A tetragonal zirconia / ha nano-array bioactive composite coating grown on a zirconium alloy surface and a method thereof

Abstract

The application discloses a kind of tetragonal phase zirconium oxide / HA nano array bioactive composite coatings grown on zirconium alloy surface and method, belong to zirconium alloy surface treatment technical field, with Zr-2.5Nb alloy as anode, with pulse power constant voltage mode in containing calcium, phosphorus alkaline electrolyte Micro-arc oxidation reaction is carried out, voltage is 300-500V, Ca, P porous calcium stable tetragonal phase ZrO2 coating containing is generated on the surface of Zr-2.5Nb alloy, in 60-140 ℃ alkaline solution First hydrothermal reaction is carried out, then in containing calcium, phosphorus 60-140 ℃ alkaline mixed solution Second hydrothermal reaction is carried out, HA nano array bioactive coating is uniformly grown on the surface of tetragonal phase zirconium oxide coating, can effectively realize the modification to Zr-2.5Nb alloy surface, reach the purpose of promoting its bone integration ability and improving material mechanical property.

Description

Technical Field

[0001] This invention belongs to the field of zirconium alloy surface treatment technology, specifically a method for growing a tetragonal zirconium oxide / HA nanoarray bioactive composite coating on the surface of a zirconium alloy. Background Technology

[0002] Zirconium and its alloys have shown great promise in the field of biomedical implants (such as orthopedic and dental implants) due to their excellent mechanical properties and biocompatibility. However, like titanium alloys, zirconium alloys are bioinert materials and lack the ability to promote osseointegration, which to some extent limits their application in orthopedic implants.

[0003] Zr-2.5Nb alloy is a commonly used zirconium alloy. In order to improve the bone integration ability of Zr-2.5Nb alloy, surface modification is required.

[0004] Zirconia, a bio-inert ceramic, possesses high fracture and flexural strength and is often referred to as ceramic steel. At room temperature, zirconia typically exists as a monoclinic phase, but by adding stabilizers, its tetragonal phase stability can be enhanced, forming room-temperature stable tetragonal zirconia. Utilizing the phase transformation properties of tetragonal zirconia can improve the material's fracture toughness, which is crucial for enhancing the long-term durability of implants. The preparation of calcium-stabilized tetragonal zirconia on the surface of a zirconium alloy, compared to common yttrium-stabilized tetragonal zirconia ceramics, results in finer grains, reaching the nanoscale, which is significant for improving the material's mechanical properties.

[0005] In addition, hydroxyapatite (HA), as a bioactive ceramic, is mainly composed of Ca. 10 (PO4)6(OH)2 is a major inorganic component of bones and teeth and is widely used as a bone substitute. HA not only has good biocompatibility but also effectively promotes bone growth. After implantation, it forms chemical bonds with surrounding tissues at the interface. Its nanostructure can significantly enhance the function of mesenchymal stem cells in vitro, promoting osteoblast adhesion, proliferation, and differentiation, further accelerating the bone integration process.

[0006] Therefore, preparing calcium-stabilized tetragonal zirconium oxide and HA bioactive coating on Zr-2.5Nb alloy can effectively modify its surface, thereby promoting its osseointegration ability and improving the mechanical properties of the material. However, there are currently only reports on preparing tetragonal zirconium oxide / HA bioactive double coating on titanium alloy using micro-arc oxidation and hydrothermal methods, but this method is not applicable to Zr-2.5Nb alloy. Summary of the Invention

[0007] To address the problems existing in the prior art, this invention provides a method for growing a tetragonal zirconium oxide / HA nanoarray bioactive composite coating on the surface of a zirconium alloy, thereby solving the problem of preparing calcium-stabilized tetragonal zirconium oxide and HA bioactive coating on Zr-2.5Nb alloy. This method can effectively modify the surface of Zr-2.5Nb alloy, thereby promoting its osseointegration ability and improving the mechanical properties of the material.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A tetragonal zirconia / HA nanoarray bioactive composite coating grown on the surface of a zirconium alloy, wherein the zirconium alloy is a Zr-2.5Nb alloy, the tetragonal zirconia coating covers the surface of the zirconium alloy, the tetragonal zirconia coating is a porous calcium-stabilized tetragonal zirconia coating containing Ca and P, the HA nanoarray bioactive coating is uniformly grown on the surface of the tetragonal zirconia coating, the HA nanoarray bioactive coating is hexagonal prism-shaped and nearly perpendicular to the porous structure surface, which can significantly improve hydrophilicity, which is beneficial to promoting osteoblast adhesion and proliferation and improving bone integration capacity.

[0010] A method for growing a tetragonal zirconium oxide / HA nanoarray bioactive composite coating on a zirconium alloy surface includes the following steps:

[0011] S1, using Zr-2.5Nb alloy as the anode, a micro-arc oxidation reaction was carried out in an alkaline electrolyte containing calcium and phosphorus in a constant voltage mode with a pulse power supply. The voltage was 300-500V. A tetragonal ZrO2 coating containing Ca and P porous calcium-stabilized phase was generated on the surface of Zr-2.5Nb alloy to obtain composite a.

[0012] S2, the composite a undergoes a first hydrothermal reaction in an alkaline solution at 60-140℃, followed by a second hydrothermal reaction in a mixed alkaline solution containing calcium and phosphorus at 60-140℃. The HA nanoarray bioactive coating grows uniformly on the surface of the tetragonal zirconia coating, forming a composite material, thus completing the growth of a tetragonal zirconia / HA nanoarray bioactive composite coating on the surface of the zirconium alloy.

