Preparation method and application of Al2O3 self-reinforced zirconia medical ceramic material

Abstract

The application discloses a preparation method and application of Al2O3 self-reinforced zirconia medical ceramic material and belongs to the field of biological ceramic material preparation. The preparation method comprises the following steps: firstly, aluminum particles are surface passivated, then the surface passivated aluminum particles are mixed with Y2O3-ZrO2 ceramic powder, a dispersing agent and a binder to prepare slurry, green bodies are obtained through spray granulation and dry pressing forming, and finally, finished products are prepared through atmosphere sintering, oxygen absorption reaction and high-temperature sintering. The volume expansion effect of in-situ generated Al2O3 artificially introduces a beneficial local compressive stress field in the zirconia matrix, effectively compensates for the phase change strengthening effect lost due to the increase of yttria content, realizes the synergistic improvement of the mechanical properties and anti-aging performance of the zirconia full ceramic material, and solves the problems of insufficient anti-aging performance of the zirconia full ceramic material in the prior art, significant decrease of the strength after the increase of yttria, and insufficient strengthening effect of the traditional Al2O3 second phase.

Description

Technical Field

[0001] This invention relates to the field of bioceramic material preparation technology, specifically to a method for preparing and applying Al2O3 self-reinforced zirconia medical ceramic material. Background Technology

[0002] Yttrium oxide-stabilized tetragonal zirconia polycrystalline ceramics (Y-TZP), especially 3Y-TZP (containing 3 mol% yttrium oxide), have become one of the preferred materials in the field of dental restoration (such as crowns, bridges, and implant abutments) due to their excellent mechanical properties, good biocompatibility, and aesthetics. Their high toughness mainly stems from the stress-induced phase transformation toughening mechanism: under the stress field at the crack tip, the metastable tetragonal phase (t-ZrO2) transforms into the monoclinic phase (m-ZrO2), accompanied by volume expansion, thereby absorbing crack propagation energy and generating compressive stress, hindering further crack propagation.

[0003] However, 3Y-TZP faces severe low-temperature degradation (LDT) problems when used long-term in a humid environment (approximately 37°C, containing water vapor). Water molecules combine with lattice oxygen on the material's surface and within, lowering the phase transition energy barrier and inducing a spontaneous t→m phase transition on the material surface. This non-stress-induced, uncontrollable phase transition leads to surface micro-protrusions and microcracks. Over time, these cracks propagate inwards, significantly reducing the material's strength and toughness, severely shortening the lifespan of the restoration.

[0004] To enhance the anti-aging properties of zirconia ceramics in dental restorations, one common strategy is to increase the molar content of its stabilizer, yttrium oxide, for example, by introducing 4Y-TZP or 5Y-TZP (tetragonal polycrystalline zirconia) systems. These materials, by increasing the yttrium doping ratio, significantly suppress the low-temperature degradation of zirconia in humid and hot environments, thereby delaying the propagation of microcracks and the decline in mechanical properties caused by surface phase transformation. However, this optimization approach presents a significant performance trade-off. The toughening mechanism of tetragonal zirconia mainly relies on the stress-induced t→m phase transformation (the transition from tetragonal to monoclinic phase), a process accompanied by volume expansion, which can form a compressive stress zone at the crack tip, hindering crack propagation. Increasing the yttrium oxide content raises the phase transformation activation energy, making the tetragonal phase too stable, and the material struggles to trigger an effective toughening phase transformation even under high stress. This results in a significant decrease in the material's strength and fracture toughness. This degradation of mechanical properties is particularly critical in clinical applications, especially in high-load-bearing posterior tooth restorations (such as fully anatomical crowns or fixed bridge abutments), where the material must simultaneously resist cyclic masticatory loads and impact fracture. Insufficient strength and toughness can lead to premature porcelain chipping or overall fracture of the restoration, severely impacting its long-term success rate. Therefore, balancing anti-aging properties with mechanical reliability remains a core challenge that urgently needs to be addressed in the development of high-performance zirconia materials.

[0005] Alumina (Al₂O₃) is a high-performance bioceramic material with excellent biocompatibility, chemical stability, low thermal conductivity, insulation, and superior mechanical properties, making it an ideal choice for dental materials such as implants and restorations. Furthermore, Al₂O₃ is frequently used as an additive in zirconia. Adding alumina to a zirconia matrix can produce multi-dimensional synergistic modification effects: (1) Suppressing low-temperature aging. The added Al2O3 tends to be distributed at the zirconia grain boundaries during sintering. Its high elastic modulus can "clamp" the zirconia grains, limiting the free volume expansion space required for the t→m phase transformation. At the same time, alumina can reduce the diffusion channels of water or hydroxyl ions along the grain boundaries into the interior of the lattice, delaying or suppressing the induction of surface phase transformation.

[0006] (2) Promotes the densification of the zirconia matrix during sintering. Pure zirconia typically requires ultra-high temperatures or long holding times to achieve high density due to its slow ion diffusion. Alumina, on the other hand, forms a liquid phase or enhances grain boundary diffusion during sintering. 3+ Radius smaller than Zr 4+ A small amount of Al at high temperature 3+ Solid solution enters the zirconia lattice, creating lattice distortion and vacancies, which accelerates ion migration. In addition, alumina particles form pinning points, providing additional surface diffusion channels in the early stages of sintering.

