CN117626377A - Aluminum alloy surface carbon nano tube composite film and micro-arc oxidation preparation process thereof - Google Patents
Aluminum alloy surface carbon nano tube composite film and micro-arc oxidation preparation process thereof Download PDFInfo
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- 238000007745 plasma electrolytic oxidation reaction Methods 0.000 title claims abstract description 71
- 229910000838 Al alloy Inorganic materials 0.000 title claims abstract description 68
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 66
- 239000002041 carbon nanotube Substances 0.000 title claims abstract description 64
- 229910021393 carbon nanotube Inorganic materials 0.000 title claims abstract description 63
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 239000002131 composite material Substances 0.000 title abstract description 6
- 239000003792 electrolyte Substances 0.000 claims abstract description 46
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims abstract description 27
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims abstract description 24
- KWYUFKZDYYNOTN-UHFFFAOYSA-M Potassium hydroxide Chemical compound [OH-].[K+] KWYUFKZDYYNOTN-UHFFFAOYSA-M 0.000 claims abstract description 24
- 239000002238 carbon nanotube film Substances 0.000 claims abstract description 23
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 claims abstract description 18
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 claims abstract description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000008367 deionised water Substances 0.000 claims abstract description 13
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 13
- 239000010935 stainless steel Substances 0.000 claims abstract description 11
- 229910001220 stainless steel Inorganic materials 0.000 claims abstract description 11
- 239000004115 Sodium Silicate Substances 0.000 claims abstract description 9
- 239000011775 sodium fluoride Substances 0.000 claims abstract description 9
- 235000013024 sodium fluoride Nutrition 0.000 claims abstract description 9
- NTHWMYGWWRZVTN-UHFFFAOYSA-N sodium silicate Chemical compound [Na+].[Na+].[O-][Si]([O-])=O NTHWMYGWWRZVTN-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910052911 sodium silicate Inorganic materials 0.000 claims abstract description 9
- 239000002904 solvent Substances 0.000 claims abstract description 8
- 238000000034 method Methods 0.000 claims description 17
- 239000000956 alloy Substances 0.000 claims description 16
- 238000005530 etching Methods 0.000 claims description 15
- 229910045601 alloy Inorganic materials 0.000 claims description 14
- 230000008569 process Effects 0.000 claims description 14
- 229910000553 6063 aluminium alloy Inorganic materials 0.000 claims description 13
- 230000010287 polarization Effects 0.000 claims description 11
- 230000003647 oxidation Effects 0.000 claims description 7
- 238000007254 oxidation reaction Methods 0.000 claims description 7
- 238000001291 vacuum drying Methods 0.000 claims description 5
- 238000004140 cleaning Methods 0.000 claims description 4
- 238000005260 corrosion Methods 0.000 abstract description 27
- 230000007797 corrosion Effects 0.000 abstract description 24
- -1 ammonium aluminum carbonate hydroxide Chemical compound 0.000 abstract description 6
- 238000004381 surface treatment Methods 0.000 abstract description 2
- 239000010410 layer Substances 0.000 description 72
- 230000000052 comparative effect Effects 0.000 description 58
- 238000000576 coating method Methods 0.000 description 12
- 239000011248 coating agent Substances 0.000 description 10
- 239000011159 matrix material Substances 0.000 description 10
- 229910018072 Al 2 O 3 Inorganic materials 0.000 description 9
- 239000011148 porous material Substances 0.000 description 8
- 239000000758 substrate Substances 0.000 description 8
- 230000015556 catabolic process Effects 0.000 description 7
- 239000012528 membrane Substances 0.000 description 7
- 238000001341 grazing-angle X-ray diffraction Methods 0.000 description 6
- 239000002994 raw material Substances 0.000 description 5
- 229910002706 AlOOH Inorganic materials 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 238000001228 spectrum Methods 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000005033 Fourier transform infrared spectroscopy Methods 0.000 description 3
- 238000009826 distribution Methods 0.000 description 3
- FAHBNUUHRFUEAI-UHFFFAOYSA-M hydroxidooxidoaluminium Chemical compound O[Al]=O FAHBNUUHRFUEAI-UHFFFAOYSA-M 0.000 description 3
- 229910017089 AlO(OH) Inorganic materials 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N Ammonia Chemical compound N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 2
- 238000001069 Raman spectroscopy Methods 0.000 description 2
- 238000001237 Raman spectrum Methods 0.000 description 2
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
- 238000010521 absorption reaction Methods 0.000 description 2
- 238000004458 analytical method Methods 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 229910052799 carbon Inorganic materials 0.000 description 2
- 125000004432 carbon atom Chemical group C* 0.000 description 2
- 239000000919 ceramic Substances 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000001652 electrophoretic deposition Methods 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 229910021389 graphene Inorganic materials 0.000 description 2
- 238000002329 infrared spectrum Methods 0.000 description 2
- BASFCYQUMIYNBI-UHFFFAOYSA-N platinum Chemical compound [Pt] BASFCYQUMIYNBI-UHFFFAOYSA-N 0.000 description 2
- 238000012360 testing method Methods 0.000 description 2
- 229910000831 Steel Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 150000001408 amides Chemical class 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 238000005452 bending Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 229910001593 boehmite Inorganic materials 0.000 description 1
