CN104789957A - Microwave preparation method of flower-shaped hydroxyapatite coating layer on surface of magnesium alloy - Google Patents

Abstract

The invention relates to a microwave preparation method of a flower-shaped hydroxyapatite coating on the surface of a magnesium alloy. The pretreated magnesium alloy sample is soaked in a conversion coating solution, and the conversion coating solution is placed in a microwave chemical reactor , heating the conversion coating solution to boiling and keeping it for 2-10 minutes; then immediately take out the coated magnesium alloy sample, rinse it with deionized water, and dry it. The hydroxyapatite coating is a flower-like structure formed by clusters of hydroxyapatite nanorods, the length of the nanorods is 300-900nm, and the diameter of the nanorods is 30-90nm. The coating thickness is 2-10 μm. The nanostructured hydroxyapatite coating not only improves the biological activity of magnesium alloys, but also improves the corrosion resistance of magnesium alloys in simulated body fluids. The preparation process of the coating is simple, economical and environmentally friendly, and has great commercial promotion value.

Description

Microwave preparation method of flower-like hydroxyapatite coating on magnesium alloy surface

technical field

The invention relates to a microwave preparation method of a flower-like hydroxyapatite coating on the surface of a magnesium alloy, and belongs to the technical field of surface modification of degradable magnesium alloy implants.

Background technique

Magnesium alloy has good biocompatibility, and its density is close to that of human bone tissue. Compared with materials such as titanium alloy, stainless steel, and cobalt-chromium alloy, which are widely used in clinical practice, the elastic modulus (41-45GPa) of magnesium alloy is similar to that of bone tissue. (10-30GPa) is more matched, which is beneficial to reduce the "stress shielding" effect of the interface between the implant and human bone tissue, and promote the growth of bone tissue. Moreover, magnesium alloy can be completely degraded and absorbed in the body. As an implant, it does not need a second operation to remove it. It is considered to be the most promising new type of degradable and absorbable metal implant material in orthopedics. It can be widely used in bone internal fixation and bone tissue engineering. Porous scaffolds and oral implants, etc. However, the degradation rate of magnesium alloys in tissue and body fluids is too fast, and the failure period of mechanical properties is only 6 to 8 weeks, while the clinical bone healing time generally takes about 12 weeks. The local high magnesium ions caused by the rapid degradation of magnesium alloys seriously affect the injury. Tissue growth and healing. For now, the rapid degradation of magnesium alloys in physiological environments has become a major obstacle limiting their clinical applications. Surface modification of magnesium alloy with hydroxyapatite coating is considered to be one of the effective ways to delay the rapid degradation of magnesium alloy and improve its biocompatibility.

Hydroxyapatite is the main inorganic component of natural bone, accounting for about 60wt.% in bone. Hydroxyapatite has good biological activity, and can form a tight combination with the soft and hard tissues of the human body in a short time after being implanted in the human body. Hydroxyapatite with nanometer or submicron structure is beneficial to the adhesion, proliferation, differentiation, secretion of collagen, phagocytosis and degradation of osteoblasts, promotion of calcification, and the normal reconstruction process of natural bone. It is an excellent alternative to hard tissue repair. The material has been successfully applied in the fields of dentistry, plastic surgery and maxillofacial reconstruction. The preparation of hydroxyapatite coating on the surface of magnesium alloy can not only show the excellent mechanical properties of magnesium alloy matrix, but also exert the excellent biological activity and physical barrier effect of hydroxyapatite coating.

