Ultrahigh-temperature ceramic precursor, preparation method thereof, modified high-performance inorganic fiber and application

Abstract

The invention provides an ultrahigh-temperature ceramic precursor, a preparation method thereof, a modified high-performance inorganic fiber and application, and relates to the technical field of high-temperature-resistant materials. The preparation of the ultra-high-temperature ceramic precursor comprises the following steps: placing a transition metal compound mixed solution in a low-temperature environment, standing, adding a coordination agent and an exchange agent, reacting, filtering in a low-temperature nitrogen atmosphere, adding a mixed solvent into the filtrate, heating and refluxing, and carrying out a polymerization reaction to obtain the ultra-high-temperature ceramic precursor. The superhigh-temperature ceramic precursor provided by the invention forms a high-temperature protective coating on the surface of a high-performance inorganic fiber and other materials, and meanwhile, a transition metal ion solution is placed under a low-temperature condition through a metal ion stabilization method, so that the internal structure of transition metal ions is more stable, and uniform dispersion at a molecular level is achieved; and the uniformity of the elements can be kept in the curing and cracking processes, and the phenomenon of coating stripping caused by mismatching of thermal shrinkage coefficients of a coating and a substrate material in an extreme environment is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of ultrahigh temperature ceramic materials, and in particular to an ultrahigh temperature ceramic precursor and a preparation method thereof, modified high-performance inorganic fiber, and applications thereof. Background Art

[0002] Ultra-high temperature ceramics (UHTCs) are a class of transition metal borides, carbides, and nitrides with a high melting point of over 3000°C and excellent high-temperature oxidation resistance, ablation resistance, and thermal shock resistance. As an ideal thermal protection material, they are expected to be used in space rocket engines, hypersonic vehicles, space shuttles, nose cones and leading edges of hypersonic vehicles within the atmosphere, and thermal protection systems and propulsion systems of hypersonic vehicles, as well as electrodes, crucibles and related components for high-temperature metal smelting and continuous casting, as well as heating elements.

[0003] Hafnium-tantalum carbides (HTCs) are the materials with the highest known melting point (4215°C). HTO is the oxidation product of HTCs. It has excellent high-temperature performance, excellent chemical and physical stability, no phase change in a wide temperature range, and has a thermal conductivity similar to that of yttria-stabilized zirconia (YSZ) ceramics ( ~ 2.89 Wm -1 K -1 ) and thermal expansion coefficient (α~9.59×10 -6 ℃ -1 ), as a thermal barrier coating material for UHTCs, it has great advantages and application prospects.

[0004] The preparation methods of HTO ceramics are mainly divided into solid phase method and liquid phase method. The solid phase method generally adopts hot pressing sintering or pressureless sintering method, such as Liu Siying et al. ( Corrosion Science, Volume 208, November 2022) HTO powder was prepared by solid phase method, using HfO2 and Ta2O5 as raw materials, ball milled and then treated at 1600℃ for 20 h later, HTO powder is obtained and sintered at 1600°C. However, the preparation method of this powder is complex, the preparation cycle is long, and the energy consumption is high. Chinese invention patent CN118184353A discloses a high-entropy ceramic block and its preparation method, in which a mixed powder of multiple single-component carbides is ball-milled to obtain an amorphous ceramic powder with uniform composition; a carbon-containing ceramic body is prepared: an amorphous ceramic powder is mixed with a carbon source to obtain a carbon-containing mixed powder, and the mixed powder is made into a carbon-containing ceramic body suitable for reactive infiltration through a tableting process and a slurry sedimentation process; high-entropy ceramics are formed in situ by melt infiltration: a carbon-containing ceramic body is embedded in a transition metal or its alloy; a dense high-entropy ceramic block is obtained; however, the infiltration process requires a temperature of 20 to 300°C above the melting point of the metal or alloy, a holding time of 10 to 120 minutes, and a cooling rate of 5 to 10°C / min. However, since no pressure is applied during the sintering process of pressureless sintering, it is difficult for ultra-high temperature ceramic composite materials to be dense, so a higher sintering temperature or the addition of sintering aids is required.

[0005] Liquid phase methods include liquid phase sintering, sol-gel method and precursor method. For example, Li He et al. ( Ceramics International , Volume 47, Issue 12, 15 June 2021, Pages 17711-17718) HTO powder is prepared by a liquid phase method. The resulting product particles have obvious agglomeration phenomenon, and sintering molding can only be completed at above 1400°C. Obviously, the liquid phase sintering method used in the prior art requires high energy consumption, extremely high requirements for equipment, and is time-consuming. The sol-gel method uses a non-sintering method, which can greatly reduce the sintering temperature, but the preparation process is relatively complicated. The precursor method can significantly reduce the sintering temperature, which is significantly lower than powder metallurgy and sol-gel methods. For example, Chinese invention patent CN116535208A provides a hafnium tantalum oxide ceramic powder that can successfully sinter a single-phase Hf6Ta2O with a stable crystal structure at 800°C in a short time. 17 Ceramics have the advantages of simple process, short cycle, wide source of raw materials, low equipment requirements, etc., and the prepared hafnium tantalum oxide ceramic powder has the dispersion of metal elements at the molecular level; However, the above method adopts programmed temperature stepwise curing and then calcination at 600℃~1500℃, which is a complicated process. On the other hand, the obtained Hf6Ta2O 17 Ceramics are very prone to coating peeling in extreme environments due to the mismatch between the thermal shrinkage coefficient of the coating and the base material, making it still unable to meet the requirements of use in extreme environments.

[0006] On the other hand, high-performance inorganic fibers, such as carbon fibers and silicon carbide fibers, are widely used in aerospace, automotive, and energy equipment due to their high strength, high modulus, low density, and excellent corrosion resistance. However, the inert surface and poor oxidation resistance of carbon fibers limit their application in high-temperature or extreme environments. To improve their performance, surface modification has become a popular approach. Techniques for modifying carbon fibers using polycarbosilanes and polysilazanes have garnered significant attention in recent years. These methods involve introducing precursors onto the fiber surface through solution impregnation, chemical vapor deposition (CVD), or sol-gel methods, followed by high-temperature pyrolysis to form a ceramic coating or composite interface. This modification approach offers the following advantages: 1. The ceramic coating improves the chemical compatibility of the carbon fibers with the resin / metal matrix, enhancing the shear strength of the composite interface. 2. The ceramic layer effectively blocks oxygen diffusion, slowing down the oxidation loss of the carbon fibers at high temperatures. 3. By manipulating the molecular structure of the precursors (e.g., by introducing elements such as boron and aluminum), the fibers can be endowed with properties such as ablation resistance and radiation resistance. The outstanding advantage of this technology is its ability to balance coating uniformity, thermal expansion coefficient matching, and process economy. For example, volume shrinkage during precursor pyrolysis may cause coating cracking, which requires optimization through nanofiller doping or gradient pyrolysis processes. The development of low-temperature curing precursors (such as reactive silicone oil-modified polysiloxanes) can reduce energy consumption and promote industrial application. However, the preparation cost of precursors such as polycarbosilane and polysilazane is relatively high. Although the polymer layer has certain aging and degradation resistance, it is very prone to swelling and peeling in extreme environments, especially in extreme environments with high water and oxygen erosion at temperatures above 2500°C, which limits the application of carbon fiber in aerospace, high-end military and other fields.

