An anodizing electrolyte, a preparation method thereof and application thereof in preparing titanium dioxide nanotubes

Abstract

This invention relates to the field of titanium dioxide nanotube preparation technology, specifically to an anodic oxidation electrolyte, its preparation method, and its application in the preparation of titanium dioxide nanotubes. Considering the technical deficiencies of existing TiO2 nanotube array film preparation techniques, this invention provides an anodic oxidation electrolyte composed of glycerol, ammonium chloride, and L-malic acid. By utilizing the malate ions of L-malic acid to modify the conductivity of the electrolyte, the oxidation time is shortened while obtaining titanium dioxide nanotubes with large pore sizes and rough surfaces, thereby enhancing the adsorption and loading capacity of the titanium dioxide nanotubes.

Description

Technical Field

[0001] This invention relates to the field of titanium dioxide nanotube preparation technology, specifically to an anodic oxidation electrolyte, its preparation method, and its application in the preparation of titanium dioxide nanotubes. Background Technology

[0002] Titanium and its alloys are attracting increasing attention in various applications, particularly in medicine, for different implants and surgical instruments, due to their excellent biocompatibility, low toxicity, and relatively low density. High corrosion resistance is considered one of the most important issues in the design and manufacture of implants and surgical instruments. Forming an oxide film on the metal surface can effectively improve the corrosion resistance of titanium, and a thin and dense oxide film can spontaneously form and adhere well to the titanium surface.

[0003] Natural passivation films are amorphous and only a few nanometers (1.5-10 nm) in size, exhibiting poor corrosion and wear resistance. Therefore, porous anodic oxides prepared by anodic oxidation have attracted widespread attention due to their potential applications. Among them, porous anodic titanium nanotubes (PATNTs) are a novel type of inorganic photosensitive semiconductor with significant application prospects in photoelectrocatalysis, dye-sensitized solar cells, self-cleaning, and photocatalytic water splitting. Therefore, the anodic oxidation of titanium and titanium alloys is likely to become a very popular research topic in the next decade and beyond.

[0004] The prior art application number 200710177076.1 discloses a "method for preparing gradient TiO2 nanotube array films using a multi-step anodic oxidation method", which specifically discloses that the organic electrolyte is composed of ammonium fluoride and glycerol. The gradient TiO2 nanotube array structure is obtained by repeating anodic oxidation with an aqueous electrolyte and anodic oxidation with an organic electrolyte. However, in practical applications, it was found that the organic electrolyte composed only of ammonium fluoride and glycerol has a high viscosity. While reducing the water content of the electrolyte, it slows down the diffusion rate of fluoride ions, thus prolonging the anodic oxidation time. The high viscosity of the electrolyte also results in small pore size and smooth surface of the obtained nanotube array, which in turn leads to poor adsorption and loading capacity of titanium nanotubes. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention provides an anodic oxidation electrolyte, its preparation method, and its application in the preparation of titanium dioxide nanotubes. Considering the technical defects in the preparation of existing TiO2 nanotube array films, this application provides an anodic oxidation electrolyte composed of glycerol, ammonium chloride, and L-malic acid. By using the malate ions of L-malic acid to change the conductivity of the electrolyte, the diffusion rate of chloride ions is improved, thereby shortening the oxidation time and obtaining titanium dioxide nanotubes with large pore size and rough surface, thus improving the adsorption and loading capacity of titanium dioxide nanotubes.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] This invention adds L-malic acid to the electrolyte, wherein the malate ion in L-malic acid is C4H5O5. - By incorporating a large amount of L-malate anionic electrolyte into the anodic titanium oxide framework, the electrolyte alters the anion concentration in the electrolyte, thereby changing the electrolyte's conductivity. Under electrochemical conditions, this allows the anion C4H5O5 to... - It is more easily attracted by titanium anodes; the more malate ions there are, the better the conductivity of the electrolyte, which promotes the diffusion of chloride ions, which is more conducive to the formation of anodic oxide film, and thus more conducive to the formation of titanium dioxide nanoarrays.

[0008] Similar to the anodizing process of aluminum, whether a dense or porous titanium oxide film is obtained during the anodizing of metallic Ti is determined by the nature of the electrolyte. When the electrolyte contains fluoride ions, perchlorate ions, chloride ions, or bromide ions, a porous anodic titanium oxide film, i.e., anodic TiO2 nanotubes, is generally obtained during Ti anodizing. In other electrolytes that do not contain fluoride or chloride ions, a dense titanium oxide film is obtained.

