CHARACTERIZATION OF SOME PYROLYZED POLYCARBOSILANES BY TRANSMISSION ELECTRON-MICROSCOPY

Four different polymers were pyrolyzed up to 1000 degree C. The techniques of transmission electron microscopy (TEM) use one of all the scattered beams emitted by the specimen, selected by a suitable objective aperture displaced relative to the selected area electron diffraction (SAD) pattern. The regions emitting a given beam or portion of a diffraction ring appear in the image as bright domains in a dark field. The various radial positions of the aperture used are indicated. In position 1 turbostratic carbons and various forms of silica can be imaged in DF; SiC is excluded. In position 2, a crystalline SiC 111 DF image is formed, superimposed to a weak carbon 10 DF image. In position 3, only SiC crystals can be imaged. If the material is amorphous, small and faintly bright dots appear for any aperture centering and any focusing value. They correspond to the statistical distribution of couples of atoms within the specimen. 11 Refs.