[0013] Preferably, the solvent of the alkaline electrolyte in S1 is deionized water, and the solutes are calcium sodium ethylenediaminetetraacetate, sodium dihydrogen phosphate, and sodium hydroxide. The concentration of calcium sodium ethylenediaminetetraacetate is 0.01-0.2 mol / L, the concentration of sodium dihydrogen phosphate is 0.02-0.2 mol / L, and the concentration of sodium hydroxide is 0.05-0.25 mol / L.

[0014] Preferably, the micro-arc oxidation reaction described in S1 is carried out at a frequency of 50-200 Hz and a duty cycle of 7.5-26%.

[0015] Preferably, the micro-arc oxidation reaction described in S1 is carried out at a voltage of 300-500V for 3-30 minutes.

[0016] Preferably, the alkaline solution described in S2 is a sodium hydroxide solution with a pH of 8-12.

[0017] Preferably, the first hydrothermal reaction described in S2 is carried out at 60-140°C for 0.5-5 hours.

[0018] Preferably, the second hydrothermal reaction described in S2 is carried out at 60-140°C for 10-48 hours.

[0019] Preferably, the solvent of the alkaline mixed solution in S2 is deionized water, and the solutes are calcium sodium ethylenediaminetetraacetate, sodium dihydrogen phosphate, and sodium hydroxide. The concentration of calcium sodium ethylenediaminetetraacetate is 0.2-0.5 mol / L, the concentration of sodium dihydrogen phosphate is 0.1-0.6 mol / L, and the concentration of sodium hydroxide is such that the pH of the alkaline mixed solution is 8-11.

[0020] Preferably, the Zr-2.5Nb alloy described in S1 is obtained by the following process: the initial Zr-2.5Nb alloy is polished sequentially with 400-grit sandpaper, 800-grit sandpaper and 1500-grit sandpaper, then ultrasonically cleaned sequentially with acetone, deionized water and ethanol for 10-20 minutes each, and finally dried at 55-65°C for 25-35 minutes.

[0021] The composite a obtained in S1 was rinsed with deionized water, then dried at 55-65℃ for 25-35 min, and then subjected to the first hydrothermal reaction. After the first hydrothermal reaction, the resulting composite b was rinsed with deionized water, then dried at 55-65℃ for 25-35 min, and then subjected to the second hydrothermal reaction. The composite material was rinsed with deionized water, then dried at 55-65℃ for 25-35 min, thus completing the growth of a tetragonal phase zirconia / HA nanoarray bioactive composite coating on the zirconium alloy surface.

[0022] Compared with the prior art, the present invention has the following beneficial technical effects:

[0023] This invention discloses a tetragonal zirconium oxide / HA nanoarray bioactive composite coating grown on the surface of a zirconium alloy. Calcium-stabilized tetragonal zirconium oxide is generated on the surface of a Zr-2.5Nb alloy. 2+It is a strong stabilizer of the tetragonal phase, entering the crystal lattice to form a substitutional solid solution. It can be rapidly cooled to avoid eutectoid decomposition, allowing the high-temperature tetragonal zirconia phase to be retained at room temperature. Utilizing the stress-induced phase transformation of tetragonal zirconia, the fracture toughness of the material can be improved. The porous zirconia coating is rich in calcium and phosphorus, which is conducive to the nucleation and growth of HA nanorods, and the zirconia grains reach the nanoscale, improving the mechanical properties of the material. The bioactive coating HA nanorods uniformly covering the porous zirconia structure are well-crystallized, hexagonal prisms with a diameter of about 50-120 nm, a spacing of about 60-300 nm, and a height of 500-800 nm, nearly perpendicular to the surface of the porous structure. This can significantly improve hydrophilicity, which is conducive to promoting the adhesion and proliferation of osteoblasts and improving bone integration capacity. It combines the dual functions of calcium-stabilized tetragonal zirconia and hydroxyapatite.

