Precoated fiber light-cured paste and silicon carbide ceramic matrix composite

Abstract

The application discloses a pre-coated fiber photocuring slurry and a silicon carbide ceramic matrix composite material, and a preparation method of the pre-coated fiber photocuring slurry is as follows: chopped fibers, resin and a dispersing aid are added into a dispersing medium, and are uniformly ball milled to obtain a pre-dispersed solution in which the fibers are uniformly dispersed; the pre-dispersed solution is dried, crushed and spheroidized to obtain spherical pre-coated fiber powder; the spherical pre-coated fiber powder is uniformly mixed with photocuring resin and a photoinitiator to obtain the pre-coated fiber photocuring slurry; and a preparation method of the silicon carbide ceramic matrix composite material is as follows: the pre-coated fiber photocuring slurry is subjected to photocuring 3D printing to obtain a resin blank, the resin blank is subjected to secondary heat curing and high-temperature carbonization and debinding to obtain a C / C blank, and the C / C blank is subjected to high-temperature vacuum infiltration to obtain the silicon carbide ceramic matrix composite material; and the problems that the silicon carbide ceramic matrix composite material prepared by using a photocuring slurry in the prior art has a large silicon-rich phase, poor ceramic performance and anisotropic shrinkage in a carbonization process are solved.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide ceramic matrix composites, specifically to a pre-coated fiber photocurable slurry and a silicon carbide ceramic matrix composite. Background Technology

[0002] SiC ceramic matrix composites have wide applications in chemical, aerospace and other fields due to their low density, high modulus, low thermal expansion and high corrosion resistance. Photopolymerization 3D printing of silicon carbide ceramic matrix composites is a slurry-based layer-by-layer printing technology with advantages such as high forming accuracy and the ability to fabricate complex internal structures.

[0003] Patent application [CN 112723890 A] discloses a method for preparing photocurable ceramic slurry and silicon carbide ceramics, comprising the following raw materials in the following mass percentages: SiC@SiO2 powder: 25%-60%; photocurable resin: 10%-40%; carbon source resin: 10%-40%; photoinitiator: 0.1%-2%; dispersant: 2%-6%. The SiC@SiO2 powder comprises a SiC core and a SiO2 shell coating the surface of the SiC core. The carbon source resin has a residual carbon rate of greater than or equal to 40% at 800℃. The SiO2 shell, while improving the forming efficiency of the photocurable ceramic slurry, can react with the carbon source resin during sintering to generate a secondary phase SiC, thereby reducing / eliminating the introduced SiO2 shell. Through the reaction sintering process, rapid manufacturing of complex and delicate SiC ceramic parts is achieved.

[0004] To improve the fluidity of slurry, patent application [CN 115490522 A] discloses a photocurable silicon carbide ceramic slurry and its application. The silicon carbide ceramic slurry is composed of SiC ceramic powder and a photocurable slurry. The SiC ceramic powder consists of SiC powder A with a particle size of 200-500 nm and SiC powder B with a particle size of 600-2000 nm. The volume fraction of the SiC ceramic powder in the silicon carbide ceramic slurry is 30-50 vol.%. The photocurable slurry is composed of a prepolymer, diluent, photoinitiator, dispersant, light diffusing agent, and additives. The light diffusing agent is selected from at least one of silica microspheres, organosilicon microspheres, styrene resin, and acrylic resin. Through the grading and matching of SiC ceramic powder particle sizes, good fluidity of the ceramic slurry under high solids content conditions is achieved, ensuring the accuracy of photocurable molding.

[0005] To improve the toughness of SiC ceramic matrix composites, publication number [CN 115991604 A] discloses an in-situ Ti3SiC2 toughened photocurable 3D printed Cf / SiC composite material and its preparation method. The photocurable slurry uses chopped carbon fibers and SiC powder as fillers. Because the chopped carbon fibers improve the crack deflection path, the fracture toughness of the SiC ceramic matrix composite material is significantly improved. Publication number [CN 111056853A] discloses a photocurable slurry using pure chopped carbon fibers as fillers, which, through photocuring 3D printing, high-temperature debinding, and high-temperature melt infiltration, yields a SiC ceramic matrix composite material with a complex structure.

[0006] Although the above methods can prepare photocurable ceramic slurries that can be well molded, when the filler in the slurry is SiC powder, the prepared SiC ceramic matrix composite material is Si bonded to SiC. Metallographic testing shows that there is a large silicon-rich phase, resulting in poor ceramic performance. On the other hand, because carbon fibers have a large aspect ratio and the single-layer thickness in photocuring is generally 20-200μm, the short carbon fibers in the photocurable slurry are prone to orientation under the action of the scraper. This causes the shrinkage of the photocured resin preform along the scraper direction and perpendicular to the scraper direction to be anisotropic during the subsequent high-temperature degreasing and carbonization process. Summary of the Invention

[0007] The purpose of this invention is to provide a pre-coated fiber slurry for photopolymerization 3D printing and its preparation method. The pre-coated spherical fiber powder is used as a filler, which solves the defects of the large silicon-rich phase and insufficient performance in SiC ceramic matrix composites prepared by existing SiC powder slurries. On the other hand, it solves the problem of shrinkage anisotropy after the slurry prepared by pure fiber as filler is photopolymerized and degreased and carbonized at high temperature.

[0008] The technical solution adopted in this invention is:

[0009] The preparation method of pre-coated fiber photocurable slurry includes the following steps:

[0010] Step 1: Add the chopped fibers, coating resin, and dispersing agent to the dispersion medium, and ball mill them evenly to obtain a pre-dispersion in which the fibers are uniformly dispersed.

