lecture ch1 l12

8/10/2019 Lecture CH1 L12

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GEOPOLYMER FOAMS BY

GELCASTING

Marcelo Strozi Cilla(1,2),

Mrcio Raymundo Morelli(1), Paolo Colombo(2,3)

(1) Federal University of So Carlos, Graduate Program on Materials Science and

Engineering, So Carlos, Brazil

(2) University of Padova, Department of Industrial Engineering, Padova, Italy

(3) The Pennsylvania State University, Department of Materials Science and Engineering,

USA

Email: [email protected] ; [email protected] ;[email protected]


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CELLULAR CERAMICS

High permeability and (geometric) surface area;

Good insulating properties;

High refractoriness;

Chemical resistance and good mechanical properties.


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GEOPOLYMERS

Chains or networks of mineral molecules (highlighted in

white) linked with covalent bonds with a variable

microstructure, which are obtained by the reaction of

aluminosilicates in a

highly alkaline medium.

L.Gardiner/Windows to the Universe


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Geopolymer

Timeline


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GEOPOLYMER FOAMSHave the same properties of ceramic foams, but usually for

their fabrication the typical route used in the cement industry

to produce aerated concrete is employed.

closed porosity

Kamseu, E., et al., Bulk composition and microstructure dependence of effective thermal conductivity of porous inorganic polymer cements,

Journal of the European Ceramic Society 32, 8 (2012) 1593-1603.


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Why dont we

apply the

processing routes

used to produce

cellular ceramics in order to obtain

cellular geopolymers with open,

interconnected cells structure?


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We employed two alternative routes to

obtain open cell geopolymer foams:

Gelcasting;

Saponification/peroxide/gelcasting

combined route.


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Gelcasting: consists in vigorously stirring a slurry containing a

suitable surfactant followed by setting of the liquid foam.

Saponification: as proposed by Medpelli [1], it is based on the

saponification reaction of a triglyceride oil in the alkaline

suspension, which forms water-soluble soap and glycerol

molecules, which can be extracted after the curing process with

hot water to generate geopolymers with high specific surface

area.

The combined use of the two techniques leads to interconnectedporosity: the in situformation of the soap molecules is

exploited to generate macro-porosity(and we also added

peroxides to contribute to the macro-pore formation).

[1] D. Medpelli, J. Seo, D. Seo, Geopolymer with Hierarchically Meso-/Macroporous Structures from Reactive Emulsion Templating,

Journal of the American Ceramic Society, 97, 1 (2014) 7073.


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MATERIALS:

Metakaolin

Fly ash class F

Potassium silicate

Potassium hydroxide

SiO2/Al2O3= 3.78

K2O/SiO2 = 0.24

H2O/K2O = 16.00

For the gelcasting route, two types of non-ionic surfactant(Tween 80 and Triton X-100) were used, and for the

saponification/peroxide/gelcasting combined route

vegetable oil and hydrogen peroxide were used.


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METHODSGelcasting route

M. S. Cilla, P. Colombo, M. R. Morelli, Geopolymer foams by gelcasting, Ceramics International, 40, 4 (2014) 5723-5730.


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and saponification/peroxide/gelcasting combined route.

M. S. Cilla, P. Colombo, M. R. Morelli , Open cell geopolymer foams by a novel saponification/peroxide/gelcasting combined route, Journal of

the European Ceramic Society, 34, 12 (2014) 3133-3137.


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For both routes, selected properties of the produced foams

were evaluated: permeability and specific surface area

(important for filtration or adsorption applications).

Total and open porosity;

Specific surface area (BET);

Mechanical Strength;

Permeability;

Microstructure (SEM).


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From samples

not heat treated

Gelcasting RouteCombined

RouteTween 80Triton

X-100

Total porosity

(vol%)60 - 75 60 - 78 84 - 90*

Open porosity

(vol%)

40 - 54 47 - 56 6984*

Specific

surface area

(m2/g)

44 50 - 85*

Mechanicalstrength (MPa)

0.503.00 0.450.50*

Average cell

size (m)272555 318522*

* Currently being studied to further extend the range of obtainable values


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Gelcasting Route

M. S. Cilla, M. R. Morelli, P. Colombo, Effect of process parameters on the physical properties of porous geopolymers obtained by gelcasting,

Ceramics International, http://dx.doi.org/10.1016/j.ceramint.2014.05.074

Concrete, bricks,castables, starch

fillers

Fibrous andgranular filters,gelcating foams

Replica foams,honeycombs


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Combined Route

M. S. Cilla, P. Colombo, M. R. Morelli , Open cell geopolymer foams by a novel saponification/peroxide/gelcasting combined route, Journal of

the European Ceramic Society, 34, 12 (2014) 3133-3137.

Concrete, bricks,castables, starch

fillers

Fibrous andgranular filters,gelcating foams

Replica foams,honeycombs


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Gelcasting Route


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Combined Route


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By using the gelcasting route, it was possible to produce

foams with a total pore volume as high as ~78 vol%, withan amount of open porosity as high as ~56 vol%;

The combined route, based on the in situformation of

surfactant molecules, led to an increase of the total and

open porosity (to ~90 and 84%, respectively), and gave

values for the permeability coefficients k1and k2indicating

the suitability of the produced components for use in

filtration or adsorption applications;These results, as well as the advantage of using a

sustainable and cheaper process, encourage additional

efforts to optimize the fabrication of highly porous

ceramics with interconnected porosity from geopolymers.

CONCLUSIONS


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ACKNOWLEDGMENTS


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And finally...

Thank you very much for your

attention.

Any questions?

lecture ch1 l12

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