A silicon carbide fiber reinforced ceramic matrix composite grid and method of making the same

Abstract

The application belongs to the technical field of composite material preparation in extreme service environment, and particularly discloses a silicon carbide fiber reinforced ceramic matrix composite grid and a preparation method thereof. The grid comprises a plurality of grid units arranged in an array, the grid unit is a hole structure in one of a regular hexagon, a square or a Kagome shape, adjacent grid units share a side wall to form a monolithic grid structure, and an outer contour of the monolithic grid structure is a polygon. The silicon carbide fiber reinforced ceramic matrix composite grid and the preparation method thereof are adopted to maximize the continuity of fibers, and the structural forming precision and the compactness and uniformity are considered. The prepared grid has excellent performances such as light weight, high strength, high temperature resistance, radiation resistance and low thermal expansion, and is suitable for extreme service scenes such as nuclear energy positioning grids and aerospace satellite bearing platforms.

Description

Technical Field

[0001] This invention relates to the field of composite material preparation technology for extreme service environments, and in particular to a silicon carbide fiber reinforced ceramic matrix composite grid and its preparation method. Background Technology

[0002] In advanced nuclear energy, aerospace, and other high-end equipment fields, extreme service environments place extremely high demands on the comprehensive performance of structural materials. In advanced nuclear energy systems, fuel assembly positioning grids bear the core functions of fuel rod support, positioning, and flow field control, requiring long-term stable operation under high temperature, high pressure, strong neutron irradiation, and flow-induced vibration environments. Traditional zirconium alloy positioning grids are susceptible to high-temperature oxidation and hydrogen embrittlement failure under accident conditions, and their abrasion with the fuel cladding can easily lead to cladding damage, posing a key bottleneck to improving reactor safety performance. Silicon carbide fiber-reinforced silicon carbide ceramic matrix (SiC) f The SiC composite material has high strength, high toughness, excellent high-temperature mechanical stability, extremely low irradiation swelling rate, and good wear and corrosion resistance, and is recognized as the core candidate material for the positioning grid of accident-tolerant fuel assemblies.

[0003] In the aerospace field, high-resolution Earth observation and deep space exploration satellites are rapidly developing towards larger sizes and higher precision. Their supporting platforms must simultaneously meet multiple requirements, including extreme lightweighting, ultra-high specific stiffness, near-zero thermal expansion, and resistance to aging in the space environment. Traditional metal honeycomb and resin-based composite honeycomb structures have inherent defects such as high coefficients of thermal expansion, poor damp-heat stability, and low upper temperature limits, making them unable to meet the dimensional stability requirements of next-generation high-performance satellite platforms. f The SiC composite grating structure combines the intrinsic performance advantages of ceramic matrix composites with the lightweight and high specific stiffness characteristics of grating structures, making it an ideal structural form for high-precision aerospace bearing platforms.

[0004] In the existing technology, SiC f The large-scale engineering application of SiC composite geogrids still faces many technical bottlenecks: On the one hand, the molding of fiber preforms for complex topological geogrid structures is difficult. Existing processes often involve first preparing composite material sheets and then removing the material through machining to form the geogrid structure. This process cuts continuous fibers, severely weakens the mechanical properties of the composite material, and results in low material utilization and high processing costs. On the other hand, when using chemical vapor infiltration (CVI) for densification, the uneven pore distribution of complex geogrid structures can easily lead to premature surface closure and insufficient internal density. Furthermore, the built-in mandrel can hinder the diffusion of reactive gases, resulting in uneven deposition in different parts of the structure and difficulty in controlling dimensional accuracy. Currently, there is no mature process capable of realizing complex SiC configurations. fThe near-net-shape forming and uniform densification of SiC composite material grids limit the engineering application of this type of structure in high-end fields.

[0005] Therefore, developing a monolithic silicon carbide fiber-reinforced ceramic matrix composite grid with continuous fibers, precise structure, and dense uniformity, and its preparation method, is key to promoting the application of this type of material in extreme service scenarios. Summary of the Invention

[0006] The purpose of this invention is to provide a silicon carbide fiber reinforced ceramic matrix composite grid and its preparation method. It addresses the shortcomings of existing silicon carbide fiber reinforced ceramic matrix composite grids, such as poor fiber continuity, low structural forming accuracy, uneven densification, and inability to meet the requirements of extreme service conditions. The invention achieves near-net-shape integral forming and uniform densification of complex grid structures, and fully utilizes the reinforcing and toughening effect of continuous fibers.