[0009] This invention can prepare titanium nanotubes with a larger specific surface area and a rougher surface, thus improving the adsorption and loading capacity of titanium nanotubes and solving the technical defects of poor adsorption and loading capacity.

[0010] In addition, given that existing electrolytes are generally toxic electrolytes containing strong acids, strong alkalis, or fluoride ions, this invention aims to develop a low-cost, green, and environmentally friendly anodic oxidation electrolyte. The electrolyte of this application achieves environmental protection while solving the defects inherent in existing titanium dioxide nanotubes.

[0011] An anodic oxidation electrolyte is composed of glycerol, ammonium fluoride, L-malic acid and water; in the anodic oxidation electrolyte, the volume percentage of glycerol is 90 vol%, the concentration of ammonium fluoride is 0.1-0.15 mol / L, and the concentration of L-malic acid is 0.1-0.15 mol / L.

[0012] This invention also protects a method for preparing anodizing electrolyte, comprising the following steps:

[0013] Glycerol, ammonium fluoride aqueous solution and L-malic acid aqueous solution are mixed at volume percentages of 90%, 9-9.5% and 1-0.5% respectively, and the sum of the volume percentages of the three is 100% to obtain the anodic oxidation electrolyte.

[0014] This invention also protects the application of anodic oxidation electrolyte in the preparation of titanium dioxide nanotubes.

[0015] Preferably, the application method is as follows:

[0016] Using a titanium sample as the anode and a non-titanium sample as the cathode, the anode and cathode were placed together in the anodic oxidation electrolyte and electrically connected to the power supply by a wire, and constant voltage oxidation was carried out at room temperature.

[0017] Preferably, the constant pressure oxidation voltage is 120V and the oxidation time is 2 to 2.5 hours.

[0018] Preferably, the non-titanium sample is a non-titanium metal sample or a carbon material.

[0019] Preferably, the non-titanium metal sample is selected from nickel, copper, iron, or chromium samples.

[0020] Preferably, the carbon material is selected from graphite, graphene, or carbon black.

[0021] Preferably, the titanium sample needs to be surface cleaned before use. The specific treatment method is as follows: the titanium metal is successively subjected to grinding, alkaline washing, acid washing and ultrasonic cleaning to obtain the titanium sample.

[0022] Preferably, the polishing operation is as follows: the titanium sheet is polished sequentially using sandpaper of 180#, 320#, 600#, 1200#, and 2000# to obtain polished titanium;

[0023] The alkaline washing process is as follows: Immerse the polished titanium in a 5 mol / L NaOH solution at 60-65℃ for 5-6 minutes, then wash with water until neutral to obtain alkaline-washed titanium;

[0024] The pickling process is as follows: a mixture of hydrofluoric acid, concentrated nitric acid, and distilled water is used as the pickling solution to clean the alkaline titanium until the sample surface is completely white. The sample is then washed with water until it is neutral to obtain the pickled titanium.

[0025] The volume ratio of hydrofluoric acid, concentrated nitric acid, and distilled water is 2 mL: 3 mL: 10 mL.

[0026] The ultrasonic cleaning procedure is as follows: acid-washed titanium is ultrasonically cleaned in ethanol for 15-20 minutes to obtain a titanium sample.

[0027] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0028] 1. This invention provides a TA1 industrial pure titanium anodizing electrolyte. TA1 titanium alloy is an α-type titanium alloy, mainly composed of titanium and aluminum, with other additive elements including manganese, molybdenum, zirconium, iron, silicon, and vanadium. The anodizing electrolyte is composed of glycerol, ammonium fluoride, and L-malic acid. Compared to electrolytes composed only of glycerol and ammonium fluoride, this application uses L-malic acid to change the anion concentration of the electrolyte, thereby promoting the diffusion of fluoride ions and accelerating the diffusion rate of fluoride ions, which is beneficial to nanotube growth. It can prepare titanium dioxide nanotubes with larger specific surface area and rougher surface. By adjusting the electrolyte, the morphology of titanium dioxide nanotubes can be controlled, resulting in titanium dioxide nanotubes with stronger adsorption and loading capacity. Moreover, this electrolyte is colorless, odorless, non-toxic, and inexpensive.