[0007] Based on the problems existing in the prior art, the present invention has made technical improvements to the precursor sintering method of the prior art, and provides a ceramic precursor for coatings that can be used in extreme environments with high water and oxygen erosion above 2500°C, which can ensure that the coating will not peel off under high temperature conditions due to the mismatch between the thermal shrinkage coefficient of the coating and the substrate material. Summary of the Invention

[0008] In order to overcome the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide an ultra-high temperature ceramic precursor and its preparation method, modified high-performance inorganic fiber, and application, so as to overcome the defects of the prior art in that the production energy consumption is high and the coating obtained before use exists in an ultra-high temperature environment.

[0009] To achieve the above objectives, the present invention provides the following technical solutions.

[0010] One aspect of the present invention provides a method for preparing an ultrahigh temperature ceramic precursor, the specific steps comprising: S1. The transition metal compound is dissolved in an organic solvent and mixed uniformly, and placed in a low temperature environment and allowed to stand to obtain a mixed solution; S2. A ligand and an exchange agent are added to the mixed solution to carry out a coordination reaction; S3. After filtering the reaction system obtained in S2 under a low-temperature nitrogen atmosphere, a mixed solvent is added to the filtrate, and the mixture is heated under reflux to perform a polymerization reaction, thereby obtaining the ultrahigh temperature ceramic precursor.

[0011] In some specific embodiments, in S1, the transition metal compound is a combination of chlorides of any three or more of hafnium, zirconium, titanium, tantalum, niobium, and tungsten.

[0012] In some specific embodiments, the transition metal compound is a combination of any three or more of hafnium tetrachloride, zirconium tetrachloride, titanium tetrachloride, tantalum pentachloride, niobium pentachloride, tungsten hexachloride, hafnocene dichloride, zirconocene dichloride, titanocene dichloride, tantalum trichloride, iridium trichloride, yttrium trichloride, lanthanum trichloride, and strontium tetrachloride.

[0013] Preferably, the transition metal compound is a combination of at least three of hafnium tetrachloride, zirconium tetrachloride, titanium tetrachloride, tantalum pentachloride, niobium pentachloride, tungsten hexachloride, hafnocene dichloride, and zirconocene dichloride.

[0014] In some specific embodiments, the organic solvent is any one or a combination of anhydrous ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and methyl tert-butyl ether.

[0015] Preferably, the organic solvent is any one of n-propanol, n-butanol, ethylene glycol monomethyl ether, and methyl tert-butyl ether, or a combination thereof.

[0016] In some specific embodiments, the molar amount of the organic solvent is 3 to 20 times the total molar amount of the transition metal compound.

[0017] Preferably, the molar amount of the organic solvent is 5 to 10 times the total molar amount of the transition metal compound.

[0018] In some specific embodiments, the temperature of the low-temperature environment is -76°C to 10°C.

[0019] Preferably, the temperature of the low temperature environment is -40°C to -20°C.

[0020] In some specific embodiments, the standing time is 10 min to 3 h.

[0021] In some specific embodiments, in S2, the dripping speed of the ligand and the exchanger is 0.1 to 3 drops / s.

[0022] In some specific embodiments, the stirring speed is 500-3000 rpm.

[0023] The speed of the hydrolysis reaction is regulated by controlling the dripping speed and stirring speed of the coordination agent and the exchange agent, so that the various metal elements can be evenly distributed.

[0024] In some specific embodiments, the complexing agent includes any one or a combination of acetylacetone, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, pyridine, bipyridine, etc., but is not limited thereto.

[0025] Preferably, the complexing agent includes any one or a combination of acetylacetone, ethylene glycol dimethyl ether, bipyridine, etc., but is not limited thereto.

[0026] In some specific embodiments, the molar amount of the ligand is 0.5 to 6 times the total molar amount of the transition metal compound.

[0027] Preferably, the molar amount of the ligand is 2 to 3 times the total molar amount of the transition metal compound.

[0028] In some specific embodiments, the exchange agent includes any one or a combination of tetrahydrofuran, triethylamine, tert-butylene lithium, pyromellitic lithium, tert-butylene lithium, and 1,3-butadiene lithium, but is not limited thereto.

[0029] Preferably, the exchange agent includes any one or a combination of tetrahydrofuran, triethylamine, and lithium terephthalene, but is not limited thereto.

[0030] In some specific embodiments, the molar amount of the exchange agent is 0.5 to 4 times the total molar amount of the transition metal compound.

[0031] Preferably, the molar amount of the exchange agent is 1 to 2 times the total molar amount of the transition metal compound.

[0032] In some specific embodiments, the reaction time of the coordination reaction is 1 to 24 hours.

[0033] Preferably, the reaction time of the coordination reaction is 2 to 4 hours.

[0034] In some specific embodiments, in S3, the temperature of the low-temperature nitrogen atmosphere is -20°C to 10°C.

[0035] In some specific embodiments, the mixed solvent is a mixture of water and the organic solvent.

[0036] The organic solvent in this step can be the same as that in S1.

[0037] In some specific embodiments, the mass ratio of water to the organic solvent is 1:(1-5).

[0038] Preferably, the mass ratio of water to the organic solvent is 1:(2-4).

[0039] In some specific embodiments, the heating reflux temperature is 80-130° C., and the time is 1-6 h.

[0040] Preferably, the heating reflux temperature is 100-120° C., and the time is 2-5 h.

[0041] As one aspect of the invention, the present invention also provides an ultra-high temperature ceramic precursor solution prepared by the aforementioned preparation method.

[0042] As one aspect of the invention, the present invention provides an application of the ultra-high temperature ceramic precursor provided by the above technical solution in the surface modification of high-performance inorganic fibers.

[0043] As one aspect of the invention, the present invention provides a modified high-performance inorganic fiber, comprising a high-performance inorganic fiber layer and a high-temperature resistant coating attached to the surface of the fiber material layer.

[0044] Preferably, the high temperature resistant coating comprises: coating the ultra-high temperature ceramic precursor as described above on the surface of the high performance inorganic fiber, and calcining it at high temperature to obtain the coating on the surface of the high performance inorganic fiber layer.

[0045] Preferably, the high-temperature calcination temperature is 600-1300°C.

[0046] In some specific embodiments, the high-performance inorganic fiber is any one of carbon fiber, silicon carbide fiber, zirconium carbide fiber, etc., but is not limited thereto.

