A porous alumina ceramic material, a preparation method and applications thereof

Abstract

This invention relates to the field of high-purity aluminum and aluminum alloy production technology, and particularly to a porous alumina ceramic material, its preparation method, and its application. The material comprises a composite aggregate and an organic binder, wherein the mass ratio of the composite aggregate to the organic binder is 47:3. The composite aggregate comprises 9 wt%–17 wt% inorganic binder and 83 wt%–91 wt% aggregate particles. The inorganic binder comprises: 40 wt%–50 wt% B₂O₃, 20 wt%–29 wt% Al₂O₃, 10 wt%–15 wt% SiO₂, 9.4 wt%–14.4 wt% MgO, 0–0.5 wt% Na₂O, 0–0.5 wt% K₂O, and 0–10 wt% Re₂O₃, where Re is a rare earth element. This method uses corundum or α-Al₂O₃ as a framework and rare earth composite oxides as an inorganic binder. A high-temperature reaction forms sintering necks between the aggregate particles, resulting in a porous alumina ceramic with a bimodal pore distribution. Two different pore sizes are distributed in situ on the surface of the skeleton particles and the sintered neck, achieving a dual-capture filtration effect for aluminum molten inclusions. This solves the problem that filters with large pore sizes cannot simultaneously filter small-grain-sized impurities.

Description

Technical Field

[0001] This invention relates to the field of high-purity aluminum and aluminum alloy production technology, specifically to a porous alumina ceramic material, its preparation method, and its application. Background Technology

[0002] Due to the increasing global aluminum production and the growing proportion of refined aluminum, coupled with rising demands for higher aluminum quality, an efficient method is needed to remove solid impurity ions from molten aluminum during the manufacturing process. Filters are typically used to remove impurities from molten aluminum, thereby improving the yield of aluminum products and preventing defects in the final product.

[0003] Using porous ceramic materials as filters to remove inclusions from molten aluminum alloys is a common practice. The principle lies in the interception, adsorption, and deposition of inclusions by the ceramic material. Among them, porous ceramics with alumina or silicon carbide as the framework have advantages such as high porosity and low cost, and are currently the most widely used porous ceramic materials for aluminum melt purification.

[0004] Chinese invention patent CN113979772A discloses a porous ceramic, its binder, its preparation method, and its application. Al2O3, SiO2, alkaline earth metal oxides, and B2O3 are used as inorganic binders. The method involves calcining and crushing the inorganic binder, then adding water glass or resin binder, mixing, molding, and sintering to prepare an aluminum melt filter with a compressive strength exceeding 10 MPa at both room temperature and 800°C, and an average pore size of less than 0.15 mm. While the porous ceramic obtained by this method possesses characteristics such as high strength, high rigidity, and small pore size, meeting various working conditions, its essence lies in using inorganic binders to bond aggregate particles together, forming a bonding layer on the ceramic particle surface to connect the ceramic particles and achieve the preparation of porous ceramic materials. However, this filter only has one type of large-pore void formed by the accumulation and bonding of aggregate particles, thus limiting its filtration capacity and failing to capture small crystalline impurities in the aluminum melt, thereby affecting the filtration quality. Summary of the Invention

[0005] To address the problem that existing filters have large pore sizes and insufficient filtration capacity due to the aggregation and bonding of aggregate particles, this invention provides a porous alumina ceramic material, its preparation method, and its application.

[0006] To achieve the above objectives, the present invention employs the following technical solution:

[0007] This invention provides a porous alumina ceramic material comprising the following raw material components: composite aggregate and organic binder, wherein the mass ratio of the composite aggregate to the organic binder is 47:3;

[0008] The composite aggregate comprises 9 wt% to 17 wt% inorganic binder and 83 wt% to 91 wt% aggregate particles;

[0009] The inorganic binder comprises: 40wt%–50wt% B2O3, 20wt%–29wt% Al2O3, 10wt%–15wt% SiO2, 9.4wt%–14.4wt% MgO, 0–0.5wt% Na2O, 0–0.5wt% K2O, and 0–10wt% Re2O3, wherein Re is a rare earth element;

[0010] The aggregate particles are corundum or α-Al2O3.

[0011] Preferably, Re is Y, Yb, La, or Lu.

