A storage-stable metal-modified polycarbosilane precursor, and a method of making and using the same

Abstract

The application belongs to the technical field of novel ceramic material preparation, and particularly discloses an easily-stored metal-modified polycarbosilane precursor, a preparation method and application thereof. On the basis of boron-modified polycarbosilane, a plurality of metal elements are further introduced to modify the polymer precursor, the raw materials used are low in cost, the synthesis process is mild, the introduction amount of the metal elements is flexibly adjustable, the production can be easily enlarged, the obtained polymer precursor can be stored at room temperature for a long time, and is not prone to water absorption and damp. Furthermore, the composite material prepared by using the metal-modified polymer precursor can ensure the introduction of the metal elements into the matrix without introducing new defects, the properties of each part of the ceramic matrix are uniform and stable, and the good and stable mechanical properties of the composite material are ensured; compared with the unmodified ceramic matrix in the oxidation environment, the introduction of boron and metal elements enables the matrix to form an oxide sealing phase at a gradiently increased temperature, so as to prevent the invasion of oxidation medium such as water and oxygen, and protect the fibers and the interface from erosion.

Description

Technical Field

[0001] This invention belongs to the field of novel ceramic material preparation technology, specifically relating to an easily stored metal-modified polycarbosilane precursor, its preparation method, and its application. Background Technology

[0002] Ceramic matrix composites have broad application prospects in the field of aerospace thermal structure materials due to their excellent properties such as low density, high strength, and resistance to high temperatures and corrosion. However, binary ceramic systems, represented by silicon carbide ceramics, cannot provide effective protection over a wide temperature range when used as the matrix of composite materials. Their thermal shock performance at peak temperatures is insufficient to meet the requirements of aircraft operating on multiple flights. This is mainly because silicon carbide-based composites inevitably contain defects such as pores. Oxidizing media such as oxygen and water can diffuse through these channels to the interfaces and fibers of the composite material, causing oxidative damage and degradation of the silicon carbide fibers and their interface layers. Since fibers and interfaces are the load-bearing and load-transfer units of the composite material, their damage directly leads to a decline in the composite material's performance and a shortened service life.

[0003] Existing literature reports that introducing multiple high-melting-point metal elements into a silicon carbide ceramic matrix gradually forms various oxides under progressively increasing oxidation temperatures, creating a gradient glassy protective layer. This can seal the pores of the composite material over a wide temperature range, effectively protecting it and significantly expanding its operating temperature range, thus achieving the goal of reusable ceramic matrix composites. However, existing reports typically employ simple physical mixing methods to introduce inorganic compounds such as metal carbides, or use expensive organic materials to synthesize precursors under harsh conditions. Furthermore, the resulting precursors are hygroscopic and inconvenient to store.

[0004] Precursor conversion (also known as precursor pyrolysis or precursor polymer impregnation pyrolysis) is a process for preparing ceramic matrix composites that has emerged in recent decades. This method has advantages such as simple molding processes and low preparation temperatures. Furthermore, the ceramic products obtained through the pyrolysis of liquid precursor solutions exhibit uniform composition and can be controlled at the atomic / molecular scale. Chinese patent CN115180950B (Central South University, Wang Yalei's team) utilizes the precursor conversion method to convert single-source precursors (such as (Ti, Zr, Hf)C / SiC ceramic precursors) prepared from multiple metal element complexes (such as tetrakis(dimethylamino) metal salts and tetrakis(diethylamino) metal salts) into multi-element carbide / silicon carbide nanocomposite ceramic powders at high temperatures. This effectively solves the problems of multi-element single-phase solid solution, uneven distribution of nano-ceramic phases, and grain coarsening, significantly improving the mechanical properties and oxidation and ablation resistance of the composite material. However, this method uses high-cost raw materials and carries significant safety risks in the synthesis process, making it difficult to scale up production.

