Next: Imaging Processing Up:
Sample Preparation and Imaging Techniques
Previous: Sample Preparation
2.2 Image Acquisition
The specimen is placed in the SEM viewing chamber, and signals are
collected for the backscattered electrons and X-rays. Typical accelerating
voltage and probe current for the backscattered electron images are
12 kV and 2 nA, respectively. For the X-ray images, the probe current
is increased to about 10 nA. For cements, in addition to the backscattered
electron signal, X-ray images are collected for Ca, Si, Al, Fe, S, K, and Mg.
For fly ash, other X-ray signals may be desirable such as Cl, Zn, or Pb.
Because these X-ray images are collected at the same location as the
backscattered electron image, this series of images can be combined to
determine the mineral phase present at each location (pixel) in the
two-dimensional image (typically 512 pixels by 400 pixels in size). Typically,
magnifications of 250X or 500X are employed for obtaining the SEM