[0012] Preferably, the aggregate particles have a particle size of 100–1000 μm, B2O3 has a particle size of 2.5–3.5 μm, Al2O3 has a particle size of 400–600 nm, SiO2 has a particle size of 4–6 μm, MgO has a particle size of 200–500 nm, rare earth oxides Re2O3 have a particle size of 2–5 μm, Na2O has a particle size of 3–5 μm, and K2O has a particle size of 3–5 μm.

[0013] This invention also provides a method for preparing porous alumina ceramic materials, comprising:

[0014] An inorganic binder is obtained by mixing 40wt%–50wt% of B2O3, 20wt%–29wt% of Al2O3, 10wt%–15wt% of SiO2, 9.4wt%–14.4wt% of MgO, 0–0.5wt% of Na2O, 0–0.5wt% of K2O, and 0–10wt% of Re2O3, wherein Re is a rare earth element.

[0015] 9 wt% to 17 wt% of inorganic binder is mixed with 83 wt% to 91 wt% of aggregate particles to obtain composite aggregate, wherein the aggregate particles are corundum or α-Al2O3;

[0016] Dextrin, ISOBAM-104, and water are mixed to obtain an organic binder;

[0017] The composite aggregate and organic binder were mixed at a mass ratio of 47:3 to obtain a mixture.

[0018] The mixture is filled into a mold to form the shape, and then demolded and dried to obtain a green body;

[0019] The green body is calcined at high temperature to obtain porous alumina ceramic material.

[0020] Further, the method for mixing 40wt%–50wt% B₂O₃, 20wt%–29wt% Al₂O₃, 10wt%–15wt% SiO₂, 9.4wt%–14.4wt% MgO, 0–0.5wt% Na₂O, 0–0.5wt% K₂O, and 0–10wt% Re₂O₃ to obtain the inorganic binder is as follows:

[0021] 40wt%–50wt% of B2O3, 20wt%–29wt% of Al2O3, 10wt%–15wt% of SiO2, 9.4wt%–14.4wt% of MgO, 0–0.5wt% of Na2O, 0–0.5wt% of K2O and 0–10wt% of Re2O3 are mixed to obtain a mixed powder.

[0022] Add ZrO2 grinding balls to the mixed powder, and use anhydrous ethanol as the dispersion medium to ball mill the mixed powder to obtain a uniformly mixed powder.

[0023] Remove anhydrous ethanol from the well-mixed powder, dry and keep it at a warm temperature, and sieve to obtain an inorganic binder.

[0024] Furthermore, during ball milling, a mixture of grinding balls with diameters of 5mm, 10mm, and 15mm is used, with a mass ratio of 3:4:3 and a mass ratio of the mixed grinding balls to the mixed powder of 4:1. The ball milling time is 20–24 hours, the drying temperature is 75℃–85℃, and the holding time is 20–24 hours.

[0025] Furthermore, the mass ratio of dextrin, ISOBAM-104 and water is 1:1:(3-10), and the molecular weight of ISOBAM-104 is 40,000-50,000.

[0026] Furthermore, the method for high-temperature calcination of the green blanks is as follows:

[0027] The green body is embedded in mullite powder and heated to 1000℃ in air atmosphere and held for 1.5 to 3 hours, then heated to 1100℃ to 1350℃ and held for 1 to 5 hours to obtain porous alumina ceramic material.

[0028] Preferably, the heating rate is 4℃ / min to 6℃ / min.

[0029] Such as the application of porous alumina ceramic materials in removing solid impurities from molten aluminum.

