酯基功能化离子液体作为钢/钢摩擦副润滑剂的摩擦学性能研究

Tribological Properties of the Functionalized Ionic Liquids Containing Ester-group as Lubricants of Steel/Steel Contact

合成了含酯基官能团的咪唑类离子液体;研究了其物化性质及热稳定性;通过与非功能化的烷基咪唑离子液体对比,在SRV摩擦磨损试验机上研究了常温及高温条件下酯基功能化离子液体作为钢/钢摩擦副润滑剂的摩擦学性能;用SEM和XPS对磨斑表面进行了分析.结果表明:酯基功能化离子液体具有很高的热稳定性;酯基团的引入使得离子液体的黏度有所增加,导致其在较低载荷下的减摩性能降低,但引入的酯基官能团增强了离子液体对金属表面的化学吸附力,使其抗磨性能显著提高,在高载荷下离子液体分解所产生的活性元素氟与摩擦副表面的金属发生摩擦化学反应,生成以氟化亚铁和氧化铁为主体的边界润滑膜,从而降低了摩擦和磨损.同时发现含有TF2N-阴离子的功能化离子液体较含有BF4-阴离子的功能化离子液体具有更好的抗磨性能;含有较长N-烷基链的功能化离子液体的抗磨减摩性能较好.

A series of functionalized imidazolium ionic hquids （ILs） containing ester - group are synthesized and their physicochemical properties and thermal stabilities are studied. The tribological properties of the synthesized ionic liquids as lubricants for a steel - on - steel system are evaluated on an SRV friction and wear tester at room temperature and 100 ~C and compared with nonfunctionalized IL. The worn surfaces are analyzed by using SEM and XPS. It is found that all the functionalized ILs synthesized have high thermal stability. The introduction of ester - group increases the viscosities of ILs, which leads to worse friction - reducing ability at low loads, but it also increases the chemical adsorption of ILs, resulting in a significant increase in the anti - wear abihty of the ILs. At high loads, tribochemical reactions take place between the active elements, such as fluorine which is released from the ILs, and fresh metal surfaces of rubbing pairs to form the admixture reaction films. The films are mainly composed of ferric fluoride mixed with ferric oxide, leading to low friction coefficient and good wear resistance. In addition, it is found that the functionalized ILs bearing Tf2N anions have better anti - wear ability than the ones bearing BF4 anions, and the ILs containing longer alkyl chains show better friction reducing and anti -wear abilities than the ones containing shorter alkyl chains.