Silicon carbide ceramic filter with bionic structure design and 3D printing method thereof

Abstract

The invention belongs to the technical field of advanced functional ceramics, and particularly relates to a silicon carbide ceramic filter with bionic structural design and a 3D printing method thereof. Comprising the following steps: constructing a silicon carbide ceramic filter structure: constructing a three-dimensional unit cell structure with a deflection angle of 0 degree, + / -45 degrees or 60 degrees by taking glass sponge octagonal meshes as a bionic prototype, and periodically and repeatedly arranging in a three-dimensional space along X-axis, Y-axis and Z-axis directions to obtain a filter structure with a multi-stage communicated bionic pore system; and preparing the water-based SiC slurry with the solid content of more than or equal to 70wt%. Performing 3D printing by using a pneumatic-screw composite extrusion direct writing process to obtain a ceramic structure initial blank, and performing sintering post-treatment to obtain the silicon carbide ceramic filter. The prepared filter is high in bending strength and high in molten metal inclusion removal rate, has complex structure forming capacity, efficient filtering performance and stable mechanics, and provides a new way for efficient and low-cost preparation of silicon carbide ceramic complex parts.

Description

Technical Field

[0001] This invention belongs to the field of advanced functional ceramics technology, specifically relating to a silicon carbide ceramic filter with a biomimetic structural design and its 3D printing method. Background Technology

[0002] Porous ceramics are a new type of ceramic material. Due to their high porosity and low bulk density, they have shown great application potential in fields such as purification and filtration, sensor materials, and composite material reinforcement. Ceramic filters can remove impurities from high-temperature molten metal and eliminate defects such as shrinkage porosity, gas pores, and slag inclusions in castings. In particular, they can effectively improve the surface quality and internal material properties of castings in the precision casting process of steel, and have high application value.

[0003] Application No. 202411537966.9 discloses a ceramic filter for precision casting of high-temperature alloys and its preparation method. A ceramic premix is ​​prepared using zirconia and other raw materials. Modified carbon fibers are implanted onto a polyurethane sponge precursor, followed by impregnation with the premix, drying, and segmented calcination to obtain a zirconia ceramic filter. However, filters manufactured using this method suffer from drawbacks such as uncontrollable internal pore structure, complex and imprecise process flow, low filtration efficiency, and long manufacturing cycle. Application No. 202411559568.7 discloses a 3D-printed ceramic filter and its preparation slurry and method. A photosensitive resin premix is ​​used as the liquid phase, and a zirconia mixture is used as the solid phase. Dispersants and other additives are added. The mixture is ball-milled, filtered, and degassed under vacuum to form a ceramic slurry. The slurry is then formed using DLP photopolymerization 3D printing. The green body is sintered in segments and naturally cooled to obtain a zirconia ceramic filter. However, filters manufactured using this method have a weak internal structure design, limiting filtration performance; they rely too heavily on macroscopic structural design and lack active microscopic pore control strategies; and the material cost is high.

[0004] Existing publicly available methods for preparing ceramic filters rely on mold manufacturing, resulting in long manufacturing processes and low material utilization; while 3D printing methods rely too much on macroscopic structures and lack multi-level pore active control strategies. Summary of the Invention

[0005] To address the aforementioned issues, this invention provides a biomimetic silicon carbide ceramic filter and its 3D printing method. Based on water-based SiC slurry as a solvent system and a glass sponge biomimetic ceramic filter structure design, and focusing on the construction of a SiC ceramic direct-write 3D printing process system, the relationship between materials, processes, structures, and properties is established through a pneumatic-screw composite direct-write extrusion 3D printing molding process. This achieves integrated manufacturing of porous ceramic structures, and the prepared filter can effectively trap inclusions in molten metal, reducing internal defects in castings and significantly improving the mechanical properties and service life of castings.

[0006] To achieve the above objectives, the specific technical solution provided by the present invention is as follows: The first objective of this invention is to provide a 3D printing method for a silicon carbide ceramic filter with a biomimetic structural design, comprising the following steps: S1. Constructing a silicon carbide ceramic filter structure: Using the octagonal mesh of glass sponge as a biomimetic prototype, construct a three-dimensional unit cell structure with a deflection angle of 0°, ±45° or 60°. The unit cells are periodically repeated in three-dimensional space along the X-axis, Y-axis and Z-axis directions, forming an overall filter structure with a multi-level interconnected biomimetic pore system.

[0007] S2. Prepare water-based SiC slurry with a solid content ≥70wt%.

[0008] S3. 3D printing of ceramic structure blanks was carried out using a pneumatic-screw composite extrusion direct writing process.

[0009] S4. The initial ceramic structure blank is dried, degreased, and sintered to obtain a silicon carbide ceramic filter.

[0010] Furthermore, the three-dimensional unit cell structure is a cube with a size of 3mm to 5mm.

[0011] Furthermore, the multi-level interconnected biomimetic pore system includes nanoscale material pores, micrometer-scale material pores, and millimeter-scale and above structural pores.

