KR102378971B1 - Manufacturing method for metal foam - Google Patents

Abstract

The present application relates to a method for manufacturing a metal foam. In the present application, it is possible to provide a method for simply and effectively manufacturing a metal foam having desired properties.

Description

Manufacturing method of metal foam {MANUFACTURING METHOD FOR METAL FOAM}

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

Metal foam has various useful properties such as lightness, energy absorption, heat insulation, fire resistance, or environment-friendly properties. Accordingly, the metal foam can be applied to various fields, including lightweight structures, transport machines, building materials or energy absorbing devices. In addition, since the metal foam has a high specific surface area and can further improve the flow of fluids or electrons such as liquids and gases, it is applied to substrates for heat exchange devices, catalysts, sensors, actuators, secondary cells, fuel cells, etc. and can be usefully used. For example, the metal foam may be manufactured by the method for manufacturing the metal foam disclosed in Patent Document 1 (Korean Patent Publication No. 10-2018-0041342).

In general, in the foaming process of the slurry containing the metal powder, the metal foam has a problem in that the volume is excessively increased in the foaming process due to the foaming agent contained in the slurry, and cracks occur in the metal foam. For this reason, metal foam is manufactured by thickly coating the slurry and foaming under high humidity conditions.

Korean Patent Publication No. 10-2018-0041342

An object of the present application is to provide a method capable of effectively manufacturing a metal foam having a desired characteristic.

In the present application, the term metal foam refers to a porous structure including a metal as a main component. In the above, having a metal as a main component means that the proportion of the metal or metal alloy 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 based on the total weight of the metal foam. It means a case of weight % or more, 85 weight % or more, 90 weight % or more, or 95 weight % or more. The upper limit of the ratio of the metal included as the main component is not particularly limited, and may be, for example, 100% by weight.

Among the physical properties mentioned in the present application, when the measured temperature affects the corresponding physical properties, unless otherwise specified, the physical properties are measured at room temperature. The term room temperature is a natural temperature that has not been heated or reduced, and for example, may mean any temperature within the range of about 10 °C to 30 °C, a temperature of about 23 °C or about 25 °C. .

In the present application, the unit "parts by weight" means a relative weight of a component to other components, and does not mean an absolute value such as g, kg, lb, or the like.

The manufacturing method of the metal foam of the present application includes at least the step of foaming the metal foam precursor formed in the slurry containing the metal powder. In the present application, the term metal foam precursor refers to a structure before a process performed to form a metal foam, such as the sintering, that is, a structure before the metal foam is generated. In addition, even if the metal foam precursor is called a porous metal foam precursor, it does not necessarily have to be porous by itself, and if it can finally form a metal foam that is a porous metal structure, it can be called a porous metal foam precursor for convenience. there is.

The metal foam precursor may be in the form of a film, sheet, or layer, and the metal foam thus prepared may also be in the form of a film, sheet or layer.

In the present application, after forming a metal foam precursor to a certain thickness with a specific slurry, a foaming process is performed under a specific humidity condition to form a metal foam. In this way, there is no defect such as cracks on the surface, and the metal foam having the desired pore characteristics can be effectively manufactured.

For example, the foaming process and the like may be performed in an atmosphere with a relative humidity of less than 65%. The foaming process and the like, in another example, may be performed in a relative humidity atmosphere of 60% or less, 55% or less, 50% or less, 45% or less, or 40% or less. The relative humidity may be 20% or more, 25% or more, or 30% or more in another example. In one example, in each process of the manufacturing method of the metal foam of the present application, the process humidity atmosphere may not be separately controlled. That is, the humidity atmosphere in the above range may be formed by not using a separate device for creating a high-humidity atmosphere during foaming in the method of the present application.

In the present application, the metal foam precursor may be formed using a slurry including at least a metal powder, an aqueous solvent, an organic solvent, and a surfactant.

