Preparation method of high-activity nano alpha-alumina powder for artificial ceramic joint, product and application thereof

Abstract

The application discloses a preparation method of high-activity nano alpha-alumina powder for artificial ceramic joints, and a product and application thereof. Firstly, aluminum hydroxide colloid is prepared through a precipitation reaction and is ground and refined into nano-sized particles, and then a layer of phosphate colloid is precipitated on the aluminum hydroxide colloid particles as a wrapping layer through the precipitation reaction; the twice precipitated colloid is calcined to obtain a precursor of a phosphate crystal wrapping gamma-alumina crystal; the precursor is calcined to make the wrapped gamma-alumina shrink and transform into nano-sized alpha-alumina; and finally, the phosphate wrapping layer is removed through strong acid decomposition, so that the alpha-alumina powder with a particle size of 20-200 nm is obtained. The application first realizes a new technical system of preparing nano alpha-alumina powder by separating aluminum hydroxide with phosphate wrapping, and the artificial ceramic joint made of the alpha-alumina powder has excellent water-heat aging resistance and biocompatibility, and fully meets the use requirements of medical artificial ceramic joints.

Description

Technical Field

[0001] This invention relates to the field of bioceramics technology, and in particular to a method for preparing highly active nano-α-alumina powder for artificial ceramic joints, as well as its products and applications. Background Technology

[0002] In recent years, with the accelerating aging process, the joint market has continued to expand, and the prevalence of artificial joint replacement surgery in medical institutions has been increasing, with the number of surgeries showing a year-on-year upward trend. This has led to a significant increase in demand for artificial joints, and the product line has been continuously expanded to cover various types, including hip and knee joints. Against this backdrop, artificial ceramic joints have become the preferred material for joint replacement surgery due to their wear resistance, biocompatibility, and long lifespan, especially suitable for young or highly active patients.

[0003] Corundum alumina (α-Al₂O₃), as the most thermodynamically stable crystalline state of alumina, possesses excellent properties such as high hardness, superior wear resistance, good physicochemical stability, strong corrosion resistance, and biological inertness. Its α-phase crystal structure remains stable even at temperatures above 1200℃, with a thermal expansion coefficient of 8.1 × 10⁻⁶. -6 The temperature is ℃, and the hardness is 1500-2000 Hv. However, corundum alumina ceramics are inherently brittle, with a bending strength of only 400-500 MPa. Long-term impact and compression environments can easily cause cracks or even breakage, making it difficult to guarantee the safety and reliability of alumina ceramics in use, which seriously limits the application of alumina as an artificial joint ceramic.

[0004] To improve the strength and toughness of alumina ceramics, the main material used in artificial ceramic joints is currently zirconia-toughened alumina composite ceramic material (ZTA), in which 83% is α-alumina ceramic and 17% is tetragonal zirconia ceramic. For example, the alumina composite ceramic joint (83% Al2O3-17% ZrO2 composite phase) produced by the German company BIOLOX® delta has a flexural strength of 1200 MPa and a wear rate of <0.1 mm. 3With millions of tests conducted and FDA 510(k) approved, clinical data covers 200,000 cases. Although zirconia-toughened alumina ceramics offer significant improvements in strength and toughness compared to pure alumina ceramics, the presence of tetragonal zirconia drastically reduces their anti-aging properties. Tetragonal zirconia contains yttrium ions, which readily combine with hydroxide ions and detach from the zirconia crystals under prolonged exposure to humid and warm environments, leading to a phase transition from tetragonal to monoclinic zirconia. Furthermore, the tetragonal zirconia content (17 vol%) exceeds the percolation threshold (16 vol%), meaning that aging in humid environments can proceed unimpeded once the phase transition begins, potentially resulting in complete ceramic breakage. According to CeramTec, the fracture rate of the third-generation composite alumina ceramic Biolux® forte femoral head is 0.021%, and that of the lining is 0.032%. Currently, the clinical lifespan of zirconia-toughened alumina ceramic joints is 15–20 years. Many young patients require a second replacement surgery after the artificial joint's lifespan expires, enduring secondary pain.

