Aerospace Ceramics

Not pottery... but advanced materials that have highly specialized applications.

Aerospace ceramics, such as Alumina, Silicon Nitride and Aluminum Nitride are currently being used to manufacture critical components. These inorganic, non-metallic materials retain dimensional stability through a range of high temperatures and exhibit high mechanical strength. They are chemical resistance and have a high stiffness-to-weight ratio, providing manufacturers with the ability to produce high performance components.

Aerospace ceramics are innovative products made from a range of ceramic, glass, precious metal, piezoelectric and dielectric materials.

They are critical components in their applications in aircraft instrumentation and control systems, missile guidance systems, satellite positioning equipment, ignition systems, fire detection and suppression, instrument displays and engine monitoring equipment.

Piezoelectric ceramics

Piezoelectric ceramics and dielectric ceramics are used in aerospace transducers and sensors such as accelerometers (for measurement of vibration), gyroscopes (for measurement of the acceleration and pitch of aircraft, missiles and satellites) and level sensors.

Piezoelectric refers to the effect of mechanical pressure causing a crystalline structure to produce a voltage proportional to the pressure. Conversely, when an electric field is applied, the structure changes shape, producing dimensional changes in the material. Engineered piezoelectric polycrystalline ceramics offer several advantages over natural piezoelectric crystals, such as of Quartz, Rochelle Salt and Tourmaline. Ceramics are more versatile with physical, chemical and piezoelectric characteristics that can be precisely tailored to specific applications.

The Boeing 777, uses piezoelectric ceramics in the 60 ultrasonic fuel tank probes located on each aircraft. The ultrasonic transducers are installed at a variety of locations in each fuel tank. A pulsed electric field is applied to the piezo ceramic material, which then responds by oscillating. The resulting sound waves are reflected off the surface of the fuel and picked up by the piezo-electric ceramic transducer. A digital signal processor interprets the measurement of the sound waves in order to continually indicate the amount of fuel left. Ultrasonic fuel probes are also used in fighter aircraft and other level sensing applications because of their ability to provide highly accurate readings, regardless of the orientation of the aircraft.

Aero engine seals

Aerospace ceramics are also ideally suited for applications that provide a physical interface between different components, due to their ability to withstand the high temperatures, vibration and mechanical shock typically found in aircraft engines and other high stress locations. Ceramics are commonly found in aero engine seals for gas turbine engines, fuel line assembly, and thermocouples. Where ceramic/metal assemblies are required, joining the two materials generally involves metallizing the ceramic surface and then brazing the components together.

Aero Engine Component Repair

Advanced brazing materials for aero engine component repair also use pre-sintered preforms (PSP) for high temperature braze repair applications. With turbine temperatures reaching up to 1300ºC (2350ºF) and the presence of hot corrosive gases, components experience considerable erosion and wear.

The pre-sintered preforms consist of a blend of superalloy and low melting point braze and are customized to fit the shape of the component and then tack-welded into place and brazed. The ability to provide a range of near net thicknesses can eliminate the need for most post-braze machining and extend the life of engine components by up to 300 percent, making it a more reliable and cost effective method than traditional welding which requires post-braze machining or grinding.

The powerful physical, thermal and electrical properties of advanced ceramic materials are ideal for the high performance and low cost sought by aerospace.