[0047] As one of the aspects of the invention, the present invention also provides a method for preparing an ultra-high temperature ceramic pre-powder, comprising adding an effective polar precipitant to the aforementioned ultra-high temperature ceramic precursor solution to co-precipitate transition metal ions, and the resulting precipitate is the ultra-high temperature ceramic powder.

[0048] In some specific embodiments, the effective polar precipitant includes but is not limited to one or a combination of two or more of ammonia water, sodium hydroxide solution, triethylamine, ethanol, formic acid, and acetic acid.

[0049] Preferably, the effective polar precipitant is one or a combination of two or more of ammonia water, sodium hydroxide solution, and triethylamine.

[0050] In some specific embodiments, the molar amount of the effective polar precipitant is 2 to 8 times the total molar amount of the transition metal.

[0051] In some specific embodiments, the effective polar precipitant is added dropwise at a rate of 0.5 to 2 drops / s.

[0052] In some specific embodiments, the stirring speed is 1000-1500 rpm.

[0053] Preferably, the molar amount of the effective polar precipitant is 4 to 6 times the total molar amount of the transition metal.

[0054] As one aspect of the invention, the present invention further provides an ultra-high temperature ceramic pre-powder, which is prepared using the aforementioned method for preparing an ultra-high temperature ceramic pre-powder.

[0055] As one aspect of the invention, the present invention also provides a composite material for extreme environments, which comprises at least a high-temperature resistant base material and a film layer formed by coating the surface of the high-temperature resistant base material with the aforementioned ultra-high-temperature ceramic precursor, or the aforementioned ultra-high-temperature ceramic pre-powder.

[0056] Preferably, the coating comprises: first coating the ultrahigh temperature ceramic precursor on the surface of a high temperature resistant base material to form the film layer, and then calcining the coating to obtain the composite material for extreme environments.

[0057] Preferably, the coating comprises: forming a film layer on the surface of a high-temperature resistant base material by spraying, CVD or plasma sputtering the ultra-high temperature ceramic pre-powder; and then calcining the coating to obtain the composite material for extreme environments.

[0058] Preferably, the coating method includes any one of brush coating, immersion, spin coating, etc., but is not limited thereto.

[0059] Preferably, the calcination temperature is 600-1500°C.

[0060] More preferably, the calcination temperature is 800-1300°C.

[0061] Preferably, the high temperature resistant substrate material is any one of silicon carbide ceramic sheet / plate, zirconium carbide ceramic sheet / plate, high temperature resistant metal sheet / plate, high temperature resistant alloy sheet / plate, silicon carbide fiber, zirconium carbide fiber, carbon fiber, etc., but is not limited thereto.

[0062] More preferably, the high temperature resistant substrate material is any one of a silicon carbide ceramic sheet / plate and a zirconium carbide ceramic sheet / plate.

[0063] The technical effects of the technical solution of the present invention are as follows: 1. The technical solution of the present invention adopts a precursor method to prepare transition metal oxide ceramics (TMO) for high-temperature protective coatings. Because TMO has different thermal shrinkage coefficients at different temperatures, the metal ion stabilization method provided by the present invention allows the transition metal ion solution to be placed under low temperature conditions, making the internal structure of the transition metal ions more stable, and the various transition metal elements are evenly dispersed at the molecular level. The uniformity of the elements can be maintained during the solidification and cracking process. The cracking and conversion at a certain temperature prepares a TMO solid solution with uniform element distribution and precise stoichiometric ratio. The resulting ceramic powder is perfectly compatible with various types of plates and block structure materials, and the phenomenon of coating peeling due to the mismatch of the thermal shrinkage coefficients of the coating and the substrate material will not occur.

[0064] 2. The present invention uses an effective polar precipitant for the first time to controllably hydrolyze the TMO precursor. The addition of the effective polar precipitant greatly improves the preparation efficiency of the TMO pre-powder. Compared with the traditional method of obtaining the TMO pre-powder by vacuum distillation, drying, and finally pre-calcination, the traditional method not only has a long process time, but also a large amount of organic solvent cannot be recovered. In particular, the ablation of a large amount of organic matter during the drying and pre-calcination processes will produce toxic and harmful gases, causing environmental pollution. The present invention controls the hydrolysis rate through the effective polar precipitant and its dripping rate, stirring rate, dripping concentration, etc., and adds it to make the element distribution of the TMO pre-powder more uniform. On the other hand, during the dripping process of the effective polar precipitant, the organic solvent and the organic coordination groups in the precursor can be efficiently separated, and the separation efficiency is high, so that during the subsequent calcination process, almost no or very little toxic and harmful gases are released.

[0065] 3. The precursor method adopted in the present invention is to coat the film first and then calcine, which can greatly reduce the calcination temperature, thereby reducing the energy consumption of preparing the coating. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is a photo of the SiC fiber with the hafnium-zirconium-tantalum-tungsten ceramic coating prepared in Example 1 of the present invention.

[0067] Figure 2 This is a SEM photograph of the SiC fiber with the hafnium-zirconium-tantalum-tungsten ceramic coating prepared in Example 1 of the present invention.

[0068] Figure 3 This is a SEM photograph of the zirconium carbide material with the hafnium tantalum yttrium ceramic coating prepared in Example 8 of the present invention.

[0069] Figure 4 This is a hardness test chart of the zirconium carbide material with the hafnium tantalum yttrium ceramic coating prepared in Example 8 of the present invention.

[0070] Figure 5 This is a HRTEM photograph of the hafnium tantalum lanthanum tungsten ceramic coating prepared in Example 9 of the present invention.

[0071] Figure 6 This is the SEM characterization of the crystal form of the titanium, niobium, lanthanum and strontium ceramic powder prepared in Comparative Example 9 of the present invention.

[0072] Figure 7 This is the XRD spectrum of the ceramic powder containing titanium, niobium, lanthanum and strontium prepared in Comparative Example 1 of the present invention.

[0073] Figure 8 This is the XRD spectrum of the ceramic powder containing titanium, niobium, lanthanum and strontium prepared in Comparative Example 2 of the present invention.

[0074] Figure 9 These are the XRD spectra of the materials prepared in Examples 1 to 4 of the present invention. DETAILED DESCRIPTION

[0075] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions in the embodiments of the present invention are clearly and completely described. Obviously, the described embodiments are part of the embodiments of this application, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts shall fall within the scope of protection of the present invention.

[0076] The disclosures of all patent and non-patent literature cited herein are incorporated herein by reference in their entirety.

