A porous ceramic filter with controllable pore gradient and preparation method thereof

Abstract

The present invention discloses a porous ceramic filter with controllable pore gradient and a preparation method thereof. The porous ceramic filter adopts a variable gradient truss filter structure with a pore gradient obtained by computer-aided design, and adopts a prepared photosensitive resin-ceramic powder mixed slurry and 3D printing. The node distribution density of each level of the porous ceramic filter gradually increases according to the hierarchical order from top to bottom, and the three-dimensional hole volume corresponding to each level gradually decreases according to the hierarchical order from top to bottom, thereby achieving a graded filtering and non-clogging filtering effect. In addition, the variable gradient truss filter structure is composed of a double inverted pyramid unit pillar structure, and the double inverted pyramid unit pillar structure of the next level plays a reinforcing and supporting role for the double inverted pyramid unit pillar structure of the previous level, thereby improving the anti-scouring performance of the porous ceramic filter.

Description

Technical Field

[0001] The invention relates to the technical field of porous ceramics, in particular to a porous ceramic filter with controllable pore gradient and a preparation method thereof. Background Art

[0002] In the field of metal casting, impurities in molten metal have an important influence on the mechanical properties and mechanical properties of metal castings. In order to obtain metal castings with high performance requirements, it is necessary to find ways to reduce the content of impurities in molten metal. Therefore, as people's requirements for the performance of casting products are increasing, how to remove impurities in molten metal has attracted the attention and research of more and more scholars.

[0003] Among the many methods of removing impurities, porous ceramic filters have the characteristics of large filtration area, thermal shock resistance, chemical stability, metal scouring resistance and high filtration efficiency. Therefore, in the metal melt filtration and purification technology, as a new type of high-efficiency filter, people pay attention to it and it has been widely used in the field of metal melt purification and filtration. Porous ceramics can also be subdivided into granular ceramic sintered bodies, foam ceramics and honeycomb ceramics according to the pore structure, and the latter two are mostly used.

[0004] Although the foam ceramic filter has a good filtering effect, it has low high temperature strength and poor impact resistance. The long-term impact of molten metal at high temperature may cause the structure to break and enter the molten metal, causing secondary pollution. In addition, its uneven pores cannot fully exert the filtering effect of each filter hole. Moreover, there are unconnected holes in the foam ceramic, which will cause molten metal to remain. These defects limit its wide application in the field of metal casting.

[0005] Compared with foam ceramics, honeycomb ceramics have high resistance to thermal shock and high casting temperature. Its straight hole design ensures the balance between flow and strength, and can effectively filter the molten metal. However, the straight hole design limits the size of filtered impurities. When the micropore diameter is designed to be too large, only impurity particles with larger particle sizes can be filtered, and impurity particles with smaller particle sizes will escape from the micropores; when the diameter is too small, larger impurity particles will quickly block the pores, greatly reducing the filtering effect. In addition, its relatively simple hole design has limited ability to change the movement trajectory of impurity particles, which leads to a low removal rate of inclusions. Summary of the invention

[0006] The first purpose of the present invention is to overcome the shortcomings and deficiencies of the prior art and to provide a porous ceramic filter with controllable pore gradient, which can achieve graded filtration, is not easy to clog and is resistant to scouring.

[0007] The second object of the present invention is to provide a method for preparing a porous ceramic filter with controllable pore gradient, which method can quickly and accurately produce a porous ceramic filter with controllable pore gradient.

