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MATSE 201: Exam 2 Review
Crystal Defects, Diffusion, Phase Diagrams & Transformations, Polymers
28
Science
Undergraduate 3
10/27/2010

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Term
point defect
how many D?
Definition
0 D
Term
linear defect
how many D?
Definition
1 D
Term
planar defect
how many D?
Definition
2 D
Term
solid solution
Definition
homogeneous mixture where crystal structure is maintained when solute atoms are added (no new crystal structure formed)
Term
3 types of point defects
Definition
vacancies
self-interstitials
impurities
Term
Linear defects are also called
Definition
dislocations
Term
3 types of linear defects
Definition
edge dislocation
screw dislocation
mixed dislocation
Term
edge dislocation
Definition
extra half plane of atoms in a crystal
Term
screw dislocation
Definition
[image]
Term
mixed dislocation
Definition
both screw and edge dislocations
Term
Burger's vector vs.
dislocation line
Definition
dislocation line of edge: perpendicular
dislocation line of screw: parallel
Term
find Burger's vector
Definition
[image]
Term
5 types of planar defects
Definition
external surfaces
grain boundaries
twin boundaries
stacking faults
phase boundaries
Term
external surface
Definition
dangling bonds have higher energy, so material wants to minimize this surface area
Term
grain boundaries
Definition
mismatch of crystal orientation
Term
twin boundary
Definition
grain boundary with mirror symmetry
Term
phase boundary defect
Definition
exist in multiphase materials across which there is a sudden change in characteristics
Term
microstructure
Definition
grain size and shape
Term
Frenkel defect
Definition
point defect that occurs in ionic materials
cation moves to interstitial site
Term
Schottky defect
Definition
point defect that occurs in ionic materials
missing ion pair (1 cation and 1 anion missing)
Term
for diffusion to take place,
Definition
there must be a place for the atom to go
atom must have enough energy to overcome the barrier of breaking bonds and causing lattice distortion
Term
diffusion
Definition
spontaneous movement of matter caused by atomic /molecular kinetic energy
Term
activation energy for self diffusion _____ with bond energy
Definition
activation energy up and bond energy up
Term
phase
Definition
chemically and structurally homogeneous state of matter
Term
component
Definition
a substance in a phase
Term
diffusion length
Definition
2 root(Dt)
Term
Hume-Rothery Rules
Definition
1. <15% difference in size
2. <0.5 difference in electronegativity
3. same valence
4. same crystal structure
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