Water-soluble amorphous alumina-based ceramic precursors and alumosols: Structural and chemical characterization

We examined the solid-state water-soluble amorphous precursors that are formed by partial thermal decomposition of Al(NO 3) 3·9H 2O (aluminum nitrate nonahydrate: ANN) using Raman and FTIR and solid-state magic-angle spinning NMR spectroscopy. We also studied the species formed in the aqueous alumosols formed by dissolution of the pre-ceramic precursors using 27Al NMR spectroscopy. Species identified in the alumosols included the Al 3+(H 2O) 6 monomer, the [AlO 4Al 12(OH) 24(H 2O) 12] 7+(Al 13) Keggin ion, and the Al 30 polycation, [Al 30O 8(OH) 56(H 2O) 24] 18+, as well as various other oligomers or nanoparticles containing IV-, V- and VI-coordinated Al 3+ ions.