Preparation method of magnesium alloy plasma electrolytic oxidation fluorescence degradation coating

Abstract

The invention discloses a preparation method of a magnesium alloy plasma electrolytic oxidation fluorescence degradation coating, and relates to the technical field of degradable magnesium alloy surface functional coatings. The method comprises: 1, magnesium alloy pretreatment; 2, ultrasonic oil removal; 3, preparing an HAp: Eu < 3 + > precursor solution; 4, preparing HAp: Eu < 3 + > nanoparticles by a microwave heating method; 5, carrying out negative electrification treatment on the surfaces of the HAp: Eu < 3 + > nanoparticles; 6, micro-arc oxidation treatment I; 7, performing micro-arc oxidation treatment II; according to the method, HAp: Eu < 3 + > is introduced into the magnesium alloy micro-arc oxidation coating, the crystal field sensitive luminescence behavior of the HAp: Eu < 3 + > can reflect the coating microstructure and the selective dissolution process of Ca1 / Ca2 sites in a real-time and lossless mode, a quantifiable correlation is established between an optical signal and an electrochemical degradation behavior, and therefore the monitoring sensitivity of early degradation and local corrosion is remarkably improved. Meanwhile, controllable degradation and self-healing adjustment of the coating can be achieved, and industrial popularization is facilitated.

Description

Technical Field

[0001] This invention relates to the field of functional coating technology for biodegradable magnesium alloy surfaces. Background Technology

[0002] Magnesium and its alloys have attracted widespread attention in recent years as potential biodegradable implant materials due to their excellent biocompatibility, osteoconductivity, and mechanical properties similar to natural bone tissue. Mg-based implants can gradually degrade in vivo, thus avoiding secondary removal surgery and offering significant clinical advantages. However, the rapid corrosion of magnesium and its alloys in physiological environments remains a key factor limiting their practical application. Excessive degradation can lead to premature loss of mechanical strength, increased local pH, hydrogen accumulation, and inflammatory reactions, thereby affecting the safety and reliability of the implant. To improve the corrosion resistance of Mg alloys, researchers both domestically and internationally have developed various surface modification techniques, including polymer coatings, chemical conversion films, alloying treatments, and ceramic protective coatings. Among these, plasma electrolytic oxidation (PEO) technology is considered one of the most promising technologies for improving the corrosion resistance of Mg alloys due to its advantages such as high coating bonding strength, tunable pore structure, good wear resistance, and the ability to introduce functional components into the electrolyte. Hydroxyapatite (HAp), as a major inorganic component of bone tissue, possesses excellent bioactivity and biocompatibility, and is often used to enhance the biological properties of implant surfaces. Combining HAp with PEO coatings has been shown to simultaneously improve surface corrosion resistance and bioactivity. However, the degradation process of PEO@HAp coatings in physiological environments is complex, influenced by the coating microstructure, interfacial ion exchange, and the stability of calcium sites (Ca1 / Ca2) in the HAp lattice. Traditional degradation assessment methods, such as electrochemical testing and mass loss analysis, are often destructive or intermittent, and have low sensitivity to early interfacial localized dissolution processes.

[0003] Therefore, there is an urgent need for a new technology that can achieve non-destructive, real-time, and quantitative monitoring to reveal the degradation kinetics of bioactive coatings on degradable metals. Summary of the Invention

[0004] This invention specifically discloses a method for utilizing europium-doped hydroxyapatite (HAp:Eu) 3+ This invention relates to a method for real-time optical monitoring and degradation of magnesium alloy plasma electrolytic oxidation (PEO) coatings using Eu as an optical probe. The invention utilizes Eu, which possesses crystal field-sensitive luminescence properties. 3+The method of this invention generates quantifiable changes in luminescence intensity and spectral structure during the coating dissolution-reprecipitation process, and establishes a quantitative correlation with corrosion kinetics, thereby enabling real-time monitoring and control of coating degradation behavior. This method simultaneously provides optical signals, electrochemical responses, and coating structure change information, accurately determining the degradation process without damaging the coating. It overcomes the shortcomings of traditional electrochemical and mass loss methods, such as intermittency, destructiveness, and insufficient sensitivity, providing a new technical approach for assessing the degradation behavior and predicting the lifetime of degradable magnesium-based implants.

[0005] A method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating is specifically carried out according to the following steps:

[0006] I. Magnesium Alloy Pretreatment:

[0007] The magnesium alloy is ground and polished to obtain a pretreated magnesium alloy;

[0008] II. Ultrasonic degreasing:

[0009] The pretreated magnesium alloy was immersed in a degreasing solution, ultrasonically treated, removed, rinsed, and dried to obtain the degreased magnesium alloy.

[0010] III. Preparation of HAP:Eu 3+ Precursor solution:

[0011] ① Dissolve Ca(NO3)2·4H2O and Eu(NO3)3·6H2O in deionized water to obtain solution A;

[0012] ② Dissolve (NH4)2HPO4 in deionized water to obtain solution B;

[0013] ③ Under stirring conditions, solution B is added dropwise to solution A to obtain a mixed solution; the pH of the mixed solution is adjusted to 10~10.5, and stirring is continued to obtain HAp:Eu 3+ Precursor solution;

[0014] IV. Preparation of HAP:Eu by Microwave Heating 3+ Nanoparticles:

[0015] HAp:Eu 3+ The precursor solution was transferred to a microwave reactor and heated from room temperature to 90℃~110℃ using a 500W microwave power. The temperature was maintained for 2~4 hours, then increased to 170℃~190℃ and maintained for 9~11 hours. After natural cooling to room temperature, the solution was centrifuged, washed, and freeze-dried to obtain HAp:Eu. 3+ Nanoparticles;

[0016] V. HAp:Eu 3+ Nanoparticle surface negative electrochemical treatment:

[0017] ① HAp:Eu 3+ Nanoparticles were added to deionized water, followed by the addition of polyethylene glycol, and then ultrasonically dispersed to obtain a suspension.