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

[0031] This invention discloses a porous alumina ceramic material. The material uses corundum or α-Al₂O₃ as a framework, rare earth composite oxides as an inorganic binder, and an organic binder to prepare the porous alumina ceramic material. Sintering necks are formed between the aggregate particles. These sintering necks connect the aggregate particles, and B₂O₃ and Al₂O₃ on the surface of the aggregate particles and the sintering necks react in situ to generate 9Al₂O₃·2B₂O₃ whiskers, forming a porous alumina ceramic with a bimodal pore distribution, i.e., oxygen... The large pore size (50–500 μm) formed between the alumina and aggregate particles is used to filter large particles. The sintered neck between the aggregate particles consists of 9Al₂O₃·2B₂O₃ whiskers with high specific surface area and rare earth aluminosilicate glass phase, with pore size between the whiskers ranging from 0.4 to 2 μm. During high-temperature filtration of molten aluminum, the rare earth aluminosilicate glass melt on the surface of the 9Al₂O₃·2B₂O₃ whiskers can adsorb small-sized grains, thus achieving a dual capture effect for aluminum inclusions in the molten aluminum. The addition of rare earth oxides can increase the low-temperature viscosity of the aluminosilicate glass, while also improving the high-temperature resistance and corrosion resistance of the amorphous phase in the porous ceramic, thereby improving the high-temperature mechanical properties of the porous ceramic. On the other hand, the high-temperature stability of the amorphous phase at the molten aluminum filtration temperature (up to 750 °C) can reduce the contamination of the molten aluminum by the porous ceramic material itself. The length of the 9Al₂O₃·2B₂O₃ whiskers is between 2 and 18 μm, and the aspect ratio is between 5 and 20. Porous alumina ceramic filter materials have a porosity of 33.4% to 40.9% and a bending strength of 4.5 to 16.8 MPa. They can filter molten metal at working temperatures of 700℃ to 900℃, and are therefore widely used in the production of high-purity aluminum and aluminum alloys.

[0032] This invention also provides a method for preparing porous alumina ceramic materials. The method involves mixing 40wt%–50wt% B₂O₃, 20wt%–29wt% Al₂O₃, 10wt%–15wt% SiO₂, 9.4wt%–14.4wt% MgO, 0–0.5wt% Na₂O, 0–0.5wt% K₂O, and 0–10wt% Re₂O₃ to obtain an inorganic binder. Then, 9wt%–17wt% of the inorganic binder is mixed with 83wt%–91wt% of aggregate particles to uniformly coat the aggregate particles with the inorganic binder, resulting in a composite aggregate. An organic binder is then prepared, and the composite aggregate and organic binder are mixed at a mass ratio of 47:3 to obtain a mixture. The mixture is then filled into a mold, shaped, demolded, dried, and calcined at high temperature to obtain the porous alumina ceramic material. An organic binder forms sintering necks between aggregate particles, connecting the alumina aggregates to form a porous ceramic. B₂O₃ and Al₂O₃ react in situ on the surfaces of the aggregate particles and the sintering necks to generate 9Al₂O₃·2B₂O₃ whiskers. The large pore size formed between the alumina aggregate particles in the prepared porous ceramic material is used to filter large particles. The sintering necks between the aggregate particles are composed of 9Al₂O₃·2B₂O₃ whiskers with high specific surface area and a rare-earth aluminosilicate glass phase. When filtering molten aluminum, the rare-earth aluminosilicate glass melt of the 9Al₂O₃·2B₂O₃ whiskers can adsorb small-sized grains. Therefore, the porous alumina ceramic material prepared by this method can achieve a dual-capture filtration effect for aluminum inclusions in molten aluminum. The preparation method is simple, requires no extensive equipment modifications, is low-cost, economically beneficial, and suitable for industrialization.

[0033] The present invention also provides an application of the porous alumina ceramic material as described above in removing solid impurity ions from molten aluminum, which can achieve sufficient filtration of impurities in molten aluminum, resulting in fewer defects in aluminum products and a high yield. Attached Figure Description

[0034] Figure 1 This is a schematic diagram of a method for preparing a porous alumina ceramic material according to the present invention.

[0035] Figure 2 This is a low-magnification SEM image of the porous ceramic material obtained in Example 9 of the present invention.

[0036] Figure 3 This is a high-magnification SEM image of the porous ceramic material obtained in Example 9 of the present invention.

[0037] Figure 4 This is a pore size distribution diagram of the porous ceramic material obtained in Example 9 of the present invention. Detailed Implementation

[0038] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0039] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0040] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0041] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0042] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0043] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0044] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0045] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0046] This invention provides a porous alumina ceramic material comprising the following raw material components: composite aggregate and organic binder, wherein the mass ratio of the composite aggregate to the organic binder is 47:3;

[0047] The composite aggregate comprises 9 wt% to 17 wt% inorganic binder and 83 wt% to 91 wt% aggregate particles;

[0048] The inorganic binder comprises: 40wt%–50wt% B2O3, 20wt%–29wt% Al2O3, 10wt%–15wt% SiO2, 9.4wt%–14.4wt% MgO, 0–0.5wt% Na2O, 0–0.5wt% K2O, and 0–10wt% Re2O3, wherein Re is a rare earth element, preferably Y, Yb, La, or Lu;

[0049] The aggregate particles are corundum or α-Al2O3.

