Systems and methods for ion exchange membrane assisted electrochemical deposition of hydroxyapatite

Abstract

This invention provides a system and method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition. A magnesium alloy substrate with a micro-arc oxidation coating is placed in a buffer zone for at least one round of electrochemical deposition. Each round of electrochemical deposition includes the following steps: opening the channel between the anion region and the buffer zone; simultaneously connecting the magnesium alloy substrate to the positive electrode of a pulsed power supply placed in the buffer zone; connecting the platinum electrode in the anion region to the negative electrode of the pulsed power supply for a first electrodeposition; subsequently closing the channel between the cation region and the buffer zone and opening the channel between the cation region and the buffer zone; connecting the magnesium alloy substrate to the negative electrode of the pulsed power supply; and connecting the platinum electrode in the cation region to the positive electrode of the pulsed power supply for a second electrodeposition. Through stepwise ion migration control and electric field focusing technology, preferential nucleation and C-axis preferential growth of hydroxyapatite at the bottom of MAO micropores are achieved.

Description

Technical Field

[0001] This invention relates to the field of biomedical materials, and specifically to a method for preparing a doped and modified hydroxyapatite coating, particularly a system and method for preparing fluorine and zinc ion co-doped hydroxyapatite using ion exchange membrane-assisted electrochemical deposition technology. Background Technology

[0002] Novel medical magnesium alloys are considered a promising next-generation orthopedic implant material due to their mechanical properties being highly compatible with human bone, excellent biocompatibility, and unique in vivo degradability. However, the rapid degradation rate of magnesium alloys in physiological environments leads to a mismatch between their "decreased mechanical support performance" and "bone regeneration cycle," becoming a core bottleneck restricting their clinical translation. Furthermore, rapid corrosion, accompanied by severe hydrogen evolution and local alkalization, easily induces aseptic inflammation, tissue effusion, and even osteolysis, significantly reducing long-term implant stability. Therefore, while retaining the advantages of magnesium alloys in terms of lightweight, degradability, and biocompatibility, precisely controlling their degradation behavior, improving early corrosion resistance, and imparting osteoinductive activity have become core scientific and engineering challenges in the surface modification of medical magnesium alloys.

[0003] Micro-arc oxidation (MAO), as the mainstream technology for in-situ construction of ceramic oxide layers, can quickly form a porous ceramic layer on the surface of magnesium alloys, which can improve corrosion resistance and biocompatibility to a certain extent. However, its inherent "volcanic crater"-like interconnected microporous structure provides a rapid channel for the penetration of corrosive media. Under long-term service, interface corrosion and coating failure will still occur, making it difficult to meet the protection requirements of orthopedic implants throughout their entire life cycle.

[0004] To address this issue, the mainstream preparation methods for hydroxyapatite coatings on magnesium alloy surfaces (sol-gel, hydrothermal synthesis, and traditional electrochemical deposition) all suffer from inherent drawbacks that are difficult to overcome when adapting to the porous structure of MAO and the thermal / chemical sensitivity of the magnesium matrix. The sol-gel method has two prominent problems: First, the solvent evaporation and volume shrinkage during the sol-gel transformation can easily induce internal stress at the coating and pore interface, which can then induce penetrating cracks. Second, the formation of high-crystallinity HA depends on high-temperature sintering, which is fundamentally contradictory to the thermal sensitivity of magnesium alloys. Furthermore, the mismatch between the thermal expansion coefficients of the coating and the substrate often leads to coating peeling and failure.

[0005] Hydrothermal synthesis faces the dual challenges of interface control and process matching: the adsorption sites of HA nuclei on the MAO surface are difficult to control precisely, resulting in uneven coating growth and poor thickness and composition uniformity; simultaneously, the HA / MAO interfacial bonding strength is highly dependent on the strong coupling effect of multiple parameters such as temperature, pressure, and ion concentration, and even slight deviations in parameter matching can easily lead to coating peeling. Although introducing fluorination or polymer interlayers can improve interfacial properties to some extent, it often increases process complexity and may introduce impurity elements. Furthermore, the synergistic challenges of controlling the loading of functional ions, such as Zn²⁺, remain. + Ag + Cu² + Plasma is prone to aggregation, making it difficult for doped HA crystals to achieve both long-term stability and flexible control of biological activity.

[0006] Traditional electrochemical deposition methods also have significant limitations: to maintain Ca²⁺ + PO4³ - Ions are stable, and the electrolyte is typically weakly acidic (pH≈6), while the MAO coating and residual magnesium metal are highly sensitive to acidic environments. In the initial deposition stage, the hydrogen evolution from the chemical reaction and the hydrogen evolution from the cathode electrolysis overlap, easily forming a "micropore bridging" phenomenon at the pore openings, leading to insufficient pore filling. Simultaneously, ion transport in the mixed electrolyte is controlled by both convection and electromigration, resulting in uneven supersaturation distribution. This easily causes explosive nucleation and disordered orientation of HA in the early stages of deposition, while ion depletion at the interface in the later stages causes the Ca / P ratio of the generated HA to deviate significantly from the theoretical value of 1.67. Furthermore, the local pH fluctuations caused by continuous hydrogen evolution often rely on buffer components for regulation, and the resulting co-deposition of impurity ions may still weaken the expected biological functions of the ion-doped HA film.

