JP7848802B2 - Method for manufacturing a porous metal and a porous metal - Google Patents

Description

This disclosure relates to a method for manufacturing a porous metal and to a porous metal. This application claims priority under Japanese Patent Application No. 2021-111516, filed on 5 July 2021, and under Japanese Patent Application No. 2021-190099, filed on 24 November 2021. All contents contained in said Japanese Patent Application are incorporated herein by reference.

Traditionally, porous metal materials have been used in a variety of applications, such as battery electrodes, catalyst supports, metal composites, and filters, due to their high porosity and thus large surface area.

Japanese Patent Publication No. 2013-237882

A method for manufacturing a porous metal according to one aspect of this disclosure is:
A method for manufacturing a porous metal body composed of a metal material,
A step of preparing a molded body containing support powder and the above-mentioned metal material,
A step of producing a composite molded body in which at least a portion of the molded body is in contact with the metal material, and the heating temperature is maintained for 5 minutes or more at a temperature above the melting point of the metal material and below the melting point of the support powder, thereby dissolving the metal material into the molded body.
The process includes bringing at least a portion of the composite molded body into contact with a first solvent to remove at least a portion of the support powder from the composite molded body and obtain the porous metal body.
The above metal material contains a first metal component containing aluminum,
The relative density of the above molded product is between 50% and 99.9%.

A porous metal according to one aspect of this disclosure is:
A porous metal body composed of a metal body containing aluminum,
Porosity is 50% or more,
The compressive strength is 0.5 MPa or higher.

A porous metal according to another aspect of this disclosure is a porous metal manufactured by the above-described method for manufacturing a porous metal.

Figure 1 is a schematic diagram showing the procedure for a method of manufacturing a porous metal body according to one aspect of the present disclosure. Figure 2 shows an external view of a porous metal according to one aspect of the present disclosure, obtained by SEM. Figure 3A is a SEM cross-sectional image of a porous metal according to one aspect of the present disclosure. Figure 3B shows a partially magnified image of a cross-section of a porous metal according to one aspect of the present disclosure and the results of EDX analysis. Figure 4 is a graph showing the correlation between compressive stress (vertical axis) and strain (horizontal axis) in a compression test using a porous metal material.

[Issues this disclosure aims to address]
As a method for manufacturing such a porous metal body, for example, Japanese Patent Application Publication No. 2013-237882 (Patent Document 1) discloses a method for manufacturing porous aluminum, which includes a mixing step of mixing aluminum powder and support powder having a particle size 10 times or more that of the aluminum powder in a volume ratio of aluminum powder:support powder = 3:7 to 1:19; a rolling step of rolling the mixed powder; a heat treatment step of heat treating the rolled body of the mixed powder at a temperature higher than the melting point of the aluminum powder; and a support powder removal step of removing the support powder from the heat-treated rolled body to form voids.

As described above, various porous metal materials such as porous aluminum are known, but when using them as structural members or current collectors for battery electrodes, there is room for further improvement, such as adjusting the strength or brittleness of the porous metal material.

This disclosure is made in view of the above circumstances and aims to provide a method for manufacturing a porous metal having excellent brittleness and excellent compressive strength, and the porous metal itself.

[Effects of this disclosure]
According to the above, a method for manufacturing a porous metal having excellent brittleness and excellent compressive strength, and the porous metal described above can be provided.

[Description of Embodiments in this Disclosure]
First, the embodiments of this disclosure will be listed and described.
[1] A method for manufacturing a porous metal according to one aspect of the present disclosure is:
A method for manufacturing a porous metal body composed of a metal material,
A step of preparing a molded body containing support powder and the above-mentioned metal material,
A step of producing a composite molded body in which at least a portion of the molded body is in contact with the metal material, and the heating temperature is maintained for 5 minutes or more at a temperature above the melting point of the metal material and below the melting point of the support powder, thereby dissolving the metal material into the molded body.
The process includes bringing at least a portion of the composite molded body into contact with a first solvent to remove at least a portion of the support powder from the composite molded body and obtain the porous metal body.
The above metal material contains a first metal component containing aluminum,
The relative density of the above molded article is between 50% and 99.9%. A method for manufacturing a porous metal having these characteristics can produce a porous metal having excellent brittleness and excellent compressive strength.

[2] The first metal component is preferably pure aluminum or an aluminum alloy. A method for manufacturing a porous metal having these characteristics can produce a porous metal having excellent corrosion resistance in addition to excellent brittleness and excellent compressive strength.

[3] The above aluminum alloy preferably contains at least one element selected from the group consisting of silicon, magnesium, iron, copper, manganese, chromium, zinc, zirconium, and boron. A method for producing a porous metal having such characteristics can produce a porous metal with excellent heat resistance.

