A ceramic matrix composite (CMC) and a method of making the same

Abstract

The present application relates to the field of advanced ceramic materials, in particular to a ceramic matrix composite (CMC) and a preparation method thereof. The present application aims to solve the technical problems of long preparation process period, poor structural uniformity and insufficient toughness of traditional CMC. The present application uses surface-modified alumina ceramic microspheres as reinforcing bodies, the surface of the microspheres is sequentially modified with hexagonal boron nitride nanosheets and metal nickel catalyst, and is mixed with silicon carbide nanoparticles and polycarbosilane precursor to form a slurry, and a complex component is formed by multi-material additive manufacturing. The present application uses a 3D printing technology combining photocuring and material extrusion to prepare a green body; the green body is then subjected to ultraviolet curing and heat treatment in an inert atmosphere in stages, so that the precursor polymer is crosslinked and solidified while the carbon nanowires are catalytically grown in situ; finally, sintering is carried out under pressure conditions to realize densification of the matrix. The present application greatly shortens the preparation period, and the obtained composite material has a uniform structure, a dense matrix and excellent mechanical properties.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of advanced ceramic materials, in particular to a ceramic matrix composite material (CMC) and a preparation method thereof. BACKGROUND

[0002] Ceramic matrix composites have a wide application prospect in the fields of aerospace and energy due to their high specific strength, high temperature resistance, corrosion resistance and other excellent properties. However, the intrinsic brittleness, low fracture toughness and poor impact resistance of ceramic materials limit their reliability and further application. Traditional toughening strategies mainly involve introducing second-phase reinforcements to form composite materials, thereby hindering crack propagation within the material and improving fracture toughness. For example, the addition of continuous fibers, whiskers, particles or nanotubes as reinforcing phases in the ceramic matrix can achieve toughening through crack deflection, bridging and pull-out mechanisms. In particular, one-dimensional nanocarbon materials such as carbon nanotubes have been widely studied as ceramic toughening phases due to their extremely high strength and modulus. However, carbon-based nanomaterials are easily oxidized in high-temperature air, starting at 450-500°C, which limits their application in high-temperature environments such as aircraft engines. Currently, high-performance ceramic matrix composites often use continuous fiber toughening, and the preparation process includes chemical vapor infiltration and polymer infiltration and pyrolysis. However, these traditional processes have the problems of long cycle time and high cost. For example, patent CN117923950A discloses a ceramic matrix composite heat dissipation substrate and a preparation method and application thereof. The heat dissipation substrate comprises a Cf / silicon carbide layer, a CVD-silicon carbide layer, a silicon nanolayer and a copper silicide layer. The CVD-silicon carbide layer is coated on the outer surface of the Cf / silicon carbide layer, the silicon nanolayer is covered on the upper surface of the CVD-silicon carbide layer, and the copper silicide layer is covered on the upper surface of the silicon nanolayer. The Cf / silicon carbide layer is a carbon fiber cloth reinforced silicon carbide ceramic matrix composite material. These processes also have limitations for the preparation of complex-shaped parts. Typically, a simple-shaped preform needs to be prepared first and then machined into a final shape, resulting in large material waste and difficulty in machining hard ceramics. Based on the above background, the existing technology has the following problems to be solved urgently:

[0003] (1) The preparation cycle of ceramic matrix composites is long and the process is complex, making it difficult to efficiently prepare dense composites;

[0004] (2) The distribution of reinforcing phases in the matrix is uneven, and the interfacial bonding is not ideal, resulting in anisotropy and instability of the macroscopic properties of the composite material;

[0005] (3) The toughening mechanism of the composite material is single, and the total toughening effect is limited, making it difficult to meet higher toughness requirements.

[0006] Therefore, it is necessary to provide a new ceramic matrix composite material and a preparation method thereof, which can shorten the preparation cycle while achieving the homogenization of the composite material structure and significantly improve the toughness and reliability of the material through multiple toughening mechanisms. SUMMARY

[0007] The present application aims at providing a ceramic matrix composite material with novel structure design and process route and a preparation method thereof, so as to significantly shorten the preparation period, improve the internal structure uniformity of the material, and effectively toughen the ceramic matrix, thereby overcoming the technical problems of long process period, poor uniformity and insufficient toughness of the traditional ceramic matrix composite material.

[0008] A ceramic matrix composite material (CMC) and a preparation method thereof, and the technical scheme is as follows:

[0009] S1: 45-55 parts of isopropyl alcohol salt of aluminum are dissolved in 100 parts of deionized water, nitric acid is added to adjust the pH to 1-2 to form a stable sol, the sol is used as an aqueous phase, and is added dropwise into 230-240 parts of a cyclohexane solution containing 2wt% Span-80 nonionic surfactant, and is stirred at a speed of 300 rpm to form a uniform emulsion, then 0.4-0.6 parts of hexamethylenetetramine is added, and stirring is carried out at 80℃ for 1 hour to make aluminum sol droplets generate aluminum hydroxide gel and solidify into balls; after phase separation, the wet gel microspheres are separated by washing with acetone, and dried microsphere precursors are obtained by vacuum drying at 60℃; the precursors are calcined; then the surface of the microspheres is modified to prepare polydopamine modified alumina microspheres;

[0010] Further, the calcination in step S1 is specifically: calcining at a rate of 2℃ / min to 1200℃ in a muffle furnace for 2 hours.

