A CaO-ZrO2 porous ceramic filter, its preparation method and application

Abstract

The application belongs to the technical field of liquid metal purification, and provides a CaO-ZrO2 porous ceramic filter and a preparation method and application thereof. The application obtains a preform by impregnating a reticular porous template in slurry A and drying; sprays slurry B on the preform to obtain an embryo, and obtains the CaO-ZrO2 porous ceramic filter after calcination. The application adopts a template replication method-air spraying-in-situ sintering technology, and has the advantages of simple preparation process and low cost. The slurry B is attached to the surface of the zirconia hole rib through the air spraying process on the preform, defects are filled, and the CaO-ZrO2 composite hole rib is constructed. The composite hole rib improves the mechanical properties, thermal shock resistance and non-metallic inclusion adsorption efficiency in the molten metal liquid. The application can be used in the molten metal filtering environment of 1600 DEG C to 1800 DEG C.

Description

Technical Field

[0001] This invention relates to the field of liquid metal purification technology, and in particular to a CaO-ZrO2 porous ceramic filter, its preparation method, and its application. Background Technology

[0002] Filtration of non-metallic inclusions in molten metal plays a crucial role in improving the quality and performance of castings. Currently, most filters used for molten metal filtration are high-temperature resistant porous ceramic filters. These filters effectively intercept non-metallic inclusions in molten metal through mechanical interception and deep adsorption mechanisms. They also regulate the flow of scum, transforming turbulent flow into laminar flow, preventing secondary optimization and thus purifying and homogenizing the metal. Ceramic filters are widely used in the production processes of automotive parts, diesel engine parts, compressors, wind power castings, and large castings in the metallurgical industry. They have significantly improved the quality and competitiveness of Chinese castings, increased the profits of casting enterprises, and are of great significance for improving energy efficiency and reducing carbon emissions in my country.

[0003] Ceramic filters can be classified into foam ceramic filters and straight-pore ceramic filters according to their structure; according to their material, they are mainly made of zirconia, alumina, silicon carbide, and magnesium oxide; and according to their filtration method, they can be divided into direct filters and reaction filters. Zirconia ceramic filters, due to their excellent high-temperature resistance, corrosion resistance, high strength, and good thermal shock resistance, have become the preferred filters for special steels, high-value-added steels, or alloy castings. Calcium oxide filters, due to their excellent thermodynamic stability, desulfurization and dephosphorization performance, and carbon adsorption performance, are often used as reaction filters. However, calcium oxide particles are highly susceptible to hydration, making their storage and preparation extremely difficult. Currently, neither zirconia nor calcium oxide porous ceramic filters can simultaneously satisfy the requirements of simple processing and excellent performance.

[0004] Currently, technicians have conducted in-depth research and technological development to solve the comprehensive performance problems of ceramic filters. For example, Chinese patent application number CN201210115537.3 discloses a special zirconia foam ceramic filter with high high-temperature strength and good thermal shock resistance, and its preparation method. This method involves adding a large amount of nano-zirconia, a small amount of nano-zirconia, and trace amounts of calcium oxide, magnesium oxide, and aluminum oxide to zirconia, followed by ball milling, slurry coating, and high-temperature sintering in a nitriding furnace to obtain a high-strength, thermally shock-resistant zirconia porous ceramic filter. Adding nano-zirconia promotes sintering and improves thermal shock stability. Nano-zirconia generates ZrN under a nitrogen atmosphere, utilizing the good plasticity and toughness of metallic materials to mutually wet and encapsulate with the ceramic, penetrating into the gaps between the ceramic phases to form a continuous film structure, strengthening toughness and improving thermal shock resistance. However, this technology requires sintering at a high temperature of 1850℃ under a controlled nitrogen atmosphere, which not only consumes a lot of energy but also has a relatively complex process, significantly increasing the preparation cost of zirconia porous ceramics; therefore, it is not suitable as an industrial production method for zirconia porous ceramic filters. For example, Chinese patent application CN201911404444.0 discloses a method for preparing a zirconia-based foam ceramic filter. Its characteristic is the addition of magnesium oxide and cerium oxide during the electrofusion of zirconia, controlling the cooling process to eliminate the volume effect of the zirconia material, promote slow grain growth, and thus improve and stabilize its mechanical strength and high-temperature mechanical properties. Then, the electrofused zirconia is mixed with trace amounts of tungsten carbide and sintered to improve its high-temperature erosion resistance. While this method effectively improves the mechanical strength and high-temperature erosion resistance of zirconia ceramic filters, the preparation process is complex, requiring an electric arc furnace for electrofusion of zirconia and an argon furnace to provide an argon atmosphere for sintering, resulting in huge energy consumption and failing to meet the important energy conservation and emission reduction targets of the metallurgical industry. For instance, Chinese patent application CN201710034200.2 discloses a calcium oxide filter and its preparation method, characterized by the addition of a small amount of zirconia to calcium oxide to increase toughness, the use of anhydrous resin or paraffin to coat the surface of calcium oxide particles to form a protective film, followed by pressing and sintering. This technology features high operating temperature, stable high-temperature performance, and good resistance to hydration, but the filters produced have low porosity, poor strength, and low filtration efficiency.

