Preparation method of alumina fiber reinforced composite material

Abstract

The invention discloses a preparation method of an alumina fiber reinforced composite material, and belongs to the technical field of composite material preparation. In order to solve the problems of low efficiency and high internal porosity of the composite material in the existing slurry impregnation process, the method mainly comprises the following steps: placing an alumina fiber fabric preform in a gypsum molding tool, and carrying out alumina slurry impregnation and high-temperature heat treatment. According to the invention, the composite material with compact and uniform interior can be obtained through single-time impregnation, the impregnation efficiency is improved, the alumina fiber reinforced composite material with low density and high strength is prepared, the method is suitable for preparing products with different shapes such as plate shapes, column shapes and cover bodies, the process is simple, and the cost is low.

Description

Technical Field

[0001] The invention belongs to the technical field of composite material preparation, and specifically relates to a method for preparing an alumina fiber reinforced composite material. Background Art

[0002] Continuous fiber reinforced alumina composite materials have the characteristics of high temperature resistance, oxidation resistance, excellent dielectric properties, low thermal expansion coefficient and good material structure design, and are excellent high temperature resistant aerospace materials. At present, the preparation methods of alumina fiber reinforced composite materials that are widely used at home and abroad include slurry impregnation-sintering process and sol-gel process. The sol-gel process is to impregnate the liquid phase alumina precursor into the alumina fiber preform, and then generate the alumina phase by high temperature sintering. This process requires multiple impregnations of the precursor and multiple high temperature heat treatments, with a long preparation cycle and high preparation cost. The slurry impregnation method directly impregnates the alumina slurry into the fabric preform, with high impregnation efficiency and can be formed in one time. However, the difficulty of the process is how to prepare alumina slurry with a high solid content to maximize the impregnation efficiency and impregnation uniformity.

[0003] At present, alumina fiber reinforced composite materials have entered the engineering application stage in the aerospace field. The center cone, mixer and core fairing components prepared by CHI in the United States have been successfully applied to the GE-passport 20 engine. Germany has also successfully prepared alumina / alumina composite combustion chamber liners, which remain intact after testing under test conditions. On this basis, Germany's DLR prepared WHIPOX-Al 2 O 3 / Al 2 O 3 The composite combustion chamber liner showed cracks after 10 hours of simulated environmental testing, but the component was intact as a whole and no catastrophic damage occurred. Summary of the invention

[0004] In view of the problems that the existing slurry impregnation process for preparing alumina fiber composite materials requires multiple impregnations, has low impregnation efficiency, and has high internal porosity of the composite materials, the present invention provides a method for quickly preparing internally uniform alumina fiber reinforced alumina composite materials at low cost.

[0005] The technical solution adopted by the present invention to solve the above technical problems is as follows:

[0006] A method for preparing an alumina fiber reinforced composite material comprises the following steps:

[0007] 1) After uniformly mixing high-purity nano-alumina powder and deionized water, the mixture is uniformly dispersed using a high-speed disperser to obtain an alumina slurry;

[0008] 2) Weave alumina fibers into a fabric preform and remove the sizing agent;

[0009] 3) Mix gypsum powder and deionized water evenly, fill them into a mold for curing to obtain a gypsum forming tooling;

[0010] 4) Place the fabric preform with the sizing agent removed conformally in the gypsum forming tooling, inject alumina slurry, then seal the entire gypsum forming tooling, let it stand at room temperature for a period of time and then demold, and remove the excess slurry adhering to the fabric surface to obtain a green composite material;

[0011] 5) Perform high-temperature heat treatment on the green composite material, and obtain an alumina fiber-reinforced composite material product after precision machining.

[0012] Preferably, in step 1), the particle size of the high-purity nano-alumina powder is <300 nm, and the mass ratio of the high-purity nano-alumina powder to deionized water is 1.5:1 to 1.8:1.

[0013] Preferably, in step 2), the alumina fiber is a continuous alumina continuous fiber with an alumina mass content of ≥60%.

[0014] Preferably, in step 2), the alumina fiber further includes glass fiber or quartz fiber.

