Short-fiber-doped reinforced aluminum oxide ceramic-based composite material and preparation method thereof

Abstract

The invention relates to a short-fiber-doped reinforced aluminum oxide ceramic matrix composite material and a preparation method thereof. The short-fiber-doped reinforced aluminum oxide ceramic matrix composite material comprises pretreated aluminum oxide fiber cloth and chopped fibers; aluminum oxide powder and the pretreated chopped fibers are mixed to prepare aluminum oxide ceramic slurry; uniformly coating the aluminum oxide ceramic slurry on the surface of pretreated aluminum oxide fiber cloth, drying to obtain prepreg, superposing the prepreg, and performing vacuum-assisted hot press molding to obtain a green body; the green body is heated to 600-900 DEG C for curing and sintering, and a rough blank is obtained; the rough blank is subjected to vacuum circulation impregnation with aluminum sol, presintering is conducted at the temperature of 600-800 DEG C, final sintering is conducted at the temperature of 1000-1200 DEG C, and the doped short fiber reinforced aluminum oxide ceramic-based composite material is obtained. The density and structural integrity of the composite material are remarkably improved, the prepared composite material has excellent normal-temperature tensile strength and structural stability, the whole technological process is simplified, and the production efficiency is high.

Description

Technical Field

[0001] This invention relates to alumina ceramic composite materials, and more specifically to a doped short fiber reinforced alumina ceramic matrix composite material and its preparation method. Background Technology

[0002] Alumina fiber-reinforced alumina ceramic matrix composites (i.e., alumina / alumina ceramic matrix composites) use alumina fibers as reinforcement and alumina ceramics as the matrix. Due to their excellent high-temperature stability and oxidation resistance, they have become core candidate materials for extreme environments such as hot-end components of aero-engines and nuclear reactor liners. Compared to silicon carbide-based ceramic composites, they can effectively avoid oxidation reactions in medium- and high-temperature oxidizing environments, significantly extending their service life, and their application scenarios continue to expand with the engineering needs of extreme environments.

[0003] However, existing alumina / alumina ceramic matrix composites are prone to crack formation and rapid propagation within the matrix under stress, resulting in low fracture toughness and insufficient tensile strength. To improve these mechanical property defects, some studies have attempted to reinforce the surface of alumina fiber cloth by laying short fibers, but since short fibers cannot form an effective reinforcing network, they are unable to prevent crack propagation. Summary of the Invention

[0004] To address the problems of easy crack propagation and poor short fiber reinforcement in the existing technologies, this invention aims to provide a short fiber-reinforced alumina ceramic matrix composite material and its preparation method.

[0005] The preparation method of the doped short fiber reinforced alumina ceramic matrix composite material according to the present invention includes the following steps: S1, pretreating alumina fiber cloth and chopped fibers to remove surface organic impurities, wherein the chopped fibers are selected from one or more of carbon fiber, alumina fiber, and silicon carbide fiber; S2, mixing alumina powder and pretreated chopped fibers to prepare an alumina ceramic slurry, wherein the mass fraction of the chopped fibers in the alumina ceramic slurry is 0.5-3%; S3, uniformly coating the alumina ceramic slurry onto the surface of the pretreated alumina fiber cloth, and drying it to obtain a prepreg; S4, stacking the prepregs and performing vacuum-assisted hot pressing to obtain a green body; S5, heating the green body to 600-900℃ for curing and sintering to obtain a rough blank; S6, vacuum cyclically impregnating the rough blank with alumina sol, pre-sintering at 600-800℃, and then finally sintering at 1000-1200℃ to obtain the doped short fiber reinforced alumina ceramic matrix composite material.

[0006] In a preferred embodiment, the pretreatment method of step S1 includes: placing alumina fiber cloth and chopped fibers in a muffle furnace and heating them at a heating rate of 5-10℃ / min, and holding the temperature at 500-700℃ for 1-2 hours.

[0007] In a preferred embodiment, the length of the chopped fiber is 200μm-5mm.

