MME391 Ceramic Materialsdepo.btu.edu.tr/dosyalar/metalurji/Dosyalar/Ceramic_Materials_2...MME391...

Asst. Prof. Dr. Ayşe KALEMTAŞ

MME391 CeramicMaterials


Bursa Technical University, Metallurgical and Materials Engineering Department

Office Hours: Tuesday, 10:00-11:[email protected], [email protected]

mailto:[email protected]











CLASSIFICATION OF CERAMICS

Ceramic Materials

Advanced Ceramics Traditional Ceramics

Made from artificial or

chemically modified raw

materials.

Mainly made from natural raw materials such as

kaolinite (clay mineral), quartz and feldspar.


Advanced Ceramics

Chemically prepared powders

Precipitation, spray drying, freeze

drying, vapor phase, sol-gel

Slip casting, injection molding, sol-gel,

hot-pressing, HIPing, rapid prototyping,

Electric furnace, hot press, reaction

sintering, vapor deposition, plasma

spraying, microwave furnace

Erosion, laser machining, plasma

spraying, ion implantation, coating

Light microscopy, X-ray diffraction, electron

microscopy, scanned probe microscopy, neutron

diffraction, surface analytical methods

Raw Materials

Preparation

Forming

High temperature

processing

Finishing

Characterization

Traditional

Ceramics

Raw minerals

- Clay

- Silica

Potters wheel, slip

casting, pressing

Flame kiln

Erosion, glazing

Visible examination,

light microscopy

Advanced versus Traditional Ceramics


Raw Material Selection Criterias

Raw material cost

Market factors

Technical process parameters

Performance of the desired product

Market price of the product


CERAMIC RAW MATERIALS

Ceramic Materials

Naturally occurring minerals Synthetic materials

their origin locations in which they can be found their relative abundance

Naturally occurring minerals requireextraction, which is often a regional industrylocated close to abundant quantities of thenatural deposit.

Most minerals need to go through some formof physical or chemical processing before use.The collective term for these processes isbeneficiation.

When you understand how oxides aremanufactured, it will be clear why they areoften impure and why Si, Na, Ca are themajor impurities.

borides (TiB2, BN, etc.) carbides (SiC, B4C, TiC, etc.) nitrides (AlN, Si3N4, TiN, etc.) oxides (TiO2, Al2O3, etc.)

These ceramics are becoming morecommon, but are generally expensiveand desire special processingenvironments.

For many nonoxides the mainimpurities are often components ofthe starting material which was notreacted, e.g., Al in AlN or Si in Si3N4.


CERAMIC RAW MATERIALSCategory Purity, % Materials

Crudematerials

VariableShales, stoneware clay, tile clay, crude

bauxite, crude kyanite, natural ball clay, bentonite

Industrialminerals

85-98

Ball clay, kaolin, refined bentonite, pyrophyllite, talc, feldspar, nepheline syenite, wollastonite, spodumene, glass sand, potter’sflint (quartz), kyanite, bauxite, zircon, rutile,

chrome ore, calcined kaolin, dolomite

Industrialinorganicchemicals

98-99.9

Calcined alumina (Bayer process), calcinedmagnesia (from brines, seawater), fused

alumina, fused magnesia, aluminum nitride,silicon carbide, silicon nitride, barium

carbonate, titania, calcined titanates, ironoxide, calcined ferrites, zirconia, stabilized

zirconia, calcined zirconates

Specialinorganicchemicals

99.9 Various materials (Si3N4, TiB2, SiC, BN, etc)


Synthetic Materials

OXIDES

The raw materials used for oxideceramics are almost entirelyproduced by chemical processes toachieve a high chemical purity and toobtain the most suitable powders forcomponent fabrication.

NON-OXIDES

Most of the important non-oxideceramics do not occur naturallyand therefore must be synthesized.The synthesis route is usually one ofthe following:

Combine the metal directly withthe nonmetal at high temperatures.

Reduce the oxide with carbon athigh temperature (carbothermalreduction) and subsequently react itwith the nonmetal.


Natural Raw Naterials


Minerals

• Minerals are defined as (1) naturallyoccurring, (2) inorganic substanceswith a narrow range of (3) chemicalcomposition and (4) characteristicphysical properties.

• An example: The naturally occurringform of the compound sodium chlorideis the mineral halite.


MineralsMohs Hardness Scale

Mohs' scale of mineral hardness quantifies the scratch resistance of minerals by comparing the ability of a harder material to scratch a softer material.