[0012] Furthermore, in the pneumatic-screw composite extrusion direct writing 3D printing process, the printing speed is 600-1000 mm / min, the printing air pressure is 0.1 MPa-0.6 MPa, and the printing layer height is 0.4 mm-0.6 mm.

[0013] Furthermore, in the pneumatic-screw composite extrusion direct writing 3D printing process, the nozzle diameter is 0.8mm to 1.2mm and the screw speed is 30rpm to 100rpm.

[0014] Furthermore, the water-based SiC slurry is composed of silicon carbide, sintering aid, pore-forming agent, binder, dispersant and water. The amount of sintering aid is 12wt% to 20wt% of the mass of silicon carbide, the amount of pore-forming agent is 0.1wt% to 10wt% of the mass of silicon carbide, the amount of binder is 7wt% to 16wt% of the mass of silicon carbide, and the amount of dispersant is 0.3wt% to 0.5wt% of the mass of silicon carbide.

[0015] Furthermore, the sintering aids are silicon micro powder and alumina powder, with the amount of silicon micro powder being 2wt% to 5wt% of the mass of silicon carbide and the amount of alumina powder being 10wt% to 15wt% of the mass of silicon carbide; the pore-forming agent is graphite; the binder is sodium alginate and silica sol, with the amount of silica sol being 1wt% to 10wt% of the mass of silicon carbide; and the dispersant is polyethylene glycol.

[0016] Furthermore, sintering is carried out by raising the temperature at a rate of 0.1℃ / min to 5℃ / min to 500℃ to 600℃, holding for 1h to 3h, and then raising the temperature at a rate of 0.1℃ / min to 5℃ / min to 1300℃ to 1400℃, holding for 1h to 3h.

[0017] The second objective of this invention is to provide a silicon carbide ceramic filter prepared using the above-described preparation method.

[0018] Furthermore, the silicon carbide ceramic filter has a metal molten metal inclusion removal rate of ≥60%, a bending strength of ≥3MPa, and a linear expansion rate of <5%.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention provides a 3D printing method for a biomimetic silicon carbide ceramic filter. Using water-based SiC slurry as a solvent system, and based on a glass sponge geometric network, it innovatively designs three biomimetic filter units with different structures. By combining computational fluid dynamics simulation with 3D printing technology, and adjusting the material composition ratio, post-processing parameters, and different process parameters, the SiC ceramic 3D printing process meets the mechanical performance requirements of the filter material. Using biomimetic filter units with different structures, and combining computational fluid dynamics simulation with 3D printing technology, a biomimetic flow channel optimization design system with flow rate and pressure drop as core evaluation indicators was established. Through metal melt casting tests on the SiC filter, its excellent mechanical properties and service life were demonstrated. Finally, the relationship between material, process, structure, and performance was established, achieving integrated manufacturing of porous ceramic structures. The prepared filter has high flexural strength, high removal rate of metal molten inclusions, and combines complex structure forming capability, high-efficiency filtration performance, and stable mechanical properties. It can be widely used in molten metal purification filtration and catalyst carrier fields, providing a new approach for the efficient and low-cost preparation of complex silicon carbide ceramic parts.

[0020] This invention is based on the design of porous ceramic material formulations, the design of multi-level pore structure control of porous ceramics, and the establishment of a SiC ceramic direct-write 3D printing process system. It establishes the relationship between materials, processes, structures, and properties, and realizes the integrated manufacturing of porous ceramic structures and functions. It obtains an overall filter structure with a multi-level interconnected biomimetic pore system, which includes nanoscale material pores, micrometer-level material pores, and millimeter-level and above structural pores. Attached Figure Description

[0021] Figure 1 This is a flowchart illustrating the fluid simulation for the filter configuration design of this invention.

[0022] Figure 2 This is a diagram of the single-cell structure of the silicon carbide ceramic filter in Embodiment 1 of the present invention.

[0023] Figure 3 This is a 3D printed green image of the silicon carbide ceramic filter of Embodiment 1 of the present invention.

[0024] Figure 4 The impurity removal rate of the silicon carbide ceramic filter in Embodiment 1 of the present invention.

[0025] Figure 5 The figure shows the metal casting test results of the silicon carbide ceramic filter in Embodiment 1 of the present invention. Detailed Implementation

[0026] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0027] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0028] This invention provides a 3D printing method for a biomimetic silicon carbide ceramic filter, comprising the following steps: S1. Constructing a silicon carbide ceramic filter structure: Using the octagonal mesh of glass sponge as a biomimetic prototype, construct a three-dimensional unit cell structure with a deflection angle of 0°, ±45° or 60°. The unit cells are periodically repeated in three-dimensional space along the X, Y and Z axes, forming an overall filter structure with a multi-level interconnected biomimetic pore system.

