KR20210038105A - Manufacturing method for metal foam - Google Patents

Abstract

The present application relates to a method of manufacturing a metal foam. The metal foam manufacturing method of the present application can produce a metal foam having excellent porosity, material properties, and thin thickness in a short time without limitation of the applied metal component and the type of substrate supporting the metal foam. The present invention comprises a step of sintering a green structure.

Description

Manufacturing method for metal foam {Manufacturing method for metal foam}

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

Metal foam has a variety of useful properties such as light weight, energy absorption, heat insulation, fire resistance, or eco-friendliness. Accordingly, the metal foam can be applied to various fields including lightweight structures, transport machinery, building materials or energy absorbing devices. In addition, metal foam not only has a high specific surface area, but can further improve the flow of fluids or electrons such as liquids and gases, so it is applied to substrates for heat exchange devices, catalysts, sensors, actuators, secondary cells, fuel cells, etc. And can be usefully used.

In general, a metal foam is manufactured by forming a metal foam precursor using a slurry containing a metal component and sintering the metal foam precursor. As a method of sintering the metal foam precursor, heat is applied using a heating device such as a furnace or an electromagnetic field is applied to generate an eddy current in a metal component, and Joule heat generated by the resistance of the metal component. ) (Also referred to as “induction heating”) is known. However, in the case of the former, since the process of raising the temperature to a specific temperature and cooling it is necessarily accompanied due to the heat treatment characteristics, there is a problem that it takes for a long time. In the latter case, it can be sintered for a relatively fast time. However, in the latter case, the types of applicable metal components are limited. This is because in the latter case, only metal components that can generate heat by applying an electromagnetic field can be applied. In addition, in the latter case, the type of substrate supporting the metal foam precursor is also limited. In the latter case, it is sintered by heat generation of a metal component, so the material of the substrate must not be easily deformed even by the application of heat.

In the present application, a method for manufacturing a metal foam having excellent porosity, material properties, and thin thickness, etc., without limitation of the type of the applied metal component and the substrate supporting the metal foam, is provided. It has one purpose.

In the present application, the term metal foam refers to a porous structure containing a metal as a main component. In the above, the use of metal as the main component means that the ratio of the metal or metal alloy based on the total weight of the metal foam is 55% by weight or more, 60% by weight or more, 65% by weight or more, 70% by weight or more, 75% by weight or more, 80 It means a case of at least 85% by weight, at least 90% by weight, or at least 95% by weight. The upper limit of the proportion of the metal contained 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 measurement temperature affects the property, the properties are measured at room temperature, unless otherwise specified. The term room temperature is a natural temperature that is not heated or reduced, and may mean, for example, 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” refers to the relative weight of a component with respect to other components, and does not mean an absolute value such as g, kg, or lb.

The present application relates to a method of manufacturing a metal foam. The method of manufacturing the metal foam of the present application includes at least sintering the green structure.

In the present application, the green structure is a structure before undergoing a process performed to form a metal foam such as sintering, that is, a structure before the metal foam is generated, and is sometimes referred to as a metal foam precursor. In addition, the green structure, even if it is also referred to as a porous metal foam precursor or a porous green structure, does not necessarily have to be porous by itself, and if it can finally form a metal foam that is a porous metal structure, for convenience, a porous green structure or It may also be referred to as a porous metal foam precursor.

The green structure may be formed using at least a slurry, and the slurry may include a metal component, an organic solvent, and a binder.

In the present application, since a specific sintering method is adopted, there is an advantage that the type of metal component applied to the slurry is not particularly limited. For example, as the metal component, a component including a certain metal or an alloy containing the metal can be applied. As a non-limiting example, the metal includes copper, molybdenum, iron, nickel, cobalt, silver, platinum, gold, aluminum, chromium, indium, tin powder, magnesium, phosphorus, zinc, manganese, or a combination thereof. Can be applied. In the above, the alloy containing the metal may mean two or more types of alloys among the exemplified metals.

In one example, the metal component forming the green structure may be in the form of a powder. For example, the metal or alloys thereof in the metal component may have an average particle diameter in the range of about 1 μm to 100 μm. The average particle diameter is, in other examples, 5 μm or more, 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, 55 It may be greater than or equal to μm or greater than or equal to 60 μm, and may be less than or equal to 95 μm, less than or equal to 90 μm, less than or equal to 85 μm, less than or equal to 80 μm, less than or equal to 75 μm, less than or equal to 70 μm, less than or equal to 65 μm, or less than or equal to 60 μm. The average particle diameter may be selected in an appropriate range in consideration of the shape of the desired metal foam, for example, the thickness or porosity of the metal foam, and this is not particularly limited. In the present application, the average particle diameter of the metal component 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 shape of the metal powder is also selected in consideration of a desired porosity or pore size, and is not particularly limited. For example, when the metal component is in a powder form, the metal component in the powder form is dentritic. It may be a component of.

