JP2004244689A - Method for manufacturing porous material, and porous material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a porous material, which can freely control sizes of vacancies in a micro-region and improve an aspect ratio of the vacancy, and to provide a porous material which has the fine vacancies with the high aspect ratio. <P>SOLUTION: The method for manufacturing the porous material comprises melting a raw material and solidifying it to prepare an alloy having two or more phases regularly crystallized; and subsequently removing at least one of the two or more phases crystallized in the alloy, to form the vacancies in the positions at which the removed phases existed. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a method for manufacturing a porous body and a porous body.
[0002]
[Prior art]
BACKGROUND ART From the viewpoint of adding a filter function and a catalyst function and reducing the weight, a porous body having fine pores penetrating from the surface or from the surface to the inside has attracted attention. Conventionally, such a porous body has been implemented by using a fine processing technique such as laser processing, an electrochemical method (anodic oxidation), or foaming.
[0003]
In the above-mentioned methods such as laser processing, it is difficult to form holes of the order of μm, and it is also difficult to form holes having a depth (high aspect ratio) larger than the hole diameter of the holes. Was. Further, in the electrochemical method, since the pore size is determined by self-organization, the size is limited to the order of nm, and it is difficult to produce a porous body having pores having a pore size of the order of μm. there were. Further, in the method using the foaming, only holes of the order of mm can be formed, and it is difficult to form a porous body having fine holes, and the aspect ratio of the holes is also sufficient. Couldn't be larger.
[0004]
[Problems to be solved by the invention]
The present invention provides a method for producing a porous body, and a method for producing a porous material having a fine and high aspect ratio, in which the size of pores can be freely controlled in a minute area and the aspect ratio of the pores can be improved. It is an object to provide a porous body having the following.
[0005]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides:
Dissolving the raw materials and then solidifying to produce an alloy system in which two or more phases are regularly crystallized;
Removing at least one of the two or more phases crystallized in the alloy system and forming a void in a portion where the removed phase is located;
And a method for producing a porous body.
[0006]
According to the present invention, the target porous body is composed of an alloy system in which two or more phases are regularly crystallized, and by selectively removing at least one phase of the alloy system, It is obtained by forming holes. Therefore, if the size of the phase to be removed in the alloy system is defined within a predetermined range, the phase is removed, and thus fine pores in a wide range from the order of nm to the order of μm, specifically 0.1 μm. A porous body having pores with a size of 1 nm to 100 μm can be easily manufactured.
[0007]
In addition, since the phase to be removed extends inside the alloy system, the pores obtained by removing the phase have a sufficiently large depth and a high aspect ratio, specifically, 1000 Voids having the above aspect ratio can be formed.
[0008]
When the alloy system is obtained by melting and solidifying from a raw material, it is preferable to apply a magnetic field during the solidification process. This makes it possible to easily obtain an alloy system having a fine regular structure without depending on the composition of the raw material, the production method such as the melting method and the solidification method, and the production conditions.
[0009]
Further, when the phase is removed from the alloy system, the phase is removed by immersing the alloy system in a predetermined solution and leaching it, or the alloy system is immersed in a predetermined electrolytic solution to perform electrochemical removal. It is preferable to perform the processing by performing the processing. By using such a method, the phase can be easily removed. When the phase is removed by an electrochemical treatment, it is preferable that a surfactant and a viscosity modifier are contained in the electrolytic solution. Thus, the above-described selective phase removal can be easily performed.
[0010]
Further, after the above-described alloy system is manufactured, it is preferable to subject the alloy system to plastic working before performing phase removal. As a result, the size of the regular structure in the alloy system can be reduced, and the size of the phase to be removed can be sufficiently reduced. Therefore, a porous body having fine pores of a desired size can be easily obtained.
[0011]
Further, in the present invention, it is preferable that the alloy system after the formation of the holes is subjected to an electrochemical treatment to crystallize the elements contained in the alloy system. For example, by including an element such as Ni, Co, or Ti in the alloy system, the element can be crystallized on the inner surface of the pore, and a catalytic action or corrosion resistance can be added. .
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be described in detail based on embodiments of the invention.
1 to 5 are views for explaining each step of the manufacturing method of the present invention. FIG. 1 is a diagram of a solidification apparatus used for producing an alloy system constituting a porous body. In an apparatus 10 shown in FIG. 1, a heating element 12 is provided in a furnace 11, and an electromagnet 13 is provided so as to cover the periphery of the furnace 11. A coil 14 is built in the electromagnet 13. Further, a cooling device 15 is provided below the heating element 12. Further, a lowering device 16 is provided below the furnace 11, and a raw material Y is attached to a distal end of a movable rod 17 provided in the device 16.
[0013]
The raw material Y is melted by the heating element 12 in the furnace 11 and, at the same time, is pulled down by the device 16 under the magnetic field applied by the electromagnet 13. Then, it is solidified in a predetermined magnetic field by the cooling device 15 to obtain a predetermined alloy system X. This alloy system X needs to contain two or more phases in order to selectively remove at least one phase constituting the alloy in a later step. For example, the alloy X can be composed of a monotectic alloy, a eutectic alloy, a peritectic alloy, or the like.
