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Home , Crown glass (optics), Glass transition, Zerodur

Material Science II Materials

Chapter 5:

F. Filser & L.J. Gauckler ETH-Zürich, Departement Materials [email protected]

SS 2007

Ceramics: Glass, Chap 5 slide 1 Material Science II Persons in Charge of this Lecture

• I. Akartuna, HCI G 538, phone 36842, [email protected] F. Krauss HCI G 538, phone 3 68 34, [email protected]

• Dr. F. Filser, HCI G 529, phone 26435, [email protected]

• Prof. Dr. L.J. Gauckler HCI G 535, phone 25646, [email protected]

• Dipl.-Ing. J. Kübler EMPA Dübendorf, phone 044 823 4223, [email protected]

Ceramics: Glass, Chap 5 slide 2 Material Science II

Materials Science I: Ceramics

Introduction on ceramic materials, technology, applications structures of ceramic materials Potential well of bonding and physical properties & Examples of Structural ceramic materials Examples of structural ceramic materials

Ceramics: Glass, Chap 5 slide 3 Material Science II Overview & schedule

Mar 19, 07 term start Mar 20, 07 Glass and Glass-Ceramics (FF) Mar 27, 07 Toughness (JK) Apr 03, 07 Strength & Weibull statistics (JK) Apr 10, 07 Sub-critical crack growth, SPT-Diagrams (JK) Apr 17, 07 Proof-testing, , thermal properties (JK) Apr 24, 07 part (Prof. D. Schlüter) Jun 22, 07 term finish

Ceramics: Glass, Chap 5 slide 4 Material Science II Learning Targets

• Definition of glass as a “frozen”

• – temperature – behavior

• Structure of Glass, Network

• Network formers, network modifiers, and Zwischenoxide

• Optical properties (, , transmission)

• Chemical resistance and

• Fabrication of glass

• Glass ceramics, nucleation rate und crystal growth rate

Ceramics: Glass, Chap 5 slide 5 Material Science II V-T-Diagram for Crystal and for Glass Formation

lt e M

supercooled liquid Volume frozen ΔV solidification liquid Glass Vol -Vol fast melt cryst slow Crystal

T Tg f Temperature Tg

• are frozen . • They don’t posses a (distinct) temperature but a temperature. • The glass transition temperature and the of a glass depend on the cooling rate. • We don’t observe a energy of formation during the solidification of a glass melt. • In glass state the disorder of the melt is preserved. Ceramics: Glass, Chap 5 slide 6 Material Science II History: W. H. Bragg and W. Lawrence Bragg

W.H. Bragg (father) and William Lawrence Bragg (son) developed a simple relation for angles, now call Bragg’s law. n ⋅λ d = 2⋅sinθ

Ceramics: Glass, Chap 5 slide 7 Material Science II Another View of Bragg´s Law

nλ = 2d sinθ

Ceramics: Glass, Chap 5 slide 8 Material Science II Laue - Powder X-ray Diffraction

Film

Tube

Powder

Ceramics: Glass, Chap 5 slide 9 Material Science II Bragg diffraction of

glassy and crystalline material (PbF2)

Ceramics: Glass, Chap 5 slide 10 Material Science II Laue-Diagram for a Single Crystal

(Points) film

aperture single crystal

Ceramics: Glass, Chap 5 slide 11 Material Science II Zachariasen’s Network-Hypothesis

2-dimensionel visualization of a

- regular SiO4 -network (SiO2 - quartz, left) and of a - irregular network (glass, right)

Ceramics: Glass, Chap 5 slide 12 Material Science II

[SiO4] - Network

[SiO4] - network with network modifiers Na and Ca Ceramics: Glass, Chap 5 slide 13 Material Science II Glass

Short range order = Glass

Si4+

O2-

O2- 4- [SiO4] Tetrahedron Si4+

O2- O2- O2- z.B. 4+ O2- Si Na+, + Ceramics: Glass, Chap 5 K slide 14 Material Science II Network Former

α↓ → thermocycling↑

SiO2 Tg↑→ η↑ mech. strength ↑

α↑ → thermocycling↓ T ↓→ η↓ B O g 2 3 acid resistance mech. strength ↓

UV transparency ↑

P2O5 IR transparency ↓ chem. resistance ↓

Network former and their influence on the glass‘ properties.