[0011] Step 2: Dry, pulverize, and spheroidize the pre-dispersion liquid prepared in Step 1 to obtain spherical pre-coated fiber powder;

[0012] Step 3: Mix the spherical pre-coated fiber powder prepared in Step 2 with the photocurable resin and photoinitiator to obtain the pre-coated fiber photocurable slurry.

[0013] In step 1, the ratio of chopped fiber: resin: dispersing agent: dispersion medium is as follows (by mass).

[0014] =1:(0.1-0.7):(0.05-0.2):(1-4).

[0015] The chopped fibers in step 1 are chopped carbon fibers or chopped SiC fibers with a length between 50μm and 10mm, and the dispersion medium is a solvent that can dissolve the resin, such as deionized water, anhydrous ethanol, or acetone.

[0016] The coating resin in step 1 is a benzoxazine resin containing unsaturated functional groups, represented as:

[0017]

[0018] At least one of R1 and R2 is an unsaturated functional group, which is a photocurable unsaturated group.

[0019] Furthermore, the photocurable unsaturated group is an allyl, propargyl, or maleimide group.

[0020] In step 2, the drying temperature is more than 10°C higher than the boiling point of the dispersion medium, more than 10°C higher than the softening point of the resin, and more than 20°C lower than the initial curing temperature of the resin.

[0021] In step 3, the ratio of spherical pre-coated fiber powder to photocurable resin to photoinitiator is as follows:

[0022] =1:(0.5-2):(0.002-0.08).

[0023] The photocurable resin in step 3 refers to a mixture of polythiols and low-viscosity acrylate monomers. The polythiols include trimethylolpropane tri(3-mercaptopropionic acid) ester (TMPMP) and pentaerythritol tetra(3-mercaptopropionic acid) ester (PETMP), etc. The low-viscosity acrylate monomers include acrylamide (ACMO), 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), monofunctional or polyfunctional acrylate monomers. The mass ratio of polythiols to acrylates is (1-3):(1-19).

[0024] In step 3, the photoinitiator is an initiator that can generate free radicals through photoinitiation.

[0025] The preparation method for silicon carbide ceramic matrix composites using the above-mentioned pre-coated fiber photocurable slurry includes:

[0026] The prepared pre-coated fiber photocurable slurry was photocured and 3D printed to obtain a resin preform. The resin preform was subjected to secondary thermal curing and high-temperature carbonization debinding to obtain a C / C preform. The C / C preform was subjected to high-temperature vacuum melting and infiltration to obtain a SiC ceramic matrix composite material.

[0027] The aforementioned photopolymer 3D printing uses stereolithography (SLA) or digital light processing (DLP) for molding, with a light intensity of 10-50 mW / cm². 2 The thickness of a single-layer cured layer is 20-200μm.

[0028] The carbonization temperature is 800-1500℃, the high-temperature vacuum melting and infiltration temperature is 1450-1900℃, the vacuum degree range is 0.01-100Pa, and the melting and infiltration time is 0.5-8h.

[0029] The secondary thermosetting mainly refers to the secondary thermosetting of benzoxazine resin containing unsaturated functional groups. Specifically, the benzoxazine resin containing unsaturated functional groups is kept at the initial exothermic temperature for 0.5-1h and at the peak exothermic temperature for 0.5-10h.

[0030] The infiltrator used for high-temperature vacuum melting is one or more of elemental Si, Si-Zr alloy, Hf-Si-B alloy, and Hf-Zr-Si-Ta alloy; wherein, Si-Zr alloy is a binary alloy containing Si and Zr elements, Hf-Si-B alloy is a ternary alloy containing Hf, Si, B, etc., and Hf-Zr-Si-Ta alloy is a quaternary alloy containing Hf, Zr, Si, Ta, etc.

[0031] Compared with the prior art, the present invention has the following beneficial technical effects:

[0032] This invention involves adding chopped fibers, coating resin, and dispersing agents to a dispersion medium, and ball milling them to obtain a pre-dispersion liquid with uniformly dispersed fibers. This ensures that the chopped fibers are evenly distributed in the pre-dispersion liquid, preparing for subsequent coating and spheroidization processes. The pre-dispersion liquid is then dried, pulverized, and spheroidized to obtain spherical pre-coated fiber powder. Drying removes the dispersion medium, while pulverization and spheroidization further refine the fibers and form near-spherical fiber aggregates, which helps improve the uniformity and efficiency of the subsequent photocuring process. The spherical pre-coated fiber powder is then mixed with photocuring resin. The photoinitiator is mixed evenly to obtain a pre-coated fiber photocurable slurry. This ensures sufficient contact between the fiber powder and the photocurable resin, allowing for photocuring under the action of the photoinitiator. This mixing process ensures that the fiber powder participates uniformly in the reaction during photocuring, further enhancing its bonding strength with the resin. This transforms the high aspect ratio fiber monofilaments into spherical fiber aggregates, effectively avoiding fiber orientation issues under the action of the doctor blade during photocuring. Furthermore, the spherical pre-coated fiber powder ensures good fluidity of the photocurable slurry even with high filler content. This solves the problems of large silicon-rich phase and insufficient performance in SiC ceramic matrix composites prepared from SiC powder slurries in existing technologies, as well as the anisotropic shrinkage problem after photocuring and high-temperature degreasing and carbonization of slurries prepared with pure fibers as fillers.

