V.M. Sglavo – GlassEng - UNITN 2017 Free energy of mixture ...· V.M. Sglavo – GlassEng - UNITN

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V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

Phaseseparationinglass

Free energy of mixture: Gm = Hm - T Sm

entropy-Sm

entalpy-Hm

Termodinamica strutturale, J.H. Brophy, R.M. Rose, J. Wulff,, Ambrosiana Ed., 1975

A,Baf3ine idealsituation A,Bnotaf3ine

Halloy

Halloy

Halloy

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

freeenergy-Gm

completemiscibilityinonesinglephase

incompletemiscibilitytwophases

Termodinamica strutturale, J.H. Brophy, R.M. Rose, J. Wulff,, Ambrosiana Ed., 1975

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

G(c)= G(c0)+ Gc c0(c c0)+ 12

2Gc2 c0

(c c0)2 + .....

Ifc=c0-c0

G TC: complete miscibilityT < TC: immiscibility

spinode

unstablezone

metastablezones

Separationmechanisms:- nucleationandgrowth(metastablezone)largevariationofG

- spinodaldecomposition(unstablezone)gradualvariationofcomposition(spontaneous)

Struttura e genesi dello stato vetroso, A. Maddalena, Cleup, 1983

TEMPERATURE

FREEENERGY

COMPOSITION

composition

distance

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

nucleationandgrowthspinodaldecomposition

interconnectedstructure islesstructure

Introduction to glass science and technology, J. E. Shelby, The Royal Society of Chemistry, 1997

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

stableimmiscibility metastableimmiscibility

Immiscibility diagrams

Tg

Introduction to glass science and technology, J. E. Shelby, The Royal Society of Chemistry, 1997

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

Homogenous and biphasic glass

homogenousislesseparation(SiO2richmatrix)

interconnectedseparation

islesseparation(SiO2-Na2Omatrix)

SiO2 Na2O

Introduction to glass science and technology, J. E. Shelby, The Royal Society of Chemistry, 1997

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

Examples:

sodium-borosilicate glass

Introduction to glass science and technology, J. E. Shelby, The Royal Society of Chemistry, 1997

barium-silicate glass

sodium-silicate glass

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

lithium-sodium-silicate glass alkali-borosilicate glass

microporousand/orVycorglass

TC=111Cwith2mol%Al2O3

Introduction to glass science and technology, J. E. Shelby, The Royal Society of Chemistry, 1997

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

V.M. Sglavo GlassEng - UNITN 2017

Technological implications

- trasparence - opacity (d visible wavelength = 450-700 nm)

- heterogeneous nucleation crystallization

- production of high silica glass (Vycor)

sodium-borosilicateglass

thermaltreatment chemicaletchinginhotacidsolution(HCl)

sinteringspinodaldecomposition:96%SiO2+sodium-borosilicateglass

96%SiO2porousglass(d=2-200nm)

96%SiO2glass