[0018] ② Under stirring conditions, sodium citrate solution is added dropwise to the suspension, and stirring continues to yield HAp:Eu with a negatively charged surface. 3+ Nanoparticle solution;

[0019] VI. Micro-arc oxidation treatment I:

[0020] First, add the micro-arc oxidation electrolyte I to the stainless steel cup. Then, connect the stainless steel cup to the negative terminal of the micro-arc oxidation power supply, and connect the pretreated magnesium alloy to the positive terminal of the micro-arc oxidation power supply. Then, operate at a current density of 3 A / dm³. 2 ~5A / dm 2 The first micro-arc oxidation reaction was carried out under the conditions of duty cycle of 20%~30% and frequency of 1000Hz~2000Hz; magnesium alloy after one micro-arc oxidation treatment was obtained.

[0021] The micro-arc oxidation electrolyte I described in step six is ​​composed of trisodium phosphate, sodium hexametaphosphate, potassium hydroxide, glycerol and water;

[0022] VII. Micro-arc oxidation treatment II:

[0023] ① HAP:Eu, which is negatively charged on the surface 3+ Sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium hydroxide, disodium ethylenediaminetetraacetate, calcium glycerophosphate, calcium disodium ethylenediaminetetraacetate, sodium silicate, sodium hexametaphosphate, and glycerol were added to the nanoparticle solution and stirred until homogeneous to obtain micro-arc oxidation electrolyte II.

[0024] ② First, add the micro-arc oxidation electrolyte II into the stainless steel cup, then connect the stainless steel cup to the negative terminal of the micro-arc oxidation power supply, and connect the magnesium alloy after the first micro-arc oxidation treatment to the positive terminal of the micro-arc oxidation power supply. Then, at a current density of 10A / dm³... 2 ~20A / dm 2 A second micro-arc oxidation reaction was carried out under the conditions of a duty cycle of 40%~60% and a frequency of 50Hz~100Hz to obtain a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating.

[0025] Advantages of this invention:

[0026] I. This invention introduces HAP:Eu into the micro-arc oxidation coating of magnesium alloys. 3+ This achieves integrated functionality encompassing coating protection, bioactivity, and optical monitoring. HAp:Eu 3+The field-sensitive luminescence behavior of this composite coating can reflect the coating's microstructure and the selective dissolution process of Ca1 / Ca2 sites in real time and without damage, enabling a quantifiable correlation between optical signals and electrochemical degradation behavior, thereby significantly improving the monitoring sensitivity of early degradation and localized corrosion. Simultaneously, while providing excellent corrosion protection, this composite coating maintains good biocompatibility and redeposition induction ability, allowing for controllable degradation and self-healing regulation.

[0027] Second, the entire preparation process of this invention is compatible with conventional micro-arc oxidation equipment, the process is simple, and it is easy to promote industrialization. It provides an efficient and reliable technical approach for constructing intelligent biodegradable magnesium-based implants with real-time feedback capabilities. Attached Figure Description

[0028] Figure 1 Different Eu samples prepared for Examples 4 3+ Atomic content of HAp:Eu 3+ SEM images of nanoparticles, where (a) shows Eu in Example 1. 3+ The atomic content is 4 at.%, (b) is the Eu content in Example 2. 3+ The atomic content is 8 at.%, and (c) is the Eu content in Example 3. 3+ The atomic content is 12 at.%, and (d) is the Eu content in Example 4. 3+ The atomic content is 16 at.%;

[0029] Figure 2 PEO@HAp:Eu prepared in Example 3 3+ XRD patterns of the coating at different immersion times;

[0030] Figure 3 PEO@HAp:Eu prepared in Example 3 3+ SEM images of the surface morphology of the coating at different immersion times, contact angle and elemental variation diagrams. The immersion times in (a) to (j) are 3 days, 6 days, 9 days, 12 days, 15 days, 18 days, 21 days, 24 days, 27 days and 30 days, respectively.

[0031] Figure 4 PEO@HAp:Eu prepared in Example 3 3+ Fluorescence spectra of the coating at different immersion times and I ED / I MD ratio;

[0032] Figure 5 PEO@HAp:Eu prepared in Example 3 3+ Polarization curves of the coating at different immersion times. Detailed Implementation

[0033] Specific Implementation Method 1: This implementation method is a method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating, specifically completed according to the following steps:

[0034] I. Magnesium Alloy Pretreatment:

[0035] The magnesium alloy is ground and polished to obtain a pretreated magnesium alloy;

[0036] II. Ultrasonic degreasing:

[0037] The pretreated magnesium alloy was immersed in a degreasing solution, ultrasonically treated, removed, rinsed, and dried to obtain the degreased magnesium alloy.

[0038] III. Preparation of HAP:Eu 3+ Precursor solution:

[0039] ① Dissolve Ca(NO3)2·4H2O and Eu(NO3)3·6H2O in deionized water to obtain solution A;

[0040] ② Dissolve (NH4)2HPO4 in deionized water to obtain solution B;

[0041] ③ Under stirring conditions, solution B is added dropwise to solution A to obtain a mixed solution; the pH of the mixed solution is adjusted to 10~10.5, and stirring is continued to obtain HAp:Eu 3+ Precursor solution;

[0042] IV. Preparation of HAP:Eu by Microwave Heating 3+ Nanoparticles:

[0043] HAp:Eu 3+ The precursor solution was transferred to a microwave reactor and heated from room temperature to 90℃~110℃ using a 500W microwave power. The temperature was maintained for 2~4 hours, then increased to 170℃~190℃ and maintained for 9~11 hours. After natural cooling to room temperature, the solution was centrifuged, washed, and freeze-dried to obtain HAp:Eu. 3+ Nanoparticles;

[0044] V. HAp:Eu 3+ Nanoparticle surface negative electrochemical treatment:

[0045] ① HAp:Eu 3+ Nanoparticles were added to deionized water, followed by the addition of polyethylene glycol, and then ultrasonically dispersed to obtain a suspension.