[0033] Furthermore, by selecting benzoxazine resin with unsaturated functional groups that has photocurability as the resin matrix for pre-coated carbon fibers, the pre-coated carbon fiber powder can be effectively combined with the photocurable resin during the photocuring process. Compared with other thermosetting resins such as phenolic resin and bismaleimide resin, benzoxazine resin has a smaller dimensional shrinkage rate during curing, which is beneficial to maintaining the dimensional stability of the structural parts after secondary thermocuring after photocuring.

[0034] This invention utilizes a pre-coated fiber photocurable slurry for photocuring 3D printing. Since the pre-coated fiber photocurable slurry does not contain SiC powder, it effectively reduces the size of free silicon in SiC ceramic matrix composites, thereby improving the ceramic properties of the SiC ceramic matrix composites. The prepared pre-coated fiber photocurable slurry is formed using photocuring 3D printing technology. Photosensitive resin undergoes a polymerization reaction under ultraviolet light of a specific wavelength, thus stacking the material layer by layer. During this process, the shape and thickness of each layer can be precisely controlled by computer-controlled ultraviolet light irradiation, ultimately obtaining the desired preform. The resin preform undergoes secondary thermocuring, and the printed preform is then subjected to secondary... Thermosetting further promotes the polymerization reaction of photosensitive resin, improving the strength and stability of the preform. High-temperature carbonization and degreasing solve the problem of shrinkage anisotropy. The preform is carbonized at high temperature and degreased during the carbonization process to remove non-carbon elements, such as volatile components and residual solvents in the resin. This step is to obtain a C / C preform with high carbon content and excellent performance. The C / C preform is then subjected to high-temperature vacuum melting and infiltration. Molten silicon is used to fill the pores of the C / C preform to form a SiC ceramic matrix composite material, further improving the density and performance of the material. Attached Figure Description

[0035] Figure 1 This is a flowchart of the preparation method of the present invention.

[0036] Figure 2 These are several types of click reactions based on thiol groups.

[0037] Figure 3 The structure of Bala is a light-curable benzoxazine resin containing allyl groups.

[0038] Figure 4 DSC curves were used to determine the softening point and initial curing temperature of Bala, a light-curable benzoxazine resin containing allyl groups.

[0039] Figure 5The structure of HPMI-fa is a photocurable benzoxazine resin containing bismaleimide groups.

[0040] Figure 6 To determine the softening point and initial curing temperature of the photocurable benzoxazine resin HPMI-fa with bismaleimide groups, DSC curves were generated.

[0041] Figure 7 Microstructure diagram of SiC ceramic matrix composite material prepared from SiC powder slurry.

[0042] Figure 8 Microstructure diagram of SiC ceramic matrix composite material prepared from pre-coated carbon fiber agglomerate slurry.

[0043] Figure 9 This is a schematic diagram showing the orientation of fibers in uncoated pure fiber pulp under the action of a doctor blade.

[0044] Figure 10 A schematic diagram illustrating the shrinkage characteristics of slurry prepared from pure carbon fiber (Cf), wherein, Figure 10 (a) is the molded resin preform. Figure 10 (b) shows the appearance of the sample after carbonization along the scraper direction. Figure 10 (c) shows the appearance of the sample after carbonization in the direction perpendicular to the scraper in the plane.

[0045] Figure 11 The images show the microstructures of uncoated carbon fibers and precoated carbon fiber aggregates. Figure 11 (a) is a microscopic morphology diagram of uncoated carbon fiber aggregates. Figure 11 (b) is a microscopic morphology diagram of the pre-coated spherical carbon fiber agglomerates. Detailed Implementation

[0046] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0047] It should be noted that the terms "first," "second," etc., in the specification, claims, and accompanying drawings of this invention are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that the embodiments of the invention described herein can be implemented in orders other than those illustrated or described herein. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover a non-exclusive inclusion; for example, a process, method, system, product, or apparatus that comprises a series of steps or units is not necessarily limited to those steps or units explicitly listed, but may include other steps or units not explicitly listed or inherent to such processes, methods, products, or apparatus.

[0048] See Figure 1 The preparation method of pre-coated fiber photocurable slurry includes the following steps:

[0049] Step 1: Add chopped fibers, coating resin, and dispersing agent to the dispersion medium, grind and mix them evenly in a ball mill to obtain a pre-dispersion liquid with uniform fiber dispersion.

[0050] Step 2: Dry, pulverize, and spheroidize the pre-dispersion liquid prepared in Step 1 to obtain spherical pre-coated fiber powder;

[0051] Step 3: Mix the spherical pre-coated fiber powder prepared in Step 2 with the photocurable resin and photoinitiator to obtain the pre-coated fiber photocurable slurry.

[0052] In step 1, the ratio of chopped fiber to resin to dispersant to dispersion medium by mass is 1:(0.1-0.7):(0.5-0.2):(1-4).

[0053] The chopped fibers in step 1 are chopped carbon fibers or chopped SiC fibers with a length between 50μm and 10mm, and the dispersion medium is a solvent that can dissolve the resin, such as deionized water, anhydrous ethanol, or acetone.

[0054] The coating resin in step 1 is a benzoxazine resin containing unsaturated functional groups, represented as:

[0055]

[0056] At least one of R1 and R2 is an unsaturated functional group, which can be an allyl, propargyl, or maleimide group capable of undergoing a mercapto click reaction, etc. See [link to relevant documentation]. Figure 2 .

[0057] The dispersing agents in step 1 mainly include organic polymer dispersing agents such as methylcellulose (MC) and small molecule surfactant dispersing agents such as sodium dodecylbenzenesulfonate (SDBS).