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 238000005524 ceramic coating Methods 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 238000012512 characterization method Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- ZOMNIUBKTOKEHS-UHFFFAOYSA-L dimercury dichloride Chemical class Cl[Hg][Hg]Cl ZOMNIUBKTOKEHS-UHFFFAOYSA-L 0.000 description 1
- 230000005684 electric field Effects 0.000 description 1
- 238000006056 electrooxidation reaction Methods 0.000 description 1
- 238000002149 energy-dispersive X-ray emission spectroscopy Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 230000003628 erosive effect Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 230000008018 melting Effects 0.000 description 1
- 238000002844 melting Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 230000008520 organization Effects 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 125000004430 oxygen atom Chemical group O* 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 229910052697 platinum Inorganic materials 0.000 description 1
- CHWRSCGUEQEHOH-UHFFFAOYSA-N potassium oxide Chemical compound [O-2].[K+].[K+] CHWRSCGUEQEHOH-UHFFFAOYSA-N 0.000 description 1
- 229910001950 potassium oxide Inorganic materials 0.000 description 1
- 150000003140 primary amides Chemical class 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 238000007712 rapid solidification Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000011780 sodium chloride Substances 0.000 description 1
- 238000007619 statistical method Methods 0.000 description 1
- 239000010959 steel Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- 230000008719 thickening Effects 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/04—Anodisation of aluminium or alloys based thereon
- C25D11/06—Anodisation of aluminium or alloys based thereon characterised by the electrolytes used
-
- C—CHEMISTRY; METALLURGY
- C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
- C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
- C25D11/00—Electrolytic coating by surface reaction, i.e. forming conversion layers
- C25D11/02—Anodisation
- C25D11/026—Anodisation with spark discharge
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- Materials Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Other Surface Treatments For Metallic Materials (AREA)
Abstract
The invention relates to the technical field of aluminum alloy surface treatment, in particular to a carbon nano tube composite film layer on the surface of an aluminum alloy and a micro-arc oxidation preparation process thereof. The micro-arc oxidation preparation process comprises the following steps: immersing an aluminum alloy serving as an anode in electrolyte, and performing micro-arc oxidation on the surface of the aluminum alloy by adopting a direct current pulse micro-arc oxidation device by using a stainless steel container as a cathode to obtain a carbon nano tube film layer on the surface of the aluminum alloy; the electrolyte comprises the following components: 8-12g/L of sodium silicate, 1.0-3.0g/L of sodium hydroxide, 1.0-3.0g/L of potassium hydroxide, 1.0-3.0g/L of sodium fluoride, 2-5mL/L of triethanolamine, 2-5mL/L of hydrogen peroxide, 1.4-1.6g/L of carbon nano tube and deionized water as solvent. According to the invention, the carbon nano tube and the ammonium aluminum carbonate hydroxide are introduced into the film layer on the surface of the aluminum alloy, so that the corrosion resistance of the film layer is greatly improved.
Description
Technical Field
The invention relates to the technical field of aluminum alloy surface treatment, in particular to a carbon nano tube composite film layer on the surface of an aluminum alloy and a micro-arc oxidation preparation process thereof.
Background
The aluminum alloy material has high specific strength, good electric conductivity and heat conductivity, low density and good processability, and is widely applied to the fields of automobiles, machinery manufacturing industry, large ships, aviation, aerospace and the like. However, in the practical application process, the service life of the aluminum alloy is seriously shortened due to lower corrosion resistance. The ceramic layer is prepared on the surface of the aluminum alloy material in situ by utilizing the micro-arc oxidation technology, so that the direct corrosion of the corrosion medium to the matrix can be effectively organized.
However, during the micro-arc oxidation, the ceramic layer breaks down under the instantaneous high temperature and pressure conditions, thereby generating a large number of pores and micro-cracks, which cause the corrosive medium (O 2 、Cl - 、H 2 O) is liable to enter the substrate surface through these defects, resulting in corrosion of the substrate. In the prior art, the corrosion resistance of the aluminum alloy is generally improved by adopting a method of optimizing electrolyte composition and electric parameters in the micro-arc oxidation process or adopting multilayer coating superposition. By optimizing the electrical parameters in the micro-arc oxidation process, the corrosion current density of the substrate can be reduced by two orders of magnitude, and the corrosion resistance of the substrate still needs to be further improved.
For example, the term et Al tested for phase composition, organization, interfacial adhesion strength, etc. by varying the negative voltage value, which indicated that different negative voltages resulted in α -Al 2 O 3 Is different in content, when negative voltage is-100V, alpha-Al 2 O 3 The porosity of the coating surface is significantly reduced by two orders of magnitude below the substrate (Xiang M Z, li T L, zhao Y, et al The Influence of Negative Voltage on Corrosion Behavior of Ceramic Coatings Prepared by MAO Treatment on Steel. Coatings. 2022, 12:710.).