[0014]
The application of a magnetic field is not an essential element in the above-described solidification process, but by applying such a magnetic field, two or more components can be obtained without depending on the composition of the raw material Y and further on the production conditions such as the solidification rate. An alloy system X in which phases are regularly crystallized can be obtained. From such a viewpoint, the magnitude of the applied magnetic field is set to 0.5T to 10T.
[0015]
FIG. 2 is a diagram schematically showing a cross section of alloy system X. Through the above-described steps, the alloy system X comes to have a configuration in which, for example, the metal phase B is dispersed in a rod shape in the base material of the metal phase A.
[0016]
Further, through the above-described solidification process, each phase in the alloy system X is considerably miniaturized. However, as described in detail below, at least one phase constituting the alloy system X is selectively removed. Thus, the size of the phase to be removed is directly reflected on the size of the pore. Therefore, when the phases constituting the alloy system X are not sufficiently refined, it is preferable to subject the alloy system X to plastic working to further refine the size of the constituent phases.
[0017]
The type of the plastic working is not particularly limited, and examples thereof include extrusion and rolling.
[0018]
FIG. 3 is a diagram schematically showing an apparatus for selectively removing a constituent phase from alloy system X obtained through the above-described steps. In the removing device 20 shown in FIG. 3, a container 25 is filled with a predetermined solution 27. The alloy system X is immersed in the container 27, and only a predetermined phase is selectively leached and removed from the alloy system X. As a result, pores are formed at the positions of the alloy X where the phase has been removed, and a target porous body can be obtained.
[0019]
The solution 27 is composed of a highly soluble solution such as an acid or an alkali. The specific composition and concentration are determined according to the composition of the alloy X and the like.
[0020]
FIG. 4 is a view schematically showing another apparatus for selectively removing a predetermined constituent phase from the alloy system X. In the apparatus 30 shown in FIG. 4, the electrolyte 30 is filled in the container 30, and the reference electrode 38 and the counter electrode 39 are arranged so as to be immersed in the electrolyte 37. When a predetermined voltage is applied between the reference electrode 38 or the counter electrode 39 and the alloy system X which is a working electrode, and the alloy system X is immersed in the electrolytic solution 37, only a predetermined phase from the alloy system X is selectively corroded and corroded. Elute. As a result, pores are formed at positions where the phase has been removed, and a target porous body can be obtained.
[0021]
In this case, by controlling the magnitude of the voltage applied between the reference electrode 38 or the counter electrode 39 and the alloy system X, that is, by controlling the potential of the alloy system X with respect to the reference electrode 38 or the counter electrode 39, the state of corrosion and elution of the alloy system X is controlled. Can be controlled. For example, by setting a state in which the dissolution rate of a predetermined phase is applied to a high potential, only the target phase can be selectively removed from the alloy system X.
[0022]
Further, if the potential for dissolution is set to a high potential for a phase other than the predetermined phase, other phases, for example, a phase constituting a base material of the alloy X, are added to the phase to be removed from the alloy X. Can also be partially removed. Therefore, the number of pores of the finally obtained porous body, that is, the porosity can be arbitrarily set.
[0023]
Such a state can be adopted, for example, in the case of removing only the In phase from the separately crystallized Al phase and In phase in an Al—In alloy. The latter state can also be employed in the case where the Al phase is partially removed in addition to the In phase in the Al—In alloy.
[0024]
In the electrochemical method using the apparatus shown in FIG. 4, a surfactant or a viscosity modifier can be contained in the electrolytic solution 37. Thereby, the target phase can be selectively removed more effectively. A commercially available surfactant can be used as the surfactant, and phosphoric acid or the like can be used as the viscosity modifier.
[0025]
FIG. 5 is a diagram for explaining a preferred embodiment of the present invention. The alloy system X that has undergone the above-described steps is covered with a resin material 41 or the like to be insulated, and a lead wire 42 is attached to the lower surface of the alloy system X. Then, an additional electrochemical treatment is performed on the alloy system X by flowing a predetermined current through the lead wire 42. Thereby, other elements contained in the alloy system X can be crystallized on the inner surface of the pores of the alloy system X, and a predetermined function can be added to the finally obtained porous body. it can.
[0026]
For example, by adding a trace amount of the additional element in the raw material Y in advance, the additional element can be crystallized from the alloy system X on the inner surface of the pores by the additional electrochemical treatment described above, Functions such as catalytic action and corrosion resistance can be added to the target porous body. Examples of the additional element include Ni, Co, and Ti. Note that the resin material 41 may not be provided.
[0027]
As described above, through the steps of FIG. 1 to FIG. 4 or the steps of FIG. 1 to FIG. 5, a wide range of nm order to μm order, specifically 0.1 nm to 100 μm, A porous body having pores with a ratio of 1000 or more can be produced.
[0028]
As described above, the size of the pores in the porous body of the present invention can be set in an extremely wide range as compared with a conventional one, and exhibits an extremely high aspect ratio.
[0029]
The size of the hole indicates the diameter when the hole shape is circular, and indicates the length of one side when the hole shape is rectangular.
