(Georgia Institute of Technology, 2016-02-09)
McDowell, Matthew T.
Dynamic materials processes such as phase
transformations, corrosion, and nucleation/growth can play key roles during operation of devices for electrochemical
energy storage and conversion; often, these processes are not well understood at the nanoscale. In situ experiments,
which involve characterization of materials under realistic electrochemical environments, can provide unique insight
into the operation of materials within devices. This talk will show how in situ transmission electron microscopy (TEM) and other ex situ techniques have revealed
important nanoscale transformation and degradation mechanisms in two different electrochemical systems, lithium‐ion
batteries and solar fuels devices. Together, the results demonstrate the importance of understanding materials behavior
in energy systems, and they provide guidelines for engineering improved electrochemical devices.
(Georgia Institute of Technology, 2008-06)
Lucas, Marcel; Leach, Austin M.; McDowell, Matthew T.; Hunyadi, Simona E.; Gall, Ken; Murphy, Catherine J.; Riedo, Elisa
The plastic deformation of a pentagonal silver nanowire is studied by nanoindentation using an atomic force microscope (AFM). AFM images of the residual indent reveal the formation of a neck and surface atomic steps. To study the microscopic deformation mechanism, the indentation force-depth curve is converted to an indentation stress-strain curve and compared to the tensile stress-strain curves predicted by the atomistic simulations
of pentagonal silver nanowires. The indentation stress-strain curve exhibits a series of yielding events, attributed to the nucleation and movement of dislocations. The maximum stress measured during nanoindentation (2 Gpa ) is comparable to the tensile yield strength predicted by atomistic simulations.