Method for preparing porous zirconia ceramic through low-temperature sintering

Abstract

The invention discloses a method for preparing porous zirconia ceramic by low-temperature sintering, which comprises the following steps: S1, mixing citric acid, zirconium acetylacetonate and absolute ethyl alcohol according to a certain proportion to obtain a colloidal solution A; s2, mixing inorganic yttrium salt, inorganic zirconium salt and water according to a certain proportion to obtain a mixed solution B; s3, slowly adding the colloidal solution A into the mixed solution B obtained in the step S2; s4, drying the colloidal solution to obtain a dried precursor; s5, carrying out low-temperature calcination on the dried precursor to obtain nano yttrium-stabilized zirconia powder; s6, performing ball milling and spray granulation on the powder to obtain spherical granulation powder with uniform particle size; s7, carrying out dry pressing molding and cold isostatic pressing molding to obtain a to-be-sintered ceramic biscuit; and S8, sintering in a muffle furnace to obtain the final porous zirconia ceramic. After the powder is subjected to ball milling, granulation, dry pressing and cold isostatic pressing, the zirconia ceramic which is uniform in pore diameter and has nano-scale pores is prepared through low-temperature sintering.

Description

Technical Field

[0001] This invention belongs to the field of ceramic preparation technology, and in particular relates to a method for preparing porous zirconia ceramics by low-temperature sintering. Background Technology

[0002] Porous zirconia ceramics have wide applications in high-temperature catalysis and hydrogen filtration. However, their practical application still faces several challenges. High-purity raw materials are expensive, sintering temperatures typically exceed 1500℃, and the addition of pore-forming agents usually complicates the process and makes it difficult to produce ceramics with uniform pore size and nanoscale pores. Therefore, there is an urgent need for high-purity, highly sinterable zirconia powders to enable the production of zirconia ceramics with uniform pore size and nanoscale pores at low temperatures. Summary of the Invention

[0003] The main technical problem solved by this invention is to provide a method for preparing porous zirconia ceramics by low-temperature sintering. After the powder is ball-milled, granulated, dry-pressed, and cold isostatically pressed, zirconia ceramics with uniform pore size and nanoscale pores are prepared by low-temperature sintering.

[0004] To solve the above-mentioned technical problems, one technical solution adopted by the present invention is: a method for preparing porous zirconia ceramics by low-temperature sintering, comprising the following steps: S1: Citric acid, zirconium acetylacetonate, and anhydrous ethanol are mixed in a certain proportion to obtain colloidal solution A; S2: Inorganic yttrium salt, inorganic zirconium salt and water are mixed in a certain proportion and heated to dissolve, to obtain mixed solution B; S3: Slowly add the colloidal solution A obtained in step S1 to the mixed solution B obtained in step S2 and stir until a uniform colloid is formed; S4: Dry the colloidal liquid obtained in step S3 to obtain a dried precursor; S5: The dried precursor obtained in step S4 is calcined at low temperature to obtain nano-yttrium stabilized zirconium oxide powder; S6: The yttrium-stabilized zirconium oxide powder obtained in step S5 is ball-milled and spray-granulated to obtain spherical granulated powder with uniform particle size; S7: The yttrium-stabilized zirconia granulated powder obtained in step S6 is subjected to dry pressing and cold isostatic pressing to obtain a ceramic green body to be sintered. S8: Place the ceramic blank formed in step S7 onto an alumina sintering plate and sinter it in a muffle furnace to obtain the final porous zirconia ceramic.

[0005] Furthermore, in step S1, the mass ratio of citric acid, zirconium acetylacetonate, and anhydrous ethanol is 1:(1-40):(1-500). In step S2, the mass ratio of inorganic yttrium salt, inorganic zirconium salt and water is 1:(1-40):(1-400); The mass ratio of zirconium acetylacetonate in colloidal solution A to inorganic zirconium salt in mixed solution B is 1:(1-40).

[0006] Furthermore, in step S2, the inorganic yttrium salt includes at least one of yttrium chloride hexahydrate, yttrium nitrate hexahydrate, and yttrium acetate tetrahydrate; The inorganic zirconium salt includes at least one of zirconium chloride, zirconium nitrate pentahydrate, and zirconium oxychloride octahydrate.

[0007] Furthermore, the dissolution temperature in step S2 is 30–100°C, and the dissolution time is 1–40 h.

[0008] Furthermore, the stirring time in step S3 is 1 to 20 hours.

[0009] Furthermore, the drying temperature in step S4 is 30–100°C, and the drying time is 1–40 h.

[0010] Furthermore, in step S5, the calcination temperature is 400–1200℃, and the calcination time is 1–10 h.

