mG-2 Flashcards
Which materials are crystalline?
metals, many ceramics, some polymers
When are materials typically noncrystalline?
complex structures, rapid cooling
What does amorphous mean?
noncrystalline
Do most engineering applications use single or polycrystals?
polycrystals
What is the term for properties that vary with direction?
anisotropic
Are single crystals anisotropic or isotropic?
anisotropic
If the grains of a polycrystal are randomly oriented is it anisotropic or isotropic?
isotropic
If the grains of a polycrystal are textured is it anisotropic or isotropic?
anisotropic
What is polymorphism?
two or more distinct crystal structures for the same material
Describe how to find crystallographic directions
- find x,y,z change in positions
- clear fractions
- write as numbers without commas in brackets []
- express negative numbers with a bar over the number
equation for linear density
LD = number of atoms / unit length of direction vector
number of atoms refers to radius
What is the algorithm for finding crystallographic planes?
- Read off intercepts of plane with axes (if no intercept use infinity)
- Take reciprocals of intercepts
- Reduce to smallest integer values
- Enclose in parentheses, no
commas i.e., (hkl)
What is the name of the indices used for crystallographic planes?
Miller indices
equation for planar density
PD = number of atoms centered on the plane / area of the plane
(number of atoms refers to radius)
x-ray diffraction give us what information?
crystal structure and interplanar spacing determinations