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April 2007

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Subject:
From:
Chuck Herrington <[log in to unmask]>
Reply To:
JEOL-Focused Probe Users List <[log in to unmask]>
Date:
Thu, 5 Apr 2007 09:00:43 -0400
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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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*

Joe Geller and I published a paper in the 1992 Microbeam Analysis Journal
titled "Bulk Composition from Electron Beam Excited X-ray Analysis"
addressing this issue of rastered analysis to obtain an average composition.
The basic conclusion was that it is not a good idea to perform analyses in
this fashion. It is also true that a beam raster is not uniform in electron
dose so that a defocused beam is better.

I only perform a rastered analyses for these PtAlNi coatings because the
companies that apply the coatings have built the raster technique into their
QC inspection procedures. It is so rooted that I was unable to convince them
to change the procedures. It has a history and at this point gives them a
relative indication of the quality of their coatings.

I was interested in the X-ray peak overlap and ZAF issues that were raised.
I will do a series of experiments to evaluate this system in more detail.
Thanks.

Chuck Herrington
Geller Micro┼nalytical Lab, Inc.
978-887-7000
[log in to unmask]

-----Original Message-----
From: JEOL-Focused Probe Users List [mailto:[log in to unmask]] On
Behalf Of Ron Rasch
Sent: Thursday, April 05, 2007 12:23 AM
To: [log in to unmask]
Subject: [PROBE-USERS] beam raster analysis

JEOL Probe Users Listserver

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

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*

Hi,

this answer brings a question to my mind.
When is it possible to do a quantitative analysis on a probe with a rastered
beam on an inhomogeneous sample?

I sometimes get asked this, but even though the software allows it, I always
say no. I assumed that the matrix correction for every point in the raster
will be based on the average x-ray intensity, yet this might be different
than the matrix correction required at a given point in an inhomogeneous
sample.

Have I missed something?

Thanks,
Ron



----------------------------------------------------------
JEOL Probe Users Listserver

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

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*

Most of the samples we receive are of this type (Platinum-Aluminide coatings
of engine parts).  I use pure element standards and have pretty good
success. The difficulty is that the material is very inhomogeneous and the
customer usually wants an average composition. They require analyses with a
beam raster over a certain area of the coating. I usually have a set of
about 10-12 elements in the analysis.

Chuck Herrington
Geller Micro┼nalytical Lab, Inc.
978-887-7000
[log in to unmask]


   _____

From: JEOL-Focused Probe Users List [mailto:[log in to unmask]] On
Behalf Of Ellery Frahm
Sent: Wednesday, April 04, 2007 12:01 PM
To: [log in to unmask]
Subject: [PROBE-USERS] Ni-Pt-Al standard?


JEOL Probe Users Listserver

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


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* Probe folks,


I have a post-doc researcher here in one of our engineering departments who
is interested in analyzing a Ni-Pt-Al system. I've been trying pure metals
as standards for his samples, but obviously I'd like to minimize any
absorption or fluorescence issues there might be. Does anyone have any
experience with such a system? Do you know of suitable standards for such a
system, or have you just used pure metals?

Thanks,
Ellery

--------------------

Ellery E. Frahm

Research Fellow & Manager

Electron Microprobe Laboratory

University of Minnesota - Twin Cities

Department of Geology & Geophysics

Lab Website: http://probelab.geo.umn.edu

Personal Website: http://umn.edu/~frah0010

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