JP6760640B2 - Manufacturing method of anodic oxide porous alumina - Google Patents

Description

The present invention relates to anodized porous alumina in which pores are arranged finely and with high regularity and a method for producing the same. Regarding the membrane and its manufacturing method.

Anodized porous alumina obtained by anodizing aluminum in an acidic bath is expected to have various applications such as filters, catalyst carriers, and template materials because it has a hole array structure in which pores of uniform size are arranged. It is a functional material that can be produced.
One of the characteristics of anodized porous alumina is that when anodization is performed under appropriate conditions, the pores form a regular arrangement in a self-organizing manner (Non-Patent Document 1).
Since the pore period of anodic oxide porous alumina changes depending on the anodic oxidation voltage, 35 nm can be obtained by optimizing various conditions such as the type, concentration, bath temperature, and anodic oxidation time of the electrolytic solution under each voltage condition. It has been clarified that anodized porous alumina in which pores are regularly arranged in the range of 500 nm can be produced (Non-Patent Document 2).
Further, the pore diameter of porous alumina formed by anodic oxidation has a size of 1/4 to 1/3 of the pore cycle, and if the pore walls are dissolved by etching treatment using an acidic aqueous solution, Since it is possible to expand the pore diameter, it is possible to produce highly regular porous alumina in which the pore cycle and the pore diameter are controlled according to the application. Since the self-organizing ordered arrangement of pores progresses with the growth of the alumina film, at least the aspect ratio (pore depth / fineness) is required to produce porous alumina having high pore arrangement regularity. Pore period value) It is necessary to form a porous layer of 20 or more. Regarding the production of porous alumina having a pore period of 500 nm or more, it has been possible to produce porous alumina by performing anodization under high voltage conditions using an aqueous solution of citric acid, malic acid, tartaric acid, etc. Has been reported (Non-Patent Documents 3 to 8).

However, in the studies so far, the formation of a porous alumina layer having an aspect ratio of more than 20 has not been reported, and as a result, the formation of a porous alumina layer in which pores are self-organized and regularly arranged has been realized. Absent. In a recent report, Kikuchi et al. Can form a film with an aspect ratio of more than 20 in porous alumina with a pore period of 710 nm in anodization using etidronic acid, and as a result, the pores are self-organized. It has been reported that arranged porous alumina can be obtained (Non-Patent Document 9).
However, it is difficult to form porous alumina having a pore period larger than 710 nm by anodic oxidation using etidronic acid, and production of highly regular porous alumina having a pore period exceeding 720 nm has not been realized.
On the other hand, it is also possible to produce porous alumina in which pores are regularly arranged by subjecting the surface of the Al material used for anodic oxidation in advance to form a recess that functions as a starting point for pore generation. (Non-Patent Document 10).
It has been reported that based on such a textured process, it is possible to produce porous alumina in which the pore period is regularly arranged in the range of 1 μm to 3 μm (Non-Patent Document 11).
According to the textured process, since pore generation is induced from the recessed portion, highly regular porous alumina can be produced relatively easily, but the size of the obtained sample is limited to the mold size used. There is a problem that it is difficult to prepare a large-area sample. In addition, the textured process is difficult to apply to curved surfaces, and there are large manufacturing restrictions, such as the difficulty of forming highly regular porous alumina on the surface of roll-shaped Al based on the textured treatment. There is a problem.

