A micro-arc oxidation solution for aluminum alloy and its micro-arc oxidation process

Abstract

This invention relates to the field of micro-arc oxidation technology and discloses a micro-arc oxidation solution for aluminum alloys and its micro-arc oxidation process. Phytic acid and hydroxylated carbon nanotubes undergo a hydrothermal reaction, resulting in a chemical bonding reaction that grafts phytic acid structures onto the surface of the carbon nanotubes. This improves the dispersibility of carbon nanotubes in the micro-arc oxidation solution and alleviates the agglomeration problem, facilitating subsequent micro-arc oxidation treatment. Phytic acid-modified carbon nanotubes are used as an additive, compounded with sodium silicate, sodium fluoride, glycerol, etc., to optimize the micro-arc oxidation solution formulation and process. A ceramic layer is formed on the aluminum alloy surface. The addition of carbon nanotubes improves the wear resistance and strength of the ceramic layer. Furthermore, the abundant phosphate groups in the phytic acid grafted onto the carbon nanotubes can coordinate and chelate with Al on the aluminum alloy surface, thereby improving the bonding force and strength between the ceramic layer and the aluminum alloy.

Description

Technical Field

[0001] This invention relates to the field of micro-arc oxidation technology, specifically to a micro-arc oxidation liquid for aluminum alloys and its micro-arc oxidation process. Background Technology

[0002] Aluminum alloys possess excellent mechanical properties, chemical stability, and processing performance, making them widely used in industries such as construction, transportation, and aerospace. However, aluminum alloys also have some drawbacks, such as high wear resistance, high coefficient of friction, and significant wear, which limit their application areas. Micro-arc oxidation technology is used to treat the surface of aluminum alloys, causing a phase structure change in the amorphous oxide layer on the surface, generating a unique dense ceramic film with high microhardness, high wear resistance, and high corrosion resistance.

[0003] Micro-arc oxidation solutions mainly consist of silicates, conductive agents, passivating agents, and additives, which significantly influence the performance of the micro-arc oxidation ceramic layer formed on aluminum alloy surfaces. Carbon nanotubes possess excellent mechanical strength, high chemical stability, and strong heat resistance, making them promising candidates for application in micro-arc oxidation processes. For example, the study "Preparation of Magnesium-based Hydroxyapatite / Carbon Nanotube Composite Bio-coating by Micro-arc Oxidation and Its Performance Research" describes the preparation of hydroxyapatite / carbon nanotube nanocomposite powder via chemical precipitation, which was then used as an additive in the electrolyte. This powder was then used to prepare a composite active coating on magnesium alloy surfaces using micro-arc oxidation, resulting in improved bioactivity and corrosion resistance. This invention aims to utilize phytic acid to treat the surface of carbon nanotubes, using it as an additive in the micro-arc oxidation solution to form a ceramic layer with high wear resistance and strength on aluminum alloy surfaces. Summary of the Invention

[0004] (a) Technical problems to be solved

[0005] This invention provides a micro-arc oxidation liquid containing phytic acid-modified carbon nanotubes, which optimizes the micro-arc oxidation process and forms a ceramic layer with high wear resistance and high strength on the surface of aluminum alloy.

[0006] (II) Technical Solution

[0007] The preparation process of an aluminum alloy micro-arc oxidation solution is as follows:

[0008] (1) Disperse hydroxylated carbon nanotubes in an aqueous solution of phytic acid, and carry out hydrothermal reaction in an aqueous reaction vessel at 100-140℃ for 24-48h. After the reaction, filter the solvent and wash with deionized water to obtain phytic acid modified carbon nanotubes.

[0009] (2) Add phytic acid-modified carbon nanotubes to deionized water, stir and disperse to prepare a solution with a concentration of 1-3 g / L, and then add sodium silicate, inorganic alkali, sodium fluoride, glycerol and sodium dodecylbenzene sulfonate in sequence. Stir and dissolve to prepare an aluminum alloy micro-arc oxidation solution.

[0010] Preferably, the amount of hydroxylated carbon nanotubes used is 5-30% of phytic acid.

[0011] Preferably, the concentration of sodium silicate in the aluminum alloy micro-arc oxidation solution is 9-15 g / L.

[0012] Preferably, the concentration of inorganic alkali in the aluminum alloy micro-arc oxidation solution is 1.5-5 g / L, and the inorganic alkali includes potassium hydroxide or sodium hydroxide.

[0013] Preferably, the concentration of sodium fluoride in the micro-arc oxidation solution of the aluminum alloy is 2-4 g / L.

