A cold-sintered zirconia ceramic and its preparation method

Abstract

The present invention provides a cold-sintered zirconia ceramic and a preparation method thereof. The preparation method of the cold-sintered zirconia ceramic of the present invention is based on the principle of biomimetic mineralization to prepare the cold-sintered zirconia ceramic. By introducing an amorphous ZrO2 precursor into the ZrO2 powder, it can undergo a controllable crystallization reaction at low temperature, thereby forming ultrafine ZrO2 nanophases in the grain boundary region; utilizing the acidic environment generated in-situ during the precursor generation process to stimulate the non-equilibrium dissolution on the surface of the ZrO2 grains, and realizing the directional precipitation and structural healing in the grain boundary region under high pressure; by precisely controlling the precursor addition amount and firing parameters, the relative density of the cold-sintered body is ≥85%; after annealing treatment, a three-dimensional interlocked nanostructure network is constructed at the grain boundaries, and the average grain size of the final sample is controlled below 250 nm.

Description

Technical Field

[0001] The present invention relates to the technical field of advanced ceramic material preparation, and in particular to a cold-sintered zirconia ceramic and a preparation method thereof. Background Art

[0002] The sintering process optimization of zirconia ceramics has been a long-standing technical problem in this field. Limited by the inherent low thermal conductivity characteristics (<2 W / m·K) and high sintering activation energy (typical value ≥500 kJ / mol) of ZrO2 materials, traditional solid-phase sintering processes can only achieve densification under ultra-high temperature (>1450 °C) and extremely long firing cycles (>48 h). Under such extreme sintering conditions, the following adverse phase transformations will occur inside the material: 1) The abnormal growth of ZrO2 grains exceeds the critical size; 2) The irreversible transformation of the high-temperature metastable phase to the monoclinic phase m-ZrO2, which leads to the deterioration of the material properties. In the prior art, the sintering activity of powders is improved by refining grains. For example, a technical solution for preparing ultrafine ZrO2 powders by the hydrothermal method is disclosed in the prior art. The sintering activity is improved by increasing the specific surface area of the powder (>30 m 2 / g), and the sintering temperature is reduced to 1250 °C. However, this process has defects such as a complex powder preparation process (requiring high-pressure autoclave equipment) and high costs (the utilization rate of the precursor <70%).

[0003] Based on the defects existing in the preparation of current zirconia ceramics, it is necessary to make improvements. Summary of the Invention

[0004] The purpose of the present invention is to provide a cold-sintered zirconia ceramic and a preparation method thereof in view of the problems and deficiencies existing in the prior art.

[0005] The present invention adopts the following technical solutions:

[0006] In the first aspect, the present invention provides a preparation method of a cold-sintered zirconia ceramic, comprising the following steps:

[0007] Adding a soluble zirconium salt into water to obtain a soluble zirconium salt solution;

[0008] Adding a stabilizer to the soluble zirconium salt solution to obtain a first mixed solution;

[0009] Adding a precipitating agent to the first mixed solution, and stirring to obtain a precursor;

[0010] Adding Y2O3-stabilized ZrO2 powder and a binder to the precursor, and dispersing to obtain a slurry;

[0011] Performing spray granulation on the slurry to obtain granulated powder;

[0012] Place the granulated powder in a cold sintering device, keep the pressure at 300 - 800 Mpa for 10 - 60 min, then heat it at a heating rate of 5 - 20 °C / min to 180 - 450 °C, and keep it warm for 30 - 180 min to obtain a cold sintered body;

[0013] After drying the cold sintered body, anneal it to obtain a cold sintered zirconia ceramic.

[0014] Preferably, the stabilizer includes at least one of soluble yttrium salts, soluble calcium salts, and soluble magnesium salts.

[0015] Preferably, the soluble yttrium salt includes at least one of yttrium nitrate, yttrium chloride, and yttrium sulfate;

[0016] The soluble calcium salt includes at least one of calcium chloride and calcium nitrate;

[0017] The soluble magnesium salt includes at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate.

