Re: [sdpd] Inert atmosphere sample scan problem?

[Lachlan Cranswick <L.M.D.Cranswick...@dl.ac.uk>]

At 18:58 30/07/02 -0000, you wrote:
>I have a sample that's been packed under nitrogen and I want to know 
>if there is any way I could do a room temperature scan without any 
>contact with air during sample preparation and during scanning.  
>
>I could think of preparing a sample on a sample holder in a glove 
>box, but transferring from the glove box to the x-ray machine would 
>be a problem.

Two things we did in Melbourne on a standard Philips 1710/1050 
XRD (with sample spinner) on very hygroscopic materials:
(the Philips 1050/1710 gonoimeter is fully enclosed)

1.  Replace the Philips lead glass window on the goniometer sample 
    cover with a home made dry nitrogen flow device focussed on
    the sample area.  This worked very well - 
    even for long weekend scans.  The short time to
    insert the sample (packed in a glove box) from a desiccator
    into the XRD machine did not have a noticeable effect.

The surrounding area was tested for any X-ray leaks - plus there
was also a full XRD enclosure.

---------

2.  Make a 2 stage clip on teflon XRD sample holder - analogous to the
    Philips "clip on" circular back pack sample holders (forgotten
    the PW part number) - done in  such as way that 2 or 6 micron thick 
    mylar is "clipped" on to the sample (or polypropylene -  whatever 
    is most appropriate).

      the 1st stage is a base where the sample is loaded.
      the 2nd stage is a ring that clips over the 1st stage - with
        metal springs to force contact between them.
   
    You pack the sample into the 1st stage
    Put the mylar/plastic sheet over 1st stage
    Then clip on the second stage.  

    Done and ready to insert into the XRD.
   
This can be done easily in a glove bag with clumsy gloves.  
The samples started to degrade after a few hours (though 
they were only 20 minute scans so this was 
not a problem)- though greasing the sides of the 1st 
stage with vacuum grease (where the mylar contacted the sample 
holder) could extend the time before the sample started to degrade.

Be wary that the 2 stage teflon sample holder can flex a bit - so
they could jam in the Philips PW1775 automatic sample changer 
cassettes. But they were very reliable using the side single 
sample loading stage on the PW1775.

Lachlan.

-----------------------
Lachlan M. D. Cranswick

Collaborative Computational Project No 14 (CCP14)
    for Single Crystal and Powder Diffraction
  Birkbeck University of London and Daresbury Synchrotron Laboratory 
Postal Address: CCP14 - School of Crystallography,
                Birkbeck College,
                Malet Street, Bloomsbury,
                WC1E 7HX, London,  UK
Tel: (+44) 020 7631 6850   Fax: (+44) 020 7631 6803
E-mail: l.m.d.cranswick...@dl.ac.uk   Room: B091
WWW: http://www.ccp14.ac.uk/


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