[0058] The drying in step 2 refers to casting drying. To ensure that the material is fully dried, the drying temperature should be 10°C or higher than the boiling point of the dispersion medium. To ensure good coating, the drying temperature should be 10°C or higher than the resin softening point. To avoid excessive resin curing, the drying temperature should be 20°C or higher than the initial curing temperature of the resin.

[0059] The crushing in step 2 refers to the use of conventional rotary vane mechanical crushing equipment.

[0060] The spheroidization in step 2 mainly refers to the spheroidization treatment of the mechanically pulverized powder in spheroidizing equipment such as stirred mills and airflow vortex pulverizers.

[0061] In step 3, the ratio of spherical pre-coated fiber powder to photocurable resin to photoinitiator is as follows:

[0062] =1:(0.5-2):(0.002-0.08).

[0063] The photocurable resin in step 3 refers to a mixture of polythiols and low-viscosity acrylate monomers. The polythiols include trimethylolpropane tri(3-mercaptopropionic acid) ester (TMPMP) and pentaerythritol tetra(3-mercaptopropionic acid) ester (PETMP), etc. The low-viscosity acrylate monomers include acrylamide (ACMO), 1,6-hexanediol diacrylate (HDDA), trimethylolpropane triacrylate (TMPTA), monofunctional or polyfunctional acrylate monomers. The mass ratio of polythiols to acrylates is (1-3):(1-19).

[0064] In step 3, the photoinitiator is one or more of 2,4,6-trimethylbenzoyl-diphenylphosphine oxide (TPO) and phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (819).

[0065] The preparation method of silicon carbide ceramic matrix composite material using the above-mentioned pre-coated fiber photocurable slurry includes:

[0066] The prepared pre-coated fiber photocurable slurry was photocured and 3D printed to obtain a resin preform. The resin preform was subjected to secondary thermal curing and high-temperature carbonization debinding to obtain a C / C preform. The C / C preform was subjected to high-temperature vacuum melting and infiltration to obtain a SiC ceramic matrix composite material.

[0067] The aforementioned stereolithography 3D printer employs stereolithography (SLA) or digital light processing (DLP) technologies, with a light intensity of 10-50 mW / cm². 2 The thickness of a single-layer cured layer is 20-200μm.

[0068] The carbonization temperature is 800-1500℃, the high-temperature vacuum melting and infiltration temperature is 1450-1900℃, the vacuum degree range is 0.01-100Pa, and the melting and infiltration time is 0.5-8h.

[0069] The secondary thermosetting mainly refers to the secondary thermosetting of benzoxazine resin containing unsaturated functional groups. Specifically, the benzoxazine resin containing unsaturated functional groups is kept at the initial exothermic temperature for 0.5-1h and at the peak exothermic temperature for 0.5-10h.

[0070] The high-temperature vacuum melting infiltration process uses one or more of the following as the infiltration agent: elemental Si, Si-Zr alloy, Hf-Si-B alloy, and Hf-Zr-Si-Ta alloy; wherein, Si-Zr alloy is a binary alloy containing Si and Zr elements, Hf-Si-B alloy is a ternary alloy containing Hf, Si, B, etc., and Hf-Zr-Si-Ta alloy is a quaternary alloy containing Hf, Zr, Si, Ta, etc.

[0071] Example 1

[0072] The preparation method of pre-coated fiber photocurable slurry includes the following steps:

[0073] Step 1: Cut short fibers (TC-HC-60-3mm) with a length of 3mm and benzoxazine resin Bala containing allyl groups, see [link to article]. Figure 3 The dispersing agent methylcellulose (MC) is added to the dispersion medium deionized water, and the mixture is ground and mixed evenly in a ball mill to obtain a pre-dispersion liquid in which the fibers are uniformly dispersed. By mass ratio, the ratio of short-cut pitch-based carbon fiber to allyl-containing photocurable benzoxazine resin to dispersing agent methylcellulose is 1:0.7:0.05:3. If the amount of resin is too small, it will not be able to form a good coating on the fibers. If the amount of resin is too large, the fiber content in the final product will be too small, and it will not be able to play a good role in strengthening and toughening. For the specific preparation method of allyl-containing benzoxazine resin Bala, please refer to the patent application with publication number [CN111138613B] entitled "A Method for Preparing Benzoxazine Resin Using Primary Amine Salt".

[0074] Step 2: Dry, pulverize, and spheroidize the pre-dispersion prepared in Step 1 to obtain spherical pre-coated fiber powder; because the boiling point of the dispersant deionized water is 100℃, the drying temperature determined based on the dispersant should be greater than 110℃; because the softening point of the allyl-containing photocurable benzoxazine resin is 69℃, and the initial curing temperature of the allyl-containing photocurable benzoxazine resin is 160℃, see [reference missing]. Figure 4Therefore, the drying temperature determined based on the resin softening point and curing temperature is 79-140℃. The drying temperature of the pre-dispersed liquid is the intersection of the drying temperature determined based on the dispersant and the drying temperature determined based on the resin, i.e., 110-140℃. Here, 110℃ is used for drying. After drying, the material is crushed and spheroidized to obtain allylbenzoxazine-coated short-cut pitch-based carbon fiber TC-HC-60-3mm / Bala powder.

[0075] Step 3: Mix the TC-HC-60-60-3mm / Bala powder prepared in Step 2, acrylate monomer HDDA, and polythiol TMPMP evenly, then add photoinitiator TPO and continue stirring until evenly mixed. The mass ratio of TC-HC-60-60-3mm / Bala powder: acrylate monomer HDDA: polythiol TMPMP: photoinitiator TPO = 1:0.1:1:0.005 to obtain TC-HC-60-60-3mm / Bala / HDDA / TMPMP slurry.

