A multi-component ultra-high temperature ceramic fiber and a method of making the same

Abstract

A kind of multi-component ultra-high temperature ceramic fiber and its preparation method, belong to continuous ultra-high temperature ceramic fiber preparation technical field.Different from the method for preparing ultra-high temperature ceramic fiber by using the blend of silicon-based ceramic precursor and ultra-high temperature metal component precursor as raw material, the preparation method of the ultra-high temperature metal component precursor can realize the uniform dispersion of multi-component, and the refractory metal component content in the precursor is high, which can effectively improve the temperature resistance grade of the fiber and the high-temperature mechanical properties, oxidation resistance and other properties.The non-fusible treatment of fiber precursor is realized by using a combination of various pre-crosslinking methods, effectively solving the problems of difficult non-fusible treatment of fiber precursor caused by low softening point and few active groups of the precursor, and difficult to obtain shaped ceramic fiber.The ultra-high temperature ceramic fiber prepared by the present application has excellent high-temperature mechanical properties and oxidation resistance, and can be used as a reinforcing material for ultra-high temperature ceramic fiber reinforced ceramic matrix composites.

Description

Technical Field

[0001] This invention relates to novel continuous ultra-high temperature ceramic fibers and their preparation methods, belonging to the field of continuous ultra-high temperature ceramic fiber preparation technology. Background Technology

[0002] Oxygen-free ultra-high temperature ceramic fibers possess excellent properties such as low density, high temperature resistance, long-term oxidation resistance, and high strength. They are key basic materials for preparing long-term oxidation-resistant ultra-high temperature ceramic matrix composites and have broad application prospects in aerospace, aviation, weaponry, shipbuilding and other fields. They are one of the key strategic materials for the development of high-tech weapons and equipment as well as aviation and aerospace industries.

[0003] Currently, the most mature and industrially produced oxygen-free ultra-high temperature ceramic fibers are SiC fibers prepared using the organic precursor conversion method. SiC fibers have evolved into three generations. The first generation of SiC fibers are oxygen-containing ceramic fibers (mainly represented by Nicalon 2000 and Tyranno LOX-M, with a relatively high oxygen content of approximately 10-13%). The second generation of SiC fibers are mainly oxygen-free ceramic fibers represented by Hi-Nicalon and Ube Industries' Tyranno LOX-E and Tyranno ZM. The third generation of SiC fibers are near-stoichiometric SiC fibers, mainly including Nippon Carbon's Hi-Nicalon Type S, Ube Industries' Tyranno SA, and Dow Corning's Sylranic fibers. Research shows that introducing ultra-high temperature metal elements and B and N elements into SiC fibers can effectively improve their high-temperature stability and oxidation resistance, thereby increasing the temperature resistance of Si-based ceramic fibers. The main method for introducing metal elements is to react oxygen-containing organometallic compounds with Si-based ceramic precursors containing Si-H bonds to form metal-containing organic polymers. Due to the limitations of the metal introduction method and the performance of the precursor spinning process, the amount of these metal elements introduced is usually no more than 3% by weight, making it difficult to form multiphase ceramic fibers with high metal doping content. Summary of the Invention

[0004] The technical problem solved by this application is to overcome the shortcomings of the prior art and provide a multi-component ultra-high temperature ceramic fiber and its preparation method. A novel preparation method for a precursor containing ultra-high temperature metal components is designed. The ceramic precursor is prepared by combining catalytic polymerization reaction and aminolysis reaction. This method can not only achieve uniform dispersion of multi-components, but also has a high content of refractory metal components in the precursor, which can effectively improve the temperature resistance and high-temperature mechanical and antioxidant properties of the fiber.

[0005] Another objective of this invention is to provide an efficient pre-crosslinking treatment method for precursor fibers with low softening points, thereby obtaining high-performance non-melting fibers. This effectively solves the problem of difficulty in non-melting treatment of fiber precursor fibers and difficulty in obtaining shaped ceramic fibers caused by the low softening point and few active groups of such precursors.

[0006] Another objective of this invention is to provide a novel method for preparing multi-component ultra-high temperature ceramic fibers. Through the design and control of processes such as the preparation of spinnable ultra-high temperature ceramic precursors, melt spinning, pre-crosslinking treatment, and high-temperature sintering, continuous ultra-high temperature ceramic fibers can be prepared.

