Lect18_notes

Effect is masked compared to atomic number contrast

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Unformatted text preview: ions, electrons can penetrate more deeply into the crystal by traveling along paths of low atom density Such paths are known as channels •  The resultant modulation variation is small ~ 5% between channeling and non-channeling. Effect is masked compared to atomic number contrast CBEMS 164 – XRD, SEM & Microanalysis: Lecture 16 ! 20 Electron Channeling! •  Channeling condition occurs when Bragg diffraction condition is satisfied nλ = 2d sin θ •  Weak signal - need to maximize gain (contrast) with a suitable zero offset (brightness) CBEMS 164 – XRD, SEM & Microanalysis: Lecture 16 ! 21 Crystals – Surfaces and Interfaces! •  Crystals extend in space until they end at either: –  A surface –  A grain boundary –  A phase boundary (a boundary between two different phases) CBEMS 164 – XRD, SEM & Microanalysis: Lecture 16 ! 22 An Example of an EBSD Application! •  After deformation, metals can develop a preferred orientation for the grains –  e.g. after cold rolling, grains tend to orient themselves such that one crystallographic plane tends to be parallel to the rolling direction CBEMS 164 – XRD, SEM & Microanalysis: Lecture 16 ! 23 Rolling Structure and Recrystall...
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This note was uploaded on 01/16/2014 for the course CBEMS 164 taught by Professor Porter,j during the Fall '08 term at UC Irvine.

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