Patent CN113981502A discloses an aluminum alloy surface corrosion-resistant antifriction composite coating, which comprises a micro-arc oxidation coating and an electrophoretic deposition coating, wherein the micro-arc oxidation coating is covered on an aluminum alloy substrate, the micro-arc oxidation coating is porous, the electrophoretic deposition coating is covered on the porous, and the obtained coating with a double-layer structure can obviously improve the corrosion resistance of the aluminum alloy and reduce the corrosion current density by three orders of magnitude compared with a substrate. However, there is a greater risk of flaking between the bilayer structure coatings, and the degree of improvement in corrosion resistance of aluminum alloys is limited by the way of adding only the coating. Further research is still needed on how to further improve the corrosion resistance of the surface film layer.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide the carbon nano tube composite film layer on the surface of the aluminum alloy, and by adding a certain amount of carbon nano tubes into the electrolyte and combining with the adjustment of other components of the electrolyte, the carbon nano tubes and the ammonium aluminum carbonate hydroxide are introduced into the film layer, so that the corrosion resistance of the film layer is greatly improved; the invention also provides a micro-arc oxidation preparation process.
One of the objects of the present invention is:
the micro-arc oxidation preparation process of the carbon nano tube film layer on the surface of the aluminum alloy comprises the following steps:
immersing an aluminum alloy serving as an anode in electrolyte, and performing micro-arc oxidation on the surface of the aluminum alloy by adopting a direct current pulse micro-arc oxidation device by using a stainless steel container as a cathode to obtain a carbon nano tube film layer on the surface of the aluminum alloy;
the electrolyte comprises the following components: 8-12g/L of sodium silicate, 1.0-3.0g/L of sodium hydroxide, 1.0-3.0g/L of potassium hydroxide, 1.0-3.0g/L of sodium fluoride, 2-5mL/L of triethanolamine, 2-5mL/L of hydrogen peroxide, 1.4-1.6g/L of carbon nano tube and deionized water as solvent.
Most preferably, the electrolyte composition is: 10g/L of sodium silicate, 2.0g/L of sodium hydroxide, 2.0g/L of potassium hydroxide, 2.0g/L of sodium fluoride, 3mL/L of triethanolamine, 3mL/L of hydrogen peroxide and 1.5g/L of carbon nano tube, and the solvent is deionized water.
Unlike conventional electrolyte composition, the present invention has the advantages of sodium silicate, sodium hydroxide and hydrogenOn the basis of conventional components of potassium oxide, sodium fluoride and the like, triethanolamine and hydrogen peroxide (H) are also added 2 O 2 ) And Carbon Nanotubes (CNTs). In the micro-arc oxidation process, on one hand, CNTs enter the film layer in a micro-arc oxidation mode, so that breakdown voltage can be reduced, and corrosion resistance of the film layer is improved. On the other hand, al in the aluminum alloy matrix 3+ With O in electrolyte 2- And OH (OH) - Reacting to generate AlOOH (boehmite); the bond energy of C-N bond in triethanolamine is smaller, bond breaking occurs under certain condition, and the triethanolamine is combined with active oxygen atoms to generate an amide bond structure (-NH-CO-NH-), and under the instantaneous high-temperature and high-pressure environment, the structure can generate ammonia (NH) due to hydrolysis reaction 3 ) The method comprises the steps of carrying out a first treatment on the surface of the Simultaneous CNTs with H 2 O 2 O generated under discharge conditions 2 React with chiral carbon atoms (C) to form CO 2 ；NH 3 、CO 2 Further reacts with AlOOH to obtain NH 4 AlO（OH）HCO 3 I.e. Aluminum Ammonium Carbonate Hydroxide (AACH). The generated AACH has a 'rod-shaped' structure and is distributed around the holes of the micro-arc oxidation film layer, so that the AACH can prevent corrosive medium (O 2 、Cl - 、H 2 O) enters the surface of the matrix through these defects, thereby further improving the corrosion resistance of the aluminum alloy matrix.
The specific reaction process is as follows:
Al→Al 3+ +3e - ；
2H 2 O 2 →2O 2- +4H + +O2↑；
H 2 O→H + +OH - ；
Al 3+ +O 2- +OH - →AlOOH↓；
C * +O 2 →CO 2 ；
NH 3 +H 2 O→NH 4 + +OH - ；
CO 2 +H 2 O→HCO 3 - +H + ；
AlOOH+HCO 3 - +NH 4 + →NH 4 AlO(OH)HCO 3 。
preferably, the aluminum alloy is 6063 aluminum alloy.
Preferably, the operating parameters of the micro-arc oxidation are: the working mode adopts constant voltage, positive voltage is 380-420V, negative voltage is 48-52V, working frequency is 350-450HZ, positive-negative pulse ratio is 1:1, positive duty ratio is 30-35%, negative duty ratio is 20-25%, and oxidation time is 10-20min.