[0024] This invention discloses a method for growing a tetragonal zirconia / HA nanoarray bioactive composite coating on a zirconium alloy surface. The method involves micro-arc oxidation on a Zr-2.5Nb alloy surface using a pulsed power supply in a constant voltage mode, generating spark discharge spots in the micropores of the Zr-2.5Nb alloy surface. Subsequently, a porous, calcium-stabilized, rough tetragonal ZrO2 coating containing Ca and P is formed on the alloy surface. Increased surface roughness of the coating can improve osteogenicity and enhance the adhesion between the implant and the host bone. Higher voltage is more conducive to the rapid formation of a zirconia coating with large pore size, low pore number, and high hardness. However, voltages exceeding 500V are prone to localized breakdown of the coating layer, leading to decreased bonding strength. The micro-arc oxidation method for preparing calcium-stabilized tetragonal zirconia achieves nanoscale grain size, which is beneficial for improving the mechanical properties of the material. The solid solution of Ca in the zirconia is advantageous... A bioactive HA coating was further generated using hydrothermal methods. A first hydrothermal reaction was then carried out in an alkaline solution at 60-140℃. High-temperature thermal activation caused the calcium and phosphorus ions in the outermost layer of the porous calcium-stabilized tetragonal ZrO2 coating to react with the alkaline solution, forming HA crystal nuclei on the ZrO2 coating surface. In the second hydrothermal reaction, the alkaline mixed solution provided calcium and phosphorus elements, allowing the crystal nuclei to grow further, resulting in a uniformly grown bioactive HA nanorod array on the porous calcium-stabilized tetragonal zirconium oxide surface. Hydrothermal temperatures below 60℃ could not provide sufficient motive force for HA growth, resulting in thinner HA nanorods. At hydrothermal temperatures above 140℃, the HA nanorods were unevenly distributed with increased spacing. Thus, a firmly bonded porous calcium-stabilized tetragonal zirconium oxide / HA bioactive composite coating was prepared on the Zr-2.5Nb alloy surface. The calcium-stabilized tetragonal zirconium oxide / HA bioactive composite coating obtained by this invention has good bonding strength, with a film-substrate bonding strength exceeding 20N. Its nanorod array design closely resembles the nanofiber morphology of natural bone, exhibiting biomimetic effects. It can improve the biocompatibility of Zr-2.5Nb alloy, enhance the cellular response and osteoconductive capacity of implants, and promote new bone formation. This has significant implications for zirconium alloy orthopedic implants and hard tissue repair, effectively enhancing the bioactivity of zirconium alloy surfaces and promoting bone integration. It is expected to provide new ideas and methods for the research and development of biomedical implants, and promote the application prospects of zirconium alloys in the orthopedic field.

[0025] Furthermore, the micro-arc oxidation alkaline electrolyte and hydrothermal solution prepared by this invention have simple compositions and do not contain sodium β-glycerophosphate (β-GP), which reduces manufacturing costs and is beneficial for large-scale production. Attached Figure Description

[0026] Figure 1a This is a SEM image of the surface morphology of the calcium-stabilized tetragonal zirconia coating obtained by micro-arc oxidation in Example 1 of the present invention.

[0027] Figure 1bThis is the surface EDS energy spectrum of the calcium-stabilized tetragonal zirconia coating obtained by micro-arc oxidation in Example 1 of the present invention.

[0028] Figure 2 This is a SEM image of the cross-sectional morphology of the calcium-stabilized tetragonal zirconium oxide coating obtained by micro-arc oxidation in Example 1 of the present invention.

[0029] Figure 3 The image shows the XRD pattern of the calcium-stabilized tetragonal zirconium oxide coating obtained by micro-arc oxidation in Example 1 of this invention.

[0030] Figure 4a The image shows the surface morphology of the calcium-stabilized tetragonal zirconium oxide-HA bioactive coating obtained by micro-arc oxidation and hydrothermal method in Example 1 of this invention.

[0031] Figure 4b The above is the surface EDS energy spectrum of the calcium-stabilized tetragonal zirconium oxide-HA bioactive coating obtained by micro-arc oxidation and hydrothermal method in Example 1 of the present invention.

[0032] Figure 4c This is a SEM image of the cross-sectional morphology of the calcium-stabilized tetragonal zirconium oxide-HA bioactive coating obtained by micro-arc oxidation and hydrothermal method in Example 1 of the present invention.

[0033] Figure 4d for Figure 4c A magnified view of the area within the white box.

[0034] Figure 4e for Figure 4a A magnified view of the area within the white box.

[0035] Figure 5 The image shows the XRD pattern of the calcium-stabilized tetragonal zirconium oxide-HA bioactive coating obtained by micro-arc oxidation and hydrothermal method in Example 1 of this invention.

[0036] Figure 6a Contact angle diagrams of a calcium-stabilized tetragonal zirconia coating obtained by micro-arc oxidation in Example 1 of this invention, and a calcium-stabilized tetragonal zirconia-HA bioactive coating obtained by micro-arc oxidation and hydrothermal methods, on a Zr-2.5Nb substrate.

[0037] Figure 6b This is a roughness diagram of the Zr-2.5Nb matrix.

[0038] Figure 6c This is a roughness diagram of the calcium-stabilized tetragonal zirconia coating obtained by micro-arc oxidation in Example 1 of the present invention.

[0039] Figure 6d This is a roughness diagram of the calcium-stabilized tetragonal zirconium oxide-HA bioactive coating obtained by micro-arc oxidation and hydrothermal method in Example 1 of the present invention.

[0040] Figure 7a This is a scratch morphology diagram of the calcium-stabilized tetragonal zirconium oxide coating obtained by micro-arc oxidation in Example 1 of the present invention, and a schematic diagram of the coating adhesion force calculated based on the coating peeling location.

[0041] Figure 7b This is a scratch morphology diagram of the calcium-stabilized tetragonal zirconium oxide-HA bioactive coating obtained by micro-arc oxidation and hydrothermal method in Example 1 of the present invention, and a schematic diagram of the coating adhesion force calculated based on the coating peeling location.

[0042] Figure 8a This is a SEM image of the surface morphology of the calcium-stabilized zirconia coating obtained by micro-arc oxidation in Example 2 of the present invention.

[0043] Figure 8b The image shows the surface morphology of the calcium-stabilized tetragonal zirconium oxide-HA bioactive coating obtained by micro-arc oxidation and hydrothermal methods in Example 2 of this invention.

[0044] Figure 8c for Figure 8b A magnified view of the area within the white box.

[0045] Figure 9a This is a SEM image of the surface morphology of the calcium-stabilized tetragonal zirconia coating obtained by micro-arc oxidation in Example 3 of the present invention.

