阅读说明：本技术 金属泡沫的制备方法 (Method for producing metal foam ) 是由 金昭镇 柳东雨 李振圭 于 2018-07-06 设计创作，主要内容包括：本发明涉及用于制备金属泡沫的方法,并且更具体地,涉及用于制备金属泡沫的包括如下步骤的方法：通过包含抗溶剂、分散剂、粘合剂和金属组分的浆料形成金属泡沫前体；以及烧结金属泡沫前体。本发明可以提供用于通过简单且有效的过程制备薄且具有适当的孔隙率和孔径的金属泡沫的方法。(The present invention relates to a method for producing a metal foam, and more particularly, to a method for producing a metal foam comprising the steps of: forming a metal foam precursor by a slurry comprising an anti-solvent, a dispersant, a binder, and a metal component; and sintering the metal foam precursor. The present invention can provide a method for preparing a metal foam which is thin and has appropriate porosity and pore size by a simple and efficient process.)

1. A method for preparing a metal foam comprising the steps of: forming a metal foam precursor with a slurry comprising a metal component, a dispersant, a binder, and an anti-solvent; and sintering the metal foam precursor.

2. The method for producing metal foam according to claim 1, wherein the proportion of the metal component in the slurry is 45% by weight or more.

3. The process for preparing a metal foam according to claim 1, wherein the binder is an alkyl cellulose, polyalkylene carbonate, polyvinyl alcohol or polyvinyl acetate.

4. The method for preparing metal foam according to claim 2, wherein the slurry comprises the binder in a range of 1 to 500 parts by weight with respect to 100 parts by weight of the metal component.

5. The method for producing metal foam according to claim 1, wherein the dispersant is an alcohol.

6. The method for preparing metal foam according to claim 2, wherein the slurry comprises the dispersant in a range of 30 parts by weight to 2000 parts by weight with respect to 100 parts by weight of the binder.

7. The process for preparing a metal foam according to claim 1, wherein the anti-solvent is one or more selected from the group consisting of: monohydric alcohols, polyhydric alcohols, alkanolamines, alkyl ethers, aryl ethers, esters, ketones, alkylbenzenes, arylbenzenes, and halogenated benzenes.

8. The method for preparing metal foam according to claim 2, wherein the slurry comprises the anti-solvent in a range of 0.5 to 2000 parts by weight with respect to 100 parts by weight of the binder.

9. The method for producing metal foam according to claim 2, wherein the total weight of the dispersant and the anti-solvent in the slurry is in the range of 10 parts by weight to 1000 parts by weight with respect to 100 parts by weight of the metal component.

10. The method for producing metal foam according to claim 2, wherein the weight ratio of the dispersant to the anti-solvent (dispersant/anti-solvent) is in the range of 0.5 to 20.

11. The method for preparing a metal foam according to claim 1, wherein the pore size of the prepared metal foam is in the range of 0.1 μm to 200 μm.

12. The method for preparing a metal foam according to claim 1, wherein the porosity of the prepared metal foam is in the range of 30% to 90%.

13. The method for preparing a metal foam according to claim 1, wherein the metal foam is in the form of a film or sheet.

14. The method for producing metal foam according to claim 13, wherein the thickness of the film or the sheet is 500 μm or less.

Technical Field

This application claims benefit based on priority of korean patent application No. 10-2017-.

The present application relates to a method for producing a metal foam.

Background

Metal foam is also known by various names such as metal foam and refers to a metal structure containing a number of pores. These metal foams have various and useful properties such as light weight property, energy absorption property, heat insulation property, fire resistance property, or environmental friendly property, etc., and can be applied to various fields including structures, transportation machinery, building materials, or energy absorption devices, etc., or heat exchangers, catalysts, sensors, actuators, secondary batteries, fuel cells, Gas Diffusion Layers (GDLs) or microfluidic flow controllers, etc.

Conventionally, various methods for producing metal foams are known, but it is a difficult problem to manufacture metal foams having both a thin thickness and a desired porosity. In particular, a method of preparing a metal foam having pore diameters controlled at a desired level while being thin and having a desired porosity is almost unknown.

Disclosure of Invention

Technical problem

The present application relates to a method for producing a metal foam. It is an object of the present application to enable the preparation of metal foams that are thin and have a suitable porosity and pore size by a simple and efficient process.

