Aluminum anodic oxidation electrolyte for improving adhesion density of electrode foil oxidation film

Abstract

The invention discloses an aluminum anodic oxidation electrolyte for improving the adhesion density of an electrode foil oxidation film, and relates to the technical field of anodic oxidation, the electrolyte comprises 3%-10% of ammonium dihydrogen phosphate, 0.5%-3% of sulfuric acid, 0.01%-0.2% of nano titanium dioxide or nano aluminum oxide, 0.05%-0.5% of an organic buffer agent, and the balance deionized water; the organic buffering agent is used for stabilizing the pH value in a range of 4.5-6.0; nano titanium dioxide or nano aluminum oxide is used as an oxidation film nucleation center to promote directional crystallization of gamma '-Al2O3; the sulfuric acid component improves the conductivity of the electrolyte; ammonium dihydrogen phosphate generates an aluminum phosphate barrier layer on the surface layer of the oxidation film to enhance the waterproof performance of the film layer; according to the electrolyte, the adhesion density and crystallinity of an oxidation film can be remarkably improved, the uniformity and waterproof performance of a film layer are improved, the specific volume stability and the formation efficiency are improved, and the electrolyte is suitable for continuous production of the high-performance aluminum electrolytic capacitor.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of anodic oxidation, in particular to an aluminum anodic oxidation electrolyte for improving the adhesion density of an oxide film of an electrode foil. BACKGROUND

[0002] Aluminum electrolytic capacitors are widely used in electronic products such as household appliances, communication equipment, power supply devices, etc. due to their high specific capacity, low cost and excellent voltage resistance. The surface oxide film formed on the anode foil as the core electrode material directly affects the leakage current, capacity stability and service life of the capacitor. In the prior art, a dense oxide film is usually generated on the surface of the etched foil through an aluminum anodic oxidation electrolysis process to improve its dielectric properties and formation specific capacity. However, in mass production, the thickness uniformity, density and adhesion of the oxide film are difficult to control stably, resulting in fluctuations in capacitor performance and a decrease in yield.

[0003] Most existing aluminum anodic oxidation electrolysis processes use a high-conductivity formation liquid system to promote the growth of the oxide film through direct current or pulse current. In order to improve the performance of the oxide film, existing technologies attempt to improve it by optimizing the proportion of the formation liquid formula (such as adding organic acid salts, phosphate salts, borate salts, etc.), adjusting the formation current density and temperature curve. However, in large-scale continuous production, there are still differences in the oxidation rate of different areas of the anode foil, especially in the winding or long strip type formation production line, due to the edge effect, uneven current distribution and changes in mass transfer conditions, resulting in inconsistent film thickness distribution, which in turn affects the dielectric constant and film adhesion density.

[0004] Currently, the common problems in domestic formation processes in terms of formation specific capacity yield, oxide film shrinkage control and appearance quality include low formation efficiency, severe oxide film shrinkage, insufficient physical toughness and crack resistance, poor oxide film consistency, and unstable appearance quality. These problems are particularly evident in the anodic oxidation treatment of low-voltage etched foils. Low-voltage formation processes require the generation of high-dielectric-constant film layers under low-voltage conditions, which puts higher requirements on the chemical stability, reaction kinetics and film uniformity of the electrolyte system.

[0005] The formation production process is essentially an anodic oxidation reaction of aluminum foil in a specific electrolyte, which forms a composite oxide film containing high-dielectric-constant components on its surface. This process not only involves the thermodynamic and kinetic control of the oxidation reaction, but also takes into account the diffusion, migration and stability of active components in the electrolyte. The existing formation liquid system still has deficiencies in reaction rate control, film structure regulation and adhesion density improvement, which makes it difficult to meet the requirements of high-performance aluminum electrolytic capacitors for film uniformity and reliability.

