Scientists in the Naval Research
Laboratory's (NRL's) Chemistry and Optical Sciences Divisions
have developed composite aerogels for use as high-surface area
electrodes, catalysts and battery structures, advanced thermoelectric
materials, and as architectures around which to design chemical,
physical, and optical sensors. Since aerogels provide both high
surface areas and highly open spaces, they are especially well-suited
to catalytic and sensing applications, where rapid transport
of reactants and large, accessible surface areas are critical
to performance. NRL has received external support for this program
from the Office of Naval Research and the Defense Advanced Research
Projects Agency.
Aerogels are an advanced class
of materials composed of approximately 10-nanometer particles
connected in a highly porous, three-dimensional network. Aerogels
are a combination of both particles and pores, which is the key
to their unique properties. The most widely studied aerogel
composition is silica.
During the past year, the NRL
team, led by Drs. Debra Rolison and Celia Merzbacher, has provided
design flexibility and expanded the range of aerogel properties
by using the gel's building block, colloidal silica sol, as a
"nanoglue" to trap suspended particles or colloids
into the network of the wet gel. This technique has been used
to make composite aerogels of silica with a range of physically
and chemically diverse particulates.
When the second phase of the
composite is present above a certain threshold, its transport
characteristics are imparted to the composite aerogel, even though
it retains the low density and openness characteristic of pure
silica aerogels. Although a carbon-silica composite aerogel
is approximately 80% open space, it blocks transmission of He-Ne
laser light, even though a pure silica aerogel transmits the
beam of laser light with minimal scattering.
Real-world surfaces are actually
nanoscale domains that differ from the underlying bulk and that
dictate many of the technologically most relevant catalytic and
electrical properties of the material. "Our research program
on aerogels demonstrates how a fundamental effort to design and
characterize nanostructured platforms leads to improvements in
the properties of technologically relevant materials and the
design of new materials," comments Dr. Rolison.
The U.S. Naval Research Laboratory is the Navy's full-spectrum corporate laboratory, conducting a broadly based multidisciplinary program of scientific research and advanced technological development. The Laboratory, with a total complement of nearly 2,500 personnel, is located in southwest Washington, D.C., with other major sites at the Stennis Space Center, Miss., and Monterey, Calif. NRL has served the Navy and the nation for over 85 years and continues to meet the complex technological challenges of today's world. For more information, visit the NRL homepage or join the conversation on Twitter, Facebook, and YouTube.
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