Volume 10, Number 3 • May/June 2002 • Small Business/SBIR

SBIR Increases Durability of Composite Ceramics

A new coating material can greatly extend the lifetime of ceramic composites, making them more than 1,000 times more durable.

SBIR Phase I and II grants awarded to Advanced Ceramics Corporation (ACC) of Lakewood, OH by Glenn Research Center have led to the development of a family of high-temperature and doped boron nitride coatings that offer tremendous improvement in interface durability. The grants are part of a NASA campaign to study propulsion materials within its high-speed aircraft program.

These ACC-developed interface coatings circumvent moisture that complicates composite manufacture and ultimately degrades composite performance at high temperatures. The moisture-resistant coatings extend the shelf life of composite materials and resist thermal oxidation in moist air. Ceramic fibers woven into fabrics can now be coated with this advancement. The coating work is seen as a boon to the ceramic composites industry.

Wet oxidation is a major issue for fiber-reinforced ceramic matrix composites operating under combustion conditions. Loss of the boron nitride interface between the silicon carbide fibers and the silicon carbide matrix leads to rapid material property degradation. During the Phase II effort, commercial sales of these coatings on silicon carbide fibers have grown considerably.

Ceramic composites are a new type of material made by reinforcing refractories with high-strength ceramic fibers. They are as strong as metal, yet can withstand higher temperatures. One immediate use for composite materials is in turbine engines–an application that can make the engines far more efficient.

Industrial gas-fired power turbines that have ceramic composite combustor liners and shrouds can compress fuel and air at higher temperatures than all-metal turbines, which increases efficiency. The turbine can produce more kilowatt hours from the same fuel than it could if metal combustor liners and shrouds were used–a big advantage in the competitive and very cost-conscious power turbine industry.

Aircraft turbine engines with composite liners and shrouds also weigh less than all-metal turbines, allowing the aircraft to carry a larger payload or fly a longer distance using the same fuel. “More payload and more distance from the same engine and the same fuel” is the mantra of civil aviation. Q

For more information, contact Mike Dowell of Advanced Ceramics Corporation, phone: 440/878-5699, fax: 440/878-5927, dowellm@advceramics.com. Please mention you read about it in Innovation.

NASA Official: Jonathan Root • Web Design: Printing & Design Office, NASA Headquarters • Credits