A ceramic matrix composite connecting fastener and a method of manufacturing the same

Abstract

The application discloses a ceramic matrix composite connecting fastener and a preparation method thereof. The ceramic matrix composite connecting fastener comprises a fixed part and a connecting part. The upper end of the fixed part is connected with the lower end of the connecting part. The fixed part comprises a fixed part cavity, a fixed part connecting layer and a fixed part base which are sequentially arranged from outside to inside. The ceramic matrix composite connecting fastener can solve the problems of fracture and damage of the ceramic matrix composite connecting fastener when the temperature greatly changes, and the problems of easy oxidation, brittleness and damage of the ceramic matrix composite connecting fastener when the temperature is at 800-1000 DEG C for a long time, so that the carbon fiber reinforced silicon carbide ceramic matrix composite connecting fastener can be used for a long time under the service condition of a wide temperature range.

Description

Technical Field

[0001] This invention relates to the field of ceramic matrix composite technology, and more specifically to a ceramic matrix composite fastener and its preparation method. Background Technology

[0002] Carbon fiber reinforced silicon carbide ceramic matrix composites (C f SiC (SiC) possesses high strength, low density, and excellent heat resistance, making it a composite material with great potential. Compared to similar metal-based materials, it is lightweight, high-strength, and has strong thermal shock resistance, with a short-term ablation temperature ≤1700℃, enabling it to operate in extreme environments. Therefore, SiC... f SiC ceramic matrix composites are widely used in the aerospace field as connectors, such as screws, especially for rigid connections of thermal protection structural components of aircraft.

[0003] But traditional C f The following problems exist with SiC ceramic matrix composite connectors:

[0004] (1) When the operating temperature changes drastically, the structural components may break at the connection due to the different anisotropy of thermal expansion and uneven stress distribution. In particular, the screw head and screw rod may break due to external force and thermal stress generated by the screw itself, causing damage to the connecting parts.

[0005] (2) When the operating temperature exceeds 1200℃ for a short time and is around 800-1000℃ for a long time, the SiO2 protective layer formed by SiC oxidation is not dense enough. At this time, the material's anti-oxidation effect is extremely poor, and the carbon fiber is easily oxidized and becomes brittle. When the heat protection component faces long-term vibration, the screw is easily broken, causing damage to the connection mechanism.

[0006] Therefore, how to enable carbon fiber reinforced silicon carbide ceramic matrix composite connectors to be used for a long time under wide temperature range service conditions has become an urgent problem to be solved in this field. Summary of the Invention

[0007] The purpose of this invention is to provide a ceramic matrix composite fastener and its preparation method, which solves the problem of fracture and damage of ceramic matrix composite fasteners when the temperature changes drastically and the problem of easy oxidation and brittleness of ceramic matrix composite fasteners when the temperature is maintained at 800-1000℃ for a long time, thereby enabling carbon fiber reinforced silicon carbide ceramic matrix composite fasteners to be used for a long time under wide temperature range service conditions.

[0008] According to one aspect of the present invention, a ceramic matrix composite fastener is provided, comprising a fixing portion and a connecting portion; the upper end of the fixing portion is connected to the lower end of the connecting portion; the fixing portion comprises a fixing portion cavity, a fixing portion connecting layer, and a fixing portion base arranged sequentially from the outside to the inside; the ceramic matrix composite fastener exhibits a pull-out fracture load ≥4650N after oxidation at 800°C for 2.5 hours; the ceramic matrix composite material does not exhibit fatigue fracture for ≥100 hours after calcination at 1600°C; and its coefficient of thermal expansion is ≤-0.8×10⁻⁶. -6 / ℃.

[0009] The ceramic matrix composite connecting fastener can be a ceramic matrix composite screw, the fixing part is the end of the ceramic matrix composite screw, and the connecting part is the screw shank of the ceramic matrix composite screw.

[0010] The advantages of this invention over the prior art are that, by connecting one end of the fixing part to the connecting part, the fixing part is located outside the connected component, and the connecting part is located inside the connecting component, thus achieving the fixation of the connecting component;

[0011] The fixing part, including the fixing cavity, achieves thermal shock resistance to the external environment, and ensures that the surface of the ceramic matrix composite connector remains undamaged even when the external temperature reaches 1700℃ for a short period of time. The fixing part, including the fixing connecting layer and the fixing base, provides a high-strength connection between the fixing cavity and the fixing base, preventing separation during use. Furthermore, the fixing base prevents breakage under extreme temperature changes and avoids oxidation and brittleness of the ceramic matrix composite connector when the temperature is maintained between 800 and 1000℃ for extended periods. This allows the carbon fiber reinforced silicon carbide ceramic matrix composite fasteners to be used for extended periods under wide temperature range conditions.