[0011] Further, the surface modification in step S1 is specifically: dispersing 35-45 parts of alumina microspheres in 180-190 parts of a mixed solution of ethanol / water with a volume ratio of 1:1, adding 0.3-0.5 parts of dopamine hydrochloride and 0.7-0.9 parts of Tris buffer, and stirring magnetically at room temperature for 12 hours, then washing the polydopamine coated microspheres with deionized water and vacuum drying to prepare polydopamine modified alumina microspheres;

[0012] S2: 1.5-2.5 parts of hexagonal boron nitride powder are added into 45-50 parts of N,N-dimethylformamide solvent, ultrasonic stripping is carried out for 2 hours, 8-12 parts of polydopamine modified alumina microspheres are added, stirring is carried out at room temperature for 6 hours and ultrasonic stripping is carried out for 5 minutes, the precipitate boron nitride-Al2O3 microspheres are collected after standing, and are washed and dried with anhydrous ethanol to obtain boron nitride-Al2O3 microspheres;

[0013] S3: Take 8-12 parts of the boron nitride-Al2O3 microspheres prepared in step S2 and add them to 100 parts of deionized water. Add 2-3 parts of nickel nitrate hexahydrate and stir at room temperature for 2 hours. Then slowly evaporate the solvent to dryness and place it in air at 120°C for 1 hour. Then, under an argon atmosphere, heat to 350°C and keep warm for 1 hour. After cooling, take it out to obtain alumina microspheres with boron nitride nanosheets and NiO particles on the surface, denoted as Ni-boron nitride-Al2O3.

[0014] Furthermore, the drying and heat preservation described in step S3 specifically involves drying at 120°C for 1 hour, and then heating to 350°C and heat preservation for 1 hour under an argon atmosphere.

[0015] S4: Take 4-6 parts of Ni-boron nitride-Al2O3 microspheres, 0.5-1.5 parts of β-SiC nanoparticles, and 1.5-2.5 parts of polycarbosilane prepared in step S3 and mix them in a planetary ball mill jar. Add 3-5 parts of acrylate photosensitive monomer, a 1:1 volume ratio mixture of ethoxytrifluoroacetone acrylate and hydroxyethyl methacrylate, 0.05-0.15 parts of 1-hydroxycyclohexylphenyl ketone photoinitiator, and 0.15-0.25 parts of polyethylene glycol ether dispersant; ball mill at 500 rpm for 1 hour to prepare a photocurable ceramic slurry.

[0016] Furthermore, the acrylate photosensitive monomer mentioned in step S4 is specifically a mixture of ethoxytrifluoroacetone acrylate and hydroxyethyl methacrylate in a volume ratio of 1:1.

[0017] S5: Using 3D printing technology, first spread a 50μm thick film of ceramic slurry prepared in step S4 on the base plate, selectively expose and cure the predetermined area with 405nm wavelength UV light for 5 seconds, switch to material extrusion mode, and use 365nm UV-LED to irradiate and cure the sprayed filament slurry. After completing one layer of printing, the platform moves down and repeats the next layer of slurry-photocuring and extrusion-curing cycle. Place it under a xenon lamp source for overall irradiation for 2 minutes to obtain a cubic block green body.

[0018] S6: The green body prepared in step S5 is placed in the quartz tube of a tube furnace and subjected to segmented heating heat treatment under the protection of high-purity argon gas flow. Then it is cooled to room temperature. The entire pyrolysis process is maintained with argon gas flow to ensure an inert environment, resulting in a porous green body. Then pressure-assisted sintering is performed to prepare a ceramic matrix composite material.

[0019] Furthermore, the segmented heating heat treatment described in step S6 specifically involves: first heating to 200-300°C at a rate of 2°C / min and holding at that temperature for 1 hour, then heating to 850-950°C at a rate of 5°C / min and holding at that temperature for 2 hours.

[0020] Further, the pressure-assisted sintering described in step S6 specifically involves: placing the porous blank in a graphite mold and sending it into a vacuum hot press furnace for sintering and densification, with the sintering time being 10... -3 The process is carried out under vacuum, with the temperature increased to 1300–1500°C at a rate of 20°C / min. At this temperature, a uniaxial pressure of 18–22 MPa is applied, and the temperature is held for 1–2 hours. Then, the furnace is closed and cooled to room temperature.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] 1. This invention uses photopolymer additive manufacturing to directly form complex green bodies, eliminating traditional molding and machining steps, and completes densification through a single hot pressing and sintering process. It eliminates the need for repeated polymer infiltration and pyrolysis impregnation cycles, significantly shortening the preparation cycle, resulting in high process integration and greatly improving production efficiency.

