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: marcelocilla@ufscar.br ; paolo.colombo@unipd.it ;morelli@power.ufscar.br
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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?
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