[0012] The connection portion, including the connection portion matrix, avoids breakage and damage when the temperature changes drastically. It also avoids the problem of ceramic matrix composite fasteners easily oxidizing and becoming brittle and easily damaged when the temperature is maintained at 800-1000℃ for a long time. Furthermore, it avoids the problem of relative displacement between the connection portion matrix and the connecting component during use, thereby preventing the problem of reduced connection strength between the ceramic matrix composite fastener and the connecting component during use.

[0013] Furthermore, the fixing cavity includes carbon fiber; the fixing connecting layer includes silicon-carbon composite; the fixing substrate and connecting part include zirconium calcium phosphate; or, the fixing substrate and connecting part include zirconium calcium phosphate and silicon carbide whisker material; preferably, the fixing substrate and connecting part contain a cavity inside.

[0014] The beneficial effects of adopting the previous technical solution are as follows: by including carbon fiber in the fixing cavity, the thermal shock resistance of the fixing cavity to the external environment is improved, and the surface of the ceramic matrix composite fastener is not damaged when the external temperature reaches 1700℃ for a short time; by including zirconium calcium phosphate in the fixing matrix, the internal crystal structure of the fixing matrix is ​​formed by [ZrO6] octahedrons and [PO4] tetrahedrons linked at their vertices along the c-axis, forming a stable three-dimensional framework, with some voids in the framework filled by calcium ions; at the same time, it has relatively high thermal expansion anisotropy, and the internal structure of the fixing matrix and thermal expansion anisotropy together contribute to achieving low thermal expansion, even a thermal expansion coefficient ≤ -0.8×10 -6 / ℃; on the one hand, combining the advantages of the above materials, the surface C f / SiC composite materials can prevent heat transfer to the interior, thus preventing the CZP ceramic matrix from fracturing due to excessive instantaneous temperature differences. On the other hand, the CZP ceramic matrix doped with silicon carbide whiskers can provide a certain mechanical support, preventing the surface C... f / SiC ceramic oxidation causes fracture. From the outside to the inside, each layer of material has a different function and combines the advantages of each other, which greatly improves the service life of composite material fasteners.

[0015] This avoids the problem of fracture and damage to the fixing part matrix when the temperature changes drastically, and also avoids the problem of easy oxidation and brittleness of ceramic matrix composite connectors when the temperature is maintained at 800-1000℃ for a long time. This enables the carbon fiber reinforced silicon carbide ceramic matrix composite fasteners to be used for a long time under wide temperature range service conditions. Preferably, the fixing part matrix includes zirconium calcium phosphate and silicon carbide whiskers. That is, the introduction of silicon carbide whiskers makes the zirconium calcium carbonate grains in the fixing part matrix small and uniformly distributed, which is beneficial to improving the strength of the fixing part matrix, and the silicon carbide whiskers improve the connection strength between the fixing part matrix and the fixing part connection layer.

[0016] The high connection strength between the fixing part cavity and the fixing part substrate is achieved by the fixing part connection layer including a silicon-carbon composite.

[0017] According to another aspect of the present invention, a method for preparing ceramic matrix composite fasteners is provided, comprising the following steps:

[0018] Preparation of the preform for the fixed cavity;

[0019] The inner surface of the prefabricated cavity of the fixing part is coated or impregnated with a first material, the first material including silica sol or silicone rubber;

[0020] Prepare a first mold, which includes a first cavity whose lower inner wall matches the outer surface of the prefabricated cavity of the fixing part and a second cavity whose upper inner wall matches the outer surface of the connecting part;

[0021] The preform of the fixing cavity after being coated or impregnated with the first material is placed into the first cavity of the first mold and the bottom of the first cavity is sealed. The second material is added into the first cavity and the second cavity to obtain a semi-finished ceramic matrix composite connector. The second material includes zirconium calcium phosphate or the second material includes zirconium calcium phosphate and silicon carbide whiskers.

[0022] The ceramic matrix composite connector semi-finished product is sintered to obtain the ceramic matrix composite connector;

[0023] The fixed part cavity preform and the first and second materials inside the cavity are sintered to obtain the fixed part;

[0024] The second material located outside the cavity of the fixed cavity preform is sintered to obtain the connecting part.