[4] The above metal material further contains a second metal component,
The second metal component described above preferably contains at least one element selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, chromium, and beryllium. A method for producing a porous metal having these characteristics improves the wettability between the metal material and the support powder, and allows for the production of a porous metal having even better brittleness and even better compressive strength.

[5] The second metal component is preferably pure titanium. A method for producing a porous metal having these characteristics improves the wettability between the metal material and the support powder, and allows for the production of a porous metal having even better brittleness and even better compressive strength.

[6] The support powder is preferably an ionic compound. A method for producing a porous metal body having these characteristics improves production efficiency because the support powder is easily soluble in the first solvent.

[7] The above ionic compound preferably contains at least one selected from the group consisting of sodium chloride, potassium chloride, and magnesium sulfate. A method for producing a porous metal having these characteristics improves production efficiency because the support powder is easily soluble in the first solvent.

[8] The molded body further contains a third metal component,
The third metal component described above preferably contains at least one element selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, chromium, and beryllium. A method for producing a porous metal having these characteristics improves the wettability between the metal material and the support powder, and allows for the production of a porous metal having even better brittleness and even better compressive strength.

[9] The third metal component is preferably pure titanium, titanium hydride, or titanium nitride. A method for producing a porous metal having these characteristics improves the wettability between the metal material and the support powder, and allows for the production of a porous metal having even better brittleness and even better compressive strength.

[10] A porous metal according to one aspect of the present disclosure is a porous metal manufactured by the above-described method for manufacturing a porous metal. A porous metal having such characteristics has excellent brittleness and excellent compressive strength.

[11] A porous metal according to another aspect of the present disclosure is
A porous metal body composed of a metal body containing aluminum,
Porosity is 50% or more,
The compressive strength is 0.5 MPa or higher.
Porous metal materials possessing these characteristics exhibit excellent brittleness and superior compressive strength.

[Details of the Embodiment of the Present Invention]
Hereinafter, one embodiment of the present disclosure (hereinafter also referred to as "this embodiment") will be described. However, this embodiment is not limited thereto. In this specification, the notation in the form of "A to Z" means the upper and lower limits of a range (i.e., A or greater and Z or less). If no unit is specified for A, but a unit is specified only for Z, the unit for A and the unit for Z are the same.

≪Method for manufacturing porous metal materials≫
The method for manufacturing a porous metal according to this embodiment is a method for manufacturing a porous metal composed of a metal material,
A step of preparing a molded body containing support powder and the above-mentioned metal material,
A step of producing a composite molded body in which at least a portion of the molded body is in contact with the metal material, and the heating temperature is maintained for 5 minutes or more at a temperature above the melting point of the metal material and below the melting point of the support powder, thereby dissolving the metal material into the molded body.
The process includes bringing at least a portion of the composite molded body into contact with a first solvent to remove at least a portion of the support powder from the composite molded body and obtain the porous metal body.
The above metal material contains a first metal component containing aluminum,
The relative density of the above molded body is between 50% and 99.9%. The structure and composition of the above porous metal will be described later.

<Process for preparing a molded body containing support powder and metal material>
In this process, a molded body containing support powder and a metal material are prepared.

(metallic material)
In this embodiment, "metallic material" means a single metal, alloy, or metal-containing compound (e.g., hydride, nitride, etc.) that serves as the source of the metal or alloy constituting the porous metal body. The metallic material includes a first metallic component containing aluminum.

The first metallic component described above constitutes the main phase (main component) of the metallic material. In one aspect of this embodiment, the metallic material can also be understood as containing an aluminum-containing main phase. Here, "first metallic component" is a concept that includes elemental metals and alloys. The shape of the metallic material is not particularly limited and may be, for example, in the form of a metal lump such as a rectangular prism or a cylindrical shape, or it may be in the form of a powder or metal chips. The metallic material may also be in a molten state (liquid). From the viewpoint of suppressing the formation of an oxide film, the shape of the metallic material is preferably in the form of a metal lump.

The content ratio of the above-mentioned first metal component is preferably 50% by mass or more and 100% by mass or less, more preferably 55% by mass or more and 99.8% by mass or less, and even more preferably 55% by mass or more and 99% by mass or less, based on the above-mentioned metal material.

The first metal component mentioned above is preferably pure aluminum or an aluminum alloy. Here, "pure aluminum" means a metal consisting only of aluminum, and a metal consisting of aluminum and unavoidable impurities. Examples of unavoidable impurities include iron and silicon. The content of the unavoidable impurities may be, for example, 0.01% by mass or more and 0.5% by mass or less, based on the total amount of pure aluminum.