[0029] 2. This invention provides a pretreatment process for TA1 industrial pure titanium anodizing, which can obtain a clean and smooth surface, preparing it for anodizing.

[0030] 3. Thanks to the addition of L-malic acid to the electrolyte, the titanium dioxide nanotube array obtained by the TA1 industrial pure titanium anodizing process of this invention is uniform, with a large nanotube pore size, an average pore size of about 300 nm, and a rough surface; while using only glycerol and ammonium fluoride as electrolyte, the titanium dioxide nanotubes obtained have a pore size of about 80 nm and a smooth inner wall; the change in the structure of titanium dioxide makes its loading capacity and adsorption stronger. Attached Figure Description

[0031] Figure 1 This is a schematic diagram of the anodizing apparatus.

[0032] Figure 2 Here is a SEM image of titanium dioxide nanotubes from Example 1;

[0033] Figure 3 Here is a SEM image of the titanium dioxide nanoarray from Example 1;

[0034] Figure 4 SEM image of the outermost oxide film coating in Example 1;

[0035] Figure 5 Here is a SEM image of the titanium dioxide nanoarray in Comparative Example 1;

[0036] Figure 6 This is a SEM image of the titanium dioxide nanotube wall in Comparative Example 1.

[0037] Figure 1 Explanation of reference numerals in the attached figures

[0038] 1-Nickel sheet; 2-Clamp; 3-Wire; 4-Titanium sheet; 5-Power supply; 6-Electrolyte; 7-Beaker. Detailed Implementation

[0039] The specific embodiments of the present invention are described in detail below, but it should be understood that the scope of protection of the present invention is not limited to the specific embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention. Unless otherwise specified, the experimental methods described in the embodiments of the present invention are conventional methods.

[0040] This application uses glycerol, ammonium fluoride, and L-malic acid as electrolytes. By mixing L-malic acid into glycerol and ammonium fluoride, the technical defect of slow chloride ion diffusion in organic electrolytes is overcome. Specifically, L-malic acid can change the anion concentration in the electrolyte, thereby changing the conductivity of the electrolyte and promoting chloride ion diffusion. As a result, while shortening the oxidation time, titanium dioxide nanotubes with large pore size and rough surface are obtained, improving the adsorption and loading capacity of titanium dioxide nanotubes.

[0041] The present invention also conducted a comparative study, comparing the titanium dioxide nanotubes prepared using the method of Example 1 of this application with those prepared using an organic electrolyte containing only glycerol and ammonium fluoride. The maximum pore size of the nanotubes prepared using the method of Example 1 of this application can reach 400 nm, and the average pore size can reach 300 nm. The nanotubes prepared using the organic electrolyte containing only glycerol and ammonium fluoride in Comparative Example 1 have a maximum pore size of less than 200 nm and an average pore size of 80 nm. In addition, in comparison, the surface of the titanium dioxide nanotubes prepared using glycerol, ammonium fluoride, and L-malic acid as electrolyte is rough, while the surface of the titanium dioxide nanotubes prepared using glycerol and ammonium fluoride as electrolyte is smooth.

[0042] The titanium samples in Examples 1-5 of this invention were obtained using the following treatment method:

[0043] (1) Titanium sheet sample cutting: The initial titanium material is a whole roll. In order to facilitate the experimental operation, it is cut into small pieces with a size of 3cm×2cm along its length direction using tin shears. Since the titanium sheet is relatively soft, it is easy to warp during the cutting process. Therefore, after the cutting is completed, the titanium sheet needs to be hammered flat for later use.

[0044] (2) Manual polishing: Polish the titanium sheet in sequence with sandpaper of 180#, 320#, 600#, 1200# and 2000#. Use 180# sandpaper to roughly remove the natural oxide layer, machining marks and industrial oil residue on the surface of the titanium sheet. The other sizes of sandpaper are used to reduce the surface roughness. After polishing, rinse the surface of the titanium sheet with clean water to remove the stains and residues, then rinse with alcohol and dry with a hair dryer. Separately pack for use.

[0045] (3) Alkali washing: This step is intended to wash away the residual oil stains from machining and the grease left after touching the surface of the titanium sheet. These will have a certain impact on the subsequent anodizing step, so the titanium sheet sample needs to be treated with alkali. The alkali washing solution is a 5 mol / L NaOH solution. Pour the degreasing solution into a beaker and then put it into a constant temperature water bath and heat it to 60°C. Then put the titanium sheet sample into it and wash it with alkali for 5 minutes. After degreasing, be sure to wash it with hot water first, and then rinse it with cold water to thoroughly clean the alkali solution on the surface.