[0025] The advantages of this invention over the prior art are that the ceramic matrix composite fastener includes a fixing part and a connecting part; one end of the fixing part is connected to the connecting part; the fixing part includes a fixing part cavity, a fixing part connecting layer, and a fixing part substrate; that is, the fixing part cavity preform is sintered to become the fixing part cavity; the first material in the fixing part cavity, combined with a small amount of the inner surface of the preform and a small amount of the second material, is sintered to become the fixing part connecting layer; the second material is sintered to become the fixing part substrate; the fixing part substrate includes zirconium calcium phosphate, or the fixing part substrate includes zirconium calcium phosphate and silicon carbide whiskers;

[0026] The connecting part is obtained by sintering the second material located outside the cavity of the fixed cavity preform, thereby realizing that the connecting part includes a connecting part matrix, and the connecting part matrix includes zirconium calcium phosphate, or the connecting part matrix includes zirconium calcium phosphate and silicon carbide whiskers;

[0027] This achieves thermal shock resistance of the fixed cavity to the external environment and ensures that the surface of the ceramic matrix composite connector is not damaged when the external temperature reaches 1700℃ for a short time.

[0028] The fastening connection layer achieves high connection strength between the fastening cavity and the fastening substrate, preventing separation of the fastening cavity and the substrate during use. Furthermore, the fastening substrate prevents breakage under extreme temperature changes and avoids the oxidation and brittleness issues common in ceramic matrix composite fasteners when exposed to prolonged temperatures of 800–1000°C. This allows carbon fiber reinforced silicon carbide ceramic matrix composite fasteners to be used for extended periods under wide temperature ranges. It also prevents breakage under extreme temperature changes and avoids oxidation and brittleness issues common in ceramic matrix composite fasteners when exposed to prolonged temperatures of 800–1000°C. Additionally, it prevents relative displacement between the fastening substrate and the connecting components during use, thus avoiding a decrease in connection strength between the ceramic matrix composite fasteners and the connecting components during operation.

[0029] Furthermore, the method for preparing the preform of the fixing cavity includes the following steps:

[0030] The carbon fiber cloth is impregnated with a polycarbosilane solution; the impregnated carbon fiber cloth is then used to prepare a preform of the fixing cavity through a second mold; the mass ratio of the polycarbosilane solution to the carbon fiber cloth after impregnation is 1:(8.56-11.12).

[0031] The preform of the fixed cavity is dried, cured, and pyrolyzed under negative pressure to obtain the preform of the fixed cavity.

[0032] Furthermore, the second mold includes a second core mold and a second mold shell;

[0033] The second core mold has a core mold A part with the same shape as the fixing part;

[0034] The second core mold is located inside the second mold shell, and the shape of the cavity formed between the second core mold and the second mold shell is adapted to the shape of the preform of the fixing part cavity;

[0035] The specific steps for preparing the preform of the fixing cavity through the second mold after impregnation of carbon fiber cloth are as follows:

[0036] Several layers of impregnated carbon fiber cloth are wrapped around the surface of the core mold A part of the second core mold, and then the second mold shell is fitted over the outside of the second core mold and pressed tightly; preferably, the several layers are 1-10 layers;

[0037] The beneficial effect of adopting the above technical solution is that the preform of the fixing cavity of carbon fiber reinforced silicon carbide material is prepared by the above solution, and the cavity preform prepared by the above method has a compact structure, forming a dense SiC layer in the carbon fiber.

[0038] Furthermore, when the preform of the fixing cavity is dried and cured under negative pressure, the drying temperature is 90-120℃ and the curing time is 3.5-4.5 hours.

[0039] When the preform of the fixed cavity is dried, cured, and then pyrolyzed, the pyrolysis temperature is 1000-1200℃, and the pyrolysis time is 0.8-1.2 hours; and / or,

[0040] The polycarbosilane solution comprises polycarbosilane and xylene, n-hexane, or divinylbenzene; the mass ratio of the polycarbosilane to xylene, n-hexane, or divinylbenzene is 1:(1-1.2).

[0041] The beneficial effect of adopting the above technical solution is that the polycarbosilane solution does not contain a binder, and the preform of the fixed cavity is obtained by pressing and molding, thereby achieving low porosity and high density of the preform of the fixed cavity.

[0042] Furthermore, when the second material includes calcium zirconium phosphate, the specific process for preparing the second material is as follows: A 0.5-1 mol / L aqueous solution of (NH4)2HPO4 is added to a 0.3-0.8 mol / L aqueous solution of ZrOCl2·8H2O, and the pH is adjusted to 8-9; the material is then dried, calcined, ball-milled, and sieved to obtain the second material; the molar ratio of ZrOCl2·8H2O to (NH4)2HPO4 is (3.5-5.5):(5.5-6.5).