The specific kind of the metal powder is determined according to the purpose and is not particularly limited. Examples of the metal powder include copper powder, molybdenum powder, iron powder, nickel powder, cobalt powder, silver powder, platinum powder, gold powder, aluminum powder, chromium powder, indium powder, tin powder, magnesium powder, phosphorus powder. , any one powder selected from the group consisting of zinc powder and manganese powder, a metal powder in which two or more of them are mixed, or a powder of an alloy of two or more kinds of metals among the above metals may be exemplified, but is not limited thereto .

The size of the metal powder is also not particularly limited as being selected in consideration of a desired porosity or pore size, but, for example, the average particle diameter of the metal powder is in the range of about 0.1 μm to about 200 μm. there may be The average particle diameter is about 0.5 μm or more, about 1 μm or more, about 2 μm or more, about 3 μm or more, about 4 μm or more, about 5 μm or more, about 6 μm or more, about 7 μm or more, or about 8 μm in another example. may be more than In another example, the average particle diameter may 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 powder, a mixture of metal powders having different average particle diameters may be applied. The average particle diameter may be selected in an appropriate range in consideration of the desired shape of the metal foam, for example, the thickness or porosity of the metal foam. In the present specification, the average particle size of the metal powder may be obtained by a known particle size analysis method, and for example, the average particle size may be a so-called D50 particle size.

The shape of the metal powder is also selected in consideration of a desired porosity or pore size, and is not particularly limited, but, for example, the metal powder may be a dentritic metal powder.

The ratio of the metal component (metal powder) in the slurry is not particularly limited, and may be selected in consideration of a desired viscosity or process efficiency. In one example, the proportion of the metal component in the slurry may be about 0.5 to 95% by weight, but is not limited thereto. In another example, the ratio is 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. 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 about 90% or more 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, 25% or less, 20% or less, 15% or less, 10% or less, or 5% or less, but is not limited thereto.

The slurry for forming the metal foam precursor includes a metal powder, an aqueous solvent, an organic solvent, and a surfactant.

If the ratio and type of the aqueous solvent, organic solvent and surfactant are adjusted in the slurry, a fine emulsion is formed in the metal foam precursor, and this emulsion can determine the pore properties of the metal foam. If necessary, the metal foam precursor may be subjected to a foaming process. For example, due to the difference in vapor pressure between the organic solvent and the aqueous solvent, it is possible to control the pore properties of the metal foam while the component having a greater vapor pressure is vaporized in the foaming process.

As the aqueous solvent in the above, water or other polar solvents may be applied, and water may be typically applied. Such an aqueous solvent may be included in a ratio of 60 parts by weight to 140 parts by weight based on 100 parts by weight of the metal powder in the slurry. The proportion of the aqueous solvent may be 70 parts by weight or more or 80 parts by weight or more, 130 parts by weight or less, or 120 parts by weight or less in another example.

As the organic solvent, an appropriate kind may be selected. For example, as the organic solvent, an emulsion capable of forming an emulsion through the action of the aqueous solvent and a surfactant to be described later, and having an appropriate vapor pressure, a foaming process may be performed by vaporization may be selected. As such an organic solvent, a hydrocarbon type organic solvent can be applied, for example. As the hydrocarbon-based organic solvent, an organic solvent having 4 to 12 carbon atoms may be applied, and specific examples include n-pentane, neopentane, hexane, cyclohexane, isohexane, heptane, isoheptane, octane, toluene, benzene, iso Propyl ether and the like may be applied. Such an organic solvent may be included in a ratio of 5 parts by weight or less based on 100 parts by weight of the metal powder in the slurry. Preferably, the ratio of the organic solvent is about 4.5 parts by weight or less, 4 parts by weight or less, 3.5 parts by weight or less, 3 parts by weight or less, 2.5 parts by weight or less, 2 parts by weight or less, 1.5 parts by weight or less, based on 100 parts by weight of the metal powder; It may be included in a ratio of 1 part by weight or less or 0.9 parts by weight or less. In particular, the ratio of the organic solvent in the manufacturing method of the present application may be as small as possible in the above range in consideration of the physical properties of the metal foam. The ratio is, in one example, 0.01 parts by weight or more, 0.05 parts by weight or more, 0.1 parts by weight or more, 0.15 parts by weight or more, 0.2 parts by weight or more, 0.25 parts by weight or more, 0.3 parts by weight or more, 0.35 parts by weight compared to 100 parts by weight of the metal powder. parts by weight or more, 0.4 parts by weight or more, 0.45 parts by weight or more, 0.5 parts by weight or more, 0.55 parts by weight or more, 0.6 parts by weight or more, 0.65 parts by weight or more, or 0.7 parts by weight or more.