[0018] Preferably, the soluble zirconium salt includes at least one of zirconyl chloride and zirconium nitrate;

[0019] The precipitant includes oxalic acid or phosphoric acid, and the concentration of the precipitant is 0.8 - 1.0 M.

[0020] Preferably, the binder includes an aqueous polyvinyl alcohol solution and an acrylic emulsion;

[0021] The mass ratio of the aqueous polyvinyl alcohol solution to the acrylic emulsion is 1:1;

[0022] The concentration of the aqueous polyvinyl alcohol solution is 10 wt%.

[0023] Preferably, in the step of adding the stabilizer to the soluble zirconium salt solution, based on the molar amount of zirconium salt in the soluble zirconium salt solution, the addition amount of the stabilizer is 3 - 10 mol% of the zirconium salt; the concentration of the soluble zirconium salt solution is 1 - 2 M;

[0024] In the step of adding the precipitant to the first mixed solution, the volume ratio of the precipitant to the soluble zirconium salt solution is (220 - 700):250;

[0025] In the step of adding Y₂O₃ - stabilized ZrO₂ powder and the binder to the precursor, the mass of the added Y₂O₃ - stabilized ZrO₂ powder is 25 - 45% of the mass of the precursor;

[0026] The mass of the added binder is 10 - 15% of the mass of the Y₂O₃ - stabilized ZrO₂ powder.

[0027] Preferably, the doping amount of Y₂O₃ in the Y₂O₃ - stabilized ZrO₂ powder is 0.5 - 3 mol%.

[0028] Preferably, the cold-sintered body is dried at 150-200 °C for 10-15 h.

[0029] Preferably, after the cold-sintered body is dried, it is heated to 700-1100 °C at a heating rate of 5-10 °C / min and annealed for 1-3 h.

[0030] In a second aspect, the present invention also provides a cold-sintered zirconia ceramic prepared by using the described preparation method.

[0031] The cold-sintered zirconia ceramic and its preparation method of the present invention have the following beneficial effects compared with the prior art:

[0032] 1. The preparation method of the cold-sintered zirconia ceramic of the present invention prepares the cold-sintered zirconia ceramic based on the principle of biomimetic mineralization. The core of this solution lies in: (1) The in-situ crystallization mechanism of the precursor. An amorphous ZrO2 precursor is introduced into the ZrO2 powder, which can undergo a controllable crystallization reaction at a low temperature (<400 °C), thereby forming ultrafine ZrO2 nanophases (grain size <30 nm) in the grain boundary region; the acid-excited dissolution-precipitation mechanism. (2) Utilize the acidic environment generated in-situ during the generation of the precursor to stimulate the non-equilibrium dissolution on the surface of the ZrO2 grains, and achieve directional precipitation and structural healing in the grain boundary region under high pressure; (3) The grain boundary nano-strengthening effect. By precisely controlling the addition amount of the precursor and the firing parameters, the relative density of the cold-sintered body is ≥85%. After annealing treatment, a three-dimensional interlocked nanostructure network is constructed at the grain boundaries, and the average grain size of the final sample is controlled below 250 nm;

[0033] 2. The preparation method of the cold-sintered zirconia ceramic of the present invention can significantly reduce the sintering temperature; the relative density of the cold-sintered zirconia ceramic prepared by the present invention is 91-95%, the Vickers hardness is 10.8-13.5 GPa, and the average grain size is 173.28-233.77 nm. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the following drawings are only some embodiments of the present invention, and those of ordinary skill in the art can also obtain other drawings based on these drawings without creative efforts.

