NiO nanostructured powders were synthesized by an ultrasonic spray pyrolysis (USP) technique. The powders were characterized using low temperature adsorption (BET), X-ray diffraction, scanning electron microscopy (SEM), and a transmission electron microscopy (TEM). The final product of the ultrasonic spray pyrolysis is hollow micro spheres with 5-7 mu m in diameter. The microspheres are built from nanoparticles with 40-60 nm in diameter. (C) 2016 Elsevier Ltd. All rights reserved.