[0007] (3) Suppressing grain coarsening. The mechanical properties of zirconia ceramics are strongly dependent on grain size. The uniform distribution of Al2O3 particles at the zirconia grain boundaries can generate grain boundary pinning. When the grain boundaries attempt to move, they encounter inert alumina particles, which generate a drag force, effectively preventing abnormal grain growth.

[0008] (4) Strengthening effect. Al2O3 itself is a high-performance ceramic, and when combined with zirconium oxide, it can achieve a "strong-strong combination". Enhanced strength and hardness: Alumina has a higher hardness than zirconium oxide, and adding a small amount can also improve the flexural strength of the composite ceramic.

[0009] Therefore, considering the need to improve the anti-aging properties and strength of zirconia all-ceramic materials, the existing technical solution is to introduce an Al2O3 second phase while increasing the yttrium oxide content. This leverages the mismatch in thermal expansion coefficients and elastic modulus between Al2O3 and the zirconia matrix, as well as the inhibitory effect of Al2O3 on coarsening during sintering, to induce microcracks in the ceramic matrix, promoting crack deflection and achieving composite strengthening. However, compared to the strengthening effect of zirconia's phase transformation toughening mechanism, the strengthening effect of adding an Al2O3 second phase is still relatively limited. The fundamental reason is that 3Y-TZP generates a volume expansion effect during phase transformation toughening, thus forming compressive stress with a "pinning effect" within the matrix, which can actively inhibit crack initiation; while the reinforcement of the second phase particles mainly relies on the passive inhibition of crack propagation. Therefore, how to effectively compensate for or even reverse the strength reduction caused by adjusting the anti-aging component ratio while maintaining or improving the anti-aging properties of zirconia materials has become a key technical problem urgently needing to be solved in this field. Summary of the Invention

[0010] To address the aforementioned technical problems, the present invention aims to provide a method for preparing and applying Al2O3 self-reinforced zirconia medical ceramic materials, thereby resolving issues such as insufficient anti-aging properties of existing zirconia all-ceramic materials, significant strength reduction after adding yttrium oxide, and insufficient strengthening effect of traditional Al2O3 second phase addition.

[0011] The technical solution of the present invention to solve the above-mentioned technical problems is as follows: In a first aspect, the present invention provides a method for preparing Al2O3 self-reinforced zirconia medical ceramic material, comprising the following steps: Preparation of S1, Y2O3-ZrO2 ceramic powder: ZrOCl2·8H2O, Y(NO3)3·6H2O were mixed with deionized water, and Y2O3-ZrO2 ceramic powder was obtained by precipitation and heat treatment. S2, Aluminum particle surface passivation: Aluminum particles are heated in an alkaline solution in a water bath to obtain surface-passivated aluminum particles. S3. Green body preparation: First, the Y2O3-ZrO2 ceramic powder obtained from S1 and the surface passivated aluminum particles obtained from S2 are mixed, and a dispersant and a binder are added and mixed in a dispersion medium to obtain a mixed slurry. Then, the mixed slurry is spray granulated to obtain granulated powder. Finally, the granulated powder is dry-pressed to obtain a green body. S4, Atmosphere sintering: The green body obtained from S3 was sintered under an inert atmosphere to obtain a pre-densified ceramic. S5, Oxygen absorption reaction: The pre-densified ceramic obtained from S4 was subjected to an oxygen absorption reaction in a mixed atmosphere of oxygen and argon to obtain zirconia ceramics with in-situ Al2O3 formation. S6. High-temperature sintering: The zirconia ceramic with in-situ Al2O3 generated in S5 was sintered at high temperature in air atmosphere to obtain Al2O3 self-reinforced zirconia medical ceramic material.

[0012] The beneficial effects of this invention are as follows: This invention abandons the traditional single anti-aging + strengthening approach and proposes a synergistic anti-aging + strengthening approach, thereby effectively improving the anti-aging properties of zirconia all-ceramic materials. Specifically, this invention replaces Al2O3 particles in the traditional process with surface-passivated aluminum particles. The internal aluminum particles absorb oxygen during high-temperature aerobic sintering to generate Al2O3, achieving a volume expansion effect similar to zirconia phase transformation strengthening. This introduces a local compressive stress field at the matrix lattice and grain boundaries, simulating the compressive stress effect generated by phase transformation strengthening from the outside. The outer Al2O3 layer promotes the sintering of the surrounding zirconia matrix, avoiding stress concentration and defect formation. Ultimately, this achieves a simultaneous improvement in the anti-aging properties and strength of zirconia all-ceramic materials. Finally, without introducing additional impurities or changing the main body of the existing preparation process, a synergistic improvement in the mechanical properties and anti-aging properties of zirconia all-ceramic materials is achieved.

[0013] Furthermore, the molar content of Y2O3 in the Y2O3-ZrO2 ceramic powder in S1 is 4.5%.

