Porous silicon carbide filtering material, preparation method and application

Abstract

The invention relates to the technical field of preparation of high-purity electronic aluminum alloys, in particular to a porous silicon carbide filtering material, a preparation method and application, a SiO2 thin film is formed on the surface of silicon carbide, a sintering neck is formed by utilizing the synergistic effect of the SiO2 thin film and a composite oxide sintering aid, aggregate particles are effectively connected, the bearing capacity of the sintering neck is remarkably improved, and the porous silicon carbide filtering material is prepared. The porous silicon carbide ceramic filter material has the advantages that the porous silicon carbide ceramic filter material is used as a raw material, the compressive strength and thermal shock resistance of the porous silicon carbide ceramic filter material are further improved, the service life of a filter is prolonged, small-size pores are formed by using 9Al2O3. 2B2O3 whiskers generated by in-situ reaction of aggregate particles and B2O3 and Al2O3 on the surface of a sintering neck, and the porous silicon carbide ceramic filter material with pore bimodal distribution is obtained. The pore size distribution and the porosity of the porous silicon carbide ceramic filtering material are optimized, and the problems that the pore size distribution among silicon carbide aggregates of an existing porous ceramic material is single, the overall strength is limited, and the filtering precision and the filtering service life are difficult to meet the higher aluminum melt purification requirement are solved.

Description

Technical Field

[0001] The invention relates to the technical field of high-purity electronic aluminum alloy preparation, and in particular to a porous silicon carbide filter material, a preparation method and an application thereof. Background Art

[0002] With the global low-carbon economic transformation and the rapid development of high-end manufacturing, the market demand for aluminum alloys as a key lightweight material continues to rise. High-purity electronic aluminum alloys are widely used in consumer electronics, new energy vehicles, aerospace and other fields due to their excellent electrical conductivity, thermal conductivity, corrosion resistance and processing performance. However, the performance of high-purity electronic aluminum alloys is highly dependent on their purity and inclusion content. Even trace amounts of impurity elements can significantly affect their electrical conductivity, mechanical properties and processing properties. For example, impurities such as iron and silicon can reduce the electrical conductivity of aluminum alloys, while gas impurities such as hydrogen and oxygen can cause defects such as pores and looseness, affecting the density and mechanical properties of the material. In order to meet the stringent requirements of high-end application fields for high-purity electronic aluminum alloys, aluminum melt purification technology has emerged. Aluminum melt purification technology refers to the use of physical, chemical or physical and chemical methods to remove impurity elements and gases in the melt during the aluminum alloy smelting process, thereby improving the purity of the aluminum alloy.

[0003] Porous ceramic filters can purify impurities in aluminum melt by virtue of their purification mechanism of intercepting large-sized impurities with their pore size. Among them, porous ceramics with refractory materials such as silicon carbide and alumina as the skeleton have the advantages of good thermal shock resistance, high porosity, economy and environmental protection. They are currently the most widely used porous ceramic materials for purifying aluminum melts. The performance of porous ceramic filters is closely related to their preparation process. In recent years, domestic and foreign scholars have conducted extensive research on the preparation technology of porous ceramic filters and achieved a series of results. For example, the Chinese invention with publication number CN113979772A discloses a method for preparing porous ceramics, comprising calcining 5-50% Al2O3, 5-33% SiO2, 2-50% alkaline earth metal oxides and 1-43% B2O3 at 1200-1350°C to obtain a binder, and evenly mixing 5-28 parts of the binder with 100 parts of white corundum particles, pressing and sintering to obtain a porous ceramic having the characteristics of high porosity, good strength, excellent thermal shock resistance, etc., and can be used for aluminum melt filtration; the Chinese invention with publication number CN119390451A discloses a method for preparing porous ceramics, comprising calcining 5-50% Al2O3, 5-33% SiO2, 2-50% alkaline earth metal oxides and 1-43% B2O3 at 1200-1350°C to obtain a binder, and evenly mixing 5-28 parts of the binder with 100 parts of white corundum particles, pressing and sintering to obtain a porous ceramic having the characteristics of high porosity, good strength, excellent thermal shock resistance, etc., and can be used for aluminum melt filtration; The invention discloses a preparation process of a porous ceramic filter, which uses silica sol and additives as binders; uses sulfonated lignin, polyvinyl alcohol, sodium silicate, dextrin calcium silicate cement, and carboxymethyl cellulose as additives; uses alumina, boron nitride, yttrium oxide, yttrium-stabilized zirconium oxide, and aluminum nitride as additives, and mixes large-particle silicon carbide and silicon carbide powder by dry ball milling to obtain aggregate particles, then adds additives for mixing, molding, and sintering to prepare an aluminum liquid filter with a compressive strength of >4.8MPa at a high temperature of 750°C, a porosity of which is 40%-55%, and a pore size distribution of 850-1600μm. Although the porous ceramics obtained by the above methods have the characteristics of high strength and high porosity and can meet the needs of various working conditions, their essence is to use composite oxide sintering aids to bond aggregate particles together, so that a bonding layer is formed on the surface of ceramic particles to connect the ceramic particles, thereby realizing the preparation of porous ceramic materials. The porous ceramic materials prepared in this way often make the pore size distribution between silicon carbide aggregates single and the overall strength limited. The main filtration mechanism is that different pore sizes intercept impurities of different sizes. The filtration efficiency for small-sized impurities (≤1μm) is extremely low, resulting in filtration accuracy and filtration life that are difficult to meet the higher requirements of aluminum melt purification. Summary of the invention

[0004] In view of the problems in the prior art that the pore size distribution between silicon carbide aggregates of porous ceramic materials is single, the overall strength is limited, and the filtration accuracy and filtration life are difficult to meet the higher requirements of aluminum melt purification, the present invention provides a porous silicon carbide filter material, a preparation method and an application.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions: The present invention provides a method for preparing a porous silicon carbide filter material, comprising: Pre-treating silicon carbide particles at high temperature in an air atmosphere so that the surface of the silicon carbide particles is covered with a SiO2 film to obtain aggregate particles; The aggregate particles are mixed with an organic binder and a composite oxide sintering aid, so that the organic binder and the sintering aid are evenly coated on the surface of the aggregate particles to obtain a mixed material; wherein, the composite oxide sintering aid comprises at least 40% to 50% of B2O3, 20% to 30% of Al2O3 and 10% to 15% of SiO2 by mass fraction; Mixing the mixed material with water to obtain a blank; The blanks are sequentially formed, dried and sintered at high temperature to obtain porous silicon carbide ceramic filter materials.

