A Novel Sweating-Lubricating Epoxy Composite Coating Filled with Ionic Liquid-Incorporated Hollow Silica Microspheres

Abstract

Ionic liquids (ILs) are promising high-performance lubricants with remarkable lubrication and antiwear capabilities in tribology. In this article, first solid-state (at room temperature) IL-incorporated SiO2 hollow microspheres (IL-SiO2) were synthesized at high temperature, and then a novel epoxy (EP) composite coating filled with IL-SiO2 hollow microspheres (IL-SiO2/EP) was successfully fabricated. The effects of IL- SiO2 on the mechanical and tribological properties of the IL-SiO2/EP coating were investigated. It was found the IL-SiO2/EP coating possessed low friction and high wear resistance. When the IL ratio in the silica hollow microspheres was 58%, the flexural strength and hardness of the IL-SiO2/EP coating surpassed those of the SiO2/EP coating and pure EP coating. When the IL-SiO2 content was 15 wt% in the composite, the friction coefficient and wear rate of the IL-SiO2/EP coating were both minimized and were 46.2 and 81.6% lower than those of the SiO2/EP coating, respectively. It was indicated that the addition of ILs overcame the heat and electron accumulation of SiO2/EP coating in the friction process. The solid-state ILs were melted by friction heat and load into the lubricating liquid and released from the hollow silica microspheres to the worn surfaces, which was similar to sweating by the human body. In addition, the liquid-state ILs combined with the debris of EP through chemical bonding to form an internal continuous and steady lubricating protective film, which could directly protect the worn surfaces from abrasion. This IL-SiO2/EP composite coating can be used to design and fabricate new sweating-lubricating functional coatings.