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September 2011

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Subject:
From:
Brian Joy <[log in to unmask]>
Reply To:
JEOL-Focused Probe Users List <[log in to unmask]>
Date:
Sat, 3 Sep 2011 12:05:33 -0400
Content-Type:
text/plain
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JEOL Probe Users Listserver

Moderator: Ellery Frahm, [log in to unmask],
Electron Microprobe Lab, University of Minnesota

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*

Thanks for the replies.  In my initial message, I forgot to state that I 
had observed the interference colors on polished brass, which (space 
permitting) I include along with the material to be coated in order to 
monitor coat thickness.

I never encountered this problem of an easily fragmented carbon coat 
using an old Edwards 305 coater (vintage 1972).  I found that coats on 
polished brass were very robust and could only be removed by polishing.  
I don't know if it makes any difference, but, in that case, I was using 
rods composed of compressed amorphous carbon rather than graphite.

The reason this concerns me so much is that I'm in the process of 
re-polishing and re-coating the standards collection here at Queen's for 
use with our new JXA-8230.  Many of the old standards are mounted in 
brass holders, and I've mounted a few new ones in brass rounds myself.  
I've found that the old carbon coats (some of them decades old) have 
adhered quite well to the brass and cannot be removed without polishing.

Brian Joy
Queen's University


On 9/2/2011 12:50 PM, Straszheim, Warren E [BIOTC] wrote:
> JEOL Probe Users Listserver
>
> Moderator: Ellery Frahm, [log in to unmask],
> Electron Microprobe Lab, University of Minnesota
>
> Post a message: send your message to [log in to unmask]
>
> Unsubscribe: send "SIGNOFF PROBEUSERS" to [log in to unmask]
>
> On-line help and FAQ: http://probelab.geo.umn.edu/listserver.html
>
>
>
> *
>
> Why did you go and apply the drop of methanol? You might have left well enough alone.<G>
>
> My experience with carbon or gold coatings is that they are not very robust. We have some clients that like to sputter layers of gold for other purposes than for conductivity inside the microscope. Often it is for a reflective surface. Then they find that the layer wipes off somewhat easily. I can usually use a dry cotton swab to wipe the layer off of a glass slide with a little rubbing.
>
> The coatings will do fine for conductivity under the beam, but they do not adhere particularly well. I would recommend not putting them to the test.
>
> Probably there is someone out there with more experience that can tell us what might be expected under the best conditions, or what might be done to make the coatings adhere better.
>
> Warren Straszheim
> Iowa State University and Ames Laboratory
>
> -----Original Message-----
> From: JEOL-Focused Probe Users List [mailto:[log in to unmask]] On Behalf Of Brian Joy
> Sent: Friday, September 02, 2011 10:45 AM
> To: [log in to unmask]
> Subject: [PROBE-USERS] problem with carbon coating
>
> JEOL Probe Users Listserver
>
> Moderator: Ellery Frahm, [log in to unmask],
> Electron Microprobe Lab, University of Minnesota
>
> Post a message: send your message to [log in to unmask]
>
> Unsubscribe: send "SIGNOFF PROBEUSERS" to [log in to unmask]
>
> On-line help and FAQ: http://probelab.geo.umn.edu/listserver.html
>
>
>
> *
>
> Hi everyone,
>
> I'd like to ask a question regarding a problem I've been having while
> carbon coating.  I am using a Denton Desk V coater with turbomolecular
> pump and rods consisting of compressed powdered graphite (from Ted Pella,
> 1/8" diameter, grade 1 "spec-pure").  I can obtain coats of appropriate
> thickness (i.e., between 1st-order red and 2nd-order blue) that look very
> good.  However, after coating polished brass or glass, when I place a drop
> of methanol on the surface of the coat, the coat disintegrates within a
> matter of seconds.  Has anybody seen this sort of behavior before?  I
> assume that it must be due to presence of contamination under the coat.
> I've checked the inlet to the roughing pump, and I see no oil residue
> after several months of use.  Any suggestions?
>
> Brian
>
>


-- 
Brian Joy
Electron Microprobe and ESEM Lab
Queen's Facility for Isotope Research
Department of Geological Sciences and Geological Engineering
Queen's University
36 Union Street
Kingston, Ontario K7L 3N6

cell phone: 530-220-0434
lab phone: 613-533-2595
fax: 613-533-6592


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