[0046] (4) Pickling: Pickling is to immerse the metal sample in acid (or acidic salt) to remove the oxide film, oxide scale and rust on the metal surface. Since titanium alloys are easily oxidized in the air, this oxide film will hinder the anodizing experiment, affect the formation of the oxide film, and lead to uneven anodizing and easy spotting. Therefore, it is necessary to pickle to remove the surface oxide film. The experiment uses a pickling solution of hydrofluoric acid: concentrated nitric acid: distilled water = 2mL: 3mL: 10mL. During the pickling process, attention should be paid to the pickling time not being too long. When a light yellow flocculent deposit appears on the surface of the titanium sheet sample, gently shake it so that the surface of the titanium sheet sample fully shows the original white of titanium. Then quickly take the titanium sheet sample out of the pickling solution and rinse off the residual pickling solution on the surface with clean water.

[0047] (5) Ultrasonic cleaning: The acid-washed titanium sheet sample was ultrasonically cleaned in alcohol for 15 minutes to remove the acid washing solution and residual stains on the surface of the titanium sheet sample.

[0048] (6) Sample sealing: After ultrasonic cleaning, the titanium sheet sample is rinsed with alcohol and dried. It is then placed in a vacuum drying oven for later use to prevent oxidation of the titanium sheet sample.

[0049] The technical solution is further illustrated below with examples and comparative examples, as follows:

[0050] Example 1

[0051] The preparation method of titanium dioxide nanoarrays includes the following steps:

[0052] The anodizing process is constant-voltage oxidation. By observing the effect of different voltages on the morphology of nanotubes during anodizing, the appropriate voltage for preparing smooth and flat nanotubes is determined. This process requires connecting the anodized titanium sheet sample to the positive electrode, clamping it with a fixture, and then immersing it in the electrolyte. The negative electrode material should not be the same as the positive electrode material; a material that does not easily undergo chemical reactions should be selected. In this invention, nickel sheet is selected as the negative electrode material. To ensure sufficient reaction, the area of ​​both the positive and negative electrodes immersed in the electrolyte is more than half of the total area. The distance between the positive and negative electrodes is controlled at 5 cm. It should be noted that some thick parts may have excessive thickness differences due to being too close to the cathode plate, which is more obvious during hard anodizing and results in uneven color. At the same time, the ions in the electrolyte conduct electricity, and the greater the distance, the greater the impedance. Therefore, based on the sample size in this experiment, the anode-cathode distance is selected as 5 cm.

[0053] Anodizing was completed by controlling the voltage at 120V and oxidizing for 2 hours in an electrolyte consisting of glycerol, 0.1 mol / L ammonium fluoride aqueous solution, and 0.1 mol / L L-malic acid aqueous solution.

[0054] The volume percentage ratio of glycerol, ammonium fluoride aqueous solution, and L-malic acid aqueous solution is 90%:9%:1%.

[0055] Example 2

[0056] The preparation method of titanium dioxide nanoarrays includes the following steps:

[0057] The anodizing process is constant-voltage oxidation. By observing the effect of different voltages on the morphology of nanotubes during anodizing, the appropriate voltage for preparing smooth and flat nanotubes is determined. This process requires connecting the anodized titanium sheet sample to the positive electrode, clamping it with a fixture, and then immersing it in the electrolyte. The negative electrode material should not be the same as the positive electrode material; a material that does not easily undergo chemical reactions should be selected. In this invention, nickel sheet is selected as the negative electrode material. To ensure sufficient reaction, the area of ​​both the positive and negative electrodes immersed in the electrolyte is more than half of the total area. The distance between the positive and negative electrodes is controlled at 4 cm. It should be noted that some thick parts may have excessive thickness differences due to being too close to the cathode plate, which is more obvious during hard anodizing and results in uneven color. At the same time, the ions in the electrolyte conduct electricity, and the greater the distance, the greater the impedance. Therefore, based on the sample size in this experiment, the anode-cathode distance is selected as 4 cm.

[0058] Anodizing was completed by controlling the voltage at 120V and oxidizing for 2 hours in an electrolyte consisting of glycerol, 0.15 mol / L ammonium fluoride aqueous solution, and 0.15 mol / L L-malic acid aqueous solution.

