Synthesis,Characterization And Investigation On The Tribological Properties Of Two-dimensional Transition Metal Dichalcogenides And Composites

In recent years,reducing friction and wear-related mechanical failures in moving mechanical systems has gained increased attention due to that wear can cause huge energy waste in industrial production under the special working conditions such as high temperature,low temperature,high vacuum,high load and strong radiation.Accordingly,the search for novel materials,coatings,and lubricants that can potentially reduce friction and wear is very important.Recently,graphene and its related twodimensional materials?such as transition metal dichalcogenides?have become one of the hot topics in materials science due to their unique high specific surface structure and potential applications in catalysis,energy storage and electronic devices.However,its tribological potential as lubricants is still in its nascent stage.This article focuses on the application of its tribological performance in reducing friction,and its future development is prospected.The main points in this thesis are summarized as follow:1,A facile and scalable process for the synthesis of MoS₂/G composites was developed.The morphology and microstructure of the composites were examined by using a wide range of microscopic and spectroscopic techniques.The formation process for the MoS₂/G composites was investigated.The tribological properties of MoS₂/G composites as liquid additives were investigated.Its tribological metrics?including friction coefficient of ?0.09 and wear rate of ?2.08 × 10-5 mm3/Nm?demonstrate superior anti-wear and friction-reducing properties.In addition,we have used the as synthesized MoS₂/G as a lubrication additive to evaluate the tribological properties of epoxy resin.The results indicated that the introduction of MoS₂/G at low contents has significantly enhanced the wear resistance and meanwhile led to a significant decrease in the friction coefficient.2,A very simple and easy method by ball milling commercial MoS₂ and graphite was developed for the scalable production of MoS₂/G composites.The morphology and microstructure of the composites were investigated by Raman spectroscopy,X-ray diffraction?XRD?,field emission scanning electron microscopy?FESEM?,high resolution transmission electron microscopy?HRTEM?and selected area electron diffraction?SAED?.We found that MoS₂ nansheets stick on the surface of graphite,which act in a similar manner to Scotch tape in micromechanical exfoliation processes.The tribological properties of MoS₂/G as additives in epoxy coating were investigated.The results indicated that the introduction of MoS₂/G at low contents has significantly enhanced the wear resistance and meanwhile led to a significant decrease in the friction coefficient.The effect of applied load on the tribological properties of epoxy composite coating was also investigated.The results indicated that the friction coefficient decreases with the increasing applied load,the wear rate increases on the increasing load.3,A scalable and effective method was developed to prepare NbSe2 nanosheets and its composites through ball milling.The influence of ball milling time on the morphology of the product was investigated.The results indicated that the correlation length of ordered stacking in c-direction decreases strongly within the actual milling time.The tribological properties of NbSe2 nanosheets and NbSe2/G as additives in epoxy coating were investigated.It found that the friction coefficients of the epoxy composite coating sharply decreased to lowest value from about 0.337 to 0.062?reduced by 80%?with increased NbSe2 nanosheets content from 0 to 20 wt%,the wear rates also decreased sharply;The introduction of NbSe2/G at a low fraction contributed to better friction-reducing and anti-wear performances of epoxy composite coatings,whilet the higher content of filler leds to destruction of the continuity,decrease of the binding strength between the matrix and fillers,and worsening of the friction and wear behaviors of coatings.