[0014] Preferably, the concentration of glycerol in the aluminum alloy micro-arc oxidation solution is 1-2.5 g / L.

[0015] Preferably, the concentration of sodium dodecylbenzenesulfonate in the aluminum alloy micro-arc oxidation solution is 2-4 g / L.

[0016] Preferably, the micro-arc oxidation process using aluminum alloy micro-arc oxidation solution is as follows:

[0017] The aluminum alloy surface is polished until smooth, then acetone is added for degreasing. A constant current micro-arc oxidation equipment is then used to perform micro-arc oxidation treatment on the aluminum alloy surface, with the operating current controlled at 3-6 A / dm². 2 The voltage is 400-600V, the power supply frequency is 500-1000Hz, the duty cycle is 6-10%, and the micro-arc oxidation treatment time is 10-30min.

[0018] (III) Beneficial Technical Effects

[0019] Phytic acid and hydroxylated carbon nanotubes undergo a hydrothermal reaction to form a chemical bond, grafting phytic acid structures onto the surface of carbon nanotubes. This improves the dispersibility of carbon nanotubes in the micro-arc oxidation solution, alleviates the aggregation problem of carbon nanotubes, and facilitates subsequent micro-arc oxidation treatment.

[0020] Phytic acid-modified carbon nanotubes were used as an additive, compounded with sodium silicate, sodium fluoride, glycerol, etc., to optimize the micro-arc oxidation liquid formula and micro-arc oxidation process, forming a ceramic layer on the aluminum alloy surface. The addition of carbon nanotubes improved the wear resistance and strength of the ceramic layer. Furthermore, the abundant phosphate groups of phytic acid grafted onto the carbon nanotubes could coordinate and chelate with Al on the aluminum alloy surface, thereby improving the bonding force and bonding strength between the ceramic layer and the aluminum alloy. Detailed Implementation

[0021] Example 1

[0022] (1) 0.1g of hydroxylated carbon nanotubes were dispersed in an aqueous solution containing 2g of phytic acid. The solution was placed in an aqueous reaction vessel and subjected to a hydrothermal reaction at 120°C for 48h. After the reaction, the solvent was filtered and the solution was washed with deionized water to obtain phytic acid-modified carbon nanotubes.

[0023] (2) Phytic acid-modified carbon nanotubes were added to deionized water and stirred to disperse them, resulting in a solution with a concentration of 1 g / L. Then, sodium silicate, potassium hydroxide, sodium fluoride, glycerol, and sodium dodecylbenzenesulfonate were added sequentially and stirred to dissolve, thus preparing an aluminum alloy micro-arc oxidation solution. The concentration of sodium silicate was controlled at 15 g / L, the concentration of potassium hydroxide at 3 g / L, the concentration of sodium fluoride at 4 g / L, the concentration of glycerol at 1 g / L, and the concentration of sodium dodecylbenzenesulfonate at 2 g / L.

[0024] (3) Grind the aluminum alloy surface until smooth, then add acetone for degreasing. Use a constant current micro-arc oxidation device to perform micro-arc oxidation treatment on the aluminum alloy surface, controlling the working current to be 3A / dm. 2 The voltage was 400V, the power supply frequency was 800Hz, the duty cycle was 7%, and the micro-arc oxidation treatment time was 30min.

[0025] Example 2

[0026] (1) 0.2g of hydroxylated carbon nanotubes were dispersed in an aqueous solution containing 2g of phytic acid. The solution was placed in an aqueous reaction vessel and subjected to a hydrothermal reaction at 100℃ for 48h. After the reaction, the solvent was filtered and the solution was washed with deionized water to obtain phytic acid modified carbon nanotubes.

[0027] (2) Phytic acid-modified carbon nanotubes were added to deionized water and stirred to disperse them, resulting in a solution with a concentration of 3 g / L. Then, sodium silicate, potassium hydroxide, sodium fluoride, glycerol, and sodium dodecylbenzenesulfonate were added sequentially and stirred to dissolve, thus preparing an aluminum alloy micro-arc oxidation solution. The concentration of sodium silicate was controlled at 9 g / L, the concentration of potassium hydroxide at 5 g / L, the concentration of sodium fluoride at 3 g / L, the concentration of glycerol at 2 g / L, and the concentration of sodium dodecylbenzenesulfonate at 2 g / L.

[0028] (3) Grind the aluminum alloy surface until smooth, then add acetone for degreasing. Use a constant current micro-arc oxidation device to perform micro-arc oxidation treatment on the aluminum alloy surface, controlling the working current to be 5A / dm. 2 The voltage was 500V, the power supply frequency was 1000Hz, the duty cycle was 10%, and the micro-arc oxidation treatment time was 10min.