In this embodiment, "aluminum alloy" means an alloy whose main component is the element aluminum. The above aluminum alloy may be a 1000 series alloy or a 6000 series alloy in the International Alloy Symbols.

The content of the above-mentioned aluminum element is preferably 35% by mass or more and 99.9% by mass or less, and more preferably 40% by mass or more and 99% by mass or less, based on the above-mentioned aluminum alloy.

In one aspect of this embodiment, the aluminum alloy preferably contains at least one element selected from the group consisting of silicon, magnesium, iron, copper, manganese, chromium, zinc, zirconium, and boron.

The silicon content is preferably 0% by mass or more and 20% by mass or less, more preferably greater than 0% by mass and 15% by mass or less, and even more preferably 0.3% by mass or more and 12% by mass or less, based on the above aluminum alloy.

The magnesium content is preferably 0% by mass or more and 5.0% by mass or less, more preferably greater than 0% by mass and 3.0% by mass or less, and even more preferably 0.5% by mass or more and 2.2% by mass or less, based on the aluminum alloy.

The iron content is preferably 0% by mass or more and 3.0% by mass or less, more preferably greater than 0% by mass and 2.0% by mass or less, and even more preferably 0.2% by mass or more and 0.7% by mass or less, based on the above aluminum alloy.

The copper content is preferably 0% by mass or more and 6.0% by mass or less, more preferably greater than 0% by mass and 5.0% by mass or less, and even more preferably 0.06% by mass or more and 3.6% by mass or less, based on the aluminum alloy.

The manganese content is preferably 0% by mass or more and 4.0% by mass or less, more preferably greater than 0% by mass and 2.0% by mass or less, and even more preferably 0.01% by mass or more and 0.7% by mass or less, based on the above aluminum alloy.

The chromium content is preferably 0% by mass or more and 2.0% by mass or less, more preferably greater than 0% by mass and 1.0% by mass or less, and even more preferably 0.01% by mass or more and 0.2% by mass or less, based on the aluminum alloy.

The zinc content is preferably 0% by mass or more and 10.0% by mass or less, more preferably greater than 0% by mass and 7.5% by mass or less, and even more preferably 0.06% by mass or more and 5.2% by mass or less, based on the aluminum alloy.

The zirconium content is preferably 0% by mass or more and 1.0% by mass or less, more preferably greater than 0% by mass and 0.5% by mass or less, and even more preferably 0.04% by mass or more and 0.12% by mass or less, based on the aluminum alloy.

The content of the above boron element is preferably 0% by mass or more and 0.5% by mass or less, more preferably greater than 0% by mass and 0.1% by mass or less, and even more preferably greater than 0% by mass and 0.04% by mass or less, based on the above aluminum alloy.

The above metal material further contains a second metal component,
The second metallic component described above preferably contains at least one element selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, chromium, and beryllium. Here, "second metallic component" is a concept that includes elemental metals, alloys, and metal-containing compounds (e.g., hydrides, nitrides, etc.). The second metallic component is more preferably pure titanium. "Pure titanium" means a metal consisting only of titanium, as well as a metal composed of titanium and unavoidable impurities. Examples of unavoidable impurities include iron. The content of the unavoidable impurities may be, for example, 0.01% by mass or more and 1.0% by mass or less, based on the total amount of pure titanium.

The second metal component described above constitutes a secondary phase (sub-component) of the metal material. In one aspect of this embodiment, the metal material can also be understood as including the secondary phase. The inclusion of the secondary phase in the metal material improves the wettability between the metal material and the support powder in the manufacturing method according to this embodiment, enabling the production of a porous metal body with superior brittleness and superior compressive strength.

The content of the second metal component described above is preferably greater than 0% by mass and 65% by mass or less, and more preferably greater than 0% by mass and 50% by mass or less, based on the metal material described above. In one aspect of this embodiment, the content of the second metal component described above may be greater than 0% by mass and 0.2% by mass or less, or 0.2% by mass or more and 50% by mass or less, based on the metal material described above. If the second metal component described above contains multiple metal elements, the sum of the content percentages of each metal element becomes the content percentage of the second metal component described above.

(Molded body containing support powder)
In this embodiment, "support powder" refers to powder used to support the structure of the porous metal during the manufacturing process of the porous metal. The melting point of the support powder is preferably equal to or greater than the melting point of the metal material. Furthermore, the support powder is preferably an ionic compound.

The above ionic compound preferably contains at least one selected from the group consisting of sodium chloride, potassium chloride, and magnesium sulfate.

