Download PowerPoint 簡報 - National Cheng Kung University

Modern Ceramic
Dr.-Ing. Dipl.-Ing. 郭 瑞 昭
Materials Science & Eng.
National Cheng Kung University
National Chen Kung University, 20.12. 2004
What is ceramics ?
The word ceramics, derives its name from the Greek keramos,
meaning “pottery”, which in turn is derived from an older Sanskrit
Root, meaning “to burn”. The Greeks used the term to mean
“burned earth”. Thus the word was used to refer to a product
obtained through the action of fire upon earthy materials.
Most people, when they hear the word ceramic, think of
art, dinnerware, pottery, tiles, brick and toilets. The above
mentioned products are referred to as traditional ceramics.
Outline
• History
• Processing
• Structure
• Properties
• Performance
History
One of the major problems encountered in the teaching
of science, is the frequent lack of any social or historical
perspective.
Science does not evolve in a vacuum, but is constrained
By the mores and morals of society at large.
Newton
•Newton wrote more voluminously on alchemy than he ever
did on the laws of motion.
•He spent an inordinate amount of time on arcane religious
Philosophy.
•He was also a complete misogynist and was probably paranoid.
Newton’s consuming interest in the mystical reflects the
times in which he lived.
Material Ages
Stone Age
(End of Ice Age)
~2,000,000 BC
8,000 BC
Bronze Age
3,200 BC
Iron Age
1,200 BC
Silicon Age
1950 AD
New Material Age
1990-
Material Timeline I
Neolithic age:
8,000 BC
6,000 BC
5,000 BC
5,000 BC
Chalcolithic age:
4,500 BC
4,000 BC
Clay tokens are used in Mesopotamia to
record business transsactions
Copper smelting is developed.
Gold, silver and copper ornaments are
fashioned from nuggets in e.g. the Balkans.
Babylon is built with fired-brick and
bitumen mortar.
Copper is smelted in Eastern Europe and Egypt.
Meteoric iron is used to make small tools and
ornaments
Material Timeline II
Bronze age:
3,500 BC
3,000 BC
1,500 BC
Early Iron age:
1,400 BC1,200 BC
Earliest known use of Bronze is found in Sumer:
first urban civilization
Glass is first used in the Middle East as a glaze
on pottery
Glass vessels are produced in Egypt and
Mesopotamia
The Hittites in Anatolia introduce methods to
produce large quantities of smelted iron.
Classification of Ceramics
Ceramic Materials
Glasses
Clay
(Amorphous, Products
silica based)
Glass
Ceramics
(polycrystalline,
eg. Pyroceram)
Refractories
Alumina, Silica
high purity oxides
Graphite
Abrasives
Diamond
SiC
Silica Sand
Alumina
Cements
Calcium
Silicon
Advanced
Ceramics
Si N 4
3
SiC, BC, WC
ZrO
2
Ceramic-Matrix
Composites
(fibre and whisker
reinfored)
Advanced Ceramics
• Advanced ceramic materials have been developed
over the past half century
• Applied as thermal barrier coatings to protect metal
structures, wearing surfaces, or as integral
components by themselves.
• Engine applications are very common for this class of
material which includes silicon nitride (Si3N4), silicon
carbide (SiC), Zirconia (ZrO2) and Alumina (Al2O3)
• Heat resistance and other desirable properties have
lead to the development of methods to toughen the
material by reinforcement with fibers and whiskers
opening up more applications for ceramics
Performance
Aerospace
Space shuttle tiles, thermal barriers,
high temperature glass window, fuel cells
Aerospace
955
315
650
1465
Temperatures are in
Celsius degrees.
Temps marked with
an * signify ascent
temperatures.
*1175
*425
*430
*405
980
* 420
Diagram of space shuttle's ascent and descent temperatures
Consumer Uses
Glassware, windows, pottery, Corning ware, magnets
Dinnerware, ceramic tiles, lenses, home electronics,
Microwave transducers
Automotive
Catalytic converters, ceramic filters, airbag sensors,
ceramic rotors, valves, spark plugs, pressure sensors,
thermistors, vibration sensors, oxygen sensors, safety
Glass windshield, piston
Rotor (Alumina)
Gears (Alumina)
Medical (Bioceramics)
Orthopedic joint replacement, prosthesis, dental restoration,
bone implants
Military
Structural components for ground, air, naval vehicle, missiles
sensors
CeramicHigh-temperature
Discontinuous
Outer hard
skin
stability and
transparency to
Projectile
microwave radiation
Personnel
and
Equipment
ceramic radomes (front row)
on Patriot missiles
Inner
ductile
skin
Ceramic Armor System
lightweight ceramic armor
Computers
Insulators, resistors, superconductors, capacitors,
Ferroelectric components, microelectronic packaging
Other Industries
Bricks, cement,membranes and filters, lab equipment
Coating
Properties of Engineering Ceramics
• Ceramics are typically,
– hard and brittle
– high melting point materials with low electrical
– thermal conductivity
– good chemical and thermal stability
– high compressive strengths
Mechanical Properties
• Ceramics and glasses are BRITTLE.
• They fail in the elastic region.
• They fail by crack growth.
• They are better in COMPRESSION than TENSION.
• Cracks open up in tension, but close in compression
Mechanical Properties
Mechanical properties depend upon the POROSITY.
Structure
CERAMICS ARE INORGANIC COMPOUNDS
OXIDES - NITRIDES – CARBIDES
Ceramics have more complex crystal structures than metals.
Structure
WHY?
• The structure has to accommodate anions of different sizes,
and has to preserve charge neutrality.
• IONIC or COVALENT bonds.
The diversity in their properties stems from their
bonding and crystal structures.
Two types of bonding mechanisms occur in ceramic
materials, ionic and covalent. Often these
mechanisms co-exist in the same ceramic material.
Each type of bond leads to different characteristics.
Processing
Ceramics Processing
P
P
injection
liquid
powder
Rubber mold pestle
P
powder
powder
Extrusion molding
Injection molding
P
slurry
powder
product
plaster
Die pressing
Slip casting
Slip Casting
Sinter
and
Serve
Powder Pressing Process
Filling
Mould
Compaction
Green part
ejected - then
sintered
Sintering Process
Pressed Ceramic
Particles
Sintered for
a short time
Sintered for
a long time
Microstructure
sintering
forming
Raw powder
Formed product
Sintered product