[0077] As used in the present invention, the terms "comprises," "includes," "contains," "covers," "has," "with," or any other variations thereof are intended to cover non-exclusive inclusions. For example, a process, method, article, or apparatus that includes a list of elements is not necessarily limited to only those elements, but may include other elements not expressly listed or inherent to the process, method, article, or apparatus. In addition, unless expressly indicated to the contrary, "or" refers to an inclusive "or" and not an exclusive "or." For example, conditions A or B satisfy any of the following: A is true (or exists) and B is false (or does not exist), A is false (or does not exist) and B is true (or exists), and both A and B are true (or exist). The phrase "one or more" is intended to cover non-exclusive inclusions. For example, one or more of A, B, and C means any of the following: A alone, B alone, C alone, a combination of A and B, a combination of B and C, a combination of A and C, or a combination of A, B, and C.

[0078] In addition, "a" or "an" is used to describe elements and components described herein. This is done not only for convenience but also to provide a general sense of the scope of the invention. This description should be understood to include one or at least one, a kind or at least one, and the singular also includes the plural unless it is obvious that it is intended otherwise.

[0079] The present invention provides a method for preparing an ultra-high temperature ceramic precursor for extreme environment coatings. The method comprises placing a mixed solution formed by transition metal compounds in a low-temperature environment to make the internal temperature of the metal atoms uniform and stable; then adding a ligand and an exchange agent; filtering the resulting reaction system under a low-temperature nitrogen atmosphere; adding a mixed solvent to the filtrate; and heating under reflux to carry out a polymerization reaction to obtain the ultra-high temperature ceramic precursor.

[0080] After the precursor material is coated or sputtered to form a film, it is calcined to obtain a coating that can be used in extreme environments.

[0081] The ultra-high-temperature ceramic precursor provided by the present invention is a transition metal alloy polymer precursor material. Transition metals have high valence states and functionality, resulting in extremely high reactivity of the M-OR bond, making hydrolysis and polycondensation reactions difficult to control. However, the present invention uses common transition metal salts (such as metal chlorides) as raw materials. Through polymer reactions such as transesterification, hydrolysis, and condensation of organic molecules, the desired transition metal elements, such as hafnium, tantalum, zirconium, titanium, lanthanum, yttrium, and tungsten, are introduced into the polymer molecular structure. This results in a transition metal polymer with excellent solubility and stability, and a high content of the main element, ensuring precursor stability and a high cracking conversion rate.

[0082] The ultra-high temperature ceramic precursor provided by the present invention is also an organic-inorganic hybrid molecule, whose molecular stability is poorer than that of traditional polymers. The ligand molecules used to stabilize metal atoms are sensitive to polar molecules such as water molecules, carboxyl groups, and hydroxyl groups, and are prone to coordination dissociation. Therefore, requirements are put forward for stabilizing the precursor molecular structure in the synthesis scheme; at the same time, controlled hydrolysis is achieved by adding ligand molecules during the precursor conversion process to achieve co-precipitation and uniform dispersion of transition metal elements.

[0083] The present invention utilizes the uniform dispersion of transition elements in the ultra-high temperature ceramic precursor at the molecular level, and can maintain the uniformity of the elements during the solidification and cracking process. At a certain temperature, the cracking and transformation are carried out to prepare a TMO solid solution with uniform element distribution and precise stoichiometric ratio. By clarifying the relationship between the composition, structure, cracking process of the ultra-high temperature ceramic precursor and the composition, structure and properties of the cracking product, the controllable preparation of the TMO alloy is achieved.

[0084] Specifically, using inorganic transition metal salts as raw materials, the steps include: first, obtaining an organic transition metal salt through an ester exchange reaction for subsequent hydrolysis and condensation; second, obtaining an organic transition metal polymer through a hydrolysis and condensation reaction of the organic transition metal salt, the purpose of the hydrolysis and condensation reaction is to uniformly disperse different transition metal elements at the atomic level; third, uniformly precipitating the transition metal polymer through controlled hydrolysis, thereby significantly reducing the temperature and energy during subsequent sintering; fourth, sintering to obtain a ceramic powder resistant to extreme environments.

[0085] Based on the above analysis, the present invention provides a method for preparing an ultrahigh temperature ceramic precursor, comprising the following specific steps: Step 1: First, one or more transition metal chlorides are dissolved in an organic solvent and placed in a low temperature environment to stabilize the internal temperature to obtain a mixed solution.

[0086] Step 2: Add a certain amount of ligand and exchange agent to the mixed solution in step 1 at a rate of 0.1 to 3 drops / s to carry out the reaction.

[0087] Step 3: Filter the reaction solution in step 2 under a low-temperature N2 atmosphere to obtain a clear filtrate, add a mixture of water and an organic solvent to the filtrate and heat under reflux to obtain a copolymer precursor solution.

[0088] Step 4: Add an effective polar precipitant to the solution from Step 3 to co-precipitate the metal ions in the precursor, resulting in a ceramic pre-powder. Because the precursor is a highly reactive liquid, it reacts with the hydroxyl groups on the substrate surface and adsorbs onto the substrate through a chemical reaction, eliminating the need for an additional precipitant.

[0089] Step 5: The copolymer precursor solution in step 3 or the ceramic pre-powder in step 4 can be made into an ultra-high temperature thermal protective coating according to the requirements of the processing technology; the precursor solution can be directly coated on the high temperature resistant base material by brushing, soaking, spin coating, etc., and the pre-powder can be coated on the high temperature resistant base material by spraying, plasma sputtering, etc.; the coated material is calcined at high temperature to obtain a high temperature resistant material with a thermal protective coating.

[0090] In some specific embodiments, the transition metal chloride is any one or a combination of hafnium tetrachloride, zirconium tetrachloride, titanium tetrachloride, tantalum pentachloride, niobium pentachloride, tungsten hexachloride, hafnocene dichloride, zirconocene dichloride, titanocene dichloride, tantalum trichloride, iridium trichloride, yttrium trichloride, lanthanum trichloride, and strontium tetrachloride, but is not limited thereto.

[0091] More preferably, the transition metal chloride is any one or a combination of hafnium tetrachloride, zirconium tetrachloride, titanium tetrachloride, tantalum pentachloride, niobium pentachloride, tungsten hexachloride, hafnocene dichloride, and zirconocene dichloride, but is not limited thereto.

[0092] In some specific embodiments, the organic solvent can be any one or a combination of anhydrous ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and methyl tert-butyl ether, but is not limited thereto.

[0093] More preferably, the organic solvent is any one of n-propanol, n-butanol, ethylene glycol monomethyl ether, and methyl tert-butyl ether, or a combination of several of them.

[0094] In some specific embodiments, the molar amount of the organic solvent is 3 to 20 times the total molar amount of the transition metal.

[0095] More preferably, the molar amount of the organic solvent is 5 to 10 times the total molar amount of the transition metal.

[0096] In some specific embodiments, the low temperature environment is -76°C to 10°C.

[0097] More preferably, the low temperature environment is -40°C to -20°C.

[0098] In some specific embodiments, the complexing agent is preferably any one of acetylacetone, ethylene glycol dimethyl ether, and bipyridine, or a combination thereof, but is not limited thereto.

