Transmission electron microscopes are a valuable scientific tool for observing the properties of materials. In a TEM, a beam of electrons is passed through a material. The interactions are recorded and provided to the operator. These microscopes are highly precise and can magnify materials down to the atomic level.
Transmission electron microscopes were created back in the 1930s when it was realized that optical microscopes would be limited by the optics available. Electron microscopes have evolved ever since then. At this point, individual atoms can be observed when placed on a carbon substrate.
In a TEM, a voltage is applied to a tungsten filament. Electrons will be emitted into a vacuum chamber which are focused using electromagnets. By varying the voltage applied to the filament, the magnitude of strength of the electron beam can be varied and, as a result, magnification changed.
By observing materials on this level, it is possible to search for preexisting flaws or signs of deformation. The crystalline lattice structure of a material can be observed for signs of stress. It is also possible to observe metals for signs of creep in order to better understand how often a piece of mechanical equipment should be inspected. A good example of this would be in an aging turbine system with tight rotor blade tolerances. Casing inspections are time consuming and expensive. Performing it too often debilitates the system’s effectiveness while not often enough could lead to catastrophic failure.
Photo credit: David Morgan