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Abstract

We aim to develop a fundamental understanding of materials dynamics (from {micro}s to ns) in systems where the required combination of spatial and temporal resolution can only be reached by the dynamic transmission electron microscope (DTEM). In this regime, the DTEM is capable of studying complex transient phenomena with several orders of magnitude time resolution advantage over any existing in-situ TEM. Using the unique in situ capabilities and the nanosecond time resolution of the DTEM, we seek to study complex transient phenomena associated with rapid processes in materials, such as active sites on nanoscale catalysts and the atomic level mechanisms and microstructural features for nucleation and growth associated with phase transformations in materials, specifically in martensite formation and crystallization reactions from the amorphous phase. We also will study the transient phase evolution in rapid solid-state reactions, such as those occurring in reactive multilayer foils (RMLF). Program Impact: The LLNL DTEM possesses unique capabilities for capturing time resolved images and diffraction patterns of rapidly evolving materials microstructure under strongly driven conditions. No other instrument in the world can capture images with <10 nm spatial resolution of interesting irreversible materials processes such as phase transformations, plasticity, or morphology changes with 15 nsmore » time resolution. The development of this innovative capability requires the continuing collaboration of laser scientists, electron microscopists, and materials scientists experienced in time resolved observations of materials that exist with particularly relevant backgrounds at LLNL. The research team has made observations of materials processes that are possible by no other method, such as the rapid crystallization of thin film NiTi that identified a change in mechanism at high heating rates as compared to isothermal anneals through changes in nucleation and growth rates of the crystalline phase. The project is designed to reveal these fundamental processes and mechanisms in rapid microstructure evolution that form the foundation of understanding that is an integral part of the DOE-BES mission.« less