Volume Change during the Formation of Nanoporous Gold by Dealloying

Abstract

We report a macroscopic shrinkage by up to 30 vol % during electrochemical dealloying of Ag-Au. Since the original crystal lattice is maintained during the process, we suggest that the formation of nanoporous gold in our experiments is accompanied by the creation of a large number of lattice defects and by local plastic deformation.

Deformation Behavior of Nanoporous Metals

“…This trend seems to correlate with shrinkage and the buildup of tensile stress during dealloying which can induce crack formation. [8] In this context, it is interesting to note that thin-films and nanowires can accommodate this tensile stress better than macrocopic 3D samples as they are less constraint with regard to shrinkage: For example, nanoporous Au nanowires have been successfully prepared from Ag 82 Au 18 alloys, [5] whereas a 3D sample prepared from such Ag-rich alloys would typically disintegrate during dealloying due to extensive cracking. The key to crack free material is to avoiding dealloying conditions which lead to extensive buildup of tensile stress.…”

“…The material can be very uniform, even on a macroscopic length scale, and typically exhibits a specific surface area in the order of a few m 2 /g. [12] The best-studied example is the formation of nanoporous gold (np-Au) via selective removal of Ag from a AuAg alloy, [7,8,11] but other alloys such as AuAl 2 , [13] MnCu (np-Cu), [14] and CuPt (np-Pt) [15] have also been successfully dealloyed. The process can be easily extended to twodimensional thin-film samples by using commercially available white-gold leaves with a thickness of a few hundred nanometers [7] or thin sputterdeposited alloy films.…”

“…Nanoporous metal foams have been made in various shapes such as nanowires, [5,6] thin-films, [7,8] and macroscopic 3D samples. [8,9] Their morphology ranges from disordered three-dimensional network structures (sponge-like morphology) to well-defined periodic thin-film structures with excellent long-range order which are mostly used for photonic applications.…”

“…[8,9] Their morphology ranges from disordered three-dimensional network structures (sponge-like morphology) to well-defined periodic thin-film structures with excellent long-range order which are mostly used for photonic applications. This section provides a short review of the synthesis of nonperiodic nanoporous metal foams which can be prepared in the form of Synthesis techniques include top-down (dealloying) and bottom-up strategies (filter casting and templating) as well as combinations thereof.…”

Nanoporous Gold—Testing Macro-scale Samples to Probe Small-scale Mechanical Behavior

“…Email: weissmueller@tuhh.de network of nanoscale ligaments that contain the occupied lattice sites. [6,7] When alloyed with Pt, samples of NPG can be made with characteristic mean ligament diameters, L, down to the unusually small scale of 5 nm, [8,9] and thermal coarsening results in self-similar growth to L close to 1 μm. [10,11] This affords studies of size-dependence with L spanning more than two orders of magnitude in size, a dynamic range that is not typically accessible with other types of nanomaterial and that provides for particularly significant experimental data on size-effects.…”