Advanced Ceramics in the Aerospace Industry
Electrical and structural uses of advanced ceramic materials are increasing globally.
Ceramics are increasingly being used in commercial and military aircraft, and have been used in space shuttles for many years. Ceramic materials are generally lighter than metals, and this low mass makes them highly appealing to the aerospace industry. However, the cost of working with an advanced ceramic material is such that a clear advantage must be established by using it. Once a benefit has been identified for a product or system (e.g., being able to run at a higher temperature or increased electrical activity), a range of ceramics is available.
Advanced ceramics underpin the electronics industry, and the average aircraft is packed full of electronics. Gradually, these electrical components, such as sensors, antennas, capacitors and resistors, are getting increasingly smaller and more capable. Therefore, this is a major area of development for advanced ceramics.
As far back as the 1990s, the design team of Concorde, the world’s only supersonic airliner at the time, selected a machinable glass ceramic* because it needed a lightweight and electrically insulating technical material for use in the engine control and management system. The glass ceramic material is stable at high temperatures and can be machined like plastic, making it an attractive option for this application.
*MACOR® machinable glass ceramic, developed by Corning Inc.
Structural ceramics (crystalline inorganic non-metals) are used in aerospace as thermal barrier coatings (TBCs) in the hot part of the engine. In addition, these materials are being used in composites either as reinforcement and/or as a matrix such as in ceramic matrix composites (CMCs). Being lightweight and tough tends to be a main driver for using a ceramic composite. From here, engineers need to assess how a composite will perform at an elevated temperature in an air atmosphere and what impact erosion will have on the system and at what rate.
Ceramics are lighter than most metals and stable at temperatures substantially above high-grade technical plastics. As a result of these and other properties, structural ceramic applications include thermal protection systems in rocket exhaust cones, insulating tiles for the space shuttle, missile nose cones, and engine components. The U.S. Space Shuttle Orbiter program team decided to use the machinable glass ceramic at all hinge points, windows, and doors on the reusable Space Shuttle Orbiter. In addition, large pieces of the glass ceramic have been used in a NASA space-borne gamma radiation detector.
Technical ceramics have been used for various parts of the engine for the past 30-40 years, but a lot of activity currently surrounds the development of silicon carbide (SiC/SiC composites) for use in jet engine turbines, mainly concentrated on the turbine blades. The main driver is fuel efficiency, as engineers seek to run the jet engine without the need for cooling channels that currently stop the metal alloy blades from melting. If the blades were made of ceramic composites, which could deal with temperatures of 1,500-1,600°C, the engine could run at higher temperatures. Energy efficiency would therefore increase, which leads to less fuel and the airplane’s ability to fly further or more efficiently.
Ceramics are integral to the aeronautics and aerospace industries. They are ubiquitous in the electrical systems and facilitate the drive toward more powerful, yet smaller electrical devices. Structural ceramics are increasing in popularity and deployment, and they offer huge potential for transforming aircraft engine capabilities that could dramatically influence the aeronautics of the future.