[0014] The beneficial effects of adopting the above-mentioned further technical solution are as follows: The present invention uses 4.5 mol% Y2O3 to prepare Y2O3-ZrO2 ceramic powder, which retains some phase transformation strengthening effect compared with 5Y-PSZ (5 mol% Y2O3 addition). Al2O3 particles are introduced to further improve its strength, while its own anti-aging effect avoids the low-temperature aging effect caused by phase transformation strengthening.

[0015] Furthermore, S1 specifically includes the following steps: ZrOCl2·8H2O, Y(NO3)3·6H2O and deionized water were mixed and stirred, while ammonia solution was added dropwise. The mixture was allowed to stand to precipitate, then washed, dried, and finally heat-treated. After ball milling and sieving, Y2O3-ZrO2 (4.5 mol% Y2O3) ceramic powder was obtained.

[0016] Further, the mass ratio of ZrOCl2·8H2O, Y(NO3)3·6H2O, and deionized water is (80-100):(7.84-11.2):500; the stirring method is magnetic stirring at a speed of 800-1200 rpm; the concentration of the ammonia solution is 3-5 mol / L; the ammonia solution is added dropwise until the pH of the system reaches 10, then the addition is stopped and the mixture is allowed to stand for 10-15 h. The ball milling time is 10-30 h; the sieve mesh is 800 mesh; and the mixture is heat-treated at 600-700℃ under an argon atmosphere for 4-6 h.

[0017] Furthermore, the aluminum particles in S2 have a particle size of 1-10 μm; the alkaline solution is a sodium hydroxide solution with a concentration of 0.1-0.5 mol / L; and the water bath heating temperature is 40-60℃ for 10-30 min.

[0018] The beneficial effects of adopting the above-mentioned further technical solution are as follows: The present invention achieves the preparation of an Al2O3 layer on the surface of aluminum particles by passivating the particle surface through water bath treatment in an alkaline solution. This process replaces the traditional Al2O3 second phase addition process. The outer Al2O3 layer can promote the sintering of the zirconia matrix during sintering and avoid stress concentration and the formation of defects. The inner aluminum particles absorb oxygen to generate Al2O3 during the oxygen sintering process, which effectively inhibits the abnormal growth of zirconia grains, promotes material densification, and further improves the reliability of the material.

[0019] Furthermore, the aluminum particles in S2 are ultrasonically cleaned in anhydrous ethanol before surface passivation.

[0020] Furthermore, the ultrasonic cleaning time in S2 is 30-60 min, followed by vacuum drying at 60-80℃.

[0021] Furthermore, after the surface passivation of S2 is completed, the aluminum particles are washed with deionized water until the pH is neutral, then dehydrated with anhydrous ethanol and vacuum dried at 40-60℃.

[0022] Furthermore, in S3, the amount of surface-passivated aluminum particles added is 0.1%-1% of the mass of Y2O3-ZrO2 ceramic powder; the dispersant is ammonium polyacrylate, and the amount added is 0.5%-2% of the total mass of Y2O3-ZrO2 ceramic powder and surface-passivated aluminum particles; the binder is polyvinyl alcohol, and the amount added is 3%-5% of the total mass of Y2O3-ZrO2 ceramic powder and surface-passivated aluminum particles.

[0023] Furthermore, the stirring rate in S3 is 600-800 rpm, and the time is 4-6 h; the inlet temperature of spray granulation is 160-180℃, and the outlet temperature is 80-100℃; during dry pressing, the pressure is first increased to 10-50 MPa and held for 5-8 min, then increased to 100-150 MPa and held for 10-15 min, and finally increased to 180-220 MPa and held for 10-15 min.

[0024] Furthermore, the inert atmosphere in S4 includes argon gas, with a flow rate of 180-240 mL / h; the sintering conditions are as follows: first, heat to 200-300℃ at a rate of 0.5-1℃ / min and hold for 1-2 h, then heat to 400-500℃ at a rate of 0.3-0.5℃ / min and hold for 2-4 h, and finally heat to 1250-1350℃ at a rate of 2-5℃ / min and hold for 18-36 h, and after sintering, cool to room temperature at a rate of 1-3℃ / min.

[0025] Furthermore, the total flow rate of the mixed gas in S5 is 190-260 mL / h, and the flow rate ratio of argon to oxygen is (18-25):1. The conditions for the oxygen absorption reaction are as follows: first, heat to 350-550℃ at a rate of 3-5℃ / min and hold for 2-4 h; then heat to 650-750℃ at a rate of 1-2℃ / min and hold for 1-2 h; finally, heat to 1250-1350℃ at a rate of 0.5-1℃ / min and hold for 4-6 h; and finally, cool to room temperature at a rate of 3-5℃ / min.

[0026] The beneficial effects of adopting the above-mentioned further technical solution are as follows: The present invention carries out an oxygen absorption reaction in a mixed atmosphere of oxygen and argon, so that the aluminum inside forms Al2O3 in situ, thereby achieving a volume expansion effect similar to the phase transformation strengthening of zirconia. A beneficial local compressive stress field is introduced into the zirconia matrix, which compensates for the phase transformation strengthening effect lost due to the increase of yttrium oxide content, thereby achieving a simultaneous improvement in anti-aging properties and strength.

