Re: Paleontology microscopy

On 31 Jan 2006 06:25:26 -0800, "bbandli" <bbandli@xxxxxxxxxx> wrote:

>> I have raw specimens collected from the field. They are as-collected.
>> So the problem is how to prepare them for best SEM observation and/or
>> LM observation.
>>
>
>Hi Gary,
>
>I've been following this thread and I still don't know what exactly you
>want to know about your samples? I understand you want to use LM
>and/or SEM (possibly with EDS, or EBSD) but what exactly do you want to
>know about your samples, this will be important to better determine
>which technique is best. My grad advisor always told me "if your only
>tool is a hammer, then every problem is a nail" After a few years that
>statement finally made some sense ;-).
>
>If you are going to be using SEM, I would suggest you try to find a
>facility with Variable Pressure (environmental) SEM capabilities. I've
>had a little experience looking at fossils with our "traditional" high
>vacuum SEM and if the material is porous or if the fossil is in a
>significant amount of porous matrix it becomes extremely difficult to
>achieve the vacuum necessary. There are a couple of solutions to this,
>one is to produce a replica of the area of interest, this will only be
>useful for topology and there will be no chemical information from your
>original sample contained in the replica. The replication process uses
>a rubber-like substance similar to the material used to make dental
>molds. I'm sure there are several sources out there that provide
>step-by-step techniques for doing this. The other is to simply reduce
>the size of the material by trimming away as much of the matrix
>material as possible. If you are planning on making sections of the
>samples, then size shouldn't be an issue. Also, if you are planning on
>doing EBSD (electron backscatter diffraction) the samples will need to
>be prepared in some very specific ways so as not to induce the near
>surface strain that is caused by traditional thin section polishing
>techniques. Finally, with a high vac. SEM the sample will need to be
>made conductive by applying a thin film of carbon, AuPd or some other
>conductive material. This is generally unnecessary with VPSEM.
>
>I think the LM prep has been fairly well covered by previous posts to
>this thread, but again, the prep may be dependent on what you want to
>find out. There was also mention of AFM, I have been playing with one
>in our lab for a couple of months now, and it is a worthwhile technique
>to learn more about. In the hands of a skilled operator, some very
>interesting properties can be observed.
>
>Good Luck,
>
>Bryan

My SEM has VP mode. I don't have any problems so far in high vac mode
around 500V-1KV.

The problem is what to actually see. I.e., what to look for that is
significant and not redundant such that it has been studied to the
point of routine. What do I look for? Since these are not my normal
types of specimens, I am in unchartered waters.

The mineral specimens for EBSD are polished to get any patterns. This
is not a problem.
Gary Gaugler, Ph.D.
Microtechnics, Inc.
Granite Bay, CA 95746
916.791.8191
gary@microtechnics dot com
.

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