[0030]
【Example】
The Al-32.1 wt% In alloy was solidified at a growth rate of 100 mm / hour or less using an apparatus as shown in FIG. 1 to generate two fine metal phases in which In rods were dispersed in the Al base material. . Next, the alloy was subjected to a rolling treatment, and the size of the In phase was set to 0.1 μm to 10 μm. Next, the alloy was placed in an electrolytic device as shown in FIG. The electrolyte is a 10% nitric acid aqueous solution, the reference electrode is made of silver chloride, the counter electrode is made of platinum, and a predetermined voltage is applied between the reference electrode and the Al-In alloy serving as a working electrode. The In phase was selectively removed from the alloy.
[0031]
At this time, when the potential of the Al-In alloy was set to 0 to 2 V with respect to the potential of the silver chloride, it was confirmed that only the In phase was selectively corroded and eluted. FIG. 6 shows a micrograph of the porous body thus obtained. As is clear from FIG. 6, the porous body obtained through such a selective removal step has a plurality of holes with a large depth of about 10 μm and a high aspect ratio.
[0032]
When the potential of the platinum electrode was set to 0 V to 2 V, it was confirmed that the Al base material was partially corroded and eluted in addition to the In phase.
[0033]
In the Al-In alloy system described above, it was confirmed that the above-described pores could be formed even when the In content was changed from 17% by weight to 51.5% by weight. It was also confirmed that the above-described pores could be formed even when the nitric acid concentration in the aqueous nitric acid solution was changed in the range of 5 to 20%.
[0034]
As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above description, and any modifications or changes may be made without departing from the scope of the present invention. Changes are possible.
[0035]
【The invention's effect】
As described above, according to the present invention, it is possible to freely control the size of pores in a minute region, and to improve the aspect ratio of the pores, a method for manufacturing a porous body, and A porous body having fine and high aspect ratio pores can be provided.
[Brief description of the drawings]
FIG. 1 is a diagram of a solidification apparatus used in a method for producing a porous body of the present invention.
FIG. 2 is a sectional view of an alloy system constituting the porous body of the present invention.
FIG. 3 is a selective removal device used in the method for producing a porous body of the present invention.
FIG. 4 is a selective removal device used in the method for producing a porous body of the present invention.
FIG. 5 is a process chart in a preferred embodiment of the method for producing a porous body of the present invention.
FIG. 6 is a surface micrograph of a porous body of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 10 solidification device 11 furnace 12 heating element 13 electromagnet 14 coil 15 cooling device 16 pulling-down device 17 movable rod X alloy-based Y raw material 20, 30 selective removal device 25, 35 container 27 solution 37 electrolyte solution 38 reference electrode 39 counter electrode 41 resin material 42 Lead

Claims (18)

Dissolving the raw materials and then solidifying to produce an alloy system in which two or more phases are regularly crystallized;
Removing at least one of the two or more phases crystallized in the alloy system, and forming pores in a portion where the removed phase is located;
A method for producing a porous body, comprising: The method according to claim 1, wherein the coagulation is performed in the presence of a magnetic field. The method according to claim 2, wherein the magnetic field is 0.5T to 10T. The method for producing a porous body according to any one of claims 1 to 3, wherein the removal of the phase is performed by immersing the alloy system in a predetermined solution and leaching the alloy system. The method for producing a porous body according to any one of claims 1 to 3, wherein the removing of the phase is performed by immersing the alloy system in a predetermined electrolytic solution and electrochemically removing the alloy system. The method for manufacturing a porous body according to claim 5, wherein a negative voltage is applied to the electrolyte to remove only a predetermined phase of the alloy system to be removed. A positive voltage is applied to the electrolyte, and in addition to the predetermined phase of the alloy system to be removed, other portions of the alloy system are also electrically dissolved and removed to form additional holes. The method for producing a porous body according to claim 5, wherein: The method for producing a porous body according to any one of claims 5 to 7, wherein a surfactant is contained in the electrolytic solution. The method for producing a porous body according to any one of claims 5 to 8, wherein a viscosity modifier is contained in the electrolytic solution. The porous body according to any one of claims 1 to 9, further comprising a step of subjecting the alloy system to plastic working after producing the alloy system to refine the regular structure. Manufacturing method. The method for producing a porous body according to claim 10, wherein the plastic working is extrusion. The method for producing a porous body according to claim 10, wherein the plastic working is rolling. After forming the holes, the method further comprises a step of subjecting the alloy system to an electrochemical treatment to crystallize an element contained in the alloy system on an inner surface of the holes. Item 13. The method for producing a porous body according to any one of Items 1 to 12. The method for producing a porous body according to any one of claims 1 to 13, wherein an aspect ratio of the holes is 1000 or more. The method for producing a porous body according to any one of claims 1 to 14, wherein the size of the pores is 0.1 nm to 100 m. A porous body having pores having an aspect ratio of 1000 or more. The porous body according to claim 16, wherein the size of the pore is 0.1 nm to 100 m. The porous body according to claim 16, wherein an element different from the base material is crystallized on the inner surface of the pore.

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