Tribological properties and insulation effect of nanometer TiO2 and nanometer SiO2 as additives in grease

•Synthesize two insulating greases which can be used in electrical equipment.•Nanometer SiO2 and TiO2 can greatly increase the grease volume resistivity.•Nanometer TiO2 possess good tribological properties.•Nanometer SiO2 possess good friction-reducing property.

New greases were synthesized using oleophilic nanometer-TiO2 and nanometer-SiO2 as additives. When the additives in naphthenic oil is 0.1 wt%, the alternating current (AC) breakdown strength is enhanced by 10.4% and 8.2% at power frequency, respectively. Also the grease volume resistivities are improved by 23% and 30% compared with base grease, which use naphthenic oil as base oil. The greases tribological behaviors were explored. Scanning electron microscope linked with energy dispersive X-ray spectroscope was utilized in order to analyze these scratches. The good tribological characteristics of nanometer-TiO2 greases and the good friction-reducing characteristic of nanometer-SiO2 greases are ascribed to the nanoparticles mechanical effect, and are also ascribed to the protect film generated by Ti and Si deposited or metallic oxide.