Hierarchical geopolymers with mesoporous matrices and lamellar macro-porosities were produced for the first time by ice-templating (freeze-casting) technique in a water-based solegel system. Starting from an aqueous solution of metakaolin and potassium silicate, geopolymerization was triggered through a maturation step without reaching complete consolidation. Different amounts of water (20, 50, 70 vol.%) were then mixed with the geopolymer paste to induce lamellar ice growth by unidirectional freezing. The consolidation was completed during freeze-casting and drying. Ice-templated hierarchical geopolymers had 53e83% total porosity and N2 BET specific surface area values from 4 to 46 m2 g1, depending on the amount of water added. A broad mesopore Barret Joyner Halenda distribution was detected between 4 and 100 nm with maxima from 5 to 7 nm, while macropores in the 1-to-100 mm range were identified by Hg intrusion porosimetry. Lamellar monoliths (height 25 mm) were produced with a selected composition (50 vol.% of additional water) in order to assess the reproducibility of the ice-templating technique combined with geopolymerization.

Synthesis of porous hierarchical geopolymer monoliths by ice-templating

BENITO MARTIN, PATRICIA;VACCARI, ANGELO;BUGANI, SIMONE;
2015

Abstract

Hierarchical geopolymers with mesoporous matrices and lamellar macro-porosities were produced for the first time by ice-templating (freeze-casting) technique in a water-based solegel system. Starting from an aqueous solution of metakaolin and potassium silicate, geopolymerization was triggered through a maturation step without reaching complete consolidation. Different amounts of water (20, 50, 70 vol.%) were then mixed with the geopolymer paste to induce lamellar ice growth by unidirectional freezing. The consolidation was completed during freeze-casting and drying. Ice-templated hierarchical geopolymers had 53e83% total porosity and N2 BET specific surface area values from 4 to 46 m2 g1, depending on the amount of water added. A broad mesopore Barret Joyner Halenda distribution was detected between 4 and 100 nm with maxima from 5 to 7 nm, while macropores in the 1-to-100 mm range were identified by Hg intrusion porosimetry. Lamellar monoliths (height 25 mm) were produced with a selected composition (50 vol.% of additional water) in order to assess the reproducibility of the ice-templating technique combined with geopolymerization.
2015
E. Papa; V. Medri; P. Benito; A. Vaccari; S. Bugani; J. Jaroszewicz; W. Swieszkowski; E. Landi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/499767
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