[0099] In some specific embodiments, the molar amount of the ligand is 0.5 to 6 times the total molar amount of the transition metal.

[0100] More preferably, the molar amount of the ligand is 2 to 3 times the total molar amount of the transition metal.

[0101] In some specific embodiments, the exchange agent is one or a combination of tetrahydrofuran, triethylamine, lithium tert-butylene, lithium 1,3-butadiene, lithium pyromellitene, lithium tert-butyne, and lithium 1,3-butadiene.

[0102] More preferably, the exchange agent is any one of tetrahydrofuran, triethylamine, and lithium terephthalene, or a combination of several of them.

[0103] In some specific embodiments, the molar amount of the exchange agent is 0.5 to 4 times the total molar amount of the transition metal.

[0104] More preferably, the molar amount of the exchange agent is 1 to 2 times the total molar amount of the transition metal.

[0105] In some specific embodiments, the reaction time is 1 to 24 hours.

[0106] More preferably, the reaction time is 2 to 4 hours.

[0107] Preferably, the organic solvent is any one of anhydrous ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and methyl tert-butyl ether, or a combination thereof.

[0108] More preferably, the organic solvent is any one of n-propanol, n-butanol, ethylene glycol monomethyl ether, and methyl tert-butyl ether, or a combination of several of them.

[0109] Preferably, the ratio (mass ratio) of water to organic solvent is H2O:organic solvent=1:(1-5).

[0110] More preferably, the ratio (mass ratio) of water to organic solvent is preferably H2O:organic solvent=1:(2-4).

[0111] Preferably, the heating reflux temperature is 80-130° C. and the time is 1-6 h.

[0112] More preferably, the heating reflux temperature is 100-120° C., and the time is 2-5 h.

[0113] Preferably, the effective polar precipitant is one or a mixture of two or more of ammonia water, sodium hydroxide solution, triethylamine, ethanol, formic acid, and acetic acid, but is not limited thereto.

[0114] Further preferably, the effective polar precipitant is one or a mixture of two or more of ammonia water, sodium hydroxide solution, and triethylamine, but is not limited thereto.

[0115] Preferably, the molar amount of the effective polar solvent is 2 to 8 times the total molar amount of the transition metal.

[0116] More preferably, the molar amount of the effective polar solvent is 4 to 6 times the total molar amount of the transition metal.

[0117] Preferably, the calcination temperature is 600-1500°C.

[0118] More preferably, the calcination temperature is preferably 800-1300°C.

[0119] Preferably, the high temperature resistant substrate material can be any one of silicon carbide ceramic sheet / plate, zirconium carbide ceramic sheet / plate, high temperature resistant metal sheet / plate, high temperature resistant alloy sheet / plate, silicon carbide fiber, zirconium carbide fiber, carbon fiber, etc., but is not limited thereto.

[0120] More preferably, the high temperature resistant substrate material is any one of silicon carbide ceramic sheet / plate, zirconium carbide ceramic sheet / plate, carbon fiber and the like.

[0121] Ultra-high-temperature ceramic powders produced using this technical solution can be used in space rockets, hypersonic vehicles, space shuttles, and hypersonic vehicles. In particular, they are used in engine nozzle baffles for space rockets and cutting-edge materials for hypersonic vehicles. The resulting extreme-environment coatings can withstand high temperatures exceeding 2500°C, including water and oxygen erosion. Modified carbon fiber and SiC fiber composites can be applied to high-end supercar exhaust nozzles and internal combustion chambers, extending the service life and lifespan of these components.

[0122] Unless otherwise defined, the meaning of all technical and scientific terms used herein is the same as that generally understood by those of ordinary skill in the art to which this disclosure belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the disclosed composition embodiments, suitable methods and materials are described below. Unless citing a specific paragraph, all publications, patent applications, patents and other references mentioned herein are incorporated herein by reference in their entirety. In the event of a conflict, this specification and the definitions included therein shall prevail. In addition, materials, methods and examples are illustrative only and not restrictive.

[0123] The technical solutions, implementation processes and principles of the present invention will be further explained below through specific examples. It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. The described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention. Unless otherwise stated, the reagents and raw materials used in the following examples are commercially available, and the test methods for which specific conditions are not specified are generally carried out under conventional conditions or according to the conditions recommended by the manufacturers. Furthermore, unless otherwise stated, the experimental methods, detection methods, and preparation methods disclosed in the present invention all adopt conventional techniques in this technical field. These technologies have been fully described in the existing literature.

[0124] The technical solution of the present invention is described in detail below through specific embodiments.

[0125] Example 1 This embodiment provides a method for preparing SiC fiber with hafnium-zirconium-tantalum-tungsten ceramic coating for extreme environment coating, the specific steps comprising: Step 1: First, dissolve equal molar amounts of hafnium tetrachloride, zirconium tetrachloride, tungsten hexachloride, and tantalum pentachloride in n-propanol that is 10 times the total molar amount of the transition metals. Place the solution at -20°C and let it stand for 10 minutes to stabilize the internal temperature to obtain a mixed solution.

[0126] Step 2: Add 2 times the molar amount of ethylene glycol dimethyl ether and 1 times the molar amount of lithium terephthalene to the mixed solution in step 1 at a rate of 1 drop / s, stir at 800 rpm, and react for 4 hours to obtain a reaction solution.

[0127] Step 3: Filter the reaction solution obtained in step 2 under a 0°C N2 atmosphere to obtain a clear filtrate, add a mixture of 1 mol of water and 3 mol of n-propanol to the filtrate and heat under reflux at 80°C to obtain a copolymer precursor solution.

[0128] Step 4: Add 25% ammonia solution to the copolymer precursor solution obtained in step 3 at a rate of 1 drop / s. The amount of ammonia solution added is 4 times the total molar amount of the transition metal. The stirring speed is 1200 rpm to co-precipitate the transition metal in the precursor to obtain a ceramic pre-powder.

[0129] Step 5: The ceramic pre-powder from Step 4 is applied to the surface of the SiC fiber using plasma sputtering to a thickness of 2μm. The fiber is then calcined at 900°C for 2 hours to produce a high-temperature resistant material with thermal protection, namely, SiC fiber with a hafnium-zirconium-tantalum-tungsten ceramic coating. SiC fiber can also be replaced with zirconium carbide fiber, carbon fiber, or other fibers, forming a transition metal ceramic coating on the fiber surface to achieve surface modification and impart high-temperature resistance.

[0130] See Figure 1 , which is a physical photo of the SiC fiber with hafnium-zirconium-tantalum-tungsten ceramic coating obtained in this embodiment.

[0131] See Figure 2 The following is an SEM photograph of the SiC fiber coated with hafnium-zirconium-tantalum-tungsten ceramic obtained in this example. The SEM image shows a uniform layer of HTO ceramic coating on the fiber surface, effectively protecting the integrity of the SiC fiber structure at high temperatures and preventing damage during calcination. Furthermore, no delamination or peeling of the HTO coating was observed, indicating good contact between the coating and the fiber substrate, and a matching thermal expansion coefficient.

