Abstract
The tribological performance of Si3N4ball sliding against Ti3SiC2disc 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/Ti3SiC2contacts. [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/Ti3SiC2contacts lubricated by lithium-based ILs was mainly attributed to the formation of surface protective films composed of various tribochemical products.
Highlights
Titanium silicon carbide (Ti3SiC2) is the most studied material in the Mn+1AXn (n = 1 to 3) phase system, which combines the prominent properties of both metal and ceramic
Lithiumbased ionic liquids (ILs) from LiTFSI and oligoether compounds had better viscosity-temperature characteristics than those generated from LiTFSI and organic compounds bearing acylamino groups
The excellent tribological behavior of Si3N4/Ti3SiC2 contacts under the lubrication of lithiumbased ILs was attributed to the formation of a surface protective film composed of fluoride, sulfate, TiO, TiO2, SiO2, or/and Si3N4, which had an important function in reducing friction and wear of Si3N4/Ti3SiC2 contacts
Summary
Our group first reported the application of lithium-based ILs as lubricants in the field of tribology [26,27,28] These lubricants are synthesized by blending an appropriate molar ratio of lithium salts with organic compounds bearing acylamino groups (such as 2-oxazolidinone (OZO) and urea), synthetic esters (such as bis(2-ethylhexyl) adipate and pentaerythritol oleate), or oligoethers (such as triglyme (G3), tetraglyme (G4), and polyethylene glycol). This process significantly reduces the cost associated with IL preparation (the synthesis and purification of the most reported ILs are difficult and costly because of their complicated structures). The lubrication mechanism was demonstrated based on the data of scanning electron microscopy (SEM) and X-ray photoelectron spectrometry (XPS)
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