[0008] The first object of the present invention is achieved by the following technical scheme: a porous ceramic filter with controllable pore gradient, comprising an outer wall of the porous ceramic filter and a porous ceramic variable gradient truss filter structure located inside the outer wall of the porous ceramic filter, wherein the variable gradient truss filter structure is divided into a plurality of levels, and the truss filter structure of each level is composed of a plurality of double inverted pyramid unit pillar structures, wherein the volume of the double inverted pyramid unit pillar structure of the next level is smaller than the volume of the double inverted pyramid unit pillar structure of the previous level, and a plurality of double inverted pyramid unit pillar structures of the next level are connected to and support the same double inverted pyramid unit pillar structure of the previous level;

[0009] The endpoints of each double inverted pyramid unit support structure serve as nodes of the truss filtering structure. The node distribution density of each level gradually increases in a top-down order, and the three-dimensional hole volume corresponding to each level gradually decreases in a top-down order.

[0010] Preferably, the double inverted pyramid unit pillar structure is composed of four truss rods, which are arranged according to the spatial diagonal of the cube and distributed in a circular array, and the inclination angle of each truss rod is not greater than 45°; the four truss rods intersect each other, and there is a unique node at one-third of the length of each truss rod.

[0011] Preferably, each double inverted pyramid unit pillar structure is connected to adjacent double inverted pyramid unit pillar structures in the same level through nodes; except for the truss filtering structure at the lowest level, in the truss filtering structure at any level, each lower end node of each double inverted pyramid unit pillar structure is connected to four upper end nodes of the double inverted pyramid unit pillar structure belonging to the next level.

[0012] Preferably, the porous ceramic filter is further provided with a quadrilateral truss structure below the lowest truss filter structure, the quadrilateral truss structure having a plurality of quadrilateral truss structure units, and a plurality of lower end nodes of the lowest level truss filter structure are connected via the quadrilateral truss structure units.

[0013] Furthermore, a plurality of quadrilateral truss structure units are arranged in a two-dimensional array, and the double inverted pyramid unit support structures at each level are arranged in a two-dimensional array.

[0014] Furthermore, the porous ceramic filter is made of a photosensitive resin-ceramic powder mixed slurry, and the outer wall of the filter, the porous ceramic variable gradient truss filter structure and the quadrilateral truss structure are integrally formed by 3D printing.

[0015] Preferably, the volume of the truss filtering structure of each level decreases gradually from top to bottom in a geometric multiple relationship, and the node density of each level increases gradually from top to bottom in the same geometric multiple relationship.

[0016] Furthermore, the total number of levels of the variable gradient truss filtering structure is at least three; the volume of the double inverted pyramid unit pillar structure of the next level is reduced to one eighth of the volume of the double inverted pyramid unit pillar structure of the previous level through three-dimensional equiaxing, and the node density of the next level is eight times the node density of the previous level.

[0017] The second object of the present invention is achieved by the following technical solution: a method for preparing a porous ceramic filter with controllable pore gradient, the method being suitable for accurate and rapid printing of a variable gradient truss filter structure that can be parameterized and designed, comprising the following steps:

[0018] S1. According to actual use requirements, a three-dimensional model of a double inverted pyramid unit pillar structure is designed using design software, and then a layer of truss filtering structure is constructed according to the arrangement of a two-dimensional array;

[0019] S2, reducing the volume of the truss filter structure of the layer, and then constructing the next layer of truss filter structure according to the arrangement of the two-dimensional array;

[0020] S3, according to the actual filtering requirements, repeat step S2 to increase the number of truss layers, so as to construct a three-dimensional model of the variable gradient truss filtering structure;

[0021] S4. For the lowest truss filtering structure of the variable gradient truss filtering structure, the lower end of the lowest truss filtering structure is connected by a quadrilateral truss to further strengthen the variable gradient truss filtering structure;

[0022] S5. According to actual use requirements, a three-dimensional model of the outer wall of the filter is established, and combined with the three-dimensional model of the variable gradient truss filter structure, so as to establish a three-dimensional model of a porous filter with controllable pore gradient;

[0023] S6. Save the porous filter model in STL format, and slice the porous filter three-dimensional model using slicing software to obtain a porous structure slice file;

[0024] S7. Prepare ceramic slurry suitable for 3D printing according to actual requirements such as usage strength, heat resistance, and micro-porosity;

[0025] S8, importing the porous structure slice file into a 3D printer, and printing layer by layer in combination with the ceramic slurry obtained in step S7 to obtain a porous ceramic filter blank;

[0026] S9, washing, drying, degreasing, and sintering the porous ceramic filter blank printed in step S8 to obtain a final porous ceramic filter with controllable pore gradient.

