A method for producing an oxide fiber-reinforced alumina-based composite material

Abstract

The application belongs to the field of advanced ceramic composite material preparation, and particularly relates to a preparation method of an oxide fiber reinforced alumina-based composite material, which comprises the following steps: mixing 500nm alumina powder, 100nm alumina powder and 100nm 3YSZ powder according to a mass ratio of 65-70:5-10:20-30 to obtain a composite powder; and mixing the composite powder with a mixed solution according to a mass ratio of 43-45:55-57, wherein the mixed solution is prepared from an aluminum sol, water and a dispersing agent according to a mass ratio of 45-49:13-15:1; and the alumina whisker is uniformly in-situ grown in the composite material by combining hot-pressing assisted forming, repeated aluminum sol impregnation and high-temperature sintering, so as to construct a fiber-whisker-matrix multi-scale reinforced structure, and the mechanical properties and high-temperature service stability of the composite material are improved while the excellent heat insulation performance is maintained.

Description

Technical Field

[0001] This invention relates to the field of advanced ceramic composite material preparation technology, and in particular to a method for preparing an oxide fiber reinforced alumina-based composite material. Background Technology

[0002] Oxide fiber-reinforced alumina matrix composites are a novel type of high-temperature ceramic matrix composite. They possess the advantages of alumina ceramics, such as high temperature resistance, oxidation resistance, corrosion resistance, high hardness, and high chemical stability, while also exhibiting the high damage tolerance, excellent thermal shock resistance, and low density of fiber-reinforced composites. Furthermore, oxide fiber-reinforced alumina matrix composites possess excellent high-temperature mechanical properties and thermal insulation properties, enabling them to operate for extended periods in oxidizing environments. Therefore, they hold promise for widespread application in aerospace thermal protection systems, hypersonic vehicle thermal structural components, aero-engine hot-end components, and other high-temperature thermal insulation structures. Although oxide fiber-reinforced alumina matrix composites offer excellent comprehensive performance and broad application prospects, their overall performance is still limited by the manufacturing process and interface structure, which somewhat hinders their further engineering applications.

[0003] Currently, oxide fiber reinforced alumina matrix composites are mainly prepared using processes such as slurry impregnation, sol impregnation, hot pressing sintering, and vacuum infiltration. While increasing the sintering temperature, extending the holding time, or increasing the matrix densification can improve the overall strength of the composite, it can easily lead to over-sintering at the fiber-matrix interface, reducing the toughening effects such as crack deflection, fiber pull-out, and bridging. Furthermore, to further improve the mechanical properties of the material, existing technologies typically employ the addition of whiskers or nano-reinforcing phases. However, these methods suffer from problems such as easy agglomeration and uneven dispersion of the reinforcing phases, poor interfacial bonding stability, and complex processes, making it difficult to fully utilize the reinforcing phase's role and simultaneously achieve both the mechanical and thermal insulation properties of the composite. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by proposing a method for preparing oxide fiber reinforced alumina matrix composites.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A method for preparing an oxide fiber reinforced alumina-based composite material includes the following steps: (1) Slurry preparation: 500nm alumina powder, 100nm alumina powder and 100nm 3YSZ powder are mixed at a mass ratio of 65-70:5-10:20-30 to obtain composite powder; the composite powder is mixed with a mixed solution at a mass ratio of 43-45:55-57, the mixed solution is prepared by aluminum sol, water and dispersant at a mass ratio of 45-49:13-15:1; the mixed material is placed in a ball mill jar and ball milled at a speed of 300-500 rpm for 1-3 hours to prepare a uniform and stable mousse-like ceramic slurry; (2) Preparation of fiber preform: After cutting the alumina fiber fabric with an areal density of 370±20g / cm³, it is heat-treated in air at 600-750℃ for 1-2h to complete the degumming treatment; the degummed alumina fiber fabric is layered according to the preset layup method, and uniformly impregnated with the ceramic slurry prepared in step (1), and then hot-pressed at 120-150℃ and 5-10MPa for 1-2h to obtain the composite material preform, wherein the volume fraction of alumina fiber in the composite material preform is 40-50 vol%. (3) Pre-firing treatment: The composite material preform prepared in step (2) is pre-firing at 800-900℃ for 1.5-2.0h to obtain a composite material preform with fixed strength and interconnected pore structure; (4) Repeated impregnation with aluminum sol: The composite material preform obtained in step (3) is completely impregnated in aluminum sol, so that the aluminum sol can fully penetrate into the pores inside the preform. After impregnation, the preform is dried. The impregnation-drying process is repeated 0-4 times to increase the precursor content inside the preform. (5) High-temperature sintering and in-situ growth of whiskers: The preform that has undergone repeated impregnation treatment is placed at 1200-1400℃ for high-temperature sintering for 1.5-2.5h. The aluminum sol is converted into aluminum oxide at high temperature, and aluminum oxide whiskers are grown in-situ on the fiber surface and the matrix surface. Finally, the oxide fiber reinforced aluminum oxide matrix composite material modified with in-situ aluminum oxide whiskers is obtained.