[0008] In a preferred embodiment, the chopped fibers are a single or mixed combination of chopped fibers with lengths of 200μm-500μm and 1mm-5mm.

[0009] In a preferred embodiment, in step S2, alumina powder, deionized water, chopped fibers, dispersant, binder, and sintering aid are mixed and ball-milled to obtain a uniformly dispersed alumina ceramic slurry.

[0010] In a preferred embodiment, the alumina powder has a particle size of 200-500 nm, and the mass fraction of the alumina powder in the alumina ceramic slurry is 40-60%.

[0011] In a preferred embodiment, the dispersant is selected from at least one of polyethylene glycol, polyacrylamide, and polyethyleneimine, and the mass fraction of the dispersant in the alumina ceramic slurry is 0.1-0.5%; the binder is polyvinyl alcohol, and the mass fraction of the binder in the alumina ceramic slurry is 1-3%; the sintering aid is selected from at least one of TiO2, MgO, and MnO2, and the mass fraction of the sintering aid in the alumina ceramic slurry is 0.1-1%.

[0012] In a preferred embodiment, the aluminum sol in step S6 has a solid content of 10-20 wt% and a viscosity of ≤10 mPa·s.

[0013] The doped short fiber reinforced alumina ceramic matrix composite material according to the present invention is prepared by the above-described preparation method.

[0014] In a preferred embodiment, the density of the composite material is 2.3-2.7 g / cm³. 3 Its tensile strength at room temperature is 90-125 MPa.

[0015] This invention utilizes a synergistic process of chopped fibers and alumina powder to prepare ceramic slurry. Combining pretreatment, vacuum-assisted hot pressing, curing and sintering, and a segmented sintering process following vacuum cyclic impregnation with alumina sol, this process not only achieves uniform dispersion of the chopped fibers within the composite material, forming a continuous reinforcing network to effectively block crack propagation and optimize crack propagation behavior, but also avoids fiber thermal damage and deterioration of interfacial bonding through the segmented sintering process. Simultaneously, the full penetration and filling of the pores in the preform by the alumina sol significantly improves the density and structural integrity of the composite material. This successfully solves the problems of insufficient mechanical properties and uneven dispersion of short fibers in traditional alumina ceramic matrix composites. Ultimately, the resulting composite material possesses excellent room-temperature tensile strength and structural stability. Furthermore, the entire process is simplified, highly efficient, and cost-controllable, meeting the application requirements of high-performance ceramic matrix composites for extreme environments in aerospace, nuclear energy, and other fields. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the process flow for the doped short fiber reinforced alumina ceramic matrix composite material according to the present invention.

[0017] Figure 2 This is a tensile property diagram of the alumina fiber-reinforced alumina matrix composite material according to the present invention. Detailed Implementation

[0018] The technical solution of the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings. These embodiments are only used to explain the present invention and are not intended to limit the scope of protection of the present invention.

[0019] like Figure 1 As shown, the preparation method according to the present invention includes pretreatment of alumina fiber cloth and chopped fibers. Specifically, the alumina fiber cloth and chopped fibers are placed in a muffle furnace and heated at a heating rate of 5-10℃ / min, and held at 500-700℃ for 1-2 hours. In a preferred embodiment, the chopped fibers are selected from one or more of carbon fiber, alumina fiber, and silicon carbide fiber. In a preferred embodiment, the alumina fiber cloth is a two-dimensional fabric woven from alumina fibers, and can be plain weave, satin weave, twill weave, etc.