[0050] The aggregate particles have a particle size of 100–1000 μm, B2O3 has a particle size of 2.5–3.5 μm, Al2O3 has a particle size of 400–600 nm, SiO2 has a particle size of 4–6 μm, MgO has a particle size of 200–500 nm, rare earth oxides Re2O3 have a particle size of 2–5 μm, Na2O has a particle size of 3–5 μm, and K2O has a particle size of 3–5 μm.

[0051] See Figure 1 This invention provides a method for preparing porous alumina ceramic materials, comprising:

[0052] S1: A mixture of 40wt%–50wt% B₂O₃, 20wt%–29wt% Al₂O₃, 10wt%–15wt% SiO₂, 9.4wt%–14.4wt% MgO, 0–0.5wt% Na₂O, 0–0.5wt% K₂O, and 0–10wt% Re₂O₃ yields an inorganic binder, wherein Re represents a rare earth element. Specifically:

[0053] 40wt%–50wt% of B2O3, 20wt%–29wt% of Al2O3, 10wt%–15wt% of SiO2, 9.4wt%–14.4wt% of MgO, 0–0.5wt% of Na2O, 0–0.5wt% of K2O and 0–10wt% of Re2O3 are mixed to obtain a mixed powder.

[0054] ZrO2 grinding balls were added to the mixed powder, and the mixed powder was ball-milled for 20-24 hours using anhydrous ethanol as the dispersion medium to obtain a uniformly mixed powder. The ZrO2 grinding balls were a mixture of grinding balls with diameters of 5 mm, 10 mm and 15 mm, with a mass ratio of 3:4:3 and a mass ratio of 4:1 between the mixed grinding balls and the mixed powder.

[0055] Remove anhydrous ethanol from the uniformly mixed powder, dry it at 75℃~85℃ and keep it at that temperature for 20~24h, and then sieve it to obtain an inorganic binder.

[0056] S2: Mix 9wt%–17wt% of inorganic binder with 83wt%–91wt% of aggregate particles to obtain composite aggregate, wherein the aggregate particles are corundum or α-Al2O3; specifically:

[0057] 9 wt% to 17 wt% of inorganic binder and 83 wt% to 91 wt% of aggregate particles are placed in a mixing tank and mechanically stirred for 2 to 3 hours to uniformly coat the aggregate particles with inorganic binder, thus obtaining composite aggregate.

[0058] S3: Mix dextrin, ISOBAM-104 (isobutylene-alt-maleic anhydride), and water to obtain an organic binder, specifically:

[0059] Dextrin, ISOBAM-104 and water are mixed in a mass ratio of 1:1:(3-10) and mechanically stirred for 2-3 hours to obtain an organic binder; the molecular weight of ISOBAM-104 is 40,000-50,000.

[0060] S4: Mix the composite aggregate and organic binder at a mass ratio of 47:3 to obtain a mixture, specifically:

[0061] The composite aggregate and organic binder are mixed at a mass ratio of 47:3 and mechanically stirred for 4–6 hours to obtain the mixture.

[0062] S5: Fill the mold with the mixture, shape it, demold and dry it to obtain a green body, specifically:

[0063] The mixture is filled into a mold and shaped, then dried at 75℃~85℃ to obtain a green body.

[0064] S6: The green body is calcined at high temperature to obtain porous alumina ceramic material. Specifically, the green body is placed in an air furnace, and mullite with a particle size of 3-5 mm is used as a embedding powder. Under air atmosphere, the temperature is first raised to 1000℃ at a heating rate of 4℃ / min-6℃ / min and held for 1.5-3 hours. Then, the temperature is raised to 1100℃-1350℃ at a heating rate of 4℃ / min-6℃ / min and held for 1-5 hours to obtain porous alumina ceramic material.