[0029] It should be noted that this invention is based on a biomimetic design of a glass sponge geometric network, featuring a unique octagonal mesh structure. This invention uses this unique microstructure as the basis for biomimetic design of the filter configuration. Intersecting diagonal rods form a mesh-like mixed porous lattice shape on the sides of a square unit cell along the face-centered direction. Each unit cell is designed as a cubic structure, and these unit cells are repeatedly arrayed along the X, Y, and Z axes to ultimately form a cubic lattice structure. The unit cells have three configurations: 0° deflection angle, 45° deflection angle, and 60° deflection angle. The 0° deflection angle unit cell structure is a face-centered cubic structure, with a more complex stress transmission path compared to a simple cubic structure, exhibiting a highly curved ordered arrangement; the 45° deflection angle unit cell structure forms a mesh-like mixed porous lattice shape on the sides of a square unit cell along the face-centered direction through intersecting diagonal rods. In a single-cell structure, the two middle layers of 45° and 135° diagonal lines divide the single-cell structure into four parts, of which the two diagonal cube structures are exactly the same; the single-cell structure with a 60° deflection angle is the same as the single-cell structure with a 45° deflection angle.

[0030] In this invention, the three-dimensional unit cell structure is a cube with a size of 3mm to 5mm.

[0031] S2. Prepare water-based SiC slurry with a solid content ≥70wt%.

[0032] In this invention, the water-based SiC slurry is composed of silicon carbide, sintering aid, pore-forming agent, binder, rheology modifier, dispersant, and water. The sintering aid is used in an amount of 12wt%–20wt% of silicon carbide, and consists of silicon micropowder and alumina powder. The amount of silicon micropowder is 2wt%–5wt% of silicon carbide, and the amount of alumina powder is 10wt%–15wt% of silicon carbide. The particle size of the sintering aid must be significantly smaller than that of silicon carbide, with both silicon micropowder and alumina powder having a particle size of 0.1μm–1μm. The pore-forming agent is used in an amount of 0.1wt%–10wt% of silicon carbide, and is graphite with a particle size of 10μm–100μm. The binder is used in an amount of 7wt%–16wt% of silicon carbide, and consists of sodium alginate and silica sol, with the silica sol having an amount of 1wt%–10wt% of silicon carbide. In this invention, sodium alginate, in addition to its binding function, also improves the rheological properties of the water-based SiC slurry. The amount of dispersant used is 0.3wt% to 0.5wt% of the silicon carbide mass. The dispersant is polyethylene glycol, with a molecular weight of 100 to 500. In a preferred embodiment, the molecular weight of polyethylene glycol is 300. The silicon carbide is α-SiC powder, and the impurities are mainly Fe2O3, free carbon, and SiO2. The median particle size D of the silicon carbide is... 50 The size ranges from 1μm to 10μm.

[0033] In this invention, the specific method for preparing a water-based SiC slurry with a solid content ≥70wt% includes the following steps: mixing deionized water, dispersant and binder to form a liquid phase; mixing silicon carbide, sintering aid and pore-forming agent to form a solid phase; adding the solid phase to the liquid phase; stirring at 800r / min for 2min; and homogenizing at 1500r / min for 4min to form a colloid, thereby obtaining a water-based SiC slurry. Through shear thinning behavior, the colloid can be easily extruded under pressure and quickly solidified after printing for 3D shape control.

[0034] S3. 3D printing of ceramic structure blanks was carried out using a pneumatic-screw composite extrusion direct writing process.

[0035] In this invention, the printing speed is 600mm / min to 1000mm / min, the printing air pressure is 0.1MPa to 0.6MPa, the printing layer height is 0.4mm to 0.6mm, the nozzle diameter is 0.8mm to 1.2mm, and the screw speed is 30rpm to 100rpm.

[0036] It should be noted that this invention, by employing direct-write 3D printing technology, can achieve biomimetic structural design and precise control of multi-level pores without the need for molds, thus solving the problems of random structures and complex processes in traditional methods.

[0037] S4. The initial ceramic structure blank is dried, degreased, and sintered to obtain a silicon carbide ceramic filter.

[0038] In this invention, sintering is carried out by heating at a rate of 0.1℃ / min to 5℃ / min to 500℃ to 600℃, holding at that temperature for 1h to 3h, and then heating at a rate of 0.1℃ / min to 5℃ / min to 1300℃ to 1400℃, holding at that temperature for 1h to 3h.

[0039] In this invention, the ceramic structural blank is first placed in a constant temperature and humidity environment with a relative humidity of 80% to 95% and a temperature of 40°C to 50°C for 6 hours to dry. Then, the constant temperature and humidity drying process described above is continued for 12 to 15 hours. The overall structural blank after constant temperature and humidity drying is placed in an oven with the temperature set at 100°C for 10 to 20 minutes to dry.

