Hollow oxide fiber and method for producing the same

Abstract

The application provides a hollow oxide fiber and a preparation method thereof, and belongs to the technical field of heat protection materials.The preparation method comprises the following steps: S1, mixing a metal salt, a dopant, a spinning aid and a solvent to obtain a fiber precursor solution; S2, spinning the fiber precursor solution by using a centrifugal spinning method to obtain a strip-shaped precursor fiber with a U-shaped cross section; and S3, driving the strip-shaped precursor fiber to close by using high temperature to form the hollow oxide fiber.The preparation method of the hollow oxide fiber is simple, efficient, low in cost and free of a template, and the prepared hollow oxide fiber is smooth in surface, small in diameter, low in density, low in thermal conductivity and excellent in heat insulation performance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat protection materials, in particular to a hollow oxide fiber and a preparation method thereof. BACKGROUND

[0002] With the continuous improvement of the flight speed of hypersonic vehicles, the heat protection problem of the vehicles is also more and more complex and important. Ceramic fiber thermal insulation materials are a kind of extremely potential heat protection materials, which are widely used in the field of aerospace high-temperature thermal insulation. In micro-nano ceramic fibers, heat transfer mainly includes gas heat conduction, solid heat conduction and radiation heat transfer. The solid heat transfer of hollow fiber can only be transmitted in the pipe wall, and the hollow structure also restricts the gas molecules inside, so the solid thermal conductivity and gas thermal conductivity are lower. In addition, under high temperature conditions, the hollow fiber has a larger infrared radiation scattering cross section, so the radiation heat transfer is reduced. Therefore, compared with the solid structure fiber, the hollow structure design is beneficial to reduce the thermal conductivity and improve the thermal insulation performance of the fiber material.

[0003] At present, the methods for preparing hollow oxide fibers mainly include template method, coaxial electrospinning method and phase inversion method. The template method has problems such as that the prepared fiber is seriously dependent on the morphology of the template, the inorganic salt loading is low, the impregnation coating uniformity is poor, and the fiber length is limited by the discontinuity of the template. The coaxial electrospinning method has problems such as complex spinning process and difficult to control parameters. The diameter and wall thickness of the hollow fiber prepared by the phase inversion method mainly depend on the inner and outer diameters of the concentric hole spinneret, but the pore size of the concentric hole spinneret is mostly in millimeter level, and it is a challenge to further reduce the size of the hollow fiber by using the concentric hole spinneret in practical application. SUMMARY

[0004] In view of one or more technical problems in the prior art, the present application provides a hollow oxide fiber and a preparation method thereof. The preparation method of the hollow oxide fiber provided by the present application is simple, efficient, low in cost, and does not require a template. The prepared hollow oxide fiber is highly symmetrical, smooth and wrinkle-free in surface, small in diameter, low in density, low in thermal conductivity, and has excellent heat insulation performance.

[0005] In a first aspect, the present application provides a preparation method of a hollow oxide fiber, which comprises:

[0006] S1. mixing a metal salt, a dopant, a spinning aid and a solvent to obtain a fiber precursor solution;

[0007] S2. spinning the fiber precursor solution by centrifugal spinning to obtain a strip-shaped precursor fiber with a U-shaped cross section;

[0008] S3. closing the strip-shaped precursor fiber by high temperature driving to form a hollow oxide fiber.

[0009] Preferably, the amount of the metal salt is not less than 12% of the mass of the fiber precursor solution, preferably 12-12.5%.

[0010] Preferably, the metal salt is one or more of zirconium salt, aluminum salt, barium salt, and tin salt.

[0011] Preferably, the amount of the dopant is not more than 2% of the mass of the fiber precursor solution, preferably 1-1.5%.

[0012] Preferably, the dopant is one or more of yttrium nitrate hexahydrate, cerium nitrate hexahydrate, magnesium chloride dihydrate, and magnesium chloride dihydrate.

[0013] Preferably, the spinning aid accounts for 7.5-13.5% of the mass of the fiber precursor solution, preferably 8.5-12.5%.

[0014] Preferably, the spinning aid is one or more of polyvinylpyrrolidone, polyvinyl alcohol, and polyacrylonitrile.