[0076] The preparation method of silicon carbide ceramic matrix composite material using the above-mentioned pre-coated fiber photocurable slurry includes:

[0077] The prepared TC-HC-60-3mm / Bala / HDDA / TMPMP slurry was placed in a DLP-type photopolymerization molding machine with a light intensity of 15mW / cm². 2 A single-layer cured thickness of 20 μm is obtained to form a resin preform; the resin preform is then subjected to secondary thermosetting and high-temperature carbonization debinding to obtain...

[0078] TC-HC-60-3mm / Bala / HDDA / TMPMP carbon-carbon preform; secondary thermosetting: heating to 160℃ at a heating rate of 1℃ / min and holding for 1h, then heating to 270℃ at a heating rate of 3℃ / min and holding for 2h; degreasing and carbonization: carbonizing the TC-HC-60-3mm / Bala resin preform at 1500℃; the prepared TC-HC-60-3mm / Bala carbon-carbon preform was subjected to high-temperature vacuum infiltration of elemental Si at 1900℃ and a vacuum of 100Pa for 8h to obtain the TC-HC-60-3mm / Bala / HDDA / TMPMP / Si ceramic composite material.

[0079] Example 2

[0080] The preparation method of pre-coated fiber photocurable slurry includes the following steps:

[0081] Step 1: Short-cut pitch-based carbon fibers (TC-HC-60-3mm) with a length of 3mm are bonded to HPMI-fa resin containing bismaleimide groups. (See [link to relevant documentation]). Figure 5The dispersing agent methylcellulose (MC) is added to the dispersion medium deionized water, and the mixture is ground and mixed evenly in a ball mill to obtain a pre-dispersion liquid with uniform fiber dispersion. By mass ratio, the ratio of short-cut pitch-based carbon fiber: HPMI-fa resin containing bismaleimide groups: methylcellulose dispersing agent is 1:0.1:0.2:1 to obtain a pre-dispersion liquid with uniform fiber dispersion. If the amount of resin is too small, it will not be able to form a good coating on the fiber; if the amount of resin is too large, the fiber content in the final product will be too small, and it will not be able to play a good role in strengthening and toughening.

[0082] The preparation method of HPMI-fa resin containing bismaleimide groups is as follows:

[0083] 10.78 g (110 mmol) of maleic anhydride and 10.92 g (100 mmol) of 4-aminophenol were added to a 250 mL flask, along with 50 mL of DMF. Under low temperature, 30 mL of DMF containing 5 g of P2O5 and 3 g of H2SO4 was added dropwise over half an hour. After the addition was complete, the temperature was slowly raised to 70 °C and reacted for 3 hours. After the reaction was complete, the reaction solution was cooled and poured into 500 mL of distilled water. The bottom precipitate was dried in a vacuum oven at 50 °C for 24 hours to obtain para-maleimide-based phenol (HPMI). 1.89 g (0.01 mol) of HPMI, 0.97 g (0.01 mol) of furanylmethylamine, 0.66 g (0.022 mol) of paraformaldehyde, and 50 mL of toluene were added to a 100 mL flask. In a round-bottom flask, the solid was dissolved by stirring with a magnet. The reaction temperature was slowly raised to 110°C and the mixture was reacted for 6 hours. The resulting solution was then washed with NaOH and distilled water. The organic layer was then further purified by column chromatography using a mixed solvent of n-hexane and ethyl acetate in a ratio of 4:1. The crystalline product was dried in a vacuum oven at 50°C for 24 hours to obtain the HPMI-fa resin of para-maleimide-phenol-2-furanmethylamine benzoxazine, which is a bismaleimide group.

[0084] Alternatively, add 10.78 g (110 mmol) maleic anhydride, 10.92 g (100 mmol) aminophenol, 30 mL DMF and 120 mL toluene to a 250 mL round-bottom flask, stir the mixture at room temperature for 1 h, then add 1.40 g p-toluenesulfonic acid to the flask while stirring with a magnetic stirrer, and then heat the reaction mixture to reflux for 5 h until the slurry becomes a clear solution. Next, pour the mixture into 500 mL of deionized water. The precipitate was collected by filtration and then washed with sodium bicarbonate (5 wt%) solution and water. The crude sample was recrystallized in isopropanol to give a pale yellow crystalline product (yield approximately 56%) ortho-maleimide-based phenol (abbreviated as oHPMI). 1.89 g, 0.01 mol of oHMPI, 0.93 g, 0.01 mol of aniline, 0.66 g, 0.022 mol of paraformaldehyde, and 40 mL of toluene were added to a 100 mL single-necked flask. The solid was dissolved under magnetic stirring and heated to reflux for 6 hours. The solution was then diluted with 1 M... The product was washed with NaOH aqueous solution and distilled water, and then concentrated using a rotary evaporator. The crude product was further purified by recrystallization in acetone-toluene at a ratio of 1:1 to produce white crystalline needle-like product, which was then dried in a vacuum oven at 50°C for 24 hours (yield of about 91%) to obtain ortho-maleimide phenol-aniline type benzoxazine (abbreviated as oHPMI-a), which is HPMI-fa resin with bismaleimide group.