Most preferably, the operating parameters of the micro-arc oxidation are: the working mode adopts constant voltage, positive voltage 400V, negative voltage 50V, working frequency 400HZ, positive and negative pulse ratio 1:1, positive duty ratio 35%, negative duty ratio 25% and oxidation time 15min.
Preferably, in the micro-arc oxidation process, the temperature of electrolyte in the stainless steel container is below 25 ℃.
Preferably, after the micro-arc oxidation is finished, the 6063 aluminum alloy subjected to the micro-arc oxidation treatment is washed by deionized water, and vacuum drying is carried out for 1-5 hours at the temperature of 60-90 ℃ to obtain the carbon nanotube film layer on the surface of the aluminum alloy.
The second object of the present invention is:
provides the aluminum alloy surface carbon nano tube film layer prepared by the micro-arc oxidation preparation process, and the self-corrosion current density is lower than 8 multiplied by 10 -8 A/cm 2 The polarization impedance value is more than 3 multiplied by 10 6 Ω·cm 2 。
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the invention, a certain amount of carbon nanotubes are added into the electrolyte, and the carbon nanotubes are introduced into the film layer on the surface of the aluminum alloy, so that the breakdown voltage can be reduced, and the corrosion resistance of the film layer can be improved;
(2) The invention also adjusts the components of the electrolyte, and on the basis of adding the carbon nano tube, triethanolamine and hydrogen peroxide are also introduced, each component in the electrolyte reacts in the micro-arc oxidation process to generate aluminum ammonium carbonate hydroxide, the aluminum ammonium carbonate hydroxide takes a 'rod-shaped' structure and is distributed around the holes of the micro-arc oxidation film layer, thus being capable of preventing corrosive medium (O 2 、Cl - 、H 2 O) entering the radicals through these defectsThe body surface is further improved in corrosion resistance of the aluminum alloy matrix;
(3) The self-corrosion current density of the carbon nanotube film layer on the surface of the aluminum alloy obtained by the micro-arc oxidation preparation process is lower than 8 multiplied by 10 -8 A/cm 2 The polarization impedance value is more than 3 multiplied by 10 6 Ω·cm 2 。
Drawings
FIG. 1 is a microscopic morphology of the aluminum alloy surface film prepared in example 1 and comparative examples 1-3; in fig. 1, (a) represents comparative example 1, (b) represents comparative example 2, (c) represents example 1, and (d) represents comparative example 3;
FIG. 2 is a graph showing pore size distribution morphology of the aluminum alloy surface film layers prepared in example 1 and comparative examples 1-3; in fig. 2, (a) represents comparative example 1, (b) represents comparative example 2, (c) represents example 1, and (d) represents comparative example 3;
FIG. 3 is a graph showing the microscopic morphology of the aluminum alloy surface film layers prepared in example 1 and comparative examples 1, 4-5; in FIG. 3, (a) represents comparative example 1, (b) represents comparative example 4, (c) represents comparative example 5, and (d) represents example 1;
FIG. 4 is XRD patterns of the surface film layers of the aluminum alloys prepared in example 1 and comparative examples 1 to 3;
FIG. 5 is a Raman spectrum of the aluminum alloy surface film layers prepared in example 1 and comparative examples 1-3, prepared in example 1;
FIG. 6 is a GIXRD spectrum of the surface film layer of the aluminum alloy prepared in example 1;
fig. 7 is an infrared spectrum of the aluminum alloy surface film layer prepared in example 1.
Detailed Description
The invention is further described below with reference to the drawings and examples. The raw materials used in the examples, unless otherwise specified, were all commercially available conventional raw materials; the process used in the examples, unless otherwise specified, is conventional in the art.
Example 1
A micro-arc oxidation preparation process of a carbon nano tube film layer on the surface of an aluminum alloy comprises the following steps:
the electrolyte is prepared from the following raw materials: 10g/L of sodium silicate, 2.0g/L of sodium hydroxide, 2.0g/L of potassium hydroxide, 2.0g/L of sodium fluoride, 3mL/L of triethanolamine, 3mL/L of hydrogen peroxide and 1.5g/L of carbon nano tube, and the solvent is deionized water;
immersing 6063 aluminum alloy as an anode in electrolyte, taking a stainless steel container as a cathode, carrying out micro-arc oxidation on the surface of the 6063 aluminum alloy by adopting a direct current pulse micro-arc oxidation device, wherein the micro-arc oxidation work mode adopts constant voltage, positive voltage is 400V, negative voltage is 50V, working frequency is 400HZ, positive and negative pulse ratio is 1:1, positive duty ratio is 35%, negative duty ratio is 25%, oxidation time is 15min, and the temperature of the electrolyte in the stainless steel container is below 25 ℃ in the micro-arc oxidation process;
and cleaning the 6063 aluminum alloy subjected to the micro-arc oxidation treatment by deionized water, and vacuum drying at 80 ℃ for 3 hours to obtain the carbon nanotube film layer on the surface of the aluminum alloy.