[0023] 2. This invention ensures the uniform distribution and accurate positioning of reinforcing phases such as alumina microspheres and silicon carbide particles in the matrix through multi-material 3D printing. The macroscopic composition of the composite material is uniform, avoiding the agglomeration or segregation of reinforcing phases. Additive manufacturing can prepare complex shaped parts, reduce post-processing, and improve material utilization.

[0024] 3. This invention comprehensively utilizes multiple mechanisms such as microsphere toughening, two-dimensional sheet toughening, and one-dimensional nano-toughening to improve the crack resistance of composite materials as cracks propagate, and significantly enhance impact toughness and damage tolerance.

[0025] 4. The composite material of this invention maintains high strength and hardness while improving toughness. The introduction of boron nitride interface phase and nano-carbon toughening phase does not significantly reduce the matrix strength; on the contrary, due to stress dispersion and crack passivation, the strength of the material is more stable. The addition of nickel and the formation of graphitized carbon nanowire network give the composite material excellent thermal conductivity and self-conductivity. Attached Figure Description

[0026] Figure 1 This is a flow chart of the preparation process of a ceramic matrix composite material (CMC) according to the present invention.

[0027] Figure 2 This is a comparison chart of the mechanical test results of Examples 1-3 and Comparative Examples 1-3. Detailed Implementation

[0028] The following embodiments further explain and illustrate the technical solutions of the present invention. It is particularly noted that each specific embodiment is a concretization and explanation of the technical solution and should not be considered as a limitation on the scope of protection of the present invention. Those skilled in the art still have the right to modify the technical solutions of these embodiments and make equivalent substitutions for some or all of the technical features, and these modifications or substitutions do not change the essence of the corresponding technical solutions, nor do they cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions described in the present invention. Figure 1 The diagram shows the preparation process of a ceramic matrix composite material (CMC). The detailed preparation steps are as follows:

[0029] This ceramic matrix composite comprises an alumina ceramic microsphere reinforcement, a boron nitride nanosheet interface phase, an in-situ grown carbon nanowire toughening phase, and a silicon carbide ceramic matrix derived from polycarbosilane. The alumina microspheres, mimicking the microstructure of natural materials such as nacre and spherical structures in bone tissue, are uniformly dispersed within the matrix. Their surfaces are first coated with a layer of graphite-like boron nitride nanosheets to act as a "flexible" interface layer, followed by the loading of nanoscale nickel catalyst particles. The matrix portion is filled with pre-added silicon carbide nanoparticles, which are transformed from the polycarbosilane precursor into a silicon carbide-based ceramic phase during sintering. In the subsequent heat treatment stage, the nickel catalyst in-situ catalyzes the in-situ cracking of polycarbosilane, resulting in the in-situ growth of carbon into a network of carbon nanowires that penetrate between the matrix and the microsphere reinforcement, forming a three-dimensional interconnected toughening framework.

[0030] 1. Preparation of surface-modified alumina ceramic microspheres

[0031] Aluminum isopropoxide was dissolved in deionized water, and a small amount of nitric acid was added to adjust the pH to form a stable sol. This sol was used as the aqueous phase and slowly added dropwise to an organic phase containing cyclohexane, with a nonionic surfactant pre-dissolved in the organic phase. After stirring and emulsifying to form a homogeneous emulsion, hexamethylenetetramine was added to the aqueous phase, causing aluminum hydroxide gel to form within the aluminum sol droplets and solidify into spheres. After standing and phase separation, the wet gel microspheres were washed with acetone, vacuum dried, and then calcined to obtain white, dense alumina ceramic microspheres. Next, the microsphere surface was modified: the alumina microspheres were dispersed in an ethanol / water mixture, and dopamine hydrochloride and Tris buffer were added; dopamine self-polymerized to form a polydopamine coating on the microsphere surface, endowing the microsphere surface with abundant active functional groups and adhesion. The PDA-coated microspheres were washed with deionized water and vacuum dried to prepare polydopamine-modified alumina microspheres.

[0032] 2. Assembly of boron nitride nanosheets

[0033] Hexagonal boron nitride powder was mixed with N,N-dimethylformamide and ultrasonically exfoliated to obtain a dispersion. Polydopamine-modified alumina microspheres were added to this dispersion, allowing boron nitride nanosheets to be fully adsorbed onto the microsphere surface. Due to the π-π interactions and hydrogen bonds provided by the polydopamine layer, the boron nitride nanosheets adhered firmly to the microsphere surface, forming a coating layer. After standing, the precipitate was collected, washed with anhydrous ethanol to remove unattached boron nitride nanosheets, and dried to obtain alumina microspheres uniformly coated with boron nitride nanosheets. The boron nitride nanosheets enhanced the bonding between the alumina microspheres and the matrix, improving the strength and stiffness of the composite material and exhibiting a significant toughening effect.

[0034] 3. Supported nickel catalyst

[0035] Alumina microspheres coated with boron nitride nanosheets were mixed with nickel nitrate hexahydrate, allowing the nickel nitrate solution to fully penetrate the gaps between the microspheres and adsorb onto the surface of the boron nitride nanosheets. The solvent was then slowly evaporated to dryness, yielding nickel salt-coated microspheres. Drying further promoted the partial decomposition of nickel nitrate and improved adhesion. The microspheres were then heated under an argon atmosphere to completely decompose the remaining nickel nitrate into nickel oxide nanoparticles that adhered to the microsphere surface. After cooling, the microspheres were removed, yielding alumina microspheres with a surface modified with boron nitride nanosheets and NiO particles.

