Design of alumina monoliths by emulsion-gel casting: Understanding the monolith structure from a rheological approach. (5th November 2018)

• Record Type: Journal Article
• Authors: Nayak, Nayan; Vitorino, Nuno; Frade, Jorge R.; Kovalevsky, Andrei V.; Alves, Vitor D.; Crespo, João G.; Portugal, Carla A.M.
• Is Part Of: Materials & design. Volume 157(2018)
• Page Start: 119
• Page End: 129
• Publication Date: 2018-11-05
• Subjects: Alumina monoliths -- Emulsion-gel casting -- Viscoelastic properties -- Porous structure -- Chromatography; Materials -- Periodicals; Engineering design -- Periodicals; Matériaux -- Périodiques; Conception technique -- Périodiques; Electronic journals; 620.11
• DOI: 10.1016/j.matdes.2018.07.017
• Languages: English
• ISSNs: 0264-1275

Abstract

Abstract: Multimodal porous cellular alumina structures (monoliths) were prepared by an emulsion-gel casting technique using eco-friendly and inexpensive lipids such as corn oil, castor oil, margarine and their mixtures as the dispersed phase. The monoliths obtained showed good mechanical stability, exhibiting compressive strengths in the range of 8–50 N·mm −2 . Mercury intrusion porosimetry analysis showed that the monoliths produced presented porosities ranging from 28% to 60% and average pore sizes within 0.2–3.2 μm. The formation of the porous networks was interpreted based on combined droplet coalescence, flocculation and Ostwald ripening effects. The presence of such effects along the emulsion storage time led to changes in their viscoelastic and morphological properties, which were found to correlate with structural descriptors of monoliths after sintering (e.g. average pore sizes and porosity). These correlations open up the possibility to anticipate the final structure of the monoliths and adjust emulsion-gel conditions to produce customized cellular structures with fine-tuned porosities and pore sizes, envisaging their application in membrane processes or chromatography. Graphical abstract: Unlabelled Image Highlights: Multimodal porous alumina cellular structures were produced by emulsion-gel casting using non-toxic dispersed phases Formation of porous network interpreted based on droplet coalescence, flocculation and Ostwald ripening effects Correlations between monolith structural descriptors, changes of emulsion viscoelastic and morphological properties were found Pore size distribution of sintered monoliths are favoured by the presence of droplet coalescence effects