[0065] Example 1

[0066] Weigh out 45.0 wt% B₂O₃, 25.0 wt% Al₂O₃, 10.0 wt% SiO₂, 9.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 10.0 wt% rare earth oxide La₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, use anhydrous ethanol as the dispersion medium, and ball mill for 24 h to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove anhydrous ethanol, dry for 3 h, and then place it in an oven and keep it at 80℃ for 24 h. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0067] 87 wt% of corundum particles with an average particle size of 700 μm were added as aggregate particles, along with 13 wt% of inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours on a planetary ball mill to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0068] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0069] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 35.5%, a flexural strength of 11.5 MPa, and an average length of 12 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0070] Example 2

[0071] Weigh out 45.0 wt% B₂O₃, 25.0 wt% Al₂O₃, 10.0 wt% SiO₂, 9.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 10.0 wt% rare earth oxide Lu₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, and use anhydrous ethanol as the dispersion medium. Mill the mixture in a planetary ball mill for 24 hours to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove the anhydrous ethanol, dry for 3 hours, and then place it in an oven at 80℃ for 24 hours. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0072] 87 wt% of corundum particles with an average particle size of 700 μm and 13 wt% of inorganic binder were added as aggregate particles and placed in a ball mill jar. The mixture was ball-milled for 2 hours on a planetary ball mill to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0073] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0074] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 34.0%, a flexural strength of 15.0 MPa, and an average length of 16 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0075] Example 3

[0076] Weigh out 47.0 wt% B₂O₃, 21.0 wt% Al₂O₃, 11.0 wt% SiO₂, 11 wt% MgO, and 10.0 wt% rare earth oxide Lu₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, and use anhydrous ethanol as the dispersion medium. Mill the mixture in a planetary ball mill for 24 hours to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove the anhydrous ethanol, dry for 3 hours, and then place it in an oven at 80°C for 24 hours. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0077] 87 wt% corundum particles (average particle size 700 μm) were added as aggregate particles, along with 13 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0078] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0079] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 37.3%, a flexural strength of 7.2 MPa, and an average length of 10 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0080] Example 4

[0081] Weigh out 45.0 wt% B₂O₃, 25.0 wt% Al₂O₃, 10.0 wt% SiO₂, 9.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 10.0 wt% rare earth oxide Y₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, and use anhydrous ethanol as the dispersion medium. Mill the mixture in a planetary ball mill for 24 hours to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove the anhydrous ethanol, dry for 3 hours, and then place it in an oven at 80℃ for 24 hours. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0082] 87 wt% corundum particles (average particle size 700 μm) were added as aggregate particles, along with 13 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0083] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0084] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 34.1%, a flexural strength of 14.7 MPa, and an average length of 13 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0085] Example 5

[0086] Weigh out 44.0 wt% B₂O₃, 26.0 wt% Al₂O₃, 10.0 wt% SiO₂, 9.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 10.0 wt% rare earth oxide Yb₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, and use anhydrous ethanol as the dispersion medium. Mill the mixture in a planetary ball mill for 24 hours to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove the anhydrous ethanol, dry for 3 hours, and then place it in an oven at 80°C for 24 hours. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0087] 87 wt% corundum particles (average particle size 700 μm) were added as aggregate particles, along with 13 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0088] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0089] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 34.8%, a flexural strength of 14.3 MPa, and an average length of 15 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0090] Example 6

[0091] Weigh out 50.0 wt% B₂O₃, 20.0 wt% Al₂O₃, 10.0 wt% SiO₂, 14.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 5.0 wt% rare earth oxide La₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, use anhydrous ethanol as the dispersion medium, and ball mill for 24 h to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove anhydrous ethanol, dry for 3 h, and then place it in an oven and keep it at 80℃ for 24 h. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0092] 91 wt% corundum particles (average particle size 700 μm) were added as aggregate particles, along with 9 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0093] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0094] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 40.9%, a flexural strength of 8.5 MPa, and an average length of 17 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0095] Example 7

