Songwei Zhang

Tribological performance and lubrication mechanism of alkylimidazolium dialkyl phosphates ionic liquids as lubricants for Si 3 N 4 -Ti 3 SiC 2 contacts

The tribological performance of Si3N4-Ti3SiC2 contacts lubricated by alkylimidazolium dialkyl phosphates ionic liquids (ILs) was investigated using an Optimol SRV-IV oscillating reciprocating friction and wear tester at room temperature (25°C) and 100°C. Glycerol and tributyl phosphate (TBP) were also selected as lubricants for Si3N4-Ti3SiC2 contacts to study the tribological properties under the same experimental conditions for comparison. Results show that the alkylimidazolium dialkyl phosphates ILs were effective in reducing the friction and wear for Si3N4-Ti3SiC2contacts, and their performance is superior to that of glycerol and TBP. The SEM/EDS and XPS results reveal that the excellent tribological endurance of alkylimidazolium dialkyl phosphates ILs is mainly attributed to the high load-carrying capacity of the ILs and the formation of surface protective films consisting of TiO2, SiOx, titanium phosphate, amines, and nitrogen oxides by the tribochemical reactions.

Tribological performance of silahydrocarbons used as steel-steel lubricants under vacuum and atmospheric pressure

The silahydrocarbons of tetraalkylsilanes with different substituted alkyl groups (named as SiCH) were synthesized and evaluated as lubricants for steel-steel contacts by a home-made vacuum four-ball tribometer (VFBT-4000) under atmospheric pressure and under vacuum pressure (5 × 10-4 Pa). The SiCH oils possess better thermal stability, low temperature fluidity, and lower saturated vapor pressure than those of multialkylatedcyclopentanes (MACs). The tribological performances of the SiCH oils are also superior to those of MACs and PFPE-Z25 in terms of friction-reduction ability and antiwear capacity under sliding friction at vacuum. The SEM/EDS and XPS results reveal that the boundary lubricating film consisting of (-O-Si-R-)n compounds is formed by tribochemical reactions and serious adhesion wear under atmospheric pressure and the film consisting of (-Si-R-Si-)n compounds is formed on the worn surface under vacuum pressure.

Improved Tribological Performance of Amorphous Carbon (a-C) Coating by ZrO2 Nanoparticles

Nanomaterials, such as Graphene, h-BN nanoparticles and MoS2 nanotubes, have shown their ability in improving the tribological performance of amorphous carbon (a-C) coatings. In the current study, the effectiveness of ZrO2 nanoparticles (ZrO2-NPs) in lubricating the self-mated nonhydrogenated a-C contacts was investigated in boundary lubrication regime. The results showed that 13% less friction and 50% less wear compared to the base oil were achieved by employing ZrO2-NPs in the base oil in self-mated a-C contacts. Via analyzing the ZrO2-NPs and the worn a-C surface after tests, it was found that the improved lubrication by ZrO2-NPs was based on “polishing effects”, which is a new phenomenon observed between a-C and nanoparticles. Under the “polishing effect”, micro-plateaus with extremely smooth surface and uniform height were produced on the analyzed a-C surface. The resulting topography of the a-C coating is suitable for ZrO2-NPs to act as nano-bearings between rubbing surfaces. Especially, the ZrO2-NPs exhibited excellent mechanical and chemical stability, even under the severe service condition, suggesting that the combination of nonhydrogenated a-C coating with ZrO2-NPs is an effective, long lasting and environment-friendly lubrication solution.

The extreme pressure and lubricating behaviors of potassium borate nanoparticles as additive in PAO

ABSTRACT The potassium borate nanoparticles (nPB) as lubricant additive were prepared with an eco-friendly method. The tribological properties of nPB and ZDDP as lubricant additives in polyalphaolefin (PAO) were systematically evaluated using a four-ball tribometer and a SRV fretting friction and wear tester, which suggested that nPB exhibited excellent extreme pressure capacity, and better anti-wear and friction-reducing properties than ZDDP. Results of surface analyses show that the good lubricating properties and excellent load-carrying capacity of nPB in PAO are ascribed to the boundary protecting films, which were composed of some easy-shearing compounds: B2O3, FexBy and Fe2O3.