STRUCTURAL AND MORPHOLOGICAL TRANSFORMATIONS DURING NIO AND NI PARTICLES GENERATION FROM CHLORIDE PRECURSOR BY ULTRASONIC SPRAY-PYROLYSIS

Submicrometer NiO and Ni powders were obtained by ultrasonic spray pyr olysis of aqueous solutions of NiCl2 followed by thermal decomposition of generated aerosols in an oxidation or N-2/H-2 reduction atmosphere , respectively. Particle sizes of the prepared powders can be controll ed by the change of reaction temperature and the concentration of init ial solutions. Pyrolysis temperatures in the range from 973 to 1273 K, non-agglomerated ideally spherical NiO and relatively spherical Ni pa rticles with a mean diameter of 0.5-0.8 mu m were obtained. Generation of NiO particles proceeds gradually from NiCl2 . 6H(2)O dehydration a nd NiCl2 oxidation to NiO formation. Ideal spheres of NiO particles we re prepared due to sufficient residence time of droplets in the drying and pyrolysis process and due to the conditions needed for the volume precipitation. The process of nickel formation proceeds through all p revious transformations followed by the reduction of NiO into nickel. Insufficient residence time of droplets in the case of nickel preparat ion is the cause of incomplete spheroidization of particles.