[0132] See Figure 9 , is the XRD spectrum of the hafnium-zirconium-tantalum-tungsten ceramic coating prepared in Example 1. As can be seen from the figure, it has an obvious crystalline structure.

[0133] Example 2 This comparative example provides a method for preparing a titanium, niobium, lanthanum, strontium ceramic coating for extreme environment coatings, the specific steps comprising: Step 1: First, dissolve equal molar amounts of titanium tetrachloride, niobium pentachloride, lanthanum trichloride, and strontium tetrachloride in n-propanol that is 15 times the total molar amount of the transition metals. Place the solution at 10°C and let it stand for 10 minutes to stabilize its internal temperature.

[0134] Step 2: Add 6 times the molar amount of pyridine and 2 times the molar amount of 1,3-butadiene lithium to the solution in step 1 at a rate of 1 drop / s, stir at 800 rpm, and react for 8 hours.

[0135] Step 3: Filter the reaction solution in step 2 under a low-temperature N2 atmosphere to obtain a clear filtrate, add a mixture of 1 mol of water and 5 mol of isobutanol to the filtrate and heat under reflux at 130°C to obtain a copolymer precursor solution.

[0136] Step 4: Add acetic acid (8 times the total molar amount of transition metal) to the solution in step 3 at a rate of 0.5 drops / s and a stirring speed of 1200 rpm to co-precipitate the metal ions in the precursor to obtain a ceramic pre-powder.

[0137] Step 5: The ceramic pre-powder from Step 4 is deposited onto the carbon fiber surface using chemical vapor deposition (CVD) to form a 500 nm thick coating. The coated material is then calcined at 1300°C for 1 hour to obtain a high-temperature resistant material with a thermal protective coating.

[0138] Example 3 The only difference between this embodiment and embodiment 2 is the calcination temperature in step five. Specifically, in step five, the ceramic pre-powder in step four is deposited on the carbon fiber by chemical vapor deposition (CVD), and the coated material is calcined at 600°C for 2.5 hours to obtain a high-temperature resistant material with a thermal protective coating.

[0139] Example 4 The only difference between this embodiment and embodiment 2 is the calcination temperature in step five. Specifically, in step five, the ceramic pre-powder in step four is deposited on the carbon fiber by chemical vapor deposition (CVD), and the coated material is calcined at 700°C for 2 hours to obtain a high-temperature resistant material with a thermal protective coating. The thickness of the coating is 800 nm.

[0140] See Figure 9 , which is the XRD spectrum of the titanium, niobium, lanthanum, strontium ceramic coating prepared in Example 2-Example 4. It can be seen from the figure that it has an obvious crystal form.

[0141] Example 5 The difference between this embodiment and embodiment 2 is only the coating process and calcination temperature in step five. Specifically, step five: the ceramic pre-powder in step four can be made into an ultra-high temperature thermal protective coating according to the requirements of the processing technology, and the SiC fiber is coated by screen printing, and the coating thickness is 3μm.

[0142] The coated material is calcined at 600°C for 1 hour to obtain a high-temperature resistant material with a thermal protective coating.

[0143] Example 6 This Example differs from Example 2 only in the addition rate of pyridine and 1,3-butadiene lithium in Step 2. Specifically, Step 2 involves adding 6 times the molar amount of pyridine and 2 times the molar amount of 1,3-butadiene lithium to the solution in Step 1 at a rate of 3 drops / s, stirring at 800 rpm, and reacting for 8 hours. All other conditions and steps remain the same.

[0144] Example 7 This Example differs from Example 2 only in the addition rate of pyridine and 1,3-butadiene lithium in Step 2. Specifically, Step 2 involves adding 6 times the molar amount of pyridine and 2 times the molar amount of 1,3-butadiene lithium to the solution in Step 1 at a rate of 1 drop / s, stirring at 2000 rpm, and reacting for 8 hours. All other conditions and steps remain the same.

[0145] Example 8 This Example differs from Example 2 only in the addition rate of pyridine and 1,3-butadiene lithium in Step 2. Specifically, Step 2 involves adding 6 times the molar amount of pyridine and 2 times the molar amount of 1,3-butadiene lithium to the solution in Step 1 at a rate of 1 drop / s, stirring at 800 rpm, and reacting for 8 hours. All other conditions and steps remain the same.

[0146] Example 9 The only difference between this embodiment and embodiment 2 is that in step 4, the amount of acetic acid solution added is 6 times the total molar amount of the transition metal.

[0147] Example 10 The only difference between this embodiment and embodiment 2 is that in step 4, the amount of acetic acid solution added is 4 times the total molar amount of the transition metal.

[0148] Example 11 The only difference between this embodiment and embodiment 2 is that in step 4, the amount of acetic acid solution added is 6 times the total molar amount of the transition metal.

[0149] Example 12 This embodiment provides a method for preparing a zirconium carbide material for a hafnium tantalum yttrium ceramic coating for an extreme environment coating, the specific steps comprising: Step 1: First, dissolve equal molar amounts of hafnium tetrachloride, yttrium trichloride, and tantalum pentachloride in n-propanol at 8 times the total molar amount of the transition metals, place the solution at -10°C, and let it stand for 10 minutes to stabilize the internal temperature to obtain a mixed solution.

[0150] Step 2: Add 3 times the molar amount (based on the molar amount of the transition metal, the same for the following steps) of acetylacetone and 1.5 times the molar amount of triethylamine to the mixed solution in step 1 at a rate of 0.5 drops / s, stir at 800 rpm, and react for 4 hours to obtain a reaction solution.

[0151] Step 3: Filter the reaction solution in step 2 under a -10°C N2 atmosphere to obtain a clear filtrate, add a mixture of 1 mol of water and 2 mol of n-propanol to the filtrate and heat under reflux at 80°C to obtain a precursor solution.

[0152] Step 4: Soak the zirconium carbide bulk material in the precursor solution in step 3, and coat the surface of the zirconium carbide material by soaking for 5 minutes; calcining the coated material at a high temperature of 750°C for 2.5 hours to obtain a high-temperature resistant material with thermal protection function, that is, a zirconium carbide material with a hafnium tantalum yttrium ceramic coating.

[0153] See Figure 3 , is an SEM photo of the zirconium carbide material with hafnium tantalum yttrium ceramic coating. From the high-magnification SEM image, it can be seen that the grains are fully sintered and tightly bonded, indicating that the HTO powder has good sintering behavior.

[0154] See Figure 4 , which is a hardness test chart of zirconium carbide material with hafnium tantalum yttrium ceramic coating. The test method includes using a Webster hardness tester, with specific reference to GB / T 4340.1-2009 and GB / T 16534-2009. As can be seen from the figure, the HTO block has a strong hardness of 635 HV due to its good sintering performance and dense block.