[0007] To achieve the above objectives, the present invention provides a silicon carbide fiber reinforced ceramic matrix composite grid, comprising a plurality of grid units arranged in an array. The grid units are perforated structures of one of regular hexagonal, square or kagome shapes. Adjacent grid units share sidewalls to form an integral grid structure. The outer contour of the integral grid structure is polygonal.

[0008] Preferably, the outer contour of the integral grid structure is either rectangular or regular hexagonal, and the number of its grid units is distributed in an N×M array, such as 7 or 19 hexagonal grid units forming a regular hexagonal structure.

[0009] This invention provides a method for preparing a silicon carbide fiber-reinforced ceramic matrix composite grid, comprising the following steps: S1. Mold design and fabrication: Process the grid core mold and external shaping constraint tooling according to the structural dimensions of the target grid; cut the silicon carbide fiber cloth according to the grid sidewall thickness, fiber orientation and layup design. S2. Pre-fixation and marking of fiber cloth: The cut silicon carbide fiber cloth is pre-fixed with low residual carbon resin to maintain the preset shape and improve the laying operation. The sewing path line is marked on the surface of the pre-fixed fiber cloth to obtain the pre-fixed and marked silicon carbide fiber cloth. S3. Prefabricated body stitching and forming: Fix the grid core mold, and lay the silicon carbide fiber cloth obtained in S2 layer by layer on the edge surface of the core mold; use continuous fiber sutures to sew along the marked suture path lines to make each layer of fiber cloth fit tightly and fix it to the core mold. Repeat the layering and sewing operation until the laying of all grid units and the outer contour laying are completed to obtain a fiber-continuous silicon carbide fiber grid prefabricated body. S4. Heat treatment to remove resin: Place the preform obtained in S3 into a vacuum furnace or an inert atmosphere furnace, and heat it to 1000-1200℃ at a rate of 1-10℃ / min, and hold it for 1-4 hours to obtain the heat-treated preform. This heat treatment completely removes the low-carbon adhesive used for pre-curing, and at the same time, it slows down the release of internal stress generated during the preform laying and stitching process. S5. Interfacial phase deposition: The preform obtained in S4 is transferred to a chemical vapor deposition furnace, and a reaction source gas is introduced to deposit a pyrolytic carbon interfacial layer (PyC) or a boron nitride interfacial layer (BN). S6. Substrate Deposition and Densification: Silicon carbide ceramic substrates are deposited using chemical vapor infiltration (CVI) technology. The entire process is divided into two stages: shaping deposition and densification deposition. a) Shaping and Deposition Stage: Retain the core mold and external shaping and constraint fixtures, and perform two depositions, each lasting 30-50 hours. Silicon carbide is deposited at a low deposition rate to preferentially fill the micropores in the fiber bundles and form a continuous initial matrix skeleton, so that the preform can obtain sufficient structural rigidity and shape retention capability. During the deposition process, the workpiece is inverted at least once by 180° to improve the deposition uniformity of the upper and lower parts. After the shaping and deposition is completed, the core mold and external shaping and constraint fixtures are removed. b) Dense deposition stage: Remove the internal core mold and external shaping tooling to eliminate the core mold's obstruction of the diffusion of the reaction gas and continue silicon carbide deposition; after every 50 to 100 hours of deposition, remove the workpiece from the furnace and invert it at 180° or flip it at 90° to balance the deposition rate of each part. Repeat the deposition cycle until the composite material reaches the predetermined bulk density and obtain a dense grid blank. S7. Post-processing: The grid blank obtained in S6 is machined to ensure that the flatness, parallelism and external dimensions of the end face meet the assembly requirements; depending on the application requirements, the surface can be further polished or coated with anti-oxidation, anti-corrosion and functional modification coatings to obtain the final product.

[0010] Preferably, in S2, the low-carbon-residue resin is a thermosetting phenolic resin ethanol solution with a mass fraction of 1% to 20%. After pre-curing, the resin content of the fiber cloth is low, and the amount of residual carbon after heat treatment is extremely small, so its impact on the final performance of the composite material is negligible.

[0011] Preferably, in S3, the suture is a silicon carbide fiber suture or a carbon fiber suture, and the suture stitch distance is in the range of 3~8mm to ensure the bonding force between the layers and the structural integrity.

[0012] Preferably, in step S4, the pressure of the vacuum furnace is ≤10. -2 Pa.

