(Georgia Institute of Technology, 2016-07-18)
Liu, Chunzi
Many bright colors in nature are generated by the optical effects of biological structures. These intricate structures, combined with the absorption and reflection effects of the chemical pigments within, provide the observed color with high visibility and some other startling optical properties. A prominent example comes from the iridescent colors observed on the wing scales of Morpho, a family of subtropical butterflies. Iridescent color refers to the color which changes with varying viewing angle. It is proposed that a layered structure alternating in refractive indices produces the observed colors on the butterfly wing scales, but this generalized idea does not explain some optical effects observed through a variety of methods. This research suggests that the structures in the lower lamina also contributes to the macroscopic optical effects. The observation methods used in this research include optical microscopy, spectroscopy, integrating sphere analysis, and scatterometry. The scatterometry visualizes the far field optical effects from all viewing angles simultaneously. Elementary explanations are proposed for the unexpected patterns observed in the experiments.
(Georgia Institute of Technology, 2016-05)
Hong, Junghwa
Spherical porous carbon particles find applications in gas storage, biological and medical
sorbents, energy storage devices and other demanding applications. At the same time, the common
routes for their synthesis are elaborate and costly. Here we report on our study of a low-cost
synthesis of spherical carbons with uniform and tunable diameter. The application of a lowtemperature
hydrothermal process greatly accelerates the rate of cross-linking within polymer
precursors, allowing formation of individual spherical carbon particles upon subsequent polymer
carbonization. By reducing the precursor concentration we have demonstrated particle size
reduction from 1,250 to 140 nm. The as-produced particles exhibit disordered microstructure with
very smooth particle surface and open internal micro-porosity.