CERAMICSTypes and Applications

CERAMICS Keramikos (Greek - burnt stuff) Properties are achieved normally

through a high-temperature heat treatment (firing)

Materials composed of at least two elements

Primary components: Silicates Carbons

COMMONLY FABRICATED CERAMICS

Glass Clay Refractories Cement Abrasives Advanced Ceramics

COMMONLY FABRICATED CERAMICS

CLAY

widely used ceramic raw material

inexpensive ingredient

found naturally in great abundance

used as mined without any upgrading of quality

CLAY

• forms a plastic mass that is very amenable to shaping when mixed with water in proper proportions

• dried, and then fired at an elevated temperature to improve its mechanical strength

CLAY

STRUCTURAL CLAY PRODUCTS

STRUCTURAL CLAYSpecifications for raw materials used in most structural clay products: Plastic enough for shaping Dry without excessive cracking and

warping Have low and wide vitrification range Low carbonate content Have a spread in particle size Contain non-clay constituents

include building bricks, tiles, and sewer pipes used in applications in which structural integrity is

important (resistant to mechanical and chemical stress)

proportions above are often found directly in shale deposits, so that blending is often not necessary.

STRUCTURAL CLAY

made from 35 -55% clays or argillaceous (clayey) shales, 25-45% quartz, and 25-55% feldspar clay portion acts as a former, providing shaping ability quartz (silica) serves as a filler, providing strength to

the formed object feldspar serves as a fluxing agent, lowering the

melting temperatures of the clay and quartz during firing

STRUCTURAL CLAY

properties determined by particle size, firing temperature, and ultimate microstructure coarser filler particles are used, and lower firing

temperatures are employed—typically in the range of 1,050° to 1,100° C

Resulting microstructure: large secondary particles in a matrix of fine-grained mullite and glass—all containing a substantial volume of large pores.

STRUCTURAL CLAY

Because of the presence of large and small particles in their microstructures, fired clay products have relatively high compressive strengths – good for structural applications if underfired: low strength and poor resistance to frost

and freezing, due to small pores in the clay regions If overfired: ware has too much glass; it is strong but

brittle and is susceptible to failure under mechanical and thermal stress.

STRUCTURAL CLAY

WHITEWARES

become white after the high-temperature firing

porcelain, pottery, tableware, china, and plumbing fixtures

many contain nonplastic ingredients, influences the drying and firing processes and the characteristics of the finished piece

STRUCTURAL CLAY

mostly composed of a mixture of kaolin, ball clay and ground non-clay materials including feldspar, quartz, talc and others higher alumina materials such as kyanite

and specially treated kaolins are being incorporated in some of the whiteware products

STRUCTURAL CLAY

CEMENT

CEMENTS Plaster of Paris,

concrete, lime Used in binding

materials (i.e. sand and gravel to form concrete) or surfaces, or to coat against chemical attack

CEMENTS

hardens by the evaporation of the plasticizing liquid (i.e. water, alcohol, or oil) by internal chemical change, by hydration, or by the growth of interlacing sets of crystals, or by their reaction with the oxygen or carbon dioxide in the atmosphere.

Microscopic Image of Cement

CEMENTS Processed according to

sequence: calcination, grinding, addition of gypsum (retards/slows cement setting process) Calcination – grinding

and intimately mixing clay and lime-bearing minerals in proper proportions, heating to 1400oC in a rotary kiln

COMPOSITION

PROPERTIES Powder form is mixed with water to

form a paste that may be molded into any size and shape

bond develops at room temperature (unlike refractory bricks, or clay)

may act as a bonding phase that chemically binds particulate aggregates into a single cohesive structure

May have properties of refractories

TYPES 1. Portland Cement

obtained by pulverizing clinker consisting of hydraulic calcium silicates, to which no additions (except for a little H2O or untreated CaSO4) have been made before calcinations

typically used in construction

TYPES 2. Pozzolan Cement

strong slow-hardening type of cement from finely divided siliceous and aluminous materials that react chemically with slaked lime at ordinary temperature in the presence of moisture

3. Controlled Cement cement that prevents shrinking and

cracking upon setting

TYPES 4. High alumina cement

characterized by a very rapid rate of strength development and superior resistance to sea water and sulfate-bearing water.