The ratio of the metal component in the slurry is not particularly limited, and may be selected in consideration of a desired degree 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 other examples, the ratio may be at least about 1%, at least about 1.5%, at least about 2%, at least about 2.5%, at least about 3%, at least about 5%, at least 10%, at least 15%, at least 20%, 25%. At least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, or at least 80%, or 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, 25% or less, 20% or less, 15% or less, 10% or less, or may be about 5% or less, but is not limited thereto.

The type of organic solvent applied to the slurry is not particularly limited. As the organic solvent, an appropriate component can be applied in consideration of the solubility of a component of the slurry, such as the metal component or a binder described later. As the organic solvent contained in the slurry, for example, alcohol may be applied. Examples of alcohols include methanol, ethanol, propanol, pentanol, octanol, 2-methoxyethanol, 2-ethoxyethanol, 2-butoxyethanol, glycerol, texanol or terpineol, and the like. A monohydric alcohol having 1 to 20 carbon atoms or a dihydric alcohol (glycol) having 1 to 20 carbon atoms or a higher polyhydric alcohol such as ethylene glycol, propylene glycol, pentanediol, hexanediol, or octanediol may be used, but the type is It is not limited to the above.

As a suitable organic solvent, an alcohol having 9 to 20 carbon atoms such as taxanol, an alcohol having a carbon number of 9 to 20 such as terpineol, and containing a double bond and/or a cyclic structure, or ethylene glycol or propylene glycol Glycols 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 may be exemplified, but are not limited thereto.

The ratio of the organic solvent in the slurry is also not particularly limited. The organic solvent may be included, for example, in a ratio of about 30 to 2,000 parts by weight based on 100 parts by weight of the binder. In another example, the ratio is about 50 parts by weight or more, about 100 parts by weight or more, about 150 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 It may be at least about 600 parts by weight, or at least about 650 parts by weight, 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, or about 900 parts by weight. It may be about parts by weight or less.

The slurry contains a binder. The binder may serve as a pore holder and may be a component for forming pores in the finally formed metal foam, or may serve to support the metal component contained in the slurry so as not to be scattered. As the binder, without particular limitation, for example, it may be appropriately selected according to the type of a water-soluble binder or a metal component and/or an organic solvent applied at the time of 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, a 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 proportion of the binder is also not particularly limited. The ratio of the binder can be appropriately adjusted according to the porosity required for the metal foam. For example, the binder may be included in the slurry in a ratio of 1 to 500 parts by weight based on 100 parts by weight of the metal component. The ratio is, in another example, 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 parts 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 At least about 90 parts by weight, at least about 100 parts by weight, at least about 110 parts by weight, at least about 120 parts by weight, at least about 130 parts by weight, at least about 140 parts by weight, at least about 150 parts by weight, about 200 parts by weight Or more or 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, about 50 parts by weight or less, about 40 parts by weight or less, about 30 parts by weight or less, It may be about 20 parts by weight or less or about 15 parts by weight or less.

The slurry may further contain other known additives. On the other hand, the slurry applied in the present application may be particularly suitable for forming a thin metal foam, and to form voids in the metal foam, for example, a foaming agent such as alcohol, an organic solvent, and a surfactant are applied. Thus, the components may have a composition different from that of a slurry forming an emulsion (droplet). That is, the slurry applied in the present application may not contain a separate blowing agent and/or surfactant.

The method of forming the green structure using the above slurry is not particularly limited. In the field of manufacturing a metal foam, various methods for forming a green structure are known, and all of these methods can be applied in the present application. For example, the green structure may be applied in a manner that maintains the slurry in an appropriate template, or manufactured in a manner that includes applying the slurry to a substrate and then applying heat to dry it. It could be. In particular, through the latter drying process, the organic solvent contained in the slurry is evaporated, and voids of the metal foam may be formed during the evaporation of the organic solvent. In the above, a method of applying the slurry is not particularly limited, and a known application method such as dip coating, die coating, and bar coating may be applied.

In addition, the drying may be performed at a temperature higher than the boiling point of the organic solvent, but within a range in which the frame or substrate supporting the slurry is not damaged.

