A foil forming method for forming a dense oxide film and a formed foil

Abstract

The invention discloses a foil forming method and a formed foil for forming a dense oxide film. The foil forming method comprises a hydrothermal treatment step and a forming step implemented in sequence, wherein the hydrothermal treatment step at least comprises: immersing the foil in a sodium aluminate-ammonia aqueous solution for a closed hydrothermal treatment. Under the treatment, Al 3+ The aluminum hydroxide layer is formed by reacting with ammonia water and deposited on the foil surface. After drying and calcining, a dense layer of γ-alumina is formed on the foil surface. When multi-stage formation is performed based on this layer of γ-alumina, not only is the oxide film formed on the foil surface denser than the existing process, which is beneficial to shorten the boost time and Tr60 time of the aluminum electrolytic capacitor foil, but the preparation process is simple and suitable for industrial production.

Description

Technical Field

[0001] The invention belongs to the technical field of chemically formed foil materials, and in particular relates to a foil chemically formed method for forming a dense oxide film and a chemically formed foil. Background Art

[0002] Chemical foil is a product of specially made high-purity aluminum foil that has been subjected to electrochemical or chemical corrosion to expand its surface area, and then to an oxide film formed on the surface through electrochemical reaction. Medium and high voltage chemical foil for aluminum electrolytic capacitors is a special electronic material, one of the basic industries, and a weak link in China's electronics industry. It has now been included in the national key development and support industries. High-grade medium and high voltage chemical foil is also a key basic industrial material for China's electronics industry to replace imports, so the production of medium and high voltage chemical foil products has a broad market prospect.

[0003] The oxide film formed by the formed foil must be γ-alumina, which has the advantages of high pore volume and high specific surface area. However, the formed foil for aluminum electrolytic capacitors manufactured by the existing method still has problems such as low density of the oxide film, long Tr60 time, and long boost time. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a foil forming method and a formed foil for forming a dense oxide film.

[0005] In order to achieve the above-mentioned object of the invention, the technical solution of the present invention includes:

[0006] A foil forming method for forming a dense oxide film comprises a hydrothermal treatment step and a forming step which are performed in sequence, wherein the hydrothermal treatment step at least comprises:

[0007] The foil was immersed in a sodium aluminate-ammonia aqueous solution for closed hydrothermal treatment.

[0008] The chemical formation method of the present invention comprises the steps of immersing the foil in a sodium aluminate-ammonia aqueous solution and performing a hydrothermal treatment in a closed environment; under this treatment, the Al 3+ It reacts with ammonia water to form a layer of aluminum hydroxide medium deposited on the foil surface. After drying and calcining, a dense layer of γ-alumina is formed on the foil surface. When multi-stage formation is carried out based on this layer of γ-alumina, not only is the oxide film formed on the foil surface denser than the existing process, which is beneficial to shorten the boost time and Tr60 time of aluminum electrolytic capacitor foil formation, but the preparation process is simple and suitable for industrial production.

[0009] The present invention has been found through experiments that ammonia and Al 3+The ratio directly affects the formation rate of γ-alumina and the thickness of the oxide film. Therefore, preferably, in the sodium aluminate-ammonia aqueous solution, the ammonia concentration is 5-15 mol / L, and the ratio of ammonia to Al3+ is (1-10):1 on a molar basis.

[0010] Furthermore, in the sodium aluminate-ammonia aqueous solution, the ratio of ammonia water to Al3+ is (1-3):1 on a molar basis.

[0011] Furthermore, the temperature of the closed hydrothermal treatment is 85-95° C., and the time of the closed hydrothermal treatment is 2-5 minutes.

[0012] Furthermore, the hydrothermal treatment step further comprises:

[0013] The foil was hydrothermally treated by immersing it in pure water;

[0014] The hydrothermal treatment occurs before the closed hydrothermal treatment.

[0015] Furthermore, the temperature of the hydrothermal treatment is 85-95° C., and the time of the hydrothermal treatment is 2-5 minutes.

[0016] Furthermore, after the hydrothermal treatment step, the foil is taken out, dried, and calcined before being subjected to a chemical conversion step.