[0040] In this invention, based on the design of porous ceramic material formulations, the design of multi-level pore structure control of porous ceramics, and the establishment of a SiC ceramic direct-write 3D printing process system, the relationship between materials, processes, structures, and properties is established to realize the integrated manufacturing of porous ceramic structures and functions, resulting in an overall filter structure with a multi-level interconnected biomimetic pore system. The multi-level interconnected biomimetic pore system includes nanoscale material pores, micrometer-level material pores, and millimeter-level and above structural pores.

[0041] Among them, the multi-level pore control method mainly includes the control of nano-pore characteristics of raw materials, the control of micro-pore characteristics of direct writing forming process, and the control of macro-pores in structural design.

[0042] The aforementioned nano-pore characteristic control refers to the control of pore size by changing the mass fraction of ceramic raw materials and pore-forming agents in the material formulation. Micro-pore characteristic control in direct-write forming refers to adjusting the multi-level pores, such as porosity and pore size distribution, in the 3D printing process through 3D printing parameters, pore-forming processes, and post-processing. Process pore control refers to controlling foaming and pore-forming process parameters such as stirring speed and time, controlling 3D printing parameters such as printing spacing, and adjusting post-processing parameters. Macro-pore control in structural design refers to directly manufacturing macro-pores in 3D printing through filter design. Macro-pore control is achieved through filter structure design and 3D printing at different scales. By precisely controlling the size, shape, distribution, and connectivity of pores, the mechanical properties, porosity, and pore size and shape of the material can be effectively adjusted. The research on direct-write forming process refers to establishing mechanisms for optimizing forming parameters, researching drying processes, and controlling post-sintering process parameters. The forming process parameters refer to the design and optimization of parameters such as printing speed, printing spacing, nozzle diameter, printing layer height, screw speed, and feed air pressure. The drying process refers to the process by which material particles move closer together and expel free water from their bodies. The post-sintering process parameters refer to the process of sintering ceramic samples prepared with different material contents at different temperatures to compare their mechanical properties such as flexural strength.

[0043] It should be noted that, as Figure 1 As shown, the filter configuration design of this invention requires fluid simulation. By comparing the flow rate of molten iron before and after passing through the filter and changing the unit cell size, the flow stabilization effect, impurity removal effect and pressure drop of different filters are compared, thereby optimizing the filter structure design.

[0044] In summary, this invention innovatively designs three biomimetic filter units with different structures using water-based SiC slurry as the solvent system. By combining computational fluid dynamics simulation with 3D printing technology, and by adjusting the material composition ratio, post-processing parameters, and different process parameters, the SiC ceramic 3D printing process meets the mechanical performance requirements of the filter material. Using biomimetic filter units with different structures, and combining computational fluid dynamics simulation with 3D printing technology, a biomimetic flow channel optimization design system with flow rate and pressure drop as the core evaluation indicators was established. Through metal melt casting tests on the SiC filter, its excellent mechanical properties and service life were demonstrated. Finally, the relationship between material, process, structure, and performance was established, achieving integrated manufacturing of porous ceramic structures. The prepared filter has high flexural strength, high removal rate of metal molten inclusions, and combines complex structure forming capability, high-efficiency filtration performance, and stable mechanical properties. It can be widely used in molten metal purification filtration and catalyst carrier fields, providing a new approach for the efficient and low-cost preparation of complex silicon carbide ceramic parts.

[0045] The following specific examples will provide further explanation.

[0046] Example 1 A 3D printing method for a silicon carbide ceramic filter with a biomimetic structural design, such as Figure 1 As shown, it includes the following steps: S1. Constructing a silicon carbide ceramic filter structure: using an octagonal mesh of glass sponge as a biomimetic prototype, such as... Figure 2 As shown, a 45° three-dimensional unit cell structure is constructed, with each unit cell being a cube measuring 4mm × 4mm × 4mm. This unit cell is formed by interwoven ribs in spatial directions of 0°, 90°, and ±45°, creating a biomimetic octagonal mesh structure. By periodically repeating this unit cell along the X, Y, and Z axes, a three-dimensional solid model of a filter with an overall size of 16mm × 16mm × 12mm can be constructed. This design creates a "twisted-connected" spatial path for the fluid channels, which helps improve the collision capture efficiency of inclusions.

[0047] S2. Preparation of a water-based SiC slurry with a solid content of 77wt%: The water-based SiC slurry is composed of α-SiC powder, Al2O3 powder, silica powder, sodium alginate, silica sol, graphite, polyethylene glycol, and deionized water. The silicon carbide is α-SiC powder, and the amount of silica powder is 3wt% of the silicon carbide mass. The silica powder has a D... 50 =20μm; the amount of alumina powder used is 12wt% of the mass of silicon carbide, and the D of the alumina powder is... 50=5μm. The amount of graphite used is 5wt% of the mass of silicon carbide, and the particle size is 50μm. The amount of sodium alginate used is 8wt% of the mass of silicon carbide, and the amount of silica sol used is 8wt% of the mass of silicon carbide. The amount of polyethylene glycol used is 0.5wt% of the mass of silicon carbide.