[0007] The technical solution provided in this application is as follows:

[0008] A multi-component ultra-high temperature ceramic fiber and its preparation method, comprising the following steps:

[0009] S1: A ceramic precursor containing Si, B, C, N and M elements is added to a melt spinning tank. The material is heated to 150-250℃ to melt into a homogeneous liquid. The pressure is increased to 0.4-1MPa for melt spinning to obtain fiber filaments, wherein M is one of Hf, Ti and Zr elements.

[0010] S2: Pre-crosslink the fiber filaments to obtain non-melting fiber filaments;

[0011] S3: The pre-crosslinked fiber filaments are subjected to non-melting treatment to obtain non-melting fiber filaments;

[0012] S4: Under an inert atmosphere, the fiber filaments are ceramicized by heating to 800-2000℃ at a heating rate of 0.1-5℃ / min, and finally ceramic fibers are obtained.

[0013] The obtained ceramic fiber composition contains Si, B, C, N and M elements, wherein M is one of Hf, Ti or Zr.

[0014] The pre-crosslinking treatment in step S2 is performed by UV curing crosslinking.

[0015] The conditions for UV curing crosslinking are as follows: during the UV curing process, the intensity of the UV light is 40-90 mW / cm². 3 Irradiation time: 1 min - 10 min.

[0016] The non-melting treatment in step S3 includes cross-linking with active gas or cross-linking by electron beam radiation.

[0017] By first performing partial pre-crosslinking and then undergoing non-melting treatment, the degree of crosslinking of the fiber is improved.

[0018] The synthesis steps of the ceramic precursor containing Si, B, C, N, and M elements are as follows:

[0019] (1) Add dihalogenated metallocene and metallic sodium in an organic solvent in proportion. Add organic dihalogenated silane dropwise to the system at 80-150℃ to carry out catalytic polymerization reaction. Then remove the precipitate in the reaction system to obtain solution 1.

[0020] (2) Boron trichloride gas is passed into solution 1 to obtain solution 2, and nitrogen-containing compounds are slowly added to solution 2. After stirring thoroughly, the temperature is raised to 150-250℃ to carry out aminolysis reaction, and the solvent and small molecule by-products formed during the synthesis process are removed to obtain the final product.

[0021] The dihalogenated metallocene is selected from hafnium dichlorodecene or dichlorodisubstituted cyclopentadienyl hafnium; the sodium metal is sodium metal; the organic solvent is selected from at least one of n-hexane, tetrahydrofuran, petroleum ether, toluene or xylene; the organic dihalogenated silane is at least one of dimethyldichlorosilane, methylethyldichlorosilane, methylphenyldichlorosilane or chloromethylvinyldichlorosilane.

[0022] The nitrogen-containing compound is one or more of ammonia, n-propylamine, and hexamethyldisilazane.

[0023] The molar ratio of hafnium dichlorocerocene to sodium metal is 1:5 to 1 to 1:12, the molar ratio of dimethyldichlorosilane to hafnium dichlorocerocerocene is 2:1 to 10:1, and the molar ratio of boron trichloride to hafnium dichlorocerocerocene is 1:1 to 5:1.

[0024] In the above preparation method, under the action of metallic sodium, dihalogenated metallocene and organo-based dihalosilane undergo sodium condensation reaction to obtain SiCM precursor; boron trichloride reacts with nitrogen-containing compounds to obtain (Si)BCN precursor; after heating, SiCM precursor and (Si)BCN precursor undergo aminolysis reaction to obtain ceramic precursor.

[0025] In summary, this application includes at least the following beneficial technical effects:

[0026] (1) The present invention provides a method for preparing ultra-high temperature multi-component ceramic fibers. The method combines catalytic polymerization reaction and aminolysis reaction to prepare multi-component ultra-high temperature ceramic fibers. Improvements are made in many aspects such as molecular structure design, synthesis process control and feed ratio regulation, so that the refractory metal component content in the precursor is high, the components are evenly dispersed, the molecular weight is controllable, and the spinning process performance is good. Compared with the prior art, it can effectively improve the temperature resistance of ceramic fibers.

