- In an unusual experiment, researchers managed to melt gold at room temperature.
- They applied a strong electric field to change the state of the metal surface and observed the process using Transmission Electron Microscopy.
As a precious metal, gold has been used for several thousands of years all over the world, for jewelry, coinage, and even arts. As of 2015, more than 186,000 tonnes of gold exists above ground, out of which nearly 50% is used in jewelry, 20% in private investments, 20% in official sectors, and 10% in industries.
Gold is known for its high ductility, malleability, resistance to corrosion, and electrical conductivity. Due to these special properties, it’s widely used in almost all types of computing devices. Also, it’s used in tooth restoration, colored-glass generation, and infrared shielding.
The melting point of gold is 1064°C, and boiling point is way higher than that: 2970°C. However, researchers at Chalmers University of Technology, Sweden, performed an unusual experiment, in which they managed to melt gold at room temperature (25°C).
Apart from high temperatures, an electric field of enough strength can change the state of the metal surface. The field-assisted ionization and evaporation techniques have been extensively studied using Transmission Electron Microscopy (TEM)- a method that enables excitation and observation (on atomic scales) at the same time.
In this work, researches have used TEM to demonstrate how strong electric fields trigger reversible switching between crystalline and disordered phases of gold surfaces at room temperature.
They put a tiny piece of gold under TEM and applied an electric field step-by-step to intensively high levels. They wanted to observe how high magnification levels influence atoms of gold.
Then they analyzed the microscope recordings and found something interesting. The surface layer of the element had literally melted at room temperature. This provides as new fundamental information of gold and opens up exciting opportunities in materials science.
How Did This Happen?
Illustration showing gold atoms under high electric field | Credit: Alexander Ericson
Under the influence of strong electric field, the atoms of gold became excited, losing their perfect crystalline, ordered structure and breaking their links (bonds) with each other. The molecular dynamics simulations show that this change in structure occurs mainly due to the vanishing energy cost in producing surface defects in strong electric fields.
The researchers further examined the process and discovered that it was possible to transform the molten structure into a solid gold again. They demonstrated (at atomic scales) how changes in the surface layer can be controlled by applying an external electric field that decouples the uppermost layer from the underlying bulk.
The ability to melt gold in this way enables numerous feasible applications. For instance, it could be utilized in various kind of transistors, catalysts, and sensors. It could also help in researches addressing low-dimensional phases of matter and fundamental aspects in surface physics.