JPH08134694A - Very highly alkali-proof aluminum oxide composite film and its production - Google Patents

Abstract

PURPOSE: To obtain an aluminum oxide composite film having satisfactory durability by coating a porous aluminum oxide coating film formed by anodic oxidation with an inorg. oxide by a sol-gel method. CONSTITUTION: A porous aluminum oxide coating film formed by anodically oxidizing Al or Al alloy in an acid soln. is coated with an inorg. oxide, preferably ZrO2 by a sol-gel method and the coated coating film is heat-treated to seal the pores in the film. The heat treatment is preferably carried out by heating to 150-350 deg.C in an oxygen-contg. atmosphere or with hot water or pressurized steam.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a super alkali resistant aluminum oxide composite film and a method for producing the same. More specifically, the present invention relates to a super alkali resistant aluminum oxide composite film and a method for producing the same, which are useful in advanced technical fields in which the development of a film having durability and wear resistance is required.

[0002]

2. Description of the Related Art Conventionally, when aluminum or an aluminum alloy is anodized in an inorganic acid such as sulfuric acid, phosphoric acid or chromic acid, an organic acid such as oxalic acid or malonic acid, or a mixed acid solution thereof, It is known that an aluminum oxide film is formed on the surface. However, the anodic coating has inferior chemical resistance, especially alkali resistance due to the presence of fine pores, and is also inferior in wear resistance, electrical insulation, etc., so it is better to immerse the coating in boiling water as an improvement measure. Then, a method of sealing the pores of the film by a hydration reaction (sealing) or immersing the film in a water-soluble acrylic resin paint and electrophoretically depositing an organic resin on or in the film A method of sealing the pores of the coating with a coating is practically used.

However, in these conventional methods,
The aluminum oxide coating could not be used in a more severe environment because of its insufficient ability to seal the pores of the coating. That is, it seems that in the conventional method, the sealing of the pores is not always perfect, the alkali resistance is inferior, and deterioration, peeling, breakage, etc. of the sealing material cannot be avoided in a severe environment.

Therefore, although the aluminum oxide film formed by anodic oxidation is excellent in its properties such as heat resistance and strength, there is a big limitation in practical use thereof. In particular, it has been regarded as a serious problem for application to advanced technical fields such as aviation, space, other super durable structural materials, and electronic devices. In recent years, attempts have been made to increase the functionality by filling the pores of the coating with functional substances such as molybdenum disulfide and ferromagnetic materials, but chemical properties such as alkali resistance and durability In reality, it is not satisfactory from the viewpoint of improving the sex.

The present invention has been made in view of the above circumstances, has solved the drawbacks of the prior art and has a new aluminum oxide anodized oxide having excellent alkali resistance and excellent durability. The purpose is to provide a film.

[0006]

As a solution to the above problems, the present invention provides a super alkali resistant inorganic material in which a porous aluminum oxide film formed by anodic oxidation is covered with a sol-gel method inorganic oxide. An oxide composite film is provided. The present invention also provides, as a method for producing this composite film, a porous aluminum oxide film obtained by anodizing aluminum or an alloy thereof in an acid solution, using a sol-
A method of coating an inorganic oxide by a gel method and then heating is also provided. Further, the present invention also provides a method for treating the obtained composite film in hot water or pressurized steam to repair defects in the composite film.

[0007]

In the above composite membrane of the present invention, the pores of the porous aluminum oxide are gel-sealed by the inorganic oxide coating,
Furthermore, by coating the surface, the structure becomes excellent in denseness, and excellent characteristics such as super alkali resistance are realized. The sealing of the pores in the present invention should be called "gel sealing" by the sol-gel reaction and is essentially different from the conventionally known "sealing" by the hydrothermal reaction. is there.

Although anodized films of aluminum usually have a good acid resistance but a poor alkali resistance, in the case of the composite film of the present invention, such a defect is solved, and it has been heretofore known. Excellent super-alkaline resistance not found in The super alkali resistant aluminum oxide composite film of the present invention having such excellent properties is
The film produced by anodic oxidation in an acid solution is manufactured by, for example, immersing the film in a sol solution mainly containing a metal alkoxide and then heating. It is desirable that the dipping is repeated a plurality of times depending on the thickness of the anodized film. The number of repetitions is the size of the pores,
It can be appropriately selected depending on the thickness of the film. In general, the thinner the coating, the lesser the number of times.