[0155] Example 13 This embodiment provides a method for preparing a hafnium tantalum lanthanum tungsten coating for extreme environment coatings, the specific steps comprising: Step 1: First, dissolve equal molar amounts of hafnium tetrachloride, tungsten hexachloride, tantalum pentachloride, and lanthanum trichloride in n-propanol that is 8 times the total molar amount of the transition metals. Place the solution at -40°C and let it stand for 10 minutes to stabilize its internal temperature.

[0156] Step 2: Add 3 times the molar amount (based on the molar amount of the transition metal, the same for all following steps) of bipyridine and 1.5 times the molar amount of tetrahydrofuran to the solution in step 1 at a rate of 2 drops / s, stir at 800 rpm, and react for 4 hours.

[0157] Step 3: Filter the reaction solution in step 2 under a -10°C low-temperature N2 atmosphere to obtain a clear filtrate, add a mixture of 1 mol of water and 3.5 mol of n-propanol to the filtrate and heat under reflux at 80°C to obtain a copolymer precursor solution.

[0158] Step 4: Add 5 times the amount of sodium hydroxide solution to the solution in step 3 at a rate of 2 drops / s and a stirring speed of 1500 rpm to co-precipitate the metal ions in the precursor to obtain a ceramic pre-powder.

[0159] Step 5: The ceramic pre-powder from Step 4 can be processed into an ultra-high-temperature thermal protective coating based on the required processing technology. The high-entropy alloy is coated using a process such as plasma sputtering. The coated material is calcined at 850°C for 1.5 hours to obtain a high-temperature resistant material with a thermal protective coating.

[0160] Figure 5 The HRTEM image of the hafnium tantalum lanthanum tungsten ceramic coating of this embodiment is shown, indicating that the ceramic coating has a complete crystal structure.

[0161] Comparative Example 1 The difference between this comparative example and Example 4 is only that the standing temperature in step 1 is different. Specifically, step 1: dissolving equimolar amounts of titanium tetrachloride, niobium pentachloride, lanthanum trichloride, and strontium tetrachloride in n-propanol with an amount 15 times the total molar amount of the transition metals, and placing the solution at 25° C. to stabilize its internal temperature to form a mixed solution.

[0162] The other steps are the same.

[0163] See Figure 7 , is the XRD spectrum of the ceramic powder with titanium, niobium, lanthanum and strontium prepared in this ratio 1. No obvious crystal diffraction peaks were observed, indicating that the prepared material was not crystallized and was not dense after sintering.

[0164] Comparative Example 2 This comparative example differs from Example 4 only in the amount of pyridine added in step 2. Specifically, step 2 involves adding 8 times the molar amount of pyridine and 2 times the molar amount of 1,3-butadiene lithium to the solution in step 1 at a rate of 1 drop / s, and reacting for 8 hours. All other steps remain the same.

[0165] See Figure 8 , is the XRD spectrum of the ceramic powder with titanium, niobium, lanthanum and strontium prepared in this ratio 2. No obvious crystal diffraction peak was observed, indicating that the prepared material was not crystallized and the sintering was not dense.

[0166] Will Figure 7 、 Figure 8 and Figure 9By comparison, it can be seen that compared with Comparative Examples 1 and 2, Examples 1 to 4 can obtain complete crystal structures under the temperature conditions of the examples, while Comparative Examples 1 and 2 fail to crystallize under the same temperature conditions as Example 4, that is, no crystal structure is formed.

[0167] Comparative Example 3 This comparative example differs from Example 4 only in the amount of pyridine added in step 2. Specifically, step 2 involves adding 0.4 times the molar amount of pyridine and 2 times the molar amount of 1,3-butadiene lithium to the solution in step 1 at a rate of 1 drop / s, and reacting for 8 hours. All other steps remain the same.

[0168] Comparative Example 4 This comparative example differs from Example 4 only in the amount of 1,3-butadienelithium added in step 2. Specifically, step 2 involves adding a 6-fold molar amount of pyridine and a 1-fold molar amount of 1,3-butadienelithium to the solution in step 1 at a rate of 1 drop / s, and reacting for 8 hours. All other steps remain the same.

[0169] Comparative Example 5 This comparative example differs from Example 4 only in the amount of 1,3-butadienelithium added in step 2. Specifically, step 2 involves adding a 6-fold molar amount of pyridine and a 4-fold molar amount of 1,3-butadienelithium to the solution in step 1 at a rate of 1 drop / s, and reacting for 8 hours. All other steps remain the same.

[0170] Comparative Example 6 This comparative example differs from Example 4 only in the amount of 1,3-butadienelithium added in step 2. Specifically, step 2 involves adding a 6-fold molar amount of pyridine and a 4-fold molar amount of 1,3-butadienelithium to the solution in step 1 at a rate of 1 drop / s, and reacting for 8 hours. All other steps remain the same.

[0171] Comparative Example 7 This comparative example differs from Example 4 only in the addition rate of pyridine and 1,3-butadiene lithium in Step 2. Specifically, Step 2 involves adding 6 times the molar amount of pyridine and 2 times the molar amount of 1,3-butadiene lithium to the solution in Step 1 at a rate of 5 drops / s, and reacting for 8 hours. All other steps remain the same.

[0172] Comparative Example 8 This comparative example differs from Example 4 only in that the mixed solution is not subjected to a low-temperature standing step in step 1. Specifically, in step 1, equimolar amounts of titanium tetrachloride, niobium pentachloride, lanthanum trichloride, and strontium tetrachloride are dissolved in n-propanol at a concentration 15 times the total molar amount of the transition metals to form a mixed solution. All other steps are identical.

[0173] See Figure 6The SEM characterization of the crystal form of the titanium niobium lanthanum strontium ceramic powder obtained in this comparative example shows that even though it is calcined at 1200°C, the titanium niobium lanthanum strontium ceramic has been sintered into shape as a whole, but there are some holes under the high-power SEM microscope, and it cannot be sintered densely.

[0174] Comparative Example 9 This comparative example differs from Example 4 only in that the coprecipitation step (step 4) is omitted. Instead, the solvent in the copolymerization precursor solution (step 3) is removed to produce a ceramic pre-powder. This ceramic pre-powder can then be processed into an ultra-high-temperature thermal protective coating. A high-entropy alloy coating is formed using methods such as plasma sputtering and CVD. The coated material is then calcined at 1300°C to obtain a high-temperature resistant material with a thermal protective coating.

[0175] See Table 1 for the test results of hardness, densification degree, and line ablation rate and mass ablation rate at 3000° C. for each embodiment and comparative example.

[0176] Hardness test method: Use Webster hardness tester, test standards GB / T 4340.1-2009 and GB / T 16534-2009.

[0177] Densification test method: refer to GB / T 3850-2015 and ISO 3369:2006.