[0046] ② Under stirring conditions, sodium citrate solution is added dropwise to the suspension, and stirring continues to yield HAp:Eu with a negatively charged surface. 3+ Nanoparticle solution;

[0047] VI. Micro-arc oxidation treatment I:

[0048] First, add the micro-arc oxidation electrolyte I to the stainless steel cup. Then, connect the stainless steel cup to the negative terminal of the micro-arc oxidation power supply, and connect the pretreated magnesium alloy to the positive terminal of the micro-arc oxidation power supply. Then, operate at a current density of 3 A / dm³. 2 ~5A / dm 2 The first micro-arc oxidation reaction was carried out under the conditions of duty cycle of 20%~30% and frequency of 1000Hz~2000Hz; magnesium alloy after one micro-arc oxidation treatment was obtained.

[0049] The micro-arc oxidation electrolyte I described in step six is ​​composed of trisodium phosphate, sodium hexametaphosphate, potassium hydroxide, glycerol and water;

[0050] VII. Micro-arc oxidation treatment II:

[0051] ① HAP:Eu, which is negatively charged on the surface 3+ Sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium hydroxide, disodium ethylenediaminetetraacetate, calcium glycerophosphate, calcium disodium ethylenediaminetetraacetate, sodium silicate, sodium hexametaphosphate, and glycerol were added to the nanoparticle solution and stirred until homogeneous to obtain micro-arc oxidation electrolyte II.

[0052] ② First, add the micro-arc oxidation electrolyte II into the stainless steel cup, then connect the stainless steel cup to the negative terminal of the micro-arc oxidation power supply, and connect the magnesium alloy after the first micro-arc oxidation treatment to the positive terminal of the micro-arc oxidation power supply. Then, at a current density of 10A / dm³... 2 ~20A / dm 2 A second micro-arc oxidation reaction was carried out under the conditions of a duty cycle of 40%~60% and a frequency of 50Hz~100Hz to obtain a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating.

[0053] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that the magnesium alloy in step one has dimensions of 100mm × 30mm × 5mm; and in step one, the magnesium alloy is polished sequentially using 60#, 180#, 600#, and 2000# SiC sandpaper. All other steps are the same as in Specific Implementation Method One.

[0054] Specific Implementation Method Three: This implementation method differs from Specific Implementation Method One or Two in that the degreasing solution described in step two is composed of sodium carbonate, hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene ether, decyl glucoside, sodium citrate, sodium silicate, and water. The other steps are the same as in Specific Implementation Method One or Two.

[0055] Specific Implementation Method Four: This implementation method differs from Specific Implementation Methods One to Three in that the concentration of sodium carbonate in the degreasing solution described in step two is 3 g / L to 5 g / L, the concentration of hexadecyltrimethylammonium bromide is 0.5 g / L to 2 g / L, the concentration of fatty alcohol polyoxyethylene ether is 0.5 g / L to 2 g / L, the concentration of decyl glucoside is 4 g / L to 6 g / L, the concentration of sodium citrate is 3 g / L to 5 g / L, and the concentration of sodium silicate is 4 g / L to 6 g / L. The other steps are the same as in Specific Implementation Methods One to Three.

[0056] Specific Implementation Method Five: This implementation method differs from Specific Implementation Methods One to Four in the following ways: the ultrasonic treatment power in step two is 100W, and the ultrasonic treatment time is 10-20 minutes; the temperature of the degreasing solution in step two is 30°C-50°C; the rinsing in step two involves rinsing the magnesium alloy with distilled water 3-5 times; and the drying in step two involves drying with a hair dryer. Other steps are the same as in Specific Implementation Methods One to Four.

[0057] Specific Implementation Method Six: This implementation method differs from Specific Implementation Methods One to Five in the following ways: In step three ①, the mass-to-volume ratio of Ca(NO3)2·4H2O, Eu(NO3)3·6H2O, and deionized water is (7g~8g):(1g~2g):120mL; in step three ②, the mass-to-volume ratio of (NH4)2HPO4 to deionized water is (2g~3g):80mL; in step three ③, the volume ratio of solution A to solution B is 120:80; in step three ③, the stirring speed is 500r / min~800r / min; in step three ③, the stirring time is 20min~40min; in step three ③, the dropping rate is 100 drops / min~110 drops / min; in step three ③, ammonia water is used to adjust the pH of the mixed solution to 10~10.5. Other steps are the same as in Specific Implementation Methods One to Five.

[0058] Specific Implementation Method Seven: This implementation method differs from Specific Implementation Methods One to Six in that: the heating rate in step four is 5℃ / min to 10℃ / min; in step four, the mixture is naturally cooled to room temperature, centrifuged at 6000 r / min, then ultrasonically cleaned for 20 to 30 minutes in a 100W ultrasonic cleaner using deionized water as the cleaning agent, and finally placed in a freeze dryer at -40℃ to -50℃, vacuumed to 0.06 mbar, and freeze-dried for 45 to 50 hours. Other steps are the same as in Specific Implementation Methods One to Six.

[0059] Specific Implementation Method Eight: The difference between this implementation method and Specific Implementation Methods One to Seven is that the HAp:Eu mentioned in step Five① is... 3+The mass-to-volume ratio of nanoparticles, polyethylene glycol, and deionized water is 5g:(0.5g~1g):800mL; the ultrasonic dispersion time in step 5.① is 10min~20min; the concentration of the sodium citrate solution in step 5.② is 0.05mol / L~0.2mol / L; the volume ratio of the sodium citrate solution to the suspension in step 5.② is 1:10; the dropping rate in step 5.② is 100 drops / min~120 drops / min; the stirring speed in step 5.② is 500r / min, and the stirring time is continued for 20min~40min. Other steps are the same as in specific embodiments one to seven.

[0060] Specific Implementation Method Nine: This implementation method differs from Specific Implementation Methods One to Eight in that: in step six, the concentration of trisodium phosphate in the micro-arc oxidation electrolyte I is 8 g / L to 10 g / L, the concentration of sodium hexametaphosphate is 8 g / L to 10 g / L, the concentration of potassium hydroxide is 2 g / L to 4 g / L, and the concentration of glycerol is 90 mL / L to 100 mL / L; the time for the first micro-arc oxidation reaction in step six is ​​100 s to 150 s. Other steps are the same as in Specific Implementation Methods One to Eight.