[0013] Preferably, in step S4, the temperature is programmed to rise to 1100°C at a rate of 5°C / min and held for 3 hours to obtain the heat-treated preform.

[0014] Preferably, in S5, when depositing the pyrolytic carbon interface layer, propylene is used as the carbon source gas, argon is used as the dilution gas, the deposition temperature is 950~1000℃, the deposition pressure is 100~600Pa, the deposition time is 8~16h, and the interface layer thickness is 100~500nm.

[0015] Preferably, in S5, boron trichloride and ammonia are used as the reaction source when depositing the boron nitride interface layer.

[0016] Preferably, in S6, the number of cyclic depositions is 6 to 8.

[0017] Therefore, the present invention employs the above-mentioned silicon carbide fiber reinforced ceramic matrix composite grid and its preparation method, and the beneficial effects are as follows: (1) Fibers are continuous and intact, and mechanical properties are excellent: The present invention adopts the preform forming technology of core mold assisted laying + overall stitching, and directly constructs the continuous fiber skeleton of the grid structure on the core mold, realizing the overall preparation of the complex structure fiber preform, completely avoiding the subsequent destructive mechanical processing of the dense composite material, maximizing the preservation of the continuity and integrity of the reinforcing fiber, so that the composite material can give full play to the reinforcing and toughening effect of the continuous fiber, and the specific strength and specific modulus are significantly better than the grid components prepared by mechanical processing.

[0018] (2) Near-net-shape integral molding with high structural precision: This invention uses a precision-machined graphite core mold and a shaping tooling stitching process to produce grid structures with high precision and high repeatability of various topological configurations such as regular hexagons, squares, and Kagome. The grid nodes are reliably connected, the wall thickness is uniform and consistent, and the overall dimensional accuracy is controllable. It is particularly suitable for scenarios such as nuclear fuel positioning grids and aerospace satellite bearing platforms where assembly precision requirements are strict.

[0019] (3) Staged densification, balancing uniformity and precision: This invention pioneers a staged CVI densification strategy of “shaping deposition-demolding-densification deposition”. In the shaping stage, the core mold is retained to ensure the accuracy of the structural shape and slowly fills the pores in the bundle to form a rigid matrix skeleton. After demolding, densification deposition is carried out to eliminate the diffusion obstruction of the reaction gas by the core mold, which greatly improves the filling efficiency and uniformity of the pores between the bundles. At the same time, with multiple inversion operations, the problem of uneven deposition caused by the core mold blocking in the traditional process is solved, and uniform and sufficient densification of the complex grid structure is achieved.

[0020] (4) Clear application orientation and broad prospects: The SiC prepared by this invention fSiC composite material grids possess comprehensive properties such as lightweight, high strength, high rigidity, high temperature resistance, radiation resistance, near-zero thermal expansion, excellent creep resistance, and dimensional stability. They can directly meet the urgent needs of major national strategic fields such as advanced nuclear energy system fuel assembly positioning grids and high-precision aerospace satellite support platforms for high-performance structural materials, and have broad engineering application value and promotion prospects.

[0021] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0022] Figure 1 This is a schematic diagram showing the dimensions of the hexagonal seven-hole grid prefabricated body according to Embodiment 1 of the present invention; Figure 2 This is a schematic diagram of the structure of the graphite core mold for the grille according to Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the external graphite shaping tooling for the grille according to Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the stitching path of the grid preform in Embodiment 1 of the present invention; Figure 5 This is a SEM image of the cross-section of silicon carbide fibers after PyC interface deposition in Embodiment 1 of the present invention. Figure 6 This is a regular hexagonal seven-hole SiC according to Embodiment 1 of the present invention. f / Actual image of SiC composite material grid. Detailed Implementation

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0024] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0025] Example 1 A silicon carbide fiber-reinforced ceramic matrix composite grid, specifically a regular hexagonal grid. For example... Figure 1As shown, the grid consists of seven regular hexagonal grid cells arranged in a hexagonal array (in a honeycomb pattern): one regular hexagonal hole in the center, surrounded by six other regular hexagonal holes. Adjacent grid cells share sidewalls, resulting in an overall hexagonal shape. The inner side length of a single grid cell is 5.6 mm, the design thickness of one sidewall is t = 1 mm, the overall outer contour dimension across sides is 18.81 mm, the axial height is h = 20 mm, and a 1 mm manufacturing allowance is provided at the edges. This structure can be directly used as a nuclear fuel assembly positioning grid. It is understood that, depending on actual needs, this structure can be expanded into a rectangular or hexagonal array with a larger number of grid cells, and the overall shape can be rectangular, regular hexagonal, or other polygonal.

