Structural characterization of geomaterial foams — Thermal behavior

The structural evolution of in-situ inorganic foam based on sodium or/and potassium is investigated. The synthesis of foam based on an alkaline polysialate, is achieved at slightly elevated temperature by the alkaline activation of raw minerals and industrial waste. The structural evolution is studied through differential thermal analysis/thermogravimetric analysis (DTA-TGA) coupled with mass spectrometry, in-situ X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and 29Si, 27Al magic-angle spinning nuclear magnetic resonance spectroscopy (MAS-NMR). The role of alkali cations is observed, and they are shown to have a significant effect on structure changes with temperature, leading to the onset of a crystalline phase in potassium-based foam. Shifts of MDI reflect the competition that takes place during heating between the evolution of the zeolite phase and the amorphization of the material.

► Structural evolution with temperature of in situ inorganic foam is investigated.
► Impacts of alkali cations, type of silica and potassium concentration are studied.
► Potassium has a significant effect leading to a crystalline phase formation in foam.
► The size distribution of silica allows the control of the crystalline phase amount.
► Main parameter of crystallization is the potassium concentration in initial mixture.