Synthesis of WS2 nanostructuresfrom the reaction of WO3 with CS2 and mechanicalcharacterization of WS2 nanotube composites

Abstract

Tungsten disulfide (WS2) nanometer sheets, spheres, fibers and tubes were generated by a synthetic pathway that avoids the useof H2S as the source of sulfur and employs insteadCS2 vapor, carriedby an Ar or N2/H2 stream in a heated tubular furnace, for the reaction withWO3 precursor powders. The experiments were conducted at temperatures between 700 and1000 °C, while the reaction times expanded between 30 min and 24 h. Characterization methods used toanalyze the products of the synthesis include TEM, SEM, XRD and EDX. We found a strongcorrelation between precursor and product microstructure, although the temperature andreaction times play a critical role in the products’ microstructural features as well.WS2 inorganic fullerene (IF) nanospheres are generated in a wide window ofconditions, while nanotubes and nanofibers are only produced at hightemperatures or long reaction times. A proposed growth mechanism based on theCS2 synthetic approach is presented. Nanoindentation and nano-impulse techniqueswere used to characterize the mechanical properties of polymer matrix–WS2 nanotube composites, finding them superior to equivalent SWCNTcomposites. The improvements in toughness of nanocomposites based onWS2 can be attributed to geometrical and morphological effects that assisted several tougheningmechanisms such as crack pinning and the formation of an immobilized polymericinterphase around the nanotubes.