Alumina fiber reinforced alumina-based composite material and ultrasonic-assisted impregnation preparation method thereof

Abstract

The invention relates to an alumina fiber reinforced alumina-based composite material and an ultrasonic-assisted impregnation preparation method thereof. The preparation method comprises the following steps: pretreating alumina fiber cloth, and preparing alumina ceramic slurry; the pretreated alumina fiber cloth is arranged in the alumina ceramic slurry, and dipping is carried out under the ultrasonic effect; laminating, laying, hot-pressing and drying to obtain a green body; curing and sintering the green body to form a rough blank; and carrying out dipping treatment on the rough blank by adopting alumina sol, drying after dipping, sintering after drying, and repeating the dipping, drying and sintering processes to obtain the alumina fiber reinforced alumina-based composite material. According to the invention, through a composite process of combining ultrasonic-assisted impregnation with alumina sol cyclic impregnation, the filling and impregnation effect of the slurry on fibers is remarkably improved, so that the slurry uniformly permeates into fiber bundles and fabric gaps, the internal pore defects of the material are reduced, and the density and mechanical properties of the composite material are greatly improved.

Description

Technical Field

[0001] This invention relates to alumina ceramic composite materials, and more specifically to an alumina fiber-reinforced alumina matrix composite material and its ultrasonic-assisted impregnation preparation method. Background Technology

[0002] Alumina fiber-reinforced alumina matrix composites (Al2O3 / Al2O3), as a class of high-performance ceramic matrix composites, have shown great application potential in fields with stringent high-temperature performance requirements, such as aerospace hot-end components and high-temperature industrial equipment, thanks to their outstanding high-temperature oxidation resistance, high strength, and low density. Compared to non-oxide ceramic matrix composites, Al2O3 / Al2O3 composites also possess excellent resistance to water oxidation corrosion, effectively reducing fiber performance degradation caused by oxidation. They can operate stably for extended periods in complex environments where water and oxygen coexist, thus becoming an ideal replacement material for hot-end components in aerospace and other fields.

[0003] Currently, the preparation of Al2O3 / Al2O3 composite materials generally adopts the slurry method. This method usually involves manually brushing a prepared alumina ceramic slurry onto the surface of a two-dimensional alumina fiber cloth to form a prepreg; subsequently, after lay-up, hot pressing, and sintering, the Al2O3 / Al2O3 composite material is finally obtained.

[0004] However, the aforementioned traditional preparation methods suffer from two insurmountable technical bottlenecks in the prepreg preparation stage, which severely affect the performance and application effects of the final composite material:

[0005] Firstly, there is poor process consistency. The implementation of manual brushing process relies heavily on the operator's experience, making it impossible to accurately control the uniformity of the slurry coating and easily leading to uneven slurry distribution within the preform. This problem directly causes thickness fluctuations in the finished composite material, resulting in performance differences between different batches and even between products from the same batch, making it difficult to meet the stringent requirements of high-end equipment for material performance stability.

[0006] Secondly, the slurry penetration effect is limited. Due to the strong bundle-like structure of alumina fibers and their dense internal structure, it is difficult for the high-viscosity, low-flowability, high-solids-content alumina ceramic slurry to fully penetrate into the fiber bundle using only the pressure and capillary action applied by manual brushing. This results in most of the slurry only adhering to the surface of the fiber cloth and the larger pores between the fiber bundles, leaving a large number of continuous unfilled pores inside the fiber bundles after sintering. These pores become structural defects in the material, significantly reducing the density of the composite material and negatively impacting its mechanical properties, thus limiting the application of Al2O3 / Al2O3 composites in more demanding applications. Summary of the Invention

[0007] To address the problems of uneven slurry distribution and insufficient penetration into the fiber bundles in the manual brushing preparation of Al2O3 / Al2O3 composite materials, the present invention aims to provide an alumina fiber reinforced alumina matrix composite material and its ultrasonic-assisted impregnation preparation method.

[0008] The ultrasonic-assisted impregnation preparation method for alumina fiber-reinforced alumina matrix composite material according to the present invention includes the following steps: S1, pretreating alumina fiber cloth to remove the surface organic coating to obtain pretreated alumina fiber cloth, mixing alumina powder, solvent and dispersant to obtain an alumina ceramic slurry, wherein the particle size of the alumina powder is 0.1~1μm; S2, placing the pretreated alumina fiber cloth in the alumina ceramic slurry, and impregnating it under ultrasonic action to disperse the alumina powder into the interior of the alumina fibers to obtain an alumina cloth prepreg tape; S3, stacking and laying the alumina cloth prepreg tape, and hot-pressing and drying the finished green body to remove the moisture in the green body to obtain a green body; S4, solidifying and sintering the green body to form a rough body; S5, impregnating the rough body with alumina sol, drying it after impregnation, sintering it after drying, and repeating the impregnation, drying and sintering process to obtain an alumina fiber-reinforced alumina matrix composite material.