[0006] Based on the above, it is found that the existing technology at least has the following technical problems:

[0007] The existing formation liquid system has disadvantages in reaction rate, film structure and adhesion density, and it is difficult to meet the technical problems of high uniformity and high reliability of the film layer required by high-performance aluminum electrolytic capacitors. SUMMARY

[0008] The present application aims to provide an aluminum anodic oxidation electrolyte for improving the adhesion density of the oxide film of the electrode foil, so as to solve the technical problems that the existing formation liquid system has disadvantages in reaction rate, film structure and adhesion density, and it is difficult to meet the technical problems of high uniformity and high reliability of the film layer required by high-performance aluminum electrolytic capacitors.

[0009] The technical effects of the preferred technical solutions in the various technical solutions provided by the present application are described in detail below.

[0010] In order to solve the above technical problems, the present application provides the following technical solutions:

[0011] The present application provides an aluminum anodic oxidation electrolyte for improving the adhesion density of the oxide film of the electrode foil, comprising the following components in mass percentage: 3-10% of ammonium dihydrogen phosphate; 0.5-3% of sulfuric acid; 0.01-0.2% of nano-titanium dioxide or nano-aluminum oxide; 0.05-0.5% of an organic buffer for stabilizing the pH value in the range of 4.5-6.0; and the balance of deionized water; wherein the nano-titanium dioxide or nano-aluminum oxide serves as a nucleation center for promoting the directional crystallization of γ'-Al2O3, and cooperates with the organic buffer to stabilize the reaction environment during the anodic oxidation process, thereby improving the adhesion density, specific capacity and production efficiency of the oxide film.

[0012] In one embodiment, the organic buffer is piperazine, a weak alkaline amino acid salt or a combination thereof.

[0013] In one embodiment, the piperazine is one or more of anhydrous piperazine, piperazine dihydrochloride or piperazine hexahydrate.

[0014] In one embodiment, the weak alkaline amino acid salt is a combination of one or more of sodium glycinate, sodium alaninate, sodium glutamate and sodium aspartate.

[0015] In one embodiment, the particle size of the nano-titanium dioxide or nano-aluminum oxide is less than 50 nm.

[0016] In one embodiment, the electrolyte further contains 0.01-0.1% of a surfactant for improving the dispersibility of the nano-titanium dioxide or nano-aluminum oxide in the electrolyte, preventing particle agglomeration, and improving the nucleation uniformity and adhesion density of the oxide film.

[0017] In one embodiment, the surfactant is a non-ionic or zwitterionic surfactant, including one of polyethylene glycol, alkyl glycoside, betaine.

[0018] In one embodiment, the anodization process conditions are: temperature 60-70℃, current density 0.3-0.4 A / dm 2 2 , treatment time 15-20 minutes.

[0019] Compared with the prior art, the aluminum anodization electrolyte provided by the application has the following beneficial effects:

[0020] (1) Improved film adhesion density and crystallinity

[0021] By introducing 0.01%-0.2% of nano-titanium dioxide or nano-aluminum oxide into the electrolyte, it acts as a nucleation center during oxidation, promoting the directional crystallization of γ'-Al2O3, thereby significantly improving the crystallinity and structural stability of the oxidation film.

[0022] (2) Improved electrolyte conductivity and film generation rate

[0023] By introducing 0.5%-3% of sulfuric acid component into the formula, the overall conductivity of the electrolyte is increased, so that the anodization reaction can also proceed quickly and uniformly under low voltage formation conditions, effectively reducing the film formation speed difference between the edge area and the center area.

[0024] (3) Improved film uniformity and production consistency

[0025] Using 0.05%-0.5% of organic buffer to stabilize the pH value of the electrolyte in the range of 4.5-6.0, avoiding local acid etching and amorphous film generation, reducing film defects, and improving film uniformity and reliability.

