Binary composite oxide ceramic fiber and preparation method thereof

Abstract

The invention relates to the technical field of ceramic materials, and particularly discloses a binary composite oxide ceramic fiber and a preparation method thereof. The preparation method comprises the following steps: (1) preparing a precursor solution; (2) preparing hybrid binary composite oxide ceramic nanofibers; and (3) preparing the binary composite oxide ceramic nanofiber. The binary composite oxide ceramic fiber provided by the invention realizes continuous and stable production under a specific process and proportion, and the fiber is good in one-time formability, high in purity, good in toughness and good in heat insulation performance.

Description

Technical Field

[0001] The present invention relates to the technical field of ceramic materials, and specifically discloses a binary composite oxide ceramic fiber and a preparation method thereof. Background Art

[0002] Ceramic fibers have the advantages of low density, high strength, high temperature resistance, oxidation resistance, and good mechanical vibration resistance, and are key high-temperature insulation materials required in the thermal protection fields such as aerospace vehicles, nuclear power generation, and chemical metallurgy. Among them, oxide ceramic fibers have become a type of ceramic fiber that has been studied quite a lot in the prior art due to their good high-temperature resistance and low thermal conductivity.

[0003] The invention patent with the application number 202111091769.5 discloses a preparation method of a flexible high-temperature resistant SiO 2 ceramic nanofiber membrane. The SiO 2 ceramic nanofiber membrane is prepared by a sol-gel electrospinning method, can be applied at 800 - 1200 °C without changing the fiber morphology and structure, and has a low thermal conductivity, and can be applied in high-temperature fields, especially in high-temperature and humid environments. However, the fiber membrane prepared from a single oxide by this invention may have relatively poor deformation performance, and there is still room for improvement in the tensile strength.

[0004] The invention patent with the application number 202310406959.4 discloses a flexible zinc oxide-silicon dioxide nanofiber membrane and a preparation method thereof. The core layer silicon dioxide spinning solution is prepared from silicon dioxide sol and an aqueous solution of polyvinyl alcohol, and the shell layer zinc acetate spinning solution is prepared from an aqueous solution of zinc acetate, an aqueous solution of polyvinyl alcohol, and glacial acetic acid. The core layer silicon dioxide spinning solution and the shell layer zinc acetate spinning solution are respectively injected into a core-shell double-flow micro-control injection system for electrospinning, and then heated and calcined in sequence to obtain a flexible zinc oxide-silicon dioxide nanofiber membrane. The binary oxide ceramic nanofiber membrane disclosed in this invention not only has the characteristics of high temperature resistance, corrosion resistance, high flexibility, and not easy to break when curled, but also has excellent air permeability. However, the continuity may be insufficient when preparing nanofibers by this invention, and the requirements for electrospinning equipment are relatively high. Summary of the Invention

[0005] Aiming at the defects of the prior art, the present invention discloses a binary composite oxide ceramic fiber and a preparation method thereof. The binary composite oxide ceramic fiber provided by the present invention realizes continuous and stable production under specific processes and ratios, and has good one-time forming property of the fiber, high purity, good toughness, and good heat insulation performance.

[0006] In order to achieve the above object, the technical scheme adopted by the present invention is as follows:

[0007] On the one hand, the present invention provides a method for preparing binary composite oxide ceramic fibers, comprising the following steps:

[0008] (1) Preparation of precursor solution: Prepare an aqueous solution containing a silicon source compound and a zirconium source compound, add a complexing agent, mix evenly, and stir and react at room temperature for 2-4 h to obtain a precursor solution;

[0009] (2) Preparation of hybrid binary composite oxide ceramic nanofibers: Mix a spinning aid with the precursor solution in step (1) evenly at 50-70 °C, then add a binder, stir and react at room temperature for 1 h, and use the electrospinning process to spin and obtain hybrid zirconia ceramic nanofibers;

[0010] (3) Preparation of binary composite oxide ceramic nanofibers: Vacuum-dry the hybrid zirconia ceramic nanofibers in step (2), then add a sintering aid, and use the high-temperature calcination process to sinter and obtain binary composite oxide ceramic nanofibers.

[0011] In some embodiments of the present invention, the fiber diameter of the binary composite oxide ceramic fibers is 2-10 μm, and the fiber length is 10-50 mm.

[0012] In some embodiments of the present invention, in step (1), the silicon source compound is tetraethyl orthosilicate, and the zirconium source compound is at least one of tetrabutyl zirconate and zirconium acetate.

