*********************************
There is now a CONTENT FREEZE for Mercury while we switch to a new platform. It began on Friday, March 10 at 6pm and will end on Wednesday, March 15 at noon. No new content can be created during this time, but all material in the system as of the beginning of the freeze will be migrated to the new platform, including users and groups. Functionally the new site is identical to the old one. webteam@gatech.edu
*********************************
THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING
GEORGIA INSTITUTE OF TECHNOLOGY
Under the provisions of the regulations for the degree
DOCTOR OF PHILOSOPHY
on Monday, May 20, 2019
1:00 PM
in Love 210
will be held the
DISSERTATION DEFENSE
for
Ke Qiu
"Cellulose Nanocrystal/Polymer Nanocomposites: Processing Strategies, Structure Variation and Explored Applications"
Committee Members:
Prof. Karl Jacob, Advisor, MSE
Prof. Hamid Garmestani, MSE
Prof. Donggang Yao, MSE
Prof. Preet Singh, MSE
Prof. Kyriaki Kalaitzidou, ME
Abstract:
Interest in the most ubiquitous and abundant organic compound—cellulose, harvested from the forest product, has increased notably over recent decades. This bio-based material has been used essentially in bio-composites or in the paper industry; mainly due to its high mechanical reinforcement ability or barrier property respectively. Its nano-scale dimensions and its capacity to form a strong entangled nanoporous network have encouraged the emergence of new high-value applications. The principle reason to utilize cellulose nanocrystals (CNCs) and cellulose nanofibrils (CNFs) as a reinforcing material is that we can potentially exploit the high crystal modulus of cellulose as well as the ability to chemically modify their surface structure. Its high stiffness arises from the hydrogen bond networks formed on the glucose residues from one chain with oxygen molecules on another chain. By selecting the appropriate polymer of choice, the polymer matrix will be bonded strongly with cellulose.
The first part of this thesis is to compare different processing strategies to overcome the critical challenge of use CNC in composite, which is related to their homogeneous dispersion within a polymer matrix. Different solvent-assisted routes to improve CNC dispersion in the epoxy-based composite were assessed. The optical, thermal, mechanical properties of the epoxy resin with different hardener structure were investigated. It was found the compatibility of CNC in polymer matrices will strongly affect its reinforcing properties.
The second part of this thesis is exploring new applications for CNCs, which is one of the significant efforts required in the Agenda 2020 nanocellulose roadmap. A low cost, biodegradable polyelectrolyte membrane with promising potential in green power generation was fabricated using the nanocellulose based nanocomposite. A highly compatible polymer matrix PVA was used to produce nanocomposite with high CNC loading. The PVA/CNC based film was chemically modified to fabricate polyelectrolyte membrane. The hydration, electrochemical and barrier performance of the crosslinked membrane were conducted to develop an understanding of the novel low dimensional proton conductor as fuel cell electrolyte for the direct methanol fuel cell application.
