ENGINEERING 232 - Engineering of Materials
Analytical electron microscopes are used in
the microcharacterization of materials. The
scanning electron microscope
(SEM) makes possible the study of the fine structure of surfaces, while the
transmission electron microscope (TEM) yields data about internal structure
and composition. Each instrument may be used in multiple modes to result in
different but complementary data from the same material.
LAB I: SEM
Click on the picture to see SEM micrographs of
surface of the broken ends of metal slugs of various
compositions. The slugs were prepared during a lab session demonstrating
mechanical properties of materials using the Instron to stretch the slugs to
their breaking point. The SEM reveals that the materials have different
microstructure that, in part, accounts for their different behavior under
LAB II: TEM and X-ray energy dispersive spectroscopy (EDS)
on the picture to see TEM micrographs showing cross-sections of the fractured
metals described above. The TEM yields brightfield
images that show internal structures, darkfield
images that indicate corresponding crystalline materials,
diffraction patterns showing the arrangement of the
crystal planes, and lattice images showing the
spacing between the rows of atoms making up a crystalline material.
on the picture to see EDS spectra from the metal samples showing their elemental
A problem resolved by TEM and x-ray EDS.
is a commonly-occurring environmental hazard. According to government
regulations, both elemental and compositional analyses, at a level satisfied only by
the use of TEM coupled with EDS, are mandated by law before an area may be
declared environmentally safe from asbestos contamination. Click on the image to
view examples of these complementary data types.