[0007] In summary, existing methods for preparing hydroxyapatite generally suffer from problems such as "insufficient initial protection, unstable interfacial bonding, and difficulty in functional regulation" when addressing the surface modification needs of magnesium alloys. These issues make it difficult to meet the requirements of implanted materials for precise control throughout their entire life cycle, from "initial stable protection to mid-term long-term induction and late-term coordinated degradation." Summary of the Invention

[0008] The purpose of this invention is to provide a system and method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition. It employs an innovative strategy of "ion exchange membrane assistance - electric field focusing - stepwise ion doping," using an ion exchange membrane to construct a physically isolated weakly alkaline environment to eliminate hydrogen evolution interference and acidic solution corrosion, and utilizing an electric field focusing to drive PO4… 3- OH - Ca 2+ Plasma migrates directionally into the depths of MAO micropores in a stepwise manner, inducing preferential nucleation of HA at the bottom of the pores and selective growth along the c-axis, while F is simultaneously applied. - and Zn2+ A stepwise doping strategy was used to construct an FZ-HA composite film with a highly tough inner layer and a corrosion-resistant and antibacterial outer layer. This aims to solve the problems of disordered crystal orientation, insufficient corrosion resistance, and limited biological functions of hydroxyapatite crystals prepared by existing methods.

[0009] To achieve the above objectives, this technical solution provides a method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition, comprising: S1. Place the pH buffer solution in the buffer zone of the electrochemical deposition apparatus, place the anion solution in the anion zone of the electrochemical deposition apparatus, and place the cation solution in the cation zone of the electrochemical deposition apparatus, wherein the anion solution contains at least OH-. - and PO4 3- The cation solution contains at least Ca 2+ ; S2: The magnesium alloy substrate with the micro-arc oxidation coating is placed in a buffer zone for at least one round of electrochemical deposition, wherein each round of electrochemical deposition includes the following process: The channel between the anion region and the buffer zone is opened, and the magnesium alloy substrate is connected to the positive terminal of the pulse power supply placed in the buffer zone. The platinum electrode in the anion region is connected to the negative terminal of the pulse power supply for a first electrodeposition. Then the channel between the cation region and the buffer zone is closed and opened again. The magnesium alloy substrate is connected to the negative terminal of the pulse power supply, and the platinum electrode in the cation region is connected to the positive terminal of the pulse power supply for a second electrodeposition.

[0010] As mentioned earlier, this scheme uses ion exchange membrane isolation and electric field-driven stepwise deposition of anions and cations to controllably grow hydroxyapatite with consistent orientation and co-doped with fluorine and zinc on the micro-arc oxidation layer of magnesium alloy, thereby achieving integrated corrosion resistance and antibacterial function.

[0011] The structure of the electrochemical deposition apparatus in this scheme is as follows: Figure 1 As shown, the electrochemical deposition device includes a buffer zone, a cation zone, and an anion zone. The buffer zone of the electrochemical deposition device is equipped with a pulse power supply. Both the cation and anion zones are equipped with platinum electrodes, and the cation and anion zones are isolated from each other. The cation zone is equipped with a cation exchange membrane, and a cation gate is provided between the cation exchange membrane and the buffer zone. The anion zone is equipped with an anion exchange membrane, and an anion gate is provided between the anion exchange membrane and the buffer zone.

[0012] In some embodiments, a controllable cation gate is installed on the side of the cation exchange membrane in the cation region of this solution near the buffer zone for selectively opening cation channels; similarly, an anion gate is also installed on the side of the anion exchange membrane in the anion region near the buffer zone for selectively opening anion channels.

[0013] It should be noted that the anion regions need to be completely isolated from each other, forming controllable ion transport channels with the buffer zone only through their respective ion exchange membranes and gates.

[0014] In some embodiments, the cation exchange membrane is disposed on the side of the cation region near the buffer zone, and the anion exchange membrane is disposed on the side of the anion region near the buffer zone.

[0015] In some embodiments, the pH value of the pH buffer is 7.0 to 9.5. This scheme specifically sets the pH of the pH buffer to be weakly alkaline to avoid the corrosion of the magnesium alloy substrate and micro-arc oxidation coating by traditional weakly acidic electrolytes, improve the stability of the substrate and coating, and can significantly suppress the violent hydrogen evolution reaction during the electrodeposition process, eliminate the "bridging" phenomenon at the micropore openings, and ensure that hydroxyapatite is fully filled into the depth of the micropores.