[0017] Furthermore, the drying process is carried out in an inert atmosphere, and the temperature of the drying process is not greater than 200°C;

[0018] The temperature of the calcination treatment is 400-750° C., and the duration of the calcination treatment is 3-12 minutes.

[0019] Furthermore, the drying temperature is 80-120°C and the drying time is 5-10 minutes;

[0020] The temperature of the calcination treatment is 500-650° C., and the duration of the calcination treatment is 3-8 minutes.

[0021] Another aspect of the present invention provides a chemically formed foil, which is produced by the above-mentioned foil chemically formed method.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] (1) The chemical conversion method of the present invention comprises the steps of immersing the foil in a sodium aluminate-ammonia aqueous solution and performing a hydrothermal treatment in a closed environment; under this treatment, Al 3+It reacts with ammonia water to form a layer of aluminum hydroxide medium deposited on the foil surface. After drying and calcining, a dense layer of γ-alumina is formed on the foil surface. When multi-stage formation is carried out based on this layer of γ-alumina, not only is the oxide film formed on the foil surface denser than the existing process, which is beneficial to shorten the boost time and Tr60 time of aluminum electrolytic capacitor foil formation, but the preparation process is simple and suitable for industrial production.

[0024] (2) In the sodium aluminate-ammonia solution used in the present invention, the ammonia water and the Al 3+ The ratio is preferably (1-10):1, and more preferably (1-3):1; at this ratio, the formation rate of γ-alumina is faster, and the thickness of the oxide film formed after chemical formation is appropriate. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described in detail below in conjunction with specific embodiments.

[0026] Example 1

[0027] The present embodiment provides a foil formation method for forming a dense oxide film, comprising a hydrothermal treatment step and a formation step implemented in sequence, wherein the hydrothermal treatment step at least comprises: immersing the foil in a sodium aluminate-ammonia aqueous solution for closed hydrothermal treatment.

[0028] Specifically, a foil forming method for forming a dense oxide film in this embodiment includes the following steps:

[0029] S1: Boil the aluminum foil in purified water at 95°C for 5 min;

[0030] S2: immersing the aluminum foil treated in step S1 into an excess of sodium aluminate-ammonia aqueous solution that at least completely submerges the aluminum foil, and then sealing and heating to 95° C. to perform a sealed hydrothermal treatment for 2 minutes; after the sealed hydrothermal treatment, taking out the foil, drying it at 120° C. for 5 minutes, and passing argon gas for gas protection during the drying process; then calcining the foil at 650° C. for 3 minutes, and passing argon gas for gas protection during the calcination process; finally, cooling to room temperature, thereby obtaining an aluminum foil having a dense γ-alumina oxide film on the surface;

[0031] The sodium aluminate-ammonia solution has an ammonia concentration of 5 mol / L. 3+ The ratio is 1:1;

[0032] S3: performing chemical treatment on the aluminum foil treated in step S2 to obtain chemically formed foil;

[0033] The chemical formation treatment method can adopt any one known in the prior art. This embodiment uses a six-stage chemical formation method as an example for illustration; the six-stage chemical formation method comprises the following steps:

[0034] S3-1: Boil the foil in purified water at a temperature of about 95°C for 5 minutes, take it out, wash it, and place it in a primary formation tank containing an electrolyte of 0.2% phosphate and 0.3% citric acid at 85°C, 106V, 25mA / cm 2 Under the conditions of , the reaction was carried out for 8 minutes to obtain a primary reaction aluminum foil;

[0035] S3-2: Take out and wash, place in a secondary formation tank containing 0.1% phosphate, 0.2% citric acid, 0.1% azelaic acid electrolyte, and heat at 85°C, 159V, 25mA / cm 2 Under the conditions of , the reaction was carried out for 4 minutes to obtain secondary reaction aluminum foil;

[0036] S3-3: Take out and wash, place in a three-stage formation tank containing 0.05% phosphomolybdate, 0.2% citric acid, 0.3% adipate, and 2% boric acid electrolyte, and heat at 85°C, 370V, 25mA / cm 2 Under the conditions of , the reaction was carried out for 8 minutes to obtain a three-stage reaction aluminum foil;