[0020] like Figure 1As shown, the preparation method according to the present invention includes mixing alumina powder and pretreated chopped fibers to prepare an alumina ceramic slurry. The inventors discovered that traditional short fiber reinforcement methods directly lay short fibers on the surface of a fiber cloth, resulting in short fibers only distributed between the fiber cloth layers and unable to uniformly penetrate into the matrix, making it difficult to form a continuous reinforcing network. To solve this problem, the inventors attempted to increase the layup density, but agglomeration and uneven distribution still occurred. Finally, they determined to incorporate chopped fibers into the slurry to achieve uniform mixing of the short fibers and alumina powder, allowing the short fibers to be uniformly dispersed throughout the composite material, forming a three-dimensional reinforcing network that effectively blocks crack propagation. In a preferred embodiment, the chopped fibers are selected from one or more of carbon fibers, alumina fibers, and silicon carbide fibers. Results show that carbon fibers, alumina fibers, and / or silicon carbide fibers can form a good synergy with the alumina matrix. In a preferred embodiment, the mass fraction of the chopped fibers in the alumina ceramic slurry is 0.5-3%. The results show that when the content of chopped fibers is below 0.3 wt%, the reinforcing effect is weak; above 3 wt%, it leads to slurry agglomeration and difficulty in molding; 0.5%-3 wt% can balance moldability and reinforcing effect. In a preferred embodiment, the mass fraction of the chopped fibers in the alumina ceramic slurry is 0.5%-1%. In a preferred embodiment, the length of the chopped fibers is 200 μm-5 mm. The results show that chopped fibers below 100 μm have almost no toughening effect (cannot bridge cracks), and fibers above 5 mm are prone to agglomeration during ball milling. In a preferred embodiment, the chopped fibers are a single or mixed combination of chopped fibers with lengths of 200 μm-500 μm and 1 mm-5 mm. The results show that a single or mixed combination of 200 μm-500 μm and 1 mm-5 mm fibers can ensure dispersibility while also providing bridging and pull-out toughening. In a preferred embodiment, the chopped fibers are a single chopped fiber with a length of 1 mm-2 mm. In a preferred embodiment, the chopped fibers are a mixture of chopped fibers with lengths of 200 μm-300 μm and 1 mm-2 mm. Specifically, alumina powder, deionized water, chopped fibers, dispersant, binder, and sintering aid are mixed and ball-milled to obtain a uniformly dispersed alumina ceramic slurry. In a preferred embodiment, the alumina powder has a particle size of 200-500 nm. In a preferred embodiment, the alumina powder has a particle size of 200 nm. In a preferred embodiment, the alumina powder has a mass fraction of 40-60% in the alumina ceramic slurry. In a preferred embodiment, the alumina powder has a mass fraction of 50-52% in the alumina ceramic slurry. In a preferred embodiment, the dispersant is selected from at least one of polyethylene glycol, polyacrylamide, and polyethyleneimine, and the dispersant has a mass fraction of 0.1%-0.5% in the alumina ceramic slurry. In a preferred embodiment, the dispersant is polyethylene glycol, and its mass fraction in the alumina ceramic slurry is 0.3%.In a preferred embodiment, the binder is polyvinyl alcohol, and the mass fraction of the binder in the alumina ceramic slurry is 1%-3%. In another preferred embodiment, the mass fraction of the binder in the alumina ceramic slurry is 1%. In a preferred embodiment, the sintering aid is selected from at least one of TiO2, MgO, and MnO2, and the mass fraction of the sintering aid in the alumina ceramic slurry is 0.1-1%. In another preferred embodiment, the sintering aid is TiO2 and MgO, with TiO2 having a mass fraction of 0.3% and MgO having a mass fraction of 0.1% in the alumina ceramic slurry. In a preferred embodiment, the ball milling process parameters are: ball milling speed 200-300 rad / min, ball milling time 4-10 h, ball milling beads are alumina balls or zirconia balls with a diameter of 3-5 mm, and ball-to-material ratio 2-4:1. In another preferred embodiment, the ball milling time is 5-8 h, and the ball-to-material ratio is 3:1.

[0021] like Figure 1 As shown, the preparation method according to the present invention includes uniformly coating an alumina ceramic slurry onto the surface of an alumina fiber cloth, and obtaining a prepreg after drying. In a preferred embodiment, the drying environment parameters are: temperature 10-30℃, relative humidity 50-60%. In a preferred embodiment, the drying temperature is 20-25℃.

