MATS_15101: Crystallography Flashcards
What is another name for motif?
Basis
What is the name for a unit cell with only one lattice point in it?
A primitive cell
What is another name for lattice planes?
Crystal planes
Which principal metallic crystal structure is not a unit cell?
- BCC
- FCC
- HCP
HCP
Which principal metallic crystal structure(s) are close-packed?
- BCC
- FCC
- HCP
FCC and HCP
The ‘ABAB’ stacking sequence corresponds to?
to what principal metallic crystal structure
HCP
The ‘ABCABC’ stacking sequence corresponds to?
to what principal metallic crystal structure
FCC
Which has a higher value constant pressure heat capacity or constant volume heat capacity?
Constant pressure heat capacity
This is because expansive work is done to maintain constant pressure situation
True or False:
Alloying increases thermal conductivity of materials
False
True or False;
Thermal conductivity is aided by microstructural order
True
A higher degree of crystallinity in polymers, cermics and metals (which are generally crystalline materials) increases thermal conductivity. A rise in temperature which disrupts the metal lattice by increased vibrationary motion** reduces** its thermal conductivity
State the trend for thermal conductivity in ceramics
Decreases steadily initially but then increases at higher temperatures
Why is a higher degree of crystallinity helpful for thermal conductivity in polymers?
It increases the area for coordinated lattice vibrations (the primary conduction method in ceramics)
What is a phonon?
A quantum of vibrational energy
What is a photon?
A quantum of electro magnetic energy
What is the mathematical relationship between thermal conductivity (k) and electrical conductivity (s) of a given material?
k = LsT
‘k is equal to LisT’
Compressive thermal stress has a — value?
Negative or positive?
Negative
Heating the material, expansion occurs
Tensile thermal stress has a — value?
Negative or positive?
Positive
Cooling the material