[0036] 4. Preparation of UV-curable ceramic slurry

[0037] The Ni-BN-Al2O3 microspheres, β-SiC nanoparticles and polycarbosilane prepared above were mixed and placed in a planetary ball mill jar. Acrylic photosensitive monomers, photoinitiators and dispersants were added, and the mixture was ball milled at high speed to make the components uniformly mixed and grind and disperse the agglomerated particles to obtain a photocurable ceramic slurry.

[0038] 5. Additive manufacturing

[0039] This 3D printing technique combines stereolithography and material extrusion for shaping. During the printing process, a cycle of slurry spreading-selective photopolymerization and high-viscosity slurry extrusion-curing is alternated, allowing different material components to be deposited at different locations according to design requirements. This multi-material additive manufacturing method can form complex shapes in a single step, precisely arranging each reinforcing phase at the target location. This achieves uniform distribution and directional arrangement of the reinforcement in the composite material, avoiding the problems of reinforcing phase agglomeration or uneven distribution in traditional processes.

[0040] Specifically, the above-mentioned slurry is shaped using 3D printing equipment. This equipment includes a working tank for film deposition and photocuring, and a material extrusion printhead, enabling alternation between two processes. First, a thin film of ceramic slurry is spread on a substrate. Using digital light processing, a predetermined area is selectively exposed and cured with 405nm wavelength UV light, and the remaining uncured slurry is scraped off and collected. Then, the process switches to material extrusion mode, extruding slurry streaks, primarily filling large-volume areas and supporting structures. During extrusion, a 365nm UV-LED simultaneously illuminates the ejected filamentary slurry, causing it to solidify instantly after deposition. This extrusion-curing process continues until the layer is completely filled. After one layer is printed, the platform moves down, and the slurry-photocuring and extrusion-curing cycle is repeated for the next layer, resulting in a cubic block-shaped green sample. During the printing process, all material components are deposited and cured along with the slurry. Ni-BN-Al2O3 microspheres and SiC nanoparticles are uniformly distributed in the cured organic matrix with tight interlayer bonding and no delamination defects. Subsequently, the green body is placed under a xenon lamp light source and irradiated for 2 minutes to further solidify the remaining resin that has not fully undergone photoreaction, thereby improving the mechanical strength of the green body.

[0041] 6. Simultaneous curing - catalyst activation

[0042] The photocured green body was placed in the quartz tube of a tube furnace and subjected to segmented heating heat treatment under the protection of a high-purity argon gas flow. This process caused the polycarbosilane to undergo bridging and cross-linking reactions upon heating. During this process, the polycarbosilane released small amounts of methane, hydrogen, and other small molecules, achieving a transformation from a linear to a network structure. The entire pyrolysis process maintained an argon gas flow to ensure an inert environment. The pyrolyzed and activated green body was then sent to a vacuum hot press furnace for sintering and densification. Sintering was carried out under vacuum with uniaxial pressure applied. At this point, the material was highly dense, and the alumina microspheres were completely preserved and uniformly distributed within the matrix, exhibiting isotropic properties.

[0043] A "simultaneous curing-catalyst activation" process is adopted. On the one hand, the photosensitive resin is cured in the green body by ultraviolet light irradiation, thereby ensuring the stability of the shape and size of the green body in subsequent operations. On the other hand, the cured green body is placed in an inert atmosphere and heated in stages to induce the cross-linking and curing of the polycarbosilane precursor and further pyrolysis into ceramic. During this process, the nickel catalyst precursor supported on the surface of the microspheres is reduced to metallic Ni nanoparticles and reacts with the carbon source generated by cracking, catalyzing the in-situ growth of carbon nanowires. This simultaneous process transforms the polymer matrix from an organic phase to an inorganic ceramic phase, thereby constructing a three-dimensional toughening network composed of CNWs within the material, avoiding additional CVD processes. Transition metals such as Ni have high carbon solubility and diffusivity, making them ideal catalysts for carbon nanotube / wire growth. On the surface of Ni particles, carbon atoms continuously precipitate and form graphitized slender carbon filaments, ultimately presenting a graphite-structured carbon nanowire toughening phase. The growth process of this in-situ toughening phase is completed simultaneously with the solidification process of the matrix. It not only makes full use of the residual carbon generated by the pyrolysis of polycarbosilane to improve the crystallinity of ceramics and avoid the problem of residual carbon deteriorating mechanical properties, but also constructs a nano-reinforcing network that runs through the entire composite material.