In the present application, a specific sintering method described later is adopted, and since the method is configured so that sintering of the green structure can be performed at a relatively low temperature, the substrate (or frame) on which the slurry is applied to form the green structure The kind has an advantage that is not particularly limited. Therefore, in the conventional induction heating or heating method using a furnace, etc., the substrate or frame is limited to a metal substrate that is not damaged even at a high temperature, but in this application, in addition to the above metals, PET (polyethylene therephthalate), COP (cycloolefin polymer), A substrate or frame made of a polymer such as PC (polycarbonate), or a carbon-based substrate such as graphite foil may be applied.

The shape of the green structure is not particularly limited as it is determined according to the desired metal foam. In one example, the green structure 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 in the range of 5 μm to 200 μm. By controlling the thickness in this range, it is possible to manufacture a metal foam having suitable properties according to the purpose. In other examples, the thickness is 10 μm or more, 15 μm or more, 20 μm or more, 25 μm or more, 30 μm or more, 35 μm or more, 40 μm or more, 45 μm or more, 50 μm or more, 55 μm or more, 60 μm or more May be 190 μm or less, 180 μm or less, 170 μm or less, 160 μm or less, 150 μm or less, 140 μm or less, 130 μm or less, 120 μm or less, 110 μm or less, 100 μm or less, 90 μm or less, 80 μm It may be less than or equal to 70 μm.

In the present application, a metal foam is manufactured by sintering the green structure described above. In the present application, as a method for such sintering, a method of light irradiation (hereinafter, may also be referred to as “light sintering”), rather than simple heating using a conventional furnace or induction heating by application of an electromagnetic field, etc., is used. Apply. In this way, when the light sintering method is applied, a metal foam having excellent material properties (porosity, strength, thin thickness, etc.) can be produced in a short time, and the metal component or metal foam constituting the metal foam There is an advantage that the frame or substrate for supporting the precursor (or green precursor) is not limited to a specific component or material.

The method of irradiating light to the green structure is not particularly limited. In the present application, the green structure may be sintered by irradiating various types of light such as ultraviolet rays, electromagnetic rays, infrared rays, or electron beams with the light. For example, the sintering may be performed by irradiating the green structure with pulsed electromagnetic radiation. In the above, the pulsed electromagnetic radiation may mean radiation that is irradiated in the form of a pulse and falls within a range of an electromagnetic wave wavelength. Accordingly, in the present application, a method of sintering the green structure by irradiating light having a wavelength range of 200 nm to 1500 nm in a pulse form may be applied. If this method is applied, there may be an advantage in that sintering of the metal component applied to the metal foam can be sufficiently performed without large heat generation within a short time.

The irradiation condition of the pulsed electromagnetic radiation may be appropriately adjusted without limitation in order to achieve the above-described object.

In one example, the pulse width of the pulsed electromagnetic radiation may be in the range of 100 μs to 10 ms. The pulse width, in another example, may be 0.5 ms or more, 1 ms or more, 1.5 ms or more, or 2 ms or more, and may be 9 ms or less, 8 ms or less, 7 ms or less, 6 ms or less, 5 ms or less, or 4 ms or less. I can. In the above, the meaning of the pulse width is well known in the industry, and may mean, for example, a time interval of a single pulse.

In one example, the pulse rate of the pulsed electromagnetic radiation may be in the range of 0.1 Hz to 1 kHz. The pulse rate, in another example, may be 0.5 Hz or more, 1 Hz or more, 1.5 Hz or more, 2 Hz or more, and 500 Hz or less, 100 Hz or less, 50 Hz or less, 30 Hz or less, 10 Hz or less, 5 Hz or less Or 3 Hz or less. In the above, the pulse rate may mean a time taken from a single pulse to the next pulse, that is, a period in which a pulse is repeated when electromagnetic radiation is irradiated in a pulse form.

In one example, the voltage of the pulsed electromagnetic radiation may be in the range of 350 V to 500 V. The voltage, in another example, may be 360 V or more, 370 V or more, 380 V or more, 390 V or more, or 400 V or more, and 490 V or less, 480 V or less, 470 V or less, 460 V or less, 450 V or less, It may be 440 V or less, 430 V or less, 420 V or less, 410 V or less, or 400 V or less.

In one example, the pulse number of the pulsed electromagnetic radiation may be in the range of 1 to 100. The number of pulses, in another example, may be 2 or more, 3 or more, 4 or more, 5 or more, 6 or more, 7 or more, 8 or more, 9 or more, or 10 or more, and 90 or less, 80 or less, 70 or less, 60 or less, It may be 50 or less, 40 or less, 30 or less, 20 or less, or 10 or less. In the above, the number of pulses may mean the number of times the electromagnetic radiation is irradiated in the form of a pulse when the pulsed electromagnetic radiation is irradiated during the light sintering process.