[0005] Therefore, how to provide a CaO-ZrO2 porous ceramic filter with excellent comprehensive performance that can be applied to the filtration of high-temperature molten metal has become an urgent problem to be solved by those skilled in the art. Summary of the Invention

[0006] In view of this, the present invention provides a CaO-ZrO2 porous ceramic filter, its preparation method, and its application. Its purpose is to solve the technical problems of existing ceramic filters, such as complex processes, low strength, and low filtration efficiency.

[0007] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0008] This invention provides a method for preparing a CaO-ZrO2 porous ceramic filter, comprising the following steps:

[0009] S1. Powder A, polycarboxylate, carboxymethyl cellulose, binder A and water are mixed and then ball-milled to obtain slurry A;

[0010] Powder B, polycarboxylate, binder B and water are mixed and then ball-milled to obtain slurry B;

[0011] S2. The mesh porous template is immersed in slurry A, and then subjected to slurry spinning, primary drying, and secondary drying in sequence to obtain the zirconia porous ceramic preform.

[0012] S3. Spray slurry B onto a zirconia porous ceramic preform and dry it to obtain a CaO-ZrO2 porous ceramic green body.

[0013] S4. The CaO-ZrO2 porous ceramic green body is sintered to obtain the CaO-ZrO2 porous ceramic filter.

[0014] Furthermore, in step S1, powder A comprises zirconium oxide with fine, medium, and coarse particle sizes in a mass ratio of 10–20:20–30:50–70; and fine-particle-size D... 50 The D particle size is 0.5–1 μm, which is medium. 50 The D particle size is 3–8 μm, with a coarse particle size. 50 The size is 30–50 μm; the zirconium oxide includes one or more of yttrium-stabilized zirconium oxide, magnesium-stabilized zirconium oxide, and cerium-stabilized zirconium oxide.

[0015] Furthermore, in step S1, during the preparation of slurry A, the amount of polycarboxylate used is 0.5–1.5 wt% of powder A, the amount of carboxymethyl cellulose used is 0.2–0.8 wt% of powder A, the amount of binder A used is 10–20 wt% of powder A, and the amount of water used is 25–35 wt% of powder A; binder A includes zirconium sol; the ball milling time is 1–4 h.

[0016] Further, in step S1, in the preparation of slurry B, the amount of polycarboxylate used is 0.5-1.5 wt% of powder B, the amount of binder B used is 2-5 wt% of powder B, and the amount of water used is 23-46 wt% of powder A; powder B includes calcium carbonate and nano-sized zirconium oxide, and the mass ratio of calcium carbonate to nano-sized zirconium oxide is 80-95:5-20; the D of the nano-sized zirconium oxide... 50 The wavelength is 40–60 nm; binder B includes starch and dextrin; the ball milling time is 4–8 h.