[0013] Preferably, the zirconium source compound is tetrabutyl zirconate.

[0014] In some embodiments of the present invention, the mass ratio of the silicon source compound to the zirconium source compound is (6-10):1.

[0015] Preferably, the mass ratio of the silicon source compound to the zirconium source compound is 8:1.

[0016] The present invention controls the mass ratio of the silicon source compound and the zirconium source compound, and to a certain extent improves the ductility of the binary composite oxide ceramic fibers. Due to the good synergistic effect between the amorphous phase and the crystalline phase structure, when it is used as a precursor solution, it has extremely high spinnability, increases the continuous uniformity of the fiber structure, solves the adverse effects of poor continuity and poor primary formability of common oxide ceramics in the prior art on the performance, and increases the toughness of the binary composite oxide ceramic fibers; at the same time, it may also be because the out-of-control growth of crystallization is effectively avoided when specific proportions of binary oxides are used in combination, further balancing the high-temperature resistance and heat insulation performance of the binary composite oxide ceramic fibers.

[0017] In some embodiments of the present invention, the spinning aid is modified polyvinyl alcohol, and the preparation steps of the modified polyvinyl alcohol are as follows:

[0018] Mix polyvinyl alcohol with 4-vinyl aniline, add an initiator, heat up to 90 - 100 °C and react for 1 - 3 h. After precipitation and drying, a pre-product is obtained. Then mix the pre-product with absolute ethanol, centrifuge to remove the precipitate, and dry, wash and dry the remaining product to obtain the modified polyvinyl alcohol.

[0019] In some embodiments of the present invention, the mass ratio of polyvinyl alcohol to 4-vinyl aniline is 1:(0.5 - 0.7).

[0020] Preferably, the mass ratio of polyvinyl alcohol to 4-vinyl aniline is 1:0.6.

[0021] The present invention modifies polyvinyl alcohol by adding 4-vinyl aniline. Probably due to the long-chain structure and the presence of vinyl groups in the modified polyvinyl alcohol molecular chain, while polyvinyl alcohol plays the function of a spinning aid, it can also rapidly diffuse in the system and form a stable adsorption effect. At this time, the reduction of the surface tension of the system is also beneficial to the dispersion and compatibility of the spinning aid and the precursor solution, which is beneficial to continuous and stable spinning production. The introduction of aniline bonds also improves the thermal stability during forming to a certain extent, which is beneficial to the one-time forming of fibers and improves the purity of the binary composite oxide ceramic fibers.

[0022] In some embodiments of the present invention, the mass proportion of the spinning aid in the precursor solution is 5 - 20 wt%.

[0023] Preferably, the mass proportion of the spinning aid in the precursor solution is 12.3 wt%.

[0024] Preferably, the complexing agent is acetic acid.

[0025] In some embodiments of the present invention, the preparation steps of the binder are as follows:

[0026] Mix methacrylamide and N,N'-methylenebisacrylamide, then add an initiator and a silica sol binder, heat up to 55 - 70 °C and react for 3 - 6 h to obtain the binder.

[0027] Preferably, the concentration of the silica sol binder is 20 - 30 wt%.

[0028] In some embodiments of the present invention, the mass ratio of methacrylamide, N,N'-methylenebisacrylamide and the silica sol binder is (0.1 - 0.3):(0.01 - 0.05):1.

[0029] The present invention also modifies the silica sol binder by introducing methacrylamide and N,N'-methylenebisacrylamide. During the in-situ crosslinking process, it is possible that there is an electrostatic synergistic effect between the amide bonds of methacrylamide and N,N'-methylenebisacrylamide and the silica in the silica sol binder. At the same time, there is also a certain steric hindrance effect, which promotes the dispersion of the silica sol binder in the precursor solution, enables it to play a good overlapping role among the effective components of the precursor solution, and also avoids the adverse effect of the migration and aggregation of the silica sol binder, which often occurs in the prior art, on the fiber forming performance.

[0030] Preferably, the sintering aid is chromium oxide.

[0031] In some embodiments of the present invention, the process parameters of the electrospinning are as follows: the inner diameter of the injection needle is 0.7 mm, the spinning rate is 1.5 - 2 mL / h, the spinning distance is 0.30 - 0.55 m, the DC power supply voltage is 25 - 30 kV, the temperature is 20 - 30 °C, and the humidity is 45 - 50%.