The Mohs scale was invented in 1812, by the German mineralogist Friedrich Mohs. Mohs based his scale on ten minerals.

Mineral Hardness

Talc 1

Gypsum 2

Calcite 3

Fluorite 4

Apatite 5

Feldspar 6

Quartz 7

Topaz 8

Corundum 9

Diamond 10

http://www.allaboutgemstones.com/mohs_hardness_scale.html


Minerals


1. TalcTalc is the world's softest mineral and the lowest mineral on the Mohs scale.Talc is a hydrated magnesium sheet silicate which is highly insoluble in water.Talc is translucent to opaque with a iridescent or pearly luster. Talc is used incosmetics such as talcum powder, as a lubricant, and in paper manufacturing.

Absolute Hardness: 1Chemical Composition: Mg3Si4O10(OH)2

2. GypsumGypsum is a soft mineral composed of calcium sulfate dihydrate. Gypsumoccurs in nature as flattened or twinned crystals and transparent cleavablemasses called selenite. When Gypsum has a silky and fibrous texture it is calledSatin Spar.

Absolute Hardness: 2Chemical Composition: CaSO4á2H2O

3. CalciteCalcite is an anhydrous carbonate, and one of the most widely distributedminerals on the Earth's surface. It is a common constituent of sedimentaryrocks. In crystallized form, Calcite has a vitreous luster.

Absolute Hardness: 9Chemical Composition: CaCO3

Mohs Hardness Scale

http://www.allaboutgemstones.com/glossary_gemology.html




Minerals


4. FluoriteFluorite (fluor-spar) is a mineral composed of calcium fluoride. It is anisometric mineral with a cubic crystal habit. Fluorite is named for itsproperty of fluorescence, or its ability to fluoresce under ultraviolet light.

Absolute Hardness: 21Chemical Composition: CaF2

5. ApatiteApatite (hydroxylapatite, fluorapatite, chlorapatite) is a group of phosphateminerals and is one of few minerals that are produced by biologicalorganisms. Hydroxylapatite is the major component of tooth enamel.

Absolute Hardness: 48Chemical Composition: Ca5(PO4)3(OH-,Cl-,F-)

6. OrthoclaseOrthoclase (aka feldspar) in an igneous rock forming tectosilicate (silicate)mineral and is a key component in granite. Orthoclase derives its nameform the Greek word for "straight fracture" because of its two cleavages atright angles to each other. Orthoclase crystallizes in the monoclinic crystalsystem.

Absolute Hardness: 72Chemical Composition: KAlSi3O8

Mohs Hardness Scale




http://www.allaboutgemstones.com/rock_cycle_igneous.html





Minerals

Mohs Hardness Scale7. QuartzQuartz is one of the most common minerals found inthe Earth's crust. It has a hexagonal crystal structuremade of trigonal crystallized silica (silicon dioxide). Thetypical shape of a Quartz crystal is a six-sided prismthat ends in six-sided pyramids.

Absolute Hardness: 100Chemical Composition: SiO2

8. TopazTopaz is a silicate or "nesosilicate" mineral created froma combination of aluminium and fluorine. It crystallizesin the orthorhombic system and it's crystals areprismatic in form.

Absolute Hardness: 200Chemical Composition: Al2SiO4(OH-,F-)2



Minerals

9. CorundumCorundum is the crystalline form of aluminium oxide and one ofthe basic rock-forming minerals. Corundum is naturally clear orcolored by impurities. Due to its hardness, Corundum is used asan abrasive in sandpaper. Emery is an impure and less abrasivevariety of Corundum.

Absolute Hardness: 400Chemical Composition: Al2O3

10. DiamondDiamond is the hardest natural occurring material. Diamond is anatural allotrope of carbon. The crystal bond structure ofdiamonds give the stone its hardness and differentiates it fromgraphite, which is the main allotrope of carbon.

Absolute Hardness: 1500Chemical Composition: C

Mohs Hardness Scale



WEATHERING

• Mechanical Weathering– Physical disintegration of rock (with no

chemical alteration)

• Chemical Weathering– Chemical alteration of minerals within the

rock– Usually softening or dissolving the minerals– Forming clays, oxides and solutes


WEATHERING

• The result of mechanicalweathering– Rock falls and slides– Crushing and abrasion

Rocks physically broken apart intosediment(but composition does NOT change)

Increases surface area(lots of crushed broken pieces)


WEATHERINGMECHANICAL WEATHERING ABRASION

WATER WIND


WEATHERING

ANIMALS

Animals that burrow in ground can cause weathering


WEATHERING

• Sediments of:– Parent rock– Mineral particles– Angular fragments

Sediments from Mechanical Weathering


WEATHERING

Breakdown of rocks by chemical reactions that change thecomposition of rocks

What is Chemical Weathering?

