Easily-stored metal modified polycarbosilane precursor as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of preparation of novel ceramic materials, and particularly discloses an easy-to-store metal modified polycarbosilane precursor as well as 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 used raw materials are low in cost, the synthesis process is mild, the introduction amount of the metal elements is flexible and adjustable, expanded production is facilitated, and the obtained polymer precursor can be stored at room temperature for a long time and is not prone to being affected with damp due to water absorption. Moreover, according to the composite material prepared by using the metal modified polymer precursor, new defects cannot be introduced while metal elements are ensured to be introduced into a matrix, the properties of all parts of the ceramic matrix are uniform and stable, and good and stable mechanical properties of the composite material are ensured; in an oxidation environment, compared with an unmodified ceramic matrix, boron and metal elements are introduced, so that the matrix can form an oxide plugging phase at a gradient rising temperature, invasion of oxidation media such as water and oxygen is prevented, and fibers and an interface are protected from erosion.

Description

Technical Field

[0001] The invention belongs to the technical field of preparation of novel ceramic materials, and in particular relates to an easily storable metal-modified polycarbosilane precursor and a preparation method and application thereof. Background Art

[0002] Ceramic-based composites have broad application prospects in the field of aviation thermal structural materials due to their low density, high strength, high temperature resistance and corrosion resistance. However, binary ceramic systems represented by silicon carbide ceramics as the matrix of composite materials cannot provide effective protection in a wide temperature range, and the thermal vibration performance of high peak temperature is difficult to meet the needs of aircraft for multiple flights. This is mainly because composite materials with silicon carbide as the matrix inevitably have defects such as pores. Oxidizing media such as oxygen and water can diffuse to the interface and fiber of the composite material through these channels, causing oxidation damage and degradation of silicon carbide fibers and their interface layers. The fibers and interfaces are the load-bearing and load-transmitting units of the composite material. Their damage will directly lead to a decrease in the performance of the composite material and shorten the service life of the composite material.

[0003] It has been reported in the literature that introducing a variety of high melting point metal elements into the silicon carbide ceramic matrix, gradually forming a variety of oxides at a gradually increasing oxidation temperature, and gradiently forming a glass phase protective layer, can block the pores of the composite material in a wide temperature range, maintain effective protection for the composite material, significantly expand its operating temperature range, and achieve the goal of reusability of ceramic-based composite materials. However, existing reports usually use simple physical mixing methods to introduce inorganic compounds such as metal carbides, or use expensive organic matter to synthesize precursors in harsh environments, and the resulting precursors are easy to absorb water and are not easy to store.

[0004] The precursor conversion method (also known as the precursor pyrolysis method or the precursor polymer impregnation pyrolysis method) is a process for preparing ceramic-based composite materials that has emerged in recent decades. This method has the advantages of simple molding process and low preparation temperature, and the ceramic product obtained by pyrolysis of the liquid precursor solution has the characteristics of uniform composition and can be regulated at the atomic / molecular scale. Chinese patent CN115180950B (Central South University, Wang Yalei team) uses the precursor conversion method to convert a single-source precursor (such as (Ti, Zr, Hf) C / SiC ceramic precursor) prepared from a variety of metal element complexes (such as tetrakis(dimethylamino) metal salts, tetrakis(diethylamino) metal salts) into a multi-element carbide / silicon carbide nanocomposite ceramic powder at high temperature, effectively solving the problems of multi-element single-phase solid solution, uneven distribution of nanoceramic phases and grain coarsening, and significantly improving the mechanical properties and anti-oxidation ablation properties of the composite material. However, the raw materials used in this method are relatively expensive, and the synthetic process has a high safety risk, and it is not easy to expand production.