At present, a variety of methods can be used to prepare hydroxyapatite coating on the surface of magnesium alloy. Among them, Guan Shaokang et al. (Patent No. 200910065998.2) prepared a hydroxyapatite coating on the surface of pure magnesium or magnesium alloy by pulse electrodeposition process. Yao Zhongping (application number 201310099462.9) first prepared a micro-arc oxidation layer on the surface of the magnesium alloy, and then placed the magnesium alloy with the micro-arc oxidation layer in the suspension of hydroxyapatite powder, and then used the hydrothermal method to form a micro-arc oxidation layer on the surface of the magnesium alloy. Preparation of hydroxyapatite coatings. Lu Wei et al. (Application No. 201310420659.8) used a bionic process to soak the pretreated magnesium alloy in the conversion coating solution for 5-100 hours, and then prepared a hydroxyapatite coating on the surface of the magnesium alloy after heat treatment. Cai Shu et al. (application number 201210381119.9) prepared a mesoporous nano-hydroxyapatite coating on the surface of a magnesium alloy by using a sol-gel dipping and pulling process. The above-mentioned various hydroxyapatite coatings can improve the corrosion resistance of the magnesium alloy substrate to varying degrees, but due to the limitation of the preparation process, there are still some deficiencies, such as: hydroxyapatite prepared by pulse electrodeposition technology The density of the coating is not high, and the protective effect on the magnesium alloy substrate is limited; it is difficult to prepare a thick hydroxyapatite coating by using sol-gel technology, and the protective effect on the magnesium alloy substrate is not ideal; using hydrothermal or bionic It takes a long time to prepare hydroxyapatite coating by technology, and the production efficiency is too low.

It should be pointed out that the traditional biomimetic coating process is to soak the metal implant in a supersaturated modified biomimetic solution and keep it at a certain temperature for a certain period of time to deposit a layer of CaP coating on the surface of the metal implant in situ. Since the magnesium alloy is easily corroded in the biomimetic solution and produces air bubbles to reduce the quality of the biomimetic coating, the magnesium alloy substrate needs to be pretreated to improve its corrosion resistance in the biomimetic solution and shorten the immersion of the magnesium alloy substrate in the biomimetic solution as much as possible. time in order to improve the quality of the prepared biomimetic coating. For example, Chen et al., 2011. A simple route towards a hydroxyapatite-Mg(OH) ₂ conversion coating for magnesium. Corrosion Science and Gray-Munro et al., 2008. The mechanism of deposition of calcium phosphate coatings from solution onto magnesium alloy AZ31.Journal of Biomedical Materials Research Part A reported that the hydroxyapatite coating prepared on the surface of magnesium alloy by traditional biomimetic coating process mostly has a particle agglomerated structure and usually does not have a nanostructure. Current studies have confirmed that the hydroxyapatite coating with nano or submicron structure will significantly promote the adhesion and growth of osteoblasts on the coating surface due to its large specific surface area, thereby promoting implant implantation. Afterwards, it can rapidly bond with the host bone to improve the success rate of implantation.

Contents of the invention

The object of the present invention is to provide a microwave preparation method of flower-shaped hydroxyapatite coating on the surface of magnesium alloy. The method has multiple advantages, among which the most important is that the prepared nanostructured hydroxyapatite coating not only improves the biological activity of magnesium alloys, but also significantly improves the corrosion resistance of magnesium alloys in simulated body fluids.

At present, microwave energy, as a new type of heat source, has been increasingly used in the fields of drying, sintering, sterilization, greening, and liquid-phase chemical synthesis. Civilian microwave heating mainly has two frequencies: 915MHz or 2450MHz. The principle of microwave heating is to rearrange the free charges in the heated material and rotate the dipoles repeatedly under the polarization of the alternating electromagnetic field, thereby generating strong vibration and friction. In this microscopic process, the alternating electromagnetic energy is transformed into It is the internal energy of the medium, which causes the temperature of the medium to rise. Its heating method does not require heat conduction from the surface to the inside, so microwave heating belongs to volume heating. Generally speaking, compared with conventional electric heating, microwave heating can significantly speed up the reaction process, optimize the reaction process, and obtain new substances, new shapes, and new structures that cannot be obtained by conventional electric heating techniques. Therefore, using microwave radiation + bionic method to prepare hydroxyapatite coating on the surface of medical magnesium alloy has the advantages of simple and fast process, energy saving and environmental protection, and the thickness of the coating is controllable, in order to obtain a coating with good corrosion resistance. Hydroxyapatite coated magnesium alloy material.

The present invention can be realized through the following technical solutions in order to achieve the above object:

A microwave preparation method for a flower-shaped hydroxyapatite coating on the surface of a magnesium alloy comprises immersing a pretreated magnesium alloy sample in a conversion coating solution, placing the conversion coating solution in a microwave chemical reactor, and converting the The coating solution is heated to boiling and kept for 2 to 10 minutes; then the coated magnesium alloy sample is immediately taken out, rinsed with deionized water, and dried.

