Advanced Materials 20151 Ch3.ppt - site.iugaza.edu.pssite.iugaza.edu.ps/aabuzarifa/files/Advanced-Materials-20151_Ch3.pdf · Rethwisch 8e crystobalite. Dr. Anwar Abu-Zarifa . Islamic

CERAMICS

Chapter 3

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Dr. Anwar Abu-Zarifa . Islamic University Gaza . Department of Industrial Engineering

Structures & Properties of Ceramics

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• How do the crystal structures of ceramic materials differ from those for metals?

• How do point defects in ceramics differ from those defects found in metals?

• How are the mechanical properties of ceramics measured, and how do they differ from those for metals?

• In what ways are ceramic phase diagrams different from phase diagrams for metals?

The Porsche Carrera GT's carbon-ceramic (silicon carbide) disc brake

Dr. Anwar Abu-Zarifa . Islamic University Gaza . Department of Industrial Engineering 3

Mid‐16th century ceramic tilework on the Dome of the Rock, Jerusalem

A ceramic is an inorganic, nonmetallic solid materialcomprising metal, nonmetal or metalloid atomsprimarily held in ionic and covalent bonds.

The word "ceramic comes from the Greek wordκεραμικός (keramikos), "of pottery" or "for pottery“.

The crystallinity of ceramic materials ranges fromhighly oriented to semi‐crystalline, and oftencompletely amorphous (e.g., glasses).

Varying crystallinity and electron consumption in theionic and covalent bonds cause most ceramicmaterials to be good thermal and electrical insulatorsand extensively researched in ceramic engineering.

Generalities such as high melting temperature, highhardness, poor conductivity, high moduli of elasticity,chemical resistance and low ductility are the norm,with known exceptions to each of these rules (e.g.piezoelectric ceramics, glass transition temperature,superconductive ceramics, etc.).

Many composites, such as fiberglass and carbon fiber,while containing ceramic materials, are notconsidered to be part of the ceramic family.


Spectrum of Ceramics Uses

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Most frequently silicates, oxides, nitrides and carbides Typically insulative to the passage of electricity andheat

More resistant to high temperatures and harshenvironments than metals and polymers.

Hard but very brittle.

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General Comparison of Materials

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Property Ceramic Metal PolymerHardness Very High Low Very LowElastic modulus Very High High Low

Thermal expansion High Low Very Low

Ductility Low High High

Corrosion resistance High Low Low

Wear resistance High Low Low

Electrical conductivity Depends on material High Low

Density Low High Very Low

Thermal conductivity Depends on material High Low

Magnetic Depends on material High Very Low


CeramTec Medical Engineering (2013)CeramTec – The Ceramic Experts

Ceramic Engineering 1


Ceramic Engineering 2


Structure of Ceramics

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• Bonding:-- Can be ionic and/or covalent in character.-- % ionic character increases with difference in

electronegativity of atoms.

Adapted from Fig. 2.7, Callister & Rethwisch 8e. (Fig. 2.7 is adapted from Linus Pauling, The Nature of the Chemical Bond, 3rd edition, Copyright 1939 and 1940, 3rd edition. Copyright 1960 byCornell University.)

• Degree of ionic character may be large or small:

SiC: small

CaF2: large


Periodic table with ceramics compounds indicated by acombination of one or more metallic elements (in lightcolor) with one or more nonmetallic elements (in darkcolor).

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Example of Crystal Structure

Fluorite structure(AX2)(CaF2)

Barium titanate structure(ABX3)(BaTiO3)

Spinel structure(AB2X4)(MgAl2O4)

12http://www.eng.uwo.ca/es021/ES021b_2007/Lecture%20Notes/Chap%2012-13%20SN%20-%20Ceramics.pdf

Rock salt structure NaCl


VMSE: Ceramic Crystal Structures

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http://www.wiley.com/college/callister/0470125373/vmse/xtalp.htm


Silicate CeramicsMost common elements on earth are Si & O2

SiO2 (silica) polymorphic forms are quartz, crystobalite, &tridymite

The strong Si‐O bonds lead to a high melting temperature(1710ºC) for this material

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Si4+

O2-

Adapted from Figs. 12.9-10, Callister & Rethwisch 8e crystobalite


SilicatesBonding of adjacent SiO4

4‐ accomplished by the sharing ofcommon corners, edges, or faces

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Mg2SiO4 Ca2MgSi2O7

Adapted from Fig. 12.12, Callister & Rethwisch 8e.

Presence of cations such as Ca2+, Mg2+, & Al3+

1. maintain charge neutrality, and2. ionically bond SiO4

4- to one another

VARIOUS COMBINATIONS

For example, Forsterite (Mg2SiO4)


One of the most common clay minerals, kaolinite, has a relatively simple twolayersilicate sheet structure. Kaolinite clay has the formula Al2(Si2O5)(OH)4 inwhich the silica tetrahedral layer, represented by (Si2O5)-2.

The structure of kaoliniteclay. (Adapted from W. E. Hauth,“Crystal Chemistry of Ceramics,”American Ceramic Society Bulletin,Vol. 30, No. 4, 1951, p. 140.)


