Precision fabrication of gold nanowires

A new generation of ultra-low-density (less than 20 milligrams per cubic centimeter) metal foams for laser targets has been made from metal nanowire suspensions via a unique freeze-casting process. In order to optimize the density, geometry, composition, and mechanical properties of these metal foams, it is necessary to develop nanowire stock materials of highly controlled dimensions (5 to 100 nanometers in diameter and 0.5 to 5 micrometers in length) for a variety of pure metals. To accomplish this goal, target fabrication experts, led by Michael Bagge-Hansen (MSD), have been developing the capability to electrodeposit metals into nanoporous anodized aluminum oxide (AAO) membranes. This process enables independent control of nanowire dimensions—via the AAO template—and nanowire composition, thereby enabling the team to produce high-quality foams with compositions and densities to meet the emerging needs for advanced laser targets. Proof of concept was recently demonstrated for gold nanowires using a commercially available AAO template and adapting an electrodeposition protocol developed in-house for depositing thick gold films. The team plans to explore this technique further and use it to create new foam morphologies and compositions. This work was supported by the Laboratory Directed Research and Development Program (18-ERD-032).