Influence of the metal complexation on size and composition of Cu/Ni nano-particles prepared by sol-gel processing

Nanocomposites of the composition Cu0.6Ni0.4·5SiO2 were prepared from nickel and copper acetate, (EtO)3Si(CH2)3NHCH2CH2NH2 (DIAMO), and Si(OEt)4 (TEOS). To study the influence of the complexing silane on the composition and size distribution of the alloy particles, the DIAMO/metal ratio in the starting mixtures was varied, while the molar equivalents of DIAMO plus TEOS was kept constant. UV investigations showed that up to 2–2.5 equivalents of DIAMO are used for complexation of the metal ions. After drying, and oxidation of the metal-containing xerogels, separate NiO and CuO particles were observed by XRD. Their dispersion decreased with an increasing DIAMO/metal ratio in the starting mixtures. After reduction of the oxide particles only one crystalline alloy phase was observed when the DIAMO/metal ratio was≤1. For higher ratios a Cu-rich and a Ni-rich phase was found, their composition approaching pure Cu or Ni with an increasing portion of DIAMO. The size of the alloy particles was about the same as that of the NiO and CuO particles before reduction. However, complexation by one or two DIAMO moieties per metal atom lead to particularly narrow size distributions of the alloy particles.