Surfactants may be included to form a suitable microemulsion in the metal foam precursor and/or to provide suitable control of the vaporization described above.

Various types of surfactants may be used without particular limitation as long as they are selected to form the emulsion in consideration of the applied aqueous solvent and organic solvent.

For example, as the surfactant, any one selected from the group consisting of an amphoteric surfactant, a nonionic surfactant, and an anionic surfactant, or a mixture of two or more thereof may be applied. In some cases, even when any one type of surfactant among amphoteric surfactants, nonionic surfactants and anionic surfactants is used, a mixture of two or more surfactants having different structures within the one type may be applied.

The anionic surfactant may mean a case in which the part exhibiting surface activity is an anion, as is known. Anionic surfactants include, for example, carboxylate surfactants, sulfate surfactants, isethionate surfactants, sulfosuccinate surfactants, taurates Surfactants and/or glutamate surfactants may be applied.

As the carboxylate surfactant in the above, as a fatty acid-based surfactant, a surfactant generated by a saponification reaction of a fatty acid and an alkali metal salt may be applied. In this case, a surfactant to which a fatty acid having 12 to 22 carbon atoms is applied may be appropriate to ensure bubble stability. Examples of such fatty acids may include lauric acid, myristic acid, palmitic acid, oleic acid, linoleic acid, stearic acid and/or behenic acid. Potassium hydroxide, sodium hydroxide, etc. may be applied as the alkali metal salt, and the ratio of the alkali metal salt may be adjusted so that the pH range is about 6 to 12 for uniform foam formation.

In the above, as the sulfate surfactant, an alkyl sulfate salt having 8 to 20 carbon atoms, or an added mole number of ethylene oxide in the range of 2 to 30, an alkyl ether sulfate salt having 10 to 40 carbon atoms, etc. may be applied, As the isethionate surfactant, an alkyl isethionate salt including an alkyl group having 10 to 20 carbon atoms may be applied, but is not limited thereto.

A nonionic surfactant may mean a surfactant that does not dissociate into ions, as is known. Examples of the nonionic surfactant include an alkyl polyglycoside surfactant, a fatty acid alkanol amide surfactant, an amine oxide surfactant, an ethylene oxide-added higher alcohol surfactant, and/or an oil-based surfactant to which ethylene oxide is added. (ex. Ethoxylated castor oil, etc.) may be applied.

The amphoteric surfactant is a surfactant having an anionic moiety and a cationic moiety at the same time, and for example, a betaine-based or sultaine-based surfactant may be applied. Examples of the betaine include cocamidopropyl betaine, lauramidopropyl betaine, cocobetaine or lauryl betaine, and the sultaine-based examples include lauryl hydroxy sultaine, lauramidopropyl hydroxy sultaine. , cocamidopropylhydroxy sultaine and/or coco sultaine may be exemplified.

The surfactant may be included in a ratio of 1 to 15 parts by weight based on 100 parts by weight of the metal powder in the slurry. In another example, the ratio may be 1.05 parts by weight or more, 1.1 parts by weight or more, 1.15 parts by weight or more, 1.2 parts by weight or more, or 1.25 parts by weight or more, and 14.5 parts by weight or less, 14 parts by weight or less, 13.5 parts by weight or less, 13 It may be about 12.5 parts by weight or less, or 12.5 parts by weight or less. The slurry may further include necessary components in addition to the above components. For example, the slurry may further include a binder.