Example 2
A micro-arc oxidation preparation process of a carbon nano tube film layer on the surface of an aluminum alloy comprises the following steps:
the electrolyte is prepared from the following raw materials: 8g/L of sodium silicate, 1.0g/L of sodium hydroxide, 1.0g/L of potassium hydroxide, 1.0g/L of sodium fluoride, 1mL/L of triethanolamine, 2mL/L of hydrogen peroxide and 1.4g/L of carbon nano tube, and the solvent is deionized water;
immersing 6063 aluminum alloy as an anode in electrolyte, taking a stainless steel container as a cathode, carrying out micro-arc oxidation on the surface of the 6063 aluminum alloy by adopting a direct current pulse micro-arc oxidation device, wherein the micro-arc oxidation work mode adopts constant voltage, positive voltage is 420V, negative voltage is 52V, working frequency is 450HZ, positive and negative pulse ratio is 1:1, positive duty ratio is 35%, negative duty ratio is 25%, oxidation time is 20min, and the temperature of the electrolyte in the stainless steel container is below 25 ℃ in the micro-arc oxidation process;
and cleaning the 6063 aluminum alloy subjected to the micro-arc oxidation treatment by deionized water, and vacuum drying at 70 ℃ for 5 hours to obtain the carbon nanotube film layer on the surface of the aluminum alloy.
Example 3
A micro-arc oxidation preparation process of a carbon nano tube film layer on the surface of an aluminum alloy comprises the following steps:
the electrolyte is prepared from the following raw materials: 12g/L of sodium silicate, 3.0g/L of sodium hydroxide, 3.0g/L of potassium hydroxide, 3.0g/L of sodium fluoride, 5mL/L of triethanolamine, 5mL/L of hydrogen peroxide and 1.6g/L of carbon nano tube, and the solvent is deionized water;
immersing 6063 aluminum alloy as an anode in electrolyte, taking a stainless steel container as a cathode, carrying out micro-arc oxidation on the surface of the 6063 aluminum alloy by adopting a direct current pulse micro-arc oxidation device, wherein the micro-arc oxidation work mode adopts constant voltage, positive voltage is 380V, negative voltage is 48V, working frequency is 350HZ, positive and negative pulse ratio is 1:1, positive duty ratio is 30%, negative duty ratio is 20%, oxidation time is 10min, and the temperature of the electrolyte in the stainless steel container is below 25 ℃ in the micro-arc oxidation process;
and cleaning the 6063 aluminum alloy subjected to the micro-arc oxidation treatment by deionized water, and vacuum drying for 1h at the temperature of 90 ℃ to obtain the carbon nanotube film layer on the surface of the aluminum alloy.
Comparative example 1
The present comparative example differs from example 1 only in that no carbon nanotubes were added to the electrolyte, i.e., the concentration of carbon nanotubes in the electrolyte was 0g/L.
Comparative example 2
The present comparative example differs from example 1 only in that the concentration of carbon nanotubes in the electrolyte was changed to 1.0g/L.
Comparative example 3
The present comparative example differs from example 1 only in that the concentration of carbon nanotubes in the electrolyte was changed to 2.0g/L.
Comparative example 4
The present comparative example differs from example 1 only in that no hydrogen peroxide was added to the electrolyte.
Comparative example 5
The present comparative example differs from example 1 only in that no triethanolamine was added to the electrolyte.
The aluminum alloy surface film layers obtained in the above examples and comparative examples were characterized and tested as follows, wherein: observing the microscopic morphology of the film layer by adopting a quata 250 field emission environment scanning electron microscope; carrying out statistical analysis on the surface pores of the film layer by adopting Image Pro software; WJGS-009X-ray diffractometer manufactured by Bruker AXS, germany, was used for grazing incidenceXRD (GIXRD), raman spectrometer detects the phase of the film; detecting functional groups possibly existing in the film layer by adopting a Fourier transform infrared spectrometer (FT-IR) produced by the high-power instrument company of thermoelectric Nile in the United states; electrochemical testing is carried out on the membrane layer by adopting a CHI660E type electrochemical workstation, wherein a three-electrode system respectively uses a sample as a working electrode, a platinum sheet as an auxiliary electrode and the area is 1cm 2 The reference electrode was a saturated calomel electrode, using a NaCl solution with a concentration of 3.5wt.% as the corrosion medium.
The performance characterization and test results are as follows:
1. in order to observe the influence of the CNTs addition amount in the electrolyte on the film microstructure, a quata 250 field emission environment scanning electron microscope is used to observe the film microstructure of the aluminum alloy surface films prepared in example 1 and comparative examples 1-3, as shown in FIG. 1, (a) represents comparative example 1, (b) represents comparative example 2, (c) represents example 1, and (d) represents comparative example 3.
