Copper (I) oxide powder generation by spray pyrolysis

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Abstract
Copper oxide powders were prepared by the spray pyrolysis of copper nitrate solutions over a range of temperatures (400–1300 °C) and residence times (3–7 s). Phase-pure [by x-ray diffraction (XRD)] copper (I) oxide was obtained at 800–1300 °C in an inert (nitrogen) atmosphere. The particles varied from smooth, solid spheres at 1300 °C to irregularly shaped and hollow particles at 800 °C with dense particles of Cu2O being made only at 1000 °C or higher. The particles were polycrystalline with an average crystallite size of 42 nm at 800 °C, while at 1000–1200 °C, the particles were single crystals. Spray pyrolysis in forming gas (7% H2–N2) atmosphere at 500–700 °C gave Cu while spray pyrolysis in air yielded CuO over 800–1000 °C and a mixture of Cu2O/CuO at 1200 °C. These results show that solid, phase-pure Cu2O particles can be produced by aerosol-phase densification at temperatures below its melting point (1235 °C).