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An SMU-led research team has developed a more cost-effective, energy-efficient material called high-entropy oxide (HEO) nanoribbons that can resist heat, corrosion and other harsh conditions better than current materials.

These HEO nanoribbons— in the journal Science—can be especially useful in fields like aerospace, energy, and electronics, where materials need to perform well in extreme conditions.

And unlike high entropy materials that have been created in the past, the nanoribbons that SMU's Amin Salehi-Khojin and his team developed can be 3D-printed or spray-coated at room temperature for manufacturing components or coating surfaces. This makes them more energy-efficient and cost-effective than traditional high-entropy materials, which typically exist as bulk structures and require high-temperature casting.

What are high-entropy oxide (HEO) nanoribbons?

Nanoribbons are extremely thin, narrow pieces of material, usually just a few nanometers (one billionth of a meter) thick and spanning from tens to hundreds of nanometers in width.

HEO nanoribbons belong to a special type of these ribbon-like strips called high-entropy materials or alloys, which have a high degree of disorder within their atomic structure.

Think of it like making a fruit salad. Rather than relying mostly on grapes with just a few bananas or apples, you use equal amounts of apples, bananas, grapes, oranges, and berries—creating a more diverse and balanced fruit salad.

High-entropy materials follow the same principle.

"Most materials are made primarily from one or two elements, but high-entropy materials combine five or more elements in roughly equal proportions," explained Salehi-Khojin. "This even distribution leads to a highly disordered atomic structure—what scientists call 'high entropy'—which can enhance the material's strength, resistance to heat, and ability to withstand stress or corrosion."

Materials of the future

What Salehi-Khojin, with help from researchers at the University of Illinois Chicago, Stockholm University and University of Washington, have done for the first time, is figure out how to make these low-dimensional high-entropy materials for cost-effective and energy-efficient manufacturing.

Science study co-author Ilias Papailias, who is a Research Assistant Professor at SMU Lyle's Mechanical Engineering Department, said a new synthesis method was developed to precisely control the morphology of high-entropy materials.

"First, a sulfur element was used to etch the samples into two-dimensional (2D) structures, followed by an oxidation process to convert the 2D structures to one-dimensional (1D)," Papailias said.

"This technique provides over two orders of magnitude control on the width and size of the nanoribbons produced by this approach," Papailias added. "It has been discovered that during the oxidation process, the nucleation of 1D ribbons occurs, eventually converting them to full 1D systems upon extended oxidation, as confirmed by a wide range of in-situ experiments."

The Science study showed that the nanoribbons created by Salehi-Khojin—called 1D-HEO—maintained their structure at exceptionally high temperatures (up to 1,000 °C). The same was shown to be true under elevated pressure (up to 12 gigapascals) and prolonged exposure to harsh acid and base chemical environments (pH = 2.3 and 13 for 7 days).

While more testing is needed before this material can be practically utilized, Salehi-Khojin said the hardness and resilience of 1D-HEO would make it an ideal candidate for applications that require heat resistance, pressure tolerance, and durability under high mechanical loads.

"This new method can revolutionize the material science field by introducing new entropy structures," said Salehi-Khojin, who began research on these nanoribbons at the UIC.