JP3224563B2 - A method for enlarging the active surface area of alloy materials in which intermetallic compounds are uniformly dispersed - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a material in which an intermetallic compound is uniformly dispersed and crystallized, for example, for an electrode of an electrolytic capacitor, an aluminum alloy containing a valve metal is electrolytically etched to expose the intermetallic compound and expose the surface area. It is about how to expand.

[0002]

2. Description of the Related Art An electrode of an electrolytic capacitor as described above is used for enlarging the surface of an alloy material and using the enlarged surface to improve the characteristics.

Conventionally, electrodes (anodes) of electrolytic capacitors include:
Metal plates or foils of aluminum (Al) or tantalum (Ta) are often used. These anode materials are roughened by electrolytic etching to increase the surface area in order to increase the capacitance, and are also subjected to anodizing to form an insulating film.

[0004] In other words, in order to manufacture a large-capacity capacitor, it is necessary to increase the surface area of the electrode material and to form a thin and highly insulating film on the surface. Conventionally used Al foil is oxidized to form an Al ₂ O ₃ film. The dielectric constant of Al ₂ O ₃ is approximately 7 to 10, and other metals such as Ta and Ti
Oxide film (Ta ₂ O ₅ or TiO ₂ ) is not so high. Therefore, by means of mechanical or chemical or electrochemical etching, the surface area is increased and, on the other hand, the formation of an oxide film is improved, while the anodization is improved, for example a conversion film with an ammonium borate solution and an ammonium phosphate solution. Attempts have been made to increase the capacitance by a method such as forming a composite film of a chemical conversion film.
Even by these methods, sufficiently high characteristics have not been improved.

Recently, it has been proposed that a large capacity electrolytic capacitor be obtained by using an alloy obtained by adding another valve metal to pure Al as an anode material and manufacturing the alloy by a rapid solidification method. Etc. suggested. That is, for example, Japanese Unexamined Patent Publication No. 1-124212 discloses this.
An alloy electrode containing at least one kind of valve metal such as Ti, Ta, Zr, Hf and Nb in Al, and finely dispersing and crystallizing the intermetallic compound of these valve metals and Al is presented. As a specific method for producing this electrode material, a rapid solidification method using a rapidly rotating roll is exemplified.

The Al alloy foil containing such a valve metal is also subjected to the above-mentioned chemical or electrochemical etching to increase its surface area. The conventional etching method has a problem that the amount of exposure of the intermetallic compound is insufficient and the active surface may not be sufficiently enlarged.

[0007]

In the above alloy foil, Al and other valve metals (Ti, Zr, etc.) are contained in the foil.
And the intermetallic compound is crystallized with, oxides such as Ti, Zr forming the intermetallic compound has a high dielectric constant several times as compared to the Al oxide, increase the capacitance of the electrolytic capacitor can do. Also, in the Al alloy foil produced by the rapid solidification method, since these intermetallic compounds crystallize as dendrites having a large number of branches in the cooling and solidifying stage, the intermetallic compound composed of this valve metal is used. Exposure would greatly increase the active surface area of the foil.

In view of the above, the present invention has improved an electrolytic etching method which has not been considered to be sufficient in the past. In an alloy foil used for an electrode for an electrolytic capacitor or the like, the exposed surface of an intermetallic compound in the foil was reduced. It is an object to provide a method for increasing the effective surface area at most.

[0009]

To achieve the above object, the present invention provides: (1) an alloy material in which an intermetallic compound is uniformly dispersed and crystallized ;
A method for enlarging an active surface area, comprising performing electrolysis in a non-aqueous solvent-based electrolyte using a metal material as an anode, selectively etching a metal matrix, and exposing an intermetallic compound surface.

(2) An alloy material in which an intermetallic compound is uniformly dispersed and crystallized is treated in an aqueous solvent-based electrolytic solution to etch a peripheral metal matrix of the intermetallic compound. A method for expanding an active surface area, comprising treating and exposing an active surface of an intermetallic compound.

[0011]

As described above, the alloy foil of the present invention is obtained by finely dispersing an intermetallic compound, and the particle size and distribution density of the intermetallic compound can be adjusted by the composition of the alloy and the production conditions. it can.

Generally, as the content of alloying elements increases, the number of intermetallic compounds crystallized increases. The On cooling during alloy production, crystallisation is reduced when faster the cooling rate,
Slower and crystallization amount is increased.

[0014] The quenched foil produced using the cooling roll is
On the roll surface and on the opposite free surface, the intermetallic compound
Although slightly different sizes out crystals, the relationship between the cooling rate, may be considered to be the same tendency as above, usually from 10 ² to 10 ⁶
Cooling rate of ° C / sec. Further, the content of the alloy element in the alloy foil must be 1 at% or more. If the content is too large, the withstand voltage of the dielectric material is reduced. Therefore, it is preferable that the content is not more than 60%.

The alloy foil used in the present invention may be any as long as the intermetallic compound is finely dispersed. For example, as an electrode material of an electrolytic capacitor, Al, Ti, Zr, Ta,
An Al-based alloy to which at least one of Hf, Si, Zn, Nb, Bi and Mg is added is used.

[0016]

When an alloy foil in which an intermetallic compound of an appropriate size is dispersed and crystallized in the above-mentioned Al base alloy is subjected to a usual electrochemical method, for example, electrolytic etching with a hydrochloric acid solution, the Al matrix takes precedence. However, as corrosion progresses, intermetallic compounds also dissolve at the same time.
In addition, when the progress of corrosion is adjusted, A
l metal remains.

The intermetallic compound has a very large surface area because it forms a thin oxide film having a high dielectric constant and is a dendritic crystal having many branches depending on the constituent metals. Therefore, the exposed surface of the intermetallic compound having such properties cannot be sufficiently obtained by the conventional method.

