TEM studies of augite (100) deformation twinning boundaries, quartz sand coatings, and manganese valence state.

摘要

This thesis mainly addresses characterization of earth and environmental materials using a wide range of electron microscopy methods, among which high-resolution transmission electron microscopy (HRTEM), electron energy-loss spectroscopy (EELS), and EELS-based energy-filtered transmission electron microscopy (EFTEM) are highlighted.;HRTEM and EFTEM reveal that not only atomic structures change but also chemical variations occur at augite (100) deformation twinning boundaries. These results also suggest that other proposed structure models of twin boundaries in complex inorganic solids are oversimplified. Real twin boundaries may be complicated, involving structural and chemical variations compared to those of the host.;Quartz grains are commonly armored with micro-scale thickness coatings in aquifer environment. Rigorous characterization of these coatings using TEM needs a suitable sample preparation protocol. Focused Ion Beam (FIB) technique makes this type of work not only possible, but routine. Mineral phases in the coating, their textural relationship, and the interface structure between quartz and its associated coating is examined in detail.;Determination of Mn valence state ranging from Mn2+ to Mn4+ using Mn L2,3 electron energy-loss near-edge spectra is studied systematically. Different methods, including I(L3 )/I(L2) intensity ratio vs. Mn valence state, Gaussian peak fitting of Mn L3 peak, and multiple linear squares fitting of both Mn L3 and L2 peaks, are tried to get the best result. In addition, oxygen K edges for Mn oxides are discussed in terms of their dependence on crystal structures.