[0032] In some embodiments of the present invention, the process parameters of the high-temperature calcination are as follows: the temperature is gradually increased to 700 - 900 °C at a heating rate of 2 - 5 °C / min, and held for 1 - 2 h.

[0033] On the other hand, the present invention also provides a binary composite oxide ceramic fiber obtained by the above preparation method, and the binary composite oxide ceramic fiber at least has the following characteristics: the thermal conductivity is 0.025 - 0.043 W / (mK).

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) The binary composite oxide ceramic fiber disclosed in the present invention realizes continuous and stable production under specific processes and ratios, and the fiber has good primary formability, high purity, good toughness, and good heat insulation performance.

[0036] (2) By regulating the ratio of the composite oxide silicon source compound and the zirconium source compound, the present invention improves the ductility of the binary composite oxide ceramic fiber to a certain extent. Through the good synergistic effect between the amorphous phase and the crystalline phase structure, the strength and toughness of the binary composite oxide ceramic fiber are increased and coordinated; at the same time, the high-temperature resistance and heat insulation performance of the binary composite oxide ceramic fiber are further balanced.

[0037] (3) The present invention modifies polyvinyl alcohol by adding 4-vinyl aniline. While polyvinyl alcohol functions as a spinning aid, it can rapidly diffuse in the system and form a stable adsorption effect. At this time, the reduction of the surface tension of the system is also beneficial to the dispersion and compatibility of the spinning aid and the precursor solution, which is conducive to continuous and stable spinning production. The introduction of aniline bonds also improves the thermal stability during forming to a certain extent, which is beneficial to the one-time forming of fibers and improves the purity.

[0038] (4) The present invention modifies the silica sol binder by introducing methacrylamide and N,N'-methylenebisacrylamide, enabling the silica sol binder to disperse in the precursor solution and then play a good bonding and overlapping role, avoiding the adverse effects of the migration and aggregation phenomenon of the silica sol binder that often occurs in the prior art on the fiber forming performance. Specific embodiments

[0039] The present invention will be described below in conjunction with specific implementation embodiments. It should be noted that the following examples are examples of the present invention, only for illustrating the present invention, and not for limiting the present invention. Without departing from the gist or scope of the present invention, other combinations and various improvements within the concept of the present invention can be made.

[0040] Unless otherwise specified, the reagents used below can be easily obtained from commercial companies. Among them, polyvinyl alcohol (PVA2488) is purchased from Kaimaoxing (Hebei) Cellulose Co., Ltd.

[0041] Unless otherwise specified, the post-treatment steps such as "precipitation", "drying", "washing" and "vacuum drying" used below are conventional operations of those skilled in the art and can be selected according to actual operations.

[0042] Preparation Example 1

[0043] The preparation steps of the modified polyvinyl alcohol are as follows:

[0044] Mix 10 g of polyvinyl alcohol with 6 g of 4-vinyl aniline, add 0.03 g of benzoyl peroxide, raise the temperature to 95 °C and react for 2 h. After precipitation and drying, a pre-product is obtained. Then mix the pre-product with 50 mL of absolute ethanol, centrifuge to remove the precipitate, and dry, wash and dry the remaining product to obtain the modified polyvinyl alcohol.

[0045] Preparation Example 2

[0046] The preparation steps of the modified polyvinyl alcohol are the same as those in Preparation Example 1, except that the addition amount of 4-vinyl aniline is 4 g.

[0047] Preparation Example 3

[0048] The preparation steps of the modified polyvinyl alcohol are the same as those in Preparation Example 1, except that the addition amount of 4-vinyl aniline is 8 g.

[0049] Preparation Example 4

[0050] The preparation steps of the binder are as follows:

[0051] Mix 2 g of methacrylamide and 0.3 g of N,N'-methylenebisacrylamide, then add 0.1 g of ammonium persulfate and 10 g of 25 wt% silica sol, heat up to 60 °C, and react for 4.5 h to obtain the binder.

[0052] Preparation Example 5

[0053] The preparation steps of the binder are the same as those in Preparation Example 4, except that the addition amount of methacrylamide is 3.5 g.

[0054] Preparation Example 6

[0055] The preparation steps of the binder are the same as those in Preparation Example 4, except that the addition amount of N,N'-methylenebisacrylamide is 0.55 g.