The binder is not particularly limited and may be appropriately selected according to, for example, a water-soluble binder, a metal component, an aqueous solvent, an organic solvent, and/or a surfactant applied during the preparation of the slurry. For example, as the binder, an alkyl cellulose having an alkyl group having 1 to 8 carbon atoms, such as methyl cellulose or ethyl cellulose, polyalkylene carbonate having an alkylene unit having 1 to 8 carbon atoms, such as polypropylene carbonate or polyethylene carbonate, or A polyvinyl alcohol-based binder such as polyvinyl alcohol or polyvinyl acetate (hereinafter, may be referred to as a polyvinyl alcohol compound) may be exemplified, but is not limited thereto.

The binder may be included in a ratio of 10 to 20 parts by weight based on 100 parts by weight of the metal powder in the slurry. In another example, the proportion is 10.5 parts by weight or more, 11 parts by weight or more, 11.5 parts by weight or more, 12 parts by weight or more, or 12.5 parts by weight or more, or 19 parts by weight or less, 18 parts by weight or less, 17 parts by weight or less, 16 parts by weight or less. parts by weight or less, 15 parts by weight or less, 14 parts by weight or less, or 13 parts by weight or less. Under this ratio, it is possible to effectively manufacture a metal foam having a desired pore property.

In the case of the present application, the slurry used in the manufacturing process of the metal foam may not substantially include a component acting as a plasticizer. The fact that the slurry of the present application does not substantially contain any component means that the ratio of the component is 1 part by weight or less, 0.5 parts by weight or less, 0.1 parts by weight or less, 0.05 parts by weight or less, or 0.01 parts by weight relative to 100 parts by weight of the metal powder. or less, or substantially 0 parts by weight.

Generally, a plasticizer is applied to the slurry applied to the foaming method to prevent defects such as defects in the foaming process. In the present application, the process can be performed without the application of such a plasticizer to form a metal foam having excellent properties. A plasticizer generally used in the metal foam manufacturing process is a polyhydric alcohol such as ethylene glycol, an ether-based compound such as tris(2-ethylhexyl)phosphate, or an ester-based compound such as bis(2-ethylhexyl)phthalate. Therefore, the slurry of the present application may not include the polyhydric alcohol, ether, or ester, or may include it in a ratio within the above range.

However, the slurry may contain additionally necessary known additives in addition to the above-mentioned components.

A method of forming the metal foam precursor using the slurry as described above is not particularly limited. Various methods for forming a metal foam precursor are known in the field of manufacturing metal foam, and all of these methods may be applied in the present application. For example, the metal foam precursor may form the metal foam precursor by maintaining the slurry in an appropriate template or coating the slurry in an appropriate manner.

When manufacturing a metal foam in the form of a film or sheet according to one example of the present application, it may be advantageous to apply a coating process. For example, after forming a precursor by coating the slurry on an appropriate substrate, a desired metal foam may be formed through a sintering process to be described later.

The form of such a metal foam precursor is not particularly limited as being determined according to the desired metal foam. In one example, the metal foam precursor may be in the form of a film or a sheet. For example, when the precursor is in the form of a film or sheet, the thickness may be about 300 μm or less or about 250 μm or less. By controlling the thickness in this range, it is possible to manufacture a metal foam having suitable properties according to the purpose. In another example, the thickness may be controlled to about 50 μm or more, about 70 μm or more, about 90 μm or more, about 110 μm or more, about 130 μm or more, or about 150 μm or more.

In the process of forming the metal foam precursor, foaming may be achieved while the microemulsion is vaporized by the foaming process performed. For example, the foaming process may be performed by maintaining the molded slurry at a temperature within the range of about 20°C to 100°C for an appropriate time. The temperature is in another example about 25 °C or higher, 30 °C or higher, 35 °C or higher, or 40 °C or higher, or 95 °C or lower, 90 °C or lower, 85 °C or lower, 80 °C or lower, 75 °C or lower. It may be below C, below 70°C, below 65°C, below 60°C, or below 55°C. The holding time of the foaming process may be selected in consideration of the desired degree of foaming, and may be in the range of approximately 1 minute to 1 hour, but is not limited thereto.