[0029] Example 3

[0030] (1) 0.5g of hydroxylated carbon nanotubes were dispersed in an aqueous solution containing 2g of phytic acid. The solution was placed in an aqueous reaction vessel and subjected to a hydrothermal reaction at 140℃ for 24h. After the reaction, the solvent was filtered and the solution was washed with deionized water to obtain phytic acid modified carbon nanotubes.

[0031] (2) Phytic acid-modified carbon nanotubes were added to deionized water and stirred to disperse them, resulting in a solution with a concentration of 1 g / L. Then, sodium silicate, sodium hydroxide, sodium fluoride, glycerol, and sodium dodecylbenzenesulfonate were added sequentially and stirred to dissolve, thus preparing an aluminum alloy micro-arc oxidation solution. The concentration of sodium silicate was controlled at 12 g / L, sodium hydroxide at 5 g / L, sodium fluoride at 3 g / L, glycerol at 2.5 g / L, and sodium dodecylbenzenesulfonate at 4 g / L.

[0032] (3) Grind the aluminum alloy surface until smooth, then add acetone for degreasing. Use a constant current micro-arc oxidation device to perform micro-arc oxidation treatment on the aluminum alloy surface, controlling the working current to be 6A / dm. 2 The voltage was 600V, the power supply frequency was 1000Hz, the duty cycle was 10%, and the micro-arc oxidation treatment time was 20min.

[0033] Example 4

[0034] (1) 0.6g of hydroxylated carbon nanotubes were dispersed in an aqueous solution containing 2g of phytic acid. The solution was placed in an aqueous reaction vessel and subjected to a hydrothermal reaction at 120℃ for 24h. After the reaction, the solvent was filtered and the solution was washed with deionized water to obtain phytic acid modified carbon nanotubes.

[0035] (2) Phytic acid-modified carbon nanotubes were added to deionized water and stirred to disperse them, resulting in a solution with a concentration of 2 g / L. Then, sodium silicate, potassium hydroxide, sodium fluoride, glycerol, and sodium dodecylbenzenesulfonate were added sequentially and stirred to dissolve, thus preparing an aluminum alloy micro-arc oxidation solution. The concentration of sodium silicate was controlled at 10 g / L, the concentration of potassium hydroxide at 1.5 g / L, the concentration of sodium fluoride at 4 g / L, the concentration of glycerol at 1 g / L, and the concentration of sodium dodecylbenzenesulfonate at 4 g / L.

[0036] (3) Grind the aluminum alloy surface until smooth, then add acetone for degreasing. Use a constant current micro-arc oxidation device to perform micro-arc oxidation treatment on the aluminum alloy surface, controlling the working current to be 3A / dm. 2 The voltage was 400V, the power supply frequency was 1000Hz, the duty cycle was 6%, and the micro-arc oxidation treatment time was 20min.

[0037] Example 5

[0038] (1) 0.2g of hydroxylated carbon nanotubes were dispersed in an aqueous solution containing 2g of phytic acid. The solution was placed in an aqueous reaction vessel and subjected to a hydrothermal reaction at 100℃ for 48h. After the reaction, the solvent was filtered and the solution was washed with deionized water to obtain phytic acid modified carbon nanotubes.

[0039] (2) Phytic acid-modified carbon nanotubes were added to deionized water and stirred to disperse them, resulting in a solution with a concentration of 2 g / L. Then, sodium silicate, sodium hydroxide, sodium fluoride, glycerol, and sodium dodecylbenzenesulfonate were added sequentially and stirred to dissolve, thus preparing an aluminum alloy micro-arc oxidation solution. The concentration of sodium silicate was controlled at 12 g / L, the concentration of sodium hydroxide at 1.5 g / L, the concentration of sodium fluoride at 3 g / L, the concentration of glycerol at 1 g / L, and the concentration of sodium dodecylbenzenesulfonate at 4 g / L.

[0040] (3) Grind the aluminum alloy surface until smooth, then add acetone for degreasing. Use a constant current micro-arc oxidation device to perform micro-arc oxidation treatment on the aluminum alloy surface, controlling the working current to be 3A / dm. 2 The voltage was 400V, the power supply frequency was 500Hz, the duty cycle was 8%, and the micro-arc oxidation treatment time was 20min.

