General Competition (April 1992)

Novel Near-Net-Shape Processing of Engineered Ceramics

Sponsor: Honeywell (formerly Garrett Ceramic Components - Div of AlliedSignal Aerospace)

• Project duration: 7/1/1992 - 6/30/1995
• Total project (est.): $2,116,055.00
• Requested ATP funds: $1,161,853.00

A major obstacle to the widespread use of advanced engineering ceramics is the difficulty of machining these extremely hard, brittle materials to a final shape, particularly if the shape is complex or requires very fine dimensional tolerances. A number of "near-net-shape" techniques have been developed to allow mixtures of preceramic materials to be molded or cast into complex shapes which are then fired to produce the ceramic. However they all have significant limitations -- a tendency to produce molding defects or distorted or warped parts, for example, or long processing times. Researchers at the Department of Energy's Oak Ridge National Laboratory (ORNL, operated by Martin Marietta Energy Systems, Inc.) have developed a promising alternative casting technology -- gelcasting. In gelcasting, powdered ceramic precursors are mixed with a polymer precursor and solvent (usually water) to make a fluid slurry which can be poured into a mold. The gel is then polymerized, locking the ceramic powder in a polymer matrix. The solvent is removed, the part is heated to burn out the polymer, and fired to produce the ceramic. Gelcasting has been shown to produce excellent near-net-shape parts in a wide variety of industrially important ceramics for use in aerospace, automotive and industrial applications regardless of size or complexity with few of the mechanical problems of other casting technologies. There is one major drawback: a most promising approach to aqueous gelcasting in its present form relies on acrylamide, a cumulative neurotoxin. Industrial safety concerns have prevented its widespread use. To overcome this, Garrett Ceramic Components, a unit of Allied-Signal Aerospace, proposes to work with ORNL to develop a low-cost, non-toxic alternative to the acrylamide system that retains its excellent process characteristics, and study the important process control parameters necessary to move aqueous gelcasting into commercial production systems.

For project information:

Ronald H. Walecki, (310) 512-5916

ATP Project Manager

Dilip Banerjee, (301) 975-3538
dilip.banerjee@nist.gov