| Abstract Scope |
Geopolymers are a type of chemically bonded ceramics of chemical formula M2O•Al2O3•4SiO2•11H2O. They are refractory, inorganic polymers formed from both aluminum and silicon sources containing AlO4- and SiO4 tetrahedral units, under highly alkaline conditions (NaOH, KOH, CsOH) at room temperature. They result in an amorphous, nano-particulate, nanoporous, impervious, acid-resistant structure. The strained nature of the 5-coordination aluminum cation polyhedra is identified as the reason why metakaolin-based geopolymer ceramics are made from solution, rather than with high temperature diffusion. Applications of geopolymers in high temperature environments require characterization of the crystalline phases that develop. In this work, we examined the temperature-driven structural evolution of samples belonging to the K[AlSi2O6]-Cs[AlSi2O6] pseudo-binary synthesized by heat treatment of pure geopolymer using in situ high-temperature synchrotron X-ray powder diffraction. The data was analyzed by Rietveld refinement and the mechanisms underlying the thermal expansion and phase transitions were elucidated by statistical methods. |