Nature’s Shield, Nature’s Gifts How Protecting Coastal Habitats Protect and Enrich Us.
Searching for One of Nature’s Missing Crystal Structures
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Transcript of Searching for One of Nature’s Missing Crystal Structures
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Thomas McConkie, David Allred, Gus Hart, Brian Hicks
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What missing crystal structures?Setup and PreparationExperimental MethodsResultsContinuing the Search
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“Where are natures missing structures?”Gus Hart, Nov. 11, 2007
L13 Structure
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Vacuum systemRoughing, Turbo and Cryo Pumps.Leaked checked system to minimize
unwanted interference by outside air. Base pressure of (~10-6 torr).
Sputtering Gun
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SputteringEven coating on all
surfacesSputtering plasma: Ar+PtCd
Magnetron SputteringLower pressure
(~10-3 torr).Better quality
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Composition
Crystal Structur
e
EDAXEnergy dispersive X-ray spectroscopy
STE
M
Scanning Transmission electron microscopy
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Pure platinumTEM grid substrateComposition:
PtCrystal Structure:
Face Center Cubic (FCC)
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Constructive Interference
Destructive Interference
Patterns of high and low intensities due to constructive and destructive interference of the incident beam (gives spacing in the crystal structure)
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FCC Peaks
Super lattice peaks
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Super lattice peaks
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Platinum and CadmiumVery little Cadmium Substrate:
TEM GridsComposition ratio:
~1 Cd : 3Pt on Cd rich side.
More Cadmium
More Platinum
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~3 Pt : 1 Cd ratio was achieved.
Were not able to detect any of the super lattice peaks.
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Where are you?
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Grow thicker sample and subject to bulk x-ray analysis~8 μm thick
Look for super lattice peaks.Check for Composition using EDAX and
crystal structure using STEM.
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Special thanks to :NSF
Richard VanfleetJeff FarrerLiz Strein
Branton Campbell