Synthesis and characterization of nanostructured ferrites for ferrofluids

ARANA, M.; PAULA BERCOFF; JACOBO S.E.

Natal

Otro; International Institute of Physics; 2013

Mn-Zn NPs were synthetized by two methods: sol-gel autocombustion and mecanochemistry in a high-energy ball mill. In the first case we didn?t use the particles to prepare a ferrofluid (FF), because these were not small enough. We found that magnetic and structural properties were enhanced when we doped the spinel with lithium and we could explain this behavior with a cation distribution model corroborated with experiments. In the second case, the lithium doping did not enhance the properties but the resulting powders from the milling were 17 nm NPs. We modified the NPs surface and coated them with a polymer. The stabilized NPs were suspended in chitosan and the resulting FF was stable for 12 h, with SAR values promising for hyperthermia. Carbon-coated magnetite NPs were synthetized by the mechanochemical method using hematite and amorphous carbon as precursors. The powders were milled 18 hours and annealed for 2 h in Ar at 500 ºC. After milling for 18 hours and annealing, the sample contained a single crystalline phase. The NPs had a saturation magnetization of 78.0 emu/g (close to bulk value) and the sample was composed of amorphous carbon clusters with magnetite 10 nm NPs. This system seems appropriate for biomedical applications. Structural and magnetic properties of NPs were investigated by X ray diffraction (XRD), vibrating sample magnetometry (VSM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and high resolution transmission electron microscopy (HR-TEM). XRD patterns were refined with the Rietveld method. A device ?to be attached to the VSM? was designed and constructed in order to mesure the thermal conductivity of FFs as a function of an external applied field