[0005] In summary, there are currently few safe, low-cost, and mild methods for preparing mono-source multi-metal-doped modified polycarbosilane precursors. There is an urgent need to develop a method for preparing metal-modified polycarbosilane precursors that is simple in preparation steps, mild in conditions, easy to control, and low in cost, while improving the storage stability of mono-source polymer precursors. Summary of the Invention

[0006] The main technical problem solved by this invention is to provide a method for preparing metal-modified polycarbosilane precursors. Compared with existing methods, the raw materials used are inexpensive, the synthesis process is mild, the operation is simple, the amount of metal element introduced is flexible and adjustable, and the prepared single-source multi-metal modified polymer precursor can be stored at room temperature for a long time and is not easily absorbing water and moisture.

[0007] Meanwhile, this invention provides a metal-modified polycarbosilane precursor and its application.

[0008] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is as follows:

[0009] A method for preparing an easily storable metal-modified polycarbosilane precursor includes the following steps:

[0010] (Solid) boron-modified polycarbosilane was dissolved in a solvent to obtain a solution;

[0011] A metal alkoxide and a metallocerochlore were added to the solution, and the mixture was heated under a protective atmosphere to obtain a metal-modified polycarbosilane precursor.

[0012] This invention uses (solid) boron-modified polycarbosilane as a raw material. After preparing a solution, (sec-)butoxide and dichlorodicyclopentadiene salts of the corresponding metals are added to the solution according to the desired metal content. The reaction is carried out under a protective atmosphere until the solution becomes clear and transparent, yielding a multi-metal-doped polycarbosilane precursor. The single-source multi-metal modified polymer precursor prepared by this method has the characteristics of adjustable metal element content in derived ceramics and excellent high-temperature oxidation resistance. The prepared solution is suitable as an impregnating agent for the PIP process to prepare metal-modified ceramic matrix composites or ceramic matrix coatings. The method of this invention has simple preparation steps, mild conditions, convenient control, and low cost, making it easy to scale up and apply.

[0013] As a preferred embodiment of the present invention, the boron-modified polycarbosilane is prepared using the method disclosed in patent CN114957675B (China Aviation Manufacturing Research Institute), or the method disclosed in other (patent or non-patent) documents.

[0014] Specifically, the preparation method of the boron-modified polycarbosilane includes the following steps:

[0015] (1) Prepare an organic solution of solid polycarbosilane (PCS);

[0016] The mass concentration of solid polycarbosilane in the solution is 10-80 wt%.

[0017] The organic solvent is a hydrocarbon solvent or an ether solvent;

[0018] (2) Under an inert atmosphere, the organic solution and hexamethyldisilazane monomer are simultaneously added dropwise to the boron trichloride organic solution to carry out the reaction;

[0019] Boron trichloride can be used in hydrocarbon solvents or ether solvents;

[0020] The reaction is divided into an initial stage and a stable stage. For either the organic solution or the hexamethyldisilazane monomer, the dropping rate in the initial stage is lower than that in the stable stage. In the initial stage, a white mist-like byproduct is generated. The reaction temperature is controlled at -20 to 10°C using a cooling device. After the mist-like byproduct disappears, the stable stage begins. The dropping rate is increased, and the reaction temperature is controlled at 10 to 90°C.

[0021] (3) The mixture after the reaction is subjected to vacuum distillation to obtain a porous solid material;

[0022] The temperature for vacuum distillation is 20-250℃;

[0023] (4) The porous solid material is broken into powder by external force, which is boron modified polycarbosilane powder.

[0024] Specifically, the hydrocarbon solvent is selected from one or more of xylene, n-hexane, n-heptane, etc. The ether solvent is selected from one or more of tetrahydrofuran, 2-methyl-tetrahydrofuran, butyl ether, etc. Other preparation conditions and parameters can be found in patent CN114957675B.

[0025] In a preferred embodiment of the present invention, the solvent is selected from one or more of N,N-dimethylformamide, xylene, n-hexane, diethylene glycol dimethyl ether, toluene, tetrahydrofuran, etc.

[0026] In a preferred embodiment of the present invention, the mass concentration of boron-modified polycarbosilane in the solution is 10-80 wt%, preferably 40-60 wt%.

