Facile synthesis of metastable Ni–P nanostructured materials by a novel bottom-up strategy

• Simple synthetic routes for metastable Ni–P nanostructured materials.
• The Ni–P alloy is prepared by bottom-up strategy.
• The polyol method modified by the addition of hypophosphite was used.
• After SPS treatment, the metastable alloy is transformed into a composite material.
• The nanostructured material containing Ni and Ni3P phases.

A novel bottom-up strategy combining chimie douce and non-conventional consolidation process to elaborate Ni–P metastable alloy is described here. The chimie douce method consists on the polyol process, modified by the addition of hypophosphite (strong reducing agent). It allows elaborating Ni–P nanopowder. The consolidation of the as-obtained nanoparticles is carried out by Spark Plasma Sintering (SPS). The microstructure of the powder and nanostructured dense sample was studied and characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray (EDX), thermogravimetric analysis (TGA), differential thermal analysis (DTA) and FTIR spectroscopy. The nanopowder is formed of the metastable Ni–P alloy, with a composition of about 3.44% in phosphorus. Unlike Ni–P alloys prepared by electroless or electrodeposition, the nanoparticles developed show good crystallinity. They have spherical morphologies with a size of about 100 nm and are formed by aggregation of crystallites about 8 nm in diameter. Various analysis techniques showed that SPS treatment induced the transformation of the metastable Ni–P alloy in a two phases: almost pure nickel and a new phase with chemical formula Ni3P. This latter is in form of spherical particles with about 130 nm in diameter, while the nickel grains have a polygonal shape with 330 nm in diameter.

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