SiC / TiB2 ceramic fiber as well as preparation method and application thereof

Abstract

The invention provides a SiC / TiB2 ceramic fiber, the oxygen content in the fiber is less than 0.5 wt%, the mass percentage of TiB2 is adjustable in a range of 0.1-5%, the particle size of TiB2 is 50-60 nm, and the crystal phase of TiB2 is uniformly distributed in the SiC fiber; the preparation method of the SiC / TiB2 ceramic fiber comprises the following steps: carrying out secondary crosslinking (the temperature is 150-600 DEG C) on the organic fiber containing Ti, Si and C elements in a boron-containing mixed atmosphere, carrying out heat preservation treatment (the temperature is 1600-1900 DEG C, and the heat preservation time is 10 minutes to 2 hours) at high temperature, and cooling to room temperature to obtain the SiC / TiB2 ceramic fiber. And TiB2 is used as a second crystal phase and pinned at the grain boundary of the beta-SiC crystal phase, so that the decomposition of beta-SiC in an ultrahigh-temperature environment is remarkably inhibited, and the temperature resistance of the SiC / TiB2 composite ceramic fiber can be improved to 2000 DEG C or above.

Description

Technical Field

[0001] The invention relates to the technical field of ceramic fibers, in particular to a SiC / TiB2 ceramic fiber and a preparation method and application thereof. Background Art

[0002] High-performance ceramic fibers are important reinforcements for advanced composite materials, with many excellent properties such as high temperature resistance, oxidation resistance, wear resistance and creep resistance. Commercial SiC fibers have been successfully prepared by the precursor conversion method. However, the operating temperature of all SiC fibers is currently below 2000°C.

[0003] TiB2 is the most stable compound of boron and titanium, with a melting point of 2980°C, a small thermal expansion coefficient, and excellent thermal shock resistance. As the second phase, it can improve the overall high-temperature resistance of the ceramic fiber, thereby making the SiC / TiB2 composite ceramic fiber have better temperature resistance than pure SiC fiber. Summary of the invention

[0004] The present invention provides a SiC / TiB2 ceramic fiber and a preparation method and application thereof, which are used to overcome the problem that the temperature resistance of pure SiC fiber in the prior art is not high enough.

[0005] The technical solution of the present invention is to first provide a SiC / TiB2 ceramic fiber, the oxygen content in the fiber is less than 0.5wt%, the mass percentage of TiB2 is adjustable in the range of 0.1-5%, the particle size of TiB2 is 50-60nm, and its crystalline phase is uniformly distributed in the SiC fiber.

[0006] The present invention also provides a method for preparing the above SiC / TiB2 ceramic fiber, comprising the following steps:

[0007] The organic fiber containing Ti, Si and C elements obtained by the first crosslinking is subjected to a second crosslinking in a boron-containing mixed atmosphere, and then subjected to heat preservation treatment at a high temperature and then cooled to room temperature to obtain SiC / TiB2 ceramic fiber.

[0008] Furthermore, the temperature of the second cross-linking is 150-600° C., the temperature of the heat preservation treatment is 1600-1900° C., and the heat preservation time is 10 min-2 h.

[0009] Furthermore, the above-mentioned boron-containing mixed atmosphere includes a boride gas, and the boride gas is any one or more of diborane, tetraborane, pentaborane, decaborane, borazine, boron trifluoride, boron trichloride, and boron tribromide; the boride gas accounts for 5 to 50% of the total volume of the boron-containing mixed atmosphere.

[0010] Furthermore, the above-mentioned boron-containing mixed atmosphere also includes an inert gas.

[0011] Furthermore, the first cross-linking method includes any one of electron beam irradiation cross-linking, air cross-linking, and ultraviolet cross-linking, or a combination of several of them.

[0012] Furthermore, the preparation method of the above-mentioned organic fiber containing Ti, Si and C elements is as follows: polycarbosilane and tetrabutyl titanate are dissolved in an organic solvent, which is then placed in a reaction vessel, and the temperature is raised from room temperature to above 200°C under a nitrogen atmosphere and kept warm. After the reaction is completed, the reaction is cooled to room temperature, and the obtained liquid is filtered and the organic solvent is evaporated by vacuum distillation, and the precursor is cooled to room temperature to obtain a precursor. The precursor is spun, oxidized in an air atmosphere or cross-linked for the first time by electron beam irradiation to obtain an organic fiber containing Ti, Si and C elements.