Ceramics: Glass, Chap 5 slide 15 Material Science II Network Modifier

Li2O η↓↓

Na2O η↓

a K2O Glass becomes „longer“ CaO chem. resistance ↑

a. Glasses are termed “long” or “short” glasses according to their Viscosity-Temperature-Function.

Ceramics: Glass, Chap 5 slide 16 Material Science II Zwischenoxide

MgO Glass becomes “longer“ Glass becomes “longer“

Al2O3 mech. strength ↑ chem. resistance ↑

Tg↓ n ↑ PbO electrical resistance ↑ Absorption of x-rays (40-80 weight-%) n ↑ TiO 2 resistance against acids ↑ chem. resistance ↑ ZrO 2 tarnish for enamels ZnO hardness ↑ CdO absorption of thermal neutrons (30-60 weight-%)

Ceramics: Glass, Chap 5 slide 17 Material Science II Typical Glass Compositions I

>99.9 weight-% SiO2 pure vitreous silica in the ppm-range (quartz glass) α=0.5·10-6 K-1

96 weight-% SiO2, 3 weight-% B2O3, rest alkali, Glass impurities in the ppm-range α=0.8·10-6 K-1

SiO2 72,

Commercial window glass Al2O3 1.5, MgO 3.5

CaO 8.5, Na2O 14.5 (weight-%)

chem. laboratory glass SiO2 72, B2O3 10

(aluminium-borosilicate Al2O3 3, glass) CaO 1, MgO 1, Na2O 5 (weight-%)

Ceramics: Glass, Chap 5 slide 18 Material Science II

Typical Glass Compositions II

SiO2 28, optical glass PbO 70, (heavy ) Na2O 1, K2O 1 (weight-%)

SiO2 29, glass for X-ray protection PbO 62, BaO 9 (weight%)

B2O3 83, X-ray transparent glass BeO 2,

Li2O 15 (weight%)

P2O5 72, „hydrofluoric acid“ resisting Al O 18, glass 2 3 ZnO 10 (weight%)

Ceramics: Glass, Chap 5 slide 19 Material Science II Viscosity of Glass Melts

B logη =+A TT− 0 η = 1013 dPa·s Vogel-Fulcher-Tamman Equation

• Glass softens steadily but doesn‘t melt (at a distinct temperature)! • The viscosity of glass is a steady curve which spans 16 to 18 orders of magnitude. • „Melt“ exists for temperature higher than Tg (= infexion point of its viscosity curve), „“ exists for a temp. lower than Tg. Ceramics:• VFT-equation Glass, Chap describes 5 the viscosity for temperatures higher than Tg. slide 20 Material Science II “long” Glass – “short” Glass

long glass in log dPas η

short glass

T in °C

η-T-function of Dow-Corning‘s glasses („long" glass, „short" glass)

Ceramics: Glass, Chap 5 slide 21 Material Science II Elongation of Glass I

Δl α =1/l i th o ΔT

Dilatometry for the determination of Tg and α of a glass.

Ceramics: Glass, Chap 5 slide 22 Material Science II Cooling Rate Influence of the cooling rate on the formation of glass. volume melt

fast

normal cooling

glass slow

Tgs Tgn Tgf temperature

• Tg and density of a glass depend on the cooling rate. • A low cooling rate (i.e. slow cooling) leads to higher density than a high cooling rate.

Ceramics: Glass, Chap 5 slide 23 Material Science II Elongation of Glass II

Contraction and elongation curves of a glass. 0: equilibrium curve; 1: normal cooling; 2: slow cooling; 3: fast cooling; 3’: normal heating

Ceramics: Glass, Chap 5 slide 24 Material Science II Density as function of the alkali amount

Density of binary alkalisilicate glasses

Ceramics: Glass, Chap 5 slide 25 Material Science II Density as a function of the network former and its amount

Density variation of a binary alkalisilicate glass in function of the

replacement of SiO2 by other oxides in the same weight amount.

Ceramics: Glass, Chap 5 slide 26 Material Science II Reduction of the strength caused by flows

theoretic strength Flaws in strength of glass structure glass

strength of brand Micro flaws in new acid polished the surface glass strength

strength of normal glass ware Macro flaws in strength of damaged the surface glass ware

Strength of glass and its reasons

Ceramics: Glass, Chap 5 slide 27 Material Science II Pre-stressing

tension compression

surface

a) b)

surface

Stress profiles for the a) thermal and the b) chemical method of pre-stressing.

