石墨烯基水润滑添加剂研究进展

Research Progress of Graphene as Additives of Water-based Lubricants

随着工业的飞速发展和人们环保意识的日益增强,传统润滑油在避免环境污染等方面越来越难以满足人们的使用要求,而环境友好型润滑剂成为摩擦学研究的重要方向。水基润滑剂具有成本低、冷却性能优、可生物降解和安全性能好等优点,是一种典型的绿色环保型润滑剂,既可以满足生态环境保护的使用要求,又可以满足某些特殊环境的使用需求。但在实际应用中,需要引入纳米添加剂来解决水介质的运动黏度小、润滑性能有限和易腐蚀等问题。石墨烯基材料是一种具有优异力学性能的片层结构纳米材料,且片层之间的滑动属于超润滑滑动,作为水基润滑添加剂使用潜力巨大。然而,石墨烯是由类苯环为单元组合而成的稳定结构,片层之间存在强烈的π-π相互作用,在水基介质中很容易产生聚集沉淀。因此,近年来许多学者开始采用不同的方法对石墨烯基材料进行功能化修饰,逐渐发现修饰后的石墨烯基材料在水基溶液中具有较好的分散稳定性,并且保持石墨烯原有的力学和润滑性能,作为添加剂显著提升了水基介质的润滑性能。本文归纳了目前石墨烯面向水润滑潜在应用的常用改性方法:(1)利用氧化石墨烯等片层上的含氧基团作为“锚固点”与修饰分子发生化学反应的共价键功能化修饰;(2)利用修饰分子与石墨烯基材料之间的π-π相互作用、离子相互作用和氢键等作用力进行结合的非共价键功能化修饰;(3)对石墨烯基材料进行尺寸调控。修饰后得到的石墨烯基水润滑添加剂能够有效降低工件间的摩擦系数和磨损率,并提高水基润滑剂的缓蚀效率。但是,石墨烯基材料作为水基润滑添加剂使用,其在水中达到长期的分散稳定性还具有一定的挑战性。并且目前所采用的多为油基润滑剂的评价体系,缺少对其冷却性能和生物降解性的测试标准与方法,因此需要建立一套针对石墨烯基水润滑添加剂的完整、系统的评价体系。

With the rapid development of industry and people’s increasing emphasis on environmental protection,traditional lubricants can no longer meet people’s needs in terms of avoiding environmental pollution,therefore,the environmentally friendly lubricants become an important direction in tribological research.Water-based lubricant has been used as green and eco-friendly lubricant to meet the needs of certain special environments and protect ecological requirements due to the advantages of low cost,excellent cooling performance,biodegradability,and safety performance.However,the shortcomings of water-based lubricant such as low kinematic viscosity,limited lubricating properties and easy corrosion limit the development of water lubrication technology in practical applications,so it is necessary to introduce nano-additives to solve these problems.The graphene-based material is a sheet-structured nanomaterial with excellent mechanical properties,and the sliding between the sheets belongs to ultra-lubricated sliding,so it can be used as a water-based lubricating additive.However,graphene is a stable material composed of a benzene-like ring unit and there is a strongπ-πinteraction between the sheets,which easily causes aggregate precipitation in water.Therefore,in recent years,many researchers have used different methods to functionally modify graphene-based materials.It has been found that the modified graphene-based materials have better dispersion stability in water-based solutions and maintain the original mechanics of graphene.So it can be used as an additive to significantly improve the lubrication properties of water-based solutions.This paper summarizes the current methods of graphene modification for potential applications of water lubricating additives:(1)the covalently modification of graphene-based materials prepared by chemical reaction between the modified molecule and the oxygen-containing group of graphene oxide.(2)Functional modification of graphene-based materials obtained by non-covalent bonding ofπ-πinteraction,ionic interaction and hydrogen bonding between modified molecules and graphene-based materials.(3)The size control of graphene-based materials.The modified graphene-based water-lubricating additive can effectively reduce the friction coefficient and wear rate of workpieces,and improve the corrosion inhibition efficiency of water-based lubricants.However,the graphene-based materials are used as a water-based lubricant additive which achieve long-term dispersion stability in water also has some challenges.At present,the evaluation system of water-based lubricants mostly adopts the evaluation system of oil-based lubricants,and lacks the test standards and methods for cooling performance and biodegradability.Therefore,it is necessary to establish a complete and systematic evaluation system for graphene-based water lubricating additives.