[0046] Figure 9b This is a SEM image of the surface morphology of the calcium-stabilized tetragonal zirconium oxide-HA bioactive coating obtained by micro-arc oxidation and hydrothermal method in Example 3 of the present invention.

[0047] Figure 9c for Figure 9b A magnified view of the area within the white box. Detailed Implementation

[0048] The present invention will be further described in detail below with reference to specific embodiments. These descriptions are for explanation purposes only and are not intended to limit the scope of the invention.

[0049] This invention discloses a method for preparing a calcium-stabilized tetragonal zirconium oxide / HA nanoarray bioactive coating on the surface of a zirconium alloy. The method utilizes micro-arc oxidation to prepare calcium-stabilized tetragonal zirconium oxide, achieving nanoscale grain size, which is beneficial for improving the mechanical properties of the material. The solid solution of Ca in the zirconium oxide facilitates further hydrothermal generation of the HA bioactive coating. The commonly used chemical reagent β-glycerophosphate (β-GP) is abandoned in favor of the lower-cost sodium dihydrogen phosphate. The method specifically includes the following steps:

[0050] Step 1: Using Zr-2.5Nb alloy as the anode and stainless steel as the cathode, Zr-2.5Nb alloy is a high-strength, high-hardness, high-corrosion-resistant, and high-impact-resistant alloy material. It is cylindrical in shape with a diameter of 14-40mm. A micro-arc oxidation reaction is carried out in an alkaline electrolyte containing calcium and phosphorus using a pulsed power supply constant voltage mode. Spark discharge spots are generated in the micropores on the surface of Zr-2.5Nb alloy. Subsequently, a porous calcium-stabilized tetragonal ZrO2 coating containing Ca and P is formed on the alloy surface. (Zirconium oxide has dissolved Ca and P elements, and the ZrO2 coating is a ceramic film, which is conducive to the growth of HA nanorods.) The coating is rinsed with deionized water and dried for later use. The electrolyte consists of 0.01-0.2 mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca), 0.02-0.2 mol / L sodium dihydrogen phosphate, and 0.05-0.25 mol / L sodium hydroxide, with deionized water as the solvent. The electrolyte temperature is maintained at 10-25℃. The pulse power supply has a voltage of 300-500V, a frequency of 50-200Hz, a duty cycle of 7.5-26%, and a micro-arc oxidation treatment time of 3-30 min. Increasing the concentrations of calcium sodium ethylenediaminetetraacetate (EDTA-Ca) and sodium dihydrogen phosphate in the electrolyte is beneficial for increasing the Ca and P content in the zirconia coating. Increasing the micro-arc oxidation voltage is beneficial for rapidly forming a zirconia coating with large pore size, low pore number, and high hardness; however, excessively high voltage can easily lead to localized breakdown of the film layer and a decrease in bonding strength. The longer the micro-arc oxidation treatment time, the denser the film layer, but the roughness also increases.

[0051] Step two involves placing the alloy with a porous calcium-stabilized tetragonal zirconia coating obtained in Step one into a high-temperature, high-pressure reactor containing a sodium hydroxide solution with a pH of 8-12 for a primary hydrothermal reaction at 60-140°C for 0.5-5 hours. After cooling, the sample is removed, rinsed with deionized water, and dried. The primary hydrothermal reaction, activated by high temperature, allows the calcium and phosphorus ions in the outermost layer of the Ca and P-containing porous calcium-stabilized tetragonal ZrO2 coating obtained in Step one through micro-arc oxidation to react with the alkaline solution, forming HA crystal nuclei on the ZrO2 coating surface. The sample after the primary hydrothermal reaction is then placed in a high-temperature, high-pressure reactor containing a mixed calcium and phosphorus solution for a secondary hydrothermal reaction at 60-140°C for 10-48 hours. The secondary hydrothermal reaction provides sufficient calcium and phosphorus elements in the hydrothermal solution, allowing further growth on the crystal nuclei generated in the primary hydrothermal reaction, resulting in a bioactive coating HA nanorod array uniformly grown on the porous calcium-stabilized tetragonal zirconia surface. The calcium-phosphorus mixed solution consists of 0.2-0.5 mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca) and 0.1-0.6 mol / L sodium dihydrogen phosphate, with deionized water as the solvent and sodium hydroxide used to adjust the pH to 8-11. As the hydrothermal time increases, the average diameter and length of the nanorod-shaped HA nanoparticles formed on the ZrO2 coating in step one gradually increase. The hydrothermal temperature needs to be within a certain range. If the hydrothermal temperature is too low, it cannot provide sufficient momentum for HA growth, resulting in thinner HA nanorods. If the hydrothermal temperature is too high, the HA nanorods will be unevenly distributed with increased spacing. The hydrothermal solution needs to be alkaline; however, if the pH is too high, HA tends to form in the hydrothermal solution and cannot grow on the coating surface.

[0052] In step one of this invention, the Zr-2.5Nb alloy is polished sequentially with 400, 800, and 1500 grit sandpaper, then cleaned sequentially with acetone, deionized water, and ethanol, ultrasonicated for 10-20 minutes, and dried in an oven at 60°C for half an hour before use (subsequent examples will not be repeated).

[0053] The surface coating obtained in steps one and two of this invention is rinsed with deionized water and dried in an oven at 60°C for half an hour before use.

