METALLIC FOAM BODY WITH CONTROLLED GRAIN SIZE ON ITS SURFACE, PROCESS FOR ITS PRODUCTION AND USE THEREOF

Abstract

The invention relates to a metallic foam body, comprising (a) a metallic foam body substrate made of at least one metal or metal alloy A; and (b) a layer of a metal or metal alloy B present on at least a part of the surface of the metallic foam body substrate (a), wherein A and B differ in their chemical composition and/or in the grain size of the metal or metal alloy, and wherein the metal or metal alloy A and B is selected from a group consisting of Ni, Cr, Co, Cu, Ag, and any alloy thereof; obtainable by a process comprising the steps (i) provision of a porous organic polymer foam; (ii) deposition of at least one metal or metal alloy A on the porous organic polymer foam; (iii) burning off of the porous organic polymer foam to obtain the metallic foam body substrate (a); and (iv) deposition by electroplating of the metallic layer (b) of a metal or metal alloy B at least on a part of the surface of the metallic foam body (a). The invention moreover relates to a process for the production of the metallic foam body and a use of the metallic foam body.

Claims

1-15. (canceled)

16. A metallic foam body, comprising (a) a metallic foam body substrate made of at least one metal or metal alloy A; and (b) a layer of a metal or metal alloy B present on at least a part of the surface of the metallic foam body substrate (a), wherein A and B differ in their chemical composition and/or in the grain size of the metal or metal alloy, and wherein the metal or metal alloy A and B is selected from a group consisting of Ni, Cr, Co, Cu, Ag, and any alloy thereof; obtainable by a process comprising the steps (i) provision of a porous organic polymer foam; (ii) deposition of at least one metal or metal alloy A on the porous organic polymer foam; (iii) burning off of the porous organic polymer foam to obtain the metallic foam body substrate (a); and (iv) deposition by electroplating of the metallic layer (b) of a metal or metal alloy B at least on a part of the surface of the metallic foam body (a).

17. A metallic foam body according to claim 16, wherein step (ii) comprises the steps (ii1) deposition of a first metallic layer containing a metal or metal alloy A1 by a chemical or physical vapor deposition method; and (ii2) deposition of a second metallic layer containing a metal or metal alloy A2 by electroplating; wherein the metal or metal alloy A1 and A2 is selected from a group consisting of Ni, Cr, Co, Cu, Ag, and any alloy thereof, and wherein A1 and A2 are identical or different.

18. A metallic foam body according to claim 17, wherein the average thickness of the first metallic layer is up to 0.1 m and the average thickness of the second metallic layer is from 5 to 50 m.

19. A metallic foam body according to claim 16, wherein the porous organic polymer foam is selected from the group consisting of polyurethane (PU) foam, poly ethylene foam and polypropylene foam.

20. A metallic foam body according to claim 16, wherein the thickness of struts in the metallic foam body substrate (a) is in the range of from 5 to 100 m.

21. A metallic foam body according to claim 16, wherein the average thickness of the layer (b) of the metal or metal alloy B is from 5 to 200 m.

22. A metallic foam body according to claim 16, wherein A2 and B are silver.

23. A metallic foam body according to claim 22, wherein the contents of silver is at least 99.999 atom % and the contents of the elements Al, Bi, Cu, Fe, Pb, and Zn is not more than 0.001 atom %.

24. A metallic foam body according to claim 16 having a pore size of from 100 and 5000 m, a strut thickness in the range of from 5 to 100 m, an apparent density in the range of from 300 to 1200 kg/m.sup.3, a specific geometric surface area in the range of from 100 to 20000 m.sup.2/m.sup.3 and a porosity in the range of from 0.50 to 0.95.

25. A metallic foam body according to claim 16, wherein the layer (b) of the metal or metal alloy B is present on the entire surface of the metallic foam body substrate (a).

26. A process for the production of a metallic foam body, wherein the metallic foam body comprises (a) a metallic foam body substrate made of at least one metal or metal alloy A; and (b) a layer of a metal or metal alloy B present on at least a part of the surface of the metallic foam body substrate (a), wherein A and B differ in their chemical composition and/or in the grain size of the metal or metal alloy, and wherein the metal or metal alloy A and B is selected from a group consisting of Ni, Cr, Co, Cu, Ag, and any alloy thereof; comprising the steps (i) provision of a porous organic polymer foam; (ii) deposition of at least one first metal or metal alloy A on the porous organic polymer foam; (iii) burning off of the porous organic polymer foam to obtain the metallic foam body substrate (a); and (iv) deposition by electroplating of the metallic layer (b) of a metal or metal alloy B at least on a part of the surface of the metallic foam body substrate (a).

27. A process according to claim 26, comprising the steps (i1) provision of a porous polyurethane foam; (ii3) deposition of Ag in a thickness of 5 to 50 m onto the polyurethane foam; and (iii1) burning off the polyurethane foam at a temperature in the range of from 300 to 850 C. to obtain the metallic foam body substrate (a); and (iv1) deposition of Ag in a thickness of 1 to 200 m by electroplating onto the metallic foam body substrate (a) obtained in step (ii1).

28. Use of the metallic foam body of claim 16 in a physical adsorption or absorption process or in a chemical process.

29. Use according to claim 28, wherein the metallic foam body of claim 1 is used as a precursor for a catalyst or as a catalyst in a process for the production of formaldehyde by oxidation of methanol.

30. Use according to claim 29, wherein the metallic foam body contains at least 99.999 atom % silver and not more than 0.001 atom % of the elements Al, Bi, Cu, Fe, Pb, and Zn.

Description

EXAMPLE

[0068] A metallic foam body was produced by providing firstly a porous polyurethane foam with an average pore size of 450 m as a 1.6 mm sheet. The polyurethane foam was subjected to sputtering with Ni (alternatively with Ag) to make the polyurethane foam electrically conductive. Then silver was electroplated in an average thickness of 20 m. Thereafter, the polyurethane foam was burned off in air at a temperature of 700 C. After the burning off of the polyurethane foam the grain size had increased in comparison to the grain size directly after the deposition of the silver layer. Thereafter, a second silver layer with an average thickness of 20 m was plated. The grain size of the final metallic foam body was similar to the grain size directly after deposition of the silver layer before the polyurethane foam was burned off. The Figure shows a cross section to the obtained silver foam, more particular a cross section of a double electroplated Ag foam strut. In the Figure, 1, 3 and 5 refer to the grain sizes in a first electroplated layer and 2, 4, 6 refer to the grain sizes in a second electroplated Ag layer. It can be clearly seen that the grain size is larger in the first electroplated layer compared to the second electroplated layer.

Comparison Example

[0069] The Example was repeated except that a silver layer with an average thickness of 40 m was electroplated after the polyurethane had been rendered electrically conductive. The grain size of the final metallic foam body was larger than the grain size of the final metallic foam body of the Example.