[0059] The volume percentage ratio of glycerol, ammonium fluoride aqueous solution, and L-malic acid aqueous solution is 90%:9.5%:0.5%.

[0060] Example 3

[0061] The preparation method of titanium dioxide nanoarrays includes the following steps:

[0062] The anodizing process is constant-voltage oxidation. By observing the effect of different voltages on the morphology of nanotubes during the anodizing process, the appropriate voltage for preparing smooth and flat nanotubes is determined. This process requires connecting the anodized titanium sheet sample to the positive electrode, clamping it with a fixture, and then immersing it in the electrolyte. The negative electrode material should not be the same as the positive electrode material; a material that does not easily undergo chemical reactions should be selected. In this invention, nickel sheet is selected as the negative electrode material. To ensure sufficient reaction, the area of ​​both the positive and negative electrodes immersed in the electrolyte is more than half of the total area. The distance between the positive and negative electrodes is controlled at 3 cm. It should be noted that some thick parts may have excessive thickness differences due to being too close to the cathode plate, which is more obvious during hard anodizing and results in uneven color. At the same time, the ions in the electrolyte conduct electricity, and the greater the distance, the greater the impedance. Therefore, based on the sample size in this experiment, the anode-cathode distance is selected as 3 cm.

[0063] Anodizing was completed in an electrolyte consisting of glycerol, 0.15 mol / L ammonium fluoride aqueous solution, and 0.1 mol / L L-malic acid aqueous solution, with the voltage controlled at 120 V and oxidation time of 2.5 h.

[0064] The volume percentage ratio of glycerol, ammonium fluoride aqueous solution, and L-malic acid aqueous solution is 90%:9.5%:0.5%.

[0065] Example 4

[0066] The preparation method of titanium dioxide nanoarrays includes the following steps:

[0067] The anodizing process is constant-voltage oxidation. By observing the effect of different voltages on the morphology of nanotubes during anodizing, the appropriate voltage for preparing smooth and flat nanotubes is determined. This process requires connecting the anodized titanium sheet sample to the positive electrode, clamping it with a fixture, and then immersing it in the electrolyte. The negative electrode material should not be the same as the positive electrode material; a material that does not easily undergo chemical reactions should be selected. In this invention, nickel sheet is selected as the negative electrode material. To ensure sufficient reaction, the area of ​​both the positive and negative electrodes immersed in the electrolyte is more than half of the total area. The distance between the positive and negative electrodes is controlled at 4 cm. It should be noted that some thick parts may have excessive thickness differences due to being too close to the cathode plate, which is more obvious during hard anodizing and results in uneven color. At the same time, the ions in the electrolyte conduct electricity, and the greater the distance, the greater the impedance. Therefore, based on the sample size in this experiment, the anode-cathode distance is selected as 4 cm.

[0068] Anodizing was completed by controlling the voltage at 120V and oxidizing for 2 hours in an electrolyte consisting of glycerol, 0.1 mol / L ammonium fluoride aqueous solution, and 0.15 mol / L L-malic acid aqueous solution.

[0069] The volume percentage ratio of glycerol, ammonium fluoride aqueous solution, and L-malic acid aqueous solution is 90%:9%:1%.

[0070] Example 5

[0071] The preparation method of titanium dioxide nanoarrays includes the following steps:

[0072] The anodizing process is constant-voltage oxidation. By observing the effect of different voltages on the morphology of nanotubes during the anodizing process, the appropriate voltage for preparing smooth and flat nanotubes is determined. This process requires connecting the anodized titanium sheet sample to the positive electrode, clamping it with a fixture, and then immersing it in the electrolyte. The negative electrode material should not be the same as the positive electrode material; a material that does not easily undergo chemical reactions should be selected. In this invention, nickel sheet is selected as the negative electrode material. To ensure sufficient reaction, the area of ​​both the positive and negative electrodes immersed in the electrolyte is more than half of the total area. The distance between the positive and negative electrodes is controlled at 3 cm. It should be noted that some thick parts may have excessive thickness differences due to being too close to the cathode plate, which is more obvious during hard anodizing and results in uneven color. At the same time, the ions in the electrolyte conduct electricity, and the greater the distance, the greater the impedance. Therefore, based on the sample size in this experiment, the anode-cathode distance is selected as 3 cm.

