Bionic Al / SiC composite material with three-dimensional network multilevel structure and preparation method of bionic Al / SiC composite material

Abstract

The invention relates to a bionic Al / SiC composite material with a three-dimensional network multilevel structure and a preparation method of the bionic Al / SiC composite material, and belongs to the technical field of new material preparation. According to the method, through the collaborative process of freeze casting and organic foam impregnation, the problem that in the prior art, the multilevel aperture and the complex network structure are difficult to cooperatively regulate and control is solved. The preparation method comprises the following specific steps: preparing tert-butyl alcohol-based ceramic slurry, impregnating the slurry with polyurethane foam, performing freeze casting molding, removing a solvent through freeze drying, performing high-temperature sintering to form SiC ceramic with a three-dimensional reticular hierarchical pore structure, and finally preparing the Al / SiC composite material through a vacuum pressure infiltration process. Wherein a sintering aid is added into the slurry, so that the sintering temperature is obviously reduced; the specification (40-60 ppi) of polyurethane foam, the solid phase content (20-30 vol.%) of slurry, the freezing speed (0-90 DEG C) and the content (5-20 wt.%) of a sintering aid are regulated and controlled. And the cross-scale collaborative design of micron-scale directional holes and millimeter-scale mesh holes is realized. The Al / SiC composite material prepared by the invention has the advantages that the compressive strength, fracture toughness and other properties are obviously higher than those of the traditional single-aperture porous ceramic, and the Al / SiC composite material is suitable for the fields of manufacturing and energy absorption of precise instruments, electronic packaging and optical devices.

Description

Technical Field

[0001] This invention relates to the field of new material preparation technology. Background Technology

[0002] With the ever-increasing demands on material performance in modern industry and cutting-edge technology fields, single metal or ceramic materials can no longer simultaneously meet the comprehensive requirements of high strength, high modulus, good toughness, and functional integration. Ceramic-metal composites, by combining the high strength, high hardness, and low coefficient of thermal expansion of the ceramic phase with the good plasticity, toughness, and high thermal conductivity of the metallic phase, achieve complementary and synergistic performance enhancement, showing broad prospects in lightweight, high-reliability, and thermal management applications such as aerospace, electronic packaging, and automotive manufacturing. Among many composite material systems, the Al / SiC system stands out. The aluminum matrix provides lightweight, high thermal conductivity, and easy processing properties, while the SiC reinforcing phase significantly improves the material's specific strength, specific stiffness, and wear resistance. Furthermore, aluminum and silicon carbide have a certain thermodynamic compatibility, and with proper processing, harmful interfacial reactions can be suppressed, achieving effective load transfer. Therefore, this system is widely used in the manufacture of precision instruments, electronic packaging, and optical devices.

[0003] In the preparation of Al / SiC composites with porous ceramic frameworks, cryo-casting and organic foam impregnation are two representative techniques. Cryo-casting, based on solvent-directed crystallization and template assembly principles, achieves directional arrangement of slurry particles by controlling the direction and rate of ice crystal growth, thereby forming biomimetic materials with ordered porous structures. This technique has advantages such as flexible processing and strong controllability of microstructure, enabling the preparation of anisotropic porous materials. For example, Deville et al. achieved precise control of the pore size and orientation of porous alumina materials by optimizing the composition of water-based slurry and freezing conditions (S. Deville, E. Saiz, APTomsia, Ice-templated porous aluminastructures, Acta Materialia 55 (2007) 1965–1974). Furthermore, Liu H et al. used bubble freeze casting technology to simulate the multi-scale channel structure of natural vines, achieving rapid, non-powered liquid transport and demonstrating the potential of freeze casting in biomimetic structural design (Liu H, Jiang J, Zhai W. Bubble freeze casting artificial rattan[J]. Chemical Engineering Journal, 2022.). However, traditional freeze casting technology mainly relies on a single ice crystal template, making it difficult to achieve coordinated control of multi-level pore sizes and complex network structures.

