Nanoporous gold is an exciting topic that has been highly researched due to its potential in applications including sensing, catalysts, gas storage, and heat exchangers, made possible by its high surface area to volume ratio and high porosity. However, these applications tend to require a specific morphology, which is often difficult to control. In this work, significant strides have been made in tuning the morphology of nanoporous gold by studying the effect of different fabrication parameters on the ligament diameter, pore diameter, and ligament length, three characteristics which are most discussed in previous studies concerning nanoporous gold. This material also, generally shows a brittle behavior despite it consisting of a normally ductile constituent element, limiting many commercial applications. There have been multiple simulated studies on the tensile mechanical properties and the fracture mode of this material, but limited experimental tensile testing research exists due to technical difficulty of conducting such experiments with small fragile samples. We examine the tensile mechanical behavior of nanoporous gold with ligament sizes ranging from 10 to 30 nm using in situ tensile testing under an environmental scanning electron microscope (ESEM). A specially designed tensile stage and sample holders are used to deform the sample inside the ESEM, allowing us to observing both the macro and microscopic structure changes. Our experimental results advance our understandings of how porous structure influence the mechanical properties of nanoporous gold, and they also serve to increase the accuracy of future simulation studies that will take this material a step towards commercial use by providing a thorough understanding of its structural mechanical limitations. / MS / Nanoporous gold is a porous metal developed through acidic corrosive techniques. Pores generally range from 10 to 100 nm in diameter. The general fabrication process involves placing an alloy of silver and gold into nitric acid, in which silver will dissolve into the acid leaving gold behind. The gold atoms will rearrange themselves into a porous structure wherein the gold volume and the pore volume are completely interconnected. In this work the fabrication process was altered in several different ways, to affect the structure of the gold volume and the pore volume. The altered fabrication processes include amount of time in nitric acid, change of concentration of nitric acid, adding stirring to the solution, and adding temperature variation. The changes in the structure were measured and graphed. Nanoporous gold was also subject to an in situ tensile test in a scanning electron microscope to see the method of crack propagation. Using this information we can gain a further understanding of the structural properties and the mechanical strength of nanoporous gold.
| Identifer | oai:union.ndltd.org:VTETD/oai:vtechworks.lib.vt.edu:10919/91899 |
| Date | 25 January 2018 |
| Creators | Frei, Katherine Rebecca |
| Contributors | Materials Science and Engineering, Murayama, Mitsuhiro, Corcoran, Sean G., Reynolds, William T. Jr. |
| Publisher | Virginia Tech |
| Source Sets | Virginia Tech Theses and Dissertation |
| Detected Language | English |
| Type | Thesis |
| Format | ETD, application/pdf |
| Rights | In Copyright, http://rightsstatements.org/vocab/InC/1.0/ |
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