Nanoparticles have long been utilized as additives in engine oil because they significantly improve the tribological qualities of lubricants and contact surfaces. They can also enhance the anti-wear qualities of friction parts in mechanical systems and improve the performance properties because of their small size, which allows them to access even places with minor surface roughness.
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Nanoparticles have a high aspect ratio, which makes them excellent catalysts. The nanoparticles distribute throughout the fuel, promoting better air-fuel mixing and increasing physicochemical characteristics during ignition, improving performance, heat transfer, and exhaust quality. They are also required in lesser amounts since they're so small — fewer than 100 nm in diameter.
What is Tribology?
Tribology is the study of the behavior of interacting surfaces in relative motion, such as lubrication, wear, friction, and design variables. These factors need to be optimized to increase the performance and consistency of the tribological method. Wear, friction, and lubrication are the three main subjects of tribology.
Friction is the barrier to relative movement, wear is the mechanical loss caused by that movement, and lubrication is the application of a fluid (or, in certain situations, a solid) to reduce friction and wear.
Tribology is extremely significant in today's environment because mechanical components lose so much energy due to friction. We must reduce the quantity of energy squandered if we want to utilize less energy.
Utilization of Tribology in Engine Oil Analysis
It is widely employed in oil analysis these days because it meticulously evaluates the condition of the oil-based on small metal particles created by the interaction of two surfaces. Moreover, it also aids in detecting any impurity or contaminant in the lubricant, which has a significant impact on fuel economy and engine durability.
Tribological studies in engine oil analysis can identify the source of worn components (dampers, gearbox, clutch discs, and so on), track the amount of wear on the degrading internal components, and recommend when a repair is needed to avoid a failure in service.
Nanoparticles Used in Engine Oil/Fuel
Numerous researches on the usage of nanoparticles as additives in engine oil lubrication have taken palce in the previous two decades. The inclusion of nanoparticles in the engine oil can minimize abrasive wear.
Metals such as Copper, silver, and nickel, as well as metal oxides such as titanium dioxide, silicon dioxide, and zinc oxide, are employed s additives in engine oil.
Utilization of TiO2 Nanoparticles as Additives in Engine Oil
TiO2 is a nanoparticle that has received much attention as an additive since it demonstrated stable friction when added to lubricating oil. It generates a thin TiO2 tribo-protective coating on the damaged surfaces, lowering the coefficient of friction in the contact region and lowering the pressure and temperature.
It also has a larger load-bearing capacity. The average size of the TiO2 nanoparticles employed as an additive in engine oil in this study was 18-21 nm.
In addition to TiO2 nanoparticles, a Triton X surfactant can be added to the oil in varying quantities to provide stability and prevent the nanoparticles from agglomerating in the oil. The nanoparticles roll between the friction surfaces as they separate with the creation of tribo-film, reducing friction and wear. Additionally, the heat and pressure generated during the procedure allow the nanoparticles to compact after use, referred to as a surface mending and polishing effect.
Recent Researches in Evaluating the Effects of Nanoparticles on Engine Oil Tribology
Birleanu et al. (2022) emphasized the importance of using TiO2 as an additive in engine oil by presenting comprehensive results from SEM, EDS, coefficient of friction (COF), wear depth scar, and flash temperature parameter (FTP), demonstrating that it improves engine oil tribological performance in a variety of ways by affecting its wear, friction, thermal, chemical, and physical properties.
According to the research, TiO2 nanoparticles increased lubricant performance by increasing the flash temperature parameter's value (FTP). The addition of TiO2 wt% reduced the wear of the ball specimens used and the rubbing time, resulting in the lowest coefficient of friction for the 0.075 wt.%.
Furthermore, it serves as an anti-wear lubricant addition on the specimen's worn surface, and micrograph results show that it is considerably smoother, implying that less material was transferred.
All of these findings for TiO2 nanoparticles are far better than the lubricant oil without any addition of nanoparticles which strongly support its implementation in engineering applications to improve engine efficiency.