[0004] Organic foam impregnation technology uses porous polymer foam as a template to impregnate ceramic slurry, followed by sintering to remove the organic template, thereby obtaining a three-dimensional network ceramic framework. Patent CN202211517646.8 proposes a method for preparing SiC ceramics using a three-dimensional carbon foam framework, combined with chemical vapor deposition (CVD) and reactive silicate processes; however, its structure is limited by the pore size distribution of the template itself. Another patent, CN201710466058.9, uses a porous carbon fiber template to construct a SiC nanowire network through multiple impregnation-pyrolysis cycles, but still faces problems such as complex processes, high costs, and long production cycles. Although this method can prepare ceramic materials with interconnected three-dimensional pores, traditional organic foam impregnation technology still struggles to introduce oriented micro-level structures into the macroscopic network.

[0005] In summary, neither cryogenic casting nor organic foam impregnation methods, as a single technology, can efficiently construct multi-level biomimetic structures that combine macroscopic interconnected networks with microscopic directional arrangements within materials. This limits further improvements in the performance of Al / SiC composites. Meanwhile, the multi-level structures of natural biomaterials (such as bamboo and bone) offer insights into addressing these challenges. Bamboo possesses vascular bundles and thin-walled cells arranged along its growth direction, endowing it with high specific strength and bending resistance; bone exhibits a composite structure of dense cortical bone and porous cancellous bone, achieving lightweight while maintaining mechanical properties. Mimicking these biological structures provides important inspiration for designing next-generation high-performance composite materials.

[0006] To address the aforementioned technical problems, this invention proposes a synergistic process combining foam impregnation and cryogenic casting to simultaneously construct SiC ceramic green bodies with multi-level biomimetic structures. This method uses a three-dimensional polymer foam as a macroscopic template. After impregnating a SiC ceramic slurry with tert-butanol as a solvent, it is immediately subjected to directional freezing, thereby simultaneously achieving two template effects: the polymer foam replicates a three-dimensional macroscopic network structure, while tert-butanol crystals displace SiC particles during directional growth, forming microscopic circular channels arranged along a temperature gradient. The resulting green body, after freeze-drying and sintering, possesses both three-dimensional interconnected macropores and directional micropores, coupling a macroscopic vascular bundle structure similar to bamboo and a microscopic anisotropic pore structure similar to bone. Finally, industrially pure Al or Al alloy melt is filled into the porous SiC ceramic using a vacuum pressure infiltration process to prepare an Al / SiC composite material with a three-dimensional interpenetrating ceramic network and metallic phase. This method provides a new approach for developing structure-function integrated metal matrix composites. Summary of the Invention

[0007] The key technical problem to be solved by this invention is to prepare a novel SiC porous ceramic with multi-level pore size and complex network structure through cryogenic casting technology combined with organic foam impregnation, and finally to prepare an Al / SiC composite material through vacuum pressure melting process.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A biomimetic Al / SiC composite material with a three-dimensional network hierarchical structure and its preparation method, wherein the preparation method includes the following steps:

[0010] 1. Preparation of tert-butanol-based ceramic slurry: Dispersant and binder were dissolved separately in tert-butanol at 50℃, and then mixed with SiC (5µm) ceramic powder. A certain mass of Al2O3 (0.5µm) and MgO (0.5µm) powders were added as sintering aids. The added Al2O3–MgO powder accounted for 5–20 wt.% of the total ceramic powder, with an Al2O3:MgO mass ratio of 6:1. The slurry was prepared by ball milling at 300 r / min for 4 h. After ball milling, the slurry was vacuum stirred to remove gas for 15 min to obtain the tert-butanol-based ceramic slurry.

[0011] 2. Organic foam impregnation: Cut polyurethane foam to a suitable size according to the polytetrafluoroethylene mold, place it in the mold, pour ceramic slurry into the mold, and allow the polyurethane foam to be fully impregnated.

[0012] 3. Cryogenic casting: The mold is placed on a copper plate, and a copper rod connected to the copper plate is inserted into liquid nitrogen. A constant freezing temperature of 0 to -90℃ is set for directional freezing, and tert-butanol freezing is used to form a SiC billet with a directional pore structure.

