JPH08246190A - Anodically oxidized film and its formation - Google Patents

Abstract

PURPOSE: To obtain an appropriate pore radius distribution of the anodically oxidized film as a caralyst carrier surface by controlling the treating temp. at the time of subjecting an alumina coating film, that is formed through subjecting aluminum, an aluminum alloy or the like to anodic oxidation, to hydration sealing treatment. CONSTITUTION: In this formation, hydration sealing treatment of an alumina film after anodic oxidation of aluminum or the like is performed at a temp. within the range of 5 to 45 deg.C for several minutes to several hours by using deaerated water having a >=2×10<5> Ω specific resistance and then, the treated coating film is calcined at a temp. within the range of 300 to 500 deg.C. By performing this treatment, an oxide coating film having at least one peak of the pore radius distribution within the range of 25 to 250Å is formed. As the water used for the hydration sealing treatment, deionized water is desired because of the easiness of its production. In this sealing treatment, the lower the treating temp. and the longer the treating time, the more closely the pore radius distribution in the range of 25 to 250Å approaches a flat and on the other hand, the higher the treating temp., the more the tendency of having a maximum of the pore radius distribution within the range of 25 to 250Å becomes noticeable and also, even a pore size distribution curve having two maxima within the range of 20 to 300Å can easily be obtained. Therefore, the treating temp. and treating time are adjusted so as to obtain a desired pore radius distribution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anodized film and a method for forming the same, and more particularly to an anodized film having at least one peak of pore radius distribution between 25Å to 250Å and a method for forming the anodized film.

[0002]

2. Description of the Related Art Porous alumina coatings obtained by anodic oxidation technology of aluminum are known, and are used as insulating coatings for electrolytic capacitors, surface treatment of aluminum sashes and ornaments, anticorrosion treatment of surfaces such as car bodies and aircraft, and curtain walls. It is used for various purposes such as color development. On the other hand, since the porous oxide film obtained by anodization has a large pore radius of about 300 Å, the BET surface area is small and it is insufficient as a catalyst carrier.

On the other hand, in recent years, anodic oxide films have been formed at 50 ° C.
In the case of hot water treatment with water or steam as described above, the pore radius becomes about 20Å, and as a result, the BET surface area is remarkably increased, and it has been found that it can be sufficiently used as a catalyst carrier surface (JP-A-2- 144154 and 40-2
No. 00475). However, it was not possible to have a pore radius distribution of 20 Å or more by these hot water treatments (Altopia, vol. 10, pp. 9-12 (19).
93)).

[0004]

The above-mentioned hot water treatment is technically a hydration sealing treatment of alumina pores, but the present inventors have found that even at a low temperature of 10 ° C. or lower, it takes a long time. The present inventors have found that hydration sealing treatment is possible, and that the pore radius of alumina can be widely controlled when the treatment temperature is 45 ° C. or lower, and thus reached the present invention.

Therefore, the first object of the present invention is to obtain 25Å ~
An object of the present invention is to provide an anodized film having at least one peak of pore radius distribution between 250Å. A second object of the present invention is to provide a metal substrate having on its surface an anodized film having at least one peak of pore radius distribution between 25Å and 250Å. A third object of the present invention is to provide a method for forming an anodized film having at least one peak of pore radius distribution between 25Å and 250Å.

[0006]

The above objects of the present invention have been achieved by an anodized film having at least one peak of pore radius distribution between 25Å to 250Å and a method for forming the anodized film. In the present invention, the target metal is not particularly limited as long as it can form an anodized film, but in general, aluminum alone, a metal provided with an aluminum layer, or duralumin containing 60% by weight or more of aluminum, etc. Is an alloy of.

The substrate provided with the anodic oxide film may have any shape, and may have a plate shape, a sheet shape, a
The shape may be ribbon, tubular, honeycomb, or the like. In this case, the substrate provided with the anodic oxide coating may be the one on which the metal surface is still anodized, but as will be described later, only the anodic oxide coating is produced once, and the anodic oxide coating is applied to, for example, a plastic sheet or It may be one that adheres to the surface of paper or porous zeolite.

The anodic oxidation in the present invention may be carried out by a known method, and as the treatment liquid, for example, a chromic acid aqueous solution, an oxalic acid aqueous solution, a sulfuric acid aqueous solution or the like can be used. Depending on the pH of the treating solution, the temperature of the solution, and the type of acid, a porous alumina film of 300 Å to a maximum of several hundred μm is formed.

In the present invention, after anodic oxidation, the specific resistance is 2 × 10.
^Five Degassed water at 5 ° C to 45 ° C that is Ωcm or more
Å ~ 25 by hydration sealing treatment using
Have at least one pore radius distribution peak between 0 and
After forming the anodic oxide film,
By firing, an anode having this pore radius distribution
Fix the oxide film.

If the hydration sealing treatment temperature is 5 ° C. or lower, necessary treatment is required.
If the processing time becomes too long, and if it exceeds 45 ° C, the hydration sealing will occur.
Since the reaction is too fast and the pore radius becomes about 20Å,
The fabric becomes difficult to control. Moreover, the specific resistance is 2 × 1.
0^Five Water above Ωcm should be removed by distillation or ion exchange method.
It can be easily obtained, but especially from the viewpoint of manufacturability.
It is preferable to use ion-exchanged water.

