Bruce Mayer, PE Registered Electrical & Mechanical Engineer BMayer@ChabotCollege

[email protected] • ENGR-45_Lec-27_Ceramic_Apps.ppt1

Bruce Mayer, PE Engineering-45: Materials of Engineering

Bruce Mayer, PERegistered Electrical & Mechanical Engineer

[email protected]

Engineering 45

CeramicCeramicApps/Apps/

ProcessesProcesses



Learning Goals – Ceramic AppsLearning Goals – Ceramic Apps

The Classification of Ceramic Types Review Several Ceramic-Material

Applications How Ceramic

Processing Differs From That of Metals



Taxonomy of CeramicsTaxonomy of Ceramics

Glasses Clay products

Refractories Abrasives Cements Advanced ceramics

-optical -composite

reinforce -containers -household

-whiteware -bricks

-bricks for high T (furnaces)

-sandpaper -cutting -polishing

-composites -structural

engine -rotors -valves -bearings

-sensors Ceramic Properties• Tmelt for GLASS is

moderate, but large for other CERAMICS.

• Small toughness, ductility; large elastic moduli & creep resistance

Applications:• High T, wear resistant, novel

uses by charge neutrality

Fabrication• some glasses can be

easily formed

• other ceramics can not be formed or cast



Application - RefractoriesApplication - Refractories Need a material to use in

high temp furnaces

Consider Silica (SiO2) - Alumina (Al2O3) system

Phase diagram shows Tetrahedral Structures as Candidates:• Mullite (3Al2O3•2SiO2),

alumina (Al2O3), and crystobalite (form of SiO2)

Most FireBrick is taken from the Mullite + Crystobalite Field

Composition (wt% alumina)

T(°C)

1400

1600

1800

2000

2200

20 40 60 80 1000

alumina +

mullite

mullite + L

mulliteLiquid

(L)

mullite + crystobalite

crystobalite + L

alumina + L

3Al2O3-2SiO2



FireBrick CompositionFireBrick Composition

Chemical Analysis wt%PA-20

(2000F/1100C)PA-23

(2300F/1250C) PA-26

(2600F/1425C)Alumina – Al203 43 43 40

Silica – SiO2 52 52 57Ferric Oxide – Fe2O3 1 1 1Titanium Oxide – TiO2 2 2 2Calcium Oxide – CaO 3 3 0

Magnesium Oxide – MgO 0 0 0Alkalies, as Na2O & K2O 1 1 0

Density (kg/cu-m) 625 705 785



Application – Die BlanksApplication – Die Blanks Rod/Wire Drawing Dies need WEAR

Resistant Properties• DIAMOND Thin-Films

are VERY Hard

Die surface• 4 µm polycrystalline diamond particles that are

sintered on to a cemented tungsten carbide substrate.

• polycrystalline diamond helps control fracture and gives uniform hardness in all directions.

tensile force

AoAddie

die

Courtesy Martin Deakins, GE Superabrasives, Worthington, OH. Used with permission.



Application – Cutting ToolsApplication – Cutting Tools Tools for Difficult Applications:

• Grinding: glass, tungsten carbide, other ceramics

• Cutting Si-wafers• Oil Drilling (think rocks)

Solutions:• manufactured single crystal or

polycrystalline diamonds in a metal or resin matrix.

• optional coatings (e.g., Ti to help diamonds bond to a Co matrix via alloying)

• polycrystalline diamonds self-sharpen by microfracturing along crystalline planes

bladesoil drill bits

coated singlecrystal diamonds

polycrystallinediamonds in a resinmatrix.

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



Application – SensorsApplication – Sensors Ex: Oxygen sensor: ZrO2

Principle: Make diffusion of ions fast for rapid response.

Approach: • Add Ca impurity to:

– increase O2- vacancies

– increase O2- diffusion

Operation:• voltage difference produced

when O2- ions diffuse between external and references gases.

A Ca2+ impurity removes a Zr4+ and a

O2- ion.

Ca2+

reference gas at fixed oxygen content

O2- diffusion

gas with an unknown, higher oxygen content

-+voltage difference produced!

sensor



MEMS in MotionMEMS in Motion

Lead Wire

Comb Drive Electrostatic Engine



• Pressing: Gob

Parison mold

Pressing operation

• Blowing:

• Fiber drawing:

wind up

suspended Parison

Finishing mold

Compressed air

GLASSFORMING

PARTICULATE FORMING

CEMENTATION

Ceramic Fabrication Methods-ICeramic Fabrication Methods-I



Recall Glass StructureRecall Glass Structure Basic Unit

Si04 tetrahedron4-

Si4+

O2-

Quartz = Crystalline SiO2

Glass is AMORPHOUS• Amorphous structure occurs

by adding impurities; e.g., Na+, Mg2+ ,Ca2+, Al3+

Impurities interfere with the formation of thecrystallinestructure

Si4+

Na+

O2-

SodaLimeGlass



Glass PropertiesGlass Properties Specific volume (1/ρ)

vs Temperature (T): Crystalline materials:

• crystallize at melting temp, Tm

• have abrupt change in spec. vol. at Tm

Glasses: • do not crystallize

• Spec. vol. varies smoothly with T

• Glass transition temp, Tg → Chg in Slope

Glass (amorphous solid)

T

Specific volume

Liquid (disordered)Supercooled

Liquid

Crystalline (i.e., ordered) solid

TmTg

Glass (amorphous solid)

