Bulk Nanostructured Metal from Multiply-Twinned Nanowires.

Using chemically synthesized silver nanowires with 5-fold twinning planes as a model system, a bottom-up process to generate a bulk nanostructured metal has been demonstrated. Although the nanowires would be shortened and deformed during densification, they are chosen as a model system because they are currently the most scalable and convenient way to obtain Ag particles with high twinning densities. Direct cold pressing of a silver nanowire filter cake did not generate a sufficiently cohesive sample, while hot pressing at 190 °C for 8 h resulted in extensive sintering, eliminating the nanowire morphology. Copper was then electroplated on the silver nanowires as a binder and filler to increase the densification upon hot pressing; despite nonuniform plating across the thickness of the filter cake, the thermal stability of the nanowires was increased, allowing hot pressing at 390 °C. Finally, a uniform copper coating on silver nanowires was achieved by electroless plating, leading to cohesive bulk metal after hot pressing.