[0048] The binder and silica sol were dissolved in deionized water, and polyethylene glycol was added. After mixing thoroughly, a liquid phase was obtained. Silicon carbide powder, alumina, and silica micropowder were mixed to obtain a solid phase. The solid phase was added to the liquid phase and stirred at 800 rpm for 2 minutes. Then, the mixture was placed in a homogenizer and stirred at 1500 rpm for 4 minutes to obtain a silicon carbide slurry with a solid content of 77%.

[0049] S3. At room temperature, 3D printing of a ceramic preform is performed on a hydrophobic polyethylene film using a pneumatic-screw composite extrusion direct writing process, as shown in the figure. Figure 3 As shown in the figure. The printing process parameters are as follows: nozzle diameter 1mm, printing speed 800mm / min, printing air pressure 0.3MPa, printing gap 100μm, printing layer height 0.5mm, and screw speed 50rpm.

[0050] S4. The ceramic preform and the hydrophobic polyethylene film are placed together in a constant temperature and humidity environment with a relative humidity of 85% and dried at 40℃ for 6 hours to separate the overall structure of the ceramic preform from the hydrophobic polyethylene film. The ceramic preform is then subjected to the same constant temperature and humidity drying process for 12 hours. After drying, the ceramic preform is placed in an oven at 100℃ and dried for 15 minutes to obtain a silicon carbide ceramic precursor. The silicon carbide ceramic precursor is then placed in a sintering furnace and heated to 600℃ at a rate of 1℃ / min, held for 2 hours, and then heated to 1400℃ at a rate of 1.5℃ / min and held for 3 hours. After cooling in the furnace, a silicon carbide ceramic filter is obtained.

[0051] Example 2 A 3D printing method for a silicon carbide ceramic filter with a biomimetic structural design, such as Figure 1 As shown, it includes the following steps: S1. Construction of a silicon carbide ceramic filter structure: Using the octagonal mesh of glass sponge as a biomimetic prototype, a three-dimensional unit cell structure with a 60° angle is constructed. Each unit cell is a cube with dimensions of 4mm × 4mm × 4mm. This unit cell is formed by ribs interwoven in spatial directions of 0°, 90°, and ±60°, forming a biomimetic octagonal mesh structure. By periodically repeating this unit cell along the X, Y, and Z axes, a three-dimensional solid model of a filter with overall dimensions of 16mm × 16mm × 12mm can be constructed. This design creates a "twisted-connected" spatial path for the fluid channel, which helps to improve the collision capture efficiency of impurities.

[0052] S2. Preparation of a water-based SiC slurry with a solid content of 77wt%: The water-based SiC slurry is composed of α-SiC powder, Al2O3 powder, silica powder, sodium alginate, silica sol, graphite, polyethylene glycol, and deionized water. The silicon carbide is α-SiC powder, and the amount of silica powder is 3wt% of the silicon carbide mass. The silica powder has a D... 50 =20μm; the amount of alumina powder used is 12wt% of the mass of silicon carbide, and the D of the alumina powder is... 50 =5μm. The amount of graphite used is 5wt% of the mass of silicon carbide, with a particle size of 50μm. The amount of sodium alginate used is 8wt% of the mass of silicon carbide, and the amount of silica sol used is 8wt% of the mass of silicon carbide. The amount of polyethylene glycol used is 0.5wt% of the mass of silicon carbide.

[0053] The binder and silica sol were dissolved in deionized water, and polyethylene glycol was added. After mixing thoroughly, a liquid phase was obtained. Silicon carbide powder, alumina, and silica micropowder were mixed to obtain a solid phase. The solid phase was added to the liquid phase and stirred at 800 rpm for 2 minutes. Then, the mixture was placed in a homogenizer and stirred at 1500 rpm for 4 minutes to obtain a silicon carbide slurry with a solid content of 77%.

[0054] S3. A ceramic preform is obtained by 3D printing on a substrate using a pneumatic-screw composite extrusion direct writing process. The printing process parameters are as follows: nozzle diameter 1 mm, printing speed 800 mm / min, printing air pressure 0.3 MPa, printing gap 100 μm, printing layer height 0.5 mm, and screw speed 50 rpm.

[0055] S4. The ceramic preform and the hydrophobic polyethylene film are placed together in a constant temperature and humidity environment with a relative humidity of 85% and dried at 40℃ for 6 hours to separate the overall structure of the ceramic preform from the hydrophobic polyethylene film. The ceramic preform is then subjected to the same constant temperature and humidity drying process for 12 hours. After drying, the ceramic preform is placed in an oven at 100℃ and dried for 15 minutes to obtain a silicon carbide ceramic precursor. The silicon carbide ceramic precursor is then placed in a sintering furnace and heated to 600℃ at a rate of 1℃ / min, held for 2 hours, and then heated to 1300℃ at a rate of 1.5℃ / min and held for 3 hours. After cooling in the furnace, a silicon carbide ceramic filter is obtained.