In the process of forming the metal foam precursor, an appropriate drying process may be performed. For example, the metal foam precursor may be formed by drying for a certain period of time after the foaming process. The drying conditions are not particularly limited and, for example, may be controlled at a level at which the solvent contained in the slurry can be removed to a desired level. For example, the drying may be performed by maintaining the foamed slurry at a temperature within the range of about 50 °C to 250 °C, about 70 °C to 180 °C, or about 90 °C to 150 °C for a suitable time. can The drying time may also be selected within an appropriate range.

The metal foam may be manufactured by sintering the metal foam precursor formed in the above manner. In this case, a method of performing sintering for manufacturing the metal foam is not particularly limited, and a known sintering method may be applied. That is, the sintering may be performed by applying an appropriate amount of heat to the metal foam precursor in an appropriate manner.

In this case, the conditions for sintering are the state of the applied metal foam precursor, for example, the type of metal powder, the amount or type of aqueous solvent, organic solvent, and/or surfactant, and the metal powder is connected to form a porous structure. It can be controlled so as to be possible, and specific conditions are not particularly limited.

For example, the sintering may be performed by maintaining the precursor at a temperature in the range of about 500 °C to 2000 °C, in the range of 700 °C to 1500 °C, or in the range of 800 °C to 1200 °C. and the holding time may also be arbitrarily selected. The holding time may be in the range of about 1 minute to about 10 hours in one example, but is not limited thereto.

The metal foam manufactured according to the present application can be utilized in various applications requiring a porous metal structure. In particular, according to the present application, it can be utilized for various purposes, has excellent mechanical strength, and can quickly and easily manufacture a metal foam in the form of a thin film or sheet, thereby improving productivity.

In the present application, it is possible to provide a method for simply and effectively manufacturing a metal foam having desired properties.

1 to 4 are photographs of the metal foam of Examples 1 to 4, respectively.
5 to 6 are photographs of the metal foam of Comparative Examples 1 and 2, respectively.
7 is a photograph taken with a scanning electron microscope (SEM) of the surface of the metal foam prepared in Comparative Example 2;

Hereinafter, the present application will be described in more detail through examples. However, the following examples describe one example of the present application in more detail, and do not limit the content of the present application.

Example 1.

7 g of water as an aqueous solvent, 0.33 g and 0.67 g of methyl cellulose and hydroxypropyl methylcellulose as a binder, respectively, 0.4 g of a commercially available amphoteric surfactant as a surfactant, 0.3 g of ethylene glycol as a plasticizer and n-hexane as an organic solvent To the mixture in which 0.1 g was mixed, 8 g of copper powder was mixed to prepare a slurry. As the copper powder, dentrite copper powder (Makin metal powder, Dentritic copper powder) having an average particle diameter (D50 particle diameter) of about 60 μm in the long axis direction was applied. The slurry was coated in the form of a film to form a metal foam precursor having a thickness of about 100 μm. The metal foam precursor was foamed by maintaining it for about 1 minute in an oven maintaining a temperature of 35° C. and a relative humidity of 35%. The foamed metal foam precursor was dried in an oven maintaining a temperature of 100°C. Then, the dried metal foam precursor was sintered in a reducing atmosphere at a temperature of 1000° C. to prepare a metal foam in the form of a film. 1 is a photograph of the metal foam prepared in Example 1. 1 , it can be seen that a metal foam having a thin thickness and no surface cracks can be manufactured.

Example 2

7 g of water as an aqueous solvent, 0.33 g and 0.67 g of methyl cellulose and hydroxypropyl methylcellulose as a binder, respectively, 0.4 g of a commercially available amphoteric surfactant as a surfactant, 0.3 g of ethylene glycol as a plasticizer, and n- as an organic solvent In a mixture containing 0.1 g of hexane, 8 g of copper powder was mixed to prepare a slurry. As the copper powder, dendritic copper powder (Makin metal powder, Dentritic copper powder) having an average particle diameter (D50 particle diameter) of about 60 μm in the long axis direction was applied. The slurry was coated in the form of a film to form a metal foam precursor having a thickness of about 300 μm. The metal foam precursor was foamed for about 1 minute in an oven maintaining a temperature of 35° C. and a relative humidity of 35%. The foamed metal foam precursor was dried in an oven maintaining a temperature of 100°C. Then, the dried metal foam precursor was sintered in an oven maintaining a temperature of 1000° C. to prepare a metal foam. 2 is a photograph of the metal foam prepared in Example 2. According to FIG. 2 , it can be seen that, as in Example 1, a metal foam having a thin thickness and no surface cracks can be manufactured by a non-wet method.