[0027] Preferably, the design software includes but is not limited to Rhino, solidworks, and UG;

[0028] 3D printing methods include but are not limited to digital light processing ceramic 3D printing method, laser selective sintering ceramic 3D printing, laser selective melting ceramic 3D printing, and stereolithography ceramic 3D printing;

[0029] The ceramic slurry suitable for 3D printing is a composite slurry obtained by fully mixing alumina ceramics and photosensitive resin.

[0030] Compared with the prior art, the present invention has the following advantages and effects:

[0031] (1) The porous ceramic filter of the present invention adopts a variable gradient truss filter structure, and the node distribution density of the layers gradually increases in a top-down order, and the three-dimensional hole volume corresponding to each layer also gradually decreases from top to bottom, thereby realizing the pore change of the porous filter and achieving the purpose of graded filtration. Among them, the aperture formed by the first layer of truss filter structure is relatively large, which can be used to filter larger impurity particles. As the node density in each layer gradually increases from top to bottom, the size of the impurity particles filtered also decreases step by step, so it can filter impurity particles of various pore sizes, making up for the defect of the traditional porous ceramic filter filtering impurity particles with limited diameter.

[0032] (2) The porous ceramic filter of the present invention is not easy to clog. Each level of the truss filter structure composed of a double inverted pyramid unit support structure can filter impurity particles of corresponding volume. Larger impurity particles are adsorbed in the upper level filter structure, and smaller impurity particles are adsorbed in the lower level. Therefore, by reasonably designing the filter aperture distribution range and gradient size according to the impurity particles contained, clogging can be prevented while effectively filtering.

[0033] (3) In the design of the variable gradient truss filter structure of the present invention, the lower-level double inverted pyramid unit support structure provides support for the upper-level double inverted pyramid unit support structure, thereby strengthening the support strength of the filter structure and effectively improving the filter's ability to resist metal liquid impact.

[0034] (4) The present invention prepares a porous ceramic filter with controllable pore gradient through a 3D printing method, which can not only ensure the volume accuracy of the molding structure and guarantee the excellent performance of the filter, but also achieve rapid printing, save costs, and facilitate promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1This is an axonometric view of the porous ceramic filter with controllable pore gradient according to the present invention when viewed from the bottom downward.

[0036] Figure 2 for Figure 1 Bottom view of the porous ceramic filter.

[0037] Figure 3 for Figure 1 Axonometric view of a porous ceramic filter looking from the bottom up.

[0038] Figure 4 for Figure 1 Top view of a porous ceramic filter.

[0039] Figure 5 for Figure 1 Cross-sectional view of a porous ceramic filter.

[0040] Figure 6 This is the axonometric view of the double inverted pyramid unit pillar structure.

[0041] Figure 7 It is a front view of the double inverted pyramid unit pillar structure.

[0042] Figure 8 This is an axonometric view of a quadrilateral truss structure.

[0043] Fig. 9 The present invention is a flow chart of the method for preparing a porous ceramic filter with controllable pore gradient.

[0044] Among them, 1-double inverted pyramid unit pillar structure; 11-a double inverted pyramid unit pillar structure in the first level; 12-a double inverted pyramid unit pillar structure in the second level; 2-the only node in the double inverted pyramid unit pillar structure; 21-the node where four truss rods of a double inverted pyramid unit pillar structure in the first level intersect; 3-node; 4-quadrilateral truss structure; 41-quadrilateral truss structure unit; 5-filter outer wall. DETAILED DESCRIPTION

[0045] The present invention is further described in detail below in conjunction with embodiments and drawings, but the embodiments of the present invention are not limited thereto.