[0061] Specific Implementation Method Ten: The difference between this implementation method and Specific Implementation Methods One to Nine is that: in step Seven①, the HAP:Eu in the micro-arc oxidation electrolyte II... 3+ The mass ratio of nanoparticles, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium hydroxide, disodium ethylenediaminetetraacetate, and glycerol calcium phosphate is 5:10:3:2:20:25; the HAP:Eu ratio in the micro-arc oxidation electrolyte II described in step seven ① is... 3+ The mass-to-volume ratio of nanoparticles, disodium calcium ethylenediaminetetraacetate, sodium silicate, sodium hexametaphosphate, and glycerol is 5g:10g:3g:10g:100mL; the time for the second micro-arc oxidation reaction described in step seven ② is 300s~400s. Other steps are the same as in specific embodiments one to nine.

[0062] The beneficial effects of the present invention are verified using the following embodiments:

[0063] Example 1: A method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating, specifically completed according to the following steps:

[0064] I. Magnesium Alloy Pretreatment:

[0065] The magnesium alloy was polished sequentially using 60#, 180#, 600#, and 2000# SiC sandpaper to obtain the pretreated magnesium alloy.

[0066] The magnesium alloy mentioned in step one has dimensions of 100mm × 30mm × 5mm;

[0067] II. Ultrasonic degreasing:

[0068] The pretreated magnesium alloy was immersed in a degreasing solution at 40°C, and then ultrasonically treated for 10 minutes at a power of 100W. After being taken out, the magnesium alloy was rinsed 5 times with distilled water and dried with a hair dryer to obtain the degreased magnesium alloy.

[0069] The degreasing solution described in step two is composed of sodium carbonate, hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene ether, decyl glucoside, sodium citrate, sodium silicate, and water. The concentration of sodium carbonate is 4 g / L, the concentration of hexadecyltrimethylammonium bromide is 1 g / L, the concentration of fatty alcohol polyoxyethylene ether is 1 g / L, the concentration of decyl glucoside is 5 g / L, the concentration of sodium citrate is 4 g / L, and the concentration of sodium silicate is 5 g / L.

[0070] III. Preparation of HAP:Eu 3+ Precursor solution:

[0071] ① Dissolve 7.55g Ca(NO3)2·4H2O and 0.59g Eu(NO3)3·6H2O in 120mL of deionized water to obtain solution A;

[0072] ② Dissolve 2.64g of (NH4)2HPO4 in 80mL of deionized water to obtain solution B;

[0073] ③ Under stirring conditions, solution B is added dropwise to solution A to obtain a mixed solution; the pH of the mixed solution is adjusted to 10.5, and stirring is continued for 30 minutes to obtain HAp:Eu 3+ Precursor solution;

[0074] The stirring speed mentioned in step 3③ is 500 r / min;

[0075] The dripping rate described in step 3③ is 110 drops / min;

[0076] IV. Preparation of HAP:Eu by Microwave Heating 3+ Nanoparticles:

[0077] HAp:Eu 3+ The precursor solution was transferred to a microwave reactor and heated from room temperature to 90℃~110℃ using a 500W microwave power, held for 2h~4h, then heated to 170℃~190℃, held for 9h~11h, and allowed to cool naturally to room temperature. It was then centrifuged at 6000r / min, and ultrasonically cleaned for 30min using deionized water in a 100W ultrasonic cleaner. Finally, it was placed in a -50℃ freeze dryer, evacuated to 0.06mbar, and freeze-dried for 50h to obtain HAp:Eu. 3+Nanoparticles (Ca (1-x) Eu x ] 10 (PO4)6(OH)2, where x = 4 at.%);

[0078] The heating rate described in step four is 10°C / min;

[0079] V. HAp:Eu 3+ Nanoparticle surface negative electrochemical treatment:

[0080] ① Add 5g of HAp:Eu 3+ Nanoparticles were added to 800 mL of deionized water, followed by the addition of 0.5 g of polyethylene glycol. The mixture was then ultrasonically dispersed for 10 min to obtain a suspension.

[0081] ② Under stirring conditions, 80 mL of sodium citrate solution was added dropwise to the suspension, and stirring was continued for 30 min to obtain HAp:Eu with a negatively charged surface. 3+ Nanoparticle solution;

[0082] The concentration of the sodium citrate solution mentioned in step 5② is 0.1 mol / L;

[0083] The dripping rate described in step 5② is 120 drops / min;

[0084] The stirring speed mentioned in step 5② is 500 r / min;

[0085] VI. Micro-arc oxidation treatment I:

[0086] First, add the micro-arc oxidation electrolyte I to the stainless steel cup. Then, connect the stainless steel cup to the negative terminal of the micro-arc oxidation power supply, and connect the pretreated magnesium alloy to the positive terminal of the micro-arc oxidation power supply. Then, operate at a current density of 4 A / dm³. 2 The first micro-arc oxidation reaction was carried out for 120s under the conditions of a duty cycle of 20% and a frequency of 2000Hz; a magnesium alloy after one micro-arc oxidation treatment was obtained.

[0087] The micro-arc oxidation electrolyte I mentioned in step six is ​​composed of trisodium phosphate, sodium hexametaphosphate, potassium hydroxide, glycerol and water, wherein the concentration of trisodium phosphate is 10 g / L, the concentration of sodium hexametaphosphate is 10 g / L, the concentration of potassium hydroxide is 3 g / L and the concentration of glycerol is 100 mL / L.

[0088] VII. Micro-arc oxidation treatment II:

[0089] ① HAP:Eu, which is negatively charged on the surface 3+10g sodium dihydrogen phosphate, 3g disodium hydrogen phosphate, 2g potassium hydroxide, 20g disodium ethylenediaminetetraacetate, 25g calcium glycerophosphate, 10g calcium disodium ethylenediaminetetraacetate, 3g sodium silicate, 10g sodium hexametaphosphate and 100mL glycerol were added to the nanoparticle solution and stirred until homogeneous to obtain micro-arc oxidation electrolyte II.

