NRL Develops Advanced Aerogels

5/20/1999 - 23-99r
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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.

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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 approximately 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 90 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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