[0043] or,

[0044] When the second material includes calcium zirconium phosphate and silicon carbide whiskers, the specific process for preparing the second material is as follows: silicon carbide whiskers are added to a ZrOCl2·8H2O aqueous solution with a concentration of 0.3-0.8 mol / L, and then a (NH4)2HPO4 aqueous solution with a concentration of 0.5-1 mol / L is added to the ZrOCl2·8H2O aqueous solution. The pH is then adjusted to 8-9. The second material is obtained by drying, calcining, ball milling, and sieving.

[0045] The molar ratio of ZrOCl2·8H2O, (NH4)2HPO4 and silicon carbide whiskers is (3.5-5.5):(5.5-6.5):(0.05-0.2); preferably, the (NH4)2HPO4 aqueous solution is added at a flow rate of 60-90 ml / min.

[0046] The beneficial effect of adopting the above technical solution is that by adding (NH4)2HPO4 aqueous solution to ZrOCl2·8H2O aqueous solution, it is beneficial to control the size of the obtained zirconium calcium phosphate particles and avoid particle agglomeration. The above two solution concentrations ensure the reaction rate while avoiding particle agglomeration, which is beneficial to obtain small and uniform zirconium calcium phosphate crystal particles, and also beneficial to the high strength of the fixed part matrix and the connecting part matrix obtained in subsequent sintering.

[0047] The second material includes calcium zirconium phosphate and silicon carbide whiskers. The silicon carbide whiskers are added to an aqueous solution of ZrOCl2·8H2O, so that the calcium zirconium phosphate obtained by the reaction of (NH4)2HPO4 with ZrOCl2·8H2O is dispersed on the surface of the silicon carbide whiskers and is uniformly attached, which effectively avoids the problem of calcium zirconium phosphate agglomeration. At the same time, the prepared fixing part matrix and connecting part matrix have high strength, and the silicon carbide whiskers in the fixing part matrix can easily react with the silica sol attached to the surface of the fixing part cavity during the sintering process, which is conducive to achieving a firm bond between the fixing part matrix and the fixing part connecting layer, and thus facilitates a firm bond between the fixing part cavity and the fixing part matrix through the fixing part connecting layer.

[0048] This results in a stable three-dimensional framework formed by connecting the vertices of [ZrO6] octahedrons and [PO4] tetrahedrons along the c-axis, with some voids filled by calcium ions. Simultaneously, it exhibits relatively high thermal anisotropy. The internal structure of the fixing component and this thermal anisotropy together contribute to achieving low thermal expansion, even a coefficient of thermal expansion ≤ -0.8 × 10⁻⁶. -6 / ℃.

[0049] Furthermore, the thickness of the first material coated or impregnated on the inner surface of the prefabricated cavity of the fixing part is 0.5-0.8 mm.

[0050] The advantage of adopting the previous technical solution is that it helps to achieve a firm bond between the fixed part cavity and the fixed part base through the fixed part connecting layer, while not affecting the high temperature thermal shock resistance of the fixed part cavity.

[0051] Furthermore, the first mold comprises a first cavity and a second cavity, wherein the first cavity has the same shape as the preform of the fixing cavity, and the second cavity has the same shape as the connecting part.

[0052] Furthermore, when sintering the semi-finished ceramic matrix composite fastener, the temperature is raised to 1100-1200℃ at a heating rate of 3-5℃ / min and held for 5-10min to obtain the ceramic matrix composite fastener.

[0053] Furthermore, after the heat preservation period, the temperature is lowered from 1100-1200℃ to 500-550℃ at a cooling rate of 8-12℃ / min, and then lowered to room temperature at a cooling rate of 3-4℃ / min. The cooling rate from 1100-1200℃ to 500-550℃ is 8-12℃ / min, and the cooling rate from 500-550℃ to room temperature is 3-4℃ / min; preferably, the heating rate from room temperature to 600-800℃ is 4-5℃ / min, and the heating rate from 600-800℃ to 1100-1200℃ is 3-4℃ / min.

[0054] The advantages of adopting the above technical solution are that the sintering temperature is 1100-1200℃, and the lower temperature is conducive to obtaining small zirconium calcium phosphate grains; the heating rate further helps to achieve small and uniform zirconium calcium phosphate grain structure; and the cooling rate from 1100-1200℃ to 500-550℃ is 8-12℃, which helps to achieve small and uniform grain distribution in the fixed part matrix and the connecting part matrix. Attached Figure Description

[0055] Figure 1 This is a schematic diagram of the structure of the ceramic matrix composite connecting fastener of the present invention;

[0056] Figure 2 This is a perspective view of the second core mold of the present invention;

[0057] Figure 3 This is a schematic diagram of the carbon fiber cloth after being wound and impregnated with the second core mold according to the present invention;

[0058] Figure 4 This is a cross-sectional view of the second mold shell of the present invention.