[0027] Furthermore, the conditions for high-temperature sintering in S6 are: heating rate of 3-5℃ / min, sintering temperature of 1450-1550℃, and holding time of 6-8 h.

[0028] The beneficial effects of adopting the above-mentioned further technical solutions are as follows: the present invention removes internal defects and thermal stress of materials through high-temperature sintering.

[0029] In a second aspect, the present invention provides an Al2O3 self-reinforced zirconia medical ceramic material, which is prepared by the above-described preparation method.

[0030] A third aspect of the present invention provides the application of the above-mentioned Al2O3 self-reinforced zirconia medical ceramic material in oral restorative materials.

[0031] The beneficial effects of this invention are as follows: The Al2O3 self-reinforced zirconia medical ceramic material prepared by this invention has excellent mechanical properties, good biocompatibility and aesthetics, and can be applied to the preparation of various oral restoration materials, with broad application prospects.

[0032] The present invention has the following beneficial effects: 1. Achieving in-situ compressive stress self-reinforcement: By generating Al2O3 in situ, a beneficial local compressive stress field is artificially introduced into the zirconia matrix, which effectively compensates for the phase transformation strengthening effect lost due to the increase of yttrium oxide content.

[0033] 2. High process compatibility and purity: No additional additives or changes to the existing ceramic sintering process are required. The aluminum powder used is converted into Al2O3, a sintering aid for zirconia ceramics, after the reaction. The overall purity of the material is high and there are no harmful impurities.

[0034] 3. Improved sintering and microstructure: The highly active Al2O3 generated in situ is uniformly distributed at the grain boundaries, effectively inhibiting the abnormal growth of zirconia grains, promoting densification, obtaining a fine-grained and uniform microstructure, and further improving the reliability of the material. Attached Figure Description

[0035] Figure 1 This is a process flow diagram for preparing the Al2O3 self-reinforced zirconia medical ceramic material of the present invention; Figure 2 The XRD pattern of the aluminum particle raw material used in Example 3 of this invention; Figure 3 This is a spot scan of the surface energy spectrum of the passivated aluminum particles obtained in S2 of Example 3 of the present invention; Figure 4 This is a spot scan of the internal energy spectrum of the passivated aluminum particles obtained in S2 of Example 3 of the present invention; Figure 5 This is a spot scan of the internal energy spectrum of the oxygen absorption product obtained in S5 of Example 3 of the present invention; Figure 6 Images of the biaxial bending test equipment, test mold, and samples from Example 1 before and after testing; Figure 7The images show the fracture failures of the materials prepared in Examples 1-3 and Comparative Example 1 after undergoing biaxial bending tests. Figure 8 This is a load-displacement curve of the material obtained in Example 1 during the biaxial bending test. Figure 9 This is a load-displacement curve of the material obtained in Example 2 during the biaxial bending test. Figure 10 This is a load-displacement curve of the material obtained in Example 3 during the biaxial bending test. Figure 11 This is a load-displacement curve of the material prepared in Comparative Example 1 during the biaxial bending test. Detailed Implementation

[0036] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified in the examples, conventional conditions or conditions recommended by the manufacturer should be followed. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0037] Example 1: A method for preparing Al2O3 self-reinforced zirconia medical ceramic material (process flow diagram as follows) Figure 1 (As shown), including the following steps: Preparation of S1,Y2O3-ZrO2 (4.5 mol%Y2O3) ceramic powder: ZrOCl2·8H2O, Y(NO3)3·6H2O, and deionized water were mixed at a mass ratio of 70:7.84:500 and magnetically stirred at 1000 rpm. Simultaneously, 4 mol / L ammonia solution was added dropwise until the pH of the system reached 10. The mixture was allowed to stand for 12 h to precipitate. Then, the mixture was washed and dried. Finally, it was heat-treated at 650℃ under an argon atmosphere for 4 h, ball-milled for 24 h, and then sieved through an 800-mesh sieve to obtain Y2O3-ZrO2 (4.5 mol% Y2O3) ceramic powder.

[0038] S2, Aluminum particle surface passivation: A suitable amount of aluminum particles with an average particle size of 1 μm was placed in a beaker, submerged in anhydrous ethanol, and ultrasonically cleaned for 30 min. After cleaning, the particles were vacuum dried at 60 °C. The dried aluminum particles were then added to a 0.1 mol / L sodium hydroxide solution and heated in a water bath at 40 °C for 10 min. After the reaction was complete, the particles were repeatedly washed with deionized water until the pH was neutral, then dehydrated with anhydrous ethanol, and finally vacuum dried at 40 °C to obtain surface-passivated aluminum particles.

