A paper by Peter Wilson et al. was published in ACS Applied Materials & Interfaces. This study shows that graphitic coatings, which consist of multilayer disordered graphene sheets, can be used for the thermal protection of delicate metal nanostructures. We studied cobalt slanted nanopillars grown by glancing angle deposition that were shown to melt at temperatures much lower than the melting point of bulk cobalt. After graphitic coatings were conformally grown over the surfaces of Co nanopillars by chemical vapor deposition, the resulting carbon-coated Co nanostructures retained their morphology at elevated temperatures, which would damage the uncoated structures. Thermal stabilization was also demonstrated for carbon-coated Ti nanopillars. The results of this study may be extended to other metallic and possibly even nonmetallic nanostructures that need to preserve their morphology at elevated temperatures in a broad range of applications.
Great job, Peter!
UNL Communications has published a press release about this study.
[Team develops chemical solution for graphene challenges | University Communications | 2/16/2015]
If it can’t stand the heat, get out the graphene.
UNL chemists and electrical engineers have published a new study showing that coats of graphene — a honeycombed sheet of carbon only one atom thick — can protect delicate nanostructures against temperatures that would otherwise melt them.
“As you decrease the size of nanoscale objects, their melting point decreases, as well,” said Alexander Sinitskii, an assistant professor of chemistry who co-authored the study. “We have shown that graphene makes nanostructures thermally stable, which means it expands their working range of temperatures. In other words, it gives engineers a few hundred extra degrees of usability with these materials.”
Sinitskii and his colleagues demonstrated that graphene buffers a class of thin-film materials especially susceptible to thermal damage.
They further established that graphene protects nanostructures based on cobalt and titanium, metals that feature significantly different physical and chemical properties. Their results suggest that graphene could be employed to protect many other metallic — and possibly even nonmetallic — materials that might be used in nanotechnology, Sinitskii said.
The researchers “grew” graphene coats onto nanostructures by exposing them to acetylene, an inexpensive chemical commonly used for industrial purposes. The acetylene decomposes on nanostructure surfaces at elevated temperatures, Sinitskii said, yielding carbon atoms that temporarily dissolve into a metal before rising to its surface and forming the distinctive hexagonal pattern of graphene.
The natural elasticity of graphene — the thinnest, strongest and most conductive material yet discovered — allowed the researchers to grow it on both two-dimensional and three-dimensional nanostructures.
“Because graphene conforms to surfaces, we can cover any arbitrary shape with it,” Sinitskii said. “The fact that the procedure is so general — that it can be applied to practically any nanostructure — makes it very useful.”
While citing optical sensors as one likely benefactor of graphene coating, Sinitskii said many different forms of nanotechnology could take advantage of this newly discovered thermal protection.
The team’s study appeared in the January edition of the journal ACS Applied Materials and Interfaces. Sinitskii’s co-authors included Peter Wilson, graduate student in chemistry; Adam Zobel, post-baccalaureate student; Alexey Lipatov, graduate student in chemistry; Eva Franke-Schubert, associate professor of electrical engineering; and Tino Hofmann, research assistant professor of electrical engineering.
The team, which conducted its research through UNL’s Center for Nanohybrid Functional Materials and the Nebraska Center for Materials and Nanoscience, received funding from the National Science Foundation.
Written by: Scott Schrage | University Communications