[0015] Preferably, the solvent is one or more of N,N-dimethylformamide, anhydrous ethanol, and water.

[0016] Preferably, the spinning head aperture of the centrifugal spinning is 0.2-0.5 mm.

[0017] The rotation speed of the centrifugal spinning is 2500-3000 r / min.

[0018] The temperature of the centrifugal spinning is 20-30℃; and / or

[0019] The humidity of the centrifugal spinning is 50-60%.

[0020] Preferably, the high-temperature driving is to raise the temperature to not less than 800℃, preferably 800-1100℃, and keep the temperature for 1-2 h.

[0021] Preferably, the high-temperature driving is performed in an oxygen-containing atmosphere, preferably an air or oxygen atmosphere; and / or

[0022] During the high-temperature driving, when the temperature is lower than 800℃, the temperature raising rate is 0.5-1℃ / min.

[0023] The present application provides, in a second aspect, a hollow oxide fiber prepared by the method of the first aspect.

[0024] Preferably, the diameter of the hollow oxide fiber is 2-8 μm, and the wall thickness is 1-3 μm.

[0025] Preferably, the hollow oxide fiber has a hollow structure distributed on the fiber wall of the hollow oxide fiber along the length direction of the hollow oxide fiber.

[0026] Compared with the prior art, the present application has at least the following beneficial effects:

[0027] The present application first mixes a metal salt, a dopant, a spinning aid and a solvent to obtain a spinnable fiber precursor solution, then performs centrifugal spinning on the fiber precursor solution to obtain a strip-shaped precursor fiber with a U-shaped cross section, and finally uses high temperature to drive the strip-shaped precursor fiber with a U-shaped cross section to automatically bend and close to form a hollow oxide fiber. Compared with the preparation process of the existing hollow oxide fiber, the preparation method of the hollow oxide fiber of the present application is simple and efficient, low in cost, and has improved inorganic salt loading capacity, and does not need a template (a biological template or a metal substrate), but only relies on high temperature to drive the strip-shaped precursor fiber with a U-shaped cross section to automatically bend and close to form a hollow oxide fiber with a hollow structure, thereby overcoming the problem that the preparation of the existing hollow oxide fiber needs to rely on a template and the fiber is discontinuous, and providing a new idea for the preparation of an oxide hollow fiber.

[0028] The hollow oxide fiber of the present application is highly symmetrical, smooth and wrinkle-free in surface, small in diameter, low in density, low in thermal conductivity, and has excellent heatproof and heat insulation performance, and can be used at a temperature above 1400℃. Compared with the traditional solid oxide fiber, the hollow oxide fiber of the present application has significantly reduced gas heat conduction, solid heat conduction and radiation heat transfer in a high temperature environment, and has obviously improved heatproof and heat insulation performance. BRIEF DESCRIPTION OF DRAWINGS

[0029] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0030] Figure 1 is a high-magnification microstructure diagram of the precursor fiber prepared in Example 1 of the present application

[0031] Figure 2 is a low-magnification microstructure diagram of the precursor fiber prepared in Example 1 of the present application

[0032] Figure 3 is a high-magnification microstructure of the hollow zirconia fiber prepared in Example 1 of the present application

[0033] Figure 4 is an X-ray diffraction pattern of the zirconia fiber prepared in Example 1 of the present application

[0034] Figure 5 is a high-magnification micrograph of the hollow zirconia fiber prepared in Example 4 of the present application;

[0035] Figure 6 is a low-magnification microstructure of the precursor fiber prepared in Comparative Example 1 of the present application;

[0036] Figure 7 is a low-magnification microstructure of the precursor fiber prepared in Comparative Example 2 of the present application;

[0037] Figure 8 is a low-magnification microstructure of the precursor fiber prepared in Comparative Example 3 of the present application;

[0038] Figure 9 is a low-magnification microstructure of the precursor fiber prepared in Comparative Example 4 of the present application;

[0039] Figure 10 is a high-magnification micrograph of the hollow zirconia fiber prepared in Comparative Example 6 of the present application. DETAILED DESCRIPTION

[0040] In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the following will clearly and completely describe the technical solutions in the embodiments of the present application with reference to the accompanying drawings; obviously, the described embodiments are some but not all of the embodiments of the present application; based on the embodiments of the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the scope of protection of the present application.

