Researchers Create Rare, Large Symmetrical Crystals: Accident Leads to Important Discovery
Troy, N.Y. — Researchers at Rensselaer have created large
symmetrical crystals that rarely occur in nature. These
crystals could be harder than conventional engineering
materials. The accidental discovery was made during attempts to
make superconducting nanostructures with a simple technique
used to create carbon nanotubes.
Pulickel Ajayan and Ganapathiraman Ramanath, faculty members
in materials science and engineering at Rensselaer, used boron
carbide, a common engineering material, in the high-temperature
experiment. In the ashes, they discovered large crystals with
five-fold crystallographic symmetry.
Nanosize five-fold symmetrical, or icosahedral, crystals are
fairly common, but these larger micron-size crystals with
five-fold symmetry are rare in nature because their smaller
units cannot repeat their pattern infinitely to form
space-filling structures. As the nuclei of these crystals grow,
the strain on the crystals increases. This causes them to
revert to their common bulk crystal structures.
Ajayan believes that the inherent structure of boron carbide,
which has icosahedral units in the unit cell, allows the
crystals to grow to micron size without the strain. “These
crystals are unique due to their high symmetry. Because of the
hardness inherent to the crystal structure, we could anticipate
a better material for engineering, specifically coatings. It is
exciting and fulfilling to find something that is quite rare in
nature, although we need to conduct further measurements to
understand its potential,” Ajayan said.
The researchers, their post-doctoral research associates
(Bingqing Wei and Robert Vajtai), and a graduate student (Yung
Joon Jung) collaborated with colleagues at the University of
Ulm in Germany.
Their research appeared as the cover story in the June 13,
2002 issue of the Journal of Physical Chemistry.
Contact: Megan Galbraith
Phone: (518) 276-6531