[0073] Anodizing was completed by controlling the voltage at 120V and oxidizing for 140 min in an electrolyte consisting of glycerol, 0.13 mol / L ammonium fluoride aqueous solution, and 0.12 mol / L L-malic acid aqueous solution.

[0074] The volume percentage ratio of glycerol, ammonium fluoride aqueous solution, and L-malic acid aqueous solution is 90%:9.3%:0.7%.

[0075] Comparative Example 1

[0076] The preparation steps are the same as in Example 1, except that the electrolyte does not contain L-malic acid, and the voltage is changed from 120V to 60V. This is because research has shown that in an electrolyte composed only of glycerol and ammonium fluoride, the titanium dioxide nanotube walls collapse after anodizing at 120V, making it impossible to obtain a nanotube structure. Specifically:

[0077] The preparation method of titanium dioxide nanotubes includes the following steps:

[0078] The anodizing process is constant-voltage oxidation. By observing the effect of different voltages on the morphology of nanotubes during anodizing, the appropriate voltage for preparing smooth and flat nanotubes is determined. This process requires connecting the anodized titanium sheet sample to the positive electrode, clamping it with a fixture, and then immersing it in the electrolyte. The negative electrode material should not be the same as the positive electrode material; a material that does not easily undergo chemical reactions should be selected. In this invention, nickel sheet is selected as the negative electrode material. To ensure sufficient reaction, the area of ​​both the positive and negative electrodes immersed in the electrolyte is more than half of the total area. The distance between the positive and negative electrodes is controlled at 5 cm. It should be noted that some thick parts may have excessive thickness differences due to being too close to the cathode plate, which is more obvious during hard anodizing and results in uneven color. At the same time, the ions in the electrolyte conduct electricity, and the greater the distance, the greater the impedance. Therefore, based on the sample size in this experiment, the anode-cathode distance is selected as 5 cm.

[0079] Anodizing was completed by controlling the voltage at 60V and oxidizing for 2 hours in an electrolyte consisting of glycerol and 0.1 mol / L ammonium fluoride aqueous solution.

[0080] The volume percentage ratio of glycerol to ammonium fluoride aqueous solution is 90%:10%.

[0081] In Examples 1-5 of this invention, titanium dioxide nanoarrays with large pore size and rough surface were prepared. The titanium dioxide nanoarray of Example 1 is used as the research object for comparison with the titanium dioxide nanoarray of Comparative Example 1. The specific research methods and results are shown below:

[0082] A schematic diagram of the anodizing apparatus is shown below. Figure 1 As shown, using Figure 1 The device enables the preparation of the titanium dioxide nanoarray of this application and Comparative Example 1.

[0083] After anodizing, the morphology of the nanotubes was observed using SEM images. Since L-malic acid electrolyte molecules can affect the conductivity of the electrolyte, which is beneficial to the formation of nanotubes, SEM was used to observe the morphology of the nanotubes after anodizing. It was found that under the electrolyte and experimental conditions of Example 1, the maximum pore size of the prepared nanotubes could reach 400 nm, the average pore size could reach 300 nm, and the nanotubes had a rough surface with a scaly structure and uniform array. Therefore, the titanium nanotubes prepared in this experiment have a larger specific surface area and a rougher surface, exhibiting better adsorption and loading capacity.

[0084] Figure 2 The results show that the nanotubes prepared by this invention have larger pore sizes, and the outer walls of the nanotubes are rougher, resulting in a larger specific surface area compared to... Figure 5 For nanotubes with an average diameter of 80 nm, particle adsorption is more favorable, and Figure 6It is easy to see that the outer wall of the nanotubes prepared without the addition of L-malic acid electrolyte is relatively smooth, which is not conducive to particle adsorption to a certain extent.

[0085] Figure 3 The results show that nanotubes can maintain a relatively uniform array even with large pore sizes.

[0086] Figure 4 The results show that the nanotubes are still covered by a titanium oxide layer, and the oxide film grows on the surface of the titanium substrate in a "defect-preferred manner", which is manifested as the oxide film growing in an "island-like" form.

[0087] The comparative experiment used a low-cost, environmentally friendly anodic oxidation electrolyte with a composition of 90 vol% glycerol and 0.1 mol / L ammonium fluoride. Figure 5-6 As shown, glycerol can increase the viscosity of the electrolyte and reduce the water content of the electrolyte, but it slows down the diffusion rate of fluoride ions. Therefore, the titanium dioxide nanotubes prepared have small and smooth pores.