The longer the hydration sealing treatment is performed at low temperature, the longer 25 Å
While the pore radius distribution of ~ 250Å becomes nearly flat, the higher the temperature, the more it has a maximum value within the pore radius range, and the maximum value should be set at two points between 20Å ~ 300Å. Is also easy. The treatment time may be appropriately adjusted within the range of several minutes to several hours depending on the temperature for the hydration sealing treatment and the desired pore radius distribution.

Two peaks are 25 Å depending on the processing conditions.
It is also possible to make it fall within the range of ~ 250Å or only one peak can fall within the range of 25Å to 250Å. The pore radius in the present invention is measured by the nitrogen desorption method or the mercury intrusion method. Further, when the anodic oxide film is obtained alone, for example, the known hydrochloric acid / copper chloride solution method (Ichimura et al., Chemical Engineering 59th Annual Meeting, J123, 1994) is used.
Year).

The anodic oxide coating of the present invention can be applied, for example, as a separation membrane functioning as a molecular sieve, depending on the distribution of pore radius. The substrate having an anodized film of the present invention can be used as a high heat transfer catalyst carrier, as a high-density magnetic film by depositing a metal in pores, as an EL device by doping a phosphor in the pores, or conventionally. It can be applied as a decorative article or the like having a dark color tone.

[0014]

The anodic oxide film having a pore structure of the present invention can be applied to various uses according to the pore radius distribution. Further, the substrate having an anodized film surface of the present invention can be used as a catalyst carrier corresponding to a plurality of reactions or can realize a decorative article having a color tone different from the conventional one. Further, the method of controlling the pore radius distribution of the anodic oxide coating of the present invention is a simple method of treating with ion-exchanged water or the like at 5 ° C to 45 ° C, so that industrialization is extremely easy.

[0015]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Examples 1 to 3 and Comparative Example 1. JIS-A10
After washing 50 standard aluminum having a thickness of 0.3 mm in a 20 wt% sodium hydroxide aqueous solution for 3 minutes, 30
A pretreatment was performed in which a neutralization treatment was performed for 1 minute in a nitric acid aqueous solution of wt%. Then, the current density was set to 50 A / m ^{2 in} a 4 wt% oxalic acid aqueous solution at 20 ° C., and anodization treatment was performed for 16 hours.

Then anodized aluminum surface
The specific resistance is about 10⁶ Ωcm and degassed 4
Using ion-exchanged water at 0 ° C for 0 hours (anode
Oxidation only, Comparative Example 1), 1 hour (Example 1), 1.5
Time (Example 2) and 2 hours (Example 3) Hydration sealing treatment
Then, air calcination is performed at 450 ° C for 3 hours to obtain a porous anode.
An oxide film was formed. Pore radius of the obtained anodized film
The results of the distribution measured by the nitrogen desorption method are shown in Fig. 1.
That's right.

Comparative Example 2. Hydration and sealing treatment at 50 ° C for 15
The same procedure as in Example 1 was carried out except that the heating was carried out for a minute, and it was confirmed that the pore radius of the anodized film was 20Å and the hydration sealing reaction was extremely fast, so that only the pore radius of 20Å was formed. . The pore radius distribution of the obtained anodized film is as shown in FIG.

Comparative Example 3. The hydration sealing treatment was carried out in the same manner as in Example 1 except that the hydration sealing treatment was carried out at 4 ° C. for 3 hours. The pore radius of the anodized film was 280Å, and the progress of the hydration sealing treatment was extremely slow. It was confirmed that it was not appropriate. The pore radius distribution of the obtained anodized film is as shown in FIG.

From these results, the anodic oxide coating of the present invention has at least one peak of pore radius distribution between 25Å to 250Å, and the suitable temperature for the hydration sealing treatment is 5 ° C to 45 ° C. It was demonstrated to be in the range of ° C. still,
These data were in agreement with the observation data by SEM photographs after anodization.

[Brief description of drawings]

FIG. 1 Pore radius distribution curve when hydration sealing treatment was performed at 40 ° C.

FIG. 2 Pore radius distribution curve when hydration sealing treatment is performed at 50 ° C.

FIG. 3 Pore radius distribution curve when hydration sealing treatment is performed at 4 ° C.

Claims (4)

[Claims] 1. An anodized film having at least one peak of pore radius distribution between 25Å and 250Å. 2. The anodic oxide film according to claim 1, which has two peaks of pore radius distribution between 20Å and 300Å. 3. A metal substrate having the anodized film according to claim 1 or 2 on its surface. 4. The anodized metal surface has a specific resistance of 2
× 10^Five 5 ° C to 45 degassed and above Ωcm
After hydrating and sealing with water at ℃ for several minutes to several hours, 30
25 Å ~ characterized by baking at 0 ° C to 500 ° C
At least one peak of pore radius distribution between 250Å
A method of forming an anodized film having.