KR20220050858A - Preparation method for metal foam - Google Patents

Abstract

The present application provides a preparation method of metal foam. In the present application, it is possible to provide a method for effectively modifying the surface of metal foam while maintaining the uniformity of pores the metal foam has, the porosity or mechanical strength, and the inherent advantages of a used metal material. The preparation method of metal foam comprises the steps of: sintering a metal structure including a metal component to obtain a porous metal sintered body; and making the porous metal sintered body contact with oxygen immediately after the sintering.

Description

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

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

Metal foam has various useful properties, such as light weight, energy absorption, heat insulation, fire resistance, or environment-friendly properties, and thus can be applied to various fields including lightweight structures, transport machines, building materials or energy absorption devices. . In addition, since the metal foam has a high specific surface area and can further improve the flow of fluids such as liquids and gases or electrons, a heat dissipation material, a substrate for a heat exchange device, a catalyst, a sensor, an actuator, a secondary battery, a fuel cell , a gas diffusion layer (GDL), a microfluidic flow controller, and the like, may be usefully used.

In order to maximize the field of application of the metal foam as described above, it may be necessary to modify the surface, such as adjusting the surface area of the metal foam.

For example, when the metal foam is complexed with a polymer material, interfacial adhesion between the inorganic material metal foam and the organic material polymer may not be sufficiently secured.

However, it is not easy to modify the surface while maintaining the inherent advantages of the metal foam.

The present application provides a method for manufacturing a metal foam, specifically, a method for manufacturing a surface-modified metal foam.

An object of the present application is to provide a method capable of effectively modifying the surface of a metal foam while maintaining the uniformity of pores, porosity or mechanical strength, and inherent advantages of the metal material used.

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

Among the physical properties mentioned in this specification, when the measured pressure affects the corresponding physical property, unless otherwise specified, the physical property is measured at normal pressure, that is, atmospheric pressure (about 1 atm).

In the present application, the term metal foam or metal skeleton refers to a porous structure including two or more metals as a main component. In the above, having a metal as a main component means that the ratio of the metal is 55 wt% or more, 60 wt% or more, 65 wt% or more, 70 wt% or more, 75 wt% or more, 80 wt% based on the total weight of the metal foam or metal skeleton 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.

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

The manufacturing method of the metal foam of the present application includes the steps of sintering a metal structure including a metal component to obtain a porous metal sintered body; and contacting the porous metal sintered body with oxygen following the sintering step. A protrusion-shaped oxide can be grown on the surface of the metal foam through contact with the oxygen under appropriate conditions, and the oxide can control the surface area of the metal foam without compromising the advantages of the metal foam.

In the above, the protrusion shape means a shape having an aspect ratio in the range of about 1 to 8. In another example, the aspect ratio of the protrusion shape may be about 7.5 or less, 7 or less, 6.5 or less, 6 or less, 5.5 or less, 5 or less, 4.5 or less, 4 or less, 3.5 or less, or 3 or less. In the above, the aspect ratio of the oxide may be the ratio (L/S) of the largest dimension (L) and the smallest dimension (S) among dimensions such as height to width of the oxide confirmed through an optical microscope or the like, and this When the above dimensions (L, S) are dimensions in the same unit. By the presence of such a protrusion-shaped oxide, the desired effect can be excellently achieved.

In the above, the area ratio of the metal oxide present on the surface of the metal foam may be in the range of 5% to 60%. In another example, the area ratio may be about 7% or more or 10% or more, or 55% or less, 50% or less, 45% or less, 40% or less, 35% or less, or about 30% or less. The area ratio is a percentage of the area in which the oxide is present compared to the total area of the metal foam, and for example, it is confirmed through the area of the oxide and the area of the metal foam confirmed by an optical microscope, or the weight of the metal foam and the oxide It can also be converted through weight or the like.