[0016] In some embodiments, the pH buffer is selected from one or two of phosphate buffer, Tris-HCl buffer, and carbonate buffer.

[0017] Furthermore, the phosphate buffer contains potassium dihydrogen phosphate (KH2PO4), disodium hydrogen phosphate (Na2HPO4), sodium chloride (NaCl), and potassium chloride (KCl), with a pH of 7.0–8.5.

[0018] Furthermore, the Tris-HCl buffer contains Tris base and hydrochloric acid (HCl), with a pH of 7.0–9.0.

[0019] Furthermore, the carbonate buffer contains sodium carbonate (Na2CO3) and sodium bicarbonate (NaHCO3), with a pH of 9.0–9.5.

[0020] In some embodiments, the temperature of the pH buffer solution is between 25°C and 60°C. The advantage of this design is that it can regulate the ion migration and diffusion rate, ensure that the nucleation and growth process of hydroxyapatite is stable and controllable, and avoid the loose coating and disordered orientation caused by explosive nucleation. In addition, appropriately increasing the temperature can improve the crystallinity of hydroxyapatite and the density of the coating, while reducing the viscosity of the electrolyte and improving the ability of ions to transport to the depth of MAO micropores, so as to achieve full filling of micropores.

[0021] In some embodiments, the thickness of the micro-arc oxidation coating on the magnesium alloy surface is 0.1 μm to 100 μm, and the diameter of the surface micropores is 0.1 to 10 μm.

[0022] Regarding anionic solutions: In some embodiments, OH- in the anion solution - and PO4 3-The ions are derived from one or more of potassium hydroxide (KOH), sodium hydroxide (NaOH), sodium phosphate (Na3PO4), disodium hydrogen phosphate (Na2HPO4), sodium dihydrogen phosphate (NaH2PO4), potassium phosphate (K3PO4), dipotassium hydrogen phosphate (K2HPO4), and potassium dihydrogen phosphate (KH2PO4).

[0023] To further improve the mechanical properties and density of hydroxyapatite films, F is generally used. - Doping occurs, and correspondingly, the anion solution further contains F. - ion.

[0024] At this time, F in the anion solution - The ions are derived from one or more of sodium fluoride (NaF), potassium fluoride (KF), and sodium monofluorophosphate (Na2PO3F).

[0025] In some embodiments, the pH value of the anionic solution is 7.0~10.

[0026] In some embodiments, the temperature of the anionic solution is 25°C to 60°C.

[0027] When the anion solution contains only OH- - and PO4 3- At that time, OH - and PO4 3- The physical quantities of these components account for 50%–80% and 20%–50%, respectively. However, when the anionic solution contains only OH-... - PO4 3- and F - At that time, PO4 3- OH - F - The percentages of the substances are 50-85%, 15-50%, and 0-5%, respectively.

[0028] Regarding cationic solutions: The cation solution contains soluble calcium salts and pH adjusters; that is, the Ca in the cation solution... 2+ It comes from soluble calcium salts.

[0029] In some embodiments, Ca 2+ The ions are derived from one or more of the following: calcium chloride (CaCl2), calcium nitrate (Ca(NO3)2), calcium bromide (CaBr2), calcium iodide (CaI2), calcium acetate ((CH3COO)2Ca), calcium glycerophosphate, calcium citrate, calcium gluconate, calcium lactate, and calcium malate.

[0030] In some embodiments, the pH adjuster is derived from one or more of "citric acid-sodium citrate", "acetic acid-sodium acetate", "sodium dihydrogen phosphate-disodium hydrogen phosphate", "malic acid-sodium malate", and "lactic acid-sodium lactate".

[0031] In some embodiments, the pH of the cation solution is 4.0 to 7.0.

[0032] In some embodiments, the temperature of the cation solution is 25°C to 60°C.

[0033] To further improve the antibacterial properties of hydroxyapatite films, Zn can generally be used. 2+ Doping occurs, and correspondingly, the cation solution further contains Zn. 2+ ion.

[0034] At this time, Zn in the cation solution 2+ The ions are derived from one or more of zinc sulfate (ZnSO4·7H2O), zinc chloride (ZnCl2), zinc nitrate (Zn(NO3)2), zinc bromide (ZnBr2), zinc acetate (Zn(CH3COO)2·2H2O), zinc gluconate, zinc lactate, and zinc citrate.

[0035] To further enhance the corrosion inhibition and protection effects of hydroxyapatite, Ce can generally be used. 3+ Doping occurs, and correspondingly, the cation solution further contains Ce. 3+ ion.

[0036] At this time, Ce in the cation solution 3+ The ions are derived from one or more of cerium nitrate (Ce(NO3)3·6H2O), cerium chloride (CeCl3·7H2O), cerium sulfate (Ce2(SO4)3·8H2O), and cerium acetate (Ce(CH3COO)3).

