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Porous Ceramics - Sample Preparation for SEM

Application Note for Leica EM RES102 - Material Research

Ceramic membrane filters with pore sizes down to a few nanometres must be investigated in cross-section with regard to the structure of the pores. The smallest pores are of special interest.

In most cases, conventional grinding methods cannot be used for such problems, as the pore structure would be distorted. This applies in particular to the pores in the nanometre range. They will be blurred by the grinding, with the result that they will no longer be recognizable in the microscope. On the other hand, the SEM investigation of this material is extremely difficult, as the structures in which we are interested lie at the limits of the resolution, and, as an insulator, the ceramic also limits the resolution.

With the use of slope cutting, a cross-section through the complete layer structure can be produced, which is then be examined in the scanning electron microscope.

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Preparation Conditions: Mechanical Pre-Preparation
Grinding the cross section to achieve a flat surface and a 90° angle between surface and cross sectional surface.

Ion milling

Sample holder:45°-sloped cutting holder
Acceleration voltage:7 kV
Milling time:180 - 220 min
Sample movement:Oscillation (60°)

 

Results
Using ion beam slope cutting, clean cuts through the complete structure of the membrane filter were successfully produced. The layer structure with the different pore sizes is clearly recognizable. The pore structure was not distorted due to the ion beam incidence, being parallel to the slope. Even pores of a few nanometres can be resolved in the scanning electron microscope.

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