class ceramics iium note 1

8/2/2019 Class Ceramics IIUM Note 1

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CREAMICS (MME 3207)

Class hours

Mondays (3:30 4:50)

Wednesdays (3:30 4:50)

Book


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Table of Contents


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The periodic table places the elements in horizontal rows of increasing

atomic number and vertical columns or groups, so that

all elements in a group display similar chemical properties. For instance,all the elements of group VII B, referred to as halides, exist as diatomic

gases characterized by a very high reactivity. Conversely, the elements ofgroup VIII, the noble gases, are monoatomic and are chemically extremely

inert.

A large majority of the elements are solids at room temperature, andbecause they are shiny, ductile, and good electrical and thermal

conductors, they are considered metals.A fraction of the elements most notably, N, O, H, the halides, and the

noble gases are gases at room temperature.The remaining elements are covalently bonded solids that, at room

temperature, are either insulators (B, P, S, C) or semiconductors (Si, Ge).

These elements are referred to as nonmetallic elemental solids(NMESs).


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(a) The first three electron energy states for the Bohr hydrogen atom.(b) Electron energy states for the first three shells of the wave-mechanical hydrogen atom.

Comparison of the (a) Bohr and (b) wavemechanical atom models in terms ofelectron distribution.


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Schematic representation of the relative energies of theelectrons for the various shells and subshells.


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Schematic representation of the filled and lowestunfilled energy states for a sodium atom.


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In metals, the bonding is predominantly metallic, where delocalized

electrons provide the "glue" that holds the positive ion cores together.

This delocalization of the bonding electrons has far-reachingramifications since it is responsible for properties most associated withmetals: ductility, thermal and electrical conductivity, reflectivity, and other

distinctive

properties.

Polymers consist of very long, for the most part, C-based chains to

which other organic atoms (for example; C, H, N, Cl, F) and moleculesare attached. The bonding within the chains is strong, directional, and

covalent, while the bonding between chains is relatively weak. Thus, theproperties of polymers as a class are dictated by the weaker bonds, and

consequently they possess lower melting points, higher thermal

expansion coefficients, and lower stiffnesses than most metals orceramics.


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PE

Semiconductors are covalently bonded solids that, in addition to

Si and Ge, include GaAs, CdTe, and InP, among others. The

usually strong covalent bonds holding semiconductors togethermake their mechanical properties quite similar to those of

ceramics (i.e.: brittle and hard).


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Ceramic MaterialsMetallic and nonmetallic elements are chemically bondedtogether.

Inorganic but can be either crystalline, noncrystalline ormixture of both.

High hardness, strength and wear resistance.Very good insulator. Hence used for furnace lining for heat

treating and melting metals.Also used in space shuttle to insulate it during exit and

reentry into atmosphere.Other applications : Abrasives, construction materials,

utensils etc.

Example:- Porcelain, Glass, Silicon nitride.

Types of Materials

Ceramics can be defined as solid compounds that are formed by the

application of heat, and sometimes heat and pressure, comprising at

least two elements provided one of them is a non-metal or a nonmetallicelemental solid. The other element(s) may be a metal(s) or another

nonmetallic elemental solid(s).

A somewhat simpler definition was given by Kingery who definedceramics as, "the art and science of making and using solid articles,

which have, as their essential component, and are composed in large

part of inorganic nonmetallic materials". In other words, what is neither ametal, a semiconductor or a polymer is a ceramic.


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Dictionary of Ceramic Science and Engineering - a ratherrestrictive definition of ceramics: Any inorganic and non-metallic

product prepared by treatment at temperatures higher than540C (1,000F) or used under conditions implying these

temperatures, which includes metallic oxides and borides,carbides, nitrides and mixtures of these compounds

Concise Encyclopedia of Advanced Ceramic Materials, which presents

the common viewpoint held in Europe, distinguished materials andprocesses: ceramic materials are based on inorganic non-metallic

compounds, primarily oxides, but also nitrides, carbides, silicides; theymust contain at least 30% of crystallized phases in volume; theyexhibit a fragile behavior, with a stress-strain curve that obeys Hookes

law of linear elasticity; ceramic processes bring sintering primarilyinto play, at temperatures higher than 800C..

- Magnesia, or MgO, is a ceramic since it is a solid compound of a metal

bonded to the nonmetal O2.- Silica is also a ceramic since it combines an NMES and a nonmetal.

- TiC and ZrB2 are ceramics since they combine metals (Ti, Zr) and theNMES (C,B)

- SiC is a ceramic because it combines two NMESs.

- Ceramics are not limited to binary compounds: BaTiO3, YBa2Cu3O3, and- Ti3SiC2 are all perfectly respectable class members.

It follows that the oxides, nitrides, borides, carbides, and silicides of all metals

and NMESs are ceramics

silicates are also, by definition, ceramics. Because of the abundance ofoxygen and silicon in nature, silicates are ubiquitous; rocks, dust, clay, mud,

mountains, sand - cement, bricks, and concrete are essentially silicates, thecase could be made that we live in a ceramic world.


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Ceramicsis associated with pottery, sculpture, sanitary ware, tiles, etc.

This is incomplete because it considers only the traditional, or silicate-based,ceramics.

Today the field of ceramic science or engineering can be divided into traditional and

modern ceramics.