The average particle size of the above-mentioned support powder is preferably 1 μm or more and 5000 μm or less, and more preferably 5 μm or more and 4000 μm or less. In one aspect of this embodiment, the average particle size of the above-mentioned support powder may be 5 μm or more and 700 μm or less, or 700 μm or more and 4000 μm or less. If the average particle size of the above-mentioned support powder is 1 μm or more, it becomes possible to manufacture a porous metal body with excellent permeability to liquids or gases. If the average particle size of the above-mentioned support powder is 5000 μm or less, it becomes possible to manufacture a porous metal body with excellent ability to support catalysts. The average particle size of the above-mentioned support powder can be measured, for example, with a Morphologi G3 (trade name) manufactured by Malvern Instruments.

In this embodiment, the shape of the molded body containing the support powder is not particularly limited and can be any shape. Examples of the molded body shapes include cubes, triangular prisms, quadrangular prisms, polygonal prisms, cylinders, spheres, sheets, discs, and the like.

The molded article in this embodiment can be manufactured, for example, by the following method. First, the prepared support powder is compressed and molded using a press die. The compression conditions at this time are 50 MPa or higher. After that, the molded article is produced in the desired shape.

The relative density of the above molded article is 50% to 99.9%, preferably 55% to 99%, and more preferably 75% to 90%.

The relative density of the above molded body can be calculated using the following formula.
Relative density (%) = {M ₁ / (V ₁ × d ₁ )} × 100
_M1 : Mass of the molded body [g]
_V1 : Volume of the external shape of the molded body [ ^cm³ ]
d ₁ : Density of the material constituting the molded body [g/ ^cm³ ].

In one aspect of this embodiment, the molded article further comprises a third metal component,
The third metallic component described above preferably contains at least one element selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, chromium, and beryllium. Here, "third metallic component" is a concept that includes elemental metals, alloys, and metal-containing compounds (e.g., hydrides, nitrides, etc.). The third metallic component described above is preferably pure titanium, titanium hydride, or titanium nitride. The third metallic component described above may have the same composition as the second metallic component described above, or it may have a different composition from the second metallic component described above.

The third metal component described above constitutes an additive metal for improving the "wettability of the molded body to the metal material." In one aspect of this embodiment, the molded body can also be understood as containing the additive metal. By including the additive metal in the molded body, the manufacturing method according to this embodiment improves the wettability between the metal material and the support powder, and enables the production of a porous metal body having even better brittleness and even better compressive strength.

The content of the third metal component described above is preferably 0.1% by mass or more and 50% by mass or less, more preferably 1% by mass or more and 40% by mass or less, and even more preferably 5% by mass or more and 15% by mass or less, based on the molded body. If the third metal component described above contains multiple metal elements, the sum of the content percentages of each metal element becomes the content percentage of the third metal component described above.

<Process for producing a composite molded body in which metal material is fused into the molded body>
In this process, at least a portion of the molded body is in contact with at least a portion of the metal material, and the heating temperature is maintained at a temperature above the melting point of the metal material and below the melting point of the support powder for at least 5 minutes, thereby generating a composite molded body in which the metal material is fused into the molded body. By performing this process, the molten metal material penetrates (fused) into the gaps between the particles of the support powder in the molded body, and the composite molded body is formed.

The phrase "a state in which at least a part of the molded body is in contact with at least a part of the metal material" is not particularly limited. For example, the metal material may be placed in contact with the molded body directly above it, or the molded body may be placed in contact with the metal material directly above it. Alternatively, the molded body and the metal material may be in contact with each other on their sides. In one aspect of this embodiment, it is preferable to place the molded body in a carbon mold as shown in Figure 1, and to place the metal material in contact with the molded body directly above it. In this way, the molten metal material dissolves into the molded body by its own weight. Furthermore, as will be described later, the dissolution of the metal material into the molded body may be promoted by applying pressure to the metal material or the molded body in the direction in which the metal material penetrates the molded body.

The heating temperature is above the melting point of the metal material and below the melting point of the support powder, preferably between 680°C and 770°C, and more preferably between 690°C and 760°C. If the heating temperature is below the melting point of the metal material, the metal material tends to become difficult to dissolve into the molded body. If the heating temperature exceeds the melting point of the support powder, the support powder tends to melt, making it difficult to form the desired porous metal body with the metal material.

The time for maintaining the above heating temperature is 1 minute or more, preferably 2 minutes to 120 minutes, and more preferably 3 minutes to 90 minutes.

This process may be carried out in the atmosphere or in an inert gas atmosphere such as argon gas. From the viewpoint of suppressing the formation of oxide films on metallic materials, it is preferable to carry out this process in an inert gas atmosphere.

From the viewpoint of promoting the fusion of the above-mentioned metal material into the above-mentioned molded body, the above-mentioned metal material or the above-mentioned molded body may be pressurized in a direction that causes the above-mentioned metal material to penetrate the above-mentioned molded body.

