THE SCHOOL OF MATERIALS SCIENCE AND ENGINEERING

GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Wednesday, June 12, 2019

2:00 PM
in Love 210

will be held the

DISSERTATION PROPOSAL DEFENSE

for

Yi Li

"Investigation of Surface Chemistry and Reaction Mechanisms in Atomic Layer Deposition Modified Cellulosic Materials"

Committee Members:

Prof. Mark Losego, Advisor, MSE

Prof. Robert Moon, MSE

Prof. Christopher Luettgen, ChBE

Prof. Meisha Shofner, MSE

Prof. Kyriaki Kalaitzidou, ME

Abstract:

Cellulosic materials have been widely used in our daily life for paper products and functional polymers. Recently, nanocellulose is getting more attention because of its chiral structure, high mechanical strength, high aspect ratio and high surface areas. Nanocellulose, including cellulose nanocrystal and cellulose nanofibrils, has been used in biomaterials, battery electrodes, three-dimensional aerogels, optical films, and liquid crystal sensors. However, cellulose has a high density of hydroxyl groups that create strong intra-/inter- fiber hydrogen bonding and makes cellulose hard to dissolve and disperse in nonpolar solvents and hydrocarbon polymer matrices. Traditional methods to functionalize cellulose include surface modification or regeneration. Atomic layer deposition (ALD) is a well-known technique for nanofilm preparation that is extensively used in microelectronics and optical device manufacturing. The advantages of using vapor phase processing like ALD instead of liquid phase is: (1) gas phase can penetrate into complex fiber structure, forming a uniform modification; (2) gas phase processing can avoid using liquid chemicals and the waste disposal issue; (3) gas phase modification is more time efficient and cost effective than wet chemistry process. ALD is also compatible with cellulosic materials because it can be conducted at low temperatures that do not damage the cellulose.  ALD also features self-limiting reactions that permit conformal modification of complex structures with high aspect ratio, including fibrous paper and nanopaper.

My proposed research will focus on: (1) cellulose depolymerization as a function of TMA precursor exposure time and reaction temperatures; (2) property change of ALD reacted cellulose, mainly focus on dry strength, wet strength and surface chemistry of modified cellulose as function of reaction temperature and precursor chemistry; (3) freeze-dried aerogel nanocellulose will be ALD treated with different precursors, then study about the compressive strength change as a function of precursor chemistry and ALD cycles, also explore the wettability change of ALD treated and ‘ALD + post heat’ nanocellulose aerogel.