[0011] Furthermore, in step S6, the ball milling method is planetary ball milling, the ball milling speed is 100-400 rpm, and the ball milling time is 1-40 h.

[0012] Furthermore, the pressure for dry pressing in step S7 is 1 to 100 MPa.

[0013] Furthermore, in step S8, the sintering temperature is 1000–1600℃ and the sintering time is 1–600 min.

[0014] The beneficial effects of the present invention include at least the following: This invention prepares high-purity, ultrafine zirconia powder. After ball milling, granulation, dry pressing, and cold isostatic pressing, the powder is sintered at low temperature in air under normal pressure to prepare zirconia ceramics with uniform pore size and nanoscale pores. This process is simple, highly repeatable, and conducive to large-scale industrialization. It fully solves the current problems faced by porous zirconia ceramics and is beneficial to their large-scale practical application. Attached Figure Description

[0015] Figure 1 This is a cross-sectional SEM image of the ceramic after sintering in Example 2; Figure 2This is a cross-sectional SEM image of the ceramic after sintering in Example 3. Detailed Implementation

[0016] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0017] Example: A method for preparing porous zirconia ceramics by low-temperature sintering, comprising the following steps: S1: Citric acid, zirconium acetylacetonate, and anhydrous ethanol are mixed in a certain proportion to obtain colloidal solution A; S2: Inorganic yttrium salt, inorganic zirconium salt and water are mixed in a certain proportion and heated to dissolve, to obtain mixed solution B; S3: Slowly add the colloidal solution A obtained in step S1 to the mixed solution B obtained in step S2 and stir until a uniform colloid is formed; S4: Dry the colloidal liquid obtained in step S3 to obtain a dried precursor; S5: The dried precursor obtained in step S4 is calcined at low temperature to obtain nano-yttrium stabilized zirconium oxide powder; S6: The yttrium-stabilized zirconium oxide powder obtained in step S5 is ball-milled and spray-granulated to obtain spherical granulated powder with uniform particle size; S7: The yttrium-stabilized zirconia granulated powder obtained in step S6 is subjected to dry pressing and cold isostatic pressing to obtain a ceramic green body to be sintered. S8: Place the ceramic blank formed in step S7 onto an alumina sintering plate and sinter it in a muffle furnace to obtain the final porous zirconia ceramic.

[0018] In step S1, the mass ratio of citric acid, zirconium acetylacetonate, and anhydrous ethanol is 1:(1-40):(1-500). In step S2, the mass ratio of inorganic yttrium salt, inorganic zirconium salt and water is 1:(1-40):(1-400); The mass ratio of zirconium acetylacetonate in colloidal solution A to inorganic zirconium salt in mixed solution B is 1:(1-40).

[0019] In step S2, the inorganic yttrium salt includes at least one of yttrium chloride hexahydrate, yttrium nitrate hexahydrate, and yttrium acetate tetrahydrate; The inorganic zirconium salt includes at least one of zirconium chloride, zirconium nitrate pentahydrate, and zirconium oxychloride octahydrate.

[0020] The dissolution temperature in step S2 is 30–100°C, and the dissolution time is 1–40 h.

[0021] The stirring time in step S3 is 1 to 20 hours.

[0022] In step S4, the drying temperature is 30–100℃ and the drying time is 1–40 h.

[0023] In step S5, the calcination temperature is 400–1200℃ and the calcination time is 1–10 h.

[0024] In step S6, the ball milling method is planetary ball milling, the ball milling speed is 100-400 rpm, and the ball milling time is 1-40 h.

[0025] The pressure for dry pressing in step S7 is 1 to 100 MPa.

[0026] In step S8, the sintering temperature is 1000–1600℃ and the sintering time is 1–600 min.

[0027] Example 1 S1: Dissolve 5g of citric acid and 10g of zirconium acetylacetonate in 200g of anhydrous ethanol; S2: Dissolve 5g of yttrium nitrate hexahydrate and 87.8g of zirconium nitrate pentahydrate in 500g of deionized water at 50℃ for 20 hours. S3: Add the colloidal solution from step S1 dropwise to the solution from step S2 and stir for 10 hours to obtain a homogeneous colloidal solution; S4: Dry the homogeneous colloid from step S3 at a temperature of 60°C for 10 hours. S5: The dried precursor from step S4 is calcined in a muffle furnace at a temperature of 500℃ for 3 hours. The powder after calcination is XRD-detected and found to be tetragonal zirconium oxide. S6: The zirconia powder obtained in step S5 is ball-milled with anhydrous ethanol as solvent and zirconia balls as grinding media. The ball milling speed is 240 rpm and the ball milling time is 20 h. Then the slurry is filtered out, dried, and then passed through a 100-mesh sieve. S7: The zirconium oxide powder obtained in step S6 is subjected to dry pressing and cold isostatic pressing. The dry pressing pressure is 3MPa to obtain the ceramic blank to be sintered. S8: Place the ceramic blank formed in step S7 onto an alumina sintering plate and sinter it in a muffle furnace at a sintering temperature of 1000℃ for 10 minutes to obtain the final porous zirconia ceramic. The porosity of the sintered ceramic sample is 50%, and the flexural strength is 5MPa.

