METAL FOAM BODIES AND PROCESS FOR PRODUCTION THEREOF

Abstract

The present invention relates to processes for producing metal foam bodies, in which metal-containing powders that may comprise aluminium and chromium or molybdenum are applied to metal foam bodies that may comprise nickel, cobalt, copper and iron and then treated thermally, wherein the highest temperature in the thermal treatment of the metal foam bodies is in the range from 680 to 715° C., and wherein the total duration of the thermal treatment within the temperature range from 680 to 715° C. is between 5 and 240 seconds. Following this method of thermal treatment can achieve alloy formation at the contact surface between metal foam body and metal-containing powder, but simultaneously leave unalloyed regions within the metal foam. The present invention further comprises processes comprising the treatment of the alloyed metal foam bodies with basic solution. The present invention further comprises the metal foam bodies obtainable by these processes, which find use, for example, as support and structure components and in catalyst technology.

Claims

1-11. (canceled)

12. A process for producing a metal foam body, comprising the following steps: (a) providing a metal foam body A, comprising two metallic components, wherein the metallic components may be in the form either of (i) an alloy or (ii) an arrangement of two superposed layers of the two individual metallic components, in which case one of the metallic components forms the inner layer of the metal foam and the other metallic component forms the outer layer of the metal foam, wherein, in the case of alternative (i), the metallic components in the form of an alloy are either a combination of nickel and cobalt or a combination of nickel and copper; wherein, in the case of alternative (ii), the metallic components are selected from the combinations consisting of: nickel on the inside and cobalt on the outside; nickel on the inside and copper on the outside; and iron on the inside and nickel on the outside; (b) applying a metal-containing powder MP to metal foam body A so as to obtain metal foam body AX, wherein the metal-containing powder MP is selected from the group consisting of: a mixture of aluminium powder and chromium powder; a mixture of aluminium powder and molybdenum powder; a pulverulent alloy comprising aluminium and chromium; and a pulverulent alloy comprising aluminium and molybdenum; (c) treating metal foam body AX thermally in order to achieve alloy formation between the metallic components of metal foam body A and the metal-containing powder MP so as to obtain metal foam body B, wherein: the highest temperature of the thermal treatment of metal foam body AX is in the range from 680 to 715° C.; and the total duration of the thermal treatment in the temperature range from 680 to 715° C. is between 5 and 240 seconds.

13. The process of claim 12, wherein the metal foam body A consists of two metallic components in the form of (i) an alloy wherein the metallic components are either a combination of nickel and cobalt or a combination of nickel and copper.

14. The process of claim 13, wherein the metallic components are a combination of nickel and cobalt.

15. The process of claim 13, wherein the metal-containing powder MP used in step (b) comprises either: (iii) a mixture of aluminium powder and chromium powder; or (iv) a pulverulent alloy of aluminium and chromium.

16. The process of claim 13, wherein the metal-containing powder MP used in step (b) comprises a pulverulent alloy of aluminium and chromium.

17. The process of claim 13, wherein the metal foam body A used in step (a) has been obtained by either two successive electrolytic deposition steps, in each of which an individual metallic component is deposited on a substrate, or by a single electrolytic deposition step in which two metallic components are deposited simultaneously on a substrate, wherein the substrate is removed by thermolysis after the conclusion of all electrolytic deposition steps.

18. The process of claim 13, wherein: the mass ratio of the two metallic components in metal foam body A is in the range from 1:1 to 20:1; the ratio of the mass of aluminium to the mass of chromium or of molybdenum in the metal-containing powder MP is in the range from 4:1 to 50:1; and the ratio V of the masses of metal foam body B to metal foam body A, V=m (metal foam body B) m (metal foam body A), is in the range from 1.1:1 to 1.5:1.

19. The process of claims 13, further comprising the step: (d) treating the metal foam body B with a basic solution.

20. The process of claim 19, wherein the treatment of the metal foam body B with a basic solution is performed for a period in the range from 5 minutes to 8 hours at a temperature in the range from 20 to 120° C., and wherein the basic solution is an aqueous NaOH solution having an NaOH concentration between 2% and 30% by weight.

21. The process of claim 12, wherein the metal foam body A consists of two metallic components in the form of (ii) an arrangement of two superposed layers of the two individual metallic components, wherein one of the metallic components forms the inner layer of the metal foam and the other metallic component forms the outer layer of the metal foam, and wherein the metallic components are selected from the combinations consisting of: nickel on the inside and cobalt on the outside; nickel on the inside and copper on the outside; and iron on the inside and nickel on the outside.