[0006] Optionally, in terms of mass fractions, the ratio of the aggregate particles, the organic binder and the composite oxide sintering aid is 100:(3-5):(10-25); and the ratio of the mixture to water is 100:(3-5).

[0007] Optionally, the composite oxide sintering aid further comprises, by mass percentage, 0-20% MgO, 0-20% CaO, 0-1% Na2O and 0-1% K2O.

[0008] Optionally, the particle size of B2O3 is 200-500nm, the particle size of Al2O3 is 200-500nm, the particle size of SiO2 is 200-500nm, the particle size of MgO is 200-500nm, the particle size of CaO is 200-500nm, the particle size of Na2O is 200-500nm, and the particle size of K2O is 200-500nm.

[0009] Optionally, the preparation method of the composite oxide sintering aid is: By weight, 40% to 50% of B2O3, 20% to 30% of Al2O3, 10% to 15% of SiO2, 0% to 20% of MgO, 0% to 20% of CaO, 0% to 1% of Na2O and 0% to 1% of K2O are mixed to obtain a mixed powder; Adding ZrO2 grinding balls to the mixed powder, using anhydrous ethanol as a dispersion medium, and ball-milling the mixed powder to obtain a uniformly mixed composite oxide sintering aid; Among them, during ball milling, mixed grinding balls with diameters of 5 mm, 10 mm and 15 mm were used for ball milling; the mass ratio of 5 mm, 10 mm and 15 mm was 3:4:3, and the mass ratio of the mixed grinding balls to the mixed powder was 4:1.

[0010] Optionally, the organic binder includes dextrin and ISOBAM-104, and the mass ratio of dextrin to ISOBAM-104 is (1.5-2.5): (1.5-2.5) in parts by mass.

[0011] Optionally, the high temperature pretreatment is performed at a temperature of 900° C. to 1100° C. and for a time of 0.5 to 2 h.

[0012] Optionally, the high temperature sintering method is: The dried green body is completely buried in mullite powder with a particle size of 3 to 5 mm, and the thickness of the mullite powder layer is ≥ 20 cm; The green body embedded with mullite powder is placed at 400-600°C for 1.5-3 hours, and then the temperature is raised to 800-1000°C for 3-5 hours, and then the temperature is raised to 1200-1350°C for 6-10 hours to obtain a porous silicon carbide ceramic filter material.

[0013] A porous silicon carbide filter material prepared by the above-mentioned method for preparing a porous silicon carbide filter material, wherein the porous silicon carbide filter material has a porosity of 36.54% to 48.26%, a compressive strength of 7.63 to 24.38 MPa, can filter molten metal at a working temperature of 700°C to 800°C, and has a removal rate of 92.36% to 98.64% for aluminum liquid inclusions.

[0014] For example, the porous silicon carbide filter material is used in filtration of molten metal.

[0015] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing a porous silicon carbide filter material, wherein the method comprises pre-treating silicon carbide particles at high temperature in an air atmosphere so that the surface of the silicon carbide particles is covered with a SiO2 film to obtain aggregate particles; then, mixing the aggregate particles with an organic binder and a composite oxide sintering aid so that the organic binder and the sintering aid are evenly coated on the surface of the aggregate particles to obtain a mixed material, and mixing the mixed material with water to obtain a blank; finally, the blank is sequentially formed, dried and sintered at high temperature to obtain a porous silicon carbide ceramic filter material. Among them, by pre-treating silicon carbide particles at high temperature in an air atmosphere so that the surface of the silicon carbide particles is covered with a SiO2 film, the SiO2 film can react with the subsequent composite oxide sintering aid, and the SiO2 oxide film reacts with the composite oxide sintering aid to generate a glass phase, forming a sintering neck, effectively connecting the aggregate particles, thereby significantly improving the overall strength of the ceramic filter material. Since the bond between the aggregate particles is stronger, the compressive strength and thermal shock resistance of the finally prepared porous silicon carbide ceramic filter material can withstand the high temperature and thermal shock during the pouring of aluminum melt, thus extending the service life of the filter. At the same time, the amorphous phase formed after the reaction of the sintering aid coated on the surface isolates the interface reaction between the aluminum melt and silicon carbide during filtration, avoiding the contamination of Al4C3 impurities formed by the reaction of SiC and Al, and further improving the quality of the filtered aluminum alloy; in addition, B2O3 and Al2O3 on the surface of the aggregate particles and the sintering neck between the particles react in situ to generate 9Al2O3·2B2O3 whiskers, forming small-sized pores, and finally obtaining a porous silicon carbide ceramic filter material with a bimodal distribution of pores, that is, by optimizing the pore size distribution and porosity, it can effectively intercept tiny inclusions in the aluminum melt; on the other hand, by designing the ratio of the sintering aid, the amorphous phase formed on the surface of the aggregate particles and in the sintering neck can form a liquid phase with a certain viscosity at an operating temperature of 700℃~800℃, adsorb small-sized impurity particles (≤1μm) and utilize the dual purification mechanism of pore interception and liquid phase interface adsorption, thereby improving the filtration performance of the porous silicon carbide ceramic filter material and meeting the strict requirements of the production of high-purity electronic aluminum alloy on the purity of the aluminum melt.