Example 3

In a mixture of 7 g of water as an aqueous solvent, 0.33 g and 0.67 g of methyl cellulose and hydroxypropyl methylcellulose as a binder, respectively, 0.4 g of a commercially available amphoteric surfactant as a surfactant, and 0.06 g of n-hexane as an organic solvent, A slurry was prepared by mixing 8 g of copper powder. As the copper powder, dendritic copper powder (Makin metal powder, Dentritic copper powder) having an average particle diameter (D50 particle diameter) of about 60 μm in the long axis direction was applied. The slurry was coated in the form of a film to form a metal foam precursor having a thickness of about 175 μm. The metal foam precursor was foamed for about 1 minute in an oven maintaining a temperature of 35° C. and a relative humidity of 35%. The foamed metal foam precursor was dried in an oven maintaining a temperature of 100°C. Then, the dried metal foam precursor was sintered in an oven maintaining a temperature of 1000 ℃. By washing the sintered metal foam precursor, a metal foam in the form of a film was prepared. 3 is a photograph of the metal foam prepared in Example 3. According to FIG. 3 , it can be seen that there is no crack on the surface and a metal foam having a thin thickness can be manufactured.

Example 4

In a mixture of 7 g of water as an aqueous solvent, 0.33 g and 0.67 g of methyl cellulose and hydroxypropyl methylcellulose as a binder, respectively, 0.4 g of a commercially available amphoteric surfactant as a surfactant, and 0.06 g of n-hexane as an organic solvent, A slurry was prepared by mixing 8 g of copper powder. As the copper powder, dendritic copper powder (Makin metal powder, Dentritic copper powder) having an average particle diameter (D50 particle diameter) of about 60 μm in the long axis direction was applied. The slurry was coated in the form of a film to form a metal foam precursor having a thickness of about 225 μm. The metal foam precursor was foamed for about 1 minute in an oven maintaining a temperature of 35° C. and a relative humidity of 35%. The foamed metal foam precursor was dried in an oven maintaining a temperature of 100°C. Then, the dried metal foam precursor was sintered in an oven maintaining a temperature of 1000 ℃. According to FIG. 4 , it can be seen that there is no crack on the surface and a metal foam having a thin thickness can be manufactured.

Comparative Example 1

In a mixture of 7 g of water as an aqueous solvent, 0.33 g and 0.67 g of methyl cellulose and hydroxypropyl methylcellulose as a binder, respectively, 0.4 g of a commercially available amphoteric surfactant as a surfactant, and 0.06 g of n-hexane as an organic solvent, A slurry was prepared by mixing 8 g of copper powder. As the copper powder, dendritic copper powder (Makin metal powder, Dentritic copper powder) having an average particle diameter (D50 particle diameter) of about 60 μm in the long axis direction was applied. The slurry was coated in the form of a film to form a metal foam precursor having a thickness of about 800 μm. The metal foam precursor was foamed for about 1 minute in an oven maintaining a temperature of 35° C. and a relative humidity of 35%. After foaming, the foamed metal foam precursor was dried in an oven maintaining a temperature of 100°C. Then, the dried metal foam precursor was sintered in an oven maintaining a temperature of 1000 ℃. By washing the sintered metal foam precursor, a metal foam in the form of a film was prepared. 5 is a photograph of the metal foam prepared in Comparative Example 1. According to FIG. 5 , when the thickness at the time of slurry coating is out of the range according to the present application, it can be seen that cracks occur on the surface when the metal foam is manufactured through the method of the present application.