[0037] S3-4: Take out and wash with water, put into the liquid feeding tank containing adipic acid and its salt solution for feeding, and after washing with water, put into the four-stage formation tank containing 0.05% phosphomolybdate, 0.1% citric acid, 0.2% adipic acid and 2.5% boric acid electrolyte, and heat at 85℃, 477V, 25mA / cm 2 Under the conditions of , the reaction was carried out for 8 minutes to obtain a four-stage reaction aluminum foil;

[0038] S3-5: Take out and wash, place in a five-stage formation tank containing 0.01% phosphomolybdate, 0.1% citric acid, 3% boric acid and 3% borate, and heat at 85°C, 530V, 25mA / cm 2 Under the conditions of , the five-level chemical foil was obtained after 4 minutes of chemical reaction.

[0039] S3-6: Take out and wash, place in a six-stage primary formation tank containing 0.1% citric acid, 6% boric acid and 5% borate electrolyte, and heat at 85°C, 530V, 50mA / cm 2 The foil was then calcined at 550°C for 2-3 minutes to obtain a six-stage primary-chemical aluminum foil. The foil was placed in a six-stage secondary-chemical tank containing an electrolyte of 0.01% citric acid, 5% boric acid and 5% borate and heated at 85°C, 530V, 25mA / cm 2The foil was taken out and washed, and then placed in a 25% phosphoric acid aqueous solution and treated at 65°C for 5 minutes to obtain a six-stage three-stage aluminum foil; the foil was taken out and washed, and placed in a six-stage four-stage forming tank under the same conditions as the six-stage two-stage forming conditions, and then calcined at 550°C for 2-3 minutes to obtain a six-stage four-stage aluminum foil; the foil was taken out and washed, and placed in a six-stage five-stage forming tank under the same conditions as the six-stage two-stage forming conditions, and then placed in a 5% phosphate aqueous solution, treated at 75°C for 5 minutes, and then calcined at 150°C for 2-3 minutes to obtain a medium- and high-voltage aluminum electrolytic capacitor anode foil.

[0040] Example 2

[0041] The present embodiment provides a foil formation method for forming a dense oxide film, comprising a hydrothermal treatment step and a formation step implemented in sequence, wherein the hydrothermal treatment step at least comprises: immersing the foil in a sodium aluminate-ammonia aqueous solution for closed hydrothermal treatment.

[0042] Specifically, a foil forming method for forming a dense oxide film in this embodiment includes the following steps:

[0043] S1: Boil the aluminum foil in purified water at 95°C for 5 min;

[0044] S2: First, immerse the aluminum foil treated in step S1 into an excess of sodium aluminate-ammonia solution that at least completely submerges the aluminum foil, then seal the foil and heat it to 90°C for a sealed hydrothermal treatment for 5 minutes; then dry the foil at 120°C for 5 minutes, with argon gas passing through during the drying process for gas protection; then calcine the foil at 500°C for 8 minutes, with argon gas passing through during the calcination process for gas protection; finally cool the foil to room temperature to obtain an aluminum foil with a dense γ-alumina oxide film on the surface;

[0045] The sodium aluminate-ammonia solution has an ammonia concentration of 10 mol / L. 3+ The ratio is 2:1;

[0046] S3: The foil treated in step S2 is subjected to chemical treatment using the same six-stage chemical treatment method as in Example 1 to obtain chemically formed foil.

[0047] Example 3

[0048] The present embodiment provides a foil formation method for forming a dense oxide film, comprising a hydrothermal treatment step and a formation step implemented in sequence, wherein the hydrothermal treatment step at least comprises: immersing the foil in a sodium aluminate-ammonia aqueous solution for closed hydrothermal treatment.

[0049] Specifically, a foil forming method for forming a dense oxide film in this embodiment includes the following steps:

[0050] S1: Boil the aluminum foil in purified water at 95°C for 5 min;

[0051] S2: immersing the foil treated in step S1 into an excess of sodium aluminate-ammonia aqueous solution that at least completely submerges the foil, and then sealing and heating to 85° C. to perform a sealed hydrothermal treatment for 2 minutes; then drying at 100° C. for 10 minutes, with argon gas passing through for gas protection during the drying process; then calcining at 550° C. for 5 minutes, with argon gas passing through for gas protection during the calcining process; and finally cooling to room temperature to obtain an aluminum foil with a dense γ-alumina oxide film on the surface;

[0052] Among them, the concentration of ammonia in the sodium aluminate-ammonia solution is 5 mol / L. In terms of molar amount, the concentration of ammonia and Al 3+ The ratio is 3:1;

[0053] S3: The foil treated in step S2 is subjected to chemical treatment using the same six-stage chemical treatment method as in Example 1 to obtain chemically formed foil.