[0054] Example 1:

[0055] Step 1: Using a 30mm diameter Zr-2.5Nb alloy as the anode and stainless steel as the cathode, a micro-arc oxidation reaction was carried out in an alkaline electrolyte containing calcium and phosphorus using a pulsed power supply in constant voltage mode. This generated a porous calcium-stabilized tetragonal zirconium oxide coating on the alloy surface. The coating was rinsed with deionized water and dried in an oven at 60℃ for half an hour before use. The electrolyte consisted of 0.03mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca), 0.02mol / L sodium dihydrogen phosphate, and 0.125mol / L sodium hydroxide, with deionized water as the solvent. The electrolyte temperature was maintained at 15℃. The pulsed power supply voltage was 450V, the frequency was 100Hz, the duty cycle was 26%, and the micro-arc oxidation treatment time was 5 minutes.

[0056] See SEM images of the surface and cross-sectional microstructure of the ZrO2 coating obtained by micro-arc oxidation. Figure 1a , Figure 2 It can be seen that its surface has a uniform porous structure with a pore size of approximately 2-5 μm, and the zirconium oxide coating is about 10 μm thick, tightly bonded to the Zr-2.5Nb substrate interface. See EDS spectrum for reference. Figure 1b The ZrO2 coating is composed of four elements: Zr, O, Ca, and P. The atomic content of Ca is about 13.87%, and the atomic content of P is about 7.50%.

[0057] See XRD pattern for reference. Figure 3 The XRD peaks indicate that its main phase is tetragonal zirconium oxide, which is due to the presence of Ca. 2+ It acts as a strong stabilizer for the tetragonal phase, entering the crystal lattice to form a substitutional solid solution. This allows for rapid cooling to prevent eutectoid decomposition, enabling the high-temperature tetragonal zirconia phase to be retained at room temperature. Furthermore, the stress-induced phase transformation of tetragonal zirconia can improve the fracture toughness of the material. Calculations show that the grain size of tetragonal zirconia is approximately 20-30 nm.

[0058] Step two involves placing the porous calcium-stabilized tetragonal zirconia coating obtained in Step one into a reactor containing a sodium hydroxide solution with a pH of 12 for a first hydrothermal reaction at 90°C for 2 hours. After cooling, the sample is removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour before use. The sample that has undergone the first hydrothermal reaction is then placed in a reactor containing a calcium-phosphorus mixed solution for a second hydrothermal reaction at 120°C for 24 hours, resulting in a bioactive coating HA nanorod array uniformly grown on the porous calcium-stabilized tetragonal zirconia coating. The calcium-phosphorus mixed solution consists of 0.25 mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca) and 0.25 mol / L sodium dihydrogen phosphate, with deionized water as the solvent and sodium hydroxide used to adjust the pH to 9. After cooling, the sample is removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour before use.

[0059] SEM images of the surface microstructure of the calcium-stabilized tetragonal zirconium oxide-HA bioactive coating obtained by micro-arc oxidation and hydrothermal methods are available. Figure 4a It can be seen that the surface has a uniform nanorod structure with good crystallization. Figure 4e Specifically, it is a hexagonal prism with a diameter of approximately 69 nm, a spacing of approximately 73 nm, and a height of approximately 636 nm, nearly perpendicular to the surface of the porous structure. See the EDS spectrum for reference. Figure 4b The ZrO2-HA nanorod coating is composed of four elements: Zr, O, Ca, and P. The atomic content of Ca is approximately 17.43%, and the atomic content of P is approximately 11.57%. The calcium and phosphorus content of the sample was further increased by a hydrothermal method. Figure 4c It can be seen that the zirconium alloy substrate, zirconium oxide coating, and HA nanorod array are well bonded together. Figure 4d It can be seen that HA is a nanorod array. The EDX line scan on the right shows that the Ca and P contents within the HA nanorod layer are slightly higher than those in the zirconia coating. However, near the zirconia coating and the zirconium substrate, the Ca and P contents rapidly decrease to 0, while the Zr content rapidly increases. At room temperature, zirconia typically exists as a monoclinic phase (m-ZrO2), but this can be achieved through the solid solution of Ca... 2+ It can form a stable tetragonal zirconium oxide (t-ZrO2) at room temperature. See XRD pattern for reference. Figure 5 XRD peaks show that, compared to the ZrO2 coating obtained by micro-arc oxidation, the phase composition includes an added hydroxyapatite phase. Furthermore, tetragonal zirconium oxide inevitably transforms into monoclinic zirconium oxide under heating and in the presence of water vapor.

[0060] Contact angle (see reference) Figure 6a The contact angles of water droplets on a Zr-2.5Nb substrate, a ZrO2 coating obtained after MAO (micro-arc oxidation), and a ZrO2+HA nanorod coating obtained after MAO+HT (hydrothermal oxidation) were 59.82±3.46°, 34.94±2.68°, and 5.5±0.63°, respectively. This indicates that HA nanorods on zirconium oxide can significantly improve hydrophilicity, which is beneficial for promoting osteoblast adhesion and improving osteointegration.

[0061] Figure 6b , Figure 6c and Figure 6dTo measure the roughness of the coating using atomic force microscopy, a rough, porous zirconium oxide coating was formed on the zirconium alloy surface after micro-arc oxidation treatment. The average surface roughness of the coating was 539.67 ± 38.44 nm, which was significantly increased compared to the surface roughness of the polished Zr-2.5Nb substrate (5.25 ± 0.17 nm). After hydrothermal growth of HA nanorods, the average surface roughness of the coating increased slightly, reaching 652.33 ± 17.25 nm. The improved surface roughness of the coating can improve osteogenic formation and enhance the adhesion between the implant and the host bone.

