Study On The Preparation And Tribological Properties Of MSe₂ (M=Nb, W) Nanomaterials

Recently,MoS₂ was studied widely in the field of friction due to its special layer structure,which is integrated by Van der Waals force between layers,while internal layer by strong covalent bond,and it is rich in mineral resources.As a matter of fact,transitional metal diselenium MSe₂ (M=Nb,W) has a similar physical structure and nature with MoS₂.It can be improve the friction reduction properties of base oil as lubricating oil additives,but there is less research about them in the field of friction.So MSe₂(M=Nb,W)nanomaterials were prepared by solid state reaction,and the tribological properties were also studied in this article.In this paper,experimental investigation and theoretical analysis were carried out on the preparation process and tribological properties of transitional metal diselenium MSe₂(M=Nb,W) nanomaterials.Firstly,NbSe_x(x=2,3) micro-nanomaterials were successfully prepared by solid-state reaction.The as-prepared products were characterized by X-ray diffraction(XRD),scanning electron microscopy (SEM),transmission electron microscopy(TEM),and high-resolution transmission electron microscopy(HRTEM).The results showed that it was helpful to NbSe_x crystallize to raise temperature,the fibers with diameter 100～300 nm and length several micometers could be obtained at lower temperature,and when temperature was raised the NbSe_x sheets were produced.Secondly,NbSe₂ nanofibers were obtained from NbSe₃ nanofibers by high temperature decomposition.The as-obtained NbSe₂ nanofibers were characterized by EDS,scanning electron microscopy(SEM),TEM and HRTEM and so on.The results showed that the obtained fibers had a diameter 100～300 nm and length several tens of micometers. Thirdly,WSe₂ nanomaterials were successfully prepared by solid-state reaction.The obtained products were characterized by X-ray diffraction(XRD),scanning electron microscopy(SEM),transmission electron microscopy(TEM),and high-resolution transmission electron microscopy(HRTEM).The results showed that the obtained WSe₂ nano-materials had different morphology including nanofibers, nanosheets and nanoparticals,which grain size was about 100nm.Fourthly,the tribological properties of NbSe_x and WSe₂ nanomaterials as lubricant additive were investigated on UMT-2 friction testing machine made in USA.And tests were carried on the condition of boundary lubrication and made a comparison on the tribological properties to the different morphology of NbSe_x nanomaterials.The results showed that friction coefficient of lubricants reduce percentage was 10%to 30%,as nanomaterials add into the base oil.Fifthly,Copper-matrix composites were obtained by mechanical mixing the NbSe₂ nanomaterials and copper.The dry friction experiments of Cu-NbSe₂ composites were also carried on UMT-2 friction testing machine.And made a study of the effect on the tribological properties of Cu-NbSe₂ composites with different morphology.The results showed Cu-NbSe₂ composites had a better tribological propertiesThe last but not least,friction mechanism of transitional metal diselenium MSe₂(M=W,Nb) nanomaterials as lubricant and composites additive were discussed.The excellent tribological proerties of these nanomaterials may be due to the following factors:the special structures, the formationof lubrication films and fill up-repair mechanism.