Method for preparing tiled LDHs (layered double hydroxides) film on surface of metal matrix and application of tiled LDHs film

Abstract

The invention belongs to the technical field of metal surface treatment, and discloses a method for preparing a flat LDHs film on the surface of a metal matrix and application. The method comprises the following steps: pretreating the surface of a metal matrix; preparing an alcoholic solution containing divalent metal ion salt and trivalent metal ion salt, and adjusting the pH value to be alkaline to obtain a suspension containing LDHs microcrystals; the surface of the metal matrix is coated with suspension liquid containing LDHs microcrystals in a spinning mode, annealing is conducted, and an LDHs microcrystal layer is obtained; preparing an aqueous solution containing trivalent metal ion salt and urea, adjusting the pH value to be alkaline, and then adding a metal ion chelating agent to obtain a mixed solution; and immersing the metal matrix with the LDHs microcrystalline layer on the surface into the mixed solution, and carrying out hydrothermal reaction to obtain the tiled LDHs film on the surface of the metal matrix. According to the method, the tiled LDHs nanosheet structure film can be prepared on the surface of the metal matrix, the compactness of the film layer is improved, and then the corrosion protection effect of the film layer on metal is enhanced.

Description

Technical Field

[0001] This invention belongs to the field of metal surface treatment technology, and specifically relates to a method and application for preparing a flat LDHs film on a metal substrate surface. Background Technology

[0002] Layered bimetallic hydroxide (LDH) films grown in situ on magnesium metal substrates have attracted widespread attention in corrosion protection applications due to their attractive chemical properties, structural variability, and anion exchange capabilities. For example, based on their unique anion exchange capacity, the positively charged host layer in LDH films can not only capture corrosive species but also encapsulate corrosion inhibitors.

[0003] Currently, the common method for preparing LDHs films on magnesium metal substrates is in-situ hydrothermal growth. In-situ hydrothermal methods offer advantages such as simple operation, rich diversity in LDH chemical composition and microstructure, and high film adhesion (chemical bonding). The microstructure and composition of the magnesium metal substrate primarily influence LDH nucleation, while the growth kinetics of LDHs can be controlled by adjusting hydrothermal conditions. Typically, without intervention, LDH crystal growth is naturally random (determined by the surface state of the metal substrate), meaning the LDH sheets are randomly oriented. Based on a "competitive selectivity" growth process, LDHs tend to form intersecting lamellar structures with numerous intersecting voids of uneven size. Therefore, LDHs tend to form a relatively sparse film structure with many intersecting voids, which greatly reduces the density of the LDH film. These typical LDH intersecting voids ("micro-valleys") may interfere with or dominate the transport path of corrosive substances. For the application of LDH films in metal corrosion protection, the density of the LDH film layer and the structural characteristics of the micro-voids (orientation, size, uniformity, etc.) are the key factors affecting its corrosion protection.

[0004] Therefore, how to improve the density of LDHs films and enhance their corrosion protection performance remains an urgent problem to be solved. Summary of the Invention

[0005] The present invention aims to at least solve one of the technical problems existing in the prior art. To this end, the present invention proposes a method for preparing a planar LDHs film on the surface of a metal substrate and its application; the method can prepare a planar LDHs nanosheet structure film on the surface of a metal substrate, thereby improving the film density and enhancing its corrosion protection effect on the metal.

[0006] A first aspect of the present invention provides a method for preparing a planar LDHs film on the surface of a metal substrate, comprising the following steps:

[0007] S1. Perform surface pretreatment on the metal substrate;

[0008] S2. Prepare an alcoholic solution containing divalent and trivalent metal ion salts, adjust the pH to alkaline, and obtain a suspension containing LDHs microcrystals.

[0009] S3. Spin-coat the suspension containing LDHs microcrystals onto the surface of the pretreated metal substrate, anneal, and obtain an LDHs microcrystal layer on the surface of the metal substrate.

[0010] S4. Prepare an aqueous solution containing trivalent metal ion salts and urea, adjust the pH to alkaline, and then add a metal ion chelating agent to obtain a mixed solution.