[0005] The key to extending the lifespan of artificial ceramic joints lies in improving their resistance to aging in the frequent friction, pressure, and humid, hot human body environment. Since pure alumina ceramics have extremely strong anti-aging properties, reducing the amount of tetragonal zirconia added to composite ceramics, or using pure alumina ceramics directly, is the most direct way to improve the anti-aging ability of artificial ceramic joints. As mentioned earlier, the strength properties of traditional pure alumina ceramics are insufficient for their use as artificial joints. This is mainly because corundum alumina ceramics typically require sintering at high temperatures of 1500–1700℃. This high-temperature environment causes the internal crystals of alumina ceramics to grow to the micrometer scale, reducing grain boundaries and making it difficult to release stress through slippage. When subjected to external loads and microcracks form, these cracks propagate rapidly, making the ceramics highly brittle. Therefore, significantly reducing the sintering temperature of alumina ceramic parts, decreasing the alumina grain size from micrometers to nanometers, and increasing the number of grain boundaries can directly improve the strength and toughness of the ceramic parts. Synthesizing highly active nanoscale α-alumina powder is the key technology to achieve this goal.

[0006] Obtaining nanoscale alpha alumina industrially is difficult, especially highly reactive alumina powder below 50nm. Currently, the main manufacturers capable of stably supplying alpha alumina powder below 100nm are Daimei Chemical and Izuyu Chemical Industry Co., Ltd. in Japan. Alumina ceramic parts made from 50nm alumina powder can be sintered at temperatures below 1350℃. However, even so, the strength of pure alumina ceramic parts is still difficult to exceed 800MPa. To meet the application requirements of medical artificial joints, the strength of pure alumina ceramics must be at least close to that of tetragonal zirconia ceramics, reaching over 1000MPa. It has been reported that this requires the alpha alumina powder raw material to have a particle size as small as 20nm, and the sintering temperature of the ceramic parts must be as low as around 1200℃. Currently, there are no companies in the industry that can stably supply 20nm alpha alumina powder, and synthesizing highly reactive alpha alumina powder for artificial ceramic joints remains a pressing technical challenge that needs to be addressed. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a method for preparing highly active nano-α-alumina powder for artificial ceramic joints. This method utilizes the encapsulation and separation effect of phosphate to inhibit the agglomeration and growth of nano-sized alumina particles during the high-temperature crystallization stage, thereby achieving the synthesis of α-alumina powder with a particle size of 20–200 nm. Another objective of this invention is to provide products and applications obtained using the above-mentioned method for preparing highly active nano-α-alumina powder for artificial ceramic joints. Artificial ceramic joints with excellent anti-aging properties and biocompatibility, meeting the requirements for medical use, are prepared through low-temperature sintering at approximately 1200°C.

[0008] The objective of this invention is achieved through the following technical solution:

[0009] This invention provides a method for preparing highly active nano-α-alumina powder for artificial ceramic joints, comprising the following steps:

[0010] (1) Solution preparation

[0011] (1-1) Aluminum nitrate is mixed with trace metal ion sulfate to prepare solution A, which has an aluminum nitrate concentration of 0.5-3 mol / L and a trace metal ion concentration of 0.0002-0.06 mol / L; the trace metal ion is molybdenum or tantalum.

[0012] (1-2) Use an alkaline solution with a concentration of 0.5 to 3 mol / L as solution B;

[0013] (1-3) A soluble phosphate solution with a concentration of 0.5 to 1 mol / L was used as solution C;

[0014] (1-4) A soluble nitrate solution with a concentration of 0.5–3 mol / L is used as solution D;

[0015] (2) Synthesis of aluminum hydroxide Al(OH)3

[0016] According to the molar ratio of aluminum ions to hydroxide ions = 1:2.8-3.2, solution A and solution B are added dropwise to purified water under stirring for 0.5-4 hours to form a slurry containing aluminum hydroxide Al(OH)3 precipitate. The addition is stopped when the pH of the slurry is 6-12, and the slurry is stirred for another 0.5-4 hours. Then the precipitate is washed and dried until the moisture content is 0-0.5% to obtain amorphous aluminum hydroxide Al(OH)3.

