Study On The Preparation And Tribology Propepties Of MS₂ (M=Nb, Ta) 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. The dangling bonds on the edge of crystal have chemical activity, and to be oxidized easily in ambition, especially in humanity conditions, the friction properties of lubricants decrease. The unique closed one dimensional nanostructure (nanotubes, nanowires, nanobundles) formed with rolled up MS₂ (M=W, Mo, Nb, Ta) materials have eliminated the fringe dangling bonds, thereafter they improves the chemical stability and have very expansive application prospects on tribology.In this article, experimental investigation and theoretical analysis were carried out on the preparation process and tribology properties of transitional metal dichalcogenides one dimensional MS₂ (M=Nb,Ta) nanostructures.Firstly, the solid—phase reaction was used to produce NbS₂ and TaS₂ one dimensional nanostructures (nanowires, nanotubes) in evacuated and sealed quartz ampoules by mixed S and Nb(Ta) powder. The products' component and microstructure of MS₂ nanostructue were investigated by means of X-ray diffraction (XRD), scanning electronic microscope(SEM) and transmission electronic microscope(TEM); it indicated that the product consists of long, fairly uniform diameter MS₂ nanostructures. We described briefly the generation of NbS₂(TaS₂)nanostructures via optimization the processing parameter of prepare NbS₂ nanostructures, such as reaction temperature, holding time, cooling rate. Higher reaction temperature have better crystal than low temperature. Better NbS₂ one dimensional nanostructures was obtained by decrease the cooling rate of reaction. Lengthening the reaction time has no value for the preparation of nanowire. In order to get NbS₂ nanowire, keeping sulfur in some concentration is compulsory. Nanowire's growth mechanism was also discussed preliminary.Then, the tribology properties of dichalcogenides MS₂ nanwires as additives in oil lubrications were tested by MS-T3000. The test was carried out in different load, rotated speed and different additives concentration in oil lubrication. The results show that: when the rotated speed is 200r/min, the lubrication including 0.5wt%NbS₂(TaS₂) as additives have prefer than oil, the friction coefficient increasing accompany the load added, with the test time lenghthened, the friction coefficient have negative tendency. When the rotated speed increasing(400r/min), the friction coefficient have prefer in high load condition. The friction coefficient of lubrication is increasing with the growing of additives concentration in light load, the friction coefficient have negative characteristic when load increasing. We discussed the friction character of lubrication including MS₂ as additives. And finally, the friction mechanism of lubrication including MS₂ as additives was discussed preliminary. The lubrication has excellent tribology proerties in high load may be due to the following factors: one dimensional nanomaterials have unique dosed structures, lubrication films and fill up-repair mechanism.