[0016] In terms of mass percentage, the composite oxide sintering aid also includes 0-20% MgO, 0-20% CaO, 0-1% Na2O and 0-1% K2O. The MgO and CaO can reduce the glass transition temperature of high-alumina silicon glass, thereby reducing the sintering temperature of the ceramic filter material and avoiding the formation of magnesium-alumina spinel at high temperature. On the other hand, the SiO2 film on the surface of the silicon carbide particles participates in the reaction and combines to form an amorphous phase, which improves the bearing capacity of the sintering neck, further improves the strength and thermal shock resistance of the silicon carbide ceramic filter material, and reduces the contamination of the aluminum melt by Al4C3 impurities. Na2O and K2O are alkaline oxides, which can react with the SiO2 film or other oxides at high temperature to generate a low-melting silicate glass phase. The silicate glass phase has high toughness and elasticity, and can play a buffering role when the material is subjected to thermal shock, relieve thermal stress, and thus improve the thermal shock resistance of the material. At the same time, this liquid phase can wet the surface of the silicon carbide particles during the sintering process, fill the gaps between the particles, and promote the migration and densification of materials between the particles, thereby reducing the sintering temperature.

[0017] The organic binder includes dextrin and ISOBAM-104 (isobutylene maleic anhydride copolymer, molecular weight 40000-50000), and the mass ratio of dextrin to ISOBAM-104 is (1.5-2.5): (1.5-2.5) in parts by mass. Dextrin can evenly wrap silicon carbide particles during the mixing process to form a stable bonding network, so that the mixed material has good plasticity; ISOBAM-104 can effectively disperse silicon carbide particles, prevent particle agglomeration, and ensure that the components in the mixed material are evenly distributed, thereby improving the uniformity and performance stability of the material. At the same time, a stable bonding network can be formed to improve the strength of the green body and ensure the controllability of the preparation process.

[0018] The present invention provides a porous silicon carbide filter material prepared by the preparation method of the porous silicon carbide filter material. The porous silicon carbide filter material is tested to have a porosity of 36.54% to 48.26% and a compressive strength of 7.63 to 24.38 MPa. It has high mechanical strength and compressive resistance, can withstand the impact force and static pressure during the pouring of molten metal, and avoids rupture or deformation during the filtration process. It can effectively intercept tiny inclusions (such as micron-sized oxide particles) in the molten metal at an operating temperature of 700°C to 800°C, and has a long filtration life, and can meet the extremely high requirements for the purity of the molten metal in high-end manufacturing fields such as high-purity electronic aluminum alloys, aerospace materials, and new energy vehicle parts.

[0019] For example, the application of the above-mentioned porous silicon carbide filter material in molten metal filtration, due to its higher overall strength, richer pore size distribution and pore structure, can effectively intercept tiny inclusions (such as oxides, carbides, intermetallic compounds, etc.) in the molten metal, significantly improve the purity of the molten metal, improve the mechanical properties, conductivity and corrosion resistance of high-purity electronic aluminum alloys, and meet the stringent requirements of high-end manufacturing fields on material performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of a porous silicon carbide filter material of the present invention.

[0021] Figure 2 This is a SEM image of the porous silicon carbide filter material prepared in Example 9 of the present invention.

[0022] Figure 3 This is the pore size distribution diagram of the porous silicon carbide filter material prepared in Example 9 of the present invention.

[0023] Figure 4 These are SEM images of aluminum alloy before and after filtration test of the porous silicon carbide filter material prepared in Example 9 of the present invention, wherein a is the SEM image of the aluminum alloy before filtration, and b is the SEM image of the aluminum alloy after filtration. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0025] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0026] In this article, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible sub-ranges and individual values ​​within the range (including integers and fractions).

[0027] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0028] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0029] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0030] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0031] The present invention is further described in detail below in conjunction with specific embodiments, which are intended to explain the present invention rather than to limit it.

[0032] See also Figure 1 The present invention discloses a porous silicon carbide filter material, comprising: S1: Pre-treating the silicon carbide particles at high temperature in an air atmosphere so that the surface of the silicon carbide particles is covered with a SiO2 film to obtain aggregate particles, specifically: The silicon carbide particles are heated to 900°C to 1100°C in an air furnace at a rate of 3 to 5°C / min, and kept warm for 0.5 to 2 hours to form a layer of SiO2 film on their surface. The silicon carbide particles are taken out and sieved through a 12 to 30 mesh sieve to obtain aggregate particles; preferably, the particle size of the silicon carbide particles is 400 to 1200 μm.

[0033] S2: Mixing aggregate particles with an organic binder and a composite oxide sintering aid, so that the organic binder and the sintering aid are uniformly coated on the surface of the aggregate particles to obtain a mixed material, wherein, by mass fraction, the composite oxide sintering aid comprises at least 40% to 50% of B2O3, 20% to 30% of Al2O3 and 10% to 15% of SiO2, preferably, the composite oxide sintering aid also comprises 0 to 20% of MgO, 0 to 20% of CaO, 0 to 1% of Na2O and 0 to 1% of K2O, and more preferably, MgO is 5% to 15%, and CaO is 5% to 15%. The specific operation is: The preparation method of the composite oxide sintering aid is: 40% to 50% B2O3, 20% to 30% Al2O3, 10% to 15% SiO2, 0 to 20% MgO, 0 to 20% CaO, 0 to 1% Na2O and 0 to 1% K2O are mixed to obtain a mixed powder; the particle size of the B2O3 is 200 to 500nm, the particle size of the Al2O3 is 200 to 500nm, the particle size of the SiO2 is 200 to 500nm, the particle size of the MgO is 200 to 500nm, the particle size of the CaO is 200 to 500nm, the particle size of the Na2O is 200 to 500nm, and the particle size of the K2O is 200 to 500nm; Add ZrO2 grinding balls to the mixed powder, use anhydrous ethanol as a dispersion medium, and ball-mill the mixed powder for 20 to 24 hours to obtain a uniformly mixed powder; the diameter of the ZrO2 grinding balls is a mixed grinding ball of 5mm grinding balls, 10mm grinding balls and 15mm grinding balls, the mass ratio of 5mm grinding balls, 10mm grinding balls and 15mm grinding balls is 3:4:3, the mass ratio of mixed grinding balls to mixed powder is 4:1, and the ball mill speed is 100r / min. Use rotary evaporation to remove anhydrous ethanol from the uniformly mixed powder, dry it at 80°C and keep it warm for 8 hours, and crush the powder with a fluidized bed airflow mill to obtain a composite oxide sintering aid. The particle size of the powder after crushing by the fluidized bed airflow mill is 300 to 500nm; The organic binder includes dextrin and ISOBAM-104, and the mass ratio of dextrin to ISOBAM-104 is (1.5-2.5): (1.5-2.5) by mass. 100 parts of aggregate particles, 10-25 parts of composite oxide sintering aids and 3-5 parts of organic binders, by mass, are placed in a vertical mixer and stirred for 4 hours to allow the composite oxide sintering aid and the organic binder to evenly coat the aggregate particles to obtain a mixed material.

