Thermolysis of nickel acetylacetonate in organic surfactant and formation of metallic nickel, nickel carbide and nickel oxide nanocrystals

Nickel acetylacetonate was thermally decomposed in organic solvent containing surfactant molecules under inert atmosphere. The phases obtained were identified using XRD and hard-X-ray photoelectron spectroscopy. For the case using the oleylamine as a solvent and a surfactant, a face-centered metallic nickel with ∼50 nm grain size appeared at low reaction temperature below 240°C. At high reaction temperature above 280 °C, nanocrystals of cubic and hexagonal nickel carbide (Ni₃C) with ∼50 nm grain size appeared; the hexagonal nickel carbide had been often identified as a hexagonal close-packed metallic nickel. For the case using the 1-octadecene as a solvent and fatty acid as a surfactant, nanocrystals of nickel oxide with 3-4 nm grain size appeared. The key factors determining the phase appeared were discussed.