GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Thursday, December 5, 2019

11:00 AM
in MRDC 3515

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Morgan Watt

"The Effect of Processing on the Electrical and Morphological Properties of Bulk and Thin Film Anisotropic Filler Composites"

Committee Members:

Prof. Rosario Gerhardt, Advisor, MSE

Prof. Kyriaki Kalaitzidou, ME

Prof. Jonathan Colton, ME

Prof. Satish Kumar, MSE

Prof. Jud Ready, MSE

Abstract:

The overall objective of this study is to determine the effect of processing on the electrical and morphological properties of anisotropic filler composites. The processing method used to make a composite is extremely important and can strongly affect the percolation point, maximum conductivity, and microstructure among other properties. Therefore, creation of models that explain and connect the electrical and morphological data would have an impact on creating composites reliably and improve the knowledge base on how best to tailor composites for a given application.

The first objective is to determine the effect of different fabrication methods on CNT/PMMA composites. This was done using mechanical, solution, and melt mixing. Both solution and melt mixing are common mixing methods whereas mechanical mixing is less explored. The methods resulted in three very different microstructures. For bulk samples, mechanical mixing achieved conductivity at a much lower concentration than melt or solution mixing. Thin film samples of the same mixtures will also be made. The second objective is to create SiCw/glass composites both in thin film and bulk form using a custom hot pressing setup and spark plasma sintering, respectively, and their microwave properties will be tested.

The last three objectives are more in depth analysis of the composites. The third objective is to fit equivalent circuits to the electrical data. This has been done for CNT/PMMA bulk samples and shows the progression of the equivalent circuits with increased concentration and conductivity. The fourth objective would involve using Iso2mesh, which was created by the U.S. Army. This program takes the experimentally obtained microstructures and converts them into a usable mesh for COMSOL modeling of the electrical data matched to the specific composite microstructures. Therefore, combining the morphological and electrical data will allow better understanding of how the microstructure affects the electrical properties. The last objective will be to use small angle scattering (SAS) to quantify the features of the CNT/PMMA composites. This will allow us to analyze the microstructure further by fitting the data to the electrical models which will help quantify values such as agglomeration, interconnectivity, distance between fillers and lay out the groundwork for understanding other properties in these types of materials.