[0013] 4. Freeze-drying: The ceramic slurry is frozen and demolded. The molded green body is placed in a freeze dryer and freeze-dried for 48 hours under low temperature and low pressure (-50℃, <10Pa) conditions to remove the solvent.

[0014] 5. Sintering of the blank: The freeze-dried SiC blank is placed in a box furnace for high-temperature sintering. After the polyurethane foam decomposes and volatilizes at high temperature, a porous ceramic with a three-dimensional network multi-level structure is obtained.

[0015] 6. Pressure infiltration: The ceramic blank and industrial pure Al or Al alloy are placed in a pressure infiltration furnace and heated to 850°C under vacuum conditions. Then, argon gas at 2 MPa is introduced to infiltrate the molten Al into the interior of the ceramic. After natural cooling to room temperature, Al / SiC composite material is obtained.

[0016] The dispersant described in the technical solution is citric acid; the binder is polyvinyl butyral. The sintering aids are Al2O3 and MgO. The polyurethane foam specifications are 40ppi, 50ppi, and 60ppi, with pore sizes of 2.58±0.26mm, 1.27±0.065mm, and 0.87±0.097mm, respectively.

[0017] The oriented frozen ceramic SiC preforms described in the technical solution are all cuboids with a diameter of 24 mm and a height of 30 mm.

[0018] The high-temperature sintering process parameters for the SiC ceramic preform described in the technical solution are as follows: a heating rate of 3℃ / min from 0 to 240℃, holding at 240℃ for 10 minutes; a heating rate of 2℃ / min from 240 to 600℃, holding at 600℃ for 10 minutes to remove organic matter and polyurethane foam. Then, the temperature is increased to 1200℃ at a rate of 5℃ / min and held for 1 hour for pre-oxidation. Subsequently, argon gas is introduced and the temperature is increased to 1450℃ at a rate of 5℃ / min, held for 2 hours to obtain the SiC ceramic. The pressure infiltration process parameters are as follows: a heating rate of 5℃ / min from 0 to 200℃; a heating rate of 10℃ / min from 250 to 850℃, holding at 850℃ for 6 minutes; then, argon gas is introduced to 2 MPa to complete the pressure infiltration.

[0019] Compared with the prior art, the beneficial effects of the present invention are:

[0020] 1. The present invention discloses a biomimetic Al / SiC composite material with a three-dimensional network multi-level structure and its preparation method, which overcomes the limitation of single pore size and achieves synergistic enhancement of mechanical and functional properties. Compared with traditional cryogenic casting or organic foam impregnation techniques, which can only form macropores or homogeneous network pores in a single direction, resulting in significant anisotropy or insufficient mechanical properties of the material, the present invention, through the synergistic design of cryogenic casting and foam impregnation, prepares a material with three-dimensional through-pores and directional micropores, coupling a macroscopic vascular bundle structure similar to bamboo and a microscopic anisotropic pore structure similar to bone.

[0021] 2. The biomimetic Al / SiC composite material with a three-dimensional network multi-level structure and its preparation method described in this invention significantly optimizes the efficiency and cost of the composite process, promoting large-scale application. Compared with existing technologies such as CVD deposition, which requires multiple cycles and is time-consuming, and carbon fiber impregnation and pyrolysis, resulting in significant raw material loss, this invention shortens the total experimental cycle to a single-step impregnation-directional cryogenic molding integrated process. Simultaneously, by utilizing sintering aids Al2O3 and MgO, the sintering temperature is reduced to 1450℃, reducing energy consumption and improving raw material utilization, laying the foundation for large-scale production.

[0022] 3. The biomimetic Al / SiC composite material with a three-dimensional network multi-level structure and its preparation method described in this invention can achieve cross-scale synergistic design of micron-level directional micropores and millimeter-level network macropores by precisely controlling the polyurethane foam specifications, slurry solid phase content, and freezing temperature parameters. This results in a composite material with strong compressive strength and fracture toughness. The material is suitable for diverse applications such as high-efficiency filtration and catalyst support, overcoming the functional limitations of traditional processes. Attached Figure Description

[0023] Figure 1 This is a flowchart illustrating the preparation process of a SiC ceramic with a multi-level structure as described in this invention.