<Process for obtaining a porous metal>
In this step, at least a portion of the composite molded body is brought into contact with a first solvent to remove at least a portion of the support powder from the composite molded body and obtain the porous metal body. In this step, at least a portion of the support powder constituting the composite molded body is dissolved and removed in the first solvent. As a result, pores are formed in the portions where the support powder was present, and the composite molded body becomes a porous metal body. In this step, some of the support powder may remain in the porous metal body, but it is preferable that the support powder is completely removed from the porous metal body.

The first solvent described above is not particularly limited as long as it dissolves the support powder but does not dissolve the metal material (or is a solvent in which the metal material has very low solubility). Examples of the first solvent include water and ethylene glycol.

Methods for removing the support powder from the composite molded body using the first solvent include, for example, immersing the composite molded body in the first solvent or spraying the first solvent onto the composite molded body.

In this process, the temperature of the first solvent is not particularly limited as long as it is above the freezing point of the first solvent and below the boiling point of the first solvent, but for example, it may be between 0°C and 100°C.

The porous metal body according to this embodiment can be manufactured by the above steps. In addition to the steps described above, the manufacturing method of the porous metal body according to this embodiment may also include steps for drying the porous metal body (for example, a step to remove the first solvent remaining on the porous metal body), tempering the porous metal body, cutting the porous metal body into a predetermined shape, and polishing the porous metal body. The temperature in the drying step may be, for example, 100°C to 200°C. The tempering step is performed to improve the strength of the obtained porous metal body and is carried out, for example, by the following procedure: First, the porous metal body is held at a temperature of around 500°C for about 1 hour, and then the porous metal body is water-cooled. After that, the porous metal body is held at a temperature in the range of 25°C to 200°C for 5 to 200 hours.

≪Porous Metals≫
The porous metal body according to this embodiment is a porous metal body composed of a metal body containing aluminum,
Porosity is 50% or more,
The compressive strength is 0.5 MPa or higher.
The above-mentioned porous metal is a porous metal manufactured by the above-mentioned method for manufacturing a porous metal.

The above-described porous metal has a different structure from a porous metal composed only of open pores (for example, Cellmet® manufactured by Sumitomo Electric Industries, Ltd.). That is, the above-described porous metal has a structure that includes both open and closed pores. In the porous metal according to this embodiment, it can be seen that the open and closed pores are formed by a thin-film-like metal body (see image in Figure 2). Here, "metal body of the porous metal" means the tangible part that defines the pores in the porous metal.

The porosity of the above-mentioned porous metal is 50% or more, preferably 55% to 99.9%, and more preferably 60% to 99%.

The porosity of the above porous metal can be calculated using the following formula.
Porosity (%) = [1 - { _M² / ( _V² × _d² )}] × 100
_M2 : Mass of the porous metal [g]
_V2 : Volume of the external shape in a porous metal [ ^cm³ ]
_d² : Density of the material constituting the porous metal [g/ ^cm³ ].

The compressive strength of the above-mentioned porous metal is 0.5 MPa or more, preferably 0.7 MPa to 50 MPa, and preferably 1 MPa to 25 MPa. Here, "compressive strength of the porous metal" refers to the compressive strength when the strain of the above-mentioned porous metal reaches 50% in the compression test described later.

The compressive strength of the above-mentioned porous metal can be determined by a compression test method in accordance with JIS H 7902:2016. In this case, the shape of the porous metal is φ10 mm × height 10 mm.

The average pore size of the above-mentioned porous metal is preferably 1 μm or more and 5000 μm or less, and more preferably 5 μm or more and 4000 μm or less. An average pore size of 1 μm or more increases the strength of the porous metal. An average pore size of 5000 μm or less increases the ability to support the catalyst.

The average pore size of a porous metal can be determined by the following method. First, the measurement field of view is set using a scanning electron microscope (SEM) so that at least five pores are included, and the appearance of the porous metal is photographed. Next, the size of the pores observed within the field of view is calculated as the equivalent diameter of the area circle, and the average value of the size of each observed pore is taken as the average pore size.

The porous metal body according to this embodiment is manufactured by the immersion method as described above. Therefore, it is possible to obtain a porous metal body with a low content of oxygen-containing compounds such as aluminum oxide and excellent strength.

(Method for measuring the mass ratio of each element)
The mass percentage (mass%) of each element in the metal body of the above-mentioned porous metal can be determined by quantitative analysis using inductively coupled high-frequency plasma spectroscopy (ICP). Specifically, first, the sample, which is the metal body of the porous metal, is dissolved in a 20 mass% sodium hydroxide aqueous solution. Then, a solution of nitric acid, hydrochloric acid, and hydrofluoric acid mixed in a volume ratio of 5:1:1 is added to the sodium hydroxide aqueous solution to dissolve the residue, and the elemental concentrations in the solution are analyzed by ICP.

