mcsi ii yancy w riddle - worcester polytechnic institute · pdf filemetallography •george...
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Vice President of Technology• Nickel-Boron coatings
– On metal alloys– Tribological features
• Low coefficient of friction• Increased wear resistance• Corrosion protection
Compositional Analysis• Conservators are materials scientists too
– Metallurgist– Ceramist– Paper and fiber scientists– Biologist
• The art & science of measuring things• Some methods
– Energy Dispersive Spectroscopy (EDS)– Wavelength Dispersive Spectroscopy (WDS)– X-ray Florescence (XRF)
– Inductive Coupled Plasma (ICP)– Atomic Absorption (AA)
Conservator, Material Scientist• All objects are made of something
• Do not treat something until you understand it
• Do not use an instrument until you understand it
• Surfaces vs. Bulk material
Remember !!!
• Accuracy - Deviating within acceptable limits from a standard
• Precision – Exact in amount
• Resolution – Fineness in detail
The temperature today is 27°C
Accurate, but not preciseResolution = 10°C
Precise, but not accurateResolution = 2°C
Measurement Errors
The temperature today is 27°C
accurate, precise, and well resolved
What is missing ?
Measurement Errors
Micro vs. bulk analytical techniques
Microvolume techniques•Energy Dispersive Spectroscopy•Wavelength Dispersive Spectroscopy•X-ray Florescence
Bulk techniques•Neutron activation•Atomic Absorption•Spark spectrometry•Inductive Coupled Plasma
Choose an appropriate technique !
Energy Dispersive Spectroscopy (EDS)& X-ray Florescence (XRF)
Possible errors:•calibration•Lacks intensity•Peak shift•Si-escape peaks•Overlapping peaks•Too much background
•Sample too far from detector
•Light elements•Wrong accelerating voltage
•Software•Background
subtraction•Wrong elementsEDS & XRF are qualitative or
semi-quantitative techniques. Precision = +/- 10%
Fast data collection
Wavelength Dispersive Spectroscopy (WDS)
WDS is a (semi)-quantitative technique. Precision = +/- 1%
Slow data collectionLittle/no backgroundWell resolved
Sample Preparation & Handling
•Distance from detector•Surface contamination•Effects of etching•Corrosion/oxidation of metallic surfaces•Non-electrical conductors (sputter coating)
•Cleanliness is next to Godliness•use gloves•store samples in dry, arid location•clean in alcohol (beware of residues)•dry with forced hot air
References
J. Goldstein, et al., Scanning Electron Microscopy and X-Ray Microanalysis 3rd Edition, Plenum Press, New York
S.E.M, E.D.S., W.D.S.
Metallography•George F. Vander Voort, Metallography:
Principles & Practices,1984, ISBN: 0871706725
•Gunter Petzow, Metallographic Etching, 2nd Edition, 1999, ISBN: 0871706334
•David A. Scott, Metallography & Microstructure ofAncient & Historic Metals