[0026] (4) Enhanced film waterproofing ability and service life

[0027] Ammonium dihydrogen phosphate generates an appropriate amount of aluminum phosphate barrier layer on the surface of the oxidation film, effectively inhibiting the migration of water and other oxygen-containing substances, reducing the formation of hydrated aluminum oxide, significantly improving the waterproofing performance of the film layer, and prolonging the service life of the electrode foil.

[0028] (5) Improved specific capacity and formation efficiency

[0029] The optimized film formation environment of the electrolyte improves the dielectric properties of the oxidation film, the specific capacity value has good stability and the fluctuation range is less than ±3%, the formation time can be shortened by 10%-15%, the production efficiency is improved, the number of electrolyte recycling is increased by about 20%, and the production cost is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0030] ​In order to more clearly illustrate the technical solutions of the present application, the following will briefly introduce the drawings needed to be used in the embodiments. Obviously, the drawings described below are only some of the embodiments of the present application, and other drawings can also be obtained by those skilled in the art without any creative effort based on these drawings.

[0031] Figure 1 is one of the surface microstructure electron microscope scanning imaging diagrams of the oxide film generated on the aluminum foil by using the aluminum anodic oxidation electrolyte of the present application;

[0032] Figure 2 is the second of the surface microstructure electron microscope scanning imaging diagrams of the oxide film generated on the aluminum foil by using the aluminum anodic oxidation electrolyte of the present application. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application.

[0034] The specific embodiment provides an aluminum anodic oxidation electrolyte for improving the adhesion density of the oxide film of the electrode foil, which comprises 3% to 10% of ammonium dihydrogen phosphate, 0.5% to 3% of sulfuric acid, 0.01% to 0.2% of nano-titanium dioxide or nano-aluminum oxide, 0.05% to 0.5% of organic buffer, and the rest is deionized water; the organic buffer is used to stabilize the pH value in the range of 4.5 to 6.0; the nano-titanium dioxide or nano-aluminum oxide is used as the nucleation center of the oxide film to promote the directional crystallization of γ'-Al2O3; the sulfuric acid component improves the conductivity of the electrolyte; the ammonium dihydrogen phosphate generates an aluminum phosphate barrier layer on the surface layer of the oxide film to enhance the waterproof performance of the film layer; the electrolyte can significantly improve the adhesion density and crystallinity of the oxide film, improve the uniformity and waterproof performance of the film layer, and improve the specific capacity stability and formation efficiency, and is suitable for the continuous production of high-performance aluminum electrolytic capacitors; and the technical problems that the existing formation liquid system has deficiencies in the reaction rate, film structure and adhesion density and is difficult to meet the high uniformity and high reliability of the film layer required by the high-performance aluminum electrolytic capacitor are effectively solved.

[0035] The first embodiment of the aluminum anodic oxidation electrolyte comprises the following components in the proportion of mass percentage: 3% to 10% of ammonium dihydrogen phosphate; 0.5% to 3% of sulfuric acid; 0.01% to 0.2% of nano-titanium dioxide or nano-aluminum oxide; 0.05% to 0.5% of organic buffer for stabilizing the pH value in the range of 4.5 to 6.0; and the rest is deionized water.

[0036] Among them, the nano-titanium dioxide or nano-aluminum oxide is used as the nucleation center of the oxide film to promote the directional crystallization of γ'-Al2O3, and the organic buffer is used to stabilize the reaction environment in the anodic oxidation process, thereby improving the adhesion density, specific capacity and production efficiency of the oxide film.

[0037] Improve the film adhesion density and crystallinity, by introducing 0.01% to 0.2% of nano-titanium dioxide or nano-aluminum oxide with a particle size of less than 50 nm in the electrolyte, which acts as a nucleation center during oxidation, promoting directional crystallization of γ'-Al2O3, thereby significantly improving the crystallinity and structural stability of the oxide film.

[0038] Improve the electrolyte conductivity and film formation rate, by introducing 0.5% to 3% of sulfuric acid component in the formula, increasing the overall conductivity of the electrolyte, so that the anodic oxidation reaction can also be carried out quickly and uniformly under low voltage formation conditions, effectively reducing the film formation speed difference between the edge area and the center area.

