| Molybdenum disulfide (MoS2), a typical transition metal dichalcogenides (TMDs), have a sandwich interlayer structure formed by stacking of the by S-M-S layers, which are loosely bound to each other only by Van der Waals forces and easily cleaved. Due to its unique structure, MoS2 is particularly important for solid lubrication or as an additive for lubricating oils and greases and has enjoyed the reputation of "the king of lubrication" for a long time. As we know, nanosized MoS2 such as nanorods, nanosheets usually have better tribological properties either in friction reduction or wear resistance than bulk MoS2. Therefore, development of high-performance nano-lubricating materials is a focus of research in the field of friction and lubrication. In this paper, we develop a mild and facile hydrothermal method to prepare MoS2-based naocomposites and have also investigated their tribological properties as lubrication additives in base oil. Moreover these fundamental data presented here will possibly provide useful theoretical and application supports for lubrication materials. The main points in this thesis are summarized as follows:1. Surfactant-assisted hydrothermal synthesis and tribological properties of MoS2 nanomaterialsNovel MoS2 nanoflowers with high purity were successfully synthesized via a facile CTAB-assisted hydrothermal route. The influence of reaction time, surfactant and pH value of initial mixture on the formation of MoS2 nanostructures was investigated. A possible evolutionary process of the MoS2 nanoflowers is proposed to explain the formation of various MoS2 nanostructures on the basis of the experimental results. In additional, the tribological properties of the as-prepared MoS2 powders as additives in HVI500 base oil were investigated on UMT-2 multispecimen tribo-tester, which indicated the addition of MoS2 nanoflowers can improves the tribological properties of base oil.Similarly, MoS2 hollow microspheres were synthesized by a facile hydrothermal solution route with the assistance of Pluronic F-127 (Ethylene Oxide/Propylene Oxide Block Copolymer). The experimental results indicated reaction time and surfactant have significant effects on the morphology of the as-prepared products. A possible formation mechanism has also been investigated on the basis of a series of transmission electron microscopy (TEM) studies of the product obtained at different durations. The tribological properties of the as-prepared products as additives in paraffin were investigated by UMT-2 multispecimen tribotester. Tribological performance evidenced that the obtained MoS2 hollow microspheres possessed superior anti-wear and friction-reducing properties as a lubrication additive, which will penetrate more easily into the interface with base oil, and form continuous film in concave of rubbing surface, enhancing the tribological properties.2. Mixed surfactant-assisted hydrothermal synthesis and tribological properties of MoS2 hierarchical nanomaterialsThe method based on mixed surfactant-assisted hydrothermal route was extended. MoS2 flower-like hollow microspheres were synthesized by a facile hydrothermal route with the help of single surfactant Benzyltriethylammonium chloride (TEBAC); MoS2 core-shell microspheres were synthesized with the help of TEBAC and CTAB; Similarly, MoS2 flower-like nanorods were synthesized with the help of TEBAC and D-glucose. Moreover, various factors such as reaction time and surfactant on the formation of MoS2 nanostructures were investigated. In additional, the tribological properties of the as-prepared MoS2 powders as additives in paraffin base oil were investigated on UMT-2 multispecimen tribo-tester, which indicated the addition of all MoS2 hierarchical nanomaterials can improves the tribological properties of base oil.3. Hydrothermal synthesis and tribological properties of MoS2 coupled with Metal Sulfide (ZnS, Bi2S3) naocompositesMoS2/ZnS ultrathin nanosheets have been synthesized by a facile hydrothermal process. The experimental results indicated the mole ratio of Mo and Zn or Mo and S have significant effects on the morphology of the as-prepared naocomposites. The tribological properties of the as-prepared products as additives in paraffin were investigated by UMT-2 multispecimen tribotester. Tribological performance evidenced that the obtained MoS2/ZnS ultrathin nanosheets possessed superior anti-wear and friction-reducing properties as a lubrication additive. Especially, the base oil with 2% MoS2/ZnS composites have lower and stable friction coefficient compared with other mass fraction of the additives.Similarly, MoS2/Bi2S3 nanosheets have been synthesized by a facile hydrothermal process using Bi(NO3)3 as Bi source instead of ZnSO4 in the previous experimen. The experimental results indicated the mole ratio of Mo and Bi or Mo and S have significant effects on the morphology of the as-prepared naocomposites. The tribological properties of the as-prepared products as additives in paraffin were investigated by UMT-2 multispecimen tribotester. Tribological performance evidenced that the obtained MoS2/Bi2S3 nanosheets possessed superior anti-wear and friction-reducing properties as a lubrication additive, which will penetrate more easily into the interface with base oil, and form continuous film in concave of rubbing surface, enhancing the tribological properties.4. Hydrothermal synthesis and tribological properties of MoS2-based 2D nanocompositesMoS2/GR composite nanotubes were successfully synthesized via a facile NaCl-assisted hydrothermal route using grapheme prepared by modifed Hummer’s methods as precursor. The influence of NaCl and grapheme amount of initial mixture on the formation of MoS2/GR nanostructures was investigated. Tribological properties of the as-prepared composites as additives in paraffin were investigated by UMT-2 multispecimen tribotester. Tribological performance evidenced that the obtained MoS2/GR composite nanotubes possessed superior anti-wear and friction-reducing properties as a lubrication additive. Especially, the base oil with 1%MoS2/GR composites have lower and stable friction coefficient compared with other mass fraction of the additives.Similarly, g-C3N4/MoS2 composite nanosheets were successfully synthesized via a facile hydrothermal route using g-C3N4 nanosheets as precursor. The experimental results indicated g-C3N4 amount and surfactant have significant effects on the morphology of the as-prepared products. Tribological properties of the as-prepared composites as additives in paraffin were investigated by UMT-2 multispecimen tribotester, which indicated g-C3N4/MoS2 composite nanosheets possessed superior anti-wear and friction-reducing properties as a lubrication additive. Especially, the base oil with 2% g-C3N4/MoS2 composites have lower and stable friction coefficient compared with other mass fraction of the additives, and penetrate more easily into the interface with base oil, and form continuous film in concave of rubbing surface, enhancing the tribological properties. |