[0027] (2) The present invention provides a method for preparing ultra-high temperature multi-component ceramic fibers. The method of first using ultraviolet light curing to improve the cross-linking degree of the fiber precursor and then performing cross-linking treatment in an active atmosphere can effectively improve the cross-linking degree of the fiber precursor and avoid the problem that the fiber precursor prepared by melt spinning is easy to melt at a low temperature due to the low softening point of the precursor, making it difficult to maintain the fiber shape.

[0028] (3) The content of refractory metal hafnium in the ceramic fiber prepared by this invention can reach 40wt%. By utilizing the various active groups in the prepared precursor and employing various pre-crosslinking treatment methods, the fiber filaments can be fully infusible, which can effectively avoid fiber fusion during the ceramicization process. Attached Figure Description

[0029] Figure 1 These are microscopic morphological photographs of the fiber precursor in Example 1 of this invention;

[0030] Figure 2 This is the XRD pattern of the ceramic fiber in Embodiment 1 of the present invention;

[0031] Figure 3 These are microscopic morphological photographs of the fiber precursor in Example 2 of this invention;

[0032] Figure 4 This is the XRD pattern of the ceramic fiber in Embodiment 2 of the present invention;

[0033] Figure 5 This is an HRTEM image of ceramic fibers in Embodiment 2 of the present invention.

[0034] Figure 6 This is a macroscopic photograph of the ceramic fiber in Comparative Example 1 of this invention. Detailed Implementation

[0035] The present application will be further described in conjunction with the following embodiments and accompanying drawings.

[0036] Example 1

[0037] In this embodiment, a multi-component ultra-high temperature ceramic fiber and its preparation method are as follows:

[0038] (1) A ceramic precursor containing Si, B, C, N, and Hf elements with a softening point of 80℃ was added to a melt spinning tank. The material was heated to 150℃ to melt into a homogeneous liquid. After holding at this temperature for 1 hour, the pressure was increased to 0.5 MPa for melt spinning to obtain fiber precursors. The microstructure of the obtained fiber precursors is as follows: Figure 1 As shown, the obtained precursor fiber has a smooth surface and a fiber diameter of approximately 18 μm.

[0039] The preparation method of the above-mentioned ceramic precursor is as follows: hafnium dichlorodecane and metallic sodium are added to xylene solvent in a molar ratio of 1:7. Methylvinyl dichlorosilane is slowly added dropwise to the system at 90°C to carry out a catalytic polymerization reaction, wherein the molar ratio of dimethyl dichlorosilane to hafnium dichlorodecane is 4:1, and the reaction time is 4 hours. After that, the precipitate in the reaction system is removed to obtain solution 1. Boron trichloride gas is passed into solution 1 to obtain solution 2, wherein the molar ratio of boron trichloride to hafnium dichlorodecane is 2:1. Ammonia gas is slowly passed into solution 2 until the gas overflowing from the system is measured to be neutral or weakly alkaline. After thorough stirring, the temperature is raised to 200°C to carry out an aminolysis reaction for 2 hours. Finally, the solvent and small molecule by-products formed during the synthesis process are removed to obtain the final product.

[0040] (2) The obtained fiber filaments were subjected to pre-crosslinking treatment under ultraviolet light with an intensity of 50 mW / cm². 3 The irradiation time was 5 minutes, and the pre-crosslinked fiber filaments were obtained after pre-crosslinking treatment. The pre-crosslinked fiber filaments were then placed in an NH3 atmosphere at 250℃ for further crosslinking treatment and kept at the temperature for 4 hours to finally obtain non-melting fibers.

[0041] (3) Under an inert atmosphere, the fiber filaments are heated to 1200℃ at a heating rate of 1℃ / min to ceramicize them, and finally ceramic fibers are obtained.

[0042] The Hf element content in the fiber was determined to be 32% by ICP method, and the diameter of the final ceramic fiber was approximately 12 μm. Figure 2 The image shows an XRD pattern of the fiber, revealing HfC microcrystals precipitated within it.

