Chapter 4: Imperfections In Solids Flashcards
A deviation from perfection; normally applied to crystalline materials in which there is a deviation from atomic/molecular order and/or continuity
Imperfections
A crystalline defect associated with one or at most, several atomic sites.
Point defect
A one-dimensional defect along a line of atoms/molecules
Linear defects
A two-dimensional defect along a plane or face.
Interfacial defect/boundary
An atom of foreign element present in the structure of a material
Impurity
A normally occupied lattice site from which an atom or ion is missing
Vacancy
A thermal energy constant having the value of 1.38x10^-23 J/atomK (8.62x10^-5 eV/atomK)
Boltzmann’s constant (k)
A host atom or ion positioned on an interstitial lattice site
Self-interstitial
A linear crystalline defect associated with the lattice distortion produced in the vicinity of the end of an extra half-plane of atoms within a crystal. The Burgers vector is perpendicular to the dislocation line.
Edge Dislocation
The line that extends along the end of the extra half-plane of atoms for an edge dislocation and along the center of the spiral of a screw dislocation.
Dislocation Line
A linear crystalline defect associated with the lattice distortion created when normally parallel planes are joined together to form a helical ramp.mThe Burgers vector is parallel to the dislocation line.
Screw Dislocation
A dislocation that has both edge and screw components
Mixed dislocation
A vector that denotes the magnitude and direction of lattice distortion associated with a dislocation.
Burgers vector (b)
CONCEPT CHECK: The surface energy of a single crystal depends on crystallographic orientation. Does this surface energy increase or decrease with an increase in planer density? Why?
A boundary on the surface of a material where surface atoms are not bonded to the maximum number of nearest neighbors
External surface
Separates two grains or crystals having two different crystallographic orientations and can be described in terms of dislocation arrays
Grain Boundary
Exists in multiphase materials where a different phase exists on each side of the boundary. Each phase has distinctive physical and/or chemical characteristics
Phase boundary
A grain boundary that atoms on one of the boundary’s sides are located in mirror-image positions to the atoms ion the boundary’s other side
Twin Boundary
An interruption in the ABCABCABC stacking sequence of close-packed planes in FCC metals
Stacking Fault
A boundary that separates regions having different directions of magnetization in ferromagnetic and ferrimagnetic materials
Ferromagnetic Domain Wall
The structural features of an alloy (e.g. grain and phase structure) subject to observation under a microscope
Microstructure
The investigation of microstructural elements using some type of microscope
Microscopy
A photograph made with a microscope that records a microstructure image
Photomicrograph
For materials that are ——to visible light, only the surface can be observed using optical microscopy
- transparent
- translucent
- opaque
Opaque
a specimen’s surface must be ground and polished using ——to a mirror-like finish.
- abrasive papers and powders
- chemical regents
- hard cutting tools
Abrasive papers and powders
Etching is done using ——to make the microstructure more easily observable
- abrasive papers and powders
-chemical reagents
- hard cutting tools
Chemical regents
Electron microscopes are capable of magnifications for optical microscopes
- higher than
- lower than
- similar to
Higher than