[0017] Furthermore, in step S2, the material of the mesh porous template includes polyurethane, 3D printing resin, or nylon; the structure of the mesh porous template is three layers of gradient holes, with the hole diameters divided into large, medium, and small from the outside to the inside, the large hole diameter being 2-3 mm, the medium hole diameter being 1.2-1.5 mm, and the small hole diameter being 0.5-1 mm; the immersion time is 20-60 min.

[0018] Furthermore, in step S2, the temperature for the first drying is 20–30°C, and the drying time is 12–18 hours; the temperature for the second drying is 80–110°C, and the drying time is 24–48 hours.

[0019] Furthermore, in step S3, the amount of slurry B sprayed is 8-12 g / m³. 2 The spraying rate is 0.5–3.5 m / min; the drying temperature is 80–110 °C, and the drying time is 12–24 h.

[0020] Furthermore, in step S4, the sintering temperature is 1200–1500°C, the sintering time is 1–5 h, and the heating rate from room temperature to the sintering temperature is 2–5°C / min.

[0021] This invention provides a CaO-ZrO2 porous ceramic filter prepared by the above preparation method.

[0022] The present invention also provides the application of the above-mentioned CaO-ZrO2 porous ceramic filter in the filtration of high-temperature molten metal.

[0023] As can be seen from the above technical solution, compared with the prior art, the beneficial effects of the present invention are as follows:

[0024] This invention provides a CaO-ZrO2 porous ceramic filter, its preparation method, and its application. The process includes the following steps: impregnating a mesh porous template in slurry A and then drying it to obtain a preform; spraying slurry B onto the preform to obtain a green body; and calcining the green body to obtain the CaO-ZrO2 porous ceramic filter.

[0025] This invention features simple process and low cost. The products made have high strength at room temperature, high strength at high temperature, excellent thermal shock resistance, good filtration efficiency, and high filtration accuracy, and can be used in molten metal filtration environments of 1600-1800℃.

[0026] The CaO-ZrO2 porous ceramic prepared by this invention exhibits excellent strength at both room temperature and high temperature. First, this invention utilizes a rational particle size distribution to fill the gaps between large particles with small and medium particles, while releasing free water between these gaps. This results in a slurry with a density closest to the required bulk density, reducing slurry viscosity, improving rheological properties, and increasing solids content. Good flowability allows the slurry to adhere uniformly to the porous mesh template, reducing defect formation. The high solids content of the slurry increases the density of the green body, thus enhancing the strength of the CaO-ZrO2 porous ceramic. Second, the raw materials used in this invention are yttrium / magnesium / cerium stabilized zirconium oxide fine powder and calcium carbonate, without the addition of sintering aids. After high-temperature sintering, a CaO-ZrO2 porous ceramic is formed with a zirconium oxide phase as the matrix and a calcium zirconate-calcium oxide phase as the coating. The formation of calcium zirconate not only connects and covers the calcium oxide formed from the decomposition of calcium carbonate, increasing the green body density and strength, but also fills some micropores, slowing down the hydration rate. Third, nano-zirconia in slurry B can mix more uniformly with calcium carbonate. Air spraying allows the mixed slurry to adhere to the surface of the pores, filling and repairing defects in the zirconia preform. During high-temperature sintering, the finer zirconia particles are more active and can more easily fill the pores formed by the high-temperature decomposition of calcium carbonate particles, forming calcium zirconate in situ, resulting in wider and thicker sintering necks between CaO particles and a tighter bond. Therefore, the prepared CaO-ZrO2 porous ceramic exhibits good strength at both room temperature and high temperature.

