Research on Low Frequency Composite Transducers Fabricated Using a Sol-gel Spray-on Method
Open Access
- Author:
- Cyphers, Robert Lee
- Graduate Program:
- Engineering Science and Mechanics
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- November 14, 2012
- Committee Members:
- Bernhard R Tittmann, Thesis Advisor/Co-Advisor
Clifford Jesse Lissenden Iii, Thesis Advisor/Co-Advisor
Mark William Horn, Thesis Advisor/Co-Advisor - Keywords:
- piezoelectric composites
ultrasound
sol-gel
low frequency - Abstract:
- Ultrasonic nondestructive evaluation is currently used in countless applications to maintain a system’s operational integrity. Piezoelectric transducers are the devices commonly used in this field to search for defects. A sol-gel fabrication method utilizing a spray-on deposition method has proven to produce ultrasonic transducers useful in harsh environments. This procedure produces thin film transducers, which adhere directly to a substrate making it favorable in use with irregular surface geometries. These transducers operate at relatively high frequencies due to their minute thickness. The objective of this research is to investigate the ability for low frequency operation into the low kilohertz range. Depositing thicker layers of piezoelectric composites, including bismuth titanate and lead zirconate titanate, led to adhesion problems between the metal substrates and ceramic material. Delamination of the piezoelectric elements was determined to be caused by a large mismatch in thermal expansion coefficients. Adaptations were made to the stainless steel substrates being used in order to overcome this problem. Additionally, invar substrates were used to greatly decrease the mismatch in thermal expansion coefficients between the substrate and ceramic composite. Fabricated samples were found to operate efficiently as longitudinal transducers at frequen- cies well into the low kilohertz range. Transducers were tested in modes of pulse-echo and through-transmission, acting as both the transmitter and receiver. The results presented in this thesis show that sol-gel spray-on fabricated transducers have the ability to operate effectively at frequencies as low as 250 kHz.