[0041] The present application provides, in a first aspect, a preparation method of a hollow oxide fiber, the preparation method comprising:

[0042] S1. mixing a metal salt, a dopant, a spinning aid and a solvent to obtain a fiber precursor solution;

[0043] S2. spinning the fiber precursor solution by a centrifugal spinning method to obtain a belt-shaped precursor fiber having a U-shaped cross section;

[0044] S3. closing the belt-shaped precursor fiber by high-temperature driving to form a hollow oxide fiber.

[0045] The present application firstly mixes metal salt, dopant, spinning aid and solvent to obtain a spinnable fiber precursor solution, then centrifugal spinning is performed on the fiber precursor solution to obtain a strip-shaped precursor fiber with a U-shaped cross section, and finally high temperature is used to drive the strip-shaped precursor fiber with a U-shaped cross section to automatically bend and close to form a hollow oxide fiber. Compared with the preparation process of the existing hollow oxide fiber, the preparation method of the hollow oxide fiber of the present application is simple and efficient, low in cost, and has improved inorganic salt loading capacity, and does not need a template (biological template or metal substrate), but only relies on high temperature to drive the strip-shaped precursor fiber with a U-shaped cross section to automatically bend and close to form a hollow oxide fiber with a hollow structure, thereby overcoming the problem that the preparation of the existing hollow oxide fiber needs to rely on a template and the fiber is discontinuous, and providing a new idea for the preparation of the oxide hollow fiber.

[0046] It should be noted that the U-shaped cross section of the present application refers to the cross section of the strip-shaped fiber.

[0047] In some preferred embodiments of the present application, in step S1, the metal salt, the dopant and the solvent are first mixed uniformly, and then the spinning aid is added and mixed uniformly to obtain the fiber precursor solution.

[0048] In some preferred embodiments of the present application, in step S2, the fiber precursor solution is injected into a centrifugal spinning device for spinning, and collected by a collecting device to obtain a strip-shaped precursor fiber with a U-shaped cross section.

[0049] In some preferred embodiments of the present application, the spinning includes: adding the fiber precursor solution into a single-hole spinning head through a syringe, and applying a centrifugal force on the fiber precursor solution by high-speed rotation of the spinning device.

[0050] In some preferred embodiments of the present application, in step S2, the centrifugal spinning is followed by a drying step; the drying temperature is 50-80℃, and the time is 12-24h.

[0051] According to some preferred embodiments, the amount of the metal salt is not less than 12% of the mass of the fiber precursor solution, and is preferably 12-12.5% (for example, it can be 12%, 12.1%, 12.2%, 12.3%, 12.4% or 12.5%);

[0052] Preferably, the metal salt is one or more of a zirconium salt, an aluminum salt, a barium salt and a tin salt. In some preferred embodiments, the zirconium salt is preferably at least one of zirconium oxychloride octahydrate and zirconium nitrate; the aluminum salt is preferably aluminum chloride; the barium salt is preferably barium acetate; and the tin salt is preferably tin chloride.

[0053] According to some preferred embodiments, the amount of the dopant is no more than 2% of the mass of the fiber precursor solution, preferably 1-1.5% (for example, it can be 1.1%, 1.2%, 1.3%, 1.4% or 1.5%);

[0054] The content of the dopant in the present application should not be too high, otherwise it will affect the performance of the fiber. For example, for zirconia fiber, if the content of the dopant is too high, cubic phase zirconia fiber will be formed, which has a lower thermal shock resistance than the tetragonal phase zirconia fiber of the present application.

[0055] Preferably, the dopant is one or more of yttrium nitrate hexahydrate, cerium nitrate hexahydrate, magnesium chloride dihydrate and magnesium chloride dihydrate.