[0039] S3. Green body preparation: First, the Y2O3-ZrO2 (4.5 mol% Y2O3) ceramic powder obtained by S1 was placed in a beaker. Passivated aluminum particles obtained by S2 were added at a dosage of 0.1 wt%, and the mixture was submerged in deionized water. Then, 0.5% of the total mass of the Y2O3-ZrO2 ceramic powder and passivated aluminum particles in ammonium polyacrylate and 3% in polyvinyl alcohol solution were added. The mixture was magnetically stirred at 600 rpm for 4 hours to obtain a mixed slurry. Finally, the mixed slurry was spray-granulated, with the inlet temperature controlled at 160℃ and the outlet temperature at 80℃ to obtain a mixed powder. The obtained mixed powder was added to a dry-pressing mold and dry-pressed using a hydraulic press. First, the pressure was increased to 10 MPa and held for 5 min; then increased to 100 MPa and held for 10 min; finally, the pressure was increased to 180 MPa and held for 10 min to obtain an aluminum-doped Y2O3-ZrO2 green body.

[0040] S4, Atmosphere sintering: The aluminum-doped Y₂O₃-ZrO₂ green body obtained from S3 was placed in a sintering furnace, and argon gas was introduced at a flow rate of 180 mL / h. The heating program was as follows: first, the temperature was increased to 200℃ at 0.5℃ / min and held for 1 h; then, the temperature was increased to 400℃ at 0.3℃ / min and held for 2 h; finally, the temperature was increased to 1250℃ at 2℃ / min and held for 18 h. After sintering, the temperature was cooled to room temperature at 1℃ / min to obtain aluminum-doped Y₂O₃-ZrO₂ ceramic with a certain density.

[0041] S5, Oxygen absorption reaction: The aluminum-doped Y₂O₃-ZrO₂ ceramic with a certain density obtained in S4 was placed in a sintering furnace, and an oxygen-argon mixed atmosphere was introduced, with an argon:oxygen flow rate ratio of 18:1 (total flow rate of 190 mL / h). The heating program was as follows: first, the temperature was increased to 350℃ at 3℃ / min and held for 2 h; then, the temperature was increased to 650℃ at 1℃ / min and held for 1 h; finally, the temperature was increased to 1250℃ at 0.5℃ / min and held for 4 h. After sintering, the temperature was cooled to room temperature at 3℃ / min to allow aluminum to oxidize in situ to form Al₂O₃.

[0042] S6. High-temperature sintering: The sample obtained after the S5 oxygen absorption reaction was placed in a sintering furnace and sintered at high temperature in an air atmosphere. The temperature was increased to 1450℃ at 3℃ / min and held for 6 h. Then, the sample was cooled to room temperature in the furnace to remove internal defects and thermal stress, thus obtaining Al2O3 self-reinforced zirconia medical ceramic material.

[0043] Example 2: A method for preparing Al2O3 self-reinforced zirconia medical ceramic material (process flow diagram as follows) Figure 1 (As shown), including the following steps: Preparation of S1,Y2O3-ZrO2 (4.5 mol%Y2O3) ceramic powder: First, ZrOCl2·8H2O, Y(NO3)3·6H2O, and deionized water were mixed at a mass ratio of 80:8.96:500 and magnetically stirred at 1000 rpm. Simultaneously, 4 mol / L ammonia solution was added dropwise until the pH of the system reached 10. The mixture was then allowed to stand for 12 h to precipitate. After washing and drying, the mixture was heat-treated at 650℃ for 5 h under an argon atmosphere. Finally, it was ball-milled for 24 h and sieved through an 800-mesh sieve to obtain Y2O3-ZrO2 (4.5 mol% Y2O3) ceramic powder.

[0044] S2, Aluminum particle surface passivation: A suitable amount of aluminum particles with an average particle size of 5 μm was placed in a beaker, submerged in anhydrous ethanol, and ultrasonically cleaned for 45 min. After cleaning, the particles were vacuum dried at 70 °C. The dried aluminum particles were then added to a 0.3 mol / L sodium hydroxide solution and heated in a water bath at 50 °C for 20 min. After the reaction was complete, the particles were repeatedly washed with deionized water until the pH was neutral, then dehydrated with anhydrous ethanol, and finally vacuum dried at 50 °C to obtain surface-passivated aluminum particles.

[0045] S3. Green body preparation: First, the Y2O3-ZrO2 (4.5 mol% Y2O3) ceramic powder obtained by S1 was placed in a beaker, and passivated aluminum particles obtained by S2 were added at an addition rate of 0.5 wt%, followed by immersion in deionized water. Then, 1.5% of the total mass of Y2O3-ZrO2 ceramic powder and passivated aluminum particles in ammonium polyacrylate and 4% in polyvinyl alcohol solution were added, and the mixture was magnetically stirred at 700 rpm for 5 hours to obtain a mixed slurry. Finally, the mixed slurry was spray-granulated, with the inlet temperature controlled at 170℃ and the outlet temperature at 90℃ to obtain a mixed powder. The obtained mixed powder was added to a dry pressing mold and dry-pressed using a hydraulic press. First, the pressure was increased to 30 MPa and held for 6 min; then the pressure was increased to 125 MPa and held for 12 min; finally, the pressure was increased to 200 MPa and held for 13 min to obtain an aluminum-doped Y2O3-ZrO2 green body.