According to the present invention, the metal matrix is formed by etching with a non-aqueous solvent-based electrolyte instead of or in combination with a conventionally used aqueous solvent such as the above-mentioned (hydrochloric acid solution). It melts preferentially and leaves the surface of the crystallized substance (intermetallic compound) in the foil in a sufficiently exposed state. In other words, when etching in a non-aqueous solvent-based electrolyte, the matrix is selected by placing the alloy foil on the anode side and conducting a short-term electrolysis with constant potential electrolysis or a constant voltage for several seconds to several tens of seconds. Dissolved and the surface of the crystallized material appears.

As the non-aqueous solvent-based electrolyte, for example, 1
0% methyl salicylate-2% tetromethylammonium chloride-methanol, acetylacetone-tetramethylammonium chloride-methyl alcohol, triethanolamine-tetramethylammonium chloride-methyl alcohol, trichloroacetylacetone-tetramethylammonium chloride There are light-methyl alcohol type, sulfosatilic acid-lithium chloride alcohol type and the like.

According to the present invention, in addition to the etching treatment using only the non-aqueous solvent electrolytic solution, as a pretreatment, the surface area of the alloy foil and the surface area of the alloy foil can be improved by performing an electrolytic etching treatment using a conventional aqueous solvent solution. The active surface area can be increased.

That is, the metal matrix is first selectively dissolved so as not to dissolve the intermetallic compound in the alloy foil by ordinary etching. That is, as shown schematically in FIG. 1A, when the Al-based Zr alloy foil 1 is subjected to electrolytic etching with, for example, a hydrochloric acid solution, the Al matrix 2 is selectively etched, and a deep pit 3 is formed. However, Al-Zr intermetallic compounds in the foil (dendrites)
4 is covered with an Al matrix as shown in the partial enlarged view of FIG. In this state, the surface area is considerably increased. When this is etched with a non-aqueous solvent-based electrolyte, the Al matrix is further dissolved as shown in FIG. 2 (a), and the dendrite (Al-Zr intermetallic compound) is ) To expose the branches. That is, an active intermetallic compound is exposed, and the effective (active) surface area can be increased.

As described above, if the metal matrix is deeply pitted by the usual electrolytic etching method (without dissolving the intermetallic compound), the exposure of the intermetallic compound can be performed extremely easily with a nonaqueous solvent solution. it can.

The combination of the ordinary etching and the non-aqueous solvent electrolytic solution treatment may be any method in which each is combined independently or is a continuous process.

[0024]

EXAMPLE A roll made of Cu having a diameter of 300 mm and a width of 50 mm was rotated in an inert gas at a speed of 1300 rpm. The nozzle was ejected from the nozzle below the container at an ejection pressure of cm ² to obtain an alloy foil having a thickness of 100 to 120 μm.

[0025]

[Table 1]

As shown in Table 2, a normal etching solution and a non-aqueous solvent solution were prepared, and the rapidly solidified alloy foil was subjected to the etching treatment alone or in combination under the treatments shown in the same table.

[0027]

[Table 2]

The etched foil was further subjected to formation by passing an electric current of 20 V with an ammonium borate solution, and the capacitance was measured. Table 3 shows the combinations of the etching methods and the measurement results of the capacitance. In the same table, the case where only the conventional etching method is performed is also shown for comparison.

[0029]

[Table 3]

As is clear from Table 3, instead of the ordinary (conventional) method, a single electrolytic etching was performed using a non-aqueous solvent-based electrolytic solution. The processing method of the present invention in which the above combination is performed has a considerably improved CV product as compared with the processing of the conventional method alone shown as a comparative example. This means that the surface of the intermetallic compound can be sufficiently exposed by the method of the present invention, the surface area can be considerably increased, and the CV product can be improved.

[0031]

As described above, the etching according to the present invention exposes the intermetallic compound together with the deep pitting of the metal foil, thereby making it possible to obtain a metal foil having an increased surface area. For example, it is extremely useful as an electrode of an electrolytic capacitor. Therefore, a capacitor having a large capacitance can be obtained. In addition, the present invention is not limited to the electrodes, and can be applied to catalyst materials, battery materials, and the like, and includes these materials.

[Brief description of the drawings]

FIGS. 1 (a) and 1 (b) are explanatory views showing the etching state of an alloy foil obtained by a normal etching method applied to the present invention.

FIGS. 2 (a) and 2 (b) are explanatory views showing an etching state of an alloy foil obtained by a non-aqueous solvent electrolytic etching treatment of the present invention.

[Explanation of symbols]

 1: alloy foil 2: matrix 3: pitting corrosion 4: intermetallic compound

Continued on the front page (72) Michio Endo 1618 Ida, Nakahara-ku, Kawasaki City, Kanagawa Prefecture New Nippon Steel Corporation Advanced Technology Research Laboratories (72) Inventor Yuichi Sato 20-1 Shintomi, Futtsu City, Chiba Prefecture Nippon Steel Corporation (58) Field surveyed (Int.Cl. ⁷ , DB name) C25F 3/04 H01G 9/04

Claims (2)

(57) [Claims] An alloy material in which an intermetallic compound is uniformly dispersed and crystallized is electrolyzed in a non-aqueous solvent-based electrolyte using the metal material as an anode, and a metal matrix is selectively etched to form an intermetallic compound. An active surface area enlarging method characterized by exposing a surface. 2. An alloy material in which an intermetallic compound is uniformly dispersed and crystallized is treated in an aqueous solvent-based electrolytic solution to etch a peripheral metal matrix of the intermetallic compound, and then subjected to a non-aqueous solvent electrolytic solution electrolytic treatment. And exposing an active surface of the intermetallic compound.