A multilayer dense composite film on pure magnesium surface and preparation method thereof

Abstract

The present invention discloses a multilayer dense composite film on the surface of pure magnesium and a preparation method thereof. The multilayer dense composite film is composed of a titanium dioxide film and a tantalum film. The preparation method comprises the following steps: (1) placing pure magnesium on a stage of a magnetron sputtering furnace, installing a target material, then evacuating and introducing argon gas, and then pre-sputtering the pure magnesium; (2) turning on a radio frequency power supply and a metal oxide target baffle, and after sputtering the metal oxide, turning off the power supply and the baffle; (3) turning on a direct current power supply and a tantalum target baffle, adjusting the direct current power, and after sputtering tantalum, turning off the power supply and the baffle; (4) repeating steps (2) and (3). The present invention uses titanium dioxide as an intermediate layer and utilizes magnetron sputtering to prepare a titanium dioxide-tantalum composite film. The outer tantalum film has good biological properties and can directly contact the internal environment. The inner oxide film has good bonding ability and effectively prevents the composite film from falling off. The composite film can significantly improve the corrosion resistance and mechanical properties of pure magnesium.

Description

Technical Field

[0001] The invention relates to a pure magnesium surface composite film and a preparation method thereof, in particular to a pure magnesium surface multilayer dense composite film and a preparation method thereof. Background Art

[0002] Pure magnesium and magnesium alloys have low density and high specific strength, and have the advantages of degradability, good biocompatibility and biomechanical compatibility, and bone conductivity. Traditional bioinert medical materials represented by stainless steel, titanium alloys, nickel-titanium shape memory alloys, and cobalt-based alloys will exist stably for a long time in the human physiological environment and require reoperation to remove, which increases the difficulty of surgery and rehabilitation costs. Therefore, new medical metal materials have gradually come into people's view, among which magnesium alloys, as "degradable biomedical metal materials", have shown great application potential and development prospects. The excellent biosafety, good load transfer, and spontaneous degradability of magnesium alloys themselves provide a solid foundation for their application in medical fields such as bone transplantation / vascular support. However, the poor corrosion resistance of magnesium alloys limits their wide application in the biomedical field. Especially in Cl-rich environments. - In corrosive media and real human environments, the high degradation rate of magnesium alloys will lead to accelerated component loss and significant mechanical attenuation, which will delay tissue healing and cause premature failure of implants. Therefore, how to reduce the probability of galvanic corrosion of magnesium alloys and effectively improve the corrosion resistance of magnesium alloys is a core issue that needs to be solved urgently.

[0003] At present, alloying, heat treatment, plastic processing and surface modification are four common means to improve the degradation performance of magnesium alloys. The first three improvement methods cannot fully limit the galvanic corrosion generated inside the alloy, making surface modification treatment more advantageous. Surface modification is to artificially prepare one or more surface layers on the surface of magnesium alloy materials that are different from the chemical composition, organizational structure and performance of the matrix. Appropriate surface modification methods can improve the corrosion resistance of magnesium alloys to varying degrees. At the same time, it can also improve the biocompatibility and bioactivity of the alloy, antibacterial, self-repair and other functional effects. Compared with corrosion in the physiological environment in vitro, magnesium alloys are often in a more complex stress state in vivo.

[0004] The invention patent with publication number CN102703874 discloses a method for preparing a tantalum film on the surface of a magnesium alloy by magnetron sputtering deposition, which is achieved through the following steps: 1. Cleaning of the sample; 2. Preparation before coating; 3. Coating. The tantalum film layer prepared on the magnesium alloy by magnetron sputtering deposition technology in this patent has good corrosion resistance, wear resistance and biocompatibility. However, due to the large difference in thermal expansion coefficients between the magnesium matrix and the precious metal tantalum, the interface stress is large and the bonding performance is poor. Summary of the invention

[0005] Purpose of the invention: In order to solve the technical problems existing in the prior art, the present invention aims to provide a multilayer dense composite film on the surface of pure magnesium, which can improve the bonding strength between pure magnesium and tantalum, produce a tantalum film with high density, and improve the corrosion resistance of pure magnesium. In addition, the present invention also provides a method for preparing the multilayer dense composite film on the surface of pure magnesium.