In the present application, the term metal structure refers to a structure before a process performed to form a metal foam, such as sintering, that is, a structure before the metal foam is generated. In addition, even if the metal structure is called a porous metal structure, 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 may be called a porous metal structure for convenience.

In the present application, the metal structure may be formed using a slurry including at least a metal component, a dispersant, and a binder.

The type of the metal component included in the metal structure is not particularly limited, and an appropriate type may be selected according to the purpose. For example, as the metal component, one or more or two or more selected from the group consisting of tin, copper, nickel, aluminum, molybdenum, silver, platinum, gold, aluminum, magnesium, and iron may be used.

The metal component forming the metal structure may be in the form of a powder. For example, the metals in the metal component may have an average particle diameter in a range of about 0.1 μm to about 200 μm. 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 metals in the metal component, those having different average particle diameters may be applied. The average particle diameter may be selected from an appropriate range in consideration of the desired shape of the metal foam, for example, the thickness or porosity of the metal foam, which is not particularly limited.

In the above, 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.

In one example, the metal component may include at least a metal having an appropriate relative permeability and conductivity. Application of such a metal may allow the sintering to be performed more smoothly when sintering by an induction heating method according to an example of the present application is performed.

For example, as the metal, a metal having a relative magnetic permeability of 90 or more may be used. In the above, the relative permeability (μ _r ) is the ratio (μ/μ ₀ ) of the magnetic permeability (μ) of the material and the magnetic permeability (μ ₀ ) in the vacuum. The metal used in the present application has a relative magnetic permeability of 95 or more, 100 or more, 110 or more, 120 or more, 130 or more, 140 or more, 150 or more, 160 or more, 170 or more, 180 or more, 190 or more, 200 or more, 210 or more, 220 or more, 230 or more, 240 or more, 250 or more, 260 or more, 270 or more, 280 or more, 290 or more, 300 or more, 310 or more, 320 or more, 330 or more, 340 or more, 350 or more, 360 or more, 370 or more, 380 or more , 390 or more, 400 or more, 410 or more, 420 or more, 430 or more, 440 or more, 450 or more, 460 or more, 470 or more, 480 or more, 490 or more, 500 or more, 510 or more, 520 or more, 530 or more, 540 or more, 550 or more or more, 560 or more, 570 or more, 580 or more, or 590 or more. The upper limit of the relative permeability is not particularly limited because the higher the value, the higher the heat is generated when an electromagnetic field for induction heating, which will be described later, is applied. In one example, the upper limit of the relative permeability may be, for example, about 300,000 or less.

The metal may be a conductive metal. In the present application, the term conductive metal has a conductivity at 20°C of about 8 MS/m or more, 9 MS/m or more, 10 MS/m or more, 11 MS/m or more, 12 MS/m or more, 13 MS/m or more, or 14.5 MS/m or higher metals or alloys thereof. The upper limit of the conductivity is not particularly limited, and may be, for example, about 30 MS/m or less, 25 MS/m or less, or 20 MS/m or less.

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

By applying the conductive magnetic metal, sintering can be performed more effectively when an induction heating process to be described later is performed. Such a metal may be exemplified by nickel, iron or cobalt, but is not limited thereto.

When the conductive magnetic metal is included, the ratio of the conductive magnetic metal in the metal component is not particularly limited. For example, the ratio may be adjusted so that an appropriate Joule heat can be generated when an induction heating method to be described later is applied. For example, the metal component may include 30 wt% or more of the conductive magnetic metal based on the total weight of the metal component. In another example, the proportion of the conductive magnetic metal in the metal component is 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 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. For example, since heat generated by induction heating by application of an electromagnetic field can be adjusted according to the strength of the applied electromagnetic field, electrical conductivity and resistance of a metal, the ratio may be changed according to specific conditions.

The metal structure may be formed using a slurry including a dispersant and a binder together with a metal component including the metal.

The ratio of the metal component 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.

