Technician Support for Geoscience Research in Transmission Electron Microscopy

Arizona State University, Scottsdale AZ

Investigators

Abstract

0113345 Buseck This grant provides partial salary support for an electron microscopist who will help maximize the geological, mineralogical, and geochemical capabilities of two TEMs that will be installed in 2001 within the ASU Center for High Resolution Electron Microscopy. These instruments were obtained to develop new techniques and measurements in materials science and physics, and the goal of the new position is to become familiar with those techniques and adapt them for research in the geological sciences. One of the instruments will have an electron beam that can be made less than 0. 2 nm in diameter. We will use this capability to analyze grain boundaries, dislocation cores, and surface layers on the atomic scale and will obtain crystallographic data from within unit cells through electron nanodiffraction. The other instrument will contain a Gatan imaging filter for measurements that will allow elemental mapping on the sub-nanometer scale. It will also have an environmental cell for studies under controlled atmospheres. This cell will maintain a relatively high gas pressure of up to 50 torr in the sample chamber, while retaining the high-resolution capabilities of the TEM. Specimen heating and dynamic image recording will allow chemical reactions to be followed at close to the atomic scale. We will use this to study minerals that are unstable in the vacuum of the electron microscopes. These include clay minerals, the green rusts, gypsum and related hydrated sulfates as well as dehydroxylation reactions and valence changes in minerals. ***