[0006] Technical solution: The multilayer dense composite film on the surface of pure magnesium described in the present invention takes pure magnesium as the matrix. The multilayer dense composite film is composed of a metal oxide film and a tantalum film. The metal oxide film is used to induce and promote the growth of the tantalum film and enhance the bonding strength between the composite film and the pure magnesium matrix.

[0007] Furthermore, the metal oxide is titanium dioxide.

[0008] The method for preparing the multilayer dense composite film on the surface of pure magnesium according to the present invention comprises the following steps:

[0009] (1) placing the cleaned pure magnesium on a stage in a magnetron sputtering furnace, installing a target material, which is a metal oxide target and a tantalum target, and then starting to evacuate to a high vacuum state, and then introducing argon gas to adjust the gas pressure, and pre-sputtering the pure magnesium;

[0010] (2) After the pre-sputtering is completed, the RF power supply and the baffle of the metal oxide target are turned on, the RF power is adjusted to 100-300 W, and the metal oxide is sputtered. After the sputtering is completed, the RF power supply and the baffle of the metal oxide target are turned off;

[0011] (3) turning on the DC power supply and the baffle of the tantalum target, adjusting the DC power to 100-200 W, sputtering tantalum, and after the sputtering is completed, turning off the DC power supply and the baffle of the tantalum target;

[0012] (4) Repeat steps (2) and (3) to obtain pure magnesium with a multi-layer dense composite film.

[0013] Furthermore, in step (1), the distance between the pure magnesium and the target is 5-8 cm, and the vacuum degree is ≤6×10 -4 Pa, the gas pressure is 1-3Pa, and the pre-sputtering time is 5-15min. On the one hand, the sample is cleaned, and on the other hand, the surface is activated to facilitate the adsorption of active atoms.

[0014] Furthermore, in step (2), the sputtering time of the metal oxide is 5-120 minutes.

[0015] Furthermore, in step (3), the sputtering time of tantalum is 5-60 minutes.

[0016] Furthermore, in step (4), the number of repetitions is 1-3 times.

[0017] Principle of the invention: The present invention aims at the technical problem of interface stress caused by mismatch of thermal expansion coefficients between pure magnesium substrate and precious metal tantalum, and proposes to add an intermediate layer in the middle to reduce the thermal expansion coefficient, thereby improving the bonding strength of the coating. A multilayer dense composite film with titanium dioxide as the intermediate layer is prepared on a pure magnesium substrate through magnetron sputtering process optimization. The composite film can flexibly adjust the performance of the material surface, overcome the shortcomings of a single coating such as high porosity, low density and penetration defects, and greatly improve the bonding strength and corrosion resistance of the composite film and the pure magnesium substrate.

[0018] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages:

[0019] (1) The present invention uses titanium dioxide as an intermediate layer and utilizes magnetron sputtering to prepare a titanium dioxide-tantalum composite film. The outer tantalum film has good biological properties and can directly contact the body environment, while the inner titanium dioxide film has good bonding ability and effectively prevents the film from falling off. The prepared composite film has uniform composition, low porosity, large deposition area, low substrate heating, can operate within a wide range of gas pressure, has high bonding strength with the substrate, and the thickness and composition of the composite film are easy to control;

[0020] (2) The present invention utilizes magnetron sputtering technology to prepare a composite film of a dioxide film and a tantalum film under different parameter conditions. By rationally controlling the sputtering parameters, effective regulation of the microstructure and mechanical properties of the composite film is achieved, and the preparation atmosphere of the preparation method used for the treatment of large quantities of pure magnesium substrates is clean and pollution-free. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Surface morphology of the multilayer dense composite film on the surface of pure magnesium prepared in Examples 1 and 2 of the present invention, (a) Example 1, (b) Example 2;

[0022] Figure 2 The hardness distribution diagram of the multilayer dense composite film on the surface of pure magnesium obtained in Example 1 and Example 2 of the present invention and the pure magnesium of Comparative Example 1;

[0023] Figure 3 Polarization curves of the multilayer dense composite film on the surface of pure magnesium prepared in Examples 1 and 2 of the present invention and the pure magnesium in Comparative Example 1. DETAILED DESCRIPTION

[0024] The present invention is further described below in conjunction with specific embodiments and drawings.