Technical scheme

In the present application, the term metal foam or metal skeleton means a porous structure comprising a metal or metal alloy as a main component. Here, the fact that metal or the like is used as the main component means that the proportion of metal or the like is 55 wt% or more, 60 wt% or more, 65 wt% or more, 70 wt% or more, 75 wt% or more, 80 wt% or more, 85 wt% or more, 90 wt% or more, or 95 wt% or more based on the total weight of the metal foam or the metal skeleton. The upper limit of the proportion of the metal and the like contained as the main component is not particularly limited. For example, the proportion of metal may be 100 wt% or less, or less than about 100 wt%.

The term porous nature may mean a porosity of at least 30% or greater, 40% or greater, 50% or greater, 60% or greater, 70% or greater, 75% or greater, or 80% or greater. The upper limit of the porosity is not particularly limited, and may be, for example, less than about 100%, about 99% or less, or about 98% or less. The porosity can be calculated in a known manner by calculating the density of the metal foam or the like.

The method for preparing a metal foam of the present application may comprise the step of sintering a metal foam precursor. In the present application, the term metal foam precursor means the structure prior to a process, such as sintering, performed in order to form the metal foam, i.e. the structure prior to forming the metal foam. In addition, even when the metal foam precursor is referred to as a porous metal foam precursor, it itself is not necessarily porous, and may be referred to as a porous metal foam precursor for convenience as long as it can finally form a metal foam as a porous metal structure.

In the present application, the metal foam precursor may be formed using a slurry including at least a metal component, a dispersant, an anti-solvent, and a binder.

In one example, the anti-solvent may be a solvent that does not dissolve the binder while having miscibility with the dispersant. The anti-solvent may be an anti-solvent for the binder applied to the slurry. The meaning of the term anti-solvent is well known in the art. That is, the anti-solvent may mean a solvent in which the binder exhibits low solubility with respect to the relevant solvent so that the relevant binder can be precipitated, and the meaning of such an anti-solvent is well known, for example, in the field of application and the like (such as a so-called anti-solvent deposition method). The term anti-solvent may be a solvent that may have miscibility with the dispersant in the slurry to be mixed without dissolving the binder. For example, if the binder is a polymer, the term anti-solvent may be a solvent that may have miscibility with the dispersant to be mixed without swelling the polymeric binder.

The metal foam precursor may be formed using a slurry comprising the metal component, a dispersant, a binder, and an anti-solvent, and may be formed, for example, by coating the slurry on a suitable substrate. In addition, if necessary, a drying process or the like may be appropriately performed after the process.

The type of substrate applied in forming the metal foam precursor is not particularly limited. For example, the substrate may be a substrate for treatment having peeling properties or the like that is finally removed after the metal foam is prepared. In addition, the metal foam having the base material formed thereon may be integrated and applied, and in such a case, as the base material, a metal base material or the like may be applied, wherein the kind of the base material is not limited.

The metal component contained in the slurry may form a metal foam. Therefore, the kind of the metal component may be selected in consideration of the physical properties required for the metal foam or the process conditions of the sintering step.

Here, as the metal component, metal powder may be applied. Examples of the applicable metal powder are determined according to purposes, which are not particularly limited, but may be exemplified by any one powder selected from the group consisting of: copper powder, molybdenum powder, silver powder, platinum powder, gold powder, aluminum powder, chromium powder, indium powder, tin powder, magnesium powder, phosphorus powder, zinc powder, and manganese powder, metal powder mixed with two or more of the foregoing, or powder of an alloy of two or more of the foregoing, but is not limited thereto.

If necessary, the metal component may include a metal component having a relative magnetic permeability and an electric conductivity within a predetermined range as an optional component. Such metal components may assist in the selection of the induction heating method during sintering. However, since sintering does not necessarily have to be performed by an induction heating method, the metal component having the above-described magnetic permeability and electric conductivity is not an essential component.