[0013] Furthermore, the above spinning includes any one of melt spinning, electrostatic spinning, centrifugal spinning, air spinning, dry spinning and wet spinning.

[0014] Furthermore, the mass ratio of the polycarbosilane to tetrabutyl titanate is in the range of (50:1)-(10:1).

[0015] The present invention further provides an application of the above SiC / TiB2 ceramic fiber, which is applied to high-performance ceramic-based composite materials that can withstand ultra-high temperatures of 2000°C.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. In the SiC / TiB2 ceramic fiber provided by the present invention, TiB2 is uniformly distributed in the SiC fiber with a particle size range of 50-60nm. TiB2, as the second crystalline phase, is pinned at the grain boundary of the β-SiC crystalline phase, which significantly inhibits the decomposition of β-SiC in an ultra-high temperature environment, thereby being able to improve the temperature resistance of the SiC / TiB2 composite ceramic fiber to above 2000°C, which has better temperature resistance than pure SiC fiber.

[0018] 2. In the preparation method of SiC / TiB2 ceramic fiber provided by the present invention, polycarbosilane and butyl titanate are first used as raw materials, and organic fibers containing Ti, Si and C elements are obtained by primary crosslinking. Then, the organic fibers are secondary crosslinked in a boron-containing mixed atmosphere, and then heat-insulated at high temperature. Such a "secondary crosslinking" process further increases the degree of crosslinking of the organic fibers, thereby effectively avoiding the melting of the organic fibers during cracking.

[0019] 3. In the preparation method of SiC / TiB2 ceramic fiber provided by the present invention, after secondary crosslinking, the Ti element and B element inside the organic fiber containing Ti, B, Si and C elements are converted into TiB2 phase in situ during high-temperature treatment. Compared with technical means such as directly adding TiB2 nanopowder into SiC fiber, on the one hand, the uniformity of distribution of TiB2 in the fiber is ensured, and on the other hand, the growth particle size of TiB2 is easy to control, achieving two goals at one stroke, being easy to operate and having high production efficiency.

[0020] 4. The SiC / TiB2 ceramic fiber of the present invention can be applied to ceramic-based composite materials that can withstand environments of 2000°C and above. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without paying creative work.

[0022] Figure 1 This is the SEM photograph of the SiC / TiB2 fiber prepared in Example 1.

[0023] Figure 2 This is the XRD photograph of the SiC / TiB2 fiber product prepared in Example 1 after being heated at 2100°C for 1 hour. DETAILED DESCRIPTION

[0024] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0025] In addition, the technical solutions between the various embodiments of the present invention can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by the present invention.

[0026] Unless otherwise specified, all drugs / reagents used were commercially available.

[0027] Example 1

[0028] A method for preparing SiC / TiB2 ceramic fiber comprises the following steps:

[0029] First, organic fibers containing Ti, Si and C elements are synthesized as follows:

[0030] Dissolve 500g of polycarbosilane and 50g of tetrabutyl titanate in 1L of xylene, then place it in a reaction vessel, raise the temperature from room temperature to above 200°C in a nitrogen atmosphere and keep it warm, and cool it to room temperature after the reaction is completed. Filter the obtained liquid and distill the xylene out by vacuum distillation, cool it to room temperature, and obtain a precursor polymer containing metal elements Ti, Si, and C. Place 10g of the synthesized precursor in a spinning barrel, melt-spin at a temperature range of 360-390°C, and collect the fibers with a roller. The collected fibers are placed in a pre-oxidation furnace and oxidized in an air atmosphere to obtain organic fibers containing Ti, Si and C elements, with an oxygen content of >10.0wt%.

[0031] Then, SiC / TiB2 fibers were prepared as follows:

[0032] The obtained organic fibers containing Ti, Si and C elements were placed in a graphite furnace, and the organic fibers were further cross-linked at 300°C in a mixed atmosphere of boron trichloride and argon. The temperature was then raised to 1800°C and kept at this temperature for 30 minutes. The fibers were cooled to room temperature to obtain SiC / TiB2 fibers, whose oxygen content was less than 1wt% according to elemental analysis.

[0033] The scanning electron microscope photo of the SiC / TiB2 fiber prepared in this example is shown in FIG. Figure 1 As shown, the fiber morphology is smooth and uniform. The tensile strength of the fiber is >1.5GPa, the modulus is >300GPa, the TiB2 content is about 3wt%, and the oxygen content is less than 0.5wt%. The XRD picture of the SiC / TiB2 fiber sample prepared in this embodiment after being heated at 2100℃ for 1 hour is as follows Figure 2 It can be seen that there are obvious SiC and TiB2 grains in the fiber, and there is no change in the crystalline phase of the fiber after being kept at an ultra-high temperature of 2100℃ for 1 hour, indicating that the fiber is relatively stable under ultra-high temperature conditions.

