School of GeoSciences

e-Beam Damage

The imaging of mineral grains mounted in epoxy resin often results in the grains being surrounded by a damaged area of resin. This is especially true if the sample has been subjected to high e-beam currents used for X-ray mapping, CL and BSE imaging. The resulting isolated grain can be unsuitable for further analytical measurements and so the resilience of the resin to e-beam impact can be an important parameter in determining the resin to use.

e-damage

Sample preparation

Samples of 13 resins were mounted in individual 25mm diameter, 5mm deep, Al-rings. The three Beuhler hot press resins; TransOptic, ProbeMet and KonductoMet were mounted without the Al-rings.

The mounts were then ground using Beuhler UltraPrep nickel bonded diamond 74 micron and 20 micron discs followed by 1200 and 2500 silicon carbide paper. They were polished with 3 micron diamond for 15 minutes and then with 0.3 micron Al-oxide for 10 minutes, washed and then ultrasonically cleaned with 10% Decon 90. The samples were finally cleaned with ethanol prior to carbon coating using a Deton coater to produce a thin conducting film across the sample surface.

 

Measurement Procedure

The epoxy resins were carbon coated before being loaded into the Scanning Electron Microscope, the electron beam was adjusted so that it had a current of 5nA, 20Kv and scanned an area at 5000x magnification for 10 minutes. The size and depth of the resulting raster pits were measured using the Tencor alpha-step 200 profilometer.

KonductoMet and ProbeMet were both too heterogeneous to produce a disctinct raster pit while TransOptic blistered under the beam showing a positive profile in comparison to the pits produced in the other samples.

 

Epoxy Resin Shore Hardness Sputter Depth (micons)
Robnor Resin 81.4 +/- 0.63 0.9
Petropoxy 85.3 +/- 0.78 1.4
Epoheat 80.1 +/- 0.5 0.8
Korapox 79.4 +/- 0.84 0.9
EpoxiCure (Room Temperature) 85.3 +/- 0.46 0.7
Specifix 82.8 +/- 0.45 0.8
Epothin 79.1 +/- 0.71 1.1
Epoifx 80.1 +/- 0.8 0.8
Ciba Geigy 82.1 +/- 1.23 0.7
Epoxicure (65'C) 84.9 +/- 0.18 0.9