5. Special or Corrosion Resisting cement used in large quantities for the fabrication of

corrosion-proof linings for chemical equipment

ABRASIVE CERAMICS

ABRASIVE CERAMICS silicon carbide,

tungsten carbide (WC), aluminum oxide (or corundum), and silica sand.

Diamonds, both natural and synthetic (relatively expensive)

ABRASIVE CERAMICS substance used to wear,

grind, polish an or cut away other material

bonded to a wheel by means of glassy ceramic or an organic resin

commonly used in household cleaning products and manufacturing processes

STRUCTURE

Principle Construction of Coated Abrasives (cloth backing)

The surface structure should contain some porosity; a continual flow of air currents or liquid coolants within the pores that surround the refractory grains prevents excessive heating.

STRUCTURE

porosity

Al2O3 abrasive grains

Bonding phase

Photomicrograph of an aluminum oxide bonded ceramic abrasive

PROPERTIES The size, shape, and hardness of a

substance’s particles determine its characteristics as an abrasive. Coarse, larger grains normally remove

material faster than smaller grains. Wear Resistant High degree of toughness Refractoriness

withstand high temperatures without melting or decomposing

TYPES 1. Coated Abrasives

Abrasive powder is coated on some type of paper or cloth material

Ex. Sandpaper

TYPES 2. Loose Abrasive

Grains Employed in

grinding, lapping, and polishing wheels

Delivered in some type of oil- or water-based vehicle.

REFRACTORIES

PROPERTIES capacity to withstand high

temperatures without melting or decomposing

capacity to remain unreactive and inert when exposed to severe environments.

ability to provide thermal insulation

- performance depends on composition

- bulk densities range from 2.1 to 3.3 g/cm^3.

Aluminum melting furnace

PROPERTIESPorosity

one microstructural variable that must be controlled to produce a suitable refractory brick. 

an decrease in porosity will increase strength, load-bearing capacity, and resistance to attack by corrosive materials.

thermal insulation characteristics and resistance to thermal shock are diminished as porosity is decreased.

COMPOSITION

TYPES Fireclay

primary ingredients are high-purity fireclays, alumina and silica mixtures usually containing between 25 and 45 wt% alumina.

mechanical integrity will not be compromised with the presence of a small amount of liquid phase.

upgrading the alumina content will increase the maximum service temperature.

TYPES Silica

acid refractories prime ingredient is silica has a high-temperature load-bearing

capacity. used in arched roofs of steel and glass-

making furnaces readily attacked by slags composed of a high

proportion of CaO and/or MgO

TYPES Basic

rich in periclase or MgO, may also contain calcium, chromium, and iron compounds.

presence of silica is deleterious to their high-temperature performance

resistant to attack by slags containing high concentrations of MgO and CaO

has extensive applications in some steel-making open hearth furnaces

Lime Klin

SPECIAL REFRACTORIESExamples: high-purity oxide materials

alumina, silica, magnesia, beryllia (BeO), zirconia (ZrO2), and mullite (3Al2O3-2SiO2).

Carbide compounds Silicon Carbide (SiC)

used for electrical resistance heating elements (crucible material) and internal surface components.

carbon and graphite very refractory but limited in application due to

their susceptibility to oxidation at temperatures > 800oC. 

expensive

APPLICATIONS High-duty fireclay brick

linings for cement and lime klins, blast furnaces and incinerators

High-alumina brick boiler furnaces, spent-acid

regenerating furnaces, phosphate furnaces

APPLICATIONS Superduty fireclay

bricks linings for

aluminum-melting surfaces, rotary kilns, blast furnaces, and hot-metal transfer ladles

Silica brick chemical reactor

linings, glass tank parts, coke ovens

Rotary Klin

APPLICATIONS  Magnesite brick

basic-oxygen-process furnace linings for steelmaking

Zircon brick glass-tank bottom

paving and continuous-casting nozzles

Continuous-casting Nozzles

GLASS

GLASS Amorphous (literally, without form -

noncrystalline) silicates containing other oxides (i.e. CaO, Na2O, K2O, Al2O3) Typical soda-lime glass consists of

approximately 70 wt% SiO2, balance maintained by Na2O (soda) and CaO (lime).