[0035] Figure 1 It is a schematic diagram of preparing a cold-sintered zirconia ceramic based on the principle of biomimetic mineralization of the present invention;

[0036] Figure 2Schematic diagram of the gradual growth of ZrO2 grains at the grain boundary positions based on the principle of biomimetic mineralization of the present invention, resulting in the healing of the grain boundaries;

[0037] Figure 3 Cross-sectional scanning electron micrograph of the cold-sintered zirconia ceramic prepared in Example 1;

[0038] Figure 4 Further elaborates on the principle of preparing the cold-sintered zirconia ceramic in Example 1 based on the principle of biomimetic mineralization of the present invention;

[0039] Figure 5 Cross-sectional scanning electron micrograph of the cold-sintered zirconia ceramic in Example 2 of the present invention;

[0040] Figure 6 Cross-sectional scanning electron micrograph of the cold-sintered zirconia ceramic in Example 3 of the present invention;

[0041] Figure 7 Cross-sectional scanning electron micrograph of the cold-sintered zirconia ceramic in Example 4 of the present invention. Detailed implementation manners

[0042] Next, in combination with the implementation manners of the present invention, the technical solutions in the implementation manners of the present invention will be clearly and completely described. Obviously, the described implementation manners are only a part of the implementation manners of the present invention, rather than all of the implementation manners. Based on the implementation manners in the present invention, all other implementation manners obtained by those of ordinary skill in the art without making creative efforts belong to the scope of protection of the present invention.

[0043] In the description of the present invention, it should be understood that the relationships indicating orientations or positions such as "upper" are based on the orientations or positions shown in the drawings, or the orientations or positions in which the products of the present invention are customarily placed during use, or the orientations or positions commonly understood by those skilled in the art. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and thus cannot be construed as a limitation of the present invention.

[0044] The description order of the following embodiments does not limit the preferred order of the embodiments. Additionally, in the description of this application, the term "comprising" means "including but not limited to". The various embodiments of the present invention may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and brevity and should not be construed as a rigid limitation on the scope of the present invention; therefore, it should be considered that the described range description has specifically disclosed all possible sub-ranges and individual values within that range. For example, it should be considered that the range description from 1 to 6 has specifically disclosed sub-ranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and individual numbers within the range, such as 1, 2, 3, 4, 5, and 6, and this applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it means including any cited number (fraction or integer) within the indicated range.

[0045] An embodiment of the present application provides a method for preparing a cold-sintered zirconia ceramic, comprising the following steps:

[0046] S1. Add a soluble zirconium salt to water to obtain a soluble zirconium salt solution;

[0047] S2. Add a stabilizer to the soluble zirconium salt solution to obtain a first mixed solution;

[0048] S3. Add a precipitating agent to the first mixed solution, stir to obtain a precursor;

[0049] S4. Add Y2O3-stabilized ZrO2 powder and a binder to the precursor, disperse to obtain a slurry;

[0050] S5. Spray granulate the slurry to obtain granulated powder;

[0051] S6. Place the granulated powder in a cold sintering device, hold the pressure at 300 - 800 Mpa for 10 - 60 min, then heat it at a heating rate of 5 - 20 °C / min to 180 - 450 °C, and hold the temperature for 30 - 180 min to obtain a cold-sintered body;

[0052] S7. After drying the cold-sintered body, anneal it to obtain a cold-sintered zirconia ceramic.

[0053] Current prior art reports that when preparing zirconia ceramics, the sintering temperature is reduced to 1250 °C. However, in the actual process, due to the slow heating rate and high sintering temperature (even when reduced to 1250 °C), the sintering cycle of zirconia is too long, resulting in grain growth and performance degradation. In the present invention, cold sintering is carried out on the granulated powder. The advantages of cold sintering are as follows: on the one hand, through cold sintering treatment, the sample obtains a relatively high initial density. Therefore, during subsequent annealing treatment, the heating rate is fast, the annealing temperature is low, and the holding time is short, greatly shortening the entire sintering cycle. On the other hand, more importantly, the cold sintering temperature is low, and the grain size does not show obvious growth behavior, which is beneficial to the material properties.