Ceramics: Glass, Chap 5 slide 28 Material Science II Chemical Resistance of Glasses

• hydrofluoric acid HF attack (corrosion)

• diluted aqueous acids attack

• base attack

• combined water and acid / base attack

Ceramics: Glass, Chap 5 slide 29 Material Science II Chemical Resistance of Glass against Hydrofluoric Acid HF

SiO2 + 6HF → H2SiF6 + 2H2O

• Hydrofluoric acid breaks up the SiO2 structures of silicate based glasses.

• Easy soluble silicon hexaflourid SiF6 (hexafluoro silcia) is formed during the reaction.

Ceramics: Glass, Chap 5 slide 30 Material Science II Chemical resistance of glass against aqueous acids

Attack by aqueous acids: ion exchange reaction

-Si-O-Na+ + H+ → -Si-OH + Na+

Leaching time

Distance from the surface

• Gel – layer at the surface which is proton saturated • This gel layer serves as a diffusion barrier. • The thicker this gel-layer the more difficult for ions (Na+, H+) to diffuse through this layer. -> Passivation! Ceramics: Glass, Chap 5 slide 31 Material Science II Chemical resistance of glass against bases

-Si-O-Si- + X-OH→ -Si-OH + SiO-X (X=Li, Na, K)

• Bases attack directly in a detrimental way the network of the glass in contrast to acids. Bases destroy the network.

• The SiO2 molecules are dissolved and remain in the solution as poly-silicates. • No protection layer is formed in this type of corrosion process

• BUT always a new surface forms which is continuously attacked by the hydroxide-ions of the solution.

Ceramics: Glass, Chap 5 slide 32 Material Science II Chemical resistance of glass against water and combined acid / base exposure

• Pure water at pH 7-9 corrodes glass because of free protons + (H3O ) by auto protolysis. • The glass corrodes by leach-out of alkaline cat ions.

• The alkaline cat ions increase the pH of the water by formation of hydroxyl ions (OH-).

• The hydroxyl ion start to solubilise the glass network and /or the gel layer.

• Thus, hydroxyl ions are consumed, and the proton concentration in the solution increases and the cycle starts over.

Ceramics: Glass, Chap 5 slide 33 Material Science II Time dependence of glass corrosion

• Type I:

• A surface layer is formed which acts as a protection layer (adsorption protection layer).

• vitreous silica in neutral salt solution accounts for this type.

• Type II:

• A protection layer is formed by leaching out of alkalines. The glass network remains stable.

• Attack of acids at silicate glasses accounts for this type.

• Type III:

• Leaching and reaction at the surface form two protection layers of different composition.

• The glass network remains stable.

Ceramics: Glass, Chap 5 slide 34 Material Science II Time dependence of glass corrosion

• Type IV:

• Leaching and wear (material removal) take place at the same time.

• A new leached out layer is formed at the surface which will be continously shifted more and more inside the bulk glass by the wear of the glass network (i.e. material removal).

• Alkalisilicate glasses in water account for this type.

• Type V:

• Constant wear of the glass network and material removal.

• No leaching layer is formed!

• Hydofluoric acid and strong base attack at silicate glasses account for this type.

Ceramics: Glass, Chap 5 slide 35 Material Science II Time dependence of glass corrosion

Case 1: For the types I, II and III corrosion stops after formation of a protection layer (passivation), i.e. the corrosion front c moves on with a decreasing speed. dc ∝ te−αt dt Case 2: For type IV corrosion involves two competing reactions:

(1) the diffusion: ct∝

(2) the dissolution: ct∝

Case 3: For type V reaction or corrosion rate has a constant value: dc = a dt

Case 4: progressive corrosion takes place when we have the solution deficiency on the glass surface. Then, the corrosion reaction changes the pH-value of the solution which leads to a “stronger” corrosion at a higher rate. The wear or corrosion rate increases with reaction time: dc = at dt

Ceramics: Glass, Chap 5 slide 36 Material Science II Reaction progress for the corrosion of glasses

progressive (Case 4)

limited (Case 2)

passivated (Case 1)

constant (Fall 3)

time t

Reaction rates for the different cases.