[0026] Its preparation method is as follows: Step 1: Mold Design and Fabrication First, a silicon carbide fiber plain weave fabric is woven using a third-generation continuous silicon carbide fiber machine. The fiber fabric configuration and layup angles include four layup patterns: twill fabric 0° / 90°, twill fabric +45° / -45°, plain weave fabric 0° / 90°, and plain weave fabric +45° / -45°. By combining plain and twill fabrics with multi-directional angle layups, the mechanical properties of the grid surface are balanced in all directions. Based on the target grid's dimensional design drawings, a grid core mold matching the target grid and matching external shaping and constraint tooling are precisely machined using high-strength graphite. The grid core mold structure is as follows: Figure 2 As shown, corresponding to the inner contour of the grid unit, the side length of a single prism is 5.6mm, perfectly matching the inner side length of the grid. The total height of the core mold is 200mm, allowing for one-time molding of long blanks. All edges are machined with a 1mm transition radius to prevent fiber bending and damage during layup, ensuring fiber continuity. The matching external shaping and constraint fixtures are as follows: Figure 3 As shown, the fixture is a regular hexagonal sleeve structure with a total height of 220mm. The distance between the edges of the inner wall of the sleeve is 19.5mm, which matches the machining allowance reserved for the outer contour of the grid blank. The side wall of the fixture is 5mm thick, and threaded holes with a diameter of 10mm are evenly opened on the side wall. The center distance between adjacent holes is 20mm, which serves to fix the mold and ensure uniform flow of the reaction atmosphere, so as to ensure that the atmosphere can fully contact all parts of the preform during the CVI process. At the same time, the required shape and quantity of fiber cloth are precisely cut according to the unfolded size of the core mold.

[0027] Step 2: Pre-setting and marking of the fiber cloth: A 5% (w / w) thermosetting phenolic resin ethanol solution was used as a temporary binder. The cut silicon carbide fiber cloth was completely immersed in the solution for 5 minutes, then removed and air-dried at room temperature until constant weight. This pre-curing treatment ensured the fiber cloth maintained a stiff shape, facilitating subsequent curved surface covering operations. Figure 4As shown, according to the layup and sewing scheme, the corresponding sewing path lines are marked on the pre-cured fiber cloth using a high-temperature resistant marker. The sewing stitch distance (sewing density) is set to 5mm to ensure that the fiber cloth layers are tightly bonded and evenly stressed after sewing.

[0028] Step 3: Prefabricated body stitching and shaping: The graphite core mold is horizontally fixed on the operating platform. Pre-formed and marked silicon carbide fiber cloth is laid layer by layer onto the edge surface of the core mold according to the designed layup sequence and angle. Each layer of fiber cloth is then locked together using continuous silicon carbide fiber sutures along the marked suture path, ensuring a tight fit between the fiber cloth and the core mold edge without warping or misalignment. This layup and suturing process is repeated until the required 7 grid units are achieved. After laying and suturing the sidewalls of the 7 regular hexagonal grid units, a final layer of silicon carbide fiber cloth is suturing to form the overall regular hexagonal outline, resulting in a continuous silicon carbide fiber grid prefabricated body with a total height of 200mm, a sidewall thickness of 1mm, and an inner side length of 5.6mm.

[0029] In this embodiment, the fiber cloth is laid in the following order: plain weave 0° / 90° layer, twill weave +45° / -45° layer, twill weave 0° / 90° layer, and plain weave +45° / -45° layer are stacked alternately, with the total number of layers corresponding to a sidewall thickness of 1 mm, to ensure that the mechanical properties in all directions of the grid surface are balanced.

[0030] Step 4: Heat treatment to remove resin. The entire mold containing the preform is placed in a high-temperature vacuum furnace and evacuated to 10°C. -2 After Pa, the temperature is increased to 1100℃ at a rate of 5℃ / min and held at this temperature for 3 hours. This process completely pyrolyzes and removes the phenolic resin, while relieving the internal stress of the preform during weaving and sewing. After heat treatment, the preform is cooled to room temperature in the furnace and then removed.