[0009] In a preferred embodiment, in step S1, the alumina fiber cloth is pretreated by heating it to 500-700°C at a rate of 5-10°C / min and holding it at that temperature for 1-2 hours.

[0010] In a preferred embodiment, in step S1, the solvent is aluminum sol, silica sol, or mullite sol; and / or the dispersant may be polyethylene glycol, polyacrylamide, ammonium citrate, or polyethyleneimine; and / or the mixing ratio of alumina powder, solvent, and dispersant is 40~60wt%: 49~49.9wt%: 0.1~1wt%.

[0011] In a preferred embodiment, in step S1, the mixed alumina powder, solvent and dispersant are ball-milled to obtain an alumina ceramic slurry. The ball milling speed is 200~500 rad / min, the ball milling time is 3~6 h, the ball milling beads are zirconia or alumina balls with a diameter of 3~5 mm, and the ball-to-material ratio is 2~4:1.

[0012] In a preferred embodiment, in step S2, the ultrasonic frequency is 28~40kHz and the ultrasonic immersion time is 10~30 minutes.

[0013] In a preferred embodiment, in step S2, the single-layer or multi-layer pretreated alumina fiber cloth is ultrasonically impregnated; and / or during ultrasonic impregnation, a tension of 10~30N is applied to the surface of the fiber cloth by rollers to keep it flat and uniform during the impregnation process; and / or after impregnation, a roller pressing process is performed to remove excess slurry and ensure that the prepreg tape has a uniform thickness.

[0014] In a preferred embodiment, in step S3, the total number of layers of the alumina cloth prepreg tape is 10 to 20; the hot-press drying pressure is 600 to 1000 kPa, the heating rate is 2 to 5 °C / min, and the temperature is maintained at 100 to 150 °C for 6 to 10 hours.

[0015] In a preferred embodiment, in step S4, the sintering atmosphere is an air atmosphere or an inert atmosphere, the heating rate is 5~10℃ / min, and the temperature is held for 1~3 hours after reaching 600~900℃.

[0016] In a preferred embodiment, in step S5, the solid content of the alumina sol is 20-40%, the particle size is 1-20 nm, and the viscosity is ≤50 mPa·s; and / or the sintering heating rate is 5-10 °C / min, and the sintering temperature is 800-1200 °C; and / or the cycle is stopped when the weight gain of the composite material is ≤2% compared to the previous cycle, and the total number of densification cycles for the alumina ceramic composite material prepared by this method is ≤3.

[0017] The alumina fiber-reinforced alumina matrix composite material according to the present invention is obtained according to the above-described ultrasonic-assisted impregnation preparation method.

[0018] In a preferred embodiment, the tensile strength of the alumina fiber-reinforced alumina matrix composite material is ≥220 MPa. In a preferred embodiment, the tensile strength of the alumina fiber-reinforced alumina matrix composite material is 225~250 MPa.

[0019] This invention effectively solves the technical problems of uneven slurry distribution and difficulty in penetrating the fiber bundles in the traditional manual brush coating process for preparing alumina fiber-reinforced alumina matrix composites by combining ultrasonic-assisted impregnation with alumina sol cyclic impregnation. This significantly improves the filling and impregnation effect of the slurry on the fibers, allowing it to penetrate evenly into the fiber bundles and fabric gaps, reducing internal porosity defects and improving the density and mechanical properties of the composite material. Furthermore, the precise controllability of ultrasonic process parameters reduces reliance on operator experience, ensuring controllable product thickness, structural consistency, and batch-to-batch repeatability. The alumina ceramic composite material prepared by this method requires ≤3 cycles of densification. The overall process is simple and efficient, improving production efficiency and providing a versatile technical approach for the preparation of related ceramic matrix composites, ultimately resulting in a composite material with excellent comprehensive performance. Attached Figure Description

[0020] Figure 1 This is a flowchart of the ultrasonic-assisted impregnation preparation method of alumina fiber reinforced alumina matrix composite material according to the present invention.

[0021] Figure 2 This is a cross-sectional view of the alumina ceramic composite material according to Embodiment 1 of the present invention.

[0022] Figure 3 This is a cross-sectional view of the alumina ceramic composite material according to Embodiment 2 of the present invention.

[0023] Figure 4 This is a cross-sectional view of the alumina ceramic composite material according to Comparative Example 1 of the present invention.

