Investigation of the Interaction, Rheological and Tribological Properties of Bis(pinacolato)diboron with Lithium Grease

In this article, Lewis acid–base complex of lithium 12-hydroxystearate (LHS) with diboron compound is formed by the introduction of bis(pinacolato)diboron (B2Pin2) into lithium grease. The interaction between Lewis acid B2Pin2 and Lewis base RCO2− of LHS is characterized by various techniques. Moreover, the rheological and tribological behaviors of the base grease are evaluated at low and moderate temperature. The results indicate that the addition of B2Pin2 can noticeably enhance the rheological property of the base grease because the formation of Lewis acid–base complex is beneficial for improving the soap fiber structure strength, and B2Pin2 could also help reduce the friction and wear of the grease during the sliding process, which likely owing to the boundary lubrication film generated by B2Pin2 adsorption on the rubbing surface and tribochemical reaction between borate esters and steel surfaces. The improvement of mechanical stability and tribological properties is beneficial to increasing the grease service life. Graphical Abstract

Antioxidant behavior and tribological performance of a novel multifunctional additive in complex lithium grease

Purpose This paper aims to contrastively investigate the antioxidant behavior and tribological performance of a novel multifunctional additive (PBT) and dialkyldithiophosphate (ZDDP) in complex lithium grease (CLG). Design/methodology/approach PBT was successfully synthesized through esterification reaction. The antioxidant behavior of PBT and ZDDP was investigated by thermal analysis, and meanwhile, their tribological performance was evaluated by Optimol SRV-IV oscillating reciprocating friction and wear tester (SRV-IV test) and MRS-1J four-ball tester (Four-ball test). Furthermore, their anticorrosion ability was determined by copper strip corrosion test. Findings Four-ball tests showed that the extreme pressure property of PBT was a little inferior to that of ZDDP. Besides, all the other results demonstrated that PBT showed more superior antioxidation stability, friction-reduction and antiwear ability, as well as anticorrosion performance than ZDDP. Originality/value This work provides a study of hindered phenol derivative as a multifunctional additive in lubricant grease, which can contribute to the development of substitution of ZDDP.

Synthesis, Tribological Properties and Mechanism of Nickel Nanoparticles as Additives in Lithium Grease

The advanced nano-additives can effectively improve the tribological properties of grease, which can greatly reduce friction consumption. Therefore, we prepared nickel nanoparticles by direct reduction method using Ni(HCOO)2 • 2H2O as the basic raw material. The morphology and structure of the nanoparticles were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), FT-IR spectrometer (FT-IR) and thermal gravimetric analysis (TGA). In order to investigate the lubrication performance of nickel nanoparticles in lithium grease, friction experiments were carried out on four-ball friction tester and TE77 ball-on-plate reciprocating model. Then, the worn surfaces were analyzed by scanning electron microscope and white light interferometry. Meanwhile, the element composition and valence state on friction surfaces were detected by energy dispersive spectrometer and X-ray photoelectron spectroscopy. Based on the experimental results, it was concluded that the nickel nanoparticles can effective improved the tribological properties by interlayer sliding. Moreover, the nickel nanoparticles could promote the formation of friction film on boundary lubrication surface and chemical reaction film between friction pairs. This study could provide a new direction for metal nano-additives to improve the tribological properties of grease.

Tribological study of TiO2 nanoparticles modified with stearic acid as additives in lithium grease

Purpose The purpose of this paper is to improve the properties of metal nanoparticles which are easy to agglomerate and hard to disperse evenly, thus limiting the application of metal nanoparticles in grease. A novel technology was proposed for modifying metal oxide to improve the dispersibility of nanoparticles. Design/methodology/approach SA-TiO2 nanoparticles were synthesized using an in-situ esterification method followed by surface modification with stearic acid. The microstructure of the nanoparticles was characterized by scanning electron microscope, transmission electron microscope and Fourier transform infrared spectroscopy and their thermal stability was evaluated by thermogravimetric analyzer. The tribological properties of the SA-TiO2 nanoparticles as additives in lithium grease were evaluated with a four-ball tester and TE77 reciprocating friction tester. The worn surfaces of the steel balls were investigated by EDS and XPS. Findings The prepared nanoparticles can be well dispersed in the lithium grease and possess much better tribological properties compared to traditional nanoparticles. The results indicated that the excellent tribological performance of SA-TiO2 was attributed to the chemical reaction film composing of Fe2O3, iron oxide and other organic compounds. Originality/value This paper provides a method to prevent the agglomeration of nano-TiO2 by surface modification with stearic acid. And the prepared nanoparticles can effectively improve the tribology performance of lithium grease.

Performance of silicon oil-based Magneto-Rheological fluids used for MR dampers: an experimental approach

Aim: The aim of this work was preparation of the model Magneto Rheological (MR) fluids to be used under the effect of an applied magnetic field operated under very low power requirement for the purpose of vibration reduction in automotive damper. Background: Magneto-Rheological fluids are non-Newtonian fluids, which consist of magnetic particles scattered in a base liquid – a matter that can change their characteristics when applying the magnetic field. From the previous researches, Magneto-Rheological fluids have different properties according to the preparation accuracy, ingredients, particle size and shape, type of carrier fluids and stabilizer. Also, the response of Magneto-Rheological fluids to the magnetic flux varied. Methods: : A specimen of MR fluid is prepared using four different dynamic viscosities base fluids: Silicone oil JETTA (50mpa.s, 100mpa.s, 150mpa.s and 200mpa.s) are mixed with high purity spherical shape particles of Carbonyl Iron (CI). ABRO liquid white lithium grease is added to the specimen, and its effect is determined. Results: The presence of additives has no effect on the magnetic behavior; but rather increases dynamic viscosity, especially in the presence of the external magnetic field, which is considered as a stabilizing factor. Conclusion: Adding the white lithium grease as a stabilizer delays the sedimentation of the prepared sample by 1023%. The lowest sample in sedimentation rate has the highest viscosity, which satisfies 2.7% in 24 hours, but it shows a negative effect on the magneto-rheological properties, which leads to unstable viscosity readings due to MR fluid agglutination. Working temperature is a critical parameter that can affect the behavior of MR fluid; the viscosity of MR fluid under the effect of magnetic field is inversely proportional to the working temperature. Sample DELTA is the most promising for the application in automotive dampers which are used to decrease vehicle vibration. :

Investigation of the Interaction, Rheological and Tribological Properties of Bis(pinacolato)diboron with Lithium Grease During Mechanical Aging

In this article, Lewis acid–base complex of lithium 12-hydroxystearate (LHS) with diboron compound is formed by the introduction of bis(pinacolato)diboron (B2Pin2) into lithium grease. The interaction between Lewis acid B2Pin2 and Lewis base RCO2− of LHS is characterized by various techniques. Moreover, the rheological and tribological behaviors of the base grease are evaluated at low and moderate temperature, and the results indicate that the addition of B2Pin2 noticeably enhanced the rheological, friction-reducing, and anti-wear (AW) properties of the base grease, which likely owing to the fact that the formation of Lewis acid–base complex is beneficial for improving the soap fiber structure strength, helping to prevent the mechanical degradation of the lithium grease during mechanical aging process.

Tribological Properties of Al2O3 Nanoparticles as Lithium Grease Additives

The tribological properties of Lithium grease specimens with different concentrations of Al2O3 nanoparticles were investigated using a pin on disc apparatus under different sliding speeds and normal loads. Results showed that Al2O3 nanoparticles enhanced the tribological properties of lithium grease and reduced the COF and wear scar width by approximately 57.9% and 47.5% respectively.