[0027] The CaO-ZrO2 porous ceramic prepared by this invention exhibits excellent thermal shock resistance. First, during the sintering cooling process, residual compressive stress forms on the surface of the calcium zirconate-calcium oxide coating within the composite structure's pores because the linear expansion coefficient of the calcium zirconate-calcium oxide coating is lower than that of the zirconium oxide framework layer. This residual compressive stress effectively inhibits the initiation and propagation of cracks caused by thermal stress, thus significantly improving the thermal shock resistance of the CaO-ZrO2 porous ceramic. Second, calcium carbonate and dextrin decompose at high temperatures to form calcium oxide and numerous micropores, enabling the material to passivate crack tips and hinder further propagation of thermal stress cracks during thermal shock. Third, nano-zirconia can uniformly fill CaO grains, increasing the material's bulk density and forming calcium zirconate in situ around calcium oxide, thickening and enlarging the sintering necks between calcium oxide particles, thereby increasing the material's strength and improving its thermal shock resistance. Therefore, the prepared CaO-ZrO2 porous ceramic possesses excellent thermal shock resistance.

[0028] The CaO-ZrO2 porous ceramic prepared by this invention exhibits excellent filtration efficiency and precision. First, the calcium zirconate-calcium oxide coating possesses a strong adsorption capacity for non-metallic inclusions in molten metal. It reacts with neutral and acidic oxides in the molten metal to form a dense and continuous calcium aluminate interface layer, enabling the adsorption of active elements such as sulfur, phosphorus, aluminum, and titanium in the molten metal, as well as micro-control of the alloy composition. It also prevents structural spalling caused by the molten metal penetrating the material's pores and cracks. Second, during the formation of the calcium zirconate-calcium oxide coating, calcium carbonate decomposes, dextrin burns off, and calcium oxide reacts and sinters with nano-zirconia, resulting in numerous micropores on the coating surface. These micropores not only increase the surface roughness of the CaO-ZrO2 porous ceramic, increasing the contact area with the molten metal, reducing wettability, and increasing the contact angle with the molten metal, but also enhance the material's reactivity, promoting reaction with inclusions and increasing the adhesion points for inclusion adsorption and deposition, making it easier for fine inclusions to be adsorbed by the filter. Fourth, the mesh porous template used in this invention has a three-layer gradient pore structure. Compared with traditional disordered pore porous ceramic filters, the three-layer gradient pores are less prone to clogging when filtering molten metal, resulting in better filtration efficiency. Compared with traditional uniform pore size ceramic filters, the three-layer gradient pores can filter more fine inclusions, resulting in higher filtration precision. Therefore, the prepared CaO-ZrO2 porous ceramic has good filtration efficiency and filtration precision.

[0029] The CaO-ZrO2 porous ceramics prepared by this invention are lower in cost and simpler to process. The method used in this invention to prepare the CaO-ZrO2 porous ceramics is a template replication method, which involves coating a slurry onto the surface of a 3D-printed paraffin, resin, or organic polymer template, followed by template burn-off, to prepare the CaO-ZrO2 porous ceramics. Compared to self-foaming and injection molding processes, the template replication method involved in this invention is simpler, lower in cost, and more efficient, enabling large-scale industrial production.

[0030] In summary, this invention employs zirconia slurry coating, composite slurry spraying, and high-temperature in-situ sintering techniques. Based on the pre-firing of zirconia foam ceramic, a mixed slurry of fine zirconia powder and calcium carbonate is adhered to the surface of the pores via air spraying, filling and repairing defects in the zirconia pores. Finally, high-temperature sintering forms a CaO-ZrO2 porous ceramic filter with composite pores (calcium zirconate-calcium oxide coating, zirconia matrix). The formation of the composite pore structure significantly improves the room temperature / high temperature strength, thermal shock resistance, and adsorption efficiency of non-metallic inclusions in molten metal of the prepared CaO-ZrO2 porous ceramic filter.