[0022] like Figure 1 As shown, the preparation method according to the present invention includes stacking the prepregs and then performing vacuum-assisted hot pressing to obtain a green body. In a preferred embodiment, the prepregs are stacked in a 0° / 45° interval cycle or a 0° / 45° / 45° / 0° interval cycle. In a preferred embodiment, the total number of prepreg layers is 12. In a preferred embodiment, the vacuum-assisted hot pressing parameters are: pressure 600-900 kPa, heating rate 2-5°C / min, and holding at 100-150°C for 6-10 hours.

[0023] like Figure 1 As shown, the preparation method according to the present invention includes heating the green blank to 600-900℃ for solidification and sintering to obtain a rough blank. In a preferred embodiment, the solidification and sintering parameters are: heating rate 5-10℃ / min, holding at 600-900℃ for 1-3 hours to remove residual organic matter and form a preliminary dense matrix framework. In a preferred embodiment, the temperature is raised to 800℃ and held for 2 hours.

[0024] like Figure 1As shown, the preparation method according to the present invention includes vacuum cyclic impregnation of the rough blank with alumina sol, pre-sintering at 600-800℃, and then final sintering at 1000-1200℃ to obtain a short-fiber reinforced alumina ceramic matrix composite material. Results show that when the short-cut fibers are directly incorporated into the slurry, they form a weak bond with the alumina powder during sintering. This bond is neither too strong, leading to cracks penetrating the fibers, nor too weak, causing fiber detachment. No additional surface modification is required, simplifying the process and reducing costs. The inventors attempted traditional one-time high-temperature sintering (directly heating to 1000-1200℃), and found that the composite material suffered from thermal stress impact, fiber breakage, excessively strong interfacial bonding, and a significant decrease in tensile strength. They ultimately determined a segmented sintering process of pre-firing and final firing. Pre-firing at 600-800℃ promotes the initial sintering of aluminum oxides and stabilizes the weak bonding interface between the fiber and the matrix. Final firing at 1000-1200℃ densifies the matrix, avoiding fiber damage and interfacial deterioration while ensuring material density and strength. In a preferred embodiment, the vacuum cyclic impregnation process parameters are: impregnation pressure of -0.08 to -0.12 MPa, single impregnation time of 6-10 hours, and cyclic impregnation stopping when the composite material weight gain is less than 2%. In another preferred embodiment, the impregnation pressure is -0.1 MPa, and the single impregnation time is 8 hours. In a preferred embodiment, the aluminum sol solid content is 10-20 wt%, and the sol viscosity is ≤10 mPa·s. The results show that aluminum sol with a solid content of 10-20 wt% and a viscosity of ≤10 mPa·s can fill the pores of the blank and strengthen the bond between the fiber and the matrix.

[0025] The doped short fiber reinforced alumina ceramic matrix composite material obtained by the above preparation method has a density of 2.3-2.7 g / cm³. 3 The tensile strength at room temperature is 90-125 MPa. In a preferred embodiment, the density is 2.39-2.67 g / cm³. 3 The tensile strength at room temperature is 90.18-120.13 MPa. In a preferred embodiment, the density is 2.43 g / cm³. 3 The tensile strength at room temperature is 109.63 MPa.

[0026] Example 1

[0027] Alumina fiber cloth and chopped carbon fiber were placed in a muffle furnace for heat treatment to remove the organic coating on the fiber surface; the heating rate of the muffle furnace was 5℃ / min, and the temperature was held at 600℃ for 2 hours.

[0028] An alumina slurry was prepared, wherein the alumina powder had a particle size of 200 nm and the alumina powder content in the slurry was 50 wt% (mass fraction). The slurry also contained a dispersant, polyethylene glycol 4000 (0.3 wt%), a binder, polyvinyl alcohol (1 wt%), sintering aids (TiO2 0.3 wt%, MgO 0.1 wt%), and short-cut carbon fibers (0.5 wt%, 1-2 mm in length). The above raw materials were placed in a ball mill jar and ball-milled at a speed of 200 rad / min for 8 hours. The ball milling beads were alumina balls with a diameter of 5 mm, and the ball-to-powder ratio was 4:1, resulting in a uniformly dispersed alumina ceramic slurry.