[0039] Improve film uniformity and production consistency, use 0.05% to 0.5% of organic buffer, including piperazine or weakly basic amino acid salt, to stabilize the electrolyte pH value in the range of 4.5 to 6.0, avoid local acid etching and amorphous film formation, reduce film defects, and improve film uniformity and reliability.

[0040] Enhance the waterproofing ability and service life of the film layer, ammonium dihydrogen phosphate generates an appropriate amount of aluminum phosphate barrier layer on the surface of the oxide film, effectively inhibiting the migration of water and other oxygen-containing substances, reducing the formation of hydrated aluminum oxide, and significantly improving the water resistance of the film layer, prolonging the service life of the electrode foil.

[0041] Improve specific capacity and formation efficiency, the optimized film formation environment of the electrolyte improves the dielectric properties of the oxide film, the specific capacity value is stable and the fluctuation range is less than ±3%, the formation time can be shortened by 10% to 15%, the production efficiency is improved, the number of electrolyte recycling is increased by about 20%, and the production cost is reduced.

[0042] As one of the optional embodiments:

[0043] Regarding the composition of the above-mentioned organic buffer: the organic buffer is piperazine (Piperazine), weakly basic amino acid salt or a combination thereof.

[0044] Specifically, piperazine is one or more of anhydrous piperazine (Piperazine, anhydrous), piperazine dihydrochloride (Piperazine dihydrochloride, C4H 10 N2·2HCl) or piperazine hexahydrate (Piperazine hexahydrate, C4H 10 N2·6H2O).

[0045] Specifically, the weakly basic amino acid salt is a combination of one or more of sodium glycinate, sodium alaninate, monosodium glutamate (MSG), and sodium aspartate.

[0046] The organic buffer can be directly dissolved in deionized water in a formula proportion in practical application, and other electrolyte components are sequentially added. The synergistic effect of piperazine and the weakly basic amino acid salt stabilizes the pH value of the electrolyte in the range of 4.5-6.0 in the whole anodic oxidation process, thereby preventing local acid etching and amorphous film formation, ensuring uniform and dense oxidation film, and improving the adhesion density and dielectric properties.

[0047] The stabilizing measure effectively solves the problems of large pH value fluctuation and unstable film quality in the existing formation liquid, and significantly improves the film consistency and the repeatability of production batches.

[0048] The type of the organic buffer can be replaced by other low-toxicity organic compounds having a buffering capacity for the pH value, including tris-hydroxymethyl aminomethane and piperidine derivatives.

[0049] Further, the organic buffer is added in a staged manner or in a solid slow-release coated form, so as to adapt to different production line process tempos.

[0050] The particle size of the nano-titanium dioxide or nano-aluminum oxide is less than 50 nm.

[0051] In application, the nano-titanium dioxide or nano-aluminum oxide needs to be subjected to ultrasonic dispersion treatment before use, so as to ensure uniform distribution of the particles in the electrolyte. In the anodic oxidation process, these nano-particles participate in film formation as nucleation centers, promote directional crystallization of γ'-Al2O3, improve the crystallinity and adhesion density of the film, and inhibit irregular expansion of pores.

[0052] The measure effectively solves the problems of loose film structure and disordered grain arrangement in the existing formation liquid, and enhances the mechanical strength and dielectric stability of the film.

[0053] Further, the particle size of the nano-titanium dioxide or nano-aluminum oxide is controlled to be less than 20 nm, so as to enhance the nucleation effect.

[0054] The type of the nano-particle can also be nano-zirconium oxide and nano-silicon nitride, which are materials with high dielectric constant or stability; before use, the nano-titanium dioxide, nano-aluminum oxide, nano-zirconium oxide, and nano-silicon nitride are subjected to dispersion treatment in combination with a surface modifier, so as to improve the suspension stability of the particles in the electrolyte.

