Cross Sectioning of Oil Shale Rock

Application Note for Leica EM TIC 3X - Natural Resources

June 28, 2016

Goal: High quality sample preparation of large areas to investigate the sample in the SEM.

Sample Size: Ø 25 mm, 12 mm thick

Process Description (benchmark values for this particular sample): Mechanical pre-preparation with Leica EM TXP: The sample was glued with super glue onto a standard SEM stub. This stub was clamped in the SEM stub adaptor of the Leica EM TXP for pre-preparation prior to ion beam milling.

For this mechanical preparation step diamond lapping foils of 9μm subsequently 2μm and finally 0.5μm grain size were used. It took about 1.5 hours. The sample was removed from the stub with a razor blade after TXP processing and fixed onto the holder of the rotary stage of the Leica EM TIC 3X.

The preparation should prove if a large area ~25mm of this sample can be ion beam polished with the EM TIC 3X rotary stage.

Ion beam (flat) milling:

TIC 3X rotary stage
Acceleration voltage7 kV
Gun current3 mA
Milling time40 min
Rotation speed~40 rpm
Lateral movement+/- 10 mm

 

Following images were taken with a table top SEM. Hence, high quality images can’t be achieved. However, following images prove an ion beam impact in the center and on 25mm rim of the oil shale sample. It shows improvements compared to the mechanical polishing step on the high mag images.

Fig.1: Centre: After Leica EM TXP (0.5 µm diamond finish)
Fig.2: After ion beam milling
Fig.3: Centre: higher mag., after Leica EM TXP (0.5 µm diamond finish), *Crack not clearly defined due to smearing artifacts
Fig.4: After ion beam milling, 1: Better structured; 2: Clearly defined crack
Fig.5: Rim of 25 mm sample: low mag., after Leica EM TXP (0.5 µm diamond finish)
Fig.6: After ion beam milling, *Sample detail on following images
Fig.7: Rim of 25 mm sample: higher mag., after Leica EM TXP (0.5 μm diamond finish)
Fig.8: After ion beam milling, 1: Better structured, smearing artifacts removed; 2: Scratches removed; 3: Dust particle
Fig.9: Rim of 25 mm sample: higher mag., after Leica EM TXP (0.5 μm diamond finish)
Fig.10: After ion beam polishing
Fig.11: High Res SEM Image
 

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