A “stable” material by physics standards means that it retains its properties unless drastic measures are taken to change them. Metastable materials, on the other hand, are materials that transform into more stable forms under the right conditions — but sometimes these materials exhibit more desirable traits than their stable counterparts.
The Department of Army has awarded a three-year grant to researchers at the University of Notre Dame to develop techniques to prepare some metastable metals for use in extreme conditions. The first metal being examined is a type of metastable nickel, but researchers will also investigate others, such as tungsten or cobalt, said Khachatur Manukyan, research assistant professor in the Department of Physics and affiliated member of ND Energy.
Under usual conditions, nickel is stable in the form of a cubic crystalline structure. But scientists have long known about a metastable variety, called hexagonal close-packed (HCP) nickel, in which the atoms are arranged differently. Some have claimed to have already created this material in the lab. However, others are skeptical because the processes can also create nickel carbide, which is difficult to discern from HCP nickel, according to Manukyan, the lead researcher on the project that also includes Tengfei Luo, professor of aerospace and mechanical engineering, and Alexander Mukasyan, research professor of chemical engineering.
“There was a debate in the scientific literature and because of this, nobody really knows how this material behaves,” he said. Manukyan and collaborators will try to prepare this form of nickel from an amorphous state (where the atoms have no ordered arrangements), and then allow it to crystallize using processing methods. If the material is cooled quickly, researchers predict the nickel produced will be the metastable type.
“If successful, we’ll see how we can stabilize the materials,” he said, citing the most famous example of a metastable material – a diamond. Diamond, made from carbon, is metastable, while graphite, also made from carbon, is considered stable under typical conditions. And yet, diamonds have many properties that are superior to those of graphite.
“Like diamond, maybe these new metallic phases we develop will also have exciting properties that we all know, and that will drive the application of these new materials,” Manukyan said.
The Army is supporting the process with about a $460,000 grant over three years because of potential uses which could span from structural engineering materials to quantum computing.
In addition to the team of Manukyan, Luo, and Mukasyan, two graduate students – one who will tackle theoretical materials science, and the other who will look at the experimental aspects, will assist. Manukyan also plans to get undergraduates involved as well.
The work will take place in Notre Dame’s nuclear science laboratory of the Institute for Structure and Nuclear Astrophysics.