Characterization of particles created by laser-driven hydrothermal processing

This study examined particles created by laser-driven hydrothermal processing, an innovative technique used for the ablation of submerged materials. Two naturally occurring materials, obsidian and tektite, were used as targets for this technique. Characterization of sample materials before and after laser processing was conducted through multiple techniques such as optical microscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy dispersive X-ray spectroscopy. Examination of the untreated base material, in bulk and crushed form, established a baseline for comparison to particles created by laser processing of the same material. Characterization methods provided data of micron- and nano-sized particles, including their crystal structure, microstructure, and chemical composition. The bulk and crushed obsidian and tektite samples contained inclusions and particles rich in several transition elements, most notably iron and titanium. Analysis of liquid media collected after laser processing of bulk obsidian and tektite samples revealed fine particles rich in the same elements. Evidence suggests laser-driven hydrothermal processing separates heavy elements from the mostly amorphous silica matrix encountered in the materials examined.http://archive.org/details/characterization1094549424Lieutenant Commander, United States Coast GuardApproved for public release; distribution is unlimited