[0059] The markings shown in the attached figures are: 1. Connecting part; 2. Fixing part; 3. Fixing part base; 4. Fixing part connecting layer; 5. Fixing part cavity; 6. Core mold A part; 7. Impregnated carbon fiber cloth. Detailed Implementation

[0060] To better understand the technical solution of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings.

[0061] Example 1:

[0062] One aspect of this embodiment provides a ceramic matrix composite fastener, including a fixing part 2 and a connecting part 1; one end of the fixing part 2 is connected to the connecting part 1; the fixing part 2 includes a fixing part cavity 5, a fixing part connecting layer 4, and a fixing part base 3;

[0063] The fixing cavity 5 includes carbon fiber; the connecting layer of the fixing part 2 includes silicon-carbon composite; the fixing matrix 3 includes calcium zirconium phosphate; and the connecting matrix includes calcium zirconium phosphate.

[0064] The ceramic matrix composite material connector exhibits a tensile fracture load of 4660 N after oxidation at 800°C for 2.5 hours; the ceramic matrix composite material does not exhibit fatigue fracture after sintering at 1600°C for 100 hours; and its coefficient of thermal expansion is -0.8 × 10⁻⁶. -6 / ℃;

[0065] The ceramic matrix composite connecting fastener is a ceramic matrix composite screw, the fixing part 2 is the end of the ceramic matrix composite screw, and the connecting part 1 is the screw shank of the ceramic matrix composite screw;

[0066] The fixing cavity 5, comprising carbon fiber, achieves thermal shock resistance to external environmental temperatures, and ensures that the surface of the ceramic matrix composite connector remains undamaged even when the external temperature reaches 1700℃ for a short period. The fixing matrix 3, comprising zirconium calcium phosphate, achieves a stable three-dimensional framework formed by connecting the vertices of [ZrO6] octahedrons and [PO4] tetrahedrons along the c-axis, with some voids in the framework filled by calcium ions. It also exhibits relatively high thermal expansion anisotropy. The internal structure of the fixing matrix 3 and its thermal expansion anisotropy together contribute to achieving low thermal expansion.

[0067] Another aspect of this embodiment provides a method for preparing ceramic matrix composite connecting fasteners, including the following steps: preparing a preform of a fixing cavity;

[0068] The method for preparing the preform of the fixed cavity includes the following steps:

[0069] The carbon fiber cloth is impregnated with a polycarbosilane solution; the impregnated carbon fiber cloth 7 is used to prepare a preform of the fixing cavity through a second mold; the mass ratio of polycarbosilane solution to carbon fiber cloth in the impregnated carbon fiber cloth is 10.3:1.

[0070] The polycarbosilane solution comprises polycarbosilane and xylene; the mass ratio of the polycarbosilane to xylene is 1:1.1.

[0071] The carbon fiber cloth is impregnated with a polycarbosilane solution; the impregnated carbon fiber cloth 7 is then used to prepare a preform of the fixing cavity through a second mold;

[0072] The second mold includes a second core mold and a second mold shell; the second core mold is provided with a core mold A part 7 that has the same shape as the fixing part 2;

[0073] The second core mold is located inside the second mold shell, and the shape of the cavity formed between the second core mold and the second mold shell is adapted to the shape of the preform of the fixing part cavity;

[0074] Nine layers of impregnated carbon fiber cloth 7 are wrapped around the surface of the core mold A part 7 of the second core mold, and then the second mold shell is fitted onto the outside of the second core mold and pressed tightly.

[0075] The preform of the fixed cavity is dried, cured, shaped, and pyrolyzed under negative pressure to obtain the preform of the fixed cavity.

[0076] When the preform of the fixed cavity is dried and cured under negative pressure, the drying temperature is 105℃ and the curing time is 4.3 hours.

[0077] When the preform of the fixed cavity is dried and then pyrolyzed, the pyrolysis temperature is 1100℃ and the pyrolysis time is 1 hour.

[0078] The inner surface of the prefabricated cavity of the fixing part is coated or impregnated with a first material, the first material including silica sol; the thickness of the coating or impregnation of the first material on the inner surface of the prefabricated cavity of the fixing part is 0.65 mm.

[0079] The second material is prepared by adding a 0.75 mol / L aqueous solution of (NH4)2HPO4 to a 0.55 mol / L aqueous solution of ZrOCl2·8H2O, and then adjusting the pH to 8.5; drying, calcining, ball milling, and sieving are performed to obtain the second material; the molar ratio of ZrOCl2·8H2O to (NH4)2HPO4 is 4.5:6; the flow rate of adding the (NH4)2HPO4 aqueous solution is 75 ml / min.

