Preparation of Macroscopic Low-Density Gold Foams with Good Machinability

Uniform, macroscopic monoliths (ranging from a few millimeters to a centimeter) of low-density gold foams with similar to 95% porosity and similar to 10-mu m-diameter pores were prepared by the casting of gold-coated polystyrene core-shell particles followed by the thermal removal of the polymer core. The Au foams were composed of unique hollow gold spheres and showed superior mechanical integrity and resilience compared to the foams we previously reported. Highly efficient seeding and electroless gold-plating methods in this study caused a significant morphological transition in the gold coatings from coarse particles to fine particles, and finally, to a continuous layer. A modified, scalable casting approach to form large uniform monoliths (up to similar to 1-cm diameter) and a gentle baking condition to minimize undesirable densification of the final foams enabled us to develop a simple, efficient synthetic route to nanostructured macroscopic low-density gold foams. To demonstrate the improved mechanical stability and machinability, a representative monolithic Au foam (similar to 0.9 g/cm(3)) was carefully cut into the hollow cylinder of gold foams by a series of machining and processing steps. Finally, we tried to understand the unique mechanical behaviors and properties of this gold foam by nanoindentation measurement.

Automated summary

Uniform macroscopic monoliths of low-density gold foams with high porosity and small diameter pores were prepared by casting and thermal removal of polystyrene core-shell particles. The gold foams showed superior mechanical integrity and resilience compared to previous foams. Efficient gold-plating methods caused morphological transition in the gold coatings and a modified casting approach enabled the synthesis of large uniform monoliths. The mechanical stability and machinability of the gold foam were demonstrated through cutting and nanoindentation measurement.