Ceramics: Glass, Chap 5 slide 37 Material Science II Transmission of a light beam through glass

reflected light reflected light

transmitted light

incident light beam

glass air air

Way of a light beam transmitting a interface of two media (air, glass)

Ceramics: Glass, Chap 5 slide 38 Material Science II Influence of Alkaline content

on the nD

Variation to the refractive index as a function of the alkaline content of binary alkalisilicate glasses.

Ceramics: Glass, Chap 5 slide 39 Material Science II

Influence of the network former on the refractive index

Variation of the refractive index nD of a Na2O - SiO2 - glass (20-80 weight%) if SiO2 (network former) is substituted according to weight by other network former (Al2O3, B2O3) or elements.

Ceramics: Glass, Chap 5 slide 40 Material Science II Fraunhofer Lines

h g F‘ F e d C‘ C r

Hg Hg Cd H Hg He Cd H He purple blue blue blue green yellow red red red

404.66 435.84 479.99 486.13 546.07 587.56 643.85 656.27 706.52

Ceramics: Glass, Chap 5 slide 41 Material Science II What is Dispersion? The dependence of the refractive index from the light-wavelength.

h g F‘ F e d C‘ C r

Hg Hg Cd H Hg He Cd H He purple blue blue blue green yellow red red red 404.6 435.8 479.9 486.1 546.0 643. 656.2 706.5 587.56 6 4 9 3 7 85 7 2 prism screen

white light

Dispersion splits white light in its colours !!!! That effect is fatal for optical applications of glass!!! Ceramics: Glass, Chap 5 slide 42 Material Science II What is Dispersion? The dependence of the refractive index from the light-wavelength.

h g F‘ F e d C‘ C r

Hg Hg Cd H Hg He Cd H He purple blue blue blue green yellow red red red 435. 479.9 486.1 546.0 643. 656.2 706.5 nF – nC 404.66 587.56 84 9 3 7 85 7 2 ϑrel = ------nD – 1

nd – 1 ν = ------nF – nC

Ceramics: Glass, Chap 5 slide 43 Material Science II Dispersion und Refractive index

Flint glasses

Crown glasses

nd – 1 ν = ------n – n nD-ν-Diagram of optical glasses F C

Ceramics: Glass, Chap 5 slide 44 Material Science II Dispersion and Refractive Index

nd – 1 ν = ------nF – nC

nD-ν-Diagramm optischer Gläser

Ceramics: Glass, Chap 5 slide 45 Material Science II

Chromatic Aberration

Chromatic aberration in case of a bi-convex and bi-concave .

Ceramics: Glass, Chap 5 slide 46 Material Science II

Crown Glass Flint Glass

Correction of the chromatic aberration by combining two suitable .

Ceramics: Glass, Chap 5 slide 47 Material Science II Transmission through Glass

Wave Number Transmission

Wave Length

Transmissions spectrum of a commercial float glass (thickness 1mm)

Ceramics: Glass, Chap 5 slide 48 Material Science II UV-Rim in Glasses Transmission

Wave Length

UV rim of glasses of various composition

1: SiO2-Glass very pure, 2: SiO2-Glass normal,

3: Na2O - 3 SiO2 Glass very pure,

4: Na2O-3 SiO2-Glass, normal

Ceramics: Glass, Chap 5 slide 49 Material Science II Transmission spectrum of Glasses I ) λ ( τ Spectral Transmission

Wave Length λ [nm]

Transmission spectra of coloured glasses.

Ceramics: Glass, Chap 5 slide 50 Material Science II Transmission spectrum of Glasses II

Transmission spectra of colored glasses.

