GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Tuesday, December 10, 2019

3:00 PM
in MRDC 3515

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Jyotsna Ramachandran

"Studies on Strong, Lowdensity, Porous Carbon Fibers from Polyacrylonitrile Based Blends and Copolymers"

Committee Members:

Prof. Satish Kumar, Advisor, MSE

Prof. Donggang Yao, MSE

Prof. Karl Jacob, MSE

Prof. Mary Lynn Realff, MSE

Prof. Paul Russo, MSE/CHEM

Prof. Sankar Nair, ChBE

Prof. Guoliang Liu, CHEM, Virginia Tech

Abstract:

High strength and high modulus carbon fibers are produced by carbonization of polyacrylonitrile (PAN) precursor fibers processed through gel spinning. Making these carbon fibers porous adds functionality to them but this also leads to a loss in their mechanical integrity. Imparting structural integrity to porous carbon fibers forms the core of this dissertation proposal. Porous carbon fibers from gel spun precursor, possessing high mechanical strength could create a spectrum of applications of lightweight, self-sustaining structural reinforcements with energy storage or filtering capabilities. One could envision the body of an aircraft or car made with porous carbon fiber that could store energy and lead to energy efficient smart vehicles. 

There are two approaches from the view of materials that are used in this study to achieve the desired fibers with mechanical integrity. The first approach explores the conditions to introduce porosity in carbon fibers produced by gel spinning of blends of PAN and sacrificial polymer. Sacrificial polymers including poly(acrylic acid) (PAA), poly(methyl methacrylate) (PMMA), poly(styrene-co-acrylonitrile)(SAN), are chosen based on their incompatibility for blending with the carbon source, PAN. Pore size, distribution and morphology in the carbon fibers are found to be dependent on factors including the choice of sacrificial polymer, blend ratio, solvent and coagulation conditions used for spinning, stabilization and carbonization conditions. The second approach involves the gel spinning of di-block copolymers containing PAN. The ratio and molecular weight of the di-block copolymers, in addition to the previously mentioned processing factors, play a huge role in determining the strength and morphology of the resulting fibers.

From the design structure of fibers, two different geometries for both the blends and the di-block copolymers, namely, the single component and the bi-component (core-sheath) are being studied. The bi-component fibers with a solid support structure provides mechanical strength to the porous network. The goal is to study the effect of the processing parameters and geometry to choose the optimal system of porous fibers without much loss in mechanical integrity. Different characterization techniques including, but not limited to, tensile testing, rheometer, thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), dynamic mechanical analysis (DMA), X-ray diffraction (XRD), scanning electron microscopy, are used to evaluate the structural property and performance of the  resultant porous carbon fibers.

The objective of this study is to produce gel spun porous carbon fibers that are strong, light and porous.