[0044] This invention achieves high densification of materials in a single sintering process through transient eutectic liquid-phase-assisted hot-pressing sintering. Specifically, a solidified and activated preform is placed in a vacuum / inert atmosphere hot-press furnace, and sintering is performed under appropriate pressure and rapid heating. During this process, a nickel catalyst reacts with the silicon / carbon components in the matrix to generate a low-eutectic-point Ni-Si alloy phase. When the temperature exceeds the eutectic point, Ni₂Si exhibits a small amount of liquid phase, i.e., transient liquid-phase sintering occurs. This liquid phase effectively wets solid particles such as silicon carbide and Al₂O₃, promoting particle rearrangement and densification, and reducing the temperature and time required for sintering. This invention utilizes the in-situ generated eutectic liquid phase to achieve dense sintering at a lower temperature. After holding at sintering temperature for a period of time, the density approaches the theoretical density. Subsequently, during cooling, the liquid phase solidifies, and precipitates such as Ni₂Si are distributed as dispersed particles and thin films at the matrix grain boundaries. On the one hand, these intermetallic compound particles fill grain boundaries and residual pores, improving the material's density and interfacial bonding strength; on the other hand, their presence helps alleviate interfacial stress between the ceramic matrix and alumina microspheres, and improves the material's thermal and electrical conductivity. This pressure-assisted one-step sintering process eliminates the need for repeated infiltrations, significantly shortening the preparation cycle.

[0045] Example 1

[0046] Table 1 Raw Material Information Table

[0047] Raw material name Model / dosage form CAS number Isopropyl alcohol salt of aluminum Liquid 555-31-7 Nitric acid 68% aqueous solution 7697-37-2 Span-80 non-ionic surfactant Liquid 1338-43-8 Cyclohexane Liquid 110-82-7 Hexamethylenetetramine White crystalline powder 100-97-0 Acetone Liquid 67-64-1 Ethanol 95% anhydrous 64-17-5 Dopamine hydrochloride White crystalline powder 62-31-7 Tris buffer pH = 8.5 77-86-1 Hexagonal boron nitride White powder 10043-11-5 N, N-dimethylformamide Liquid 68-12-2 Nickel nitrate hexahydrate Green crystalline powder 13478-00-7 Argon gas High purity 7440-37-1 β-SiC nanopowder Gray nanopowder 409-21-2 Polycarbosilane - 68584-35-8 Ethoxy trifluoroacetophenone acrylate Liquid 114712-80-8 Hydroxyethyl methacrylate Liquid 868-77-9 1-hydroxy cyclohexyl phenyl ketone White crystalline powder 947-19-3 Polyethylene glycol ether Liquid 25990-96-9

[0048] A ceramic matrix composite material (CMC) and its preparation method are as follows:

[0049] S1: Dissolve 50 parts of aluminum isopropoxide in 100 parts of deionized water, adjust the pH to 1.5 with nitric acid to form a stable sol, and add it dropwise to 235 parts of a cyclohexane solution containing 2 wt% Span-80 nonionic surfactant. After stirring and emulsifying at 300 rpm to form a uniform emulsion, add 0.5 parts of hexamethylenetetramine and stir at 80℃ for 1 hour to form aluminum hydroxide gel in the aluminum sol droplets and solidify it into spheres. After standing and phase separation, wash the wet gel microspheres with acetone and separate them. Dry the dried microsphere precursor by vacuum drying at 60℃. Place it in a muffle furnace and calcine it at 1200℃ at a rate of 2℃ / min for 2 hours.

[0050] Next, the surface of the microspheres was modified: 40 parts of the microsphere precursor were dispersed in 185 parts of a 1:1 volume ratio ethanol / water mixed solution, 0.4 parts of dopamine hydrochloride and 0.8 parts of Tris buffer were added, and the reaction was carried out magnetically at room temperature for 12 hours. The microspheres coated with polydopamine were washed with deionized water and vacuum dried to prepare polydopamine modified alumina microspheres.

[0051] S2: Take 2 parts of hexagonal boron nitride powder, add it to 47 parts of N,N-dimethylformamide solvent, and ultrasonically exfoliate for 2 hours. Add 10 parts of polydopamine-modified alumina microspheres, stir at room temperature for 6 hours and sonicate for 5 minutes. After standing, collect the precipitate boron nitride-Al2O3 microspheres, wash and dry with anhydrous ethanol to obtain boron nitride-Al2O3 microspheres.

[0052] S3: Take 10 parts of the boron nitride-Al2O3 microspheres prepared in step S2 and add them to 100 parts of deionized water. Add 2.5 parts of nickel nitrate hexahydrate and stir at room temperature for 2 hours. Then slowly evaporate the solvent to dryness and place it in air at 120°C for 1 hour. Then, under an argon atmosphere, heat to 350°C and keep warm for 1 hour. After cooling, take it out to obtain alumina microspheres with boron nitride nanosheets and NiO particles on the surface, denoted as Ni-boron nitride-Al2O3.

[0053] S4: Take 5 parts of Ni-boron nitride-Al2O3 microspheres, 1 part of β-SiC nanoparticles and 2 parts of polycarbosilane prepared in step S3 and mix them in a planetary ball mill jar. Add 4 parts of acrylate photosensitive monomer, which is a mixture of ethoxytrifluoroacetone acrylate and hydroxyethyl methacrylate in a volume ratio of 1:1, 0.1 parts of 1-hydroxycyclohexylphenyl ketone photoinitiator and 0.2 parts of polyethylene glycol ether dispersant; ball mill at 500 rpm for 1 hour to prepare photocurable ceramic slurry.

