ISSN   1004-0595

CN  62-1224/O4

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环境友好型氨基酸基离子液体作为水润滑添加剂的摩擦学机制研究

Tribological Mechanism of Environment-Friendly Amino Acid-Based Ionic Liquids as Water Lubrication Additives

  • 摘要: 本文中以美国食品药品监督管理局(Food and Drug Administration, FDA)批准的食品添加剂月桂酰肌氨酸钠和氨基酸为原料,采用简单的质子交换反应合成了2种氨基酸基离子液体Lys-LS和Arg-LS,并将其用作水基润滑添加剂. 利用SRV-V微动摩擦磨损试验机和全自动真彩共聚焦显微镜考察了2种离子液体添加剂的摩擦学性能,并采用扫描电镜(SEM)、石英晶体微天平(QCM)和X射线光电子能谱仪(XPS)深入探究了其润滑机理. 研究结果表明:2种氨基酸基离子液体添加剂具有良好的热稳定性且可以显著抑制铸铁在水中的腐蚀. 与去离子水相比,当Lys-LS和Arg-LS的添加质量分数为0.5%时,水基润滑液的摩擦系数和磨损体积分别降低了约70%和85%,具有显著的减摩抗磨效果. 机理分析结果表明,离子液体在界面处形成的摩擦化学反应膜与物理/化学吸附膜协同作用,有效地阻止了滑动摩擦副之间的直接接触,进而赋予水基润滑液优异的摩擦学性能. 2种润滑添加剂制备简单,安全无毒且绿色环保,有望作为水基金属加工液和难燃液压液的关键润滑添加剂使用.

     

    Abstract: The utilization of water-based lubricants in certain applied fields, as an alternative to oil-based lubricants that are prone to causing environmental pollution, represents one of the effective strategies for achieving green tribology. To tackle the issues of subpar lubrication properties and susceptibility to corrosion of friction interface for water-based lubrication, two amino acids-based ionic liquids, Lys-LS and Arg-LS, were synthesized in this manuscript by a simple proton exchange reaction using L-lysine or L-arginine and Lauroyl sarcosine, and were utilized as water-based lubricant additives. The thermal decomposition 5% temperatures of Lys-LS and Arg-LS reached 219.8 ℃ and 217.5 ℃, respectively, exhibiting exceptional thermal stability. The corrosion resistance properties of Lys-LS and Arg-LS aqueous solutions against first-grade gray cast iron sheets were assessed in accordance with the methodologies outlined in the national standard GB 6144-2010. Both the corrosion area and the number of corrosion stains were significantly reduced compared to deionized water when the two amino acids-based ionic liquids were incorporated at a mass fraction of ≥ 0.5%. The tribological properties of Lys-LS and Arg-LS additives were investigated using an SRV-V fretting friction and wear tester and automatic true-color confocal microscope. Compared with deionized water, the friction coefficient and wear volume of the water-based lubricants were reduced by about 70% and 85%, respectively, when Lys-LS and Arg-LS were supplemented at a concentration of 0.5%, providing a significant friction reduction and anti-wear performance. The micro-morphological analysis results of the wear spot surface revealed that the wear surface was smoother after lubricated by the aqueous solution containing ionic liquids additives, and at the same time, the adhesive wear and corrosive wear were effectively suppressed. The lubrication mechanisms of two ionic liquids additives were investigated in depth using the quartz crystal microbalance (QCM) and the X-ray photoelectron spectroscopy (XPS). The QCM tests indicated that the two amino acid-based ionic liquids could be effectively adsorbed onto the rubbing interface during the friction process to form a stable adsorption films. The XPS analysis results revealed that the tribochemical reaction occurred between the two additives and the surface of the friction pair, and a tribological protective films enriched with C, Fe, O and N elements were generated. The tribochemical reaction films and physical/chemical adsorption films formed by the ionic liquids at the interface worked synergistically to effectively prevent direct contact between the sliding pairs, endowing the water-based lubricant with excellent tribological properties. The two amino acids-based ionic liquids additives were characterized by simple preparation, non-toxicity and greenness, and were promising to be employed as critical additives for metalworking fluids and flame-retardant hydraulic fluids.

     

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