Removal of sulfur from commercial kerosene using nanocrystalline NiFe2O4 based sorbents

Magnetic resonance of the NiFe2O4 nanoparticles in the gigahertz range

We report an adjustable magnetic resonance frequency from 1.45 to 2.54 GHz for NiFe2O4 nanoparticles which were prepared by a sol-gel process. X-ray diffraction and scanning electron microscopy results indicate that the samples are polycrystalline nanoparticles, and the size of the particles increases obviously with the thermal treatment temperature. The consequence of the surface composition suggests that the oxygen defects are present in the nanoparticle surface, and this surface magnetic state can show a strong surface anisotropy. With decreasing size of the particle, the surface magnetic effect is predominant, resulting in an increase of resonance frequency for NiFe2O4 nanoparticles. This finding provides a new route for NiFe2O4 materials that can be used in the gigahertz range.

Nanoscale characterization and magnetic reversal mechanism investigation of electrospun NiFe2O4 multi-particle-chain nanofibres

NiFe(2)O(4) multi-particle-chain nanofibres have been successfully fabricated using electrospinning followed by calcination, and their morphology, chemistry and crystal structure were characterized at the nanoscale. Individual NiFe(2)O(4) nanofibres were found to consist of many nanocrystallites stacked along the nanofibre axis. Chemical analysis shows that the atomic ratio of Ni : Fe is 1 : 2, indicating that the composition was NiFe(2)O(4). The crystal structure of individual NiFe(2)O(4) multi-particle-chain nanofibres proved to be polycrystalline with a face centered cubic (fcc) structure. The nanocrystallites in the nanofibres were revealed to have a single-crystal structure with random crystallographic orientations. The magnetic measurements reveal that the NiFe(2)O(4) multi-particle-chain nanofibres have a coercivity force of 166 Oe. A "chain of sheets" micromagentism model was proposed to interpret the observed magnetic behaviour of the NiFe(2)O(4) multi-particle-chain nanofibres. Simulation studies of the coercivity are in good agreement with the experimental results at room temperature. It is believed that this work will significantly expand the use and application of these compounds in the field of biomagnetic nano-devices and improve understanding of the magnetic origin of spinel ferrites.