Graphite-Controlled Fabrication of Ultrathin WSe2 Nanosheets with Tower-Like Structure and Their Tribological Properties

Uniform hexagonal tungsten diselenide (WSe2) nanosheets, with thicknesses as small as 10 nm and diameters as small as 100 nm, self-assembled into tower-like arrays, were successfully synthesized by the solid-state reaction of the elementsWand Se in the presence of graphite in a sealed stainless steel reactor at 800 degrees C. However, scattered submicrometerWSe(2) sheets, 250 nm thick and 1-3 mu m in diameter, were obtained in the absence of graphite. Subsequently, the formation mechanism of this assembled structure was proposed. Furthermore, the lubricity of as-fabricated arrays added into paraffin in steel-steel interaction was investigated by a ball-on-disc tribometer, as compared to that of commercial graphite and as-obtained submicrometer WSe2 sheets, respectively. The results showed that the addition of small amounts (0.5 wt%) of as-fabricated arrays greatly improved the friction reduction and antiwear properties of paraffin and did well then the same amount of commercial graphite and submicrometer WSe2 sheets, suggesting that as-fabricated arrays are an excellent lubricating material. Therefore, this process provides a strategy for the large-scale, cost-effective, and environmental friendly preparation and tribological application of small-sized laminar transition-metal dichalcogenide with good lubricity.