In what sounds like the basis for a horribly expensive magic trick, researchers at Sweden’s Chalmers University of Technology have demonstrated how gold can be made to melt at room temperature. This was achieved by applying an electric field to a cone-shaped gold object. The effect was seen when viewing the gold under an advanced electron microscope. At this magnification, the researchers observed the outmost two to three atomic layers of gold melting.
“We saw that a few atomic surface layers melted, meaning that the gold atoms moved around a lot and lost their ordered and solid structure,” Dr. Ludvig de Knoop, a physicist at Chalmers University, told Digital Trends. “The discovery was surprising since it had not been observed before. It was also very exciting when we learned that we could revert the surface melted layer back to being solid by decreasing the electric field.”
To understand the mechanism they were seeing, the researchers turned to computational modeling. This revealed that the surface melted phase did not come from an increase in temperature. “What the models showed was that defects form easily at the surface in the high electric fields that we applied to the cone — hence creating a disordered, or surface melted layer,” Dr. Mikael Juhani Kuisma, another researcher on the project, told us.
The discovery is interesting on a basic science level, but it could also have practical applications. According to Chalmers’ Professor Eva Olsson, being able to shift between a solid and molten structure opens up the door for various novel applications. These could include new types of sensors, catalysts, contactless components, and more.
Don’t expect to be able to melt larger blocks of gold (or other metals) by increasing the electric field, however. That means that any dreams of weaponizing this technology — or using it for a high-tech Oceans Eleven-style heist — likely won’t be achievable.
“I would say that this is not possible since the needed electric field is around 25,000,000,000 V/m, even though the voltage we use only is 100 V,” Ludvig de Knoop said. “The reason for this is that the gold cone only is a couple of nanometers wide at the apex. So for any practical applications to be feasible, some kind of nano-patterning will be required. In other words, melting the surface of any larger object would require a voltage which is not available.”
A paper describing the work was recently published in the journal Physical Review Materials.