[0090] ② First, add the micro-arc oxidation electrolyte II to the stainless steel cup, then connect the stainless steel cup to the negative terminal of the micro-arc oxidation power supply, and connect the magnesium alloy after the first micro-arc oxidation treatment to the positive terminal of the micro-arc oxidation power supply. Then, at a current density of 15 A / dm³... 2 A second micro-arc oxidation reaction was carried out for 360 s under conditions of 50% duty cycle and 50 Hz frequency to obtain a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating (PEO@HAp:Eu). 3+ coating).

[0091] Example 2: The difference between this example and Example 1 is: Step 3, preparation of HAp:Eu 3+ Precursor solution:

[0092] ① Dissolve 7.24g Ca(NO3)2·4H2O and 1.19g Eu(NO3)3·6H2O in 120mL of deionized water to obtain solution A;

[0093] ② Dissolve 2.64g of (NH4)2HPO4 in 80mL of deionized water to obtain solution B;

[0094] ③ Under stirring conditions, solution B is added dropwise to solution A to obtain a mixed solution; the pH of the mixed solution is adjusted to 10.5, and stirring is continued for 30 minutes to obtain HAp:Eu 3+ Precursor solution;

[0095] The stirring speed mentioned in step 3③ is 500 r / min;

[0096] The dripping rate described in step 3③ is 110 drops / min;

[0097] IV. Preparation of HAP:Eu by Microwave Heating 3+ Nanoparticles:

[0098] HAp:Eu 3+The precursor solution was transferred to a microwave reactor and heated from room temperature to 90℃~110℃ using a 500W microwave power, held for 2h~4h, then heated to 170℃~190℃, held for 9h~11h, and allowed to cool naturally to room temperature. It was then centrifuged at 6000r / min, and ultrasonically cleaned for 30min using deionized water in a 100W ultrasonic cleaner. Finally, it was placed in a -50℃ freeze dryer, evacuated to 0.06mbar, and freeze-dried for 50h to obtain HAp:Eu. 3+ Nanoparticles (Ca (1-x) Eu x ] 10 (PO4)6(OH)2, where x = 8 at.%);

[0099] The heating rate described in step four is 10°C / min. All other steps and parameters are the same as in Example 1.

[0100] Example 3: The difference between this example and Example 1 is: Step 3, preparation of HAp:Eu 3+ Precursor solution:

[0101] ① Dissolve 6.92g Ca(NO3)2·4H2O and 1.78g Eu(NO3)3·6H2O in 120mL of deionized water to obtain solution A;

[0102] ② Dissolve 2.64g of (NH4)2HPO4 in 80mL of deionized water to obtain solution B;

[0103] ③ Under stirring conditions, solution B is added dropwise to solution A to obtain a mixed solution; the pH of the mixed solution is adjusted to 10.5, and stirring is continued for 30 minutes to obtain HAp:Eu 3+ Precursor solution;

[0104] The stirring speed mentioned in step 3③ is 500 r / min;

[0105] The dripping rate described in step 3③ is 110 drops / min;

[0106] IV. Preparation of HAP:Eu by Microwave Heating 3+ Nanoparticles:

[0107] HAp:Eu 3+The precursor solution was transferred to a microwave reactor and heated from room temperature to 90℃~110℃ using a 500W microwave power, held for 2h~4h, then heated to 170℃~190℃, held for 9h~11h, and allowed to cool naturally to room temperature. It was then centrifuged at 6000r / min, and ultrasonically cleaned for 30min using deionized water in a 100W ultrasonic cleaner. Finally, it was placed in a -50℃ freeze dryer, evacuated to 0.06mbar, and freeze-dried for 50h to obtain HAp:Eu. 3+ Nanoparticles (Ca (1-x) Eu x ] 10 (PO4)6(OH)2, where x = 12 at.%);

[0108] The heating rate described in step four is 10°C / min. All other steps and parameters are the same as in Example 1.

[0109] Example 4: The difference between this example and Example 1 is: Step 3, preparation of HAp:Eu 3+ Precursor solution:

[0110] ① Dissolve 6.60g Ca(NO3)2·4H2O and 2.38g Eu(NO3)3·6H2O in 120mL of deionized water to obtain solution A;

[0111] ② Dissolve 2.64g of (NH4)2HPO4 in 80mL of deionized water to obtain solution B;

[0112] ③ Under stirring conditions, solution B is added dropwise to solution A to obtain a mixed solution; the pH of the mixed solution is adjusted to 10.5, and stirring is continued for 30 minutes to obtain HAp:Eu 3+ Precursor solution;

[0113] The stirring speed mentioned in step 3③ is 500 r / min;

[0114] The dripping rate described in step 3③ is 110 drops / min;

[0115] IV. Preparation of HAP:Eu by Microwave Heating 3+ Nanoparticles:

[0116] HAp:Eu 3+The precursor solution was transferred to a microwave reactor and heated from room temperature to 90℃~110℃ using a 500W microwave power, held for 2h~4h, then heated to 170℃~190℃, held for 9h~11h, and allowed to cool naturally to room temperature. It was then centrifuged at 6000r / min, and ultrasonically cleaned for 30min using deionized water in a 100W ultrasonic cleaner. Finally, it was placed in a -50℃ freeze dryer, evacuated to 0.06mbar, and freeze-dried for 50h to obtain HAp:Eu. 3+ Nanoparticles (Ca (1-x) Eu x ] 10 (PO4)6(OH)2, where x = 16 at.%);

[0117] The heating rate described in step four is 10°C / min. All other steps and parameters are the same as in Example 1.