[0029] Alumina ceramic slurry is evenly applied to the surface of heat-treated alumina fiber fabric and dried in an environment with a temperature of 20°C and a relative humidity of 60% until the weight of the material reaches 80% of the original weight (including the weight of the fiber fabric itself and the undried weight after coating with ceramic slurry), thus obtaining prepreg.

[0030] The dried prepreg was stacked on a flat plate covered with a release cloth, with a total of 12 layers. The layering method was 0°, 45°, 45° and 0° interval cycle. Then, vacuum-assisted hot pressing was performed. The hot pressing parameters were: pressure 900 kPa, heating rate 2℃ / min, and holding at 150℃ for 6 hours to obtain the green body.

[0031] The green blank was solidified and sintered with the following parameters: heating rate 10℃ / min, heating to 800℃ and holding for 2 hours to obtain a composite material blank.

[0032] The blank was vacuum cyclically impregnated in a commercial alumina sol with a solid content (mass fraction of solid components) of 10-20 wt% and a viscosity of ≤10 mPa·s for 8 hours at a pressure of -0.1 MPa. After impregnation, it was first pre-sintered at 800℃ and then finally sintered at 1100℃ until the weight gain of the composite material was less than 2%, and the cycle was ended to obtain the doped short fiber reinforced alumina ceramic matrix composite material.

[0033] The prepared alumina composite sample was cut into standard test strips, and its density was measured to be 2.39 g / cm³. 3 The tensile strength at room temperature is 90.18 MPa.

[0034] Example 2

[0035] Alumina fiber cloth and chopped alumina fibers were placed in a muffle furnace for heat treatment to remove the organic coating on the fiber surface; the heating rate of the muffle furnace was 5℃ / min, and the temperature was held at 700℃ for 1 hour.

[0036] An alumina slurry was prepared, wherein the alumina powder had a particle size of 200 nm and the alumina powder content in the slurry was 51 wt%. The slurry also contained a dispersant, polyethylene glycol 4000 (0.3 wt%), a binder, polyvinyl alcohol (1 wt%), sintering aids (TiO2 0.3 wt%, MgO 0.1 wt%), and short-cut alumina fibers (1 wt%, 1-2 mm in length). The above raw materials were placed in a ball mill jar and ball-milled at a speed of 300 rad / min for 5 hours. The grinding beads were zirconia balls with a diameter of 5 mm, and the ball-to-powder ratio was 3:1, resulting in a uniformly dispersed alumina ceramic slurry.

[0037] Alumina ceramic slurry is evenly applied to the surface of heat-treated alumina fiber fabric and dried in an environment with a temperature of 20°C and a relative humidity of 60% until the material weight reaches 80% of the original weight, thus obtaining prepreg.

[0038] The dried prepreg was stacked on a flat plate covered with a release cloth, with a total of 12 layers. The layering method was 0° and 45° interval cycle. Then, vacuum-assisted hot pressing was performed. The hot pressing parameters were: pressure 900 kPa, heating rate 2℃ / min, and holding at 150℃ for 10 hours to obtain the green body.

[0039] The green blank was solidified and sintered with the following parameters: heating rate 10℃ / min, heating to 800℃ and holding for 2 hours to obtain a composite material blank.

[0040] The blank was vacuum cyclically impregnated in a commercial alumina sol with a solid content of 10-20 wt% and a viscosity of ≤10 mPa·s for 8 hours at a pressure of -0.1 MPa. After impregnation, it was first pre-sintered at 800℃ and then finally sintered at 1100℃ until the weight gain of the composite material was less than 2%, and the cycle was ended to obtain the doped short fiber reinforced alumina ceramic matrix composite material.

[0041] The prepared alumina composite sample was cut into standard test strips, and its density was measured to be 2.67 g / cm³. 3 The tensile strength at room temperature is 120.13 MPa.