[0056] Example 3 A 3D printing method for a silicon carbide ceramic filter with a biomimetic structural design, such as Figure 1 As shown, it includes the following steps: S1. Constructing a silicon carbide ceramic filter structure: A cubic unit cell with an orthogonal structure, measuring 4mm × 4mm × 4mm, is constructed. Each unit cell is composed of interwoven ribs arranged at 0°, 90°, and 0° in space, meaning the internal structures of the unit cell are perpendicular to each other, forming a biomimetic octagonal mesh structure. By periodically repeating this unit cell along the X, Y, and Z axes, a three-dimensional solid model of a filter with an overall size of 16mm × 16mm × 12mm can be constructed. This design creates a "twisted-connected" spatial path for the fluid channels, which helps improve the collision capture efficiency of inclusions.

[0057] S2. Preparation of a water-based SiC slurry with a solid content of 77wt%: The water-based SiC slurry is composed of α-SiC powder, Al2O3 powder, silica powder, sodium alginate, silica sol, graphite, polyethylene glycol, and deionized water. The silicon carbide is α-SiC powder, and the amount of silica powder is 3wt% of the silicon carbide mass. The silica powder has a D... 50 =20μm; the amount of alumina powder used is 12wt% of the mass of silicon carbide, and the D of the alumina powder is... 50 =5μm. The amount of graphite used is 5wt% of the mass of silicon carbide, and the particle size is 50μm. The amount of sodium alginate used is 8wt% of the mass of silicon carbide, and the amount of silica sol used is 8wt% of the mass of silicon carbide. The amount of polyethylene glycol used is 0.5wt% of the mass of silicon carbide.

[0058] S3. At room temperature, a ceramic preform was obtained by 3D printing on a substrate using a pneumatic-screw composite extrusion direct writing process. The printing process parameters were as follows: nozzle diameter 1 mm, printing speed 800 mm / min, printing air pressure 0.3 MPa, printing gap 100 μm, printing layer height 0.5 mm, and screw speed 50 rpm.

[0059] S4. The ceramic preform and the hydrophobic polyethylene film are placed together in a constant temperature and humidity environment with a relative humidity of 85% and dried at 40℃ for 6 hours to separate the overall structure of the ceramic preform from the hydrophobic polyethylene film. The ceramic preform is then subjected to the same constant temperature and humidity drying process for 12 hours. After drying, the ceramic preform is placed in an oven at 100℃ and dried for 15 minutes to obtain a silicon carbide ceramic precursor. The silicon carbide ceramic precursor is then placed in a sintering furnace and heated to 600℃ at a rate of 1℃ / min, held for 2 hours, and then heated to 1300℃ at a rate of 1.5℃ / min and held for 3 hours. After cooling in the furnace, a silicon carbide ceramic filter is obtained.

[0060] Example 4 A 3D printing method for a silicon carbide ceramic filter with a biomimetic structural design differs from Example 1 in that each unit cell is a cube with dimensions of 3mm × 3mm × 3mm.

[0061] Example 5 A 3D printing method for a silicon carbide ceramic filter with a biomimetic structural design differs from Example 1 in that each unit cell is a cube with dimensions of 5mm × 5mm × 5mm.

[0062] Example 6 A 3D printing method for a biomimetic silicon carbide ceramic filter differs from Example 1 in that: S1, constructing the silicon carbide ceramic filter structure: using an octagonal mesh of glass sponge as a biomimetic prototype, the filter is divided into several regions along the flow direction of the molten metal. Each region uses unit cells of different sizes, forming a gradient change in "filtration accuracy from high to low, and flow resistance from large to small," specifically: Different types of unit cells are distributed at different heights in the filter. The smallest unit cell size (3×3×3mm) is used in areas with high filtration precision, mainly bearing the filtration load. Medium-sized unit cells (4×4×4mm) are used in the transition zone, acting as a bridge between the upper and lower layers while reducing flow resistance. The outlet zone (5×5×5mm) further reduces pressure drop, allowing the molten metal to flow out smoothly. Each of the three layers occupies one-third of the total height.

[0063] When the integrated model is imported into the slicing software, the nozzles will automatically fill the path in different areas according to the instructions during printing, thus printing the required gradient structure in one go.

[0064] Comparative Example 1 A method for preparing a silicon carbide ceramic filter includes the following steps: Traditional foam structure (pore density 10ppi) An organic foam impregnation process was adopted, using polyurethane foam with a pore density of 10 ppi as a three-dimensional template. After hydrophilization treatment, it was impregnated into a slurry. The slurry consisted of ceramic powder, binder, and solvent. The ceramic powder was α-SiC powder, accounting for 60 wt% of the slurry. The binder consisted of clay and silica sol, with clay accounting for 10 wt% of the slurry and silica sol (based on solid content) accounting for 15 wt%. Approximately 5 wt% of α-Al2O3 micro powder was added as a sintering aid. After ball milling, the slurry formed a uniform suspension with a viscosity of approximately 3000–5000 mPa·s.

