Thought you might be interested in this news release
from ScienceDaily (http://www.sciencedaily.com):
______________________________________________________
 
 
Sandia,UNM Mimic Structure Of Seashells To Create Strong, Tough Coatings
 
ALBUQUERQUE, N.M. -- Humanity has valued seashells for their beauty as
rnaments and utility as tools for thousands of years. But even alchemists
ever tried transmuting base materials into the very fine interlayering
ecessary to create a shell's strength, hardness, and toughness.
 
Now, in a paper published in the July 16 Nature, researchers at the
Department of Energy's (DOE) Sandia National Laboratories and the
University of New Mexico (UNM) disclose a rapid and efficient method to
self-assemble diverse materials into coatings that mimic seashell
structures.
 
The process permits rapid formation of tough, strong, optically
transparent coatings suitable for applications such as automotive finishes,
as well as coatings for implements and optical lenses.
 
A preliminary analysis shows the coating to be more than twice as hard as
the same materials mixed randomly.
 
The secret of easily accreting these very thin laminations had eluded
scientists for years. Laminations based upon the seashell model are
important because of the improved properties achieved by alternating layers
of flexible, cushioning biopolymers with hard layers of calcium carbonate.
Abalone shell, for example, composed of approximately one percent polymer
and 99 percent aragonite (CaCO3) by volume, is two times harder and 1,000
times stronger than its constituent materials.
 
Cracks that begin in any calcium carbonate layer are immediately
intercepted by a polymer layer. The crack thus requires still more energy
before it can propagate through succeeding calcium carbonate layers, thus
improving their resistance to fractures.
 
The process, developed by Sandia researchers Alan Sellinger and Jeff
Brinker, working with UNM students Pilar Weiss and Yungfeng Lu, is based on
the scientifically well-known tendency of two-sided detergent molecules,
composed of hydrophilic (water-loving) and hydrophobic (water-hating)
portions, to spontaneously form spherical molecular assemblies called
micelles.
 
In water, micelles arrange themselves so that the water-loving part of the
detergent is in contact with water, while the water-hating, hydrophobic
part is shielded in the micellar interior. This arrangement is useful when
washing dishes because oils are quickly adsorbed in the hydrophobic
interiors, allowing them to be rinsed away. Similarly, in the composite
process, micelles separate and organize inorganic molecules around the
micelles' hydrophilic exterior and organic molecules within the hydrophobic
interiors.
 
During the coating process, the intentional evaporation of water further
arranges the micelles into alternating layers of organic and inorganic
molecules -- called precursors -- in a single step. A low- temperature heat
treatment polymerizes the organic and inorganic layers and bonds their
interfaces. Previous nanocomposite assembly processes involved tedious,
sequential deposition of individual organic and inorganic layers. This
approach produces, after much time, only layered constructions. The Sandia
process takes only a few seconds and can easily be modified to achieve 1-,
2-, or 3-dimensional connectivity of the reinforcing polymer phase.
 
The work was funded in part by the UNM/National Science Foundation's
enter for Micro-Engineered Materials, DOE's Basic Energy Sciences, and
Sandia's Laboratory-Directed Research and Development Program.
 
Sandia is a multiprogram DOE laboratory, operated by a subsidiary of
Lockheed Martin Corp. With main facilities in Albuquerque, N.M., and
Livermore, Calif., Sandia has major research and development
responsibilities in national security, energy, and environmental
technologies.
 
___________________________________________________________
Dr. Bruce G. Livett PhD
Reader and Deputy Head
Department of Biochemistry and Molecular Biology
University of Melbourne
Parkville
Victoria 3052
AUSTRALIA
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