Effect of ZrO2 nanoparticles on thermophysical and rheological properties of three synthetic oils

Performance and Antiwear Mechanism of 1D and 2D Nanoparticles as Additives in a Polyalphaolefin

This work is focused on the thermophysical and tribological study of eight nanolubricant compositions based on a polyalphaolefin (PAO 20) and two different nanoadditives: multi-walled carbon nanotubes (MWCNTs) and hexagonal boron nitride (h-BN). Regarding the thermophysical properties, density and dynamic viscosity of the base oil and the nanolubricants were measured in the range of 278.15-373.15 K, as well as their viscosity index, with the aim of evaluating the variation of these properties with the addition of the nanoadditives. On the other hand, their lubricant properties, such as contact angle, coefficient of friction, and wear surface, were determined to analyze the influence of the nanoadditives on the tribological performance of the base oil. The results showed that MWCNTs and h-BN nanoadditives improved the wear area by 29% and 37%, respectively, at a 0.05 wt% concentration. The density and dynamic viscosity increased compared with the base oil as the nanoadditive concentration increased. The addition of MWCNTs and h-BN nanoparticles enhanced the tribological properties of PAO 20 base oil.

Investigation of the Applicability of Y2O3–ZrO2 Spherical Nanoparticles as Tribological Lubricant Additives

Long-term environmental goals will motivate the automotive industry, component suppliers, and lubricating oil developers to reduce the friction of their tribosystems to improve overall efficiency and wear for increased component lifetime. Nanoscale ceramic particles have been shown to form a protective layer on components’ surface that reduces wear rate with its high hardness and chemical resistance. One such ceramic is yttria (Y2O3), which has an excellent anti-wear effect, but due to its rarity it would be extremely expensive to produce engine lubricant made from it. Therefore, part of the yttria is replaced by zirconia (ZrO2) with similar physical properties. The study presents the result of the experimental tribological investigation of nanosized yttria–zirconia ceramic mixture as an engine lubricant additive. Yttria-stabilized zirconia (YSZ) nanoparticle was used as the basis for the ratio of the ceramic mixture, so that the weight ratio of yttria–zirconia in the resulting mixture was determined to be 11:69. After the evaluation of the ball-on-disc tribological measurements, it can be stated that the optimal concentration was 0.4 wt%, which reduced the wear diameter by 30% and the wear volume by 90% at the same coefficient of friction. High-resolution SEM analysis showed a significant amount of zirconia on the surface, but no yttria was found.

Comparison between thermophysical and tribological properties of two engine lubricant additives: electrochemically exfoliated graphene and molybdenum disulfide nanoplatelets

Recently graphene and other 2D materials were suggested as nano additives to enhance the performance of nanolubricants and reducing friction and wear-related failures in moving mechanical parts. Nevertheless, to our knowledge there are no previous studies on electrochemical exfoliated nanomaterials as lubricant additives. In this work, engine oil-based nanolubricants were developed via two-steps method using two different 2D nanomaterials: a carbon-based nano additive, graphene nanoplatelets (GNP) and a sulphide nanomaterial, molybdenum disulfide (MoS₂) nanoplatelets (MSNP). The influence of these nano additives on the thermophysical properties of the nanolubricants, such as viscosity index, density and wettability, was investigated. The unique features of the electrochemical exfoliated GNP and MSNP allow the formulation of nanolubricant with unusual thermophysical properties. Both the viscosity and density of the nanolubricants decreased by increasing the nanoplatelets loading. The effect of the nano additives loading and temperature on the tribological properties of nanolubricants was investigated using two different test configurations: reciprocating ball-on-plate and rotational ball-on-three-pins. The tribological specimens were analysed by scanning electron microscopy (SEM) and 3D profiler in order to evaluate the wear. The results showed significant improvement in the antifriction and anti-wear properties, for the 2D-materials-based nanolubricants as compared with the engine oil, using different contact conditions. For the reciprocal friction tests, maximum friction and worn area reductions of 20% and 22% were achieved for the concentrations of 0.10 wt% and 0.20 wt% GNP, respectively. Besides, the best anti-wear performance was found for the nanolubricant containing 0.05 wt% MSNP in rotational configuration test, with reductions of 42% and 60% in the scar width and depth, respectively, with respect to the engine oil.

Tribological Behavior of Nanolubricants Based on Coated Magnetic Nanoparticles and Trimethylolpropane Trioleate Base Oil

The main task of this work is to study the tribological performance of nanolubricants formed by trimethylolpropane trioleate (TMPTO) base oil with magnetic nanoparticles coated with oleic acid: Fe₃O₄ of two sizes 6.3 nm and 10 nm, and Nd alloy compound of 19 nm. Coated nanoparticles (NPs) were synthesized via chemical co-precipitation or thermal decomposition by adsorption with oleic acid in the same step. Three nanodispersions of TMPTO of 0.015 wt% of each NP were prepared, which were stable for at least 11 months. Two different types of tribological tests were carried out: pure sliding conditions and rolling conditions (5% slide to roll ratio). With the aim of analyzing the wear by means of the wear scar diameter (WSD), the wear track depth and the volume of the wear track produced after the first type of the tribological tests, a 3D optical profiler was used. The best tribological performance was found for the Nd alloy compound nanodispersion, with reductions of 29% and 67% in friction and WSD, respectively, in comparison with TMPTO. On the other hand, rolling conditions tests were utilized to study friction and film thickness of nanolubricants, determining that Fe₃O₄ (6.3 nm) nanolubricant reduces friction in comparison to TMPTO.

Experimental comparison between ZnO and MoS2 nanoparticles as additives on performance of diesel oil-based nano lubricant

This study compares the tribological and thermophysical features of the lubricating oil using MoS₂ and ZnO nano-additives. The average size of MoS₂ and ZnO nanoparticles were 90 nm and 30 nm, respectively. The nanoparticles were suspended using Triton X-100 in three different concentrations (0.1, 0.4 and 0.7 wt.%) in a commercial diesel oil. Tribological properties such as mass loss of the pins, friction coefficient, and worn surface morphologies and thermophysical properties such as viscosity, viscosity index, flash point and pour point of resulting nano lubricant were evaluated and compared with those of pure diesel oil. The tribological behavior of nano lubricants was evaluated using a pin-on-disc tribometer. The worn surface morphologies were observed by scanning electron microscopy. The overall results of this experiment reveal that the addition of nano-MoS₂ reduces the mass loss values of the pins in 93% due to the nano-MoS₂ lubricant effect. With 0.7 wt.% in nanoparticles content, the viscosity of MoS₂ and ZnO nano lubricants at 100 °C increased by about 9.58% and 10.14%, respectively. Pure oil containing 0.7 wt.% of each nanoparticle increased the flash point because of its small size and surface modifying behavior compared to the pure oil. Moreover, the addition of ZnO nanoparticles with pure oil lubricant is more suitable than MoS₂ nanoparticles for improving the thermophysical properties of pure oil.