[0062] The adhesion of coatings is typically tested using the scratch test method. During testing, the scratch tester automatically loads the sample, and the indenter continuously moves across the sample surface. As the load increases, the coating on the sample surface breaks down and peels off, generating acoustic emission signals. The measured acoustic emission signals are recorded and combined with the location of the scratch peeling observed under a scanning electron microscope to determine the critical load on the coating surface. (See also: Coating adhesion test). Figure 7a and Figure 7b Calculations showed that the bonding strength between calcium-stabilized tetragonal zirconia obtained by micro-arc oxidation and the substrate was 25.4 N, while the bonding strength between the calcium-stabilized tetragonal zirconia-HA bioactive coating obtained by micro-arc oxidation and hydrothermal methods and the calcium-stabilized tetragonal zirconia was 24.8 N. ① indicates the surface without peeling. The EDS diagram shows that the contents of Ca, P, O, and Zr are... Figure 4b The elemental contents are similar. Location ② is the surface after peeling. The EDS image shows that it still consists of Ca, P, O, and Zr. Compared to location ①, the Zr content is significantly increased, while the contents of Ca, P, and O are decreased. The presence of Ca, P, O, and Zr at the peeled location indicates that the peeled area is ZrO2 obtained from micro-arc oxidation, not the Zr-2.5Nb matrix. Therefore, the resulting adhesion is the cohesive adhesion of the coating.

[0063] Example 2:

[0064] Step 1: Using a 20mm diameter Zr-2.5Nb alloy as the anode and stainless steel as the cathode, a micro-arc oxidation reaction was carried out in an alkaline electrolyte containing calcium and phosphorus using a pulsed power supply in constant voltage mode. This generated a porous calcium-stabilized tetragonal zirconia coating on the alloy surface. The coating was rinsed with deionized water and dried in an oven at 60℃ for half an hour before use. The electrolyte consisted of 0.01mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca), 0.02mol / L sodium dihydrogen phosphate, and 0.125mol / L sodium hydroxide, with deionized water as the solvent. The electrolyte temperature was maintained at 25℃. The pulsed power supply voltage was 450V, the frequency was 100Hz, the duty cycle was 26%, and the micro-arc oxidation treatment time was 5 minutes.

[0065] Step two: The alloy with the porous calcium-stabilized tetragonal zirconia coating obtained in Step one was subjected to a first hydrothermal reaction in a reactor containing a sodium hydroxide solution with a pH of 12 at 90°C for 2 hours. After cooling, the sample was removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour for later use. The sample that underwent the first hydrothermal reaction was then subjected to a second hydrothermal reaction in a reactor containing a calcium-phosphorus mixed solution at 120°C for 24 hours, resulting in a bioactive HA nanorod array uniformly grown on the porous calcium-stabilized tetragonal zirconia coating. The calcium-phosphorus mixed solution consisted of 0.25 mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca) and 0.25 mol / L sodium dihydrogen phosphate, with deionized water as the solvent and sodium hydroxide used to adjust the pH of the solution to 9. After cooling, the sample was removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour for later use.

[0066] SEM images of the surface microstructures of porous calcium-stabilized tetragonal zirconia coatings obtained by micro-arc oxidation and calcium-stabilized tetragonal zirconia-HA bioactive coatings obtained by micro-arc oxidation and hydrothermal methods are provided. Figure 8a Figure 8b and Figure 8c Furthermore, as can be seen from the table below, Example 2 has a similar EDS elemental composition and XRD phase composition to Example 1.

[0067] element Ca P Zr O sum At% 6.93 2.11 28.26 62.70 100

[0068] Example 3:

[0069] Step 1: Using a 15mm diameter Zr-2.5Nb alloy as the anode and stainless steel as the cathode, a micro-arc oxidation reaction was carried out in an alkaline electrolyte containing calcium and phosphorus using a pulsed power supply in constant voltage mode. This generated a porous calcium-stabilized tetragonal zirconia coating on the alloy surface. The coating was rinsed with deionized water and dried in an oven at 60℃ for half an hour before use. The electrolyte consisted of 0.02mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca), 0.02mol / L sodium dihydrogen phosphate, and 0.125mol / L sodium hydroxide, with deionized water as the solvent. The electrolyte temperature was maintained at 20℃. The pulsed power supply voltage was 450V, the frequency was 100Hz, the duty cycle was 26%, and the micro-arc oxidation treatment time was 5 minutes.

[0070] Step two: The alloy with the porous calcium-stabilized tetragonal zirconia coating obtained in Step one was subjected to a first hydrothermal reaction in a reactor containing a sodium hydroxide solution with a pH of 12 at 90°C for 2 hours. After cooling, the sample was removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour for later use. The sample that underwent the first hydrothermal reaction was then subjected to a second hydrothermal reaction in a reactor containing a calcium-phosphorus mixed solution at 120°C for 24 hours, resulting in a bioactive HA nanorod array uniformly grown on the porous calcium-stabilized tetragonal zirconia coating. The calcium-phosphorus mixed solution consisted of 0.25 mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca) and 0.25 mol / L sodium dihydrogen phosphate, with deionized water as the solvent and sodium hydroxide used to adjust the pH of the solution to 9. After cooling, the sample was removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour for later use.

