Nanoporous metals by alloy corrosion

Contact: Jörg Weissmüller

Selective corrosion of solid solutions or intermetallic compounds has been known since ancient times, especially in the purification of noble metals and in the gilding of surfaces. More recently, it has been recognized and studied as an essential element of stress corrosion cracking. These studies are closely linked to the development of concepts such as the thermodynamics of non-equilibrium processes and percolation theory in the early 20th century. Only a few years ago, it was recognized that the products of alloy corrosion, namely macroscopic bodies made of nanoporous metal, are fascinating study objects in the nanosciences.

Our investigations aim to produce such materials with extremely small structure size while maintaining thermal and mechanical stability. By manipulating the surface properties, functional and structural materials with new properties can be produced.

Selected Publications:

S. Parida, D. Kramer, C.A. Volkert, H. Rösner, J. Erlebacher and J. Weissmüller
Volume Change during the Formation of Nanoporous Gold by Dealloying
Phys. Rev. Lett. 7 (2006) 035504

H. Rösner, S. Parida, D. Kramer, C.A. Volkert and J. Weissmüller
Reconstructing a Nanoporous Metal in Three Dimensions: An Electron Tomography Study of Dealloyed Gold Leaf
Adv. Eng. Mater. 9 (2007) 535

J. Weissmüller, R. C. Newman, H.-J. Jin, A. M. Hodge and J. W. Kysar
Nanoporous Metals by Alloy Corrosion: Formation and Mechanical Properties
Mater. Res. Soc. Bulletin 34 (2009) 553

Durch Legierungskorrosion können makroskopische Körper hergestellt werden, die durchgehend auf Nanometer-Skala porös sind. Die Probe aus nanoporösem Gold links in der Abbildung hat eine Ligamentgröße von 4nm und enthält etwa 1015 Ligamente. Rechts eine Probe der massiven Ausgangslegierung vor der Korrosion

Alloy corrosion can be used to produce macroscopic bodies that are porous on the nanometer scale. The sample of nanoporous gold on the left in the figure has a ligament size of 4nm and contains about 10¹⁵ ligaments. On the right a sample of the base alloy before the corrosion.

Oben die tomographische Rekonstruktion (auf Basis von transmissionselektronenmikroskopischen Hellfeldbildern) der Ligamentstruktur von nanoporösem Gold. Unten die Abbildung der Kristallitorientierung der polykristallinen Probe aus nanoporösem Gold (Orientierungsabbildung im Rasterelektronenmikroskop). Die kristalline Kohärenzlänge ist sehr viel größer als die Ligamentabmessung.

Top the tomographic reconstruction (based on transmission electron microscopic bright field images) of the ligament structure of nanoporous gold. Below is the image of the crystallite orientation of the polycrystalline sample of nanoporous gold (orientation image in a scanning electron microscope). The crystalline coherence length is much larger than the ligament size.

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