[0031] Step 5: Interfacial Phase Deposition The preform was transferred to a chemical vapor deposition furnace to deposit the PyC interface. The specific process was as follows: heating rate 5℃ / min, deposition temperature 980℃, deposition pressure 300Pa, deposition time 12h, dilution argon flow rate 400mL / min, and propylene (C3H6) carbon source gas flow rate 150mL / min. After deposition, a uniform and continuous pyrolytic carbon interface layer was formed on the surface of each silicon carbide fiber, such as... Figure 5 As shown, a pyrolytic carbon interface layer with a thickness of about 200 nm is uniformly coated on the surface of each silicon carbide fiber. This interface layer can precisely control the bonding strength between the fiber and the matrix. Through the energy absorption mechanism of interface debonding and fiber pull-out, the composite material is endowed with excellent toughness, avoiding catastrophic brittle fracture of ceramic materials.

[0032] Step Six: Matrix Deposition and Densification Using trichloromethylsilane (MTS) as a precursor, hydrogen as a carrier gas, and argon as a dilution gas, silicon carbide ceramic substrates were deposited using a chemical vapor infiltration process. The entire process was divided into two stages: shaping deposition and densification deposition. The shaping and deposition stage involves retaining the core mold and external shaping fixtures, setting the deposition temperature to 1000℃ and the deposition pressure to 500Pa, and controlling a low precursor flow rate to achieve slow deposition. After the first continuous deposition for 50 hours, the workpiece is removed, inverted 180°, and placed back into the furnace for another 50 hours of deposition. The inversion improves the deposition uniformity of the upper and lower parts, avoiding the gradient defect of "dense on top and sparse on the bottom".

[0033] After the shaping deposition is completed, the micropores in the fiber bundle are initially filled to form a continuous silicon carbide initial matrix skeleton. The preform obtains sufficient structural rigidity and shape retention capability. At this time, the internal graphite core mold and the external shaping tooling are removed.

[0034] Densification deposition stage: The demolded grid blank is placed back into the deposition furnace, and the precursor flow rate and deposition pressure are appropriately increased to continue silicon carbide deposition for densification. Each deposition cycle lasts 50 hours. After each deposition cycle, the workpiece is removed from the furnace, rotated 90° axially, and then reinserted for deposition. Multiple rotations balance the deposition rates on the inner and outer walls of the grid and at different heights, preventing localized insufficient density. After seven cycles of deposition, a dense, monolithic SiC is obtained. f / SiC composite material grating blank.

[0035] Step 7, Post-processing: For monolithic SiC f The upper and lower end faces of the long blank of the SiC composite material grid are precision ground to ensure that the flatness and parallelism meet the assembly requirements. It is then cut into multiple unit grids with a height of 20mm to obtain a regular hexagonal seven-hole grid of silicon carbide fiber reinforced ceramic matrix composite material. Figure 6 As shown.

[0036] According to testing and in accordance with GB / T 1453-2022 standard, the composite material grid prepared in this embodiment has a flat compressive strength of 23.5 MPa and a flat compressive elastic modulus of 545.3 MPa; according to GB / T 145-2022 standard, the composite material grid prepared in this embodiment has a lateral compressive strength of 0.42 MPa and a lateral compressive modulus of 37.1 MPa; and a coefficient of thermal expansion at 1000℃ of 4.7 × 10⁻⁶. -6 / K, meeting the high-temperature and high-radiation service requirements of fuel assembly positioning grids for advanced nuclear energy systems.

[0037] Example 2 A silicon carbide fiber-reinforced ceramic matrix composite grid, specifically a square grid, differs from Embodiment 1 in that: The core mold is a right-angled prism, which is simple to process; the cutting, laying and sewing paths of the fiber cloth are all orthogonal straight lines, and the dimensions are easy to control.

[0038] Example 3 A silicon carbide fiber-reinforced ceramic matrix composite grid, specifically a Kagome-shaped grid, differs from Example 1 in that: The core mold is an alternating array of hexagons and triangles, with complex topology and dense nodes; there are many fiber lay-up corners and complex fiber overlap at the nodes, making it difficult to control the uniformity of densification; however, it has the best thermal shock resistance and impact resistance, and the highest reliability in extreme environments.

[0039] Therefore, the present invention adopts the above-mentioned silicon carbide fiber reinforced ceramic matrix composite grid and its preparation method, which maximizes the preservation of fiber continuity and takes into account the structural forming accuracy and density uniformity. It can be widely used in extreme service scenarios with stringent requirements for lightweight, high temperature resistance, radiation resistance and dimensional stability, such as advanced nuclear energy system fuel assembly positioning grid, high-precision aerospace satellite bearing platform, and high temperature thermal protection structure.