[0024] Figure 5 This is a tensile property diagram of the alumina ceramic composite material according to the present invention. Detailed Implementation

[0025] The preferred embodiments of the present invention are given below with reference to the accompanying drawings and described in detail.

[0026] like Figure 1 As shown, the ultrasonic-assisted impregnation preparation method for alumina fiber-reinforced alumina matrix composites according to the present invention first includes pretreating the alumina fiber cloth to remove the surface organic coating, thereby obtaining the pretreated alumina fiber cloth. In a preferred embodiment, the alumina fiber cloth is a two-dimensional fabric woven from alumina fibers, and can be woven in plain weave, satin weave, twill weave, or other weave patterns. In a preferred embodiment, the pretreatment is a heat treatment. In a preferred embodiment, the temperature is increased to 500-700°C at a rate of 5-10°C / min and held for 1-2 hours. In a specific embodiment, the heating rate of the heat treatment is 10°C / min or 5°C / min, and the temperature is increased to 600°C and held for 2 hours or 700°C and held for 1 hour, respectively. In a preferred embodiment, the pretreatment is carried out in a muffle furnace.

[0027] like Figure 1As shown, the ultrasonic-assisted impregnation preparation method for alumina fiber-reinforced alumina matrix composites according to the present invention further includes preparing an alumina ceramic slurry by mixing alumina powder, solvent, and dispersant. In a preferred embodiment, the alumina powder has a particle size of 0.1~1μm and a purity ≥99%. In a specific embodiment, the alumina powder has a particle size of 200nm. In a preferred embodiment, the solvent is aluminum sol, silica sol, or mullite sol. In a preferred embodiment, the sol has a solid content of 20~40wt%, a particle size of 10~40nm, and a pH of 2~5. In a specific embodiment, the solvent is aluminum sol with a solid content of 20wt%, a particle size of 10nm, and a pH of 3. In a preferred embodiment, the dispersant can be polyethylene glycol, polyacrylamide, ammonium citrate, or polyethyleneimine. In a specific embodiment, the dispersant is polyethylene glycol 4000. In a preferred embodiment, after mixing the alumina powder, solvent, and dispersant, a uniformly dispersed alumina ceramic slurry is obtained by ball milling. In a preferred embodiment, the mixing ratio of alumina powder, solvent, and dispersant is 40-60 wt% : 49-49.9 wt% : 0.1-1 wt%. In a specific embodiment, the mixing ratio of alumina powder, solvent, and dispersant is 50 wt% : 49.5 wt% : 0.5 wt%. In a preferred embodiment, the ball milling speed is 200-500 rad / min, the ball milling time is 3-6 h, the grinding balls are zirconia or alumina balls with a diameter of 3-5 mm, and the ball-to-material ratio is 2-4:1. In a specific embodiment, the ball milling speed is 200 rad / min, the ball milling time is 6 h, the grinding balls are alumina balls with a diameter of 5 mm, and the ball-to-material ratio is 4:1.

[0028] like Figure 1As shown, the ultrasonic-assisted impregnation preparation method of the alumina fiber-reinforced alumina matrix composite material according to the present invention further includes ultrasonic impregnation treatment. Specifically, the pretreated alumina fiber cloth is placed in an alumina ceramic slurry and impregnated under ultrasonic action to promote the uniform dispersion of alumina powder in the solvent, so that the slurry fully wets the fiber cloth and the alumina particles are more uniformly dispersed in the interior of the dense fiber bundles to obtain an alumina cloth prepreg tape. It should be understood that the alumina powder with a particle size of 0.1~1μm in the slurry is the core component for filling the pores of the fiber bundle and improving the density of the material. When the solvent in the slurry is aluminum sol, the 10-40nm nano-sized alumina particles it contains are smaller than the 0.1~1μm alumina powder, making it easier to penetrate into the tiny pores inside the fiber bundle, playing a secondary filling role. This, combined with the larger alumina powder particles, creates a coarse-fine mix, further improving the density of the material. When the solvent in the slurry is silica sol or mullite sol, the dispersed phases of silica or mullite will also penetrate into the fiber bundle. These are aluminosilicate components and play an auxiliary role in filling the pores. In a preferred embodiment, the ultrasonic frequency is 28~40kHz, and the ultrasonic impregnation time is 10~30 minutes. In a specific embodiment, the ultrasonic frequency is 40kHz, and the ultrasonic impregnation time is 10 minutes. In a preferred embodiment, single-layer or multi-layer pretreated alumina fiber cloth is ultrasonically impregnated. In a specific embodiment, four layers of pretreated alumina fiber cloth are used for ultrasonic impregnation. In a preferred embodiment, during ultrasonic impregnation, a tension of 10-30N is applied to the surface of the fiber cloth using rollers to keep it flat and uniform during the impregnation process, ensuring effective slurry wetting. In a preferred embodiment, after impregnation, a roller pressing process is performed to remove excess slurry and ensure uniform prepreg thickness.

