Multi-scale Simulation of Templated Casting: Understanding the Solidification Dynamics of Pb Nanowires

Experimental studies have indicated that it is possible to grow metallic nanowire by templated casting, but many questions are still unanswered because of nano-scale phenomena and complexity of the process. More importantly, how to grow large-diameter single-crystal nanowires is still under investigation. Here, a coupled three-dimensional modified finite element and cellular automaton model is used to simulate templated casting of Pb nanowires with diameters of 30 nm, 50 nm, 100 nm, and 200 nm. Using this multiscale model, the macro- and nano-scale physics, such as temperature distribution, melt flow, crystal front shape and microstructure of nanowires, including nucleation and growth of crystals, are investigated during the solidification. The crystal front has concave shape where concavity increases with nanowire size. The reason for using multi-crystal nanowire for large nanowires is discussed; the crystal front shape and solidification latent heat were found to be the main parameters for transitioning from single to multi-crystal nanowires.