Structural and Magnetic Properties of PdxNi1-x (x=0 and 0.54) Metallic Nanoparticles in an Ordered Mesoporous Carbon Template

In the frame of developing nanocomposites, the confinement of nanosized metals or alloys in nanostructured porous materials is a key point. Using a wetness method starting from metal salt precursors [PdCl2, Ni(NO)(3)], we have succeeded in the synthesis of two nanocomposites in which nanoclusters of either Pd54Ni46 alloy or Ni have been dispersed in a carbon template (CT). For the CT-PdNi nanocomposite, XRD and TEM analyses show the dispersion of 5 nm nanoparticles inside the pores of the CT. For the CT-Ni nanocomposite, the metal particles are close to 10 nm and are mostly located at the CT surface and are partly oxidized. XRD, EDX, and EELS analysis as well as magnetic measurements have demonstrated that Pd and Ni elements have fully reacted in the CT-PdNi nanocomposite to form the Pd54Ni46 alloy. The magnetic properties of the CT-PdNi composite are compared with those of the CT-Ni one. The CT-PdNi has a lower blocking temperature T-B than CT-Ni, confirming the smaller size of the nanoparticles. For CT-Ni nanocomposite, the coexistence of both Ni and NiO phases leads to a slight asymmetry of the hysteresis loop, and the M-H curve does not reach the saturation magnetization. In contrast, the CT-PdNi composite displays a larger hysteresis loop without asymmetry, confirming that alloying Pd with Ni prevents Ni from oxidation.