[0011] S5. The metal substrate with the LDHs microcrystalline layer obtained in step S3 is immersed in the mixture and subjected to hydrothermal reaction to obtain a flat LDHs film on the surface of the metal substrate.

[0012] In some embodiments of the present invention, the metal matrix is ​​a magnesium alloy matrix, and the magnesium alloy type includes AZ31B, AZ31, AZ91 or ZK60.

[0013] In some embodiments of the present invention, step S1 includes surface pretreatment including polishing, cleaning and drying the metal substrate.

[0014] In some embodiments of the present invention, the surface pretreatment includes: mechanically polishing the metal substrate with silicon carbide sandpaper, then ultrasonically cleaning it in ethanol aqueous solution and deionized water respectively after polishing, and then drying it.

[0015] In some embodiments of the present invention, the mechanical polishing is performed by sequentially polishing with silicon carbide sandpaper of grades 800#, 1200#, 1500#, and 3000#.

[0016] In some embodiments of the present invention, in step S2, the divalent metal ion salt includes one or more of magnesium nitrate, ferrous sulfate, and zinc nitrate, and the concentration of the divalent metal ion salt is 0.02-0.1 mol / L; the trivalent metal ion salt includes one or more of aluminum nitrate, titanium trichloride, and ferric nitrate, and the concentration of the trivalent metal ion salt is 0.01-0.05 mol / L.

[0017] For example, in step S2, the concentration of the divalent metal ion salt can be any point value or any two-point range between 0.02-0.1 mol / L, such as 0.02 mol / L, 0.04 mol / L, 0.06 mol / L, 0.08 mol / L, 0.1 mol / L, etc.; the concentration of the trivalent metal ion salt can be any point value or any two-point range between 0.01-0.05 mol / L, such as 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, etc.

[0018] In some embodiments of the present invention, in step S2, the alcohol solution includes one or both of aqueous ethanol and aqueous ethylene glycol.

[0019] In some embodiments of the present invention, in steps S2 and S4, adjusting the pH to alkaline means adjusting the pH to 9.5-10.5.

[0020] In some embodiments of the present invention, in steps S2 and S4, the pH is adjusted to be alkaline by adding an aqueous ammonia solution with a mass percentage of 1%.

[0021] In some embodiments of the present invention, step S3, the spin coating includes sequentially spin coating at a rotation speed of 400-600 r / min for 10-30 s, spin coating at a rotation speed of 1400-1600 r / min for 10-30 s, and spin coating at a rotation speed of 2900-3100 r / min for 10-30 s. By progressively increasing the rotation speed, the uniformity and adhesion of the microcrystalline layer on the substrate surface can be further improved.

[0022] In some embodiments of the present invention, in step S3, the annealing temperature is 200-300°C and the annealing time is 0.5-2 hours.

[0023] For example, in step S3, the annealing temperature can be any point value or any two-point range value between 200-300℃, such as 200℃, 220℃, 240℃, 260℃, 280℃, 300℃, etc.; the annealing time can be any point value or any two-point range value between 0.5-2h, such as 0.5h, 1h, 1.5h, 2h, etc.

[0024] In some embodiments of the present invention, in step S3, the thickness of the LDHs microcrystalline layer is 0.5-2 μm.

[0025] For example, in step S3, the thickness of the LDHs microcrystalline layer can be any point value or any two-point range value between 0.5-2μm, such as 0.5μm, 1μm, 1.5μm, 2μm, etc.

[0026] In some embodiments of the present invention, the trivalent metal ion salt in step S4 is the same type as the trivalent metal ion salt in step S2.

[0027] In some embodiments of the present invention, in step S4, the concentration of the trivalent metal ion salt is 2-5 mmol / L, the molar ratio of urea to the trivalent metal ion salt is 1:(2-5), and the molar ratio of the metal ion chelating agent to the trivalent metal ion salt is 1:(1-2).

[0028] For example, in step S4, the concentration of the trivalent metal ion salt can be any point value or any two-point range between 2 and 5 mmol / L, such as 2 mmol / L, 3 mmol / L, 4 mmol / L, 5 mmol / L, etc.; the molar ratio of urea to trivalent metal ion salt can be any point value or any two-point range between 1:(2-5), such as 1:2, 1:3, 1:4, 1:5, etc.; the molar ratio of the metal ion chelating agent to trivalent metal ion salt can be any point value or any two-point range between 1:(1-2), such as 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, 1:2, etc.