H. Masuda and K. Fukuda, Science, 268, 1466 (1995). Masuda, Yanagishita, Kondo, Nishio, Zeolite, 26, 45 (2009)). S. Ono, M. Saito, M. Ishiguro, and H. Asoh, J. Electrochem. Soc., 151, B473 (2004), A. Mozalev, I. Mozaleva, M. Sakairi, H. Takahashi, Electrochimca Acta, 50, 5065 (2005), S. Z. Chu, K. Wada, S. Inoue, M. Isogai, Y. Katsuta and A. Yasumori, J. Electrochem. Soc., 153, B384 (2006), Q. Wang, Y. Long, B. Sun, J. Porous Mater., 20, 785 (2013), X. Chen, D. Yu, L. Cao, X. Zhu, Y. Song, H. Huang, L. Lu, X. Chen, Mater. Res. Bull., 57, 116 (2014), J. Bellemare, F. Sirois, and D. Menard, J. Electrochem. Soc., 161, E75 (2014) T. Kikuchi, O. Nishinaga, S. Natsui, and O. Suzuki, Electrochimica Acta, 156, 235 (2015).) H. Masuda, H. Yamada, M. Satoh, H. Asoh, M. Nakao, T. Tamamura, Appl. Phys. Lett., 71, 2770 (1997)). Q. Lin, S. Leung, K. Tsui, B. Hua and Z. Fan, Nanoscale Res. Lett., 8, 268 (2013)).

In short, the conventionally proposed porous alumina has a pore period as large as exceeding 700 nm, is applicable to a large area, and is a method for producing porous alumina that can be applied to roll-shaped bare metal. Has not been proposed, and therefore porous alumina with such a large pore period has not been proposed.
Therefore, it is an object of the present invention to have anodized porous alumina having a pore period larger than 700 nm and capable of producing a large area or a curved surface, and having such a pore period for a large area. It is an object of the present invention to provide a method for producing porous alumina, which is applicable to roll-shaped bare metal, and a porous alumina through-hole membrane using the porous alumina and a method for producing the same.

As a result of diligent studies to solve the above problems, the present inventors can cope with a large area by simply scaling up the apparatus used for anodic oxidation according to the self-organization process. Focusing on the advantage that it can be applied to surfaces with curvature, as a result of examining porous alumina anodized by such a self-assembling process, the above purpose was achieved by adding a specific acid to the acidic electrolytic solution. (To obtain anodized porous alumina having a pore cycle as described above), the present invention has been completed.
That is, the present invention provides the following inventions.
1. 1. Anodized porous alumina in which the period of pores is 720 nm or more and regularly arranged pores are arranged in an ideal triangular lattice in a range of 4 × 4 or more in length and width.
2. 2. The anodized porous alumina according to 1, wherein the pores are arranged in an ideal triangular lattice in a range of 5 × 5 or more in length and width.
3. 3. The anodized porous alumina according to 1, wherein the pores are arranged in an ideal triangular lattice in a range of 6 × 6 or more in length and width.
4. The anodized porous alumina according to 1, wherein the pores are arranged in an ideal triangular lattice in a range of 7 × 7 or more in length and width.
5. 6. Anodized porous alumina according to any one of 1 to 4, wherein the film thickness is 15 μm or more. 7. Anodized porous alumina according to any one of 1 to 5, wherein the difference between the thickest portion and the thinnest portion is within 20% of the thickness of the thickest portion. The anodic oxide porous alumina according to any one of 1 to 6, wherein the number of lateral holes formed on the pore wall surface of each of the above pores is 5 or less for one pore.
8. The anodic oxide porous alumina according to any one of 1 to 7, wherein the copper concentration is 30 ppm or less.
9. 8. The anodic oxide porous alumina according to 8, wherein the copper concentration is 20 ppm or less.
10. 9. Anodized porous alumina according to 9, wherein the copper concentration is 10 ppm or less.
11. The anodic oxide porous alumina according to any one of 1 to 10, wherein the period of the pores is 750 nm or more.
12. 11. The anodic oxide porous alumina according to 11, wherein the period of the pores is 1 μm or more.
13. It is provided with an anodic oxidation step of anodicating an aluminum material, and in the anodic oxidation step, the acidic electrolytic solution used for anodic oxidation is a basic acid and 1% by weight or less of phosphoric acid or phosphate in the entire electrolytic solution. The method for producing anodized porous alumina according to any one of 1 to 12, wherein the method comprises.
14. 13. The method for producing anodized porous alumina according to 13, wherein at least one of citric acid, malic acid and tartaric acid is contained as the basic acid.
15. The method for producing anodized porous alumina according to any one of 12 to 14, wherein the acidic electrolytic solution contains a solution containing an organic solvent miscible with water.
16. 15. The anodic oxidation according to 15, wherein the organic solvent is at least one selected from the group consisting of ethanol, methanol, propanol, isopropyl alcohol, ethylene glycol, tetrahydrofuran, acetone, dimethylformamide, triethylamine and dimethyl sulfoxide. Method for producing porous alumina.
An anode in which pores are regularly arranged from the surface, which is obtained by selectively dissolving and removing the anodized porous alumina according to 17.1 and then anodizing again under the same voltage conditions as in the production of the anodized porous alumina. Porous alumina oxide.
An anodicated porous alumina through-hole membrane through which each pore in the anodized porous alumina according to any one of 18.1 to 12 is penetrated.
A method for producing an anodic oxide porous alumina through-hole membrane according to 19.18.
After forming porous alumina on the surface of the aluminum base metal by anodic oxidation, anodization is performed under predetermined voltage conditions using concentrated sulfuric acid as the electrolytic solution to form a highly soluble alumina layer at the bottom of the film, giving priority to the alumina layer. A method for producing an anodized porous alumina through-hole membrane, which comprises a removing step of dissolving and removing the aluminum oxide.

