Melting gold normally requires temperatures upwards of 1,064° C (1,947° F), but physics is never quite that simple. A team of researchers has now found a way to melt gold at room temperature using an electric field and an electron microscope.
Although we're all familiar with the phenomenon of melting, most of us don't really think about the physics behind the process. Essentially, when something melts all that's happening is that the bonds between its molecules break down and they begin to move more freely. For instance, they might transition from the well-ordered structure of an ice cube to the less ordered state of a shapeless puddle of water.
Heat is the usual trigger for the change, but it's not the only one – pressure plays a part too. Experimenting with those conditions has let scientists do all sorts of unexpected things recently, like making water freeze at temperatures well above its usual boiling point.
In the new study, the researchers tested another trigger: an electric field. The team placed a small piece of gold in an electron microscope, and observed it at the highest level of magnification. Then, they slowly ramped up the strength of an electric field to see how the gold atoms reacted.
When they looked back at the data afterwards, the researchers realized that the electric field had excited the atoms in the top layers of the gold. That made them break free of the bulk of the object, effectively melting the material at room temperature. The change was also reversible, as switching off the electric field can solidify the gold again.
"I was really stunned by the discovery," says Ludvig de Knoop, first author of the study. "This is an extraordinary phenomenon, and it gives us new, foundational knowledge of gold."
The team isn't entirely sure how the technique works to melt gold at ambient temperatures, but it may be due to a phenomenon known as low-dimensional phase transition. The researchers plan to investigate that in the future, which may help unlock some applications for the discovery.
"Because we can control and change the properties of the surface atom layers, it opens doors for different kinds of applications," says Eva Olsson, an author of the study. "For example, the technology could be used in different types of sensors, catalysts and transistors. There could also be opportunities for new concepts for contactless components."
The research was published in the journal Physical Review Materials.
Source: Chalmers University of Technology