[0046] Example 1

[0047] This embodiment discloses a porous ceramic filter with controllable pore gradient, such as Figure 1 to Figure 4 As shown, the porous ceramic filter includes a porous ceramic filter outer wall 5 and a porous ceramic variable gradient truss filter structure located inside the porous ceramic filter outer wall.

[0048] like Figure 5As shown, the variable gradient truss filtering structure is divided into multiple levels. In this embodiment, the total number of levels of the variable gradient truss filtering structure can be set to at least three. Each level of the truss filtering structure is composed of multiple double inverted pyramid unit pillar structures 1, and each level of the double inverted pyramid unit pillar structures is arranged in a two-dimensional array.

[0049] like Figure 6 and Figure 7 As shown, the double inverted pyramid unit pillar structure is composed of four truss rods, which are arranged according to the spatial diagonal of the cube and distributed in a circular array. The inclination angle of each truss rod is no more than 45°, and no additional support and support removal process is required during 3D printing. The four truss rods intersect each other, and there is a unique node 2 at one-third of the length of each truss rod. For example Figure 1 , Figure 2 and Figure 5 In the first-level double inverted pyramid unit pillar structure 11 , four truss rods intersect at a node 21 .

[0050] like Figure 5 As shown, the volume of the double inverted pyramid unit pillar structure of the next level is smaller than the volume of the double inverted pyramid unit pillar structure of the previous level. The endpoints of each double inverted pyramid unit pillar structure serve as nodes 3 of the truss filtering structure, and each double inverted pyramid unit pillar structure is connected to adjacent double inverted pyramid unit pillar structures in the same level through nodes. The node distribution density of each level gradually increases according to the hierarchical order from top to bottom, and the three-dimensional hole volume corresponding to each level gradually decreases according to the hierarchical order from top to bottom, thereby realizing the pore change of the porous filter to achieve graded filtration.

[0051] In this embodiment, the volume of the truss filtering structure of each level decreases gradually in a geometric multiple relationship from top to bottom, and the node density of each level increases gradually in the same geometric multiple relationship from top to bottom. For example, the volume of the double inverted pyramid unit pillar structure of the next level is reduced to one-eighth of the volume of the double inverted pyramid unit pillar structure of the previous level through three-dimensional isometric reduction. Correspondingly, the node density of the next level is eight times the node density of the previous level.

[0052] Multiple lower-level double inverted pyramid unit pillar structures are connected to and support the same upper-level double inverted pyramid unit pillar structure. Specifically, except for the lowest-level truss filtering structure, in any level of the truss filtering structure, each lower end node of each double inverted pyramid unit pillar structure is connected to four upper end nodes of the double inverted pyramid unit pillar structures belonging to the lower level. For example, the second-level double inverted pyramid unit pillar structure 12 provides support for the first-level double inverted pyramid unit pillar structure 11 through node 3.

[0053] like Figure 3 , Figure 4 and Figure 5 As shown, the porous ceramic filter is further provided with a quadrilateral truss structure 4 below the lowest truss filter structure. The quadrilateral truss structure has a plurality of quadrilateral truss structure units 41. The quadrilateral truss structure units can be seen in Figure 8 The plurality of quadrilateral truss structural units are arranged in a two-dimensional array. The plurality of lower end nodes of the bottom-level truss filtering structure are connected through the quadrilateral truss structural unit to ensure the structural strength of the bottom-level truss filtering structure.

[0054] The above-mentioned porous ceramic filter can be made of a photosensitive resin-ceramic powder mixed slurry such as a composite slurry of alumina ceramic and photosensitive resin. The outer wall of the filter, the porous ceramic variable gradient truss filter structure and the quadrilateral truss structure can be integrally formed by 3D printing.