[0046] S4, Atmosphere sintering: The aluminum-doped Y₂O₃-ZrO₂ green body obtained from S3 was placed in a sintering furnace, and argon gas was introduced at a flow rate of 210 mL / h. The heating program was as follows: first, the temperature was increased to 250℃ at 0.8℃ / min and held for 1.5 h; then, the temperature was increased to 450℃ at 0.4℃ / min and held for 3 h; finally, the temperature was increased to 1300℃ at 3.5℃ / min and held for 24 h. After sintering, the temperature was cooled to room temperature at 2℃ / min to obtain aluminum-doped Y₂O₃-ZrO₂ ceramic with a certain density.

[0047] S5, Oxygen absorption reaction: The aluminum-doped Y₂O₃-ZrO₂ ceramic with a certain density obtained in S4 was placed in a sintering furnace, and an oxygen-argon mixed atmosphere was introduced, with an argon:oxygen flow rate ratio of 22:1 (total flow rate of 230 mL / h). The heating program was as follows: first, the temperature was increased to 450℃ at 4℃ / min and held for 3 h; then, the temperature was increased to 700℃ at 1.5℃ / min and held for 1.5 h; finally, the temperature was increased to 1300℃ at 0.75℃ / min and held for 5 h. After sintering, the temperature was cooled to room temperature at 4℃ / min to allow aluminum to oxidize in situ to form Al₂O₃.

[0048] S6. High-temperature sintering: The sample obtained after the S5 oxygen absorption reaction was placed in a sintering furnace and sintered at high temperature in an air atmosphere. The temperature was increased to 1500℃ at a rate of 4℃ / min and held for 7 h. Then, the sample was cooled to room temperature in the furnace to remove internal defects and thermal stress, thus obtaining Al2O3 self-reinforced zirconia medical ceramic material.

[0049] Example 3: A method for preparing Al2O3 self-reinforced zirconia medical ceramic material (process flow diagram as follows) Figure 1 (As shown), including the following steps: Preparation of S1,Y2O3-ZrO2 (4.5 mol%Y2O3) ceramic powder: ZrOCl2·8H2O, Y(NO3)3·6H2O, and deionized water were mixed at a mass ratio of 100:11.2:500 and magnetically stirred at 1000 rpm. Simultaneously, 4 mol / L ammonia solution was added dropwise until the pH of the system reached 10. The mixture was allowed to stand for 12 h to precipitate. Then, the mixture was washed and dried. Finally, it was heat-treated at 650℃ under an argon atmosphere for 6 h, ball-milled for 24 h, and then sieved through an 800-mesh sieve to obtain Y2O3-ZrO2 (4.5 mol% Y2O3) ceramic powder.

[0050] S2, Aluminum particle surface passivation: A suitable amount of aluminum particles with an average particle size of 10 μm was placed in a beaker, submerged in anhydrous ethanol, and ultrasonically cleaned for 60 min. After cleaning, the particles were vacuum dried at 80 °C. The dried aluminum particles were then added to a 0.5 mol / L sodium hydroxide solution and heated in a water bath at 60 °C for 30 min. After the reaction was complete, the particles were repeatedly washed with deionized water until the pH was neutral, then dehydrated with anhydrous ethanol, and finally vacuum dried at 60 °C to obtain surface-passivated aluminum particles.

[0051] S3. Green body preparation: First, the Y2O3-ZrO2 (4.5 mol% Y2O3) ceramic powder obtained by S1 was placed in a beaker. Passivated aluminum particles obtained by S2 were added at a dosage of 1 wt%, and the mixture was submerged in deionized water. Then, a solution of 2% ammonium polyacrylate and 5% polyvinyl alcohol (polyvinyl alcohol) based on the total mass of the Y2O3-ZrO2 ceramic powder and passivated aluminum particles was added. The mixture was magnetically stirred at 800 rpm for 6 h to obtain a mixed slurry. Finally, the mixed slurry was spray-granulated, with the inlet temperature controlled at 180℃ and the outlet temperature at 100℃ to obtain a mixed powder. The obtained mixed powder was added to a dry-pressing mold and dry-pressed using a hydraulic press. The pressure was first increased to 50 MPa and held for 8 min; then increased to 150 MPa and held for 15 min; finally, increased to 220 MPa and held for 15 min to obtain an aluminum-doped Y2O3-ZrO2 green body.

[0052] S4, Atmosphere sintering: The aluminum-doped Y₂O₃-ZrO₂ green body obtained from S3 was placed in a sintering furnace, and argon gas was introduced at a flow rate of 180 mL / h. The heating program was as follows: first, the temperature was increased to 300℃ at 1℃ / min and held for 2 h; then, the temperature was increased to 500℃ at 0.5℃ / min and held for 4 h; finally, the temperature was increased to 1350℃ at 5℃ / min and held for 36 h. After sintering, the temperature was cooled to room temperature at 3℃ / min to obtain aluminum-doped Y₂O₃-ZrO₂ ceramic with a certain density.

