Identification of a third phase in Cu-Al2O3 nanocomposites prepared by chemical routes

Nanocomposite of Cu-Al2O3 have been prepared through their nitrates by two processes, namely: (1) addition of CuO to aqueous solution of aluminum nitrate, and (2) dissolution of the nitrates of copper and aluminum in water, followed by decomposition to their oxides and then preferential hydrogen reduction of CuO for both processes 1 and 2. The composite powders (containing 0.5-5 wt.% of Al2O3), prepared by both the routes have been found to have nanoparticles. The composite powders have been cold pressed into briquettes and sintered at 950 deg. C for 2 h. Studies on their microstructures have been carried out through X-ray diffraction (XRD), conventional and high-resolution transmission electron microscopy (CTEM and HRTEM) and quantitative scanning transmission electron microscopy (STEM) X-ray mapping. The composites prepared through both routes, have been found to contain a third phase (CuxAlyOz), possibly CuAlO2 and/or CuAl2O4 along with Cu and Al2O3 phases. However, in the composite prepared by process 2, the Al and O were dispersed more homogeneously, maintaining a continuity in the matrix