[0025] Example 1: The multilayer dense composite film on the surface of pure magnesium described in the present invention is composed of a titanium dioxide film and a tantalum film, and the preparation method is as follows:

[0026] (1) Place pure magnesium wiped with anhydrous ethanol on the stage in a magnetron sputtering furnace, with high-purity titanium dioxide target and tantalum target as the targets below the sample;

[0027] (2) Turn on the plasma sputtering film forming equipment and its matching cold water pump, use a mechanical pump to pump the gas pressure of the coating furnace to below 5 Pa, and then use a molecular pump to further pump the furnace pressure to 6×10 -4 Pa, to keep the furnace in high vacuum state;

[0028] (3) The furnace was filled with argon gas to 1 Pa, and pure magnesium was pre-sputtered for 10 minutes;

[0029] (4) After pre-sputtering, the RF power supply and the baffle of the titanium dioxide target were turned on, the RF power was adjusted to 200 W, and titanium dioxide was sputtered for 2 hours. After the titanium dioxide sputtering was completed, the baffle of the titanium dioxide target and the RF power supply were turned off;

[0030] (5) Turn on the tantalum target baffle and DC power supply, adjust the DC power to 200W, and sputter tantalum for 0.5 hours. After the tantalum sputtering is completed, turn off the baffle, DC power supply, and argon gas source in turn, cool the furnace to room temperature, and then vent and sample to obtain Mg-TiO 2 -He.

[0031] Example 2: The multilayer dense composite film on the surface of pure magnesium described in the present invention is composed of a titanium dioxide film and a tantalum film, and the preparation method is as follows:

[0032] (1) Place pure magnesium wiped with anhydrous ethanol on the stage in a magnetron sputtering furnace, with high-purity titanium dioxide target and tantalum target as the targets below the sample;

[0033] (2) Turn on the plasma sputtering film forming equipment and its matching cold water pump, use a mechanical pump to pump the gas pressure of the coating furnace to below 5 Pa, and then use a molecular pump to further pump the furnace pressure to 6×10 -4 Pa, to keep the furnace in high vacuum state;

[0034] (3) The furnace was filled with argon gas to 1 Pa, and pure magnesium was pre-sputtered for 10 minutes;

[0035] (4) After pre-sputtering, the RF power supply and the baffle of the titanium dioxide target were turned on, the RF power was adjusted to 200 W, and titanium dioxide was sputtered for 2 hours. After the titanium dioxide sputtering was completed, the baffle of the titanium dioxide target and the RF power supply were turned off;

[0036] (5) Open the tantalum target baffle and DC power supply, adjust the DC power to 200 W, sputter tantalum for 0.5 hours, and after the tantalum sputtering is completed, turn off the baffle and DC power supply in turn;

[0037] (6) Turn on the RF power supply and the baffle of the titanium dioxide target, adjust the RF power to 200 W, sputter titanium dioxide for 2 hours, and turn off the baffle of the titanium dioxide target and the RF power supply after the titanium dioxide sputtering is completed;

[0038] (7) Turn on the tantalum target baffle and DC power supply, adjust the DC power to 200 W, and sputter tantalum for 0.5 hours. After the tantalum sputtering is completed, turn off the baffle, DC power supply, and argon gas source in turn, cool the furnace to room temperature, and then vent and sample to obtain Mg-TiO 2 -Ta-TiO 2 -He.

[0039] Comparative Example 1: Untreated pure magnesium.

[0040] The multilayer dense composite film on the surface of pure magnesium prepared in Example 1 and Example 2 and the untreated pure magnesium in Comparative Example 1 were characterized and tested. The results are shown in Figure 1-Figure 3 .like Figure 1 , showing that Mg-TiO 2 / Ta、Mg-TiO 2 / Ta-TiO 2 / -Ta SEM image, Figure 1 (a) Composite coatings were prepared on pure magnesium surfaces using magnetron sputtering technology; Figure 1 (b) Multilayer coating prepared by magnetron sputtering technology, the surface is cellular.