[0034] Example 2

[0035] A method for preparing SiC / TiB2 ceramic fiber comprises the following steps:

[0036] First, organic fibers containing Ti, Si and C elements are synthesized as follows:

[0037] 500g of low softening point polycarbosilane and 36g of tetrabutyl titanate were dissolved in 1L of xylene, and then placed in a reaction vessel, heated from room temperature to above 200°C under a nitrogen atmosphere and kept warm, and cooled to room temperature after the reaction was completed. The obtained liquid was filtered and the xylene was evaporated by vacuum distillation, cooled to room temperature, and a precursor was obtained. 10g of the synthesized precursor was placed in a spinning barrel, melt-spun at a temperature range of 360-390°C, and the fibers were collected with a roller. The collected fibers were cross-linked by electron beam irradiation to obtain organic fibers containing Ti, Si and C elements.

[0038] Then, SiC / TiB2 fibers were prepared as follows:

[0039] The obtained organic fiber containing metal element Ti, Si and C elements was placed in a graphite furnace, and the organic fiber was further cross-linked at 150°C in a mixed atmosphere of boron trichloride and argon, and then heated to 1900°C and kept at this temperature for 10 minutes, and cooled to room temperature to obtain SiC / TiB2 fiber. The tensile strength of the fiber is >2.0GPa, the modulus is >330GPa, and the TiB2 content is about 1.5%.

[0040] Example 3

[0041] A method for preparing SiC / TiB2 ceramic fiber comprises the following steps:

[0042] First, organic fibers containing Ti, Si and C elements are synthesized as follows:

[0043] 500g of low softening point polycarbosilane and 10g of tetrabutyl titanate were dissolved in 1L of xylene, and then placed in a reaction vessel, and heated from room temperature to above 200°C in a nitrogen atmosphere and kept warm, and cooled to room temperature after the reaction was completed. The obtained liquid was filtered and the xylene therein was evaporated by vacuum distillation, and cooled to room temperature to obtain a precursor. The precursor was configured into an electrospinning solution, and organic fibers containing metal elements Ti, Si and C elements were obtained after electrospinning, and then pre-oxidized in an air atmosphere.

[0044] Then, SiC / TiB2 fibers were prepared as follows:

[0045] The obtained organic fibers containing Ti, Si and C elements are placed in a graphite furnace, and the organic fibers are further cross-linked at 600°C in a mixed atmosphere of diborane and nitrogen. The temperature is then raised to 1600°C and kept at this temperature for 2 hours. The fibers are cooled to room temperature to obtain SiC / TiB2 fibers with a TiB2 content of approximately 0.7wt%.

[0046] Example 4

[0047] A method for preparing SiC / TiB2 ceramic fiber comprises the following steps:

[0048] First, organic fibers containing Ti, Si and C elements are synthesized as follows:

[0049] Dissolve 500g of polycarbosilane and 50g of tetrabutyl titanate in 1L of xylene, then place it in a reaction vessel, raise the temperature from room temperature to above 200°C in a nitrogen atmosphere and keep it warm, and cool it to room temperature after the reaction is completed. Filter the obtained liquid and evaporate the xylene therein by vacuum distillation, cool it to room temperature, and obtain a precursor polymer containing metal elements Ti, Si, and C. Place 10g of the synthesized precursor in a spinning barrel, melt-spin at a temperature range of 360-390°C, and collect the fibers with a roller. The collected fibers are placed in a pre-oxidation furnace and oxidized in an air atmosphere to obtain organic fibers containing Ti, Si and C elements, with an oxygen content of the fibers >7.0wt%.

[0050] Then, SiC / TiB2 fibers were prepared as follows:

[0051] The obtained organic fibers containing Ti, Si and C elements were placed in a graphite furnace, and the organic fibers were further cross-linked at 300°C in a mixed atmosphere of boron trichloride and argon. The temperature was then raised to 1800°C and kept at this temperature for 30 minutes. After being cooled to room temperature, SiC / TiB2 fibers were obtained, and the oxygen content of the fibers was less than 0.5wt% according to elemental analysis.

[0052] The TiB2 content in the SiC / TiB2 fiber prepared in this example is about 3 wt%.

