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ADVANCED MATERIALS & PROCESSES •
MARCH 2014
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Optical microscopes —
Individual particles are
observed and their size is estimated. This
manual particle sizing is simple to perform,
but is tedious and time-consuming. In recent
years, optical microscopes evolved to include
cameras and motorized stages. By interfacing both
to a computer, automating the particle detection/siz-
ing process is possible. It is practical to routinely meas-
ure distributions consisting of thousands of particles
and sort them by size and shape. However, the chemi-
cal composition of the particles remains unknown.
Alternative method
Determining the elemental composition of these
microscopic particles helps define the contaminant’s
origin and provides concrete information that allows
manufacturers to conduct quality control analyses to
improve production processes. When a product
needs to be verified as suitably free of a specific kind
or class of particulate contaminant, such as a toxic or
abrasive material, other methods can waste time an-
alyzing benign materials in the sam-
ple. Integrated microscopy allows for
rapid search of large areas in a sample, target-
ing problem particles while disregarding empty space.
Scanning electron microscopy combined with
energy-dispersive x-ray spectroscopy (SEM/EDX)
provides efficient, accurate microanalysis that iden-
SEM image of a particle
lodged inside a fuel injector.