Scientists working at the Laboratory have recently demonstrated a novel method for chemically modifying and enhancing silica-based aerogels without sacrificing the aerogels' unique properties. Aerogels are low-density, transparent materials used in a wide range of applications, including thermal insulation, porous separation media, inertial confinement fusion experiments and cometary dust capture agents.Made of silica, one of the Earth's most abundant materials, aerogels are as much as 99 percent air, giving them not only the highest thermal insulation value and highest surface area, but also the lowest acoustic conductivity and density of all known solid materials. The aerogels' extraordinary thermal insulation ability makes them capable of withstanding temperatures in excess of a thousand degrees Fahrenheit. Because they are composed mostly of air, there is little solid content available for maintaining the structural integrity of the aerogel, making them brittle.
In research reported Wednesday at the 228th national meeting of the American Chemical Society, Laboratory scientist Kimberly DeFriend of Polymers and Coatings (MST-7) described a process for modifying silica aerogels with silicon and transition metal compounds using chemical vapor techniques to create a silicon multilayer or a mixed-metal oxide that enhance the current physical properties of aerogels for more demanding applications. With the addition of a silicon monolayer, an aerogel's strength can be increased four-fold.
Aerogels are synthesized at Los Alamos using sol-gel processing and super-critically dried with either carbon dioxide or a solvent. This sol-gel processing method allows the gel to be formed in the shape of its mold, making it possible to create a variety of shapes. The introduction of silicon multilayers or transition metal compounds allows the aerogels to retain their most valuable porosity and density characteristics while enhancing weaker characteristics like mechanical strength.
Los Alamos has recently begun to expand and advance its ability to synthesize and manufacture the aerogels. This improved capability will allow Laboratory scientists to not only more closely study and improve on the quality of the aerogels, but also help to better meet the Laboratory's inertial confinement fusion and high-energy-density physics aerogel target needs.
In addition to DeFriend, the Los Alamos aerogel team includes Douglas Loy, Arthur Nobile, Jr., Kenneth Salazar, James Small, Jonathan Stoddard and Kennard Wilson, Jr., all of MST-7.
--Todd Hanson