solution. The polycondensation process described in step S1 is as follows: polycondensation is carried out in a vacuum oven at a temperature of 40 to 150°C and a pressure of 5 to 80 kPa until the sol viscosity is 50 to 350 mPa·s. In step S1, the molar ratio of tetraethyl orthosilicate:ethanol:water:hydrochloric acid is 1:1~3:1~3:0.005~0.01; The hydrolysis process described in step S1 is as follows: stirring at 300-800 r / min for 6-72 h at room temperature; The linear silica sol spinning solution prepared in step S1 has a degree of polymerization greater than 3000 and a degree of branching ≤ 0.

2. S2. Flexible silica nanofiber yarns are prepared from linear silica spinning sol using an airflow-assisted conjugate electrospinning process. In step S2, an airflow nozzle is installed over the electrospinning nozzle, with an airflow-assisted air pressure of 50-500 kPa and an air hole size of 16-26 G. The electrospinning nozzle size in step S2 is 18-28G, the liquid supply rate is 0.1-10ml / h, the metal funnel rotation speed is 50-300r / min, and the winding speed is 0.5-5r / min. The spinning voltage of the conjugate spinning nozzle is 5–30 kV, and the spinning angle is 15°–75°. The spinning voltage of the conjugate spinning negative nozzle is 5–30 kV, and the spinning angle is 15°–75°. The spinning temperature is room temperature and the humidity is 20-60%. The linear silica sol spinning solution is extruded from the airflow-assisted electrostatic spinning nozzle. The silica precursor forms flexible silica nanofiber yarn under the combined action of airflow and electric field. S3. The flexible silica nanofiber yarn is placed in a muffle furnace with an air atmosphere and calcined at high temperature to obtain a continuous flexible silica nanofiber yarn.

2. The method for preparing template-free flexible silica nanofiber yarn with airflow assistance according to claim 1, characterized in that: The calcination process described in step S3 is as follows: the flexible silica nanofiber yarn is heated from room temperature to 250-400°C at a rate of 5°C / min, and then kept at that temperature for 60-120 min.

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