[0055] Example 2

[0056] This embodiment discloses a method for preparing a porous ceramic filter with controllable pore gradient. The method is suitable for accurate and rapid printing of a variable gradient truss filter structure that can be parameterized and designed. The porous ceramic filter in Example 1 is prepared, such as Fig. 9 As shown, the steps are as follows:

[0057] S1. According to actual use requirements, a three-dimensional model of a double inverted pyramid unit pillar structure is designed using Rhino design software, and then a layer of truss filtering structure is constructed according to the arrangement of a two-dimensional array; of course, in other embodiments, other design software such as solidworks and UG can also be used;

[0058] S2, reducing the volume of the truss filter structure of the layer. Specifically, the volume of the truss filter structure of the layer in this embodiment is reduced to one eighth of the original volume by three-dimensional isometrics, and then constructing the next layer of truss filter structure according to the arrangement of the two-dimensional array;

[0059] S3, according to the actual filtering requirements, repeat step S2 to increase the number of truss layers, so as to construct a three-dimensional model of the variable gradient truss filtering structure; Figure 5 As shown, the total number of truss layers in this embodiment is four;

[0060] S4, for the bottom truss filtering structure of the variable gradient truss filtering structure, the bottom end of the bottom truss filtering structure is connected by quadrilateral trusses arranged in a two-dimensional array, so that the variable gradient truss filtering structure is further enhanced;

[0061] S5. According to actual use requirements, a three-dimensional model of the outer wall of the filter is established, and the three-dimensional model of the outer wall of the filter is combined with the three-dimensional model of the variable gradient truss filter structure through Boolean operations, combination and other methods, so as to establish a three-dimensional model of a porous filter with controllable pore gradient;

[0062] S6. Save the porous filter model in STL format, and slice the porous filter three-dimensional model using slicing software to obtain a porous structure slice file;

[0063] S7. Prepare ceramic slurry suitable for 3D printing according to actual requirements such as use strength, heat resistance, micro porosity, etc.;

[0064] S8, importing the porous structure slice file into a 3D printer, and printing layer by layer in combination with the ceramic slurry obtained in step S7 to obtain a porous ceramic filter blank;

[0065] S9, washing, drying, degreasing, and sintering the porous ceramic filter blank printed in step S8 to obtain a final porous ceramic filter with controllable pore gradient.

[0066] Here, the ceramic slurry suitable for 3D printing is a composite slurry obtained by fully mixing alumina ceramic and photosensitive resin. 3D printing adopts a digital light processing ceramic 3D printing method. Of course, in other embodiments, other 3D printing methods such as laser selective sintering ceramic 3D printing, laser selective melting ceramic 3D printing, and stereolithography technology ceramic 3D printing can also be used.

[0067] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A porous ceramic filter with controllable pore gradient, characterized in that: It includes a porous ceramic filter outer wall and a porous ceramic variable gradient truss filter structure located inside the porous ceramic filter outer wall, the variable gradient truss filter structure is divided into multiple levels, each level of the truss filter structure is composed of multiple double inverted pyramid unit pillar structures, the volume of the double inverted pyramid unit pillar structure of the next level is smaller than the volume of the double inverted pyramid unit pillar structure of the previous level, and multiple double inverted pyramid unit pillar structures of the next level are connected to and support the same double inverted pyramid unit pillar structure of the previous level; The volume of the truss filter structure at each level decreases from top to bottom in a geometric multiple relationship, and the node density at each level increases from top to bottom in the same geometric multiple relationship; The endpoints of each double inverted pyramid unit support structure serve as nodes of the truss filtering structure. The node distribution density of each level gradually increases in a top-down order, and the three-dimensional hole volume corresponding to each level gradually decreases in a top-down order. Each double inverted pyramid unit pillar structure is connected to adjacent double inverted pyramid unit pillar structures in the same level through a node; Except for the lowest level truss filtering structure, in any level of truss filtering structure, each lower end node of each double inverted pyramid unit pillar structure is connected to four upper end nodes of the double inverted pyramid unit pillar structure belonging to the next level; The double inverted pyramid unit pillar structure is composed of four truss rods, which are arranged according to the spatial diagonal of the cube and distributed in a circular array. The inclination angle of each truss rod is not greater than 45°; the four truss rods intersect each other, and there is a unique node at one-third of the length of each truss rod.