[0053] S5, Oxygen absorption reaction: The aluminum-doped Y₂O₃-ZrO₂ ceramic with a certain density obtained in S4 was placed in a sintering furnace, and an oxygen-argon mixed atmosphere was introduced, with an argon:oxygen flow rate ratio of 25:1 (total flow rate of 260 mL / h). The heating program was as follows: first, the temperature was increased to 550℃ at 5℃ / min and held for 4 h; then, the temperature was increased to 750℃ at 2℃ / min and held for 2 h; finally, the temperature was increased to 1350℃ at 1℃ / min and held for 6 h. After sintering, the temperature was cooled to room temperature at 5℃ / min to allow aluminum to oxidize in situ to form Al₂O₃.

[0054] S6. High-temperature sintering: The sample obtained after the S5 oxygen absorption reaction was placed in a sintering furnace and sintered at high temperature in an air atmosphere. The temperature was increased to 1550℃ at a rate of 5℃ / min and held for 8 h. Then, the sample was cooled to room temperature in the furnace to remove internal defects and thermal stress, thus obtaining Al2O3 self-reinforced zirconia medical ceramic material.

[0055] Comparative Example 1: A zirconia dental all-ceramic material is prepared in a manner that differs from that of Example 1 in that steps S1 and S2 are omitted, and 5Y-PSZ ceramic particles are used directly as raw materials in step S3. The remaining steps are the same as in Example 1.

[0056] Comparative Example 2: A zirconia dental all-ceramic material is prepared in a way that differs from that in Example 2 in that steps S1 and S2 are omitted, and 5Y-PSZ ceramic particles are used directly as raw materials in step S3. The remaining steps are the same as in Example 2.

[0057] Comparative Example 3: A zirconia dental all-ceramic material is prepared in a way that differs from that in Example 3 in that steps S1 and S2 are omitted, and 5Y-PSZ ceramic particles are used directly as raw materials in step S3. The remaining steps are the same as in Example 3.

[0058] Experimental Example 1: XRD and EDS Energy Dispersive Spectroscopy Analysis XRD analysis was performed on the aluminum particles before passivation in Example 3, and energy dispersive spectroscopy (EDS) was performed on the products formed after passivation and after the oxygen absorption reaction. The experimental results are as follows: Figures 2-5 As shown.

[0059] The results showed that the aluminum particles before passivation had no other impurities. Figure 2 After passivation, the surface of the aluminum particles exhibits a significant oxygen peak (). Figure 3 The central region exhibits a low-oxygen peak pattern similar to that before passivation. Figure 4 This indicates that the passivation process successfully formed an Al2O3 layer on the surface of the aluminum particles. This Al2O3 layer will help prevent the fusion of the molten aluminum particles during the subsequent heating process. After the oxygen absorption reaction, the central region of the product also exhibits a high oxygen peak. Figure 5 This indicates that the aluminum particles have been completely converted into Al2O3 after the oxygen absorption reaction.

[0060] Test Example 2: Biaxial Bending Test Biaxial bending tests were performed on the zirconia dental all-ceramic materials prepared in Examples 1-3 and Comparative Examples 1-3, respectively.

[0061] According to the biaxial bending strength test standard in ISO 6872:2024, the international standard for dental ceramic materials, a universal testing machine was used for biaxial bending strength testing. The sample size was 15 (± 0.5) mm × 1.5 (± 0.2) mm, the loading range was 2 kN, the loading speed was 0.5 mm / min, and the preload force was set to 5 N. The computer collected relevant data through load and displacement sensors. The biaxial bending strength was obtained by the following calculation formula:

[0062] in: In the formula: σ is the biaxial bending strength, MPa; P is the maximum load, N; b is the thickness of the sample, in mm; υ is the Poisson's ratio of the material, taken as 0.25; r1 is the radius of the supporting circle, in mm; r2 is the radius of the load area, in mm; r3 is the sample radius, in mm.

[0063] The biaxial bending performance test process is as follows: Figure 6 As shown in the figure, the test mold and the sample of Example 1 before and after the test are included.

[0064] The actual images of the fracture failures of Examples 1-3 and Comparative Example 3 after biaxial bending tests are shown below. Figure 7 As shown, the load-displacement correlation data during biaxial bending tests of different materials are respectively as follows: Figures 8-11 As shown in Table 1, the biaxial bending strength results are as follows.

[0065] Table 1. Biaxial Bending Strength Results

[0066] Depend on Figures 8-11 It can be seen that the Al2O3 self-reinforced zirconia dental all-ceramic materials prepared in Examples 1-3 still exhibit the typical brittle fracture characteristics of ceramic materials. However, the peak load of their load-displacement curves is significantly higher than that of the comparative example, indicating that the fracture strength of the material has been significantly improved. The results listed in Table 1 show that the biaxial bending strength of the Al2O3 self-reinforced zirconia dental all-ceramic materials prepared in Examples 1-3 of this invention all exceed 500 MPa, fully meeting the mechanical property requirements of the international standard ISO 6872:2024 for dental ceramic materials (anterior restorations ≥100 MPa, molar restorations ≥500 MPa). Among them, the sample of Example 3 after Al2O3 self-reinforcement treatment has the highest biaxial bending strength of 694 MPa, while the biaxial bending strength of Comparative Example 3 (unreinforced zirconia dental all-ceramic material) is 537 MPa. According to this calculation, the biaxial bending strength of the sample of Example 3 is improved by 29.2% compared with Comparative Example 3, showing a significant strengthening effect.

