Systematic synthesis of mixed-metal oxides in NiO-Co3O4, NiO-MoO3, and NiO-CuO systems via liquid-feed flame spray pyrolysis

We report here on the systematic synthesis of three nanopowder series along the NiO-Co(3)O(4), NiO-MoO(3), and NiO-CuO tie lines. Sixteen individual samples were produced via liquid-feed flame spray pyrolysis (LF-FSP) and analyzed by SSA, SEM, EDX, FTIR, TGA-DTA, and XRD. The LF-FSP process is a general aerosol combustion synthesis route to a wide range of lightly agglomerated oxide nanopowders. The materials reported here were produced by aerosolizing ethanol solutions of propionate and ammonium molybdate precursors synthesized by reacting the metal nitrate with propionic acid. Particular ratios of the precursors were selected to control the compositions of the samples produced. The powders typically consist of single crystal particles < 35 nm in diameter and with specific surface areas (SSAs) of 20-50 m(2) g(-1). X-Ray powder diffraction (XRD) studies show a gradual change in their patterns from pure NiO to pure MO(x) (M = Co, Mo, Cu). Most compositions yielded single phase materials but mixed phase materials were also detected. We believe that higher vapor pressures of the ions produced for the transition metals studied resulted in SSAs about a third lower than those measured typically in nanopowders containing NiO.