In this embodiment, the metal body of the porous metal preferably has an aluminum content of 35% by mass or more and 99.9% by mass or less, and more preferably 40% by mass or more and 99% by mass or less, based on the metal body of the porous metal.

In one aspect of this embodiment, it is preferable that the metal body of the porous metal further contains at least one element selected from the group consisting of silicon, magnesium, iron, copper, manganese, chromium, zinc, zirconium, and boron.

The content of the silicon element described above is preferably 0% by mass or more and 20% by mass or less, more preferably greater than 0% by mass and 15% by mass or less, and even more preferably 0.3% by mass or more and 12% by mass or less, based on the metal body of the porous metal.

The magnesium content is preferably 0% by mass or more and 5.0% by mass or less, more preferably greater than 0% by mass and 3.0% by mass or less, and even more preferably 0.5% by mass or more and 2.2% by mass or less, based on the metal body of the porous metal.

The iron content is preferably 0% by mass or more and 3.0% by mass or less, more preferably greater than 0% by mass and 2.0% by mass or less, and even more preferably 0.2% by mass or more and 0.7% by mass or less, based on the metal body of the porous metal.

The copper content is preferably 0% by mass or more and 6.0% by mass or less, more preferably greater than 0% by mass and 5.0% by mass or less, and even more preferably 0.06% by mass or more and 3.6% by mass or less, based on the metal body of the porous metal.

The manganese content is preferably 0% by mass or more and 4.0% by mass or less, more preferably greater than 0% by mass and 2.0% by mass or less, and even more preferably 0.01% by mass or more and 0.7% by mass or less, based on the metal body of the porous metal.

The chromium content is preferably 0% by mass or more and 2.0% by mass or less, more preferably greater than 0% by mass and 1.0% by mass or less, and even more preferably 0.01% by mass or more and 0.2% by mass or less, based on the metal body of the porous metal.

The zinc element content is preferably 0% by mass or more and 10.0% by mass or less, more preferably greater than 0% by mass and 7.5% by mass or less, and even more preferably 0.06% by mass or more and 5.2% by mass or less, based on the metal body of the porous metal.

The zirconium content is preferably 0% by mass or more and 1.0% by mass or less, more preferably greater than 0% by mass and 0.5% by mass or less, and even more preferably 0.04% by mass or more and 0.12% by mass or less, based on the metal body of the porous metal.

The content of the boron element described above is preferably 0% by mass or more and 0.5% by mass or less, more preferably greater than 0% by mass and 0.1% by mass or less, and even more preferably greater than 0% by mass and 0.04% by mass or less, based on the metal body of the porous metal.

In one aspect of this embodiment, the metal body of the porous metal further contains a fourth metal component,
The fourth metallic component described above preferably further includes at least one element selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, and beryllium. Here, "fourth metallic component" is a concept that includes elemental metals and alloys.

The content ratio of the fourth metal component described above is preferably greater than 0% by mass and 65% by mass or less, more preferably 0.1% by mass or more and 50% by mass or less, and even more preferably 18% by mass or more and 25% by mass or less, based on the metal body of the porous metal. If the fourth metal component described above contains multiple metal elements, the sum of the content ratios of each metal element becomes the content ratio of the fourth metal component described above.

If the metal body of the porous metal contains the fourth metal component, the fourth metal component may form an alloy with aluminum. Furthermore, the alloy of aluminum and the fourth metal component may be dispersed in particulate form within the metal body of the porous metal (see Figures 3A and 3B).

When dispersed as particulate matter, the average particle size of the alloy of the aluminum and the fourth metal component may be 0.1 μm or more and 100 μm or less, or 1 μm or more and 50 μm or less. The average particle size of the alloy can be determined from the SEM cross-sectional image of the porous metal body as the equivalent diameter of an equal-area circle.

The porous metal material according to this embodiment has been described above. Because the porous metal material has high porosity and therefore a large surface area, it can be used in a variety of applications, such as battery electrodes, electrolysis apparatus electrodes (for example, electrodes for hydrogen production apparatus), catalyst supports (catalyst supports for plants, etc.), metal composite materials, filters (grease filters for kitchens, filters for air purifiers, etc.), and capacitors. Furthermore, the porous metal material exhibits excellent wear resistance, liquid and gas support, liquid and gas supply capabilities, shock absorption, light weight, fire resistance, sound absorption, specific stiffness, and specific surface area. Therefore, the above-mentioned porous metal can be used as structural members (electromagnetic shielding materials, lightweight structural materials, etc.), various housings, exterior and interior parts of mobile bodies, vibration isolation table parts for machine tools, bearings, parts for spacecraft and planetary probes (antennas, wheels, power sources, heat insulating tiles, etc.), sound absorbing materials (silencers for data centers, etc.), heat dissipation materials (heat sinks, etc.), biomaterials (spinal column fixation devices, fracture fixation materials, artificial joints, artificial valves, etc.), and cooling equipment.

