Processing and Characterization of Air-Sprayed Bismuth Titanate Ultrasonic Transducers.

Area of Science:

• Materials Science
• Acoustics
• Engineering

Background:

• Harsh environments in industrial applications necessitate robust transducers for ultrasonic nondestructive evaluation (NDE).
• Bismuth titanate (BIT) possesses a high Curie temperature, suitable for high-temperature transduction.
• Existing NDE technologies face limitations in extreme temperature conditions.

Purpose of the Study:

• To develop and characterize air-sprayed bismuth titanate transducers for high-temperature NDE.
• To evaluate the thermal tolerance and operational stability of these transducers under harsh conditions.
• To assess the feasibility of BIT transducers for field deployment in demanding industrial settings.

Main Methods:

• Fabrication of BIT transducers via air-spraying onto stainless steel substrates.
• Characterization of transducer properties: coating thickness, center frequency, bandwidth, and signal-to-noise ratio.
• Thermal aging at 375 °C and thermal cycling up to 250 °C and 400 °C to assess performance and stability.

Main Results:

• Developed coatings (40-70 μm) with a center frequency of ~7 MHz and broad bandwidth (3-20 MHz).
• Thermal aging led to increased resonance frequency, reduced thickness, microstructural changes, and decreased signal amplitude, yet transducers remained operational.
• Thermally aged transducers exhibited stable ultrasonic performance during thermal cycling, outperforming pristine ones.

Conclusions:

• Air-sprayed BIT transducers are viable for high-temperature NDE applications.
• The developed transducers show resilience and operational stability even after exposure to elevated temperatures and thermal cycling.
• These BIT transducers represent a promising advancement for safe operations in power generation, propulsion, and chemical processing industries.