Design and Manufacture of an Ultrasonic Transducer for Long-term High Temperature Operation

A novel design of ultrasonic transducers suitable for high temperatures is introduced. The transducers are targeted for trouble-free continuous operation at 700-800 째C for at least two years, with sufficiently wide bandwidth to yield good temporal resolution. The design and manufacturing procedures were formatted as a multistep sequence, adaptable to a variety of transducer specifications within a wide range of signal center frequencies (500 kHz to 10 MHz) and a wide range of signal bandwidths. Two transducer designs were pursued based on two different piezoelectric crystals as the active element: gallium phosphate and lithium niobate. A high Curie temperature of 1200 째C for lithium niobate and a high phase transition temperature of 970 째C for gallium phosphate, make the two piezoelements suitable for our application. A one-dimensional transducer model was used to model the transducer when used as a transmitter-receiver. The optimized acoustic impedance of the transducer backing element was determined to obtain desired signal center frequency of 3 MHz with 3 dB bandwidth of 90-95%. The concept of porous ceramics as a new generation of high temperature backing element is described. An acoustic model for wave propagation in such a medium was employed to estimate the optimal porosity and pore size for the backing element. Various high temperature adhesives and brazing alloys were investigated to bond stable bonding at high temperatures. An aluminum-based brazing alloy was found to yield reliable bonding between lithium niobate piezoelement and porous zirconia backing and alumina matching layer. None of the bonding agents resulted in acceptable bonding in the case of gallium phosphate piezoelement. The performance of the prototyped transducer at high temperature was tested on a steel plate. Despite some fluctuations in back-wall signal amplitude, clear signals were obtained.

Department dc:contributor.department

Mechanical and Industrial Engineering

Year dc:date.issued

2016

Author dc:creator

• Amini, Mohammad Hossein

Advisors dc:contributor.advisor

• Sinclair, Anthony N
• Coyle, Thomas W

• High temperature Environments
• Long-term operation
• Non-Destructive Testing
• Piezoelectric Transducers
• ULtrasonics

Handle dc:identifier.uri

http://hdl.handle.net/1807/76180

OAI identifier oai:identifier

oai:utoronto.scholaris.ca:1807/76180