In one example, as the metal powder that may be optionally added, a metal powder having a relative magnetic permeability of 90 or more may be used. Term(s) forRelative magnetic permeability (mu) _r) Is the magnetic permeability (mu) of the relevant material and the magnetic permeability (mu) in vacuum ₀) Ratio of (mu/mu) ₀). In another example, the relative permeability may be 95 or greater, 100 or greater, 110 or greater, 120 or greater, 130 or greater, 140 or greater, 150 or greater, 160 or greater, 170 or greater, 180 or greater, 190 or greater, 200 or greater, 210 or greater, 220 or greater, 230 or greater, 240 or greater, 250 or greater, 260 or greater, 270 or greater, 280 or greater, 290 or greater, 300 or greater, 310 or greater, 320 or greater, 330 or greater, 340 or greater, 350 or greater, 360 or greater, 370 or greater, 380 or greater, 390 or greater, 400 or greater, 410 or greater, 420 or greater, 430 or greater, 440 or greater, 450 or greater, 460 or greater, 470 or greater, 480 or greater, 490 or greater, 500 or greater, 520 or greater, 430 or greater, 440 or greater, 450 or greater, 460 or greater, 470 or greater, 480 or greater, 490 or greater, 500 or greater, 520 or greater, 570 or greater, 530 or greater, 560 or greater, or a magnetic permeability may be greater than the magnetic permeability of the magnetic materials, 580 or greater, or 590 or greater. The upper limit of the relative permeability is not particularly limited, because the higher the value, the more advantageous in the case where induction heating is applied. In one example, the upper limit of the relative permeability may be, for example, about 300,000 or less.

The metal powder that may be optionally added may also be a conductive metal powder. In the present application, the term conductive metal powder may mean a powder of a metal or an alloy thereof having an electrical conductivity of about 8MS/m or more, 9MS/m or more, 10MS/m or more, 11MS/m or more, 12MS/m or more, 13MS/m or more, or 14.5MS/m at 20 ℃. The upper limit of the conductivity is not particularly limited, and may be, for example, about 30MS/m or less, 25MS/m or less, or 20MS/m or less.

In the present application, the metal powder having the relative magnetic permeability and the electric conductivity may also be simply referred to as conductive magnetic metal powder.

Specific examples of such conductive magnetic metal powder may be exemplified by powders of nickel, iron, cobalt, or the like, but are not limited thereto.

If used, the proportion of the electrically conductive magnetic metal powder in the entire metal powder is not particularly limited. For example, the ratio may be adjusted so that the ratio can generate appropriate joule heat upon induction heating. For example, the metal powder may contain 30% by weight or more of the conductive magnetic metal powder based on the weight of the entire metal powder. In another example, the proportion of the electrically conductive, magnetic metal powder in the metal powder may be about 35 wt% or more, about 40 wt% or more, about 45 wt% or more, about 50 wt% or more, about 55 wt% or more, 60 wt% or more, 65 wt% or more, 70 wt% or more, 75 wt% or more, 80 wt% or more, 85 wt% or more, or 90 wt% or more. The upper limit of the proportion of the conductive magnetic metal powder is not particularly limited, and may be, for example, less than about 100% by weight, or 95% by weight or less. However, the above ratios are exemplary ratios.

The size of the metal powder is also selected in consideration of desired porosity or pore size, etc., but is not particularly limited, wherein the average particle diameter of the metal powder may be, for example, in the range of about 0.1 μm to about 200 μm. In another example, the average particle size can be about 0.5 μm or greater, about 1 μm or greater, about 2 μm or greater, about 3 μm or greater, about 4 μm or greater, about 5 μm or greater, about 6 μm or greater, about 7 μm or greater, or about 8 μm or greater. In another example, the average particle size can be about 150 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less. As the metal in the metal particles, metals having different average particle diameters may also be applied. The average particle diameter may be selected from an appropriate range in consideration of a desired shape of the metal foam (e.g., thickness or porosity of the metal foam, etc.).

Here, the average particle diameter of the metal powder may be obtained by a known particle size analysis method, and for example, the average particle diameter may be a so-called D50 particle diameter.

The ratio of the metal component (metal powder) in the slurry as described above is not particularly limited, and may be selected in consideration of desired viscosity and process efficiency. In one implementation, the proportion of the metal component in the slurry may be from about 0.5% to 95% on a weight basis, but is not limited thereto. In another example, the ratio can be about 1% or more, about 1.5% or more, about 2% or more, about 2.5% or more, about 3% or more, about 5% or more, 10% or more, 15% or more, 20% or more, 25% or more, 30% or more, 35% or more, 40% or more, 45% or more, 50% or more, 55% or more, 60% or more, 65% or more, 70% or more, 75% or more, or 80% or more, or can be about 90% or less, about 85% or less, about 80% or less, about 75% or less, about 70% or less, about 65% or less, 60% or less, 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, 30% or less, 15% or less, or 20% or less, or 30% or less, or 20% or less, or a combination thereof, Or 5% or less, but not limited thereto.