[0042] Example 3

[0043] Alumina fiber cloth and chopped silicon carbide fiber were placed in a muffle furnace for heat treatment to remove the organic coating on the fiber surface; the heating rate of the muffle furnace was 5℃ / min, and the temperature was held at 600℃ for 2 hours.

[0044] An alumina slurry was prepared, wherein the alumina powder had a particle size of 200 nm and the alumina powder content in the slurry was 52 wt%. The slurry also contained polyethylene glycol (0.3 wt%) as a dispersant, polyvinyl alcohol (1 wt%) as a binder, sintering aids (0.3 wt% TiO2 and 0.1 wt% MgO), and short-cut silicon carbide fibers (1 wt%, with a length of 200-300 μm and a mixture of 1-2 mm fibers). The above raw materials were placed in a ball mill jar and ball-milled at a speed of 200 rad / min for 8 hours. The grinding beads were alumina balls with a diameter of 5 mm, and the ball-to-powder ratio was 4:1, resulting in a uniformly dispersed alumina ceramic slurry.

[0045] Alumina ceramic slurry is evenly applied to the surface of heat-treated alumina fiber fabric and dried in an environment with a temperature of 20°C and a relative humidity of 60% until the material weight reaches 80% of the original weight, thus obtaining prepreg.

[0046] The dried prepreg was stacked on a flat plate covered with a release cloth, with a total of 12 layers. The layering method was 0°, 45°, 45° and 0° interval cycle. Then, vacuum-assisted hot pressing was performed. The hot pressing parameters were: pressure 900 kPa, heating rate 2℃ / min, and holding at 150℃ for 6 hours to obtain the green body.

[0047] The green blank was solidified and sintered with the following parameters: heating rate 10℃ / min, heating to 800℃ and holding for 2 hours to obtain a composite material blank.

[0048] The blank was vacuum cyclically impregnated in a commercial alumina sol with a solid content of 10-20 wt% and a viscosity of ≤10 mPa·s for 8 hours at a pressure of -0.1 MPa. After impregnation, it was first pre-sintered at 800℃ and then finally sintered at 1100℃ until the weight gain of the composite material was less than 2%, and the cycle was ended to obtain the doped short fiber reinforced alumina ceramic matrix composite material.

[0049] The prepared alumina composite sample was cut into standard test strips, and its density was measured to be 2.43 g / cm³. 3 The tensile strength at room temperature is 109.63 MPa.

[0050] Comparative Example 1 (Undoped short-cut fibers)

[0051] Alumina fibers were arranged in a muffle furnace for heat treatment to remove the organic coating on the fiber surface; the heating rate of the muffle furnace was 5℃ / min, and the temperature was held at 700℃ for 1 hour.

[0052] An alumina slurry was prepared, wherein the alumina powder had a particle size of 200 nm and the alumina powder content in the slurry was 50 wt%. The slurry also contained polyethylene glycol (0.3 wt%) as a dispersant, polyvinyl alcohol (2 wt%) as a binder, and sintering aids (TiO2 0.3 wt%, MgO 0.1 wt%), without the addition of chopped fibers. The above raw materials were placed in a ball mill jar and ball-milled at a speed of 300 rad / min for 5 hours. The ball milling beads were zirconia balls with a diameter of 5 mm, and the ball-to-powder ratio was 4:1, resulting in a uniformly dispersed alumina ceramic slurry.

[0053] Alumina ceramic slurry is evenly applied to the surface of heat-treated alumina fiber fabric and dried in an environment with a temperature of 20°C and a relative humidity of 60% until the material weight reaches 80% of the original weight, thus obtaining prepreg.

[0054] The dried prepreg was stacked on a flat plate covered with a release cloth, with a total of 12 layers. The layering method was 0° and 45° interval cycle. Then, vacuum-assisted hot pressing was performed. The hot pressing parameters were: pressure 900 kPa, heating rate 2℃ / min, and holding at 150℃ for 10 hours to obtain the green body.