[0067] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing Al2O3 self-reinforced zirconia medical ceramic material, characterized in that, Includes the following steps: Preparation of S1, Y2O3-ZrO2 ceramic powder: ZrOCl2·8H2O, Y(NO3)3·6H2O were mixed with deionized water, and Y2O3-ZrO2 ceramic powder was obtained by precipitation and heat treatment. S2, Aluminum particle surface passivation: Aluminum particles are heated in an alkaline solution in a water bath to obtain surface-passivated aluminum particles. S3. Green body preparation: First, the Y2O3-ZrO2 ceramic powder obtained from S1 and the surface passivated aluminum particles obtained from S2 are mixed, and a dispersant and a binder are added and mixed in a dispersion medium to obtain a mixed slurry. Then, the mixed slurry is spray granulated to obtain granulated powder. Finally, the granulated powder is dry-pressed to obtain a green body. S4, Atmosphere sintering: The green body obtained from S3 was sintered under an inert atmosphere to obtain a pre-densified ceramic. S5, Oxygen absorption reaction: The pre-densified ceramic obtained from S4 was subjected to an oxygen absorption reaction in a mixed atmosphere of oxygen and argon to obtain zirconia ceramics with in-situ Al2O3 formation. S6. High-temperature sintering: The zirconia ceramic with in-situ Al2O3 generated in S5 was sintered at high temperature in air atmosphere to obtain Al2O3 self-reinforced zirconia medical ceramic material.

2. The preparation method of Al2O3 self-reinforced zirconia medical ceramic material according to claim 1, characterized in that, The molar content of Y2O3 in the Y2O3-ZrO2 ceramic powder in S1 is 4.5%.

3. The method for preparing Al2O3 self-reinforced zirconia medical ceramic material according to claim 1, characterized in that, The aluminum particles in S2 have a particle size of 1-10 μm; the alkaline solution is a sodium hydroxide solution with a concentration of 0.1-0.5 mol / L; the water bath heating temperature is 40-60℃ and the time is 10-30 min.

4. The method for preparing Al2O3 self-reinforced zirconia medical ceramic material according to claim 1, characterized in that, The amount of surface-passivated aluminum particles added in S3 is 0.1%-1% of the mass of Y2O3-ZrO2 ceramic powder; the dispersant is ammonium polyacrylate, and the amount added is 0.5%-2% of the total mass of Y2O3-ZrO2 ceramic powder and surface-passivated aluminum particles; the binder is polyvinyl alcohol, and the amount added is 3%-5% of the total mass of Y2O3-ZrO2 ceramic powder and surface-passivated aluminum particles.

5. The method for preparing Al2O3 self-reinforced zirconia medical ceramic material according to claim 1, characterized in that, The stirring rate in S3 is 600-800 rpm, and the time is 4-6 h; the inlet temperature of spray granulation is 160-180℃, and the outlet temperature is 80-100℃; during dry pressing, the pressure is first increased to 10-50 MPa and held for 5-8 min, then increased to 100-150 MPa and held for 10-15 min, and finally increased to 180-220 MPa and held for 10-15 min.

6. The method for preparing Al2O3 self-reinforced zirconia medical ceramic material according to claim 1, characterized in that, The inert atmosphere in S4 includes argon gas, with a flow rate of 180-240 mL / h. The sintering conditions are as follows: first, heat to 200-300℃ at a rate of 0.5-1℃ / min and hold for 1-2 h; then heat to 400-500℃ at a rate of 0.3-0.5℃ / min and hold for 2-4 h; finally, heat to 1250-1350℃ at a rate of 2-5℃ / min and hold for 18-36 h; after sintering, cool to room temperature at a rate of 1-3℃ / min.

7. The method for preparing Al2O3 self-reinforced zirconia medical ceramic material according to claim 1, characterized in that, The total flow rate of the mixed gas in S5 is 190-260 mL / h, and the flow rate ratio of argon to oxygen is (18-25):

1. The conditions for the oxygen absorption reaction are as follows: first, heat the gas to 350-550℃ at a rate of 3-5℃ / min and hold for 2-4 h; then heat the gas to 650-750℃ at a rate of 1-2℃ / min and hold for 1-2 h; finally, heat the gas to 1250-1350℃ at a rate of 0.5-1℃ / min and hold for 4-6 h; and finally, cool the gas to room temperature at a rate of 3-5℃ / min.

8. The method for preparing Al2O3 self-reinforced zirconia medical ceramic material according to claim 1, characterized in that, The conditions for high-temperature sintering in S6 are: heating rate of 3-5℃ / min, sintering temperature of 1450-1550℃, and holding time of 6-8h.

9. An Al2O3 self-reinforced zirconia medical ceramic material, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The application of the Al2O3 self-reinforced zirconia medical ceramic material according to claim 9 in oral restorative materials.

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