Metallic glass is an emerging type of material, so its secrets are still being discovered. While working with the stuff, a team of Yale researchers created a brand new type of metallic glass, by shrinking samples down to the nanoscale until it forms a unique crystalline phase.
Normally, solid metals have a rigid, crystalline atomic structure, but as their name suggests, metallic glasses are more like glass, with a random arrangement of atoms. Composed of complex alloys, they get their unusual structure when molten metal is cooled down extremely quickly, which prevents crystals from forming. The end result is a material that's as pliable as plastic during production but strong as steel afterwards, making them useful for objects like golf clubs and gears for robots.
The Yale researchers developed their new version of the material by making metallic glass nanorods with a diameter of just 35 nanometers. At a scale that tiny, there's no room for a crystal nucleus to form. The researchers dub the process "nucleus starvation," and it resulted in a new crystalline phase of the material.
"This gives us a handle to control the number of nuclei we provide in the sample," says Judy Cha, lead researcher on the project. "When it doesn't have any nuclei — despite the fact that nature tells us that there should be one — it generates this brand new crystalline phase that we've never seen before. It's a way to create a new material out of the old."
While it's difficult to tell exactly what applications this new form might have, the researchers say that the process of making it is the main advantage. By creating metallic glass nanorods of different diameters, the researchers can control how many nuclei they have and, as a result, open up a range of new crystalline phases. Testing the properties of those new materials could lead to some unexpected applications down the track.
"As we were doing this, more and more interesting phenomena popped up," says Cha. "We're unearthing all these interesting phenomena that occur at the nanoscale. We don't really know a lot about these systems, and when we work with them in smaller, nanometer scales, then a new science and a new physics emerge. That's exciting because it tells us that there are these new playgrounds emerging that we simply haven't paid much attention to before, and that there is still more to be explored."
The research was published in the journal Nature Communications.
Source: Yale University
Update (Dec. 9, 2017): This article originally confused a crystal nucleus with an atomic nucleus. As some commenters have pointed out, the two are very different phenomena. The article has now been corrected to clarify that the study refers to crystal nuclei. We sincerely apologize for the error and thank those who brought it to our attention.