[0053] Example 5

[0054] A method for preparing SiC / TiB2 ceramic fiber comprises the following steps:

[0055] First, organic fibers containing Ti, Si and C elements are synthesized as follows:

[0056] Dissolve 500g of polycarbosilane and 50g of tetrabutyl titanate in 1L of xylene, then place it in a reaction vessel, raise the temperature from room temperature to above 200°C in a nitrogen atmosphere and keep it warm, and cool it to room temperature after the reaction is completed. Filter the obtained liquid and distill the xylene out by vacuum distillation, cool it to room temperature, and obtain a precursor polymer containing metal elements Ti, Si, and C. Place 10g of the synthesized precursor in a spinning barrel, melt-spin at a temperature range of 360-390°C, and collect the fibers with a roller. The collected fibers are placed in a pre-oxidation furnace and oxidized in an air atmosphere to obtain organic fibers containing Ti, Si and C elements, with an oxygen content of >12.0wt%.

[0057] Then, SiC / TiB2 fibers were prepared as follows:

[0058] The obtained organic fibers containing Ti, Si and C elements were placed in a graphite furnace, and the organic fibers were further cross-linked at 300°C in a mixed atmosphere of boron trichloride and argon. The temperature was then raised to 1800°C and kept at this temperature for 30 minutes. After being cooled to room temperature, SiC / TiB2 fibers were obtained, and the oxygen content of the fibers was less than 0.5wt% according to elemental analysis.

[0059] The TiB2 content in the SiC / TiB2 fiber prepared in this example is about 3 wt%.

[0060] The above description is only a preferred embodiment of the present invention, and does not limit the patent scope of the present invention. All equivalent structural changes made by using the contents of the present invention specification and drawings under the inventive concept of the present invention, or directly / indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. A SiC / TiB2 ceramic fiber, characterized in that: The oxygen content in the fiber is less than 0.5wt%, the mass percentage of TiB2 is adjustable within the range of 0.1-5%, the particle size of TiB2 is 50-60nm, and its crystal phase is uniformly distributed in the SiC fiber.

2. A method for preparing SiC / TiB2 ceramic fiber as claimed in claim 1, characterized in that: The following steps are involved: The organic fiber containing Ti, Si and C elements obtained by the first crosslinking is subjected to a second crosslinking in a boron-containing mixed atmosphere, and then subjected to heat preservation treatment at a high temperature and then cooled to room temperature to obtain SiC / TiB2 ceramic fiber.

3. The preparation method according to claim 2, characterized in that: The temperature of the second cross-linking is 150-600° C., the temperature of the heat preservation treatment is 1600-1900° C., and the heat preservation time is 10 min-2 h.

4. The preparation method according to claim 2, characterized in that: The boron-containing mixed atmosphere includes boride gas, and the boride gas is any one or more of diborane, tetraborane, pentaborane, decaborane, borazine, boron trifluoride, boron trichloride, and boron tribromide; the boride gas accounts for 5-50% of the total volume of the boron-containing mixed atmosphere.

5. The preparation method according to claim 2, characterized in that: The boron-containing mixed atmosphere also includes inert gas.

6. The preparation method according to claim 2, characterized in that: The first cross-linking method includes any one of electron beam irradiation cross-linking, air cross-linking, and ultraviolet cross-linking, or a combination of the two.

7. The preparation method according to claim 2, characterized in that: The preparation method of the organic fiber containing Ti, Si and C elements is as follows: Polycarbosilane and tetrabutyl titanate are dissolved in an organic solvent, which is then placed in a reaction vessel, and the temperature is raised from room temperature to above 200°C and kept warm in a nitrogen atmosphere. After the reaction is completed, the reaction is cooled to room temperature, and the obtained liquid is filtered to remove the organic solvent therein by vacuum distillation, and then cooled to room temperature to obtain a precursor. The precursor is spun, oxidized in an air atmosphere, or cross-linked for the first time by electron beam irradiation to obtain an organic fiber containing Ti, Si and C elements.

8. The preparation method according to claim 7, characterized in that: The spinning includes any one of melt spinning, electrostatic spinning, centrifugal spinning, air spinning, dry spinning and wet spinning.

9. The preparation method according to claim 7, characterized in that: The mass ratio of the polycarbosilane to tetrabutyl titanate is in the range of (50:1)-(10:1).

10. An application of the SiC / TiB2 ceramic fiber as claimed in claim 1, characterized in that: Used in high-performance ceramic-based composite materials that can withstand ultra-high temperatures of 2000°C.

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