Sensors to operate in very high temperatures

Newcastle University is developing wireless sensors that can withstand the very high temperatures of hostile environments such as nuclear power plants.

Researchers at the university are working on radiation and gas detectors that can operate at temperatures of several hundred degrees using electronics made from silicon carbide (SiC).

The team has developed the necessary components and are now working to integrate them into a device about the size of an iPhone that could be used in a variety of locations such as power plants, aircraft engines and even volcanoes.

‘If someone sets off a bomb on the underground, for example, this will still sit on the wall and tell you what’s going on,’ said Dr Alton Horsfall, a senior lecturer at Newcastle’s School of Electrical, Electronic and Computer Engineering. ‘If a dirty bomb has gone off you want to know what’s happened before you send anyone in.’

The university’s sensors can detect a variety of radiation types and gases including hydrogen sulphide and sulphur dioxide in concentrations of tens of parts per million at temperatures of 200-300°C.

SiC is used for the electronic components rather than silicon because it continues to operate at much higher temperatures. ‘Silicon’s a wonderful material to about 175°C and then it goes horribly wrong whereas silicon carbide runs to around 600°C on a practical level,’ said Horsfall.

The increased temperature resistance is due to the much stronger bonds between the silicon and carbon atoms, which also require more energy to release electrons for electrical conduction.

But this also makes it more difficult to manufacture into components. Silicon carbide wafers are also smaller and more expensive than ones made from silicon, although the cost is falling.

Newcastle’s success so far has been in developing the necessary components for the sensors. ‘You can’t use batteries very well so we’ve got energy-harvesting technology,’ said Horsfall. ‘We can build power management with the ability to boost voltages on a self-starting system.

‘We can then fasten these onto a comms board that uses our technologies as well. We can build capacitors that get to ridiculous temperatures – we’ve got one to 650°C. We can also do optoelectronic communication, building photodiodes and LEDs that run at around 1Ghz and 300°C.’

The initial work was funded by the EPSRC with contributions from the Technology Strategy Board (TSB) and other organisations. Newcastle University is now looking for funding to produce a prototype device and develop it for a specific application.