As the dispersant contained in the slurry, for example, alcohol may be applied. As the alcohol, monohydric alcohols having 1 to 20 carbon atoms, such as methanol, ethanol, propanol, pentanol, octanol, pentanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, glycerol, texanol, or terpineol; or diols (diols) having 1 to 20 carbon atoms, such as ethylene glycol, propylene glycol, pentanediol, hexanediol or octanediol; or a polyol, etc., but the kind is not limited to the above.

Suitable dispersants may be exemplified by alcohols having 9 to 20 carbon atoms, such as texanol; alcohols having a double bond and/or a cyclic structure while having 9 to 20 carbon atoms, such as terpineol; or a glycol having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms, such as ethylene glycol or propylene glycol, and the like, but is not limited thereto.

The dispersant may be included in a proportion of, for example, about 30 parts by weight to 2000 parts by weight with respect to 100 parts by weight of the binder. In another example, the ratio can be about 50 parts by weight or greater, about 100 parts by weight or greater, about 150 parts by weight or greater, about 200 parts by weight or greater, about 300 parts by weight or greater, about 400 parts by weight or greater, about 500 parts by weight or greater, about 550 parts by weight or greater, about 600 parts by weight or greater, or about 650 parts by weight or greater, and can be about 1800 parts by weight or less, about 1600 parts by weight or less, about 1400 parts by weight or less, about 1200 parts by weight or less, about 1000 parts by weight or less, or about 900 parts by weight or less.

The slurry may comprise a binder. The binder may improve dispersibility of the metal particles contained in the slurry, so that the process of applying the slurry on the substrate may be easily performed, and may be used to support the metal foam precursor in the step of sintering the metal foam precursor. The kind of such a binder is not particularly limited, and it may be appropriately selected according to the kind of metal particles applied at the time of preparing the slurry, the kind of a dispersant, or the like. For example, the binder may be exemplified by alkylcelluloses having an alkyl group having 1 to 8 carbon atoms, such as methylcellulose or ethylcellulose; polyalkylene carbonates having an alkylene unit having 1 to 8 carbon atoms, such as polyethylene carbonate or polypropylene carbonate; polyvinyl alcohol; or polyvinyl acetate, and the like, but not limited thereto.

The content of the binder in the slurry is not particularly limited, and may be selected according to the porosity required for the metal foam. In one example, the binder may be included in a ratio of about 1 to 500 parts by weight with respect to 100 parts by weight of the metal component. In another example, the ratio may be about 2 parts by weight or greater, about 3 parts by weight or greater, about 4 parts by weight or greater, about 5 parts by weight or greater, about 6 parts by weight or greater, about 7 parts by weight or greater, about 8 parts by weight or greater, about 9 parts by weight or greater, about 10 parts by weight or greater, about 20 parts by weight or greater, about 30 parts by weight or greater, about 40 parts by weight or greater, about 50 parts by weight or greater, about 60 parts by weight or greater, about 70 parts by weight or greater, about 80 parts by weight or greater, about 90 parts by weight or greater, about 100 parts by weight or greater, about 110 parts by weight or greater, about 120 parts by weight or greater, about 130 parts by weight or greater, about 140 parts by weight or greater, about 150 parts by weight or greater, about 200 parts by weight or greater, or about 250 parts by weight or greater, and may be about 450 parts by weight or less, about 400 parts by weight or greater, and may be about 450 parts by weight or less, About 350 parts by weight or less, about 300 parts by weight or less, about 250 parts by weight or less, about 200 parts by weight or less, about 150 parts by weight or less, about 100 parts by weight or less, about 90 parts by weight or less, about 80 parts by weight or less, about 70 parts by weight or less, about 60 parts by weight or less, about 50 parts by weight or less, about 40 parts by weight or less, about 30 parts by weight or less, about 20 parts by weight or less, or about 15 parts by weight or less.