The anodic oxide porous alumina of the present invention is so large that the pore period exceeds 700 nm, and can be manufactured even on a large area or a curved surface.
Further, according to the method for producing anodized porous alumina of the present invention, the anodized porous alumina of the present invention can be applied to a large area and also to a curved surface such as a roll-shaped bare metal.
Further, since the anodic oxide porous alumina through-hole membrane of the present invention is made by using the anodic oxide porous alumina of the present invention, the pore period is so large that it exceeds 700 nm, and it can be manufactured even on a large area or a curved surface.
Further, according to the method for producing an anodized porous alumina through-hole membrane of the present invention, the anodized porous alumina through-hole membrane of the present invention can be easily obtained.

FIG. 1 is a fracture perspective view schematically showing a main part of the anodic oxide porous alumina of the present invention. FIG. 2 is an electron micrograph (drawing substitute photograph) of the highly regular anodized porous alumina having a pore period of 750 nm obtained in Example 1.

Hereinafter, the present invention will be described in more detail.
<Anodic Porous Alumina>
The anodized porous alumina of the present invention has a pore period of 720 nm or more, and regularly arranged pores are arranged in an ideal triangular lattice pattern in a range of 4 × 4 or more in the vertical and horizontal directions without using a textured treatment. Has been done.
Here, the period of the pores is equal to the distance between the center positions of the pores, as shown by P in FIG. The number of vertical and horizontal pores is the number of pores in the vertical direction (arrow L direction) and the number of pores in the horizontal direction (arrow S direction) shown in FIG. 1, respectively.
Further, as shown in FIG. 1, the ideal triangular lattice shape is a structure in which pores are arranged in a triangular lattice pattern without defects or disorder of arrangement, and adjacent triangular lattices have substantially the same shape (for example, positive). Refers to an array having a triangle).

(pore)
The pores in the present invention are self-organized and regularly arranged without artificially imparting depressions that function as starting points for pore generation.
As described above, the period of the pores is 720 nm or more, preferably 750 nm or more, more preferably 800 nm or more, more preferably 900 nm or more, and most preferably 1 μm or more. The upper limit of the pore cycle is not particularly limited, but is preferably 2 μm or less. Pore cycles of less than 720 nm reduce utility in the desired application.
The aspect ratio (value of pore depth / pore period) of the pores is preferably 20 or more. That is, as shown in FIG. 1, the pores 3 have a circular opening on the surface and are perforated downward in the vertical direction from the opening to form a rod-shaped void, and the depth of the void is formed. The ratio (aspect ratio) between the plumb bob and the pore period is preferably in the above range.
Further, as described above, the pores are in the range of 4 × 4 or more in the vertical and horizontal directions, preferably in the range of 5 × 5 or more in the horizontal direction, and more preferably in the range of 6 × 6 or more in the horizontal direction. More preferably, they are arranged in an ideal triangular lattice in a range of 7 horizontal × 7 or more.

