Seminar

Nigel Browning
Fundamental & Computational Sciences Directorate
Pacific Northwest National Laboratory
Richland, WA

October 9, 2015

The last few years have seen a paradigm change in (scanning) transmission electron microscopy ((S)TEM) with unprecedented improvements in spatial, spectroscopic and temporal resolution being realized by aberration correctors, monochromators and pulsed photoemission sources. Spatial resolution now extends to the sub-angstrom level, spectroscopic resolution into the sub-100meV regime and temporal resolution for single shot imaging is now on the nanosecond timescale (stroboscopic imaging extends this even further to femtoseconds). The challenge now in performing experiments in an (S)TEM is to implement the in-situ capabilities that will allow both engineering and biological systems to be studied under realistic environmental conditions. Performing experiments using in-situ stages or full environmental microscopes presents numerous challenges to the traditional means of analyzing samples in an electron microscope – we are now dealing with the variability of dynamic process rather than a more straightforward static structure. In this presentation, I will discuss the recent developments in the design and implementation of in-situ stages being pursued at the Pacific Northwest National laboratory (PNNL). Examples of the use of these capabilities for the direct imaging of interfaces and defects, to identify the fundamental processes involved in nucleation and growth of nanostructures from solution, and to investigate the electrochemical processes taking place in next generation battery systems will be presented. As the in-situ stages have been designed to be incorporated into both high spatial resolution aberration corrected (S)TEM as well as into high temporal resolution Dynamic TEM (DTEM), the potential for future experiments to study fast dynamics, including those in live biological structures, will also be discussed.

Karl T. Mueller
Laboratory Fellow, Physical and Computational Sciences Directorate, Pacific
Northwest National Laboratory, Richland, WA 99352
Professor, Department of Chemistry, Penn State University, University Park, PA
16802

Nuclear magnetic resonance (NMR) is a powerful tool for investigating complex systems especially when we are fortunate enough to have sensitivity, selectivity, resolution, and available spectrometer time working in our favor. However, we are not always so fortunate. With many collaborative friends and colleagues, we are able to take both simple and complicated NMR experiments and apply them to solve difficult problems in materials and chemical sciences. My research teams at PNNL and Penn State have applied solid-­‐ and solution-­‐state NMR studies to problems in materials, energy, and environmental sciences, especially focusing on the nature of reactive sites on surfaces and solvation dynamics in battery electrolyte systems. Where sensitivity concerns are present, the use of nuclides such as 31P and 19F (or even 13C in enriched probe molecules) and the employment of methods such as “surface-­‐selective” cross-­‐polarization have provided quantification and identification of reactive sites. In addition, the use of pulsed-­‐field-­‐gradient diffusion methods for measuring translational motion reveals key features of ion solvation that control performance in multi-­‐component battery electrolytes. These ideas and
related NMR methods can then be used to probe dynamics or kinetics, and examples will be provided where the exceptional information content provided by NMR experiments, combined with both quantum chemical and classical molecular dynamics simulations, proves critical for addressing complex problems.

Date: October 9, 2015
Presenter: Nigel D. Browning
Organization: Pacific Northwest National Lab
Title: In-Situ (S)TEM/DTEM: From High Spatial Resolution to High Temporal Resolution Link to Abstract