Xray Powder Diffraction of Small Amounts of Materials XRPD'

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X-ray Powder Diffraction of Small Amounts of
Materials (?XRPD).
NATURA IN MINIMIS MAXIMA (Nature is greatest in
the smallest things)

• Joseph H. Reibenspies Nattamai Bhuvanesh
• Texas A M University
• Peter Lee Yuegang Zhang
• Argonne National Laboratories

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Micro-Diffraction

• Only micro grams of materials available
• Forensics and Archeology
• Explosive and/or Toxic compounds
• Expensive and/or rare materials
• In-Situ Solid State Reactions
• Uniform heating/cooling
• Rapid Screening/ Combinatorial Chemistry

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Micro Diffraction at Texas A M.

• Instrumentation
• Bruker D8 GADDS Diffractometer with Fixed ?
  stage.
• Copper Radiation with Graphite Monochromator and
  pinhole 0.5mm collimator.
• Multi-wire (Hi-star) detector.
• Power 1600 watts
• Short beam stop (distance from beam stop to
  sample was reduced)
• 0.1mm loop (supplied by Hampton Research)

Buker GADDS
0.1mm nylon loop
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Argonne Advanced Photon Source
APS
Micro-Powder Diffraction
Collimator
Beam stop
MARS image plate
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Loading Sample

• The sample is adhered to the loop by gently
  dragging the loop over the sample surface

21 ng of sample
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Data Collection on the GADDS

• The detector distance and beam center are
  calibrated.
• Background frames are collected (loop less the
  sample)
• The sample is centered and omega is set at zero.
• Two long (6000 sec) exposure frames (at two
  different 2? angles) are collected
• The frames are unwarped and background frame (s)
  are subtracted.
• An area integration routine is employed to reduce
  the data.

Raw Data Frame
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Detection Limit ?

• 3 ng of Silicon powder adhered to a 0.1mm loop

6000 sec frame with background subtracted
Powder Pattern of Si to 70o 2?

• Estimated by quantitative analysis of x-ray
  diffraction patterns of silicon powder 5.8
  cps/?g (111) reflection)

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Calcite

• 5 ng of ground Calcite Ca(CO)3

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Gypsum

• 50ng

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Advantage of Ground Powder micro-samples over
Unprepared Samples.

• Well ground powders, with particulates less than
  30?m in diameters, afford x-ray powder patterns
  of superior resolution, as compared to unprepared
  samples.
• Randomization of powdered samples can be
  accomplished by standard mechanical means and
  provides for higher resolution and uniform
  scattering, as compared to unprepared stationary
  samples.
• Smaller more uniform samples that best represent
  the bulk material, are found in well ground
  powders, as compared to unprepared samples.
• Micro-amounts of powder allow for more and better
  sampling of the specimen, without significant
  destruction of the original material.

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Comparison of D8 and APS samples
D8
APS
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Data Collection at the APS
3-amino-4-hydroxybenzoic Acid
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Diffraction Method Comparison Table
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Applications

• Archeometry Pigment Identification
• Structure Determination from Powder
• Ni(BMEDAC).2SO2 ? Ni(BMEDAC) 2SO2

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Archeometry Analytical Techniquesa
Raman small spot
Identification of Gypsum
Technique Spatial Sensitivity Raman
Micro excellent excellent? XRD poor good? SEM-
EDX good good XRF good good PIXE/PIGE poor go
od IR fair good Uv-Vis fair good Optical
Micro good fair
XRD 1 ?g
aClark, R. Gibbs, P. Anal. Chem. (1998) 70,
99A.
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Archeological Pigment Samples
Lower Pecos River Rock Paintings
Synchrotron Sample 10?g
D8 Standard Diffractometer 100mg
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NiL.2SO2?NiL.1SO2 ?NiL
36hr
NiL
24hr
NiL.1SO2
12hr
NiL.2SO2
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Effusion of SO2
First 30mins NiL.2SO2 ? NiL.1SO2
14 hr NiL.1SO2 ? NiL
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TGA of NiL.xSO2
NiL.2SO2
NiL.SO2
NiL
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SO2
SO2
Ni.1SO2
NiL.2SO2
NiL
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NiL.2SO2
NiL
NiL.SO2
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Acknowledgement
PER LUCEM VIDEMUS (With Light We See)