[0034] S3: Mixing the mixed material with water to obtain a blank, specifically: 3 to 5 parts of deionized water are uniformly added to the mixed material in a spraying manner, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0035] S4: forming, drying and high-temperature sintering the blank in sequence to obtain a porous silicon carbide ceramic filter material, specifically: The blank is added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter material blank is obtained by ramming, the molding pressure is ≤3MPa, the pressure holding time is ≤2min, and the blank is placed in an oven for drying at 60°C for 24h after demolding to obtain a green blank; the green blank is buried in mullite powder with a particle size of 3-5mm, and the buried powder thickness around the green blank is ≥20cm; it is placed in an air furnace for high-temperature sintering, and is kept at 400°C-600°C for 1.5-3h, heated to 800°C-1000°C for 3-5h, and then heated to 1200°C-1350°C for 6-10h. Preferably, the heating rate is 1-3°C / min to obtain a porous silicon carbide ceramic filter material.

[0036] Example 1 Weigh 40% B2O3, 25% Al2O3, 15% SiO2, 10% MgO, 9% CaO, 0.5% Na2O and 0.5% K2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, the ball-to-material ratio is 4:1, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, the ball mill speed is 100r / min, and a mixed powder is obtained. The mixed powder is placed in a rotary evaporator to remove anhydrous ethanol, dried for 3 hours, placed in an oven, and kept warm at 80°C for 24 hours. The completely dried powder is crushed by a fluidized bed airflow mill, and the particle size of the crushed powder is 300-500nm to obtain the desired composite oxide sintering aid.

[0037] The silicon carbide particles (average particle size of 700 μm) were heated to 1000°C at a rate of 3°C / min in an air furnace and kept warm for 1 hour to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and sieved through a 24-mesh sieve to obtain aggregate particles.

[0038] Weigh 100 parts of aggregate particles, 15 parts of composite oxide sintering aid, 1.5 parts of dextrin and 1.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0039] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0040] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0041] The green body is placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm is used as buried powder. The thickness of the buried powder around the green body is 20 cm. The sintering system is: in an air atmosphere, the temperature is raised from room temperature to 600 ° C, and then kept for 2 hours, then raised to 1000 ° C, and kept for 6 hours, and finally raised to 1200 ° C, and kept for 8 hours. The heating rate is 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material is obtained. After inspection, the porosity of this porous ceramic material is 41.6%, the compressive strength is 12.84 MPa, the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles is 8.41 μm, and the removal rate of inclusions in the aluminum alloy is 93.21%.

[0042] Example 2 Weigh 45% B2O3, 25% Al2O3, 10% SiO2, 5% MgO, 14% CaO, 0.5% Na2O and 0.5% K2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, the ball-to-material ratio is 4:1, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, the ball mill speed is 100r / min, and a mixed powder is obtained. The mixed powder is placed in a rotary evaporator to remove anhydrous ethanol, dried for 3 hours, placed in an oven, and kept warm at 80°C for 24 hours. The completely dried powder is crushed by a fluidized bed airflow mill, and the particle size of the crushed powder is 300-500nm to obtain the desired composite oxide sintering aid.

[0043] The silicon carbide particles (average particle size of 1000 μm) were heated to 900°C at a rate of 5°C / min in an air furnace and kept warm for 0.5 h to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and sieved through a 15-mesh sieve to obtain aggregate particles.

[0044] Weigh 100 parts of aggregate particles, 10 parts of composite oxide sintering aid, 1.5 parts of dextrin and 1.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0045] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0046] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0047] The green body was placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm was used as buried powder. The thickness of the buried powder around the green body was 20 cm. The sintering system was: in an air atmosphere, the temperature was raised from room temperature to 600 ° C, and then kept warm for 2 hours, then raised to 1000 ° C, and kept warm for 6 hours, and finally raised to 1200 ° C, and kept warm for 8 hours. The heating rate was 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material was obtained. After inspection, the porosity of this porous ceramic material was 48.26%, the compressive strength was 7.63 MPa, and the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles was 6.72 μm.

[0048] Example 3 Weigh 40% B2O3, 29% Al2O3, 15% SiO2, 15% MgO, 0.5% Na2O and 0.5% K2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, the ball-to-material ratio is 4:1, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, the ball mill speed is 100r / min, and a mixed powder is obtained. The mixed powder is placed in a rotary evaporator to remove anhydrous ethanol, dried for 3 hours, placed in an oven, and kept warm at 80°C for 24 hours. The completely dried powder is crushed by a fluidized bed airflow mill, and the particle size of the crushed powder is 300-500nm to obtain the desired composite oxide sintering aid.

[0049] The silicon carbide particles (average particle size of 400 μm) were heated to 1100°C at a rate of 5°C / min in an air furnace and kept warm for 2 hours to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and sieved through a 30-mesh sieve to obtain aggregate particles.

