MSE PhD Proposal - Youngho Jin

Thursday, November 12, at 10 a.m.

Room 3515 MRDC

Committee:

Prof. Rosario Gerhardt, Advisor, MSE

Prof. Arun Gokhale, MSE

Prof. Seung Soon Jang, MSE

Prof. Mark D. Losego, MSE

Prof. Rao Tummala, ECE/MSE

Dr. P. Markondeya Raj, ECE

Title: Composites Containing Percolated Networks and/or Core-Shell Structures Useful for Microsystems Applications

Polymer matrix composites (PMCs) can have percolated networks of fillers or uniform core-shell structures depending on the fabrication process. PMCs with electrical percolation networks can be useful for applications such as sensors, EMI shielding, electronic-nose devices and novel interconnects, while PMCs with dielectric core-shell structures can be useful for applications such as embedded capacitors, gate dielectrics, energy storage devices and electromechanical transducers. In this proposed research, experimental and computational experiments have been conducted. First, electrical percolation in self-assembled polymer matrix conductive composites consisting of poly(methyl methacrylate) (PMMA) and antimony tin oxide (ATO) nanoparticles was investigated. The nanocomposites were fabricated by mechanical blending combined with compression molding. The matrix PMMA was transformed into space filling polyhedra and the ATO nanoparticles were distributed along the sharp edges of the matrix, forming a 3D interconnected network. Percolation was achieved at a very low ATO content (0.18 vol %). A parametric finite element approach was chosen to model this unique microstructure-driven percolation behavior. Good agreement was obtained between the experimental results and the modeling results. The simulation model developed is applicable to many different kinds of insulator-conductor composite systems and can be used to predict percolation threshold and final electrical conductivity. The effects of processing conditions in the conductive PMCs will be further investigated to improve percolation behavior. Second, a core-shell microstructure in a polymer matrix dielectric composite consisting of poly(vinylidene fluoride) (PVDF) and barium titanate (BaTiO3) was investigated. Composites with high dielectric permittivity and low dielectric loss were fabricated by a miscible/immiscible coagulation method combined with compression molding to evenly distribute nanoparticles in the polymer matrix at all length-scales. The effects of nanofiller types, distribution, and morphology in the dielectric PMCs will be investigated to improve dielectric properties. Impedance spectroscopy was used to examine the electrical and dielectric properties of both types of polymer matrix composites and to reveal interesting dependences on the size and shape of the nanoparticles used.