MCE 230_F10_lec_15 - art/380582. .. Transmission Electron...

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MCE 230 – Materials Science Fall 2010 Lecture - 15
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Imperfections in Solids
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Interfacial Defects Boundaries that have two dimensions and normally separate regions of he material Grain boundaries: Boundaries separating two small grains or crystals having different crystallographic orientations
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Interfacial Defects Twin boundary: is a special type of grain boundary which has a specific mirror lattice symmetry
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Volume Defects Much larger defects Voids, pores, crakes etc….
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Microscopic Examination Types of Microscopes: 1. Optical Microscope 2. Electron Microscope a) Transmission Electron Microscope b) Scanning Electron Microscope 3. Scanning Probe Microscope
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Optical Microscope Surface must be ground and polished Surface treatment ( etching) Light radiation is used http://en.wikipedia.org/wiki/Optical_microscope
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Scanning Electron Microscope (SEM) Electron beam is used The electron beam scan surface of the specimen only http://en.wikipedia.org/wiki/Scanning_electron_microscope SEM image of red blood cells www.britannica.com/EBchecked/topic-
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Unformatted text preview: art/380582. .. Transmission Electron Microscope (TEM) Electron beam is used The electron beam passes through the specimen Contrasts in image is produced due to beam scattering http://en.wikipedia.org/wiki/Transmission_electron_microscope Scanning Probe Microscope (SPM) Tiny probe with a very sharp tip is used (order of nanometer) www.icmm.csic.es http://mcff.mtu.edu/acmal/images/NanoIISchematic.jpg Average Grain Size Line intercept method: Draw several lines across the micrograph Count the no. of grain boundaries each line crosses Take the average of these numbers: this average represents the average no. of grains per the line length Divide the length of the line by the average number of grains. Account for magnifications x1000 L 1 n 1 L 2 n 2 L 3 n 3 Including magnification L 1 L 2 L 3 3 n L n L n L d 3 3 2 2 1 1 * avg Actual average grain diameter 1000 d ion magnificat d d * avg * avg avg...
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MCE 230_F10_lec_15 - art/380582. .. Transmission Electron...

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