[0050] Weigh 100 parts of aggregate particles, 20 parts of composite oxide sintering aid, 1.5 parts of dextrin and 1.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0051] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0052] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0053] The green body was placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm was used as buried powder. The thickness of the buried powder around the green body was 20 cm. The sintering system was: in an air atmosphere, the temperature was raised from room temperature to 600 ° C, and then kept warm for 2 hours, then raised to 1000 ° C, and kept warm for 6 hours, and finally raised to 1200 ° C, and kept warm for 8 hours. The heating rate was 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material was obtained. After inspection, the porosity of this porous ceramic material was 36.54%, the compressive strength was 24.38 MPa, the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles was 5.63 μm, and the removal rate of inclusions in the aluminum alloy was 92.36%.

[0054] Example 4 Weigh 45% B2O3, 25% Al2O3, 10% SiO2 and 20% CaO as raw materials, place them in a ball mill, add ZrO2 grinding balls, the ball-to-material ratio is 4:1, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, the ball mill speed is 100r / min, and a mixed powder is obtained. The mixed powder is placed in a rotary evaporator to remove anhydrous ethanol, dried for 3 hours, placed in an oven, and kept warm at 80°C for 24 hours. The completely dried powder is crushed by a fluidized bed airflow mill, and the particle size of the crushed powder is 300-500nm to obtain the desired composite oxide sintering aid.

[0055] The silicon carbide particles (average particle size of 700 μm) were heated to 1000°C at a rate of 5°C / min in an air furnace and kept warm for 1 hour to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and passed through a 24-mesh sieve to obtain aggregate particles.

[0056] Weigh 100 parts of aggregate particles, 15 parts of composite oxide sintering aid, 1.5 parts of dextrin and 1.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0057] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0058] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0059] The green body was placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm was used as buried powder. The thickness of the buried powder around the green body was 20 cm. The sintering system was: in an air atmosphere, the temperature was raised from room temperature to 600 ° C, and then kept warm for 2 hours, then raised to 1000 ° C, and kept warm for 6 hours, and finally raised to 1200 ° C, and kept warm for 8 hours. The heating rate was 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material was obtained. After inspection, the porosity of this porous ceramic material was 42.17%, the compressive strength was 18.68 MPa, and the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles was 7.46 μm.

[0060] Example 5 Weigh 40% B2O3, 25% Al2O3, 10% SiO2, 10% MgO, 13% CaO, 1% Na2O and 1% K2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, the ball-to-material ratio is 4:1, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, the ball mill speed is 100r / min, and a mixed powder is obtained. The mixed powder is placed in a rotary evaporator to remove anhydrous ethanol, dried for 3 hours, placed in an oven, and kept warm at 80°C for 24 hours. The completely dried powder is crushed by a fluidized bed airflow mill, and the particle size of the crushed powder is 300-500nm to obtain the desired composite oxide sintering aid.

[0061] The silicon carbide particles (average particle size of 700 μm) were heated to 1000°C at a rate of 5°C / min in an air furnace and kept warm for 1 hour to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and passed through a 24-mesh sieve to obtain aggregate particles.

[0062] Weigh 100 parts of aggregate particles, 15 parts of composite oxide sintering aid, 1.5 parts of dextrin and 1.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0063] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0064] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0065] The green body was placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm was used as buried powder. The thickness of the buried powder around the green body was 20 cm. The sintering system was: in an air atmosphere, the temperature was raised from room temperature to 600 ° C, and then kept warm for 2 hours, then raised to 1000 ° C, and kept warm for 4 hours, and finally raised to 1250 ° C, and kept warm for 8 hours. The heating rate was 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material was obtained. After inspection, the porosity of this porous ceramic material was 42.36%, the compressive strength was 23.86 MPa, and the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles was 5.36 μm.

[0066] Example 6 Weigh 40% B2O3, 30% Al2O3, 10% SiO2, 5% MgO, 14% CaO, 0.5% Na2O and 0.5% K2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, the ball-to-material ratio is 4:1, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, the ball mill speed is 100r / min, and a mixed powder is obtained. The mixed powder is placed in a rotary evaporator to remove anhydrous ethanol, dried for 3 hours, placed in an oven, and kept warm at 80°C for 24 hours. The completely dried powder is crushed by a fluidized bed airflow mill, and the particle size of the crushed powder is 300-500nm to obtain the desired composite oxide sintering aid.

[0067] The silicon carbide particles (average particle size of 700 μm) were heated to 1000°C at a rate of 4°C / min in an air furnace and kept warm for 1 hour to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and sieved through a 24-mesh sieve to obtain aggregate particles.

[0068] Weigh 100 parts of aggregate particles, 25 parts of composite oxide sintering aid, 2.5 parts of dextrin and 2.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0069] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0070] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0071] The green body was placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm was used as buried powder. The thickness of the buried powder around the green body was 20 cm. The sintering system was: in an air atmosphere, the temperature was raised from room temperature to 600 ° C, and then kept warm for 2 hours, then raised to 1000 ° C, and kept warm for 6 hours, and finally raised to 1300 ° C, and kept warm for 8 hours. The heating rate was 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material was obtained. After inspection, the porosity of this porous ceramic material was 44.0%, the compressive strength was 23.68 MPa, the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles was 9.26 μm, and the removal effect of inclusions in the aluminum alloy reached 96.72%.

[0072] Example 7 Weigh 50% B2O3, 20% Al2O3, 10% SiO2, 19% CaO, 0.5% Na2O and 0.5% K2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, the ball-to-material ratio is 4:1, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, the ball mill speed is 100r / min, and a mixed powder is obtained. The mixed powder is placed in a rotary evaporator to remove anhydrous ethanol, dried for 3 hours, placed in an oven, and kept warm at 80°C for 24 hours. The completely dried powder is crushed by a fluidized bed airflow mill, and the particle size of the crushed powder is 300-500nm to obtain the desired composite oxide sintering aid.

[0073] The silicon carbide particles (average particle size of 500 μm) were heated to 1000°C at a rate of 5°C / min in an air furnace and kept warm for 0.5 h to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and sieved through a 30-mesh sieve to obtain aggregate particles.