[0118] Figure 1 Different Eu samples prepared for Examples 4 3+ Atomic content of HAp:Eu 3+ SEM images of nanoparticles, where (a) shows Eu in Example 1. 3+ The atomic content is 4 at.%, (b) is the Eu content in Example 2. 3+ The atomic content is 8 at.%, and (c) is the Eu content in Example 3. 3+ The atomic content is 12 at.%, and (d) is the Eu content in Example 4. 3+ The atomic content is 16 at.%;

[0119] from Figure 1 It can be seen that: different Eu 3+ HAP content: Eu 3+ Nanoparticles exhibit typical rod-shaped or needle-shaped morphologies under microwave heating conditions, consistent with the characteristic structure of microwave-synthesized HAp; it can be seen that Eu 3+ The doping did not change the basic crystal growth habit of HAp, and its morphology maintained a consistent anisotropic structure.

[0120] Figure 2 PEO@HAp:Eu prepared in Example 3 3+ XRD patterns of the coating at different immersion times;

[0121] Figure 2 It showcases PEO@HAp:Eu 3+Phase evolution of the coating during 30 days of immersion in Hank's solution. Initially (days 3-9), diffraction peaks corresponding to Mg and MgO dominated, indicating that the coating mainly consisted of an oxide layer formed by PEO with limited surface reactions. As the immersion time increased to 12-21 days, the intensity of the Mg(OH)2 peak became more pronounced, confirming that the formation of the hydroxide layer was enhanced due to the continued corrosion of the substrate and the alkalinity of the Hank's solution. After 24-30 days, XRD patterns showed a significant decrease in the intensity of the metallic Mg peak, while the signals of both Mg3(PO4)2 and Mg(OH)2 increased. This trend reflects the gradual degradation of the underlying magnesium alloy and the gradual accumulation of corrosion products and redeposited phosphate phases. The gradual decrease in luminescence intensity indicates the dissolution of hydroxyapatite, while the continued presence of the hydroxyapatite diffraction peak indicates a simultaneous dissolution-reprecipitation process, in which Eu... 3+ Doped hydroxyapatite contributes to surface stability by forming a partially protective bioactive barrier during immersion.

[0122] Figure 3 PEO@HAp:Eu prepared in Example 3 3+ SEM images of the surface morphology of the coating at different immersion times, contact angle and elemental variation diagrams. The immersion times in (a) to (j) are 3 days, 6 days, 9 days, 12 days, 15 days, 18 days, 21 days, 24 days, 27 days and 30 days, respectively.

[0123] Figure 3 (aj) represents PEO@HAp:Eu at different soaking times. 3+ The SEM image of the coating under simulated physiological conditions is shown in the figure. The coating exhibits a porous structure with uniform pore distribution, a typical characteristic of PEO coatings, which facilitates nutrient diffusion and tissue inward growth. After soaking for 3-9 days, the coating surface initially exhibits a dense and relatively uniform porous structure. When the soaking time is extended to 15 days (…),… Figure 3 e) The pores are gradually covered by deposited material, which may be Mg(OH)2 or phosphate phase, indicating that biomineralization has begun and is ongoing. As the soaking time is extended to 12-18 days, PEO@HAp:Eu 3+ The coating exhibited significant partial dissolution, manifested as enlarged pores and the appearance of microcracks. These characteristics indicate the presence of Mg in the coating. 2+ / Ca 2 + / PO4 3- Active ion exchange occurred between the phosphate deposit and the surrounding medium, triggering nucleation and early growth of the phosphate deposit. When the immersion time reached 18–24 days, a distinct secondary deposition layer formed on the surface, indicating the presence of Mg in Hank's solution. 2+ Ca2+ and PO4 3- Driven by supersaturation, significant redeposition of the phosphate phase occurred. This observation is entirely consistent with XRD results, which confirmed that Mg(OH)₂ and Mg₃(PO₄)₂ were the main corrosion and mineralization products. After 30 days, the coating surface became significantly denser and covered by a thicker layer of newly formed deposits, reflecting continued mineralization and gradual degradation of the original coating matrix. Overall, the morphological evolution indicates that PEO@HAp:Eu 3+ The coating underwent a gradual, time-varying biomineralization process in Hank's solution, a behavior highly beneficial for promoting osseointegration in bone repair applications. Evolution of the water contact angle ( Figure 3 (k) further supports this transformation. During the initial 12–15 days, hydrophobicity increases, reaching a maximum at around 60°, corresponding to surface reconstruction and a moderate release of hydrophilic ions. After 15 days, the contact angle decreases, indicating enhanced surface wettability due to the formation of a more hydrophilic phosphate layer. Elemental analysis ( Figure 3 (l) confirmed these trends. With prolonged soaking time, oxygen content gradually increased, consistent with the formation of hydrated phosphate and hydroxide species. Simultaneously, magnesium content decreased due to matrix dissolution, while calcium and phosphorus contents fluctuated slightly, reflecting the competition between ion release and reprecipitation.

[0124] To clarify Eu 3+ The occupancy behavior of ions at Ca1 and Ca2 sites of hydroxyapatite incorporated into magnesium alloy PEO coatings was analyzed, and the fluorescence emission spectrum was examined. Figure 4 a) and the intensity ratio of electric dipole transition (ED) to magnetic dipole transition (MD) Figure 4 b). These optical responses are related to the unique structural features of the Ca1 and Ca2 sites. The overall emission intensity gradually decreases with increasing immersion time, which can be attributed to the HAp:Eu within the PEO coating in the ionic environment of Hank's solution. 3+ Nanoparticles gradually degrade. This degradation leads to Eu... 3+ The dissolved lattice regions and reduced number of photoluminescent centers result in a monotonic decay of luminescence intensity over 30 days. Magnetic dipole transition ( 5 D0→ 7 F1) can occur in both centrosymmetric and non-centrosymmetric environments, while electric dipole transitions ( 5 D0→ 7 F2) is highly sensitive to asymmetry, only becoming significant in non-centrosymmetric (C5) environments. Therefore, higher I ED / I MD The ratio reflects Eu 3+It occupies the low-symmetry Ca2 site, while a lower ratio indicates a transition to the high-symmetry Ca1 site. In the initial soaking stage (3-6 days), I... ED / I MD The ratio reaches its maximum value (approximately 1.9), which means that Eu 3+ Ions preferentially occupy C s Symmetrical Ca2 sites. This preference may be attributed to Eu. 3+ Its high electronegativity makes it more prone to forming covalent interactions with hydroxyl groups. In the HAp lattice, these hydroxyl groups are located within structural channels coordinated by Ca2+ cations. Therefore, Eu... 3+ The strong affinity for hydroxyl groups within the channel provides a reasonable explanation for its preferential substitution of Ca2 sites in the early stages of immersion. As immersion time increases (10-30 days), this ratio gradually decreases and stabilizes at approximately 1.2, indicating that Eu... 3+ (Ca) 2+ Ions migrate or preferentially remain at the more symmetrical Ca1 sites. This change is due to the poor structural stability of Ca2 sites under ion corrosion, leading to selective degradation and thus affecting Eu. 3+ It primarily binds to the more stable Ca1 site. 3+ The occupancy transition from Ca2 sites to Ca1 sites not only confirms its effectiveness as an intrinsic optical probe for tracking coating degradation, but also provides a theoretical basis for the rational design of luminescent bioactive coatings for magnesium alloy biomedical implants.

