glass materials in systems for energy efficient...

Glass materials in systems for energy efficient buildings

1. Group of Inorganic-Nonmetallic Materials

2. The material glass 3. Glasses in passive and active

systems for transparent facades 4. Current research projects 5. Summary

Ulrike Brokmann, Edda Rädlein Group of Inorganic-Nonmetallic Materials

bz-berlin.de

www.tu-ilmenau.de

Group of Inorganic-Nonmetallic Materials

www.tu-ilmenau.de 2

Inorganic-Nonmetallic Materials Fields of activity:

history – material development – production – post-processing - recycling

Microstructuring

Photosensitive glass

Micro capillaries

Surfaces

First reactions on juvenile glasses

Coatings

…In magnetic fields

Lorentz forces for control of melts

Nano powders for radiation shielding

FL

Bj

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The role of glass systems in energy efficient buildings Facade elements in modern

architecture • aesthetic aspects • high transmittance for visible

light • high stability against weather

construction elements for energy

management control interaction of the building with ambient conditions • defined transport of heat and

light in and out of the building

Low costs materials, long time stable systems, recycling aspects Glass Beads/Foam Glass

(< 0,07 W/m*K)

Insulation Fibers (0,035 W/m*K)

Glass enamels

Flat glass with thin functional coatings

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The material glass Glass is transparent, brittle, smooth, pore-free, made of non-hazardous raw materials, durable, recycable….

Network of silicate tetrahedra connected via corners + …

sand +

soda +

lime +

cullet

glass := solid material with the structure of a frozen-in undercooled melt

i.e. non-crystalline, no long range order but short range order

chemistry: variable

95% of produced glasses are alkali-earth alkali-silicate borosilicate leadsilicate

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Glass properties

Window glass Duran ® E-glass soda-lime-silicate borosilicate …silicate Index nd 1,52 1,473 1,547 α20/300 [10-6 K-1] 9 3,3 4,9…6 Max. T, short [ºC] 300 500 250 (long) ρ [g/cm³] 2,5 2,23 2,52…2,55

Tg [ºC] 520…550 525 657

… are depending on composition and quenching rate

Wikipedia

econtrol®

Schott

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Structure can be variied by quenching rate!

melt

Tmelting

V

Tg T

crystal

glass

undercooled melt

fast slow

very slow

Tg: glass transition temperature ≠ crystallization temperature

brittle solid

viscous liquid

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Glass surface

H H O

H H H O O O O O O O Si Si Si Si Si Si Si Si Si Si O O O O O O

H H O

2. organic polymers 3. water film: physisorbed water + ions 8…25 kJ/Mole chemisorbed water 42…125 kJ/Mole 4. OH-groups

∅ 10? nm … 300 nm

0,16 nm

< 50 nm ~ 1,5 nm

1. dust: oxides, salts, C, separating agents, buffers, …

Gel

- la

yer

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9

Dimensions of the gel layer(s) new glass cleaned glass long time, high T, historic polished glass humidity glass (various layers) 15 nm 0,1 … 1 µm µm 100 µm

800 a 100 µm

100 µm

Slemin, Römich, www.glass-ceramics.uni-erlangen.de; Wikipedia

20 a <1 µm

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Flat glass = Float glass (in most cases)

Typical composition of soda lime glass (mass %): SiO2 72 Na2O 13 K2O 0,4 CaO 9 MgO 4 Al2O3 0,5… Fe2O3 0,02...0,1…0,6 SO3 0,2… TiO2, MnO, P2O5, Cl, ZrO2, ZnO, BaO,…

network former network modifier intermediates refining agents . …

Almost all flat glass is float glass: the smoothest material man can produce in one step, rms ~ 0,2 nm. A perfect substrate for functional coatings

made from sand, soda, lime, cullet + … melting tank: < 1300 t/d for < 18 a continously, night&day global market 70.106 t/a 458 lines worldwide (91 in Western Europe + North America) Price: 300 €/t ~ potatoes!

[Bernard Savaete, 2013] …

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SnO2

SiO2

oxide Ag oxide

SiO2 ...

ITO ITO

WOx

SiO2:TiO2

Al2O3

Functional thin film coatings on flat glass

Properties application examples optical visible light IR UV

anti glare anti reflective reflecting

energy control: insulation

solar control electrical

heated panes transparent electrodes electrochromic panes anti static panes

chemical barrier layers hydrophobic, hydrophilic

displays easy to clean anti fog

mechanical scratch resistant panes

Flat glass enamel production for thick film coating on side 1

Granulation in cold water

Milling and mixing

Mixing of screen- printing paste

Printing on float glass

Firing in a glass tempering furnace (3- 6 min at 630°C)

Glass melting in rotary smelter (T = 1250°C)

Source: Glaston

Example: „thick“ coatings – glass enamel on side 1


curtain-wall facing + exploitation of thermal updraft for ventilation

Transparent solar module Vidur Solar; Corus

BIPV with thin film layer modules Forschungsverbund Berlin e.V.,

SCHOTT Solar AG

Modern architectural design + insulation + energy harvesting BIPV building integrated PV


Sometimes a problem: corrosion!

Example: fire protection glass inside a building

Example: decorative glass enamel (side 1), samples partially cleaned at the right side

U. Hoppe, TU Ilmenau


First reaction stages of glass surfaces

=> Centers of weathering, local swelling of alkali rich

regions

Atomic force microscope: fracture surface of model glass* stored in air with ca. 45 % r.h.

Goß, A.; Rädlein, E. and Frischat, G.H.: Atomic force microscopy study of silicate glass fracture surfaces in air and in water environments, Glass Sci. Technol. 76 (2003) p. 244-251

(*potassium-lime-silicate glass)

12 min

2 d 12 d

4 h


whiskers in conductive functional coatings: ITO grows faster on corrosion products surface of coating

washed float glass before coating

Consequences for processing in thin film technologies

C. Wang, et al. in Glass Science and Technology 77 (2004) 103-110


Investigation of corrosion phenomena on glass enamels

Containing Bi Containing Zn DI - water Iridescence effects,

not removable

Outdoor storage

5% NaCl solution Matt surface

0,1n H2SO4 Matt surface, Cracks,

Enamel widely removed:

5min at 30°C

24h at 80°C

Zn-frit

Bi-frit


Bi frit in 5%NaCl solution (480h, 35°C)

0

1000

2000

3000

4000

5000

6000

7000

8000

9000

10000

1 10 100 1000

sputter depth [nm]

CPS

NaAlSiTiBi

90350 nm50 nm

Example: Bi containing enamel (5% NaCl solution)

Enrichment on surface

Enrichment in surface

Leaching

Bi frit (RT, 5d)

Bi frit (RT, 20d)

Surface crystallisation: Bismuth silicate + ...

Measurement SNMS :


Bi-enamel Profile depth < 80 nm

Zn-enamel Profile depth < 200 nm

Al Ti Bi Al Ti Zn Roof

5% NaCl solution

DI water

• No comparable effects between roof and test solution

• In each test a different type of gel layer developed • Enrichment and depletion of surface active elements inside the gel layer → iridescence effects [Brokmann et al. GPD 2009]

Can lab tests simulate real atm. contact? screen printed glass enamel: schematic profiles of surface active elements, weathering and lab tests


Summary

• Glass is a sustainable material for modern building industry

• indispensable for energy saving, transformation and storage

• Efficiency of glass systems depends on the high quality of used glass products

• Storage for defined short times at constant and low relative humidity during transport and production processes

• Cleaning must remove old reaction products and may not produce new ones


glass materials in systems for energy efficient...

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