[0024] Figure 2 These are cross-sectional electron microscope images of the polyurethane foam (ac: 40ppi, 50ppi, 60ppi) specifications described in this invention.

[0025] Figure 3 These are electron microscope images of the cross-sections of multi-level SiC ceramics prepared by adjusting different polyurethane foam specifications (ac: 40ppi, 50ppi, 60ppi) and different solid content (df: 20vol.%, 25vol.%, 30vol.%) in this example.

[0026] Figure 4 The diagram shows the compressive strength properties of multi-level SiC ceramics prepared by adjusting different polyurethane foam specifications (a) and different solid phase contents (b) in this example.

[0027] Figure 5 This is a cross-sectional optical micrograph of the multi-level Al6061 / SiC composite material prepared by adjusting different polyurethane foam specifications (ac: 40ppi, 50ppi, 60ppi) and different solid content (df: 20vol.%, 25vol.%, 30vol.%) in this example;

[0028] Figure 6 This is a graph showing the flexural strength (a) and single-sided notched strength (b) of Al6061 / SiC composite materials prepared by adjusting different polyurethane foam specifications in this example.

[0029] Figure 7 These are the flexural strength (a) and single-sided notch strength (b) performance figures of Al6061 / SiC composite materials prepared by adjusting different solid phase contents in this example; Detailed Implementation

[0030] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0031] A biomimetic Al / SiC composite material with a three-dimensional network hierarchical structure and its preparation method include the following steps:

[0032] Using tert-butanol as a solvent and SiC as the main ceramic powder, a certain amount of binder, sintering aid, and dispersant were added, and the mixture was stirred and ball-milled to obtain a ceramic slurry, which was then degassed under vacuum. Polyurethane foam was embedded in a mold, and the ceramic slurry was poured in and repeatedly extruded to ensure thorough impregnation. The mold was then placed in a freezer for constant-temperature freezing, followed by vacuum drying in a freeze dryer to obtain a ceramic green body. This green body was then placed in a box furnace for high-temperature sintering to obtain a three-dimensional network multi-level structured SiC ceramic. The ceramic green body and Al alloy were placed in a pressure infiltration furnace, where molten Al was pressure-infiltrated into the ceramic interior. After natural cooling to room temperature, an Al / SiC composite material was obtained.

[0033] The following embodiments are some specific implementation examples of the present invention in practical applications, but are not limited thereto.

[0034] Example 1

[0035] Step 1: Tert-butanol was selected as the solvent, citric acid as the dispersant, and polyvinyl butyral as the binder. First, 1 wt.% citric acid and 2 wt.% polyvinyl butyral were dissolved in a certain amount of tert-butanol to ensure the binder and dispersant were fully dissolved and formed a homogeneous solution. Then, a certain amount of SiC ceramic powder was weighed and added to the prepared solution, stirred appropriately to ensure thorough mixing of the ceramic powder and solution, forming a homogeneous and stable SiC ceramic slurry. A certain mass of Al2O3 and MgO powder was added as sintering aids, with the added Al2O3–MgO powder accounting for 20 wt.% of the total ceramic powder, and the Al2O3:MgO mass ratio being 6:1. After mixing, a SiC ceramic slurry with an initial solid content of 25 vol.% was obtained. The prepared slurry was poured into an alumina ball mill jar, and alumina grinding balls were added at a ball-to-powder mass ratio of 1:1. The prepared slurry was ball-milled for 5 hours using a planetary high-energy ball mill at a speed of 300 r / min. After ball milling, the uniformly mixed ceramic slurry was placed in a vacuum degasser for 20 minutes to remove gas.

[0036] Step 2: Cut 40ppi polyurethane foam into 24mm*24mm*30mm pieces and embed them into a PTFE mold. Then pour ceramic slurry into the mold and press the polyurethane foam repeatedly at least three times to ensure thorough impregnation. Place the mold on a freezing device for constant temperature freezing at -90℃. After the slurry has completely solidified, demold to obtain the corresponding frozen preform.