[0056] Example 1

[0057] A method for preparing a binary composite oxide ceramic fiber comprises the following steps:

[0058] (1) Preparation of precursor solution: Prepare an aqueous solution containing 8 g of tetraethyl orthosilicate and 1 g of zirconium tetrabutoxide in 100 mL, add 4 g of acetic acid, mix evenly, and stir and react at room temperature for 3 h to obtain the precursor solution;

[0059] (2) Preparation of hybrid binary composite oxide ceramic nanofibers: Mix the modified polyvinyl alcohol and the precursor solution in step (1) at a mass ratio of 0.13:1 at 60 °C, then add the binder (the addition amount is 1% of the precursor solution), stir and react at room temperature for 1 h, and use the electrospinning process to spin and obtain hybrid zirconia ceramic nanofibers;

[0060] (3) Preparation of binary composite oxide ceramic nanofibers: Vacuum-dry the hybrid zirconia ceramic nanofibers in step (2), then add 0.7% of chromium oxide by mass of the hybrid zirconia ceramic nanofibers, and use the high-temperature calcination process to sinter and obtain binary composite oxide ceramic nanofibers.

[0061] The modified polyvinyl alcohol used in this example is obtained from Preparation Example 1, and the binder is obtained from Preparation Example 4.

[0062] The process parameters of electrospinning are: the inner diameter of the injection needle is 0.7 mm, the spinning rate is 1.7 mL / h, the spinning distance is 0.45 m, the DC power supply voltage is 28 kV, the temperature is 25 °C, and the humidity is 48%.

[0063] The process parameters for high-temperature calcination are as follows: gradually increase the temperature to 800 °C at a heating rate of 4 °C / min and hold for 1.5 h.

[0064] The fiber diameter of the binary composite oxide ceramic nanofibers obtained in this example is 6 μm, and the fiber length is 30 mm.

[0065] Example 2

[0066] A method for preparing binary composite oxide ceramic fibers comprises the following steps:

[0067] (1) Preparation of precursor solution: Prepare an aqueous solution of 100 mL containing 6 g of tetraethyl orthosilicate and 1 g of tetrabutyl zirconate, add 3 g of acetic acid, mix evenly, and stir and react at room temperature for 2 h to obtain a precursor solution;

[0068] (2) Preparation of hybrid binary composite oxide ceramic nanofibers: Mix the modified polyvinyl alcohol and the precursor solution in step (1) evenly at a mass ratio of 0.05:1 at 50 °C, then add a binder (the addition amount is 1% of the precursor solution), stir and react at room temperature for 1 h, and use the electrospinning process to spin hybrid zirconia ceramic nanofibers;

[0069] (3) Preparation of binary composite oxide ceramic nanofibers: Vacuum-dry the hybrid zirconia ceramic nanofibers in step (2), then add 0.7% of chromium oxide by mass of the hybrid zirconia ceramic nanofibers, and use the high-temperature calcination process to sinter to obtain binary composite oxide ceramic nanofibers.

[0070] The modified polyvinyl alcohol used in this example is obtained from Preparation Example 1, and the binder is obtained from Preparation Example 4.

[0071] The process parameters for electrospinning are as follows: the inner diameter of the injection needle is 0.7 mm, the spinning rate is 1.5 mL / h, the spinning distance is 0.30 m, the DC power supply voltage is 25 kV, the temperature is 30 °C, and the humidity is 45%.

[0072] The process parameters for high-temperature calcination are as follows: gradually increase the temperature to 900 °C at a heating rate of 2 °C / min and hold for 1 h.

[0073] The fiber diameter of the binary composite oxide ceramic nanofibers obtained in this example is 6 μm, and the fiber length is 30 mm.

[0074] Example 3

[0075] A method for preparing binary composite oxide ceramic fibers comprises the following steps:

[0076] (1) Preparation of precursor solution: Prepare an aqueous solution of 100 mL containing 10 g of tetraethyl orthosilicate and 1 g of tetrabutyl zirconate, add 4.9 g of acetic acid, mix evenly, and stir and react at room temperature for 4 h to obtain a precursor solution;

[0077] (2) Preparation of hybrid binary composite oxide ceramic nanofibers: Mix the modified polyvinyl alcohol and the precursor solution in step (1) at a mass ratio of 0.2:1 at 70 °C, then add a binder (the addition amount is 1% of the precursor solution), stir and react at room temperature for 1 h, and use the electrospinning process to spin and obtain hybrid zirconia ceramic nanofibers;

[0078] (3) Preparation of binary composite oxide ceramic nanofibers: Vacuum-dry the hybrid zirconia ceramic nanofibers in step (2), then add 0.7% of chromium oxide by mass of the hybrid zirconia ceramic nanofibers, and use the high-temperature calcination process to sinter and obtain binary composite oxide ceramic nanofibers.

