High-energy ball milling of NiZn ferrites-SiO2 nanocomposite

G. POZO LÓPEZ; S.P. SILVETTI; R.H. MUTAL; O.A. VILLAGRA; H.R. BERTORELLO

Chihuahua

Workshop; VI Latin American Workshop on Magnetism, Magnetic Materials and their Applications; 2003

CIMAV, Chihuahua, México

Composites of NiZn ferrite particles dispersed in a silica matrix were prepared by mechanical alloying by high-energy ball-milling (HEBM), using the 3:1, 6:1 and 16:1 relations between the ball mass and powder mass. HEBM was carried out for 300 h in air atmosphere and the frequency utilized for the process were 120 and 200 rpm. Small amounts of powder were removed from the vial every 20 h for structural and magnetic characterization studies.Phase analysis was done by X-ray diffraction (XRD) and the sample composition was checked by X-ray fluorescence. Variation of magnetic properties with volumetric fraction of SiO2 was studied using a vibrating sample magnetometer (VSM).Thermal transformations of the ball-milled powders were studied in air and Ar atmosphere from room temperature to 1300K with the aid of simultaneous thermal analysis (STA) obtaining information on thermal gravimetry (TG) and differential thermal analysis (DTA). After 200 hours of milling time the phase distribution consist of a majorly amorphous phase poor in silica and little amounts of other phases. The combination of different SiO2 concentrations and heat treatments produced samples with saturation magnetizations between 1 and 35 emu/g and coercivity ranging from 200 to 70 Oe, for all conditions analyzed.