CERAMIC MATERIALS
An Introduction
Introduction: Ceramic Materials
Review:
metals
• often solids at room temp
• Shiny, ductile, good electrical and thermal conductor
NMES (nonmetallic element solids)
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Covalently bonded
Solid at room temp
Either insulators of semiconductors
Nonmetallic Elemental Solids
Ceramics
Defined as:
An inorganic solid compounds comprising of metallic and
nonmetallic elements, for which the interatomic bonding is
predominantly ionic.
Solid compounds are formed by the application of heat, or
heat and pressure (thermal treatment)
Ceramics
Comprised of :
• at least one metal and nonmetallic elemental solids or a
nonmetal (ex. MgO, ZrBr2, TiC)
• at least two nonmetallic elemental solids (ex. SiO2, SiC)
• not limited to binary compounds (ex. BaTiO3, YBa2Cu3O7)
Ceramics
Includes:
• Oxides
Silica – for most glass products
• Borides
Titanium boride – for structural applications including cutting tool
and ceramic armor nozzles
• Nitrides
Boron nitride – for high-temperature insulation
• Carbides
Silicon carbide – used extensively for mechanical seals because of
its chemical and wear resistance
• Silicides – for electronic devices
• Silicates – main ingredients in most clay products/minerals
Ceramics
General Properties:
• Hard, brittle, and wear-resistant
• Electrical and thermal insulating, chemical stability and high
melting temperature (non-combustible and non-oxidizable)
• Refractory
• Some ceramics are translucent, example is window glass
• Exhibit superior electromagnetic, optical and mechanical
properties
Ceramics
Traditional vs advanced ceramics
Ceramics
Categories:
• Traditional Ceramic Materials
Silicate-based ceramics associated with pottery and bricks,
sculpture, sanitary wares, tiles, common abrasives and cement
• Advanced Ceramic Materials
Ceramics which are not clay or silicate-based and developed based
on oxides, carbides, nitrides, etc. possessing mechanical and
physical properties superior or unique compared to traditional
ceramics
Ceramics
Other applications
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Electronic packaging
Capacitors
Piezoelectric sensors and actuators
Solid electrolytes for fuel cells
Chemical sensors
Superconductors
Turbines
Ceramic engine
Tools for aggressive environment
Ceramics
Aspects of Materials Research:
• Property
• Structure
• Manufacture
Structure is the key to relate property to manufacture.
Ceramics
Elementary crystallography
1. Amorphous and crystalline
The arrangement of atoms could be in
» Long-range order (ex. Crystalline solids)
» Short-range order (ex. Amorphous or
glassy)
» Combination (ex. Semicrystalline)
A long range order is best described using a 3D pattern
that repeats throughout the length/width/height of
the material.
Ceramics
2. Unit Cell
To describe this repeating
pattern a unit cell is
identified.
Unit cell – the smallest
region in space that when
repeated, completely
describes the three
dimensional pattern of the
atoms of a crystal.
There can only be 7 ways to
stack these patterns:
• Cubic
• Rhombohedral
• Tetragonal
• Hexagonal
• Orthorhombic
• Monoclinic
• Triclinic
From the 7 crystal systems,
only 14 possible
combinations of primitive
and non-primitive cells–
Bravais Lattices
Ceramics
Ceramics
Ceramic Microstructures
Ceramics are mostly
polycrystalline
• Composed of
collection of many
crystals called
grains
• Separated by areas
of disorder called
grain boundaries
For ceramics, grain size
could be from 1 to
50µm.