In one example, the energy of the pulsed electromagnetic radiation may be in the range of ^{0.1 J/cm 2} to 100 J/cm ^2. The energy, in another example, may be 0.5 J/cm ² or more, 1 J/cm ² or more, 1.5 J/cm ² or more, 2 J/cm ² or more, or 2.5 J/cm ^{2 or} more, and 90 J/cm ² Or less, 80 J/cm ² or less, 70 J/cm ² or less, 60 J/cm ² or less, 50 J/cm ² or less, 40 J/cm ² or less, 30 J/cm ² or less, 20 J/cm ² or less , 10 J/cm ² or less or 7 J/cm ² or less.

As described above, in the case of manufacturing a metal foam by sintering the green structure through irradiation of light, there is an advantage that the metal foam can be formed in a short time. Accordingly, the light, specifically, the irradiation time of the pulsed electromagnetic radiation may be in the range of, for example, 1 second to 30 minutes. The irradiation time, in another example, may be 30 seconds or more, 1 minute or more, 3 minutes or more, or 5 minutes or more, and may be 20 minutes or less, 10 minutes or less, or 5 minutes or less.

The above-mentioned conditions of light irradiation, for example, the number of pulses, energy of radiation, and pulse rate may be appropriately changed in consideration of the type of metal component to be applied, the type of frame or substrate supporting the green structure, and the like.

In addition, the light irradiation may be performed in the presence of an inert gas such as a specific atmospheric atmosphere, for example, argon or a mixed gas of argon and nitrogen.

In one example, the sintering may be performed only through the above-described light irradiation, and appropriate heat may be applied together with the light irradiation, or may be performed while applying an electromagnetic field or the like.

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

As described above, metal foam may be formed by sintering the green structure. On the other hand, since sintering through a general heating method increases the sintering time, a metal foam having a thickness thinner than that of the green structure is formed. However, in the present application, by adopting a specific sintering method, since the green structure can be sintered without large heat generation in a short time, such a metal foam may also be in the form of a film or a sheet like the green structure. In addition, the thickness of the metal foam may be the same as the above-described green structure, or even if different, the difference may be very slight. The difference (thickness of green structure-thickness of metal foam) is, for example, more than 0 μm and less than 30 μm, less than 25 μm, less than 20 μm, less than 15 μm, less than 10 μm, less than 5 μm, or less than 1 μm. It may be within range. By controlling the thickness in this range, it is possible to manufacture a metal foam having suitable properties according to the purpose.

The metal foam may have a porosity within a specific range. For example, the porosity of the metal foam manufactured by the above method may be 80% or less. In another example, the porosity may be 77% or less, 75% or less, 73% or less, or 70% or less, and 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, or It can be more than 70%. The porosity can be calculated in a known manner by calculating the density of metal foam.

In addition, the metal foam may have an average size of pores constituting it within a specific range. For example, the average size of the pores of the metal foam may be adjusted according to the composition of the slurry, the thickness of the metal precursor, and sintering conditions. The average pore size of the metal foam may be, for example, 20 μm or less, and in other examples, it may be 0.1 μm or more, 1 μm or more, 5 μm or more, 10 μm or more, 15 μm or more, or 17 μm or more.

Such a metal foam can be applied to various applications requiring a porous metal structure. In particular, according to the method of the present application, it is possible to manufacture a metal foam in the form of a film or a sheet having a desired level of porosity, pore size and thickness, etc., as described above, so that the use of the metal foam can be expanded compared to the existing one. There are also benefits that can be done.

The metal foam manufacturing method of the present application can produce a metal foam having excellent porosity, material properties, and thin thickness, without limitation of the applied metal component and the type of substrate supporting the metal foam, in a short time. There is an advantage.

1 and 2 are SEM photographs of the green structure of the embodiment.
3 and 4 are SEM photographs of the metal foam of the embodiment.
5 and 6 are SEM photographs of a metal foam of a comparative example.

The present application will be described in detail through the following examples, but the scope of the present application is not limited by the following examples.

[How to measure]

Porosity measurement

The porosity of the green structure or metal foam in Examples and Comparative Examples was measured by inverse calculation using the size, density, and weight of the manufactured metal foam specimen.

SEM photo shoot

Cross-sectional photographs of green structures or metal foams in Examples and Comparative Examples were taken using a scanning electron microscope (SEM), JSM7610F, JEOL.