[0055] The green blank was solidified and sintered with the following parameters: heating rate 10℃ / min, heating to 800℃ and holding for 2 hours to obtain a composite material blank.

[0056] The blank was vacuum cyclically impregnated in commercial alumina sol with a solid content of 10-20 wt% for 8 hours at an impregnation pressure of -0.1 MPa. After impregnation, it was first pre-sintered at 800℃ and then finally sintered at 1100℃ until the weight gain of the composite material was less than 2%, thus obtaining alumina fiber reinforced alumina matrix composite material.

[0057] The prepared alumina composite sample was cut into standard test strips, and its density was measured to be 2.24 g / cm³. 3 The tensile strength at room temperature is 81.47 MPa.

[0058] Comparative Example 2 (doped with short-cut fibers but without segmented sintering)

[0059] Alumina fiber cloth and chopped alumina fibers were placed in a muffle furnace for heat treatment to remove the organic coating on the fiber surface; the heating rate of the muffle furnace was 5℃ / min, and the temperature was held at 700℃ for 1 hour.

[0060] An alumina slurry was prepared, wherein the alumina powder had a particle size of 200 nm and the alumina powder content in the slurry was 51 wt%. The slurry also contained a dispersant, polyethylene glycol 4000 (0.3 wt%), a binder, polyvinyl alcohol (1 wt%), sintering aids (TiO2 0.3 wt%, MgO 0.1 wt%), and short-cut alumina fibers (1 wt%, 1-2 mm in length). The above raw materials were placed in a ball mill jar and ball-milled at a speed of 300 rad / min for 5 hours. The grinding beads were zirconia balls with a diameter of 5 mm, and the ball-to-powder ratio was 3:1, resulting in a uniformly dispersed alumina ceramic slurry.

[0061] Alumina ceramic slurry is evenly applied to the surface of heat-treated alumina fiber fabric and dried in an environment with a temperature of 20°C and a relative humidity of 60% until the material weight reaches 80% of the original weight, thus obtaining prepreg.

[0062] The dried prepreg was stacked on a flat plate covered with a release cloth, with a total of 12 layers. The layering method was 0° and 45° interval cycle. Then, vacuum-assisted hot pressing was performed. The hot pressing parameters were: pressure 900 kPa, heating rate 2℃ / min, and holding at 150℃ for 10 hours to obtain the green body.

[0063] The green blank was solidified and sintered with the following parameters: heating rate 10℃ / min, heating to 800℃ and holding for 2 hours to obtain a composite material blank.

[0064] The blank was vacuum cyclically impregnated in a commercial alumina sol with a solid content of 10-20 wt% and a viscosity of ≤10 mPa·s for 8 hours at a pressure of -0.1 MPa. After impregnation, it was sintered directly at 1100℃ without segmented sintering until the weight gain of the composite material was less than 2%, thus obtaining alumina fiber reinforced alumina matrix composite material.

[0065] The prepared alumina composite sample was cut into standard test strips. The test results showed that its density was 2.45 g / cm³ and its room temperature tensile strength was 106.47 MPa.

[0066] The tensile properties of the doped short fiber reinforced alumina ceramic matrix composites of Examples 1-3 and the alumina fiber reinforced alumina matrix composites of Comparative Examples 1-2 are as follows: Figure 2As shown in the figure. A comparison of the data from Examples 1-3 and Comparative Example 1 reveals that the density and tensile strength of the composite material are significantly improved after doping with chopped fibers. The results indicate that doping with chopped fibers is an effective technical means to improve the insufficient mechanical properties of alumina ceramic matrix composites in this application. Through dispersion and bridging mechanisms in the matrix, the chopped fibers not only improve the material density but also optimize its crack propagation behavior, thereby achieving both reinforcement and toughening effects. A comparison of the data from Example 2 and Comparative Example 2 shows that segmented sintering can effectively avoid fiber damage, optimize interfacial bonding, and achieve synergistic toughening and reinforcement through chopped fibers and segmented sintering. It should be noted that the performance of Example 1 is lower than that of Comparative Example 2 because the chopped fiber mass fraction (0.5 wt%) is lower than that of Comparative Example 2 (1 wt%). This further verifies the rationality of the chopped fiber mass fraction range (0.5-3 wt%) defined in this invention. Within this range, the synergistic effect of the chopped fiber mass fraction and segmented sintering jointly determines the final material performance.

