Extreme environments in several critical industries, such as aerospace, energy, transportation, and defense, require sensors to measure and monitor many things in harsh conditions to ensure people’s machine safety and integrity.
For example, in the petrochemical industry, high-pressure pipelines must be monitored in climates ranging from scorching desert heat to near-arctic cold. While many nuclear reactors operate at the range of 300-1000 degrees Celsius, the deep geothermal wells hold temperatures up to 600 degrees Celsius.
Now, a research team at the University of Houston has developed a new piezoelectric sensor that has been shown to work in temperatures as high as 900 degrees Celsius (1,650 degrees Fahrenheit), which is the temperature mafic volcanic lava, the hottest type of lava on Earth, erupts.
“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, corresponding author of a study.
Previously, researchers developed an 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 above 350 degrees Celsius, which is higher than conventional sensors made of aluminum zirconate titanate (PZT), but only by a small margin.
The team believed the decrease in sensitivity was due to the bandgap not being wide enough. To test this hypothesis, they created a sensor containing aluminum nitride (AlN). “The hypothesis was proven by the sensor operating at about 1000 degrees Celsius, which is the highest operation temperature among the piezoelectric sensors,” said Nam-In Kim, the first author of the article.
While both AlN and GaN have unique and excellent properties suitable for use in sensors in extreme environments, the researchers were happy to discover that AlN has a wider bandgap and higher temperature range. However, the team had to deal with the challenges associated with synthesizing and producing high-quality, flexible, thin-film AlN.
As the team has successfully demonstrated the potential of the high-temperature piezoelectric sensors with AlN, they will test it further in harsh real-world conditions. The sensor’s flexibility 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.
“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. “AlN sensors can operate in neutron-exposed atmospheres and at very high-pressure ranges thanks to its stable material properties.”
- Nam-In Kim, Miad Yarali, Mina Moradnia, Muhammad Aqib, Che-Hao Liao, Feras AlQatari, Mingtao Nong, Xiaohang Li, Jae-Hyun Ryou. Piezoelectric Sensors Operating at Very High Temperatures and in Extreme Environments Made of Flexible Ultrawide-Bandgap Single-Crystalline AlN Thin Films. Advanced Functional Materials, 2023. DOI: 10.1002/adfm.202370056