[Production Example]

Example

Green structure

Dendrite copper powder, binder (polyvinyl acetate), and organic solvent (alpha-terpineol) having a major axis length of approximately 60 μm in a weight ratio of 5:0.5:4.5 (copper powder:binder:organic solvent) Blending to prepare a slurry. The slurry was coated to a thickness of about 75 μm on a graphite foil substrate having a thickness of about 250 μm. Then, it was dried using a known dryer at a temperature of 120°C. As a result, the organic solvent was removed, and a green structure in the form of a film having a thickness of about 75 μm was prepared. FIG. 1 is a SEM photograph of the green structure, and FIG. 2 is a photograph magnified by 2 times of the photograph of FIG. 1.

Metal foam

The green structure was photosintered to prepare a film-type metal foam. Photosintering was specifically performed while purging with hydrogen/argon gas and irradiating pulsed electromagnetic xenon radiation to the green structure. PulseForge 2300 (Novacentrix) was applied as an irradiation device, and the irradiation conditions of pulsed electromagnetic radiation are as follows:

Applied voltage: about 400 V

Pulse width: about 4 ms

Pulse rate: about 2.3 Hz

Number of pulses: 10

Energy: about 4 J/cm ²

Irradiation time: about 5 minutes

The SEM photograph of the metal foam manufactured by the above method is shown in FIG. 3, and a photograph of the photograph of FIG. 3 enlarged by 2 times is shown in FIG. 4. The thickness of the metal foam was about 75 μm, and the porosity was about 70%. It can be seen that by the above method, a metal foam having a porosity equivalent to that of the examples to be described later can be manufactured in a shorter time.

Comparative example

Green structure

A green structure in the form of a film was manufactured in the same manner as the green structure prepared in Examples, except that the coating thickness was set to 150 μm. The thickness of the green structure was about 150 μm.

Metal foam

In order for the green structure to be maintained in a hydrogen/argon gas atmosphere and a temperature of about 1000° C. for 2 hours, sintering was performed by applying an external heat source in an electric furnace (furnace) to prepare a film-shaped metal foam. The porosity of the metal foam was about 65%, and its thickness was about 80 μm.

Claims (18)

A method of manufacturing a metal foam comprising the step of sintering the green structure by irradiating light to a green structure formed by using a slurry including a metal or a metal component including an alloy containing the metal, an organic solvent, and a binder. The method of claim 1, wherein the green structure is manufactured by applying the slurry on a substrate and then drying the green structure. The method of claim 2, wherein the substrate is a metal substrate, a carbon-based substrate, or a polymer substrate. The method of claim 1, wherein the metal is copper, molybdenum, iron, nickel, cobalt, silver, platinum, gold, aluminum, chromium, indium, tin powder, magnesium, phosphorus, zinc, manganese, or a combination thereof. Way. The method of claim 1, wherein the metal component has an average particle diameter in the range of 1 μm to 100 μm. The method of claim 1, wherein the organic solvent is alcohol. The method of claim 1, wherein the binder is alkyl cellulose, polyalkylene carbonate, polyvinyl alcohol, polyalkylene oxide, or polyvinyl acetate. The method of claim 1, wherein the proportion of the metal component in the slurry is 45% by weight or more. The method of claim 1, wherein the slurry comprises an organic solvent within a range of 30 to 2000 parts by weight based on 100 parts by weight of the binder. The method of claim 1, wherein the slurry comprises a binder in a range of 1 to 500 parts by weight based on 100 parts by weight of the metal component. The method of claim 1, wherein the irradiation of light is performed by irradiating the green structure with pulsed electromagnetic radiation. The method of claim 11, wherein the pulse width of the pulsed electromagnetic radiation is within a range of 100 μs to 10 ms. The method of claim 11, wherein the pulse rate of the pulsed electromagnetic radiation is in the range of 0.1 Hz to 1 kHz. 12. The method of claim 11, wherein the voltage of the pulsed electromagnetic radiation is in the range of 350 V to 500 V. The method of claim 11, wherein the pulse number of the pulsed electromagnetic radiation is in the range of 1 to 100. The method of claim 11, wherein the energy of the pulsed electromagnetic radiation is in the range of ^{0.1 J/cm 2} to 100 J/cm ^2. The method for manufacturing a metal foam according to claim 11, wherein the irradiation time of the pulsed electromagnetic radiation is within a range of 1 second to 30 minutes. The method of claim 1, wherein the green structure is in the form of a film or sheet.

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