Sample preparation andPresentation    XRD Webinar June 19 2012
Contents The goal of sample preparation Different analytical questions may require different sample preparation techniques...
An ideal ‘powder’  Consists of very many, randomly  oriented crystallites  Depending on the analytical needs the  optimal ...
An ideal powder  Particles too small, or wrongly ground  Peaks get broader at the cost of the  maximum intensity  Crystall...
Need a fine powder? Grind!
Coarse powder
Effect of spinning
Effect of spinning
Grinding devices
Swing Mill
Planetary Ball Mill
Effect of grinding
Issues to pay attention to  Take care that you grinding doesn’t  affect the crystal structure, or  induces strain into the...
Sieving                                80 Effective Particle Size (µm)                                70                  ...
Preparing a flat specimen  Cavity front loading  Cavity Back loading  Spray (atomizing) (on a zero  background holder)  Su...
The specimen holderReference surface mustbe flat within 13µm
Cavity Front Loading
Cavity Back loading
Cavity Back Loading
Effect of Back Loading  Equant  Elongate  Tabular  Bladed
Effect of Back loading  For Equant particle shape the effect  of Back Loading versus Front  Loading is small and BL is usu...
Effect of Back Loading
Zero Background holder Needed when: Sample is transparent to X-rays Very small amount of sample is available and the speci...
Zero Background Holder Obliquely cut single crystal Most commonly either Si, or Quartz Direction of the cut is chosen to a...
Zero Background Holder
Dusting on a 0-BG holder
Compare with Back Loading
Compare with Back Loading
Alternative Presentations  Protect the specimen during the  measurement  Specimen presentation for  transmission measureme...
Protecting your specimen  Mount your specimen in a reaction  chamber (the Anton Paar XRK900,  for example) and flush with ...
Transmission Het monster wordt in een holle ring tussen twee folieën geklemd De folieën worden m.b.v. drie in elkaar passe...
Capillair  Gebruikt erg weinig monster  Voorkomt meestal  voorkeursoriëntatie  Beschermt tegen invloeden  van buitenaf  Is...
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Sample preparation and Presentation XRD Webinar June 19 2012 AJK Analytical Services

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Transcript of "Sample preparation and Presentation XRD Webinar June 19 2012 AJK Analytical Services"

  1. 1. Sample preparation andPresentation XRD Webinar June 19 2012
  2. 2. Contents The goal of sample preparation Different analytical questions may require different sample preparation techniques Sample related issues in X-ray diffraction An overview of various sample preparation and presentation techniques Some Special cases
  3. 3. An ideal ‘powder’ Consists of very many, randomly oriented crystallites Depending on the analytical needs the optimal crystallite size may vary from 40µm down to <1µm Crystallites too big Unreliable intensities Crystallite size of 40µm only 12 crystals contributing to the intensity profile at any time To obtain a 1% you need about 53000 contributing crystals
  4. 4. An ideal powder Particles too small, or wrongly ground Peaks get broader at the cost of the maximum intensity Crystallites not randomly oriented (preferred orientation, or texture) Deviating relative intensities One very dominant orientation Sometimes just one reflection is visible (Mica and Muscovite, for example)
  5. 5. Need a fine powder? Grind!
  6. 6. Coarse powder
  7. 7. Effect of spinning
  8. 8. Effect of spinning
  9. 9. Grinding devices
  10. 10. Swing Mill
  11. 11. Planetary Ball Mill
  12. 12. Effect of grinding
  13. 13. Issues to pay attention to Take care that you grinding doesn’t affect the crystal structure, or induces strain into the crystallites (pharmaceuticals, but also cryolite; the solvent of alumina for the elctrolysis must be dealt with carefully) The material of the grinding vessel is of paramount importance (Cross) Contamination
  14. 14. Sieving 80 Effective Particle Size (µm) 70 60 50 40 30 20 10 0 0 200 400 600 800 1000 1200 Mesh
  15. 15. Preparing a flat specimen Cavity front loading Cavity Back loading Spray (atomizing) (on a zero background holder) Suspending (on a zero background holder) Side drifting
  16. 16. The specimen holderReference surface mustbe flat within 13µm
  17. 17. Cavity Front Loading
  18. 18. Cavity Back loading
  19. 19. Cavity Back Loading
  20. 20. Effect of Back Loading Equant Elongate Tabular Bladed
  21. 21. Effect of Back loading For Equant particle shape the effect of Back Loading versus Front Loading is small and BL is usually not needed For Elongate and Tabular shapes the effect of BL is not always sufficient Most effect of BL is expected for Bladed particle shape
  22. 22. Effect of Back Loading
  23. 23. Zero Background holder Needed when: Sample is transparent to X-rays Very small amount of sample is available and the specimen must be presented as a flat plate Sample cannot be packed properly
  24. 24. Zero Background Holder Obliquely cut single crystal Most commonly either Si, or Quartz Direction of the cut is chosen to avoid any reflections occurring in the reflection sphere (i.e. no reflecting lattice planes parallel to the crystal surface)
  25. 25. Zero Background Holder
  26. 26. Dusting on a 0-BG holder
  27. 27. Compare with Back Loading
  28. 28. Compare with Back Loading
  29. 29. Alternative Presentations Protect the specimen during the measurement Specimen presentation for transmission measurements Capillaries
  30. 30. Protecting your specimen Mount your specimen in a reaction chamber (the Anton Paar XRK900, for example) and flush with an inert gas Cover your specimen with a transparent foil, which does not give a diffraction pattern Mount the specimen inside a glass capillary tube (Mark tube)
  31. 31. Transmission Het monster wordt in een holle ring tussen twee folieën geklemd De folieën worden m.b.v. drie in elkaar passende ringen (vaak teflon) gespannen Of het monster wordt in een capillair gemonteerd
  32. 32. Capillair Gebruikt erg weinig monster Voorkomt meestal voorkeursoriëntatie Beschermt tegen invloeden van buitenaf Is lastig te vullen
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