Text

theses

Piezoelectric sensors and actuators are needed for a wide range of applications from physiological measurement to industrial monitoring systems. Sensors that can be easily integrated with the host, while maintaining high sensitivity and reliability over a wide range of frequencies are not readily feasible and economical with homogenous piezoelectric materials. It is well known that two-phase piezoelectric-epoxy composites offer several benefits over their single phase counterparts, as the properties of the constituent phases combine to improve the range of applicability. However, the piezoelectric properties of these materials suffer from the electrically insulating properties of the epoxy matrix. The electrical properties of the matrix may be enhanced by including electrically conducting inclusions however, less is known about the mechanisms that drive the changes in these properties. Hence, this experimental investigation of sensor materials builds on the previous work in two-phase piezoelectric composites, where the aims are to understand the roles that specific fabrication parameters and inclusion composition play in determining the piezoelectric and dielectric performance the aforementioned composites. The materials under investigation will be comprised of Lead Zirconate Titanate, Epofix Cold-Setting Embedding Resin and multi-walled carbon nanotubes, i.e. the piezoelectric, epoxy and electrical inclusions respectively. Our work suggests that inclusion of MWCNTs enhances the piezoelectric and dielectric properties with increasing volume fraction below the percolation threshold. This work seeks to understand how the processing parameters: poling temperature, poling type and particle distribution influence the contact resistance, space charge double layer at the piezoelectric and conductor interfaces and electric field intensity at the piezoelectric boundary, which all ultimately dictate the piezoelectric and dielectric performance of the composite materials. Conventional solid oxide mixing, spin coating and deposition techniques will be used to fabricate the bulk and thick films. The piezoelectric and dielectric performance will be determined from the measurement of the piezoelectric strain coefficients, d33 and d31, dielectric constant, impedance and dielectric spectrum, dielectric loss tangent, and capacitance. These measurements will be correlated with inclusion size, shape, distribution, and surface morphology observations obtained from the scanning electron microscope (SEM) and transmission electron microscope (TEM).

ETD_5493

Ph.D.

Includes bibliographical references

by Sankha Banerjee

doi:10.7282/T3154FBH

ETD doctoral

The author owns the copyright to this work.