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Published byKerry Colin Harvey Modified over 8 years ago
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SEM (scanning electron microscope) A type of electron microscope that images the sample surface by scanning it with a high- energy beam of electrons in a raster scan pattern.
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How does SEM work? Electron beam interacts with the material, causing a variety of signals to be emitted- revealing details of the material’s shape, homogeneity and elemental composition.
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SEM Images Low accelerating voltages – finer surface structure images can generally be obtained.
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SEM Images High accelerating voltages – the beam penetration and diffusion area become larger, resulting in unnecessary signals being generated from within the specimen.
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SEM Images LichenUnknown
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Electron Microprobe 1149 Snee Hall
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probelab.geo.umn.edu/electron_microprobe.html A. Electrons are generated by heating a tungsten filament similar to the one in a light bulb. B. Electrons pass through lenses that condense the beam, remove aberrations and focus the beam C. The electrons hit the sample - This knocks out inner electrons in the sample - The atom is now in an excited state. An outer electron drops down to the inner energy level releasing energy in the form of x- rays at the same time. D. X-rays are then reflected through a crystal E. The reflected rays are then counted and recorded by a detector.
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Electron Microprobe Uses Non - destructive Compositional Analysis – Quantitative – Qualitative Precise X-Ray intensities High Spectral Resolution http://www.authorstream.com/Presentation/Janelle-19809-Electron-Beam-MicroAnalysis- Geol-619-1-History-Electrons-as-Entertainment-ppt-powerpoint/
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Applications of the Electron Microprobe
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Case Study One – What is under the fingernails?
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Paint?
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Lichen? SEM image
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Insect Wing? SEM image
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Electron Microprobe Analysis Since the fingernail is an organic compound, there was a large carbon peak. Other elements such as calcium and sulfur might be found in fingernails normally.
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Other Applications of Electron Microprobe
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GEOLOGY- Chemical analysis of rocks, dating, plate tectonics
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Archeology Compositional distinctions between 16th century ‘fac¸on-de- Venise’ and Venetian glass vessels excavated in Antwerp, Belgium † I. De Raedt,a K. Janssens*a and J. Veeckmanb aDepartment of Chemistry, University of Antwerp, Universiteitsplein 1, B-2610 Antwerp, Belgium. E-mail: koen@uia.ua.ac.be bExcavation Department of the City of Antwerp, Godefriduskaai 36, B-2000 Antwerp, Belgium Received 29th October 1998, Accepted 10th December 1998 At JEOL 6300 SEM/EDX Based on chemical analysis, 50% of the glassware was from Italy
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FORENSIC SCIENCE SEMGSR The SEM solution for Automated Analysis and Classification of Gunshot Residue SEM/ Microprobe is used to analyze inorganic compounds in gunshot residue
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STUDY POTENTIAL ELECTROCATALYSTS FOR FUEL CELLS 1.Sputter different concentrations of metals onto a substrate (Based on lecture by Hector Abruna)
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2. Perform Thermal imaging to determine areas of higher electrochemical activity 3. Use scanning electrochemical microscopy (SECM) to test sample’s ability to oxidize hydrogen/formic acid and reduce oxygen.
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Now we need to determine the chemical composition Of the product before bulk manufacture Obtain composition with microprobe and Rutherford backscattering (RBS) SEM-Observe texture and crystal grain size GADDS-Determine crystal structure
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Niobium/Tin Film Studies
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Unannealed Sample- 2 to 1 Niobium to Tin Element Line Net Counts Weight %Atom % Error Compnd % Nb L 64150 67.40 72.53+/- 0.47 67.40 Nb M 0 --- Sn L 17107 32.60 27.47+/- 0.33 32.60 Sn M 0 --- Total 100.00
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Annealed Sample - Oxygen accounted the missing mass- the niobium was probably oxidized. Large peak seen for Niobium. About 10% of mass unaccounted for.
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Butterfly Wings -The Sequel-
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Light Microscope Images Butterfly Scales showing overlapping pattern 10µ 20µ Individual scales showing ribbing pattern
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Light Microscope views Fringe ScalesTips of Fringe scales 10 µ 20 µ
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Fringe Scales of Wing 100 µ 50µ Optical Microscope - Transmitted Light Optical Microscope – Reflected Light
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Unpolarized vs Polarized Light Wing Scale Unpolarized Light 50x objective lens Wing Scale Polarized Light 50x objective lens 10 µ
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