[0054] S5: Spread a 50μm thick film of ceramic slurry prepared in step S4 onto the substrate; selectively expose and cure the predetermined area with 405nm wavelength UV light for 5 seconds using digital light processing, scrape off and collect the remaining uncured slurry, then switch to material extrusion mode, and use a 0.25mm diameter nozzle to extrude slurry stripes according to the sample cross-section filling path, mainly filling large volume areas and supporting structures; during the extrusion process, a 365nm UV-LED simultaneously illuminates the extruded filamentary slurry, causing it to solidify and set instantly after deposition. This extrusion-curing process lasts for about 30 seconds until the layer is filled; after completing one layer of printing, the platform is lowered by 50μm, and the next layer of slurry-curing and extrusion-curing cycle is repeated, printing a total of 50 layers. Then, the green body is placed under a xenon lamp source for overall irradiation for 2 minutes to obtain a cubic block green body;

[0055] S6: The green body prepared in step S5 is placed in the quartz tube of a tube furnace and subjected to segmented heating heat treatment under the protection of high-purity argon gas flow. First, the temperature is increased to 250°C at 2°C / min and held for 1 hour. Then, the temperature is increased to 900°C at 5°C / min and held for 2 hours. After furnace cooling to room temperature, argon gas flow is maintained throughout the pyrolysis process to ensure an inert environment, resulting in a porous green body. Then, pressure-assisted sintering densification is performed. The porous green body is placed in a graphite mold and sent to a vacuum hot press furnace for sintering densification at 10°C. -3 The process was carried out under vacuum, with the temperature increased to 1400℃ at a rate of 20℃ / min. At this temperature, a uniaxial pressure of 20MPa was applied and the temperature was held for 1.5 hours. Then, the furnace was closed and cooled to room temperature to prepare the ceramic matrix composite material.

[0056] Example 2

[0057] The preparation method is the same as in Example 1, but with the following differences:

[0058] S1: 45 parts of aluminum isopropoxide; pH adjusted to 1 with nitric acid; 230 parts of cyclohexane solution containing 2 wt% Span-80 nonionic surfactant; 0.4 parts of hexamethylenetetramine.

[0059] Next, the surface of the microspheres was modified: 35 parts of alumina microspheres were dispersed in 180 parts of a 1:1 volume ratio ethanol / water mixed solution, and 0.3 parts of dopamine hydrochloride and 0.7 parts of Tris buffer were added.

[0060] S2: 1.5 parts hexagonal boron nitride powder, 45 parts N,N-dimethylformamide solvent, and 8 parts polydopamine-modified alumina microspheres;

[0061] S3: 8 parts of boron nitride-Al2O3 microspheres prepared in step S2, and 2 parts of nickel nitrate hexahydrate;

[0062] S4: 4 parts of Ni-boron nitride-Al2O3 microspheres, 0.5 parts of β-SiC nanoparticles, 1.5 parts of polycarbosilane, 3 parts of acrylate photosensitive monomers, 0.05 parts of 1-hydroxycyclohexylphenyl ketone photoinitiator, and 0.15 parts of polyethylene glycol ether dispersant prepared in step S3;

[0063] S6: First, raise the temperature to 200℃ at 2℃ / min, then continue to raise the temperature to 850℃ at 5℃ / min; for sintering, raise the temperature to 1300℃ at 20℃ / min, apply a uniaxial pressure of 22MPa at this temperature, and hold for 2 hours.

[0064] Example 3

[0065] The preparation method is the same as in Example 1, but with the following differences:

[0066] S1: 55 parts of aluminum isopropoxide; pH adjusted to 2 with nitric acid; 240 parts of cyclohexane solution containing 2 wt% Span-80 nonionic surfactant; 0.6 parts of hexamethylenetetramine.

[0067] Next, the surface of the microspheres was modified: 45 parts of alumina microspheres were dispersed in 190 parts of a 1:1 volume ratio ethanol / water mixed solution, and 0.5 parts of dopamine hydrochloride and 0.9 parts of Tris buffer were added.

[0068] S2: 2.5 parts hexagonal boron nitride powder, 50 parts N,N-dimethylformamide solvent, and 12 parts polydopamine-modified alumina microparticles;

[0069] S3: 12 parts of boron nitride-Al2O3 microspheres prepared in step S2, and 3 parts of nickel nitrate hexahydrate;

[0070] S4: 6 parts of Ni-boron nitride-Al2O3 microspheres, 1.5 parts of β-SiC nanoparticles, 2.5 parts of polycarbosilane, 5 parts of acrylate photosensitive monomers, 0.15 parts of 1-hydroxycyclohexylphenyl ketone photoinitiator, and 0.25 parts of polyethylene glycol ether dispersant prepared in step S3.

