In the petrochemical industry pipeline pressures must be monitored at climates ranging from hot desert heat to near arctic cold. Various nuclear reactors operate at a range of 300-1000 oC, while deep geothermal wells hold temperatures up to 600 oC.
“Highly sensitive, reliable and durable sensors that can tolerate such extreme environments are necessary for the efficiency, maintenance and integrity of these applications,” said Jae-Hyun Ryou, associate professor of mechanical engineering at UH and corresponding author of a study published in Advanced Functional Materials.
The UH research team previously developed III-N piezoelectric pressure sensor using single-crystalline Gallium Nitride (GaN thin films) for harsh-environment applications. However, the sensitivity of the sensor decreases at temperatures higher than 350 oC, which is marginally higher than those of conventional transducers made of lead zirconate titanate (PZT).
The team believed the decrease in sensitivity was due to the bandgap not being wide enough. To test the hypothesis, they developed a sensor with aluminium nitride (AlN).
“The hypothesis was proven by the sensor operating at about 1000 oC, which is the highest operation temperature among the piezoelectric sensors,” said Nam-In Kim, first author of the article and a post-doctoral student working with the Ryou group.
While AlN and GaN have unique and excellent properties that are suitable for use in sensors for extreme environments, the researchers found that AlN offered a wider bandgap and an even higher temperature range.
Now that the researchers have successfully demonstrated the potential of the high-temperature piezoelectric sensors with AlN, they will test it further in real-world harsh conditions.
“Our plan is to use the sensor in several harsh scenarios, for example, in nuclear plants for neutron exposure and hydrogen storage to test under high pressure,” Ryou said in a statement. “AlN sensors can operate in neutron-exposed atmospheres and at very high-pressure ranges thanks to its stable material properties.”
According to Houston, the flexibility of the sensor offers additional advantages that will make it useful for future applications in the form of wearable sensors in personal health care monitoring products and for use in precise-sensing soft robotics.
The researchers added that they look forward to their sensor being commercially viable.
“It's hard to put a specific date on when that might be, but I think it's our job as engineers to make it happen as soon as possible,” said Kim.
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