[0088] Figure 6 The image shown is a magnified view of the titanium dioxide nanotubes prepared in Comparative Example 1. It is easy to see that the nanotubes prepared at a voltage of 60V have smooth and flat walls and do not contain the scaly structure shown in this application.

[0089] In addition, traditional electrolytes are mostly strongly acidic (containing HF), and this application can also make up for the shortcomings of existing electrolytes in terms of safety and environmental protection; the electrolyte of this application is colorless, odorless, non-toxic, and will not pollute the environment.

[0090] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. An anodic oxidation electrolyte, characterized in that, The anodic oxidation electrolyte is used for the anodic oxidation of TA1 industrial pure titanium and is composed of glycerol, ammonium fluoride, L-malic acid and water. In the anodic oxidation electrolyte, the volume percentage of glycerol is 90 vol%, the concentration of ammonium fluoride is 0.1~0.15 mol / L, and the concentration of L-malic acid is 0.1~0.15 mol / L.

2. A method for preparing the anodic oxidation electrolyte according to claim 1, characterized in that, Includes the following steps: Prepare an aqueous solution of ammonium fluoride with a concentration of 0.1 mol / L and an aqueous solution of L-malic acid with a concentration of 0.1 mol / L for later use; Glycerol, ammonium fluoride aqueous solution and L-malic acid aqueous solution are mixed at volume percentages of 90%, 9-9.5% and 1-0.5% respectively, and the sum of the volume percentages of the three is 100% to obtain the anodic oxidation electrolyte.

3. The application of the anodic oxidation electrolyte according to claim 1 in the preparation of titanium dioxide nanotubes.

4. The application of the anodic oxidation electrolyte according to claim 3 in the preparation of titanium dioxide nanotubes, characterized in that, The application method is as follows: Using a titanium sample as the anode and a non-titanium sample as the cathode, the anode and cathode were placed together in the anodic oxidation electrolyte and electrically connected to the power supply by a wire, and constant voltage oxidation was carried out at room temperature.

5. The application of the anodic oxidation electrolyte according to claim 4 in the preparation of titanium dioxide nanotubes, characterized in that, The constant-pressure oxidation is performed at a voltage of 120V for a time of 2 to 2.5 hours.

6. The application of the anodic oxidation electrolyte according to claim 4 in the preparation of titanium dioxide nanotubes, characterized in that, The non-titanium sample is a non-titanium metal sample or a carbon material.

7. The application of the anodic oxidation electrolyte according to claim 6 in the preparation of titanium dioxide nanotubes, characterized in that, The non-titanium metal sample is selected from nickel, copper, iron, or chromium samples.

8. The application of the anodic oxidation electrolyte according to claim 6 in the preparation of titanium dioxide nanotubes, characterized in that, The carbon material is selected from graphite, graphene, or carbon black.

9. The application of the anodic oxidation electrolyte according to claim 4 in the preparation of titanium dioxide nanotubes, characterized in that, The titanium sample was subjected to surface cleaning treatment before use. The specific treatment method was as follows: the titanium metal was successively subjected to grinding, alkaline washing, acid washing and ultrasonic cleaning to obtain the titanium sample.

10. The application of the anodic oxidation electrolyte according to claim 9 in the preparation of titanium dioxide nanotubes, characterized in that, The polishing process involves sequentially polishing the titanium sheet with sandpaper of grades 180#, 320#, 600#, 1200#, and 2000# to obtain polished titanium. The alkaline washing process is as follows: Immerse the polished titanium in a 5 mol / L NaOH solution at 60-65℃ for 5-6 minutes, then wash with water until neutral to obtain alkaline-washed titanium; The pickling process is as follows: a mixture of hydrofluoric acid, concentrated nitric acid, and distilled water is used as the pickling solution to clean the alkaline titanium until the sample surface is completely white. The sample is then washed with water until it is neutral to obtain the pickled titanium. The volume ratio of hydrofluoric acid, concentrated nitric acid, and distilled water is 2 mL: 3 mL: 10 mL. The ultrasonic cleaning procedure is as follows: acid-washed titanium is ultrasonically cleaned in ethanol for 15-20 minutes to obtain a titanium sample.

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