[0056] According to some preferred embodiments, the amount of the spinning aid is 7.5-13.5% of the mass of the fiber precursor solution (for example, it can be 7.5%, 8%, 8.5%, 8.6%, 8.9%, 9%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12%, 12.5%, 13% or 13.5%), preferably 8.5-12.5% (for example, it can be 8.5%, 8.6%, 8.9%, 9%, 9.1%, 9.5%, 10%, 10.5%, 11%, 11.5%, 12% or 12.5%);

[0057] By controlling the content of the spinning aid in the fiber precursor solution, the present application obtains a fiber precursor solution with suitable viscosity and spinnability, and through centrifugal spinning, a precursor fiber with a U-shaped cross-section is obtained. The inventors have found that when the content of the spinning aid in the fiber precursor solution is less than 7.5%, spindle string beads appear in the precursor fiber, and the phenomenon of spindle string beads is more obvious (more spindle string beads) as the content of the spinning aid decreases. When the content of the spinning aid in the fiber precursor solution is greater than 13.5%, the precursor fiber obtained is a completely flat fiber without a U-shaped cross-section, which cannot automatically bend and close to form a hollow fiber under high temperature driving. Therefore, the amount of the spinning aid is controlled in the above range.

[0058] Preferably, the spinning aid is one or more of polyvinylpyrrolidone, polyvinyl alcohol and polyacrylonitrile.

[0059] Preferably, the solvent is one or more of N,N-dimethylformamide, anhydrous ethanol and water. In some preferred embodiments of the present application, using anhydrous ethanol as the main solvent can greatly accelerate the gelation process of the precursor fiber, and the precursor fibers obtained are not easy to stick together.

[0060] According to some preferred embodiments, the spinning head aperture of the centrifugal spinning is 0.2-0.5 mm (for example, it can be 0.2 mm, 0.25 mm, 0.3 mm, 0.35 mm, 0.4 mm, 0.45 mm or 0.5 mm);

[0061] The rotation speed of the centrifugal spinning is 2500-3000 r / min (for example, it can be 2500 r / min, 2600 r / min, 2700 r / min, 2800 r / min, 2900 r / min or 3000 r / min);

[0062] The temperature of the centrifugal spinning is 20-30℃ (for example, it can be 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃ or 30℃); and / or

[0063] The humidity of the centrifugal spinning is 50-60% (for example, it can be 50%, 51%, 52%, 53%, 54%, 55%, 56%, 57%, 58%, 59% or 60%).

[0064] After obtaining a fiber precursor solution with suitable viscosity and spinnability, the present application obtains a ribbon-shaped precursor fiber with U-shaped cross section through centrifugal spinning. The present inventors have found that the centrifugal spinning process is sensitive to the humidity of the centrifugal spinning. The humidity should be controlled within a certain range to obtain a ribbon-shaped precursor fiber with U-shaped cross section. If the humidity of the centrifugal spinning is too low (less than 50%), a cylindrical precursor fiber is obtained. If the humidity of the centrifugal spinning is too high (more than 60%), the jet cannot be solidified to form a fiber.

[0065] According to some preferred embodiments, the high-temperature driving is to raise the temperature to not less than 800℃, preferably 800-1100℃ (for example, it can be 800℃, 850℃, 900℃, 950℃, 1000℃, 1050℃ or 1100℃), and keep the temperature for 1-2 h.

[0066] In the present application, the ribbon-shaped precursor fiber with U-shaped cross section can be completely closed to obtain a hollow oxide fiber under the high-temperature driving with a temperature of 800℃ or above. If the temperature is too low, the ribbon-shaped precursor fiber cannot be completely closed. In the high-temperature driving process, the high temperature not only plays a role in calcination, but also provides a driving force for the automatic bending and closing of the ribbon-shaped precursor fiber. When the sintering temperature reaches above the decomposition temperature of the spinning aid, the spinning aid is completely decomposed and removed. The dopant forms a stable solid solution with zirconia to ensure that the martensitic phase transition does not occur when the temperature changes, and a tetragonal zirconia fiber is obtained.

[0067] According to some preferred embodiments, the high-temperature driving is carried out in an oxygen-containing atmosphere, preferably, the oxygen-containing atmosphere is an air or oxygen atmosphere; and / or

[0068] In the high-temperature driving process, when the temperature is below 800℃, the temperature rising rate is 0.5-1℃ / min (for example, it can be 0.5℃ / min, 0.6℃ / min, 0.7℃ / min, 0.8℃ / min, 0.9℃ / min or 1℃ / min).