22. The process of claim 21, wherein nickel forms the inner layer and cobalt the outer layer of the metal foam body.

23. The process of claim 21, wherein the metal-containing powder MP used in step (b) comprises either (iii) a mixture of aluminium powder and chromium powder; or (iv) a pulverulent alloy of aluminium and chromium.

24. The process of claim 21, wherein the metal-containing powder MP used in step (b) comprises a pulverulent alloy of aluminium and chromium.

25. The process of claim 21, wherein the metal foam body A used in step (a) has been obtained by either two successive electrolytic deposition steps, in each of which an individual metallic component is deposited on a substrate, or by a single electrolytic deposition step in which two metallic components are deposited simultaneously on a substrate, wherein the substrate is removed by thermolysis after the conclusion of all electrolytic deposition steps.

26. The process of claim 21, wherein: the mass ratio of the two metallic components in metal foam body A is in the range from 1:1 to 20:1; the ratio of the mass of aluminium to the mass of chromium or of molybdenum in the metal-containing powder MP is in the range from 4:1 to 50:1; and the ratio V of the masses of metal foam body B to metal foam body A, V=m (metal foam body B)/m (metal foam body A), is in the range from 1.1:1 to 1.5:1.

27. The process of claims 21, further comprising the step: (d) treating the metal foam body B with a basic solution.

28. The process of claim 27, wherein the treatment of the metal foam body B with a basic solution is performed for a period in the range from 5 minutes to 8 hours at a temperature in the range from 20 to 120° C., and wherein the basic solution is an aqueous NaOH solution having an NaOH concentration between 2% and 30% by weight.

29. The process of claims 12, further comprising the step: (d) treating the metal foam body B with a basic solution.

30. The process of claim 29, wherein the treatment of the metal foam body B with a basic solution is performed for a period in the range from 5 minutes to 8 hours at a temperature in the range from 20 to 120° C., and wherein the basic solution is an aqueous NaOH solution having an NaOH concentration between 2% and 30% by weight.

31. A metal foam body obtainable by the process of claim 12.

Description

EXAMPLES

1. Providing of Metal Foam Bodies

[0086] Three metal foam bodies (a, b, c) of a cobalt-nickel alloy were provided (Co/Ni=9:1) (manufacturer: AATM, dimensions: 220 mm×180 mm×1.6 mm, weight per unit area: 1000 g/m.sup.2, average pore diameter: 580 μm), which had been produced by simultaneous electrolytic deposition of nickel and cobalt on a polyurethane foam and subsequent thermolysis of the plastic components.

2. Applying of Metal-Containing Powders

[0087] Subsequently, binder solution (polyethyleneimine (2.5% by weight) in water) was first sprayed onto all metal foam bodies, and then a pulverulent aluminium-chromium alloy (manufacturer: AMG, average particle size: <63 μm, Al/Cr=70/30, with 3% by weight of added ethylenebis(stearamide)) was applied as a dry powder (about 400 g/m.sup.2).

3. Thermal Treatment

[0088] Thereafter, all metal foam bodies were subjected to a thermal treatment under nitrogen atmosphere in a furnace. First of all, the furnace was heated from room temperature to the maximum temperature within about 15 min, which was maintained for a defined period of time, followed by quenching by contacting with nitrogen atmosphere at 200° C.

[0089] Maximum temperature for metal foam body a:

[0090] 700° C. for 2 minutes

[0091] Temperature progression for metal foam body b:

[0092] 600° C. for 2 minutes

[0093] Temperature progression for metal foam body c:

[0094] 750° C. for 2 minutes

4. Determination of Extent of Alloying

[0095] At the end, the extent of alloy formation in the metal foam bodies was determined. For this purpose, cross sections of the metal foam bodies were examined under the microscope and scanning electron microscope.

[0096] This gave the following result:

[0097] While superficial alloy formation had taken place in metal foam body a, but unalloyed regions remained within the metal foam, no alloy formation took place in the case of metal foam body b, and alloy formation in metal foam body c is so far advanced that no unalloyed regions remained within the metal foam.

[0098] This result clearly shows that departure from the thermal treatment conditions according to the invention has the effect that superficial alloy formation leaving unalloyed regions within the metal foam is difficult to achieve.