碳酸钙纳米颗粒复合超分子凝胶润滑剂的摩擦学性能研究

Tribological Properties of a Composite Lubricant CaCO_(3)-Supramolecular

采用碳酸钙纳米颗粒与全氟聚醚型超分子凝胶复合得到了一种新型的纳米颗粒复合超分子凝胶润滑剂.超分子凝胶具有错综复杂的网络结构,有效地提高了碳酸钙纳米颗粒在全氟聚醚润滑油中的分散稳定性.此外,碳酸钙纳米颗粒作为添加剂极大地提高了超分子凝胶的润滑性能,使其表现出较好的耐高温性能,以及较高的承载力.采用差式扫描量热仪、热重分析仪和流变分析仪对该复合润滑剂的热力学性能进行表征,结果显示该复合润滑剂具有很好的热稳定性以及较好的力学性能.最后,通过X射线光电子能谱(XPS)对其摩擦机理进行表征,结果表明碳酸钙纳米颗粒复合超分子凝胶润滑剂优异的摩擦学性能可归因于碳酸钙纳米颗粒在摩擦副表面形成了易剪切的薄膜,以及小尺寸的纳米粒子在摩擦过程中对摩擦表面进行的自修复效应.

A new breed of lubricant using CaCO_(3)nanoparticles as an additive for PFPE-supramolecular gels(CaCO_(3)-supramolecular composite)was fabricated successfully.It aimed to solve the problems that nanoparticles with excellent anti-wear and anti-friction performance as additives were insoluble into PFPE oils,which limited the application of nanoparticles in the field of aerospace lubricant.Many researchers have found that gelators self-assembled in the liquid(water,organic solvent,oils)to form complicated 3-D networks that have spatial confinement effect for nanoparticles,which could increase the dispersion stability of CaCO_(3)nanoparticles in PFPE oil.Nature precipitation was used to explore the dispersion stability of CaCO_(3)nanoparticles with a diameter of 100 nm as a lubricant additive in PFPEsupramolecular gels.The results showed that the network of PFPE-supramolecular gels had good spatial confinement effect for CaCO_(3)nanoparticles and it would not self-aggregate even after 3 months.In addition,the thermostability and mechanical strength of PFPE-supramolecular gels were improved due to the excellent thermal and mechanical stability of nanoparticles.The thermostability was evaluated by differential scanning calorimetry(DSC)and(thermal gravimetric analyzer)TG.The results showed that the sol-gel transition temperature of CaCO_(3)-supramolecular composite and PFPEsupramolecular gels were about 123℃,which indicated the CaCO_(3)nanoparticles had no effect on the gelation property of PFPE-supramolecular gels.However,the TG results showed that the thermal decomposition temperature of CaCO_(3)-supramolecular composite(269℃)was higher than PFPE-supramolecular gels(260℃)due to the participation of CaCO_(3)nanoparticles.The rheological property of CaCO_(3)-supramolecular composite was expressed by rheometer,which showed high shear strength,shear thinning and good creep-recovery properties.The shear strength of CaCO_(3)-supramolecular composite(180 Pa)was much higher than PFPE-supramolecular gels(56 Pa),which was attributed to the high strength of CaCO_(3)nanoparticles.Usually,nanoparticles as lubricant additives significantly improve the tribological property.The fretting friction testing machine(SRV-IV)was used to appraise the tribological properties of CaCO_(3)-supramolecular composite and PFPE-supramolecular gels,which showed that the CaCO_(3)nanoparticles as lubricant additives composite had higher extreme pressure,lower friction efficient and volume of wear scar under a temperature of 120℃ and a load of 500 N.The extreme pressure of CaCO_(3)-supramolecular composite was increased by 550 N compared to PFPE-supramolecular gels.The friction coefficient and volume of wear scar were reduced by 36.90% and 87.36% under a load of 500 N at room temperature with 5.0%(mass fraction)CaCO_(3)nanoparticles as additives in PFPE-supramolecular gels.Finally,the lubricating mechanism of CaCO_(3)-supramolecular composite was characterized by X-ray photoelectron spectrometer.The results showed that the excellent tribological properties of CaCO_(3)-supramolecular composite were attributed to the shear-film on the worn surface and the self-repairing performance of CaCO_(3)nanoparticles.Some of the gelators adsorbed on the worn surface produced lubricant film to avoid its direct contact and reduce wear.And the spherical CaCO_(3)nanoparticles as bearings during the sliding process improved the anti-friction and anti-wear properties of CaCO_(3)-supramolecular composite.