[0054] Example 4

[0055] The present embodiment provides a foil formation method for forming a dense oxide film, comprising a hydrothermal treatment step and a formation step implemented in sequence, wherein the hydrothermal treatment step at least comprises: immersing the foil in a sodium aluminate-ammonia aqueous solution for closed hydrothermal treatment.

[0056] Specifically, a foil forming method for forming a dense oxide film in this embodiment includes the following steps:

[0057] S1: Boil the aluminum foil in purified water at 95°C for 5 min;

[0058] S2: immersing the foil treated in step S1 into an excess of sodium aluminate-ammonia aqueous solution that at least completely submerges the foil, and then sealing and heating to 95° C. for a sealed hydrothermal treatment for 2 minutes; then drying at 80° C. for 10 minutes, with argon gas passing through for gas protection during the drying process; then calcining at 550° C. for 5 minutes, with argon gas passing through for gas protection during the calcining process; and finally cooling to room temperature to obtain an aluminum foil with a dense γ-alumina oxide film on the surface;

[0059] Among them, the concentration of ammonia in the sodium aluminate-ammonia solution is 15 mol / L. In terms of molar amount, the concentration of ammonia and Al 3+ The ratio is 2:1;

[0060] S3: The foil treated in step S2 is subjected to chemical treatment using the same six-stage chemical treatment method as in Example 1 to obtain chemically formed foil.

[0061] Example 5

[0062] The present embodiment provides a foil formation method for forming a dense oxide film, comprising a hydrothermal treatment step and a formation step implemented in sequence, wherein the hydrothermal treatment step at least comprises: immersing the foil in a sodium aluminate-ammonia aqueous solution for closed hydrothermal treatment.

[0063] Specifically, a foil forming method for forming a dense oxide film in this embodiment includes the following steps:

[0064] S1: Boil the foil in purified water at 95°C for 2 min;

[0065] S2: immersing the aluminum foil treated in step S1 into an excess of sodium aluminate-ammonia aqueous solution that at least completely submerges the aluminum foil, and then sealing and heating to 95° C. to perform a sealed hydrothermal treatment for 2 minutes; after the sealed hydrothermal treatment, taking out the foil, drying it at 120° C. for 5 minutes, and passing argon gas for gas protection during the drying process; then calcining the foil at 650° C. for 3 minutes, and passing argon gas for gas protection during the calcination process; finally, cooling to room temperature, thereby obtaining an aluminum foil having a dense γ-alumina oxide film on the surface;

[0066] The sodium aluminate-ammonia solution has an ammonia concentration of 5 mol / L. 3+ The ratio is 5:1;

[0067] S3: The foil treated in step S2 is subjected to chemical treatment using the same six-stage chemical treatment method as in Example 1 to obtain chemically formed foil.

[0068] Example 6

[0069] The present embodiment provides a foil formation method for forming a dense oxide film, comprising a hydrothermal treatment step and a formation step implemented in sequence, wherein the hydrothermal treatment step at least comprises: immersing the foil in a sodium aluminate-ammonia aqueous solution for closed hydrothermal treatment.

[0070] Specifically, a foil forming method for forming a dense oxide film in this embodiment includes the following steps:

[0071] S1: Boil the foil in purified water at 85°C for 5 min;

[0072] S2: immersing the aluminum foil treated in step S1 into an excess of sodium aluminate-ammonia aqueous solution that at least completely submerges the aluminum foil, and then sealing and heating to 95° C. to perform a sealed hydrothermal treatment for 2 minutes; after the sealed hydrothermal treatment, taking out the foil, drying it at 120° C. for 5 minutes, and passing argon gas for gas protection during the drying process; then calcining the foil at 650° C. for 3 minutes, and passing argon gas for gas protection during the calcination process; finally, cooling to room temperature, thereby obtaining an aluminum foil having a dense γ-alumina oxide film on the surface;

[0073] The sodium aluminate-ammonia solution has an ammonia concentration of 5 mol / L. 3+ The ratio is 10:1;

[0074] S3: The foil treated in step S2 is subjected to chemical treatment using the same six-stage chemical treatment method as in Example 1 to obtain chemically formed foil.