The surface pretreatment of the magnesium alloy is preferably as follows: the surface of the magnesium alloy is polished to 1200-2000 mesh, then ultrasonically cleaned in acetone, deionized water, and ethanol for 3-10 minutes, and dried; then the magnesium alloy is soaked in NaOH solution Keep warm at 60-90°C, then rinse with deionized water and dry.

The conversion coating solution is preferably: using Ca(NO ₃ ) ₂ , CaCl ₂ or Ca(CH ₃ COO) ₂ as Ca source to prepare Ca ²⁺ aqueous solution, and using NH ₄ H ₂ PO ₄ , Na ₂ HPO ₄ or Prepare PO ₄ ^3- water solution with NaH ₂ PO ₄ as P source; then add PO ₄ ^3- water solution dropwise into Ca ²⁺ aqueous solution, and finally use dilute acid to adjust the pH value of the mixed solution to 5~6, and magnetically stir for 1~2h ; Wherein, the concentration of Ca ²⁺ in the mixed solution is 4-6 mmol/L, and the concentration of PO ₄ ^3- is 1-2 mmol/L.

The dilute acid is preferably one of dilute nitric acid, dilute hydrochloric acid, and acetic acid, and its concentration is 1-20 mol/L.

The magnesium alloy is preferably one of AZ31, AZ61, AZ80 or AZ91.

The microwave frequency generated by the microwave chemical reactor is 915MHz or 2450MHz.

The flower-shaped hydroxyapatite coating on the surface of the magnesium alloy prepared by the present invention, the hydroxyapatite coating is a flower-like structure formed by clusters of hydroxyapatite nano-rods, the length of the nano-rods is 300-900nm, and the diameter of the nano-rods is 30-90nm. The thickness of the coating is 2-10 μm.

To sum up, the core of the present invention is to prepare a conversion coating solution containing Ca ²⁺ and PO ₄ ³⁻ , and the pH value of the conversion coating solution is 5-6. Taking full advantage of the rapid rotation and vibration of water molecules in the conversion coating solution under microwave radiation, the nucleation and growth of hydroxyapatite in the conversion coating solution are accelerated, and the growth of hydroxyapatite nuclei into hydroxyl Apatite nanorods. In addition, the proper pH of the conversion coating solution ensures that the resulting coating is a pure phase of HA. Furthermore, after NaOH solution treatment, a layer of Mg(OH) ₂ is formed on the surface of the magnesium alloy, and Mg(OH) ₂ has an adsorption effect on hydroxyapatite crystal nuclei, and promotes the growth of hydroxyapatite crystal grains. The synergistic effect of the above three aspects makes it possible to quickly synthesize a flower-like hydroxyapatite coating with a certain thickness on the surface of magnesium alloy by microwave liquid phase method.

The flower-shaped hydroxyapatite coating on the surface of a medical magnesium alloy is characterized in that: the hydroxyapatite coating is composed of a large number of hydroxyapatite nano-rod clusters to form a flower-like structure, and the length of the nano-rods is 300- 900nm, the diameter of the nanorod is 30-90nm.

Compared with prior art, advantage and positive effect of the present invention are:

(1) The present invention utilizes the microwave liquid phase method to prepare the hydroxyapatite coating on the surface of the magnesium alloy, and the coating forms a flower-like structure by clustering a large number of hydroxyapatite nanorods, and the length of the nanorods is 300-900nm. The diameter of the nanorod is 30-90nm. The nanostructured hydroxyapatite has a large specific surface area, which can promote the adhesion and growth of osteoblasts on the coating surface, and greatly improve the biological activity of the magnesium alloy.

(2) The present invention significantly improves the corrosion resistance of magnesium alloys in simulated body fluids. The thickness of the hydroxyapatite coating is controlled by changing the microwave catalytic reaction time. The thickness of the coating is 2-10 μm. Since the thickness of the hydroxyapatite coating is thicker, it is beneficial to better exert the physical barrier effect of the coating and weaken the The contact of the magnesium alloy with the electrolyte solution improves the corrosion resistance of the magnesium alloy implant in the physiological environment of the human body.

(3) The present invention has high reliability. For magnesium alloy samples of any shape and size, a hydroxyapatite coating can be prepared on the surface.

(4) The present invention is a low-temperature preparation technology, the maximum heat treatment temperature is 100°C (the boiling point of water), and the mechanical and electrochemical properties of the magnesium alloy substrate will not be reduced due to the higher heat treatment temperature.

