Nanocrystalline NiZn Ferrite/SiO2 composites synthesized by mechanical alloying

G. POZO LÓPEZ; S.P. SILVETTI; S.E. URRETA

Buenos Aires

Congreso; XXII Congreso Interamericano de Ingeniería Química y V Congreso Argentino de Ingeniería Química (XXII CIIQ / V CAIQ); 2006

Asociación Argentina de Ingenieros Químicos

Magnetic NiZn ferrite/SiO2 nanocomposites were prepared by mechanical alloying alpha-Fe2O3 (hematite), ZnO, NiO and SiO2 powders, for milling times between 1h and 260 h, at room temperature. The as milled powders were then isothermally annealed for 1 h. at temperatures between 673 K and 1273 K, under quite air and argon flux atmospheres, respectively. At each process stage, the resulting heterostructures were characterized by X-ray diffraction techniques and their magnetic properties monitored by MH loops and apparent fluctuations field measurements. Before the heat treatment, the M-H curves exhibit a relatively large superparamagnetic contribution; after annealing at 1273 K a predominant ferromagnetic contribution may be detected in the M-H loop. These results are interpreted considering the different magnetic phases obtained, their crystal sizes and their mutual interactions, which are found to strongly depend on the milling time, and also on the temperature and atmosphere of the final heat treatment.