The atomic pair distribution function (PDF) method was used to study the structure of cesium aluminosilicate geopolymer (Cs2OÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚Â·Al2O3ÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚Â·4SiO2ÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚Â·xH2O, with x ÃƒÆ’Ã‚Â¢Ãƒâ€šÃ‹â€ Ãƒâ€šÃ‚Â¼ 11). The geopolymer was prepared by reacting metakaolin with cesium silicate solution followed by curing at 50 ÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚Â°C for 24 h in a sealed container. Heating of Cs-geopolymer above 1000 ÃƒÆ’Ã¢â‚¬Å¡Ãƒâ€šÃ‚Â°C resulted in formation of crystalline pollucite (CsAlSi2O6). PDF refinement of the pollucite phase formed displayed an excellent fit over the 10ÃƒÆ’Ã‚Â¢Ãƒâ€šÃ‹â€ Ãƒâ€šÃ¢â‚¬â„¢30 ÃƒÆ’Ã†â€™Ãƒâ€šÃ¢â‚¬Â¦ range when compared with a cubic pollucite model. A poorer fit was attained from 1ÃƒÆ’Ã‚Â¢Ãƒâ€šÃ‹â€ Ãƒâ€šÃ¢â‚¬â„¢10 ÃƒÆ’Ã†â€™Ãƒâ€šÃ¢â‚¬Â¦ due to an additional amorphous phase present in the heated geopolymer. On the basis of PDF analysis, unheated Cs-geopolymer displayed structural ordering similar to pollucite up to a length scale of ÃƒÆ’Ã‚Â¢Ãƒâ€šÃ‹â€ Ãƒâ€šÃ‚Â¼9 ÃƒÆ’Ã†â€™Ãƒâ€šÃ¢â‚¬Â¦, despite some differences. Our results suggest that hydrated Cs+ ions were an integral part of the Cs-geopolymer structure and that most of the water present was not associated with Al-OH or Si-OH bonds.
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