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CARBON WORLDS
'White graphene' halts rust in high temps
by Staff Writers
Houston TX (SPX) Oct 15, 2013


Rice University researchers have discovered that hexagonal boron nitride (h-BN) can keep metals from rusting in high temperatures. At top, electron microscope images show uncoated nickel foil oxidized after half an hour in oxygen-rich conditions in a furnace at 1,100 degrees Celsius. At bottom, a transparent 5-nanometer coat of h-BN protects nickel subjected to the same conditions. (Credit: Zheng Liu/Rice University). For a larger version of this image please go here.

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, Rice University researchers have discovered.

One or several layers of the material sometimes called "white graphene" keep materials from oxidizing - or rusting - up to 1,100 degrees Celsius (2,012 degrees Fahrenheit), and can be made large enough for industrial applications, they said.

Oxidation prevention is already big business, but no products available now work on the scale of what the Rice lab is proposing. The 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," said Lou, an associate professor of mechanical engineering and materials science. "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."

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

It's effectively invisible as well, which may make it useful for protecting solar cells from the elements, he said. "Essentially, this can be a very useful structural material coating," Lou said.

The researchers made small sheets of h-BN via chemical vapor deposition (CVD), a process they said 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," Ajayan said. "At a few nanometers wide, they're a totally non-invasive coating. They take almost no space at all."

Lead authors are Rice postdoctoral researcher Zheng Liu and graduate student Yongji Gong. Co-authors are Rice graduate student Lulu Ma and Senior Faculty Fellow Robert Vajtai; Wu Zhou, a Wigner Fellow, and Juan Carlos Idrobo, a staff scientist at Oak Ridge National Laboratory; Jingjiang Yu of Agilent Technologies; Jeil Jung, a research fellow at the National University of Singapore and a postdoctoral researcher at the University of Texas at Austin; and Allan MacDonald, the Sid W. Richardson Foundation Regents Chair Professor at the University of Texas at Austin. Ajayan is the Benjamin M. and Mary Greenwood Anderson Professor in Mechanical Engineering and Materials Science and of chemistry at Rice.

The Rice study led by materials scientists Pulickel Ajayan and Jun Lou appears in the online journal Nature Communications.

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Carbon Worlds - where graphite, diamond, amorphous, fullerenes meet






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CARBON WORLDS
Simple chain of carbon atoms may be world's strongest material
Houston (UPI) Oct 11, 2013
A material dubbed carbyne may be the strongest material in the world, stronger even than graphene or diamond, scientists at Rice University in Texas report. Carbyne is a chain of carbon atoms held together by either double or alternating single and triple atomic bonds. That makes it a true one-dimensional material, the Rice scientists said, unlike atom-thin sheets of graphene tha ... read more


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