v.m. sglavo – glasseng - unitn 2017 free energy of mixture ... · v.m. sglavo – glasseng -...
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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: ΔGm = ΔHm - T ΔSm
entropy-ΔSm
entalpy-ΔHm
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-ΔGm
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)+∂G∂c c0
(c− c0)+12∂2G∂c2
c0
(c − c0)2 + .....
Ifc’=c0-Δc<c0<c”=c0+Δc
€
G = G(c0)+12∂2G∂c2
c0
Δc2
€
ΔG = G −G(c0)=12∂2G∂c2
c0
Δc2
€
∂2G∂c2
c0
> 0
€
∂2G∂c2
c0
< 0
ÚΔG>0
ÚΔG<0
Free energy variation associated to composition fluctuations
c0
Struttura e genesi dello stato vetroso, A. Maddalena, Cleup, 1983
FREEENERGY,G
COMPOSITION(MOLARFRACTIONOFB)
V.M. Sglavo – GlassEng - UNITN 2017
V.M. Sglavo – GlassEng - UNITN 2017
V.M. Sglavo – GlassEng - UNITN 2017
T > 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
homogenous“isles”separation(SiO2richmatrix)
interconnectedseparation
“isles”separation(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/orVycor®glass
TC=111°Cwith2mol%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 Ò crystallization
- production of high silica glass (Vycor®)
sodium-borosilicateglass
thermaltreatment chemicaletchinginhotacidsolution(HCl)
sinteringspinodaldecomposition:96%SiO2+sodium-borosilicateglass
96%SiO2porousglass(d=2-200nm)
96%SiO2glass
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