[0037] In some embodiments, Ca in the cation solution 2+ The molar percentage of ions is 10-50%, Zn 2+ and Ce 3+ The molar percentages of ions are 0~30% and 0~30%, respectively.

[0038] It should be noted that traditional ED electrolyte systems maintain Ca 2+ PO4 3-Ion stabilization typically employs a weakly acidic electrolyte (pH≈6), but the MAO coating and residual metallic magnesium are highly sensitive to acidic environments. In the early stages of deposition, the superposition of hydrogen evolution from chemical reactions and hydrogen evolution from cathode electrolysis easily leads to a "micropore bridging" phenomenon at the pore openings, resulting in insufficient pore filling. Simultaneously, ion transport in the mixed electrolyte is controlled by both convection and electromigration, and uneven supersaturation distribution easily causes explosive nucleation and disordered orientation of HA in the early stages of deposition. Later, due to ion depletion at the interface, the Ca / P ratio of generated HA significantly deviates from the theoretical value of 1.67. Although the ED process provides a highly tunable platform for functional ion doping and drug / biomacromolecule loading, enabling the realization of Mg²⁺… + Zn² + Sr² + Simultaneous loading and sustained release of plasma and antibiotics are possible, but the local pH fluctuations caused by continuous electrolytic hydrogen desorption often require the introduction of buffer components. The resulting co-deposition of impurity ions may still weaken the expected biological functions of ion-doped HA films.

[0039] This invention constructs a physically isolated weakly alkaline environment through an ion-exchange membrane, effectively assisting the electrochemical deposition process and significantly reducing interference from electrolytic hydrogen deposition and the risk of substrate / coating corrosion. It utilizes a step-by-step electric field focusing technology to achieve PO4³⁺ deposition. - OH - Ca² + Plasma migrates directionally deep into the micropores of the micro-arc oxidation (MAO) coating, inducing preferential nucleation of hydroxyapatite at the pore bottom and its strictly preferential growth along the C-axis. Columnar hydroxyapatite nucleates and extends longitudinally within the micropores of the MAO coating, effectively repairing structural defects on the coating surface. With prolonged deposition time, columnar hydroxyapatite gradually covers the coating surface, its main components being O, P, and Ca, forming a dense repair layer. Further, through F... - and Zn² + After ion co-doping modification, hydroxyapatite retains its columnar structure, with granular zinc phosphate covering visible in localized areas. Elemental distribution analysis confirms uniform distribution of F and Zn, verifying that this technique can achieve F... - and Zn² + Effective doping of hydroxyapatite ultimately yields a multifunctional hydroxyapatite composite coating that combines excellent mechanical properties, corrosion resistance, and antibacterial functions.

[0040] Regarding electrochemical deposition conditions: It should be noted that the number of electrochemical deposition cycles in this scheme can be selected according to the desired thickness of the hydroxyapatite film; that is, the thickness of the hydroxyapatite film is directly proportional to the number of electrochemical deposition cycles. In some embodiments, the thickness of the hydroxyapatite film formed in each round of electrochemical deposition is 0.4~0.6 μm.

[0041] In some embodiments, the time for the first and second electrochemical depositions in each round of electrochemical deposition is 1 to 10 minutes to ensure that the prepared hydroxyapatite can completely cover the surface of the micro-arc oxidation coating.

[0042] In some embodiments, during each round of electrochemical deposition, the pulse power supply output voltage is ±(0.01 ~ 1.5 V), the frequency is 100~1000 Hz, and the duty cycle is 10~50%.

[0043] In some embodiments, the magnesium alloy with a hydroxyapatite film prepared according to this method achieves preferential nucleation and C-axis preferential growth of hydroxyapatite at the bottom of MAO micropores, and can also be grown by F - Zn² + Ion co-doping imparts mechanical strengthening, improved corrosion resistance and antibacterial synergistic effects to the coating, making it a high-performance biomedical composite coating.

[0044] Secondly, this solution provides a system for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition, comprising: An electrochemical deposition apparatus includes a buffer zone, a cation zone, and an anion zone. A pulsed power supply is provided in the buffer zone. Platinum electrodes are provided in both the cation and anion zones, and the cation and anion zones are isolated from each other. A cation exchange membrane is provided in the cation zone, and a cation gate is provided between the cation exchange membrane and the buffer zone. An anion exchange membrane is provided in the anion zone, and an anion gate is provided between the anion exchange membrane and the buffer zone. A magnesium alloy substrate with a micro-arc oxidation coating is placed in a buffer zone, an anionic solution is placed in an anionic zone, and a cationic solution is placed in a cationic zone, wherein the anionic solution contains at least OH-. - and PO4 3- The cation solution contains at least Ca 2+ .

[0045] The system for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition is used according to the method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition of the first aspect, that is, performing at least one round of electrochemical deposition as required by the desired thickness of the hydroxyapatite to be deposited.

