| Popis: |
Ultrafine magnetic nickel ferrite particles have a significant potential for use in many applications such as magnetic recording media, ferrofluids, microwaves, catalysis and radar-absorbing coatings [1, 2]. Nickel ferrite powders with a nominal NiFe2O4 composition were synthesized by combustion reaction and an evaluation was made of the effect of two different conditions of synthesis on the nanostructural and magnetic characteristics of the resulting powders. Two synthesization routes were studied. The first, NFB, involved the preparation of the powder using a Pyrex beaker heated directly on a hot plate at 480°C until self-ignition occurred. By the second route, NFC, the powder was obtained under the same synthesization condition as the NFB route, but a vitreous silica basin was used. The resulting powders were characterized by X-ray diffraction (XRD), nitrogen adsorption by BET and scanning electron microscopy (SEM). The first route, NFB, proved more favorable to obtain powders with high surface area and, hence, smaller crystalline sizes (5.70 nm) and a superparamagnetic behavior. The NFC route confirmed the feasibility of obtaining powders with a crystalline size of 18.00 nm and a magnetic behavior. Saturation magnetization was 33.18 emu/g and the coercivity field was 25.63 Oe for powders obtained by the NFC route. |