As can be seen from fig. 1, the film layer without CNTs added in the electrolyte of comparative example 1 has smoother surface, more micropores and uniform size, because the breakdown process is accompanied by discharge and gas release, resulting in a large number of micropores; at the same time, around the micropores, there are some smooth areas, which are formed by the rapid solidification of the electrolyte after the matrix alloy is melted and flows out through the pore channels under the condition of instantaneous high temperature. The concentrations of CNTs added to the electrolytes of comparative examples 2, 1 and 3 were 1.0g/L, 1.5g/L and 2.0g/L, respectively, and it can be seen that the surface of the membrane layer was rough, the size of micropores was large and the pore size was uneven as compared with comparative example 1 without CNTs added; when the addition amount of CNTs is 1.5g/L, the quality of the prepared film layer is better. When the addition amount of CNTs is increased to 2.0g/L, even microcracks appear on the surface of the film layer, because CNTs have good conductivity, the larger the addition amount is, the larger the conductivity of electrolyte is, and the current density on the surface of a sample is increased continuously while the voltage is increased continuously, so that the breakdown and the microcracks on the surface of the film layer are formed; meanwhile, the surface appearance of the film layer is very rough, and the film layer presents an irregularly distributed volcano-shaped structure, and the analysis reason is that in the reaction process, gas generated in the film layer escapes through a plurality of channels, and the generated outer surface layer is relatively loose, so that in the high-temperature and high-pressure environment, the melt in the film layer is sprayed outwards through micropores to form the volcano-shaped film layer.
2. In order to observe and count the surface pores of the film more intuitively, image Pro software is adopted to process the microscopic morphology graphs of the surface film of the aluminum alloy prepared in the example 1 and the comparative examples 1-3 to obtain the pore size distribution morphology graph, as shown in fig. 2, (a) represents the comparative example 1, (b) represents the comparative example 2, (c) represents the example 1, and (d) represents the comparative example 3.
As can be seen from fig. 2, the surface of the sample subjected to the micro-arc oxidation treatment is porous, randomly distributed on the surface, and the size of micropores is increased along with the increase of the concentration of CNTs. At the same time, image Pro software is used for counting the size of micropores on the surface of the membrane layer, and the result shows that after CNTs are added, the macropores on the surface of the membrane layer (the area is more than 5 mu m 2 ) The area ratio of the film layer surface macropore area ratio is obviously higher than that of a sample without CNTs, when the CNTs are respectively added at 1.0g/L and 2.0g/L, the film layer surface macropore area ratio exceeds 10%, and when the CNTs are added at 1.5g/L, the film layer surface macropore area ratio is only 8.81%, and the macropore area ratio is less, so that the corrosion of more corrosive mediums to a matrix can be effectively prevented, thereby improving the corrosion resistance.
3. In order to analyze the influence of the CNTs addition amount in the electrolyte on the film thickness, the film thicknesses of the aluminum alloy surfaces prepared in the example 1 and the comparative examples 1-3 are analyzed by adopting a quata 250 field emission environment scanning electron microscope, and the film thicknesses of the comparative examples 1, 2, 1 and 3 are as follows: 6.146 μm, 11.243 μm, 12.075 μm, 13.086 μm.
From the results, the film thickness is increased with the increase of the CNTs addition concentration in the electrolyte; and when the CNTs addition amount is small, the film thickness change is obvious, and the thickness increasing trend is slow along with the gradual increase of the CNTs addition amount. This is related to the discharge during the micro-arc oxidation, and at the initial stage of the micro-arc oxidation, with the continuous increase of the voltage, breakdown occurs in the weak surface area, forming a discharge channel, and the electrolyte is inIons (Al) of negatively charged particles fused with the matrix 3+ 、Si 4+ Etc.), the formed compounds are continuously accumulated, thereby realizing the thickening of the film layer; meanwhile, due to the addition of CNTs, the concentration of the electrolyte is increased, and the voltage rise time is shortened in the same time, so that the subsequent breakdown time is prolonged, and the thickness of a film layer after CNTs are added is larger than that of a film layer without CNTs; as the film layer is thickened, the resistance is increased, and the breakdown discharge becomes difficult, so that the growth rate of the film layer is also gradually slowed down.
4. To observe whether AACH is generated around the film holes and analyze AACH generation conditions, microscopic morphologies of the aluminum alloy surface films prepared in example 1 and comparative examples 4 to 5 were observed using a quata 250 field emission environmental scanning electron microscope, as shown in fig. 3, (a) represents comparative example 1, (b) represents comparative example 4, (c) represents comparative example 5, and (d) represents example 1.
As can be seen from fig. 3, in example 1, in addition to the holes formed by the discharge, some "rod-like" substances were generated on the surface of the micro-arc oxide film layer, and the "rod-like" substances were found to mainly contain C, al, O, N by EDS analysis, and the substances were consistent with the morphology of AACH synthesized by the hydrothermal method, thereby judging that the substances were AACH. The AACH with the 'rod-shaped' structure is covered around the holes, so that the erosion of more corrosive mediums to the matrix can be effectively prevented, and the corrosion resistance is improved. In contrast, the electrolytes of comparative example 1 and comparative examples 4 to 5 were each depleted of CNTs, hydrogen peroxide and triethanolamine, and AACH having a "rod-like" structure was not observed on the surface of the obtained micro-arc oxide film.
