OPTICAL EXAMINATION

Microscopy

Microscopic inspection of a material under High magnification imagery in the micrometer scale can be used to observe the failure locations, defects, porosity, amongst others.

SEM/EDS

A scanning electron microscope (SEM) is used to image the surface of solid samples by scanning the surface with a highly focused beam of electrons. Secondary electrons are emitted and captured by a detector. The interactions of the atoms on the surface of the sample with these high-energy electrons produce a variety of signals that contain information pertaining to the surface topography and sample composition. The information provided by these signals reveals important sample characteristics such as texture, orientation of constituent materials, and crystalline structure. SEM analysis offers a wide range of magnifications, from 10 times to more than 500,000 times. The magnification is 250 times the magnification limit of a light microscope.

A SEM can be equipped with energy dispersive spectroscopy (EDS). X-rays are emitted along with the secondary electrons when bombarded with a high-energy focused beam of electrons. As these electrons interact with the surface atoms of the sample, X-rays are generated with an energy that is characteristic of the atoms that produced them. The intensity of these X-rays is proportional to the mass fraction of the element in the sample. A solid-state spectrometer converts the detected X-rays to electrical signals proportional to the characteristic X-ray energies. When compared to a standard of known composition, the mass fraction of each element can be calculated. This analytical technique allows elemental composition of the sample to be determined.

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