Please cite this article in press as: Cilla MS, et al. Open cell geopolymer foams by a novel saponification/peroxide/gelcasting combined route. J Eur Ceram Soc (2014), http://dx.doi.org/10.1016/j.jeurceramsoc.2014.04.001 ARTICLE IN PRESS +Model JECS-9601; No. of Pages 5 Available online at www.sciencedirect.com ScienceDirect Journal of the European Ceramic Society xxx (2014) xxx–xxx Short Communication Open cell geopolymer foams by a novel saponification/peroxide/gelcasting combined route Marcelo Strozi Cilla a,b,∗ , Márcio Raymundo Morelli a , Paolo Colombo b,c a Graduate Program on Materials Science and Engineering, Federal University of São Carlos, Via Washington Luiz, km 235, São Carlos, SP, Brazil b Dipartimento di Ingegneria Industriale, Università degli Studi di Padova, Via Marzolo, 9, Padova, Italy c Department of Materials Science and Engineering, The Pennsylvania State University, University Park, PA 16802, United States Received 19 February 2014; received in revised form 31 March 2014; accepted 4 April 2014 Abstract Using a novel saponification/peroxide/gelcasting combined route it was possible to produce geopolymer foams with a total porosity of ∼85 vol%, open porosity as high as ∼70 vol%, average cell size (D50) of 318 m, and possessing a specific surface area of 50 m 2 /g. The in situ formation of surfactants by the saponification reaction of oil in the geopolymer alkaline environment led to increased total and open porosity in comparison to alternative methods for the fabrication of geopolymer foams. © 2014 Elsevier Ltd. All rights reserved. Keywords: Combined route; Geopolymer foams; Saponification; Peroxide; Gelcasting 1. Introduction The term geopolymer indicates a class of inorganic materi- als with chemical composition similar to that of zeolite and a variable microstructure (amorphous to semi-crystalline), which are obtained by the reaction of aluminosilicates with a highly alkaline medium, leading to the formation of a continuous three dimensional network. 1 These materials can consolidate at low temperature (about 80 ◦ C) and, for selected compositions, can be used at high temperature (up to 1200 ◦ C and above). Because of their ease of shaping from an aqueous slurry and the possibility of setting the component via the geopolymerization reactions, thereby enabling the retention of the produced shape, geopoly- mers offer the possibility of efficiently producing highly porous ceramic components. Several papers describe the production of porous components based on geopolymers, typically following ∗ Corresponding author at: Graduate Program on Materials Science and Engi- neering, Federal University of São Carlos, Via Washington Luiz, km 235, São Carlos, SP, Brazil. Tel.: +55 16 33518245. E-mail addresses: marcelocilla@ufscar.br, marceloscilla@gmail.com (M.S. Cilla), morelli@power.ufscar.br (M.R. Morelli), paolo.colombo@unipd.it (P. Colombo). approaches similar to those employed in the cement industry (i.e. in situ generation of gas 2–5 ), leading to the creation of mainly closed cell foams. For filtration or adsorption applica- tions, a fully interconnected cellular network is required, and therefore novel processing strategies need to be developed. The saponification reaction, recently proposed for the production of micro-/meso-porous geopolymers with high specific surface area, 6,7 has been here exploited for the first time in association with gelcasting for the generation of macrocellular open cell geopolymer foams. 8 2. Experimental procedure For these experiments, the samples were produced using the same raw materials described in reference 8 ; the geopoly- mer mixture (GP) was prepared considering the three oxide molar ratios as follows: SiO 2 /Al 2 O 3 = 3.78, K 2 O/SiO 2 = 0.24 and H 2 O/K 2 O = 16. The first step in the preparation the geopoly- mer foams was the preparation of a 15 M KOH solution, which should be used after 24 h. 9 Then, a solution of potassium- based activators and distilled water was prepared in a mixer (500 rpm, 30 min, Ika-Werke Ost Basic, Staufen, Germany). To this solution, Dolapix CE-64 (Zschimmer & Schwarz) was http://dx.doi.org/10.1016/j.jeurceramsoc.2014.04.001 0955-2219/© 2014 Elsevier Ltd. All rights reserved.