[0096] Weigh out 45.0 wt% B₂O₃, 25.0 wt% Al₂O₃, 15.0 wt% SiO₂, 14.4 wt% MgO, 0.1 wt% Na₂O, and 0.5 wt% K₂O as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, and use anhydrous ethanol as the dispersion medium. Mill the mixture in a planetary ball mill for 24 hours to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove the anhydrous ethanol, dry for 3 hours, and then place it in an oven at 80°C for 24 hours. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0097] 83 wt% corundum particles (average particle size 700 μm) were added as aggregate particles, along with 17 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0098] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0099] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 35.7%, a flexural strength of 16.8 MPa, and an average length of 15 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0100] Example 8

[0101] Weigh out 45.0 wt% B₂O₃, 25.0 wt% Al₂O₃, 10.0 wt% SiO₂, 14.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 5.0 wt% rare earth oxide La₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, use anhydrous ethanol as the dispersion medium, and ball mill for 24 h to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove anhydrous ethanol, dry for 3 h, and then place it in an oven and keep it at 80℃ for 24 h. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0102] 91 wt% corundum particles (average particle size 700 μm) were added as aggregate particles, along with 9 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0103] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0104] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1350℃ at a rate of 5℃ / min, held at 1350℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 33.4%, a flexural strength of 16.7 MPa, and an average length of 14 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0105] Example 9

[0106] Weigh out 47.0 wt% B₂O₃, 26.0 wt% Al₂O₃, 11.0 wt% SiO₂, 10.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 5.0 wt% rare earth oxide La₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, and use anhydrous ethanol as the dispersion medium. Mill the mixture in a planetary ball mill for 24 hours to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove the anhydrous ethanol, dry for 3 hours, and then place it in an oven at 80°C for 24 hours. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0107] 87 wt% corundum particles (average particle size 700 μm) were added as aggregate particles, along with 13 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0108] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0109] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 36.0%, a flexural strength of 4.9 MPa, and an average length of 7 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0110] Example 10

[0111] Weigh out 40.0 wt% B₂O₃, 29.0 wt% Al₂O₃, 15.0 wt% SiO₂, 10.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 5.0 wt% rare earth oxide La₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, and use anhydrous ethanol as the dispersion medium. Mill the mixture in a planetary ball mill for 24 hours to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove the anhydrous ethanol, dry for 3 hours, and then place it in an oven at 80°C for 24 hours. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0112] 90 wt% corundum particles (average particle size 700 μm) were added as aggregate particles, along with 10 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0113] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0114] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1100℃ at a rate of 5℃ / min, held at 1100℃ for 2 hours, and then cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 38.2%, a flexural strength of 4.5 MPa, and an average length of 2 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0115] Example 11

[0116] Weigh out 45.0 wt% B₂O₃, 25.0 wt% Al₂O₃, 10.0 wt% SiO₂, 14.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 5.0 wt% rare earth oxide La₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, use anhydrous ethanol as the dispersion medium, and ball mill for 24 h to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove anhydrous ethanol, dry for 3 h, and then place it in an oven and keep it at 80℃ for 24 h. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0117] 85 wt% corundum particles (average particle size 700 μm) were added as aggregate particles, along with 15 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours on a planetary ball mill to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:10 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0118] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0119] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 38.5%, a flexural strength of 11.9 MPa, and an average length of 18 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0120] Example 12

[0121] Weigh out 45.0 wt% B₂O₃, 25.0 wt% Al₂O₃, 10.0 wt% SiO₂, 14.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 5.0 wt% rare earth oxide La₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, use anhydrous ethanol as the dispersion medium, and ball mill for 24 h to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove anhydrous ethanol, dry for 3 h, and then place it in an oven and keep it at 80℃ for 24 h. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0122] 83 wt% corundum particles (average particle size 700 μm) were added as aggregate particles, along with 17 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0123] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0124] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 1 hour, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 36.9%, a flexural strength of 13.5 MPa, and an average length of 11 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0125] Example 13

[0126] Weigh out 45.0 wt% B₂O₃, 25.0 wt% Al₂O₃, 10.0 wt% SiO₂, 14.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 5.0 wt% rare earth oxide La₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, use anhydrous ethanol as the dispersion medium, and ball mill for 24 h to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove anhydrous ethanol, dry for 3 h, and then place it in an oven and keep it at 80℃ for 24 h. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0127] 89 wt% corundum particles (average particle size 100 μm) were added as aggregate particles, along with 11 wt% inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0128] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0129] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 5 hours, and then cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 30.8%, a flexural strength of 7.3 MPa, and an average length of 15 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0130] Example 14