[0029] like Figure 1 As shown, the ultrasonic-assisted impregnation preparation method for alumina fiber-reinforced alumina matrix composites according to the present invention further includes alumina fiber cloth layup. Specifically, the alumina cloth prepreg tape is cut and then laid in layers to prepare for subsequent hot-pressing and drying. The core is to ensure the uniformity of the preform structure through layup. In a preferred embodiment, the total number of layers after stacking the alumina cloth prepreg tape is 10 to 20. In a specific embodiment, the alumina cloth prepreg tape is obtained by ultrasonic impregnation of 0° / 90° warp and weft woven alumina fiber cloth. During layup, the prepreg tape is laid directly layer by layer, and the total number of layers after stacking the alumina cloth prepreg tape is 16. The layup process is carried out on a flat plate with a release cloth attached to avoid the prepreg tape from sticking to the flat plate. It should be understood that the layup method of the present invention includes, but is not limited to, 0° / 90°, and can also use 0° / 45°, 0° / 30°, 0° / 60° or combinations thereof. Different angle combinations can be flexibly adjusted according to the mechanical performance requirements of the composite material.

[0030] like Figure 1As shown, the ultrasonic-assisted impregnation preparation method for alumina fiber-reinforced alumina matrix composites according to the present invention further includes hot-press curing. Specifically, the preform after layup is subjected to hot-press drying treatment. The moisture in the preform is removed through the synergistic effect of heating and pressurization to obtain a dense green preform. In a preferred embodiment, the hot-press drying pressure is 600~1000 kPa, the heating rate is 2~5 °C / min, and the temperature is maintained at 100~150 °C for 6~10 h. In a specific embodiment, the pressure is 800 kPa, the heating rate is 2 °C / min, and the temperature is maintained at 150 °C for 8 h. In a preferred embodiment, an autoclave is selected as the hot-press drying equipment to ensure uniform pressure and temperature distribution, further improving the quality of the green preform.

[0031] like Figure 1 As shown, the ultrasonic-assisted impregnation preparation method for alumina fiber-reinforced alumina matrix composites according to the present invention further includes coarse blank curing and sintering. Specifically, the green blank obtained by hot pressing and drying is cured and sintered, causing the organic components in the blank to decompose and the inorganic phase to react, forming a structurally stable green blank. In a preferred embodiment, the sintering atmosphere is air or an inert atmosphere, the heating rate is 5~10℃ / min, and the temperature is raised to 600~900℃ and held for 1~3 hours. In a specific embodiment, the heating rate is 5℃ / min, and the temperature is raised to 800℃ and held for 1 hour. In a preferred embodiment, a muffle furnace is selected as the sintering equipment to ensure precise temperature control and meet the process requirements of curing and sintering.

[0032] like Figure 1 As shown, the ultrasonic-assisted impregnation preparation method for alumina fiber-reinforced alumina matrix composites according to the present invention further includes impregnation with aluminum sol. Specifically, an alumina sol is used to impregnate a rough blank, utilizing the permeability of the alumina sol to fill the internal pores of the rough blank. In a preferred embodiment, the solid content of the alumina sol is 20-40%, the particle size is 1-20 nm, and the viscosity is ≤50 mPa·s. In a specific embodiment, the solid content of the alumina sol is 20%, the particle size is 10 nm, and the viscosity is ≤10 mPa·s. It should be understood that the alumina particle size of the solvent aluminum sol is controlled between 10-40 nm, and the alumina particle size of the impregnation aluminum sol is controlled between 1-20 nm. When the particle size of both is less than or equal to 20 nm, the same type of alumina sol can be considered. Overall, the impregnation aluminum sol has a smaller particle size, making it easier for alumina particles to penetrate and fill the internal pores of the material, thereby improving the material's performance and stability. In a preferred embodiment, drying is performed after impregnation. In a preferred embodiment, commercially available aluminum sol is used to ensure stable performance and good consistency. In another preferred embodiment, a cyclic impregnation method is employed, with drying performed after each impregnation to prepare for the final sintering.

