Dapeng Feng

Tribological performance of phosphate ionic liquids as lubricants for steel-on-aluminum contact

Anti-corrosion phosphate ionic liquids were synthesized and evaluated as lubricants for the contact of steel/aluminum by using an Optimol SRV oscillating friction and wear tester under ambient conditions. Phosphate ionic liquids yield commendable tribological performance and are superior to the conventional ionic liquid lubricant 1-methy-3-hexylimidazolium hexafluorophosphate in terms of friction-reducing performance and anti-wear capacity. Contrastive experiments demonstrate that the simple mixing of two compounds (butylamine and dibutylphosphate) does not yield a mixture lubricant with better tribological properties as compared to the ionic liquid synthesized using these two compounds. The worn surfaces of aluminum discs were analyzed by using JSM-5600LV scanning electron microscope and PHI-5702 multifunctional X-ray photoelectron spectrometer. The friction reducing and anti-wear mechanisms originate from the layered structures of ionic liquids under boundary lubrication conditions and from the tribochemical interactions of ionic liquids with the fresh surface of the substrates.

Tribological Performance and Mechanism of Phosphate Ionic Liquids as Additives in Three Base Oils for Steel-on-aluminum Contact

Butylammonium dibutylphosphate and tetrabutylammonium dibutylphosphate ionic liquids (ILs) were evaluated as antiwear additives for steel-on-aluminum contact in three different base oils, a polyalphaolefin, an ester oil and an IL 1-methy-3-hexylimidazolium hexafluorophosphate, respectively, with similar viscosity and different polarities. The friction experiments were carried out on an Optimal SRV-IV oscillating reciprocating friction and wear tester at room temperature. Results indicate phosphate ILs can effectively improve the tribological properties of the base oil, especially the antiwear property, as additives for steel/aluminum contacts. For the base oils PAO10 and PAO40 with different viscosities, the higher viscosity of PAO40 can be beneficial to reducing the friction coefficient. The worn surface morphologies and chemical compositions of wear scars were analyzed by a JSM-5600LV scanning electron microscope and PHI-5702 multifunctional X-ray photoelectron spectrometer (XPS). The XPS analysis results illustrate that the phosphate IL additives in the base oils with different polarities exhibit the same tribological mechanism. A synergy exists between the adsorbed layers and boundary-lubricating films generated from the tribochemical reaction of IL and the substrate surface, which may reduce the friction coefficient and wear volume of the friction pairs.

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.

Tribological properties of crown‐type phosphate ionic liquid as additive in poly(ethylene glycol) for steel/steel contacts

Purpose – The purpose of this paper is to design the crown‐type phosphate ionic liquid additive which can dissolve in poly(ethylene glycol) (shortened to PEG) completely, and evaluate the tribological properties as additive in PEG for steel/steel contacts.Design/methodology/approach – To improve the solubility and the tribological performance of ionic liquid additive in PEG, the crown‐type phosphate ionic liquid additive was prepared. The tribological properties of the crown‐type phosphate ionic liquid additive in PEG were evaluated at different concentrations and rubbing frequencies on an Optimol SRV oscillating friction and wear tester. The morphology and chemical compounds of the wear scars were analyzed by scanning electron microscope (SEM) and X‐ray photoelectron spectroscopy (XPS).Findings – The experimental results show that the crown‐type phosphate ionic liquid additive applied in based oil exhibits better tribological properties for steel/steel contacts at different loads, concentrations and rubb...

Tribological Behavior of Si3N4/Ti3SiC2 Contacts Lubricated by Lithium-Based Ionic Liquids

The tribological performance of Si3N4 ball sliding against Ti3SiC2 disc lubricated by lithium-based ionic liquids (ILs) was investigated using an Optimol SRV-IV oscillating reciprocating friction and wear tester at room temperature (RT) and elevated temperature (100°C). Glycerol and the conventional imidazolium-based IL 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (L-F106) were used as references under the same experimental conditions. The results show that the lithium-based ILs had higher thermal stabilities than glycerol and lower costs associated with IL preparation than L-F106. The tribotest results show that the lithium-based ILs were effective in reducing the friction and wear of Si3N4/Ti3SiC2 contacts. [Li(urea)]TFSI even produced better tribological properties than glycerol and L-F106 both at RT and 100°C. The SEM/EDS and XPS results reveal that the excellent tribological endurance of Si3N4/Ti3SiC2 contacts lubricated by lithium-based ILs was mainly attributed to the formation of surface protective films composed of various tribochemical products.

Influence of Competitive Adsorption on Lubricating Property of Phosphonate Ionic Liquid Additives in PEG

Three phosphonate ionic liquids (1-butyl-3-methylimidazolium O-butyl phosphonate, N,N-dibutylammonium O-butyl phosphonate and N,N-dibutylammonium O-ethyl phosphonate) are used as additives in PEG for steel/steel contact. Moreover, the tribological performances and lubrication mechanism were studied. Results show that these ionic liquids can improve the tribological performances of the base oil significantly. The main factor that influences the tribological performances of the phosphonate ionic liquids/PEG blends is the competitive adsorption between the base oils and the additives. In addition, chemical reactions between the ionic liquids and the metal substrate are responsible for the excellent tribological performances of the phosphonate ionic liquids/PEG blends.

INVESTIGATION OF SOME LIQUID LUBRICANTS FOR POTENTIAL AEROSPACE APPLICATION

Some liquid lubricants for potential aerospace application were prepared. The lubricity of lubricants including silicon oil with and without chlorobenzene group, cyclotriphosphazene derivative X-1P and perfluoropolyether (PFPE) for both steel/steel and steel/bronze sliding pairs were investigated. Gel percolation chromatography (GPC) was used to detect the tribo-polymerization of the tested silicone oil. Materials related to friction pairs is essential, silicon oil and PFPE are not quite effective for lubrication of a steel/steel pair, but be able to reduce both friction and wear of a steel/bronze pair. Chemical reactive elemental such as chlorine, which is substituted into silicon oil, is helpful to improve the antiwear and load-carrying capacity of liquid lubricant. X-1P is also an effective liquid lubricant for both steel/steel and steel/bronze sliding pairs.Copyright