[0069] In the high-temperature driving process, when the temperature has not reached 800℃, the temperature rising rate should not be too fast (0.5-1℃ / min) to avoid the organic matter burning fiercely, resulting in more pores and cracks, and reducing the strength of the prepared fiber.

[0070] The present application provides, in a second aspect, a hollow oxide fiber prepared by the preparation method of the first aspect.

[0071] The hollow oxide fiber of the present application is highly symmetrical, smooth and wrinkle-free in surface, small in diameter, low in density and low in thermal conductivity, and has excellent heat insulation performance, and can be used at a temperature above 1400℃. Compared with the conventional solid oxide fiber, the hollow oxide fiber of the present application has significantly reduced gas heat conduction, solid heat conduction and radiation heat transfer in a high-temperature environment, and has obviously improved heat insulation performance.

[0072] According to some preferred embodiments, the diameter of the hollow oxide fiber is 2-8μm (for example, it can be 2μm, 3μm, 4μm, 5μm, 6μm, 7μm or 8μm), and the wall thickness is 1-3μm (for example, it can be 1μm, 2μm or 3μm). It should be noted that the diameter of the hollow oxide fiber herein refers to the outer diameter of the hollow oxide fiber.

[0073] The hollow oxide fiber prepared by the present application is small in size and has a micron-level diameter, which overcomes the problem that the diameter and wall thickness of the hollow fiber prepared by the existing phase inversion method mainly depend on the inner and outer diameters (millimeter level) of the concentric hole spinneret, and it is difficult to further reduce the size of the hollow fiber by using the concentric hole spinneret for spinning.

[0074] According to some preferred embodiments, the hollow structure is distributed on the fiber wall of the hollow oxide fiber along the length direction of the hollow oxide fiber.

[0075] The hollow structure is distributed on the fiber wall of the hollow oxide fiber of the present application along the length direction of the hollow oxide fiber, and compared with the fiber having only a single hollow structure, the hollow oxide fiber has better heat insulation performance.

[0076] In order to more clearly illustrate the technical solutions and advantages of the present application, the present application will be further described below in conjunction with examples.

[0077] The source of each reagent used in the examples and comparative examples is not specifically limited, and can be directly purchased or synthesized by the inventors.

[0078] Example 1

[0079] (1) 4.188 g of zirconium oxychloride octahydrate and 0.396 g of yttrium nitrate hexahydrate were added to 25 mL of anhydrous ethanol, and magnetic stirring was performed for 3 h to obtain a zirconium salt solution; 3 g of polyvinylpyrrolidone (molecular weight 1.3 x 10 6 ) was slowly added under magnetic stirring, followed by the addition of 4 mL of DMF and 3 mL of ultrapure water, and magnetic stirring was continued for 12 h to obtain a precursor solution;

[0080] (2) The temperature for spinning was controlled at 25°C, and the humidity for spinning was controlled at 55%, the obtained precursor solution was injected into a centrifugal spinning device, spinning was performed at 2500 r / min, and a collecting device was used to collect the fibers to obtain a belt-shaped precursor fiber with a U-shaped cross section, and the obtained belt-shaped precursor fiber with a U-shaped cross section was transferred to a 60°C drying oven for drying for 12 h;

[0081] (3) The dried belt-shaped precursor fiber with a U-shaped cross section was heated to 800°C at a heating rate of 1°C / min in a muffle furnace, and after being kept at 800°C for 1 h, the temperature was increased to 1100°C at a heating rate of 3°C / min, and after being kept at 1100°C for 1 h, a high-temperature driven bent closed hollow zirconia fiber was obtained.