[0027] In a preferred embodiment of the present invention, the metal alkoxide is selected from one or more of titanium n-butoxide, aluminum sec-butoxide, zirconium n-butoxide, and hafnium n-butoxide.

[0028] Specifically, the amount of the metal alkoxide added is 1-30 wt% of the mass of the boron-modified polycarbosilane, preferably 5-20 wt%.

[0029] In a preferred embodiment of the present invention, the dichlorodicyclopentene metal is selected from one or more of dichlorodicyclopentene titanium, dichlorodicyclopentene zirconium, dichlorodicyclopentene hafnium, etc.

[0030] Specifically, the amount of dichlorodicyclopentene added is 1-30 wt% of the mass of boron-modified polycarbosilane, preferably 10-25 wt%.

[0031] In a preferred embodiment of the present invention, the heating reaction temperature is controlled at 60-150°C, and the reaction time is 0.5-12 hours. Preferably, the reaction is carried out at 80-120°C for 2-6 hours.

[0032] Specifically, the heating reaction is carried out under stirring conditions. At the beginning of the reaction, the solution is turbid and contains obvious insoluble matter. As the reaction continues, the insoluble matter gradually dissolves, and the solution eventually becomes clear and transparent. After heating and stirring are stopped and the solution is cooled to room temperature, it remains clear and transparent, thus obtaining the metal-modified polycarbosilane precursor solution.

[0033] In a preferred embodiment of the present invention, after the heating reaction is completed, the solvent is removed from the reaction product to obtain (fluffy and crispy) metal-modified polycarbosilane precursor powder.

[0034] Specifically, the solvent removal is performed using a rotary evaporation system, with the heating temperature controlled at 60-150℃, preferably 80-120℃, until no liquid evaporates.

[0035] A metal-modified polycarbosilane precursor prepared by the above method.

[0036] Applications of a metal-modified polycarbosilane precursor, including but not limited to one or more of the following:

[0037] (1) Application in the preparation of ceramic matrix composites;

[0038] (2) Application in the preparation of ceramic-based coatings;

[0039] (3) Application in the preparation of ceramic fibers;

[0040] (4) Application in the preparation of bulk ceramics.

[0041] As a preferred embodiment of the present invention, the application includes the following steps:

[0042] The metal-modified polycarbosilane precursor is dissolved in a solvent to obtain a solution; or the metal-modified polycarbosilane precursor solution without removing the solvent is used directly.

[0043] Using a metal-modified polycarbosilane precursor solution as an impregnating agent, ceramic matrix composites or ceramic matrix coatings are prepared by a precursor polymer impregnation-pyrolysis (PIP) process.

[0044] Specifically, the solvent is selected from one or more of N,N-dimethylformamide, xylene, n-hexane, diethylene glycol dimethyl ether, toluene, tetrahydrofuran, etc.

[0045] Specifically, the mass concentration of the metal-modified polycarbosilane precursor in the solution is 10-80 wt%, preferably 40-60 wt%.

[0046] Specifically, the pyrolysis temperature of the PIP process is above 800°C.

[0047] As a preferred embodiment of the present invention, the application further includes the following steps:

[0048] A second phase is introduced during the preparation process to enhance and toughen ceramic matrix composites or ceramic matrix coatings.

[0049] Specifically, the raw materials used to introduce the second phase include, but are not limited to, one or more of nanoparticles, whiskers, and fibers.

[0050] The beneficial effects of this invention are:

[0051] This invention, based on (solid) boron-modified polycarbosilane, further introduces multiple metal-modified polymer precursors. The raw materials used are inexpensive, safe, and reliable; the synthesis process is mild and simple; the amount of metal elements introduced is flexibly adjustable, facilitating large-scale production. Furthermore, the prepared polymer precursors can be stored at room temperature for extended periods without absorbing moisture. Composite materials prepared using this single-source multi-metal modified polycarbosilane precursor ensure that the introduction of metal elements into the matrix does not introduce new defects. The ceramic matrix exhibits uniform and stable properties, guaranteeing excellent and stable basic mechanical properties of the composite material. In oxidizing environments, compared to unmodified ceramic matrices, the introduction of boron (B) and other metal elements allows the matrix to gradually form multiple oxide blocking phases at progressively increasing temperatures. This prevents the intrusion of oxidizing media such as water and oxygen, protecting fibers and interfaces from corrosion and improving the high-temperature oxidation resistance of the ceramic matrix composite material.