As the dispersant, for example, alcohol may be applied. Alcohol, methanol, ethanol, propanol, pentanol, octanol, ethylene glycol, propylene glycol, pentannol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, glycerol, texanol (texanol) Or a monohydric alcohol having 1 to 20 carbon atoms, such as terpineol, or a dihydric alcohol having 1 to 20 carbon atoms, such as ethylene glycol, propylene glycol, hexanediol, octanediol or pentanediol, or more polyhydric alcohols, etc. may be used However, the type is not limited to the above.

The slurry may further include a binder. The type of the binder is not particularly limited, and may be appropriately selected according to the type of metal component or dispersant 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 may be exemplified, but the present invention is not limited thereto.

The proportion of each component in the slurry is not particularly limited. This ratio may be adjusted in consideration of process efficiency such as coating properties or moldability during a process using a slurry.

For example, in the slurry, the binder may be included in an amount of about 1 to 500 parts by weight based on 100 parts by weight of the aforementioned metal component. In another example, the ratio is about 2 parts by weight or more, about 3 parts by weight or more, about 4 parts by weight or more, about 5 parts by weight or more, about 6 parts by weight or more, about 7 parts by weight or more, about 8 parts by weight or more, about 9 Part by weight or more, about 10 parts by weight or more, about 20 parts by weight or more, about 30 parts by weight or more, about 40 parts by weight or more, about 50 parts by weight or more, about 60 parts by weight or more, about 70 parts by weight or more, about 80 parts by weight or more or more, about 90 parts by weight or more, about 100 parts by weight or more, about 110 parts by weight or more, about 120 parts by weight or more, about 130 parts by weight or more, about 140 parts by weight or more, about 150 parts by weight or more, about 200 parts by weight or more; about 250 parts by weight or more, about 450 parts by weight or less, about 400 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 It may be less than or equal to about 50 parts by weight, less than or equal to about 40 parts by weight, less than or equal to about 30 parts by weight, less than or equal to about 20 parts by weight, or less than or equal to about 10 parts by weight.

In addition, in the slurry, the dispersant may be included in an amount of about 10 to 2,000 parts by weight based on 100 parts by weight of the binder. In another example, the ratio is about 20 parts by weight or more, about 30 parts by weight or more, about 40 parts by weight or more, about 50 parts by weight or more, about 60 parts by weight or more, about 70 parts by weight or more, about 80 parts by weight or more, about 90 parts by weight or more. About 100 parts by weight or more, about 100 parts by weight or more, about 110 parts by weight or more, about 120 parts by weight or more, about 130 parts by weight or more, about 140 parts by weight or more, about 150 parts by weight or more, about 160 parts by weight or more, about 170 parts by weight or more or more, about 180 parts by weight or more, about 190 parts by weight or more, about 200 parts by weight or more, about 300 parts by weight or more, about 400 parts by weight or more, about 500 parts by weight or more, about 550 parts by weight or more, about 600 parts by weight or more; about 650 parts by weight or more, about 1,800 parts by weight or less, about 1,600 parts by weight or less, about 1,400 parts by weight or less, about 1,200 parts by weight or less, about 1,000 parts by weight or less, about 800 parts by weight or less, about 600 parts by weight or less, It may be about 400 parts by weight or less, about 300 parts by weight or less, about 250 parts by weight or less, or about 200 parts by weight or less.

In the present specification, unless otherwise specified, the unit weight part means the ratio of the weight between each component.

However, the ratio of the dispersant or the binder may be adjusted in consideration of a desired porosity or pore size, and thus is not limited to the above range.

The slurry may further comprise a solvent, if desired. However, from the viewpoint of more efficiently modifying the surface of the metal foam in the process of the present application leading to contact with oxygen after sintering, it may be advantageous to use a slurry that does not contain a solvent as the slurry. As the solvent, an appropriate solvent may be used in consideration of the solubility of the components of the slurry, for example, the metal component or the binder. For example, as the solvent, one having a dielectric constant in the range of about 10 to 120 may be used. In another example, the dielectric constant may be about 20 or more, about 30 or more, about 40 or more, about 50 or more, about 60 or more, or about 70 or more, or about 110 or less, about 100 or less, or about 90 or less. Examples of the solvent include water, alcohol having 1 to 8 carbon atoms such as ethanol, butanol or methanol, dimethyl sulfoxide (DMSO), dimethyl formamide (DMF), or N-methylpyrrolidinone (NMP), but is not limited thereto. not.