[0029] In some embodiments of the present invention, in step S4, the metal ion chelating agent includes EDTA-2Na.

[0030] In some embodiments of the present invention, in step S5, the temperature of the hydrothermal reaction is 100-135°C and the time of the hydrothermal reaction is 10-24h.

[0031] For example, in step S5, the temperature of the hydrothermal reaction can be any point value or any two-point range between 100-135℃, such as 100℃, 105℃, 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, etc.; the time of the hydrothermal reaction can be any point value or any two-point range between 10-24h, such as 10h, 12h, 14h, 16h, 18h, 20h, 22h, 24h, etc.

[0032] A second aspect of the present invention provides a planar LDHs film on a metal substrate surface prepared by the method for preparing a planar LDHs film on a metal substrate surface as described in the first aspect of the present invention.

[0033] A third aspect of the present invention provides a medical implant comprising a planar LDHs membrane on the surface of a metal substrate as described in the second aspect of the present invention.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] (1) The present invention adjusts the initial crystal nucleation mode (orientation) of the LDHs film on the surface of the metal substrate by spin coating pre-crystallization treatment, so that it tends to be in a flat state. That is, the centrifugal force generated by spin coating uniformly disperses the LDHs microcrystals and lays them flat on the surface of the metal substrate, providing nucleation sites for the subsequent growth of LDHs crystals. Combined with the hydrothermal reaction growth process assisted by metal ion chelating agent, a flat LDHs nanosheet structure film is obtained, in which the LDHs microcrystals grow in a dense state almost parallel to the substrate surface.

[0036] (2) By constructing an LDHs film that is nearly parallel to the surface of the metal substrate, the present invention weakens the vertical diffusion or transport channels of corrosive ions and reduces the sensitivity to pitting corrosion. Compared with LDHs films grown by conventional processes (without spin coating and pre-crystallization treatment), the flat LDHs film prepared by the present invention can effectively block the infiltration process of corrosive media, thereby slowing down the corrosion and degradation process of metals and improving their corrosion resistance. Attached Figure Description

[0037] Figure 1 This is a SEM image of the magnesium alloy surface after treatment in step S3 of Example 1;

[0038] Figure 2 This is a SEM image of the LDHs film prepared on the surface of a magnesium alloy in Example 1.

[0039] Figure 3 The image shows a comparison of the XRD patterns of the LDHs film prepared on the surface of the magnesium alloy in Example 1 and the LDHs powder obtained from the hydrothermal reactor liquid in step S5.

[0040] Figure 4 This is a comparison of the anodic polarization curves of the LDHs films prepared on the surface of magnesium alloy in Example 1 and Comparative Example 1. Detailed Implementation

[0041] To enable those skilled in the art to more clearly understand the technical solutions described in this invention, the following embodiments are provided for illustration. It should be noted that the following embodiments do not constitute a limitation on the scope of protection claimed by this invention.

[0042] Unless otherwise specified, the raw materials, reagents or devices used in the following examples are available from conventional commercial sources or can be obtained by existing known methods.

[0043] Example 1

[0044] A method for preparing a planar LDHs film on a metal substrate surface includes the following steps:

[0045] S1. The magnesium alloy plate (AZ31B) is processed into a disc sample (20mm in diameter and 1mm in thickness) by wire cutting. Then, the magnesium alloy sample is mechanically polished with silicon carbide sandpaper of 800#, 1200#, 1500# and 3000#. After polishing, it is ultrasonically cleaned in 95wt% ethanol aqueous solution and deionized water respectively. After drying, it is ready for use.

[0046] S2. Dissolve magnesium nitrate and aluminum nitrate in a 95 wt% ethanol aqueous solution (the concentration of magnesium nitrate is 0.05 mol / L and the concentration of aluminum nitrate is 0.03 mol / L), and then add 1 wt% ammonia aqueous solution to adjust the pH to 10.0 to obtain a suspension containing LDHs microcrystals.

