Lecture 04/07 Flashcards
Describe ceramic materials
- Inorganic and nonmetallic
- 2+ elements
- Ranges from purely ionic to covalent
What are the two characteristics that influence crystal structure?
- Magnitude of the electrical charge on each of the component ions
- Size of the cations and anions
AX-Type Crystal Structures have?
Equal # of cations and anions
What are the types of AX-type crystal structures and their coordination numbers?
- Rock Salt, 6
- Cesium Chloride, 8
- Zinc Blende, 4
For AmXp-Type crystal structures, the charges on the cations and anions are?
Not the same
AmBnXp-Type Crystals have more than one type of ?
Cation
What is the ration of Si to O atoms in Silica?
1:2
Silicate ceramics have a _ arrangement
Tetrahedron
What are the three primary polymorphic crystalline forms of silica?
Quartz, cristobalite, and tridymite
What is silica glass?
Glass having a high degree of atomic randomness
Fused silica is?
Silicon with no added impurities
Glasses commonly contain what impurity ions?
Na, Ca, Al, B
Carbon can either be?
Diamond or graphite
Describe diamond
- Metastable
- Strong covalent bonds due to sp3 hybridization
Describe graphite
- Stable polymorph
- Carbon atoms are located at corners of sheets of hexagons
- Each atom’s 4th bonding electron is delocalized
- Interlayer bonds are perpendicular to the sheets and are weak van der waal
Diffusion in ionic materials generally occurs by?
Vacancy mechanism
The rate of diffusion in ionic materials is limited by?
Diffusion rate of the slowest-moving species
What are the simpler crystal structures?
Rock salt Cesium chloride Zinc blende Flourite Perovskite
Silicate ceramics include?
Crystaline silica
Layered silicated
Noncrystalline silica glass