Further, the anodic oxide porous alumina of the present invention preferably has a film thickness (D in FIG. 1) of 15 μm or more, more preferably 20 μm or more, and more preferably 50 μm or more. The upper limit of the thickness is not particularly limited, but is preferably 200 μm or less. By setting the film thickness to 15 μm or more, it is possible to obtain porous alumina in which pores are regularly arranged in a self-organizing manner as a result.
In the anodized porous alumina of the present invention, the film thickness D has a certain thickness difference, but the difference between the thickest portion and the thinnest portion is preferably within 20% of the thickness of the thickest portion. It is more preferably within 15%.
Since each pore of porous alumina grows perpendicular to the film thickness direction, when the film thickness unevenness is large, the growth direction of the pores becomes non-uniform and a regular pore arrangement cannot be obtained. Therefore, the difference in thickness is preferably within 20%, whereby porous alumina in which pores are regularly arranged in a self-organizing manner can be obtained.

The anodic oxide porous alumina of the present invention is preferably produced by a production method described later, but the pores to be formed may have horizontal holes formed on the inner wall surface thereof. In the present invention, the number of lateral holes formed on the pore wall surface of each of the above pores is preferably 5 or less, and more preferably 4 or less with respect to one pore. When the number of lateral holes is within the above range, the pore arrangement regularity is not deteriorated, and the anodic oxide porous alumina is obtained.
Further, the anodic oxide porous alumina of the present invention preferably has a copper concentration of 30 ppm or less, more preferably 20 ppm or less, and even more preferably 10 ppm or less. In order to make this copper concentration range, an aluminum material having a copper concentration within the above-mentioned copper concentration range may be used. Further, when the copper concentration is within the above range, porous alumina having a pore period of 700 nm or more can be obtained as described above.

(Other configurations)
Further, in the present invention, another metal layer or an alumina layer is provided on the front surface (the surface on which the opening is formed) or the back surface (the surface on the opposite side thereof) of the anodized porous alumina, and a metal or a semiconductor is provided in a part of the pores. , Organic substances, polymers, etc. may be filled.

<Manufacturing method of anodized porous alumina>
Next, the method for producing the anodic oxide porous alumina of the present invention will be described.
The method for producing anodized porous alumina of the present invention can be carried out by performing an anodic oxidation step of anodicating an aluminum material. In the anodic oxidation step, the acidic electrolytic solution used for anodic oxidation is composed of a basic acid and an acid. It is characterized by containing 1% by weight or less of phosphoric acid or phosphate in the whole acidic electrolytic solution.
It will be described in more detail below.

(pre-process)
First, as a pretreatment for the anodic oxidation step, a mirroring treatment of an aluminum material as a raw material is performed.
As the aluminum material to be used, as long as it is an aluminum material usually used as a material for such porous alumina, various materials such as a large-sized material and a material wound in a roll shape can be used without particular limitation.
Further, the aluminum material preferably has a copper concentration of 30 ppm or less, more preferably 20 ppm or less, and even more preferably 10 ppm or less.
When anodic oxidation is performed under a voltage condition of 100 V or higher, the porous alumina formed on the surface of the aluminum material is greatly affected by a trace amount of impurity elements contained in the bare metal. In particular, when an aluminum material containing a small amount of copper is used, porous alumina having a large number of horizontal holes is formed on the wall surface of the pores, which hinders the formation of a regular pore arrangement. Therefore, the copper concentration is kept within the above range. Is preferable. That is, in the present invention, even if anodic oxidation is performed under a high voltage condition exceeding 150 V, it is possible to effectively prevent the generation of lateral holes oriented in the direction parallel to the film surface in addition to the vertically oriented pores. Therefore, it is preferable to use the above copper concentration.
The mirroring treatment can be performed by electrolytic polishing according to a conventional method.