[0006] Preferably, in step (1), the mass ratio of the 500nm alumina powder, 100nm alumina powder, and 100nm 3YSZ powder is 67:8:25.

[0007] Preferably, in step (1), the mass ratio of the aluminum sol, water, and dispersant is 47:14:1, and the mass ratio of the composite powder to the mixed solution is 44:56.

[0008] Preferably, in step (1), the ball milling speed is 400 rpm and the ball milling time is 2 h.

[0009] Preferably, in step (2), the degumming heat treatment temperature of the alumina fiber fabric is 680-720℃ and the heat treatment time is 1.5h.

[0010] Preferably, in step (2), the hot pressing temperature is 130-140℃, the hot pressing pressure is 7-8MPa, and the hot pressing time is 1.5h.

[0011] Preferably, in step (3), the pre-firing temperature is 850°C and the pre-firing time is 2 hours.

[0012] Preferably, in step (4), the impregnation-drying process is repeated 2-4 times.

[0013] Preferably, in step (5), the high-temperature sintering temperature is 1300℃ and the sintering time is 2h.

[0014] Preferably, the dispersant is a water-based dispersant specifically for ceramic slurries.

[0015] The beneficial effects of the preparation method of the oxide fiber reinforced alumina matrix composite material in this invention are as follows: (1) Alumina fiber fabric is used as a reinforcement, which has good chemical compatibility and high temperature stability with the alumina matrix.

[0016] (2) The process of combining hot pressing-assisted molding with slurry impregnation is simple and can achieve near-net-shape molding of composite materials. The resulting composite material has low density, with a density of less than 2.5 g / cm3.

[0017] (3) By employing a repeated aluminum sol impregnation process, uniform in-situ growth of alumina whiskers is achieved within the composite material, avoiding the problems of easy agglomeration and uneven dispersion of traditional externally added whiskers. The chemical transformation process of the whiskers can be simply described as follows: (4) Construct a multi-scale reinforcement structure of fiber-whisker-matrix, give full play to the toughening mechanisms such as whisker bridging, crack deflection and whisker pull-out, and improve the mechanical properties of composite materials. Its bending strength exceeds 200MPa, Vickers hardness reaches 5GPa, and fracture energy exceeds 4000J / m2.

[0018] (5) In-situ grown alumina whiskers can effectively regulate the fiber / matrix interface structure, improving the high-temperature service stability of the material while maintaining its low thermal conductivity and excellent thermal insulation performance. The thermal conductivity of the composite material is less than 1.3 W / (m·K) at room temperature, and the thermal diffusivity is less than 1.2 mm² / s. Furthermore, after heat aging treatment at 1200℃ for 25 h, its strength retention rate exceeds 80%.

[0019] (6) The process of the present invention is simple and has good repeatability, and is suitable for the large-scale preparation of oxide ceramic matrix composites. Attached Figure Description

[0020] Figure 1 This is a SEM image of a method for preparing an oxide fiber reinforced alumina matrix composite material proposed in this invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example

[0022] Reference Figure 1 A method for preparing an oxide fiber reinforced alumina-based composite material includes the following steps: 500 nm alumina powder, 100 nm alumina powder, and 100 nm 3YSZ powder are mixed at a mass ratio of 67:8:25; an aluminum sol, water, and dispersant are prepared into a mixed solution at a mass ratio of 47:14:1, and then mixed at a powder to mixed solution mass ratio of 44:56. The mixture is added to a ball mill jar and ball-milled at 400 rpm for 2 h to prepare a uniform and stable mousse-like ceramic slurry. Satin (8Hs) AF18 alumina fiber fabric (370 g / cm3) is cut to the required size and degummed in air at 700 ℃ for 1.5 h. The degummed fiber fabric is stacked according to a predetermined layup pattern and thoroughly impregnated with the above ceramic slurry. It is then hot-pressed at 140 ℃ and 8 MPa for 1.5 h to obtain a composite material preform. At this point, the fiber volume fraction is 40 vol%. The obtained preform was placed in a muffle furnace and pre-fired at 850 °C for 2 h to form a preform with certain strength and interconnected pore structure. The preform was then impregnated in alumina sol, allowing the alumina sol to fully penetrate the internal pores of the material. After drying at room temperature, the impregnation was repeated twice. Subsequently, the impregnated preform was placed in a high-temperature furnace and sintered at 1300 °C for 2 h to convert the alumina sol into alumina and to grow alumina whiskers in situ on the surface of the fibers and matrix. The final composite material had a density of 2.29 g / cm3, a flexural strength of 207.1 MPa, a Vickers hardness of 7.31 GPa, and a fracture energy of 4524.7 J / m2. Example