[0125] Figure 5 PEO@HAp:Eu prepared in Example 3 3+ Polarization curves of the coating at different immersion times;

[0126] Figure 5 It is PEO@HAp:Eu 3+ Tafel polarization curves of the coating after immersion in Hank's solution for different times. Table 1 summarizes the PEO@HAp:Eu polarization curves. 3+ Electrochemical parameters of the coating obtained by Tafel polarization curves after immersion in Hank's solution for different times. Corrosion current density (I corr ) and corrosion potential (E corr The coating exhibits significant changes, reflecting its dynamic degradation and passivation behavior over time. In the initial stage (3-6 days), I... corr The value is from 4.26 × 10 -6 A / cm 2 Reduced to 3.39×10 - 6 A / cm 2 Meanwhile, E corrIt shifts slightly more negatively (from -1.42V to -1.47V). This trend indicates that, due to HAp:Eu 3+ A dense protective layer composed of nanoparticles and MgO was formed, effectively reducing charge transfer and corrosion rates. Large anodic and cathodic slopes (βa and βc) further confirmed the presence of a stable passivation film that simultaneously inhibits anodic dissolution and cathodic reduction processes. During 9–15 days, I… corr It increased sharply to 17.91 × 10 -6 A / cm 2 This indicates that due to HAP:Eu 3+ The partial dissolution and exposure of the underlying magnesium substrate led to partial damage to the passivation layer. The corrosion potential shifted slightly to a more negative direction (–1.48V), indicating enhanced anodic activity. Simultaneously, βa decreased to 215 mV / decade, reflecting accelerated electrochemical reactions and weakened barrier protection. After 18 days, I… corr It gradually decreased and stabilized at (6-9)×10 -6 A / cm 2 Left and right, simultaneously E corr The values ​​remained consistently negative (approximately –1.50V). This decrease indicates the formation of a secondary protective layer due to the redeposition of supersaturated phosphate species in Hank's solution. After 21 days, both βa and βc values ​​gradually increased, indicating an increase in charge transfer resistance and the establishment of a dynamic equilibrium between dissolution and redeposition processes. In summary, the corrosion evolution followed a three-stage mechanism: (i) initial stabilization and passivation stage (0–6 days); (ii) partial destruction and active corrosion stage (9–15 days); and (iii) repassivation and equilibrium formation stage (18–30 days). These results confirm that HAp:Eu 3+ The incorporation of nanoparticles improves the initial corrosion resistance of the PEO coating and promotes self-healing behavior through ion exchange and phosphate redeposition during long-term immersion.

[0127] Comparing optical signals with coating degradation behavior reveals a strong correlation between luminescence intensity and electrochemical behavior in the initial immersion stage, indicating that Eu... 3+ It can be used as an integrated optical probe to predict corrosion activity in real time. Higher spectral ratios and stronger fluorescence emission correspond to lower corrosion rates, and the positive correlation between photoluminescence decay and electrochemical corrosion current density (Icorr(t)) highlights the advantages of Eu-based probes. 3+ Optical monitoring complements traditional electrochemical methods, enabling a more comprehensive and continuous assessment of coating degradation in physiological environments. This allows fluorescence intensity to serve as a non-destructive indicator of coating stability.

[0128] Table 1

[0129]