5. For analysis of the film phase, the aluminum alloy surface film prepared in example 1 and comparative examples 1 to 3 was characterized by an X-ray diffractometer and a Raman spectrometer, respectively, the XRD spectrum is shown in FIG. 4, and the Raman spectrum is shown in FIG. 5.
As can be seen from FIG. 4, the film layer formed by micro-arc oxidation is mainly Al 2 O 3 The phases, due to the small thickness of the film, the signal of the matrix is too strong to detect other phases, and the Al peak intensity (2θ= 44.73 °) gradually increases with the increase of the CNTs addition amountA reduction; when CNTs were added, a characteristic peak appeared at the 2θ=45.5°, and was found to be AACH after comparison with the standard pdf card.
As can be seen from FIG. 5, 1350cm after CNTs are added to the electrolyte -1 (D) And 1585cm -1 (G) Characteristic peaks appear nearby, and the two peaks are just characteristic peaks of CNTs or graphene, and the combination of signals detected in an XRD spectrum shows that CNTs enter the film layer in a micro-arc oxidation mode and participate in the formation and growth of the film layer.
In addition, the surface film layer of the aluminum alloy prepared in example 1 was characterized by grazing incidence XRD, and the GIXRD spectrum thereof is shown in FIG. 6.
As can be seen from fig. 6, a weak carbon signal was detected at 2θ=31.58°, which suggests that the addition of CNTs to the electrolyte caused an increase in conductivity, and that negatively charged CNTs were cleaved into graphene flakes or active C atoms during plasma discharge. Likewise, the presence of AACH was also found in the GIXRD pattern, which is also consistent with the results of the microscopic morphology. In addition to this, alpha-Al was also detected 2 O 3 Phase and gamma-Al 2 O 3 Phase, alpha-Al 2 O 3 Due to higher hardness and stability, alpha-Al is generated in the film layer 2 O 3 When the amount of the catalyst is more, the performance is relatively better, and the gamma-Al 2 O 3 Is Al 2 O 3 Metastable phases formed at lower temperatures, gamma-Al when the temperature reaches or exceeds 1200 DEG C 2 O 3 Can be converted into alpha-Al 2 O 3 。Al 2 O 3 The phase formation principle is as follows: in the micro-arc oxidation stage, a barrier layer with higher dielectric property is arranged on the surface of the aluminum alloy, and Al is generated during anode melting 3+ And OH in electrolyte - Bonding to form Al (OH) 3 Under the action of electric field, al (OH) 3 Is adsorbed on the metal anode in a moving way, and the instantaneous high temperature in the micro-arc oxidation process can reach 2000-8000K, and a part of Al (OH) 3 Can be dehydrated to form Al due to high temperature 2 O 3 。
Further, the functional groups possibly existing in the surface film layer of the aluminum alloy prepared in example 1 were analyzed by using a fourier transform infrared spectrometer, and the infrared spectrum is shown in fig. 7.
In FIG. 7, at 3425.39cm -1 The peak appearing is the stretching vibration peak of free water at 2923.17cm -1 The sharp peak in the vicinity is methylene-CH 2 -an antisymmetric telescopic vibration peak at 2853.80cm -1 The peak appearing at this point is-CH 2 -symmetrical telescopic vibration peak, 1732.95cm -1 The peak of the stretching vibration, considered as carbonyl c=o, 1628.54cm -1 The corresponding medium intensity peak is considered to be NH in the primary amide 2 Shear vibration absorption peak (amide II peak), 1400.50cm -1 The nearby peak is saturated C-H in-plane bending vibration peak of 1070.72cm -1 Corresponds to the stretching vibration peak of monofluoro, 635.49cm -1 The broad absorption peak appearing is NH 2 Is 447.28 cm -1 The peaks that occur are believed to be caused by lattice distortion or vibrating groups.
6. The surface film layers of the aluminum alloys prepared in examples 1 to 3 and comparative examples 1 to 5 were electrochemically tested using a CHI 660E-type electrochemical workstation, and the polarization resistance values and the corresponding parameters calculated according to the Stern-Geary formula were calculated, and the results are shown in Table 1.
Wherein E is corr Represents self-corrosion potential, b a Representing the anode Tafel coefficient of the sample polarization curve, b c The Tafel coefficient of the cathode of the polarization curve of the sample, I corr Indicating the corrosion current density of the sample, R p Representing the polarization impedance value.
The Stern-Geary formula is as follows: r is R p =（b a ×b c ）/[2.303×（b a +b c ）×I corr ]。
TABLE 1
As can be seen from Table 1, the self-etching potentials of the films of examples 1 to 3 are all more positive than those of the film of comparative example 1 to which CNTs were not added, in terms of self-etching potential; when the addition amount of CNTs in comparative example 3 was 2.0g/L, the self-etching potential of the film was instead negative compared to the film without CNTs in comparative example 1; when the CNTs were added in an amount of 1.0g/L in comparative example 2, the self-etching potential of the film was positive as compared with the film without CNTs added in comparative example 1, but negative as compared with the films of examples 1 to 3; the self-etching potentials of the films of comparative examples 4-5 were all negative compared to the films of examples 1-3. The more negative the self-etching potential, the higher the activity, and the faster the electrochemical etching rate, it can be seen that the film layers of examples 1-3 have slower electrochemical etching rates.