[0074] Weigh 100 parts of aggregate particles, 20 parts of composite oxide sintering aid, 1.5 parts of dextrin and 2.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0075] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0076] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0077] The green body was placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm was used as buried powder. The thickness of the buried powder around the green body was 20 cm. The sintering system was: in an air atmosphere, the temperature was raised from room temperature to 600 ° C, and then kept warm for 2 hours, then raised to 900 ° C, and kept warm for 6 hours, and finally raised to 1250 ° C, and kept warm for 8 hours. The heating rate was 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material was obtained. After inspection, the porosity of this porous ceramic material was 41.6%, the compressive strength was 19.26 MPa, and the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles was 6.68 μm.

[0078] Example 8 Weigh 50% B2O3, 20% Al2O3, 10% SiO2, 10% MgO, 9% CaO, 0.5% Na2O and 0.5% K2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, the ball-to-material ratio is 4:1, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, the ball mill speed is 100r / min, and a mixed powder is obtained. The mixed powder is placed in a rotary evaporator to remove anhydrous ethanol, dried for 3 hours, placed in an oven, and kept warm at 80°C for 24 hours. The completely dried powder is crushed by a fluidized bed airflow mill, and the particle size of the crushed powder is 300-500nm to obtain the desired composite oxide sintering aid.

[0079] The silicon carbide particles (average particle size of 700 μm) were heated to 1000°C at a rate of 5°C / min in an air furnace and kept warm for 1 hour to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and passed through a 24-mesh sieve to obtain aggregate particles.

[0080] Weigh 100 parts of aggregate particles, 15 parts of composite oxide sintering aid, 3 parts of dextrin and 1.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0081] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0082] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0083] The green body is placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm is used as buried powder. The thickness of the buried powder around the green body is 20 cm. The sintering system is: in an air atmosphere, the temperature is raised from room temperature to 600 ° C, and then kept for 2 hours, then raised to 1000 ° C, and kept for 6 hours, and finally raised to 1300 ° C, and kept for 8 hours. The heating rate is 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material is obtained. After inspection, the porosity of this porous ceramic material is 42.36%, the compressive strength is 22.59 MPa, the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles is 7.88 μm, and the removal rate of inclusions in the aluminum alloy is 98.64%.

[0084] Example 9 Weigh 50% B2O3, 20% Al2O3, 10% SiO2, 10% MgO, 9% CaO, 0.5% Na2O and 0.5% K2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, the ball-to-material ratio is 4:1, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, the ball mill speed is 100r / min, and a mixed powder is obtained. The mixed powder is placed in a rotary evaporator to remove anhydrous ethanol, dried for 3 hours, placed in an oven, and kept warm at 80°C for 24 hours. The completely dried powder is crushed by a fluidized bed airflow mill, and the particle size of the crushed powder is 300-500nm to obtain the desired composite oxide sintering aid.

[0085] The silicon carbide particles (average particle size of 700 μm) were heated to 1000°C at a rate of 5°C / min in an air furnace and kept warm for 1 hour to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and passed through a 24-mesh sieve to obtain aggregate particles.

[0086] Weigh 100 parts of aggregate particles, 15 parts of composite oxide sintering aid, 1.5 parts of dextrin and 2.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0087] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0088] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0089] The green body was placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm was used as buried powder. The thickness of the buried powder around the green body was 20 cm. The sintering system was: in an air atmosphere, the temperature was raised from room temperature to 600 ° C, and then kept warm for 2 hours, then raised to 1000 ° C, and kept warm for 6 hours, and finally raised to 1250 ° C, and kept warm for 8 hours. The heating rate was 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material was obtained. After inspection, the porosity of this porous ceramic material was 45.12%, the compressive strength was 16.74 MPa, and the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles was 8.77 μm.

[0090] Example 10 Weigh 40% B2O3, 29% Al2O3, 10% SiO2, 5% MgO, 15% CaO and 1% Na2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, and the ball mill speed is 150r / min to obtain a mixed powder. Place the mixed powder in a rotary evaporator to remove anhydrous ethanol, dry it for 3 hours, and 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 composite oxide sintering aid.

[0091] The silicon carbide particles (average particle size of 700 μm) were heated to 1000°C at a rate of 3°C / min in an air furnace and kept warm for 1 hour to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and sieved through a 24-mesh sieve to obtain aggregate particles.

[0092] Weigh 100 parts of aggregate particles, 25 parts of composite oxide sintering aid, 2.5 parts of dextrin and 2.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0093] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0094] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0095] The green body was placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm was used as buried powder. The thickness of the buried powder around the green body was 20 cm. The sintering system was: in an air atmosphere, the temperature was raised from room temperature to 600 ° C, and then kept warm for 2 hours, then raised to 1000 ° C, and kept warm for 6 hours, and finally raised to 1350 ° C, and kept warm for 8 hours. The heating rate was 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material was obtained. After inspection, the porosity of this porous ceramic material was 41.16%, the compressive strength was 9.84 MPa, and the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles was 9.26 μm.

[0096] Embodiment 11 Weigh 44% B2O3, 22% Al2O3, 14% SiO2, 9% MgO, 10% CaO and 1% K2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, the ball-to-material ratio is 4:1, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, and the ball mill speed is 100r / min to obtain a mixed powder. Place the evenly mixed powder in a rotary evaporator to remove anhydrous ethanol, dry it for 3 hours, place it in an oven, and keep it warm at 80°C for 24 hours. Use a fluidized bed airflow mill to crush the completely dried powder. The powder particle size after crushing is 300-500nm to obtain the desired composite oxide sintering aid.

[0097] The silicon carbide particles (average particle size of 700 μm) were heated to 1000°C at a rate of 5°C / min in an air furnace and kept warm for 1 hour to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and passed through a 24-mesh sieve to obtain aggregate particles.

