CERAMICS AND ENERGY: IT'S A MATERIALS WORLD
Created by John Frye in 1952, the ceramics research group at the Laboratory was later managed by Lou Doney, Bill Harms, Jim Scott, Walt Eatherly, and Vic Tennery. During the early decades, this group concentrated on developing ceramic fuels for nuclear reactors. Unlike metal fuels, ceramic fuels would not melt during high-temperature reactor operation. The early ceramics research contributed to the adoption of ceramic uranium dioxide pellets inside zirconium alloy tubes as the standard fuel in light-water reactors worldwide. For gas-cooled reactors, ceramics research developed tiny spheres of nuclear fuel with special coatings to prevent release of fission products into the helium coolant.
Studying ceramics for nuclear reactors led the Laboratory ceramic research team into related fields. While studying uranium dioxide during the 1960s, for example, Wayne Clark and Ted Chapman invented a method for growing single crystals of this material incorporating tungsten metal fibers. This ceramic matrix composite proved useful in electronic devices.
When the Laboratory became involved in broad energy research during the 1970s, ceramics research was applied to materials in addition to nuclear fuels. As industry shifted from imported oil and natural gas to coal burned in hotter, more energy-efficient furnaces for many manufacturing processes, it became interested in identifying corrosion-resistant materials for high-temperature furnace liners and heat exchangers. Ceramics were a logical choice for such applications, and Laboratory ceramics researchers led by Vic Tennery focused on meeting these needs.
They learned that silicon nitride and silicon carbide could maintain their strength and resist corrosion at the high temperatures of advanced gas turbines and heat exchangers. On the other hand, these brittle materials can fail at high temperatures because of internal flaws produced during their manufacture.
Using electron microscopes to reveal ceramic structure, Laboratory researchers studied ways to improve the processing of these materials to make them more uniform and fracture resistant. They learned how to reduce ceramic brittleness by reinforcing the materials with silicon carbide whiskers, just as straw was used to reinforce the adobe clay used in Pueblo houses. Whisker-reinforced ceramics now are used in high-speed cutting tools.
In 1985, DOE approved a program at the Laboratory to develop ceramics for advanced heat engines, which will use fuel more efficiently than current engines. Led by Tennery, Tony Schaffhauser, Ernie Long, and Ray Johnson, Laboratory research developed structural ceramics for use in the high-wear parts of large diesel engines and experimental gas turbines being developed for transportation and electricity production.
With strong support from industry, the Laboratory opened a High Temperature Materials Laboratory in 1987. Here, Laboratory scientists and engineers cooperate with industrial and university researchers exploring ceramics and other materials development. The presence of this unique user facility has encouraged several industrial firms to build plants in Oak Ridge.
Recently, Laboratory and industrial researchers have discovered how to make silicon nitride materials self-reinforcing, thereby achieving the same goals as whisker-reinforced ceramics. The latest silicon nitride materials have found use in engines for cars and trucks. These and other new ceramics developed at the Laboratory will find wide use in industry.
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