[0033] like Figure 1As shown, the ultrasonic-assisted impregnation preparation method for alumina fiber-reinforced alumina matrix composites according to the present invention finally includes sintering. Specifically, the preform after impregnation with alumina sol and drying is subjected to final sintering, so that the colloidal particles in the alumina sol are transformed into an alumina ceramic phase, further filling the pores and improving the material density. In a preferred embodiment, the sintering heating rate is 5~10℃ / min, and the sintering temperature is 800~1200℃. In a specific embodiment, the heating rate is 5℃ / min, and the sintering temperature is 1000℃. In a preferred embodiment, controlling the heating rate during the sintering process can avoid cracking of the preform due to thermal stress and ensure the integrity of the material structure. In a preferred embodiment, the impregnation-drying-sintering process is repeated until the weight gain of the composite material in the last cycle is ≤2% compared to the previous cycle, and the cycle is stopped. The total number of densification cycles for the alumina ceramic composite material prepared by this method is ≤3. Finally, a dense alumina fiber-reinforced alumina matrix composite material is obtained.

[0034] Example 1

[0035] Alumina fiber cloth was placed in a muffle furnace for heat treatment to remove the organic coating on the fiber surface, resulting in pretreated alumina fiber cloth. The heating rate of the muffle furnace was 10℃ / min, and the temperature was maintained at 600℃ for 2 hours.

[0036] Prepare the raw materials according to the following ratio: alumina powder content of 50wt% (mass percentage), the alumina powder particle size of 200nm and purity ≥99%; dispersant is polyethylene glycol 4000, content of 0.5wt%; solvent is aluminum sol, content of 49.5wt%, of which the aluminum sol solid content is 20wt%, particle size is 10nm, and pH is 3. After mixing the above raw materials evenly, ball milling is performed. The ball milling process parameters are: ball milling speed 200rad / min, ball milling time 6h, ball milling beads are alumina balls with a diameter of 5mm, and ball-to-material ratio is 4:1, finally obtaining a uniformly dispersed alumina ceramic slurry.

[0037] The pretreated alumina fiber cloth is immersed in alumina ceramic slurry for ultrasonic impregnation at a frequency of 40 kHz for 10 min. During impregnation, a tension of 10-30 N is applied to the surface of the fiber cloth by rollers to keep it flat and uniform. After impregnation, the cloth is rolled to remove excess slurry and ensure uniform thickness. The resulting alumina prepreg is then obtained.

[0038] After the alumina prepreg tape is cut to the required size, it is laid in layers on a flat plate with a release cloth attached. The alumina prepreg tape is made of 0° / 90° warp and weft woven alumina fiber cloth by ultrasonic impregnation. During the laying, the prepreg tape is laid layer by layer, and the total number of layers after stacking is 16. The finished blank is placed in a hot autoclave for hot pressing and drying treatment. The hot pressing and drying parameters are: pressure 800KPa, heating rate 2℃ / min, and holding at 150℃ for 8h to obtain the green blank.

[0039] The green blank is placed in a muffle furnace and solidified and sintered in an air atmosphere or an inert atmosphere. The sintering parameters are: heating rate 5℃ / min, holding at 800℃ for 1 hour, and then cooling to obtain the rough blank.

[0040] Commercial alumina sol was used to impregnate the blank. The alumina sol had a solid content of 20%, a particle size of 10 nm, and a viscosity of ≤10 mPa·s. After impregnation, the blank was dried and then sintered in a muffle furnace. The sintering parameters were: heating rate of 5 °C / min, and sintering was completed after heating to 1000 °C. The above impregnation-drying-sintering process was repeated once. The weight gain of the composite material was ≤2% compared with the previous one. The cycle was then stopped, and finally, a dense alumina fiber reinforced alumina matrix composite material was obtained.

[0041] Figure 2 This is a schematic diagram of the cross-sectional microstructure of the composite material prepared by ultrasonic-assisted impregnation of the single-layer alumina fiber cloth obtained in this embodiment. In the figure, the light-colored striped structure represents the weft alumina fibers, and the dark-colored small granular structure represents the radial alumina fibers. From the cross-sectional morphology, it can be clearly observed that the ceramic slurry is uniformly and fully filled in the gaps between fibers and inside the fiber bundles, with no obvious large pores or slurry voids in the entire cross-section. Therefore, it can be seen that the present invention can effectively break the fiber bundle aggregation through ultrasonic action, promote the penetration of high-viscosity slurry into the fiber bundles, achieve uniform slurry distribution, and lay the structural foundation for the excellent performance of the composite material.

[0042] The composite material sample prepared in this embodiment has the following dimensions: 150mm ± 0.05mm (length) × 100mm ± 0.05mm (width) × 2.21mm ± 0.05mm (height), and a density of 3.05g / cm³. 3 The porosity is 20.45%, and the tensile strength of the material is 243.31±10.2MPa.

