Copper(I) oxide powder generation by spray pyrolysis

Copper oxide powders were prepared by the spray pyrolysis of copper nitrate solutions over a range of temperatures (400-1300 degrees C) and residence times (3-7 s). Phase-pure [by x-ray diffraction (XRD)I copper (I) oxide was obtained at 800-1300 degrees C in an inert (nitrogen) atmosphere. The particles varied from smooth, solid spheres at 1300 degrees C to irregularly shaped and hollow particles at 800 degrees C with dense particles of Cu2O being made only at 1000 degrees C or higher. The particles were polycrystalline with an average crystallite size of 42 nm at 800 degrees C, while at 1000-1200 degrees C, the particles were single crystals. Spray pyrolysis in forming gas (7% H-2-N-2) atmosphere at 500-700 degrees C gave Cu while spray pyrolysis in air yielded CuO over 800-1000 degrees C and a mixture of Cu2O/CuO at 1200 degrees C. These results show that solid, phase-pure Cu2O particles can be produced by aerosol-phase densification at temperatures below its melting point (1235 degrees C).