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ceramics

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Structure &
Properties
of Ceramics

Lecture 3
EBB113

Why study ceramic materials?
– Very “traditional” (crude civil engineering material) – BUT also new high-tech ceramics and applications.
• Optical (transparency) opto-electronic
• Electronic (piezoelectrics, sensors, superconductors)
• Thermo-mechanical (engine materials)
• Cutting tools
Today, the
U.S. market is
estimated to be over
$35 billion.

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Introduction
keramikos - burnt stuff in Greek → desirable properties of ceramics are normally achieved through a high-temperature heat treatment process (firing). Usually a compound between metallic and non-metallic elements. Always composed of more than one element (e.g.,Al2O3, NaCl, SiC, SiO2) Interaction bond either totally ionic or having some covalent character Properties :

• Generally hard and brittle
• Generally electrical and thermal insulators (exceptions: graphite, diamond, AlN… and others)
• Can be optically opaque, semi-transparent, or transparent High chemical stability and high melting temperature.
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Class of ceramic
Traditional Ceramics: primary raw materials is clay
Example: porcelain, bricks, tiles, glasses.

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Class of ceramic

Oxygen sensor

Now new generation of this materials
have evolved
Engineering Ceramics
High-temperature ceramic
Advance ceramic
Electroceramic

Aerospace product-Ni
Ti, Stainless steel
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Ceramics Structure

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Ceramic Crystal Structures
Ceramic which predominately ionic-composed of cation (+ve charge) and anion (-ve charge)
Atomic Bonding: Mostly ionic, some covalent.
% ionic character increases with difference in electronegativity. CaF2: large
Ionic SiC: small
12%

Ionic
89%

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Crystal Structure
Two characteristic which influence the crystal structure
1.
Magnitude of electrical charge of each component ions
2.
The relative sizes of the cation and anions

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1. Magnitude of electrical charge of each component ions
Electrically must be...
Lecture 3
EBB113
Structure &
Properties
of Ceramics