[0071] SEM images of the surface microstructures of porous calcium-stabilized tetragonal zirconia coatings obtained by micro-arc oxidation and calcium-stabilized tetragonal zirconia-HA bioactive coatings obtained by micro-arc oxidation and hydrothermal methods are provided. Figure 9a , Figure 9b and Figure 9c Furthermore, as can be seen from the table below, Example 3 has a similar EDS elemental composition and XRD phase composition to Example 1.

[0072] element Ca P Zr O sum At% 12.51 5.98 21.75 59.76 100

[0073] Example 4:

[0074] Step 1: Using a 25mm diameter Zr-2.5Nb alloy as the anode and stainless steel as the cathode, a micro-arc oxidation reaction was carried out in an alkaline electrolyte containing calcium and phosphorus using a pulsed power supply in constant voltage mode. This generated a porous calcium-stabilized tetragonal zirconia coating on the alloy surface. The coating was rinsed with deionized water and dried in an oven at 60℃ for half an hour before use. The electrolyte consisted of 0.1mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca), 0.2mol / L sodium dihydrogen phosphate, and 0.125mol / L sodium hydroxide, with deionized water as the solvent. The electrolyte temperature was maintained at 10℃. The pulsed power supply voltage was 470V, the frequency was 100Hz, the duty cycle was 26%, and the micro-arc oxidation treatment time was 3 minutes.

[0075] Step two: The alloy with the porous calcium-stabilized tetragonal zirconia coating obtained in Step one was subjected to a first hydrothermal reaction in a reactor containing a sodium hydroxide solution with a pH of 10 at 90°C for 1 hour. After cooling, the sample was removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour for later use. The sample that underwent the first hydrothermal reaction was then subjected to a second hydrothermal reaction in a reactor containing a calcium-phosphorus mixed solution at 90°C for 24 hours, resulting in a bioactive HA nanorod array uniformly grown on the porous calcium-stabilized tetragonal zirconia coating. The calcium-phosphorus mixed solution consisted of 0.25 mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca) and 0.25 mol / L sodium dihydrogen phosphate, with deionized water as the solvent and sodium hydroxide used to adjust the pH of the solution to 10. After cooling, the sample was removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour for later use.

[0076] Example 4 has similar surface microstructure, EDS elemental composition and XRD phase composition to Example 1.

[0077] Example 5:

[0078] Step 1: Using a 40mm diameter Zr-2.5Nb alloy as the anode and stainless steel as the cathode, a micro-arc oxidation reaction was carried out in an alkaline electrolyte containing calcium and phosphorus using a pulsed power supply in constant voltage mode. This generated a porous calcium-stabilized tetragonal zirconia coating on the alloy surface. The coating was rinsed with deionized water and dried in an oven at 60℃ for half an hour before use. The electrolyte consisted of 0.03mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca), 0.02mol / L sodium dihydrogen phosphate, and 0.125mol / L sodium hydroxide, with deionized water as the solvent. The electrolyte temperature was maintained at 18℃. The pulsed power supply voltage was 380V, the frequency was 200Hz, the duty cycle was 26%, and the micro-arc oxidation treatment time was 10 minutes.

[0079] Step two involves placing the alloy with the porous calcium-stabilized tetragonal zirconia coating obtained in Step one into a reactor containing a sodium hydroxide solution with a pH of 12 for a first hydrothermal reaction at 140°C for 2 hours. After cooling, the sample is removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour before use. The sample that has undergone the first hydrothermal reaction is then placed in a reactor containing a calcium-phosphorus mixed solution for a second hydrothermal reaction at 100°C for 48 hours, resulting in a bioactive HA nanorod array uniformly grown on the porous calcium-stabilized tetragonal zirconia coating. The calcium-phosphorus mixed solution consists of 0.45 mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca) and 0.45 mol / L sodium dihydrogen phosphate, with deionized water as the solvent and sodium hydroxide used to adjust the pH to 9. After cooling, the sample is removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour before use.

[0080] Example 5 has similar surface microstructure, EDS elemental composition and XRD phase composition to Example 1.

[0081] Example 6:

[0082] Step 1: Using a 35mm diameter Zr-2.5Nb alloy as the anode and stainless steel as the cathode, a micro-arc oxidation reaction was carried out in an alkaline electrolyte containing calcium and phosphorus using a pulsed power supply in constant voltage mode. This generated a porous calcium-stabilized tetragonal zirconia coating on the alloy surface. The coating was rinsed with deionized water and dried in an oven at 60℃ for half an hour before use. The electrolyte consisted of 0.2mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca), 0.2mol / L sodium dihydrogen phosphate, and 0.125mol / L sodium hydroxide, with deionized water as the solvent. The electrolyte temperature was maintained at 22℃. The pulsed power supply voltage was 300V, the frequency was 100Hz, the duty cycle was 7.5%, and the micro-arc oxidation treatment time was 30min.