The above description includes the following features.
(Note 1)
A porous metal body composed of a metal body containing aluminum,
Porosity is 50% or more,
A porous metal having a compressive strength of 0.5 MPa or more.
(Note 2)
The above-mentioned porous metal material has an average pore diameter of 1 μm or more and 5000 μm or less, as described in Appendix 1.

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

Manufacturing of porous metal materials
<Samples 1a to 17a, samples 1b to 8b, and samples 11b to 13b>
The porous metal materials of samples 1a to 17a, 1b to 8b, and 11b to 13b were prepared using the following procedure. The porous metal materials of samples 1a to 17a, 1b to 8b, and 11b to 13b correspond to the examples.

(Steps for preparing a molded body containing support powder and metal materials)
First, pure aluminum or aluminum alloys with the compositions shown in Tables 1-1 and 1-2 were prepared as metallic materials. A mass of 2 g was prepared for each sample. The metallic material was cylindrical in shape.

Next, the support powder and third metal component shown in Table 2 were prepared. Sodium chloride (average particle size 700 μm) was used as the support powder. Titanium hydride powder (average particle size 10 μm) was used as the third metal component. The support powder and the third metal component were mixed to form a cylindrical molded body (diameter 10 mm, height 10 mm). The relative density of the obtained molded body was determined by the method described above (Table 2).

(A process for producing a composite molded body in which metal material is fused into the molded body.)
After placing the obtained molded body into a carbon mold, at least a portion of the metal material was placed so that it was in contact with at least a portion of the molded body (see, for example, Figure 1). The carbon mold was heated to a temperature of 750°C and maintained for 30 minutes. The atmosphere at this time was an Ar gas atmosphere. In addition, a pressure of 20 MPa was applied to the samples that did not contain the second and third metal components. By performing the above treatment, the molten metal material was dissolved into the molded body to obtain a composite molded body.

(Process for obtaining a porous metal / Process for drying a porous metal)
The composite molded body obtained in the previous step was washed with 80°C water (first solvent) to remove the support powder, sodium chloride, and obtain a porous metal body (step for obtaining a porous metal body). The obtained porous metal body was dried in a dryer (150°C) to remove excess moisture (step for drying the porous metal body).

For samples 3a to 17a, 3b to 8b, and 11b to 13b, the porous metals were tempered according to the protocols shown in Tables 3-1 and 3-2 (process for tempering porous metals). The porous metals of samples 1a to 17a, 1b to 8b, and 11b to 13b were manufactured using the above procedure.

<Sample 18>
A porous metal body of sample 18 was prepared using the following procedure. Aluminum powder with a particle size of 50 μm was used as the aluminum powder. Sodium chloride powder with a particle size of 700 μm was used as the support powder. A mixture was prepared by mixing the above aluminum powder and the above support powder in a mixing volume ratio of 1:9. The prepared mixture was compressed without heating to produce a cylindrical rolled sample (diameter 10 mm, height 10 mm). Next, the rolled sample was heat-treated at a processing temperature of 670°C for a processing time of 30 minutes. Furthermore, the heat-treated rolled sample was immersed in running water (tap water) for 24 hours to dissolve the support powder and obtain the porous metal body of sample 18. The porous metal body of sample 18 was prepared by a method similar to the manufacturing method described in Patent Document 1 and corresponds to a comparative example.

≪Performance evaluation of porous metal materials≫
<Analysis of the physical properties of porous materials>
(Mass ratio of each element)
For samples 1a to 17a, 1b to 8b, 11b to 13b, and 18 obtained by the method described above, the mass percentage of each element in the metal body of these porous metal materials was determined by quantitative analysis using ICP. Specifically, first, the sample, which is the metal body of the porous metal material, was dissolved in a 20% by mass sodium hydroxide aqueous solution. Then, a solution of nitric acid, hydrochloric acid, and hydrofluoric acid mixed in a volume ratio of 5:1:1 was added to the sodium hydroxide aqueous solution to dissolve the residue. The elemental concentrations in the obtained solution were analyzed by ICP. Based on the atomic concentrations of each element analyzed by ICP, the mass percentage of each element was determined. The results are shown in Tables 4-1 and 4-2.