[0052] Compared with the prior art, the present invention has the following advantages:

[0053] (1) The reaction raw materials used in this invention are all common commercial chemical raw materials, which are readily available and have low unit prices.

[0054] (2) The present invention uses boron-modified polycarbosilane with fewer active groups as the base raw material. The preparation operation is simple and the conditions are mild, which is conducive to large-scale production.

[0055] (3) The amount of metal element introduced in the preparation of metal-modified polycarbosilane by the present invention can be flexibly adjusted by the feeding ratio. The prepared metal-modified polycarbosilane is suitable for a variety of common organic solvents, such as xylene, toluene, tetrahydrofuran, etc., and is easy to prepare into precursor solutions.

[0056] (4) The metal-modified polycarbosilane precursor powder prepared by the present invention can be stored at room temperature for a long time, is not easy to absorb water and moisture, has stable properties, and is easy to store and transport.

[0057] (5) The precursor solution prepared by the metal-modified polycarbosilane of the present invention can be used as an impregnating agent for preparing ceramic matrix composites and is suitable for preparing metal-modified silicon carbide ceramic matrix composites by PIP process. Attached Figure Description

[0058] Figure 1 This is a photograph of the metal-modified polycarbosilane precursor powder in the experimental example after it has been left to stand for 2 months.

[0059] Figure 2 This is a photograph of the product obtained by pyrolyzing the metal-modified polycarbosilane precursor solution at 1200℃ in the experimental example.

[0060] Figure 3 The images show SEM images and EDS-mapping area scan images of the products obtained by pyrolyzing the metal-modified polycarbosilane precursor solution at 1200℃ in the experimental example.

[0061] To more clearly illustrate the technical solution protected by this invention, the accompanying drawings in the embodiments and / or experimental examples have been briefly described above. It should be understood that the above drawings should not be construed as any limitation on the scope of protection of this invention. Detailed Implementation

[0062] The technical solution of the present invention will be described in detail below through specific embodiments. These embodiments are intended to further illustrate the content of the present invention, but are not intended to limit the scope of protection of the claims of the present invention.

[0063] Unless otherwise specified in the following examples and experimental cases, the raw materials, reagents, instruments and equipment used are all commercially available products.

[0064] Example 1

[0065] This embodiment provides an easily storable metal-modified polycarbosilane precursor and its preparation method, including the following steps:

[0066] (1) Preparation of boron-modified polycarbosilane powder

[0067] Boron-modified polycarbosilane powder was prepared using the method described in Example 1 of patent CN114957675B, comprising the following steps:

[0068] Prepare an organic solution of 20g solid polycarbosilane (PCS), with a polycarbosilane mass concentration of 50wt% and n-hexane as the organic solvent;

[0069] Under an inert atmosphere, 4.0 g of hexamethyldisilazane monomer was first added to an organic solution and stirred until homogeneous to obtain a mixed solution. Under an inert atmosphere, the mixed solution was added dropwise to 10 ml of an organic solution of boron trichloride with a concentration of 1 mol / L, and dimethane was used as the solvent for the reaction. The reaction was divided into an initial stage and a steady stage. The dropwise rate in the initial stage was slower than that in the steady stage. The reaction temperature in the initial stage was controlled at 0-5℃. A white mist-like byproduct was produced in the initial stage. After the mist-like byproduct disappeared, the steady stage began. The dropwise rate was increased and the reaction temperature was controlled at 30-40℃. The two stages were carried out for a total of 24 h.

[0070] The mixture after the reaction was subjected to vacuum distillation at a temperature controlled at 100±5℃ to obtain a porous solid material.

[0071] Boron-modified polycarbosilane powder is produced by crushing and breaking solid materials into powder using external force.

