RESUMO
High-resolution electron microscopy (HREM) was used to detect the surface Fe3O4 iron-oxide layer formed on [011] Fe4N iron nitride due to electron irradiation in the transmission electron microscope. The existence of a surface oxide layer was confirmed by both image processing and through-focus observation. Images of the iron oxide were revealed using the process of fast Fourier transformation (FFT) of experimental HREM images, filtering of the FFT patterns and inverse FFT. By through-focus observation, HREM images of iron oxide were obtained based on the tuning of contrast transfer function. Fourier filtering is effective for examining the beginning of phase transformation, because at this stage the diffraction spots of iron oxide are too weak to be detected. At the time when the iron oxide layer has developed to some extent, through-focus observation is useful to obtain an image of oxide layers.
RESUMO
High-resolution transmission electron microscopy images of room-temperature fluid xenon in small faceted cavities in aluminum reveal the presence of three well-defined layers within the fluid at each facet. Such interfacial layering of simple liquids has been theoretically predicted, but observational evidence has been ambiguous. Molecular dynamics simulations indicate that the density variation induced by the layering will cause xenon, confined to an approximately cubic cavity of volume approximately 8 cubic nanometers, to condense into the body-centered cubic phase, differing from the face-centered cubic phase of both bulk solid xenon and solid xenon confined in somewhat larger (>/=20 cubic nanometer) tetradecahedral cavities in face-centered cubic metals. Layering at the liquid-solid interface plays an important role in determining physical properties as diverse as the rheological behavior of two-dimensionally confined liquids and the dynamics of crystal growth.