Modern Ceramic 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 keramoskeramos,meaning “pottery”, which in turn is derived from an older SanskritRoot, 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 ofart, dinnerware, pottery, tiles, brick and toilets. The abovementioned products are referred to as traditional ceramics.

• History

• Processing

• Structure

• Properties

• Performance

Outline

History

One of the major problems encountered in the teachingof science, is the frequent lack of any social or historicalperspective.

Science does not evolve in a vacuum, but is constrainedBy the mores and morals of society at large.

Newton

•Newton wrote more voluminously on alchemy than he everdid on the laws of motion.

•He spent an inordinate amount of time on arcane religiousPhilosophy.

•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 ~2,000,000 BC

(End of Ice Age) 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 Clay tokens are used in Mesopotamia to

record business transsactions6,000 BC Copper smelting is developed.5,000 BC Gold, silver and copper ornaments are

fashioned from nuggets in e.g. the Balkans.5,000 BC Babylon is built with fired-brick and

bitumen mortar.Chalcolithic age:

4,500 BC Copper is smelted in Eastern Europe and Egypt.4,000 BC Meteoric iron is used to make small tools and

ornaments

Material Timeline II

Bronze age:3,500 BC Earliest known use of Bronze is found in Sumer:

first urban civilization3,000 BC Glass is first used in the Middle East as a glaze

on pottery1,500 BC Glass vessels are produced in Egypt and

MesopotamiaEarly Iron age:

1,400 BC- The Hittites in Anatolia introduce methods to1,200 BC produce large quantities of smelted iron.

Classification of Ceramics

Ceramic Materials

Glasses Clay Products

Refractories Abrasives Cements Advanced Ceramics

Glass Ceramics

(Amorphous, silica based)

(polycrystalline, eg. Pyroceram)

Alumina, Silica high purity oxides Graphite

Diamond SiC Silica Sand Alumina

Calcium Silicon

Si N3 4

SiC, BC, WC

ZrO2

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 (Al2

O3) • Heat resistance and other desirable properties hav

e 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

1175

430 405

425

420

980

1465650

315 Temperatures are in Celsius degrees. Temps marked with an * signify ascent temperatures.

*

* **

*

Diagram of space shuttle's ascent and descent temperatures

Consumer Uses

Glassware, windows, pottery, Corning ware, magnetsDinnerware, 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, safetyGlass windshield, piston

Gears (Alumina)Rotor (Alumina)

Medical (Bioceramics)

Orthopedic joint replacement, prosthesis, dental restoration,bone implants

Military

Structural components for ground, air, naval vehicle, missilessensors

ceramic radomes (front row) on Patriot missiles

High-temperature stability and transparency to microwave radiation

lightweight ceramic armor

Projectile

Outer hard skin

Ceramic-Discontinuous

Innerductileskin

PersonnelandEquipment

Ceramic Armor System

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

Die pressing

powder

P

Extrusion molding

powder

P

Injection molding

powderP

injection

slurry

product

plaster

Slip casting

Rubber mold pestle

powder

liquid

P

Slip Casting

Sinter and Serve

Powder Pressing Process

FillingMould

Compaction Green partejected - then sintered

Sintering Process

Pressed Ceramic Particles

Sintered for a short time

Sintered for a long time

Microstructure

forming sintering

Raw powder Formed product Sintered product