[0054] In some embodiments, the stabilizer includes at least one of soluble yttrium salts, soluble calcium salts, and soluble magnesium salts.

[0055] In some embodiments, the soluble yttrium salt includes at least one of yttrium nitrate, yttrium chloride, and yttrium sulfate;

[0056] In some embodiments, the soluble calcium salt includes at least one of calcium chloride and calcium nitrate;

[0057] In some embodiments, the soluble magnesium salt includes at least one of magnesium chloride, magnesium sulfate, and magnesium nitrate.

[0058] In some embodiments, the soluble zirconium salt includes at least one of zirconyl chloride and zirconium nitrate;

[0059] In some embodiments, the precipitant includes oxalic acid or phosphoric acid. The precipitant exists in the form of an aqueous solution, and the concentration of the precipitant is 0.8 - 1.0 M.

[0060] In some embodiments, the binder includes an aqueous solution of polyvinyl alcohol and an acrylic emulsion;

[0061] The concentration of the aqueous solution of polyvinyl alcohol (i.e., polypropylene glycol) is 10 wt%.

[0062] In some embodiments, the mass ratio of the aqueous solution of polyvinyl alcohol to the acrylic emulsion is 1:1.

[0063] In some embodiments, in the step of adding the stabilizer to the soluble zirconium salt solution, based on the molar amount of the zirconium salt in the soluble zirconium salt solution, the addition amount of the stabilizer is 3 - 10 mol% of the zirconium salt; the concentration of the soluble zirconium salt solution is 1 - 2 M;

[0064] In the step of adding the precipitant to the first mixed solution, the volume ratio of the precipitant to the soluble zirconium salt solution is (220 - 700):250; in the step of adding Y2O3-stabilized ZrO2 powder and the binder to the precursor, the mass of the added Y2O3-stabilized ZrO2 powder is 25 - 45% of the mass of the precursor;

[0065] The mass of the added binder is 10 - 15% of the mass of the Y2O3-stabilized ZrO2 powder.

[0066] In some embodiments, when oxalic acid is used as the precipitating agent, the precursors are hydrates of zirconium oxalate, calcium oxalate, and magnesium oxalate; when phosphoric acid is used as the precipitating agent, the precursors are hydrates of zirconium phosphate, calcium phosphate, and magnesium phosphate.

[0067] In some embodiments, the doping amount of Y2O3 in the Y2O3-stabilized ZrO2 powder (3YSZ powder) is 0.5 - 3 mol%.

[0068] In some embodiments, the cold-sintered body is dried at 150 - 200 °C for 10 - 15 h.

[0069] In some embodiments, after drying the cold-sintered body, it is heated to 700 - 1100 °C at a heating rate of 5 - 10 °C / min and annealed for 1 - 3 h.

[0070] The preparation method of the cold-sintered zirconia ceramic of the present invention is based on the principle of biomimetic mineralization to prepare the cold-sintered zirconia ceramic. The core of this solution lies in:

[0071] (1) In-situ crystallization mechanism of precursors. An amorphous ZrO2 precursor is introduced into the ZrO2 powder, which can undergo a controllable crystallization reaction at low temperature (<450 °C), thereby forming ultrafine ZrO2 nanophases (grain size <30 nm) in the grain boundary region;

[0072] (2) Acid-excited dissolution-precipitation mechanism. Utilize the acidic environment generated in-situ during the precursor generation process to stimulate the non-equilibrium dissolution on the surface of ZrO2 grains, and achieve directional precipitation and structure healing in the grain boundary region under high pressure;

[0073] (3) Grain boundary nano-strengthening effect. By precisely controlling the precursor addition amount and firing parameters, the relative density of the cold-sintered body is ≥85%. After annealing treatment, a three-dimensional interlocked nanostructure network is constructed at the grain boundaries, and the average grain size of the final sample is controlled below 250 nm.