[0072] (2) Preparation of metal-modified polycarbosilane precursors

[0073] Prepare 200g of xylene solution of boron-modified polycarbosilane with a mass concentration of 50wt%;

[0074] Weigh 15g of aluminum sec-butoxide and 12g of zirconium dichlorocerocene; under a nitrogen atmosphere, add solid zirconium dichlorocerocene and liquid aluminum sec-butoxide sequentially to the above solution, and heat while stirring. The reaction temperature is set at 90℃. As the reaction proceeds, the solution gradually changes from turbid to clear and transparent after 5 hours. The solution is rotary evaporated at 100℃ for 3 hours to obtain solid metal-modified polycarbosilane precursor powder.

[0075] This embodiment provides an application of a metal-modified polycarbosilane precursor in the preparation of ceramic matrix composites, comprising: dissolving the metal-modified polycarbosilane precursor in a solvent (xylene) to obtain a precursor solution (mass concentration of 50%), using the precursor solution as an impregnating agent, placing a 2D carbon fiber preform in the impregnating agent for vacuum impregnation for 24 hours, preparing fiber-reinforced ceramic matrix composites by PIP process, assembling the mold, and then performing high-temperature pyrolysis at 1200°C for 2 hours under vacuum in a pyrolysis furnace, with the PIP process being repeated 12 times.

[0076] Example 2

[0077] This embodiment provides an easily storable metal-modified polycarbosilane precursor and its preparation method, including the following steps:

[0078] (1) Preparation of boron-modified polycarbosilane powder

[0079] The preparation method of boron-modified polycarbosilane powder is the same as in Example 1.

[0080] (2) Preparation of metal-modified polycarbosilane precursors

[0081] Prepare 200g of xylene solution of boron-modified polycarbosilane with a mass concentration of 50wt%;

[0082] Weigh out 10g of aluminum sec-butoxide, 7g of titanium dicene dichlorodichlorodichlorodichlorodichlorodichlorodizirconia; under a nitrogen atmosphere, add the solid titanium dicene dichlorodichlorodichlorodichlorodichlorodichlorodizirconia and liquid aluminum sec-butoxide sequentially to the above solution, and heat while stirring. The reaction temperature is set at 110℃. As the reaction proceeds, the solution gradually changes from turbid to clear and transparent after 4 hours. The solution is rotary evaporated at 80℃ for 4 hours to obtain solid metal modified polycarbosilane precursor powder.

[0083] This embodiment provides an application of a metal-modified polycarbosilane precursor in the preparation of a ceramic-based coating, comprising: dissolving the metal-modified polycarbosilane precursor in a solvent to obtain a dispersant; introducing nano-silicon carbide particles into the dispersant to form a slurry; immersing the composite material in the slurry; ultrasonically impregnating the composite material and then curing it at 300°C for 1 hour to obtain a composite material precursor; and heat-treating the composite material precursor at 1200°C for 2 hours under a nitrogen atmosphere to obtain a composite material with a modified ceramic-based coating.

[0084] Example 3

[0085] This embodiment provides an easily storable metal-modified polycarbosilane precursor and its preparation method, including the following steps:

[0086] (1) Preparation of boron-modified polycarbosilane powder

[0087] The preparation method of boron-modified polycarbosilane powder is the same as in Example 1.

[0088] (2) Preparation of metal-modified polycarbosilane precursors

[0089] Prepare 200g of a diethylene glycol dimethyl ether solution of boron-modified polycarbosilane with a mass concentration of 40wt%.

[0090] Weigh out 10g of titanium n-butoxide, 12g of zirconium dichlorocerocene and 3g of hafnium dichlorocerocene; under a nitrogen atmosphere, add solid zirconium dichlorocerocene and solid hafnium dichlorocerocene, and liquid titanium n-butoxide sequentially to the above solution, and heat while stirring. The reaction temperature is set at 100℃. As the reaction proceeds, the solution gradually changes from turbid to clear and transparent after 3 hours. The solution is rotary evaporated at 100℃ for 2 hours to obtain solid metal modified polycarbosilane precursor powder.