[0065] The slurry is repeatedly squeezed to fully penetrate the foam pores; then, excess slurry in the pores is forcibly removed by roller pressing to ensure the formation of a uniform thin coating and through-holes; the green body is then dried and cured at 110℃ for 12 hours, and then the green body is slowly heated to 600℃ at ≤2℃ / min and held for 2 hours to completely decompose the organic template, and then heated to 1350℃ at 5℃ / min and held in air for 3 hours to form a strong sintering neck between the ceramic particles, and finally cooled in the furnace to obtain the foam ceramic filter.

[0066] Comparative Example 2 A method for preparing a silicon carbide ceramic filter includes the following steps: An organic foam impregnation process was adopted, using polyurethane foam with a pore density of 20 ppi as a three-dimensional template. After hydrophilization treatment, it was impregnated into a slurry. The slurry consisted of ceramic powder, binder and solvent. The ceramic powder was α-SiC powder, accounting for 60 wt% of the slurry. The binder was clay and silica sol, with clay accounting for 10 wt% of the slurry and silica sol (based on solid content) accounting for 15 wt%. Approximately 5 wt% of α-Al2O3 micro powder was added as a sintering aid. After ball milling, the slurry formed a uniform suspension with a viscosity of approximately 3000–5000 mPa·s.

[0067] The slurry is repeatedly squeezed to fully penetrate the foam pores; then, excess slurry in the pores is forcibly removed by roller pressing to ensure the formation of a uniform thin coating and through-holes; the green body is then dried and cured at 110℃ for 12 hours, and then the green body is slowly heated to 600℃ at ≤2℃ / min and held for 2 hours to completely decompose the organic template, and then heated to 1350℃ at 5℃ / min and held in air for 3 hours to form a strong sintering neck between the ceramic particles, and finally cooled in the furnace to obtain the foam ceramic filter.

[0068] The flexural strength of 3D-printed ceramic filters with different unit cell structures and ceramic foam filters with different pore densities was measured at room temperature, and the results are shown in Table 1.

[0069] Table 1. Flexural strength of ceramic filters prepared by different methods As shown in Table 1, the flexural strength of the 3D-printed ceramic filter is approximately three times that of the foam ceramic filter. Clearly, the flexural strength of the 3D-printed ceramic filter is significantly higher than that of the foam ceramic filter, fully demonstrating the superiority of the 3D-printed filter model.

[0070] Figure 4 This refers to the impurity removal rate of the silicon carbide ceramic filter in Example 1 of the present invention. For example... Figure 4 As shown, structure 1 is Comparative Example 1, structure 2 is Example 3, structure 3 is Example 1, and structure 4 is Example 2. The removal efficiency varies among filters with different structures. Under the chemical and physical adsorption of the filter pores, the 45° porous filter shows a more significant impurity removal rate, which may be related to the flow rate of the filter model. Increasing the flow rate of the filter channels to a certain extent reduces the removal rate of inclusions, and the probability of removing 50μm impurities increases. It is evident that the size of the impurity particles affects the filtration efficiency. Therefore, the 45° deflection angle structure used in this invention, while ensuring flowability, exhibits better flow field stability than traditional foam and other deflection structures, thus facilitating impurity capture.

[0071] Figure 5 This is a diagram showing the metal casting test results of the silicon carbide ceramic filter in Embodiment 1 of the present invention. Figure 5 As shown, the prepared ceramic filter underwent an actual ferroalloy casting experiment. Molten iron entered all parts of the filter without a large-scale freezing effect. During the filter removal process, the melt also flowed out from the filter structure. After casting, the ceramic filter remained undamaged and completely intact after testing. Therefore, the cast silicon carbide ceramic filter indeed exhibits sufficient thermal shock resistance, corrosion resistance, and strength, and can withstand the effects of molten iron immersion, physical residues, and residual stress. This demonstrates that 3D-printed ceramic filters can replace traditional processes in metal filtration and other applications.

[0072] Comparative Example 3 A 3D printing method for a biomimetic silicon carbide ceramic filter differs from Example 1 in that graphite is not added to the water-based SiC slurry. The silicon carbide ceramic precursor is placed in a sintering furnace and heated to 600°C at a rate of 1°C / min, then held at that temperature for 2 hours, and then heated to 1300°C at a rate of 1.5°C / min for 3 hours.

[0073] Comparative Example 4 A 3D printing method for a biomimetic silicon carbide ceramic filter differs from Example 1 in that graphite is not added to the water-based SiC slurry.

[0074] The pore characteristics of the ceramic filters prepared in Example 1, Comparative Example 3, and Comparative Example 4 were measured, and are shown in Table 2.