[0074] Further, referring to Figure 1 shown, it shows the preparation of the cold-sintered zirconia ceramic based on the principle of biomimetic mineralization of the present invention; specifically, the ZrO2 powder (i.e., the Y2O3-stabilized ZrO2 powder mentioned above) is mixed with the precursor and then spray granulated, and then enters the cold pressing and sintering process; at this time, the granulated powder is pressed into shape in the mold and gradually heated under the condition of external pressure, and the change of the microstructure during this process is as Figures 1-2 shown.

[0075] (1) The precursor is filled between ZrO2 grains (grain boundaries);

[0076] (2) When the temperature rises, the precursor loses its crystal water, thus forming amorphous ZrO2 (fine grains);

[0077] (3) Further increasing the temperature, the in-situ generated acidic environment stimulates the non-equilibrium dissolution on the surface of amorphous ZrO2 (fine grains), and achieves directional precipitation in the grain boundary region under high pressure;

[0078] (4) As the temperature continues to rise, the grains gradually grow at the grain boundary positions, "healing" the grain boundaries, and the density of the material gradually increases.

[0079] Specifically, under the condition of external pressure, as the cold sintering temperature continuously rises, the following reactions occur at the positions between ZrO2 grains (grain boundaries): the precursor is heated to remove (crystal) water → amorphous ZrO2 (fine grains) is formed → the non-equilibrium dissolution occurs on the surface of ZrO2 fine grains stimulated by acid → directional precipitation in the grain boundary region is achieved under high pressure → the grain boundaries are "healed", and the green body is initially densified. Finally, after annealing treatment, the density of the material can reach more than 90% of the theoretical density.

[0080] Based on the same inventive concept, the present invention also provides a cold-sintered zirconia ceramic prepared by the above preparation method.

[0081] The following further illustrates the cold-sintered zirconia ceramic and its preparation method of the present application with specific examples. This part further illustrates the content of the present invention in combination with specific examples, but should not be construed as a limitation to the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0082] In the following examples, the doping amount of Y2O3 in Y2O3-stabilized ZrO2 powder (3YSZ powder) is 3 mol%, and the 3YSZ powder is provided by Guangdong Orient Zirconium Industry.

[0083] In the following examples, the acrylic emulsion is Dow TX-100 acrylic emulsion, Dow Chemical.

[0084] Example 1

[0085] This example provides a preparation method of a cold-sintered zirconia ceramic, including the following steps:

[0086] S1. Add zirconyl chloride to water to obtain a 250 mL, 1 mol / L soluble zirconium salt solution;

[0087] S2. Add a 1 mol / L yttrium nitrate solution (aqueous solution) to the soluble zirconium salt solution in S1 to obtain a first mixed solution; based on the molar amount of zirconium salt in the soluble zirconium salt solution, the addition amount of the stabilizer yttrium nitrate is 3 mol% of the zirconium salt (zirconium oxychloride);

[0088] S3. Add 700 mL of a 0.8 mol / L oxalic acid solution as a precipitating agent to the first mixed solution to completely precipitate the metal ions in the first mixed solution, and continuously stir to make the precipitate completely uniform to obtain a precursor;

[0089] S4. Add Y2O3-stabilized ZrO2 powder and a binder to the precursor, and perform ball milling and dispersion to obtain a slurry; the binder includes an aqueous polyvinyl alcohol solution and an acrylic emulsion, and the mass ratio of the aqueous polyvinyl alcohol solution to the acrylic emulsion is 1:1; the doping amount of Y2O3 in the Y2O3-stabilized ZrO2 powder (3YSZ powder) is 3 mol%; the mass of the added Y2O3-stabilized ZrO2 powder is 25 wt% of the mass of the precursor; the mass of the added binder is 10 wt% of the mass of the Y2O3-stabilized ZrO2 powder;

[0090] S5. Perform spray granulation on the slurry to obtain granulated powder;

[0091] S6. Place the granulated powder in a cold sintering device, keep the pressure at 300 Mpa for 30 min, then heat it at a heating rate of 10 °C / min to 180 °C, and keep it warm for 180 min to obtain a cold sintered body;

[0092] S7. Dry the cold sintered body at 200 °C for 12 h, then heat it at a heating rate of 5 °C / min to 1100 °C, anneal it for 1 h, and naturally cool it to obtain cold sintered zirconia ceramics.

