8/2/2019 Ceramics in Aerospace
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Ceramic Engineering in Aerospace
Engineered ceramics are increasingly being used in commercial
and military aircraft, and have
been used in the space shuttle and its equipment for many years.
Ceramic applications include
thermal protection systems in rocket exhaust cones, insulating
tiles for the space shuttle, enginecomponents, and ceramic coatings
that are embedded into the windshield glass of many airplanes.
These coatings are transparent and conduct electricity for
keeping the glass clear from fog and ice.
Ceramic fibers are used as heat shields for fire protection and
thermal insulation in aircraft andspace shuttles because they
resist heat, are lightweight and do not corrode. Other
significant
characteristics include high melting temperatures, resiliency,
tensile strength and chemical
inertness.
A non-oxide ceramic called silicon nitride has excellent high
temperature strength, excellentfracture toughness, high hardness
and unique tribological properties. Silicon nitride aerospace
applications result in superior mechanical reliability and wear
resistance allowing components tobe used under minimal lubrication
without wear. These include jet engine igniters, bearings,bushings,
and other wear components.
Making Space Travel Possible
Advanced ceramics are playing a critical role in the development
of highly-efficient and cost-
effective new technologies for space travel. Morgan Technical
Ceramics division in Erlangen,
Germany has been working with a European space development
program for a number of years tosupport its research of ion
propulsion systems. A lightweight alternative to traditional
chemical
propulsion, ion engines have the potential to push spacecraft up
to ten times faster with the same
fuel consumption, thereby significantly decreasing vehicle size
and increasing travel distance.
Ion propulsion technology, which uses electricity to charge
heavy gas atoms that accelerate fromthe spacecraft at high velocity
and push it forwards, traditionally incorporated quartz
discharge
vessels. Quartz has now been replaced by a ceramic oxide called
alumina because of the need for a
material with the same dielectric properties but with higher
structural stability. Alumina is easier tofabricate and offers good
thermal shock resistance, ensuring that the chamber can withstand
the
extremes of temperature that occur during plasma ignition. It is
also lighter, which reduces the
costs associated with each launch.
Providing Accurate Fuel Measurements
One of the most successful commercial aircrafts in recent times,
the Boeing 777, uses piezoelectric
ceramic material within 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 ceramic material, which then responds by oscillating. The
resulting sound waves arereflected off the surface of the fuel and
picked up by the piezoelectric ceramic transducer. A digital
signal processor interprets the time of flight measurement of
the sound waves in order to
continually indicate the amount of fuel present. Similar
ultrasonic fuel probes are also used in
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