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

The slurry may contain known additives necessary in addition to the above-mentioned components.

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

The form of such a metal structure is not particularly limited as being determined according to a desired metal foam. In one example, the metal structure may be in the form of a film or a sheet. For example, when the structure is in the form of a film or sheet, the thickness is 2,000 μm or less, 1,500 μm or less, 1,000 μm or less, 900 μm or less, 800 μm or less, 700 μm or less, 600 μm or less, 500 μm or less, 400 μm or less It may be 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. Metal foam has a generally brittle characteristic in terms of its porous structural characteristics, and therefore it is difficult to manufacture in a film or sheet form, particularly a thin film or sheet form, and there is a problem in that it is easily broken even when manufactured. However, according to the method of the present application, it is possible to form a metal foam having a thin thickness, uniform pores formed therein, and excellent mechanical properties.

In the above, the lower limit of the thickness of the structure is not particularly limited. For example, the thickness of the structure in the form of a film or sheet may be about 1 μm or more, about 5 μm or more, 10 μm or more, or about 15 μm or more.

The porous metal sintered body may be formed by sintering the metal structure 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 structure in an appropriate manner.

When heat is applied to sinter the metal structure, the applied heat is not particularly limited. That is, heat application conditions may be appropriately adjusted in consideration of the properties of the metal used or the desired mechanical strength.

In one example, the porous metal sintered body may be formed by sintering the metal structure at any one temperature within the range of 700°C to 2,000°C.

In addition, the sintering time may also be appropriately adjusted, for example, the sintering may be performed for a time in the range of about 10 minutes to 600 minutes.

In the present application, as a method different from the conventional known method, the sintering may be performed by an induction heating method. That is, as described above, when the metal component includes a conductive magnetic metal having a predetermined magnetic permeability and conductivity, the induction heating method may be applied. While including the pores uniformly formed by this method, the mechanical properties are excellent, and the porosity can also be adjusted to a desired level can be smoothly manufactured.

The 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 conductivity and permeability, eddy currents are generated in the metal, and Joule heating is generated due to the resistance of the metal. In the present application, a sintering process through such a phenomenon may be performed. In the present application, by applying this method, the sintering of the metal foam can be performed within a short time to secure fairness, and at the same time, it is possible to manufacture a metal foam having a high porosity thin film form and excellent mechanical strength.

Accordingly, the sintering process may include applying an electromagnetic field to the metal structure. Joule heat is generated by an induction heating phenomenon in the conductive magnetic metal of the metal component by the application of the electromagnetic field, whereby the structure may be sintered. In this case, the conditions for applying the electromagnetic field are not particularly limited as being determined according to the type and ratio of the conductive magnetic metal in the metal structure. For example, the induction heating may be performed using an induction heater formed in the form of a coil or the like. In addition, induction heating, for example, may be performed by applying a current of about 100A to 1,000A. In another example, the magnitude of the applied current may be 900 A or less, 800 A or less, 700 A or less, 600 A or less, 500 A or less, or 400 A or less. The magnitude of the current may be about 150 A or more, about 200 A or more, or about 250 A or more in another example.

Induction heating, for example, may be performed at a frequency of about 100 kHz to 1,000 kHz. In another example, the frequency may be 900 kHz or less, 800 kHz or less, 700 kHz or less, 600 kHz or less, 500 kHz or less, or 450 kHz or less. The frequency may be about 150 kHz or more, about 200 kHz or more, or about 250 kHz or more in another example.