(Porosity of porous metals)
Next, the porosity of the porous metal materials was calculated for samples 1a to 17a, 1b to 8b, 11b to 13b, and 18 using the formula described above. The results are shown in Tables 3-1 and 3-2.

(Average pore size of porous metals)
Furthermore, the average pore size of the porous metal was calculated using the method described above. The results are shown in Tables 3-1 and 3-2.

(Cross-sectional observation of a porous metal)
The cross-section of the porous metal sample 7a was observed using a scanning electron microscope (SEM) (Figures 3A and 3B). The results revealed that an alloy of titanium and aluminum was dispersed as particles within the metal body of the porous metal. The average particle size of this alloy was 10 μm.

<Compression Test>
(Presence or absence of cracks when compressed to 70%)
For the porous metal materials of samples 1a to 17a, 1b to 8b, 11b to 13b, and 18, the presence or absence of cracks at 70% compression was investigated using the compression test method compliant with JIS H 7902:2016 described above. The shape of the porous metal materials was set to φ10 mm × height 10 mm. The results are shown in Tables 3-1 and 3-2. Porous metal materials that did not show cracks at 70% compression can be evaluated as having excellent brittleness.

(Compressive strength at 50% strain)
For the porous metal bodies of samples 1a to 17a, 1b to 8b, 11b to 13b, and 18, the compressive strength at 50% strain was determined using the compression test method compliant with JIS H 7902:2016 described above (see Figure 4). The shape of the porous metal bodies was set to φ10 mm × height 10 mm. The results are shown in Tables 3-1 and 3-2. The graph in Figure 4 shows the test results for sample 7a.

<Results>
According to the results in Tables 3-1 and 3-2, no cracks were observed in the porous metal materials of samples 1a to 17a, 1b to 8b, and 11b to 13b (porous metal materials of the examples) manufactured by the immersion method when compressed to 70%. Furthermore, the compressive strength of these porous metal materials at 50% strain was 0.6 MPa or higher. On the other hand, cracks were observed in the porous metal material of sample 18 (porous metal material of the comparative example) manufactured by the conventional sintering method when compressed to 70%. Furthermore, the compressive strength of the porous metal material of sample 18 at 50% strain was 0.3 MPa. From the above, it was found that the porous metal materials according to the examples have excellent brittleness and excellent compressive strength.

As described above, embodiments and examples of the present invention have been explained, but it is also intended from the outset that the configurations of each of the above embodiments and examples may be combined as appropriate.

The embodiments and examples disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present invention is indicated by the claims rather than the embodiments and examples described above, and all modifications within the scope of the claims are intended to be included in the meaning of equivalents and within the scope.

Claims (10)

A method for manufacturing a porous metal body composed of a metal material,
A step of preparing a molded body containing support powder and the metal material,
A step of producing a composite molded body in which the metal material is fused into the molded body, by maintaining a heating temperature of 5 minutes or more at a temperature above the melting point of the metal material and below the melting point of the support powder, with at least a portion of the molded body in contact with at least a portion of the metal material,
The step of bringing at least a portion of the composite molded body into contact with a first solvent to remove at least a portion of the support powder from the composite molded body and obtain the porous metal body,
The aforementioned metal material comprises a first metal component containing aluminum,
A method for manufacturing a porous metal body, wherein the relative density of the molded body is 50% or more and 99.9% or less. The method for producing a porous metal body according to claim 1, wherein the first metal component is pure aluminum or an aluminum alloy. The method for producing a porous metal according to claim 2, wherein the aluminum alloy contains at least one element selected from the group consisting of silicon, magnesium, iron, copper, manganese, chromium, zinc, zirconium, and boron. The aforementioned metal material further comprises a second metal component,
The method for producing a porous metal body according to any one of claims 1 to 3, wherein the second metal component comprises at least one element selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, chromium, and beryllium. The method for producing a porous metal body according to claim 4, wherein the second metal component is pure titanium. The method for producing a porous metal body according to any one of claims 1 to 5, wherein the support powder is an ionic compound. The method for producing a porous metal according to claim 6, wherein the ionic compound comprises at least one selected from the group consisting of sodium chloride, potassium chloride, and magnesium sulfate. The molded body further contains a third metal component,
The method for producing a porous metal body according to any one of claims 1 to 7, wherein the third metal component comprises at least one element selected from the group consisting of titanium, zirconium, hafnium, niobium, tantalum, chromium, and beryllium. The method for producing a porous metal body according to claim 8, wherein the third metal component is pure titanium, titanium hydride, or titanium nitride. A porous metal body composed of a metal body containing aluminum,
Porosity is 50% or more,
A porous metal having a compressive strength of 0.5 MPa or more.