[0043] Example 2

[0044] In this embodiment, a multi-component ultra-high temperature ceramic fiber and its preparation method are as follows:

[0045] (1) A ceramic precursor containing Si, B, C, N, and Hf elements with a softening point of 100℃ was added to a melt spinning tank. The material was heated to 170℃ to melt into a homogeneous liquid. After holding at this temperature for 1 hour, the pressure was increased to 0.6 MPa for melt spinning to obtain fiber precursors. The microstructure of the obtained fiber precursors is as follows: Figure 3 As shown, the obtained precursor fiber has a smooth surface and a fiber diameter of approximately 20 μm.

[0046] The preparation method of the above-mentioned ceramic precursor is as follows: hafnium dichlorodecane and metallic sodium are added to xylene solvent in a molar ratio of 1:7. Dimethyldichlorosilane is slowly added dropwise to the system at 90°C to carry out a catalytic polymerization reaction, wherein the molar ratio of dimethyldichlorosilane to hafnium dichlorodecane is 4:1, and the reaction time is 4 hours. After that, the precipitate in the reaction system is removed to obtain solution 1. Boron trichloride gas is passed into solution 1 to obtain solution 2, wherein the molar ratio of boron trichloride to hafnium dichlorodecane is 2:1. Ammonia gas is slowly passed into solution 2 until the gas overflowing from the system is measured to be neutral or weakly alkaline. After thorough stirring, the temperature is raised to 200°C to carry out an aminolysis reaction for 2 hours. Finally, the solvent and small molecule by-products formed during the synthesis process are removed to obtain the final product.

[0047] (2) The obtained fiber filaments were subjected to pre-crosslinking treatment under ultraviolet light with an intensity of 60 mW / cm². 3 The irradiation time was 5 minutes, and the pre-crosslinked fiber filaments were obtained after pre-crosslinking treatment. The pre-crosslinked fiber filaments were then placed in an NH3 atmosphere at 250℃ for further crosslinking treatment and kept at the temperature for 4 hours to finally obtain non-melting fibers.

[0048] (3) Under an inert atmosphere, the fiber filaments are heated to 1400℃ at a heating rate of 1℃ / min to ceramicize them, and finally ceramic fibers are obtained.

[0049] The Hf element content in the fiber was determined to be 28% by ICP method, and the diameter of the final ceramic fiber was approximately 14 μm. Figure 4 The image shows an XRD pattern of the fiber, revealing HfC microcrystals precipitated within it. Figure 5 This is a high-resolution transmission electron microscope image of the fiber, showing HfC microcrystals embedded in the ceramic matrix within the ceramic fiber.

[0050] Example 3

[0051] The only difference from Example 1 is that the molar ratio of dimethyldichlorosilane to hafnium dichlorocerocene is 2:1.

[0052] The Hf element content in the fiber was found to be 44% by ICP method, and the diameter of the final ceramic fiber was about 10 μm.

[0053] Example 4

[0054] The only difference from Example 1 is that the molar ratio of dimethyldichlorosilane to hafnium dichlorocerocene is 10:1.

[0055] The Hf element content in the fiber was determined to be 19% by ICP method, and the diameter of the final ceramic fiber was about 15 μm.

[0056] Comparative Example 1

[0057] The only difference from Example 1 is that the fiber filaments obtained in step (1) were not pre-crosslinked, and the fiber filaments obtained in step (1) were directly placed in an NH3 atmosphere at 250°C for crosslinking treatment for 4 hours, and finally non-melting fibers were obtained.

[0058] The other steps are the same as in Example 1.

[0059] The resulting fibers have fused together, making it impossible to measure the fiber diameter. Figure 6 Photographs showing the fusion of ceramic fibers during firing.

[0060] Comparative Example 2

[0061] The only difference from Example 1 is that the molar ratio of dimethyldichlorosilane to hafnium dichlorocerocene is 1:1. The Hf content in the fiber was determined to be 46% by ICP, and the diameter of the final ceramic fiber was approximately 10 μm.

[0062] In Examples 3, 1, and 4, the molar ratio of dimethyldichlorosilane to hafnium dichlorocerocene gradually increases, the Hf / Si ratio gradually decreases, and the Hf content in the resulting fibers gradually decreases. However, within the ratio range given in the claims, ceramic fibers with high refractory metal content can still be obtained, which is beneficial for improving the temperature resistance of the fibers.