[0082] It can be known from Figure 1 that the precursor fiber prepared in the example has a U-shaped cross section; it can be known from Figure 2 that the fiber obtained by centrifugal spinning in the example is staggered, has good continuity, and has a certain orientation; it can be known from Figure 3 that the precursor fiber with a U-shaped cross section prepared in the example is completely bent closed under high-temperature driving to form a hollow zirconia fiber, and the surface of the fiber is very smooth during the entire calcination process. In addition, a small hollow structure can be observed on the fiber wall of the hollow oxide fiber automatically bent closed after high-temperature calcination along the length direction of the hollow oxide fiber, which has a morphology characteristic different from that of the hollow fiber prepared by other methods. Figure 4 It can be known from

[0083] Example 2

[0084] (1) 4.188 g of zirconium oxychloride octahydrate and 0.396 g of yttrium nitrate hexahydrate were added to 25 mL of anhydrous ethanol, and magnetic stirring was performed for 3 h to obtain a zirconium salt solution; 4.2 g of polyvinylpyrrolidone (molecular weight 1.3 x 10 6), followed by adding 4 mL of DMF and 3 mL of ultrapure water, continuing magnetic stirring for 12 h to obtain a precursor solution;

[0085] (2) The temperature of spinning was controlled at 20℃, the humidity of spinning was controlled at 50%, the obtained precursor solution was injected into a centrifugal spinning device, spinning was performed at 3000 r / min, a collecting device was built to collect the fibers, a U-shaped cross-section ribbon precursor fiber was obtained, and the obtained U-shaped cross-section ribbon precursor fiber was transferred to a 60℃ drying box for drying for 12 h;

[0086] (3) The dried U-shaped cross-section ribbon precursor fiber was heated to 800℃ in a muffle furnace at a heating rate of 1℃ / min, and after holding for 1 h, it was heated to 1100℃ at a heating rate of 3℃ / min, and after holding for 1 h, a high-temperature driven curved closed hollow zirconia fiber was obtained.

[0087] Example 3

[0088] (1) 4.188 g of zirconium oxychloride octahydrate and 0.396 g of yttrium nitrate hexahydrate were added to 25 mL of anhydrous ethanol, and magnetic stirring was performed for 3 h to obtain a zirconium salt solution; 3.4 g of polyvinylpyrrolidone (molecular weight 1.3×106) was slowly added under magnetic stirring, followed by adding 4 mL of DMF and 3 mL of ultrapure water, and continuing magnetic stirring for 12 h to obtain a precursor solution;

[0089] (2) The temperature of spinning was controlled at 30℃, the humidity of spinning was controlled at 60%, the obtained precursor solution was injected into a centrifugal spinning device, spinning was performed at 2500 r / min, a collecting device was built to collect the fibers, a U-shaped cross-section ribbon precursor fiber was obtained, and the obtained U-shaped cross-section ribbon precursor fiber was transferred to a 60℃ drying box for drying for 12 h;

[0090] (3) The dried U-shaped cross-section ribbon precursor fiber was heated to 800℃ in a muffle furnace at a heating rate of 1℃ / min, and after holding for 1 h, it was heated to 1100℃ at a heating rate of 3℃ / min, and after holding for 1 h, a high-temperature driven curved closed hollow zirconia fiber was obtained.

[0091] It should be noted that the morphology of the hollow zirconia fiber obtained in Example 2 and Example 3 is not much different from that of Example 1, which will not be listed here.

[0092] Example 4

[0093] The same as Example 1, except that in step (5), the dried belt precursor fiber with U-shaped cross section is heated to 800°C at a heating rate of 1°C / min in a muffle furnace and kept for 2h, so that the high-temperature driven bending closed hollow zirconia fiber is prepared.

[0094] As can be seen from the above, the precursor fiber with U-shaped cross section prepared in this example is bent and closed to form a hollow zirconia fiber. Figure 5

[0095] Comparative Example 1

[0096] The same as Example 1, except that the amount of polyvinylpyrrolidone (molecular weight 1.3 x 10 6 ) is 2.3g.

[0097] As can be seen from the above, because the content of the spinning aid polyvinylpyrrolidone in the precursor solution is too small, the precursor fiber contains a small amount of spindle-shaped beads. Figure 6

[0098] Comparative Example 2

[0099] The same as Example 1, except that the amount of polyvinylpyrrolidone (molecular weight 1.3 x 10 6 ) is 1.6g.

