טכניון מכון טכנולוגי לישראל
הטכניון מכון טכנולוגי לישראל - בית הספר ללימודי מוסמכים  
M.Sc Thesis
M.Sc StudentOfer Rozent
SubjectElectrospinning and thermal processing of PZT nanofibers
mats for energy applications
DepartmentDepartment of Energy
Supervisors Full Professors Grader Gideon
Dr. Shter Gennady
Full Thesis textFull thesis text - English Version


Abstract

The demand and production of small-scale electronic devices is constantly growing. All these devices require individual, miniature and long-term power sources.  Usage of conventional batteries is limited due to their large size, short shelf life and frequent maintenance requirements. Piezoelectric materials can directly harvest energy from the environment by transforming mechanical energy into electrical one. PZT (Lead-zirconium-titanium oxide) based ceramics are known for their superior piezoelectric properties, making them an optimal choice for energy harvesting applications. It is suggested that piezoelectric nanofibers mats made form PZT can be integrated to the power chain of small-scale devices. Thus, the main objective of this research is the development of simple, efficient and low cost fabrication process for electrospun PZT nano-fibers mats suitable for integration into small-scale energy harvesting devices. The ceramic precursors in this work were lead bis(2-ethylhexanoate) (was replaced with lead acetate tri-hydrate for the second part of the research), zirconium n-propoxide, and titanium i-propoxide; while the polymer and solvent included polyvinyl-pyrrolidone (PVP), ethanol and acetic acid. After the electrospinning (ES), the PZT nanofibers mats are heated to form the piezoelectric phase. However, it was found that during heating, the electrospun mats undergo large shrinkage (~50%) and undesirable and uncontrolled deformation. The nanofibers mats’ deformation was studied and the main cause of the deformation was found to be a non-uniform relaxation of the PVP used in the electrospinning precursor solution. An optimal fabrication and thermal treatment process that overcomes this deformation effect is described. The effect of raw materials on the deformation was also studied and it was found that changing the lead source from lead bis(2-ethylhexanoate) to lead acetate tri-hydrate enabled the shortening of the thermal process and simplified the ES process. Moreover, lead acetate tri-hydrate is lighter (less influence during thermal treatment), cheaper and more environmentally friendly then lead bis(2-ethylhexanoate). Finally, a small-scale flexible energy harvesting device was fabricated by integrating a sintered PZT nanofibers mat into polydimethylsiloxane (PDMS) and connecting Cu electrodes.