Method for manufacturing metal foam

Abstract

The present application provides a method for manufacturing a metal foam. The present application can provide a method for manufacturing a metal foam, which is capable of forming a metal foam comprising uniformly formed pores and having excellent mechanical properties as well as the desired porosity, and a metal foam having the above characteristics. In addition, the present application can provide a method capable of forming a metal foam in which the above-mentioned physical properties are ensured, while being in the form of a thin film or sheet, within a fast process time, and such a metal foam.

Claims

1. A method for manufacturing a metal foam, the method comprising: forming a green structure using a slurry comprising a metal component comprising a conductive metal with relative magnetic permeability of 90 or more, a first solvent having a first dielectric constant of 20 or more, and a second solvent having a second dielectric constant of 15 or less; and sintering the green structure by applying an electromagnetic field to the green structure to produce a sintered product of the metal component, wherein the sintering of the green structure is only performed by induction heating, wherein the slurry comprises 100 to 250 parts by weight of the metal component relative to 100 parts by weight of a total weight of the first and second solvents, wherein the slurry comprises 1 to 6 parts by weight of the second solvent relative to 100 parts by weight of the first solvent, wherein the electromagnetic field is applied with a coil-type induction heater, and wherein the electromagnetic field is applied by applying a current in a range of 100 A to 1,000 A at a frequency in a range of 100 kHz to 1,000 kHz.

2. The method for manufacturing a metal foam according to claim 1, wherein the conductive metal has a conductivity of 8 MS/m or more at 20° C.

3. The method for manufacturing a metal foam according to claim 1, wherein the conductive metal is nickel, iron or cobalt.

4. The method for manufacturing a metal foam according to claim 1, wherein the metal component comprises 30 wt % or more of the conductive metal.

5. The method for manufacturing a metal foam according to claim 1, wherein the conductive metal has an average particle diameter in a range of 10 to 100 μm.

6. The method for manufacturing a metal foam according to claim 1, wherein a ratio of the first dielectric constant of the first solvent to the second dielectric constant of the second solvent is in a range of 5 to 100.

7. The method for manufacturing a metal foam according to claim 1, wherein the first dielectric constant of the first solvent is in a range of 20 to 100.

8. The method for manufacturing a metal foam according to claim 1, wherein the first solvent is water, an alcohol, acetone, N-methylpyrrolidine, N,N-dimethylformamide, acetonitrile, dimethylacetamide, dimethyl sulfoxide or propylene carbonate.

9. The method for manufacturing a metal foam according to claim 1, wherein the second dielectric constant of the second solvent is in a range of 1 to 15.

10. The method for manufacturing a metal foam according to claim 1, wherein the second solvent is an alkane, an alkyl ether, pyridine, ethylene dichloride, dichlorobenzene, trifluoroacetic acid, tetrahydrofuran, chlorobenzene, chloroform or toluene.

11. The method for manufacturing a metal foam according to claim 1, wherein the slurry comprises 110 to 200 parts by weight of the metal component relative to 100 parts by weight of a total weight of the first and second solvents.

12. The method for manufacturing a metal foam according to claim 1, wherein the slurry comprises 1.5 to 5 parts by weight of the second solvent relative to 100 parts by weight of the first solvent.

13. The method for manufacturing a metal foam according to claim 1, wherein the slurry further comprises a binder.

14. The method for manufacturing a metal foam according to claim 1, wherein applying the electromagnetic field comprises applying a current in a range of 150 A to 900 A.

15. The method for manufacturing a metal foam according to claim 1, wherein applying the electromagnetic field comprises applying a current having a frequency in a range of 150 kHz to 900 kHz.

16. The method for manufacturing a metal foam according to claim 1, wherein the electromagnetic field is applied for a time in a range of 1 minute to 10 hours.

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

18. The method for manufacturing a metal foam according to claim 17, wherein the film or sheet has a thickness of 5,000 μm or less.

19. The method for manufacturing a metal foam according to claim 1, wherein the first solvent is water or N-Methylpyrrolidone, and wherein the second solvent is pentane, hexane, or ethyl ether.

20. The method for manufacturing a metal foam according to claim 1 further comprising, before sintering the green structure: coating the slurry onto a substrate; heating the slurry to a first temperature in a space with a humidity of 80% or more to foam the slurry; and then heating the foamed slurry to a second temperature in a space with a humidity of 60% or less to dry the slurry and form the green structure.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1 is an SEM photograph of the produced sheet in Example 1,

(2) FIG. 2 is an SEM photograph of the produced sheet in Example 2, and

(3) FIG. 3 is an SEM photograph of the produced sheet in Example 3.

MODE FOR INVENTION

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

Example 1

(5) Methyl cellulose and hydropropyl methyl cellulose as polymeric binders are mixed with 35.0 g of water (dielectric constant at 20° C.: about 80) as a first solvent in amounts of 1.9 g and 3.6 g, respectively, stirred and dissolved. After the dissolution is completed, 54.0 g of nickel powder (having conductivity of about 14.5 MS/m, relative magnetic permeability of about 600 and average particle diameter of about 10 to 20 μm), 2.7 g of a surfactant and 2.0 g of ethylene glycol are sequentially added and stirred. Thereafter, 0.8 g of pentane (dielectric constant at 20° C.: about 1.84) to be used as a foaming agent is added and stirred.

(6) The sample prepared through the above process is bar-coated on a silicon nitride plate to a thickness of 0.5 mm, heated to 40° C. in a space having a humidity of 80% or more and foamed for 10 minutes. Thereafter, it was heated at 80° C. under a humidity of 60% or less for 30 minutes and the solvent was dried to form a green structure (film). An electromagnetic field was then applied to the green structure with a coil-type induction heater while purging with hydrogen/argon gas to form a reducing atmosphere. The electromagnetic field was formed by applying a current of about 350 A at a frequency of about 380 kHz, and the electromagnetic field was applied for about 3 minutes. After the application of the electromagnetic field, the sintered green structure was cleaned to produce a sheet having a thickness of about 1.5 mm in the form of a film. The produced sheet had a porosity of about 91%. FIG. 1 is an SEM photograph of the produced sheet.

Example 2

(7) A sheet having a thickness of about 1.7 mm was produced in the same manner as in Example 1, except that as the second solvent, hexane (dielectric constant at 20° C.: about 1.88) was used instead of pentane. The produced sheet had a porosity of about 94%. FIG. 2 is an SEM photograph of the produced sheet.

Example 3

(8) A sheet having a thickness of about 0.7 mm was produced in the same manner as in Example 2, except that as the first solvent, NMP (N-Methylpyrrolidone) (dielectric constant at 25° C.: about 32.2) was used instead of water. The produced sheet had a porosity of about 62%. FIG. 3 is an SEM photograph of the produced sheet.

Example 4

(9) A sheet having a thickness of about 1.1 mm was produced in the same manner as in Example 2, except that as the second solvent, ethyl ether (dielectric constant at 20° C.: about 4.33) was used instead of pentane. The produced sheet had a porosity of about 81%.

Comparative Example 1

(10) A sheet was produced in the same manner as in Example 1, except that the second solvent was not applied and the weight ratio (W:MC) of water (W) to methyl cellulose (MC) was 95:5. The produced sheet was very brittle and easily broken, and thus the tensile strength could not be measured, and the pores were also formed very non-uniformly.

Comparative Example 2

(11) A sheet was produced in the same manner as in Example 3, except that the second solvent was not applied and the weight ratio (NMP:MC) of NMP and methyl cellulose (MC) was 95:5. The produced sheet was very brittle and easily broken, and thus the tensile strength could not be measured, and the pores were also formed very non-uniformly.