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Freeze-casting of highly porous cellulose-nanofiber-reinforced γ-Al2O3 monolithsHermina Hudelja,
Thomas Konegger,
Bernd Wicklein,
Janko Čretnik,
Farid Akhtar,
Andraž Kocjan, 2021, original scientific article
Abstract: Freeze-casting is a powerful consolidation technique for the fabrication of highly porous and layered-hybrid materials, including ceramic-metal composites, and porous scaffolds for catalysis, bone substitutes and high- performance membranes. The aqueous suspensions to be freeze-casted usually contain dense particles facilitating macroporous, layered ceramics with dense (nonporous) struts. In the present study, hierarchical macro-mesoporous alumina (HMMA) monoliths were successfully prepared by freeze-casting of aqueous suspensions containing hierarchically-assembled, mesoporous γ‒Al2O3 (MA) powder and cellulose nanofibers (CNF). As- prepared monoliths were ultra-porous (93.1–99.2%), had low densities (0.01–0.25 g/cm3), and displayed relatively high surface areas (91–134 m2/g), but were still remarkably rigid with high compressive strengths (up to 52 kPa). Owing to the columnar porosity and mesoporous nature of the struts the freeze-casted HMMA monoliths exhibited high permeability and high thermal insulation, the latter ranging from 0.039 W/m∙K to 0.071 W/m∙K, depending on pore orientation.
Keywords: cellulose nanofiber, freeze-casting, gamma alumina, hierarchical porosity, insulative materials
Published in DiRROS: 09.05.2023; Views: 286; Downloads: 199
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