Jet engines may one day benefit from a new rust-proofing technology. Coating materials with a super thin sheet of boron nitride keeps them from rusting, even at temperatures up to 1,100 degrees Celsius (2,012 degrees Fahrenheit). (Credit: Auckland Photo News/Flickr)

At super high temps, ‘white graphene’ stops rust

Atomically thin sheets of hexagonal boron nitride (h-BN) have the handy benefit of protecting what’s underneath from oxidizing even at very high temperatures, researchers have discovered.

One or several layers of the material sometimes called “white graphene” keep materials from oxidizing—or rusting—at temperatures up to 1,100 degrees Celsius (2,012 degrees Fahrenheit). Researchers say it can be made large enough for industrial applications.

Oxidation prevention is already big business, but no products available now work on such a grand scale. With the new findings, researchers see potential for very large sheets of h-BN only a few atoms thick made by scalable vapor deposition methods.

“We think this opens up new opportunities for two-dimensional material,” says Jun Lou, an associate professor of mechanical engineering and materials science at Rice University.

“Everybody has been talking about these materials for electronic or photonic devices, but if this can be realized on a large scale, it’s going to cover a broad spectrum of applications.”

The left image shows uncoated nickel oxidized after exposure to high temperature in an oxygen-rich environment. Second from left, nickel exposed to the same conditions with a 5-nanometer coat of h-BN. The third image shows electron microscope images of two, three, four and many-layer h-BN films. The right image of an h-BN sheet shows the hexagonal arrangement of nitrogen (bright) and boron atoms. (Credit: Zheng Liu/Rice University)
The left image shows uncoated nickel oxidized after exposure to high temperature in an oxygen-rich environment. Second from left, nickel exposed to the same conditions with a 5-nanometer coat of h-BN. The third image shows electron microscope images of two, three, four and many-layer h-BN films. The right image of an h-BN sheet shows the hexagonal arrangement of nitrogen (bright) and boron atoms. (Credit: Zheng Liu/Rice University)

Ultrathin h-BN protection might find a place in turbines, jet engines, oil exploration, and underwater or in other harsh environments where minimal size and weight would be an advantage. Wear and abrasion could become an issue, the researcher say, and optimum thicknesses need to be worked out for specific applications.

Almost invisible

It’s effectively invisible as well, which may make it useful for protecting solar cells from the elements, Lou says. “Essentially, this can be a very useful structural material coating.”

For the study, published in Nature Communications, researchers made small sheets of h-BN via chemical vapor deposition (CVD), a process they say should be scalable for industrial production.

They first grew the thin material on nickel foil and found it withstood high temperature in an oxygen-rich environment. They also grew h-BN on graphene and found they could transfer sheets of h-BN to copper and steel with similar results.

“What’s amazing is that these layers are ultrathin and they stand up to such ultrahigh temperatures,” says Pulickel Ajayan, professor of mechanical engineering and materials science and of chemistry. “At a few nanometers wide, they’re a totally non-invasive coating. They take almost no space at all.”

Other researchers from Rice University, the University of Texas at Austin, Oak Ridge National Laboratory, and the National University of Singapore contributed to the study, which was supported by Army Research Office, the Office of Naval Research, the Welch Foundation, the Korean Institute of Machinery and Materials, the National Science Foundation, Oak Ridge National Laboratory, and the Department of Energy.

Source: Rice University

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