Chemical Route Processing and Structural Characterization of Cu-Al_2O_3 and Ni-Al_2O_3 Nano-composites

摘要

Studies on the synthesis and characterization of nano-structured materials have attracted the attention of many researches due to their unique properties and potential uses. In that field it is well known the particular interest in the Cu-Al_2O_3 nano-composites, specially because they possess a stable microstructure with good resistance to recrystalization and grain growth. In contrast to the hardening by precipitation mechanism, some physical and mechanical properties can be kept, even at high temperature, due to the stability and high melting point of particles such as those of Al_2O_3, which do not react with the metallic matrix constituted by copper or nickel. In that context, the Department of Materials Science and Metallurgy at PUC - Rio de Janeiro has developed a new method for the synthesis of nano-composites. This method is essentially based on a chemical route aiming at the formation of oxides followed by their preferential reduction with hydrogen and further sintering. The present work comments briefly some kinetic behavior of the copper and nickel oxides reduction with hydrogen as well as the characterization of the obtained nano-composite material. The characterization was carried out by X-ray diffraction (XRD), scanning and transmission electron microscopy (SEM and TEM) and associated microanalytical techniques. The results indicated the formation of nano-structured materials and their typical features, including a very fine dispersion of the ceramic phase. The microstructures obtained for the Cu-Al_2O_3 and the Ni-Al_2O_3 composites were of the same type, where the metallic matrix crystals average 500/600 nm in size and the Al_2O_3 particles are in the lower nanometer scale.