N/P无卤素离子液体润滑剂的链长与摩擦学性能的关系

合成了不同链长的N/P无卤素离子液体(NPILs：缩写为NP-11114，NP-11116，NP-11118)润滑剂，以聚α-烯烃(PAO 10)和卤素离子液体1-辛基3-甲基咪唑六氟磷酸盐(L-P 108)作为参照样，评价NPILs、PAO 10及L-P 108之间黏温性能、热稳定性以及室温和高温条件下的钢/钢摩擦副润滑剂的性能差异，探索了NPILs阳离子链长变化对其物理化学性质和摩擦学性能的影响规律. 结果表明：NPILs的黏度高于PAO 10和L-P 108，热分解温度低于PAO 10和L-P 108，NPILs黏度和热分解温度随着链长的增加而增加. 作为钢/钢摩擦副的润滑剂时，NPILs室温状态下减摩性能不及L-P108，但是NP-11118的抗磨性能优于L-P108；高温状态下，NPILs的减摩抗磨性能均优于L-P 108. 在常温和高温下NPILs相比PAO 10均具有优异的减摩抗磨性能，而且摩擦学性能随着烷基链长的增加而提高. 通过对磨斑表面进行扫描电镜分析证明这类离子液体具有优异的抗磨性能，通过EDS和XPS对磨斑表面的元素进行分析结果表明这类离子液体优异的摩擦学性能归因于离子液体结构中包含的N、P元素与金属基底发生摩擦化学反应所形成的具有优异减摩抗磨特性的摩擦化学反应膜.

A series of N/P-containing halogen-free ionic liquids (NPILs, abbreviated as NP-11114, NP-11116, NP-11118) lubricants with different alkyl chain lengths were synthesized. Polyalphaolefin (PAO 10) and the halogen-containing ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate (L-P 108) were used as control samples. The viscosity-temperature properties, thermal stability, and lubrication performance differences of NPILs, PAO 10 and L-P 108 as steel-on-steel friction pair lubricants under room and high temperature conditions were evaluated, and the influence of the change in cationic alkyl chain length of NPILs on their physicochemical properties and tribological performance was investigated. The results show that: the viscosity of NPILs is higher than that of PAO 10 and L-P 108, while their thermal decomposition temperature is lower than that of PAO 10 and L-P 108; the viscosity and thermal decomposition temperature of NPILs increase with the elongation of the alkyl chain. When used as lubricants for steel-on-steel friction pairs, the friction reduction performance of NPILs at room temperature is inferior to that of L-P 108, but the wear resistance of NP-11118 is better than that of L-P 108; under high temperature conditions, both the friction reduction and wear resistance performance of NPILs are superior to those of L-P 108. Both at room and high temperatures, NPILs exhibit excellent friction reduction and wear resistance performance compared to PAO 10, and their tribological performance improves with the elongation of the alkyl chain. Scanning electron microscopy (SEM) analysis of the wear scar surface confirms the excellent wear resistance of these ionic liquids; elemental analysis of the wear scar surface via Energy Dispersive X-ray Spectroscopy (EDS) and X-ray Photoelectron Spectroscopy (XPS) indicates that the excellent tribological performance of these ionic liquids is attributed to the tribochemical reaction film with excellent friction reduction and wear resistance characteristics formed by the tribochemical reaction between the N and P elements in the ionic liquid structure and the metal substrate.