2-D schemes of a) crystalline silicon dioxide; b) amorphous silicon dioxide.

PROPERTIES Optically

transparent Relatively easy to

fabricate Ex. Containers,

windows, lenses

COMMERCIAL GLASSES

T-V Dependence of Glass

Crystalline solids – nucleation occurs at specific temperature

Amorphous solids (glass) – viscosity increases as temperature decreases Temperature depends on the composition

(i.e. 96% silica – 1550oC, 108Pa-s).

T-V Dependence of Glass

GLASS-CERAMICS A crystallized form of

inorganic glasses Done through a high-

temperature heat treatment called devitrification (crystallization)

A nucleating agent (usually TiO2) is added to induce crystallization or devitrification process

Aluminum silicate glass-

ceramics

PROPERTIES

Fine-grained polycrystalline material As a result: high

mechanical strengths

SEM micrograph of a glass-ceramic

PROPERTIES Low coefficient of thermal expansion, Good dielectric properties Good biological compatibility Optical properties (opacity) can be

adjusted Excellent insulators, serving as

substrates for circuit boards

EXAMPLES

Left: Glass-ceramic china pot; Above: Glass-ceramic cooktop

ADVANCED CERAMICS

ADVANCED CERAMICS Also called “special,” “technical” and

“engineering” ceramics Exhibit superior mechanical properties,

corrosion/oxidation resistance, or electrical, optical, and/or magnetic properties

Aforementioned properties are usually paired with other properties unique to ceramics

Developed only in the past 100 years

Advanced vs. Traditional Ceramics

Advanced Ceramics

Traditional

CeramicsRaw

Materials+

Processing

Chemically prepared powdersPrecipitation, spray dry, freeze dry, vapor phase, sol-gel

•Raw minerals•Clay•Silica

Forming

Slip casting, injection molding, sol-gel, hot pressing, HIPing, rapid prototyping

•Potters wheel•Slip casting

Advanced vs. Traditional Ceramics

Advanced Ceramics

Traditional

CeramicsHigh-

temperature

Processing

Electric furnace, hot press, reaction sinter, vapor deposition, plasma spraying, microwave furnace

•Flame Kiln

Finishing

Process

Erosion, laser machining, plasma spraying, ion implantation, coating

•Erosion•Glazing

Advanced vs. Traditional Ceramics

Advanced Ceramics

Traditional

Ceramics

Characterization

Light microscopyX-ray diffractionElectron microscopyScanned probe microscopyNeutron diffractionSurface analytical methods

•Visible examination•Light microscopy

EXAMPLES Zirconia (ZrO2) Silicon Nitride (Si3N4) Silicon Carbide (SiC) Boron Carbide (B4C) Alumina (Al2O3) Graphite Diamond

TYPES Structural Ceramics

Made of components such as Si3N4, SiC, ZrO2, B4C and Al2O3

Have high hardness, low density, high-temperature mechanical strength, creep resistance, corrosion resistance, chemical inertness

Used in cutting tools, wear components, heat exchangers, and engine parts

TYPES Electronic Ceramics

Made of BaTiO3, ZnO, lead zirconate titanate [Pb(ZrxTi1−x)O3], AlN, and HTSCs

Applications are capacitor dielectrics, varistors, microelectromechanical systems (MEMS), substrates, and packages for integrated circuits

Coatings and Films modify surface properties of a material may be for economic reasons (i.e. diamond

coating) in some cases, may improve material performance

TYPES Bioceramics

Used in the human body Response varies from

Nearly inert bioceramics: include Al2O3 and ZrO2

Bioactive ceramics: include hydroxyapatite and some special glass and glass–ceramic formulations.

