FeCl(2) and NiCl(2) were used for synthesis of nanocrystalline spherical Fe-Ni alloy particles by ultrasonic spray pyrolysis and hydrogen reduction (USP-HR). Spherical ultrafine Fe-Ni particles were obtained by USP of aqueous solutions of iron-nickel chloride followed by thermal decomposition of generated aerosols in hydrogen atmosphere. Particle sizes of the produced Fe-Ni particles can be controlled by the change of the concentration of an initial solution. The effect of the precursor solution in the range of 0.05, 0.1, 0.2 and 0.4 M on the morphology and crystallite size of the Fe-Ni alloy particles are investigated under the conditions of 1.5 h running time, 900 degrees C reduction temperature, and 1.0 L/min H(2) volumetric flow rate. X-ray diffraction (XRD) studies and Scherrer crystallite size calculations show that the crystalline size was nearly 28 nm. Energy dispersive spectroscopy (EDS) was performed to determine the chemical composition of the particles. Transmission electron microscope (TEM) was used to confirm the crystalline size, that was determined using XRD results. Scanning electron microscopy (SEM) observations reveal that the precursor solution strongly influences the particle size of the synthesized Fe-Ni alloy particles. Spherical nanocrystalline Fe-Ni alloy particles in the range of 80 and 878 nm were obtained at 900 degrees C. (C) 2009 Elsevier B.V. All rights reserved.