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New process lowers cost, improves quality of ceramics
OAK RIDGE, Tenn.,
Oct. 6, 1995
Forming high-quality, complex-shaped ceramic parts quickly and cost-effectively is now possible with a new process, called gelcasting, developed by engineers at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL).
Ceramics, which are made from nonmetallic minerals that have been heated to high temperatures, or fired, are useful because of their high temperature resistance, strength, light weight, mechanical hardness and resistance to wear and corrosive chemicals. Because of these characteristics, ceramics are used to make a variety of products, ranging from automobile engine parts to fine china.
With gelcasting, manufacturers can produce components that require little or no additional shaping - called "near net shape" - of a wide range of ceramic materials, according to a team of ORNL scientists in the Metals and Ceramics Division. Manufacturers can also develop products that they would not, or could not, have previously considered, said Ogbemi Omatete, who worked with Mark Janney, Stephen Nunn and Claudia Walls in developing the new process.
Essentially, the gelcasting process combines techniques borrowed from traditional methods of producing ceramics with polymer chemistry. ORNL researchers used these techniques and their knowledge of ceramics to produce a liquid-based mixture, or "slurry," containing ceramic powder, water and simple molecules (monomers) capable of combining with other molecules. The slurry is poured into a mold of the desired shape. A chemical reaction is then initiated to form a polymer-water gel that locks the ceramic particles in place. The part is removed from the mold, dried and then fired to fully develop its strength and other properties. The process, originally developed for making turbine rotors, can be used to make parts of diverse sizes and shapes, including those with intricate structures.
Gelcasting has several advantages over other ceramic forming techniques, including a relatively short molding time, greater precision and minimal defects and warpage of components. From a manufacturing standpoint, other advantages include cheaper molds, more uniform shrinkage and reduced final machining.
ORNL researchers also emphasize that gelcasting uses chemical reagents with low toxicity, which minimizes environmental, safety, health and waste disposal issues. The process also requires only small changes in manufacturing, which makes it more easily accepted by the ceramics industry because it doesn't require costly overhauls of plant and equipment.
Gelcasting won an R&D 100 Award from Research and Development magazine this year. This award recognizes the 100 most technologically significant new products of the year.
Gelcasting is licensed by three U.S. companies: AlliedSignal Ceramic Components, LoTEC Inc. and Ceramic Magnetics Inc. AlliedSignal Ceramic Components manufactures turbine rotors for aircraft auxiliary power units; LoTEC manufactures low thermal expansion ceramics, which do not expand at high temperatures and can be used to manufacture thermal insulation for engine exhaust manifolds; and Ceramic Magnetics will use gelcasting to make large-diameter magnet rings that are used in particle accelerators for high-energy physics research.
In addition to the R&D 100 Award, the ORNL gelcasting team received the International Hall of Fame Award in 1993 from the Inventors Clubs of America. The researchers are working with several companies in seven cooperative research and development agreements and five other collaborations.
Funding for the gelcasting research was provided primarily by DOE's Energy Efficiency (EE) Office of Transportation Materials, Ceramic Technology Program. Additional funding came from EE's Office of Industrial Technologies.
ORNL, one of DOE's multiprogram national research and development facilities, is managed by Lockheed Martin Energy Systems, which also manages the Oak Ridge K-25 Site and the Oak Ridge Y-12 Plant.