[0067] In summary, this invention effectively solves the problem of insufficient mechanical properties of traditional alumina ceramic matrix composites by using a single-stage sintering process of doping short-cut fibers into the slurry, pre-firing, and final firing. It eliminates the need for repeated impregnation, significantly simplifies the production process, shortens the production cycle, greatly improves production efficiency, has significant cost advantages, is suitable for large-scale, low-cost production, and has good prospects for industrial application.

[0068] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of the invention. Various variations can be made to the above embodiments of the present invention. That is, all simple and equivalent changes and modifications made based on the claims and description of this invention fall within the protection scope of the claims. All aspects not described in detail in this invention are conventional technical content.

Claims

1. A method for producing a doped short fiber-reinforced aluminum oxide ceramic matrix composite, characterized by, The preparation method comprises the following steps: S1, pretreating the alumina fiber cloth with chopped fibers to remove surface organic impurities, wherein the chopped fibers are selected from one or more of carbon fibers, alumina fibers, and silicon carbide fibers; S2, mixing alumina powder and the pretreated chopped fibers to prepare an alumina ceramic slurry, wherein the mass fraction of the chopped fibers in the alumina ceramic slurry is 0.5-3%; S3, uniformly coating the alumina ceramic slurry on the surface of the pretreated alumina fiber cloth, and drying to obtain a prepreg; S4, stacking the prepreg and performing vacuum-assisted hot pressing to obtain a green body; S5, heating the green body to 600-900℃ for curing and sintering to obtain a rough body; S6, vacuum-cyclically immersing the rough body in an aluminum sol, pre-sintering at 600-800℃, and finally sintering at 1000-1200℃ to obtain a short-fiber-doped alumina ceramic matrix composite material.

2. The production method according to claim 1, characterized by, The pretreatment method of step S1 comprises placing the alumina fiber cloth and the chopped fibers in a muffle furnace and heating at a heating rate of 5-10℃ / min, and then maintaining the temperature at 500-700℃ for 1-2h.

3. The preparation method according to claim 1, characterized in that, The length of the chopped fibers is 200μm-5mm.

4. The preparation method according to claim 3, characterized in that, The chopped fibers are single or mixed combinations of chopped fibers with lengths of 200μm-500μm and 1mm-5mm.

5. The preparation method according to claim 1, characterized in that, In step S2, the alumina powder, deionized water, chopped fibers, dispersant, binder, and sintering aid are mixed and ball milled to obtain a uniformly dispersed alumina ceramic slurry.

6. The preparation method according to claim 5, characterized in that, The particle size of the alumina powder is 200-500nm, and the mass fraction of the alumina powder in the alumina ceramic slurry is 40-60%.

7. The preparation method according to claim 5, characterized in that, The dispersant is selected from at least one of polyethylene glycol, polyacrylamide, and polyethyleneimine, and the mass fraction of the dispersant in the alumina ceramic slurry is 0.1-0.5%; the binder is polyvinyl alcohol, and the mass fraction of the binder in the alumina ceramic slurry is 1-3%; and the sintering aid is selected from at least one of TiO2, MgO, and MnO2, and the mass fraction of the sintering aid in the alumina ceramic slurry is 0.1-1%.

8. The method of claim 1, wherein, The solid content of the aluminum sol in step S6 is 10-20wt%, and the viscosity is ≤10mPa·s.

9. A doped short fiber reinforced alumina ceramic matrix composite, characterized in that, The preparation method of any one of claims 1-8 is used.

10. The doped short fiber reinforced aluminum oxide ceramic matrix composite according to claim 9, characterized in that The density of the composite material is 2.3-2.7 g / cm 3 The tensile strength at room temperature is 90-125 MPa.

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