A Computational Method for Creating New Ceramics with Transition Metals

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Extraordinarily rugged with a melting temperature of several thousand degrees Fahrenheit. That describes the results of research into new ceramic materials sponsored by the Office of Naval Research (ONR) and recently published in the Journal Nature.

A research team, led by ONR’s Principal Investigator, Dr. Stefano Curtarolo, Duke University, developed a computational method for creating new types of ceramics using transition metals – carbonitrides or borides – through a process called Disordered Enthalpy-Entropy Descriptor (DEED).

“The applications are endless,” said Dr. Eric Wuchina, a research materials engineer who was the program officer with ONR’s Sea Warfare and Weapons department when Curtarolo’s research team was awarded the Multidisciplinary University Research Initiative (MURI). “Now we can help design any material for high voltage, breakdown resistance for strength, for high temperature capability, for high or low thermal conductivities – a variety of things that you can do because of the thermodynamic database that Professor Curtarolo has been putting together for the last 20-25 years.”

Curtarolo’s team maintains the Duke Automatic-FLOW for Materials Database (AFLOW)—a database that allows algorithms to accurately predict the properties of unexplored mixtures without having create them in the laboratory.

“We’ve used the same iron, copper, nickel and other alloys throughout history and just added stuff in to change the properties,” Wuchina said. "Rather than limit ourselves to just 10 chemical elements, this allows us to look at the whole periodic table of 100 elements – and to look at a variety of different compositions."

According to Wuchina, the variety of new compositions could create potentially millions of new materials.

“Professor Curtarolo has developed the ability to for us to look at a wide variety of materials and potential materials that have never been made and predict what their properties are going to be. And then how to make real materials out of those for applications for specific applications,” he said.

So far, DEED has predicted 900 possible new formulations of high-performance materials – 17 of which have already been successfully created in laboratories.

Instead of focusing solely on the orderly atomic structure of conventional materials, Curtarolo’s team worked to develop the predictive properties of “high-entropy” materials – that is, materials that could be created through a chaotic mixture of atoms.

“The high-entropy carbides all had a relatively uniform amount of enthalpy, so we could ignore part of the equation,” Curtarolo said. “But to predict new ceramic recipes with other transition metals, we had to address the enthalpy.”

Enthalpy is a measure of the sturdiness of a design while entropy is the number of possible designs that have similar strength. Curtarolo’s computational method not only calculates what elements need to go into creating a ceramic for a certain application, but how to arrange the microstructure – the atoms – so that it has also high temperature capabilities.

“Typically to get higher or lower thermal conductivity you will use a ceramic,” Wuchina said. “You might make it a little more porous so that it has better insulating properties, right? Well, how do you do that without harming the mechanical properties?”

That’s what makes Curtarolo’s research and computational method so unique. It allows him to predict how different compounds will behave and to what applications these new compounds would be best suited.

“The DEED process can capture and develop a wide range of materials and the materials properties that we don't have now, and it allows us to use computational tools to tell us what compositions and what microstructures are best and how to make them. And that's something that has historically been trial and error,” Wuchina said.