[0037] Step 3: Place the demolded ceramic blank into a freeze-drying device. Perform freeze-drying treatment for 48 hours under low temperature and low pressure (-50℃, <10Pa) conditions to better remove the solvent components.

[0038] Step 4: Place the freeze-dried SiC preform into a box furnace. The temperature is increased from 0 to 240℃ at a rate of 3℃ / min, held at 240℃ for 10 minutes, and then increased from 240 to 600℃ at a rate of 2℃ / min, held at 600℃ for 10 minutes to remove organic matter and polyurethane foam. Then, the temperature is increased to 1200℃ at a rate of 5℃ / min and held for 1 hour for pre-oxidation. Subsequently, argon gas is introduced, and the temperature is increased to 1450℃ at a rate of 5℃ / min, held for 2 hours to finally obtain the SiC ceramic.

[0039] Step 5: Place the ceramic preform and Al6061 aluminum alloy into a pressure infiltration furnace. The heating rate is 5℃ / min from 0 to 200℃, and 10℃ / min from 250 to 850℃. Hold at 850℃ for 6 minutes, then introduce argon gas to 2MPa to complete the pressure infiltration. After natural cooling to room temperature, the Al6061 / SiC composite material is obtained.

[0040] Example 2

[0041] The difference between this embodiment and Example 1 is that the sintering aid Al2O3–MgO powder accounts for 5 wt.% of the total ceramic powder. Cryogenic casting is performed at a temperature of -30°C with directional freezing. The remaining parameters and procedures are the same as in Example 1.

[0042] Example 3

[0043] This embodiment differs from Example 1 in that it uses a SiC ceramic slurry with an initial solid content of 30 vol.%. Cryo-casting is performed at -50°C using directional freezing. During pressure infiltration, the molten metal is pure Al, and the remaining parameters and steps are the same as in Example 1.

[0044] Example 4

[0045] The difference between this embodiment and Example 1 is that the foam specification is selected as 50ppi in the foam impregnation, and the sintering aid Al2O3–MgO powder accounts for 10wt.% of the total ceramic powder. The remaining parameters and steps are the same as in Example 1.

[0046] Example 5

[0047] This embodiment differs from Example 1 in that the cryogenic casting is performed at a temperature of -50°C with directional freezing, and the sintering aid Al2O3–MgO powder accounts for 15 wt.% of the total ceramic powder. During pressure infiltration, the molten metal is ZL205A aluminum alloy. The remaining parameters and steps are the same as in Example 1.

[0048] Example 6

[0049] The difference between this embodiment and Example 1 is that the foam specification is selected as 60ppi during the foam impregnation process. Directional freezing is performed at -70°C during cryogenic casting. During pressure infiltration, the molten metal is ZL107 aluminum alloy, and the remaining parameters and steps are the same as in Example 1.

[0050] Example 7

[0051] This embodiment differs from Example 1 in that it uses a SiC ceramic slurry with an initial solid content of 25 vol.%, and is directionally frozen at -50°C during cryogenic casting. During pressure infiltration, the molten metal is ZL102 aluminum alloy, and the remaining parameters and steps are the same as in Example 1.

[0052] Example 8

[0053] The difference between this embodiment and Example 1 is that the SiC ceramic slurry with an initial solid content of 30 vol.% was prepared. During the foam impregnation process, a foam specification of 60 ppi was selected. In the cryogenic casting, directional freezing was performed at -10°C. The remaining parameters and steps were the same as in Example 1.

Claims

1. A biomimetic Al / SiC composite material with a three-dimensional network multi-level structure, characterized in that, The SiC ceramic has a three-dimensional network multi-level interconnected pore structure with pore sizes ranging from a few micrometers (μm) to a few millimeters (mm) across different scales. The porosity is precisely controlled by the polyurethane foam specifications, freezing temperature, slurry solid content, and sintering aid content. It couples a macroscopic vascular bundle structure similar to bamboo with microscopic anisotropic pores similar to skeleton. Finally, a biomimetic Al / SiC composite material with a three-dimensional network multi-level structure, in which the ceramic network and metal interpenetrate, is prepared by vacuum pressure melting process.