[0047] S3. Add 300 μL of the suspension containing LDHs microcrystals to the surface of the magnesium alloy sample prepared in step S1, and spin coat it sequentially at a speed of 500 r / min for 30 s, at a speed of 1500 r / min for 20 s, and at a speed of 3000 r / min for 10 s. Then anneal it at 250 °C for 1 h to obtain an LDHs microcrystal layer with a thickness of 1 μm on the surface of the magnesium alloy sample.

[0048] S4. Dissolve magnesium nitrate and urea in an aqueous solution (magnesium nitrate concentration is 3 mmol / L), then add 1 wt% ammonia solution to adjust the pH to 10.0, and then add EDTA-2Na to obtain a mixed solution; wherein, the molar ratio of urea to magnesium nitrate is 1:3, and the molar ratio of EDTA-2Na to magnesium nitrate is 1:1.5.

[0049] S5. The magnesium alloy sample with the LDHs microcrystalline layer obtained in step S3 is vertically immersed in the mixture obtained in step S4 and transferred to a stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave is then sealed and placed in an oven at 110°C for 18 hours for hydrothermal reaction. After the hydrothermal reaction is completed, the magnesium alloy sample is taken out, washed with boiled and cooled deionized water, and dried in an oven at 60°C.

[0050] In the above preparation process, after step S3, the scanning electron microscope (SEM) results of the magnesium alloy sample with an LDHs microcrystalline layer on the surface are as follows: Figure 1 As shown, the micro-flaky material is uniformly distributed on the surface of the magnesium alloy sample, indicating that hydroxide nanocrystals were formed on the polished magnesium alloy surface after pre-crystallization treatment.

[0051] The SEM results of the LDHs film prepared on the magnesium alloy surface in this embodiment are as follows: Figure 2As shown, typical hexagonal LDHs sheets can be clearly observed to be laid out horizontally. The LDHs nanosheets are arranged almost parallel to the magnesium alloy surface, which significantly reduces the cross gaps of LDHs. Some LDHs sheets show a similar co-growth trend.

[0052] Furthermore, the X-ray diffraction (XRD) results of the LDHs film prepared on the magnesium alloy surface and the LDHs powder obtained from the hydrothermal reactor liquid in step S5 in this embodiment are, for example, Figure 3 As shown, the diffraction peaks of the LDHs film (Example 1) on crystal planes (003) and (006) in the diffraction pattern are broad and weak. Furthermore, the I(012) / I(003) intensity ratio is much lower than that of randomly oriented LDHs (powder), indicating that the LDHs grains are well horizontally oriented on the sample film. This is consistent with... Figure 2 The SEM observations of the LDH nanosheets were consistent.

[0053] Example 2

[0054] A method for preparing a planar LDHs film on a metal substrate surface includes the following steps:

[0055] S1. The magnesium alloy plate (AZ31B) is processed into a disc sample (20mm in diameter and 1mm in thickness) by wire cutting. Then, the magnesium alloy sample is mechanically polished with silicon carbide sandpaper of 800#, 1200#, 1500# and 3000#. After polishing, it is ultrasonically cleaned in 95wt% ethanol aqueous solution and deionized water respectively. After drying, it is ready for use.

[0056] S2. Dissolve magnesium nitrate and aluminum nitrate in a 95 wt% ethanol aqueous solution (the concentration of magnesium nitrate is 0.05 mol / L and the concentration of aluminum nitrate is 0.03 mol / L), and then add 1 wt% ammonia aqueous solution to adjust the pH to 10.0 to obtain a suspension containing LDHs microcrystals.

[0057] S3. Add 300 μL of the suspension containing LDHs microcrystals to the surface of the magnesium alloy sample prepared in step S1, spin coat at 1500 r / min for 30 s, and then anneal at 250 °C for 1 h to obtain an LDHs microcrystal layer with a thickness of 1 μm on the surface of the magnesium alloy sample.

[0058] S4. Dissolve magnesium nitrate and urea in an aqueous solution (magnesium nitrate concentration is 3 mmol / L), then add 1 wt% ammonia solution to adjust the pH to 10.0, and then add EDTA-2Na to obtain a mixed solution; wherein, the molar ratio of urea to magnesium nitrate is 1:3, and the molar ratio of EDTA-2Na to magnesium nitrate is 1:1.5.