[0005] In summary, there are few safe, low-cost and mild methods for preparing single-source multi-metal doped modified polycarbosilane precursors. It is urgent to develop a method for preparing metal-modified polycarbosilane precursors with simple preparation steps, mild conditions, convenient regulation and low cost, while improving the storage stability of single-source polymer precursors. Summary of the invention

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

[0007] At the same time, the present invention provides a metal-modified polycarbosilane precursor and application thereof.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is:

[0009] A method for preparing a metal-modified polycarbosilane precursor that is easy to store comprises the following steps:

[0010] dissolving (solid) boron-modified polycarbosilane in a solvent to obtain a solution;

[0011] Add metal alkoxide and metallocene dichloride into the solution, heat and react under a protective atmosphere to obtain a metal-modified polycarbosilane precursor.

[0012] The present invention uses (solid) boron-modified polycarbosilane as a raw material, prepares a solution, and then adds the (secondary) butoxide salt and dichlorobismuth salt of the corresponding metal into the solution according to the metal content to be introduced, and heats the solution under a protective atmosphere to react until the solution is clear and transparent, thereby obtaining a polycarbosilane precursor doped with multiple metals. The single-source multi-metal modified polymer precursor prepared by the method has the characteristics of adjustable content of derived ceramic metal elements and excellent high-temperature antioxidant properties. The prepared solution is used as an impregnating agent and is suitable for preparing metal-modified ceramic-based composite materials or ceramic-based coatings by PIP process. The method of the present invention has simple preparation steps, mild conditions, convenient regulation and control, and low cost, and is easy to be promoted and applied on a large scale.

[0013] As a preferred embodiment of the present invention, the boron-modified polycarbosilane is prepared by the method disclosed in patent CN114957675B (AVIC Manufacturing Institute), and may also be prepared by the method disclosed in other (patent or non-patent) documents.

[0014] Specifically, the method for preparing the boron-modified polycarbosilane comprises the following steps:

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

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

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

[0018] (2) under an inert atmosphere, the organic solution and the hexamethyldisilazane monomer are simultaneously dropped into the boron trichloride organic solution for reaction;

[0019] The solvent of boron trichloride is a hydrocarbon solvent or an ether solvent;

[0020] The reaction is divided into an initial stage and a stable stage. For any one of the organic solution and the hexamethyldisilazane monomer, the dripping speed in the initial stage is lower than the dripping speed in the stable stage. In the initial stage, white mist-like byproducts are generated, and the reaction temperature is controlled at -20-10°C by a cooling device. After the mist-like byproducts disappear, it is a stable stage, and the dripping speed is increased, and the reaction temperature is controlled at 10-90°C.

[0021] (3) performing vacuum distillation on the mixed solution after the reaction to obtain a porous structure solid material;

[0022] The temperature of vacuum distillation is 20-250°C;

[0023] (4) The porous solid material is broken into powder by external force, namely, the 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 refer to patent CN114957675B.

[0025] As 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 and the like.

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

[0027] As 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, hafnium n-butoxide and the like.

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

[0029] As a preferred embodiment of the present invention, the metallocene dichloride is selected from one or more of titanocene dichloride, zirconocene dichloride, hafnocenene dichloride and the like.

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

[0031] As a preferred embodiment of the present invention, the temperature of the heating reaction is controlled at 60-150°C, and the reaction time is 0.5-12 hours, preferably 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 there are obvious insolubles. As the reaction continues, the insolubles gradually dissolve and finally the solution becomes clear and transparent. The heating and stirring are stopped and the solution remains clear and transparent after cooling to room temperature, thereby obtaining a metal-modified polycarbosilane precursor solution.

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

[0034] Specifically, the solvent is removed by a rotary evaporation system, the heating temperature is controlled at 60-150° C., preferably 80-120° C., and the rotary evaporation is performed until no liquid is evaporated.

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

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

[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 comprises the following steps:

[0042] Dissolving a metal-modified polycarbosilane precursor in a solvent to obtain a solution; or directly using the metal-modified polycarbosilane precursor solution without removing the solvent;

[0043] A ceramic-based composite material or a ceramic-based coating is prepared by using a precursor polymer impregnation-pyrolysis (PIP) process using a metal-modified polycarbosilane precursor solution as an impregnating agent.

