The reason they used carnuba is that the sample contained native sulphur, which undergoes an exothermic reaction with epoxy! So that's a definite no!
We'll try and find a way to remove the sulphur and use ordinary epoxy.
I found some notes from the last time I worked with carnuba mounts, it was on our oldest SEM and the time the mount spent in the chamber was severely limited. We didn't notice any effect, but the vacuum was poor on that machine anyway so who knows.
Cheers
Glenn