[0075] Table 2. Pore characteristics of the ceramic filters prepared in Example 1, Comparative Examples 3 and 4 As shown in Table 2, the graphite content has a regulatory effect on the pore size distribution of porous ceramics, especially nanopores. It can be seen that the increase of graphite content in the material leads to increased porosity, more internal oxidized sintered parts, and larger overall nanopore size.

[0076] Different structural models were used for filtration performance testing, as shown in Table 3. Table 3. Simulation results of pressure and flow rate for filters with different unit cell sizes. Table 3 illustrates the contradictory relationship between unit cell size, pressure drop, flow rate, and filtration efficiency: smaller pore size leads to better filtration but also greater flow resistance, and vice versa. This demonstrates that changes in pore size significantly affect the flow behavior of molten metal, inclusion capture efficiency, and pressure loss. The porosity and pore size of the filter determine its resistance to molten metal. Lower porosity and smaller pore size result in greater flow resistance. Smaller pore sizes can effectively intercept more inclusions and improve filtration efficiency, but they also increase flow resistance, leading to reduced flow rate, increased pressure loss, and potentially even blockage of the molten metal. Conversely, larger pore sizes reduce flow resistance and improve the fluidity of the molten metal, but significantly decrease inclusion capture efficiency.

[0077] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. A 3D printing method for a silicon carbide ceramic filter with a biomimetic structural design, characterized in that, Includes the following steps: Constructing a silicon carbide ceramic filter structure: Using the octagonal mesh of glass sponge as a biomimetic prototype, a three-dimensional unit cell structure with a deflection angle of 0°, ±45° or 60° is constructed. The unit cells are periodically repeated in three-dimensional space along the X-axis, Y-axis and Z-axis directions, forming an overall filter structure with a multi-level interconnected biomimetic pore system. Prepare a water-based SiC slurry with a solid content ≥70wt%; A ceramic preform was obtained by 3D printing using a pneumatic-screw composite extrusion direct writing process. The silicon carbide ceramic filter is obtained by drying, degreasing and sintering the initial ceramic structure blank.

2. The 3D printing method for the biomimetic structure design of the silicon carbide ceramic filter according to claim 1, characterized in that, The three-dimensional unit cell is a cube with a size of 3mm to 5mm.

3. The 3D printing method for the biomimetic structure design of the silicon carbide ceramic filter according to claim 1, characterized in that, Multilevel interconnected biomimetic pore systems include nanoscale material pores, micrometer-scale material pores, and millimeter-scale and above structural pores.

4. The 3D printing method for the biomimetic structure design of the silicon carbide ceramic filter according to claim 1, characterized in that, In the pneumatic-screw composite extrusion direct writing 3D printing process, the printing speed is 600-1000 mm / min, the printing air pressure is 0.1 MPa-0.6 MPa, and the printing layer height is 0.4 mm-0.6 mm.

5. The 3D printing method for the biomimetic structure design of the silicon carbide ceramic filter according to claim 1, characterized in that, In the pneumatic-screw composite extrusion direct writing 3D printing process, the nozzle diameter is 0.8mm~1.2mm and the screw speed is 30rpm~100rpm.

6. The 3D printing method for the biomimetic structure design of the silicon carbide ceramic filter according to claim 1, characterized in that, The water-based SiC slurry is composed of silicon carbide, sintering aid, pore-forming agent, binder, dispersant and water. The amount of sintering aid is 12wt% to 20wt% of the mass of silicon carbide, the amount of pore-forming agent is 0.1wt% to 10wt% of the mass of silicon carbide, the amount of binder is 7wt% to 16wt% of the mass of silicon carbide, and the amount of dispersant is 0.3wt% to 0.5wt% of the mass of silicon carbide.

7. The 3D printing method for the biomimetic structure design of the silicon carbide ceramic filter according to claim 6, characterized in that, The sintering aids are silica powder and alumina powder, with the amount of silica powder being 2wt% to 5wt% of the mass of silicon carbide and the amount of alumina powder being 10wt% to 15wt% of the mass of silicon carbide; the pore-forming agent is graphite; the binders are sodium alginate and silica sol, with the amount of silica sol being 1wt% to 10wt% of the mass of silicon carbide; and the dispersant is polyethylene glycol.

8. The 3D printing method for the biomimetic structure design of the silicon carbide ceramic filter according to claim 1, characterized in that, Sintering involves raising the temperature at a rate of 0.1℃ / min to 5℃ / min to 500℃ to 600℃, holding it at that temperature for 1h to 3h, and then raising the temperature at a rate of 0.1℃ / min to 5℃ / min to 1300℃ to 1400℃, holding it at that temperature for 1h to 3h.

9. A silicon carbide ceramic filter with a biomimetic structural design, characterized in that, It is prepared using the preparation method described in any one of claims 1 to 8.

10. The silicon carbide ceramic filter with a biomimetic structural design according to claim 9, characterized in that, The silicon carbide ceramic filter has a metal molten metal inclusion removal rate of ≥60%, a bending strength of ≥3MPa, and a linear expansion rate of <5%.

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