[0041] like Figure 2 As shown in the figure, the microhardness tester was used to determine the hardness of Mg and Mg-TiO 2 / Ta、Mg-TiO 2 / Ta-TiO 2 / Ta hardness is 38HV 0.25 、58HV 0.25 、118HV 0.25 , indicating that preparing multilayer composite films on pure magnesium can improve its mechanical properties.

[0042] like Figure 3 As shown, they are Mg, Mg-TiO 2 / Ta、Mg-TiO 2 / Ta-TiO 2 / -Ta polarization curve, where Mg-TiO 2 / Ta-TiO 2 / -Ta has the smallest corrosion current and the largest corrosion voltage, indicating that this multilayer composite film can delay the corrosion of pure magnesium.

Claims

1. A multi-layer dense composite film on the surface of pure magnesium, with pure magnesium as the matrix, It is characterized in that The multi-layer dense composite film is composed of a metal oxide film and a tantalum film, wherein the metal oxide film is used to induce and promote the growth of the tantalum film and enhance the bonding strength between the composite film and the pure magnesium substrate; the metal oxide is titanium dioxide; and the preparation method of the multi-layer dense composite film on the surface of pure magnesium comprises the following steps: (1) Place the cleaned pure magnesium on the stage in the magnetron sputtering furnace, install the target material, which is a metal oxide target and a tantalum target, and then start to evacuate to a high vacuum state, then introduce argon gas to adjust the gas pressure, and pre-sputter the pure magnesium; (2) After the pre-sputtering is completed, the RF power supply and the baffle of the oxide target are turned on, and the RF power is adjusted to 100-300W to sputter the metal oxide. After the sputtering is completed, the RF power supply and the baffle of the power oxide target are turned off; (3) Turn on the DC power supply and the baffle of the tantalum target, adjust the DC power to 100-200W, sputter tantalum, and after sputtering, turn off the DC power supply and the baffle of the tantalum target; (4) Repeat steps (2) and (3) to obtain pure magnesium with a multi-layer dense composite film.

2. A method for preparing the multilayer dense composite film on the surface of pure magnesium according to claim 1, It is characterized in that The following steps are involved: (1) Place the cleaned pure magnesium on the stage in the magnetron sputtering furnace, install the target material, which is a metal oxide target and a tantalum target, and then start to evacuate to a high vacuum state, then introduce argon gas to adjust the gas pressure, and pre-sputter the pure magnesium; (2) After the pre-sputtering is completed, the RF power supply and the baffle of the oxide target are turned on, and the RF power is adjusted to 100-300W to sputter the metal oxide. After the sputtering is completed, the RF power supply and the baffle of the power oxide target are turned off; (3) Turn on the DC power supply and the baffle of the tantalum target, adjust the DC power to 100-200W, sputter tantalum, and after sputtering, turn off the DC power supply and the baffle of the tantalum target; (4) Repeat steps (2) and (3) to obtain pure magnesium with a multi-layer dense composite film.

3. The preparation method according to claim 2, further characterized in that, in step (1), the distance between the pure magnesium and the target material is 5-8 cm.

4. The preparation method according to claim 2, further characterized in that, in step (1), the high vacuum state: the vacuum degree is ≤6×10 -4 Pa.

5. The preparation method according to claim 2, further characterized in that, in step (1), the gas pressure is 1-3 Pa.

6. The preparation method according to claim 2, further characterized in that, in step (1), the pre-sputtering time is 5-15 minutes.

7. The preparation method according to claim 2, further characterized in that, in step (2), the sputtering time of the metal oxide is 5-120 minutes.

8. The preparation method according to claim 2, further characterized in that, in step (3), the sputtering time of tantalum is 5-60 minutes.

9. The preparation method according to claim 2, further characterized in that, in step (4), the number of repetitions is 1-3 times.

Images