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

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

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

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

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

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

[0050] Beneficial effects of the present invention:

[0051] The present invention further introduces a variety of metal-modified polymer precursors on the basis of (solid) boron-modified polycarbosilane. The raw materials used are low-cost, safe and reliable, the synthesis process is mild, the operation is simple, the amount of metal elements introduced is flexible and adjustable, and it is convenient for large-scale production. The prepared polymer precursor can be stored for a long time at room temperature and is not easy to absorb water and get damp. The composite material prepared using the single-source multi-metal modified polycarbosilane precursor ensures that no new defects will be introduced in the process of introducing metal elements into the matrix, and the properties of each part of the ceramic matrix are uniform and stable, ensuring the good and stable basic mechanical properties of the composite material; in an oxidizing environment, compared with the unmodified ceramic matrix, the introduction of boron (B) and metal elements allows the matrix to gradually form a variety of oxide blocking phases at a gradient temperature, preventing the intrusion of oxidizing media such as water and oxygen, protecting the fibers and interfaces from erosion, and improving the high-temperature antioxidant properties of the ceramic-based composite material.

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

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

[0054] (2) The present invention uses boron-modified polycarbosilane with fewer active groups as the basic raw material, and the preparation operation is simple, the conditions are mild, and it 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 feed 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 a precursor solution.

[0056] (4) The metal-modified polycarbosilane precursor powder prepared by the present invention can be stored for a long time at room temperature, 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-based composite materials, and is suitable for preparing metal-modified silicon carbide ceramic-based composite materials by PIP process. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] Figure 1 This is a real picture of the metal-modified polycarbosilane precursor powder in the experimental example after being left to stand for 2 months.

[0059] Figure 2 This is a physical picture of the product obtained by cracking the metal-modified polycarbosilane precursor solution at 1200°C in the experimental example.

[0060] Figure 3 These are the SEM images and EDS-mapping surface scan images of the products obtained by pyrolysis of the metal-modified polycarbosilane precursor solution at 1200°C in the experimental example.

[0061] In order to more clearly illustrate the technical solution to be protected by the present invention, the drawings in the embodiments and / or experimental examples are briefly introduced above. It should be understood that the above drawings should not be regarded as any limitation on the protection scope of the present invention. DETAILED DESCRIPTION

[0062] The technical solution of the present invention is described in detail below through specific embodiments. The following embodiments are intended to further illustrate the content of the present invention in detail, 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 examples, 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 a preparation method thereof, comprising the following steps:

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

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

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

[0069] In an inert atmosphere, first add 4.0g of hexamethyldisilazane monomer to an organic solution, stir evenly to obtain a mixed solution; in an inert atmosphere, drop the mixed solution into 10ml of an organic solution of boron trichloride with a concentration of 1mol / L for reaction, wherein the solvent of the boron trichloride is dimethane; the reaction is divided into an initial stage and a stable stage, wherein the droplet speed in the initial stage is slower than that in the stable stage, wherein the reaction temperature in the initial stage is controlled at 0-5°C, wherein white mist-like byproducts are produced in the initial stage, and the stable stage is entered after the mist-like byproducts disappear, wherein the droplet speed is increased, and the reaction temperature is controlled at 30-40°C, and the two stages react for a total of 24h;

[0070] The mixed solution after the reaction is subjected to reduced pressure distillation, and the temperature is controlled at 100±5° C. to obtain a porous structure solid material;

[0071] The solid material is crushed and destroyed into powder by external force, that is, the boron-modified polycarbosilane powder.

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

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

[0074] Weigh 15 g of aluminum 2-butoxide and 12 g of zirconocene dichloride; under a nitrogen atmosphere, add zirconocene dichloride solid and aluminum 2-butoxide liquid to the above solution in sequence, and heat while stirring. The reaction temperature is set to 90°C. As the reaction proceeds, the solution gradually changes from turbid to clear and transparent after 5 hours. Rotary evaporate the resulting solution at 100°C for 3 hours to obtain a solid metal-modified polycarbosilane precursor powder.