[0046] Compared with existing technologies, this technical solution has the following characteristics and beneficial effects: First, based on the perspective of physical isolation and weakly alkaline environment reconstruction, anion exchange membranes are used to completely isolate the anion / cation regions to be deposited from the weakly alkaline environment of MAO. This not only effectively avoids the corrosion of the magnesium matrix and MAO by the acidic electrolyte of traditional electrodeposition, but also significantly suppresses the disturbance of the stacking density of newly formed HA crystals caused by electrolytic hydrogen, providing a mild and controllable low-interference environment for the stable growth of high-quality HA.

[0047] Secondly, based on the electric field focusing and "deep-pore pinning" effect, the electric field lines are efficiently focused deep into the MAO micropores while eliminating hydrogen bubble interference. On the one hand, electrolysis induces the oxidation of residual magnesium within the pores, generating Mg. 2+ With inhaled PO4 3- / OH - The reaction seals the inner pores, preventing subsequent galvanic corrosion. On the other hand, the pulsed electric field drives the preferential nucleation and growth of calcium and phosphorus ions at the bottom of the pores, achieving full filling of the micropores. This "root-like" growth mode constructs a nano-microscale interlocking structure, which is expected to significantly improve interfacial bonding strength.

[0048] Furthermore, based on the controllable growth of HA grains under ion transport regulation, the ion exchange membrane acts as an "ion gate" to regulate the type and flux of transmembrane ions, maintain the weakly alkaline environment at the MAO interface, and inhibit violent electrochemical reactions and explosive nucleation of HA. This "slow growth" behavior simulates the in vivo biomineralization process, inducing HA to preferentially grow along the c-axis, thereby obtaining mechanical properties closer to those of natural bone tissue.

[0049] Finally, based on a stepwise deposition strategy of functional ions, a physically isolated weakly alkaline environment is created using an ion exchange membrane. This overcomes the difficult-to-reconcile thermodynamic contradictions in traditional electrolytes, such as "multiple ion coexistence easily leads to supersaturation precipitation" and "acidic dissolution-alkaline precipitation." A multifunctional FZ-HA membrane with a highly tough, F-rich inner layer and a corrosion-resistant, antibacterial, Zn-rich outer layer is constructed stepwise. Simultaneously, the membrane's selective permeability effectively blocks impurity deposition, increases the functional ion content in the doped FZ-HA membrane, and reduces the risk of adverse immune responses after implantation. Attached Figure Description

[0050] Figure 1 This is the structure of the electrochemical deposition device in this scheme.

[0051] Figure 2 These are the microstructure and elemental distribution diagrams of hydroxyapatite grown on the surface of MAO coating in Examples 1 and 2.

[0052] Figure 3 This is a thickness test diagram of hydroxyapatite grown on the surface of the MAO coating in Example 2.

[0053] Figure 4 This is a microstructure and elemental distribution diagram of F and Zn ion co-doped hydroxyapatite grown on the surface of MAO coating in Example 3.

[0054] Figure 5 This is a diagram showing the microstructure and elemental distribution of hydroxyapatite on the MAO coating surface in Example 4. Detailed Implementation

[0055] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0056] Example 1: A method for inducing preferential nucleation of hydroxyapatite in the micropores of a micro-arc oxidation coating using ion exchange membrane-assisted electrochemical deposition: Adopting such Figure 1 The electrochemical deposition apparatus shown has the same structure as described above and will not be repeated here.

[0057] S1. Take a clean beaker with a capacity of 1 L, add 500 mL of deionized water, and then add 5 g of potassium dihydrogen phosphate (NaH2PO4), 5 g of disodium hydrogen phosphate (Na2HPO4), 1 g of sodium chloride (NaCl), and 1 g of potassium chloride (KCl) in sequence. After the solids are completely dissolved, adjust the pH of the L1 solution to 7.2 using disodium hydrogen phosphate and maintain the temperature at 25℃. This solution is called L1 solution. Then pour it into the buffer zone. S2. Take a clean beaker with a capacity of 1 L, add 500 mL of deionized water, then add 2 g of sodium hydroxide (NaOH) and 5 g of sodium phosphate (Na3PO4) in sequence. After the solid is completely dissolved, use sodium dihydrogen phosphate (NaH2PO4) to adjust the pH value of the L1 solution to 8, maintain the solution at 25℃, and record it as the L2 solution. Then pour it into the anion region. S3. Take a clean beaker with a capacity of 1 L, add 500 mL of deionized water, then add 10 g of calcium nitrate (Ca(NO3)2). After the solid is completely dissolved, adjust the pH value to 6 using "acetic acid-sodium acetate" and maintain the solution at 25℃. Record this as solution L3 and then pour it into the cation zone. S4. Place the magnesium alloy substrate with micro-arc oxidation coating in the buffer zone and connect it to the positive terminal of the pulse power supply. Connect the platinum electrode in the anion region to the negative terminal of the pulse power supply. At the same time, open the gate (B1) in front of the anion exchange membrane in the anion region. At this time, the output voltage of the pulse power supply is 0.5V, the duty cycle is 25%, the pulse frequency is 500Hz, and the deposition time is 1 min. S5. First, close the gate in front of the anion exchange membrane in the anion region. Then, connect the magnesium alloy substrate with the micro-arc oxidation coating to the negative electrode of the pulse power supply and the platinum electrode in the cation region to the positive electrode of the pulse power supply. At the same time, open the gate in front of the cation exchange membrane in the cation region. At this time, the output voltage of the pulse power supply is -1V, the duty cycle is 25%, the pulse frequency is 500Hz, and the deposition time is 1 min.