(5) The present invention is simple and rapid, and it only takes 2 to 10 minutes to prepare a hydroxyapatite coating on the surface of the magnesium alloy. The microwave liquid-liquid phase method disclosed in the present invention is a new economical and environmentally friendly method craft.

The nanostructured hydroxyapatite coating of the invention not only improves the biological activity of the magnesium alloy, but also improves the corrosion resistance of the magnesium alloy in simulated body fluid. The preparation process of the coating is simple, economical and environmentally friendly, and has great commercial promotion value.

Description of drawings

Fig. 1 is the XRD spectrum of the coating and deposit prepared in Example 1 of the present invention.

FIG. 2 is a SEM photo of the surface morphology of the hydroxyapatite coating prepared in Example 1 of the present invention.

FIG. 3 is a cross-sectional SEM photo of the hydroxyapatite coating prepared in Example 1 of the present invention.

FIG. 4 is the AC impedance spectrum of the hydroxyapatite-coated magnesium alloy and the magnesium alloy die prepared in Example 1 of the present invention in simulated body fluid.

Detailed ways

The present invention will be further explained and described below in conjunction with embodiment, but does not constitute any limitation to the present invention. The raw materials used in the following examples are commercially available analytically pure raw materials.

The general preparation method is as follows:

1) Magnesium alloy surface pretreatment: sand a magnesium alloy of a certain size and shape to 1200-2000 mesh, then ultrasonically clean it in acetone, deionized water, and ethanol for 3-10 minutes, and dry it.

2) Alkali treatment of magnesium alloy: prepare 1-3 mol/L NaOH aqueous solution. Soak the polished magnesium alloy in NaOH solution at 60-90°C for 1 hour, then rinse with deionized water and dry.

3) Preparation of conversion coating solution: use Ca(NO ₃ ) ₂ , CaCl ₂ or Ca(CH ₃ COO) ₂ as Ca source to prepare Ca ²⁺ aqueous solution, and use NH ₄ H ₂ PO ₄ , Na ₂ HPO ₄ or NaH ₂ PO ₄ was used as P source to prepare PO ₄ ^3- water solution. Then the PO ₄ ^3- aqueous solution was added dropwise to the Ca ²⁺ aqueous solution, and finally the pH value of the mixed solution was adjusted to 5-6 with dilute acid, and magnetically stirred for 1-2 hours. Wherein, the concentration of Ca ²⁺ in the mixed solution is 4-6 mmol/L, and the concentration of PO ₄ ^3- is 1-2 mmol/L.

4) Preparation of hydroxyapatite conversion coating: Soak the alkali-treated magnesium alloy sample in the conversion coating solution, place the conversion coating solution in a microwave chemical reactor, and convert the conversion coating to the maximum output power. The solution is heated to boiling and kept for 2-10 minutes; then the coated magnesium alloy sample is immediately taken out, rinsed with deionized water, and dried.

Example 1

(1) Process the AZ31 magnesium alloy into a block of 10mm×10mm×2mm, polish it with 240 ^# , 1200 ^# , 2000 ^# SiC sandpaper in turn, then ultrasonically clean it in acetone, deionized water, and ethanol for 10 minutes, and dry it with hot air Dry.

(2) Prepare 150 mL of 2 mol/L NaOH deionized aqueous solution. Soak the polished magnesium alloy in NaOH solution at 60°C for 1 hour, then rinse the magnesium alloy sample with deionized water and dry it.

(3) Ca ²⁺ aqueous solution was prepared with Ca(NO ₃ ) ₂ as Ca source, and PO ₄ ^3- aqueous solution was prepared with Na ₂ HPO ₄ as P source. Then the PO ₄ ^3- aqueous solution was added dropwise into the Ca ²⁺ aqueous solution, and finally the pH value of the mixed solution was adjusted to 6 with 20M dilute nitric acid, and magnetically stirred for 1 h. Wherein, the concentration of Ca ²⁺ in the mixed solution is 6 mmol/L, and the concentration of PO ₄ ^3- is 2 mmol/L. Weigh 100mL of the mixed solution as the conversion coating solution.

(4) Soak the magnesium alloy sample after the alkali treatment in the conversion coating solution, place the conversion coating solution in a microwave chemical reactor, and the output frequency is 2450MHz microwave, and the conversion coating solution is heated to Boiling, keep 10min. Then the coated magnesium alloy samples were taken out immediately, rinsed with deionized water, and dried.

The XRD patterns of the prepared conversion coating and deposit are shown in Fig. 1, and the synthesized coating is pure phase hydroxyapatite. The surface morphology of the coating is shown in Figure 2. The coating is composed of a large number of hydroxyapatite nanorod clusters to form a flower-like structure. The length of the nanorods is 600-900nm, and the diameter of the nanorods is 60-90nm. The cross-sectional morphology of the coating is shown in Figure 3, and the thickness of the hydroxyapatite coating is ~10 μm. The AC impedance spectra of hydroxyapatite-coated magnesium alloy samples and magnesium alloy bare chips in simulated body fluids are shown in Figure 4. The AC impedance of magnesium alloy chips is ~1350ohm·cm ² The AC impedance of the magnesium-clad alloy is ~43000 ohm·cm ² .

Example 2

(1) AZ91 magnesium alloy is processed into a block of 10mm×10mm×2mm, polished with 240 ^# and 1200 ^# SiC sandpaper in turn, then ultrasonically cleaned in acetone, deionized water, and ethanol for 6 minutes, and dried with hot air.

(2) Prepare 150 mL of 3 mol/L NaOH deionized aqueous solution. Soak the polished magnesium alloy in NaOH solution at 70°C for 1 hour, then rinse the magnesium alloy sample with deionized water and dry it.

(3) Ca ²⁺ aqueous solution was prepared with CaCl ₂ as Ca source, and PO ₄ ^3- aqueous solution was prepared with NaH ₂ PO ₄ as P source. Then, the PO ₄ ^3- aqueous solution was added dropwise into the Ca ²⁺ aqueous solution, and finally the pH value of the mixed solution was adjusted to 5 with 15M dilute hydrochloric acid, and magnetically stirred for 1.5 h. Wherein, the concentration of Ca ²⁺ in the mixed solution is 4 mmol/L, and the concentration of PO ₄ ^3- is 2 mmol/L. Weigh 100mL of the mixed solution as the conversion coating solution.

(4) Soak the magnesium alloy sample after the alkali treatment in the conversion coating solution, place the conversion coating solution in a microwave chemical reactor, and the output frequency is 2450MHz microwave, and the conversion coating solution is heated to Boiling, keep 7min. Then the coated magnesium alloy samples were taken out immediately, rinsed with deionized water, and dried.

The prepared hydroxyapatite coating is composed of a large number of hydroxyapatite nanorods clustered into a flower-like structure, the length of the nanorods is 500-800nm, and the diameter of the nanorods is 50-80nm. The thickness of the hydroxyapatite coating was ~6 μm. The AC impedance of the hydroxyapatite-coated magnesium alloy is ~30000 ohm·cm ² .

Example 3

(1) AZ61 was used as the magnesium alloy substrate, polished with 240 ^# , 1200 ^# , and 1500 ^# SiC sandpaper in sequence, then ultrasonically cleaned in acetone, deionized water, and ethanol for 8 minutes, and dried with hot air.

(2) Prepare 150 mL of 1 mol/L NaOH deionized aqueous solution. Soak the polished magnesium alloy in NaOH solution at 80°C for 1 hour, then rinse the magnesium alloy sample with deionized water and dry it.

(3) Ca ²⁺ aqueous solution was prepared with Ca(CH ₃ COO) ₂ as Ca source, and PO ₄ ^3- aqueous solution was prepared with NaH ₂ PO ₄ as P source. Then the PO ₄ ^3- aqueous solution was added dropwise into the Ca ²⁺ aqueous solution, and finally the pH value of the mixed solution was adjusted to 5.5 with 8M acetic acid, and magnetically stirred for 2 h. Wherein, the concentration of Ca ²⁺ in the mixed solution is 5 mmol/L, and the concentration of PO ₄ ^3- is 1.5 mmol/L. Weigh 100mL of the mixed solution as the conversion coating solution.

(4) Soak the magnesium alloy sample after the alkali treatment in the conversion coating solution, place the conversion coating solution in a microwave chemical reactor, and the output frequency is 915MHz microwave, and the conversion coating solution is heated to Boiling, keep 5min. Then the coated magnesium alloy samples were taken out immediately, rinsed with deionized water, and dried.