[0079] The modified polyvinyl alcohol used in this example is obtained from Preparation Example 1, and the binder is obtained from Preparation Example 4.

[0080] The process parameters of electrospinning are: the inner diameter of the injection needle is 0.7 mm, the spinning rate is 2 mL / h, the spinning distance is 0.55 m, the DC power supply voltage is 30 kV, the temperature is 20 °C, and the humidity is 50%.

[0081] The process parameters of calcination are: gradually increase the temperature to 700 °C at a heating rate of 5 °C / min and hold for 2 h.

[0082] The fiber diameter of the binary composite oxide ceramic nanofibers obtained in this example is 6 μm, and the fiber length is 30 mm.

[0083] Example 4

[0084] A binary composite oxide ceramic fiber and its preparation method, the difference being that the modified polyvinyl alcohol used is obtained from Preparation Example 2.

[0085] Example 5

[0086] A binary composite oxide ceramic fiber and its preparation method, the difference being that the modified polyvinyl alcohol used is obtained from Preparation Example 3.

[0087] Example 6

[0088] A binary composite oxide ceramic fiber and its preparation method, the difference being that polyvinyl alcohol is used to replace the modified polyvinyl alcohol in equal amount.

[0089] Example 7

[0090] A binary composite oxide ceramic fiber and a preparation method thereof, wherein the difference lies in that the mass ratio of tetraethyl orthosilicate to tetrabutyl zirconate is 5:1.

[0091] Example 8

[0092] A binary composite oxide ceramic fiber and a preparation method thereof, wherein the difference lies in that the mass ratio of tetraethyl orthosilicate to tetrabutyl zirconate is 11:1.

[0093] Example 9

[0094] A binary composite oxide ceramic fiber and a preparation method thereof, wherein the difference lies in that in step (2), the mass ratio of modified polyvinyl alcohol to the precursor solution in step (1) is 0.22:1.

[0095] Example 10

[0096] A binary composite oxide ceramic fiber and a preparation method thereof, wherein the difference lies in that the binder used is obtained from Preparation Example 5.

[0097] Example 11

[0098] A binary composite oxide ceramic fiber and a preparation method thereof, wherein the difference lies in that the binder used is obtained from Preparation Example 6.

[0099] Example 12

[0100] A binary composite oxide ceramic fiber and a preparation method thereof, wherein the difference lies in that the binder used is a 25wt% silica sol binder.

[0101] Performance test:

[0102] The following performance tests were carried out on the binary composite oxide ceramic fibers obtained in the above examples, and the test results are shown in Table 1.

[0103] (1) Mechanical property test: At 20 °C, after the sample was clamped by a fixture, the mechanical properties of the binary composite oxide ceramic fiber were tested using a dynamic mechanical analyzer;

[0104] (2) Heat insulation property test: The thermal conductivity of the binary composite oxide ceramic fiber was tested using a Hot Disk instrument according to the transient plane source method of ISO 220072:2015 to characterize its heat insulation property.

[0105] Table 1

[0106]

[0107]

[0108] As can be seen from Table 1, the binary composite oxide ceramics fibers provided in Examples 1 to 3 of the present invention have good mechanical properties and heat insulation properties.

[0109] Comparing Example 4 and Example 5 with Example 1, it can be seen that when the addition amount of 4-vinyl aniline changes during the preparation of the modified polyvinyl alcohol for the binary composite oxide ceramics fibers, the mechanical properties and heat insulation properties of the binary composite oxide ceramics fibers will both decrease. This may be due to certain structural defects in the binary composite oxide ceramics fibers, which in turn affect the mechanical properties and heat insulation properties.

[0110] Comparing Example 6 with Example 1, it can be seen that when directly adding polyvinyl alcohol in an equal amount to replace the modified polyvinyl alcohol as the spinning aid, the mechanical properties and heat insulation properties of the binary composite oxide ceramics fibers will both decrease.

[0111] Comparing Example 7 and Example 8 with Example 1, it can be seen that when the mass ratio of the silicon source compound and the zirconium source compound changes during the preparation of the precursor solution, the mechanical properties and heat insulation properties of the binary composite oxide ceramics fibers will both decrease. This indicates that the specifically selected precursor solution of the present invention has high spinnability, continuous and uniform fiber structure, and strong processability.