[0071] S6: First, raise the temperature to 300℃ at 2℃ / min, then continue to raise the temperature to 950℃ at 5℃ / min; for sintering, raise the temperature to 1500℃ at 20℃ / min, apply a uniaxial pressure of 18MPa at this temperature, and hold for 1 hour.

[0072] Comparative Example 1

[0073] Following the preparation method of Example 1, but without assembling boron nitride nanosheets (i.e., without step S2), Ni particles adhere to the alumina surface. All other steps are the same.

[0074] Comparative Example 2

[0075] The preparation method of Example 1 is followed, but without introducing a nickel catalyst, i.e., step S3 is omitted. The remaining steps are the same.

[0076] Comparative Example 3

[0077] The preparation method of Example 1 was followed, but 3D printing, simultaneous curing, and pressure sintering were omitted, i.e., steps S5 and S6 were not performed. The slurry was directly molded into a green body, and then subjected to 5 cycles of impregnation pyrolysis at a temperature controlled at 1200°C. All other steps were the same.

[0078] The comprehensive properties of the ceramic matrix composites prepared in Examples 1-3 and Comparative Examples 1-3 were measured.

[0079] Bending strength test: The test was conducted in accordance with the standard ASTM C1161-18 (2023) "Standard Test Method for Bending Strength of Advanced Ceramics at Ambient Temperature". The three-point bending test was adopted, the specimen size was 3 mm × 4 mm × 40 mm, the span was 30 mm, and the loading speed was 0.5 mm / min.

[0080] Fracture toughness test: The test was conducted in accordance with the standard ASTM C1421-18 (2025) "Standard Test Method for Determining Fracture Toughness of Advanced Ceramics at Ambient Temperature". The specimen size was 2 mm × 4 mm × 20 mm. A diamond saw blade was used to prepare a notch depth of 2 mm and the loading speed was 0.05 mm / min.

[0081] The specific test comparison results are shown in Table 2. Figure 2 As shown:

[0082] Table 2. Comparison of overall performance between Examples 1-3 and Comparative Examples 1-3

[0083] Experimental group Bending strength (MPa) <![CDATA[Fracture toughness (MPa·m 1 / 2 ).]]> Example 1 545±18 7.5±0.3 Example 2 540±18 7.3±0.3 Example 3 545±15 7.4±0.2 Comparative example 1 335±15 3.5±0.3 Comparative example 2 380±17 4.2±0.2 Comparative example 3 435±15 5.3±0.2

[0084] The comparison results show that in Comparative Example 1, there is no BN nanosheet interface phase; the assembly step of BN nanosheets on the surface of alumina microspheres is omitted, i.e., Ni catalyst is directly loaded after PDA coating. This means that there is no flexible interface layer between the microsphere reinforcement and the matrix, and only Ni particles are attached to the alumina surface. Although the resulting composite material still contains carbon nanowires generated by the Ni catalyst, due to the lack of a BN interface phase, most cracks occur directly at the rigid alumina microsphere / SiC interface, resulting in excessively strong and brittle interfacial bonding without BN, which is not conducive to energy-consuming toughening. In Comparative Example 2, without the introduction of Ni catalyst, the residual carbon from the cracking of polycarbosilane will remain in the matrix in an amorphous form, unable to form carbon nanowires, ultimately resulting in poor bending strength and fracture toughness. In Comparative Example 3, the traditional molding and multiple impregnation cracking processes are used. The traditional process results in uneven distribution of the reinforcing phase, high porosity, and a long multiple impregnation cracking cycle, leading to low densification. The lack of a simultaneous curing-catalyst activation process prevents the formation of a carbon nanowire network, resulting in limited toughening effect.

Claims

1. A ceramic matrix composite material (CMC), comprising a matrix phase material and a toughening phase material, characterized in that, The matrix phase material is composed of a silicon carbide ceramic phase, which contains uniformly distributed silicon carbide nanoparticles; the toughening phase material is composed of surface-modified alumina ceramic microspheres and an in-situ grown carbon nanowire network; the surface-modified alumina ceramic microspheres are coated with hexagonal boron nitride nanosheets before sintering, and are also modified with a metallic nickel catalyst; the in-situ grown carbon nanowire network is generated in situ by the in-situ generation of carbon sources catalyzed by the metallic Ni nanoparticles formed by the reduction of the metallic nickel catalyst when they are decomposed at high temperature to form the silicon carbide ceramic phase.

2. The method for preparing a ceramic matrix composite material (CMC) according to claim 1, characterized in that, The preparation method uses surface-modified alumina ceramic microspheres as reinforcements. The surface of the microspheres is sequentially modified with hexagonal boron nitride nanosheets and a nickel catalyst, and mixed with silicon carbide nanoparticles and polycarbosilane precursors to form a slurry. Complex components are formed by multi-material additive manufacturing. Green bodies are prepared using 3D printing technology that combines photopolymerization and material extrusion. The green bodies are then subjected to ultraviolet light curing and staged heat treatment in an inert atmosphere to crosslink and solidify the precursor polymer while catalytically growing carbon nanowires in situ. Finally, the substrate is sintered under pressure to densify the matrix.