(Anodization process)
The anodic oxidation step can be carried out using an acidic electrolytic solution containing a basic acid and phosphoric acid or phosphate.
As the above-mentioned basic acid, it is preferable to use at least one of citric acid, malic acid and tartaric acid.
The content of the phosphoric acid or phosphate is 1% by weight or less in the entire acidic electrolytic solution, but preferably 0.1% by weight or less. The lower limit is not particularly limited, but is preferably 0.01% by weight.
Further, the acidic electrolytic solution is preferably an aqueous solution containing the above-mentioned basic acid and phosphoric acid or phosphate (that is, the main solvent of the electrolytic solution is water), and the content of the above-mentioned basic acid. Is preferably 1 to 10% by weight, more preferably 2 to 5% by weight, based on the total amount of the acidic electrolytic solution.

Further, the acidic electrolytic solution preferably contains a solution containing an organic solvent miscible with water as its solvent. The organic solvent is preferably at least one selected from the group consisting of ethanol, methanol, propanol, isopropyl alcohol, ethylene glycol, tetrahydrofuran, acetone, dimethylformamide, triethylamine and dimethyl sulfoxide. When the above organic solvent is used, the amount used is preferably water: organic solvent = 5 to 10: 1 in terms of volume ratio with water.
Dielectric breakdown is likely to occur in the anodic oxidation of aluminum under high voltage conditions, and once dielectric breakdown occurs, it is difficult to continue stable anodic oxidation. However, by using the above organic solvent, a high voltage is used. It is preferable to use such an organic solvent because stable dielectric breakdown can be realized even under conditions.

The anodic oxidation conditions are preferably as follows.
That is, the anodic oxidation temperature is preferably −10 ° C. to 70 ° C., more preferably 0 to 50 ° C., and even more preferably 15 to 50 ° C. The voltage is preferably 200 to 500 V, more preferably 300 to 450 V. Further, the time is not particularly limited because it needs to be changed according to the voltage and temperature, but it is preferably 5 to 200 hours, more preferably 6 to 30 hours.

(Post-process)
Further, in the present invention, after the anodic oxidation step, the post-treatment can be performed by immersing in a solution such as phosphoric acid chromate.

<Anodized Porous Alumina Through Hole Membrane>
The anodic oxide porous alumina through-hole membrane of the present invention is formed as a through hole through which each pore in the above-mentioned anodic oxide porous alumina of the present invention penetrates. Therefore, the material, pore period, etc. are the same as those of the above-mentioned anodized porous alumina, but the film thickness is different from that of the present invention, depending on the method for forming through holes. That is, when the bottom of the pores is simply dissolved to form a through hole, the film thickness itself is the same as that of the above-mentioned anodized porous alumina, but the anodized porous alumina through-hole membrane produced by the production method described later has a thickness. Since the through holes are formed by dissolving and removing the bottom portion, the film thickness is slightly thinner than the film thickness of the above-mentioned anodized porous alumina.