[0075] Comparative Example 1

[0076] The foil forming method of this comparative example is basically the same as that of Example 1, except that step S1 is not included.

[0077] Comparative Example 2

[0078] The foil forming method of this comparative example is basically the same as that of Example 1, except that step S2 is not included.

[0079] According to the group standard of China Electronic Components Industry Association "Electrode Foil for Aluminum Electrolytic Capacitors"

[0080] T / CECA22-2017, the boost time and Tr60 time of the electrolytic foil for aluminum electrolytic capacitors obtained by the existing technology (production method of electrode foil for aluminum electrolytic capacitors) are tested. Among them: the time from the start of power-on until the voltage rises to 90% (Vr) of the rated forming voltage Vf is recorded as the boost time (Tr); and the Tr60 time is recorded; the specific test results are detailed in Table 1.

[0081] Table 1

[0082] serial number Withstand voltage(V) Tr(s) Tr60(s) Example 1 532.1 149 8 Example 2 530.7 162 12 Example 3 531.5 160 14 Example 4 533.1 154 13 Example 5 529.8 172 15 Example 6 530.1 188 20 Comparative Example 1 533.5 200 28 Comparative Example 2 530.8 294 34

[0083] As shown in the above table, the formation method of the present invention can form a denser oxide film on the surface of the aluminum foil, and thus can effectively shorten the voltage rise time and Tr60 time of the aluminum electrolytic capacitor foil.

[0084] The above is only a preferred embodiment of the embodiment of the present invention, and does not impose any form of limitation on the embodiment of the present invention. Any simple modification, equivalent change and modification made according to the technical essence of the embodiment of the present invention still falls within the scope of the technical solution of the embodiment of the present invention.

Claims

1. A method for forming a dense oxide film on a foil, comprising a hydrothermal treatment step and a formation step performed sequentially, characterized in that: The hydrothermal treatment step at least comprises: The foil was immersed in a sodium aluminate-ammonia aqueous solution for closed hydrothermal treatment.

2. The foil forming method according to claim 1, characterized in that: In the sodium aluminate-ammonia solution, the ammonia concentration is 5-15 mol / L. 3+ The ratio is (1~10):

1.

3. The foil forming method according to claim 1, characterized in that: In the sodium aluminate-ammonia solution, the molar amount of ammonia and Al 3+ The ratio is (1~3):

1.

4. The foil forming method according to claim 1, characterized in that: The temperature of the closed hydrothermal treatment is 85-95° C., and the time of the closed hydrothermal treatment is 2-5 minutes.

5. The foil forming method according to claim 1, characterized in that: The hydrothermal treatment step further comprises: The foil was hydrothermally treated by immersing it in pure water; The hydrothermal treatment occurs before the closed hydrothermal treatment.

6. The foil forming method according to claim 5, characterized in that: The temperature of the hydrothermal treatment is 85-95° C., and the time of the hydrothermal treatment is 2-5 minutes.

7. The foil forming method according to claim 1, characterized in that: After the hydrothermal treatment step, the foil is taken out, dried, and calcined before undergoing the chemical conversion step.

8. The foil forming method according to claim 7, characterized in that: The drying process is carried out in an inert atmosphere, and the temperature of the drying process is not greater than 200°C; The temperature of the calcination treatment is 400-750° C., and the duration of the calcination treatment is 3-12 minutes.

9. The foil forming method according to claim 8, characterized in that: The drying temperature is 80-120°C and the drying time is 5-10 minutes. The temperature of the calcination treatment is 500-650° C., and the duration of the calcination treatment is 3-8 minutes.

10. A chemically formed foil, characterized in that: The foil is prepared by the foil forming method as described in any one of claims 1 to 9.