Definition of ceramics

Август 20, 2022

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Definition of ceramics

Содержание

2. Definition of ceramics Metals - consist of atoms held together by delocalized electrons - overcome the
3. Definition of ceramics Metals - Alloys : combinations of metallic elements or metallic and nonmetallic elements
4. Definition of ceramics Metals - SC (Simple Cubic Structure) Coordination # = 6 Atomic Packing Factor
5. Definition of ceramics Metals - BCC (Body Centered Cubic Structure) APF for a BCC = =
6. Definition of ceramics Metals - FCC (Face Centered Cubic Structure) APF for a FCC = =
7. Definition of ceramics Metals - HCP (Hexagonal Close Packed Structure) Coordination # = 12 Cd, Mg,
8. Definition of ceramics Ceramics - consist of arrays of interconnected atoms - Nonmetallic inorganic solids /
9. Definition of ceramics Ceramics - Mixed bonding – a combination of covalent, ionic, (metallic)
10. Definition of ceramics Ceramics - Crystal structures – Oxide structures ⋅ Ionic radius of oxygen anion
11. Definition of ceramics Ceramics Charge neutrality : Net charge = 0 ⋅ Composition : Ma+xAb-y ?
12. Definition of ceramics Ceramics 2 Coord. Number 0.155 - 0.225 0.225 - 0.414 0.414 - 0.732
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Слайд 2

Definition of ceramics
Metals
- consist of atoms held together by delocalized electrons

- overcome the repulsion between ion cores
- Pure : Many main-group / Transition & inner transition elements

Слайд 3

Definition of ceramics
Metals
- Alloys : combinations of metallic elements or metallic

and
nonmetallic elements
- Delocalized electrons ? characteristic properties
⋅ High electrical conductivity
⋅ High electrical conductivity
- Close packed structures ? deform plastically at room temperature
⋅ Metallic bonding ? Not directional
⋅ Lower bond energy ? Small nearest neighbor distance
⋅ Electron cloud shield cores
⋅ SC / BCC / FCC / HCP

Слайд 4

Definition of ceramics
Metals
- SC (Simple Cubic Structure)
Coordination # = 6
Atomic Packing

Factor (APF)
= Volume of atoms in unit cell / Volume of unit cell
*Hard spheres
APF for a SC = = 0.52

1 × 4/3 π (0.5a)3

Слайд 5

Definition of ceramics
Metals
- BCC (Body Centered Cubic Structure)
APF for a BCC

= = 0.68

2 × 4/3 π (31/2a/4)3

Coordination # = 8

Cr, W, Fe(α),
Ta, Mo

Слайд 6

Definition of ceramics
Metals
- FCC (Face Centered Cubic Structure)
APF for a FCC

= = 0.74
ABCABC... Stacking Sequence

4 × 4/3 π (21/2a/4)3

Coordination # = 12

Al, Cu, Au, Pb, Ni, Pt, Ag

Слайд 7

Definition of ceramics
Metals
- HCP (Hexagonal Close Packed Structure)
Coordination # = 12
Cd,

Mg,
Ti, Zn

A sites

sites

A sites

APF for a HCP = 0.74
ABAB... Stacking Sequence
c/a = 1.633

Слайд 8

Definition of ceramics
Ceramics
- consist of arrays of interconnected atoms
- Nonmetallic

inorganic solids / All inorganic semiconductors
- Oxides, Nitrides, Carbides, Borides, Silicides, Sulfides, Glass

Слайд 9

Definition of ceramics
Ceramics
- Mixed bonding – a combination of covalent, ionic,

(metallic)

Слайд 10

Definition of ceramics
Ceramics
- Crystal structures – Oxide structures
⋅ Ionic radius

of oxygen anion > Ionic radius of metal cation
⋅ Close packed oxygen ion in a lattice (FCC)
⋅ Cations in the holes
? Size relationship cation to anion
? Charge neutrality
? Crystallographic arrangements
? Stoichiometry

Слайд 11

Definition of ceramics
Ceramics
Charge neutrality : Net charge = 0
⋅

Composition : Ma+xAb-y ? a × x + (-b) × y = 0
⋅ NaCl, ZnO, Al2O3, SiO2, Nb2O5, WO3
Relative sizes of ions : Stable structures
⋅ Coordination # increases with rcation/ranion

stable

unstable

Слайд 12

Definition of ceramics
Ceramics
2
Coord.
Number
< 0.155
0.155 - 0.225
0.225 -

0.414

0.414 - 0.732

0.732 - 1.0

linear

triangular

tetrahedral

octahedral

cubic

ZnS

NaCl

CsCl

Definition of ceramics

Содержание

Definition of ceramicsMetals- consist of atoms held together by delocalized electrons

Definition of ceramicsMetals- Alloys : combinations of metallic elements or metallic

Definition of ceramicsMetals- SC (Simple Cubic Structure)Coordination # = 6Atomic Packing

Definition of ceramicsMetals- BCC (Body Centered Cubic Structure)APF for a BCC

Definition of ceramicsMetals- FCC (Face Centered Cubic Structure)APF for a FCC

Definition of ceramicsMetals- HCP (Hexagonal Close Packed Structure)Coordination # = 12Cd,

Definition of ceramicsCeramics- consist of arrays of interconnected atoms - Nonmetallic

Definition of ceramicsCeramics- Mixed bonding – a combination of covalent, ionic,

Definition of ceramicsCeramics- Crystal structures – Oxide structures ⋅ Ionic radius

Definition of ceramicsCeramics Charge neutrality : Net charge = 0 ⋅

Definition of ceramicsCeramics2 Coord. Number< 0.155 0.155 - 0.225 0.225 -

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