Consolidation by spark-plasma sintering of Ni nanoparticles

Full text: Ni nanoparticles (NPs), with average diameter of ~ 5.5 nm and embedded in an amorphous SiO₂/C matrix, were prepared for a systematic study of the interparticle dipolar interaction effect in their magnetic properties. Powder samples with different Ni concentrations were synthesized by a polymeric precursor method and consolidated by spark-plasma sintering. The consolidation, performed in an SPS 1050 Dr Sinter apparatus, was conducted at 600 ° C, under vacuum (20 - 30 Pa), and under a uniaxial compacting pressure of 50 MPa for 5 min. The powders and consolidated samples were characterized by X-ray powder diffraction (XRD) and magnetization as a function of temperature and applied magnetic field M(T, H). The XRD patterns show that both powders and consolidated samples are comprised of metallic Ni NPs with any sign of oxidation and a mean NP diameter of 5.5 nm, determined using the Scherrer equation. The results of the magnetic characterizations indicate that the NPs size distributions are similar for both type of samples but the strength of the dipolar interaction is stronger in consolidated samples by spark-plasma sintering. (author)