The application of the electromagnetic field for the induction heating may be performed within a range of, for example, 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. The application time is, in another example, 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 2 hours or less, about It may be 1 hour or less or about 30 minutes or less.

The above-mentioned induction heating conditions, for example, an applied current, a frequency, and an application time may be changed in consideration of the type and ratio of the conductive magnetic metal as described above.

The sintering of the metal structure may be performed only by the above-mentioned application of heat or induction heating, or, if necessary, the induction heating, that is, while applying appropriate heat together with the application of an electromagnetic field.

For example, the sintering may be performed by applying an external heat source to the metal structure alone or together with the application of the electromagnetic field.

In the manufacturing method of the present application, the surface is modified by contacting the metal sintered body formed as described above with oxygen. The contacting process with oxygen may be performed immediately following the sintering process. In one example, the contact with oxygen may be performed while cooling the porous metal sintered body immediately after the sintering process, and contact with oxygen when the temperature of the atmosphere in which the porous metal sintered body exists in the cooling process reaches a certain level can start The cooling may be forced cooling or natural cooling. In the present application, the oxide can be grown on the surface of the metal foam by controlling the contact condition with oxygen, and in particular, the object can be achieved by appropriately growing the oxide in the form of projections.

In one example, the contacting process with oxygen may be performed while cooling the metal foam following the sintering process, and in this case, a surface-modified metal foam may be formed in a single step.

In one example, the contact with oxygen for proper oxide growth may be performed in an atmosphere having an oxygen concentration of 1 ppm to 1,000 ppm, or may be performed in an atmosphere having an oxygen concentration of 10 ppm to 1,000 ppm. In one example, the sintering of the metal structure may be performed under an atmosphere of a reactive gas or an inert gas such as hydrogen or argon, and after performing the sintering in the reaction or inert gas atmosphere, the sintered body is cooled, and the When reached, oxygen can be injected at an appropriate concentration to perform contact with oxygen. The concentration of oxygen may be controlled by, for example, injecting oxygen to have an intended concentration in a chamber or the like.

In one example, the contact with oxygen for surface modification may be performed while cooling the porous metal sintered body. The cooling may be forced cooling or natural cooling. That is, after the sintering process for forming the metal sintered body, the surface modification process may be performed by injecting oxygen at an appropriate time while cooling the metal sintered body.

During the sintering, oxygen may not be brought into contact with the metal structure, and oxygen may be injected at an appropriate time during the cooling process after sintering to perform contact with the oxygen.

In one example, the contacting with oxygen may be initiated and conducted at a temperature of 300°C to 600°C. That is, while cooling the sintered body after sintering, when the temperature reaches the above range, oxygen may be injected to proceed in contact with oxygen. The oxygen contact starting point temperature is in another example about 320°C or more, 340°C or more, 360°C or more, 380°C or more, or 400°C or more, or 580°C or less, 560°C or less, 540°C or less, 520°C or less, or 500°C or less. may be below.

In one example, the contact with oxygen may be performed from the temperature to the point at which the maintenance temperature (ambient temperature) of the porous metal sintered body is cooled to about 10°C to 50°C.

As described above, when the contact with oxygen is performed while cooling the sintered body, the cooling rate is not particularly limited. In one example, the cooling may be natural cooling.

For example, the contacting with oxygen may be performed while the temperature falls from the oxygen contact start temperature to the oxygen contact end temperature by natural cooling, for example, for 10 minutes to 5 hours.

Through the contact with oxygen as described above, it is possible to obtain a metal foam having the desired surface properties.

The present application also relates to a metal foam. The metal foam may be manufactured by the method described above.

The metal foam may have a porosity in the range of about 40% to 99%. As mentioned, according to the method of the present application, it is possible to control the porosity and mechanical strength while including the uniformly formed pores. The porosity may be 50% or more, 60% or more, 70% or more, 75% or more, or 80% or more, or 95% or less or 90% or less.