[0015] Preferably, in step 2), the structure of the fabric preform is one of the knitting structures of needling, stitching, and three-way orthogonal.

[0016] Preferably, the method for removing the sizing agent in step 2) is: perform high-temperature treatment at 500 - 600 °C for 1 - 3 h; or, treat in deionized water at 70 - 90 °C for 48 - 72 h; or, treat in acetone at 60 - 80 °C for 24 - 48 h.

[0017] Preferably, in step 3), the mass ratio of the gypsum powder to deionized water is 1:1 to 3:1, and the curing time is 15 - 85 min.

[0018] Preferably, in step 3), the thickness of the gypsum forming tooling is 10 - 15 cm, and the shape of the gypsum mold is adjusted according to the shape of the used fabric preform.

[0019] Preferably, in step 4), demold after standing at room temperature for 24 - 72 h.

[0020] Preferably, in step 5), the temperature of the high-temperature heat treatment is 600 - 1100 °C, and the time is 1 - 2 h.

[0021] The present invention has at least the following beneficial effects compared with the prior art:

[0022] 1. The present invention uses a gypsum forming tooling to induce the adsorption of alumina particles in the alumina slurry to the outer wall of the tooling, significantly improving the single impregnation efficiency and effectively solving the problems of poor impregnation efficiency and non - concentrated impregnation effect during the impregnation of fiber fabric preforms with complex structures and large thicknesses.

[0023] 2. The alumina fiber - reinforced alumina composite material prepared by the present invention has a density lower than 3.0 g / cm 3 , a tensile strength greater than 100 MPa, a room - temperature compressive strength greater than 120 MPa, a tensile strength greater than 80 MPa at 1000 °C, and a compressive strength greater than 100 MPa at 1000 °C.

[0024] 3. The present invention can prepare different types of alumina fiber - reinforced composite materials such as plates, columns, and covers. The process is simple and the cost is low. A dense and uniform composite material can be obtained by single impregnation. Detailed Embodiments

[0025] To make the technical features, advantages, or technical effects in the above - mentioned technical solutions of the present invention more obvious and understandable, the following is a detailed description in conjunction with embodiments.

[0026] Example 1: Preparation of Continuous Alumina Fiber - Reinforced Alumina Plate

[0027] 1. Uniformly disperse commercially available high - purity nano - alumina powder and deionized water according to a feeding ratio of 6:4 by mass to obtain an alumina slurry with a solid content of 60%.

[0028] 2. Use commercially available alumina fibers (NEXTEL - 720, produced by 3M Company, USA) to weave into a flat fabric preform according to the laying and stitching weaving process. In a special cleaning tooling, add deionized water to submerge the fabric, keep it at 80 °C for 60 h, and then take it out and dry.

[0029] 3. Mix gypsum powder and deionized water in a ratio of 2:1 by mass, stir evenly with a high - speed disperser, then pour it into a mold, and demold after drying at room temperature for 60 min to obtain a gypsum forming tooling.

[0030] 4. Place the alumina fiber fabric preform into the gypsum forming tooling, then inject the prepared alumina slurry into the mold. After sealing the tooling cover, place it at room temperature for 72 h. After the water in the slurry is completely absorbed by the gypsum, carefully demold, and remove the excess slurry attached to the fabric surface to obtain a green composite material.

[0031] 5. Place the green composite material in a high - temperature sintering furnace, heat it to 1100 °C at a heating rate of 10 °C / min in an air atmosphere, hold for 1 h, cool it to room temperature and then take it out. After precision machining of the outer shape, a continuous alumina fiber - reinforced alumina plate is obtained.

[0032] The obtained sheet material was sampled and processed, and then its mechanical properties were tested. The results showed that the density of the composite material was 2.5 g / cm 3 , the average room temperature tensile strength was 103 MPa, the average room temperature compressive strength was 121 MPa, the average 1000 °C tensile strength was 89 MPa, and the average 1000 °C compressive strength was 105 MPa.

