Improved performance of bio-lubricant by nanoparticles additives

• Main Author: Abere, Julius Oluwatayo
• Other Authors: Slatter, Tom ; Lewis, Roger
• Published: University of Sheffield 2017
• Subjects: 621.8
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.725025

Nanoparticle additives are proposed to improve lubricant performance under boundary lubrication sliding, through tribofilms formation. Tribofilms consisting of the elements of the nanoparticles (NPs) could form on the sliding surface providing necessary FM and reduction in wear volume loss. The key aim of this thesis is to establish a proof-of-concept for the Polyvit NPs lubricant additives a biolubricant – rapeseed oil. The improvement potentials may either complement or replace (partially or fully) some existing additives. Lubricants and their additives are being reviewed for better alternatives regarding toxicity, biodegradability and environmental issues. The Polyvit NPs consist of alumina (Al2O3), silica (SiO2) and graphite (C); although the TEM analysis shows silica only. The NPs were mixed at 0.1 wt. % with raw rapeseed oil and a fully formulated mineral oil - SAE15W-40. Initial tribotesting suggest possible combination of the NPs with the AW additive – zinc dialkyldithiophosphate (ZDDP). This was tested experimentally on both the Plint TE 77 ball-on-flat and the Bruker UMT tribometers. Both the HFRR and UMT tests are conducted in the boundary lubrication regime at RT and 100oC respectively. The fully flooded approach is adopted with a contact load of 40 N, while the starved lubrication approach is adopted for HFRR and UMT tests under a load of 5 N. Surface chemical analyses on the SEM/EDX show the presence of the elements of the NPs and ZDDP on sliding wear tracks. Thus, boundary lubrication tribofilm of the NPs form on the wear track. Also, the presence of ZDDP enhances formation of tribofilm of both the NPs and ZDDP on the sliding wear track at RT. Addition of the Polyvit NPs and ZDDP reduce wear at RT for the biolubricant. Also, the mineral oil lubricant can have friction and wear improvements through the addition of the NPs at low and high temperature boundary lubrication sliding.