[0080] The preform of the fixing cavity is placed into the first mold, and the second material is added into the cavity of the first mold; part of the second material enters the cavity of the preform of the fixing cavity, and part of the second material is outside the cavity of the preform of the fixing cavity, thus obtaining a semi-finished ceramic matrix composite connecting fastener.

[0081] The first mold cavity includes a first cavity and a second cavity. The first cavity has the same shape as the preform of the fixing part cavity, and the second cavity has the same shape as the connecting part 1.

[0082] The ceramic matrix composite fastener semi-finished product is sintered to obtain the ceramic matrix composite fastener.

[0083] When sintering the semi-finished ceramic matrix composite fasteners, the sintering temperature is 1150℃, the heating rate is 4℃ / min, the holding temperature is 1150℃ for 8min, the cooling rate from 1150℃ to 530℃ is 10℃ / min, and the cooling rate from 530℃ to room temperature is 3.5℃ / min.

[0084] The fixed part 2 is obtained by sintering the preform of the fixed part cavity and the first material and the second material inside the cavity.

[0085] The second material located outside the cavity of the fixed cavity preform is sintered to obtain the connecting part 1.

[0086] Example 2:

[0087] The same content as in Example 1 will not be repeated here. One aspect of this embodiment provides a ceramic matrix composite fastener, wherein the fixing matrix 3 comprises zirconium calcium phosphate and silicon carbide whiskers; the connecting matrix comprises zirconium calcium phosphate and silicon carbide whiskers; the ceramic matrix composite fastener, after oxidation at 800°C for 2.5 hours, has a pull-out fracture load of 4690 N; the ceramic matrix composite material does not undergo fatigue fracture after calcination at 1600°C for 110 hours; and its coefficient of thermal expansion is -0.70 × 10⁻⁶. -6 / ℃.

[0088] Another aspect of this embodiment provides a method for preparing ceramic matrix composite fasteners, wherein the mass ratio of polycarbosilane solution to carbon fiber cloth after impregnation with polycarbosilane solution is 10.2:1.

[0089] The polycarbosilane solution comprises polycarbosilane and n-hexane; the mass ratio of the polycarbosilane to n-hexane is 1:1.05.

[0090] Eight layers of impregnated carbon fiber cloth 7 are wrapped around the surface of the core mold A part 7 of the second core mold, and then the second mold shell is fitted onto the outside of the second core mold and pressed tightly.

[0091] When the preform of the fixed cavity is dried and cured under negative pressure, the drying temperature is 115℃ and the curing time is 4 hours.

[0092] When the preform of the fixed cavity is dried and then pyrolyzed, the pyrolysis temperature is 1050℃ and the pyrolysis time is 1.15 hours.

[0093] The inner surface of the prefabricated cavity of the fixing part is coated or impregnated with a first material, the first material including silica sol; the thickness of the coating or impregnation of the first material on the inner surface of the prefabricated cavity of the fixing part is 0.6 mm.

[0094] The second material is prepared by adding zirconium calcium phosphate and silicon carbide whiskers. The specific process for preparing the second material is as follows: silicon carbide whiskers are added to a 0.7 mol / L ZrOCl2·8H2O aqueous solution, followed by the addition of a 0.9 mol / L (NH4)2HPO4 aqueous solution. The pH is then adjusted to 8.8 with ammonia. The mixture is then dried, calcined, ball-milled, and sieved to obtain the second material. The molar ratio of ZrOCl2·8H2O, (NH4)2HPO4, and silicon carbide whiskers is 5:5.6:0.15. The (NH4)2HPO4 aqueous solution is added at a flow rate of 85 ml / min.

[0095] When sintering the semi-finished ceramic matrix composite connector, the sintering temperature is as follows: the heating rate from room temperature to 700℃ is 4.8℃ / min, and the heating rate from 700℃ to 1150℃ is 3.2℃ / min; the temperature is held at 1150℃ for 9 minutes; during the cooling process, the cooling rate from 1150℃ to 520℃ is 11℃ / min, and the cooling rate from 520℃ to room temperature is 3.2℃ / min.

[0096] Example 3:

[0097] The same content as in Example 2 will not be repeated here. One aspect of this embodiment provides a ceramic matrix composite fastener, wherein the fixing matrix 3 comprises zirconium calcium phosphate and silicon carbide whiskers; the connecting matrix comprises zirconium calcium phosphate and silicon carbide whiskers; the ceramic matrix composite fastener, after oxidation at 800°C for 2.5 hours, has a pull-out fracture load of 4680 N; the ceramic matrix composite material does not exhibit fatigue fracture after calcination at 1600°C for 105 hours; and its coefficient of thermal expansion is -0.75 × 10⁻⁶. -6 / ℃.

