Date of Award

Winter 2007

Project Type

Thesis

Program or Major

Mechanical Engineering

Degree Name

Master of Science

Abstract

Geometrically complex, high aspect ratio microstructures and limited aspect ratio nanostructures have been successfully fabricated in supercooled Bulk Metallic Glass (BMG) substrates by molding against patterned Silicon and Silicon dioxide substrates. However, demand exists for similar metallic substrates with high aspect ratio, nanoscale features. Van Der Waals based interfacial energies between the supercooled liquid BMG and the Silicon cavity may represent a substantial obstacle to the direct scaling of the molding process to the nanoscale. In an effort to investigate these effects, experiments were conducted using molds of various compositions: Silicon, SiO2 and SiO2 coated with Gold. The Gold coating failed to impact molding performance due to the thin layer deposited. However, drastically superior results were obtained by using a Silicon mold possibly because of the variation in interfacial interaction between the BMG and the mold material. In order to analyze the process, two theoretical models were developed. One model predicts the achievable aspect ratio of the molded features and was found to be in qualitative agreement with experimental results. The other model analyzes the BMG in the molding process as a squeezed viscous film. Finally, a value for the surface tension of Viterloy-1b within it's supercooled liquid state was deduced from experimental data.

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