Synthesis, characterization and thermal stability of Ni3P coatings on nickel

The reaction mechanism describing the formation and surface decomposition of Ni3P has been investigated. Ni3P was synthesized as a thick film on a Ni foil by a simple solid-state reaction. X-ray diffraction confirms that the layer produced, on the surface of the Ni foil, is pure Ni3P. The solid-state reaction did not occur at 400 °C or lower temperatures. At 600 °C or higher temperatures the solid-state reaction occurred by a nucleation mechanism of synthesis and later sintering of Ni3P particles at the surface of the Ni foil. The surface of the Ni3P–Ni foil showed to be stable in air up to 300 °C. At higher temperatures, Ni3P decomposed trough a complex mechanism, including the loss of phosphorus, the formation of the phases Ni12P5 and Ni2P, and finally, oxidation of the nickel phosphides. Samples heated at 800 °C for 4 h produced a NiO layer on the surface of the Ni3P–Ni foil.