W/WS2 inorganic fullerene-like (IF) nanoparticles with core-shell structure are synthesized by the reaction of tungsten nanospheres and sulfur at relatively low temperatures (380-600 degrees C) under hydrogen atmosphere, in which tungsten nanospheres were prepared by wire electrical explosion method. Images of transmission electron microscopy and high-resolution transmission electron microscopy show that the composite particles are of core-shell structure with spherical shape and the shell thickness is about 10 nm. X-ray powder diffraction results indicate that the interlayer spacing of IF-WS2 shell decreases and approaches that of 2H-WS2 with increasing annealing temperatures, representing an expansion of 3.3-1.6%. A mechanism of IF-WS2 formation via sulfur diffusion into fullerene nanoparticles is discussed. Thermal analysis shows that the nanoparticles obtained at different temperatures exhibit similar thermal stability and the onset temperature of oxidization is about 410 degrees C. Encapsulating hard tungsten core into IF-WS2 and the spherical shape of the core-shell structures may enhance their performance in tribological applications. (C) 2006 Elsevier Ltd. All rights reserved.