[0058] The microstructure and elemental distribution of the magnesium alloy obtained in Example 1 are shown in the figure below. Figure 2 As shown in (a1, a2), it can be seen that the present invention utilizes ion exchange membrane-assisted electrochemical deposition to induce hydroxyapatite to preferentially nucleate in the micropores of the micro-arc oxidation coating and gradually grow along the C-axis.

[0059] Example 2 Similarly, adopting such Figure 1 The electrochemical deposition apparatus shown has the same structure as described above and will not be repeated here.

[0060] S1. Take a clean beaker with a capacity of 1 L, add 500 mL of deionized water, and then add 5 g of potassium dihydrogen phosphate (NaH2PO4), 5 g of disodium hydrogen phosphate (Na2HPO4), 1 g of sodium chloride (NaCl), and 1 g of potassium chloride (KCl) in sequence. After the solids are completely dissolved, use disodium hydrogen phosphate to adjust the pH value of the L1 solution to 7.3 and maintain the temperature at 25℃. This solution is called L1 solution, and then poured into the buffer zone.

[0061] S2. Take a clean beaker with a capacity of 1 L, add 500 mL of deionized water, then add 2 g of sodium hydroxide (NaOH) and 5 g of sodium phosphate (Na3PO4) in sequence. After the solids are completely dissolved, use sodium dihydrogen phosphate (NaH2PO4) to adjust the pH of the L1 solution to 8, maintain the solution at 25℃, and record it as the L2 solution. Then pour it into the anion exchange region.

[0062] S3. Take a clean beaker with a capacity of 1 L, add 500 mL of deionized water, then add 10 g of calcium nitrate (Ca(NO3)2). After the solid is completely dissolved, adjust the pH value to between 6 using "acetic acid-sodium acetate" and maintain the solution at 25℃. This solution is called L3 solution. Then pour it into the cation zone.

[0063] S4. Place the magnesium alloy substrate with micro-arc oxidation coating in the buffer zone and connect it to the positive terminal of the pulse power supply. Connect the platinum electrode in the anion region to the negative terminal of the pulse power supply. At the same time, open the gate (B1) in front of the anion exchange membrane in the anion region. At this time, the output voltage of the pulse power supply is 0.5V, the duty cycle is 25%, the pulse frequency is 500Hz, and the deposition time is 1 min.

[0064] S5. First, close the gate in front of the anion exchange membrane in the anion region. Then, connect the magnesium alloy substrate with the micro-arc oxidation coating to the negative electrode of the pulse power supply and the platinum electrode in the cation region to the positive electrode of the pulse power supply. At the same time, open the gate in front of the cation exchange membrane in the cation region. At this time, the output voltage of the pulse power supply is -1V, the duty cycle is 25%, the pulse frequency is 500Hz, and the deposition time is 1 min.

[0065] S6. Repeat steps S4 and S5 for three cycles to prepare a functional hydroxyapatite film with consistent grain growth orientation, dense structure, and good corrosion resistance and antibacterial properties on the MAO coating surface.

[0066] The microstructure and elemental distribution of the magnesium alloy obtained in Example 2 are shown in the figure below. Figure 2 As shown in (b1, b2), it can be seen that the present invention utilizes ion exchange membrane-assisted electrochemical deposition to induce hydroxyapatite to preferentially grow along the C-axis on the surface of the micro-arc oxidation coating, and exhibits a columnar dense stacked structure.

[0067] Regarding the coating thickness of the magnesium alloy prepared in Example 2, as follows: Figure 3 As shown, by Figure 3 As can be seen, the total thickness of the HA-MAO composite coating is approximately 12.1 μm (the outer HA layer is approximately 2.3 μm, and the inner MAO coating layer is approximately 9.5 μm thick), and the HA film is deeply embedded and fills the interior of the MAO micropores. This result directly confirms that this process successfully induced the "rooted" growth of HA, constructing a micro-nano-scale mechanical interlocking interface.

[0068] Example 3 Similarly, adopting such Figure 1 The electrochemical deposition apparatus shown has the same structure as described above and will not be repeated here.

