Continuous monitoring at 600 °C by CaBi4Ti4O15/Pb(Zr,Ti)O3 Sol-gel composite ultrasonic transducer

摘要

Ultrasound non-destructive testing is mainly used because it can detect internal defects, however on-line monitoring for industrial plants is difficult due to high temperatures such as 600 °C. In previous study, CaBi4Ti4O15(CBT)/Pb(Zr,Ti)O3(PZT) sol-gel composites has been developed for NDT at 600 °C and it survived after 36 h at 600 °C, though sensitivity and signal to noise ratio (SNR) was very poor so that improvement of sensitivity and SNR is required. CBT/PZT sol-gel composite film was fabricated on a titanium substrate by spray coating. A platinum top electrode was fabricated on the film, and platinum wires were connected with a top electrode and titanium substrate for high temperature durability test. Every platinum wires were bonded to platinum top electrode and the titanium substrate by high temperature silver paste. Then the CBT/PZT transducer was tested in the furnace from room temperature to 600 °C. The thermal cycle was repeated three times. After that, CBT/PZT transducer was tested in the furnace at 600 °C for 36 h. As a result, the performance of the CBT/PZT sol-gel composite ultrasonic transducer showed superior thermal durability as compared with previous study. Therefore, CBT/PZT could be a good candidate as ultrasonic transducers for continuous monitoring at 600 °C.