Claims

1. A method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating, characterized in that... The preparation method is specifically carried out according to the following steps: I. Magnesium Alloy Pretreatment: The magnesium alloy is ground and polished to obtain a pretreated magnesium alloy; II. Ultrasonic degreasing: The pretreated magnesium alloy was immersed in a degreasing solution, ultrasonically treated, removed, rinsed, and dried to obtain the degreased magnesium alloy. III. Preparation of HAP:Eu 3+ Precursor solution: ① Dissolve Ca(NO3)2·4H2O and Eu(NO3)3·6H2O in deionized water to obtain solution A; ② Dissolve (NH4)2HPO4 in deionized water to obtain solution B; ③ Under stirring conditions, solution B is added dropwise to solution A to obtain a mixed solution; the pH of the mixed solution is adjusted to 10~10.5, and stirring is continued to obtain HAp:Eu 3+ Precursor solution; IV. Preparation of HAP:Eu by Microwave Heating 3+ Nanoparticles: HAp:Eu 3+ The precursor solution was transferred to a microwave reactor and heated from room temperature to 90℃~110℃ using a 500W microwave power. The temperature was maintained for 2~4 hours, then increased to 170℃~190℃ and maintained for 9~11 hours. After natural cooling to room temperature, the solution was centrifuged, washed, and freeze-dried to obtain HAp:Eu. 3+ Nanoparticles; V. HAp:Eu 3+ Nanoparticle surface negative electrochemical treatment: ① HAp:Eu 3+ Nanoparticles were added to deionized water, followed by the addition of polyethylene glycol, and then ultrasonically dispersed to obtain a suspension. ② Under stirring conditions, sodium citrate solution is added dropwise to the suspension, and stirring continues to yield HAp:Eu with a negatively charged surface. 3+ Nanoparticle solution; VI. Micro-arc oxidation treatment I: First, add the micro-arc oxidation electrolyte I to the stainless steel cup. Then, connect the stainless steel cup to the negative terminal of the micro-arc oxidation power supply, and connect the pretreated magnesium alloy to the positive terminal of the micro-arc oxidation power supply. Then, operate at a current density of 3 A / dm³. 2 ~5A / dm 2 The first micro-arc oxidation reaction was carried out under the conditions of duty cycle of 20%~30% and frequency of 1000Hz~2000Hz; magnesium alloy after one micro-arc oxidation treatment was obtained. The micro-arc oxidation electrolyte I described in step six is ​​composed of trisodium phosphate, sodium hexametaphosphate, potassium hydroxide, glycerol and water; VII. Micro-arc oxidation treatment II: ① HAP:Eu, which is negatively charged on the surface 3+ Sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium hydroxide, disodium ethylenediaminetetraacetate, calcium glycerophosphate, calcium disodium ethylenediaminetetraacetate, sodium silicate, sodium hexametaphosphate, and glycerol were added to the nanoparticle solution and stirred until homogeneous to obtain micro-arc oxidation electrolyte II. ② First, add the micro-arc oxidation electrolyte II into the stainless steel cup, then connect the stainless steel cup to the negative terminal of the micro-arc oxidation power supply, and connect the magnesium alloy after the first micro-arc oxidation treatment to the positive terminal of the micro-arc oxidation power supply. Then, at a current density of 10A / dm³... 2 ~20A / dm 2 A second micro-arc oxidation reaction was carried out under the conditions of a duty cycle of 40%~60% and a frequency of 50Hz~100Hz to obtain a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating.

2. The method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating according to claim 1, characterized in that... The magnesium alloy mentioned in step one has dimensions of 100mm×30mm×5mm; in step one, 60#, 180#, 600#, and 2000# SiC sandpaper are used to grind and polish the magnesium alloy in sequence.

3. The method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating according to claim 1, characterized in that... The degreasing solution described in step two is composed of sodium carbonate, hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene ether, decyl glucoside, sodium citrate, sodium silicate, and water.

4. The method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating according to claim 3, characterized in that... In step two, the concentrations of sodium carbonate, hexadecyltrimethylammonium bromide, fatty alcohol polyoxyethylene ether, decyl glucoside, sodium citrate, and sodium silicate in the degreasing solution are 3 g / L to 5 g / L, 0.5 g / L to 2 g / L, 4 g / L to 6 g / L, 3 g / L to 5 g / L, and 4 g / L to 6 g / L.

5. The method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating according to claim 1, characterized in that... The ultrasonic treatment in step two has a power of 100W and a treatment time of 10-20 minutes; the temperature of the degreasing solution in step two is 30°C-50°C; the rinsing in step two involves rinsing the magnesium alloy with distilled water 3-5 times; and the drying in step two involves drying with a hair dryer.

6. The method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating according to claim 1, characterized in that... In step 3①, the mass-to-volume ratio of Ca(NO3)2·4H2O, Eu(NO3)3·6H2O, and deionized water is (7g~8g):(1g~2g):120mL; in step 3②, the mass-to-volume ratio of (NH4)2HPO4 to deionized water is (2g~3g):80mL; in step 3③, the volume ratio of solution A to solution B is 120:80; in step 3③, the stirring speed is 500r / min~800r / min; in step 3③, the stirring time is 20min~40min; in step 3③, the dropping rate is 100 drops / min~110 drops / min; in step 3③, ammonia water is used to adjust the pH of the mixed solution to 10~10.

5.

7. The method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating according to claim 1, characterized in that... The heating rate described in step four is 5℃ / min~10℃ / min; after naturally cooling to room temperature, centrifuge at 6000r / min, then use deionized water as a cleaning agent and ultrasonically clean in a 100W ultrasonic cleaner for 20min~30min, and finally place it in a freeze dryer at -40℃~-50℃, evacuate to 0.06mbar, and freeze dry for 45h~50h.

8. The method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating according to claim 1, characterized in that... The HAp:Eu mentioned in step 5① 3+ The mass-to-volume ratio of nanoparticles, polyethylene glycol, and deionized water is 5g:(0.5g~1g):800mL; the ultrasonic dispersion time in step 5.① is 10min~20min; the concentration of sodium citrate solution in step 5.② is 0.05mol / L~0.2mol / L; the volume ratio of sodium citrate solution to suspension in step 5.② is 1:10; the dropping rate in step 5.② is 100 drops / min~120 drops / min; the stirring speed in step 5.② is 500r / min, and the stirring time is 20min~40min.

9. The method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating according to claim 1, characterized in that... In step six, the concentration of trisodium phosphate in the micro-arc oxidation electrolyte I is 8 g / L to 10 g / L, the concentration of sodium hexametaphosphate is 8 g / L to 10 g / L, the concentration of potassium hydroxide is 2 g / L to 4 g / L, and the concentration of glycerol is 90 mL / L to 100 mL / L; the time of the first micro-arc oxidation reaction in step six is ​​100 s to 150 s.

10. The method for preparing a magnesium alloy plasma electrolytic oxidation fluorescent degradation coating according to claim 1, characterized in that... In step seven①, the micro-arc oxidation electrolyte II contains HAP:Eu 3+ The mass ratio of nanoparticles, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium hydroxide, disodium ethylenediaminetetraacetate, and glycerol calcium phosphate is 5:10:3:2:20:25; the HAP:Eu ratio in the micro-arc oxidation electrolyte II described in step seven ① is... 3+ The mass-to-volume ratio of nanoparticles, disodium calcium ethylenediaminetetraacetate, sodium silicate, sodium hexametaphosphate, and glycerol is 5g:10g:3g:10g:100mL; the time for the second micro-arc oxidation reaction described in step 7② is 300s~400s.

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