[0083] Step two: The alloy with the porous calcium-stabilized tetragonal zirconia coating obtained in Step one was subjected to a first hydrothermal reaction in a reactor containing a sodium hydroxide solution with a pH of 12 at 90°C for 5 hours. After cooling, the sample was removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour for later use. The sample that underwent the first hydrothermal reaction was then subjected to a second hydrothermal reaction in a reactor containing a calcium-phosphorus mixed solution at 120°C for 48 hours, resulting in a bioactive HA nanorod array uniformly grown on the porous calcium-stabilized tetragonal zirconia coating. The calcium-phosphorus mixed solution consisted of 0.5 mol / L calcium sodium ethylenediaminetetraacetate (EDTA-Ca) and 0.5 mol / L sodium dihydrogen phosphate, with deionized water as the solvent and sodium hydroxide used to adjust the pH of the solution to 10. After cooling, the sample was removed, rinsed with deionized water, and dried in an oven at 60°C for half an hour for later use.

[0084] Example 6 has similar surface microstructure, EDS elemental composition and XRD phase composition to Example 1.

[0085] The double-layer coating prepared using the process of this invention has no discontinuous interface with the substrate, exhibiting high bonding strength and good bioactivity. The HA nanorod array design closely resembles the nanofiber morphology of natural bone, demonstrating biomimetic effects and improving the biocompatibility of Zr-2.5Nb alloys. This has significant implications for zirconium alloy orthopedic implants and hard tissue repair.

Claims

1. A method for growing a tetragonal zirconium oxide / HA nanoarray bioactive composite coating on the surface of a zirconium alloy, characterized in that, Includes the following steps: S1, using Zr-2.5Nb alloy as the anode, a micro-arc oxidation reaction is carried out in an alkaline electrolyte containing calcium and phosphorus under constant voltage mode with a pulsed power supply. The solvent of the alkaline electrolyte is deionized water, and the solutes are calcium sodium ethylenediaminetetraacetate, sodium dihydrogen phosphate, and sodium hydroxide. The concentration of calcium sodium ethylenediaminetetraacetate is 0.01-0.2 mol / L, the concentration of sodium dihydrogen phosphate is 0.02-0.2 mol / L, the concentration of sodium hydroxide is 0.05-0.25 mol / L, and the voltage is 300-500 V. A tetragonal ZrO2 coating containing Ca and P porous calcium-stabilized phase is formed on the surface of the Zr-2.5Nb alloy, resulting in composite a. S2, the composite a undergoes a first hydrothermal reaction in an alkaline solution at 60-140℃, wherein the alkaline solution is a sodium hydroxide solution with pH=8-12. Then, a second hydrothermal reaction is carried out in a mixed alkaline solution containing calcium and phosphorus at 60-140℃. The solvent of the mixed alkaline solution is deionized water, and the solutes are calcium sodium ethylenediaminetetraacetate, sodium dihydrogen phosphate, and sodium hydroxide. The concentration of calcium sodium ethylenediaminetetraacetate is 0.2-0.5 mol / L, the concentration of sodium dihydrogen phosphate is 0.1-0.6 mol / L, and the concentration of sodium hydroxide is such that the pH of the mixed alkaline solution is 8-11. The HA nanoarray bioactive coating grows uniformly on the surface of the tetragonal zirconia coating, forming a composite material, thus completing the growth of a tetragonal zirconia / HA nanoarray bioactive composite coating on the zirconium alloy surface. The first hydrothermal reaction is carried out at 60-140℃ for 0.5-5 h, and the second hydrothermal reaction is carried out at 60-140℃ for 10-48 h.

2. The method for growing a tetragonal zirconium oxide / HA nanoarray bioactive composite coating on a zirconium alloy surface according to claim 1, characterized in that, The micro-arc oxidation reaction described in S1 is carried out at a frequency of 50-200 Hz and a duty cycle of 7.5-26%.

3. The method for growing a tetragonal zirconium oxide / HA nanoarray bioactive composite coating on a zirconium alloy surface according to claim 1, characterized in that, The micro-arc oxidation reaction described in S1 is carried out at a voltage of 300-500 V for 3-30 min.

4. The method for growing a tetragonal zirconium oxide / HA nanoarray bioactive composite coating on a zirconium alloy surface according to claim 1, characterized in that, The Zr-2.5Nb alloy described in S1 is obtained by the following process: the initial Zr-2.5Nb alloy is polished sequentially with 400-grit sandpaper, 800-grit sandpaper and 1500-grit sandpaper, then ultrasonically cleaned sequentially with acetone, deionized water and ethanol for 10-20 minutes each, and finally dried at 55-65 ℃ for 25-35 minutes. The composite a obtained in S1 was rinsed with deionized water, then dried at 55-65 ℃ for 25-35 min, and then subjected to the first hydrothermal reaction. After the first hydrothermal reaction, the resulting composite b was rinsed with deionized water, then dried at 55-65 ℃ for 25-35 min, and then subjected to the second hydrothermal reaction. The composite material was rinsed with deionized water, then dried at 55-65 ℃ for 25-35 min, thus completing the growth of a tetragonal zirconium oxide / HA nanoarray bioactive composite coating on the zirconium alloy surface.

5. A tetragonal zirconia / HA nanoarray bioactive composite coating grown on a zirconium alloy surface using the method described in any one of claims 1 to 4, characterized in that, The zirconium alloy is a Zr-2.5Nb alloy, and a tetragonal zirconium oxide coating is applied to the surface of the zirconium alloy. The tetragonal zirconium oxide coating is a porous calcium-stabilized tetragonal zirconium oxide coating containing Ca and P. An HA nanoarray bioactive coating is uniformly grown on the surface of the tetragonal zirconium oxide coating. The HA nanoarray bioactive coating is hexagonal prism-shaped.

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