On the microstructure of nanoporous gold: an X-ray diffraction study

Area of Science:

• Materials Science
• Nanotechnology
• Physical Chemistry

Background:

• Nanoporous gold (NPG) is a unique material with high surface area.
• Understanding its formation is crucial for applications in catalysis and sensing.
• The dealloying of bulk alloys is a common method to produce NPG.

Purpose of the Study:

• To investigate the evolution of grain structure, internal strain, and lattice misorientations in NPG during dealloying.
• To correlate structural changes with dealloying time and process parameters.
• To analyze the impact of fabrication methods on NPG characteristics.

Main Methods:

• In situ and ex situ X-ray diffraction (XRD) techniques, including powder and Laue diffraction.
• Microdiffraction experiments on nanoporous pillars.
• Focused ion beam (FIB) milling for sample preparation.

Main Results:

• Dealloying preserves the original crystallographic structure of the Ag-Au alloy.
• A small spread in lattice orientations occurs within individual grains during dealloying.
• In-plane tensile stresses develop initially and are partially released.
• The feature size of the nanoporous structure increases with dealloying time.
• FIB milling introduces surface damage to dealloyed nanoporous pillars.

Conclusions:

• The dealloying process in Ag-Au alloys leads to controlled nanoporous gold formation with specific structural evolutions.
• Lattice misorientations and internal stresses are key parameters influenced by dealloying.
• Careful consideration of fabrication techniques like FIB milling is necessary to avoid artifacts.