[0043] Example 2

[0044] The alumina fiber cloth was placed in a muffle furnace for heat treatment to remove the organic coating on the fiber surface, resulting in pretreated alumina fiber cloth. The heating rate of the muffle furnace was 5℃ / min, and the temperature was maintained at 700℃ for 1 hour.

[0045] Prepare the raw materials according to the following ratio: 50 wt% alumina powder with a particle size of 200 nm and a purity ≥99%; 0.5 wt% polyethylene glycol 4000 as dispersant; and 49.5 wt% alumina sol as solvent, of which 20 wt% is solid, 10 nm is particle size, and pH is 3. After mixing the above raw materials evenly, ball milling is performed. The ball milling process parameters are: ball milling speed 200 rad / min, ball milling time 6 h, alumina balls with a diameter of 5 mm, and a ball-to-material ratio of 4:1, ultimately obtaining a uniformly dispersed alumina ceramic slurry.

[0046] Four layers of pretreated alumina fiber cloth were placed in alumina ceramic slurry for ultrasonic impregnation at an ultrasonic frequency of 40 kHz for 10 min. During impregnation, a tension of 10-30 N was applied to the surface of the fiber cloth by rollers to keep it flat and uniform. After impregnation, the cloth was rolled to remove excess slurry and ensure uniform thickness of the prepreg. The resulting alumina prepreg was then obtained.

[0047] After the alumina prepreg tape is cut to the required size, it is laid in layers on a flat plate with a release cloth attached. The alumina prepreg tape is made of 0° / 90° warp and weft woven alumina fiber cloth by ultrasonic impregnation. During the laying, the prepreg tape is laid layer by layer, and the total number of layers after stacking is 16. The finished blank is placed in a hot autoclave for hot pressing and drying treatment. The hot pressing and drying parameters are: pressure 800KPa, heating rate 2℃ / min, and holding at 150℃ for 8h to obtain the green blank.

[0048] The green blank is placed in a muffle furnace and solidified and sintered in an air atmosphere or an inert atmosphere. The sintering parameters are: heating rate 5℃ / min, holding at 800℃ for 1 hour, and then cooling to obtain the rough blank.

[0049] Commercial alumina sol was used to impregnate the blank. The alumina sol had a solid content of 20%, a particle size of 10 nm, and a viscosity of ≤10 mPa·s. After impregnation, the blank was dried and then sintered in a muffle furnace. The sintering parameters were: heating rate of 5 °C / min, and sintering was completed after heating to 1000 °C. The above impregnation-drying-sintering process was repeated twice. The weight gain of the composite material was ≤2% compared with the previous time. The cycle was stopped, and finally, a dense alumina fiber reinforced alumina matrix composite material was obtained.

[0050] Figure 3 This is a schematic diagram of the cross-sectional microstructure of the composite material prepared by ultrasonic-assisted impregnation process using the four-layer alumina fiber cloth obtained in this embodiment. Figure 2Compared to the cross-sectional structure of single-layer ultrasonic impregnation, the cross-section of the composite material after multi-layer ultrasonic impregnation shows that the fiber bundles are neatly arranged, and the ceramic slurry can still fill the spaces between the fibers and inside the fiber bundles well, without obvious interlayer separation or insufficient slurry filling. However, compared to the cross-section of single-layer ultrasonic impregnation, the uniformity of slurry distribution in local areas is slightly different. This corresponds to the result that the strength of multi-layer ultrasonic impregnated material is slightly lower than that of single-layer ultrasonic impregnated material in the subsequent tensile property test, indicating that the number of fiber cloth layers in ultrasonic impregnation will have a certain impact on the slurry penetration effect.

[0051] The dimensions of the composite material sample prepared in this embodiment were measured to be 150mm ± 0.07mm (length) × 100mm ± 0.07mm (width) × 2.29mm ± 0.07mm (height). After being cut into standard test strips, the density was measured to be 2.99 g / cm³. 3 The porosity is 20.9%, and the tensile strength of the material is 226.53±12.6MPa.

[0052] Comparative Example 1 (Manual Brushing Method)

[0053] Alumina fiber cloth was placed in a muffle furnace for heat treatment to remove the organic coating on the fiber surface, resulting in pretreated alumina fiber cloth. The heating rate of the muffle furnace was 10℃ / min, and the temperature was maintained at 600℃ for 2 hours.

[0054] Prepare the raw materials according to the following ratio: 50 wt% alumina powder with a particle size of 200 nm and a purity ≥99%; 0.5 wt% polyethylene glycol 4000 as dispersant; and 49.5 wt% alumina sol as solvent, of which 20 wt% is solid, 10 nm is particle size, and pH is 3. After mixing the above raw materials evenly, ball milling is performed. The ball milling process parameters are: ball milling speed 200 rad / min, ball milling time 6 h, alumina balls with a diameter of 5 mm, and a ball-to-material ratio of 4:1, ultimately obtaining a uniformly dispersed alumina ceramic slurry.