2. The biomimetic Al / SiC composite material with a three-dimensional network multi-level structure as described in claim 1, characterized in that its preparation method includes the following steps: (1) Preparation of tert-butanol-based ceramic slurry: Dispersant and binder are dissolved in tert-butanol at 50°C, mixed with SiC ceramic powder and sintering aid, ball milled for 4 hours to prepare slurry, and vacuum degassed for 15 minutes. (2) Organic foam impregnation: Cut polyurethane foam and embed it into the mold, pour in the slurry and repeatedly squeeze to make it fully impregnated; (3) Directional solidification: The mold is placed on a copper plate for freeze casting to form a SiC billet with a directional pore structure; (4) Freeze-drying: Remove solvent by freeze-drying at -50℃ and <10Pa for 48h; (5) Sintering of the green body: The green body is sintered at high temperature, and the polyurethane foam is decomposed to obtain a three-dimensional network multi-level structure SiC ceramic. (6) Pressure impregnation: The billet and Al alloy are placed in a pressure impregnation furnace and impregnated by high-pressure argon gas through high-temperature fusion.

3. The method for preparing a biomimetic Al / SiC composite material with a three-dimensional network multi-level structure according to claim 2, characterized in that, The dispersant in step (1) is citric acid, the binder is polyvinyl butyral, and the mass ratio of sintering aid Al2O3 (0.5 μm) to MgO (0.5 μm) is 6:1, accounting for 5 to 20 wt.% of the total mass of ceramic powder.

4. The method for preparing a biomimetic Al / SiC composite material with a three-dimensional network multi-level structure according to claim 2, characterized in that, In step (2), the polyurethane foam is cut to a suitable size according to the mold, impregnated with slurry, and repeatedly pressed more than 5 times to ensure full filling. The SiC ceramic obtained after sintering in step (5) is constructed with a biomimetic bamboo-bone multi-level structure through a synergistic process of freeze casting and organic foam impregnation.

5. The method for preparing a biomimetic Al / SiC composite material with a three-dimensional network multi-level structure according to claim 2, characterized in that, In step (3), directional solidification is achieved by connecting liquid nitrogen with a copper plate to achieve constant temperature freezing, with a freezing temperature of 0 to -90℃.

6. The method for preparing a biomimetic Al / SiC composite material with a three-dimensional network multi-level structure according to claim 2, characterized in that, The high-temperature sintering process parameters in step (5) are as follows: 0~240℃ at a rate of 3℃ / min, 240℃ for 10min; 240~600℃ at a rate of 2℃ / min, 600℃ for 10min to remove organic matter and polyurethane foam; then 5℃ / min to 1200℃ for pre-oxidation for 1h. After introducing argon gas, the temperature was increased to 1450℃ at a rate of 5℃ / min and held for 2 hours.

7. The method for preparing a biomimetic Al / SiC composite material with a three-dimensional network multi-level structure according to claim 2, characterized in that, In step (1), the solid content of the slurry is 20-30 vol.%. By adjusting the polyurethane foam specifications (40-60 ppi) and solid content (20-30 vol.%), a cross-scale collaborative design of directional pores with a size of several to tens of micrometers and mesh pores with a size of several millimeters can be achieved.

8. The method for preparing a biomimetic Al / SiC composite material with a three-dimensional network multi-level structure according to claim 2, characterized in that, In step (6), the pressure-impregnated molten metal is industrial pure Al, Al6061 aluminum alloy, ZL205A aluminum alloy, ZL102 aluminum alloy, or ZL107 aluminum alloy.

9. A biomimetic Al / SiC composite material with a three-dimensional network multi-level structure as claimed in claim 1, characterized in that, The Al / SiC composite material exhibits significantly higher strength and fracture toughness than traditional single-size composite materials, making it suitable for the manufacturing of precision mechanical instruments, electronic packaging, aerospace devices, and energy absorption applications.

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