Ceramics Flashcards
Define Ceramics
Mix of metals and non metals
What makes a stable ceramic structure?
When anions surrounding a cation are all in contact with the cation.
Define an AX crystal structure
1 anion, 1 cation
What is the NaCl structure?
FCC anions with a cation in the center and in the center of each edge.
Coord # is 6
4 of each atom per unit cell
What is the CsCl structure?
Simple cube of cations with an anion in the center
Coord # is 8
1 of each atom per unit cell
What is the ZnS structure?
FCC anions with 4 interior tetragonal cations
Coord # is 4
4 atoms per unit cell
Define an AmXp crystal structure
Differing numbers of anions and cations
ex CaF2 : 8 simple cubes of F with 4 Ca in cube centers
Coord # is 4 for anions, 8 for cations
Define and AmBnXp crystal structure
ex BaTiO3:
Simple Cube of Barium, O’s in the faces, Ti in the center
This element in peizoelectric
What are the four forms of carbon
graphite
diamond
fullerenes
carbon nanotubes
Describe diamond
hardest ever
structure like ZnS, but all carbon
8 atoms per unit cell
Describe graphite
Layers of hexagonal carbon
Different layers held together by VanDerWaals bonds
isotropic
lubrication properties
Describe fullerenes
1985
ball shaped discrete structure
Describe carbon nanotubes
1990s
tube shaped discrete structure
Extremely strong and stiff
low density
What are the two types of pair defects in ceramics?
Frenkel: cation vacancy + cation interstitial
Schottky: cation vacancy + anion vacancy
Why are ceramics brittle?
Dislocations can’t move through ionic bonds