[0055] The optimal anodizing process conditions of the above aluminum anodizing electrolyte are: temperature 60℃-70℃, current density 0.3A / dm 2 ~0.4A / dm 2 , treatment time 15-20 minutes.

[0056] As shown in the oxidation film surface microstructure electron microscope scanning imaging diagram shown in Figure 1 and Figure 2 , by combining the aluminum anodizing electrolyte and the anodizing process conditions, a dense structure complete oxidation film is formed in actual production.

[0057] Among them, the electrolyte temperature is stably controlled at 60℃-70℃, which can accelerate the ion migration rate and improve the film forming efficiency; the current density is controlled at 0.3A / dm 2 ~0.4A / dm 2 , which can balance the film generation speed and density, and avoid the increase of film stress caused by too fast generation; the treatment time is controlled at 15-20 minutes, which can ensure that the film thickness meets the standard and the structure is complete

[0058] The specific treatment time is adjusted within 15-20 minutes according to the specific aluminum foil thickness and corrosion degree.

[0059] This process condition comprehensively improves the uniformity, adhesion density and specific capacity stability of the film layer, and solves the problems of large film thickness fluctuation and long production rhythm in existing batch production.

[0060] In further anodizing process conditions, pulse current mode is combined to improve the uniformity of current distribution; the electrolyte temperature control adopts the way of stepwise heating to optimize the nucleation process in the early stage of film formation; the treatment time is adaptively adjusted according to different aluminum foil thickness and corrosion degree to realize the optimal forming effect of different specifications of products.

[0061] The second embodiment of the aluminum anodizing electrolyte, the difference between this embodiment and the first embodiment is that the electrolyte also contains 0.01%-0.1% of a surfactant.

[0062] Among them, the surfactant is a nonionic or zwitterionic surfactant, including one of polyethylene glycol (PEG), alkyl glucoside (APG), betaine (Betaine).

[0063] In application, polyethylene glycol is PEG-400 or PEG-600; alkyl glucoside is decyl glucoside, APG-10 or octyl glucoside, APG-8; betaine is cocamide propyl betaine.

[0064] The surface active agent added into the electrolyte is used to improve the dispersibility of nano-titanium dioxide or nano-aluminum oxide in the electrolyte, prevent particle agglomeration, and improve the nucleation uniformity and adhesion density of the oxide film.

[0065] The electrode liquid formula and process conditions of the first and second embodiments were used for experiments, and the details are as follows:

[0066] Experimental Example 1: Effect of nano-additives (nano-titanium dioxide, nano-aluminum oxide) on the adhesion density and specific capacity of the oxide film

[0067] Objective: To verify the effect of nano-titanium dioxide as a nucleation center to promote the directional crystallization of γ'-Al2O3.

[0068] Substrate: Pre-etching low-pressure aluminum foil (20 μm).

[0069] Electrolyte formula (mass fraction):

[0070] Example group E1 (the technical scheme of the present application): ammonium dihydrogen phosphate 6%, sulfuric acid 1%, nano-titanium dioxide 0.05% with a particle size of 30 nm, piperazine 0.20%, surface active agent polyethylene glycol PEG-6000 0.05%, and the rest is deionized water, with pH adjusted to 5.2.

[0071] Comparative example C1: same as E1 but without nano-titanium dioxide and surface active agent.

[0072] Process conditions: temperature 65°C, current density 0.35 A / dm 2 , treatment time 18 min.

[0073] Test method: crystalline phase: XRD quantitative Rietveld; film thickness and uniformity: cross-sectional SEM + image analysis (CV%); adhesion density: indentation / scratch critical load (LC, converted to relative adhesion strength index AI); specific capacity: CV method (μF / cm 2 , under the equivalent film-forming voltage); leakage current: μA / cm 2 after 30 min of constant voltage aging.