[0085] Alternatively, 1.89 g, 0.01 mol of oHMPI, 1.07 g, 0.01 mol of p-toluidine, 0.66 g, 0.022 mol of paraformaldehyde, and 40 mL of toluene were added to a 100 mL single-necked flask and mixed under magnetic stirring. The mixture was heated to 110 °C and reacted for 6 hours. The reactants were then washed with 1 M NaOH aqueous solution and distilled water. The product was concentrated using a rotary evaporator and further purified by recrystallization in an acetone-toluene (1:1 v / v) mixture to obtain a white crystalline needle-like product. The crystals were dried under vacuum at 50 °C for 24 hours (yield approximately 85%) to obtain ortho-maleimide-phenol-p-methylaniline type benzoxazine (oHPMI-t), which is HPMI-fa resin with bismaleimide groups.

[0086] 1.89 g of 0.01 mol of oHMPI, 1.17 g of 0.01 mol of 3-aminophenylacetylene, 0.66 g of 0.022 mol of paraformaldehyde, and 40 mL of toluene were added to a 100 mL single-necked flask. The solid was dissolved by magnetic stirring, and then heated to reflux for 6 hours. After that, the solution was washed with 1 M NaOH aqueous solution and distilled water. The product was then concentrated using a rotary evaporator. White crystalline needle-like product was obtained by recrystallization in a 1:1 mixture of acetone and toluene. The product was dried in vacuum at 50 °C for 24 hours (yield of about 89%) to obtain ortho-maleimide-phenol-m-ynylaniline type benzoxazine (oHPMI-ac), which is HPMI-fa resin with bismaleimide group.

[0087] 1.89 g of 0.01 mol of oHMPI, 1.28 g of 0.01 mol of 4-chloroaniline, 0.66 g of 0.022 mol of paraformaldehyde, and 40 mL of toluene were added to a 100 mL single-necked flask. The solid was dissolved by magnetic stirring, and then heated to reflux for 6 hours. After that, the solution was washed with 1 M NaOH aqueous solution and distilled water. The product was then concentrated using a rotary evaporator. The crude product was further purified by recrystallization in a mixed solvent of acetone and toluene (1:1 v / v) to obtain a white crystalline needle-like product. This product was dried in vacuum at 50 °C for 24 h (yield approximately 83%) to obtain ortho-maleimide-phenol-p-methylaniline type benzoxazine (oHPMI-t), which is HPMI-fa resin with bismaleimide groups.

[0088] Step 2: Dry, pulverize, and spheroidize the pre-dispersion prepared in Step 1 to obtain spherical pre-coated fiber powder; since the boiling point of the dispersant deionized water is 100℃, the drying temperature determined based on the dispersant should be greater than 110℃; refer to the test data of HPMI-fa. Figure 6 The drying temperature determined based on the resin softening point and curing temperature is 134-201℃. The drying temperature of the pre-dispersion liquid is the intersection of the drying temperature determined based on the dispersant and the drying temperature determined based on the resin, i.e., 134-201℃. Here, we take 150℃. After drying, the material is crushed and spheroidized to finally obtain TC-HC-60-3mm / HPMI-fa powder.

[0089] Step 3: Mix the TC-HC-60-3mm / HPMI-fa powder prepared in Step 2, the acrylate monomer HDDA, and the polythiol TMPMP evenly. Then add the photoinitiator TPO and continue stirring until evenly mixed. The mass ratio of TC-HC-60-3mm / HPMI-fa powder to acrylate monomer HDDA: polythiol TMPMP: photoinitiator TPO is 1:0.1:1:0.005, yielding TC-HC-60-3mm / HPMI-fa /

[0090] HDDA / TMPMP slurry.

[0091] The preparation method of silicon carbide ceramic matrix composite material using the above-mentioned pre-coated fiber photocurable slurry includes:

[0092] The prepared TC-HC-60-3mm / HPMI-fa / HDDA / TMPMP slurry was placed in a DLP-type photocurable molding machine with a light intensity of 50mW / cm². 2 The single-layer cured thickness is 200μm to obtain a resin preform; the resin preform undergoes secondary thermosetting and high-temperature carbonization degreasing at a carbonization temperature of 1500℃ to obtain a TC-HC-60-3mm / HPMI-fa / HDDA / TMPMP carbon preform; secondary thermosetting: the temperature is increased to 160℃ at a heating rate of 1℃ / min and held for 1h, then increased to 270℃ at a heating rate of 3℃ / min and held for 2h; degreasing and carbonization: TC-HC-60-3mm / HPM The I-fa resin preform was carbonized at 1500℃ to obtain a TC-HC-60-3mm / HPMI-fa / HDDA / TMPMP carbon preform; the prepared TC-HC-60-3mm / HPMI-fa / HDDA / TMPMP carbon preform was subjected to high-temperature vacuum infiltration of elemental Si at 1450℃ and a vacuum of 0.01Pa for 8 hours to obtain a TC-HC-60-3mm / HPMI-fa / HDDA / TMPMP / Si ceramic composite material.

[0093] Example 3

[0094] The preparation method of pre-coated fiber photocurable slurry includes the following steps:

[0095] Step 1: Short-cut pitch-based carbon fibers (TC-HC-60-50μm) with a length of 50μm, benzoxazine resin AFBEN containing propargyl, and sodium dodecylbenzenesulfonate (SDBS) are mixed evenly. The mass ratio of short-cut pitch-based carbon fibers: photocurable benzoxazine resin AFBEN containing propargyl: sodium dodecylbenzenesulfonate (SDBS): anhydrous ethanol is 1:0.1:0.1:4, resulting in a pre-dispersion liquid with uniform fiber dispersion. If the amount of resin is too small, it will not form a good coating on the fibers; if the amount of resin is too large, the fiber content in the final product will be too small, and it will not achieve a good reinforcing and toughening effect. For the specific preparation method of benzoxazine resin AFBEN containing propargyl, please refer to the patent application with publication number [CN111138613B] entitled "A Method for Preparing Benzoxazine Resin Using Primary Amine Salts".

