MAS-NMR studies of geopolymers heat-treated for applications in biomaterials field

In the field of biomaterials applied in bony restoration, systems based on amorphous silicate network present the ability to link to bone matrix. Amorphous geopolymers of the potassium-poly(sialate)-nanopolymer type with a mole ratio Si:Al = 31 were studied for their use as potential biomaterials. This implied a heat treatment at 500 °C in order to reduce the alkalinity of the geopolymer matrix from pH 11.5 to pH 7.1 and to provide high porosity for biological compatibility. ²⁷Al and ²⁹Si MAS NMR spectroscopy has been used to characterise the foamed geopolymers obtained after different thermal treatments at 250 and 500 °C, and with three different mole ratios K₂O/SiO₂ for the potassium silicate: 0.54; 0.67 and 0.84. Best results in terms of biological compatibility were obtained with a geopolymer matrix resulting from a mole ratio K₂O/SiO₂. of 0.54, heat-treated at 500 °C.