[0131] Weigh out 45.0 wt% B₂O₃, 25.0 wt% Al₂O₃, 10.0 wt% SiO₂, 14.4 wt% MgO, 0.1 wt% Na₂O, 0.5 wt% K₂O, and 5.0 wt% rare earth oxide La₂O₃ as raw materials, place them in a ball mill jar, add ZrO₂ grinding balls, use anhydrous ethanol as the dispersion medium, and ball mill for 24 h to obtain a mixed powder. Place the uniformly mixed powder in a rotary evaporator to remove anhydrous ethanol, dry for 3 h, and then place it in an oven and keep it at 80℃ for 24 h. Pass the completely dried powder through a 200-mesh sieve to obtain the desired inorganic binder.

[0132] 87 wt% of rigid α-Al₂O₃ (average particle size 1000 μm) was added as aggregate particles, along with 13 wt% of inorganic binder. The mixture was placed in a ball mill jar and ball-milled for 2 hours to obtain aggregate particles uniformly coated with the inorganic binder. Dextrin, ISOBAM-104, and deionized water were mixed at a mass ratio of 1:1:3 and mechanically stirred for 2 hours to prepare an organic binder. The aggregate particles uniformly coated with the inorganic binder and the organic binder were mixed at a mass ratio of 47:3 and mechanically stirred for 5 hours to obtain the desired mixture.

[0133] The resulting mixture is filled into a mold and shaped. After being removed, it is placed in an oven at 80°C and dried for 12 hours to obtain a green body.

[0134] The green body was placed in an alumina crucible, and mullite with a particle size of 3-5 mm was used as the embedding powder. Under air atmosphere, the temperature was raised from room temperature to 1000℃ at a rate of 5℃ / min, held at 1000℃ for 2 hours, then raised to 1200℃ at a rate of 5℃ / min, held at 1200℃ for 2 hours, and cooled in the furnace to obtain a porous ceramic material. Testing showed that this porous ceramic material had a porosity of 38.9%, a flexural strength of 14.0 MPa, and an average length of 17 μm for the 9Al₂O₃·2B₂O₃ whiskers on the surface of the aggregate particles.

[0135] It should be noted that, among the raw material components added in the above embodiments, the particle size of B2O3 is 2.5-3.5 μm, the particle size of Al2O3 is 400-600 nm, the particle size of SiO2 is 4-6 μm, the particle size of MgO is 200-500 nm, the particle size of rare earth oxide Re2O3 is 2-5 μm, the particle size of Na2O is 3-5 μm, and the particle size of K2O is 3-5 μm.

[0136] To verify the properties of the porous alumina ceramic material prepared in this invention, SEM testing was performed on the porous alumina ceramic material prepared in Example 9. (See attached image.) Figure 2 and Figure 3 Due to the action of the inorganic binder, the framework particles (fused alumina) interconnect after sintering at high temperature, possessing large pore sizes on the order of 100 μm. The surface of the porous ceramic material has whiskers approximately 8 μm in length, with an aspect ratio of approximately 10, and small pore sizes on the order of 1 μm. See also Figure 4 This filter material has two pore sizes, mainly 1-2 μm and 150-200 μm, and the pore size has a bimodal distribution, which is consistent with the designed dual capture of aluminum liquid entrainment filtration effect.

[0137] This invention also provides an application of the porous alumina ceramic material described above in removing solid impurities from molten aluminum. It enables dual filtration of both large and small grain impurities in the molten aluminum, resulting in fewer defects in the aluminum products and a higher yield.

[0138] In summary, this invention provides a porous alumina ceramic material, its preparation method, and its application. The porous ceramic material prepared by this method uses corundum or α-Al₂O₃ as a framework and rare earth composite oxides as an inorganic binder. A sintering neck is formed between the aggregate particles through a high-temperature reaction, resulting in a porous alumina ceramic with a bimodal pore distribution. Two different pore sizes are distributed in situ on the surfaces of the framework particles and the sintering neck, achieving a dual filtration effect to capture aluminum molten inclusions.