Glass Structure

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• Quartz is crystallineSiO2:

• Basic Unit: Glass is noncrystalline (amorphous)• Fused silica is SiO2 to which no

impurities have been added• Other common glasses contain

impurity ions such as Na+, Ca2+, Al3+, and B3+

(soda glass)Adapted from Fig. 12.11, Callister & Rethwisch 8e.

Si04 tetrahedron4-

Si4+

O2-

Si4+Na+

O2-


Ceramic Phase DiagramsMgO‐Al2O3diagram (Spinel):

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Adapted from Fig. 12.25, Callister & Rethwisch 8e.

Two eutectics are found, one on either side of the spinel phase field, and stoichiometric spinel melts congruently at about 2100o.

Spinel

These diagrams are especially useful in assessing the high temperatureperformance of ceramic materials.


STRESS–STRAIN BEHAVIOR

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Adapted from Figs. Callister & Rethwisch 8e


Single-walled carbon nanotube: 1,000 GPaDiamond:1,050 – 1210 GPaCarbyne: 32,100 GPa


Adapted from Figs. Callister & Rethwisch 8e


Applications and Processing of Ceramics It is important for the engineer to realize how theapplications and processing of ceramic materials areinfluenced by their mechanical and thermalproperties, such as hardness, brittleness, and highmelting temperatures.

ceramic pieces normally cannot be fabricated usingconventional metal forming techniques.

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Classification of ceramics

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High‐performance ceramics drive the world of theautomobile

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https://www.ceramtec.com/news/archive/year/2007/id/41/


Ceramics Applications: Cutting Tools

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• Tools:-- for grinding glass, tungsten,

carbide, ceramics-- for cutting Si wafers-- for oil drilling

bladesoil drill bits

Single crystal diamonds

polycrystallinediamonds in a resinmatrix.

Photos courtesy Martin Deakins,GE Superabrasives, Worthington,OH. Used with permission.

• Materials:-- manufactured single crystal

or polycrystalline diamondsin a metal or resin matrix.

-- polycrystalline diamondsresharpen by microfracturingalong cleavage planes.


The glasses are a familiar group of ceramics;containers, lenses, and fiberglass represent typicalapplications.

They are noncrystalline silicates containing otheroxides, notably CaO, Na2O, K2O, and Al2O3, whichinfluence the glass properties. A typical soda–limeglass consists of approximately 70 wt% SiO2, thebalance being mainly Na2O (soda) and CaO (lime).

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Ceramics Applications: GLASSES



One of the most widely used ceramic raw materials is clay.This inexpensive ingredient, found naturally in greatabundance, often is used as mined without any upgradingof quality.

Most of the clay‐based products fall within two broadclassifications: the structural clay products and thewhitewares.

Structural clay products include building bricks, tiles, andsewer pipes—applications in which structural integrity isimportant. The whiteware ceramics become white after thehigh‐temperature firing. Included in this group areporcelain, pottery, tableware, and plumbing fixtures(sanitary ware).

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Ceramics Applications: CLAY PRODUCTS


Refractories

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• Materials to be used at high temperatures (e.g., in high temperature furnaces).

• Consider the Silica (SiO2) - Alumina (Al2O3) system.• Silica refractories - silica rich - small additions of alumina

depress melting temperature (phase diagram):

Fig. 12.27, Callister & Rethwisch 8e. (Fig. 12.27 adapted from F.J. Klug and R.H. Doremus, J. Am. Cer. Soc. 70(10), p. 758, 1987.)

Composition (wt% alumina)

T(ºC)

1400

1600

1800

2000

2200

20 40 60 80 1000

alumina+

mullite

mullite + L

mulliteLiquid

(L)

mullite+ crystobalite

crystobalite + L

alumina + L

3Al2O3-2SiO2


Ceramic as Refractories

https://www.youtube.com/watch?v=JcFixNVnjgs&index=2&list=PL1AE198B26227EC62


Advanced Ceramics: Materials for Engines Advantages:

Operate at high temperatures – high efficiencies Low frictional losses Operate without a cooling system Lower weights than current engines

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• Disadvantages: – Ceramic materials are

brittle– Difficult to remove internal

voids (that weaken structures)

– Ceramic parts are difficult to form and machine

• Potential candidate materials: Si3N4, SiC, & ZrO2

• Possible engine parts: engine block & piston coatings


CERAMIC JET‐ENGINE PARTS TAKING OVER THE AVIATION INDUSTRY

Source: https://jsetceramics.wordpress.com/


Source: https://jsetceramics.wordpress.com/


Advanced Ceramics: Microelectromechanical Systems (MEMS

Microelectromechanical systems (abbreviated MEMS) areminiature “smart” systems consisting of a multitude ofmechanical devices that are integrated with large numbers ofelectrical elements on a substrate of silicon.

The mechanical components are microsensors and microactuators.

One example of a practical MEMSapplication is an accelerometer (accelerator/decelerator sensor) that is used in thedeployment of air‐bag systems inautomobile crashes.



Manufacturing process of ceramic products

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Manufacturing of ceramics

Documents

Advanced Materials 20151 Ch3.ppt - site.iugaza.edu.pssite.iugaza.edu.ps/aabuzarifa/files/Advanced-Materials-20151_Ch3.pdf · Rethwisch 8e crystobalite. Dr. Anwar Abu-Zarifa . Islamic