[0041] Example 6

[0042] (1) 0.4 g of hydroxylated carbon nanotubes were dispersed in an aqueous solution containing 2 g of phytic acid. The solution was placed in an aqueous reaction vessel and subjected to a hydrothermal reaction at 120 °C for 48 h. After the reaction, the solvent was filtered and the solution was washed with deionized water to obtain phytic acid modified carbon nanotubes.

[0043] (2) Phytic acid-modified carbon nanotubes were added to deionized water and stirred to disperse them, resulting in a solution with a concentration of 1 g / L. Then, sodium silicate, potassium hydroxide, sodium fluoride, glycerol, and sodium dodecylbenzenesulfonate were added sequentially and stirred to dissolve, thus preparing an aluminum alloy micro-arc oxidation solution. The concentration of sodium silicate was controlled at 15 g / L, the concentration of potassium hydroxide at 5 g / L, the concentration of sodium fluoride at 2 g / L, the concentration of glycerol at 2.5 g / L, and the concentration of sodium dodecylbenzenesulfonate at 3 g / L.

[0044] (3) Grind the aluminum alloy surface until smooth, then add acetone for degreasing. Use a constant current micro-arc oxidation device to perform micro-arc oxidation treatment on the aluminum alloy surface, controlling the working current to be 5A / dm. 2 The voltage was 500V, the power supply frequency was 1000Hz, the duty cycle was 10%, and the micro-arc oxidation treatment time was 20min.

[0045] The wear resistance of the micro-arc oxidation coating on the aluminum alloy surface was tested using a friction and wear testing machine, following the method in GB / T 12444-2006. The adhesion between the micro-arc oxidation coating and the aluminum alloy substrate was tested using an automatic scratch tester. The microhardness of the micro-arc oxidation coating was tested using an HV-1000 micro Vickers hardness tester.

[0046] Average coefficient of friction Binding force (N) Microhardness (Hv) Example 1 0.32 94 1236 Example 2 0.30 79 946 Example 3 0.26 82 860 Example 4 0.39 86 965 Example 5 0.29 90 1104 Example 6 0.37 76 972

Claims

1. A micro-arc oxidation solution for aluminum alloys, characterized in that: The preparation process of the aluminum alloy micro-arc oxidation solution is as follows: (1) Disperse hydroxylated carbon nanotubes in an aqueous solution of phytic acid, and carry out a hydrothermal reaction in a hydrothermal reactor at 100-140℃ for 24-48h. After the reaction, filter the solvent and wash with deionized water to obtain phytic acid modified carbon nanotubes. (2) Add phytic acid-modified carbon nanotubes to deionized water, stir and disperse to prepare a solution with a concentration of 1-3 g / L, and then add sodium silicate, inorganic alkali, sodium fluoride, glycerol and sodium dodecylbenzene sulfonate in sequence. Stir and dissolve to prepare an aluminum alloy micro-arc oxidation solution.

2. The micro-arc oxidation solution for aluminum alloys according to claim 1, characterized in that: The amount of hydroxylated carbon nanotubes used is 5-30% of phytic acid.

3. The micro-arc oxidation solution for aluminum alloys according to claim 1, characterized in that: The concentration of sodium silicate in the micro-arc oxidation solution for aluminum alloy is 9-15 g / L.

4. The micro-arc oxidation solution for aluminum alloys according to claim 1, characterized in that: The concentration of inorganic alkali in the micro-arc oxidation solution of aluminum alloy is 1.5-5 g / L, and the inorganic alkali includes potassium hydroxide or sodium hydroxide.

5. The micro-arc oxidation solution for aluminum alloys according to claim 1, characterized in that: The concentration of sodium fluoride in the micro-arc oxidation solution of the aluminum alloy is 2-4 g / L.

6. The micro-arc oxidation solution for aluminum alloys according to claim 1, characterized in that: The concentration of glycerol in the micro-arc oxidation solution for aluminum alloy is 1-2.5 g / L.

7. The micro-arc oxidation solution for aluminum alloys according to claim 1, characterized in that: The concentration of sodium dodecylbenzenesulfonate in the micro-arc oxidation solution for aluminum alloy is 2-4 g / L.

8. A micro-arc oxidation process using the aluminum alloy micro-arc oxidation solution as described in claims 1-7, characterized in that: The micro-arc oxidation process is as follows: The aluminum alloy surface is polished until smooth, then acetone is added for degreasing. A constant current micro-arc oxidation equipment is then used to perform micro-arc oxidation treatment on the aluminum alloy surface, with the operating current controlled at 3-6 A / dm². 2 The voltage is 400-600V, the power supply frequency is 500-1000Hz, the duty cycle is 6-10%, and the micro-arc oxidation treatment time is 10-30min.