[0031] Testing revealed that the CaO-ZrO2 porous ceramic filter prepared by this invention exhibits a high-temperature resistance exceeding 1800℃; a room-temperature compressive strength between 3.2 and 4.2 MPa; a high-temperature (1400℃) strength between 3.0 and 4.0 MPa; and a 1100℃ oil-cooling cycle life of 5 to 10 times. The prepared CaO-ZrO2 porous ceramic filter, when used for molten metal filtration, can increase the casting yield by up to 15%. Attached Figure Description

[0032] Figure 1 SEM image of the fracture surface of the CaO-ZrO2 porous ceramic filter prepared in Example 1;

[0033] Figure 2 The image shows a SEM image of the coating surface of the CaO-ZrO2 porous ceramic filter prepared in Example 1. Detailed Implementation

[0034] This invention provides a method for preparing a CaO-ZrO2 porous ceramic filter, comprising the following steps:

[0035] S1. Powder A, polycarboxylate, carboxymethyl cellulose, binder A and water are mixed and then ball-milled to obtain slurry A;

[0036] Powder B, polycarboxylate, binder B and water are mixed and then ball-milled to obtain slurry B;

[0037] S2. The mesh porous template is immersed in slurry A, and then subjected to slurry spinning, primary drying, and secondary drying in sequence to obtain the zirconia porous ceramic preform.

[0038] S3. Spray slurry B onto a zirconia porous ceramic preform and dry it to obtain a CaO-ZrO2 porous ceramic green body.

[0039] S4. The CaO-ZrO2 porous ceramic green body is sintered to obtain the CaO-ZrO2 porous ceramic filter.

[0040] In this invention, in step S1, powder A includes zirconium oxide with fine, medium, and coarse particle sizes in a mass ratio of 10-20:20-30:50-70, preferably 13:23:64; fine-particle-size D... 50 The particle size is 0.5–1 μm, preferably 0.6–0.9 μm, and more preferably 0.7–0.8 μm; the D of the medium particle size 50 The particle size is 3–8 μm, preferably 4–7 μm, and more preferably 5–6 μm; the coarse particle size D 50 The micrometer size is 30–50 μm, preferably 35–45 μm, and more preferably 40 μm; the zirconium oxide includes one or more of yttrium-stabilized zirconium oxide, magnesium-stabilized zirconium oxide, and cerium-stabilized zirconium oxide.

[0041] In this invention, in step S1, the Y2O3 content in yttrium-stabilized zirconium oxide is preferably 4-10%, the CeO2 content in cerium-stabilized zirconium oxide is preferably 5-15%, and the MgO content in magnesium-stabilized zirconium oxide is preferably 5-10%.

[0042] In this invention, in step S1, during the preparation of slurry A, the amount of polycarboxylate used is 0.5-1.5 wt% of powder A, preferably 0.8-1.2 wt%, more preferably 1.0 wt%; the amount of carboxymethyl cellulose used is 0.2-0.8 wt% of powder A, preferably 0.4-0.6 wt%, more preferably 0.5 wt%; the amount of binder A used is 10-20 wt% of powder A, preferably 12-18 wt%, more preferably 14-16 wt%; the amount of water used is 25-35 wt% of powder A, preferably 27-32 wt%, more preferably 30 wt%; binder A includes zirconium sol; the ball milling time is 1-4 h, preferably 2-3 h.

[0043] In this invention, in step S1, during the preparation of slurry B, the amount of polycarboxylate used is 0.5–1.5 wt% of powder B, preferably 0.8–1.2 wt%, more preferably 1.0 wt%; the amount of binder B used is 2–5 wt% of powder B, preferably 3–4 wt%; the amount of water used is 23–46 wt% of powder A, preferably 25–40 wt%, more preferably 30–35 wt%; powder B comprises calcium carbonate and nano-sized zirconium oxide, the mass ratio of calcium carbonate to nano-sized zirconium oxide is 80–95:5–20, preferably 83–92:8–17, more preferably 85–90:10–15; the average particle size of calcium carbonate is preferably ≤5 μm, and the purity of calcium carbonate is ≥98.5%; the D of the nano-sized zirconium oxide... 50 The wavelength is 40–60 nm, preferably D. 50 =50nm; binder B includes starch and dextrin; ball milling time is 4-8h, preferably 5-7h, and more preferably 6h.