[0093] Example 2

[0094] This example provides a method for preparing cold sintered zirconia ceramics, including the following steps:

[0095] S1. Add zirconium oxychloride to water to obtain a 250 mL, 1 mol / L soluble zirconium salt solution;

[0096] S2. Add a 1 mol / L yttrium nitrate solution (aqueous solution) to the soluble zirconium salt solution in S1 to obtain a first mixed solution; based on the molar amount of zirconium salt in the soluble zirconium salt solution, the addition amount of the stabilizer yttrium nitrate is 6 mol% of the zirconium salt (zirconium oxychloride);

[0097] S3. Add 220 mL of a 1 mol / L phosphoric acid solution as a precipitating agent to the first mixed solution to completely precipitate the metal ions in the first mixed solution, and continuously stir to make the precipitate completely uniform to obtain a precursor;

[0098] S4. Add Y2O3-stabilized ZrO2 powder and a binder to the precursor, and ball-mill and disperse them to obtain a slurry; the binder includes an aqueous polyvinyl alcohol solution and an acrylic emulsion, and the mass ratio of the aqueous polyvinyl alcohol solution to the acrylic emulsion is 1:1; the doping amount of Y2O3 in the Y2O3-stabilized ZrO2 powder (3YSZ powder) is 3 mol%; the mass of the added Y2O3-stabilized ZrO2 powder is 30 wt% of the mass of the precursor; the mass of the added binder is 10 wt% of the mass of the Y2O3-stabilized ZrO2 powder;

[0099] S5. Spray granulate the slurry to obtain granulated powder;

[0100] S6. Place the granulated powder in a cold sintering device, hold the pressure at 400 Mpa for 30 min, then heat it at a heating rate of 10 °C / min to 300 °C, and keep it warm for 120 min to obtain a cold sintered body;

[0101] S7. Dry the cold sintered body at 200 °C for 12 h, then heat it at a heating rate of 5 °C / min to 900 °C, anneal it for 3 h, and obtain cold sintered zirconia ceramics after natural cooling.

[0102] Example 3

[0103] This example provides a method for preparing cold sintered zirconia ceramics, including the following steps:

[0104] S1. Add zirconium nitrate to water to obtain a 250 mL, 1 mol / L soluble zirconium salt solution;

[0105] S2. Add a 1 mol / L calcium chloride solution (aqueous solution) to the soluble zirconium salt solution in S1 to obtain a first mixed solution; based on the molar amount of zirconium salt in the soluble zirconium salt solution, the added amount of the stabilizer calcium chloride is 10 mol% of the zirconium salt (zirconium nitrate);

[0106] S3. Add 400 mL of a 1 mol / L phosphoric acid solution as a precipitating agent to the first mixed solution to completely precipitate the metal ions in the first mixed solution, and continuously stir to make the precipitate completely uniform to obtain a precursor;

[0107] S4. Add Y2O3-stabilized ZrO2 powder and a binder to the precursor, and ball-mill and disperse them to obtain a slurry; the binder includes an aqueous polyvinyl alcohol solution and an acrylic emulsion, and the mass ratio of the aqueous polyvinyl alcohol solution to the acrylic emulsion is 1:1; the doping amount of Y2O3 in the Y2O3-stabilized ZrO2 powder (3YSZ powder) is 3 mol%; the mass of the added Y2O3-stabilized ZrO2 powder is 45 wt% of the mass of the precursor; the mass of the added binder is 10 wt% of the mass of the Y2O3-stabilized ZrO2 powder;