HydrolysisFeldspar + Water = Clay

Feldspar

A Clay Cliff

OCCURS WHEN Water combines with mineralsmost often in granite (mica and feldspars) to form CLAY


WEATHERING



CARBONATION (causes dissolving)

Rainwater containing carbon dioxide dissolves

minerals (all rain water is slightly

acidic)

Most strongly affected are calcite minerals:

Limestone and marble


WEATHERING



RUSTING-OXIDATION

OXIDATION OCCURS when oxygen combines chemically with iron to form iron oxide


WEATHERING

Breakdown of rocks by chemicalreactions that change thecomposition of rocks


Dissolving-ACID RAINsulfuric acid-pollution in air dissolves

in rainwater and eats away at buildings & rocks


WEATHERING

• Chemical Weathering– Dissolving Dissolved ions– Oxidation Iron in Ferromag. Minerals Iron Oxides (e.g.,

Hematite)– Formation of Clays from silicates (e.g., Feldspar)


WEATHERING

• Chemical Weathering– Dissolving Dissolved ions– Oxidation Iron in Ferromag. Minerals Iron Oxides (e.g., Hematite)

– Formation of Clays from silicates (e.g., Feldspar)

Oxidation: 4FeSiO3 + O2 + H2O FeO(OH) + 4SiO2

Hydration: CaSO4 + 2H2O CaSO4·2H2O


WEATHERING

CLIMATE CONTROLS WEATHERING

PHYSICAL WEATHERING:COLD AND MOIST ALTERNATE FREEZE / THAW

CHEMICAL WEATHERING:WARM AND MOIST (just like a chemical

reaction)

IN BOTH CASES – WATER IS THE PRIMARY INGREDIENT THAT PROMOTES WEATHERING


WEATHERING

Soil Formation and Weathering Related

to Climate


WEATHERING

Weathering Products of Common Rock-Forming Minerals


Minerals

Minerals may be subdivided into two majors groups:

– Oxides O2-

– Carbonates (CO3)2-

– Sulfides S2-

– Sulfates (SO4)2-

– Halides Cl-, F-, Br-

– Native elements (single elements; e.g., Au)

• Silicates (most abundant)

• Non-silicates (~8% of Earth’s crust):


Minerals

FerromagnesianSilicates (Fe, Mg)

Non-ferromagnesianSilicates (K, Na, Ca, Al)

OxidesCarbonatesSulfides/sulfatesNative elements


Minerals

• Silicates– Tetrahedron

• fundamental building block

• 4 oxygen ions surrounding a much smaller silicon ion

Silicates are by far the mostabundant mineral groupaccounting for more than90% of the Earth's crust.Silicates are the major rock-forming minerals. It followsthat oxygen and silicon arethe most abundant elementsin the crust.


Non-Silicates

• Usually form at low temperatures–Carbonates

• Calcite - CaCO3

• Dolomite - CaMg(CO3)2–Evaporite Minerals

• Gypsum - CaSO4-2H2O• Halite - NaCl

–Oxides• Hematite


Non-Silicates


NATURAL RAW MATERIALS

Clays

Silica

Feldspar

Talc

Wollastonite

Aluminum Minerals

Lithium Minerals

Flourine Minerals



Non-uniform, crude materials from natural deposits clays.(Montmorillonite, illite, etc.)



The preparation, particularly of clay, by exposure tothe weather for a long period. This helps to oxidize anypyrite present, rendering it soluble, so that this andother soluble impurities are to some extent leached out;the water content also becomes more uniform andagglomerates of clay are broken down with aconsequent increase in plasticity.

Weathering is simply the chemical and/or physicalbreakdown of a rock material. Weathering involvesspecific processes acting on rock materials at or nearthe surface of the Earth.

Weathering products of common rock-forming minerals


Element Abundances

All others: 1.5%

SILICATES

Common cations thatbond with silica anions


Abundance of Minerals

* : Ceramic Materials: Science and Engineering, by C. Barry Carter and M. Grant Norton, Springer, 2007, 348.

Abundance of Minerals in the Earth’s Crust *


QUESTIONS

MME391 Ceramic Materialsdepo.btu.edu.tr/dosyalar/metalurji/Dosyalar/Ceramic_Materials_2...MME391...

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