Leaves Based Lubricant Additive Towards Improving Tribological Properties

Three kinds of crop leaf-surface waxes were extracted from wheat,corn and broomcorn leaves,respectively.The crop leaf-surface waxes as lubricant additives were added to synthetic ester and the friction and wear properties of prepared lubricants for steel-aluminum and steel-copper friction pair were investigated in detail.The scanning electron microscopy(SEM)and secondary ion mass spectrometry(SIMS)were employed to explore the friction mechanisms.The results show that crop leaf-surface waxes could successfully reduce the friction and wear of steel-aluminum and steel-copper sliding friction pairs as compared with pure synthetic ester.For example,when the concentration of wheat leaf-surface wax as additive was 2%,the COFs was decreased by 58%;the four additives can be ranked by the anti-wear capability as follows:Corn>Wheat>Glycerol>Broomcorn to steel-aluminum sliding friction pairs.The SIMS spectra of positive and negative ions on the worn surfaces have reduced the exposure of Al and increased short chain ions counts.The good friction reduction and antiwear abilities are attributed to the adsorption or reaction films formed by leafsurface wax on worn surface.

Classification and spectrum optimization method of grease based on infrared spectrum

The infrared(IR)absorption spectral data of 63 kinds of lubricating greases containing six different types of thickeners were obtained using the IR spectroscopy.The Kohonen neural network algorithm was used to identify the type of the lubricating grease.The results show that this machine learning method can effectively eliminate the interference fringes in the IR spectrum,and complete the feature selection and dimensionality reduction of the high-dimensional spectral data.The 63 kinds of greases exhibit spatial clustering under certain IR spectrum recognition spectral bands,which are linked to characteristic peaks of lubricating greases and improve the recognition accuracy of these greases.The model achieved recognition accuracy of 100.00%,96.08%,94.87%,100.00%,and 87.50%for polyurea grease,calcium sulfonate composite grease,aluminum(Al)-based grease,bentonite grease,and lithium-based grease,respectively.Based on the different IR absorption spectrum bands produced by each kind of lubricating grease,the three-dimensional spatial distribution map of the lubricating grease drawn also verifies the accuracy of classification while recognizing the accuracy.This paper demonstrates fast recognition speed and high accuracy,proving that the Kohonen neural network algorithm has an efficient recognition ability for identifying the types of the lubricating grease.

Conductivity and tribological properties of IL-PANI/WS_(2) composite material in lithium complex grease

An ionic liquid-polyaniline/tungsten disulfide(IL-PANI/WS_(2))composite was synthesized in 1-butyl-3-methylimidazole tetrafluoroborate(LB104)aqueous solution by in-situ polymerization and characterized by Fourier transform infrared spectroscopy.A current-carrying friction and wear tester was used to study the tribological properties of steel-steel and copper-copper friction pairs lubricated by an IL-PANI/WS_(2) lithium complex grease(LCG).After the experiment,scanning electron microscope was used to observe the surface morphology of the wear scar on the steel and copper plates,and X-ray photoelectron spectrometer was used to analyze the elemental composition of the wear scar surface.The results show that compared with greases containing IL-PANI and WS_(2),greases containing IL-PANI/WS_(2) exhibit better antiwear performance when lubricating steel-steel friction pairs and better tribological performance and electrical conductivity when lubricating copper-copper friction pairs.Therefore,it can be concluded that WS_(2) and IL-PANI have a synergistic effect.

Tribological properties of conductive lubricating greases

Three kinds of new conductive lubricating greases were prepared using lithium ionic liquids as the base oil and the polytetrafluoroethylene(PTFE)as the thickener.These lithium ionic liquids([Li(PEG)X])were obtained by blending lithium salts(LiBF4,LiPF6 and LiNTf2)with poly(ethylene glycol)(PEG)because lithium salts have an extremely high solubility in PEG.The conductivities and contact resistances of the prepared lubricating greases were investigated using the DDSJ‐308A conductivity meter and the reciprocating ball‐on‐disk UMT‐2MT sliding tester.In addition,their tribological properties were investigated in detail.Scanning electron microscopy and X‐ray photoelectron spectroscopy were employed to explore the friction mechanisms.The results suggest that the prepared lubricating greases have high conductivities and excellent tribological properties.The high conductivities are attributed to ion diffusion or migration of the lithium ionic liquids with an external electric field,and the excellent tribological properties depend on the formation of boundary protective films.

Leaf-surface wax of desert plants as a potential lubricant additive

Using an MFT-R4000 tester at room temperature,the leaf-surface wax of two desert plants,Ammopiptanthus mongolicus(AM)and Reaumuria soongorica(RS),was extracted and evaluated for its potential as a lubricant additive in polyalphaolefin(PAO)for steel-steel contact.Gas chromatography-mass spectrometry analysis was performed to identify the composition of the AM leaf-surface wax,and scanning electron microscopy and X-ray photoelectron spectroscopy were used to investigate its friction mechanisms.The results suggest that the leaf-surface wax could successfully reduce the friction and wear of steel-steel sliding pairs compared with PAO containing molybdenum dithiocarbamate additives.AM,in particular,showed high-performance wear resistance and friction-reducing properties.Its excellent tribological properties were attributed to the wax composition of leaf-surface fatty acids,alcohol,and esters.