[0044] In this invention, in step S2, the material of the mesh porous template includes polyurethane, 3D printing resin, or nylon; the structure of the mesh porous template is three layers of gradient holes, with the hole diameters divided into large, medium, and small from the outside to the inside, the large hole diameter being 2-3 mm, the medium hole diameter being 1.2-1.5 mm, and the small hole diameter being 0.5-1 mm; the polyurethane template is preferably a three-layer hole with 10 PPI-20 PPI-30 PPI, and the 3D printing resin template is preferably a three-layer hole with 2.5 mm-1.3 mm-0.8 mm; the immersion time is 20-60 min, preferably 30-50 min, and more preferably 40 min.

[0045] In this invention, in step S2, the temperature of the first drying is 20-30°C, preferably 22-28°C, and more preferably 24-26°C; the drying time is 12-18 hours, preferably 14-16 hours; the temperature of the second drying is 80-110°C, preferably 90-100°C; and the drying time is 24-48 hours, preferably 30-40 hours, and more preferably 35 hours.

[0046] In this invention, in step S2, the slurry is preferably slurryed by extrusion or centrifugation.

[0047] In this invention, in step S3, the amount of slurry B sprayed is 8-12 g / m³. 2 Preferably 10g / m 2 The spraying rate is 0.5–3.5 m / min, preferably 1–3 m / min, and more preferably 2 m / min; the drying temperature is 80–110°C, preferably 90–100°C; and the drying time is 12–24 h, preferably 15–20 h.

[0048] In this invention, in step S4, the sintering temperature is 1200-1500℃, preferably 1400℃; the sintering time is 1-5h, preferably 2-4h, and more preferably 3h; the heating rate from room temperature to the sintering temperature is 2-5℃ / min, preferably 3-4℃ / min.

[0049] This invention provides a CaO-ZrO2 porous ceramic filter prepared by the above preparation method.

[0050] The present invention also provides the application of the above-mentioned CaO-ZrO2 porous ceramic filter in the filtration of high-temperature molten metal.

[0051] The technical solutions provided by the present invention will be described in detail below with reference to the embodiments, but they should not be construed as limiting the scope of protection of the present invention.

[0052] Example 1

[0053] Zirconia particles of three sizes—fine (D50 = 0.8 μm), medium (D50 = 5 μm), and coarse (D50 = 40 μm)—with equal amounts of yttrium-stabilized, magnesium-stabilized, and cerium-stabilized zirconia were sized to obtain powder A. Powder A was then mixed with 1 wt% polycarboxylate, 0.4 wt% carboxymethyl cellulose, 15 wt% zirconium sol, and 30 wt% water, and ball-milled for 4 hours to obtain slurry A. Powder B was prepared by mixing 80 wt% calcium carbonate powder with 20 wt% nano-sized (D50 = 50 nm) zirconia powder. Powder B was then mixed with 1 wt% polycarboxylate, 4 wt% dextrin, and 30 wt% water, and ball-milled for 4 hours to obtain slurry B.

[0054] The mesh porous template is immersed in the slurry A for 20 minutes, centrifuged and slurry-spun, dried at 25°C for 18 hours, and then dried at 110°C for 48 hours to obtain a zirconia porous ceramic preform.

[0055] Slurry B was sprayed onto the zirconia porous ceramic preform at a dosage of 10 g / m³. 2 The spraying rate was 3 m / min, and then the material was dried at 110℃ for 24 h to obtain a CaO-ZrO2 porous ceramic preform.

[0056] The CaO-ZrO2 porous ceramic preform was placed in a high-temperature furnace and heated to 1400°C at a rate of 5°C / min in an air atmosphere. The temperature was held for 2 hours and then cooled to room temperature with the furnace to obtain a CaO-ZrO2 porous ceramic filter.

[0057] Testing revealed that the bulk density of the CaO-ZrO2 porous ceramic filter prepared in this embodiment was 1.2 g / cm³. 3 Porosity: 87%; room temperature compressive strength: 4.2 MPa; high temperature (1400℃) strength: 4.0 MPa; high temperature resistance: >1800℃; residual strength retention rate after three 1100℃ oil cooling cycles: 50%.

