Over the past decade, a significant part of Guduru’s work has focused on coupled mechanics-chemistry problems, primarily (a) heterogeneous catalysis, (b) electrochemical energy storage materials (e.g. lithium ion battery materials) and (c) energetic materials. The distinguishing features of these problem areas are that (a) the chemical reaction rates are influenced significantly by the mechanical deformation fields; (b) mechanical failure of the constituent materials plays an important role in determining the electrochemical/chemical performance and life of the systems; and (c) the mechanical response of the materials is modified significantly by the progression of the chemical reactions. Guduru’s lab has developed in situ diagnostic techniques to measure the relevant mechanical fields and the chemo-mechanical coupling effects in real time during the electrochemical/chemical reactions.
In heterogeneous catalysis, Guduru has performed systematic and precise measurements of the influence of stress (alternatively, elastic strain) on catalytic activity in electrochemical and gas phase reactions of technological importance; in collaboration with atomistic computational colleagues, they showed that density functional theory calculations of the effect of the stress on controlling parameters such as the adsorption energy of the intermediate species not only agree with the experimental results, but can also be used in catalyst design.
In case of energy storage materials, Guduru has developed experimental methods for systematic investigation of a variety of important chemo-mechanical phenomena in electrode materials in real time. These include evolution of stress and mechanical properties during electrochemical cycling, stress-potential coupling, kinetics of propagating phase boundaries, mechanical and fracture behavior of solid electrolyte interphase (SEI).
The coupled chemo-mechanical behavior of energetic materials is a growing area of activity in Guduru’s lab. Since the relevant phenomena of interest in these materials such as strain localization, hot spot formation and initiation of burn fronts from the hot spots occur at extremely small time and spatial length scales, the lab has developed the necessary diagnostic techniques to image these phenomena at the relevant scales. Guduru lab has developed a novel high-speed visible microscopy technique with simultaneous time and spatial resolutions of 250 ns and 0.6 micron respectively – in order to measure the deformation fields associated with strain localization events such as adiabatic shear bands and shock induced pore collapse. The lab is developing a unique high-speed infrared (IR) microscope system capable of imaging temperature fields in dynamically deforming materials at sub-microsecond time resolution and diffraction limited spatial resolution. Together these high speed diagnostic techniques enable a systematic investigation of the hot-spot formation mechanisms in controlled geometries in the subsequent work.
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