[0055] Alumina ceramic slurry is evenly coated onto the surface of pretreated alumina fiber cloth using a manual brushing method. After being smoothed by brushing, it is made into a prepreg.

[0056] After the prepreg is cut to the required size, it is laid in layers on a flat plate with a release cloth attached. The alumina prepreg tape is made of 0° / 90° warp and weft woven alumina fiber cloth by ultrasonic impregnation. During the laying, the prepreg tape is laid layer by layer, and the total number of layers is 16. The finished blank is placed in a hot autoclave for hot pressing and drying. The hot pressing and drying parameters are: pressure 800KPa, heating rate 2℃ / min, and holding at 150℃ for 8h to obtain the green blank.

[0057] The green blank is placed in a muffle furnace and solidified and sintered in an air atmosphere or an inert atmosphere. The sintering parameters are: heating rate 5℃ / min, holding at 800℃ for 1 hour, and then cooling to obtain the rough blank.

[0058] Commercial alumina sol was used to impregnate the blank. The alumina sol had a solid content of 20%, a particle size of 10 nm, and a viscosity of ≤10 mPa·s. After impregnation, the blank was dried and then sintered in a muffle furnace. The sintering parameters were: heating rate of 5 °C / min, and sintering was completed after heating to 1000 °C. The above impregnation-drying-sintering process was repeated until the weight gain of the composite material was ≤2% compared to the previous one. The cycle was then stopped, and the alumina fiber reinforced alumina matrix composite material was finally obtained.

[0059] Figure 4 This is a schematic diagram of the cross-sectional microstructure of the composite material prepared using the traditional manual brushing process, as shown in the comparative example. The diagram clearly shows dispersed pores in the composite material cross-section, with the ceramic slurry primarily adhering to the surface of the fiber cloth and the larger pores between the fiber bundles. Some areas within the fiber bundles remain unfilled by the slurry. This indicates that the traditional manual brushing process, relying solely on brushing pressure and capillary action, cannot allow the high-viscosity slurry to fully penetrate the dense fiber bundles, resulting in structural porosity defects within the material and consequently affecting its density and mechanical properties.

[0060] The dimensions of the composite material sample prepared in this comparative example were found to be 150mm ± 0.1mm (length) × 100mm ± 0.1mm (width) × 2.25mm ± 0.1mm (height), with a measured density of 2.95g / cm³. 3 The porosity is 21.24%, and the tensile strength of the material is 216.46±16.6MPa.

[0061] Figure 5The graphs show the tensile properties of the composite materials prepared in Example 1 (single-layer ultrasonic impregnation), Example 2 (multi-layer ultrasonic impregnation), and Comparative Example 1 (manual brushing). The black curve corresponds to Example 1 (single-layer ultrasonic impregnation), which is generally stable. With increasing displacement, the tensile strength continuously increases, reaching a peak of nearly 250 MPa at a displacement of approximately 0.25 mm, and the strength decays slowly, indicating that the composite material prepared by single-layer ultrasonic impregnation has superior tensile properties, higher strength, and better stability. The red curve corresponds to Example 2 (multi-layer ultrasonic impregnation), which is similar to the single-layer ultrasonic impregnated material, but the overall peak strength is slightly lower, indicating that the penetration efficiency of the slurry into each fiber bundle is slightly lower in multi-layer simultaneous impregnation than in single-layer impregnation. The blue curve corresponds to Comparative Example 1 (manual brushing), which has the lowest peak strength (approximately 216 MPa), and the curve fluctuates relatively greatly, with a faster strength decay, indicating that the mechanical properties of the material prepared by the manual brushing process are less stable. The figure visually demonstrates through quantitative data that the ultrasonic-assisted impregnation process of this invention (especially single-layer ultrasonic impregnation) can significantly improve the tensile strength and mechanical stability of composite materials. Moreover, the single-layer ultrasonic impregnation process exhibits higher impregnation efficiency compared to multi-layer synchronous impregnation, thereby enabling the composite material to obtain better mechanical strength.

