Yongfei Cui

Dependence of phase configurations, microstructures and magnetic properties of iron-nickel (Fe-Ni) alloy nanoribbons on deoxidization temperature in hydrogen

Iron-nickel (Fe-Ni) alloy nanoribbons were reported for the first time by deoxidizing NiFe2O4 nanoribbons, which were synthesized through a handy route of electrospinning followed by air-annealing at 450 °C, in hydrogen (H2) at different temperatures. It was demonstrated that the phase configurations, microstructures and magnetic properties of the as-deoxidized samples closely depended upon the deoxidization temperature. The spinel NiFe2O4 ferrite of the precursor nanoribbons were firstly deoxidized into the body-centered cubic (bcc) Fe-Ni alloy and then transformed into the face-centered cubic (fcc) Fe-Ni alloy of the deoxidized samples with the temperature increasing. When the deoxidization temperature was in the range of 300 ~ 500 °C, although each sample possessed its respective morphology feature, all of them completely reserved the ribbon-like structures. When it was further increased to 600 °C, the nanoribbons were evolved completely into the fcc Fe-Ni alloy nanochains. Additionally, all samples exhibited typical ferromagnetism. The saturation magnetization (Ms) firstly increased, then decreased, and finally increased with increasing the deoxidization temperature, while the coercivity (Hc) decreased monotonously firstly and then basically stayed unchanged. The largest Ms (~145.7 emu·g−1) and the moderate Hc (~132 Oe) were obtained for the Fe-Ni alloy nanoribbons with a mixed configuration of bcc and fcc phases.

Study on the relaxation behavior of BaTiO 3 ceramics modified with BiMO 3 (M = Fe, Y, Al)

The 0.92BaTiO3–0.08BiMO3 (M = Fe, Y, Al) solid solutions were prepared via a conventional solid state reaction technique. X-ray diffractometer, Raman spectra, scanning electron microscope, and impedance analyzer were used to examine the effect of three additions on the crystal structure, micromorphology and dielectric properties of 0.92BaTiO3–0.08BiMO3 (M = Fe, Y, Al) solid solutions. The 0.08 BiMO3 (M = Fe, Y, Al) additions totally transform the characteristic sharp phase transition (associated with permittivity maximum) of pure BaTiO3 into a less-distinct phase transition with a broad and strongly dispersive permittivity maximum characteristic of relaxor dielectrics.