Intellectual merit Minerals at elevated pressure (P) and temperature (T) provide essential information about the interior of Earth and other planets. Knowledge of their properties and phase transitions under extreme conditions provides unique insights into seismic discontinuities, mantle plumes, mantle turnover, and other dynamic effects that occur inside planets. Transmission electron microscopes (TEMs) are the only instruments that provide the resolution needed to study high-P minerals at the atomic level. Current high-PT instruments require sample quenching, which unavoidably risks changing mineral structures and defects. With NSF grant EAR-0948535 on In-situ High-pressure Transmission Electron Microscopy Measurement"we are developing TEM methods for high-P research. We are utilizing the remarkable properties of closed graphitic cages (CGCs), including carbon nanotubes (CNTs) and nano-onions, both of which contract and thereby produce high interior pressures when bombarded by energetic electrons at elevated Ts. They thus permit using TEMs to study minerals at the atomic level while at elevated Ps. Controlled sample heating within a TEM is critical for the high-P measurements. However, it is highly challenging to obtain the required mechanical stability, minimal thermal drift, and rapid settle times, all within the small sample area of a TEM. The heating stages that were available when EAR-0948535 was written have recently been greatly superseded in thermal and mechanical stability, and thereby accuracy, by a totally new design for TEMs that is based on MEMS (micro-electro-mechanical systems) technology on tiny solid-state chips. This technology also permits analytical electron microscopy (AEM), including energy-dispersive X-ray spectroscopy (EDS), at elevated temperatures. Such analyses at high Ts were heretofore not possible in a TEM. MEMS heating systems have not yet been used in the earth sciences. The goal of the current proposal is to develop this method of heating within a TEM and its utilization for studying minerals at mantle conditions. We anticipate that the results of these developments will provide a significant improvement and expansion of high-P measurements. It will be possible, for the first time, to observe the structure, behavior, and properties of earth materials at atomic resolution in situ at the PT conditions in Earths lower crust and mantle. The results will provide fundamental new knowledge about the nature of geologically and geophysically important minerals at extreme conditions. Broader impacts of the proposed research Development of the new MEMS-based TEM heating stage and its applications will facilitate research that cuts across geophysics, mineral physics, and materials science, thereby contributing to cross-disciplinary interactions and ideas. The wide availability of TEMs in academic and industrial settings plus low-cost CGCs guarantee that this new technique will be readily transplantable to different fields and institutions. It will also promote public interest in high-P research since vivid TEM images of atomic resolution attract attention from the general public, including school children. Postdoctoral researchers and students from the US and other countries will be trained with rich hands-on experience at the established TEM facility at ASU. The results will be published in leading professional journals and disseminated through presentations and seminars at professional meetings and universities. The requested support will contribute to training of graduate students and postdoctoral researchers.
|Effective start/end date||3/15/13 → 2/28/15|
- National Science Foundation (NSF): $202,870.00