[0098] Weigh 100 parts of aggregate particles, 15 parts of composite oxide sintering aid, 1.5 parts of dextrin and 1.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0099] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0100] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0101] The green body was placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm was used as buried powder. The thickness of the buried powder around the green body was 20 cm. The sintering system was: in an air atmosphere, the temperature was raised from room temperature to 600 ° C, and then kept for 2 hours, then raised to 950 ° C, and kept for 6 hours, and finally raised to 1350 ° C, and kept for 8 hours. The heating rate was 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material was obtained. After inspection, the porosity of this porous ceramic material was 44.16%, the compressive strength was 18.64 MPa, the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles was 8.92 μm, and the removal rate of inclusions in the aluminum alloy was 95.47%.

[0102] Example 12 Weigh 45% B2O3, 20% Al2O3, 10% SiO2, 10% MgO, 14% CaO, 0.5% Na2O and 0.5% K2O as raw materials, place them in a ball mill, add ZrO2 grinding balls, use anhydrous ethanol as the dispersion medium, place them on a planetary ball mill for 24 hours, and the ball mill speed is 150r / min to obtain a mixed powder. Place the evenly mixed powder in a rotary evaporator to remove anhydrous ethanol, dry it for 3 hours, place it in an oven, and keep it warm at 80℃ for 24 hours. Pass the completely dried powder through a 200-mesh sieve to obtain the desired composite oxide sintering aid.

[0103] The silicon carbide particles (average particle size of 1000 μm) were heated to 1000°C at a rate of 5°C / min in an air furnace and kept warm for 0.5 h to form a layer of SiO2 film on the surface. The silicon carbide particles were taken out and passed through an 18-mesh sieve to obtain aggregate particles.

[0104] Weigh 100 parts of aggregate particles, 20 parts of composite oxide sintering aid, 1.5 parts of dextrin and 1.5 parts of ISOBAM-104, place in a vertical mixer, and mechanically stir for 4 hours to obtain silicon carbide aggregate particles in which the composite oxide sintering aid and the binder are uniformly coated with the composite oxide sintering aid.

[0105] The aggregate particles uniformly coated with the composite oxide sintering aid and the binder are mixed with deionized water in a mass ratio of 100:5, and mechanically stirred for 10 to 20 minutes to obtain a blank with good fluidity.

[0106] The blank was added to the mold at a uniform speed, and a tubular silicon carbide ceramic filter blank was obtained by ramming and molding, and the molding pressure was 3 MPa. After demolding, the blank was placed in an oven and dried at 60° C. for 24 hours to obtain a green body.

[0107] The green body was placed in an alumina crucible, and mullite with a particle size of 3 to 5 mm was used as buried powder. The thickness of the buried powder around the green body was 20 cm. The sintering system was: in an air atmosphere, the temperature was raised from room temperature to 600 ° C, and then kept warm for 2 hours, then raised to 1000 ° C, and kept warm for 6 hours, and finally raised to 1250 ° C, and kept warm for 8 hours. The heating rate was 1 ° C / min, and the silicon carbide ceramic porous silicon carbide filter material was obtained. After inspection, the porosity of this porous ceramic material was 43.74%, the compressive strength was 16.24 MPa, and the average length of the 9Al2O3·2B2O3 whiskers on the surface of the aggregate particles was 7.95 μm.

[0108] It should be noted that, among the raw material components added in the above embodiments, the particle size of B2O3 is 200-500nm, the particle size of Al2O3 is 200-500nm, the particle size of SiO2 is 200-500nm, the particle size of MgO is 200-500nm, the particle size of CaO is 200-500nm, the particle size of Na2O is 200-500nm, and the particle size of K2O is 200-500nm; the removal rates of inclusions in the aluminum alloy described in the above embodiments are determined by comparing the SEM images of the aluminum alloy before and after filtration, statistically analyzing the changes in the proportion of inclusions on the surface of the aluminum alloy, and quantitatively analyzing the percentage of filtered inclusions.

[0109] In order to verify the properties of the porous silicon carbide filter material prepared by the present invention, the prepared porous silicon carbide filter material was subjected to SEM testing, see Figure 2 Due to the effect of inorganic binder, SiO2 on the surface of silicon carbide particles participates in the reaction and connects with each other after sintering at high temperature to synthesize whiskers with a length of about 8.41μm and an aspect ratio of about 10. At the same time, it has small pores, i.e. pores of the order of <1μm. Figure 3 This porous silicon carbide filter material has two pore sizes, mainly 0.5-4μm and 200-300μm. The pore size has a bimodal distribution feature, which can capture impurities of different sizes; and the sintering aid designed by the ratio can form a suitable amorphous phase, with a certain viscosity at a working temperature of 700℃-800℃, to achieve an interface capture effect, which meets the designed dual capture filtration effect of aluminum liquid impurities; see Figure 4 From the SEM images before and after the aluminum alloy filtration, it was found that after passing through the porous silicon carbide filter material, the larger inclusions (>1μm) in the aluminum alloy were completely removed, and the small inclusions (≤1μm) were removed by more than 50%, and the overall inclusion removal rate reached more than 92%; it can be seen that the porous silicon carbide filter material prepared by the present invention has a stronger overall structure, richer porosity and pore length, and thus has a better filtration effect and a longer filtration life.

[0110] The present invention provides a porous silicon carbide filter material prepared by the preparation method of the porous silicon carbide filter material. The porosity of the porous silicon carbide filter material is 36.54% to 48.26%, and the compression strength is 7.63 to 24.38 MPa. The porous silicon carbide filter material has high mechanical strength and compressive strength, can withstand the impact force and static pressure in the process of molten metal pouring, avoid cracking or deformation in the filtration process, can effectively intercept tiny inclusions (such as micron-sized oxide particles) in the molten metal at an operating temperature of 700°C to 800°C, and has a long filtration life, which can meet the extremely high requirements for the purity of the molten metal in high-end manufacturing fields such as high-purity electronic aluminum alloys, aerospace materials, and new energy vehicle parts.

