Synthesis of WS2 nanostructures from the reaction of WO3 with CS2 and mechanical characterization of WS2 nanotube composites.

Tungsten disulfide (WS(2)) nanometer sheets, spheres, fibers and tubes were generated by a synthetic pathway that avoids the use of H(2)S as the source of sulfur and employs instead CS(2) vapor, carried by an Ar or N(2)/H(2) stream in a heated tubular furnace, for the reaction with WO(3) precursor powders. The experiments were conducted at temperatures between 700 and 1000 °C, while the reaction times expanded between 30 min and 24 h. Characterization methods used to analyze the products of the synthesis include TEM, SEM, XRD and EDX. We found a strong correlation between precursor and product microstructure, although the temperature and reaction times play a critical role in the products' microstructural features as well. WS(2) inorganic fullerene (IF) nanospheres are generated in a wide window of conditions, while nanotubes and nanofibers are only produced at high temperatures or long reaction times. A proposed growth mechanism based on the CS(2) synthetic approach is presented. Nanoindentation and nano-impulse techniques were used to characterize the mechanical properties of polymer matrix-WS(2) nanotube composites, finding them superior to equivalent SWCNT composites. The improvements in toughness of nanocomposites based on WS(2) can be attributed to geometrical and morphological effects that assisted several toughening mechanisms such as crack pinning and the formation of an immobilized polymeric interphase around the nanotubes.