Researchers in New Zealand and Australia have grown tiny metal snowflakes, cubes, rods and other shapes. The nanocrystals form like snow out of a liquid metal, demonstrated an intriguing new potential method for manufacturing nanoscale structures.
The team ran a series of experiments using gallium, an intriguing metal with a low melting point of just under 30 °C (86 °F), meaning the temperature on a summer’s day – or even just holding it in your hand – is enough to liquefy it. The researchers made alloys by mixing gallium with other metals like zinc, nickel, copper, tin, platinum, bismuth, silver and aluminum, and watched the dynamics of the crystals that formed.
The metals were mixed at high temperatures so both metals were in liquid form, then the alloy was cooled to the point that the secondary metal became solid while the gallium remained liquid. This caused the solid metal to precipitate out of the liquid gallium and crystallize into a range of different shapes, depending on the metal. That included cubes, rods, octahedrons, and hexagonal and rectangular plates.
But zinc’s behavior was the strangest, forming fractal structures that resembled snowflakes. On closer examination, the researchers found that the specific atomic interactions between the gallium and the different metals caused the various crystal shapes to form. In the case of zinc, for example, each atom is surrounded by six neighbors in a pattern that resembles a snowflake.
Cool as it may be, this isn’t just a matter of making tiny metal snowflakes for the sake of it. The team says the technique could be used to make nanoparticles of different shapes for use in electronics or material manufacturing.
“In contrast to top-down approaches to forming nanostructure – by cutting away material – this bottom-up approaches relies on atoms self-assembling,” said Professor Nicola Gaston, an author of the study. “This is how nature makes nanoparticles, and is both less wasteful and much more precise than top-down methods. There’s also something very cool in creating a metallic snowflake!”
The research was published in the journal Science.
Source: University of Auckland