[0075] The present embodiment provides an application of a metal-modified polycarbosilane precursor in the preparation of a ceramic-based composite material, 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 a fiber-reinforced ceramic-based composite material through a PIP process, assembling a mold, vacuumizing the pyrolysis furnace for high-temperature pyrolysis at 1200°C for 2 hours, and the number of cycles of the PIP process is 12 times.

[0076] Example 2

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

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

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

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

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

[0082] Weigh 10g of aluminum sec-butoxide, 7g of titanocene dichloride and 7g of zirconocene dichloride; under a nitrogen atmosphere, add solids of titanocene dichloride and zirconocene dichloride, and liquid aluminum sec-butoxide to the above solution in sequence, and heat while stirring. The reaction temperature is set to 110°C. As the reaction proceeds, the solution gradually changes from turbid to clear and transparent after 4 hours. The obtained solution is rotary evaporated at 80°C for 4 hours to obtain a solid metal-modified polycarbosilane precursor powder.

[0083] The present 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 prepare a slurry, immersing a composite material in the slurry, and curing at 300° C. for 1 hour after ultrasonic impregnation to obtain a composite material precursor; heating the composite material precursor to 1200° C. for heat treatment for 2 hours under a nitrogen atmosphere to obtain a composite material having a modified ceramic-based coating.

[0084] Example 3

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

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

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

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

[0089] Prepare 200 g of a 40 wt% boron-modified polycarbosilane solution in diethylene glycol dimethyl ether;

[0090] Weigh 10g of titanium n-butoxide, 12g of zirconocene dichloride and 3g of hafnocene dichloride; under a nitrogen atmosphere, add zirconocene dichloride and hafnocene dichloride solids, and titanium n-butoxide liquid to the above solution in sequence, and heat while stirring. The reaction temperature is set to 100°C. As the reaction proceeds, the solution gradually changes from turbid to clear and transparent after 3 hours. The resulting solution is rotary evaporated at 100°C for 2 hours to obtain a solid metal-modified polycarbosilane precursor powder.

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

[0092] (1) firstly, taking an appropriate amount of metal-modified polycarbosilane precursor, adding an appropriate amount of polymer binder, and hot pressing to prepare a block;

[0093] (2) dissolving the metal-modified polycarbosilane precursor in a solvent to obtain an impregnating agent, soaking the bulk precursor in the impregnating agent, and evacuating the mixture for 8 hours;

[0094] (3) taking out the block and heat treating it at 1200°C for 2 h for vacuum cracking;

[0095] (4) After cooling to room temperature, take out the block and repeat steps (2) and (3) 6 times to obtain a 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 substantially affecting the properties and performance of the polycarbosilane precursor.

[0097] Experimental example

[0098] (1) Hygroscopicity test

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

[0100] from Figure 1 It can be seen that the metal-modified polycarbosilane precursor powder prepared by the present invention has no obvious moisture absorption phenomenon after being placed for 2 months.

[0101] (2) M obtained by high temperature cracking 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, photos before and after pyrolysis, SEM images of ceramic materials after pyrolysis and EDS-mapping surface scan images such as Figure 2-3 shown.

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

[0104] from Figure 3 It can be seen that in the ceramic powder after pyrolysis, elements such as Zr, Al, Si, N, C and B are evenly distributed.

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

[0106] The C / SiC composite material prepared in Example 1 was subjected to tensile, compression and bending performance tests. The test methods were based on GJB 6475-2008 "Test method for tensile properties of continuous fiber reinforced ceramic matrix composite materials at room temperature", GJB 6476-2008 "Test method for compression properties of continuous fiber reinforced ceramic matrix composite materials at room temperature", GBT 6569-2006 "Test method for bending strength of fine ceramics" and QAVIC 06185.2-2015 "Test method for high temperature mechanical properties of continuous fiber reinforced ceramic matrix composite materials Part 2; Test method for bending properties". The test results are shown in Table 1.