T

Specific volume

Liquid (disordered)Supercooled

Liquid

Crystalline (i.e., ordered) solid

TmTg



Glass Viscosity ModulationGlass Viscosity Modulation Viscosity: relates shear

stress () & velocity gradient (dv/dy)• Units → Pa-s

Viscosity Decreases with• Increasing Temperature

• The Addition of Impuritities

dvdy

velocity gradient

dvdy

glass dv

dy

Vis

cosi

ty [

Pa•s]

1

102

106

1010

1014

200 600 10001400 1800 T(°C)

Tdeform: soft enough to deform or “work”

annealing range

fused silica

96% silica

Pyrex

soda-lime

glass



Heat Treating GlassHeat Treating Glass ANNEALING

• removes internal stress caused by uneven cooling

TEMPERING• puts SURFACE of glass

part into Compression

• suppresses growth of cracks from SURFACE scratches. Tempering Sequence

further cooledbefore cooling surface cooling

tensioncompression

compressionhot hot

cooler

cooler

• Result: Suppression of Surface Crack Growth



Ceramic Fabrication Methods-IIACeramic Fabrication Methods-IIA

PARTICULATEFORMING

GLASS FORMING

CEMENTATION

Milling and screening: desired particle size Mixing particles & water: produces a “slip” Form a "green" component

• HydroPlastic Forming;– e.g.; Extrude into a Rod

ram billet

container

containerforce

die holder

die

Ao

Adextrusion

• Slip Castingpour slip into mold

absorb water into mold “green

ceramic”

pour slip into mold

drain mold

“green ceramic” Dry; then Fire

At Hi-Temp



The Nature of a SlipThe Nature of a Slip Clay is an

Inexpensive Starting Material

Adding water to clay• allows material to

shear easily along weak van der Waals bonds

• enables extrusion

• enables slip casting

weak van der Waals bonding

charge neutral

charge neutral

Si4+

Al3+

-OHO

2-

Shear

Shear



Drying and FiringDrying and Firing Drying: Layer Size & Spacing Decrease

Firing:• T raised to 900-1400 °C

• Vitrification: glass forms from clay and flows between SiO2 particles

Si02 particle (quartz)

glass formed around the particlemicrograph of

porcelain

70m

wet slip partially dry “green” ceramic



PARTICULATEFORMING

GLASS FORMING

CEMENTATION

Ceramic Fabrication Methods-IIBCeramic Fabrication Methods-IIB

Sintering: useful for both clay and non-clay compositions.

Sintering Procedure:• GRIND to produce ceramic and/or glass particles

• INJECT into mold

• PRESS at elevated Temp to reduce pore size.

Aluminum oxide powder:• Sintered at 1700C

for 6 minutes (note Pores). 15m



Produced in extremely large quantities.

Portland cement:• mix clay and lime bearing

materials

• calcinate (heat to 1400C)

• Primary constituents:– tri-calcium silicate

– di-calcium silicate

Adding water To Portland Cement• produces a paste which

hardens

• hardening occurs due to hydration (chemical reactions with the water).

Forming: done usually minutes after hydration begins

Ceramic Fabrication Methods-IIICeramic Fabrication Methods-III

CEMENTATIONPARTICULATE FORMING

GLASS FORMING



Advanced CeramicsAdvanced Ceramics

Example = Metallic Glass• a.k.a.: “MetGlass” or “Liquid Metal”

Basic Processing Concept• Rapidly solidify from melt

– i.e., Very Fast cooling ratese.g from 1500 °F to

Rm-Temp in 55 Seconds

• Atoms have NO time to Order and become Crystalline

noncrystalline:short range order



Liquid Metal PropertiesLiquid Metal Properties

Liquid Metals are Alloys of Ni, Zr, Ti, Cu, Be



Metallic Glass Mechanical PropsMetallic Glass Mechanical Props

Metallic Glass has good mechanical properties because Metallic Glass has an amorphous structure and thus does NOT have slip Planes



SS vs MetGlassSS vs MetGlass

PropertySS304 Metallic Glass

(Zr-Al-Ni-Cu)

Density g/cm3 7.9 6.8

Tensile Strength MPa 530 1800

Young's Modulus GPa 204 102

Vickers Hardness GPa 2 5

MetGlass is Much STRONGER, but Also Much More FLEXIBLE• Good for “Springy” Structures

– e.g; Golf Club Shafts



Summary – Ceramic Apps/FabSummary – Ceramic Apps/Fab

Basic categories of ceramics: • Glasses

• Clay products (whiteware)

• Refractories (Tolerate Very High Temps)

• Cements

• Advanced Ceramics

Fabrication Techniques:• Glass Forming

– Impurities affect forming Temperature




Fabrication Techniques (cont):• Particulate forming

– Needed if ductility is limited

• Cementation (large volume, room Temperature process)– e.g.; Portland Cement

• SuperRapid Cooling – e.g.; Metallic Glass




Heat Treating Used To:• Alleviate residual stress from cooling,

• Produce fracture resistant components by putting surface into compression– Tempering



WhiteBoard WorkWhiteBoard Work

Problem 13.17• SodaLime Glass (SLG)

Loaded as Shown at Right

• Find Using Fig 13.6 the Max-Temperature if the allowed extension is 1mm over the course of a week’s time– Ref. Next Slide

1N

1 N

SLG100 mm

5 mm



Use Fig. 13.6Use Fig. 13.6

490 °C

dtd

• Where– η Viscosity

– σ Tensile Stress

– ε Tensile Strain

The Viscosity Reln

Bruce Mayer, PE Registered Electrical & Mechanical Engineer BMayer@ChabotCollege

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