Department of Materials Science and EngineeringCellulose Nanocrystals (CNC) have been regarded as a versatile precursor for carbon nanomaterials. CNC can be converted into carbon materials by hydrothermal treatment and subsequent carbonization process. Due to high crystallinity and structural regularity of CNC, carbonized CNC would give well-ordered graphitic structure compared to other cellulose-based carbon materials. In chapter 2, carbonization study of CNC covers the effect of heat treatment conditions on the structural development mechanism of CNC over the range of carbonization temperature from 1000 to 2500 oC. We have conducted experiments to study the effect of oxidative stabilization process on the structural development of CNC-based graphite. Compared to the carbonization mechanism of pristine CNC, stabilized CNC was prepared by heat treatment at 250 oC for 1hr. In addition, the resultant graphitic structure of carbonized cellulose nanocrystals was systemically analyzed by transmission electron microscopy, x-ray photoelectron spectroscopy, and Raman spectroscopy. TEM data clarified that carbonized CNC prepared from stabilized samples (S-cCNC) gave rise to more highly ordered graphitic structure with little distortion site and defect points compare to D-cCNC over the whole temperature range of carbonization. Structural development mechanisms of both C- and S-cCNCs were systematically traced by Raman spectroscopy. Peak fitting results of Raman spectra evidenced structural conversion from disordered carbon to the graphitic structure.
In chapter 3, PES/CNC composite fibers were prepared by dry-jet wet spinning and their morphology and tensile properties were characterized. CNC with high Young???s modulus, crystallinity and aspect ratio can be regarded as a nano-size reinforcing agent. Dispersion of CNC was investigated by Dynamic Light Scattering (DLS) and Scanning Electron Microscopy (SEM). Upon using bath-type sonication with a power of 20 J/s, 48 hr sonication time was required to obtain well-dispersed CNC phase in N,N-Dimethylacetamide (DMAc). Experimental results showed that the tensile modulus of PES/CNC1 composite fibers were 4.7 GPa about 17% higher than control PES fibers.clos