[0063] The difference between Example 1 and Comparative Example 1 is that Example 1 underwent pre-crosslinking before the non-melting treatment, which avoided the fiber fusion problem caused by the low softening point of the precursor, resulting in ceramic fibers with good shape and excellent performance. In Comparative Example 1, the ceramic fibers obtained without UV-cured pre-crosslinking of the precursor fused together and could not maintain their shape.

[0064] The difference between Example 1 and Comparative Example 2 is that the hafnium dichlorocerocene feed ratio was too high in Comparative Example 2, while the Hf element content in the sintered fiber only increased by 2%. An excessively high metallocene feed ratio not only fails to increase the content of ultra-high temperature metal components in the SiCM precursor but also wastes raw materials, significantly increasing synthesis costs.

[0065] The present application has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present application. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and implementation methods of the present application without departing from the spirit and scope of the present application, and all such modifications and improvements fall within the scope of the present application. The scope of protection of the present application is determined by the appended claims.

[0066] The contents not described in detail in this application specification are common knowledge to those skilled in the art.

Claims

1. A method for preparing multi-component ultra-high temperature ceramic fibers, characterized in that, include: S1: A ceramic precursor containing elements Si, B, C, N and M is melted and melt-spun to obtain fiber filaments, wherein M is one of Hf, Ti or Zr. S2: Pre-crosslink the fiber filaments to obtain pre-crosslinked fiber filaments; S3: The pre-crosslinked fiber filaments are subjected to non-melting treatment to obtain non-melting fiber filaments; S4: Ceramicizing the infusible fiber filaments to obtain ceramic fibers; In step S1, the method for preparing the ceramic precursor includes: (1) Add dihalogenated metallocene and sodium metal to an organic solvent, and add organic dihalogenated silane dropwise to the system at 80~150℃ to carry out catalytic polymerization reaction. Then remove the precipitate in the reaction system to obtain solution 1. (2) Boron trichloride gas is passed into solution 1 to obtain solution 2, and nitrogen-containing compounds are slowly added to solution 2. After thorough stirring, the temperature is raised to 150~250℃ to carry out aminolysis reaction, remove solvent and small molecule by-products formed during the synthesis process to obtain ceramic precursor; The dihalogenated metallocene, wherein the metal is one of Hf, Ti or Zr; The organic solvent is selected from n-hexane, tetrahydrofuran, petroleum ether, toluene, or xylene; The organo-based dihalosilane is selected from dimethyl dihalosilane, methyl ethyl dihalosilane, methyl phenyl dihalosilane, or chloromethyl vinyl dihalosilane; The nitrogen-containing compound is selected from ammonia, n-propylamine, or hexamethyldisilazane; In step S2, the pre-crosslinking treatment uses ultraviolet light curing crosslinking, with an ultraviolet light intensity of 40-90 mW / cm². 3 Irradiation time: 1 min - 10 min; In step S4, the ceramization treatment includes heating to 1200~2000℃ at a heating rate of 0.1-5℃ / min under an inert atmosphere.

2. The method for preparing multi-component ultra-high temperature ceramic fibers according to claim 1, characterized in that: In step S1, the ceramic precursor is added to a melt spinning tank, the material is heated to 150~250℃ to melt into a homogeneous liquid, and then pressurized to 0.4~1MPa for melt spinning.

3. The method for preparing multi-component ultra-high temperature ceramic fibers according to claim 1, characterized in that: In step S3, the non-melting treatment employs active gas crosslinking or electron beam radiation crosslinking.

4. The method for preparing multi-component ultra-high temperature ceramic fibers according to claim 1, characterized in that: The molar ratio of the dihalogenated metallocene to sodium metal is 1:5 to 1:12, and the molar ratio of the organo-based dihalogenated silane to the dihalogenated metallocene is 2:1 to 10:

1.

5. The method for preparing multi-component ultra-high temperature ceramic fibers according to claim 1, characterized in that: The molar ratio of boron trichloride to dihalogenated metallocene is 1:1 to 5:

1.

6. A multi-component ultra-high temperature ceramic fiber, characterized in that: The multi-component ultra-high temperature ceramic fiber is prepared according to any one of claims 1-5.

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