<Manufacturing method of anodized porous alumina through-hole membrane>
In the anodized porous alumina through-hole membrane of the present invention, the residual metal is selectively dissolved and removed in an etchant such as an iodomethanol solution, and then an alumina layer called a barrier layer formed on the bottom of the porous alumina film is chemically formed. It can be obtained by removing it by a physical or physical method. Various acidic solutions such as an aqueous phosphoric acid solution can be used for the chemical dissolution of the barrier layer, and various dry etching methods such as Ar ion milling are effective for the physical removal method.
Further, after the anodic oxidation, the electrolytic solution is replaced with a high-concentration sulfuric acid aqueous solution, and when the anodic oxidation is continued, a highly soluble alumina layer is formed at the bottom of the film, and the bottom of the film is selected by the subsequent treatment. Since it is possible to dissolve and remove the membrane, it is possible to easily obtain a highly regular through-hole membrane having a large cycle. The concentration of the sulfuric acid aqueous solution used at this time is preferably 10 M or more, and concentrated sulfuric acid may be used.
That is, in a particularly preferable method for producing an anodized through-hole membrane of the present invention, after forming porous alumina on the surface of an aluminum base metal by anodization (that is, producing the above-mentioned anodized porous alumina), the electrolytic solution is used as concentrated sulfuric acid. It can be carried out by performing anodic oxidation under a predetermined voltage condition, forming a highly soluble alumina layer at the bottom of the film, and performing a removal step of preferentially dissolving and removing the alumina layer.
Here, various predetermined voltage conditions can be selected under the same conditions as the voltage in the above-mentioned method for producing porous alumina. In addition, various temperature conditions and times can be similarly selected.
Further, the above-mentioned subsequent treatment and the above-mentioned dissolution / removal can be carried out by the same treatment, for example, by immersing in a phosphoric acid chromate mixed solution (aqueous solution) for 10 to 60 minutes.

(Regeneration)
Further, if the alumina layer formed in the aqueous sulfuric acid solution is thinned to 1 micron or less, a high-concentration sulfuric acid stratification having a regular pore arrangement can be formed. Therefore, after the membrane is peeled off by etching with an aqueous solution of phosphoric acid or an aqueous solution of chromic acid, it is possible to maintain a regular dent arrangement corresponding to the structure of the back surface of porous alumina on the surface of the metal, which is the same. By performing anodization again under the above voltage conditions, it becomes possible to repeatedly produce porous alumina in which pores are regularly arranged from the surface.
That is, the anodicated porous alumina of the present invention selectively dissolves and removes the above-mentioned anodicated porous alumina of the present invention, and is regenerated by anodizing again under the same voltage conditions as when the anodicated porous alumina was produced. It may be obtained by making it.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto.
[Example 1] Preparation of highly regular porous alumina with a pore period of 750 nm An aluminum plate having a purity of 99.99% and a Cu concentration of 20 ppm or less was electropolished in a mixed solution of perchloric acid and ethanol to make a mirror surface.
The obtained sample was anodized in an aqueous solution containing 0.2 M citric acid and 0.004 M phosphoric acid at a bath temperature of 50 ° C. and 300 V for 6 hours. The film thickness of the obtained sample is 80 μm (the difference between the thickest part and the thinnest part, 15% of the film thickness of the thick part), and it has an ideal triangular lattice shape in the range of 7 × 7 or more in length and width. Arranged regular porous alumina with a pore period of 750 nm was obtained. The obtained porous alumina was confirmed by an electron microscope. The result is shown in FIG.
Further, when the number of horizontal holes formed on the pore wall surface of each of the above pores was also confirmed by an electron microscope, it was confirmed that the number was 5 or less for one pore.

[Example 2] Preparation of highly regular porous alumina with a pore period of 800 nm An aluminum plate having a purity of 99.99% and a Cu concentration of 20 ppm or less was electropolished in a mixed solution of perchloric acid and ethanol to make a mirror surface.
The obtained sample was anodized in an aqueous solution containing 0.2 M citric acid and 0.003 M phosphoric acid at a bath temperature of 30 ° C. and 320 V for 17.5 hours. The film thickness of the obtained sample is 67 μm (the difference between the thickest part and the thinnest part, 15% of the film thickness of the thick part), and it has an ideal triangular lattice shape in the range of 7 × 7 or more in length and width. It was possible to produce ordered porous alumina with a pore period of 800 nm.
Further, when the number of horizontal holes formed on the pore wall surface of each of the above pores was also confirmed by an electron microscope, it was confirmed that the number was 5 or less for one pore.

