A study of the composition and microstructure of nanodispersed Cu–Ni alloys obtained by different routes from copper and nickel oxides

Mixtures of CuO and NiO were prepared by two different techniques, and then the oxides were reduced with H2. Method A involved the preparation of mechanical mixtures of CuO and NiO using different milling and pelletizing processes. Method B involved the chemical synthesis of the mixture of CuO and NiO. The route used to prepare the copper and nickel oxide mixture was found to have great influence on the characteristics of bimetallic Cu–Ni particles obtained. Observations performed using the X-ray diffraction (XRD) technique showed that although both methods led to the Cu–Ni solid solution, the diffractogram of the alloy obtained with method A revealed the presence of NiO together with the alloy. The temperature-programmed reduction (TPR) experiments indicated that the alloy is formed at lower temperatures when using method B. The scanning electron microscopy (SEM) studies revealed notable differences in the morphology and size distribution of the bimetallic particles synthesized by different routes. The results of the electron probe microanalysis (EPMA) studies evidenced the existence of a small amount of oxygen in both cases and demonstrated that the alloy synthesized using method B presented a homogeneous composition with a Cu–Ni ratio close to 1:1. On the contrary, the alloy obtained using method A was not homogeneous in all the volume of the solid. The homogeneity depended on the mechanical treatment undergone by the mixture of the oxides.

Research Highlights
► Study of the properties of Cu–Ni alloys synthesized by two different routes.
► Mixtures of Cu and Ni oxides prepared by two techniques were reduced with H2.
► Mixtures of oxides were obtained by a mechanical process and the citrate-gel route.
► The characterizations were carried out by TPR, XRD, SEM and EPMA.
► The route used to prepare oxide mixtures influences on the Cu–Ni alloy obtained.