caa a22 4500 463224175 CHVBK 20180405153221.0 cr unu---uuuuu 170326e20070501xx s 000 0 eng 10.1007/s10853-006-0820-2 doi (NATIONALLICENCE)springer-10.1007/s10853-006-0820-2 Dissolution processes, hydrolysis and condensation reactions during geopolymer synthesis: Part I—Low Si/Al ratio systems [Elektronische Daten] [L. Weng, K. Sagoe-Crentsil] Initial geopolymeric reaction processes governing dissolution of solid aluminosilicate particles in alkali solutions have been investigated using conventional experimental techniques, and the data analysed by speciation predictions of the partial charge model (PCM). For metakaolin powders activated with 5.0M NaOH, solid-state nuclear magnetic resonance (NMR) spectra disclose the existence of monomeric [Al(OH)4]− species after two hours of dissolution, consistent with PCM predictions. However, no equivalent monomeric silicate species were observed for 5.0-10.0M NaOH activator solutions characteristic of systems with nominal Si/Al≤1. The apparent absence of monomeric silicate species suggest rapid condensation of silicate units with [Al(OH)4]− to generate aluminosilicate species, as indicated by the evolution of the shoulder at around −87ppm in the 29Si NMR spectra. Of the two possible stable silicate species [SiO2(OH)2]2− and [SiO(OH)3]−, the latter appears most likely to condense with [Al(OH)4]− to produce aluminosilicate oligomers, from which larger oligomers subsequently form through further condensation with [Al(OH)4]− leading to a gradual build up of aluminosilicate networks and a lowering of system alkalinity. This dissolution and hydrolysis sequence at the early stages of synthesis suggests a reaction path wholly consistent with predictions of the partial charge model. Springer Science+Business Media, LLC, 2007 Weng L. Department of Materials Science, Shenzhen Graduate School, Harbin Institute of Technology, University Town, 518055, Xili, Shenzhen, P.R. China aut Sagoe-Crentsil K. Manufacturing & Infrastructure Technology, CSIRO, P.O. Box 56, 3190, Highett, Victoria, Australia aut Journal of Materials Science Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 42/9(2007-05-01), 2997-3006 0022-2461 42:9<2997 2007 42 10853 https://doi.org/10.1007/s10853-006-0820-2 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s10853-006-0820-2 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Weng L. Department of Materials Science, Shenzhen Graduate School, Harbin Institute of Technology, University Town, 518055, Xili, Shenzhen, P.R. China aut NATIONALLICENCE 700 1- Sagoe-Crentsil K. Manufacturing & Infrastructure Technology, CSIRO, P.O. Box 56, 3190, Highett, Victoria, Australia aut NATIONALLICENCE 773 0- Journal of Materials Science Kluwer Academic Publishers-Plenum Publishers; http://www.springer-ny.com 42/9(2007-05-01), 2997-3006 0022-2461 42:9<2997 2007 42 10853 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer