CN110724946A

CN110724946A - Impure-phase-free Mg-Al LDH coating on surface of magnesium alloy and preparation method and application thereof

Info

Publication number: CN110724946A
Application number: CN201911053990.4A
Authority: CN
Inventors: 张余; 彭峰
Original assignee: Guangdong General Hospital Guangdong Academy of Medical Sciences
Current assignee: Guangdong General Hospital Guangdong Academy of Medical Sciences
Priority date: 2019-10-31
Filing date: 2019-10-31
Publication date: 2020-01-24

Abstract

The invention belongs to the technical field of surface modification of metal materials, and particularly discloses a non-impurity-phase Mg-Al LDH coating on the surface of a magnesium alloy, and a preparation method and application thereof. The method specifically comprises the steps of soaking the magnesium alloy in hydrofluoric acid, mixing the magnesium alloy with an alkaline solution of an aluminum source, and performing hydrothermal treatment to obtain the impurity-free Mg-Al LDH coating. The coating related by the invention is completed by hydrofluoric acid and hydrothermal treatment, and the method has the advantages of simple process, low cost, no need of special equipment and contribution to large-scale industrial production. The magnesium alloy modified by the method has obviously improved corrosion resistance, and cells grow well on the surface of the material.

Description

Impure-phase-free Mg-Al LDH coating on surface of magnesium alloy and preparation method and application thereof

Technical Field

The invention belongs to the technical field of surface modification of metal materials, and particularly relates to a non-impurity-phase Mg-Al LDH coating on the surface of a magnesium alloy, and a preparation method and application thereof.

Technical Field

The medical metal materials widely used in clinic, such as titanium alloy, nickel titanium alloy and the like, are all non-degradable materials, and the implant needs to be taken out by a secondary operation, thereby bringing heavy mental and economic pressure to patients. Therefore, the development of novel degradable medical materials has important social and research significance. The magnesium alloy has complete degradability and the elastic modulus is close to that of bone tissues, and has the potential of becoming a next-generation medical implant material.

However, magnesium alloys have a low electrochemical potential and a too high corrosion rate. Too fast corrosion can generate hydrogen gas cavities around the implant, which is not beneficial to the healing of wound parts; in addition, the hydroxyl generated by corrosion can obviously raise the surrounding pH value and easily cause inflammatory reaction; more importantly, erosion leads to too rapid a reduction in the mechanical properties of the implant, which, if used as a bone implant, is highly likely to lead to implant failure. Therefore, improving the corrosion resistance of the medical magnesium alloy is a very critical step for the clinical application of the medical magnesium alloy.

Surface modification of magnesium alloys is a common method to improve their corrosion resistance. At present, a great deal of research is carried out on preparing a magnesium-based Layered Double Hydroxide (LDH) coating on the surface of a magnesium alloy so as to improve the corrosion resistance and biocompatibility of the material. However, most of the magnesium-based LDHs prepared in the research contain magnesium hydroxide phase, and the presence of magnesium hydroxide is not beneficial to the corrosion resistance of the coating to some extent (ACS appl. Mater. interfaces 2016, 835033-. There is also a study of preparing a loose magnesium hydroxide layer by putting a magnesium alloy in an aqueous solution in advance, then introducing carbon dioxide, and preparing a pure-phase Mg-Al LDH coating in situ on the surface of the magnesium alloy by hydrothermal treatment (Corrosion Science 2011,53, 3281-. The method has complicated steps and higher cost for introducing carbon dioxide. Therefore, a new simple and low-cost process needs to be developed to prepare pure-phase Mg-Al LDH coating on the surface of the magnesium alloy in situ.

Disclosure of Invention

In order to overcome the defects of the prior art, the invention mainly aims to provide a preparation method of a non-impurity-phase Mg-Al LDH coating on the surface of a magnesium alloy.

The invention further aims to provide a non-impurity-phase Mg-Al LDH coating on the surface of the magnesium alloy obtained by the method. The modified magnesium alloy material is expected to be used as a substitute for bone implant or other medical metal materials.

The invention further aims to provide the application of the impure phase-free Mg-Al LDH coating on the surface of the magnesium alloy in medical materials.

A preparation method of a non-impurity-phase Mg-Al LDH coating on the surface of a magnesium alloy specifically comprises the following steps:

and soaking the magnesium alloy in hydrofluoric acid, mixing the magnesium alloy with an alkaline solution of an aluminum source, and performing hydrothermal treatment to obtain the impurity-free Mg-Al LDH coating.

Before soaking, the magnesium alloy is preferably polished and leveled, and then a polished and leveled sample is cleaned by absolute ethyl alcohol and dried at room temperature;

the concentration of the hydrofluoric acid is 20-80 v/v%; the temperature of hydrofluoric acid during soaking is 25-60 ℃, and the soaking time is 6-72 h.

The aluminum source is at least one of aluminum nitrate, aluminum sulfate and aluminum acetate;

the alkaline solution is at least one of a sodium hydroxide aqueous solution and a potassium hydroxide aqueous solution.

The pH value of the alkaline solution containing the aluminum source is 10-13, and is preferably 12.8.

The molar concentration of the aluminum source in the alkaline solution containing the aluminum source is 0.01-0.1 mol/L, and preferably 0.02 mol/L.

The temperature of the hydrothermal treatment is 60-160 ℃, and the time is 5-15 h.

The Mg-Al LDH coating without impurity phase on the surface of the magnesium alloy prepared by the method.

The application of the non-impurity-phase Mg-Al LDH coating on the surface of the magnesium alloy in medical materials.

The invention has the technical effects that:

the surface of the modified magnesium alloy obtained by the treatment of the invention is pure-phase Mg-Al LDH, and does not contain magnesium fluoride or magnesium hydroxide impurity phase. The obtained coating has good corrosion resistance, and cells show good activity on the surface of the material. Compared with the prior art, the invention has the following beneficial effects: 1) the coating related by the invention is completed by hydrofluoric acid and hydrothermal treatment, and the method has the advantages of simple process, low cost, no need of special equipment and contribution to large-scale industrial production. 2) The magnesium alloy modified by the method has obviously improved corrosion resistance, and cells grow well on the surface of the material.

Drawings

FIG. 1 is a SEM image of AZ31 magnesium alloy after treatment of example 1(a), example 2(b), example 3(c), example 4(d), example 5(e) and example 6 (f).

FIG. 2 is an X-ray diffraction pattern of a sample obtained by post-treating AZ31 magnesium alloy according to examples 1-6; wherein (a) to (f) correspond to examples 1 to 6 in this order.

FIG. 3 shows the atomic percentages of Mg, Al and F elements on the surface of the samples of AZ31 magnesium alloy after treatment in examples 1-6.

FIG. 4 is a plot of potentiodynamic polarization in phosphate buffered saline for AZ31 magnesium alloy and samples treated in example 4.

FIG. 5 shows the change in pH of phosphate buffered saline when AZ31 magnesium alloy and the samples treated in example 4 were immersed in phosphate buffered saline.

FIG. 6 is a graph of dead and live staining of MC3T3-E1 cells after 3 days of surface culture of the magnesium alloy AZ31(a) and the sample treated in example 4 (b).

Detailed Description

The present invention will be described in further detail with reference to examples and drawings, but the embodiments of the present invention are not limited thereto.

The reagents used in the examples are commercially available without specific reference.

Example 1

And (3) sequentially removing surface oxide layers of AZ31 magnesium alloy sheets with the thickness of 2mm and the diameter of 10mm by using 600# and 1000# SiC abrasive paper, and then ultrasonically cleaning by using alcohol. Then, hydrothermal treatment was carried out, the hydrothermal solution was 50ml of 0.02M aluminum nitrate solution, and the pH was adjusted to 12.8 using sodium hydroxide or potassium hydroxide, and finally the reaction was carried out at 120 ℃ for 12 hours.

FIG. 1(a) is a scanning electron microscope image of the surface morphology of the magnesium alloy obtained by the modification treatment of the present example. As can be seen from the figure, the surface of the sample is covered by a layer of compact micro-nano sheet-shaped structure. Figure 2(a) shows the XRD pattern of the sample after treatment in this example. As can be seen from the figure, in addition to the diffraction peak of the metal Mg, the diffraction peaks of magnesium hydroxide and Mg-Al LDH are also detected, which shows that the magnesium alloy without pretreatment releases more magnesium ions in the hydrothermal process to generate a magnesium hydroxide phase. FIG. 3 shows the atomic percentages of Mg, Al and F elements on the surface of the sample after the treatment of this example. From the graph, it is understood that the F content of the sample surface is 0.

Example 2

And (3) sequentially removing surface oxide layers of AZ31 magnesium alloy sheets with the thickness of 2mm and the diameter of 10mm by using 600# and 1000# SiC abrasive paper, and then ultrasonically cleaning by using alcohol. The cleaned AZ31 magnesium alloy sheet was placed in a 40% hydrofluoric acid solution (by volume) and reacted at room temperature for 6 hours. Then, hydrothermal treatment was carried out, the hydrothermal solution was 50ml of 0.02M aluminum nitrate solution, and the pH was adjusted to 12.8 using sodium hydroxide or potassium hydroxide, and finally the reaction was carried out at 120 ℃ for 12 hours.

FIG. 1(b) is a scanning electron microscope image of the surface morphology of the magnesium alloy obtained by the modification treatment of the present example. As can be seen from the figure, the surface of the sample is covered by a layer of compact micro-nano sheet-shaped structure. Figure 2(b) shows the XRD pattern of the sample after treatment in this example. As can be seen from the figure, besides the diffraction peak of the metal Mg, the diffraction peaks of magnesium hydroxide and Mg-Al LDH are also detected, which shows that the magnesium fluoride generated in the hydrofluoric acid treatment process has insufficient protection on the substrate material of the magnesium alloy, and a large amount of magnesium ions are still dissolved out to react to generate the magnesium hydroxide. FIG. 3 shows the atomic percentages of Mg, Al and F elements on the surface of the sample after the treatment of this example. From the graph, it is understood that the F content of the sample surface is 0, which indicates that magnesium fluoride generated during the hydrofluoric acid treatment is completely dissolved during the hydrothermal process.

Example 3

And (3) sequentially removing surface oxide layers of AZ31 magnesium alloy sheets with the thickness of 2mm and the diameter of 10mm by using 600# and 1000# SiC abrasive paper, and then ultrasonically cleaning by using alcohol. The cleaned AZ31 magnesium alloy sheet was placed in a 40% hydrofluoric acid solution (by volume) and reacted at room temperature for 12 hours. Then, hydrothermal treatment was carried out, the hydrothermal solution was 50ml of 0.02M aluminum nitrate solution, and the pH was adjusted to 12.8 using sodium hydroxide or potassium hydroxide, and finally the reaction was carried out at 120 ℃ for 12 hours.

FIG. 1(c) is a scanning electron microscope image of the surface morphology of the magnesium alloy obtained by the modification treatment of the present example. As can be seen from the figure, the surface of the sample is covered by a layer of compact micro-nano sheet-shaped structure. Figure 2(c) shows the XRD pattern of the sample after treatment in this example. As can be seen from the figure, besides the diffraction peak of the metal Mg, the diffraction peaks of magnesium hydroxide and Mg-Al LDH are also detected, which shows that the magnesium fluoride generated in the hydrofluoric acid treatment process has insufficient protection on the substrate material of the magnesium alloy, and a large amount of magnesium ions are still dissolved out to react to generate the magnesium hydroxide. FIG. 3 shows the atomic percentages of Mg, Al and F elements on the surface of the sample after the treatment of this example. From the graph, it is understood that the F content of the sample surface is 0, which indicates that magnesium fluoride generated during the hydrofluoric acid treatment is completely dissolved during the hydrothermal process.

Example 4

And (3) sequentially removing surface oxide layers of AZ31 magnesium alloy sheets with the thickness of 2mm and the diameter of 10mm by using 600# and 1000# SiC abrasive paper, and then ultrasonically cleaning by using alcohol. The cleaned AZ31 magnesium alloy sheet was placed in a 40% hydrofluoric acid solution (by volume) and reacted at room temperature for 24 hours. Then, hydrothermal treatment was carried out, the hydrothermal solution was 50ml of 0.02M aluminum nitrate solution, and the pH was adjusted to 12.8 using sodium hydroxide or potassium hydroxide, and finally the reaction was carried out at 120 ℃ for 12 hours. The resulting sample was labeled LDH #.

FIG. 1(d) is a scanning electron microscope image of the surface morphology of the magnesium alloy obtained by the modification treatment of the present example. As can be seen from the figure, the surface of the sample is covered by a layer of compact micro-nano sheet-shaped structure. Figure 2(d) shows the XRD pattern of the sample after treatment in this example. As can be seen from the figure, only the diffraction peak of Mg-Al LDH was detected in addition to the diffraction peak of metallic Mg, indicating that the magnesium ions eluted from the magnesium alloy substrate and magnesium fluoride were all converted into Mg-Al LDH. FIG. 3 shows the atomic percentages of Mg, Al and F elements on the surface of the sample after the treatment of this example. From the graph, it is understood that the F content of the sample surface is 0, which indicates that magnesium fluoride generated during the hydrofluoric acid treatment is completely dissolved during the hydrothermal process.

Example 5

And (3) sequentially removing surface oxide layers of AZ31 magnesium alloy sheets with the thickness of 2mm and the diameter of 10mm by using 600# and 1000# SiC abrasive paper, and then ultrasonically cleaning by using alcohol. The cleaned AZ31 magnesium alloy sheet was placed in a 40% hydrofluoric acid solution (by volume) and reacted at room temperature for 36 hours. Then, hydrothermal treatment was carried out, the hydrothermal solution was 50ml of 0.02M aluminum nitrate solution, and the pH was adjusted to 12.8 using sodium hydroxide or potassium hydroxide, and finally the reaction was carried out at 120 ℃ for 12 hours.

FIG. 1(e) is a scanning electron microscope image of the surface morphology of the magnesium alloy obtained by the modification treatment of the present example. As can be seen from the figure, the surface of the sample is covered by a layer of compact micro-nano sheet-shaped structure. Figure 2(e) shows the XRD pattern of the sample after treatment in this example. As can be seen from the figure, only the diffraction peak of Mg-Al LDH was detected in addition to the diffraction peak of metallic Mg, indicating that the magnesium ions eluted from the magnesium alloy substrate and magnesium fluoride were all converted into Mg-Al LDH. FIG. 3 shows the atomic percentages of Mg, Al and F elements on the surface of the sample after the treatment of this example. As can be seen from the graph, the F content on the surface of the sample was about 2 at%, indicating that magnesium fluoride formed during the hydrofluoric acid treatment was not completely dissolved during the hydrothermal treatment.

Example 6

And (3) sequentially removing surface oxide layers of AZ31 magnesium alloy sheets with the thickness of 2mm and the diameter of 10mm by using 600# and 1000# SiC abrasive paper, and then ultrasonically cleaning by using alcohol. The cleaned AZ31 magnesium alloy sheet was placed in a 40% hydrofluoric acid solution (by volume) and reacted at room temperature for 72 hours. Then, hydrothermal treatment was carried out, the hydrothermal solution was 50ml of 0.02M aluminum nitrate solution, and the pH was adjusted to 12.8 using sodium hydroxide or potassium hydroxide, and finally the reaction was carried out at 120 ℃ for 12 hours.

FIG. 1(f) is a scanning electron microscope image of the surface morphology of the magnesium alloy obtained by the modification treatment of the present example. As can be seen from the figure, the surface of the sample is covered by a layer of compact micro-nano sheet-shaped structure. Figure 2(f) shows the XRD pattern of the sample after treatment in this example. As can be seen from the figure, only the diffraction peak of Mg-Al LDH was detected in addition to the diffraction peak of metallic Mg, indicating that the magnesium ions eluted from the magnesium alloy substrate and magnesium fluoride were all converted into Mg-Al LDH. FIG. 3 shows the atomic percentages of Mg, Al and F elements on the surface of the sample after the treatment of this example. As can be seen from the graph, the F content on the surface of the sample was about 2 at%, indicating that magnesium fluoride formed during the hydrofluoric acid treatment was not completely dissolved during the hydrothermal treatment.

Example 7

The AZ31 magnesium alloy and LDH # samples were subjected to electrochemical testing. The etching solution used was Phosphate Buffer (PBS), and the test temperature was room temperature. The instrument used was an electrochemical workstation (Shanghai Chenghua CHI 760C). The test sample is a working electrode, the graphite rod is a counter electrode, and the calomel electrode is a reference electrode.

FIG. 4 is a plot of zeta potential polarization of magnesium alloy and LDH # samples in PBS. As can be seen from the graph, although the LDH # sample had a reduced self-corrosion voltage compared to the AZ31 magnesium alloy, its self-corrosion current density was also reduced by 2 orders of magnitude (2.24X 10)^-5VS 9.72×10^-7A/cm²). And the polarization resistances calculated according to Tafel extrapolation are 5.40X 10, respectively⁴And 1.39X 10⁶Ω/cm². The above results show that the corrosion resistance of the modified sample is significantly improved by example 4.

Example 8

AZ31 magnesium alloy and LDH # samples were soaked in 10mL PBS solution, four replicates per group. The PBS solutions were tested for pH change on

days

1, 3, 5 and 7, respectively, with a fresh PBS solution being replaced after each test.

FIG. 5 shows the change in pH of PBS buffer. As can be seen, the LDH # sample had a smaller effect on the pH of the PBS solution than the AZ31 magnesium alloy, indicating that the substrate was corroded to a lesser extent.

Example 9

The influence of AZ31 magnesium alloy and LDH # samples on normal cell activity was evaluated using mouse osteoblast MC3T3-E1 in vitro culture experiments. The specific method comprises the following steps:

1) placing the sample subjected to ultraviolet sterilization for 12 hours into a 24-well culture plate, and dripping 1mL of the sample with the density of 5 × 10 into each well⁴cell/mL cell suspension;

2) place the cell culture plate in 5% CO₂Culturing at 37 deg.C in cell culture box with saturated humidity；

3) After 3 days of culture, live and dead cells were stained with calcein and propidium iodide, respectively, and observed with a laser confocal microscope (CLSM).

FIGS. 6(a) and (b) are dead and live staining patterns of MC3T3-E1 cells after 3 days of culture on the surface of magnesium alloy and LDH # samples, respectively. From the graph, it was found that the surface values of the AZ31 sample detected the presence of dead cells, whereas the LDH # sample surface detected the presence of a large number of live cells, covering almost the entire sample surface. The above results show that the magnesium alloy surface modified in example 4 has good cell compatibility. Is expected to be applied in the field of medical magnesium alloy surface modification.

The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.

Claims

1. A preparation method of a non-impurity-phase Mg-Al LDH coating on the surface of a magnesium alloy is characterized by comprising the following steps:

2. The method for preparing the non-hetero-phase Mg-Al LDH coating on the surface of the magnesium alloy as claimed in claim 1, wherein the method comprises the following steps:

3. The process for the preparation of a non-hetero-phase Mg-Al LDH coating for magnesium alloy surfaces as claimed in any of the claims 1 or 2, wherein:

4. The method for preparing the non-hetero-phase Mg-Al LDH coating on the surface of the magnesium alloy as claimed in claim 1, wherein the method comprises the following steps:

the pH value of the alkaline solution containing the aluminum source is 10-13;

the molar concentration of the aluminum source in the alkaline solution containing the aluminum source is 0.01-0.1 mol/L.

5. The method for preparing the non-hetero-phase Mg-Al LDH coating on the surface of the magnesium alloy as claimed in claim 1, wherein the method comprises the following steps:

the pH of the alkaline solution containing the aluminum source is 12.8;

the molar concentration of the aluminum source in the alkaline solution containing the aluminum source is 0.02 mol/L.

6. The method for preparing the non-hetero-phase Mg-Al LDH coating on the surface of the magnesium alloy as claimed in claim 1, wherein the method comprises the following steps:

7. The method for preparing the non-hetero-phase Mg-Al LDH coating on the surface of the magnesium alloy as claimed in claim 1, wherein the method comprises the following steps:

before soaking, the magnesium alloy is firstly polished to be flat, and then a sample after polishing to be flat is cleaned by adopting absolute ethyl alcohol and dried at room temperature.

8. A non-hetero-phase Mg-Al LDH coating on the surface of the magnesium alloy prepared by the method of any one of claims 1 to 7.

9. The use of a non-hetero-phase Mg-Al LDH coating on the surface of the magnesium alloy as claimed in claim 8 in medical materials.