离子液体基氧化石墨烯胶体分散稳定性研究

Dispersion Stability of Ionic Liquid-based Graphene Oxide

目的研究氧化石墨烯在离子液体中的分散稳定性及其影响因素,并验证其摩擦学性能。方法采用扩展的DLVO理论,分析计算了表面活性剂与离子液体烷基侧链长度对氧化石墨烯胶体稳定性的影响,并结合实验对理论分析结果进行评估与验证,同时采用摩擦磨损试验机对稳定的氧化石墨烯胶体的润滑性能进行测试。结果未经修饰的氧化石墨烯分散于离子液体中,总势能曲线始终为负值,颗粒间表现为吸引力,极不稳定。而对于经表面修饰的氧化石墨烯胶体而言,颗粒间的相互作用势能与表面活性剂和离子液体烷基侧链长度呈正相关。当选用的表面活性剂烷基侧链长度为9、离子液体侧链长度为6时,对应的势垒值最高,可达500kT,从而有望实现胶体的稳定分散。后续静置实验及紫外可见吸收光谱分析结果与理论分析结论保持一致。摩擦实验表明,相比于纯离子液体,稳定分散有氧化石墨烯的离子液体的润滑性能显著提升。结论采用扩展的DLVO理论可对氧化石墨烯在离子液体中的分散稳定性进行理论预判,氧化石墨烯颗粒表面吸附的活性剂及离子液体烷基侧链越长,氧化石墨烯胶体越稳定。

The work aims to investigate the dispersion stability of graphene oxide in ionic liquid and the influence factors and to verify the tribological properties. The modified DLVO theory was used to analyze the influence of the length of the alkyl side chain of the surfactant and the base carrier on the stability of the graphene oxide colloid. The results of theoretical analysis were assessed and verified according to experiments. The lubrication property of stable graphene oxide colloid was evaluated by reciprocating friction tester. The bare graphene oxide was unstable in ionic liquid since its potential curve always remained negative and the particles showed attractive force among each other. For the graphene oxide colloid system with modified surface, the interaction potential energies among particles were positively correlated with the chain length of the surfactant and base carrier. As the length of the alkyl side chain of the surfactant and the ionic liquid reached 9 and 6 respectively, the colloid showed the highest potential barrier value of 500 kT, thus realizing the stable dispersion. The results of the subsequent static experiment and UV-Vis absorption spectrum analysis were consistent with the theoretical analysis conclusion. The friction test showed that compared with pure ionic liquid, the stable ionic liquid-based graphene oxide presented better lubrication performance. The stability of ionic liquid-based graphene oxide colloidal system can be approximately predicted by the modified DLVO theory. The longer the alkyl side chain length of surfactant and ionic liquid is, the more stable the ionic liquid-based graphene oxide colloid will be.