Air Force

High temperature, high pressure sensors made of carbon nanotubes and polymer ceramics with 3D printing

Wireless sensors utilize ceramic and carbon nanotube materials to provide reliable monitoring of key systems

Electronics Sensors

CAD drawing (a) and reduced sensor (b)

There are no reliable sensors systems that can provide in-flight status checks of hypersonic missiles traveling at high altitudes through extreme temperatures ranges. Current onboard devices such as fuel sensors, accelerometers, surface acoustic wave sensors, chemical resistors, and temperature sensors only work during storage and transportation.

That’s because temperature sensors like thermocouples, thermistors, resistance thermometers, and quartz thermometers use a metallic coil inductor. In high-temperature environments, 800° to 1,400° Celsius, oxidation of the metallic coil inductor compromises the sensor.

Pressure sensors suffer from a similar weakness. In extreme environments such as a gas turbine used for grid-scale power generation, suitable pressure sensors need to withstand corrosive gas environments having high temperatures, 1,000° to 1,400° Celsius, and high pressures, from 300 to 600 PSI. The pressure sensors also require wire interconnections that break in high-temperature environments.

In both temperature and pressure sensors, a patch antenna sends its data to an external antenna for radio transmission. Again, a metal wire is found in patch antennas, which limits their temperature range to −55° to 125° Celsius.

Addressing the need for new temperature and pressure sensors operable in extreme environments, and the antennas needed to relay the information, the Air Force and Florida State University researchers have developed sensors with a ceramic coil inductor and carbon nanotubes (CNTs). This material combination leverages the stiff and strong CNTs and the thermal properties of ceramic materials.

The sensors include a ceramic coil inductor that is formed of a thin film polymer-derived ceramic (PDC) nanocomposite having a dielectric constant that increases monotonically with temperature. The sensors measure a frequency shift of an electromagnetic signal induced in the inductor to detect a change in the environment. A patch antenna is attached to the ceramic coil inductor.

The sensors can be made using additive manufacturing using a liquid state preceramic polymer and carbon nanotubes or fibers and ultraviolet curing.

Operating temperatures range from about 25° to about 1,000° Celsius and can operate under pressures ranging from zero PSI to about 40,000 PSI.

These sensors would have ideal use in chemical processing, power generation, and engine monitoring for missiles, airplanes and ground vehicles.

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