[0017] (3) Preparation of nano-aluminum hydroxide colloidal particles with a double electric layer structure

[0018] According to the molar ratio of phosphate ions to aluminum ions = 0.4 to 10 to 1, the aluminum hydroxide Al(OH)3 is stirred and dispersed in solution C to form a slurry, and further ground and refined to obtain a refined slurry; the phosphate ions in the refined slurry act as a dispersant, adsorbing on the surface of aluminum hydroxide particles to avoid agglomeration, forming colloidal aluminum hydroxide particles with a particle size of 20 to 200 nm and a double electric layer structure.

[0019] (4) Preparation of a mixed precipitate of phosphate-coated aluminum hydroxide colloidal particles

[0020] According to the molar ratio of nitrate metal ions to phosphate ions = 1:1.0-1.05, the solution D is added dropwise to the refined slurry under stirring for 0.5-4 hours. During this process, the metal ions of solution D gradually combine with the phosphate ions in the refined slurry to form water-insoluble phosphate precipitates. These precipitates are gradually formed with aluminum hydroxide colloidal particles as the core. Therefore, phosphate coats the surface of the aluminum hydroxide colloidal particles, separating the aluminum hydroxide particles. The resulting product is washed and dried until the moisture content is 0-0.5%, resulting in a mixed precipitate of phosphate-coated aluminum hydroxide colloidal particles.

[0021] (5) Preparation of phosphate-encapsulated nano-γ-alumina precursor

[0022] The mixed precipitate was calcined at 400-600℃ for 12-24 hours. The amorphous aluminum hydroxide colloid was transformed into γ-alumina crystal, and the amorphous phosphate colloid was also transformed into crystal, thus fixing the microstructure of phosphate-encapsulated alumina and obtaining phosphate-encapsulated nano-γ-alumina precursor.

[0023] (6) Preparation of phosphate-encapsulated nano-α-alumina calcined material

[0024] The phosphate-coated γ-alumina precursor was directly calcined at 800–1100°C for 4–8 hours. The γ-alumina gradually shrank and crystallized into α-alumina. The phosphate did not decompose at temperatures below 1100°C. Because the alumina particles were separated by the phosphate, they did not agglomerate and grow during the high-temperature crystallization process, remaining in a nano-state, thus obtaining phosphate-coated nano-α-alumina calcined material.

[0025] (7) Preparation of nano-α-alumina powder

[0026] The phosphate-coated nano-α-alumina calcined material is immersed in dilute nitric acid with a concentration of 30-50% for 24-72 hours while maintaining a pH ≤ 1. This decomposes the phosphate coating on the surface of α-alumina into phosphoric acid and nitrate in water. The resulting solid is then rinsed and dried to obtain nano-α-alumina powder doped with trace metal ions.

[0027] Further, in step (1-2) of the present invention, the alkaline solution is a sodium hydroxide solution or an ammonia solution. In step (1-3), the soluble phosphate solution is triammonium phosphate. In step (1-4), the metal ion in the soluble nitrate solution is calcium or magnesium.

[0028] This invention utilizes the above-mentioned method for preparing highly active nano-α-alumina powder for artificial ceramic joints. The application of this product is as follows: using the above-mentioned nano-α-alumina powder doped with trace metal ions as raw material, a green body is obtained through pressing, isostatic pressing, and bisque sintering; then, it is calcined at 1200–1220°C for 4–6 hours to obtain α-alumina ceramic parts.

[0029] Furthermore, in the application of this invention, the pressing pressure is 100-150 MPa and the time is 10-16 s, the isostatic pressing pressure is 200-320 MPa and the time is 100-180 s, and the bisque firing temperature is 960-1100℃ and the holding time is 4-12 h.

[0030] In the above scheme, the density of the α-alumina ceramic part of the present invention is 3.95~3.98g / cm³. 3 The four-point flexural strength is 986–1105 MPa, and the fracture toughness is 6.1–6.9 MPa.m 1 / 2 Wear rate <0.1×10 -8 mm³ / N·m, Vickers hardness HV > 2300, relative cell viability in vitro ≥ 96%, cell adhesion rate > 75%.

[0031] The present invention has the following beneficial effects:

[0032] (1) The present invention is based on the principle of heterogeneous crystal encapsulation to inhibit crystal growth. By encapsulating the alumina precursor with phosphate, the alumina crystals are inhibited from agglomerating and growing during the heating stage, thereby preparing highly active α-alumina powder with a particle size of 20-200 nm and doped with trace metal ions.