The metal foam may be present in the form of a thin film or sheet. In one example, the metal foam may be in the form of a film or sheet. The metal foam in the form of a film or sheet has a thickness of 2,000 μm or less, 1,500 μm or less, 1,000 μm or less, 900 μm or less, 800 μm or less, 700 μm or less, 600 μm or less, 500 μm or less, 400 μm or less, 300 μm or less. It may be 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. For example, the thickness of the metal foam in the form of a film or sheet is about 10 μm or more, about 20 μm or more, about 30 μm or more, about 40 μm or more, about 50 μm or more, about 100 μm or more, about 150 μm or more, It may be about 200 μm or more, about 250 μm or more, about 300 μm or more, about 350 μm or more, about 400 μm or more, about 450 μm or more, or about 500 μm or more.

The metal foam has excellent mechanical strength, and, for example, may have a tensile strength of 2.5 MPa or more, 3 MPa or more, 3.5 MPa or more, 4 MPa or more, 4.5 MPa or more, or 5 MPa or more. In addition, the tensile strength may be about 10 MPa or more, about 9 MPa or more, about 8 MPa or more, about 7 MPa or more, or about 6 MPa or less. Such tensile strength can be measured, for example, according to KS B 5521.

Such a metal foam can be utilized in various applications requiring a porous metal structure. In particular, according to the method of the present application, as described above, it is possible to manufacture a thin film or sheet-type metal foam having a desired level of porosity and excellent mechanical strength, and its surface properties can be adjusted, so that compared to the existing The use of metal foam can be expanded.

In the present application, it is possible to provide a method for effectively modifying the surface of the metal foam while maintaining the uniformity of pores, porosity or mechanical strength, and the inherent advantages of the metal material used.

1 is a photograph of the metal foam formed in the embodiment.
2 and 3 are photographs of the metal foam formed in Comparative Example.

Hereinafter, the present application will be specifically described through Examples and Comparative Examples, but the scope of the present application is not limited to the following Examples.

Example 1.

Copper (Cu) powder having an average particle diameter (D50 particle diameter) of about 10 to 20 μm was used as a metal component. In addition, a slurry was prepared by using alpha-terpineol as a dispersant and applying polyvinylacetate as a binder. The weight ratio of the metal component (Cu), the dispersant, and the binder in the slurry (Cu:dispersant:binder) was about 1:1.11:0.09. The slurry was coated in the form of a film having an appropriate thickness, and dried at a temperature of about 100° C. for about 40 minutes. Then, the film-shaped structure was heat-treated (sintered) at a temperature of about 900° C. for about 1 hour in a 4% hydrogen/argon gas atmosphere, and the metal components were combined while removing the organic components to prepare a porous metal sintered body. After sintering, while naturally cooling the sintered body, when the ambient temperature reaches about 500°C, oxygen gas is injected so as to have a concentration in the range of about 10 ppm to 100 ppm, and in contact with oxygen until the ambient temperature reaches room temperature (about 25° C.) made it 1 is a photograph of the sheet prepared in Example 1, and it can be seen from the photograph that an oxide in the form of a projection is grown on the surface of the metal foam. The aspect ratio of the protrusion shape was in the range of about 1 to 3, and the area ratio of the oxide was about 10% to 30%.

Example 2.

As a metal component, nickel (Ni) powder having an average particle diameter (D50 particle diameter) of about 10 to 20 μm was used. In addition, as a dispersant, alpha-terpineol was used, and ethyl cellulose (EC) was applied as a binder to prepare a slurry. The weight ratio of the metal component (Ni), the dispersant, and the binder in the slurry (Ni:dispersant:binder) was about 1:1.34:0.16. The slurry was coated in the form of a film having an appropriate thickness, and dried at a temperature of about 125° C. for about 20 minutes. Then, the film-shaped structure was heat-treated (sintered) at a temperature of about 950° C. for about 1 hour in a 4% hydrogen/argon gas atmosphere, and the metal components were combined while removing the organic components to prepare a porous metal sintered body. After sintering, while naturally cooling the sintered compact, oxygen gas is injected to a concentration in the range of about 500 ppm to 600 ppm when the ambient temperature reaches about 450 ° C. made it The obtained metal foam was in a state in which an oxide in the form of projections was grown on the surface as in Example 1. The aspect ratio of the protrusion shape was in the range of about 1 to 3, and the area ratio of the oxide was about 30% to 40%.