3. The method for preparing a ceramic matrix composite material (CMC) according to claim 2, characterized in that, Includes the following steps: S1: Dissolve 45-55 parts of aluminum isopropoxide in 100 parts of deionized water, adjust the pH to 1-2 with nitric acid, and add dropwise to 230-240 parts of a cyclohexane solution containing 2 wt% Span-80 nonionic surfactant. After stirring and emulsifying at 300 rpm to form a uniform emulsion, add 0.4-0.6 parts of hexamethylenetetramine, stir at 80℃ for 1 hour, allow to stand and separate the phases, wash the precipitate with acetone and dry it, then calcine it; finally, perform surface modification to prepare polydopamine-modified alumina microspheres. S2: Take 1.5 to 2.5 parts of hexagonal boron nitride powder, add it to 45 to 50 parts of N,N-dimethylformamide solvent, ultrasonically exfoliate for 2 hours, add 8 to 12 parts of polydopamine-modified alumina microspheres prepared in step S1, stir and let stand, collect the precipitate, wash and dry with anhydrous ethanol to obtain boron nitride-Al2O3 microspheres. S3: Take 8-12 parts of the boron nitride-Al2O3 microspheres prepared in step S2 and add them to 100 parts of deionized water. Add 2-3 parts of nickel nitrate hexahydrate, stir at room temperature for 2 hours, and then dry and keep warm to obtain alumina microspheres with boron nitride nanosheets and NiO particles on the surface, which are denoted as Ni-boron nitride-Al2O3 microspheres. S4: Take 4-6 parts of Ni-boron nitride-Al2O3 microspheres, 0.5-1.5 parts of β-SiC nanoparticles, and 1.5-2.5 parts of polycarbosilane prepared in step S3, mix them in a container, add 3-5 parts of acrylate photosensitive monomer, 0.05-0.15 parts of 1-hydroxycyclohexylphenyl ketone photoinitiator, and 0.15-0.25 parts of polyethylene glycol ether dispersant; ball mill at 500 rpm for 1 hour to prepare photocurable ceramic slurry; S5: Using 3D printing technology, first spread a 50μm thick film of ceramic slurry prepared in step S4 on the base plate, selectively expose and cure the predetermined area with 405nm wavelength UV light for 5 seconds, switch to material extrusion mode, and use 365nm UV-LED to irradiate and cure the sprayed filament slurry. After completing one layer of printing, the platform moves down and repeats the next layer of slurry-photocuring and extrusion-curing cycle. Place it under a xenon lamp source for overall irradiation for 2 minutes to obtain a cubic block green body. S6: The green body prepared in step S5 is placed in the quartz tube of a tube furnace and subjected to segmented heating heat treatment under the protection of high-purity argon gas flow. Then it is cooled to room temperature. The entire pyrolysis process is maintained with argon gas flow to ensure an inert environment, resulting in a porous green body. Then pressure-assisted sintering is performed to prepare a ceramic matrix composite material.

4. The method for preparing a ceramic matrix composite material (CMC) according to claim 3, characterized in that, The calcination described in step S1 specifically involves calcining the furnace at a rate of 2°C / min to 1200°C for 2 hours.

5. The method for preparing a ceramic matrix composite material (CMC) according to claim 3, characterized in that, The surface modification described in step S1 specifically involves mixing 35-45 parts of alumina microspheres with 180-190 parts of ethanol / water solution, 0.3-0.5 parts of dopamine hydrochloride and 0.7-0.9 parts of Tris buffer for modification.

6. The method for preparing a ceramic matrix composite material (CMC) according to claim 3, characterized in that, The stirring described in step S2 specifically involves stirring at room temperature for 6 hours and then sonicating for 5 minutes.

7. The method for preparing a ceramic matrix composite material (CMC) according to claim 3, characterized in that, The drying and heat preservation described in step S3 specifically involves drying at 120°C for 1 hour, and then heating to 350°C and holding for 1 hour under an argon atmosphere.

8. The method for preparing a ceramic matrix composite material (CMC) according to claim 3, characterized in that, The acrylate photosensitive monomer mentioned in step S4 is specifically a mixture of ethoxytrifluoroacetone acrylate and hydroxyethyl methacrylate in a volume ratio of 1:

1.

9. The method for preparing a ceramic matrix composite material (CMC) according to claim 3, characterized in that, The segmented heating heat treatment described in step S6 is as follows: first, the temperature is increased to 200-300℃ at 2℃ / min and held for 1 hour, then the temperature is increased to 850-950℃ at 5℃ / min and held for 2 hours.

10. The method for preparing a ceramic matrix composite material (CMC) according to claim 3, characterized in that, The pressure-assisted sintering described in step S6 specifically involves: placing the porous blank in a graphite mold and then sintering it in a vacuum hot press furnace at 10°C to achieve densification. -3 The process is carried out under vacuum, with the temperature increased to 1300-1500℃ at a rate of 20℃ / min. At this temperature, a uniaxial pressure of 18-22MPa is applied, and the temperature is held for 1-2 hours. Then the furnace is closed and cooled to room temperature.

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