A bond stiffness study of sol-gel spray-on transducers

Open Access
Author:
Orr, Alison D
Graduate Program:
Acoustics
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
November 21, 2014
Committee Members:
  • Bernhard R Tittmann, Thesis Advisor
Keywords:
  • sol-gel
  • transducers
  • non-destructive evaluation
  • LTspice
  • COMSOL
  • bismuth titanate
  • PZT
  • composite
Abstract:
Ferroelectric thick films (> 10 µm) are of great interest in the medical, automotive, aerospace and military industries. These thick films can be fabricated in a variety of ways, but this work focuses on the sol-gel spray-on fabrication technique. Bis- muth titanate powder is suspended within a lead zirconate titanate (PZT) sol-gel solution. The use of this a composite ceramic allows the transducer to have the high temperature capabilities of bismuth titanate, and the high response capabili- ties of PZT. These properties make this composite desirable for high temperature applications. Another important property of sol-gel spray-on transducers is that acoustic coupling material, such as ultrasonic gel, is not required; the ceramic is sprayed directly onto the substrate and left in place. This work focuses on understanding the unique bond between transducer and substrate, in particular, characterizing the transmission of ultrasonic waves through such an interface. The objective of this thesis is to theroretically and experimentally investigate the effect of the bond stiffness on the transmission of ultrasonic waves. This thesis utilizes LTspice and COMSOL Multiphysics to analyze the acoustic wave propagation between a transducer and a substrate as a function of bond stiffness. These theoretical results are compared to experimental pulse-echo data for the sol-gel spray-on, gel and silver bonds. These results show that as bond stiffness increases, ultrasonic transmisssion follows.