[Example 3] Preparation of highly regular porous alumina with a pore period of 850 nm An aluminum plate having a purity of 99.99% and a Cu concentration of 20 ppm or less was electropolished in a mixed solution of perchloric acid and ethanol to make a mirror surface.
The obtained sample was anodized in an aqueous solution containing 0.2 M citric acid and 0.003 M phosphoric acid at a bath temperature of 16 ° C. and 340 V for 14 hours. The film thickness of the obtained sample is 105 μm (the difference between the thickest part and the thinnest part, 15% of the film thickness of the thick part), and it has an ideal triangular lattice shape in the range of 7 × 7 or more in length and width. It was possible to produce ordered porous alumina with a pore period of 850 nm.
Further, when the number of horizontal holes formed on the pore wall surface of each of the above pores was also confirmed by an electron microscope, it was confirmed that the number was 5 or less for one pore.

[Example 4] Preparation of highly regular porous alumina with a pore period of 900 nm An aluminum plate having a purity of 99.99% and a Cu concentration of 20 ppm or less was electropolished in a mixed solution of perchloric acid and ethanol to make a mirror surface.
The obtained sample was anodized in an aqueous solution containing 0.2 M citric acid and 0.003 M phosphoric acid at a bath temperature of 16 ° C. and 360 V for 26 hours. The film thickness of the obtained sample is 93 μm (the difference between the thickest part and the thinnest part, 15% of the film thickness of the thick part), and it has an ideal triangular lattice shape in the range of 7 × 7 or more in length and width. It was possible to produce ordered porous alumina with a pore period of 900 nm.
Further, when the number of horizontal holes formed on the pore wall surface of each of the above pores was also confirmed by an electron microscope, it was confirmed that the number was 5 or less for one pore.

[Example 5] Preparation of highly regular porous alumina with a pore period of 950 nm An aluminum plate having a purity of 99.99% and a Cu concentration of 20 ppm or less was electropolished in a mixed solution of perchloric acid and ethanol to make a mirror surface.
The obtained sample was anodized in an aqueous solution containing 0.2 M citric acid and 0.002 M phosphoric acid at a bath temperature of 16 ° C. and 380 V for 23 hours. The film thickness of the obtained sample is 56 μm (the difference between the thickest part and the thinnest part, 15% of the film thickness of the thick part), and it has an ideal triangular lattice shape in the range of 7 × 7 or more in length and width. It was possible to produce ordered porous alumina with a pore period of 950 nm.
Further, when the number of horizontal holes formed on the pore wall surface of each of the above pores was also confirmed by an electron microscope, it was confirmed that the number was 5 or less for one pore.

[Example 6] Preparation of highly regular porous alumina with a pore period of 1 μm An aluminum plate having a purity of 99.99% and a Cu concentration of 20 ppm or less was electropolished in a mixed solution of perchloric acid and ethanol to make a mirror surface.
The obtained sample was anodized in an aqueous solution containing 0.2 M citric acid and 0.002 M phosphoric acid at a bath temperature of 16 ° C. and 380 V for 23 hours.
The film thickness of the obtained sample is 56 μm (the difference between the thickest part and the thinnest part, 15% of the film thickness of the thick part), and it has an ideal triangular lattice shape in the range of 7 × 7 or more in length and width. It was possible to produce ordered porous alumina with a pore period of 950 nm.
Further, when the number of horizontal holes formed on the pore wall surface of each of the above pores was also confirmed by an electron microscope, it was confirmed that the number was 5 or less for one pore.

