Materials Science and Engineering Crystalline and Non-Crystalline Systems X-Ray Diffraction:...
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Transcript of Materials Science and Engineering Crystalline and Non-Crystalline Systems X-Ray Diffraction:...
Materials Science and EngineeringCrystalline and Non-Crystalline SystemsX-Ray Diffraction: Determination of Crystal Structure
Crystalline and Non-Crystalline
Single Crystals◦Uninterrupted repeating
unit of a unit cell◦Often forms geometric
shapes◦Most solids form multiple
crystal orientations and breaks forming grains
Crystalline and Non-CrystallinePolycrystalline
◦Many crystalline grains in a microstructure
◦Is heavily influenced by cooling. Nucleation, Growth, and Formation of
Boundaries (figure 3.18)
◦
Crystalline and Non-CrystallineAnisotropy
◦Axis/Direction determines properties (structure – properties correlation) Isotropy – Equal properties on all axis.
◦Example: Young’s Modulus, Conductivity, Index
of Refraction can vary between [100] and [111]
Crystalline and Non-CrystallineAnisotropy
◦Inversely proportional to structural symmetry Triclinic vs Simple Cubic
Highly anisotropic (directional dependant properties)
vs Highly Isotropic (uniform shape = uniform
properties)
◦Usually see isotropy on macroscopic scale in metals due to polycarystallinity
X-Ray DiffractionMost of the information in this
chapter comes from X-Ray Diffraction.
What is diffraction!?
X-Ray DiffractionDiffraction
◦Results from constructive and destructive interference
X-Ray DiffractionDiffraction
◦Consistent overlap in 3-D space creates “diffraction pattern”
◦Used heavily in research and higher education
X-Ray DiffractionDiffraction
◦Regularly spaced obstacles capable of scattering a wave
◦Are spaced comparable to wavelength
X-Ray DiffractionX-Rays
◦Form of electromagnetic radiation◦High Energy, Low Wavelength◦Portion of X-Ray beam scatters in
different directions (locations) when hitting solid object.
X-Ray DiffractionX-Rays
◦At an angle…
Bragg’s Law◦Relationship among x-ray
wavelength, interatomic spacing, and angle of diffraction for constructive interference
(further ahead)
X-Ray DiffractionLike Orchard Rows
◦Angle of view creates perspectives
X-Ray DiffractionTechnique:
◦Sample placed on a stationary rig◦Detector turns on rotating axis
Scans part along a set range of angles.
XRD Demo/Visual X-Ray Diffraction
X-Ray Diffraction◦Example:
X-Ray Diffraction◦What are we looking at?
X-Ray Diffraction◦What are we looking at?
X-Ray DiffractionWhat are we looking at?
◦What does each variable mean?