An Interdisciplinary Study of Thermal Sprayed Volcanic Obsidian Powder

Abstract

At first glance, the fields of volcanology and thermal spray could not seem more different. One focuses on geological phenomena while the other studies the creation of coatings for a variety of applications. However, they both deal with materials at high stress, strain, and temperatures. This allows us to use thermal spray to study how volcanic materials behave under these conditions. This knowledge can be used to predict how volcanoes will erupt, if it will explode, and how the lava will flow. So far, we have used air plasma thermal spraying to deposit splats of obsidian (a common volcanic material) splats. The splats have been analyzed using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and scanning white light interferometry (three dimensional surface mapping). Both the front and backs of the splats have been analyzed. Work is being done to calculate the strain rate of the splats during impact. This data, along with particle temperature and velocity at impact values will be used to put the observations of the splats in context. Spraying will be repeated at different temperatures and velocities so that a relation can be found between these two variables and splat strain rate and morphology. One of the end goals of the project is to find the temperature and strain threshold where the obsidian changes from exhibiting shear thinning to brittle fracture. This project will ultimately make progress in the fields of volcanology, thermal spray, and materials engineering.