[0091] This embodiment provides an application of a metal-modified polycarbosilane precursor in the preparation of bulk ceramics, including:

[0092] (1) First, take an appropriate amount of metal-modified polycarbosilane precursor, add an appropriate amount of polymer binder, and hot press to prepare it into a block shape;

[0093] (2) Take the metal-modified polycarbosilane precursor and dissolve it in a solvent to obtain an impregnating agent. Soak the bulk precursor in the impregnating agent and evacuate for 8 hours.

[0094] (3) Remove the block and perform vacuum pyrolysis by heat treatment at 1200℃ for 2 hours;

[0095] (4) After cooling to room temperature, remove the bulk material and repeat steps (2) and (3) 6 times to obtain modified bulk SiC ceramic.

[0096] In other embodiments of the present invention, the raw materials for preparing the metal-modified polycarbosilane precursor can be adjusted arbitrarily within a given range without significantly affecting the properties and performance of the polycarbosilane precursor.

[0097] Experimental Example

[0098] (1) Moisture absorption performance test

[0099] The metal-modified polycarbosilane precursor powder prepared in Example 1 was left to stand for 2 months to observe whether the material absorbed moisture. The test results are as follows: Figure 1 As shown.

[0100] from Figure 1 It can be seen that the metal-modified polycarbosilane precursor powder prepared by this invention does not show obvious moisture absorption after being stored for 2 months.

[0101] (2) M obtained from high-temperature pyrolysis x Characterization of SiC ceramic powder

[0102] The metal-modified polycarbosilane precursor solution prepared in Example 1 was completely pyrolyzed at 1200°C to obtain M. x -SiC metal-modified ceramic materials, photographs before and after pyrolysis, SEM images and EDS-mapping surface scan images of the pyrolyzed ceramic materials, as shown in the following figures. Figure 2-3 As shown.

[0103] from Figure 2 It can be seen that the product obtained after high-temperature pyrolysis of the metal-modified polycarbosilane precursor is a black ceramic powder.

[0104] from Figure 3 It can be seen that Zr, Al, Si, N, C and B are uniformly distributed in the pyrolyzed ceramic powder.

[0105] (3) Mechanical properties and antioxidant properties test

[0106] The C / SiC composite material prepared in Example 1 was subjected to tensile, compressive, and flexural property tests. The test methods were in accordance with GJB 6475-2008 "Test Method for Tensile Properties of Continuous Fiber Reinforced Ceramic Matrix Composites at Room Temperature", GJB 6476-2008 "Test Method for Compressive Properties of Continuous Fiber Reinforced Ceramic Matrix Composites at Room Temperature", GBT 6569-2006 "Test Method for Flexural Strength of Fine Ceramics", and QAVIC 06185.2-2015 "Test Method for High-Temperature Mechanical Properties of Continuous Fiber Reinforced Ceramic Matrix Composites Part 2: Flexural Properties Test Method". The test results are shown in Table 1.

[0107] Table 1. Performance test results of the ceramic matrix composite material prepared in Example 1.

[0108]

[0109] As can be seen from Table 1, the C / SiC composite material prepared using the metal-modified polycarbosilane precursor of the present invention has excellent mechanical properties and high-temperature oxidation resistance.

[0110] This invention aims to provide a mild method for preparing multi-metal modified polycarbosilane precursors, as existing multi-metal modified polymer precursors are limited in variety and difficult to prepare. The technical route of this invention, based on boron-modified polycarbosilanes, uses inexpensive metal (sec-)butoxide and dichlorodicyclopentadiene salts as high-temperature metal sources to prepare boron-modified solid polycarbosilane precursors containing multiple metals, which can be used to prepare ceramic matrix composites with multi-metal modified matrix. Compared with previous methods, the preparation method of this invention has advantages such as milder conditions, simpler operation, flexible and adjustable metal element introduction, and suitability for large-scale production. It aims to overcome the shortcomings of limited variety and difficult preparation of single-source multi-metal modified polymer precursors, providing a simple, mild, flexible, and convenient method for preparing multi-metal modified polycarbosilane precursors, with good prospects for widespread application and high economic value.