[0033] Example 2: Preparation of continuous alumina fiber-reinforced alumina radome

[0034] 1. The commercially available high-purity nano-alumina powder was uniformly dispersed with deionized water according to a feeding ratio of 6:4 by mass to obtain an alumina slurry with a solid content of 60%.

[0035] 2. The commercially available alumina fiber (NEXTEL-720, produced by 3M Company, USA) was woven into the shape of a radome body by a layer-stitching weaving process. In a special cleaning tooling, acetone was added to submerge the fabric, and after keeping it at 70 °C for 36 h, it was taken out and dried.

[0036] 3. Gypsum powder and deionized water were mixed in a ratio of 3:1 by mass, stirred evenly with a high-speed disperser, and then poured into a mold. After drying at room temperature for 85 min, it was demolded to obtain a gypsum forming tooling.

[0037] 4. The alumina fiber fabric preform was placed in the gypsum forming tooling, and then the prepared alumina slurry was injected into the mold. After sealing the mouth cover of the tooling and placing it at room temperature for 24 h, after the moisture in the slurry was completely absorbed by the gypsum, it was carefully demolded. After removing the excess slurry adhering to the fabric surface, a green composite material was obtained.

[0038] 5. The green composite material was placed in a high-temperature sintering furnace. In an air atmosphere, it was heated to 800 °C at a heating rate of 10 °C / min, held for 1 h, cooled to room temperature and then taken out. After precision machining of the outer shape, an alumina fiber-reinforced alumina composite radome was obtained.

[0039] The obtained radome was sampled and processed, and then its mechanical properties were tested. The results showed that the density of the composite material was 2.5 g / cm 3 , the average room temperature tensile strength was 109 MPa, the average room temperature compressive strength was 120 MPa, the average 1000 °C tensile strength was 95 MPa, and the average 1000 °C compressive strength was 104 MPa.

[0040] Example 3: Preparation of continuous alumina fiber-reinforced alumina window

[0041] 1. The commercially available high-purity nano-alumina powder was uniformly dispersed with deionized water according to a feeding ratio of 6:4 by mass to obtain an alumina slurry with a solid content of 60%.

[0042] 2. The commercially available alumina fibers (NEXTEL-550, produced by 3M Company, USA) are woven into a preform of antenna window fabric according to the needle-punching weaving process, and then processed in a high-temperature furnace at 550 °C for 2 h.

[0043] 3. Gypsum powder and deionized water are mixed in a mass ratio of 1:1, stirred evenly using a high-speed disperser, and then poured into a mold with the shape of an antenna window. After drying at room temperature for 15 min, the mold is demolded to obtain the corresponding gypsum forming tooling.

[0044] 4. The alumina fiber antenna window preform is placed in the gypsum forming tooling, and then the prepared alumina slurry is injected into the mold. After sealing the tooling cover and placing it at room temperature for 48 h, when the water in the slurry is completely absorbed by the gypsum, it is carefully demolded. After removing the excess slurry attached to the fabric surface, a green composite material is obtained.

[0045] 5. The green composite material is placed in a high-temperature sintering furnace. Under an air atmosphere, it is heated to 600 °C at a heating rate of 10 °C / min, held for 2 h, cooled to room temperature and then taken out. After precision machining of the outer shape, an alumina fiber-reinforced alumina composite material antenna window is obtained.

[0046] Samples of the obtained antenna window are processed and then tested for mechanical properties. The results show that the density of the composite material is 2.6 g / cm 3 , the average room-temperature tensile strength is 115 MPa, the average room-temperature compressive strength is 131 MPa, the average 1000 °C tensile strength is 100 MPa, and the average 1000 °C compressive strength is 112 MPa.

[0047] Comparative Example 1: Continuous alumina fiber-reinforced plate prepared without using a gypsum mold

[0048] 1. Commercially available high-purity nano-alumina powder and deionized water are uniformly dispersed in a feeding ratio of 6:4 to obtain an alumina slurry with a solid content of 60%.