Resorbable bioceramics: Tricalcium phosphate (dissolves in the body)

APPLICATIONS Microelectromechanical Systems (MEMS)

Miniature “smart” systems Made up of many mechanical devices integrated

with a large number of electrical elements on a substrate of silicon

Can detect and react to changes in its environment using its microsensors, microactuators and mircoelectric components

APPLICATIONS Studies are being made on the use of ceramics Limitations of silicon in MEMS

low fracture toughness relatively low softening temperature highly active to the presence of water and oxygen

Ceramic materials are being considered because they are tougher, more refractory and more inert amorphous silicon carbonitrides (silicon carbide–

silicon nitride alloys) made from metal organic precursors are currently being studied

APPLICATIONS Accelerometer in cars used in the

deployment of air-bag systems smaller, lighter, more reliable and less

expensive than conventional air-bags system Other possible MEMS application are:

electronic displays and data storage units energy conversion devices chemical detectors (for hazardous chemical

and biological agents, and drug screening) microsystems for DNA amplification and

identification

APPLICATIONS Optical Fibers

Critical component in our modern optical communications systems

signal transmission is photonic, instead of electronic: uses electromagnetic radiation improved speed of transmission,

information density, and transmission distance

reduction in error rate no electromagnetic interference

APPLICATIONS Ceramic Ball Bearings

A bearing consists of balls and races that are in contact with and rub against one another when in use traditionally made of bearing steels that are

very hard, extremely corrosion resistant and may be polished to a very smooth surface

Silicon nitride (Si3N4) balls have begun replacing steel balls in a number of applications Hybrid bearing

APPLICATIONS Hybrid Bearings

Races are still made of steel Better tensile strength than silicon nitride

Balls are made of silicon nitride Lower density: hybrid bearing is lighter

enabling higher operation speeds Higher modulus of elasticity: more rigid and

less prone to deformations when in use so there is a reduction in noise and vibration levels

APPLICATIONS Inline skates Bicycles Electric motors Machine tool spindles Precision medical hand

tools (e.g., high-speed dental drills and surgical saws)

Textile, food processing Chemical equipment

ADVANCED CERAMICS: BREAKTHROUGH

Piezoelectric Ceramics Exhibit the unusual phenomenon of

piezoelectricity electric polarization (i.e., an electric field or

voltage) is induced in the ceramic crystal when a mechanical strain is imposed on it and vice-versa

Piezoelectric ceramics include BaTiO3, PbTiO3, lead zirconate–titanate (PZT) [Pb(Zr,Ti)O3], potassium niobate (KNbO3)

Piezoelectric Effect

Applications of Piezoelectric Ceramics

Gas lighter/igniter Sonar (in submarines) Medical ultrasonic applications Accelerometers Transformers Ink-jet/dot-matrix printers Laser beam scanners Automatic camera focusing systems and

camera shutters Sensors for burglar alarm

Sources Bayquen, Ph.D., Cecilia V.; University of Sto. Tomas. Industrial

Chemical Processes Book 2. Manila, 2007. Callister Jr., William D. Materials Science and Engineering An

Introduction. Quebecor: Quebecor Versailles, 2007. Carter, C. Barry, and M. Grant Norton. Ceramic materials

science and engineering. New York: Springer, 2007. Heimann, Robert. Classic and advanced ceramics: From

fundamentals to applications. Weinheim: WILEY-VCH, 2010. Kingery, W. D., H. K. Bowen, and D. R. Uhlmann. Introduction

to Ceramics. John Wiley & Sons., 1976. Microsoft® Encarta® 2007 [DVD]. Cement. Redmond, WA,

2006. http://www.clays.org/journal/archive/volume%2010/10-1-

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http://www.hexoloy.com/sgengineeredproductssmaller.jpg http://www.omegaslate.com/images/cyclone/vort12.gif http://www.memx.com/images/ratchet.jpg http://upload.wikimedia.org/wikipedia/commons/4/49/

Fibreoptic.jpg http://www.solusource.com/TomInfo/Content/Press

%20Release/1377_0_cronitect%20hybrid%20bearing%20LR.JPG

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