The slurry may comprise an anti-solvent. The anti-solvent has miscibility with the dispersant but does not dissolve the binder, thereby serving to increase the size of the pores of the metal foam formed by drying and sintering the slurry. The pore size of the formed metal foam can be controlled by controlling the kind and content of the dispersant and the antisolvent. The kind of the anti-solvent is not particularly limited as long as it does not dissolve the binder while being miscible with the dispersant. Further, when the binder is a polymer binder, the kind of the anti-solvent is not particularly limited as long as it does not swell the polymer binder while being miscible with the dispersant. For example, as the anti-solvent, monohydric alcohols such as isopropyl alcohol; polyols, such as ethylene glycol, diethylene glycol or glycerol; alkanolamines, such as triethanolamine or triethanolamine; alkyl ethers such as diethyl ether, isopropyl ether or n-butyl ether; aryl ethers, such as phenyl ether or benzyl ether; esters, such as sec-amyl acetate; ketones such as acetone, methyl ethyl ketone or methyl isobutyl ketone; alkylbenzenes such as cumene or diethylbenzene; aryl benzenes such as diphenyl benzene; and halogenated benzenes such as trichlorobenzene and the like, but the species are not limited thereto. Suitable antisolvents are exemplified by monovalent aliphatic alcohols having 1 to 20 carbon atoms, 1 to 16 carbon atoms, 1 to 12 carbon atoms, 1 to 8 carbon atoms, or 1 to 4 carbon atoms, such as, but not limited to, isopropanol.

The content of the anti-solvent in the slurry is not particularly limited and may be selected depending on the desired pore size. The anti-solvent may be included in a proportion of, for example, about 0.5 parts by weight to 2000 parts by weight with respect to 100 parts by weight of the binder. In another example, the ratio can be about 1 part by weight or greater, about 1.5 parts by weight or greater, about 2 parts by weight or greater, about 3 parts by weight or greater, about 4 parts by weight or greater, about 5 parts by weight or greater, about 6 parts by weight or greater, about 7 parts by weight or greater, about 8 parts by weight or greater, about 9 parts by weight or greater, about 10 parts by weight or greater, about 15 parts by weight or greater, about 20 parts by weight or greater, about 25 parts by weight or greater, about 30 parts by weight or greater, about 35 parts by weight or greater, about 40 parts by weight or greater, about 45 parts by weight or greater, about 50 parts by weight or greater, about 55 parts by weight or greater, about 60 parts by weight or greater, about 65 parts by weight or greater, about 70 parts by weight or greater, about 75 parts by weight or greater, about 80 parts by weight or greater, about 85 parts by weight or greater, about 90 parts by weight or greater, or greater, About 95 parts by weight or greater, about 100 parts by weight or greater, about 110 parts by weight or greater, about 120 parts by weight or greater, about 130 parts by weight or greater, about 140 parts by weight or greater, about 150 parts by weight or greater, about 160 parts by weight or greater, about 170 parts by weight or greater, about 180 parts by weight or greater, about 190 parts by weight or greater, about 200 parts by weight or greater, about 300 parts by weight or greater, about 400 parts by weight or greater, about 500 parts by weight or greater, about 550 parts by weight or greater, about 600 parts by weight or greater, or about 650 parts by weight or greater, and may be about 1800 parts by weight or less, about 1600 parts by weight or less, about 1400 parts by weight or less, about 1200 parts by weight or less, about 1000 parts by weight or less, about 900 parts by weight or less, about 850 parts by weight or less, about 800 parts by weight or less, about 1400 parts by weight or less, about 700 parts by weight or less, or about 750 parts by weight or less, or less, About 650 parts by weight or less, about 600 parts by weight or less, about 550 parts by weight or less, about 500 parts by weight or less, about 450 parts by weight or less, about 400 parts by weight or less, about 350 parts by weight or less, or about 300 parts by weight or less.

In the slurry, for example, the sum of the weights of the dispersant and the anti-solvent may be 10 parts by weight to 1000 parts by weight with respect to 100 parts by weight of the metal component. In another example, the ratio can be about 20 parts by weight or greater, 30 parts by weight or greater, 40 parts by weight or greater, about 50 parts by weight or greater, about 60 parts by weight or greater, about 70 parts by weight or greater, about 80 parts by weight or greater, or about 85 parts by weight, and can be about 800 parts by weight or less, about 700 parts by weight or less, 600 parts by weight or less, about 500 parts by weight or less, 400 parts by weight or less, about 300 parts by weight or less, about 200 parts by weight or less, about 150 parts by weight or less, about 100 parts by weight or less, or about 95 parts by weight or less.

In the slurry, for example, the ratio (a/B) of the weight (a) of the dispersant to the weight (B) of the antisolvent may be in the range of about 0.5 to 20 or so. In another example, the ratio may be about 1 or greater, 1.5 or greater, or 2 or greater, or may be about 18 or less, about 16 or less, about 14 or less, about 12 or less, or about 10 or less.

The slurry may or may not further comprise a solvent, if necessary. In one example, the slurry may not contain a solvent in order to achieve a desired level of porosity and freedom of pore size control. At this time, the range of the solvent not included does not include the dispersant and the antisolvent. That is, in one example, the slurry may not contain solvents other than the dispersant and the anti-solvent. As the solvent, a suitable solvent may be used in consideration of the solubility of components (e.g., metal particles, a binder, or the like) in the slurry. For example, as the solvent, a solvent having a dielectric constant in the range of about 10 to 120 may be used. In another example, the dielectric constant can be about 20 or greater, about 30 or greater, about 40 or greater, about 50 or greater, about 60 or greater, or about 70 or greater, or can be about 110 or less, about 100 or less, or about 90 or less. Such a solvent may be exemplified by water, an alcohol having 1 to 8 carbon atoms (e.g., ethanol, butanol or methanol), DMSO (dimethyl sulfoxide), DMF (dimethylformamide), NMP (N-methylpyrrolidone), or the like, but is not limited thereto.

When the solvent is applied, it may be present in the slurry in a ratio of about 50 parts by weight to 400 parts by weight with respect to 100 parts by weight of the binder, but is not limited thereto.

In addition to the above components, the slurry may contain further required known additives.

The method of performing the step of forming the metal foam precursor using the slurry as described above is not particularly limited, and the process thereof may include a known step, for example, a step of drying the applied slurry. In the field of production of metal foams, various methods of forming a metal foam precursor using a slurry are known, and in the present application, all of these methods may be applied. In one example, the drying step of forming the metal foam precursor may be a step of heat-treating the slurry applied on the substrate at a temperature of 20 ℃ to 250 ℃, 50 ℃ to 180 ℃, or 70 ℃ to 150 ℃. By the drying step, a metal foam precursor comprising a porous structure formed on a substrate may be formed.

In one example, the metal foam precursor may also be formed in a film or sheet shape.

The thickness of the metal foam precursor may be 500 μm or less, 400 μm or less, 300 μm or less, 200 μm or less, 150 μm or less, about 100 μm or less, about 90 μm or less, about 80 μm or less, about 70 μm or less, about 60 μm or less, or about 55 μm or less. Here, the lower limit of the thickness of the porous structure is not particularly limited. For example, the thickness of the porous structure may be about 5 μm or more, 10 μm or more, or about 15 μm or more.

The metal foam may be produced by a step of sintering a metal foam precursor formed in this manner. In this case, the method of performing sintering to form the metal foam is not particularly limited, and a known sintering method may be applied. That is, the sintering step may be performed by a method of applying an appropriate amount of heat to the metal foam precursor in an appropriate manner, for example, the sintering step may be performed by a method of applying an external heat source thereto at 500 to 2000 ℃, 700 to 1500 ℃, or 800 to 1200 ℃.

In the present application, sintering may be performed by an induction heating method, which is a different method from the known methods. The induction heating method means sintering using heat generated by applying an electromagnetic field to a metal foam precursor. By this method, it is possible to produce a metal foam having excellent mechanical characteristics and controlled porosity at a desired level while containing uniformly formed pores.

Here, induction heating is a phenomenon in which heat is generated in a specific metal when an electromagnetic field is applied. For example, when an electromagnetic field is applied to a metal having appropriate electrical conductivity and magnetic permeability, an eddy current is generated in the metal and joule heat occurs due to the electrical resistance of the metal. In the present application, the sintering process may proceed by such a phenomenon. In the present application, sintering of the metal foam can be performed in a short time by applying such a method, thereby securing workability and simultaneously producing the metal foam having excellent mechanical strength while being in the form of a thin film having high porosity.