[0033] (2) This invention differs from traditional powder synthesis processes such as hydrolysis, hydrothermal methods, and gas-phase methods. It proposes a new process system for preparing nano-α-alumina and, for the first time, achieves a new technology system for preparing nano-α-alumina powder by encapsulating and separating aluminum hydroxide with phosphate. By adjusting the ratio of aluminum hydroxide to phosphate colloid, α-alumina particles with a particle size range from 20 nm to 200 nm can be obtained. By doping with trace amounts of metal ions, the strength, anti-aging, and wear resistance of α-alumina ceramic joints can be improved.

[0034] (3) Using the highly active α-alumina powder doped with trace metal ions prepared in this invention as raw material to make artificial ceramic joints, it can be sintered into ceramic at a low temperature of about 1200℃ and has excellent strength, wear resistance, hydrothermal aging resistance and biocompatibility, which fully meets the requirements for use of artificial ceramic joints. Attached Figure Description

[0035] The present invention will now be described in further detail with reference to the embodiments and accompanying drawings:

[0036] Figure 1 These are transmission electron microscope images of the α-alumina powder prepared in the embodiments of the present invention and the α-alumina powder in the comparative example;

[0037] Figure 2 These are X-ray crystal diffraction patterns of α-alumina powder prepared in the embodiments of the present invention and α-alumina powder in the comparative examples. Detailed Implementation

[0038] Example 1:

[0039] 1. This embodiment describes a method for preparing highly active nano-α-alumina powder for artificial ceramic joints, the steps of which are as follows:

[0040] (1) Solution preparation

[0041] (1-1) Aluminum nitrate and molybdenum sulfate were mixed to prepare a solution A with an aluminum nitrate concentration of 1 mol / L and a molybdenum sulfate concentration of 0.005 mol / L;

[0042] (1-2) Use an ammonia solution with a concentration of 1 mol / L as solution B;

[0043] (1-3) A soluble triammonium phosphate solution with a concentration of 1 mol / L was used as solution C;

[0044] (1-4) A soluble magnesium nitrate solution with a concentration of 1 mol / L is used as solution D;

[0045] (2) Synthesis of aluminum hydroxide Al(OH)3

[0046] According to the molar ratio of aluminum ions to hydroxide ions = 1:3.2, the above solutions A and B were added dropwise to purified water under stirring for 2 hours to form a slurry containing aluminum hydroxide Al(OH)3 precipitate. The addition was stopped when the pH of the slurry reached 7, and the slurry was stirred for another 0.5 hours. The precipitate was then rinsed and dried until the moisture content was 0.5% to obtain amorphous aluminum hydroxide Al(OH)3.

[0047] (3) Preparation of nano-aluminum hydroxide colloidal particle slurry with double electric layer structure

[0048] According to the molar ratio of phosphate ions to aluminum ions = 4:1, the above aluminum hydroxide Al(OH)3 was stirred and dispersed in solution C to form a slurry, and further ground and refined by a sand mill to obtain a refined slurry. In this process, the phosphate ions in the refined slurry act as a dispersant, adsorbing on the surface of aluminum hydroxide particles to avoid agglomeration, forming aluminum hydroxide colloidal particles with a particle size of 20nm and a double electric layer structure.

[0049] (4) Preparation of a mixed precipitate of magnesium phosphate coated aluminum hydroxide colloidal particles

[0050] According to the molar ratio of magnesium ions to phosphate ions = 1:1.02, the above solution D was added dropwise to the refined slurry under stirring for 2 hours. During this process, the magnesium ions in solution D gradually combined with the phosphate ions in the refined slurry to form water-insoluble magnesium phosphate precipitates. These precipitates were gradually formed with aluminum hydroxide colloidal particles as the core. Therefore, magnesium phosphate coated the surface of the aluminum hydroxide colloidal particles, separating the aluminum hydroxide particles. The resulting product was washed and dried until the moisture content was 0.5%, resulting in a mixed precipitate of magnesium phosphate coated aluminum hydroxide colloidal particles.