[0058] Example 2

[0059] Zirconia particles of three sizes—fine (D50 = 0.8 μm), medium (D50 = 5 μm), and coarse (D50 = 40 μm)—with equal amounts of yttrium-stabilized, magnesium-stabilized, and cerium-stabilized zirconia were sized to obtain powder A. Powder A was then mixed with 1.5 wt% polycarboxylate, 0.8 wt% carboxymethyl cellulose, 15 wt% zirconium sol, and 35 wt% water, and ball-milled for 4 hours to obtain slurry A. Powder B was prepared by mixing 80 wt% calcium carbonate powder with 20 wt% nano-sized (D50 = 50 nm) zirconia powder. Powder B was then mixed with 1.5 wt% polycarboxylate, 5 wt% dextrin, and 46 wt% water, and ball-milled for 4 hours to obtain slurry B.

[0060] The mesh porous template is immersed in the slurry A for 20 minutes, centrifuged and slurryed, dried at 25°C for 18 hours, and then dried at 110°C for 48 hours to obtain a zirconia porous ceramic preform.

[0061] Slurry B was sprayed onto the zirconia porous ceramic preform at a dosage of 10 g / m³. 2 The spraying rate was 3 m / min, and then the material was dried at 110℃ for 24 h to obtain a CaO-ZrO2 porous ceramic preform.

[0062] The CaO-ZrO2 porous ceramic preform was placed in a high-temperature furnace and heated to 1500°C at a rate of 5°C / min in an air atmosphere. The temperature was held for 2 hours and then cooled to room temperature with the furnace to obtain a CaO-ZrO2 porous ceramic filter.

[0063] Testing revealed that the bulk density of the CaO-ZrO2 porous ceramic filter prepared in this embodiment was 1.3 g / cm³. 3 Porosity: 83%; room temperature compressive strength: 3.2 MPa; high temperature (1400℃) strength: 3.0 MPa; high temperature resistance: >1800℃; residual strength retention rate after three 1100℃ oil cooling cycles: 30%.

[0064] Example 3

[0065] Zirconia particles of three sizes—fine (D50 = 0.8 μm), medium (D50 = 5 μm), and coarse (D50 = 40 μm)—with equal amounts of yttrium-stabilized, magnesium-stabilized, and cerium-stabilized zirconia were sized to obtain powder A. 0.5 wt% polycarboxylate, 0.2 wt% carboxymethyl cellulose, 15 wt% zirconium sol, and 25 wt% water were added to powder A, and the mixture was ball-milled for 4 hours to obtain slurry A. Powder B was prepared by mixing 80 wt% calcium carbonate powder with 20 wt% nano-sized (D50 = 50 nm) zirconia powder. 0.5 wt% polycarboxylate, 2 wt% dextrin, and 23 wt% water were then added to powder B, and the mixture was ball-milled for 4 hours to obtain slurry B.

[0066] The mesh porous template is immersed in the slurry A for 20 minutes, squeezed and spun, dried at 25°C for 18 hours, and then dried at 110°C for 48 hours to obtain a zirconia porous ceramic preform.

[0067] Slurry B was sprayed onto the zirconia porous ceramic preform at a dosage of 10 g / m³. 2 The spraying rate was 3 m / min, and then the material was dried at 110℃ for 24 h to obtain a CaO-ZrO2 porous ceramic preform.

[0068] The CaO-ZrO2 porous ceramic preform was placed in a high-temperature furnace and heated to 1300°C at a rate of 5°C / min in an air atmosphere. The temperature was held for 2 hours and then cooled to room temperature with the furnace to obtain a CaO-ZrO2 porous ceramic filter.

[0069] Testing revealed that the bulk density of the CaO-ZrO2 porous ceramic filter prepared in this embodiment was 1.2 g / cm³. 3 Porosity: 85%; room temperature compressive strength: 4.0 MPa; high temperature (1400℃) strength: 3.8 MPa; high temperature resistance: >1800℃; residual strength retention rate after three 1100℃ oil cooling cycles: 35%.

