6/6/97
I have a customer half way across the country who would like to
examine
the possibly corroded surface of a large mold in a
plastics-forming
plant. The mold is too big to be put in the SEM and it cannot be
sectioned (big $). I suggested making a plastic film replica of
the
surface and sending it to me.
I can't seem to find my references/instructions for making
acetate (?)
replicas with acetone and I want the customer to be able to do it
right
(we have only one chance).
Any guidance would be appreciated, even from vendors. :-)
Harold J. Crossman
OSRAM SYLVANIA INC.
Lighting Research Center
71 Cherry Hill Dr.
Beverly, MA 01915
Phone: (508) 750-1717
E-mail: crossman@osi.sylvania.com
Our web sites: www.sylvania.com
www.siemens.com
drop
or two of acetone on surface to be replicated. Place the acetate
on surface. The acetone will soften the acetate so you will want
to
apply slight pressure to ensure acetate molds to surface. I use a
cotton swap, but have also used my finger.
If you need to do the top surface put the acetone on the acetate.
You can by a kit from Bueller (most likely spelled wrong) that
has
foil on the back which allow viewing with an optical microscope.
The first replica will clean the surface, save it for analysis as
in
this case it will contain corrosion products.
Do more than one just incase something goes wrong. (it does
for me.)
Good Luck
Keith Collins
COLLINS@alrc.doe.gov
Preparation
of a second stage, perhaps in Pt/C is much more tricky, but not
needed for
SEM. I used Bioden acetate film for many years but any thin
plastic
replicating
material should do well. Bioden is used with acetone or methyl
acetate.
Cut a piece of film material to size.
Place on top- of the region for replication.
Drop solvent onto plastic until its just wet all over.
Apply gentle pressure to the film just after solvent has just
evaporated to
ensure good contact.
Wait for at least 10 minutes before pulling replica off.
Pull replica off and throw this into the bin.
Repeat and "bin" second replica - to clean surface.
Retain third and subsequent replica for use.
Metallise (sputter) specimen surface before mounting and viewing.
Notes: Handle edge of replica and only with tweezers.
Mark replica's specimen site like sheet film notching; when
facing
(emulsion or replica) cut the top right corner.
When viewing in SEM reverse the polarity to gain a realistic
"hills and
valleys" impression. Single stage replicas are reversed.
You could look at a "bin" replica, after carbon coating in
backscattered
mode to check any of the extracted material and also to do EDS on
that.
Angle shadow casting with Pt (from wire wrapped around a tungsten
'V'
filament) and subsequent
carbon coating sometimes enhances features. 10 to 30 degree
angles of
evaporation are used. Low angles are best for replicas with very
little
topography.
Jim Darley
ProSciTech Microscopy PLUS
PO Box 111, Thuringowa QLD 4817 Australia
Phone +61 77 740 370 Fax: +61 77 892 313
Great microscopy catalogue, 350+ Links, MSDS
************************ http://www.proscitech.com.au