Ceramics: Glass, Chap 5 slide 51 Material Science II Colorizing Ions and their Effect I

Valency Coordination Color Ti(III) 6 purple V(III) 6 green V(V) 4 colorless Cr(III) 6 green Cr(VI) 6 yellow Mn(II) 6 colorless Mn(III) 6 purple Fe(II) 6 blue Fe(III) 6 yellow

Ceramics: Glass, Chap 5 slide 52 Material Science II Colorizing Ions and their Effect II

Valency Coordination Color Co(II) 4 blue Co(II) 6 pink Co(III) 4 green Ni(II) 4 blue Ni(II) 6 yellow Cu(I) ? colorless Cu(II) 6 blue

Ceramics: Glass, Chap 5 slide 53 Material Science II Float Glass Process

http://www.glasswebsite.com Ceramics: Glass, Chap 5 slide 54 Material Science II The Float Glass Process

Ceramics: Glass, Chap 5 http://www.glasswebsite.com/video/fgmd.asp slide 55 Material Science II Float Glass process

Ceramics: Glass, Chap 5 slide 56 Material Science II Float Glass Process

Batch Charger Furnace

Raw Materials Tin Bath (Float Furnace) Lehr Cutting System

Ceramics: Glass, Chap 5 slide 57 Material Science II Composition of commercial float glass

Glass Material Reason for Adding Composition

Sand (SiO2) 72.6 -

Soda Ash (Na2CO3) 13.0 Easier melting

Limestone (CaCO3) 8.4 Durability

Dolomite(CaMg(CO)2) 4.0 Working & weathering properties

Alumina (Al2O3) 1.0 - Others 1.0 -

Ceramics: Glass, Chap 5 slide 58 Material Science II Composition Float Glass

http://www.pilkington.com

Ceramics: Glass, Chap 5 slide 59 Material Science II Chemistry of Glass

Ceramics: Glass, Chap 5 slide 60 Material Science II Glass-Ceramics

• Structure

• Nucleation and crystal growth

• Fabrication

•Examples

• next: mechanical properties of ceramics (J. Kübler, EMPA)

Ceramics: Glass, Chap 5 slide 61 Material Science II Glass-Ceramics

• „Glass-ceramic“ refers to materials which are fabricated from glass melts by a process of controlled crystalisation.

• Glass-ceramis is a partially crystalline material which is fabricated by an incomplete crystallisation („Ceraming“) of suitable glasses.

• Brands: Ceran, , Robax, Neoceram,

Ceramics: Glass, Chap 5 slide 62 Material Science II Glass-Ceramics

Short-range order Glass

Grain with grain boundary

O2- SiO4 tetrahedron

Si4+

O2- O2- O2-

Ceramics: Glass, Chap 5 slide 63 Material Science II

Nucleation energy and radius of the nucleus

Glass (amorph) to Crystal Energy ∝ r3 Surface Energy = r2

r

Dependence of the nucleation energy from its nucleus‘ radius

Ceramics: Glass, Chap 5 slide 64 Material Science II Critical Nucleus Radius

4π Δ=GrGr32 Δ +4π σ 3 ν

-> 1. Derivative must be zero for r*

3 16πσ 4 2 Δ=Gr∗∗ =π σ 332 ()ΔGν 1 rT∗()∼ ()TTS −

∗ 1 ΔGT()∼ 2 ()TTS −

Ceramics: Glass, Chap 5 slide 65 Material Science II Nuclei Formation Rate (Nucleation Rate)

⎛⎞()EG+Δ ∗ ννKB =−Nν exp⎜⎟ ⎝⎠kT

Ceramics: Glass, Chap 5 slide 66 Material Science II Crystal Growth Rate (KG)

⎛⎞[]Δ+GE NN''=⋅⋅ν exp⎜⎟ − ⎝⎠kT ⎛⎞E NN'exp=⋅⋅ν ⎜⎟ − ⎝⎠kT Crystal Growth Rate ('NN− '') ⎡⎤⎛⎞ E ⎡ ⎛⎞ΔG ⎤ ννKG ==⋅⋅−⋅−−aa00⎢⎥exp⎜⎟⎢1 exp⎜⎟⎥ NkTkT⎣⎦⎝⎠⎣⎢ ⎝⎠⎦⎥

Ceramics: Glass, Chap 5 slide 67 Material Science II

Temperature Dependence of νKB and νKG

TS

KG, Crystal Growth

KB, Nucleation

TE

Nucleation and Crystal Growth rate

Temperature Dependence of νKB and νKG; TE: Temperature TS: Melting Temperature Ceramics: Glass, Chap 5 slide 68 Material Science II Temperature-Time (T-t)-Curve for the Fabrication of a typical Glass-Ceramics Nucleation Crystallisation Cooling Cooling Checking, Shaping Checking, Checking, Shaping Checking, Melt Forming

