Study On The Preparation Of MSe₂ (M=Nb, Ta) Nanomaterials And Tribology Propepties Of NbSe₂ Nanomaterials

Transitional metal dichalcogenides MX₂ (M=W, Mo, Nb, Ta; X=S, Se) have lamellar close-packed hexagonal structures, was used as solid lubricants extensively. However, the dangling bonds on the edge of crystal have chemical activity, adhesion of metal surface and to be oxidized easily in its working progress, which result in the friction properties of lubricants decrease. Study showed that the unique closed nanostructure can improves the chemical stability of these materials. This has the important meaning to reduce friction and wearing. In recently years, research on nanostructure of sulfides rises gradually; however, there is little study on selenides nanostructures. Compared with sulfides, selenides have a lower resistance rate, for example, MoS₂ have resistance rate of 8.9×10²Î©cm while NbSe₂ have resistance rate of 5.35×10⁴Ωcm only. This property gives NbSe₂ nicer conductivity and abrasion resistant, which make the matter a more widely application. Therefore, strengthening the research on selenides nanostructures has much meaning.In this article, experimental investigation and theoretical analysis were carried out on the preparation process and tribology properties of dimensional MSe₂ (M= Nb,Ta) nanostructures.Firstly, the solid-phase reaction was used to produce NbSe₂ and TaSe₂ nanowires in evacuated and sealed quartz ampoules by mixed Se and Nb(Ta) powder. NbSe₂ nanowires, nanorobs and nanoparticles were synthesized by the thermal decomposition of NbSe₃ obtained from the reaction of Se and Nb in airtight vessel in different condition. Based on the experiment phenomenon, the forming, growth process of NbSe₂ nanowire was discussed, and the forming of molecule lamellar, crimp and basis of top-growth model were proposed preliminary. For the initial NbSe₃ microstructure were broken in experiment, furthermore, the continued Se atom loss in the thermolysis of NbSe₃, NbSe₂ nanorobs and nanoparticles were obtained with other irregular shapes in them. In addition, the common layered NbSe₂ were synthesized via solid-phase reaction. Secondly, the as-synthesized common layered NbSe₂ and NbSe₂ nanowires were dispersed in lubricating oil. The tribological behavior of them was investigated by UMT-2 Multi-specimen test system. The results show that the oil with NbSe₂ nanowires can improve the lubricating capacity of oil better than common layered NbSe₂ in the range of experimental conditions. The friction mechanism of lubrication including MSe₂ as additives was discussed preliminary based on the analysis of experiment data and microstructure of NbSe₂ nanowires. This could be attributed to the layered structure for common NbSe₂. As for NbSe₂ nanowires, it may be due to the following factors: NbSe₂ nanowires have unique closed structures, lubrication films, fill up-repair and micro-bearing mechanism.Thirdly, mixed NbSe₂ fibers with bronze power uniformity, then copper composites sintered materials with NbSe₂ nanoparticles were prepared by a process of powder metallurgy. The friction and wear performance of composites were investigated by UMT-2 Multi-specimen test system. It was found that the incorporation of NbSe₂ nanoparticles contributed to effectively steady the friction coefficients under all kinds of loads and improve the antifriction performance of the composites, which was attributed to the self-lubricity of the NbSe₂ nanoparticles lubricating film formed on the worn composite surface. At the same time, it increases wear rate for the NbSe₂ nanoparticles loss quickly which attributed to the soft matrix.