Elucidation of the thermophysical mechanism of hexagonal boron nitride as nanofluids additives

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.

Review of two-dimensional nanomaterials in tribology: Recent developments, challenges and prospects

From our ordinary lives to various mechanical systems, friction and wear are often unavoidable phenomena that are heavily responsible for excessive expenditures of nonrenewable energy, the damages and failures of system movement components, as well as immense economic losses. Thus, achieving low friction and high anti-wear performance is critical for minimization of these adverse factors. Two-dimensional (2D) nanomaterials, including transition metal dichalcogenides, single elements, transition metal carbides, nitrides and carbonitrides, hexagonal boron nitride, and metal-organic frameworks have attracted remarkable interests in friction and wear reduction of various applications, owing to their atomic-thin planar morphologies and tribological potential. In this paper, we systematically review the current tribological progress on 2D nanomaterials when used as lubricant additives, reinforcement phases in the coatings and bulk materials, or a major component of superlubricity system. Additionally, the conclusions and prospects on 2D nanomaterials with the existing drawbacks, challenges and future direction in such tribological fields are briefly provided. Finally, we sincerely hope such a review will offer valuable lights for 2D nanomaterial-related researches dedicated on tribology in the future.

Enhancing Heat Transfer Behaviour of Ethylene Glycol by the Introduction of Silicon Carbide Nanoparticles: An Experimental and Molecular Dynamics Simulation Study

As the critical component of automotive engine coolant, ethylene glycol (E.G.) significantly matters in heat dissipation. In this study, the key aim is to investigate the heat transfer behaviour of E.G. as nano-additives base fluid. The heat transfer capability of E.G./SiC nanofluid (N.F.) was experimentally and theoretically evaluated via transient hot wire methods and equilibrium molecular dynamics (EMD) simulation, respectively. M.D. simulation exhibited a great ability to accurately forecast the thermal conductivity of N.F. compared with the experiment results. The results confirmed that the thermal stability of N.F. is relatively greater than that of E.G. base fluids. An improvement mechanism of thermal conductivity and thermal stability under an atomic scale via the analysis of mean square displacement (MSD) and radial distribution function (RDF) calculation was elaborately presented. Ultimately, the results indicated that the diffusion effect and the increasing transition rate of liquid atoms are responsible for thermal conductivity enhancement.

Effects of Plasma Treated Alumina Nanoparticles on Breakdown Strength, Partial Discharge Resistance, and Thermophysical Properties of Mineral Oil-Based Nanofluids

Mineral oil has been chosen as an insulating liquid in power transformers due to its superior characteristics, such as being an effective insulation medium and a great cooling agent. Meanwhile, the performance of mineral oil as an insulation liquid can be further enhanced by dispersing nanoparticles into the mineral oil, and this composition is called nanofluids. However, the incorporation of nanoparticles into the mineral oil conventionally causes the nanoparticles to agglomerate and settle as sediment in the base fluid, thereby limiting the improvement of the insulation properties. In addition, limited studies have been reported for the transformer oil as a base fluid using Aluminum Oxide (Al₂O₃) as nanoparticles. Hence, this paper reported an experimental study to investigate the significant role of cold plasma treatment in modifying and treating the surface of nano-alumina to obtain a better interaction between the nano-alumina and the base fluid, consequently improving the insulation characteristics such as breakdown voltage, partial discharge characteristics, thermal conductivity, and viscosity of the nanofluids. The plasma treatment process was conducted on the surface of nano-alumina under atmospheric pressure plasma by using the dielectric barrier discharge concept. The breakdown strength and partial discharge characteristics of the nanofluids were measured according to IEC 60156 and IEC 60270 standards, respectively. In contrast, the viscosity and thermal conductivity of the nanofluids were determined using Brookfield DV-II + Pro Automated viscometer and Decagon KD2-Pro conductivity meter, respectively. The results indicate that the 0.1 wt% of plasma-treated alumina nanofluids has shown the most comprehensive improvements in electrical properties, dispersion stability, and thermal properties. Therefore, the plasma treatment has improved the nanoparticles dispersion and stability in nanofluids by providing stronger interactions between the mineral oil and the nanoparticles.