[0059] S5. The magnesium alloy sample with the LDHs microcrystalline layer obtained in step S3 is vertically immersed in the mixture obtained in step S4 and transferred to a stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave is then sealed and placed in an oven at 110°C for 18 hours for hydrothermal reaction. After the hydrothermal reaction is completed, the magnesium alloy sample is taken out, washed with boiled and cooled deionized water, and dried in an oven at 60°C.

[0060] Comparative Example 1 (the difference from Example 1 is that it did not undergo spin-coating pre-crystallization treatment)

[0061] A method for preparing LDHs films on a metal substrate includes the following steps:

[0062] S1. The magnesium alloy plate (AZ31B) is processed into a disc sample (20mm in diameter and 1mm in thickness) by wire cutting. Then, the magnesium alloy sample is mechanically polished with silicon carbide sandpaper of 800#, 1200#, 1500# and 3000#. After polishing, it is ultrasonically cleaned in 95wt% ethanol aqueous solution and deionized water respectively. After drying, it is ready for use.

[0063] S2. Dissolve magnesium nitrate and urea in an aqueous solution (magnesium nitrate concentration is 3 mmol / L), then add 1 wt% ammonia solution to adjust the pH to 10.0, and then add EDTA-2Na to obtain a mixed solution; wherein, the molar ratio of urea to magnesium nitrate is 1:3, and the molar ratio of EDTA-2Na to magnesium nitrate is 1:1.5.

[0064] S3. Immerse the magnesium alloy sample prepared in step S1 vertically into the mixture obtained in step S2, and transfer it to a stainless steel autoclave with a polytetrafluoroethylene liner. Then seal the autoclave and place it in an oven at 110°C for 18 hours for hydrothermal reaction. After the hydrothermal reaction is completed, take out the magnesium alloy sample, wash it with boiled and cooled deionized water, and dry it in an oven at 60°C.

[0065] Comparative Example 2 (the difference from Example 1 is that the spin coating method is replaced by the dip coating method)

[0066] A method for preparing a planar LDHs film on a metal substrate surface includes the following steps:

[0067] S1. The magnesium alloy plate (AZ31B) is processed into a disc sample (20mm in diameter and 1mm in thickness) by wire cutting. Then, the magnesium alloy sample is mechanically polished with silicon carbide sandpaper of 800#, 1200#, 1500# and 3000#. After polishing, it is ultrasonically cleaned in 95wt% ethanol aqueous solution and deionized water respectively. After drying, it is ready for use.

[0068] S2. Dissolve magnesium nitrate and aluminum nitrate in a 95 wt% ethanol aqueous solution (the concentration of magnesium nitrate is 0.05 mol / L and the concentration of aluminum nitrate is 0.03 mol / L), and then add 1 wt% ammonia aqueous solution to adjust the pH to 10.0 to obtain a suspension containing LDHs microcrystals.

[0069] S3. Immerse the magnesium alloy sample prepared in step S1 vertically in the suspension containing LDHs microcrystals, let it stand for 30 seconds to ensure sufficient surface adsorption, and use a gradient lifting method: lift the sample at a constant speed of 5 mm / s for 30 seconds; increase the speed to 15 mm / s and continue lifting for 20 seconds; accelerate to 30 mm / s to complete the lifting and hold for 10 seconds; after lifting, suspend and stand for 60 seconds to allow the residual suspension to flow naturally; finally, place the sample in a 250℃ oven for annealing for 1 hour to obtain an LDHs microcrystalline layer with a thickness of 1 μm.

[0070] S4. Dissolve magnesium nitrate and urea in an aqueous solution (magnesium nitrate concentration is 3 mmol / L), then add 1 wt% ammonia solution to adjust the pH to 10.0, and then add EDTA-2Na to obtain a mixed solution; wherein, the molar ratio of urea to magnesium nitrate is 1:3, and the molar ratio of EDTA-2Na to magnesium nitrate is 1:1.5.