[0108] S5. Spray granulate the slurry to obtain granulated powder;

[0109] S6. Place the granulated powder in a cold sintering device, hold the pressure at 800 Mpa for 10 min, then heat it at a heating rate of 10 °C / min to 450 °C, and keep it warm for 120 min to obtain a cold sintered body;

[0110] S7. Dry the cold sintered body at 200 °C for 12 h, then heat it at a heating rate of 10 °C / min to 700 °C, anneal for 3 h, and naturally cool to obtain cold sintered zirconia ceramics.

[0111] Example 4

[0112] This example provides a method for preparing cold sintered zirconia ceramics, including the following steps:

[0113] S1. Add zirconium nitrate to water to obtain a 250 mL, 1 mol / L soluble zirconium salt solution;

[0114] S2. Add a 1 mol / L magnesium nitrate solution (aqueous solution) to the soluble zirconium salt solution in S1 to obtain a first mixed solution; calculated based on the molar amount of zirconium salt in the soluble zirconium salt solution, the addition amount of the stabilizer magnesium nitrate is 5 mol% of the zirconium salt (zirconium nitrate);

[0115] S3. Add 680 mL of a 0.8 mol / L oxalic acid solution as a precipitating agent to the first mixed solution to completely precipitate the metal ions in the first mixed solution, and continuously stir to make the precipitate completely uniform to obtain a precursor;

[0116] S4. Add Y2O3-stabilized ZrO2 powder and a binder to the precursor, and ball mill and disperse to obtain a slurry; the binder includes an aqueous solution of polyvinyl alcohol and an acrylic emulsion, and the mass ratio of the aqueous solution of polyvinyl alcohol to the acrylic emulsion is 1:1; the doping amount of Y2O3 in the Y2O3-stabilized ZrO2 powder (3YSZ powder) is 3 mol%; the mass of the added Y2O3-stabilized ZrO2 powder is 40 wt% of the mass of the precursor; the mass of the added binder is 10 wt% of the mass of the Y2O3-stabilized ZrO2 powder;

[0117] S5. Spray granulate the slurry to obtain granulated powder;

[0118] S6. Place the granulated powder in a cold sintering device, hold the pressure at 800 Mpa for 60 min, then heat it at a heating rate of 10 °C / min to 450 °C, and keep it warm for 30 min to obtain a cold sintered body;

[0119] S7. The cold-sintered body was dried at 200 °C for 12 h, then heated to 1000 °C at a heating rate of 5 °C / min, annealed for 1 h, and cooled naturally to obtain cold-sintered zirconia ceramics.

[0120] Performance testing

[0121] The results of the relative density, Vickers hardness, and grain size of the cold-sintered zirconia ceramics prepared in Test Examples 1 to 4 are shown in Table 1 below. Among them, the relative density = measured density / theoretical density (6.08 g / cm 3 ) was calculated; Vickers hardness (Hv): A pyramidal indentation was made on the polished ceramic surface using an indentation technique. Hv = 0.0018544 (P / d 2 ), where P = applied force and d = diagonal length of the indentation pyramid; Grain size: Read from the scanning electron microscope image.

[0122] Table 1 - Properties of the cold-sintered zirconia ceramics prepared in Examples 1 to 4

[0123] Example Relative density Vickers hardness Average grain size Example 1 92% 11.7 Gpa 180.07 nm Example 2 95% 13.5 Gpa 173.28 nm Example 3 91% 10.8 Gpa 233.77 nm Example 4 92% 12.6 Gpa 215.96 nm

[0124] Figure 3 This is a cross-sectional scanning electron microscope image of the cold-sintered zirconia ceramic prepared in Example 1 (the particle size distribution statistics are shown in the upper left corner).

[0125] From Figure 3 it can be seen that the average grain size of the cold-sintered zirconia ceramic prepared in Example 1 is 180.07 nm.

