The polycrystalline nickel ferrite - NiFe2O4has been obtained by ceramic route starting from a stoichiometric mixture of oxides (NiO and α-Fe2O3powders). The obtained NiFe2O4was subjected to high energy ball milling. The formation of NiFe2O4by ceramic method and also the evolution of the powder during milling were studied by X-ray diffraction. The mean crystallite size of the NiFe2O4continuously decreases with the increasing of the milling time and for all the milling time it is in nanometric range. The particles sizes are drastically reduced by milling process. For the milled samples, the particles size is ranging from tens of microns to few nanometers. The powder morphology and local chemical homogeneity were investigated by scanning electron microscopy (SEM) and respectively by energy dispersive x-ray spectrometry (EDX).

Abstract:The mechanosynthesis of Ni 3 Fe intermetallic compound was carried out in a planetary mill. The effects of milling parameters such as balls diameters and ball milling speed defined by the vials rotation speed (ω) and the disk rotation speed (Ω), on morphology, microstructure and particle sizes of Ni 3 Fe powder were studied. It was found that the impact frequency represented by the number of balls from vials is an important parameter a milling process. The smaller grain sizes and particle was obtained when milling process was performed in high frequency rate of impacts together with high balls velocity, meaning high energy conditions.

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Fe-base Superalloy/Al2O3 type composite compacts were successfully obtained by spark plasma sintering from mechanically alloyed powders. The superalloy powders without Al2O3 and superalloy/Al2O3 type composites powders with 5 and 10 %vol. Al2O3 were synthesized from elemental powders in a high energy planetary mill. The influence of the milling process on particle size evolution has been determined using a Laser Particle Size Analyzer with an analysis field of 0.1-1000 ?m. The composite compacts were obtained by spark plasma sintering. Both, composite powders, and compacts were investigated by X-ray diffraction (XRD), high temperature X-ray diffraction (HT-XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX).

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