[0074] Test data, as shown in the following table:

[0075] Index (unit) E1 C1 γ'-AI2O3 content (%) 86 68 Membrane thickness uniformity (CV, %) 3.8 9.6 Adhesion strength index AI (relative) 1.00 0.78 Specific capacitance (pF / cm 2 ) 5.9 5.3 Leakage current (pA / cm 2 ) 0.38 0.62

[0076] Conclusion: The addition of 0.05% nano-TiO2 with a particle size of 30 nm significantly improves the content of γ'-Al2O3, film thickness uniformity, and adhesion strength, while the specific capacity is increased by about 11%, and the leakage current is decreased by about 39%.

[0077] Experimental Example 2: Effect of buffer system on electrolyte pH stability and film-forming defects

[0078] Objective: To compare the buffering and defect suppressing ability of piperazine and weak base amino acid salt in acid system.

[0079] Formulation: Both contain 6% ammonium dihydrogen phosphate, 1% sulfuric acid, 0.05% nano titanium dioxide with a particle size of 30 nm, and 0.05% surfactant polyethylene glycol PEG-6000.

[0080] Among them, group E2: organic buffer is piperazine 0.20%, adjust pH=5.0;

[0081] Group E3: organic buffer is glycine sodium 0.30%, adjust pH=5.1;

[0082] Process conditions: temperature 65℃, current density 0.35A / dm 2 , treatment time 18min.

[0083] Test method: monitor the pH drift (ΔpH, 18min), surface pinhole density (pieces / mm 2 ), film porosity (mercury pressure or image method).

[0084] Test data, as follows:

[0085] Index (unit) E2 (piperazine) E3 (sodium glycinate) Process ΔpH (18 min) 0.12 0.18 Pinhole density (number / mm 2 ) 0.7 0.9 Membrane porosity (%) 13.4 14.6 Specific capacitance (pF / cm 2 )]]> 5.9 5.8 Leakage current (pA / cm 2 ) 0.38 0.41

[0086] Conclusion: Both buffers can maintain the pH of the electrolyte in the range of 4.5-6.0; piperazine is more sensitive to transient acidification, with smaller ΔpH, slightly lower pinhole and porosity, and better leakage current.

[0087] Experimental example 3: effect of nanoparticle particle size

[0088] Objective: To verify the necessity of particle size less than 50nm.

[0089] Formulation (same as E1, mass percentage is 0.05%, only change the nanoparticle particle size): group E4: titanium dioxide, particle size 20nm; group E1: titanium dioxide, particle size 30nm;

[0090] Comparative example C2: aluminum oxide, particle size 80nm.

[0091] Process conditions: temperature 65℃, current density 0.35A / dm 2 , treatment time 18min.

[0092] Test data, as follows:

[0093]

[0094]

[0095] Conclusion: Significant dispersion and nucleation advantages can be obtained with particle size ≤ 50 nm; the comparative example with particle size 80 nm shows agglomeration, poor uniformity and adhesion.

[0096] Experimental Example 4: Effect of surfactants on dispersion stability and re-use life

[0097] Objective: To verify the benefits of introducing surfactants on long-term circulation and dispersion.

[0098] Formulation (all based on E1): Test group E5: polyethylene glycol PEG-6000 0.05%; test group E6: alkyl glycoside APG-100 0.05%; comparative example C3: no surfactant.

[0099] Process conditions: temperature 65°C, current density 0.35 A / dm 2 , treatment time 18 min; continuous colouring with the same bath, number of "bath recyclable batches" (based on simultaneous achievement of specific capacity and leakage current) counted.

[0100] Test data, as follows:

[0101] Index E5 E6 C3 Suspension stability (2 h sedimentation height / initial, %) 92 90 68 Dispersion D90 (nm) 125 130 310 Tank solution recyclable batch (times) 18 17 12 Membrane thickness uniformity (CV, %) 3.9 4.1 6.8

[0102] Conclusion: The addition of 0.05% by mass of non-ionic / glycoside surfactant to the electrolyte significantly improves nanoparticle dispersion and electrolyte bath life, with clear improvement in uniformity.