[0112] Comparing Example 9 with Example 1, it can be seen that when the addition amount of the modified polyvinyl alcohol as the spinning aid in the precursor solution changes, the comprehensive properties of the binary composite oxide ceramics fibers will decrease, especially the tensile strength and fracture toughness.

[0113] Comparing Example 10 and Example 11 with Example 1, it can be seen that when the addition amounts of methylacrylamide and N,N'-methylenebisacrylamide change respectively during the preparation of the binder, the binding effect of the binder on each effective component in the precursor solution will be unstable, which in turn affects the mechanical properties of the binary composite oxide ceramics fibers after forming.

[0114] Comparing Example 12 with Example 1, it can be seen that when directly adding 25wt% silica sol binder as the binder, migration and diffusion may occur during the subsequent forming process, resulting in the coexistence of insufficient binding and excessive binding, which affects the comprehensive properties of the binary composite oxide ceramics fibers.

[0115] The above are only the preferred embodiments of the present invention and do not impose any formal restrictions on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art, within the scope of the technical solution of the present invention, can make some changes or modifications to equivalent embodiments by using the above-disclosed technical content. However, as long as it does not depart from the technical solution content of the present invention, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A method for preparing binary composite oxide ceramic fibers, characterized in that: The following steps are involved: (1) Preparation of precursor solution: preparing an aqueous solution containing a silicon source compound and a zirconium source compound, adding a complexing agent, mixing evenly, and stirring at room temperature for 2 to 4 hours to obtain a precursor solution; (2) Preparation of hybrid binary composite oxide ceramic nanofibers: The spinning aid and the precursor solution in step (1) are mixed evenly at 50-70° C., stirred for reaction at room temperature for 1 h, and the hybrid zirconia ceramic nanofibers are spun by an electrospinning process; (3) Preparation of binary composite oxide ceramic nanofibers: The hybrid zirconia ceramic nanofibers prepared in step (2) are vacuum dried, a sintering aid is added, and a high temperature calcination process is used to sinter the hybrid zirconia ceramic nanofibers to obtain binary composite oxide ceramic nanofibers.

2. The method for preparing binary composite oxide ceramic fiber according to claim 1, characterized in that: The fiber diameter of the binary composite oxide ceramic fiber is 2-10 μm, and the fiber length is 10-50 mm.

3. The method for preparing binary composite oxide ceramic fiber according to claim 1, characterized in that: In step (1), the silicon source compound is tetraethyl orthosilicate, and the zirconium source compound is at least one of tetrabutyl zirconate and zirconium acetate.

4. The method for preparing binary composite oxide ceramic fiber according to claim 1, characterized in that: The mass ratio of the silicon source compound to the zirconium source compound is (6-10):

1.

5. The method for preparing binary composite oxide ceramic fiber according to claim 1, characterized in that: The spinning aid is modified polyvinyl alcohol, and the preparation steps of the modified polyvinyl alcohol are as follows: The polyvinyl alcohol and 4-vinylaniline are mixed, an initiator is added, the temperature is raised to 90-100°C and the reaction is carried out for 1-3 hours, a pre-product is obtained by precipitation and drying, and then the pre-product is mixed with anhydrous ethanol, the precipitate is removed by centrifugation, and the remaining product is dried, washed and dried again to obtain the modified polyvinyl alcohol.

6. The method for preparing binary composite oxide ceramic fiber according to claim 5, characterized in that: The mass ratio of the polyvinyl alcohol to 4-vinylaniline is 1:(0.5-0.7).

7. The method for preparing binary composite oxide ceramic fiber according to claim 1, characterized in that: The mass proportion of the spinning aid in the precursor solution is 5-20wt%.

8. The method for preparing binary composite oxide ceramic fibers according to claim 1, characterized in that: The preparation steps of the binder are as follows: Mix methacrylamide and N,N'-methylenebisacrylamide, add initiator and silica sol binder, raise the temperature to 55-70°C, react for 3-6 hours, and obtain the binder.

9. The method for preparing binary composite oxide ceramic fibers according to claim 8, characterized in that: The mass ratio of the methacrylamide, N,N'-methylenebisacrylamide and silica sol binder is (0.1-0.3):(0.01-0.05):

1.

10. A binary composite oxide ceramic fiber obtained by the preparation method according to any one of claims 1 to 9, characterized in that: The binary composite oxide ceramic fiber has at least the following characteristics: a thermal conductivity of 0.042 to 0.063 W / (mK).

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