[0023] A method for preparing an oxide fiber reinforced alumina-based composite material includes the following steps: 500 nm alumina powder, 100 nm alumina powder, and 100 nm 3YSZ powder are mixed at a mass ratio of 69:6:25; an aluminum sol, water, and dispersant are prepared into a mixed solution at a mass ratio of 46:15:1, and then mixed at a powder to mixed solution mass ratio of 43:57. The mixture is added to a ball mill jar and ball-milled at 350 rpm for 3 h to prepare a uniform and stable mousse-like ceramic slurry. Satin (8Hs) AF18 alumina fiber fabric (380 g / cm3) is cut to the required size and degummed in air at 650 ℃ for 2 h. The degummed fiber fabric is stacked according to a predetermined layup pattern and thoroughly impregnated with the above ceramic slurry. It is then hot-pressed at 130 ℃ and 6 MPa for 2 h to obtain a composite material preform. At this point, the fiber volume fraction is 42 vol%. The obtained preform was placed in a muffle furnace and pre-fired at 800 °C for 2 h to form a preform with certain strength and interconnected pore structure. The preform was impregnated in alumina sol, dried at room temperature, and then impregnated repeatedly, for a total of 0 impregnation treatments, to further increase the precursor content. Subsequently, the impregnated preform was placed in a high-temperature furnace and sintered at 1400 °C for 1.5 h. The alumina sol was converted into alumina, and a large number of alumina whiskers grew in situ on the fiber and matrix surfaces. The final composite material had a density of 2.28 g / cm3, a flexural strength of 253.97 MPa, a Vickers hardness of 9.72 GPa, and a fracture energy of 4507.5 J / m2.

[0024] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A method for preparing an oxide fiber reinforced alumina-based composite material, characterized in that, Includes the following steps: (1) Slurry preparation: 500nm alumina powder, 100nm alumina powder and 100nm 3YSZ powder are mixed at a mass ratio of 65-70:5-10:20-30 to obtain composite powder; the composite powder is mixed with a mixed solution at a mass ratio of 43-45:55-57, the mixed solution is prepared by aluminum sol, water and dispersant at a mass ratio of 45-49:13-15:1; the mixed material is placed in a ball mill jar and ball milled at a speed of 300-500 rpm for 1-3 hours to prepare a uniform and stable mousse-like ceramic slurry; (2) Preparation of fiber preform: After cutting the alumina fiber fabric with a surface density of 370±20g / cm³, it is heat-treated in air at 600-750℃ for 1-2h to complete the degumming process. The degummed alumina fiber fabric is layered according to a preset layup method, and uniformly impregnated with the ceramic slurry prepared in step (1). Then, it is hot-pressed at 120-150℃ and 5-10MPa for 1-2 hours to obtain a composite material preform. The volume fraction of alumina fiber in the composite material preform is 40-50 vol%. (3) Pre-firing treatment: The composite material preform prepared in step (2) is pre-firing at 800-900℃ for 1.5-2.0h to obtain a composite material preform with fixed strength and interconnected pore structure; (4) Repeated impregnation with aluminum sol: The composite material preform obtained in step (3) is completely impregnated in aluminum sol, so that the aluminum sol can fully penetrate into the pores inside the preform. After impregnation, the preform is dried. The impregnation-drying process is repeated 0-4 times to increase the precursor content inside the preform. (5) High-temperature sintering and in-situ growth of whiskers: The preform that has undergone repeated impregnation treatment is placed at 1200-1400℃ for high-temperature sintering for 1.5-2.5h. The aluminum sol is converted into aluminum oxide at high temperature, and aluminum oxide whiskers are grown in-situ on the fiber surface and the matrix surface. Finally, the oxide fiber reinforced aluminum oxide matrix composite material modified with in-situ aluminum oxide whiskers is obtained.

2. The method for preparing an oxide fiber reinforced alumina-based composite material according to claim 1, characterized in that, In step (1), the mass ratio of the 500nm alumina powder, 100nm alumina powder, and 100nm 3YSZ powder is 67:8:

25.

3. The method for preparing an oxide fiber reinforced alumina-based composite material according to claim 1, characterized in that, In step (1), the mass ratio of the aluminum sol, water, and dispersant is 47:14:1, and the mass ratio of the composite powder to the mixed solution is 44:

56.

4. The method for preparing an oxide fiber reinforced alumina-based composite material according to claim 1, characterized in that, In step (1), the ball milling speed is 400 rpm and the ball milling time is 2 hours.

5. The method for preparing an oxide fiber reinforced alumina-based composite material according to claim 1, characterized in that, In step (2), the degumming heat treatment temperature of the alumina fiber fabric is 680-720℃ and the heat treatment time is 1.5h.

6. The method for preparing an oxide fiber reinforced alumina-based composite material according to claim 1, characterized in that, In step (2), the hot pressing temperature is 130-140℃, the hot pressing pressure is 7-8MPa, and the hot pressing time is 1.5h.

7. The method for preparing an oxide fiber reinforced alumina-based composite material according to claim 1, characterized in that, In step (3), the pre-firing temperature is 850℃ and the pre-firing time is 2h.

8. The method for preparing an oxide fiber reinforced alumina-based composite material according to claim 1, characterized in that, In step (4), the impregnation-drying process is repeated 2-4 times.

9. The method for preparing an oxide fiber reinforced alumina-based composite material according to claim 1, characterized in that, In step (5), the high-temperature sintering temperature is 1300℃ and the sintering time is 2h.

10. The method for preparing an oxide fiber reinforced alumina-based composite material according to claim 1, characterized in that, The dispersant is a water-based dispersant specifically for ceramic slurries.

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