[0098] Another aspect of this embodiment provides a method for preparing ceramic matrix composite fasteners, wherein the mass ratio of polycarbosilane solution to carbon fiber cloth after impregnation with polycarbosilane solution is 11:1.

[0099] The polycarbosilane solution comprises polycarbosilane and divinylbenzene; the mass ratio of the polycarbosilane to divinylbenzene is 1:1.18.

[0100] Five layers of impregnated carbon fiber cloth 7 are wrapped around the surface of the core mold A part 7 of the second core mold, and then the second mold shell is fitted onto the outside of the second core mold and pressed tightly.

[0101] When the preform of the fixed cavity is dried and cured under negative pressure, the drying temperature is 95℃ and the curing time is 3.6 hours.

[0102] When the preform of the fixed cavity is dried and then pyrolyzed, the pyrolysis temperature is 1150℃ and the pyrolysis time is 0.9 hours.

[0103] The inner surface of the prefabricated cavity of the fixing part is coated or impregnated with a first material, the first material including silica sol; the thickness of the coating or impregnation of the first material on the inner surface of the prefabricated cavity of the fixing part is 0.7 mm.

[0104] The second material is prepared by adding zirconium calcium phosphate and silicon carbide whiskers. The specific process for preparing the second material is as follows: silicon carbide whiskers are added to a 0.4 mol / L ZrOCl2·8H2O aqueous solution, followed by the addition of a 0.6 mol / L (NH4)2HPO4 aqueous solution to the ZrOCl2·8H2O aqueous solution, and the pH is adjusted to 8.2. The mixture is then dried, calcined, ball-milled, and sieved to obtain the second material. The molar ratio of ZrOCl2·8H2O, (NH4)2HPO4, and silicon carbide whiskers is 3.8:5.8:0.06. The (NH4)2HPO4 aqueous solution is added at a flow rate of 65 ml / min.

[0105] When sintering the semi-finished ceramic matrix composite fasteners, the heating rate from room temperature to 750℃ is 4.2℃ / min, and the heating rate from 750℃ to 1120℃ is 3.5℃ / min; the temperature is held at 1120℃ for 6 minutes; during the cooling process, the cooling rate from 1120℃ to 540℃ is 9℃ / min, and the cooling rate from 540℃ to room temperature is 3.8℃ / min.

[0106] The above description is merely a preferred embodiment of this application and an explanation of the technical principles employed. Those skilled in the art should understand that the scope of the invention involved in this application is not limited to the technical solutions formed by specific combinations of the above-described technical features, but should also cover other technical solutions formed by arbitrary combinations of the above-described technical features or their equivalents without departing from the inventive concept. For example, the above-described features have similar functions to (but are not limited to) those disclosed in this application.

Claims

1. A ceramic matrix composite material fastener, characterized in that, Includes fixing parts and connecting parts; The upper end of the fixing part is connected to the lower end of the connecting part; The fixing part includes a fixing part cavity, a fixing part connecting layer and a fixing part base arranged sequentially from the outside to the inside; The fixing cavity includes carbon fiber; the fixing connecting layer includes a silicon-carbon composite. The fixing base and the connecting part include zirconium calcium phosphate; or, the fixing base and the connecting part include zirconium calcium phosphate and silicon carbide whisker material; The ceramic matrix composite fastener is prepared through the following steps: Preparation of the preform for the fixed cavity; The inner surface of the prefabricated cavity of the fixing part is coated or impregnated with a first material, the first material including silica sol or silicone rubber; Prepare a first mold, which includes a lower inner wall and a first cavity that matches the outer surface of the preform of the fixing part cavity, and an upper inner wall and a second cavity that matches the outer surface of the connecting part; The preform of the fixing cavity after being coated or impregnated with the first material is placed into the first cavity of the first mold and the bottom of the first cavity is sealed. The second material is added into the first cavity and the second cavity to obtain a semi-finished ceramic matrix composite fastener; wherein the second material includes zirconium calcium phosphate or the second material includes zirconium calcium phosphate and silicon carbide whiskers. The ceramic matrix composite fastener semi-finished product is sintered to obtain the ceramic matrix composite fastener; The fixed part is obtained by sintering the preform of the cavity and the first and second materials inside the cavity; The second material located outside the cavity of the fixed cavity preform is sintered to form the connecting part.