[0126] Figure 4 The principle of preparing the cold-sintered zirconia ceramic in Example 1 based on the principle of biomimetic mineralization of the present invention is further elaborated.

[0127] From Figure 4 it can be seen that on the grain boundaries between the large zirconia grains in Example 1, the grain boundaries are filled with fine zirconia grains. These fine grains are formed by the non-equilibrium dissolution on the surface of the amorphous ZrO2 formed by the dehydration of the precursor and the directional precipitation in the grain boundary region under high pressure. This process gradually "heals" the grain boundaries.

[0128] Figure 5 This is a cross-sectional scanning electron microscope image of the cold-sintered zirconia ceramic in Example 2 of the present invention (the particle size distribution statistics are shown in the upper left corner).

[0129] From Figure 5 it can be seen that the average grain size of the cold-sintered zirconia ceramic prepared in Example 2 is 173.28 nm.

[0130] Figure 6Cross-sectional scanning electron micrograph of the cold-sintered zirconia ceramic in Example 3 of the present invention (the particle size distribution statistics are shown in the upper left corner).

[0131] As can be seen from Figure 6 the average grain size of the cold-sintered zirconia ceramic prepared in Example 3 is 233.77 nm.

[0132] Figure 7 Cross-sectional scanning electron micrograph of the cold-sintered zirconia ceramic in Example 4 of the present invention (the particle size distribution statistics are shown in the upper left corner).

[0133] As can be seen from Figure 7 the average grain size of the cold-sintered zirconia ceramic prepared in Example 3 is 215.96 nm.

[0134] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing cold-sintered zirconia ceramics, characterized in that, It includes the following steps: Add soluble zirconium salt into water to obtain a soluble zirconium salt solution; Add a stabilizer into the soluble zirconium salt solution to obtain a first mixed solution; Add a precipitating agent into the first mixed solution, stir to obtain a precursor; Add Y2O3-stabilized ZrO2 powder and a binder into the precursor, disperse to obtain a slurry; Perform spray granulation on the slurry to obtain granulated powder; Place the granulated powder in a cold sintering device, keep the pressure at 300 - 400 MPa for 30 min, then heat it at a heating rate of 10 °C / min to 180 - 300 °C, and keep it warm for 120 - 180 min to obtain a cold sintered body; After drying the cold sintered body, heat it at a heating rate of 5 °C / min to 900 - 1100 °C, and anneal for 1 - 3 h to obtain cold sintered zirconia ceramics; The stabilizer is a soluble yttrium salt, and the soluble yttrium salt is yttrium nitrate; The soluble zirconium salt is zirconyl chloride; The precipitating agent is oxalic acid or phosphoric acid, and the concentration of the precipitating agent is 0.8 - 1.0 M; The addition amount of the stabilizer is 3 - 6 mol% of the zirconium salt; the concentration of the soluble zirconium salt solution is 1 M; The volume ratio of the precipitating agent to the soluble zirconium salt solution is (220 - 700):250; The mass of the Y2O3-stabilized ZrO2 powder is 25 - 30% of the mass of the precursor.

2. The preparation method of the cold-sintered zirconia ceramic according to claim 1, characterized in that, Dry the cold sintered body at 200 °C for 10 h.

3. The preparation method of the cold-sintered zirconia ceramic according to claim 1, wherein, The binder includes an aqueous polyvinyl alcohol solution and an acrylic emulsion with a mass ratio of 1:1; The concentration of the aqueous polyvinyl alcohol solution is 10 wt%.

4. The preparation method of the cold-sintered zirconia ceramic according to claim 1, characterized in that, The doping amount of Y2O3 in the Y2O3-stabilized ZrO2 powder is 3 mol%.

5. A cold-sintered zirconia ceramic, characterized in that, It is prepared by using the preparation method described in any one of claims 1 - 4.

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