Conductive grease synthesized using nanometer ATO as an additive

A new conductive grease was synthesized using a nanometer powder,i.e.,Sb doped SnO2(ATO),as an additive.The typical properties of this new conductive grease were investigated in detail.The results indicate that ATO can dramatically improve the dropping point and reduce contact resistance.The tribological properties of the new conductive grease were investigated using the MFT-R4000 reciprocating friction and wear tester.The tribol-test results indicate that ATO can dramatically improve the tribological properties of the grease.When the ATO concentration is 0.1wt%,the grease demonstrates the best friction reduction properties;when the concentration is 0.5wt%,the grease demonstrates the best anti-wear properties.The worn surfaces were observed and analyzed by scanning electron microscopy and energy-dispersive X-ray spectroscopy,and the friction mechanisms for the new conductive grease are proposed.The excellent tribological properties of the new conductive grease are attributed to the mechanical effect of ATO,and the film formed by Sn and Sb elements or metallic oxide deposited on worn surfaces during the friction process.

A synergetic strategy based on laser surface texturing and lubricating grease for improving the tribological and electrical properties of Ag coating under current-carrying friction

Herein,a series of Ag coatings with different micro‐dimples were fabricated on copper surfaces by laser surface texturing(LST)and magnetron sputtering.Multilayer graphene lubricating grease(MGLG)was prepared using multilayer graphene as an additive.The textured Ag coatings and MGLG were characterized.Moreover,the tribological and electrical performances of the textured Ag coatings under MGLG lubrication were investigated in detail.Results demonstrated that the textured Ag coating with an appropriate dimple diameter could exhibit improved tribological and electrical properties when compared to the non‐textured Ag coating under MGLG lubrication.The characterization and analysis of the worn surfaces suggest that the synergetic effect of LST and MGLG contributes to these excellent tribological and electrical properties.

Tribological application and mechanism of epicuticular wax

The plant cuticle is a complex mixture of omnipresent, commonly monofunctional, fatty acid derivatives and taxon-specific, generally bifunctional, specialty compounds. This study explored expanded applications for these substances. Four types of plant cuticles were distilled from leaves and the resulting lipid mixtures were analyzed using gas chromatography-mass spectrometry. These were then used as additives for a synthetic ester lubricant. A reciprocating friction and wear testing machine was utilized to investigate the resulting tribological properties. The worn surfaces of the lower discs were observed and analyzed using optical microscopy and time-of-flight secondary ion mass spectrometry. The results reveal that cuticular waxes can modify the friction properties of the base oil. Furthermore, cuticular waxes demonstrate better performance when compared to the commercially available additive molybdenum dithiocarbamates. A protective adsorption film was identified as the reason for the improved friction reduction and anti-wear properties of the lubricant on the friction pair. This study provides a reference for the study of new types of non-sulfur, phosphorus, and other active element additives and demonstrates considerable potential for the economical utilization of plant leaf waxes.

Conductive and tribological properties of TiN-Ag composite coatings under grease lubrication

TiN-Ag composite coatings were prepared by pulsed bias arc ion plating.X-ray diffraction(XRD)and energy dispersive X-ray spectroscopy(EDS)were applied to analyze the compositions of the coatings.Tribological properties of the coatings were studied using an MFT-R4000 ball-on-disk friction tester in the presence of lubricating greases containing multilayer graphene.Scanning electron microscopy(SEM),Raman spectroscopy,and X-ray photoelectron spectroscopy(XPS)were used to analyze the worn surface compositions of the lubricating films.The results show that with the decrease in Ag in the film,hardness increased but electrical conductivity decreased.The coating with 10 at%Ag content shows the best friction-reducing and anti-wear properties,which can be attributed to the moderate content of Ag embedded in the TiN crystal gap that enhanced the grain bonding force to improve the anti-wear and self-lubricating ability.Graphene can be adsorbed on the coating as a solid lubricant.

Erratum to: Conductive grease synthesized using nanometer ATO as an additive

Erratum to Friction 3(1):56-64(2015)DOI 10.1007/s40544-015-0073-71.The original version of this article contained the incorrect expression on page 56,instead of“polyethylene oxide polypropylene oxide tinbutadiene styrene ether 50HB660(PAG)”.It should read“poly(ethylene glycol-ran-propylene glycol)monobutyl ether 50HB660(PAG)”as more accurate academic expression.

The rheological and tribological properties of calcium sulfonate complex greases

In this study,we synthesized two types of calcium sulfonate complex greases(barium soap and calcium soap)and investigated their physical,rheological,and tribological properties in detail.The test results showed that the evolution of their linear viscoelasticity functions with frequency were quite similar to those of traditional lubricating greases.Moreover,these two calcium sulfonate complex greases had good friction-reducing and antiwear properties at room temperature and at 150°C.In addition,by adding an organic molybdenum compound(MoDTC)to the base greases,we obtained a very low friction coefficient(0.065)for one of the greases(calcium soap)at 400 N and 500 N(maximum Hertzian pressures of 3.47 GPa and 3.74 GPa,respectively)at 150°C.X-ray photoelectron spectroscopy(XPS)analysis showed that the tribofilm was composed of some complex oxide species and CaCO3 that had formed on the worn surface.