Author Topic: Carnuba wax and microprobe  (Read 193 times)

glennpoirier

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Carnuba wax and microprobe
« on: May 19, 2021, 11:01:19 AM »
Hi all,
I have a potential client that wants to look at samples embedded in carnuba wax. Does anyone have any experience good or bad with this mounting method?
The mounts were analysed in a SEM particle analysis system
I vaguely remember using samples mounted in carnuba, but it was a long time ago and I can't remember if I had any problems or had to take any precautions. I'm mostly worried about gunking up the vacuum system. Any or all wisdom gratefully recieved.
Cheers
Glenn

Probeman

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Re: Carnuba wax and microprobe
« Reply #1 on: May 19, 2021, 02:06:02 PM »
Sounds dicey.

Melting point of carnuba wax is 180F or 82C, so pretty darn low (CrystalBond 509 which is clear melts at 250F or 121C). The brown stuff (CrystalBond 590) melts even higher and is what we had to use on our Cameca instrument at Berkeley for analysis of particles:

https://probesoftware.com/smf/index.php?topic=1351.msg9700#msg9700

It might work in a JEOL instrument, but the Cameca stages run too warm.  It's not that it would actually melt but if there are any air bubbles at all, it will soften slightly and then start moving things around.

I would also worry about vacuum contamination unless you can pump the volatiles with a cold finger.
The only stupid question is the one not asked!

glennpoirier

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Re: Carnuba wax and microprobe
« Reply #2 on: May 21, 2021, 06:43:25 AM »
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

Probeman

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Re: Carnuba wax and microprobe
« Reply #3 on: May 21, 2021, 09:18:07 AM »
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!

CrystalBond is not an epoxy, it's basically a hot glue.  Not sure if CrystalBond would react with sulfur.
The only stupid question is the one not asked!