2. A method for preparing ceramic matrix composite fasteners, characterized in that, Includes the following steps: Preparation of the preform for the fixed cavity; The inner surface of the prefabricated cavity of the fixing part is coated or impregnated with a first material, the first material including silica sol or silicone rubber; Prepare a first mold, which includes a lower inner wall and a first cavity that matches the outer surface of the preform of the fixing part cavity, and an upper inner wall and a second cavity that matches the outer surface of the connecting part; The preform of the fixing cavity after being coated or impregnated with the first material is placed into the first cavity of the first mold and the bottom of the first cavity is sealed. The second material is added into the first cavity and the second cavity to obtain a semi-finished ceramic matrix composite fastener; wherein the second material includes zirconium calcium phosphate or the second material includes zirconium calcium phosphate and silicon carbide whiskers. The ceramic matrix composite fastener semi-finished product is sintered to obtain the ceramic matrix composite fastener; The fixed part is obtained by sintering the preform of the cavity and the first and second materials inside the cavity; The second material located outside the cavity of the fixed cavity preform is sintered to form the connecting part.

3. The method for preparing ceramic matrix composite fasteners according to claim 2, characterized in that, The method for preparing the preform of the fixed cavity includes the following steps: Impregnate carbon fiber cloth with polycarbosilane solution; The impregnated carbon fiber cloth is used to prepare the preform of the fixing cavity through the second mold; The preform of the fixed cavity is dried, cured, and pyrolyzed under negative pressure to obtain the preform of the fixed cavity.

4. The method for preparing ceramic matrix composite fasteners according to claim 3, characterized in that, The second mold includes a second core mold and a second mold shell; The second core mold has a core mold A part with the same shape as the fixing part; The second core mold is located inside the second mold shell, and the shape of the cavity formed between the second core mold and the second mold shell is adapted to the shape of the preform of the fixing part cavity; The specific steps for preparing the preform of the fixing cavity through the second mold after impregnation of carbon fiber cloth are as follows: Several layers of impregnated carbon fiber cloth are wrapped around the surface of the core mold A part of the second core mold, and then the second mold shell is fitted over the outside of the second core mold and pressed tightly.

5. The method for preparing ceramic matrix composite fasteners according to claim 3, characterized in that, When the preform of the fixed cavity is dried and cured under negative pressure, the drying temperature is 90-120℃ and the curing time is 3.5-4.5 hours. When the preform of the fixed cavity is dried, cured and pyrolyzed, the pyrolysis temperature is 1000-1200℃ and the pyrolysis time is 0.8-1.2 hours. and / or The polycarbosilane solution comprises polycarbosilane and xylene, n-hexane, or divinylbenzene; the polycarbosilane is a solid; the mass ratio of the polycarbosilane to xylene, n-hexane, or divinylbenzene is 1:(1-1.2).

6. The method for preparing ceramic matrix composite connecting fasteners according to claim 2, characterized in that, When the second material includes calcium zirconium phosphate, the specific process for preparing the second material is as follows: A 0.5-1 mol / L aqueous solution of (NH4)2HPO4 is added to a 0.3-0.8 mol / L aqueous solution of ZrOCl2▪8H2O, and the pH is adjusted to 8-9; the material is then dried, calcined, ball-milled, and sieved to obtain the second material; the molar ratio of ZrOCl2▪8H2O to (NH4)2HPO4 is (3.5-5.5):(5.5-6.5). or, When the second material includes calcium zirconium phosphate and silicon carbide whiskers, the specific process for preparing the second material is as follows: Silicon carbide whiskers are added to a 0.3-0.8 mol / L ZrOCl2▪8H2O aqueous solution, and then a 0.5-1 mol / L (NH4)2HPO4 aqueous solution is added to the ZrOCl2▪8H2O aqueous solution. The pH is then adjusted to 8-9. The second material is obtained by drying, calcining, ball milling, and sieving. The molar ratio of ZrOCl2▪8H2O, (NH4)2HPO4 and silicon carbide whiskers is (3.5-5.5):(5.5-6.5):(0.05-0.2).

7. The method for preparing ceramic matrix composite fasteners according to claim 2, characterized in that, The thickness of the first material coated or impregnated on the inner surface of the prefabricated cavity of the fixed part is 0.5-0.8 mm.

8. The method for preparing ceramic matrix composite fasteners according to claim 2, characterized in that, When sintering the semi-finished ceramic matrix composite fastener, the temperature is raised to 1100-1200℃ at a heating rate of 3-5℃ / min and held for 5-10min to obtain the ceramic matrix composite fastener.

9. The method for preparing ceramic matrix composite fasteners according to claim 8, characterized in that, After the heat preservation is completed, the temperature is reduced from 1100-1200℃ to 500-550℃ at a cooling rate of 8-12℃ / min, and then reduced to room temperature at a cooling rate of 3-4℃ / min.

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