Further, in controlling the thickness of the coating layer produced by the sol-gel method, the viscosity of the sol, the pulling rate from the sol solution, etc. are also taken into consideration. For example, in the case of a porous film having a thickness of 3 μm and a large pore diameter of 100 to 150 nm, the pore size is about 20 by one dipping treatment.
Filled with 0-300 nm zirconia gel. Then
All the pores are filled with the treatment of 10 times of the dip coating, and the gel is sealed.

Then, the coating layer on the film is formed in the eleventh and subsequent treatments. After soaking, it is dried and then heat treated. In the present invention, the heat treatment is performed in an oxygen-containing atmosphere, for example, in the air or in an oxygen stream at about 150 to 350 ° C., more preferably at about 200 to 300 ° C. for about 10 minutes to 1 hour.

The immersion in the sol solution and the drying are
It is preferably carried out in an atmosphere of inert gas, air, or vacuum. This drying is preferably performed at a temperature of room temperature to about 60 ° C., and this drying also contributes to the improvement of alkali resistance. By such immersion in a sol solution and heat treatment, coating adhesion, smoothness,
A composite film having excellent characteristics such as denseness and alkali resistance is formed.

The inorganic oxide coating by the sol-gel method is
It is realized as a coating for sealing the pores of the aluminum oxide film and further for coating the surface of the film. It is also effective to further treat the produced composite membrane with hot water or pressurized steam. It is considered that the super alkaline resistance property of the composite film of the present invention is due to the defect repairing action in the composite film during the dissolution process with the alkaline solution. Further, the fact that the surface of the composite film formed by coating has water repellency is also considered to be one of the reasons for improving the super alkali resistance.

The intelligent property of such a composite film coated with an inorganic oxide to an alkaline solution is a completely new phenomenon that has not been known so far, and is also noted from the viewpoint of expanding its application to new fields. For the anodic oxidation and the sol-gel method, various methods including conventionally known means can be adopted. Then, the inorganic oxide for coating can be appropriately selected depending on the use and use conditions of the composite film, and for example, Zr, Ti, Nb, W,
Mo, Ni, Fe, Co, V, Sb, In, Bi, S
Oxides such as i, Al, Sr, Y, and various rare earth elements are selected.

[0014]

EXAMPLES Examples will be shown below to describe the super alkali resistant composite film of the present invention in more detail. Example 1 DC voltage 7 in a phosphoric acid aqueous solution having a concentration of 15% and a liquid temperature of 21 ° C.
An aluminum plate having a purity of 99.99% was anodized by applying 0V.

As a result, the diameter of the pores is about 100-15.
At 0 nm, a film with a porous structure with a film thickness of about 3 μm was produced. Next, this film was added to zirconium tetra-n-butoxide, dehydrated ethanol, ion-exchanged water and diethylene glycol, and immersed in a well-stirred zirconia sol under a nitrogen atmosphere for 5 minutes. Then, it is pulled up at a constant speed (3 mm / s), dried in a nitrogen atmosphere for 5 minutes, and then heat-treated in an oxygen stream at a temperature of 300 ° C. for 30 minutes, and this operation is repeated 15 times until the pores of the film are filled. Repeatedly produced a composite membrane. The pores are sealed with a zirconia gel, and the thickness of the coating layer on the film is about 190
was nm.

When the alkali resistance of the thus obtained composite film was measured by an electromotive force measurement test (JIS H8681), it showed an alkali resistance of 2254 seconds.
In this electromotive force test, a 10% NaOH aqueous solution was brought into contact with the film, the time until the potential of 1 mV was detected was measured, and this was expressed as the time until the film was dissolved and the substrate was exposed. Example 2 A 3 μm-thick porous aluminum phosphate oxide film with a film thickness of 3 μm formed on an aluminum substrate by the same method as in Example 1 was immersed in zirconia sol for 5 minutes, and then pulled up at a constant speed, and nitrogen was added. After drying in the atmosphere for one day (24 hours), heat treatment was carried out at 300 ° C. for 30 minutes in an oxygen stream, and this operation was repeated 15 times until the pores of the coating were filled to form a composite membrane.

