Lithium-based ionic liquids functionalized by sym-triazine and cyclotriphosphazene as high temperature lubricants

Two kinds of lithium-based and sym-triazine- or cyclotriphosphazene- functionalized ionic liquids (ILs, L-C3N3 and L-P3N3) were synthesized by simply blending an appropriate molar ratio of lithium bis(trifluoromethylsulfonyl) imide (LiTFSI) with tri(methoxyethoxyethoxyethoxy)triazine (C₃N ₃(OR)₃) or hexa(methoxyethoxyethoxyethoxy) cyclotriphosphazene (P₃N₃(OR)₆). The ILs were evaluated as high temperature lubricants for Si₃N₄/steel contact and found to have significantly improved friction-reducing and anti-wear proprieties compared with conventional alkylimidazolium ILs, 1-ethyl-3-methylimidazolium bis(trifluoro methylsulfonyl)imide (L-F102) and 1-butyl-3-methylimidazolium bis(trifluoromethyl sulfonyl)imide (L-F104), at some condition. The morphologies of the worn surfaces were analyzed by scanning electron microscope (SEM). The wear mechanisms were discussed according to the surface composition analysis by X-ray photoelectron spectroscopy (XPS).