From the self-etching current, the film layers of examples 1-3 all have a self-etching current density of less than 8X10 -8 A/cm 2 1-3 orders of magnitude lower than comparative examples 1-5, and the self-etching current density was minimized when CNTs were added in an amount of 1.5g/L in example 1. The magnitude of the self-etching current also reflects the etching rate, indicating that the film etching rates of examples 1-3 are the slowest than those of comparative examples 1-5.
From the aspect of polarization resistance, the polarization resistance of the film layers of the examples 1-3 is 1-2 orders of magnitude higher than that of the comparative examples 1-5, which shows that the film layers are more difficult to corrode and have stronger electrochemical corrosion resistance; when the addition amount of CNTs in comparative examples 2-3 is 1.0g/L and 2.0g/L, the polarization impedance value of the membrane layer is greatly increased relatively lower than that of comparative example 1, because the effect of CNTs on improving the pore diameter distribution of the membrane layer is not obvious due to the fact that the addition amount of CNTs is too low, and more CNTs are adsorbed on the surface of the membrane layer and cannot enter holes due to the fact that the addition amount of CNTs is too high; the decrease in polarization resistance of the film of comparative examples 4-5 was significant compared to example 1, because the film surface failed to form an aluminum ammonium carbonate hydroxide of "rod-like" structure, which was insufficient in the ability to block the corrosive medium from entering the substrate.
Claims (8)
1. A micro-arc oxidation preparation process of a carbon nano tube film layer on the surface of an aluminum alloy is characterized by comprising the following steps of: the method comprises the following steps:
immersing an aluminum alloy serving as an anode in electrolyte, and performing micro-arc oxidation on the surface of the aluminum alloy by adopting a direct current pulse micro-arc oxidation device by using a stainless steel container as a cathode to obtain a carbon nano tube film layer on the surface of the aluminum alloy;
the electrolyte comprises the following components: 8-12g/L of sodium silicate, 1.0-3.0g/L of sodium hydroxide, 1.0-3.0g/L of potassium hydroxide, 1.0-3.0g/L of sodium fluoride, 2-5mL/L of triethanolamine, 2-5mL/L of hydrogen peroxide, 1.4-1.6g/L of carbon nano tube and deionized water as solvent.
2. The micro-arc oxidation preparation process of the carbon nanotube film layer on the surface of the aluminum alloy, which is characterized by comprising the following steps of: the electrolyte comprises the following components: 10g/L of sodium silicate, 2.0g/L of sodium hydroxide, 2.0g/L of potassium hydroxide, 2.0g/L of sodium fluoride, 3mL/L of triethanolamine, 3mL/L of hydrogen peroxide and 1.5g/L of carbon nano tube, and the solvent is deionized water.
3. The micro-arc oxidation preparation process of the carbon nanotube film layer on the surface of the aluminum alloy, which is characterized by comprising the following steps of: the aluminum alloy is 6063 aluminum alloy.
4. The micro-arc oxidation preparation process of the carbon nanotube film layer on the surface of the aluminum alloy, which is characterized by comprising the following steps of: the operating parameters of the micro-arc oxidation are: the working mode adopts constant voltage, positive voltage is 380-420V, negative voltage is 48-52V, working frequency is 350-450HZ, positive-negative pulse ratio is 1:1, positive duty ratio is 30-35%, negative duty ratio is 20-25%, and oxidation time is 10-20min.
5. The micro-arc oxidation preparation process of the carbon nanotube film on the surface of the aluminum alloy, which is characterized in that: the operating parameters of the micro-arc oxidation are: the working mode adopts constant voltage, positive voltage 400V, negative voltage 50V, working frequency 400HZ, positive and negative pulse ratio 1:1, positive duty ratio 35%, negative duty ratio 25% and oxidation time 15min.
6. The micro-arc oxidation preparation process of the carbon nanotube film layer on the surface of the aluminum alloy, which is characterized by comprising the following steps of: in the micro-arc oxidation process, the temperature of electrolyte in the stainless steel container is below 25 ℃.
7. The micro-arc oxidation preparation process of the carbon nanotube film layer on the surface of the aluminum alloy, which is characterized by comprising the following steps of: and after the micro-arc oxidation is finished, cleaning the 6063 aluminum alloy subjected to the micro-arc oxidation treatment by deionized water, and vacuum drying at 60-90 ℃ for 1-5h to obtain the carbon nanotube film on the surface of the aluminum alloy.
8. An aluminum alloy surface carbon nanotube film obtained by applying the micro-arc oxidation preparation process of the aluminum alloy surface carbon nanotube film as set forth in any one of claims 1 to 7, which is characterized in that: self-etching current density lower than 8×10 -8 A/cm 2 The polarization impedance value is more than 3 multiplied by 10 6 Ω·cm 2 。
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