[0103] Experimental Example 5: Process window robustness (temperature and current density)

[0104] Objective: To verify performance stability within the process window defined in the claims.

[0105] Formulation: same as E1.

[0106] Process conditions: E7: 60°C, 0.30 A / dm 2 , 20 min; E1: 65°C, 0.35 A / dm 2 , 18 min; E8: 70°C, 0.40 A / dm 2 , 15 min.

[0107] Test method: film thickness uniformity (CV%), specific capacity, leakage current, capacity retention rate (%) after 1 h boiling water immersion.

[0108] Test data, as follows:

[0109]

[0110]

[0111] Conclusions: The key indicators remain stable in the range of 60-70℃, 0.30-0.40 A / dm 2 , 15-20 min, which reflects the robustness and adaptability of the process window for mass production.

[0112] XRD: Cu Kα, Rietveld method for quantifying the content of γ'-Al2O3 phase;

[0113] SEM: cross-section imaging after polishing, image analysis to calculate film thickness and CV%;

[0114] Adhesion strength: progressive load scratch, critical failure point normalized to AI;

[0115] Specific capacity and leakage: standard CV and constant voltage aging method, temperature control at 25℃;

[0116] Dispersion: laser particle size / dynamic light scattering to measure D90, sedimentation ratio to characterize stability;

[0117] Hydration resistance: capacity retention rate after boiling in water at 100℃ for 1h.

[0118] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described.

Claims

1. An aluminum anodic oxidation electrolyte for improving the adhesion density of the oxide film on the electrode foil, characterized in that, Includes the following components measured in percentage by mass: 3%–10% ammonium dihydrogen phosphate; Sulfuric acid 0.5%–3%; Nano-titanium dioxide or nano-alumina 0.01%–0.2%; Organic buffers at 0.05%–0.5% are used to stabilize the pH value within the range of 4.5–6.

0. The remainder is deionized water; The nano-titanium dioxide or nano-alumina serves as the nucleation center for the oxide film, promoting the directional crystallization of γ′-Al2O3. Combined with the organic buffer, it stabilizes the reaction environment during the anodizing process, thereby improving the adhesion density, specific volume, and production efficiency of the oxide film.

2. The aluminum anodizing electrolyte according to claim 1, characterized in that, The organic buffer is piperazine, a weakly basic amino acid salt, or a combination thereof.

3. The aluminum anodizing electrolyte according to claim 2, characterized in that, The piperazine is one or more of anhydrous piperazine, piperazine dihydrochloride, or piperazine hexahydrate.

4. The aluminum anodizing electrolyte according to claim 2, characterized in that, The weakly basic amino acid salt is one or a combination of sodium glycinate, sodium alanine, sodium glutamate, and sodium aspartate.

5. The aluminum anodizing electrolyte according to claim 1, characterized in that, The particle size of the nano-titanium dioxide or nano-alumina is less than 50 nm.

6. The aluminum anodizing electrolyte according to any one of claims 1 to 5, characterized in that, The electrolyte also contains 0.01% to 0.1% surfactant, which is used to improve the dispersibility of the nano-titanium dioxide or nano-alumina in the electrolyte, prevent particle agglomeration, and improve the uniformity of oxide film nucleation and adhesion density.

7. The aluminum anodizing electrolyte according to claim 6, characterized in that, The surfactant is a nonionic or amphoteric surfactant, including one of polyethylene glycol, alkyl glycoside, and betaine.

8. The aluminum anodizing electrolyte according to any one of claims 1 to 5, characterized in that, The anodizing process conditions are: temperature 60℃~70℃, current density 0.3A / dm³. 2 ~0.4A / dm 2 The processing time is 15 to 20 minutes.

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