[0111] For example, the application of the above-mentioned porous silicon carbide filter material in molten metal filtration, due to its higher overall strength, richer pore size distribution and pore structure, can effectively intercept tiny inclusions (such as oxides, carbides, intermetallic compounds, etc.) in the molten metal, significantly improve the purity of the molten metal, improve the mechanical properties, conductivity and corrosion resistance of high-purity electronic aluminum alloys, and meet the stringent requirements of high-end manufacturing fields on material performance.

[0112] In summary, the present invention provides a porous silicon carbide filter material, a preparation method and an application thereof. A SiO2 film is formed on the surface of silicon carbide, and a sintering neck is formed by utilizing the synergistic effect of the SiO2 film and a composite oxide sintering aid, thereby effectively connecting aggregate particles and significantly improving the bearing capacity of the sintering neck, thereby improving the compressive strength and thermal shock resistance of the porous silicon carbide ceramic filter material, and extending the service life of the filter. At the same time, 9Al2O3·2B2O3 whiskers generated by the in-situ reaction of B2O3 and Al2O3 on the surface of the sintering neck between aggregate particles and particles are used to form small-sized pores, thereby obtaining a porous silicon carbide ceramic filter material with a bimodal distribution of pores, thereby optimizing the pore size distribution and porosity of the porous silicon carbide ceramic filter material, so that the finally prepared porous silicon carbide filter material has high strength, high filtration accuracy, excellent chemical stability and thermal shock resistance, can significantly improve the purification effect of aluminum melt, and meet the stringent requirements of high-purity electronic aluminum alloy production on the purity of aluminum melt. The above description is only a preferred embodiment of the present invention and is not intended to impose any limitation on the technical solution of the present invention. Those skilled in the art should understand that, without departing from the spirit and principles of the present invention, the technical solution can also be subjected to several simple modifications and substitutions, and these modifications and substitutions are also within the scope of protection covered by the claims.

Claims

1. A method for preparing a porous silicon carbide filter material, characterized in that: include: Pre-treating silicon carbide particles at high temperature in an air atmosphere so that the surface of the silicon carbide particles is covered with a SiO2 film to obtain aggregate particles; The aggregate particles are mixed with an organic binder and a composite oxide sintering aid, so that the organic binder and the sintering aid are evenly coated on the surface of the aggregate particles to obtain a mixed material; wherein, the composite oxide sintering aid comprises at least 40% to 50% of B2O3, 20% to 30% of Al2O3 and 10% to 15% of SiO2 by mass fraction; Mixing the mixed material with water to obtain a blank; The blanks are sequentially formed, dried and sintered at high temperature to obtain porous silicon carbide ceramic filter materials.

2. The method for preparing the porous silicon carbide filter material according to claim 1, characterized in that: In terms of mass fractions, the ratio of the aggregate particles, the organic binder and the composite oxide sintering aid is 100:(3-5):(10-25); the ratio of the mixed material to water is 100:(3-5).

3. The method for preparing the porous silicon carbide filter material according to claim 1, characterized in that: In terms of mass percentage, the composite oxide sintering aid further includes 0-20% MgO, 0-20% CaO, 0-1% Na2O and 0-1% K2O.

4. The method for preparing the porous silicon carbide filter material according to claim 3, characterized in that: The particle size of B2O3 is 200-500nm, the particle size of Al2O3 is 200-500nm, the particle size of SiO2 is 200-500nm, the particle size of MgO is 200-500nm, the particle size of CaO is 200-500nm, the particle size of Na2O is 200-500nm, and the particle size of K2O is 200-500nm.

5. The method for preparing the porous silicon carbide filter material according to claim 3, characterized in that: The preparation method of the composite oxide sintering aid is: By weight, 40% to 50% of B2O3, 20% to 30% of Al2O3, 10% to 15% of SiO2, 0% to 20% of MgO, 0% to 20% of CaO, 0% to 1% of Na2O and 0% to 1% of K2O are mixed to obtain a mixed powder; Adding ZrO2 grinding balls to the mixed powder, using anhydrous ethanol as a dispersion medium, and ball-milling the mixed powder to obtain a uniformly mixed composite oxide sintering aid; Among them, during ball milling, mixed grinding balls with diameters of 5 mm, 10 mm and 15 mm were used for ball milling; the mass ratio of 5 mm, 10 mm and 15 mm was 3:4:3, and the mass ratio of the mixed grinding balls to the mixed powder was 4:

1.

6. The method for preparing a porous silicon carbide filter material according to claim 1, characterized in that: The organic binder includes dextrin and ISOBAM-104. In terms of mass fractions, the mass ratio of dextrin to ISOBAM-104 is (1.5-2.5): (1.5-2.5).

7. The method for preparing a porous silicon carbide filter material according to claim 1, characterized in that: The temperature of the high temperature pretreatment is 900° C. to 1100° C., and the time is 0.5 to 2 hours.

8. The method for preparing a porous silicon carbide filter material according to claim 1, characterized in that: The high temperature sintering method is: The dried green body is completely buried in mullite powder with a particle size of 3 to 5 mm, and the thickness of the mullite powder layer is ≥ 20 cm; The green body embedded with mullite powder is placed at 400-600°C for 1.5-3 hours, and then the temperature is raised to 800-1000°C for 3-5 hours, and then the temperature is raised to 1200-1350°C for 6-10 hours to obtain a porous silicon carbide ceramic filter material.

9. A porous silicon carbide filter material prepared by the method for preparing a porous silicon carbide filter material according to any one of claims 1 to 8, characterized in that: The porous silicon carbide filter material has a porosity of 36.54% to 48.26% and a compressive strength of 7.63 to 24.38 MPa. It can filter molten metal at a working temperature of 700° C. to 800° C., and has a removal rate of 92.36% to 98.64% for aluminum liquid inclusions.

10. Use of the porous silicon carbide filter material as claimed in claim 9 in filtering molten metal.

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