Recent Advances in Preparation and Testing Methods of Engine-Based Nanolubricants: A State-of-the-Art Review

Abstract

Reducing power losses in engines is considered a key parameter of their efficiency improvement. Nanotechnology, as an interface technology, is considered one of the most promising strategies for this purpose. As a consumable liquid, researchers have studied nanolubricants through the last decade as potential engine oil. Nanolubricants were shown to cause a considerable reduction in the engine frictional and thermal losses, and fuel consumption as well. Despite that, numerous drawbacks regarding the quality of the processed nanolubricants were discerned. This includes the dispersion stability of these fluids and the lack of actual engine experiments. It has been shown that the selection criteria of nanoparticles to be used as lubricant additives for internal combustion engines is considered a complex process. Many factors have to be considered to investigate and follow up with their characteristics. The selection methodology includes tribological and rheological behaviours, thermal stability, dispersion stability, as well as engine performance. Through the last decade, studies on nanolubricants related to internal combustion engines focused only on one to three of these factors, with little concern towards the other factors that would have a considerable effect on their final behaviour. In this review study, recent works concerning nanolubricants are discussed and summarized. A complete image of the designing parameters for this approach is presented, to afford an effective product as engine lubricant.

Tribological Properties of the Nanoscale Spherical Y2O3 Particles as Lubricant Additives in Automotive Application

“…The yttria nanoparticles were homogenized in six different concentrations (between 0.1 and 0.6 wt%). According to numerous literature sources [2,6,9,11,[19][20][21][22][23], the nanoscale ceramic particles can provide positive friction and wear reduction properties in this concentration range. Furthermore, due to the higher purchase cost of nanoscale spherical yttria (Y 2 O 3 : 8 EUR/g, on the other hand e.g., ZrO 2 : 0.18 EUR/g), the production costs of engine lubricants containing these nanoparticles would be only profitable with lower concentration values.…”

“…The homogenization of the lubricant samples to be measured is a crucial part of the experiments. Akl et al [9] presented two commonly used preparation methods to homogenize nanoparticle containing lubricants. In the single-step method, the nanoparticles, the dispersing agent and the base fluid are prepared simultaneously, meanwhile in the two-step method, the nanoparticles are mixed with the dispersing agent separately and later this mixture is homogenized into the base fluid.…”

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

“…The results of research on nanoadditives and their environmental effects and applicability have been studied by several researchers [2]. Based on the summarized tribological results, it can be said that nanoparticles are able to change the coefficient of friction, influence the type of friction, and reduce the wear of contact parts [3].…”

Study on Frictional Properties of Fine Powder Materials

“…Other advantages are insolubility in non-polar base oils, low reactivity with other additives, and high possibility of film formation, which helps to withstand high temperatures and is more durable [18]. The effectiveness of nano additives depends on certain factors, such as their compatibility with base oils, their size and morphology, their concentration, and dispersion stability [19,20].…”

“…The direction of nanomaterials has received much recent development [16][17][18][19][20][21]. Nanostructured additives are used everywhere in mechanical engineering and vehicle operation.…”