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.
E. Papa, V. Medri, P. Benito, A. Vaccari, S. Bugani, J. Jaroszewicz, et al. (2015). Synthesis of porous hierarchical geopolymer monoliths by ice-templating. MICROPOROUS AND MESOPOROUS MATERIALS, 215, 206-214 [10.1016/j.micromeso.2015.05.043].
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.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