[0028] The preparation methods of Examples 2-6 are basically the same as those of Example 1, except that the ratio of solution A and solution B and the sintering temperature are changed, as detailed in Table 1 below: Table 1 As can be seen from the cross-sectional SEM images of the embodiments and Table 1, the porous zirconia ceramics sintered at low temperature of the present invention have uniform pore size and bending strength ≥5MPa, which fully solves the problem that it is difficult to prepare porous zirconia ceramics with uniform pore size, and is conducive to its large-scale practical application.

[0029] The above are merely embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for preparing porous zirconia ceramics by low-temperature sintering, characterized in that: Includes the following steps: S1: Citric acid, zirconium acetylacetonate, and anhydrous ethanol are mixed in a certain proportion to obtain colloidal solution A; S2: Inorganic yttrium salt, inorganic zirconium salt and water are mixed in a certain proportion and heated to dissolve, to obtain mixed solution B; S3: Slowly add the colloidal solution A obtained in step S1 to the mixed solution B obtained in step S2 and stir until a uniform colloid is formed; S4: Dry the colloidal liquid obtained in step S3 to obtain a dried precursor; S5: The dried precursor obtained in step S4 is calcined at low temperature to obtain nano-yttrium stabilized zirconium oxide powder; S6: The yttrium-stabilized zirconium oxide powder obtained in step S5 is ball-milled and spray-granulated to obtain spherical granulated powder with uniform particle size; S7: The yttrium-stabilized zirconia granulated powder obtained in step S6 is subjected to dry pressing and cold isostatic pressing to obtain a ceramic green body to be sintered. S8: Place the ceramic blank formed in step S7 onto an alumina sintering plate and sinter it in a muffle furnace to obtain the final porous zirconia ceramic.

2. The method for preparing porous zirconia ceramics by low-temperature sintering according to claim 1, characterized in that: In step S1, the mass ratio of citric acid, zirconium acetylacetonate, and anhydrous ethanol is 1:(1-40):(1-500). In step S2, the mass ratio of inorganic yttrium salt, inorganic zirconium salt and water is 1:(1-40):(1-400); The mass ratio of zirconium acetylacetonate in colloidal solution A to inorganic zirconium salt in mixed solution B is 1:(1-40).

3. The method for preparing porous zirconia ceramics by low-temperature sintering according to claim 1, characterized in that: In step S2, the inorganic yttrium salt includes at least one of yttrium chloride hexahydrate, yttrium nitrate hexahydrate, and yttrium acetate tetrahydrate; The inorganic zirconium salt includes at least one of zirconium chloride, zirconium nitrate pentahydrate, and zirconium oxychloride octahydrate.

4. The method for preparing porous zirconia ceramics by low-temperature sintering according to claim 1, characterized in that: The dissolution temperature in step S2 is 30–100°C, and the dissolution time is 1–40 h.

5. The method for preparing porous zirconia ceramics by low-temperature sintering according to claim 1, characterized in that: The stirring time in step S3 is 1 to 20 hours.

6. The method for preparing porous zirconia ceramics by low-temperature sintering according to claim 1, characterized in that: In step S4, the drying temperature is 30–100°C, and the drying time is 1–40 h.

7. The method for preparing porous zirconia ceramics by low-temperature sintering according to claim 1, characterized in that: In step S5, the calcination temperature is 400–1200℃ and the calcination time is 1–10 h.

8. The method for preparing porous zirconia ceramics by low-temperature sintering according to claim 1, characterized in that: In step S6, the ball milling method is planetary ball milling, the ball milling speed is 100-400 rpm, and the ball milling time is 1-40 h.

9. The method for preparing porous zirconia ceramics by low-temperature sintering according to claim 1, characterized in that: The pressure for dry pressing in step S7 is 1 to 100 MPa.

10. The method for preparing porous zirconia ceramics by low-temperature sintering according to claim 1, characterized in that: In step S8, the sintering temperature is 1000–1600℃ and the sintering time is 1–600 min.

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