Hierarchical hollow SiO2@TiO2 sphere structure for enhancing the lubrication and photo-catalytic degradation of liquid paraffin

With the rapid development of industry, the tribological properties of liquid paraffin (LP), a common lubricating oil, has not been able to satisfy the requirement of the engineer. And the post-processing of the LP after the friction also attracts the attention of people. Herein, based on the production requirements, a novel hierarchical structure of hollow SiO2@TiO2 sphere is designed and synthesized which is used to improve the tribological performance of LP and the photo-degradation properties of waste LP. It can be observed that the addition of SiO2@TiO2 can indeed reduce the friction coefficient, enhance the wear resistance of LP and effectively degrade the waste LP into harmless inorganics. Especially, with the incorporation of 1.5 wt% SiO2@TiO2, the friction coefficient and wear area of the LP system are reduced by 41.39% and 59.68%, respectively. Besides 51.10% of waste LP was degraded into CO2 and H2O within 80 min with the inclusion of 1.5 wt% SiO2@TiO2. The possible mechanisms of hollow SiO2@TiO2 sphere in heightening the frictional and photo-degradation performance were proposed. So, the designed SiO2@TiO2 plays different roles at different stages in the application of LP which is according with the pursuit of high performance and environmentally-friendly lubricating composites.