A Novel Method for the Formation of Lithium Aluminosilicate and Lithium Aluminosilicate-Alumina Matrix Composites by Silicothermal Reaction of Li-Geopolymers

Li-geopolymer precursors containing silicon were fabricated by a solid-state method and fired in nitrogen at 1100°C–1400°C to produce lithium aluminosilicate (LAS), the amount and crystallinity of which was independent of the silicon used, as shown by X-ray diffraction and solid-state magic angle spinning nuclear magnetic resonance (MAS NMR). LAS/Al2O3 composites were formed by adding ρ-Al2O3 to the Li-geopolymer precursor and firing under nitrogen at 1400°C. Although no nitride phases were formed under these reaction conditions, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) showed a small amount of unreacted silicon in the fired samples, suggesting that it may be possible to adapt this procedure to produce LAS-nitride composites.