For sintering by the induction heating method, the metal component contained in the slurry may include a conductive metal or a conductive magnetic metal having appropriate relative permeability and conductivity.

When the sintering step is performed by induction heating, the conditions for applying the electromagnetic field are determined according to the kind and proportion of the conductive magnetic metal in the metal foam precursor, which is not particularly limited. For example, the induction heating may be performed using an induction heater formed in the form of a coil or the like. The induction heating may be performed by applying a current of, for example, about 100A to about 1000A. In another example, the magnitude of the applied current may be 900A or less, 800A or less, 700A or less, 600A or less, 500A or less, or 400A or less. In another example, the magnitude of the current may be about 150A or greater, about 200A or greater, or about 250A or greater.

The induction heating may be performed, for example, at a frequency of about 100kHz to 1000 kHz. In another example, the frequency can be 900kHz or less, 800kHz or less, 700kHz or less, 600kHz or less, 500kHz or less, or 450kHz or less. In another example, the frequency may be about 150kHz or greater, about 200kHz or greater, or about 250kHz or greater.

The application of the electromagnetic field for induction heating may be performed, for example, in the range of about 1 minute to 10 hours. In another example, the application time may be about 10 minutes or more, about 20 minutes or more, or about 30 minutes or more. In another example, the application time may be about 9 hours or less, about 8 hours or less, about 7 hours or less, about 6 hours or less, about 5 hours or less, about 4 hours or less, about 3 hours or less, about 2 hours or less, about 1 hour or less, or about 30 minutes or less.

The above-mentioned induction heating conditions such as applied current, frequency, and application time may be changed in consideration of the kind and proportion of the conductive magnetic metal particles as described above.

The sintering step may be performed by the above-mentioned induction heating only, or may also be performed by applying appropriate heat together with the induction heating (i.e., applying an electromagnetic field). For example, the sintering step may also be performed by applying an external heat source to the metal foam precursor alone or in conjunction with the application of an electromagnetic field.

The method for preparing metal foam of the present invention can provide metal foams having various pore sizes. By controlling the content of the anti-solvent contained in the slurry, the pore size of the metal foam formed by the sintering step can be easily controlled. In one example, the pore size of the metal foam produced by the method for preparing a metal foam of the present invention may be in the range of 0.1 μm to 200 μm. In another example, the pore size can be about 0.5 μm or greater, about 1 μm or greater, about 2 μm or greater, about 3 μm or greater, about 4 μm or greater, about 5 μm or greater, about 6 μm or greater, about 7 μm or greater, or about 8 μm or greater. In another example, the pore size can be about 150 μm or less, 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, 30 μm or less, or 20 μm or less.

The porosity of the formed metal foam may be in the range of about 30% to 99%, or 30% to 90%. As described above, according to the method of the present invention, the metal foam may include uniformly formed pores, and the pore size, porosity, and mechanical strength of the metal foam may be controlled. The porosity can be 50% or greater, 60% or greater, 70% or greater, 75% or greater, or 80% or greater, or can be 95% or less, 90% or less, about 85% or less, or about 80% or less.

The method for preparing a metal foam of the present application can form a thin metal foam on a substrate. The metal foam may be formed in the form of a film or sheet. In one example, the thickness of the metal foam is not particularly limited, but may be 500 μm or less, 400 μm or less, 300 μm or less, 200 μm or less, 150 μm or less, about 100 μm or less, about 90 μm or less, about 80 μm or less, about 70 μm or less, about 60 μm or less, or about 55 μm or less. Here, the lower limit of the thickness of the metal foam is not particularly limited. For example, the thickness of the metal foam may be about 5 μm or more, 10 μm or more, or about 15 μm or more.

Advantageous effects

The present application relates to a method for producing a metal foam. The present application may provide a method capable of preparing a metal foam which is thin and has appropriate porosity and pore size through a simple and efficient process.

Drawings

FIG. 1 is a scanning electron micrograph of the metal foam prepared in example 1.

FIG. 2 is a scanning electron micrograph of the metal foam prepared in comparative example 1.

Fig. 3 is a graph showing the pore size distribution of the metal foams prepared in examples and comparative examples.

Detailed Description

Hereinafter, the present application will be described by way of examples and comparative examples, but the scope of the present application is not limited to the following examples.