Another research on nanoparticles as oil additives by Ali et al. (2016) concluded that nanoparticles had a significant impact on the tribological properties of lubricating oil, with higher bearing capacity, lower mean surface roughness, lower coefficient of friction, and lower wear scar when compared to lubricating oil without nanoparticles. Furthermore, they determined that changing the size of nanoparticles has a substantial impact on the intended outcomes and must be tuned to get high-end results. Zin et al. (2015) have found that as the number of nanoparticles grew, so did the viscosity at higher temperatures.
The paper published by Birleanu et al. (2022) strongly agrees with the previous research as the results indicated that when several volume concentrations of TiO2 nanoparticles (0.01 percent, 0.025 percent, 0.050 percent, and 0.075 percent) were employed in the base lubricating oil for the examination, the sample with the greatest volume concentration of TiO2 nanoparticles showed to be the best among all. They discovered that as the nanoparticle concentration was increased, the coefficient of friction and wear of the ball decreased.
Arumugam et al. (2013) also discovered that when they used TiO2 nanoparticles with an average diameter of 50 nm and particle concentration of 5 weight percent, the coefficient of friction and wear scars decreased by approximately 15.2 percent and 11 percent, respectively.
Potential Applications of Nanoparticles in Engine Oil Tribology
The nanoparticles have vast applications in the field of engine oil tribology. However, it also acquires significant importance in the automotive, transportation, locomotive, and lubricant industry as well.
It can be applied to the most common engine and industrial machinery components such as gear, bearings, and brakes, which are in constant surface interaction resulting in wear and tear of the component.
In such conditions, the use of lubricant oil and the addition of nanoparticles gain significant importance as it acquires all the required properties for increasing the energy efficiency alongside components lifetime essential in such applications.
Importance of Investigating Engine Oil Tribology
It is essential to investigate engine oil tribology regularly because it provides awareness of machines' working state. The way oil interacts with itself and the other components in a mechanical system is critical.
Many other possible interactions, including frictional forces, wear effects, stress and strain, and lubricative conditions, are abundant inside a system. Tribology is significant as the surface often seems to be smooth, but in reality, it possesses roughness at the molecular level, which needs to be examined.
Another critical aspect of tribology is wear, which can be of three different types i.e. adhesive, abrasive or erosive, depending upon the type of interaction and environment. When the rough edges of two surfaces come into contact in a system comprising oil, it results in wear. The bigger the number of contacts between the two surfaces, the greater the chances of wear. So, if the lubrication is not as efficient as it should be, it can result in an amplified amount of wear, making the investigation of engine oil tribology more vital.
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References and Further Reading
Birleanu, C., Pustan, M., Cioaza, M., Molea, A., Popa, F., & Contiu, G. (2022). Effect of TiO2 nanoparticles on the tribological properties of lubricating oil: an experimental investigation. Scientific Reports, 12(1), 1-17. https://doi.org/10.1038/s41598-022-09245-2
Ali, M. K. A., Xianjun, H., Mai, L., Qingping, C., Turkson, R. F., & Bicheng, C. (2016). Improving the tribological characteristics of piston ring assembly in automotive engines using Al2O3 and TiO2 nanomaterials as nano-lubricant additives. Tribology International, 103, 540-554. https://doi.org/10.1016/j.triboint.2016.08.011
Zin, V., Agresti, F., Barison, S., Colla, L., & Fabrizio, M. (2015). Influence of Cu, TiO2 nanoparticles and carbon nano-horns on tribological properties of engine oil. Journal of Nanoscience and Nanotechnology, 15(5), 3590-3598. https://doi.org/10.1166/jnn.2015.9839
Arumugam, S., & Sriram, G. (2013). Preliminary study of nano-and microscale TiO2 additives on tribological behavior of chemically modified rapeseed oil. Tribology Transactions, 56(5), 797-805. https://doi.org/10.1080/10402004.2013.792977
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