[0062] This invention employs a composite process combining ultrasonic-assisted impregnation and sol-gel circulation impregnation to significantly improve the filling and impregnation effect of the slurry on alumina fibers. In particular, it effectively improves the uniformity of slurry penetration within the fiber bundles, successfully overcoming the technical bottlenecks of uneven slurry distribution and insufficient penetration within the fiber bundles that are common in traditional manual brushing methods. The resulting prepreg exhibits a more uniform slurry distribution, significantly improving the controllability of the composite material's thickness and ensuring the consistency of the final product's structure. Simultaneously, the ultrasonic-assisted impregnation process parameters are easily and precisely controlled, greatly reducing reliance on operator experience and improving process stability and batch-to-batch repeatability. The overall process is characterized by its ease of operation and high efficiency, effectively improving production efficiency and providing a widely applicable technical approach for the preparation of related ceramic matrix composites. The resulting alumina fiber-reinforced alumina matrix composite exhibits excellent overall performance.

[0063] 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 preparing alumina fiber-reinforced alumina matrix composite material using ultrasonic-assisted impregnation, characterized in that, The ultrasound-assisted impregnation preparation method includes the following steps: S1, pre-treated alumina fiber cloth to remove surface organic coating to obtain pre-treated alumina fiber cloth, and alumina powder, solvent and dispersant are mixed to obtain alumina ceramic slurry, wherein the particle size of alumina powder is 0.1~1μm; S2, the pretreated alumina fiber cloth is placed in the alumina ceramic slurry and impregnated under ultrasonic action to disperse alumina powder into the interior of the alumina fiber to obtain alumina cloth prepreg tape; S3, the alumina cloth prepreg tape is laid in layers, and the finished blank is hot-pressed and dried to remove the moisture in the blank to obtain a green blank; S4, the green blank is solidified and sintered to form a rough blank; S5, the blank is impregnated with aluminum sol, dried after impregnation, and sintered after drying. The impregnation, drying and sintering process is repeated to obtain alumina fiber reinforced alumina matrix composite material.

2. The ultrasonic-assisted impregnation preparation method according to claim 1, characterized in that, In step S1, the alumina fiber cloth is pretreated by heating it to 500-700℃ at a rate of 5-10℃ / min and holding it at that temperature for 1-2 hours.

3. The ultrasonic-assisted impregnation preparation method according to claim 1, characterized in that, In step S1, the solvent is aluminum sol, silica sol, or mullite sol; and / or the dispersant may be polyethylene glycol, polyacrylamide, ammonium citrate, or polyethyleneimine; and / or the mixing ratio of alumina powder, solvent, and dispersant is 40~60wt%: 49~49.9wt%: 0.1~1wt%.

4. The ultrasonic-assisted impregnation preparation method according to claim 1, characterized in that, In step S1, the mixed alumina powder, solvent and dispersant are ball-milled to obtain alumina ceramic slurry. The ball milling speed is 200~500 rad / min, the ball milling time is 3~6h, the ball milling beads are zirconia or alumina balls with a diameter of 3~5mm, and the ball-to-material ratio is 2~4:

1.

5. The ultrasonic-assisted impregnation preparation method according to claim 1, characterized in that, In step S2, the ultrasonic frequency is 28~40kHz and the ultrasonic immersion time is 10~30 minutes.

6. The ultrasonic-assisted impregnation preparation method according to claim 1, characterized in that, In step S2, the single-layer or multi-layer pretreated alumina fiber cloth is ultrasonically impregnated; and / or a tension of 10~30N is applied to the surface of the fiber cloth by rollers during ultrasonic impregnation to keep it flat and uniform during the impregnation process; and / or after impregnation, a roller pressing process is performed to remove excess slurry and ensure that the prepreg tape has a uniform thickness.

7. The ultrasonic-assisted impregnation preparation method according to claim 1, characterized in that, In step S3, the total number of layers of the prepreg tape after stacking is 10 to 20; the hot pressing drying pressure is 600 to 1000 kPa, the heating rate is 2 to 5 °C / min, and the temperature is maintained at 100 to 150 °C for 6 to 10 hours.

8. The ultrasonic-assisted impregnation preparation method according to claim 1, characterized in that, In step S4, the sintering atmosphere is air or inert atmosphere, the heating rate is 5~10℃ / min, and the temperature is held for 1~3h after reaching 600~900℃.

9. The ultrasonic-assisted impregnation preparation method according to claim 1, characterized in that, In step S5, the solid content of the alumina sol is 20-40%, the particle size is 1-20 nm, and the viscosity is ≤50 mPa·s; and / or the heating rate of sintering is 5-10 °C / min, and the sintering temperature is 800-1200 °C; and / or the cycle is stopped when the weight gain of the composite material is ≤2% compared with the previous cycle, and the total number of densification cycles of the alumina ceramic composite material prepared by this method is ≤3.

10. An alumina fiber-reinforced alumina-based composite material, characterized in that, The alumina fiber reinforced alumina matrix composite material is prepared by the ultrasonic-assisted impregnation method according to any one of claims 1-9.

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