[0051] (5) Preparation of magnesium phosphate-encapsulated nano-γ-alumina precursor

[0052] The above mixed precipitate was placed in an electric furnace and calcined at 400°C for 24 hours. The amorphous aluminum hydroxide colloid was transformed into γ-alumina crystal, and the amorphous magnesium phosphate colloid was also transformed into crystal, thus fixing the microstructure of magnesium phosphate-encapsulated alumina and obtaining magnesium phosphate-encapsulated nano-γ-alumina precursor.

[0053] (6) Preparation of magnesium phosphate-encapsulated nano-α-alumina calcined material

[0054] The magnesium phosphate-coated nano-γ-alumina precursor was directly placed in an electric furnace preheated to 800°C for calcination. The holding time was 4 hours. The γ-alumina gradually shrank and crystallized into α-alumina. Magnesium phosphate did not decompose at temperatures below 1100°C. Since the alumina particles were separated by magnesium phosphate, they did not agglomerate and grow during the high-temperature crystallization process and remained in a nano-state, thus obtaining magnesium phosphate-coated nano-α-alumina calcined material.

[0055] (7) Preparation of nano-α-alumina powder

[0056] The magnesium phosphate-coated nano-α-alumina calcined material was immersed in 30% dilute nitric acid for 24 hours, while maintaining a pH of ≤1 throughout. This decomposed the magnesium phosphate coating on the α-alumina surface into phosphoric acid and magnesium nitrate in the water. The resulting solid was then rinsed and dried to obtain molybdenum-doped nano-α-alumina powder.

[0057] 2. The application of molybdenum-doped nano-α-alumina powder in this embodiment is as follows:

[0058] Using the above-mentioned molybdenum-doped nano-α-alumina powder as raw material, the green body was obtained by pressing (pressure 120MPa, time 12s), isostatic pressing (pressure 290MPa, time 180s), and bisque firing (temperature 1000℃, holding time 6h); then calcination was carried out at 1200℃ for 4h to obtain α-alumina ceramic sample.

[0059] Example 2:

[0060] 1. This embodiment describes a method for preparing highly active nano-α-alumina powder for artificial ceramic joints, the steps of which are as follows:

[0061] (1) Solution preparation

[0062] (1-1) Aluminum nitrate and tantalum sulfate were mixed to prepare a solution A with an aluminum nitrate concentration of 1 mol / L and a tantalum sulfate concentration of 0.0025 mol / L;

[0063] (1-2) A sodium hydroxide solution with a concentration of 1 mol / L is used as solution B;

[0064] (1-3) A soluble triammonium phosphate solution with a concentration of 1 mol / L was used as solution C;

[0065] (1-4) A soluble calcium nitrate solution with a concentration of 1 mol / L is used as solution D;

[0066] (2) Synthesis of aluminum hydroxide Al(OH)3

[0067] According to the molar ratio of aluminum ions to hydroxide ions = 1:2.8, the above solutions A and B were added dropwise to purified water under stirring for 2 hours to form a slurry containing aluminum hydroxide Al(OH)3 precipitate. The addition was stopped when the pH of the slurry reached 7, and the slurry was stirred for another 0.5 hours. The precipitate was then rinsed and dried until the moisture content was 0.5% to obtain amorphous aluminum hydroxide Al(OH)3.

[0068] (3) Preparation of aluminum hydroxide colloidal particle slurry

[0069] According to the molar ratio of phosphate ions to aluminum ions = 2:1, the above aluminum hydroxide Al(OH)3 is stirred and dispersed in solution C to form a slurry, and further ground and refined by a sand mill to obtain a refined slurry. In this process, the phosphate ions in the refined slurry act as a dispersant, adsorbing on the surface of aluminum hydroxide particles to avoid agglomeration, forming aluminum hydroxide colloidal particles with a particle size of 50nm and a double electric layer structure.

[0070] (4) Preparation of a mixed precipitate of calcium phosphate coated aluminum hydroxide colloidal particles

[0071] According to the molar ratio of calcium ions to phosphate ions = 1:1.05, the above solution D was added dropwise to the refined slurry under stirring for 2 hours. During this process, the calcium ions in solution D gradually combined with the phosphate ions in the refined slurry to form water-insoluble calcium phosphate precipitates. These precipitates were gradually formed with aluminum hydroxide colloidal particles as the core. Therefore, calcium phosphate coated the surface of the aluminum hydroxide colloidal particles, separating the aluminum hydroxide particles. The resulting product was washed and dried until the moisture content was 0.5%, resulting in a mixed precipitate of calcium phosphate coated aluminum hydroxide colloidal particles.

