چكيده انگليسي :
In this research, at first, the performance properties including viscosity, viscosity index, thermal conductivity, flash point, and pour point and tribological properties such as friction coefficient and wear of crambe seed oil (CSO) were investigated and compared with other biolubricants, i.e, Jojoba seed oil (JSO), linseed oil (LSO), and fossil base lubricant (FBL) to replace and synergize with commercial base lubricants. Then, to improve CSO performance, copper oxide nanoparticles with sizes of 20, 38, and 60 nm, plate, spherical, and tubular shape carbon nanoparticles were added to it and to a commercial engine oil, and the effect of size and shape of nanoparticles on their thermophysical and tribological properties were studied and compared. Finally, the stability of nanolubricants was, briefly, investigated. The results of performance properties of the lubricants used in this research showed that CSO, JSO, and LSO biolubricants with viscosity indices of 231, 243, and 262, respectively, had lower viscosity changes with temperature compared to FBL with a viscosity index of 98. In addition, the CSO, JSO, and LSO biolubricants viscosity at 30oC was 73, 77, and 82 % lower than FBO with a viscosity of 180 mPa.s, respectively.The results of tribological properties showed that the studied biolubricants at all conditions had a lower friction coefficient compared to of FBL. The results showed that the wear of biolubricants used compared to that of FBL was a function of tribological conditions. The results of the effect of the nanoparticles size and shape on the thermophysical properties showed that addition of the nanoparticles of all sizes and shapes increased the nanolubricants viscosity and thermal conductivity. At 30oC, the thermal conductivity of nanolubricants containing fullerene nanoparticles, single wall carbon nano tube (SWCNT), graphene oxide (GO), and multi wall carbon nano tube (MWCNT) with a concentration of 0.5 % wt and 60 nm copper oxide nanoparticles with a concentration of 1.2 % wt was 66, 50, 34, 14, and 6 % more than that of CSO, respectively. At 30oC, the viscosity of nanolubricants containing MWCNT, SWCNT, GO, and fullerene with a concentration of 0.5 % wt, and 60 nm copper oxide nanoparticles with a concentration of 1.2 % wt was 7560, 5650, 8, 4 and 9 % higher than that of pure lubricant, respectively. The results showed that, in general, addition of nanoparticles at optimal concentrations reduced the friction coefficient and wear. SWCNT with a concentration of 0.02 % wt, fullerene with a concentration of 0.02 % wt, 20 nm copper oxide with a concentration of 0.6 % wt , GO with a concentration of 0.5 % wt, and MWCNT with a concentration of 0.02 % wt reduced the CSO wear by 75, 72, 67, 52 and 27 %, respectively, and fullerene nanoparticles with a concentration of 0.02 % wt, SWCNT with a concentration of 0.02 % wt, and 20 nm copper oxide with a concentration of 0.6 % wt concentration reduced the commercial engine oil wear by 47, 34 and 15 %, respectively. Also, nanolubricants containing carbon nanoparticles are more stable than copper oxide nanoparticles.
Overall, the comparison of performance and tribological properties of the studied bio and fossil base lubricants showed that CSO among the biolubricants examined is the closest to FBL and is a good option for replacement and synergizing with FBLs.