[0139] The above description is merely a preferred embodiment of the present invention and is not intended to limit the technical solution of the present invention in any way. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can be modified and replaced in several simple ways, and these modifications and replacements are all within the scope of protection covered by the claims.

Claims

1. A method for preparing a porous alumina ceramic material, characterized in that, The porous alumina ceramic material comprises the following raw material components: composite aggregate and organic binder, wherein the mass ratio of composite aggregate to organic binder is 47:3; The composite aggregate comprises 9wt% to 17wt% inorganic binder and 83wt% to 91wt% aggregate particles; The inorganic binder comprises: 40wt%–50wt% B2O3, 20wt%–29wt% Al2O3, 10wt%–15wt% SiO2, 9.4wt%–14.4wt% MgO, 0–0.5wt% Na2O, 0–0.5wt% K2O, and 0–10wt% Re2O3, wherein Re is a rare earth element; The aggregate particles are corundum or α-Al2O3; The aggregate particles have a particle size of 100–1000 μm, B2O3 has a particle size of 2.5–3.5 μm, Al2O3 has a particle size of 400–600 nm, SiO2 has a particle size of 4–6 μm, MgO has a particle size of 200–500 nm, rare earth oxides Re2O3 have a particle size of 2–5 μm, Na2O has a particle size of 3–5 μm, and K2O has a particle size of 3–5 μm. The preparation method includes the following steps: B2O3, Al2O3, SiO2, MgO, Na2O, K2O and Re2O3 are mixed in proportion to obtain an inorganic binder; Inorganic binders are mixed with aggregate particles to obtain composite aggregates; Dextrin, ISOBAM-104, and water are mixed to obtain an organic binder; The composite aggregate is mixed with an organic binder to obtain a mixture. The mixture is filled into a mold to form the shape, and then demolded and dried to obtain a green body; The green body is calcined at high temperature to obtain porous alumina ceramic material; the specific high-temperature calcination method is as follows: The green body is embedded in mullite powder and heated to 1000℃ in air atmosphere and held for 1.5 to 3 hours, then heated to 1100℃ to 1350℃ and held for 1 to 5 hours to obtain porous alumina ceramic material.

2. The method for preparing porous alumina ceramic material according to claim 1, characterized in that, Re can be Y, Yb, La, or Lu.

3. The method for preparing porous alumina ceramic material according to claim 1, characterized in that, The method for mixing 40wt%–50wt% B2O3, 20wt%–29wt% Al2O3, 10wt%–15wt% SiO2, 9.4wt%–14.4wt% MgO, 0–0.5wt% Na2O, 0–0.5wt% K2O, and 0–10wt% Re2O3 to obtain the inorganic binder is as follows: 40wt%–50wt% of B2O3, 20wt%–29wt% of Al2O3, 10wt%–15wt% of SiO2, 9.4wt%–14.4wt% of MgO, 0–0.5wt% of Na2O, 0–0.5wt% of K2O and 0–10wt% of Re2O3 are mixed to obtain a mixed powder. Add ZrO2 grinding balls to the mixed powder, and use anhydrous ethanol as the dispersion medium to ball mill the mixed powder to obtain a uniformly mixed powder. Remove anhydrous ethanol from the well-mixed powder, dry and keep it at a warm temperature, and sieve to obtain an inorganic binder.

4. The method for preparing porous alumina ceramic material according to claim 3, characterized in that, During ball milling, a mixture of grinding balls with diameters of 5mm, 10mm, and 15mm is used. The mass ratio of the 5mm, 10mm, and 15mm grinding balls is 3:4:3, and the mass ratio of the mixed grinding balls to the mixed powder is 4:

1. The ball milling time is 20–24 hours, the drying temperature is 75℃–85℃, and the holding time is 20–24 hours.

5. The method for preparing porous alumina ceramic material according to claim 1, characterized in that, The mass ratio of dextrin, ISOBAM-104 and water is 1:1:(3-10), and the molecular weight of ISOBAM-104 is 40,000-50,000.

6. The method for preparing porous alumina ceramic material according to claim 1, characterized in that, The heating rate is 4℃ / min to 6℃ / min.

7. The application of the porous alumina ceramic material prepared by the preparation method according to any one of claims 1-6 in the removal of solid impurities from molten aluminum.

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