[0040] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A silicon carbide fiber-reinforced ceramic matrix composite grid, characterized in that: It includes multiple grid units arranged in an array. The grid units are perforated structures of one of the following shapes: regular hexagon, square, or kagome. Adjacent grid units share sidewalls to form an integral grid structure. The outer contour of the integral grid structure is polygonal.

2. The silicon carbide fiber reinforced ceramic matrix composite grid according to claim 1, characterized in that: The outer contour of the integral grid structure is either rectangular or regular hexagonal.

3. A method for preparing a silicon carbide fiber-reinforced ceramic matrix composite grid as described in any one of claims 1 to 2, characterized in that, Includes the following steps: S1. Mold design and fabrication: Process the grid core mold and external shaping constraint tooling according to the structural dimensions of the target grid; cut the silicon carbide fiber cloth according to the grid sidewall thickness, fiber orientation and layup design. S2. Pre-curing and marking of fiber cloth: The cut silicon carbide fiber cloth is pre-cured using low residual carbon resin, and the sewing path lines are marked on the surface of the pre-cured fiber cloth to obtain pre-cured and marked silicon carbide fiber cloth. S3. Prefabricated body stitching: Fix the grid core mold, lay the silicon carbide fiber cloth obtained in S2 layer by layer on the edge surface of the core mold, and sew along the marked stitching path using continuous fiber stitching thread. Repeat the lay-up and stitching operation until all grid units are laid up and the outer contour is laid up to obtain a fiber-continuous silicon carbide fiber grid prefabricated body. S4. Heat treatment to remove resin: Place the preform obtained in S3 into a vacuum furnace or an inert atmosphere furnace, and heat it to 1000-1200℃ at a rate of 1-10℃ / min, and hold it for 1-4 hours to obtain the heat-treated preform. S5. Interfacial phase deposition: The preform obtained in S4 is transferred to a chemical vapor deposition furnace, and a reaction source gas is introduced to deposit a pyrolytic carbon interfacial layer or a boron nitride interfacial layer. S6. Substrate Deposition and Densification: Silicon carbide ceramic substrates are deposited using chemical vapor infiltration (CVI) technology. The entire process is divided into two stages: shaping deposition and densification deposition. The shaping and deposition stage: retain the core mold and external shaping constraint fixture, perform two depositions, each lasting 30 to 50 hours. During the deposition process, perform at least one 180° workpiece inversion. After the shaping and deposition is completed, remove the core mold and external shaping constraint fixture. Dense deposition stage: After every 50 to 100 hours of deposition, the workpiece is removed from the furnace and inverted at 180° or rotated at 90°. After multiple cycles of deposition, a dense grid blank is obtained. S7. Post-processing: The grid blank obtained in S6 is machined to obtain the finished product.

4. The method for preparing a silicon carbide fiber reinforced ceramic matrix composite grid according to claim 3, characterized in that, In S2, the low-carbon-residue resin is a thermosetting phenolic resin ethanol solution with a mass fraction of 1% to 20%.

5. The method for preparing a silicon carbide fiber-reinforced ceramic matrix composite grid according to claim 3, characterized in that, In S3, the suture is a silicon carbide fiber suture or a carbon fiber suture, and the suture stitch distance is in the range of 3~8mm.

6. The method for preparing a silicon carbide fiber-reinforced ceramic matrix composite grid according to claim 3, characterized in that, In S4, the pressure of the vacuum furnace is ≤10. -2 Pa.

7. The method for preparing a silicon carbide fiber reinforced ceramic matrix composite grid according to claim 3, characterized in that, In S4, the temperature is programmed to rise to 1100℃ at a rate of 5℃ / min and held for 3 hours to obtain the heat-treated preform.

8. The method for preparing a silicon carbide fiber reinforced ceramic matrix composite grid according to claim 3, characterized in that, In S5, when depositing the pyrolytic carbon interface layer, propylene is used as the carbon source gas, argon is used as the dilution gas, the deposition temperature is 950~1000℃, the deposition pressure is 100~600Pa, the deposition time is 8~16h, and the interface layer thickness is 100~500nm.

9. The method for preparing a silicon carbide fiber-reinforced ceramic matrix composite grid according to claim 3, characterized in that, In S5, boron trichloride and ammonia are used as reaction sources when depositing the boron nitride interface layer.

10. The method for preparing a silicon carbide fiber-reinforced ceramic matrix composite grid according to claim 3, characterized in that, In S6, the number of cyclic depositions is 6 to 8.

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