Structural and magnetic properties of Ni–Pt nanoalloys supported on silica

Bimetallic Ni–x%Pt/SiO2 nanoclusters at different initial platinum contents (x = 0, 2, 9, 15, 25, 35, 85 and 95 at %) are synthesized at room temperature by the radiolytic process. According to the Pt amount, the structural studies (XRD, TEM and SAED) reveal the presence after irradiation of NiSi and Ni3Pt or NiPt3 nanoalloyed clusters on amorphous silica. The Ni–Pt nanoparticles have a fcc solid solution structure and a narrow cluster size distribution. The radiation-induced nanoparticles exhibit an enhancement of the magnetization at low temperature. Moreover, unlike Ni–Pt bulk alloys, the magnetization increases with the Pt content. In the ultra divided state, platinum seems to play a major role by enhancing the nickel ion reduction and protecting Ni against corrosion during the synthesis.

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► Formation of Ni3Pt and NiPt3 nanoalloys (≈5 nm) at room temperature.
► Formation of NiSi phase at the metal/SiO2 interface.
► Magnetization enhancement at low temperature of Ni–Pt nanoparticles.
► Increase of saturation magnetization with Pt content.
► Beneficial effect of Pt on the stability of dispersed nickel.