Traditional ceramics are usually silicate-based porous microstructures that are quite

coarse, nonuniform, and multiphase. They are typically formed by mixing clays and

feldspars, followed by forming either by slip casting or on a potter's wheel, firing in aflame kiln to sinter them, and finally glazing

modern or technical ceramics are usually sophisticated raw materials, suchas binary oxides, carbides, perovskites, and even completely synthetic

materials for which there are no natural equivalents. The microstructures

of these modern ceramics were at least an order of magnitude finer andmore homogeneous and much less porous than those of their traditional

counterparts

Characteristics of ceramics are hard, wear-resistant, brittle, prone to thermalshock, refractory, electrically and thermally insulative, intrinsically transparent,

nonmagnetic, chemically stable, and oxidation-resistant.

As with all generalizations, there will be exceptions; some ceramics areelectrically and thermally quite conductive, while others are even

superconducting. An entire industry is based on the fact that some ceramicsare magnetic


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Traditional ceramics made frommarble (mixture of limestone CaCO3)

Advanced ceramics for enginesTop left to the right:Silicon nitride (Si3N4) turbochargerSi3N4 valve, cast steel diesel engine rocker arm withpartially stabilized zirconia (PSZ) cam followerand wear button, Si3N4 cam follower, and valve.Bottom left to right:valve; silioccon carbide (SiC) waterpump seal; piston pin, valve spring retainer, andvalve guide of Si3N4; and PSZ diesel head platewith integrated valve seats (ORNL)

Traditional and advanced ceramics

Traditional:Based primarily on natural

Raw materials of clay andsilicates

Advanced:Include artificial raw materials,exhibit specialized properties,require more sophisticatedprocessing

Examples:

clay, glass, cement

Examples:structural,electronic,optical

Traditional Ceramic Materials

Clays Refractories Glasses Cement Abrasives

Silica Oxide Silicate GlassFire Clay Carbide Glass Ceramics

Pottery Whitewares(porcelain,

Structural plumbing,Clay (bricks, fixtures)tiles, pipe)

Advanced Ceramic Materials

Oxides Nitrides Carbides

Abrasives Rocket Engines AbrasivesBio Ceramics Gas Turbines Resistance HeatingElectrical/Electronic Cutting tools (steel ) Steel Addi tives

Cutting Tools High Temperatures Cutting tools (Cermets)

Refractory Brick Substrates for IC chips ArmorClass Additives Coatings Ceramic Matrix CompositesNuclear Fuels Reinforcing Fibres

Taxonomy of ceramics based on applications


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Property Applications (examples)

Thermal

Insulation High-temperature furnace linings for insulation (oxide fibers such asSiO2, Al2O3, and ZrO2)

Refractories High-temperature furnace linings for insulation and containment ofmolten metals and slags

Thermal conductivity Heat sinks for electronic packages (AlN)

Electrical and dielectric

Conductivity Heating elements for furnaces (SiC, ZrO2, MoSi2)

Ferroelectricity Capacitors (Ba-titanate-based materials)

Low-voltage insulators Ceramic insulation (porcelain, steatite, forsterite)

Insulators in electronicapplications

Substrates for electronic packaging and electrical insulators ingeneral (Al2O3, AlN)

Insulators in hostileenvironments

Spark plugs (Al2O3)

Ion-conducting Sensor and fuel cells (ZrO2, Al2O3, etc.)Semiconducting Thermistors and heating elements (oxides of Fe, Co, Mn)

Nonlinear I-Vcharacteristics Current surge protectors (Bi-doped ZnO, SiC)

Gas-sensitive conduct Gas sensors (SnO2, ZnO)


Magnetic andsuperconductive

Hard magnets Ferrite magnets [(Ba, Sr)O6Fe2O3]

Soft magnets Transformer cores [(Zn, M)Fe2O3, with M = Mn, Co, Mg]; magnetictapes (rare-earth garnets)

Superconductivi ty Wires and SQUID magnetometers (YBa2Cu3O7)

Optical

Transparency Windows (soda-l ime glasses), cables for opt ical communication(ultra-pure silica)

Translucency and chemicalinertness

Heat- and corrosion-resistant materials, usually for Na lampsAl2O3MgO)

Nonlinearity Switching devices for optical computing (LiNbO3)

IR transparency Infrared laser windows (CaF2, SrF2, NaCl)

Nuclear applications

Fission Nuclear fuel (UO2, UC), fuel cladding (C, SiC), neutron moderators(C, BeO)

Fusion Tritium breeder materials (zirconates and silicates of Li, Li2O); fusionreactor lining (C, SiC, Si3N4)


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ChemicalCatalysis Filters (zeolites); purification of exhaust gases

Anticorrosion Heat exchangers (SiC), chemical equipment in corrosiveenvironments

Biocompat ibi li ty Artificial joint prostheses (Al2O3, hydroxyapateti te)

Mechanical

Hardness Cutting tools (SiC whisker-reinforced A12O3, Si3N4)

High-temperature strengthretention

Stators and turbine blades, ceramic engines (Si3N4)

Wear resistance Bearings (Si3N4)


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Classification of Ceramic Materials


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Usage of Ceramics

Ceramics for Engineering Design


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Ceramic Pigments

Simple Ceramics and Melting Temperatures


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Ceramic Materials New family of engineering ceramicsare

produced last decade

New materials and applications areconstantly found.

Now used in Auto and Biomedicalapplications.

Processing of ceramics is expensive.

Easily damaged as they are highly brittle.

Better processing techniques and high-impact ceramics are to be found.

Future Trends

Smart Materials : Change their propertiesby sensing external stimulus.

Piezoelectric materials: Produce electricfield when exposed to force and viceversa.

Used in actuators and vibrationreducers.

Future Trends


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Nanomaterials: Characteristic length < 100 nm Examples: ceramics powder and grain size

class ceramics iium note 1

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