Rapid Solidification Materials Synthesis with Nano-Liter Droplets

A new method of materials synthesis which uses precisely controlled nano-liter droplets and results in significant microstructure refinement is described. Streams of nano-liter droplets are delivered in their molten state to a temperature controlled substrate where they impinge and undergo rapid solidification. Nano-liter droplets travel in a vacuum environment where they experience a measured angular dispersion of the order of 1 micro-radian. The droplets are generated by capillary stream break-up. Novel methods of initiating the capillary wave instability are employed so that precise control and manipulation of inter-droplet separations, speeds and sizes can be achieved. Substrate motion allows lateral material growth by successive droplet deliveries. Initial experiments demonstrate microstructure refinement with two low-melting point alloys (Rose's metal and a bismuth-tin alloy). The method is also designed for use with higher melting point materials as well.