Comparative Example 2

In a mixture of 7 g of water as an aqueous solvent, 0.33 g and 0.67 g of methyl cellulose and hydroxypropyl methylcellulose as a binder, respectively, 0.4 g of a commercially available amphoteric surfactant as a surfactant, and 0.1 g of n-hexane as an organic solvent, A slurry was prepared by mixing 8 g of copper powder. As the copper powder, dendritic copper powder (Makin metal powder, Dentritic copper powder) having an average particle diameter (D50 particle diameter) of about 60 μm in the long axis direction was applied. The slurry was coated in the form of a film to form a metal foam precursor having a thickness of about 400 μm. The metal foam precursor was foamed for about 1 minute in an oven maintaining a temperature of 35° C. and a relative humidity of 35%. The foamed metal foam precursor was dried in an oven maintaining a temperature of 100°C. Then, the dried metal foam precursor was sintered in an oven maintaining a temperature of 1000 ℃. By washing the sintered metal foam precursor, a metal foam in the form of a film was prepared. 6 is a photograph of the metal foam prepared in Comparative Example 2. According to FIG. 6 , when the thickness at the time of slurry coating is out of the range according to the present application, it can be seen that cracks occur on the surface when the metal foam is manufactured through the method of the present application. 7 is a SEM photograph of the metal foam prepared in Comparative Example 2. Referring to FIG. 7 , it can be seen that when the thickness of the slurry coating is out of the range according to the present application, the slurry is over-foamed in the manufactured metal foam and a number of pore defects occur.

Claims (13)

A method for producing a metal foam, comprising the step of foaming a metal foam precursor in the form of a film having a thickness of 300 μm or less formed into a slurry containing metal powder, an aqueous solvent, an organic solvent and a surfactant in an atmosphere of relative humidity of less than 65%. The method of claim 1, wherein the slurry contains 1 part by weight or less of the organic solvent based on 100 parts by weight of the metal powder. The method of claim 1, wherein the content of the polyhydric alcohol, ether, or ester in the slurry is 1 part by weight or less based on 100 parts by weight of the metal powder. The group of claim 1, wherein the metal powder is copper powder, phosphorus powder, molybdenum powder, zinc powder, manganese powder, chromium powder, indium powder, tin powder, silver powder, platinum powder, gold powder, aluminum powder and magnesium powder. Any one selected from, a method for producing a mixture of two or more of the metal powder or an alloy powder metal foam of two or more of the above. The method of claim 1, wherein the surfactant is at least one selected from the group consisting of a nonionic surfactant, an amphoteric surfactant, and an anionic surfactant. The surfactant according to claim 1, wherein the surfactant is a carboxylate-based anionic surfactant, a sulfate-based anionic surfactant, an isethionate-based anionic surfactant, a sulfosuccinate-based anionic surfactant, and a taurate-based anionic surfactant. activators, glutamate-based anionic surfactants; betaine-based amphoteric surfactants, sultaine-based amphoteric surfactants; A group consisting of alkyl polyglucoside-based nonionic surfactants, fatty acid alkanol amide-based nonionic surfactants, amine oxide-based nonionic surfactants, ethylene oxide-added higher alcohol-based nonionic surfactants, and ethylene oxide-added oil-based nonionic surfactants A method for producing a heat dissipation film that is one or a mixture of two or more selected from. The method of claim 1, wherein the surfactant is included in the slurry in an amount of 1 to 15 parts by weight based on 100 parts by weight of the metal powder. The method according to claim 1, wherein the slurry contains 30 wt% or more of the metal powder. The method of claim 1, further comprising a binder. The method of claim 9, wherein the binder is alkyl cellulose, polyalkylene carbonate, polyvinyl alcohol, polyalkylene oxide or polyvinyl acetate. 10. The method of claim 9, wherein the slurry comprises 10 parts by weight to 20 parts by weight of the binder based on 100 parts by weight of the metal powder. The method of claim 1, wherein the foaming process is performed by maintaining the metal foam precursor at a temperature within the range of 20 °C to 100 °C. The method of claim 1, wherein a process of sintering the foamed metal foam precursor is further performed following the foaming process.

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