[0107] Table 1 Performance test results of ceramic matrix composite materials prepared in Example 1

[0108]

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

[0110] The present invention aims to provide a method for mildly preparing a multi-metal modified polycarbosilane precursor. The existing related multi-metal modified polymer precursors are relatively few in variety and difficult to prepare. The technical route of the present invention is based on boron modified polycarbosilane, and uses cheap metal (secondary) butoxide and dichlorobismuth salt as high temperature metal sources to prepare a boron modified solid polycarbosilane precursor containing multiple metals, which can be used to prepare a ceramic-based composite material with a multi-metal modified matrix. Compared with the previous route, the preparation method of the present invention has the advantages of mild conditions, simple operation, flexible and adjustable amount of metal element introduction, and suitability for large-scale amplification. It aims to overcome the defects of single-source multi-metal modified polymer precursors with few varieties and great difficulty in preparation, and provides a simple, mild, flexible and convenient method for preparing multi-metal modified polycarbosilane precursors, which has good prospects for promotion and application and high economic value.

[0111] The above descriptions are merely embodiments of the present invention and are not intended to limit the patent scope of the present invention. Any equivalent transformations made using the contents of the present invention specification, or directly or indirectly applied in other related technical fields, are included in the patent protection scope of the present invention.

Claims

1. A method for preparing a metal-modified polycarbosilane precursor that is easy to store, characterized in that: The following steps are involved: dissolving the boron-modified polycarbosilane in a solvent to obtain a solution; Add metal alkoxide and metallocene dichloride into the solution, heat and react under a protective atmosphere to obtain a metal-modified polycarbosilane precursor.

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 the boron-modified polycarbosilane in the solution is 10-80wt%, preferably 40-60wt%.

3. The preparation method according to claim 1, characterized in that: The metal alkoxide is selected from one or more of titanium n-butoxide, aluminum sec-butoxide, zirconium n-butoxide, and hafnium n-butoxide; And / or, the added amount of the metal alkoxide is 1-30wt%, preferably 5-20wt%, of the mass of the boron-modified polycarbosilane.

4. The preparation method according to claim 1, characterized in that: The metallocene dichloride is selected from one or more of titanocene dichloride, zirconocene dichloride, and hafnocene dichloride; And / or, the addition amount of the metallocene dichloride is 1-30wt% of the mass of the boron-modified polycarbosilane, preferably 10-25wt%.

5. The preparation method according to claim 1, characterized in that: The temperature of the heating reaction is controlled at 60-150° C., and the reaction time is 0.5-12 h; preferably, the reaction is carried out at 80-120° C. for 2-6 h.

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 a metal-modified polycarbosilane precursor powder; The solvent is removed by a rotary evaporation system, the heating temperature is controlled at 60-150° C., preferably 80-120° C., and the rotary evaporation is performed until no liquid is evaporated.

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

8. A use of the metal-modified polycarbosilane precursor as claimed in claim 7, characterized in that: The application includes but is not limited to one or more of the following aspects: (1) Application in the preparation of ceramic matrix composites; (2) Application in the preparation of ceramic-based coatings; (3) Application in the preparation of ceramic fibers; (4) Application in the preparation of bulk ceramics.

9. The use according to claim 8, characterized in that: The application comprises the following steps: Dissolving a metal-modified polycarbosilane precursor in a solvent to obtain a solution; or directly using the metal-modified polycarbosilane precursor solution without removing the solvent; A ceramic-based composite material or a ceramic-based coating is prepared by using a PIP process with a metal-modified polycarbosilane precursor solution as an impregnating agent.

10. The use 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 10-80wt%, preferably 40-60wt%; And / or, the cracking temperature of the PIP process is above 800°C.

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