[0071] S5. The magnesium alloy sample with the LDHs microcrystalline layer obtained in step S3 is vertically immersed in the mixture obtained in step S4 and transferred to a stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave is then sealed and placed in an oven at 110°C for 18 hours for hydrothermal reaction. After the hydrothermal reaction is completed, the magnesium alloy sample is taken out, washed with boiled and cooled deionized water, and dried in an oven at 60°C.

[0072] Comparative Example 3 (different from Example 1 in that EDTA-2Na was not added)

[0073] A method for preparing a planar LDHs film on a metal substrate surface includes the following steps:

[0074] S1. The magnesium alloy plate (AZ31B) is processed into a disc sample (20mm in diameter and 1mm in thickness) by wire cutting. Then, the magnesium alloy sample is mechanically polished with silicon carbide sandpaper of 800#, 1200#, 1500# and 3000#. After polishing, it is ultrasonically cleaned in 95wt% ethanol aqueous solution and deionized water respectively. After drying, it is ready for use.

[0075] S2. Dissolve magnesium nitrate and aluminum nitrate in a 95 wt% ethanol aqueous solution (the concentration of magnesium nitrate is 0.05 mol / L and the concentration of aluminum nitrate is 0.03 mol / L), and then add 1 wt% ammonia aqueous solution to adjust the pH to 10.0 to obtain a suspension containing LDHs microcrystals.

[0076] S3. Add 300 μL of the suspension containing LDHs microcrystals to the surface of the magnesium alloy sample prepared in step S1, and spin coat it sequentially at a speed of 500 r / min for 30 s, at a speed of 1500 r / min for 20 s, and at a speed of 3000 r / min for 10 s. Then anneal it at 250 °C for 1 h to obtain an LDHs microcrystal layer with a thickness of 1 μm on the surface of the magnesium alloy sample.

[0077] S4. Dissolve magnesium nitrate and urea in an aqueous solution (magnesium nitrate concentration is 3 mmol / L), then add 1 wt% ammonia solution to adjust the pH to 10.0 to obtain a mixed solution; wherein, the molar ratio of urea to magnesium nitrate is 1:3.

[0078] S5. The magnesium alloy sample with the LDHs microcrystalline layer obtained in step S3 is vertically immersed in the mixture obtained in step S4 and transferred to a stainless steel autoclave with a polytetrafluoroethylene liner. The autoclave is then sealed and placed in an oven at 110°C for 18 hours for hydrothermal reaction. After the hydrothermal reaction is completed, the magnesium alloy sample is taken out, washed with boiled and cooled deionized water, and dried in an oven at 60°C.

[0079] Performance testing

[0080] The products prepared in Example 1 and Comparative Example 1 were tested respectively, such as Figure 4 As shown, the conventional LDHs film prepared in Comparative Example 1 exhibits typical Tafel characteristics in its anodic polarization curve, indicating that the magnesium alloy substrate beneath the LDHs film is in a corrosive active state under these conditions, and that an anodic passivation zone and pitting potential appear. Compared to the conventional LDHs film, the LDHs film prepared in Example 1, with its E value almost parallel to the magnesium alloy substrate, shows a significantly higher E value. corr The positive offset reached -0.207V, and the self-corrosion current density was also lower than that of conventional LDHs membranes. These results indicate that the planar LDHs membrane prepared in Example 1 of this invention, compared to conventional LDHs membranes, improves the physical barrier effect against corrosive media and enhances its corrosion resistance.

[0081] Example and Performance Parameter Analysis: 1. LDHs Orientation: This describes the angle at which LDHs crystal sheets form on the magnesium substrate under different process conditions, such as near-vertical or planar arrangement. The structural morphology of the LDHs crystal sheets is observed using microscopic imaging (SEM). For example, if over 70% of the crystal sheets are nearly planar on the substrate rather than mutually supporting each other to form obvious gaps, this indicates a planar LDHs film. 2. E ocp / V: Open circuit potential value, a thermodynamic parameter for electrochemical corrosion resistance, used to comprehensively evaluate the corrosion resistance of the film. According to the ASTM G5 standard electrochemical testing specification, static testing is conducted using an electrochemical workstation (three-electrode system: working electrode (sample) | saturated calomel electrode (SCE) | platinum counter electrode; electrolyte (e.g., 3.5 wt% NaCl)). E is recorded when the potential fluctuation is <±2 mV within 5 consecutive minutes. ocp The value of E is indirectly determined using the Tafel curve method. ocp Specific numerical values ​​(ASTM G59 standard). 3. Porosity: According to the ASTM E2109 standard for characterizing porosity by image analysis, the porosity of the porous membrane layer is calculated using SEM images combined with ImageJ software (porosity P = ∑A). pores / ∑A total (×100%), and ≥5 different regions of the same sample were selected for analysis.