[0072] (5) Preparation of calcium phosphate-encapsulated nano-γ-alumina precursor

[0073] The above mixed precipitate was placed in an electric furnace and calcined at 400°C for 24 hours. The amorphous aluminum hydroxide colloid was transformed into γ-alumina crystal, and the amorphous calcium phosphate colloid was also transformed into crystal, thus fixing the microstructure of calcium phosphate-encapsulated alumina and obtaining a calcium phosphate-encapsulated nano-γ-alumina precursor.

[0074] (6) Preparation of calcium phosphate-encapsulated nano-α-alumina calcined material

[0075] The above-mentioned calcium phosphate-coated nano-γ-alumina precursor was directly placed in an electric furnace preheated to 800°C for calcination treatment. The holding time was 4 hours. The γ-alumina gradually shrank and densified and transformed into α-alumina. The calcium phosphate basically did not decompose below 1100°C. Since the alumina particles were separated by calcium phosphate, the alumina particles would not agglomerate and grow during the high-temperature transformation process and would remain in the nano-state, thus obtaining calcium phosphate-coated nano-α-alumina calcined material.

[0076] (7) Preparation of nano-α-alumina powder

[0077] The above-mentioned calcium phosphate-coated nano-α-alumina calcined material was immersed in 30% dilute nitric acid for 24 hours, while maintaining pH ≤ 1 throughout. This decomposed the calcium phosphate coating on the α-alumina surface into phosphoric acid and calcium nitrate in the water. The resulting solid was then rinsed and dried to obtain tantalum-doped nano-α-alumina powder.

[0078] 2. The application of tantalum-doped nano-α-alumina powder in this embodiment is as follows:

[0079] Using the aforementioned tantalum-doped nano-α-alumina powder as raw material, a green body was obtained by pressing (pressure 120MPa, time 12s), isostatic pressing (pressure 290MPa, time 180s), and bisque firing (temperature 1000℃, holding time 6h); then, calcination was carried out at 1220℃ for 4h to obtain α-alumina ceramic sample.

[0080] Comparative example:

[0081] α-alumina powder TM-DA produced by Daimei Chemical Industry Co., Ltd. of Japan was used as a comparative example.

[0082] Using the aforementioned α-alumina powder TM-DA as raw material, the green body was obtained by pressing (pressure 120MPa, time 12s), isostatic pressing (pressure 290MPa, time 180s), and bisque firing (temperature 1000℃, holding time 6h); then calcination was carried out at 1350℃ for 4h to obtain α-alumina ceramic sample.

[0083] like Figure 1 As shown, the α-alumina particles prepared in Example 1 of this invention are 20 nm in size, the α-alumina particles prepared in Example 2 are 50 nm in size, and the α-alumina particles in the comparative example are 200 nm in size, indicating that the α-alumina powder of this invention has a finer particle size and higher activity. Figure 2 As shown, the powder prepared in the embodiments of the present invention and the powder in the comparative example are both pure α-phase alumina.

[0084] The performance test results of the α-alumina powder and its α-alumina ceramic sample in the embodiments and comparative examples of the present invention are shown in Table 1.

[0085] Table 1 Performance indicators of α-alumina powder and ceramic samples from the embodiments and comparative examples of the present invention

[0086]