[0100] As can be seen from the above, because the content of the spinning aid polyvinylpyrrolidone in the precursor solution is further reduced compared with Comparative Example 1, the precursor fiber contains a large amount of spindle-shaped beads. Figure 7

[0101] Comparative Example 3

[0102] The same as Example 1, except that the amount of polyvinylpyrrolidone (molecular weight 1.3 x 10 6 ) is 5g.

[0103] As can be seen from the above, because the content of the spinning aid polyvinylpyrrolidone in the precursor solution is too large, the precursor fiber formed is a completely flat fiber without U-shaped cross section, which cannot be closed to form a hollow zirconia fiber in the high-temperature heat driven process. Figure 8

[0104] Comparative Example 4

[0105] The same as Example 1, except that the humidity of the spinning is 45%.

[0106] As can be seen from the above, because the humidity of the spinning is too small, the solvent is more volatile, and the precursor fiber formed is a cylindrical fiber without U-shaped cross section. Figure 9

[0107] Comparative Example 5​​​​​

[0108] It is basically the same as Example 1, except that the humidity of the spinning is 65%.

[0109] Because the humidity during spinning is too high, the solvent is difficult to evaporate, and the jet cannot solidify to form fibers.

[0110] Comparative Example 6

[0111] The process is basically the same as in Example 1, except that the dried U-shaped precursor fibers are heated to 500°C in a muffle furnace at a heating rate of 1°C / min and held for 2 hours.

[0112] Depend on Figure 10 It is known that due to the excessively low temperature driven by high temperature, the U-shaped cross-section of the ribbon precursor fiber does not bend significantly and cannot bend and close to form hollow zirconia fiber.

[0113] 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 the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for producing a hollow oxide fiber, characterized by, The preparation method comprises: S1. mixing a metal salt, a dopant, a spinning aid and a solvent to obtain a fiber precursor solution; the metal salt is a zirconium salt, the zirconium salt is zirconium oxychloride octahydrate; the dopant is yttrium nitrate hexahydrate; the spinning aid is polyvinylpyrrolidone; the amount of the metal salt is not less than 12% of the mass of the fiber precursor solution; the amount of the dopant is not more than 2% of the mass of the fiber precursor solution; the spinning aid accounts for 7.5-13.5% of the mass of the fiber precursor solution; S2. spinning the fiber precursor solution by centrifugal spinning to obtain a strip-shaped precursor fiber with a U-shaped cross section; the centrifugal spinning speed is 2500-3000 r / min; the centrifugal spinning temperature is 20-30℃; the centrifugal spinning humidity is 50-60%; S3. driving the strip-shaped precursor fiber to close by high temperature to form a hollow oxide fiber; the high temperature driving is to raise the temperature to 800-1100℃; during the high temperature driving, when the temperature is lower than 800℃, the temperature rising rate is 0.5-1℃ / min.

2. The production method according to claim 1, characterized by, The amount of the metal salt is 12-12.5% of the mass of the fiber precursor solution.

3. The production method according to claim 1, characterized by, The amount of the dopant is 1-1.5% of the mass of the fiber precursor solution.

4. The method of claim 1, wherein, The spinning aid accounts for 8.5-12.5% of the mass of the fiber precursor solution.

5. The preparation method according to claim 4, characterized in that, The solvent is one or more of N,N-dimethylformamide, anhydrous ethanol and water.

6. The method of claim 1, wherein, The spinning head aperture of the centrifugal spinning is 0.2-0.5 mm.

7. The preparation method according to claim 1, characterized in that, The high temperature driving is to raise the temperature to 800-1100℃ and keep the temperature for 1-2 h.

8. The method of claim 1, wherein, The high temperature driving is carried out in an oxygen-containing atmosphere.

9. The production method according to claim 8, characterized by, The oxygen-containing atmosphere is an air or oxygen atmosphere.

10. A hollow oxide fiber, characterized by, The hollow oxide fiber is prepared by the preparation method in any one of claims 1-9.

11. The hollow oxide fiber of claim 10, wherein, The diameter of the hollow oxide fiber is 2-8 μm, and the wall thickness is 1-3 μm.

12. The hollow oxide fiber of claim 10, wherein, The hollow structure is distributed on the fiber wall of the hollow oxide fiber along the length direction of the hollow oxide fiber.

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