[0069] S1. Take a clean beaker with a capacity of 1 L, add 500 mL of deionized water, then add 5 g of sodium carbonate (Na2CO3), 3 g of sodium bicarbonate (NaHCO3), and 2 g of potassium chloride (KCl) in sequence. After the solids are completely dissolved, adjust the pH value to 9.3 with sodium bicarbonate and maintain the temperature at 25℃. This solution is called L1. Then pour it into the buffer zone.

[0070] S2. Take a clean beaker with a capacity of 1 L, add 500 mL of deionized water, then add 2 g of potassium hydroxide, 5 g of disodium hydrogen phosphate (Na2HPO4), and 0.5 g of sodium fluoride in sequence. After the solids are completely dissolved, use sodium dihydrogen phosphate (NaH2PO4) to adjust the pH value of the L1 solution to 9, maintain the solution at 25℃, and record it as the L2 solution. Then pour it into the anion exchange region.

[0071] S3. Take a clean beaker with a capacity of 1 L, add 500 mL of deionized water, then add 10 g of glycerol calcium phosphate and 5 g of zinc acetate. After the solids are completely dissolved, adjust the pH value to between 6 using "sodium dihydrogen phosphate-disodium hydrogen phosphate" and maintain the solution at 25℃. Record this as solution L3 and then pour it into area C.

[0072] S4. Place the magnesium alloy substrate with micro-arc oxidation coating in the buffer zone and connect it to the positive terminal of the pulse power supply. Connect the platinum electrode in the anion region to the negative terminal of the pulse power supply. At the same time, open the gate (B1) in front of the anion exchange membrane in the anion region. At this time, the output voltage of the pulse power supply is 1V, the duty cycle is 30%, the pulse frequency is 1000Hz, and the deposition time is 3 min.

[0073] S5. First, close the gate in front of the anion exchange membrane in the anion region. Then, connect the magnesium alloy substrate with the micro-arc oxidation coating to the negative electrode of the pulse power supply and the platinum electrode in the cation region to the positive electrode of the pulse power supply. At the same time, open the gate in front of the cation exchange membrane in the cation region. At this time, the output voltage of the pulse power supply is -1V, the duty cycle is 30%, the pulse frequency is 1000Hz, and the deposition time is 3 minutes.

[0074] S6. Repeat steps S4 and S5 for three cycles to prepare F and Zn-doped hydroxyapatite on the MAO coating surface. The grains preferentially grow along the C-axis and present a columnar dense stacked structure, which is a functional hydroxyapatite film with good corrosion resistance and antibacterial properties.

[0075] The microstructure and elemental distribution of the magnesium alloy obtained in Example 3 are shown in the figure below. Figure 4 As shown, the present invention utilizes an ion-exchange membrane-assisted electrochemical deposition method to induce the preferential growth of F and Zn co-doped hydroxyapatite along the C-axis on the surface of a micro-arc oxidation coating.

[0076] Example 4 S1. Take a clean beaker with a capacity of 1 L, add 500 mL of deionized water, and then add 5 g of potassium dihydrogen phosphate (NaH2PO4), 5 g of disodium hydrogen phosphate (Na2HPO4), 1 g of sodium chloride (NaCl), and 1 g of potassium chloride (KCl) in sequence. After the solids are completely dissolved, use disodium hydrogen phosphate to adjust the pH value of the L1 solution to 7.3 and maintain the temperature at 25℃. This solution is called L1 solution.

[0077] S2. Take another clean beaker with a capacity of 1 L, add 500 mL of deionized water, then add 2 g of sodium hydroxide (NaOH) and 5 g of sodium phosphate (Na3PO4) in sequence. After the solid is completely dissolved, use sodium dihydrogen phosphate (NaH2PO4) to adjust the pH value of the L1 solution to 8, maintain the solution at 25℃, and record it as the L2 solution.

[0078] S3. Take another clean beaker with a capacity of 1 L, add 500 mL of deionized water, then add 10 g of calcium nitrate (Ca(NO3)2). After the solid is completely dissolved, adjust the pH value to between 6 using "acetic acid-sodium acetate" and maintain the solution at 25℃. This solution is called L3.

[0079] S4. Take a clean beaker with a capacity of 2 L and pour in the above solutions L1, L2 and L3 in sequence, and denote it as solution L4. Place the magnesium alloy substrate with micro-arc oxidation coating in the beaker and connect it to the positive terminal of the pulse power supply. At the same time, place the platinum electrode connected to the negative terminal of the pulse power supply parallel to the magnesium alloy substrate in solution L4. Adjust the output parameters of the pulse power supply to 0.5V, duty cycle to 25%, pulse frequency to 500Hz, and deposition time to 1 min.

[0080] S5. Connect the magnesium alloy substrate with the micro-arc oxidation coating to the negative terminal of the pulse power supply, connect the platinum electrode to the positive terminal of the pulse power supply, and adjust the output parameters of the pulse power supply to -1V, duty cycle to 25%, pulse frequency to 500Hz, and deposition time to 1 min.

