Date of Award

2018-01-01

Degree Name

Doctor of Philosophy

Department

Mechanical Engineering

Advisor(s)

Tzu-Liang B. Tseng

Second Advisor

Yirong Lin

Abstract

The goal of this research is to develop novel 3D printing process and design nanocomposites for piezoelectric and dielectric devices using fused deposition modeling (FDM) and stereolithography (SL) 3D printing techniques for use in sensor and energy storage applications. Techniques for electric and corona assisted in-situ poling during 3D printing were developed to improve the piezoelectric property and ease of manufacture. Poly(vinylidene fluoride) (PVDF) and barium titanate (BaTiO3, BT) are well-known for their high piezo- and dielectric constants among polymers and ceramics, while multi-walled carbon nanotubes (CNTs) were introduced to improve efficiency of stress reinforcement and conductivity for charge carriers between the two. It was investigated that filament extrusion and FDM 3D printing processes provide homogeneous dispersion of nanoparticles, removal of internal defects, and alleviation of nanoparticles' agglomeration in polymer matrix which enhance piezoelectric and mechanical properties than traditional solvent-casting. Increasing both BT and CNTs nanoparticles improves both piezoelectric and dielectric properties as well as mechanical toughness, while CNTs have a threshold at each property where increasing content switched from improving their properties to being conductive. The best combination for the maximum output current/voltage (±1 nA/340 mV) and piezoelectric coefficient (0.65 pC/N) while subjecting the materials to cyclic loads at 40 N were obtained at 0.4wt.%-CNT/18wt.%-BT/PVDF. Moreover, the best mixture of relative dielectric constant and loss properties (118 and 0.119) was obtained for the nanocomposites containing 1.7wt.%-CNT/45wt.%-BT/PVDF. In mechanical testing results, BT and CNTs nanoparticles played a significant role of improving toughness of 3D printed nanocomposites, highest tensile strength (24.2 MPa) and strain (579%) were obtained at 1wt.%-CNT/12wt.%-BT/PVDF. An effective and scalable 3D printing techniques for the manufacture of piezoelectric and dielectric nanocomposites was demonstrated.

Language

en

Provenance

Received from ProQuest

File Size

179 pages

File Format

application/pdf

Rights Holder

Hoejin Kim

Download

Share

COinS