Example 3.

As a metal component, nickel (Ni) powder and iron (Fe) powder having an average particle diameter (D50 particle diameter) of about 10 to 20 μm were mixed and used in a weight ratio of 4:1 (Ni:Fe). In addition, a slurry was prepared by using texanol as a dispersant and polyvinyl acetate as a binder. The weight ratio of the metal component (Ni/Fe), the dispersant, and the binder in the slurry (Ni/Fe:dispersant:binder) was about 1:1.74:0.26. The slurry was coated in the form of a film having an appropriate thickness, and dried at a temperature of about 110° C. for about 60 minutes. Then, the film-shaped structure was heat-treated (sintered) at a temperature of about 1000° C. for about 1 hour and 30 minutes in a 4% hydrogen/argon gas atmosphere, and the organic component was removed while the metal component was combined to prepare a porous metal sintered body. . After sintering, while naturally cooling the sintered body, oxygen gas is injected to a concentration in the range of about 800 ppm to 900 ppm when the ambient temperature reaches about 400 ° C. made it The obtained metal foam was in a state in which an oxide in the form of projections was grown on the surface as in Example 1. The aspect ratio of the protrusion shape was in the range of about 1 to 3, and the area ratio of the oxide was about 50%.

Comparative Example 1.

A metal foam was prepared in the same manner as in Example 1, except that the sintered body was cooled without contact with oxygen after sintering. 2 is a photograph for this, and it can be seen from the drawing that the surface of the metal foam is smooth, and no protrusions are formed.

Comparative Example 2.

The metal foam obtained in Comparative Example 1 was further heat treated in an electric furnace at 500° C. under atmospheric pressure for 30 minutes to obtain a metal foam having copper oxide formed on the surface. 3 is a photograph of this, and it can be seen that, unlike Comparative Example 1, in this case, a needle-shaped oxide was formed on the surface.

Claims (15)

sintering a metal structure including a metal component to obtain a porous metal sintered body; and contacting the porous metal sintered body with oxygen immediately after the sintering. The method of claim 1, wherein the metal component is at least one selected from the group consisting of copper, nickel, aluminum, molybdenum, silver, platinum, gold, aluminum, magnesium, tin and iron. The method of claim 1 , wherein the metal structure is prepared as a slurry including a metal component, a dispersant, and a binder. The method of claim 3, wherein the proportion of the metal component in the slurry is 0.5 to 95 wt%. The method of claim 3, wherein the dispersant is alcohol. The method of claim 3, wherein the binder is an alkyl cellulose, polyalkylene carbonate, or polyvinyl alcohol compound. The method of claim 3, wherein the slurry comprises 1 to 500 parts by weight of a binder based on 100 parts by weight of the metal component. The method of claim 3, wherein the slurry comprises 10 to 2,000 parts by weight of a dispersant based on 100 parts by weight of the binder. The method of claim 1, wherein the porous metal sintered body is in the form of a film or sheet. The method of claim 9, wherein the thickness of the film or sheet is 2,000 μm or less. The method of claim 1, wherein the sintering of the metal structure is performed at a temperature within the range of 700°C to 2,000°C. The method of claim 11, wherein the sintering is performed for 10 to 600 minutes. The method of claim 1, wherein the contact with oxygen is performed while cooling the porous metal sintered body. The method of claim 1, wherein the contact with oxygen is performed at a temperature of 300°C to 600°C. The method of claim 1, wherein the contact with oxygen is performed under an oxygen concentration of 1 ppm to 10,000 ppm.

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