2. The porous ceramic filter with controllable pore gradient according to claim 1, characterized in that: The porous ceramic filter is further provided with a quadrilateral truss structure below the lowest truss filtering structure. The quadrilateral truss structure has a plurality of quadrilateral truss structural units. The plurality of lower end nodes of the lowest level truss filtering structure are connected through the quadrilateral truss structural units.

3. The porous ceramic filter with controllable pore gradient according to claim 2, characterized in that: A plurality of quadrilateral truss structural units are arranged in a two-dimensional array, and a double inverted pyramid unit support structure at each level is arranged in a two-dimensional array.

4. The porous ceramic filter with controllable pore gradient according to claim 2, characterized in that: The porous ceramic filter is made of a photosensitive resin-ceramic powder mixed slurry. The outer wall of the filter, the porous ceramic variable gradient truss filter structure and the quadrilateral truss structure are integrally formed by 3D printing.

5. The porous ceramic filter with controllable pore gradient according to claim 1, characterized in that: The total number of levels of the variable gradient truss filtering structure is at least three; the volume of the double inverted pyramid unit pillar structure of the next level is reduced to one eighth of the volume of the double inverted pyramid unit pillar structure of the previous level through three-dimensional equiaxing, and the node density of the next level is eight times the node density of the previous level.

6. A method for preparing a porous ceramic filter with controllable pore gradient according to any one of claims 1 to 5, characterized in that: The method is suitable for accurate and rapid printing of a variable gradient truss filter structure that can be parameterized and designed, and comprises the following steps: S1. According to actual use requirements, a three-dimensional model of a double inverted pyramid unit pillar structure is designed using design software, and then a layer of truss filtering structure is constructed according to the arrangement of a two-dimensional array; S2, reducing the volume of the truss filter structure of the layer, and then constructing the next layer of truss filter structure according to the arrangement of the two-dimensional array; S3, according to the actual filtering requirements, repeat step S2 to increase the number of truss layers, so as to construct a three-dimensional model of the variable gradient truss filtering structure; S4. For the lowest truss filtering structure of the variable gradient truss filtering structure, the lower end of the lowest truss filtering structure is connected by a quadrilateral truss to further strengthen the variable gradient truss filtering structure; S5. According to actual use requirements, a three-dimensional model of the outer wall of the filter is established, and combined with the three-dimensional model of the variable gradient truss filter structure, so as to establish a three-dimensional model of a porous filter with controllable pore gradient; S6. Save the porous filter model in STL format, and slice the porous filter three-dimensional model using slicing software to obtain a porous structure slice file; S7. Prepare ceramic slurry suitable for 3D printing according to actual requirements such as usage strength, heat resistance, and micro-porosity; S8, importing the porous structure slice file into a 3D printer, and printing layer by layer in combination with the ceramic slurry obtained in step S7 to obtain a porous ceramic filter blank; S9, washing, drying, degreasing, and sintering the porous ceramic filter blank printed in step S8 to obtain a final porous ceramic filter with controllable pore gradient.

7. The method for preparing a porous ceramic filter with controllable pore gradient according to claim 6, characterized in that: Design software includes but is not limited to Rhino, solidworks, and UG; 3D printing methods include but are not limited to digital light processing ceramic 3D printing method, laser selective sintering ceramic 3D printing, laser selective melting ceramic 3D printing, and stereolithography ceramic 3D printing; The ceramic slurry suitable for 3D printing is a composite slurry obtained by fully mixing alumina ceramics and photosensitive resin.

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