[0096] Step 2: The pre-dispersion prepared in Step 1 is dried, pulverized, and spheroidized to obtain spherical pre-coated fiber powder. Since the boiling point of the dispersant and anhydrous ethanol is 78℃, the drying temperature determined based on the dispersant should be greater than 88℃. Since the softening point of the photocurable benzoxazine resin containing propargyl is 115℃ and the initial curing temperature of the photocurable benzoxazine resin containing propargyl is 184℃, the drying temperature determined based on the resin softening point and curing temperature is 125-164℃. The drying temperature of the pre-dispersion is the intersection of the drying temperature determined based on the dispersant and the drying temperature determined based on the resin, i.e., 125-164℃. Here, 125℃ is used for drying. After drying, the material is pulverized and spheroidized to obtain spherical pre-coated fiber powder TC-HC-60-50μm / AFBEN.

[0097] Step 3: Mix the TC-HC-60-50μm / AFBEN powder prepared in Step 2, acrylate monomer ACMO, and polythiol PETMP evenly. Then add photoinitiator 819 and continue stirring to mix evenly. The mass ratio of TC-HC-60-50μm / AFBEN powder: acrylate monomer ACMO: polythiol PETMP: photoinitiator 819 is 1:1.7:0.3:0.08 to obtain...

[0098] TC-HC-60-50μm / Bala / ACMO / PETMP slurry;

[0099] The preparation method of silicon carbide ceramic matrix composite material using the above-mentioned pre-coated fiber photocurable slurry includes:

[0100] The prepared TC-HC-60-50μm / Bala / ACMO / PETMP slurry was placed in an SLA-type photopolymerization molding machine with a light intensity of 25mW / cm². 2The single-layer curing thickness is 80μm to obtain a resin preform; the resin preform undergoes secondary thermal curing and high-temperature carbonization degreasing at a carbonization temperature of 1000℃ to obtain a TC-HC-60-50μm / Bala / HDDA / TMPMP carbon-carbon preform; secondary thermal curing: the temperature is increased to 160℃ at a heating rate of 1℃ / min and held for 1h, then increased to 270℃ at a heating rate of 3℃ / min and held for 2h; degreasing and carbonization: the TC-HC-60-50μm / Bala resin preform is carbonized at 1000℃; the prepared TC-HC-60-50μm / Bala carbon-carbon preform is subjected to high-temperature vacuum infiltration of Si-Zr alloy at 1600℃ and a vacuum of 10Pa for 8h to obtain a TC-HC-60-50μm / Bala / ACMO / PETMP / Si-Zr ceramic composite material.

[0101] Example 4

[0102] The preparation method of pre-coated fiber photocurable slurry includes the following steps:

[0103] Step 1: Short-cut pitch-based carbon fibers (TC-HC-60-10mm) with a length of 10mm, allyl-containing benzoxazine resin Bala, and sodium dodecylbenzenesulfonate (SDBS) are added to the dispersion medium acetone and mixed evenly. The mass ratio of short-cut pitch-based carbon fibers: allyl-containing photocurable benzoxazine resin: dispersant sodium dodecylbenzenesulfonate (SDBS) is 1:0.5:0.1:2, resulting in a pre-dispersion liquid with uniform fiber dispersion. If the amount of resin is too small, it will not form a good coating on the fibers; if the amount of resin is too large, the fiber content in the final product will be too small, and it will not achieve a good reinforcing and toughening effect. For the specific preparation method of allyl-containing benzoxazine resin Bala, please refer to the patent application with publication number [CN111138613B] entitled "A Method for Preparing Benzoxazine Resin Using Primary Amine Salts".

[0104] Step 2: The pre-dispersed liquid prepared in Step 1 is dried, pulverized, and spheroidized to obtain spherical pre-coated fiber powder. Since the boiling point of the dispersant acetone is 56.5℃, the drying temperature determined based on the dispersant should be greater than 66.5℃. Because the softening point of the allyl-containing photocurable benzoxazine resin is 69℃, and the initial curing temperature of the allyl-containing photocurable benzoxazine resin is 160℃, the drying temperature determined based on the resin's softening point and curing temperature is 79-140℃. The drying temperature of the pre-dispersed liquid is the intersection of the drying temperature determined based on the dispersant and the drying temperature determined based on the resin, i.e., 79-140℃; here, 80℃ is used for drying. After drying, the material is pulverized and spheroidized to obtain TC-HC-60-10mm / Bala powder.

[0105] Step 3: Mix the TC-HC-60-10mm / Bala powder prepared in Step 2, the acrylate monomer HDDA, and the polythiol TMPMP evenly, then add the photoinitiator TPO and continue stirring until evenly mixed. According to the mass ratio of TC-HC-60-60-3mm / Bala powder: acrylate monomer TMPTA: polythiol TMPMP: photoinitiator TPO = 1:0.7:0.3:0.02, the TC-HC-60-10mm / Bala / TMPTA / TMPMP slurry is obtained.

