ALBUQUERQUE, N.M. — If the Department of Energy’s Basic Energy Sciences (BES) annual awards competition was a horse race, Sandia National Laboratories’ sol-gel research program would be a championship bloodline.
The research program — designed to develop a greater understanding of the fundamental properties of sol-gel materials and their aerogel first cousins — has produced BES award winners in four of the past 10 yearly competitions.
Sol-gels are much like glasses but they are formed from a jelly-like mass of water, alcohol, and metal oxides. Sandia researchers believe that their improved understanding of sol-gels should lead to thin films that are useful for a variety of commercial applications in optics, acoustics, electronics, insulation, and sensors.
Because Sandia’s researchers can control the porosity (and thus tune the index of refraction) of sol-gel thin films, multilayer sol-gel coatings help to improve reflectivity of optical devices such as solar mirrors. And on integrated circuits sol-gel thin films seem appropriate to serve as overlayers that can reduce unwanted electrical characteristics, while ultimately contributing to faster and more compact computers. They also might be useful in chemical sensors and gas-separation filters.
A highlight of the program’s work with aerogels — the world’s lightest solids — is development of a new, easier fabrication technique, which ought to put them on a speedier path to commercial use.
Aerogels have fascinated and frustrated scientists and engineers since their invention in 1931. Although solid, the foam-like transparent material can consist of 99% air, making them ideal heat insulators for double-paned windows, as well as for refrigerators, thermos bottles, and walls. One inch of aerogel offers the same amount of insulation as 10 inches of fiberglass. Aerogels also are ideal insulators for damping sounds.
The problem: until now they have been extremely difficult to make.
The Sandia achievement, reached in conjunction with researchers at the University of New Mexico: finding a way to produce aerogels at room temperature and pressure, thereby eliminating many of the hazards and the expense associated with conventional processing methods.
Simply put, “sol-gels’ impact on society will be remarkable if they live up to their potential,” says Al Hurd, manager of Sandia’s Ceramic Processing Science Department.
Jeff Brinker, a chief Sandia sol-gel/aerogel scientist, adds, “The potential for aerogels is tremendous. But until now, an impractical process has made them not very amenable to manufacturing.”
BES awards are competed annually by DOE’s Office of Basic Energy Sciences/Division of Materials Sciences.
This year’s award for “sustained outstanding research in metallurgy and ceramics” recognizes continued achievements in sol-gel thin film deposition work at Sandia during the past 10 years.
Sandia’s sol-gel research successes began in the mid-80s, when a Labs team pioneered the use of fractals and scattering to understand sol-gel structure. The breakthrough earned Sandia its first sol-gel-related BES award in 1986. In 1988 the Sandia team came up with a diagnostic technique, imaging ellipsometry, by which researchers could measure the thickness and refractive index of a portion of a sol-gel film while the film was being deposited, or dip coated, on a surface.
Soon after that the team applied another key diagnostic tool, surface acoustic wave (SAW) analysis, that allowed pore size and distribution to be measured. That was an important advance in understanding sol-gel film microstructures.
Subsequent achievements revealed a wide range of other fundamental chemical and physical phenomena associated with thin film deposition, and researchers at Sandia and elsewhere then began to exploit those insights to create customized films and coating processes.
Perhaps the biggest breakthrough came in 1994 with development of the Sandia/UNM ambient pressure aerogel process. Aerogels result when sol-gel fabrication processing steps are changed. The basic difference is that during fabrication liquids must be driven off while the chemical structure is maintained.