[0049] 2. Commercially available alumina fibers (NEXTEL-550, produced by 3M Company, USA) are woven into a flat preform according to the lay-up and stitching weaving process. In a special cleaning tooling, deionized water is added to submerge the fabric. After holding at 80 °C for 72 h, it is taken out and dried.

[0050] 3. The fabric preform from which the sizing agent has been removed is placed in a container of appropriate size, and the prepared alumina slurry is injected into the container. After sealing the tooling cover and placing it at room temperature for 48 h, the composite blank is taken out and dried at 250 °C for 6 h. After removing the excess slurry attached to the fabric surface, a green composite material is obtained.

[0051] 4. Place the green composite material in a high-temperature sintering furnace, heat it to 1100 °C at a heating rate of 10 °C / min in an air atmosphere, hold for 1 h, and then take it out after cooling to room temperature. After precision machining of the outer shape, a continuous alumina fiber-reinforced plate is obtained.

[0052] Take samples of the obtained plate for processing and then test the mechanical properties. The results show that the density of the composite material is 2.1 g / cm 3 , the average room-temperature tensile strength is 74 MPa, the average room-temperature compressive strength is 94 MPa, the average 1000 °C tensile strength is 51 MPa, and the average 1000 °C compressive strength is 66 MPa.

[0053] Although the present invention has been disclosed as above by way of examples, it is not intended to limit the present invention. Any appropriate modifications or equivalent replacements made by those of ordinary skill in the art to the technical solutions of the present invention shall be covered within the protection scope of the present invention. The protection scope of the present invention shall be subject to that defined by the claims.

Claims

1. A method for preparing an alumina fiber reinforced composite material, characterized in that: The following steps are involved: 1) After uniformly mixing high-purity nano-alumina powder and deionized water, the mixture is uniformly dispersed using a high-speed disperser to obtain an alumina slurry; 2) weaving the alumina fibers into a fabric preform and removing the impregnating agent; 3) mixing gypsum powder and deionized water evenly, filling into a mold for curing, and obtaining a gypsum molding tool; 4) placing the fabric preform from which the impregnant has been removed in a gypsum molding tool, injecting alumina slurry, and then sealing the gypsum molding tool as a whole, demolding after leaving it at room temperature for a period of time, and removing the excess slurry attached to the surface of the fabric to obtain a composite material green body; 5) The composite material green body is subjected to high temperature heat treatment, and then fine machining is performed to obtain an alumina fiber reinforced composite material product.

2. The preparation method according to claim 1, characterized in that In step 1), the particle size of the high-purity nano-alumina powder is less than 300 nm, and the mass ratio of the high-purity nano-alumina powder to deionized water is 1.5:1 to 1.8:

1.

3. The preparation method according to claim 1, characterized in that: In step 2), the alumina fibers are continuous alumina fibers with an alumina mass content of ≥ 60%.

4. The preparation method according to claim 1, characterized in that: In step 2), the alumina fiber also includes glass fiber or quartz fiber.

5. The preparation method according to claim 1, characterized in that: The structure of the fabric preform in step 2) is a weaving structure selected from the group consisting of acupuncture, stitching, and three-way orthogonal weaving.

6. The preparation method according to claim 1, characterized in that: The method for removing the wetting agent in step 2) is: high temperature treatment at 500-600° C. for 1-3 hours; or, treatment at 70-90° C. in deionized water for 48-72 hours; or, treatment at 60-80° C. in acetone for 24-48 hours.

7. The preparation method according to claim 1, characterized in that: In step 3), the mass ratio of gypsum powder to deionized water is 1:1 to 3:1, and the curing time is 15 to 85 minutes.

8. The preparation method according to claim 1, characterized in that: In step 3), the thickness of the gypsum molding tool is 10 to 15 cm, and the shape of the gypsum mold is adjusted according to the shape of the fabric preform used.

9. The preparation method according to claim 1, characterized in that: In step 4), the mold is removed after being placed at room temperature for 24 to 72 hours.

10. The preparation method according to claim 1, characterized in that: In step 5), the temperature of the high temperature heat treatment is 600-1100° C. and the time is 1-2 hours.