[Example 7] Preparation of highly regular porous alumina through-hole membrane with a pore period of 750 nm An aluminum plate having a purity of 99.99% and a Cu concentration of 20 ppm or less was electropolished in a mixed solution of perchloric acid and ethanol to make a mirror surface. ..
The obtained sample was anodized in an aqueous solution containing 0.2 M citric acid and 0.004 M phosphoric acid at a bath temperature of 50 ° C. and 300 V for 6 hours.
Then, the electrolytic solution was replaced with concentrated sulfuric acid, and anodic oxidation was continuously carried out at 300 V for 1 hour.
By immersing the obtained sample in a mixed solution of phosphoric acid chromate for 20 minutes, the high-concentration sulfated stratification formed on the bottom of the film is selectively dissolved and removed, and the range is 7 × 7 or more in length and width. The 750 nm periodic porous alumina through-hole membrane in which the pores were self-assembled and regularly arranged in an ideal triangular lattice pattern was peeled off. The film thickness was 100 μm (difference between the thickest part and the thinnest part, 15% of the film thickness of the thick part).
Further, when the number of horizontal holes formed on the pore wall surface of each of the above pores was also confirmed by an electron microscope, it was confirmed that the number was 5 or less for one pore.

[Example 8] Preparation of highly regular porous alumina with a pore period of 1.1 μm by anodic oxidation using an electrolytic solution containing ethanol. Perchloric acid and ethanol mixed solution on an aluminum plate with a purity of 99.99% and a Cu concentration of 20 ppm or less. Electropolishing was performed inside to make a mirror surface.
The obtained sample was anodized in a water-ethanol mixed solution containing 0.2 M citric acid and 0.0025 M phosphoric acid (volume ratio of water to ethanol was 9: 1) at a bath temperature of 0 ° C. and 440 V for 192 hours. ..
Then, the electrolytic solution was replaced with concentrated sulfuric acid, and anodic oxidation was continuously carried out at 300 V for 1 hour. The film thickness of the obtained sample is 100 μm (the difference between the thickest part and the thinnest part, 15% of the film thickness of the thick part), and it has an ideal triangular lattice shape in the range of 7 × 7 or more in length and width. It was possible to prepare ordered porous alumina having a pore period of 1.1 μm.
Further, when the number of horizontal holes formed on the pore wall surface of each of the above pores was also confirmed by an electron microscope, it was confirmed that the number was 5 or less for one pore.

[Example 9] Preparation of highly regular porous alumina with a pore period of 750 nm by anodization using malic acid Electropolishing was performed on an aluminum plate having a purity of 99.99% and a Cu concentration of 20 ppm or less in a mixed solution of perchloric acid and ethanol. Mirrored.
The obtained sample was anodized in an aqueous solution containing 0.3 M malic acid and 0.004 M phosphoric acid at a bath temperature of 16 ° C. and 350 V for 30 hours. After dissolving and removing the bare metal of the obtained sample, the arrangement was confirmed from the back surface of the sample. As a result, the pore period was 750 nm, which was arranged in an ideal triangular lattice in the range of 7 × 7 or more in the vertical and horizontal directions. I was able to confirm that they were arranged regularly. The film thickness was 50 μm (difference between the thickest part and the thinnest part, 15% of the film thickness of the thick part).
Further, when the number of horizontal holes formed on the pore wall surface of each of the above pores was also confirmed by an electron microscope, it was confirmed that the number was 5 or less for one pore.

Claims (4)

A method for producing anodized porous alumina in which the period of pores is 720 nm or more and the regularly arranged pores are arranged in an ideal triangular lattice in the range of 4 × 4 or more in length and width.
It is provided with an anodic oxidation step of anodicating an aluminum material, and in the anodic oxidation step, the acidic electrolytic solution used for anodic oxidation is a basic acid and 1% by weight or less of phosphoric acid or phosphate in the entire electrolytic solution. preparative method for producing a positive electrode oxide porous alumina you comprising a. Citric acid as the underlying acid of the method of anodic porous alumina according to claim 1, characterized in that it comprises at least one of malic acid and tartaric acid. The method for producing anodized porous alumina according to any one of claims 1 to 2 , wherein the acidic electrolytic solution contains a solution containing an organic solvent miscible with water. The third aspect of claim 3 , wherein the organic solvent is at least one selected from the group consisting of ethanol, methanol, propanol, isopropyl alcohol, ethylene glycol, tetrahydrofuran, acetone, dimethylformamide, triethylamine and dimethyl sulfoxide. A method for producing anodized porous alumina.