Fabrication of copper–alumina nanocomposites by mechano-chemical routes

It is well known that Cu–Al2O3 nanocomposite materials have high potential for use in structural applications in which enhanced mechanical characteristics are required. Therefore, the present work is intended to produce nanosized powder of Cu–Al2O3 nanocomposites, with various alumina contents, and to investigate their properties. Mechano-chemical method with two different routes, were used to synthesize the Cu–Al2O3 nanocomposite powders. First, route A was carried out by addition of Cu to aqueous solution of aluminum nitrate, and second, route B was also carried out by addition of Cu to aqueous solution of aluminum nitrate and ammonium hydroxide. In both routes, the mixtures were heated in air and milled mechanically to get the oxides powders of CuO and Al2O3. The CuO was reduced in preferential hydrogen atmosphere into fine copper. The composite powders have been cold pressed into briquettes and sintered in hydrogen atmosphere. The structure and characteristics of powders as well as sintered composites produced from both routes were examined by X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS), transmission electron microscopy (TEM) and metallography techniques. The results showed that, in both routes, the alumina of nanosized particles was formed and dispersed within the copper matrix. The structure revealed the formation of CuAlO2 spinel structure at copper alumina interface. Nanocomposites produced by route B showed finer alumina particles of 30 nm compared to 50 nm produced by route A resulting in improving properties in terms of relative density and microhardness values.