Synthesis And Properties Of Tungsten Disulfide Nanofibers Via Electrospinning

WS₂is a typical transition metal disulfide with layered structures similar tographite. It has been widely used as catalysts, hydrogen and lithium storageresevoirs and so on, due to its excellent optical, electronic, catalytic and lubricativeproperties. During the past few years, one dimensional WS₂has been synthesizedby some methods including thermal decomposition, template synthesis,hydrothermal synthesis, microwave-assisted synthesis and sonochemical synthesis.Compared with the conventional methods mentioned above, electrospinning is moreeffective, versatile and can produce fibers with high aspect ratio therefore itattracted extensive attention in recent years. As far as we know, synthesizing ofWS₂nanofibers by electrospinning has not been reported.In this paper, WO₃nanofibers were prepared by electrospinning solutioncontaining polyvinyl alcohol （PVA）, ammonium meta-tungstate （AMT） and alcohol,followed by calcination. Then these WO₃nanofibers were converted to WS₂nanofibers by a sulfurization process, with S acting as the sulfuration reducer. Aftersulfurization, WS₂nanofibers with high aspect ratio were successfully obtained.The nanofibres were characterized by X-ray diffraction （XRD）, scanning electronmicroscopy （SEM）, transmission electron microscopy （TEM）, Fourier transforminfrared spectroscopy （FTIR） and wear instrument.AMT/PVA composite nanofibers were prepared by electrospinning. Theparameters to the fibers’ diameter and continuity in the electrospinning processwere studied, and the PVA concentration of12%, applied voltage of15kv, collectordistance of12cm were chosen as the optimal parameters to prepare AMT/PVAnanofibers. The nanofibres of WO₃with rough surface and diameters of250-300nmwere obtained after calcining the PVA/AMT composite fibres at550oC for3h.The influence of the vulcanizing temperature and the ratio of WO₃and S onthe product were studied. The WO₃nanofibres were complete converted to WS₂nanofibres by using the reaction between WO₃nanofibres and S （the molar ratio ofWO₃and S is1:20） at800oC for3h in an argon atmosphere. After sulfurization,WS₂nanofibres with similar diameters to WO₃were obtained, while the surfacebecame much coarser than WO₃nanofibers.Cu-WS₂power composite and Cu-WS₂power-WS₂nanofibers composite were prepared by powder metallurgy route. During the sliding process in air, theinfluence of the WS₂morphology on the friction behavior was studied. The resultsshow that adding the fibers can’t reduce the friction coefficient of the compositeobviously. It maybe coursed by two reasons, on one hand, the amount of the addingWS₂nanofibers is little, on the other hand, the WS₂nanofibers prepared byelectrospinning are stacked by particles and their morphology was difficult tomaintain.In the current work, WS₂nanofibers with high aspect ratio were successfullysysnthtized via electrospinning, which provide a new way to fabricate WS₂nanofibers. However, the WS₂nanofibers are brickle and easy to break，improvingthe process to prepare continuous fiber with high strength remains to be researched.