[0081] S6. Repeat steps S4 and S5 for three cycles to prepare a hydroxyapatite film on the MAO coating surface.

[0082] The microstructure and elemental distribution of the magnesium alloy obtained in Example 4 are shown in the figure below. Figure 5 As shown, it can be seen that not adopting the following... Figure 1 The electrochemical deposition apparatus shown produces hydroxyapatite with inconsistent morphologies on the magnesium alloy surface, which cannot completely cover the surface of the MAO coating. This makes it difficult to significantly improve the bonding strength and corrosion resistance of the MAO-HA composite coating on the magnesium alloy substrate surface.

[0083] Those skilled in the art should understand that the technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments have been described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0084] The above embodiments are merely illustrative of several implementation methods of this application, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this application should be determined by the appended claims.

Claims

1. A method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition, characterized in that, include: S1, placing a pH buffer solution in a buffer zone of an electrochemical deposition device, placing an anion solution in an anion zone of the electrochemical deposition device, and placing a cation solution in a cation zone of the electrochemical deposition device, wherein the anion solution contains at least OH - and PO4 3- , and the cation solution contains at least Ca 2+ ; S2: The magnesium alloy substrate with the micro-arc oxidation coating is placed in a buffer zone for at least one round of electrochemical deposition, wherein each round of electrochemical deposition includes the following process: The channel between the anion region and the buffer zone is opened, and the magnesium alloy substrate is connected to the positive terminal of the pulse power supply placed in the buffer zone. The platinum electrode in the anion region is connected to the negative terminal of the pulse power supply for a first electrodeposition. Then the channel between the cation region and the buffer zone is closed and opened again. The magnesium alloy substrate is connected to the negative terminal of the pulse power supply, and the platinum electrode in the cation region is connected to the positive terminal of the pulse power supply for a second electrodeposition.

2. The method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition according to claim 1, characterized in that, The electrochemical deposition apparatus includes a buffer zone, a cation zone, and an anion zone. The buffer zone is equipped with a pulsed power supply. Both the cation and anion zones are equipped with platinum electrodes and are isolated from each other. The cation zone is equipped with a cation exchange membrane, and a cation gate is provided between the cation exchange membrane and the buffer zone. The anion zone is equipped with an anion exchange membrane, and an anion gate is provided between the anion exchange membrane and the buffer zone.

3. The method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition according to claim 1, characterized in that, The pH value of the pH buffer is 7.0 to 9.5, and the pH buffer is selected from one or two of phosphate buffer, Tris-HCl buffer, and carbonate buffer.

4. The method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition according to claim 1, characterized in that, OH in anion solutions - and PO4 3- The ions are derived from one or more of potassium hydroxide, sodium hydroxide, sodium phosphate, disodium hydrogen phosphate, sodium dihydrogen phosphate, potassium phosphate, dipotassium hydrogen phosphate, and potassium dihydrogen phosphate.

5. The method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition according to claim 1, characterized in that, The anion solution further contains F - ion.

6. The method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition according to claim 1, characterized in that, The cation solution contains soluble calcium salts and pH adjusters, with a pH value of 4.0~7.

0.

7. The method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition according to claim 1, characterized in that, Ca 2+ The ions are derived from one or more of the following: calcium chloride, calcium nitrate, calcium bromide, calcium iodide (CaI2), calcium acetate, calcium glycerophosphate, calcium citrate, calcium gluconate, calcium lactate, and calcium malate.

8. The method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition according to claim 1, characterized in that, The cation solution further contains Zn 2+ Ions and / or Ce 3+ ion.

9. The method for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition according to claim 1, characterized in that, The number of electrochemical depositions is selected according to the desired thickness of the hydroxyapatite film. The thickness of the hydroxyapatite film is directly proportional to the number of electrochemical depositions. In each round of electrochemical deposition, the time for the first and second electrochemical depositions is 1 to 10 minutes, and the thickness of the hydroxyapatite film formed by each round of electrochemical deposition is 0.4 to 0.6 μm.

10. A system for preparing hydroxyapatite by ion exchange membrane-assisted electrochemical deposition, characterized in that, include: An electrochemical deposition apparatus includes a buffer zone, a cation zone, and an anion zone. A pulsed power supply is provided in the buffer zone. Platinum electrodes are provided in both the cation and anion zones, and the cation and anion zones are isolated from each other. A cation exchange membrane is provided in the cation zone, and a cation gate is provided between the cation exchange membrane and the buffer zone. An anion exchange membrane is provided in the anion zone, and an anion gate is provided between the anion exchange membrane and the buffer zone. A magnesium alloy substrate with a micro-arc oxidation coating is placed in a buffer zone, an anionic solution is placed in an anionic zone, and a cationic solution is placed in a cationic zone, wherein the anionic solution contains at least OH-. - and PO4 3- The cation solution contains at least Ca 2+ .

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