[0111] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent transformations made based on the content of the present invention specification, or direct or indirect applications in other related technical fields, are included within the patent protection scope of the present invention.

Claims

1. A method for preparing an easily storable metal-modified polycarbosilane precursor, characterized in that: Includes the following steps: Boron-modified polycarbosilane was dissolved in a solvent to obtain a solution; A metal alkoxide and a metallocerochlore were added to the solution, and the mixture was heated under a protective atmosphere to obtain a metal-modified polycarbosilane precursor. The method for preparing the boron-modified polycarbosilane includes the following steps: (1) Prepare an organic solution of solid polycarbosilane; the organic solvent is a hydrocarbon solvent or an ether solvent; (2) Under an inert atmosphere, the organic solution and hexamethyldisilazane monomer are simultaneously added dropwise to the boron trichloride organic solution to carry out the reaction; the solvent for boron trichloride is a hydrocarbon solvent or an ether solvent; The reaction is divided into an initial stage and a stable stage. For either the organic solution or the hexamethyldisilazane monomer, the dropping rate in the initial stage is lower than that in the stable stage. In the initial stage, a white mist-like byproduct is generated. The reaction temperature is controlled at -20 to 10°C using a cooling device. After the mist-like byproduct disappears, the stable stage begins. The dropping rate is increased, and the reaction temperature is controlled at 10 to 90°C. (3) The mixture after the reaction is subjected to vacuum distillation to obtain a porous solid material; (4) The porous solid material is broken into powder by external force, which is boron modified polycarbosilane powder; The metal alkoxide is selected from one or more of titanium n-butoxide, aluminum sec-butoxide, zirconium n-butoxide, and hafnium n-butoxide; The dichlorodicyclopentene metal is selected from one or more of dichlorodicyclopentene titanium, dichlorodicyclopentene zirconium, and dichlorodicyclopentene hafnium.

2. The preparation method according to claim 1, characterized in that: The solvent is selected from one or more of N,N-dimethylformamide, xylene, n-hexane, diethylene glycol dimethyl ether, toluene, and tetrahydrofuran; And / or, the mass concentration of boron-modified polycarbosilane in the solution is 10-80 wt%.

3. The preparation method according to claim 1, characterized in that: The amount of the metal alkoxide added is 1-30 wt% of the mass of the boron-modified polycarbosilane.

4. The preparation method according to claim 1, characterized in that: The amount of dichlorodicyclopentene added is 1-30 wt% of the mass of boron-modified polycarbosilane.

5. The preparation method according to claim 1, characterized in that: The heating reaction temperature is controlled at 60-150℃, and the reaction time is 0.5-12h.

6. The preparation method according to claim 1, characterized in that: After the heating reaction is completed, the solvent is removed from the reaction product to obtain metal-modified polycarbosilane precursor powder. The solvent removal is performed using a rotary evaporation system, with the heating temperature controlled between 60-150℃, until no liquid evaporates.

7. A metal-modified polycarbosilane precursor prepared by the preparation method according to any one of claims 1-6.

8. The application of the metal-modified polycarbosilane precursor as described in claim 7, characterized in that: The applications are in the preparation of ceramic matrix composites, in the preparation of ceramic matrix coatings, in the preparation of ceramic fibers, or in the preparation of bulk ceramics.

9. The application according to claim 8, characterized in that: The application includes the following steps: The metal-modified polycarbosilane precursor is dissolved in a solvent to obtain a solution; or the metal-modified polycarbosilane precursor solution without removing the solvent is used directly. Ceramic matrix composites or ceramic matrix coatings are prepared by using a metal-modified polycarbosilane precursor solution as an impregnating agent via the PIP process.

10. The application according to claim 9, characterized in that: The solvent is selected from one or more of N,N-dimethylformamide, xylene, n-hexane, diethylene glycol dimethyl ether, toluene, and tetrahydrofuran; And / or, the mass concentration of the metal-modified polycarbosilane precursor in the solution is 10-80 wt%; And / or, the pyrolysis temperature of the PIP process is above 800°C.

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