Claims

1. A method for preparing highly active nano-α-alumina powder for artificial ceramic joints, characterized in that... Includes the following steps: (1) Solution preparation (1-1) Aluminum nitrate is mixed with trace metal ion sulfate to prepare solution A, which has an aluminum nitrate concentration of 0.5-3 mol / L and a trace metal ion concentration of 0.0002-0.06 mol / L; the trace metal ion is molybdenum or tantalum. (1-2) Use an alkaline solution with a concentration of 0.5 to 3 mol / L as solution B; (1-3) A soluble phosphate solution with a concentration of 0.5 to 1 mol / L was used as solution C; (1-4) A soluble nitrate solution with a concentration of 0.5–3 mol / L is used as solution D; (2) Synthesis of aluminum hydroxide Al(OH)3 According to the molar ratio of aluminum ions to hydroxide ions = 1:2.8-3.2, solution A and solution B are added dropwise to purified water under stirring for 0.5-4 hours to form a slurry containing aluminum hydroxide Al(OH)3 precipitate. The addition is stopped when the pH of the slurry is 6-12, and the slurry is stirred for another 0.5-4 hours. Then the precipitate is washed and dried until the moisture content is 0-0.5% to obtain amorphous aluminum hydroxide Al(OH)3. (3) Preparation of nano-aluminum hydroxide colloidal particles with a double electric layer structure According to the molar ratio of phosphate ions to aluminum ions = 0.4 to 10 to 1, the aluminum hydroxide Al(OH)3 is stirred and dispersed in solution C to form a slurry, and further ground and refined to obtain a refined slurry; the phosphate ions in the refined slurry act as a dispersant, adsorbing on the surface of aluminum hydroxide particles to avoid agglomeration, forming colloidal aluminum hydroxide particles with a particle size of 20 to 200 nm and a double electric layer structure. (4) Preparation of a mixed precipitate of phosphate-coated aluminum hydroxide colloidal particles According to the molar ratio of nitrate metal ions to phosphate ions = 1:1.0-1.05, the solution D is added dropwise to the refined slurry being stirred for 0.5-4 hours. The resulting product is washed and dried until the moisture content is 0-0.5%, resulting in a mixed precipitate of phosphate-coated aluminum hydroxide colloidal particles. (5) Preparation of phosphate-encapsulated nano-γ-alumina precursor The mixed precipitate was calcined at 400–600°C for 12–24 hours to convert the amorphous aluminum hydroxide colloid into γ-alumina crystals, thus obtaining phosphate-encapsulated nano-γ-alumina precursors. (6) Preparation of phosphate-encapsulated nano-α-alumina calcined material The phosphate-encapsulated γ-alumina precursor was directly placed at 800-1100℃ for calcination, and the holding time was 4-8h. The γ-alumina gradually shrank and became dense and transformed into α-alumina, thus obtaining phosphate-encapsulated nano-α-alumina calcined material. (7) Preparation of nano-α-alumina powder The phosphate-coated nano-α-alumina calcined material is immersed in dilute nitric acid with a concentration of 30-50% for 24-72 hours while maintaining a pH ≤ 1. This decomposes the phosphate coating on the surface of α-alumina into phosphoric acid and nitrate in water. The resulting solid is then rinsed and dried to obtain nano-α-alumina powder doped with trace metal ions.

2. The method for preparing highly active nano-α-alumina powder for artificial ceramic joints according to claim 1, characterized in that: In step (1-2), the alkaline solution is a sodium hydroxide solution or an ammonia solution.

3. The method for preparing highly active nano-α-alumina powder for artificial ceramic joints according to claim 1, characterized in that: The soluble phosphate solution in steps (1-3) is triammonium phosphate.

4. The method for preparing highly active nano-α-alumina powder for artificial ceramic joints according to claim 1, characterized in that: The metal ions in the soluble nitrate solution in steps (1-4) are calcium or magnesium.

5. The product prepared by the method for preparing highly active nano-α-alumina powder for artificial ceramic joints according to any one of claims 1-4.

6. The application of the product according to claim 5, characterized in that: Using the above-mentioned nano-α-alumina powder doped with trace metal ions as raw material, the green body is obtained by pressing, isostatic pressing, and bisque sintering; then, it is calcined at 1200-1220℃ for 4-6 hours to obtain α-alumina ceramic parts.

7. The application according to claim 6, characterized in that: The pressing pressure is 100-150 MPa and the time is 10-16 s, the isostatic pressing pressure is 200-320 MPa and the time is 100-180 s, and the bisque firing temperature is 960-1100℃ and the holding time is 4-12 h.

8. The application according to claim 6, characterized in that: The density of the α-alumina ceramic part is 3.95–3.98 g / cm³. 3 The four-point flexural strength is 986–1105 MPa, and the fracture toughness is 6.1–6.9 MPa.m 1 / 2 Wear rate <0.1×10 -8 mm³ / N·m, Vickers hardness HV > 2300, relative cell viability in vitro ≥ 96%, cell adhesion rate > 75%.

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