[0178] Table 1 Comparison of hardness, densification and ablation rate at 3000℃ between the examples and the comparative examples

[0179] As can be seen from Table 1, compared with the comparative example, the hardness and densification of the material prepared in the embodiment are significantly better than those in the comparative example, and the high-temperature ablation effect is obvious. The linear ablation rate and the mass ablation rate are significantly lower than those in the comparative example, which further illustrates that the coating material provided by the technical solution of the present invention is an excellent high-temperature resistant coating, so that it can be used in extreme environments with high water and oxygen erosion above 2500°C.

[0180] The above are merely preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Those skilled in the art will readily appreciate that the present invention is susceptible to various modifications and variations. Any variation, modification, replacement, integration, or parameter change to these embodiments, which is within the spirit and principles of the present invention and which achieves the same functionality through conventional substitutions, without departing from the principles and spirit of the present invention, falls within the scope of protection of the present invention.

Claims

1. A method for preparing an ultrahigh temperature ceramic precursor, characterized in that: The specific steps include: S1. The transition metal compound is dissolved in an organic solvent and mixed uniformly, and allowed to stand at a low temperature to obtain a mixed solution; S2. Adding a ligand and an exchange agent to the mixed solution, stirring, and performing a coordination reaction; S3. The reaction system of S2 is filtered under a low-temperature nitrogen atmosphere, a mixed solvent is added to the filtrate, and the mixture is heated under reflux to perform a polymerization reaction, thereby obtaining the ultrahigh temperature ceramic precursor.

2. The method for preparing an ultrahigh temperature ceramic precursor according to claim 1, wherein: In S1, the transition metal compound is a combination of chlorides of any three or more of hafnium, zirconium, titanium, tantalum, niobium, and tungsten; And / or, the transition metal compound is a combination of any three or more of hafnium tetrachloride, zirconium tetrachloride, titanium tetrachloride, tantalum pentachloride, niobium pentachloride, tungsten hexachloride, hafnocene dichloride, zirconocene dichloride, titanocene dichloride, tantalum trichloride, iridium trichloride, yttrium trichloride, lanthanum trichloride, and strontium tetrachloride; And / or, the organic solvent is any one of anhydrous ethanol, n-propanol, isopropanol, n-butanol, isobutanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monopropyl ether, ethylene glycol monobutyl ether, and methyl tert-butyl ether, or a combination thereof; and / or, the molar amount of the organic solvent is 3 to 20 times the total molar amount of the transition metal compound; And / or, the temperature of the low temperature environment is -76°C to 10°C; And / or, the standing time is 10 min to 3 h.

3. The method for preparing an ultrahigh temperature ceramic precursor according to claim 1, wherein: In S2, the drop rate of the ligand and the exchange agent is 0.1 to 3 drops / s; The stirring speed is 500~3000rmp; The complexing agent is any one of acetylacetone, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, pyridine, and bipyridine, or a combination thereof; and / or, the molar amount of the complexing agent is 0.5 to 6 times the total molar amount of the transition metal compound; And / or, the exchange agent is any one or a combination of tetrahydrofuran, triethylamine, tert-butylene lithium, pyromellitic lithium, tert-butylene lithium, and 1,3-butadiene lithium; The molar amount of the exchange agent is 0.5 to 4 times the total molar amount of the transition metal compound; And / or, the reaction time of the coordination reaction is 1 to 24 hours; And / or, in S3, the temperature of the low-temperature nitrogen atmosphere is -20°C to 10°C; The mixed solvent is a mixture of water and the organic solvent; The mass ratio of water to the organic solvent is 1:(1-5); The heating reflux temperature is 80-130° C., and the time is 1-6 h.

4. An ultrahigh temperature ceramic precursor prepared by the preparation method according to any one of claims 1 to 3.

5. Use of an ultrahigh temperature ceramic precursor obtained by the preparation method according to any one of claims 1 to 3, or the ultrahigh temperature ceramic precursor according to claim 4, in the surface modification of high-performance inorganic fibers.

6. A modified high-performance inorganic fiber, comprising a high-performance inorganic fiber layer and a high-temperature resistant coating attached to the surface of the fiber material layer; The high temperature resistant coating comprises: The ultrahigh temperature ceramic precursor prepared by the preparation method according to any one of claims 1 to 3, or the ultrahigh temperature ceramic precursor according to claim 4, is coated on the surface of a high-performance inorganic fiber, and calcined at a high temperature to form a coating on the surface of the high-performance inorganic fiber layer; And / or, the material of the high-performance inorganic fiber layer includes any one of carbon fiber, silicon carbide fiber or zirconium carbide fiber; And / or, the high temperature calcination includes a temperature of 600~1300℃.

7. An ultra-high temperature ceramic pre-powder, characterized in that: include: An effective polar precipitant is added to the ultra-high temperature ceramic precursor prepared by the preparation method according to any one of claims 1 to 3, or to the solution of the ultra-high temperature ceramic precursor according to claim 4, and the mixture is stirred to co-precipitate the transition metal ions. The resulting precipitate is the ultra-high temperature ceramic pre-powder.

8. The ultrahigh temperature ceramic pre-powder according to claim 7, wherein: The effective polar precipitant is one or a combination of two or more of ammonia water, sodium hydroxide solution, triethylamine, ethanol, formic acid, and acetic acid; and / or, the molar amount of the effective polar precipitant is 2 to 8 times the total molar amount of the transition metal; And / or, the effective polar precipitant is added dropwise at a rate of 0.5 to 2 drops / s; And / or, the stirring speed is 1000~1500rmp.

9. A composite material for extreme environments, comprising at least a high-temperature resistant base material and a film layer formed by coating the surface of the high-temperature resistant base material with the ultra-high-temperature ceramic precursor according to claim 4 or the ultra-high-temperature ceramic pre-powder according to any one of claims 7 to 8.

10. The composite material for extreme environments according to claim 9, characterized in that: The coating comprises: first coating the ultra-high temperature ceramic precursor on the surface of the high temperature resistant base material to form the film layer, or, forming the film layer on the surface of the high temperature resistant base material by spraying, CVD or plasma sputtering the ultra-high temperature ceramic pre-powder; Then, calcination is performed to obtain the composite material for extreme environments; And / or, the coating method includes any one of brush coating, dipping or spin coating; and / or, the calcination temperature is 600-1300° C.; And / or, the high temperature resistant base material is any one of high performance inorganic fiber, silicon carbide ceramic sheet / plate, zirconium carbide ceramic sheet / plate, high temperature resistant metal sheet / plate, and high temperature resistant alloy sheet / plate.

11. Use of the ultrahigh temperature ceramic precursor prepared by the preparation method according to any one of claims 1 to 3, or the ultrahigh temperature ceramic precursor according to claim 4 in space rockets, hypersonic vehicles, space shuttles, and hypersonic carriers.

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