[0070] The above test results show that the CaO-ZrO2 porous ceramic filter prepared by the present invention has a high temperature resistance of over 1800℃; its room temperature pressure resistance is between 3.2 and 4.2 MPa, and its high temperature (1400℃) strength is between 3.0 and 4.0 MPa, making it suitable for molten metal filtration environments of 1600 to 1800℃.

[0071] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a CaO-ZrO2 porous ceramic filter, characterized in that, Includes the following steps: S1. Powder A, polycarboxylate, carboxymethyl cellulose, binder A and water are mixed and then ball-milled to obtain slurry A; Powder B, polycarboxylate, binder B and water are mixed and then ball-milled to obtain slurry B; S2. The mesh porous template is immersed in slurry A, and then subjected to slurry spinning, primary drying, and secondary drying in sequence to obtain the zirconia porous ceramic preform. S3. Spray slurry B onto a zirconia porous ceramic preform and dry it to obtain a CaO-ZrO2 porous ceramic green body. S4. The CaO-ZrO2 porous ceramic green body is sintered to obtain the CaO-ZrO2 porous ceramic filter. In step S1, powder A includes fine, medium, and coarse zirconium oxide with a mass ratio of 10~20:20~30:50~70; fine-particle-size D... 50 The D particle size is 0.5~1μm, which is medium. 50 The D particle size is 3~8μm, which is coarse. 50 30~50μm; The binder A is zirconium sol; The powder B is calcium carbonate and zirconium oxide with nano-sized particles; The binder B is starch or dextrin; The structure of the mesh porous template consists of three layers of gradually changing holes, with the hole diameters divided into large, medium, and small from the outside to the inside. The large hole diameter is 2~3mm, the medium hole diameter is 1.2~1.5mm, and the small hole diameter is 0.5~1mm.

2. The preparation method according to claim 1, characterized in that, In step S1, the zirconium oxide is one or more of yttrium-stabilized zirconium oxide, magnesium-stabilized zirconium oxide, and cerium-stabilized zirconium oxide.

3. The preparation method according to claim 2, characterized in that, In step S1, during the preparation of slurry A, the amount of polycarboxylate used is 0.5~1.5wt% of powder A, the amount of carboxymethyl cellulose used is 0.2~0.8wt% of powder A, the amount of binder A used is 10~20wt% of powder A, and the amount of water used is 25~35wt% of powder A; the ball milling time is 1~4h.

4. The preparation method according to any one of claims 1 to 3, characterized in that, In step S1, during the preparation of slurry B, the amount of polycarboxylate used is 0.5-1.5 wt% of powder B, the amount of binder B is 2-5 wt% of powder B, and the amount of water is 23-46 wt% of powder A; the mass ratio of calcium carbonate to nano-sized zirconium oxide in powder B is 80-95:5-20; the D of the nano-sized zirconium oxide... 50 The wavelength is 40~60nm; the ball milling time is 4~8h.

5. The preparation method according to claim 4, characterized in that, In step S2, the material of the mesh porous template includes polyurethane, 3D printing resin or nylon; the immersion time is 20~60min.

6. The preparation method according to claim 2, 3 or 5, characterized in that, In step S2, the temperature for the first drying is 20~30℃ and the drying time is 12~18h; the temperature for the second drying is 80~110℃ and the drying time is 24~48h.

7. The preparation method according to claim 6, characterized in that, In step S3, the amount of slurry B sprayed is 8~12g / m³. 2 The spraying rate is 0.5~3.5m / min; the drying temperature is 80~110℃, and the drying time is 12~24h.

8. The preparation method according to claim 2, 3, 5 or 7, characterized in that, In step S4, the sintering temperature is 1200~1500℃, the sintering time is 1~5h, and the heating rate from room temperature to the sintering temperature is 2~5℃ / min.

9. The CaO-ZrO2 porous ceramic filter prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the CaO-ZrO2 porous ceramic filter according to claim 9 in the filtration of high-temperature molten metal.

Images