The prepared hydroxyapatite coating is composed of a large number of hydroxyapatite nanorods clustered into a flower-like structure, the length of the nanorods is 300-700nm, and the diameter of the nanorods is 30-70nm. The thickness of the hydroxyapatite coating was ~4 μm. The AC impedance of the hydroxyapatite-coated magnesium alloy is ~18000 ohm·cm ² .

Example 4

(1) AZ80 magnesium alloy is processed into a block of 10mm×10mm×2mm, polished with 240 ^# and 1200 ^# SiC sandpaper in turn, then ultrasonically cleaned in acetone, deionized water, and ethanol for 3 minutes, and dried with hot air.

(2) Prepare 150 mL of 1.5 mol/L NaOH deionized aqueous solution. Soak the polished magnesium alloy in NaOH solution at 90°C for 1 hour, then rinse the magnesium alloy sample with deionized water and dry it.

(3) Ca ²⁺ aqueous solution was prepared with Ca(CH ₃ COO) ₂ as Ca source, and PO ₄ ^3- aqueous solution was prepared with NH ₄ H ₂ PO ₄ as P source. Then the PO ₄ ^3- aqueous solution was added dropwise into the Ca ²⁺ aqueous solution, and finally the pH value of the mixed solution was adjusted to 5.5 with 1M dilute nitric acid, and magnetically stirred for 2 h. Wherein, the concentration of Ca ²⁺ in the mixed solution is 5 mmol/L, and the concentration of PO ₄ ^3- is 2 mmol/L. Weigh 100mL of the mixed solution as the conversion coating solution.

(4) Soak the magnesium alloy sample after the alkali treatment in the conversion coating solution, place the conversion coating solution in a microwave chemical reactor, and the output frequency is 915MHz microwave, and the conversion coating solution is heated to Boiling, keep 2min. Then the coated magnesium alloy samples were taken out immediately, rinsed with deionized water, and dried.

The prepared hydroxyapatite coating is composed of a large number of hydroxyapatite nanorods clustered into a flower-like structure, the length of the nanorods is 200-500nm, and the diameter of the nanorods is 20-70nm. The thickness of the hydroxyapatite coating was ~2 μm. The AC impedance of the hydroxyapatite-coated magnesium alloy is ~12500 ohm·cm ² .

Claims (6)

1. A microwave preparation method of a flower-like hydroxyapatite coating on the surface of a magnesium alloy, characterized in that: the pretreated magnesium alloy sample is immersed in a conversion coating solution, and the conversion coating solution is placed in a microwave chemical In the reactor, the conversion coating solution is heated to boiling and kept for 2 to 10 minutes; then the coated magnesium alloy sample is immediately taken out, rinsed with deionized water, and dried. 2. The method according to claim 1, wherein the surface pretreatment of the magnesium alloy is as follows: the surface of the magnesium alloy is polished to 1200-2000 mesh, and then ultrasonically cleaned in acetone, deionized water, and ethanol for 3-3 Dry for 10 minutes; then soak the magnesium alloy in NaOH solution at 60-90°C to keep warm, then rinse with deionized water and dry. 3. The method according to claim 1, characterized in that the conversion coating solution is: with Ca(NO ₃ ) ₂ , CaCl ₂ or Ca(CH ₃ COO) ₂ as Ca source to prepare Ca ²⁺ aqueous solution, Prepare PO ₄ ^{3- water} solution by using NH ₄ H ₂ PO ₄ , Na ₂ HPO ₄ or NaH ₂ PO ₄ as P _source ^; The pH value is adjusted to 5-6, and magnetically stirred for 1-2 hours; wherein, the concentration of Ca ²⁺ in the mixed solution is 4-6 mmol/L, and the concentration of PO ₄ ^3- is 1-2 mmol/L. 4. The method according to claim 3, wherein the dilute acid is one of dilute nitric acid, dilute hydrochloric acid, and acetic acid, and its concentration is 1 to 20 mol/L. 5. The method according to claim 1, wherein the magnesium alloy is one of AZ31, AZ61, AZ80 or AZ91. 6. The method according to claim 1, characterized in that the microwave frequency generated by the microwave chemical reactor is 915MHz or 2450MHz.