[0106] The preparation method of silicon carbide ceramic matrix composite material using the above-mentioned pre-coated fiber photocurable slurry includes:

[0107] The prepared TC-HC-60-10mm / Bala / TMPTA / TMPMP slurry was placed in a DLP-type photocurable molding machine with a light intensity of 40mW / cm². 2 A single-layer cured thickness of 80μm is obtained to obtain a resin preform;

[0108] The resin preform was subjected to secondary thermosetting and high-temperature carbonization and degreasing at a carbonization temperature of 1200℃ to obtain a TC-HC-60-10mm / Bala / TMPTA / TMPMP carbon preform. Secondary thermosetting: the temperature was increased to 160℃ at a heating rate of 1℃ / min and held for 1 hour, and then increased to 270℃ at a heating rate of 3℃ / min and held for 2 hours. Degreasing and carbonization: the TC-HC-60-10mm / Bala resin preform was carbonized at 1200℃. The TC-HC-60-3mm / Bala carbon preform was subjected to high-temperature vacuum infiltration of Hf-Si-B alloy at 1800℃ and under a vacuum of 80Pa for 8 hours to obtain the TC-HC-60-10mm / Bala / TMPTA / TMPMP / Hf-Si-B ceramic composite material.

[0109] See Figure 7 , Figure 8 ,in, Figure 7 The microstructure of SiC ceramic matrix composites prepared from traditional SiC powder-containing slurries. Figure 8 The microstructure of the pre-coated carbon fiber slurry and SiC ceramic matrix composite material prepared by this invention shows that the SiC ceramic matrix composite material prepared by the slurry containing SiC powder has obvious SiC phase and silicon-rich phase; while the SiC ceramic matrix composite material prepared by the pre-coated carbon fiber slurry of this invention has no obvious silicon-rich phase and a uniform microstructure. Therefore, the SiC ceramic matrix composite material prepared by the pre-coated carbon fiber slurry of this invention has higher mechanical properties.

[0110] See Figure 9It can be seen that during the photocuring process, the fibers in the uncoated carbon fiber slurry are oriented along the direction of the scraper movement due to the shearing action of the scraper on the material, resulting in anisotropy of the formed preform.

[0111] See Figure 10 Resin preform formed by photocuring uncoated carbon fiber slurry. Figure 10 (a) Appearance of the resin preform after carbonization along the scraper direction. Figure 10 (b) Appearance of the resin preform after carbonization, perpendicular to the scraper direction. Figure 10 (c) It can be seen that the length of the sample along the scraper direction remains unchanged but the width decreases after carbonization, while the width and length of the resin preform perpendicular to the scraper direction both decrease after carbonization, indicating that the slurry prepared from uncoated carbon fibers has obvious anisotropy.

[0112] See Figure 11 , Figure 11 Figure a shows the microstructure of the uncoated carbon fiber, which exhibits a significant aspect ratio. Figure 11 Figure b shows the carbon fiber agglomerates after coating treatment. It can be seen that the carbon fiber agglomerates are spherical. It can be expected that the slurry prepared with uncoated carbon fibers will have the fibers oriented under the action of the scraper, resulting in anisotropy of the preform after molding. However, the slurry prepared with precoated carbon fibers will not have orientation problems, and the preform after molding will not have the anisotropy deficiency.

Claims

1. A method for preparing pre-coated fiber photocurable slurry, characterized in that, Includes the following steps: Step 1: Add the chopped fibers, coating resin, and dispersing agent to the dispersion medium, and ball mill them evenly to obtain a pre-dispersion in which the fibers are uniformly dispersed. Step 2: Dry, pulverize, and spheroidize the pre-dispersion liquid to obtain spherical pre-coated fiber powder; Step 3: Mix the spherical pre-coated fiber powder with the photocurable resin and photoinitiator evenly to obtain the pre-coated fiber photocurable slurry; The coating resin in step 1 is a benzoxazine resin containing unsaturated functional groups, represented as: At least one of R1 and R2 is an unsaturated functional group, and the unsaturated functional group is a photocurable unsaturated group. The photocurable resin in step 3 is a mixture of polythiols and low-viscosity acrylate monomers.

2. The method for preparing the pre-coated fiber photocurable slurry according to claim 1, characterized in that, The chopped fibers in step 1 are chopped carbon fibers or chopped SiC fibers with a length between 50 μm and 10 mm.

3. The method for preparing the pre-coated fiber photocurable slurry according to claim 1, characterized in that, In step 3, the photoinitiator is an initiator that generates free radicals through photoinitiation.

4. A pre-coated fiber photocurable slurry, characterized in that, The preparation method of the pre-coated fiber photocurable slurry according to any one of claims 1 to 3 is adopted.

5. A method for preparing silicon carbide ceramic matrix composite materials using the pre-coated fiber photocurable slurry according to claim 4, characterized in that, include: The prepared pre-coated fiber photocurable slurry was photocured and 3D printed to obtain a resin preform. The resin preform was subjected to secondary thermal curing and high-temperature carbonization debinding to obtain a C / C preform. The C / C preform was subjected to high-temperature vacuum melting and infiltration to obtain a SiC ceramic matrix composite material.

6. The method for preparing silicon carbide ceramic matrix composite materials using pre-coated fiber photocurable slurry according to claim 5, characterized in that, The aforementioned photopolymer 3D printing molding adopts stereolithography or digital light processing molding, with a light intensity of 10-50mW / cm2 and a single-layer curing thickness of 20-200 μm.

7. The method for preparing silicon carbide ceramic matrix composite materials using pre-coated fiber photocurable slurry according to claim 5, characterized in that, The high-temperature vacuum infiltration agent is one or more of elemental Si, Si-Zr alloy, Hf-Si-B alloy and Hf-Zr-Si-Ta alloy; the temperature is 1450-1900℃, the vacuum degree is 0.01-100 Pa, and the infiltration time is 0.5-8 h.

8. A silicon carbide ceramic matrix composite material, characterized in that, The silicon carbide ceramic matrix composite material was prepared using the method described in any one of claims 5 to 7.

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