Preparation and characterization of CuO–ZrO2 nanopowders

Abstract

Nanosized copper oxide–zirconia particles containing 10–30 mol% of copper were prepared by using a precipitation technique in aqueous tetramethylammonium hydroxide solutions. Two methods, in situ (INS) and step-by-step (SBS), which differed in the time when the copper salt was introduced to the synthesis procedure, were used, and this allowed a comparison of the properties of the final powders produced using the two modes of preparation. The surface areas and phase compositions were different for the samples prepared from the two different methods after calcination at 500 °C. A surface area of 168 m2 g−1 was obtained for the sample prepared with the SBS method and 121 m2 g−1 for the INS method, both contain 30 mol% copper. Tetragonal ZrO2 was observed from X-ray diffraction patterns for all samples prepared with the SBS method, however, no separate phase of copper or copper oxide was observed. It is proposed that all of the copper is finely distributed on the surface of the ZrO2 particles with the SBS method. For the samples prepared from the INS method, tetragonal ZrO2 was obtained at a low copper content and the peaks indexed to tetragonal ZrO2 shifted to higher angle with the increase of copper content, indicating copper ions being incorporated into the lattice. An amorphous compound was obtained at high copper content (30 mol%). The phase change with the calcination temperature was also investigated for the INS sample containing 30 mol% copper. The studies show that tetragonal ZrO2 and copper oxide were present after calcination at 400 °C, and tetragonal ZrO2 with a small amount of monoclinic ZrO2, as well as copper oxide, formed after calcination at 700 °C. However, after heating at 500 °C, amorphous compounds were obtained, suggesting that 500 °C could be a phase transition point. The incorporation of copper in the ZrO2 lattice resulted in a loss of order in the ZrO2 structure when calcined at 500 °C, with a further increase in the calcination temperature leading to the phase change.