Award Date

12-2011

Degree Type

Thesis

Degree Name

Master of Science in Physics

Department

Physics and Astronomy

First Committee Member

Michael Pravica, Chair

Second Committee Member

Andrew Cornelius

Third Committee Member

Stephen Lepp

Graduate Faculty Representative

Clemens Heske

Number of Pages

59

Abstract

We have performed mid- and far- Infra Red (IR) absorption, Raman spectroscopy, and angular dispersive x-ray diffraction (XRD) studies on melamine under high pressure and room temperature. We have verified the presence of two prior reported phase transitions, the first between 1-2 GPa, and the second between 7-9 GPa. We have also found evidence of a third unreported phase transition between 14-16 GPa, during which, there was a sudden disappearance of all low energy peaks (-1 ) in both the Raman and IR spectra. The far-IR peak movement experiences a discontinuity as the rate of peak movement suddenly changes. The XRD pattern shows a dramatic change in crystal structure between 11 and 16 GPa. We observed softening of the N-H symmetric and anti-symmetric vibrations with pressure, suggesting that intermolecular hydrogen bonding increases as the intermolecular distance decreases similarly to what was observed in TATB [20]. The molecular decompression data from core intra-molecular peaks of mid IR and Raman show complete reversibility, giving evidence that the melamine did not chemically decompose at high pressures. Melamine merits this investigation into its high pressure behavior as it has many similarities with some high explosives. The closest cousin to melamine is the secondary explosive TATB, which is in the same symmetry group D 3h [16]. Understanding the exact science of explosives is an extremely difficult process, therefore approaching the problem from the examination of a similar inert compound may help yield a better understanding of explosives and the novel routes to the synthesis of ultra-hard materials such as C 3 N4 .

Keywords

High pressure (Science); Explosives; Infra-red; Melamine; Raman spectroscopy

Disciplines

Biological and Chemical Physics | Condensed Matter Physics | Optics

Language

English


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