The alkali resistance of the composite film thus obtained was measured by the same method as in Example 1, and it was 40
It showed an alkali resistance of 40 seconds. Example 3 A porous aluminum phosphate oxide film having a thickness of 3 μm and formed on an aluminum substrate in the same manner as in Example 1 was dipped in a zirconia sol for 5 minutes, and then pulled up at a constant rate to the atmosphere. After drying in the air for 5 minutes, heat treatment was carried out at 300 ° C. for 30 minutes in an oxygen stream, and this operation was repeated 15 times until the pores of the coating were filled to form a composite membrane. The thickness of the coating layer on the film was about 200 nm.

The alkali resistance of the composite film thus obtained was measured in the same manner as in Example 1. The result was 93.
It showed an alkali resistance of 36 seconds. Example 4 A porous aluminum phosphate oxide film having a thickness of 3 μm and formed on an aluminum substrate in the same manner as in Example 1 was dipped in a zirconia sol for 5 minutes and then pulled up at a constant speed, and nitrogen was added thereto. After drying in the atmosphere for 5 minutes, leave it in vacuum for 5 minutes, and finally in an oxygen stream at 300 ° C.
Was heat-treated for 30 minutes, and this operation was repeated 15 times until the pores of the film were filled to form a composite film. The coating layer thickness on the film was about 310 nm.

The alkali resistance of the composite film thus obtained was measured by the same method as in Example 1.
It showed an alkali resistance of 55 seconds. Example 5 A porous aluminum phosphate oxide film having a thickness of 3 μm and formed on an aluminum substrate in the same manner as in Example 1 was dipped in a zirconia sol for 5 minutes, and then pulled up at a constant speed, and nitrogen was added. After drying in an atmosphere for 5 minutes, heat treatment was further performed in an oxygen stream at 300 ° C. for 30 minutes, and this operation was repeated 15 times until the pores of the coating were filled to form a composite membrane. Finally, the composite membrane was heated in boiling water for 45 minutes. The thickness of the coating layer on the film was about 170 nm.

The alkali resistance of the composite film thus obtained was measured in the same manner as in Example 1.
It was 060 seconds, and the film showed extremely excellent alkali resistance and a film was obtained. Comparative Example 1 A porous aluminum oxide film having a film thickness of 3 μm formed on an aluminum substrate in the same manner as in Example 1 was subjected to hydrothermal reaction as it was for hydrothermal reaction.

When the alkali resistance of this product was measured in the same manner, its alkali resistance performance was only 130 seconds. Comparative Example 2 In Example 1, the alkali resistance was similarly measured in the case where the heat treatment was not performed.
It stayed for about 50 seconds. Example 6 In the same manner as in Example 1, a film thickness of 3 was formed on an aluminum substrate.
An aluminum oxide film with a porous structure of μm was produced.

Next, to this film, ethyl silicate (tetraethyl orthosilicate), anhydrous ethanol, ion-exchanged water and nitric acid were added and immersed in a well-stirred silica gel for 5 minutes under a nitrogen atmosphere. And constant speed (3mm
/ S), and dried in the atmosphere for 5 minutes, and then heat-treated in an oxygen stream at a temperature of 300 ° C. for 30 minutes.

This operation was repeated until the pores of the film were filled to form a composite film. As a result of measuring the alkali resistance of the composite film thus obtained, the alkali resistance was 1643 seconds.

[0024]

As described in detail above, according to the present invention, it becomes possible to produce an inorganic oxide composite film having extremely excellent super alkali resistance.

Claims (8)

[Claims] 1. A super alkali resistant aluminum oxide composite film, wherein a porous aluminum oxide film formed by anodizing treatment is covered with a sol-gel method inorganic oxide. 2. The composite film according to claim 1, wherein the pores of the porous aluminum oxide film are sealed with an inorganic oxide. 3. The composite film according to claim 1, wherein the surface of the porous aluminum oxide film is covered with an inorganic oxide. 4. The composite film according to claim 1, wherein the inorganic oxide is zirconium oxide. 5. A super-alkaline resistance characterized in that a porous aluminum oxide film formed by anodizing aluminum or its alloy in an acid solution is coated with an inorganic oxide by a sol-gel method and heat-treated. Method for manufacturing aluminum oxide composite film. 6. The method for producing a super alkaline resistant aluminum oxide composite film according to claim 5, wherein the heat treatment is performed in an oxygen-containing atmosphere. 7. The method according to claim 6, wherein the heat treatment is performed at 150 to 350 ° C. 8. A method for producing a super alkaline resistant aluminum oxide composite membrane, which comprises treating the composite membrane produced by the method of claim 5 with hot water or pressurized steam.