[0082] The test analysis results are shown in Table 1.

[0083] Table 1

[0084] Group LDHs film orientation <![CDATA[E ocp / V]]> Porosity Example 1 flat -0.207 4.6％ Example 2 Jinpingpu -0.215 6.3％ Comparative Example 1 Vertical -0.227 26.5％ Comparative Example 2 Nearly flat -0.219 7.5％ Comparative Example 3 Nearly flat -0.216 8.6％

[0085] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the embodiments described. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A method for preparing a planar LDHs film on a metal substrate surface, characterized in that, Includes the following steps: S1. Perform surface pretreatment on the metal substrate; S2. Prepare an alcoholic solution containing divalent and trivalent metal ion salts, adjust the pH to alkaline, and obtain a suspension containing LDHs microcrystals. S3. Spin-coat the suspension containing LDHs microcrystals onto the surface of the pretreated metal substrate, anneal, and obtain an LDHs microcrystal layer on the surface of the metal substrate. S4. Prepare an aqueous solution containing trivalent metal ion salts and urea, adjust the pH to alkaline, and then add a metal ion chelating agent to obtain a mixed solution. S5. The metal substrate with the LDHs microcrystalline layer obtained in step S3 is immersed in the mixture and subjected to hydrothermal reaction to obtain a flat LDHs film on the surface of the metal substrate.

2. The method for preparing a planar LDHs film on a metal substrate surface according to claim 1, characterized in that, In step S1, the surface pretreatment includes polishing, cleaning, and drying the metal substrate.

3. The method for preparing a planar LDHs film on a metal substrate surface according to claim 1, characterized in that, In step S2, the divalent metal ion salt includes one or more of magnesium nitrate, ferrous sulfate, and zinc nitrate, and the concentration of the divalent metal ion salt is 0.02-0.1 mol / L; the trivalent metal ion salt includes one or more of aluminum nitrate, titanium trichloride, and ferric nitrate, and the concentration of the trivalent metal ion salt is 0.01-0.05 mol / L.

4. The method for preparing a planar LDHs film on a metal substrate surface according to claim 1, characterized in that, In steps S2 and S4, adjusting the pH to alkaline means adjusting the pH to 9.5-10.

5.

5. The method for preparing a planar LDHs film on a metal substrate surface according to claim 1, characterized in that, In step S3, the spin coating includes spin coating for 10-30 seconds at a speed of 400-600 r / min, spin coating for 10-30 seconds at a speed of 1400-1600 r / min, and spin coating for 10-30 seconds at a speed of 2900-3100 r / min.

6. The method for preparing a planar LDHs film on a metal substrate surface according to claim 1, characterized in that, In step S3, the annealing temperature is 200-300℃ and the annealing time is 0.5-2h.

7. The method for preparing a planar LDHs film on a metal substrate surface according to claim 1, characterized in that, In step S4, the concentration of the trivalent metal ion salt is 2-5 mmol / L, the molar ratio of urea to the trivalent metal ion salt is 1:(2-5), and the molar ratio of the metal ion chelating agent to the trivalent metal ion salt is 1:(1-2).

8. The method for preparing a planar LDHs film on a metal substrate surface according to claim 1, characterized in that, In step S5, the temperature of the hydrothermal reaction is 100-135℃, and the time of the hydrothermal reaction is 10-24h.

9. A planar LDHs membrane on a metal substrate obtained by the method for preparing a planar LDHs membrane on a metal substrate surface according to any one of claims 1-8.

10. A medical implant, characterized in that, Includes the planar LDHs film on the surface of a metal substrate as described in claim 9.

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