Time

Ceramics: Glass, Chap 5 slide 69 Material Science II Examples for Glass-Ceramic-Systems

Crystalline TEC System Application Phase 10-7 K cooktop, fireproof cookware fire Li O-Al O -n SiO, H- Quartz mixed 2 2 3 2 0 - 0.7 protection glass, reflecting n= 4-6 crystal telescope, gyroscope Li O - Al O -n SiO, fireproof cookware, 2 2 3 2 ß-Spodume 1.5 - 2 n= 4-10 exchanger

Na2O - Al2O3 -2 SiO2 Nepheline 11 plates

car exhaust filter, substrates for 2 MgO- 2 Al O3 – 2 Cordierite 1.5 - 3 microelectronics, composite 5 SiO 2 materials Lithium- Li O- 2 SiO 12 fabrication of microstructures 2 2 disilicate

(Na,K) bioceramics (dental implants, Phlogopite 8 - 12 Mg3AlSi3O10F2 bone substitutes)

Ceramics: Glass, Chap 5 slide 70 Material Science II Properties of Glass-Ceramics

• : -20 to 200·10-7 K-1

• strength: 60 – 600 MPa

• optical property: transparency – opaque

• chemical resistance: water soluble – inert

• electrical property: semi-conducting – isolating

• mech. machinability: brittle – machinable

Ceramics: Glass, Chap 5 slide 71 Material Science II Fabrication of Ceran cooktop panels (Schott)

1st step

2nd step

Ceramics: Glass, Chap 5 slide 72 Material Science II Advantages of glass-ceramics over ordinary ceramics

Advantages: Disadvantages:

• forming is as simple as in case of • limited to certain crystalline glass phases

• transparent pre-forms

• good reproducibility of the materials properties

• free of pores

• mono-size

• economic fabrication process

Ceramics: Glass, Chap 5 slide 73 Material Science II Summarizing: Glass & Glass Ceramics

• Glass can be regarded as frozen melt (liquid) - which solidified without crystallisation - which has a short range order but no long-range order.

• The glass structure can be described using Zachariasen‘s network model.

• Glass solidifies at the glass transition temperature Tg, - for T > Tg glass is a (liquid) melt, - for T

• Glass-ceramics is fabricated from glass by using controlled crystallisation process, and it has special properties.

Ceramics: Glass, Chap 5 slide 74 Material Science II Ersatz

Ceramics: Glass, Chap 5 slide 75 Material Science II Overview on the composition of important glass types

Glass type SiO2 Al2O3 Na2O K2O MgO CaO B2O3 PbO TiO2 F As Se Ge Te

quartz glass 100 – – – – – – – – – – – – – Kalk-Natron-glass 72 2 14 - - 10 - - - - – – – – (ordinary glass)

float glass 72 1,5 13,5 - 3,5 8,5 - - - - – – – –

lead crystal glass 60 8 2,5 12 - - - 17,5 - - – – – –

Laboratory glass 80 3 4 0,5 - - 12,5 - - - – – – –

E-glass 54 14 - - 4,5 17,5 10 - - - – – – –

enamel 40 1,5 9 6 1 - 10 4 15 13 – – – – chalcogenide – – – – – – – – – – 12 55 33 – glass 1 chalcogenide – – – – – – – – – – 13 32 30 25 glass 2

All amounts in weight -%. Ceramics: Glass, Chap 5 http://de.wikipedia.org/wiki/Glas#Einstellung_der_Glaseigenschaften slide 76 Material Science II

Ceramics: Glass, Chap 5 slide 77 Material Science II The basic idea of the float glass process

• Molten glass poured onto a bath of clean molten tin, will spread out in the same way that oil will spread out if poured onto a bath of water. • Gravity and surface tension will result in the top and bottom surfaces of the glass becoming approximately flat and parallel.

Ceramics: Glass, Chap 5 slide 78 Material Science II The basic idea of the float glass process

The equilibrium thickness (T)

2 2ρt TSSS=++()ggtti gρg ()ρρt − g

where Sg, Sgt, and St are the values of surface tension at the three interfaces.

For standard soda-lime-silica glass under a protective atmosphere and on clean tin the equilibrium thickness is approximately 7 mm.

Ceramics: Glass, Chap 5 slide 79 Material Science II The Production Process

Ceramics: Glass, Chap 5 slide 80